Dissertations / Theses on the topic 'Design and assessment of bridge structures'

Life Cycle Assessment (LCA) is the globally the most recognised method for quantifying theimpact the a product or service has on the environment through its whole life-span. Theconstruction sector plays a key role in the depletion of the natural resources and the energyconsumption on the planet. Thus it is fundamental that an environmental assessment tool likeLCA should be in close cooperation with the construction process.This thesis focuses on the environmental impact of bridge abutments, and can be divided in twoparts.The rst one focuses on enhancing the automated design in the construction eld. A Python codeis created that focuses on creating the geometry of any type of bridge abutment and conductingthe calculations for the required concrete and reinforcement. The process is attempted to becomecompletely automated.The second part introduces three alternative designs for a bridge abutment that attempt to havethe same structural properties and cooperate successfully with the superstructure, while at thesame time utilize as little material as possible. The possible reduction in material is quantiedin environmental terms after an environmental impact assessment is performed.The results show that dierent designs can have a great impact on the reduction on the materialconsumption and on the impact that the whole structure has on the environment. The resultsin this study might provide the designers with valuable motivation and guidelines to achievehigher sustainability standards in the future.

This diploma thesis is focused on design and assessement of the road bridge in Příbor city, where road I/58 crosses road I/48. There are 3 possible of solution of designed structure which are slab construction, beam construction and prefabricated structure. Each solution includes the design and assessment of individual structures, including drawings and economic evaluation. In conclusion, the three solutions have been evaluated against all of the given criteria.

This research encompasses the automated design and structural optimization of reinforced concrete slab frame bridges, considering investment costs and environmental impacts. The most important feature of this work is that it focusses on realistic and complete models of slab frame bridges rather than on optimization of only individual members or sections of a bridge. The thesis consists of an extended summary of publications and three appended papers. In the first paper, using simple assumptions, the possibility of applying cost-optimization to the structural design of slab frame bridges was investigated. The results of the optimization of an existing constructed bridge showed the potential to reduce the investment cost of slab frame bridges. The procedure was further developed in the second paper. In this paper, automated design was integrated to a more refined cost-optimization methodology based on more detailed assumptions and including extra constructability factors. This procedure was then applied to a bridge under design, before its construction. From the point of view of sustainability, bridge design should not only consider criteria such as cost but also environmental performance. The third paper thus integrated life cycle assessment (LCA) with the design optimization procedure to perform environmental impact optimization of the same case study bridge as in the second paper. The results of investment cost and environmental impact optimization were then compared. The obtained results presented in the appended papers highlight the successful application of optimization techniques to the structural design of reinforced concrete slab frame bridges. Moreover, the results indicate that a multi-objective optimization that simultaneously considers both environmental impacts and investment cost is necessary in order to generate more sustainable designs. The presented methodology has been applied to the design process for a time-effective, sustainable, and optimal design of concrete slab frame bridges.

QC 20170316

Increasing the operational speed of trains has attracted a lot of interest in the last decades and has brought new challenges, especially in terms of infrastructure design methodology, as it may induce excessive vibrations. Such demands can damage bridges, which in turn increases maintenance costs, endangers the safety of passing trains and disrupts passenger comfort. Conventional design provisions should therefore be evaluated in the light of modern concerns; nevertheless, several previous studies have highlighted some of their shortcomings. It should be emphasized that most of these studies have neglected the uncertainties involved, which preventsthe reported results from representing a complete picture of the problem. In this respect, the present thesis is dedicated to evaluating the performance of conventional design methods, especially those related to running safety and passenger comfort, using probabilistic approaches. To achieve this objective, a preliminary study was carried out using the first-order reliability method for short/medium span bridges passed by trains at a wide range of operating speeds. Comparison of these results with the corresponding deterministic responses showed that applying a constant safety factor to the running safety threshold does not guarantee that the safety index will be identical for all bridges. It also shows that the conventional design approaches result in failure probabilities that are higher than the target values. This conclusion highlights the need to update the design methodology for running safety. However, it would be essential to determine whether running safety is the predominant design criterion before conducting further analysis. Therefore, a stochastic comparison between this criterion and passenger comfort was performed. Due to the significant computational cost of such investigations, subset simulation and crude Monte-Carlo (MC) simulation using meta-models based on polynomial chaos expansion were employed. Both methods were found to perform well, with running safety almost always dominating the passenger comfort limit state. Subsequently, classification-based meta-models, e.g. support vector machines, k-nearest neighbours and decision trees, were combined using ensemble techniques to investigate the influence of soil-structure interaction on the evaluated reliability of running safety. The obtained results showed a significant influence, highlighting the need for detailed investigations in further studies. Finally, a reliability-based design optimization was conducted to update the conventional design method of running safety by proposing minimum requirements for the mass per length and moment of inertia of bridges. It is worth mentioning that the inner loop of the method was solved by a crude MC simulation using adaptively trained Kriging meta-models.
Att öka tågens hastighet har väckt stort intresse under de senaste decennierna och har medfört nya utmaningar, särskilt när det gäller broanalyser, eftersom tågen inducerar stora vibrationer. Sådana vibrationer kan öka underhållskostnaderna, äventyra säkerheten för förbipasserande tåg och påverka passagerarkomforten. Konstruktionsbestämmelser bör därför utvärderas mot bakgrund av dessa problem; dock har flera tidigare studier belyst några av bristerna i dagens bestämmelser. Det bör understrykas att de flesta av dessa studier har försummat de osäkerheter som är involverade, vilket hindrar de rapporterade resultaten från att representera en fullständig bild av problemet. I detta avseende syftar denna avhandling till att utvärdera prestandan hos konventionella analysmetoder, särskilt de som rör körsäkerhet och passagerarkomfort, med hjälp av sannolikhetsmetoder. För att uppnå detta mål genomfördes en preliminär studie med första ordningens tillförlitlighetsnmetod för broar med kort/medellång spännvidd som passeras av tåg med ett brett hastighetsspektrum. Jämförelse av dessa resultat med motsvarande deterministiska respons visade att tillämpa en konstant säkerhetsfaktor för verifieringen av trafiksäkerhet inte garanterar att säkerhetsindexet kommer att vara identiskt för alla broar. Det visar också att de konventionella analysmetoderna resulterar i brottsannolikheter som är högre än målvärdena. Denna slutsats belyser behovet av att uppdatera analysmetoden för trafiksäkerhet. Det skulle emellertid vara viktigt att avgöra om trafiksäkerhet är det dominerande designkriteriet innan ytterligare analyser genomförs. Därför utfördes en stokastisk jämförelse mellan detta kriterium och kriteriet för passagerarkomfort. På grund av den betydande. analystiden för sådana beräkningar användes delmängdssimulering och Monte-Carlo (MC) simulering med metamodeller baserade på polynomisk kaosutvidgning. Båda metoderna visade sig fungera bra, med trafiksäkerhet som nästan alltid dominerade över gränsningstillståndet för passagerarkomfort. Därefter kombinerades klassificeringsbaserade metamodeller som stödvektormaskin och beslutsträd genom ensembletekniker, för att undersöka påverkan av jord-brointeraktion på den utvärderade tillförlitligheten gällande trafiksäkerhet. De erhållna resultaten visade en signifikant påverkan och betonade behovet av detaljerade undersökningar genom ytterligare studier. Slutligen genomfördes en tillförlitlighetsbaserad konstruktionsoptimering för att föreslå ett minimikrav på erforderlig bromassa per längdmeter och tröghetsmoment. Det är värt att nämna att metodens inre loop löstes med en MC-simulering med adaptivt tränade Kriging-metamodeller.

QC 20210910

At the turn of 2010/2011, Sweden went from designing structures according to nationaldesign codes to the new European standards Eurocode. For bridge engineers, this implieda change from a combination of BRO 2004 and BSK 07 to the Eurocode as the maindocuments, complemented by national documents such as TRVK Bro 11. The normtransition did not only change the calculation methods, but also turned a phenomenonthat never was of great importance for road bridges before into something that could limitthe carrying capacity of the structure. This phenomenon is called fatigue, i.e. repeatedload cycles, where each load is much lower than the ultimate limit state capacity, thatfinally results in collapse. This master thesis investigates why fatigue is significant in the design today. This is donethrough a comparison of how the new and old regulations assesses fatigue. A bridge builtin 2011, designed by ELU Konsult AB according to the old regulations, was modelledin the finite element program LUSAS. Several lorry crossings from different fatigue loadmodels were then simulated. The output from LUSAS was then used to calculate theutilization ratios for three critical points along the bridge. The result indicates that both regulations give rise to similar stress ranges, i.e. thedifference between the maximum and minimum stress obtained during a crossing. Thedifferences between the regulations are instead within the fatigue calculations, where themajor difference is the number of lorries crossing the bridge during its lifetime. Theutilization ratio according to the old regulations for the worst exposed point is 27.0 %,corresponding to 9.13 daily crossings by heavy lorries, which is the maximum numberof daily crossings provided by BRO 2004. The lowest utilization ratio according tothe Eurocode is 70.0 %, calculated for 137 daily crossings which is the lowest amountof crossings allowed. An interpretation of the Eurocode, which allows usage of fatigue loadmodel 5 even for smaller bridges, results in a utilization ratio of 56.0% which correspondsto 90.0 daily crossings, i.e. lower than the other fatigue load models provided by theEurocode but clearly above the old regulations. The conclusion is that an alternative way of deciding the number of crossings shouldbe provided by the Eurocode. Today, the classification consists of four steps, which arevery rough. Instead, a proposal is given in this thesis which advocates usage of a linearfunction for deciding the number of design crossings based on the number of daily crossingsby lorries. The proposed alternative design method is between the two regulations withrespect to daily crossings and utilization ratio.
Vid årsskiftet 2010/2011 övergick Sverige från att dimensionera byggnadsverk enligt nationellastandarder till den nya europastandarden Eurokod. För brokonstruktörer innebar dettaen övergång från en kombination av BRO 2004 och BSK 07, till att Eurokod blev dethuvudsakligt styrande dokumentet, med bland annat TRVK Bro 11 som ett dokumentmed tillhörande nationella val. Övergången medförde inte bara att verksamma konstruktörertvingades lära sig förändrade beräkningsmetoder, utan också att ett fenomen som tidigaresällan var dimensionerande för vägbroar nu kunde vara det som ställde högst krav påbärförmågan. Detta fenomen kallas utmattning, dvs. upprepade av- och pålastningar, varoch en betydligt lägre än brons maximala bärförmåga, som i slutändan resulterar i brott. I detta examensarbete utreds det varför utmattning numera är en betydande del avdimensioneringen. Detta sker genom en jämförelse av hur de gamla och nya normernautvärderar utmattning. Som modell har en befintlig bro invigd 2011, dimensioneradav ELU Konsult AB enligt de gamla normerna, använts. Denna bro har modellerats ifinita element programmet LUSAS, varpå en mängd olika lastbilsöverfarter simulerats ochutmattningsutnyttjandet för tre utvalda kritska punkter beräknats. Resultatet indikerar att båda normerna har liknande storlekar på spänningsvidderna,dvs. skillnaden på största och minsta spänningen som uppstår vid en överfart. Däremotråder det skillnader vid utmattningsberäkningarna, där den stora skillnaden är antalettunga fordon som passerar bron under dess livslängd. Enligt de gamla normerna ärutnyttjandegraden för den värst utsatta studerade punkten 27.0 %, vilket är beräknatpå det högsta antalet dagliga passager från tunga fordon som BRO 2004 tillåter, d.v.s.9.13 dagliga passager. Enligt Eurokod uppgår den lägsta utnyttjandegraden till 70.0 %,vilket motsvarar 137 dagliga överfarter vilket är det lägsta Eurokod tillåter. Vid ettalternativt sätt att tolka Eurokod, som tillåter användandet av utmattningslastmodell5 även för mindre broar, fås en utnyttjandegrad på 56.0% vilket motsvarar 90.0 dagligaöverfarter. Detta är något lägre än de andra utmattningslastmodellerna enligt Eurokodmen fortfarande högre än det gamla regelverket. Slutsatsen av uppsatsen är att ett alternativt sätt att bestämma antalet överfarter bordeerbjudas i Eurokod, då indelningen idag består av fyra stora trappsteg vilket ger en väldigtsnäv indelning. I detta examensarbete presenteras ett förslag som innebär att antaletdimensionerande överfarter istället bör bestämmas som en rätlinjig funktion av antaletdagliga överfarter från tung trafik. Det föreslagna sättet ligger mellan de båda normernamed hänsyn till passager och utnyttjandegrad.

Condition assessment and safety verification of existing bridges and decisions as to whether bridge posting is required are addressed through analysis, load testing, or a combination of methods. Bridge rating through structural analysis is by far the most common procedure for rating existing bridges. The American Association of State Highway and Transportation Officials (AASHTO) Manual for Bridge Evaluation (MBE), First Edition permits bridge capacity ratings to be determined through allowable stress rating (ASR), load factor rating (LFR) or load and resistance factor rating (LRFR); the latter method is keyed to the AASHTO LRFD Bridge Design Specifications, which is reliability-based and has been required for the design of new bridges built with federal findings since October, 2007. A survey of current bridge rating practices in the United States has revealed that these three methods may lead to different ratings and posting limits for the same bridge, a situation that carries serious implications with regard to the safety of the public and the economic well-being of communities that may be affected by bridge postings or closures. To address this issue, a research program has been conducted with the overall objective of providing recommendations for improving the process by which the condition of existing bridge structures is assessed. This research required a coordinated program of load testing and finite element analysis of selected bridges in the State of Georgia to gain perspectives on the behavior of older bridges under various load conditions. Structural system reliability assessments of these bridges were conducted and bridge fragilities were developed for purposes of comparison with component reliability benchmarks for new bridges. A reliability-based bridge rating framework was developed, along with a series of recommended improvements to the current bridge rating methods, which facilitate the incorporation of various in situ conditions of existing bridges into the bridge rating process at both component and system levels. This framework permits bridge ratings to be conducted at three levels of increasing complexity to achieve the performance objectives, expressed in the terms of reliability, that are embedded in the LRFR option of the AASHTO Manual of Bridge Evaluation. This research was sponsored by the Georgia Department of Transportation, and has led to a set of Recommended Guidelines for Condition Assessment and Evaluation of Existing Bridges in Georgia.

La surveillance à distance des structures a émergé comme une préoccupation importante pour les ingénieurs afin de maintenir la sécurité et la fiabilité des infrastructures civiles pendant leur durée de vie. Les techniques de surveillance structurale (SHM) sont de plus en plus populaires pour fournir un diagnostic de "l'état" des structures en raison de leur vieillissement, de la dégradation des matériaux ou de défauts survenus pendant leur construction. Les limites de l'inspection visuelle et des techniques non destructives, qui sont couramment utilisées pour détecter des défauts extrêmes sur les parties accessibles des structures, ont conduit à la découverte de nouvelles technologies qui évaluent d’un seul tenant l'état global d'une structure surveillée. Les techniques de surveillance globale ont été largement utilisées pour la reconnaissance d'endommagement dans les grandes infrastructures civiles, telles que les ponts, sur la base d'une analyse modale de la réponse dynamique structurale. Cependant, en raison des caractéristiques complexes des structures oeuvrant sous des conditions environnementales variables et des incertitudes statistiques dans les paramètres modaux, les techniques de diagnostic actuelles n'ont pas été concluantes pour conduire à une méthodologie robuste et directe pour détecter les incréments de dommage avant qu'ils n'atteignent un stade critique. C’est ainsi que des techniques statistiques de reconnaissance de formes sont incorporées aux méthodes de détection d'endommagement basées sur les vibrations pour fournir une meilleure estimation de la probabilité de détection des dommages dans des applications in situ, ce qui est habituellement difficile compte tenu du rapport bruit à signal élevé. Néanmoins, cette partie du SHM est encore à son stade initial de développement et, par conséquent, d'autres tentatives sont nécessaires pour parvenir à une méthodologie fiable de détection de l'endommagement. Une stratégie de détection de dommages basée sur des aspects statistiques a été proposée pour détecter et localiser de faibles niveaux incrémentiels d'endommagement dans une poutre expérimentale pour laquelle tant le niveau d'endommagement que les conditions de retenue sont réglables (par exemple ancastrée-ancastrée et rotulée-rotulée). Premièrement, des expériences ont été effectuées dans des conditions de laboratoire contrôlées pour détecter de faibles niveaux d'endommagement induits (par exemple une fissure correspondant à 4% de la hauteur d’une section rectangulaire équivalente) simulant des scénarios d'endommagement de stade précoce pour des cas réels. Différents niveaux d'endommagement ont été simulés à deux endroits distincts le long de la poutre. Pour chaque série d'endommagement incrémentiel, des mesures répétées (~ 50 à 100) ont été effectuées pour tenir compte de l'incertitude et de la variabilité du premier mode de vibration de la structure en raison d'erreurs expérimentales et du bruit. Une technique d'analyse par ondelette basée sur les modes a été appliquée pour détecter les changements anormaux survenant dans les modes propres causées par le dommage. La réduction du bruit ainsi que les caractéristiques des agrégats ont été obtenues en mettant en œuvre l'analyse des composantes principales (PCA) pour l'ensemble des coefficients d'ondelettes calculés à des nœuds (ou positions) régulièrement espacés le long du mode propre. En rejetant les composantes qui contribuent le moins à la variance globale, les scores PCA correspondant aux premières composantes principales se sont révélés très corrélés avec de faibles niveaux d'endommagement incrémentiel. Des méthodes classiques d'essai d'hypothèses ont été effectuées sur les changements des paramètres de localisation des scores pour conclure objectivement et statistiquement, à un niveau de signification donné, sur la présence du dommage. Lorsqu'un dommage statistiquement significatif a été détecté, un nouvel algorithme basé sur les probabilités a été développé pour déterminer l'emplacement le plus probable de l'endommagement le long de la structure. Deuxièmement, se basant sur l'approche probabiliste, une série de tests a été effectuée dans une chambre environnementale à température contrôlée pour étudier les contributions relatives des effets de l’endommagement et de la température sur les propriétés dynamiques de la poutre afin d’estimer un facteur de correction pour l'ajustement des scores extraits. Il s'est avéré que la température avait un effet réversible sur la distribution des scores et que cet effet était plus grand lorsque le niveau d'endommagement était plus élevé. Les résultats obtenus pour les scores ajustés indiquent que la correction des effets réversibles de la température peut améliorer la probabilité de détection et minimiser les fausses alarmes. Les résultats expérimentaux indiquent que la contribution combinée des algorithmes utilisés dans cette étude était très efficace pour détecter de faibles niveaux d'endommagement incrémentiel à plusieurs endroits le long de la poutre tout en minimisant les effets indésirables du bruit et de la température dans les résultats. Les résultats de cette recherche démontrent que l'approche proposée est prometteuse pour la surveillance des structures. Cependant, une quantité importante de travail de validation est attendue avant sa mise en œuvre sur des structures réelles. Mots-clés : Détection et localisation des dommages, Poutre, Mode propre, Ondelette, Analyse des composantes principales, Rapport de probabilité, Température
Remote monitoring of structures has emerged as an important concern for engineers to maintain safety and reliability of civil infrastructure during its service life. Structural Health Monitoring (SHM) techniques are increasingly becoming popular to provide ideas for diagnosis of the "state" of potential defects in structures due to aging, deterioration and fault during construction. The limitations of visual inspection and non-destructive techniques, which were commonly used to detect extreme defects on only accessible portions of structures, led to the discovery of new technologies which assess the "global state" of a monitored structure at once. Global monitoring techniques have been used extensively for the recognition of damage in large civil infrastructure, such as bridges, based on modal analysis of structural dynamic response. However, because of complicated features of real-life structures under varying environmental conditions and statistical uncertainties in modal parameters, current diagnosis techniques have not been conclusive in ascertaining a robust and straightforward methodology to detect damage increments before it reaches its critical stage. Statistical pattern recognition techniques are incorporated with vibration-based damage detection methods to provide a better estimate for the probability of the detection of damage in field applications, which is usually challenging given the high noise to signal ratio. Nevertheless, this part of SHM is still in its initial stage of development and, hence, further attempts are required to achieve a reliable damage detection methodology. A statistical-based damage detection strategy was proposed to detect and localize low levels of incremental damage in an experimental beam in which the level of damage and beam restraint conditions are adjustable (e.g. fixed-fixed and pinned-pinned). First, experiments were performed in controlled laboratory conditions to detect small levels of induced-damage (e.g. 4% crack height for an equivalent rectangular section) simulated for early stage damage scenarios in real cases. Various levels of damage were simulated at two distinct locations along the beam. For each sate of incremental damage, repeat measurements (~ 50 to 100) were performed to account for uncertainty and variability in the first vibration mode of the structure due to experimental errors and noise. A modal-based wavelet analysis technique was applied to detect abnormal changes occurring in the mode shapes caused by damage. Noise reduction as well as aggregate characteristics were obtained by implementing the Principal Component Analysis (PCA) into the set of wavelet coefficients computed at regularly spaced nodes along the mode shape. By discarding components that contribute least to the overall variance, the PCA scores corresponding to the first few PCs were found to be highly correlated with low levels of incremental damage. Classical hypothesis testing methods were performed on changes on the location parameters of the scores to conclude damage objectively and statistically at a given significance level. When a statistically significant damage was detected, a novel Likelihood-based algorithm was developed to determine the most likely location of damage along the structure. Secondly, given the likelihood approach, a series of tests were carried out in a climate-controlled room to investigate the relative contributions of damage and temperature effects on the dynamic properties of the beam and to estimate a correction factor for the adjustment of scores extracted. It was found that the temperature had a reversible effect on the distribution of scores and that the effect was larger when the damage level was higher. The resulted obtained for the adjusted scores indicated that the correction for reversible effects of temperature can improve the probability of detection and minimize false alarms. The experimental results indicate that the combined contribution of the algorithms used in this study were very efficient to detect small-scale levels of incremental damage at multiple locations along the beam, while minimizing undesired effects of noise and temperature in the results. The results of this research demonstrate that the proposed approach may be used as a promising tool for SHM of actual structures. However, a significant amount of challenging work is expected for implementing it on real structures. Key-words: Damage Detection and Localization, Beam, Mode Shape, Wavelet, Principal Component Analysis, Likelihood Ratio, Temperature

Data from existing research are linked together to produce an overview of the effects of chloride-induced corrosion on reinforced concrete structures. The effects of chloride-induced corrosion on the following mechanisms have been investigated: (i) Cracking. (ii) Bond strength. (iii) Flexural strength. (iv) Shear strength. (v) Column behaviour. Models have been developed to link material and structural aspects of deterioration. Despite the complexity of the behaviour, many of the models are modifications to existing procedures contained in UK codes. Material and structural models are integrated together in a spreadsheet for assessing the variation in load-carrying capacity with time. Time to cracking and residual load-carrying capacity are found to be sensitive to small variations in key parameters such as the cover and the surface chloride level. Predictions from a spreadsheet model indicate that structures designed and built to BS 8110 should achieve their design life without the need for significant repair. The predictions also indicate that the UK Highways Agency was justified in making BD 57 more onerous than BS 5400. With validation against further test data the procedures developed in this Thesis could form the basis for codes of practice for the assessment of corrosion-damaged concrete structures and the durability design of new concrete structures.

Performance-based design (PBD) method is gradually taking over the traditional force-based design (FBD) for designing bridges in North America. Considering the importance of bridge structures in the transportation network, quantitative performance criteria were adopted in Canadian Highway Bridge Design Code (CHBDC) in 2014 and a supplement to CHBDC 2014 was published in 2016. In this study, a lifeline bridge pier is designed following the FBD method from CHBDC 2010 and PBD approach following CHBDC 2014 and the supplement to CHBDC 2014 to understand the impression of changes in bridge design codes. The dominating performance criteria in the new supplement to CHBDC 2014 for a lifeline bridge is the maintenance of repairable damage at a seismic event of 975 years return period. The performances of the designed bridge piers are assessed using 20 near-fault ground motions through incremental dynamic analysis. Fragility curves for the bridge piers are plotted to perform the seismic vulnerability analysis of the bridge piers designed following three different alternatives. A lifeline bridge pier is also designed following PBD from CHBDC 2014 using different ASTM grade steel of varying strength and fracture elongation in combination with different concrete strength. Performances of the designed bridge piers are evaluated for site-specific ground motion suits. Moreover, the impact of changing reinforcement strength on the designed bridge piers' seismic behavior is checked by fragility analysis. PBD from the supplement to CHBDC 2014 shows the highest damage probability. Whereas, the FBD from CHBDC 2010 and the PBD from CHBDC 2014 substantially reduce the risk of damage and improve the performance of the bridge pier. Practicing high strength steel reinforcement (HSR) in PBD of bridge piers can reduce the required percentage of reinforcement by 50% compared to conventionally used Grade 60 reinforcement. Construction difficulties can be avoided due to less congestion of rebars and cost of construction can be cut down without compromising the seismic performance. Damage vulnerability related to longitudinal steel strain reduces remarkably, and the collapse performance decreases when HSR are practiced in the design of bridge piers. Incorporation of high strength concrete can marginally improve the collapse performance.
Applied Science, Faculty of
Engineering, School of (Okanagan)
Graduate

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2009.
Includes bibliographical references (leaf 40).
Infrastructure in the United States is comprised of numerous structures that are decades old. The Longfellow Bridge is one of the oldest pieces of this infrastructure that is still in use and has become one of the most historic structures of the Boston area. Currently, the steel superstructure of the bridge is in poor condition while the masonry piers and abutments remain in good condition. In the near future, a major replacement of the superstructure will be required. In order for the masonry elements to be approved for a renewed design life, they must be assessed for their ability to withstand seismic loads. This assessment presents an investigation of original construction documents and identifies critical components of the bridge that require more in depth analysis. It also shows a qualitative review of expected seismic activity for the region surrounding Boston. A review of current theory related to unreinforced masonry structures is introduced and analysis is then performed on critical wall sections. Specific ground motions are applied using both constant acceleration and impulse loadings to the structure. The results of the analyses reveal a need for further investigation into retrofitting schemes as there is not a sufficient factor of safety that exists with certain pier elements. Furthermore, a failure envelope is developed and presented for several types of impulse loads in order to serve as a basis for understanding the behavioral response to potential earthquake loading.
by Nathan D. Boutin.
M.Eng.

In recent years the design of pedestrian bridges has become more slender. As a result the bridges has lower natural frequencies and are more prone to excessive vibrations when subjected to dynamic loads induced by pedestrians. Akademiska Hus are building such a bridge at Nya Karolinska Solna where the bridge will span over Solnavägenconnecting the hospital building, U2, and the research facility BioMedicum. Due to practical reasons, it is not possible to connect one of the bridge ends mechanicallyto the building which increases the risk for lateral modes in the sensitivefrequency range of 0-2.5 Hz. The increased risk of lateral modes of vibrations within the sensitive frequency range as well uncertainties when determining the dynamic response led to this thesis. This thesis covers a frequency analysis of the previously mention bridge and an evaluation of the dynamic response under pedestrian loading by implementation of several design guidelines. A literature review was conducted with the aim of giving a deeper knowledge of human induced vibrations and the relevant guidelines for modelling of pedestrian loading. Furthermore, a parametric study was conducted for parameters which might be prone to uncertainties in data. The investigated parameters were the Young’s modulus for concrete and the surrounding fill materialas well as the stiffness of the connection to BioMedicum. The parametric study yielded a frequency range of 2.20-2.93 Hz for the first lateral mode and 5.96-6.67 Hz for the first vertical mode of vibration. By including nonstructural mass the lower limit for the frequencies were lowered to 2.05 and 5.59 Hzin the first lateral and vertical mode respectively. The parametric study also showed that the largest impact on the natural frequencies were obtained by manipulating the parameters for the supports, both for BioMedicum and the substructure. The implementation of the guidelines resulted in a lateral acceleration between 0.05 and0.599 m/s2. No evaluation was conducted for the dynamic response in the vertical direction due to a natural frequency of 5.59 Hz, which is higher than the evaluation criteria stated in Eurocode 0. The results showed that the design of the Skyway bridge is dynamically sound with regard to pedestrian loading and no remedial actions are necessary.

Changes in load characteristics, deterioration with age, environmental influences and random actions may cause local or global damage in structures, especially in bridges, which are designed for long life spans. Continuous health monitoring of structures will enable the early identification of distress and allow appropriate retrofitting in order to avoid failure or collapse of the structures. In recent times, structural health monitoring (SHM) has attracted much attention in both research and development. Local and global methods of damage assessment using the monitored information are an integral part of SHM techniques. In the local case, the assessment of the state of a structure is done either by direct visual inspection or using experimental techniques such as acoustic emission, ultrasonic, magnetic particle inspection, radiography and eddy current. A characteristic of all these techniques is that their application requires a prior localization of the damaged zones. The limitations of the local methodologies can be overcome by using vibration-based methods, which give a global damage assessment. The vibration-based damage detection methods use measured changes in dynamic characteristics to evaluate changes in physical properties that may indicate structural damage or degradation. The basic idea is that modal parameters (notably frequencies, mode shapes, and modal damping) are functions of the physical properties of the structure (mass, damping, and stiffness). Changes in the physical properties will therefore cause changes in the modal properties. Any reduction in structural stiffness and increase in damping in the structure may indicate structural damage. This research uses the variations in vibration parameters to develop a multi-criteria method for damage assessment. It incorporates the changes in natural frequencies, modal flexibility and modal strain energy to locate damage in the main load bearing elements in bridge structures such as beams, slabs and trusses and simple bridges involving these elements. Dynamic computer simulation techniques are used to develop and apply the multi-criteria procedure under different damage scenarios. The effectiveness of the procedure is demonstrated through numerical examples. Results show that the proposed method incorporating modal flexibility and modal strain energy changes is competent in damage assessment in the structures treated herein.

The earthquake resistant design of structures requires that structures should sustain, safely, any ground motions of an intensity that might occur during their construction or in their normal use. However ground motions are unique in the effects they have on structural responses. The most accurate analysis procedure for structures subjected to strong ground motions is the time-history analysis. This analysis involves the integration of the equations of motion of a multi-degree-of-freedom system, MDOF, in the time domain using a stepwise solution in order to represent the actual response of a structure. This method is time-consuming though for application in all practical purposes. The necessity for faster methods that would ensure a reliable structural assessment or design of structures subjected to seismic loading led to the pushover analysis. Pushover analysis is based on the assumption that structures oscillate predominantly in the first mode or in the lower modes of vibration during a seismic event. This leads to a reduction of the multi-degree-of-freedom, MDOF system, to an equivalent single-degreeof- freedom, ESDOF system, with properties predicted by a nonlinear static analysis of the MDOF system. The ESDOF system is then subsequently subjected to a nonlinear timehistory analysis or to a response spectrum analysis with constant-ductility spectra, or damped spectra. The seismic demands calculated for the ESDOF system are transformed through modal relationships to the seismic demands of the MDOF system. In this study the applicability of the pushover method as an alternative mean to general design and assessment is examined. Initially a series of SDOF systems is subjected to two different pushover methods and to nonlinear-time-history analyses. The results from this study show that pushover analysis is not able to capture the seismic demands imposed by far-field or near-fault ground motions, especially for short-period systems for which it can lead to significant errors in the estimation of the seismic demands. In the case of near-fault ground motions the results suggest that pushover analysis may underestimate the displacement demands for systems with periods lower than half the dominant pulse period of the ground motion and overestimate them for systems with periods equal or higher than half the dominant pulse period of the ground motion. Subsequently a two-degree-offreedom, 2-DOF, is studied in the same manner with specific intention to assess the accuracy of the different load patterns proposed in the literature. For this system pushover analysis performed similarly as in the SDOF study. Finally the method is applied on a four-storey reinforced concrete frame structure. For this study pushover analysis was not effective in capturing the seismic demands imposed by both a far-field and a near-fault ground motion. Overall pushover analysis can be unconservative in estimating seismic demands of structures and it may lead to unsafe design.

Concrete structures represent a huge investment in terms of materials and energy and they lead to significant environmental impacts. Thus, there is a need to choose the most sustainable and eco-friendly alternative. From this perspective, this report aims to evaluate the environmental impacts associated with the construction of two fictitious structures: a bridge and a tunnel. To fully assess and fairly compare the environmental burdens of those two structures, the life cycle assessment (LCA) has been chosen. Prior to the case studies, the LCA process is described and a literature review related to LCAs of road structures is performed thus revealing the key facts and key figures of such studies. Based on this literature review, a simplified LCA is performed; it relies on public databases and only takes into account the construction phase. Because of data constraints, the indicators that are considered are NOx, SO2 and CO2 emissions, and the categories that are taken into account are energy consumption, global warming potential and photochemical oxidant formation. Characterization factors come from the REciPE method. Three different stages are considered and compared during this LCA study; the production of materials, the construction processes and the transportation phase. Results show that the environmental impacts of the bridge are higher than the ones of the tunnel and that the amount of concrete has a strong influence on the final results and consequently on the interpretation phase. This study also emphasizes the importance of assumptions and describes their potential influence on the final results by considering two different alternatives related to the concrete’s manufacturing. Making the concrete directly on site instead of bringing it by truck significantly decreases the environmental impacts of both structures; indeed, for the bridge structure, it leads to a diminution in CO2 emissions, global warming potential and energy consumption by more than 60%. The main constraint of this study has been the data collection for the life cycle inventory; indeed, many data were missing or coming from different public databases which result in a lack of thoroughness and precision (e.g. different geographical representativeness). Results of this study strongly depend on the various assumptions and on the data that have been collected, and technical choices, methodologies of construction or structural design mainly depend on the project’s location; consequently, results and conclusions cannot be generalized and should be handled carefully.

Techniques of performance-based design in fire safety have developed notably in the past two decades. One of the reasons for departing from the prescriptive methods is the ability of performance-based methods to form a scientific basis for the cost-risk-benefit analysis of different fire safety alternatives. Apart from few exceptions, observation of past fires has shown that the structure’s contribution to the overall fire resistance was considerably underestimated. The purpose of this research is to outline a risk-based design approach for structures in fire. Probabilistic methods are employed to ascertain uniform reliability indices in line with the classical trend in code development. Modern design codes for complex phenomena such as fire have been structured to facilitate design computations. Prescriptive design methods specify fire protection methods for structural systems based on laboratory controlled and highly restrictive testing regimes. Those methods inherently assume that the tested elements behave similarly in real structures irrespective of their loading, location or boundary conditions. This approach is contested by many researchers, and analyses following fire incidents indicated alarming discrepancy between anticipated and actual structural behaviour during real fires. In formulating design and construction codes, code writers deal with the inherent uncertainties by setting a ceiling to the potential risk of failure. The latter process is implemented by specifying safety parameters, that are derived via probabilistic techniques aimed at harmonising the risks ensuing different load scenarios. The code structure addresses the probability of failure with adequate detail and accuracy. The other component of the risk metric, namely the consequence of failure, is a subjective field that assumes a multitude of variables depending on the context of the problem. In codified structural design, the severity of failure is implicitly embodied in the different magnitudes of safety indices applied to different modes of structural response. This project introduces a risk-based method for the design of structures in fire. It provides a coherent approach to a quantified treatment of risk elements that meets the demands of performance-based fire safety methods. A number of proposals are made for rational acceptable risk and reliability parameters in addition to a damage index with applications in structural fire safety design. Although the example application of the proposed damage index is a structure subjected to fire effects, the same rationale can be easily applied to the assessment of structural damage due to other effects.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1999.
Includes bibliographical references (p. 301-306).
Future optical space systems such as interferometers and filled-aperture telescopes will extend the resolution and sensitivity offered by their on-orbit and ground-based predecessors. These systems face the challenge of achieving nanometer and milli-arcsecond precision control of stellar light passing through the optical train of a lightweight, flexible structure subjected to various disturbances. It is advantageous to assess the performance of initial concepts of these precision systems early in the design stage to aid in the requirements flowdown and resource allocation process. A complete end-to-end performance assessment methodology is developed which incorporates disturbance, sensitivity, and uncertainty analysis tools within a common state-space framework. The disturbance analysis is conducted using either a time-domain, frequency-domain, or Lyapunov approach to obtain nominal predictions of performance metric root-mean-square (RMS) values. Calculating power spectral density and cumulative RMS functions of the performance metrics allows critical system modes and frequencies to be identified, and in some instances, contributions from each of the disturbances can be determined. A Lagrange multiplier method is used to derive a governing equation for the sensitivities of the performance metrics with respect to model parameters. For a system whose structural dynamic equations are represented in modal form, the ensitivities can be calculated exactly and efficiently with respect to modal frequencies, masses, and damping ratios. The most critical modal parameters are carried into a parametric uncertainty analysis that seeks to identify the worst-case performance RMS values. A constrained optimization technique is described which searches for the worst-case performance over all allowable parameter values. When required, a performance enhancement approach is used to apply controlled structures technologies such as input/output isolation to achieve large performance changes. Structural modifications based on insight provided by a physical parameter sensitivity analysis are then employed to "fine tune" the performance to keep the worst-case values within the requirements. Analytical physical parameter sensitivities are experimentally validated on a truss structure and used to implement stiffness and mass perturbations that reduce the tip displacement of a flexible appendage. The overall framework is applied to an integrated model of the Space Interferometry Mission to demonstrate its practical use on a large order system.
by Homero L. Gutierrez, Jr.
Ph.D.

Master of Science
Department of Civil Engineering
Robert J. Peterman
Concrete box culvert floor slabs are known to have detrimental effects on river and stream hydraulics. Consequences include an aquatic environment less friendly to the passage of fish and other organisms. This has prompted environmental regulations restricting construction of traditional, four-sided box culvert structures in rivers and streams populated by protected species. The box culvert standard currently used by the Kansas Department of Transportation (KDOT) is likely to receive increased scrutiny from federal and state environmental regulators in the near future. Additionally, multiple-cell box culverts present a maintenance challenge, since passing driftwood and debris are frequently caught in the barrels and around cell walls. As more structures reach the end of their design lives, new solutions must be developed to facilitate a more suitable replacement. Since construction can cause significant delays to the traveling public, systems and techniques which accelerate the construction process should also be considered. This thesis documents development of a single-span replacement system for box culverts in the state of Kansas. Solutions were found using either a flab slab or the center span of the KDOT three-span, haunched-slab bridge standard. In both cases, the concrete superstructure is connected monolithically with a set of abutment walls, which sit on piling. The system provides an undisturbed, natural channel bottom, satisfying environmental regulations. Important structural, construction, maintenance, and economic criteria considered during the planning stages of bridge design are discussed. While both superstructural systems were found to perform acceptably, the haunched section was chosen for preliminary design. Rationale for selection of this system is explained. Structural modeling, analysis, and design data are presented to demonstrate viability of the system for spans ranging from 32 to 72 feet. The new system is expected to meet KDOT’s needs for structural, environmental, and hydraulic performance, as well as long-term durability. Another option involving accelerated bridge construction (ABC) practices is discussed.

Thesis (PhD (Civil Engineering))--University of Stellenbosch, 2005.
Electric overhead travelling bridge cranes are an integral part of many industrial processes, where they are used for moving loads around the industrial area

In the present thesis, the application of fracture mechanics in design and assessment of steel structures has been studied.The first case study concerns a ring-flange connection used in wind turbine towers. The flange is rolled from straight steel profile into a complete ring. Subsequently, at the ends of the ring are welded by way of electron beam welding. This weld providing the integrity of the ring-flange was designed against fracture. To avoid potential failure by fracture and/or fatigue, the fracture mechanics approach for engineering assessments (as described in the Swedish handbook for safety assessment of structures containing defects) was implemented to predict the maximum allowable crack size. Material properties along with the design stress and crack size are the three variables that must be taken in account in order to design a structure against fracture. To this end, toughness and mechanical properties of the weld metal were experimentally determined. The results confirmed that the material behaves in a ductile manner and the electron beam welding has a positive effect on material properties. The fatigue performance of the flange was examined using the fatigue load histogram experienced by the flange in its 20years lifetime. Detailed finite element analyses of the flange connection were conducted to determine stress distribution at the most critical location along a hypothetical crack plane. The stresses obtained from the finite element analysis were used to assess the fracture stability of the flange. The fracture and fatigue assessment results confirmed that the flange in question is susceptible to fatigue failure which turns out to be the governing criterion in order to define the maximum allowable crack size. Furthermore, a parametric study was carried out to investigate the effect of parameters such as crack eccentricity, material properties and crack geometry on the integrity of the flange connection.The second case concerned the maintenance problem of roller bearings of relatively old bridges. These tend to rupture and no satisfactory explanation exists in the literature. Two broken specimens were supplied by the Swedish Transportation Authority (Trafikverket). These were first subjected to fractographic examination to determine the crack initiation location. Afterward, Charpy, compact tension, tensile and chemical composition specimens were machined out of the broken roller pieces and the respective tests were conducted. The results showed a very brittle material but no deviations from the prescribed material properties that were set forth in the 1967 certificate of application (Zulassung) of the rollers in question. To explain the observed failures a mechanical over-stressing condition was sought. Two such over-stressing sources were investigated. First the Hertz contact solution traditionally used in the design of roller bearings (both DIN 4141 and EN 1337-4) is valid for an infinite length cylinder. At the edges of the roller contact zone, stress singularities of the sort appearing in the case of a rectangular rigid body indenting an elastic half-space are likely to appear: three-dimensional finite element analyses were conducted and a 30% edge stress increase was established. As a second source of over-stressing the imperfections of welded I-beams according to EN 1090-2 were introduced into the FE model including, as before, the girder end, the roller assembly and the abutment. A wedge-type imperfection between the lower flange of the bridge girder and the lower support plate of the roller can create detrimental stress concentrations even at values no higher than 50% of the EN 1090 limits. Finally, the effect of the contact stresses in the roller was examined with a linear elastic fracture mechanics approach. It was found that surface cracks at the roller edge may become unstable in Mode-II when traversing the limits of the contact zone as this is the area of maximum shear stress: daily thermal cycles cause such cracks to go through a full plastic cycle as they are forced to swing past both edges of the contact area of the roller. This causes plastic strain accumulation at the crack tip of even small stable cracks: this mechanism causes them to grow until they become critical. A fracture assessment diagram for one of the broken rollers was computed.
Godkänd; 2014; 20141013 (pounou); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Pourya Noury Ämne: Stålbyggnad/Steel Structures Uppsats: Fracture Mechanics in Design and Assessment of Existing Structures: Two Case Studies Examinator: Professor Milan Veljkovic, Institutionen för Samhällsbyggnad och naturresurser, Luleå tekniska universitet Diskutant: Professor Raid Karoumi, Brobyggnad inkl Stålbyggnad, Kungliga Tekniska Högskolan, Stockholm Tid: Måndag den 15 december 2014 kl 13.00 Plats: F1031, Luleå tekniska universitet

Recent advancements in numerical analysis and computational power have pushed the current bridge design specifications towards a more descriptive performance-based seismic design (PBSD) approach as compared to the conventional force-based method. One major attributes of this PBSD is to keep bridges operational and reduce the repair cost by limiting the global and local deformations of a bridge to acceptable levels under design loads. Shape memory alloy (SMA), with its distinct superelasticity, shape memory effect and hysteretic damping, is a promising material for the application in bridge piers to attain the objectives of PBSD. The objective of this research is to develop a performance-based seismic design guideline for concrete bridge pier reinforced with different types of SMAs. With the aim of providing a comprehensive design guideline, this study started with the experimental investigation of bond behavior of smooth and sand coated SMA rebar in concrete using pushout specimens. The test results were explored to evaluate the influence of concrete strength, bar diameter, embedment length, and surface condition. In addition, a plastic hinge length expression for SMA-RC bridge pier was developed which can be used for calculating the flexural displacement capacity and design of SMA-RC bridge pier. Using Incremental Dynamic Analysis (IDA), this study developed quantitative damage states corresponding to different performance levels (cracking, yielding, and strength degradation) and specific probabilistic distributions for RC bridge piers reinforced with different types of SMAs. Based on an extensive numerical study, the author proposed residual drift based damage states for SMA-RC pier. Based on the proposed damage states, a sequential procedure for the performance-based design of SMA-RC bridge pier is developed using a combination of residual and maximum drift. Finally, in order to elucidate the potential benefit and applicability of the proposed guideline, fragility curves and seismic hazard curves for different SMA-RC bridge piers are developed considering maximum and residual drift as engineering demand parameters. It is found that the SMA-RC bridge piers designed following the proposed design guideline have very low probability of damage resulting in a lower annual loss which will provide significant financial benefit in the long run.
Applied Science, Faculty of
Engineering, School of (Okanagan)
Graduate

Europe experienced the destruction of numerous infrastructures during World War II, followed by a reflation and a strong economic growth during the next two decades allowing a more perennial and durable situation. A classical bridge lasting in general around 80 years, one should observe that these constructions built after the war will have to be either replaced either seriously strengthened in a few years. Besides, since the needs also vary over time, transportation infrastructures built during those years might not be adapted to the actual needs anymore – some bridges might thus have to be widened. A case study has been chosen in order to simulate under which conditions the widening of such a bridge can be performed. This road bridge, located in Vierzon in France, is rather simple since it is made of simply supported prestressed concrete beams and of reinforced concrete piers. It has been chosen in particular for its reduced size – three spans of 30 m each and two road lanes – that corresponded well to this project. Based on some data provided when the bridge was initially built and on a visual inspection, this project suggests six technical solutions to double the actual amount of lanes. An evaluation of the performance of the solutions according to three criteria – durations of works, cost of the works, and environmental impact – is made in order to give recommendations regarding the optimal solution. The results show that in spite of being installed quickly, adding steel beams is more expensive and has a greater impact on the environment than adding prestressed concrete beams. Regarding the modification of piers, the solution suggesting widening the existing piers is preferable than adding new extra piers according to all the criteria. Consequently, among all the solutions analysed, the optimal one is also the simplest one. Finally, the limits of the study and some suggestions for improvements are indicated.

Detta examensarbete ämnar besvara huruvida Tekla Structures kan fungera som ett lämpligt 3D-modelleringsprogram för konstruktionsgruppen Nyanläggning och Bro inom Grontmij Sverige. Med goda erfarenheter av Building Information Modeling, s.k. BIM, och 3D-modellering inom andra delar av Grontmij så fanns en önskan att optimera gruppens arbetsprocesser med den senaste kunskapen inom området. Arbetet har fokuserat på att praktiskt modellera en fallstudie baserat på ett av Grontmij tidigare genomfört anläggningsprojekt. För att säkerställa fallstudiens representativitet valdes en plattrambro med stor mängd armering som ansågs ha en komplex geometri vilket potentiellt skulle fördelaktigt kunna representeras i 3D. Vid skapandet av 3D-modellen och tillhörande ritningar delades processen in i tre steg; modellering, detaljering samt visualisering. Uppbyggandet av 3D- modellen påvisade unika för- och nackdelar i varje steg där också nedlagd arbetstid jämfördes med fallstudieprojektets tidplan. Resultaten visade att stegen modellering och detaljering (armering) uppvisade stora fördelar i relation till tidsåtgång. För steget visualisering, skapandet av 2D-ritningar enligt rapportens nomenklatur, var slutsatsen den omvända. Grontmij Nyanläggning och Bro rekommenderas därför att selektivt integrera Tekla Structures fördelar i sin framtida arbetsprocess samt fortsätta utvärdera programmet inom andra relaterade områden.
This thesis intends to answer whether Tekla Structures can function as a suitable 3D modeling software for the department of Transportation & Mobility within Grontmij Sweden. Given positive experiences from Building Information Modeling, so called BIM, and 3D modeling in other areas of Grontmij there was a desire to optimize the work processes of the department with the latest knowledge in the field. This report focuses on practical modeling of a case study, based on one of Grontmij’s previously conducted construction projects. To ensure a representative case study, a heavily reinforced slab-frame bridge was selected which was considered to have a complex geometry that potentially would be advantageously represented in 3D. The process of creating the 3D model and associated drawings was divided into three stages; modeling, detailing, and visualization. The construction of the 3D model demonstrated unique advantages and disadvantages in each stage where also this thesis’ work plan was compared with the case study’s time plan. The results showed that the steps modeling and detailing (reinforcing) showed benefits in relation to the time spent. For the visualization step, i.e. the creation of 2D drawings according to the terminology of this report, the conclusion was the opposite. Grontmij’s Transportation & Mobility department is therefore recommended to selectively integrate Tekla Structures’ advantages into their future work process and continue to evaluate the program in other related fields.

For the development of performance based design on a proper scientific basis the use of the concept of risk is inevitable. However, the application of this concept to actual structural design is not simple because of the large ranges of probability and consequences of events which exist. This is compounded by a plethora of different actions that can be taken to reduce the probabilities of the events and also the magnitude of the consequences. It is the reduction in the magnitude of these consequences which is essentially the goal of design. This work aims to address the challenges posed by the application of the concepts of performance based design for structures in fire. Simple methodologies have been developed for the assessment of the consequences of an extreme event. These methodologies are based upon fundamental behaviour of structures in fire. A methodology has been developed which can be used to assess the capacity/deflection behaviour through the complete thermal deflection of floor slabs. This takes into account positive effects on the capacity of floor slabs of the membrane stress at the slabs boundaries at low deflections as well as the final capacity provided by the tensile membrane action of the reinforcement mesh at high deflections. For vertical stability of structures in fire, analytical equations to describe the behaviour of floor systems at the perimeter of a building are developed. From these equations, the resulting pull-in forces on external columns can be calculated as well as the resulting horizontal load applied to the column. From this, a simple stability assessment is proposed which can be used to assess the consequences of multiple floor fires on tall buildings. These analytical methodologies are brought together in a risk based frame- work for structural design which can be used to identify areas in a building or structural components which pose a high residual risk. These elements can be qualitatively ’ranked’ according to their relative risk and appropriate measures taken to reduce the risk to an acceptable level. The framework is illustrated via 2 case studies. The first is of a typical small office building, and the second is of a prestige office development.

Following the evolution of a damage avoidance design (DAD) frame system, with rocking beam-column joints, at the University of Canterbury, analytical studies are carried out to evaluate the performance of proposed structures, and verify the proposed design methodology. A probabilistic seismic risk assessment methodology is proposed, from which the expected annualised financial loss (EAL) of a structure can be calculated. EAL provides a consistent basis for comparison of DAD frame systems with state-of-practice ductile monolithic construction. Such comparison illustrates the superior performance of DAD frame systems. The proposed probabilistic seismic assessment methodology requires the response of the structure to be evaluated over a range of seismic intensities. This can be achieved by carrying out an incremental dynamic analysis, explicitly considering seismic randomness and uncertainty; or from a pushover analysis, and assuming an appropriate value of the dispersion. By combining this information with the seismic hazard, probabilistic response curves can be derived, which when combined with information about damage states for the particular structure, can be transformed into 'resilience curves'. Integration of information regarding the financial loss occurring due to each of the damage states, results in an estimate of EAL.

Carbon steel finds much application for use in industries including civil; manufacturing; oil and gas; as well as, renewable energy. Common examples for usage of steel include water pipelines; oil pipelines; bridges; etc. The main advantages of steel over other engineering materials are its strength and affordability. However, steel undergoes corrosion which is a degradation mechanism that occurs as a result of the electrochemical interaction between steel and its environment. There are two main options to control corrosion, aside from material selection techniques, namely, the use of protective coating systems to isolate the steel from the environment; or the use of cathodic protection. Cathodic protection involves the use of galvanic anodes or impressed current system to prevent steel corrosion. Currently the oil and gas industry accounts for the major share of consumption of galvanic anodes for the protection of steel in engineering applications. Recent incursions into deep water depths by the Oil and Gas industry in the last decade or so has brought to the fore the need to understand better the performance of steel at deep and ultra deep water depths; as well as to develop an understanding of how cathodic protection works at these water depths. So far, the bulk of industry experience lies in shallow waters and current international cathodic protection design guidelines are based on data collated at these shallow water depths. It is the objective of this research work to assess the corrosion properties of steel with deep seawater parameters and determine design current density requirements for effective cathodic protection of steel at deep and ultra deep water depths offshore.

The purpose of this research was first to study the Wildland-Urban Interface and Wildland-Urban Intermix (WUI) fire problem, and then to design, develop and implement improved fire assessment and fire protection features for structures in the these interface fire-prone areas. The findings included that several areas of the world are prone to devastating fires that claim lives and destroy property, and their fire problems continue to exacerbate. None of these compare to the property loss experienced in Southern California due to its vast development in fire prone areas. It is because of the continuing huge property loss and frequency of major WUI fires that Southern California was selected as the concentration for research and the case studies used in this paper. However, the results of the research are applicable to other interface fire-prone areas in the world. The author is motivated by a need to dramatically improve our ability to effectively deal with what is no longer a fire “threat,” but the reality that people have chosen to live in an area of the world in which wildland fires are part of natural forest dynamics. To reduce the economic and social impacts of these inevitable fires, we need to understand the causes of fire damage, and establish methods to minimize damage when fires occur. This thesis proposes several fire protection strategies for increased fire resiliency and safety of individuals. Following a search of fire history and analysis, three related fire assessment matrixes were synthesized (see Chapter Five). The Fire Profile Index is the principal fire assessment matrix. It was developed empirically and applied to historical fire spreads for a sense of accuracy. The intended users of the Fire Profile Index are design professionals, public agencies charged with oversight for development in the WUI, insurance agencies, building and landscape contractors, homeowners, potential homeowners, residents and fire service professionals. From the Fire Profile Index two derivative special-use matrixes were established for use by diverse groups. The first of these matrixes, the Developers Guide, is intended for design professionals, public agencies, insurance agencies, and building and landscape contractors. The second matrix is the WUI Fire Assessment Guide, whose intended users are those concerned with development in high fire hazard areas, who should have a fundamental knowledge of fire behavior. This group includes fire agencies, developers, homeowners, potential homeowners and insurance companies. This thesis contributes to increased residential structure fire resistiveness and occupant fire safety in the WUI, by proposing site-specific fire assessment and corresponding design features in both structures and landscapes. Chapter Seven covers the development of noncombustible fire shields to divert airflow and diminish flames and embers blown towards structures. Wind tunnel modeling research was conducted at the Aerospace Program’s wind tunnel at California Polytechnic State University, San Luis Obispo.

Les méthodes traditionnelles de dimensionnement à la fatigue s’appuient sur l’utilisation de coefficients dits de “sécurité” dans le but d’assurer l’intégrité de la structure en couvrant les incertitudes inhérentes à la fatigue. Ces méthodes de l’ingénieur ont le mérite d’être simples d’application et de donner des solutions heureusement satisfaisantes du point de vue de la sécurité. Toutefois, elles ne permettent pas au concepteur de connaître la véritable marge de sécurité de la structure et l’influence des différents paramètres de conception sur la fiabilité. Les approches probabilistes sont envisagées dans cette thèse afin d’acquérir ces informations essentielles pour un dimensionnement optimal de la structure vis-à-vis de la fatigue. Une approche générale pour l’analyse probabiliste en fatigue est proposée dans ce manuscrit. Elle s’appuie sur la modélisation des incertitudes (chargement, propriétés du matériau, géométrie, courbe de fatigue) et vise à quantifier le niveau de fiabilité de la structure étudiée pour un scénario de défaillance en fatigue. Les méthodes classiques de fiabilité nécessitent un nombre important d’évaluations du modèle mécanique de la structure et ne sont donc pas envisageables lorsque le calcul du modèle est coûteux en temps. Une famille de méthodes appelée AK-RM (Active learning and Kriging-based Reliability Methods) est précisément proposée dans ces travaux de thèse afin de résoudre le problème de fiabilité avec un minimum d’évaluations du modèle mécanique. L’approche générale est appliquée à deux cas-tests fournis par SNECMA dans le cadre du projet ANR APPRoFi
Traditional procedures for designing structures against fatigue are grounded upon the use of so-called safety factors in an attempt to ensure structural integrity while masking the uncertainties inherent to fatigue. These engineering methods are simple to use and fortunately, they give satisfactory solutions with regard to safety. However, they do not provide the designer with the structure’s safety margin as well as the influence of each design parameter on reliability. Probabilistic approaches are considered in this thesis in order to acquire this information, which is essential for an optimal design against fatigue. A general approach for probabilistic analysis in fatigue is proposed in this manuscript. It relies on the modelling of the uncertainties (load, material properties, geometry, and fatigue curve), and aims at assessing the reliability level of the studied structure in the case of a fatigue failure scenario. Classical reliability methods require a large number of calls to the mechanical model of the structure and are thus not applicable when the model evaluation is time-demanding. A family of methods named AK-RM (Active learning and Kriging-based Reliability methods) is proposed in this research work in order to solve the reliability problem with a minimum number of mechanical model evaluations. The general approach is applied to two case studies submitted by SNECMA in the frame of the ANR project APPRoFi

This case study explicates the knowledge-knower structures that are valued in the assessment of Graphic Design (GD) practical work in a multi-campus Private Higher Education (PHE) context. Assessment, which provides the measure for student success and progression, plays a significant role in Higher Education (HE). It is acknowledged that, in addition to increased pressure on educators to deliver high pass and throughput rates, there is often scrutiny of their assessment practice to ensure that it is fair, reliable, valid and transparent. The aspects of reliability and validity are particularly significant in for-profit private higher education institutions, where a strong focus on efficiency may result in added scrutiny of assessment practices. Although the assessment of GD practical work exemplifies these pressures and objectives, its characteristics and practices set it apart from many of the more standard forms of assessment found in HE. Not only is GD practical work predominantly visual rather than text-based, but complex achievements and tacit knowledge are assessed. This form of assessment traditionally relies on panel or group marking by connoisseurs who consider what is commonly termed ‘person’, ‘process’ and ‘product’ when making value judgements. Therefore, in GD assessment knowledge, the design product, the graphic designer and what the graphic designer does may all be valued. GD assessment, where outcomes are not easily stated, relies on the tacit expertise of assessors and can often be perceived to be subjective and unreliable. It therefore sits uncomfortably with results-driven HE and institutional priorities. In light of this context and the complex and social nature of GD assessment, a critical realist approach provided the guiding metatheory for this case study. Critical realism considers the unseen but real mechanisms that exist and interact within a context to create a phenomenon such as an assessment practice. In this case study the knowledge-structuring theories of Basil Bernstein and Karl Maton were used to uncover these mechanisms. Bernstein and Maton propose that new knowledge, the curriculum and pedagogy, which includes assessment, communicate the valued disciplinary knowledge and who controls these communications. For this study the institutional documents and voices of assessors provided insight into the GD assessment practice; data was generated through a lecturer survey, the study guides and assessor conversations at both the formative and summative assessment stages. Given the significance of both knowledge and expertise in GD, Specialisation, one of the Legitimation Code Theory (LCT) dimensions, provided the conceptual tool whereby the generated data were analysed and categorised, and the underlying valued knowledge-knower structures, or specialisation codes, were identified. The identified specialisation codes revealed a number of code clashes, matches and shifts, which highlighted instances of mixed or conflicting communication regarding what was valued and used in GD assessment. These clashes, matches and shifts have significant implications for curriculum design, pedagogy and assessment. As a result the findings may have relevance for students, lecturers and assessors who work in practice-based fields which require the assessment of complex achievements and rely on a specialised gaze to judge standards. Informed by the findings of this study, I argue that there is a fundamental conflict between what is valued within the broader national South African Higher Education system and Private Higher Education institutional context, and the nature of GD assessment. The broader structures, guided by a techno-rationalist approach to assessment and the pressures of massification, success, compliance and institutional efficiencies, value explicitly-stated outcomes and criteria, propositional knowledge and a positivist ideal of one correct mark for any one assessment, while the GD assessment practice values the more social and tacit elements of procedural knowledge and a specialist knower as evidenced in a largely tacit GD gaze that assessors possess and students aim to develop. The uncovering of the knowledge-knower structures used in GD assessment has the potential to make the assessed gaze more explicit to lecturers, assessors and ultimately to students. My findings offer a deeper understanding of the assessment of knower code disciplines which require a specialist gaze for the judgement of student work, and the pressures experienced in this type of assessment in a HE context.

[EN] Currently, there is a trend towards sustainability, especially in developed countries, where the concerns of society about environmental degradation and social problems have increased. Following this trend, the construction sector is one of the most influential sectors due to its high economic, environmental, and social impacts. At the same time, there is an increase in the demand for transport, which drives a need to develop and maintain the necessary infrastructure for this purpose. Taking all these factors into account, bridges become a key structure and therefore assessment of sustainability throughout their whole life-cycle is essential. The main objective of this thesis is to propose a methodology that allows assessment of the sustainability of a bridge under uncertain initial conditions (subjectivity of the decision-maker or variability of initial parameters) and optimization of the design to obtain a robust optimal bridge. To this end, an extensive bibliographic review of all the works that perform assessments of the sustainability of bridges through the valuation of criteria related to their main pillars (economic, environmental, or social) has been carried out. In this review, it has been observed that the most comprehensive way to evaluate the environmental and social pillars is through the use of life-cycle impact assessment methods. These methods allow sustainability assessment to be performed for the whole life-cycle of the bridge. This process provides valuable information to decision-makers for the assessment and selection of the most sustainable bridge. However, the decision-makers' subjective assessments of the relative importance of the criteria influence the final assessment of sustainability. For this reason, it is necessary to create a methodology that reduces the associated uncertainty and seeks robust solutions according to the opinion of decision-makers. In addition, for bridges, the design and decision-making are conditioned by the initially defined parameters. This leads to solutions that may be sensitive to small changes in these initial conditions. A robust optimal design makes it possible to obtain optimal solutions and structurally stable designs under variations of the initial conditions as well as sustainable designs that are not influenced by the preferences of the stakeholders who are part of the decision-making process. Thus, obtaining a robust optimal design becomes a probabilistic optimization process that has a high computational cost. For this reason, the use of metamodels has been integrated into the proposed methodology. Specifically, Latin hypercube sampling is used for the definition of the initial sample and a kriging model is used for the definition of the mathematical approximation. In this way, kriging-based heuristic optimization reduces the computational cost by more than 90% with respect to conventional heuristic optimization while obtaining very similar results. This thesis provides, first of all, an extensive bibliographic review of both the criteria used for the assessment of sustainability of bridges and the different methods of life-cycle impact assessment to obtain a complete profile of the environmental and social pillars. Subsequently, a methodology is defined for the full assessment of sustainability, using life-cycle impact assessment methods. Likewise, an approach is proposed that makes it possible to obtain structures with little influence from the structural parameters, as well as from the preferences of the different decision-makers regarding the sustainability criteria. The methodology provided in this thesis is applicable to any other type of structure.
[ES] Actualmente existe una tendencia hacia la sostenibilidad, especialmente en los países desarrollados donde la preocupación de la sociedad por el deterioro ambiental y los problemas sociales ha aumentado. Siguiendo esta tendencia, el sector de la construcción es uno de los sectores que mayor influencia tiene debido a su alto impacto económico, ambiental y social. Al mismo tiempo, existe un incremento en la demanda de transporte que provoca la necesidad de desarrollo y mantenimiento de las infraestructuras necesarias para tal fin. Con todo esto, los puentes se convierten en una estructura clave, y por tanto, la valoración de la sostenibilidad a lo largo de toda su vida es esencial. El objetivo principal de esta tesis es proponer una metodología que permita valorar la sostenibilidad de un puente bajo condiciones iniciales inciertas (subjetividad del decisor o variabilidad de parámetros iniciales) y optimizar el diseño para obtener puentes óptimos robustos. Para ello, se ha realizado una extensa revisión bibliográfica de todos los trabajos en los que se realiza un análisis de la sostenibilidad mediante la valoración de criterios relacionados con sus pilares principales (económico, medio ambiental o social). En esta revisión, se ha observado que la forma más completa de valorar los pilares medioambientales y sociales es mediante el uso de métodos de análisis de ciclo de vida. Estos métodos permiten llevar a cabo la valoración de la sostenibilidad durante todas las etapas de la vida de los puentes. Todo este procedimiento proporciona información muy valiosa a los decisores para la valoración y selección del puente más sostenible. No obstante, las valoraciones subjetivas de los decisores sobre la importancia de los criterios influyen en la evaluación final de la sostenibilidad. Por esta razón, es necesario crear una metodología que reduzca la incertidumbre asociada y busque soluciones robustas frente a las opiniones de los agentes implicados en la toma de decisiones. Además, el diseño y toma de decisiones en puentes está condicionado por los parámetros inicialmente definidos. Esto conduce a soluciones que pueden ser sensibles frente a pequeños cambios en dichas condiciones iniciales. El diseño óptimo robusto permite obtener diseños óptimos y estructuralmente estables frente a variaciones de las condiciones iniciales, y también diseños sostenibles y poco influenciables por las preferencias de los decisores que forman parte del proceso de toma de decisión. Así pues, el diseño óptimo robusto se convierte en un proceso de optimización probabilística que requiere un gran coste computacional. Por este motivo, el uso de metamodelos se ha integrado en la metodología propuesta. En concreto, se ha utilizado hipercubo latino para la definición de la muestra inicial y los modelos kriging para la definción de la aproximación matemática. De esta forma, la optimización heurística basada en kriging ha permitido reducir más de un 90% el coste computacional respecto a la optimización heurística conveniconal obteniendo resultados muy similares. Esta tesis proporciona en primer lugar, una amplia revisión bibliográfica, tanto de los criterios utilizados para la valoración de la sostenibilidad en puentes como de los diferentes métodos de análisis de ciclo de vida para obtener un perfil completo de los pilares ambientales y sociales. Posteriormente, se define una metodología para la valoración completa de la sostenibilidad, usando métodos de análisis de ciclo de vida. Asimismo, se propone un enfoque que permite obtener estructuras poco influenciables por los parámetros estructurales, así como por las preferencias de los diferentes decisores frente a los criterios sostenibles. La metodología proporcionada en esta tesis es aplicable a cualquier otro tipo de estructura.
[CA] Actualment existeix una tendència cap a la sostenibilitat, especialment en els països desenrotllats on la preocupació de la societat pel deteriori ambiental i els problemes socials ha augmentat. Seguint aquesta tendència, el sector de la construcció és un dels sectors que major influència té a causa del seu alt impacte econòmic, ambiental i social. Al mateix temps, existeix un increment en la demanda de transport que provoca la necessitat de desenrotll i manteniment de les infraestructures necessàries per a tal fi. En tot açò, els ponts es converteixen en una estructura clau, i per tant, la valoració de la sostenibilitat al llarg de tota la seua vida és essencial. L'objectiu principal d'aquesta tesi doctoral és proposar una metodologia que permeta valorar la sostenibilitat d'un pont baix condicions inicials incertes (subjectivitat del decisor o variabilitat dels paràmetres inicials) i optimitzar el disseny per a obtenir ponts òptims robusts. Per a això, s'ha realitzat una extensa revisió bibliogràfica de tots els treballs en els quals es realitza un anàlisis de la sostenibilitat mitjançant la valoració de criteris relacionats amb els seus pilars principals (econòmic, ambiental o social). En aquesta revisió s'ha observat que la forma més completa de valorar els pilars ambientals i socials és mitjançant l'ús de mètodes d'anàlisis de cicle de vida. Aquests mètodes permeten realitzar la valoració de la sostenibilitat al llarg de totes les etapes de la vida dels ponts. Tot aquest procediment proporciona informació molt valuosa als decisors per a la valoració i selecció del pont més sostenible. No obstant això, les valoracions subjectives dels decisors sobre la importància dels criteris influeixen en l'avaluació final de la sostenibilitat. Per aquesta raó, és necessari crear una metodologia que reduïsca la incertesa associada i busque solucions robustes enfront de les opinions dels agents implicats en la presa de decisions. A més, el disseny i la presa de decisions en ponts està condicionat pels paràmetres inicialment definits. Açò condueix a solucions que poden ser sensibles front a menuts canvis en les dites condicions inicials. El disseny òptim robust permet obtenir dissenys òptims i estructuralment estables front a variacions de les condicions inicials, i també dissenys sostenibles i poc influenciables per les preferències dels decisors que formen part del procés de presa de decisió. D'aquesta manera, el disseny òptim robust es converteix en un procés d'optimització probabilística que requereix un gran cost computacional. Per aquest motiu, l'ús de metamodels s'ha integrat en la metodologia proposta. En concret, s'ha utilitzat l'hipercub llatí per a la definició de la mostra inicial i els models kriging per a la definició de l'aproximació matemàtica. D'aquesta forma, l'optimització heurística basada en kriging ha permés reduir més d'un 90% el cost computacional respecte a l'optimització heurística convencional obtenint resultats molt similars. Aquesta tesi doctoral proporciona en primer lloc, una ampla revisió bibliogràfica, tant dels criteris utilitzats per a la valoració de la sostenibilitat en ponts com dels diferents mètodes d'anàlisis de cicle de vida per a obtenir un perfil complet dels pilars ambientals i socials. Posteriorment, es defineix una metodologia per a la valoració completa de la sostenibilitat, utilitzant mètodes d'anàlisis de cicle de vida. Així mateix, es proposa un enfocament que permet obtenir estructures poc influenciables pels paràmetres estructurals, així com per les preferències dels diferents decisors enfront dels criteris sostenibles. La metodologia proporcionada en aquesta tesi doctoral és aplicable a qualsevol altre tipus d'estructura. Nº de páginas:
I would like to acknowledge the economic support of the Spanish Ministry of Economy and Competitiveness, formerly called Spanish Ministry of Science and Innovation. This thesis has been possible thanks to the FPI fellowship and the financially support of BRIDLIFE (Research Project BIA2014-56574-R) and DIMALIFE (Project BIA2017-85098-R).
Penadés Plà, V. (2020). Life-cycle sustainability design of post-tensioned box-girder bridge obtained by metamodel-assisted optimization and decision-making under uncertainty [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/147480
TESIS

In the last three decades, seismic performance assessment of buried structures has evolved through the following stages : i) buried structures are not prone to seismically-induced damages, thus no need for detailed investigations, ii) eliminating soil-structure-earthquake interaction and use of seismically-induced free field ground deformations directly as the basis for seismic demand, thus producing conservative results, and finally iii) soil-structure and earthquake interaction models incorporating both kinematic and inertial interactions. As part of soil-structure and earthquake interacting models, simplified frame analysis established the state of practice and is widely used. Within the confines of this thesis, the results of simplified frame analysis based response of buried structures are compared with those of 2-D finite element dynamic analyses. For the purpose, 1-D dynamic and 2-D pseudo-dynamic analyses of free field and buried structural systems are performed for a number of generic soil, structure and earthquake combinations. The analyses results revealed that, in general, available closed form solutions are in pretty good agreement with the results of finite element analyses. However, due to the fact that dynamic analyses can model both kinematic and inertial effects
it should be preffered for the design of critical structures.

Le calcul des constructions vis-à-vis du séisme en prenant en compte la réponse élastique linéaire conduit le plus souvent à des dimensionnements qui ne vont pas dans le sens de l'économie. Afin de permettre à l'ingénieur de tenir compte des différentes non linéarités, la plupart des règlements modernes (règles françaises PS92, règles européennes EC8, etc. ) ont préconisé de réduire les forces issues d'un calcul élastique linéaire par un coefficient appelé : coefficient de comportement. Un logiciel d'évaluation automatique de ce coefficient a été établi, selon la méthode préconisée par les règles ps92, basée sur les critères d'égalité de déplacement et d'énergie. Dans sa phase actuelle, le logiciel traite des structures planes isostatiques encastrées à la base (type brochette). Un calcul statique équivalent est effectue. On recherche de façon itérative la valeur du coefficient de comportement qui satisfait à l'un ou l'autre des critères précédents. A chaque étape de calcul, on dimensionne le ferraillage correspondant à la valeur du coefficient de comportement Q. En plus de cette option, il est possible d'imposer un ferraillage donné et de vérifier la valeur de Q correspondante. D'autres options complémentaires, utiles au niveau de la recherche, ont été introduites. Des exemples de bâtiments à murs en béton armé et d'une pile de pont ont été traités et les valeurs du coefficient de comportement obtenues sont comparées à celles issues d'un calcul dynamique effectue à l'aide d'un programme établi antérieurement au CEBTP et à celles préconisées par les règles PS92. Le calcul statique équivalent donne des valeurs de Q dont les tendances confirment les résultats des calculs dynamiques non-linéaires. Les valeurs forfaitaires réglementaires sont soit trop sévères soit pas assez: la tendance est gouvernée par plusieurs paramètres (période, pourcentage d'armatures, contrainte moyenne de compression,). Dans la plupart des calculs, la convergence du calcul est obtenue avec un nombre d'itérations relativement bas

Thesis (MScEng)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: Structural design standards based on the principles of structural reliability are gaining worldwide acceptance and are fast becoming the new basis of structural safety verification. The application of these principles to establish a standardised basis for structural design using partial factor limit states design procedures is done in the European Standard for the Basis of Structural Design EN 1990 from which it is adapted to the South African Basis of Design Standard for Building and Industrial Structures SANS 10160-1. The basis of design requirements stipulated in EN 1990 and SANS 10160-1 apply to all aspects of structural design: This includes reliability levels of structural performance and their differentiation and management; identification of various limit states and design situations; the specification of all the basic variables; separate treatment of actions and material-based resistance. However, application of these requirements is then primarily focused on actions whilst the provision for structural concrete is then left to the materials based design standards. This two-part thesis describes a systematic assessment of the degree to which the application of the reliability framework presented in the basis of design requirements has been achieved in the present generation of structural concrete design standards. More importantly, attempts are made to identify ways in which the process can be advanced. Special attention is drawn to issues that are specific to South African conditions and practice in structural concrete. Part One of the thesis focuses on the key elements of the reliability framework presented in EN 1990 and traces to what extent the requirements have been propelled through the design stipulations of the Eurocode Standard for Design of Concrete Structures EN 1992-1-1. The implications of the different reference level of reliability between the Eurocode default value of ß = 3.8 and that characteristic of South African practice ß = 3.0 through various issues are highlighted. The use and advantage of explicit treatment of reliability performance on reliability management related to some aspects of quality control are explored. A critical aspect is the shear prediction model providing unconservative estimates of shear resistance. Part Two of the thesis focuses on characterising the model factor of the EN 1992-1-1 shear prediction model for members requiring design shear reinforcement. This is done by a comparison to a compiled experimental database with special focus on situations with high reinforcement ratios. The significance of the modelling uncertainty in shear prediction is verified by this comparison. The use of the more conceptually rational modified compression field theory (MCFT) to improve on the quality of shear predictions is investigated and proves to yield more precise values with lower scatter hence making it a more reliable tool for predicting shear. The MCFT can then be used as reference for the reliability calibration and possible improvement for the Eurocode procedure.
AFRIKAANSE OPSOMMING: Strukturele ontwerpstandaarde gebaseer op die beginsels van strukturele betroubaarheid verkry wêreldwye aanvaarding en word vinnig die nuwe basis van strukturele veiligheid bevestiging. Die toepassing van hierdie beginsels om ʼn gestandaardiseerde basis vir strukturele ontwerp is bevestig deur gebruik te maak van gedeeltelike-faktorbeperkende stadiums ontwerpprosedures in die Europese Standaard vir die Basis van Strukturele Ontwerp EN 1990 waarvandaan dit herbewerk is na die Suid-Afrikaanse Basis van Ontwerp Standaarde vir Bou en Industriële Strukture SANS 10160-1. Die basis van ontwerpvereistes bepaal in EN 1990 en SANS 10160-1 is van toepassing op alle aspekte van strukturele ontverp: Dit sluit inbetroubaarheidsvlakke van struktureele prestasie en hul diversifikasie en bestuur; identifikasie van verskeie beperkende state en ontwerpsituasies; die spesifikasie van al die basiese veranderlikes; afsonderlike behandeling van aksies en materiaal-gebaseerde weerstand. Desnieteenstaande, die toepassing van hierdie voorwaardes is dan hoofsaaklik gefokus op aksies terwyl die voorsiening van strukturele beton is dan gelaat op die materiaalgebaseerde ontwerpstandaarde. Hierdie tweeledige verhandeling beskryf ʼn stelselmatige beoordeling van die graad waartoe die toepassing van die betroubaarheidsraamwerk aangebied word in die basis van ontwerpvereistes bereik in die huidige generasie van strukturele beton-ontwerp standaarde is. Meer belangrik, pogings is aangewend om die maniere hoe die proses bevorder kan word te identifiseer. Spesiale aandag word gevestig op kwessies wat spesifiek op Suid-Afrikaanse toestande en praktyke in strukturele beton toepaslik is. Deel Een van die verhandeling fokus op die sleutel-dele van die betroubaarheidsraamwerk aangebied in EN 1990 en skets die mate waartoe die vereistes aangespoor word deur die ontwerp voorskrifte van die Eurocode Standard for the Design of Concrete Structures EN 1992-1-1. Die implikasie van die verskillende verwysingsvlakke van betroubaarheid tussen die Eurocode standaardwaarde van ß = 3.8 en die eienskap van Suid-Afrikaanse praktyk ß = 3.0 deur verskillende kwessies word uitgelig. Die gebruik en voordeel van spesifieke behandeling van betroubaarheidsuitvoering op betroubaarheidsbestuur verwantskap met sekere aspekte van kwaliteit kontrole word ondersoek. ʼn Kritiese aspek is die model vir die voorspelling van skuif-weerstand wat die onkonserwatiewe beramings vir skuif-weerstand gee. Deel Twee van die verhandeling fokus op karakterisering die modelfaktor van die EN 1992- 1-1 skuif-weerstand voorspellings-model. Dit word gedoen deur ʼn vergelyking na ʼn saamgestelde eksperimentele databasis met spesifieke fokus op situasies met hoe herbevestigingsvergelykings. Die oorheersing van die modellering- onsekerheid in skuifweerstand voorspelling is bevestig deur hierdie vergelyking. Die gebruik van ʼn meer konseptuele rasionele gemodifiseerde druk-veld teorie (bekend as MCFT) om die kwaliteit van skuif voorspelling te verbeter is ondersoek en verskaf ‘n meer presiese waarde met laer verspreiding wat lei tot ʼn meer betroubaree instrument om skuif mee te voorspel. Die MCFT word dan gebruik as verwysing vir die betroubaarheid-samestelling en moontlike verbetering van die Eurocode prosedures.

To meet the need of lightweight chassis in the near future, a technological step of introducing anisotropic materials like Carbon Fibre Reinforced Plastics (CFRP) in structural parts of cars is a possible way ahead. Though there are commercially available tools to find suitability of Fibre Reinforced Plastics (FRPs) and their orientations, they depend on numerical optimization and complexity increases with the size of the model. Nevertheless, the user has a very limited control of intermediate steps. To understand the type of material system that can be used in different regions for a lightweight chassis, especially during the initial concept phase, a more simplified, yet reliable tool is desirable.The thesis aims to provide a framework for determining fibre orientations according to the most-ideal loading path to achieve maximum advantage from FRP-materials. This has been achieved by developing algorithms to find best-fit material orientations analytically, which uses principal stresses and their orientations in a finite element originating from multiple load cases. This thesis takes inspiration from the Durst criteria (2008) which upon implementation provides information on how individual elements must be modelled in a component subjected to multiple load cases. This analysis pre-evaluates the potential of FRP-suitable parts. Few modifications have been made to the existing formulations by the authors which have been explained in relevant sections.The study has been extended to develop additional MATLAB subroutines which finds the type of laminate design (uni-directional, bi-axial or quasi-isotropic) that is suitable for individual elements.Several test cases have been run to check the validity of the developed algorithm. Finally, the algorithm has been implemented on a Body-In-White subjected to two load cases. The thesis gives an idea of how to divide the structure into sub-components along with the local fibre directions based on the fibre orientations and an appropriate laminate design based on classical laminate theory.

Small wind turbines, and especially urban-mounted turbines which require no dedicated pole, have garnered great public enthusiasm in recent years. This enthusiasm has fueled widespread growth among energy conservationists, and estimates predict that the power produced nationally by small wind will increase thirty-fold by 2013. Unfortunately, most of the wind resources currently available have been designed for larger, rural-mounted turbines; thus, they are not well suited for this nascent market. A consequence of this is that many potential urban small wind turbine owners over-predict their local wind resource, which is both costly and inefficient. According to a recent study published by Encraft Ltd., small wind turbines mounted to buildings far underperformed their rural pole mounted counterparts. As a proposed solution to this problem, this project introduces the concept of a Web-based Wind Assessment System (WWAS). This system combines all the necessary resources for potential urban small wind turbine customers into a single web-based tool. The system also presents the concept of a modular wind measurement system, which couples with the WWAS to provide real-time wind data measurements. The benefits of the system include its ease of use, flexibility of installation, data accessibility from any web browser, and expert advice. The WWAS prevents potential clients from investing in a system that may not be viable for their location. In addition, a small wind turbine is designed in this project, which has a unique modular mounting system, allowing the same baseline wind turbine to attach to various structures using interchangeable mounting hardware. This includes such accessible urban structures as street lights, building corners, flag poles, and building walls, among others. This design also utilizes concepts that address some of the challenges associated with mounting small wind turbines to existing urban structures. These concepts include: swept tip blades and lower RPM to reduce noise; vibration suppression using rubber shims; a netted duct to protect wildlife; and a direct-drive permanent magnet generator to ensure low starting torque. Finally, the cost of this system is calculated using off-the-shelf components, which minimize testing and certification expense. This small wind turbine system is designed to be grid-connected, has a 6 foot diameter rotor, and is rated at 1 kW. This design features a unique modular interchangeable mounting system. The cost for this complete system is estimated to be $2,050. If a users' site has an average wind speed of 14 mph (6.5 m/s), this system will generate a return on investment in 8.5 years, leaving over 10 years of profit. The profit for this system, at this sample average wind speed, yields over $4,000 during its 20-year design life, which is a two-fold return on investment. This project has implications for various stakeholders in the small wind turbine market, including designers, engineers, manufacturers, and potential customers. Equally important is its potential role in guiding our future national--even global--energy agenda.

Structural Reliability treats uncertainties in structural design systematically, evaluating the levels of safety and serviceability of structures. During the past decades, it has been established as a valuable design tool for the description of the performance of structures, and lately stands as a basis in the background of the most of the modern design standards, aiming to achieve a uniform behaviour within a class of structures. Several methods have been proposed for the estimation of structural reliability, both deterministic (FORM and SORM) and stochastic (Monte Carlo Simulation etc) in nature. Offshore structures should resist complicated and, in most cases, combined environmental phenomena of greatly uncertain magnitude (eg. wind, wave, current, operational loads etc). Failure mechanisms of structural systems and components are expressed through limit state functions, which distinguish a failure and a safe region of operation. For a jacket offshore structure, which comprises of multiple tubular members interconnected in a three dimensional truss configuration, the limit state function should link the actual load or load combination acting on it locally, to the response of each structural member. Cont/d.

This thesis is focused on the evaluation of existing stone structures, particularly stone bridges. It contents a summary of the most frequently used structure types and materials of historic bridges as well as it presents some contemporary technologies. Thesis also presents methods of the construction stone testing, both laboratory and in situ. The process of the assessment of existing structures from ČSN ISO 13822 is being applied on the evaluation of stone structures, taking into account their specifics. These specifics results from the natural origin of the building material. The experimental part describes the survey and assessment of an existing stone bridge in Dobromilice, including a proposal for an adequate way of reconstruction.