Dissertations / Theses on the topic 'Advance concrete'

The thesis is focused on the opinion of an office building from the perspective of two different standards and comparing their approaches. These standards is a currently valid European Standard EN 1992-1-1 (EC2) and standard according to US standards ACI 318-11. In this work were considered pillars in the second basement and on the first floor. Was also assessed locally supported slab above the 1st floor and staircase connects the individual floors. All the completed elements were assessed according to the 1st ultimate limit state.

Concrete is the most widely used construction material in the world and is responsible for 7% of global carbon emissions. It is inherently brittle, and it requires frequent repair or replacement which is economically expensive and further generates large volumes of carbon dioxide. Current methods of repair by agents such as mortar, epoxies, and bacteria result in structures with reduced strength and resiliency. Recent advances in the design of structural composites often mimic natural microstructures. Specifically, the structure of abalone nacre with its high stiffness, tensile strength, and toughness is a source of inspiration from the process of evolution. The inspiration from nacre can lead to design of a new class of architected structural materials with superb mechanical properties. This body of work first presents a method to reinforce concrete with an architected polymer phase. Second is presented how a ubiquitous enzyme, Carbonic anhydrase (CA), can be used to repair and strengthen cracked concrete, and how it can be used as an additive in fresh concrete. The first study presents an experimental and computational study on a set of bioinspired architected composites created using a cement mortar cast with brick-and-mortar and auxetic polymer phases. The impact of this unit-cell architected polymer phase on the flexural and compressive strengths, resilience, and toughness is studied as a function of microstructural geometry. All mechanical properties of the architected composite samples are found to be greater than those of control samples due to prevention of localized deformation and failure, resulting in higher strength. The microstructurally designed composites showed more layer shear sliding during fracture, whereas the control samples showed more diagonal shear failure. After initial cracking, the microstructurally designed composites gradually deformed plastically due to interlocking elements and achieved high stresses and strains before failure. Results also show that microstructurally designed composites with the architected polymer phase outperform control samples with equal volume fraction of a randomly oriented polymer fiber phase. Computational studies of the proposed unit cells are also performed, and the results suggest that the orientation of cells during loading is critical to achieve maximum performance of a cementitious composite. The implications of these results are immense for future development of high performing construction materials. The second study outlines methods for repair of concrete and lays the groundwork to develop a self-healing concrete that uses trace amounts of the CA enzyme. The CA catalyzes the reaction between calcium ions and carbon dioxide to create calcium carbonate that naturally incorporates into concrete structures with similar thermomechanical properties as concrete. The reaction is safe, actively consumes carbon dioxide, generates low amounts of heat, and avoids using unhealthy reagents, resulting in a strong structure. This repair method results in concrete samples with similar strength and water permeability as the intact materials. These results offer an inexpensive, safe, and efficient method to create self-healing concrete structures. The science underlying the creation of self-healing concrete is described, producing a material intrinsically identical to the original using the CA enzyme. Using this strategy, a preliminary self-healing concrete mix is able to self-repair fractures via hydration. This body of work addresses a major issue: Is there an efficient and ecological repair for decaying concrete infrastructure? These methods propose alternative reinforcement, alleviates high monetary and energy costs associated with concrete replacement, and consume the greenhouse gas, carbon dioxide.

Practical applications for the use of composite materials for retrofitting of reinforced concrete structural members of buildings and bridges were investigated in this research project. Carbon and glass advanced composite materials (CACM and GACM) saturated in an epoxy resin matrix were used to enhance their structural performance. The following experimental work, supported by analytical work, was carried out in the investigation: 1. Use of Advanced Composite Materials (ACM) in bridge girders to increase the service load capacity. Eleven T-shape simply supported beams, representing half scale bridge girders, were tested under repeated cyclic and monotonic load conditions. CACM laminates bonded to the soffit of the beams were used to increase the service live load carrying capacity. In some test units the laminates were cut-off whereas in others the laminates were bonded to the whole span of the beam, except at the supports. Additional GACM U-strips were applied to the sides of some beams to improve the bond performance of the longitudinal laminate and to provide additional shear stiffness and strength. The side U-strips were anchored to the beam with glass fibre filaments. One beam was subjected to one million cycles in the service load range to study the fatigue behaviour of the retrofit scheme. The fatigue test showed the excellent behaviour that can be expected from well-detailed retrofit schemes incorporating carbon and glass fibre laminates. Design recommendations are proposed based on the results obtained from the tests and from analytical work. 2. Experimental work was conducted to investigate the seismic response of ACM-strengthened/retrofitted beams that present shear and bar curtailment deficiencies. Two full-scale T-section cantilever beams were built and tested under reversed cyclic loading. One unit was tested in its "as-built" condition until a flexure-shear failure developed at the curtailment point of the negative longitudinal reinforcement. The test unit was then repaired by applying GACM laminates across the top of the-slab and to the sides of the beam in the damage region. It was again re-tested under reversed cyclic loading. The other unit was retrofitted before testing in the same manner as the previous damaged unit and then subjected to reverse cyclic loading. A seismic assessment on the prototype unit was proposed to provide a simple evaluation on the beam with deficiencies in flexural design of T-beam, shear, and longitudinal bar curtailment. The tests show that the presence of a GACM laminate can successfully correct the deficiency by relocating the negative plastic hinges to occur in the beam at the column face. To ensure the adequate seismic performance of the retrofit scheme, shear deformations in the beams must be kept to a minimum to reduce the kinking effect and potential de bonding of the ACM laminate. 3. The analytical and experimental study proposed a method for evaluating the short-term axial load strength of rectangular and square reinforced compression members confined with an ACM jacket and steel hoops. The results of this study can also be applied to the use of ACMs for column seismic retrofitting. Three 300 mm square and three 300 mm by 450 mm short reinforced columns were concentrically loaded first in tension, then in compression to failure. Either two or six layers of GACM jackets were applied to four of these columns. Two control units were tested in order to evaluate the enhancement of the axial load carrying capacity and to observe whether the ACM jackets were able to preclude premature buckling of the longitudinal reinforcement in the wrapped columns. The results clearly showed the efficiency of the jackets in enhancing the ultimate strain and strength of the columns. The jackets were also very effective in preventing longitudinal bar buckling from occurring. Designed equations in closed form were derived based on the calibration of the analytical model to provide a design of ACM-wrapped reinforced concrete column subjected to the concentric axial load.

Cette thèse de doctorat traite du renforcement en cisaillement de structures en béton armé (BA) à l’aide de matériaux composites en polymère renforcé de fibres (PRF). De nombreuses problématiques de recherche reliées au renforcement en cisaillement n’ont pas encore été résolues à ce jour. L’objectif principal du présent est d’étudier expérimentalement et analytiquement les méthodes de renforcement en cisaillement de poutres de section en Té en BA à l’aide de PRF. Le programme considère plusieurs aspects majeurs reliés au renforcement en cisaillement de poutres en BA à l’aide de tissus et de tiges en PRF, comme suit: 1) Renforcement en cisaillement de poutres en BA à l’aide de PRF collé en surface (EB: Externally Bonded) – Facteurs d’influence et modèle conceptuel de délamination: Sur la base des résultats obtenus, une nouvelle approche de design est proposée pour le calcul de la contribution au cisaillement du PRF tenant compte de l’influence de l’acier transversal (entre autres) sur la contribution du PRF à la résistance globale. Le modèle proposé montre une meilleure corrélation avec les résultats expérimentaux en comparaison aux codes et guides en vigueur; 2) Performance de systèmes d’ancrage pour poutres en BA renforcées à l’aide de PRF collé en surface: Les résultats de cette étude révèlent que les spécimens renforcés par la méthode PRF EB avec des ancrages adéquatement conçus peuvent atteindre des contributions à la résistance en cisaillement supérieures á ceux sans système d’ancrage et ceux renforcés à laide de la méthode NSMR (Near-Surface Mounted Rebar) ; 3) Renforcement en cisaillement de poutres en BA à l’aide de PRF EB: Effet du rapport largeur sur espacement des bandes en PRF : Investigation expérimentale et analytique investigation avec emphase sur l’effet du rapport largeur sur espacement des bandes en PRF sur la contribution du PRF (Vf) dans les poutres renforcées en cisaillement à l’aide de bandes en PRF EB est menée ; et 4) Comportement des poutres en BA renforcées à l’aide de la méthode ETS (embedded through-section) : Une méthode novatrice développée pour le renforcement en cisaillement est explorée. Cette méthode est très prometteuse pour le renforcement en cisaillement. Dans cette méthode, des tiges en PRF sont insérées et scellées à l’aide d’époxy dans des trous préalablement percés à travers l’âme de la poutre en BA. Les résultats d’essais ont confirmé la faisabilité de la méthode ETS, mais aussi révélé que la performance des poutres renforcées à l’aide de cette méthode est substantiellement supérieure à celle des poutres renforcées à l’aide de PRF EB et NSMR.

Major advances have been observed during the last two decades in the field of seismic engineering with further refinements of performance-based seismic design philosophies and the subsequent definition of corresponding compliance criteria. Following the globally recognized expectation and ideal aim to provide a modern society with high (seismic) performance structures able to sustain a design level earthquake with limited or negligible damage, alternative solutions have been developed for high-performance, seismic resisting systems. In the last two decades, an alternative approach in seismic design has been introduced for precast concrete buildings in seismic regions with the introduction of “dry” jointed ductile systems also called “hybrid” systems based on unbonded post-tensioned rocking connections. As a result structural systems with high seismic performance capabilities can be implemented, with the unique capability to undergo inelastic displacement similar to their traditional monolithic counterparts, while limiting the damage to the structural system and assuring full re-centring capabilities (negligible residual or permanent deformations). The continuous and rapid development of jointed ductile connections for seismic resisting systems has resulted in the validation of a wide range of alternative arrangements, encompassed under the general umbrella of “hybrid” systems. This research provides a comprehensive experimental and analytical investigations of 2- and 3-Dimensional, 2/3 scaled, exterior beam-column joints subjected both uni and bi-directional (four clove) quasic-static loading protocols into the behaviour, modelling, design and feasibility of new arrangements for “dry” jointed ductile systems for use in regions of high seismicity. In order to further emphasize the enhanced performance of these systems, a comparison with the experimental response and observed damage of 2-D and 3-D monolithic beam-column benchmark specimens is presented. However, after a lot of attention given to the behaviour of the skeleton structure, more recently the focus of research in Earthquake Engineering has concentrated on the behaviour of the floor system within the overall 3D behaviour of the building and the effects of beam elongation. The effects of beam elongation in precast frame systems have been demonstrated to be a potential source of un-expected damage, unless adequate detailing is provided in order to account for displacement incompatibilities between the lateral resisting systems and the floor. Two contributions to beam elongation are typically recognized: a) the material contribution due to the cumulative residual strain within the steel, and b) the geometrical contribution due to the presence of a neutral axis and actual depth of the beam. Regarding jointed ductile connections with re-centering characteristics, the extent of beam elongation is significantly reduced, being limited to solely the geometrical contribution. Furthermore, such effects could be minimized when a reduced depth of the beam is adopted due to the use of internal prestressing or external post-tensioning. However, damage to precast floor systems, resulting from a geometric elongation of the beam, has yet to be addressed in detail. In order to emphasize the enhanced performance in controlling and minimizing the damage of the structural elements via the use of the proposed advanced hybrid solutions, this research presents via experimental and analytical validation of two alternative and innovative solutions to reduce the damage to the floor using 2 and 3-Dimensional, 2/3 scaled, exterior beam-column joints. The first approach consists of using standard precast rocking/dissipative frame connections (herein referred to as “gapping”) in combination with an articulated or “jointed” floor. This system uses mechanical devices to connect the floor and the lateral beams which can accommodate the displacement incompatibilities in the connection. The second approach to reduce the floor damage investigates the implementation of a “non-gapping” connection, also called non-tearing-floor connection, using a top hinge at the beam-column interface, while still relying on more traditional floor-to-frame connections (i.e. topping and continuous starter bars). Additionally, further refinements and constructability issues for the non gapping connection are investigated under the experimental and analytical validation of a major 2-Dimensional, 2/3 scaled, two-story one-bay frame using non-tearing floor connections. Based on the non-tearing floor connections, a series of parametric analysis for beam-column joints and frames are carried out. Furthermore, the analysis and design of two prototype frames using different solutions is presented. The frames are subjected to cyclic adaptive pushover and inelastic time history analysis in order to investigate analytically the response characteristics of hybrid frames using non-tearing connections, as well as how the beam growth affects the frame response under earthquake loading. Computational models for hybrid PRESSS frames and a conventional reinforced concrete frames are developed and compared with the ones using non-tearing connections.

Concrete is still the most widely used construction material of modern times. In very recent years attempts have been made by using steel fibre reinforcement to improve the inherent weaknesses that concrete possesses such as its low tensile strength and the tendency to shrink on drying and to creep under stress. In this context, the use of steel fibre reinforcement together with high strength concrete corbel joints has been investigated. This study came after fibre reinforced concrete had received wide recognition for its crack and deformation control, ductility and energy absorption characteristics. In the present study, the fracture behaviour and deformation characteristics of plain conventionally reinforced concrete corbels with and without steel fibre reinforcement has been investigated. The different types of steel fibres used and other experimental materials are described in chapter 3, whereas chapter 2 gives a review of the old and current design approaches used for concrete corbel design. In chapter 4 the deformation, cracking and ultimate strength of plain high strength concrete corbels has been studied with different cube strength ranged between 25 to 90 N/mm². In chapter 5 a proposed theory to predict the ultimate strength of high and normal strength concrete corbels, conventionally reinforced, has been derived. The influence of steel fibre reinforcement on the performance of conventionally reinforced concrete corbels has been studied in chapter 6. Melt extract steel fibres were used in the majority of the corbels together with other types such as crimped, hooked and plastic fibres (polypropylene). In the same chapter 6, the theory has been extended to account for the strength gained by fibre addition. The effect of steel fibre reinforcement on the shear transfer strength has been studied in chapter 7. The theory proposed in chapter 5 has been further extended to predict the shear strength of 'push-off' type of specimens of plain and fibre reinforced concrete, with conventional steel reinforcement.

Thesis (Ph. D.)--University of California, San Diego, 2006.
Title from first page of PDF file (viewed December 6, 2006). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 246-252).

Concern for durability of reinforced concrete structures has, in recent years, coincided with an increasing interest in the use of steel fibre reinforcement. In this investigation the corrosion behaviour of conventional and steel fibre reinforcement in concrete under long term marine curing have been studied. The corrosion behaviour of reinforcement has been assessed visually, and by using electrochemical techniques. Three types of steel fibre were investigated namely low carbon steel, stainless steel melt extract, and galvanised steel. Previous studies have shown that steel fibres exhibit good corrosion resistance in concrete exposed to marine curing. It has been suggested that this is due to the discrete nature of the individual steel fibres which prevents the development of electrochemical cells with large cathode/anode area ratios. In order to determine, therefore, whether a 'size-effect' phenomenon influences steel fibre corrosion rates, concrete specimens were cast with different lengths and diameters of steel wire and subsequently exposed to marine curing. Parallel concrete specimens containing samples of conventional reinforcing bar were also manufactured. Cement replacement materials such as pulverised fuel ash, ground granulated blast furnace slag and microsilica are widely used in order to enhance specific properties of fresh or hardened concrete. In this investigation durability characteristics of concrete containing cement replacement materials were studied. These characteristics, including alkalinity of pore fluid and diffusion rates of chloride ions are of importance in relation to the passivation or corrosion of steel reinforcement.

The impact of a pipeline by a dropped object has been considered to consist of four distinct impact components: the dropped object, pipeline protection, the soil bed and the pipeline itself. The effect of these components as energy absorbers and the effect on system response has been investigated. Quasi-static and dynamic testing has been earned out to investigate the interaction between the various impact components. Quasi-static testing has been widely used to develop initial predictions, since closer observation of interaction is easier. The validity of applying these predictions to dynamic situations has been addressed using results from dynamic impact testing. The Dropped Object: Two areas have been investigated which address the dropped object within the impact system: the dropped object's impact profile and its deformability. Testing has been carried out to study the effect of typical loading profiles. Research has shown that the dropped object profile significantly effects the pipe response; a cone shaped indentor generates deformation with far less energy than either a wedge or a patch shape. The applicability of a method to predict the interaction between two deforming structures, using a method of shared energy, has been investigated for quasi-static and dynamic loading. During quasi-static testing it was found possible to predict a combined response using individual responses. During dynamic testing prediction was not possible, since inertia effects where found to dominate the response. The Concrete Protective Coating: A programme of work carried out has qualified the role of a pipeline protective coating and assessed the effect of four different types of concrete reinforcement. Summary Although the study has not been exhaustive, it is clear that reinforcements, which hold the concrete coating to the pipe, allow the coating to continue its protection. Fibres added to a concrete mix were found to reduce the damage to the pipe. However mesh reinforcements were found to hold the concrete together most effectively and provided the greatest added protection. The Soil Support: All foundations absorb some energy. Tests have been carried out to investigate the effect of a soil bed on the response of a laterally loaded pipeline. During dynamic tests on sand supported pipes it was noted that no energy was absorbed during the initial deformation, possibly corresponding to local indentation of the pipe wall. After this the sand was seen to react and absorbed a proportion of the energy, depending on the hammer's drop height. The energy absorbed by the soil continued to increase until an energy plateau was reached, after which the soil absorbed no further energy. It was noted that the displacement at which this energy plateau was reached increased as the drop height increased. Two possible causes of the energy plateau have been discussed. The first cause questioned an assumption that the pipe would deform as if on simple supports. The second possible cause suggested a change from dynamic to quasi-static response and investigated the relationship between acceleration, velocity and reaction force. Of the possible causes of the energy plateau, the most likely is thought to be soil related. Investigation into the Deformation of Locally Loaded Pipes: The investigation into pipeline deformation has been carried out using experimental, numerical and theoretical analysis methods. Quasi-static test results have been used to investigate four pipeline parameters and their influence on energy absorbed by the pipeline, (length, L, wall thickness, t, diameter, D and material yield stress, ay). This investigation led to an empirical equation, which brought all energy-displacement (E-8) curves on to a common curve, for a wide range of these variables. This empirical relationship has been developed to predict deformation, for the range of parameters investigated. Dynamic results obtained were normalised using these empirical equations and data was seen to fall into two broad groups, one group comprising seam welded pipe and one group comprising cold drawn pipe. Strain rate effects were proposed as the most likely cause of this bi-grouping. Limitations in the experimentally derived empirical relationship have been identified, resulting from an insufficient range of pipe samples tested.

The purpose of this thesis is to assess and develop a non-destructive evaluation (NDE) procedure for evaluating the integrity of rectangular and square reinforced concrete (RC) slabs. This procedure employs both dynamic frequency and deformation response signatures to track changes in the slab following dynamic excitation. Such a procedure could provide a good basis for practising engineers to conduct nondestructive testing (NDT) and evaluation of general RC structures. The response of RC floor slabs to dynamic excitation have been experimentally studied at 1/3rd scale for two aspect ratios (square and rectangular), three concrete grades, and with and without cement replacement under clamped edge conditions. The model slabs were subjected to series of quasi-static loading and unloading sequences, to increasing load levels until failure was reached. At the unloaded part of each load cycle, the slabs were subjected to dynamic excitations, alternately using a hand-held, Bruel and Kjaer (B and K) impact hammer, and broad-band burst chirp shaker excitation. For the larger square slabs, at each unloaded part of the load cycle, a 265 gm steel ball bearing dropped from a fixed, standard height to provide more robust impulse excitation. All of the slabs were instrumented with optimally located accelerometers and strain gauges to capture the slab responses. The acceleration, deflection and strain readings resulting from the dynamic excitation were recorded at incremental load steps, from the initial unloaded state up to failure, and subsequently evaluated and analysed. The results show that the changes resulting from damage are readily observable, in the fundamental and higher modes of vibration and in the load-deflection and strain responses. These changes have been examined and analysed in both the time and frequency domains, and using other techniques, to establish the viability of this approach in evaluating the integrity of RC and other complex structures.

The relatively few available practice-oriented proposals for performance-based seismic design of conventional and isolated bridges, aim primarily at a more consistent description of seismic demand and capacity of structures on the basis of simplified analysis, and to a lesser extent at the direct consideration of multi-level performance criteria using advanced analysis tools. In view of the type/device-specific existing methods, the present study presents a broad-scope methodology for the seismic design of bridges emphasising on (i) displacement-based principles, (ii) use of nonlinear dynamic analysis, and (iii) explicit consideration of multiple performance levels (PLs) and objectives (POs) in a practical design context, suitable for inclusion in design codes. The deformation-based design (Def-BD) procedure, initially developed for seismic design of conventional (non-isolated) buildings, is first tailored to concrete bridges with energy dissipation in the piers. The key issues in this respect are the proper consideration of the intended plastic mechanism under the considered PLs, and the design of the bearings. The efficiency of the proposed design methodology is demonstrated by applying it to an actual bridge selected with a view to enabling comparisons among Def-BD, the modal direct displacement-based design (MDDBD), and a force-based code-type (Code-BD) method. Refined analysis along with the consistent performance-based design format within Def-BD, result in superior seismic performance. Significant cost reductions are achieved compared to MDDBD, whereas potential cost reductions may generally be obtained compared to ‘standard’ code design. Considering the diversity of passive devices and their inherent weakness to optimise the bridge response under multiple PLs, a methodology is developed to enable the identification of the critical performance requirements and the comparative evaluation of different passive schemes at the early stages of design. Originating from an earlier study focusing on bilinear isolators, the method is extended with a view to developing generalised design equations (GDEs) capable of providing reliable estimates of peak response in linear/bilinear isolation systems with/without supplemental linear/nonlinear viscous damping under different PLs associated with code-based target spectra of different intensity. The Def-BD method is finally extended to address passive (isolation and energy dissipation) systems. Novel features are introduced, including (i) the use of GDEs for the preliminary ‘near-optimal’ selection of the basic system properties and the consideration of nonlinearity of viscous dampers, (ii) the enhancement of POs in line with the higher performance expected in the case of isolated bridges, (iii) specific conditions ensuring the effectiveness of the isolation system, and (iv) the proper consideration of the orthogonal component of seismic action under bidirectional excitation. The validity of the procedure is demonstrated by applying it to the bridge previously used to develop the Def-BD method for bridges with ‘ductile-pier’ behaviour. Alternative isolation schemes are investigated and compared with the design resulting from Eurocode 8 (Part 2), offering a useful insight into some pitfalls of modern code-based approaches. Assessment of the Def-BD designs reveals enhanced and controlled performance under multiple PLs, and significant cost reductions in the substructure design compared to the design for ‘ductile-pier’ response. On the other hand, further cost reduction observed in the case of the code-based design, results in reduced efficiency of the isolation system and improper performance of the piers. In view of the previous remarks, Def-BD emerges as a rigorous methodology, applicable to most of the common concrete bridge configurations, albeit at the expense of additional computational effort associated with the use of nonlinear dynamic analysis and the design for multiple PLs. Nevertheless, minimum iterative effort is ensured by providing design ‘routines’ that facilitate the implementation and address implications resulting from the use of nonlinear dynamic analysis. Considering the suitable formulation of Def-BD, a framework of performance-based control principles for the future extension towards the integration of advanced structural control techniques, is finally set forth.

Structural Health Monitoring (SHM) with emerging technologies like e.g. fibre optic sensors, lasers, radars, acoustic emission and Micro Electro Mechanical Systems (MEMS) made an entrance into the civil engineering field in last decades. Expansion of new technologies together with development in data communication benefited for rapid development. The author has been doing research as well as working with SHM and related tasks nearly a decade. Both theoretical knowledge and practical experience are gained in this constantly developing field. This doctoral thesis presents lessons learned in SHM and sensory technologies when monitoring civil engineering structures, mostly bridges. Nevertheless, these techniques can also be used in most applications related to civil engineering like dams, high rise buildings, off-shore platforms, pipelines, harbour structures and historical monuments. Emerging and established technologies are presented, discussed and examples are given based on the experience achieved. A special care is given to Fibre Optic Sensor (FOS) technology and its latest approach. Results from crack detection testing, long-term monitoring, and sensor comparison and installation procedure are highlighted. The important subjects around sensory technology and SHM are discussed based on the author's experience and recommendations are given. Applied research with empirical and experimental methods was carried out. A state-of-the art-review of SHM started the process but extensive literature studies were done continuously along the years in order to keep the knowledge up to date. Several SHM cases, both small and large scale, were carried out including sensor selection, installation planning, physical installation, data acquisition set-up, testing, monitoring, documentation and reporting. One case study also included modification and improvement of designed system and physical repair of sensors as well as two Site Acceptance Tests (SATs) and the novel crack detection system testing. Temporary measuring and testing also took place and numerous Structural Health Monitoring Systems (SHMSs) were designed for new bridges. The observed and measured data/phenomena were documented and analysed.  Engineers, researchers and owners of structures are given an essential implement in managing and maintaining structures. Long-term effects like shrinkage and creep in pre-stressed segmental build bridges were studied. Many studies show that existing model codes are not so good to predict these long-term effects. The results gained from the research study with New Årsta Railway Bridge are biased be the fact that our structure is indeed special. Anyhow, the results can be compared to other similar structures and adequately used for the maintenance planning for the case study. A long-term effect like fatigue in steel structures is a serious issue that may lead to structural collapse. Novel crack detection and localisation system, based on development on crack identification algorithm implemented in DiTeSt system and SMARTape delamination mechanism, was developed, tested and implemented. Additionally, new methods and procedures in installing, testing, modifying and improving the installed system were developed. There are no common procedures how to present the existing FOS techniques. It is difficult for an inexperienced person to judge and compare different systems. Experience gained when working with Fibre Optic Sensors (FOS) is collected and presented. The purpose is, firstly to give advice when judging different systems and secondly, to promote for more standardised way to present technical requirements. Furthermore, there is need to regulate the vocabulary in the field. Finally, the general accumulated experience is gathered. It is essential to understand the complexity of the subject in order to make use of it. General trends and development are compared for different applications. As the area of research is wide, some chosen, specific issues are analysed on a more detailed level. Conclusions are drawn and recommendations are given, both specific and more general. SHMS for a complex structure requires numerous parameters to be measured. Combination of several techniques will enable all required measurements to be taken. In addition, experienced specialists need to work in collaboration with structural engineers in order to provide high-quality systems that complete the technical requirement. Smaller amount of sensors with proper data analysis is better than a complicated system with numerous sensors but with poor analysis. Basic education and continuous update for people working with emerging technologies are also obligatory. A lot of capital can be saved if more straightforward communication and international collaboration are established: not only the advances but also the experienced problems and malfunctions need to be highlighted and discussed in order not to be repeated. Quality assurance issues need to be optimized in order to provide high quality SHMSs. Nevertheless, our structures are aging and we can be sure that the future for sensory technologies and SHM is promising. The final conclusion is that an expert in SHM field needs wide education, understanding, experience, practical sense, curiosity and preferably investigational mind in order to solve the problems that are faced out when working with emerging technologies in the real world applications.  The human factor, to be able to bind good relationship with workmanship cannot be neglected either. There is also need to be constantly updated as the field itself is in continuous development.
QC 20111117
SHMS of the New Årsta Railway Bridge

The current trends in the intensive production of growing/finishing pigs are to devise alternative systems which help to improve welfare by the provision of a malleable substrate, such as straw, in order that the pigs can carry out natural behaviour. This project examined the welfare of growing/finishing pigs on four treatments; a new alternative system called the Straw-Flow (c) (SF), which used roughly a 1/4 of the amount of straw of a traditional deep-straw bedded system (1.9 and 8 kg/d respectively), was compared to bare-concrete (BC), fully-slatted (FS) and deep-straw (DS) treatments using a multi-disciplinary study involving behaviour, physical health, productivity and physiology. The four pen treatments were all built within the same building and they all measured 4x2.7m. There were three replicates of entire male pigs which were randomly allocated to each treatment from approximately 28 to 89 kg. During daylight hours, the pigs on the straw-based treatments (ST), ie . the SF and the DS, spent approximately 26% of their time in straw-directed behaviour. Where there was no straw (NOST), ie , the BC and the FS, there was more inactivity (45% and 59% of time on the ST and NOST respectively, p< 0.001), behaviour directed towards the pen hardware (2% and 13% of time on the ST and NOST respectively, p&60 0.001), chewing penmates; (0.05% and 0.19% of time on the ST and NOST respectively, p< 0.07) and vacuum chewing (0.2% and 1.4% of time on the ST and NOST respectively, p< 0.001). These differences were thought to be due to a lack of suitable malleable substrate on the NOST treatments which caused a redirection in the exploratory and foraging behaviour of the pigs compared to the pigs from the ST treatments. However, there was more play on the ST compared to the NOST in the form of running and scampering (0.15% and 0.02% of time on the ST and NOST respectively, p< 0.05) and shoving and pushing penmates (2.9% and 1.8% of time on the ST and NOST respectively, p= 0.14).

The flexural performance of composite systems made of reinforced concrete, Fibre Reinforced Polymers (FRPs) and adhesives was studied during the current research. The experimental investigation was principally concentrated on the potential use of Kevlar® 49 (aramid fibre) for RC beam strengthening. The main aims of research have been; (a) to investigate the relative merits of using Aramids in comparison to other FRPs, (b) strength optimisation of systems to prevent excessive losses of ductility, (c) to examine the failure mode and crack patterns, together with salient strength factors at ultimate limit state and (d) to carry out analytical modelling using a commercial FE package. The experimental investigation comprised of testing 55 simply supported RC beams of either 1.5m or 2.6m length. In addition to the parametric studies included in points (a)-(d) above (to assess the section characteristics), further experimentation was conducted to investigate the beam performance by varying the factors of; (e) beam shear span, (f) FRP anchorage length, (g) concrete surface preparation, (h) FRP end-anchoring, (i) beam precracking, (j) introduction of air-voids within the bond line of FRP/concrete, (k) influence of cyclic loading and, (1) exposure to aggressive environment. The results from current tests confirm elements of reports from other researchers (by thorough review of literature) that all FRPs have great potential for flexural strengthening of RC members. This is valid even in cases where additional environmental degradation and/or cracking (due to serviceability loads), had taken place. Aramid fibres were found to result in favourable outcomes concerning both strength and ductility enhancements. It was determined, both from experiments and non-linear modelling, that the amount of FRP fibre content is an important factor in every strengthening application. Experimentation showed that depending on the existing condition of the structure (concrete strength, internal reinforcement ratio, section dimensions, degradation level and load configuration), there seems to be a unique level of optimum fibre content. The FRP levels in excess of the optimum were seen to lead to premature brittle tearing-off failure modes. It was also found that to prevent premature beam failure (due to incompatibility of stress at concrete and FRP interface), a maximum possible anchorage length should be considered in order to deliver an optimum section performance. The results from the analytical modelling indicated a most satisfactory agreement with the experimental data after the initial mechanical properties were calibrated. It was found that actual representation of material properties (e.g. steel constitutive law) are of great significance, for an accurate modelling of RC element loaded behaviour. The bond developed between the FRP and concrete is one of the key parameters for achieving good performance of the systems. It was determined that concrete surface preparation and priming is beneficial, while the introduction of air-voids due to poor workmanship can reduce the section load bearing capabilities. Cyclic loading on FRP strengthened sections was found to curtail the full rotational capacity utilisation of the beam. However, even the above mentioned curtailed behaviour was more advantageous than cyclically loaded beam performance without FRP strengthening.

As a response to the ever denser cities, skyscrapers have become yet more popular and are growing more and taller than ever. A new efficient structural system for skyscrapers has been proposed by Tyréns AB, called the Tubed Mega Frame. This structural system consists of hollow concrete tubes at the perimeter of the building. Since this structural system has not yet been used in any skyscraper several aspects have still not been studied or investigated. An important aspect having an impact on the system’s competitiveness compared to traditional structural systems is how a skyscraper using this new structural system could be built. This thesis treats the construction methodology of Tubed Mega Frame structures. The construction methodology of a prototype building is evaluated to connect the findings to a plausible real project. Building very tall concrete structures sets a lot of demands on the concrete used and having an effective construction is essential. The elastic modulus of the concrete has been identified as one of the most important concrete properties why this topic has been studied. Comparisons of the formulas of different codes for estimating the elastic modulus have been made to see what elasticity can be achieved. Concrete recipes that have been used in already built skyscrapers have been reviewed to see what elastic moduli are feasible to reach and expect. Pumping concrete to high levels sets demands on the concretes flowability and self-compacting concrete is necessary to use. Ways of improving the concrete properties are also studied. All studies show that the Tubed Mega Frame structural system would be possible to construct with today’s concrete and pumping technology even though improvements can be expected from future development in concrete technology. As most skyscrapers that are built today, a Tubed Mega Frame structure would preferably be built with a self-climbing formwork system rising one level at a time. From a review of available construction methodologies, the thesis shows that these systems would be applicable on a Tubed Mega Frame structure with minor adaptions of the systems. The floor cycle time, i.e. the time it takes to complete an entire floor before proceeding to the next level, has a significant importance in determining the construction time of a skyscraper. For this reason a floor cycle with all activities related to the structural system and their sequences have been developed for the prototype building. By determining all the relations that are between activities and using productivities for estimating their durations it has been possible to evaluate the time it would take to complete a standard floor. By the use of Microsoft Project the duration of a stated average floor cycle has been estimated to a little more than 4 days.
Som en reaktion på att allt fler människor bor i städer har skyskrapor kommit att växa sig allt fler och högre. Traditionellt har skyskrapor oftast utnyttjat någon form av kärna som stomsystem vilken upptar stor yta av våningsplanen. Som en möjlig metod att göra skyskrapors stomsystem effektivare har Tyréns utvecklat det nya stomsystemet Tubed Mega Frame. Då detta bärande system ännu inte har använts i någon skyskrapa är det ett flertal aspekter som inte har blivit studerade och undersökta. En viktig aspekt som är av stor vikt för systemets konkurrenskraft gentemot mer traditionella system är hur det skulle gå till att bygga en skyskrapa som använder detta nya stomsystem. Det här examensarbetet behandlar byggnationsmetodiken för Tubed Mega Frame. Byggnationen av en prototypbyggnad som använder detta system utvärderades för att koppla resultaten till en möjlig verklig byggnad. Att bygga väldigt höga konstruktioner i betong ställer stora krav på betongen som används, och att ha en effektiv byggnation är också av stor vikt. Betongens elasticitetsmodul har identifierats som en av de viktigaste egenskaperna för betongen och därför har detta område studerats djupare. En jämförelse av hur olika normer beräknar elasticitetsmodulen har gjorts och vilka elasticitetsmoduler det ger. De betongsammansättningar som har använts i tidigare skyskrapebyggande har studerats för att se vilka elasticitetsmoduler som kan förväntas. Att pumpa betong till höga höjder ställer stora krav på betongens pumpbarhet. För att göra detta möjligt är det nödvändigt att använda självkompakterande betong. Vilka olika sätt som finns tillgängliga för att styra betongens egenskaper har också studerats. Undersökningarna visar på att det skulle kunna vara möjligt att med dagens betong och pumpteknologi bygga en skyskrapa som använder Tubed Mega Frame som bärande system. Med framtida framsteg inom betongteknologi kan man även förvänta att bättre lämpad teknik kommer att utvecklas. En skyskrapa med stomsystemet Tubed Mega Frame skulle liksom de flesta av dagens skyskrapor lämpligtvis byggas med hjälp av självklättrande formsystem, och därigenom bygga en våning i taget. Studier av teknik och byggnationsmetoder som finns tillgängliga idag har visat på att dagens teknik skulle vara möjliga att applicera på Tubed Mega Frame med endast mindre justeringar. Det som har ett stort inflytande på byggtiden av en skyskrapa är våningscykeltiden, d.v.s. den tid det tar att bygga en våning innan det är möjligt att fortsätta på nästa. Av denna anledning har en våningscykel med alla relevanta moment som ingår blivit bestämd och utvärderad för prototypbyggnaden. Genom att ha klargjort alla relationer mellan olika aktiviteter och den tid de tar att utföra har det varit möjligt att utvärdera den tid en hel våningscykel skulle ta. Med hjälp av Microsoft Project har en våningscykel för en våning som bedömts som representativ för hela prototypbyggnaden kommit att ta drygt fyra dygn.

Tese de Doutoramento em Engenharia Civil - Ramo do Conhecimento Estruturas.
This thesis aims at a contribution for the reinforcement design of thin surfaces structures in concrete or masonry using the results of linear elastic finite-element analysis. To fulfill this objective, a design formulation, the cracked three-layer model, is introduced as a new theoretical model for the problem of designing cracked, orthogonally reinforced concrete membrane, plate and shell elements. After reviewing the state of the art of design models for thin surface elements based on the results of elastic analysis, the formulation and implementation of the cracked three-layer model is introduced. The proposed design model is formulated obeying the three principles of mechanics, that is, equilibrium conditions, compatibility conditions and constitutive laws. For the first principle, a three-layer modeling approach is used to express the equilibrium between the set of applied forces and resisting forces in the concrete or masonry and reinforcement. For the second and third principles, a linear distribution law for the strains through the element thickness and the basic concepts of the modified compression field theory, but assuming concrete with no tensile strength and reinforcement as perfectly plastic material, are employed. From this, the resisting forces in concrete or masonry can be evaluated and the correspondent tensile forces in the reinforcement can be determined by solving the equilibrium equations of the design model. For the implementation of the proposed design formulation, numerical routines have been developed and implemented in a Windows-based computer program named DRCShell. The design program DRCShell makes use of DIANA® 8.1 finite element program as a provider of the structural elastic analysis results and as a post-processor for the presentation of the reinforcement results. Experimental results of single element tests and numerical results by means of nonlinear analysis are compared with the predictions of the proposed design formulation. Also, application examples of thin surface structures in reinforced concrete are designed by the DRCShell program, whose results are compared with the results of traditional design formulations. Finally, for the ultimate analysis of single curvature shells in concrete or masonry, simplified design criteria are addressed. Both elastic and plastic analysis formulations are developed and applied to industrialized masonry vaults. The results obtained in terms of ultimate load and reinforcement areas are compared with experimental results and numerical results by means of nonlinear analysis. In the conclusion are summarized the discussions and the conclusions of the present work and the recommendations for future researches.
O trabalho desenvolvido nesta tese tem como objectivo principal contribuir para o dimensionamento de armaduras de estruturas laminares de betão armado, tendo como dados de partida resultados obtidos em análises linear e elástica efectuadas com programas de cálculo automático baseados no método dos elementos finitos (MEF). Para tal foi efectuada uma revisão do estado de conhecimento no âmbito dos modelos de dimensionamento de estruturas laminares de betão armado que são baseados nos resultados da analise elastica em elementos finitos, seguida do desenvolvimento de uma formulação, designada por “cracked three-layer model”, que permite calcular a quantidade de armadura, disposta ortogonalmente, em estruturas de betão submetidas a estado plano de tensão (paredes), lajes e cascas. O modelo de dimensionamento desenvolvido obedece aos princípios fundamentais que regem a maior parte dos fenómenos da engenharia estrutural: condições de equilíbrio; condições de compatibilidade; leis constitutivas dos materiais intervenientes. Para assegurar as condições de equilíbrio, o modelo desenvolvido assume que a espessura da estrutura laminar pode ser discretizada em três camadas, sendo as forças aplicadas equilibradas pelas forças resistentes garantidas pelas camadas de betão e pelas forças resistentes das armaduras que as reforçam. Para atender ao segundo princípio o modelo desenvolvido assume uma distribuição linear de extensões ao longo da espessura da estrutura laminar. Finalmente, para atender ao comportamento não linear do betão foram utilizados os conceitos essenciais do “Modified Compression Field Theory”, tendo-se, no entanto, desprezado a resistência à tracção do betão. Da aplicação destes princípios resulta um sistema de equações de equilíbrio que permite determinar os esforços instalados nas armaduras e no betão. A aplicação do modelo desenvolvido por ser estendido a estruturas de alvenaria, desde que sejam conhecidas as leis constitutivas dos materiais intervenientes. A formulação desenvolvida foi implementada num programa de cálculo automático, designado por DRCShell. Além das propriedades dos materiais intervenientes e das características geométricas da estrutura a dimensionar, fazem também parte dos dados do DRCShell os esforços obtidos da análise linear e elástica com o programa DIANA® 8.1. Este último foi também utilizado para pos-processar os resultados obtidos com o DRCShell. Para avaliar o desempenho do modelo desenvolvido, resultados obtidos em ensaios experimentais com elementos estruturais de betão armado foram comparados com os determinados com o DRCShell. Com o mesmo objectivo, procedeu-se à simulação do comportamento de elementos de betão armado, no quadro da análise não linear material segundo o MEF, tendo-se comparado os resultados obtidos com os previstos com o DRCShell. A aplicabilidade do modelo desenvolvido foi ainda aferida por intermédio do dimensionamento das armaduras de estruturas reais, e comparando os resultados obtidos com os determinados segundo formulações tradicionais de dimensionamento. O desenvolvimento de critérios de dimensionamento de estruturas constituídas por cascas de curvatura única é um outro objectivo do presente trabalho. Para tal, quer a formulação elástica como a plástica foram desenvolvidas e aplicadas a abóbadas de alvenaria. Os resultados obtidos, quer em termos de carga última como de áreas de armadura, são comparados com os registados em ensaios experimentais. O presente trabalho termina com a apresentação das conclusões extraídas da investigação desenvolvida, e com recomendações para futuras investigações.
CRAF project of the Fifth Framework Program of European Commission - CRAF/70420/BAI/4/02
Ministry of Transport, Public Works and Water Management of the Netherlands - “Onderzoek protocol 8857”
Fundação para a Ciência e a Tecnologia (FCT) - “Programa de Financiamento Plurianual da FCT” UMINHO/CEC-BI/1/04.

Doctoral Thesis in Civil Engineering
A presente tese foca-se no desenvolvimento de ferramentas numéricas para a análise e dimensionamento de elementos estruturais em betão reforçado com fibras (BRF). Neste trabalho são abordadas as mais recentes regras e recomendações de projeto expostas nos regulamentos em vigor sendo, quando necessário, complementadas com modelos mais avançados resultantes de trabalhos de investigação sobre estruturas de BRF. Com base nas atuais regras de projeto foi desenvolvido um programa de cálculo automático dedicado à análise da secção transversal de elementos estruturais de BRF, com e sem armaduras convencionais de reforço, sujeitos a esforços axial, corte e flexão, de forma a realizar as verificações de segurança relativamente aos estados limite últimos e de serviço. Foi realizada, também, uma avaliação do desempenho dos modelos de resistência ao corte propostos no fib Model Code 2010 para elementos em BRF, através da comparação da capacidade preditiva dos modelos com os resultados experimentais de uma base de dados de ensaios de corte. A presente tese abrange, do mesmo modo, o desenvolvimento de uma ferramenta numérica para a análise de elementos estruturais de BRF que conjuga o efeito da orientação e segregação das fibras nos elementos estruturais de BRF, e a resistência ao arranque das fibras. A capacidade preditiva do novo modelo foi verificada através da simulação de vigas entalhadas de betão reforçado com fibras de aço submetidas ao ensaio de flexão de 3-pontos. Adicionalmente, foram abordados alguns aspetos particulares de elementos estruturais em BRF. Neste âmbito, um novo modelo de simulação da resposta viscoelástica em fluência de materiais de matriz cimentícia, desde as idades jovens, foi desenvolvido e implementado num programa baseado no método de elementos finitos – FEMIX – tendo sido acoplado aos modelos termo-mecânicos já aí implementados. Adicionalmente, foi desenvolvido um novo modelo constitutivo especialmente dedicado à simulação da interface entre lajes de BRF apoiadas no solo e as camadas granulares da fundação da laje, com o intuito de captar os mecanismos relevantes que induzem dano neste tipo de estruturas de BRF.
This thesis is devoted to the development of numerical tools for the analysis and design of fiber reinforced concrete (FRC) structural elements. This work focuses on the description of the most recent design guidelines and recommendations obtained from design codes, being complemented with more advanced models published in academic works on FRC structures. Based on these guidelines a software was developed for the analysis of FRC cross-sections with and without conventional reinforcements, submitted to bending and shear with or without axial force, to assess the ultimate and serviceability limit state safety verifications of structural members. An assessment of the shear resistance models for FRC members proposed in the fib Model Code 2010 was conducted, by evaluating its predictive performance with the results of shear tests collected in a database. It was developed an innovative numerical tool for the analysis of FRC structures that couples the effects of fiber orientation and segregation in the FRC members, and fiber pullout resistance. The performance of the new model was assessed by simulating steel fiber reinforced concrete notched beams submitted to 3-point bending tests. Moreover, particular topics regarding some structural application of FRC were explored. In this scope, a new model capable of predicting the aging creep response of cement-based materials, since early ages, was proposed and implemented in a finite element method software – FEMIX – and was coupled with the already available thermo-mechanical models. Flooring is still the main application of FRC, and the simulation of the interface between the FRC slab and the soil supporting system is a relevant aspect for controlling crack formation and propagation, mainly due to shrinkage and thermal effects coupled with restriction to the membrane deformability of the FRC slab. A new constitutive model was developed and implemented in FEMIX, especially aimed to simulate the interface between FRC slabs supported on ground and the granular layers of the slab’s foundation, in attempt to capture relevant mechanisms that promote damage in this type of FRC structures.

碩士
義守大學
土木與生態工程學系碩士班
97
The purpose of this study is to investigate the energy dissipation analyses of reinforced concrete structural systems with advanced damping mechanism. The energy of the vibrating system is dissipated by various damping mechanisms. As a result, the damping in actual structures is usually represented in a highly idealized manner. For many purposes the actual damping can be idealized satisfactorily by a linear viscous damper or dashpot. The damping coefficient is selected so that the vibration energy dissipation is equivalent to the energy absorbed in all the damping mechanisms. In combination, it presents in the actual structures. The equivalent viscous damper is intended to model the energy dissipation. Therefore, the energy dissipation at the deformation amplitudes within the linear elastic limit of the overall structure can be represented properly. Over this range of deformations, the damping coefficient c determined from experiments may vary with the deformation amplitudes. This nonlinearity of the damping property is usually not considered explicitly in dynamic analyses. It may be handled indirectly by selecting a value for the damping coefficient that is appropriate for the expected deformation amplitude. The damping coefficient is usually taken as the deformation associated with the linearly elastic limit of the structure. The larger deformation related with the more energy dissipated can be assumed. New damping equipments have been generated to amplify the deformation of the structure.

With the rise in hazards that structures are potentially subjected to these days, ranging from pre-contemplated terror attacks to accidental and natural disasters, safeguarding structures against such hazards has increasingly become a common design requirement. The extreme loading conditions associated with these hazards renders the concept of imposing generalized codes and standards guidelines for structural design unfeasible. Therefore, a general shift towards performance-based design is starting to dominate the structural design field. This study introduces a powerful structural analysis tool for reinforced concrete structures, possessing a high level of reliability in handling a wide range of typical and extreme loading conditions in a sophisticated structural framework. VecTor3, a finite element computer program previously developed at the University of Toronto for nonlinear analysis of three-dimensional reinforced concrete structures employing the well-established Modified Compression Field Theory (MCFT), has been further developed to serve as the desired tool. VecTor3 is extended to include analysis capabilities for extreme loading conditions, advanced reinforced concrete mechanisms, and new material types. For extreme loading conditions, an advanced coupled heat and moisture transfer algorithm is implemented in VecTor3 for the analysis of reinforced concrete structures subjected to fire. This algorithm not only calculates the transient temperature through the depth of concrete members, but also calculates the elevated pore pressure in concrete, which enables the prediction of the occurrence of localized thermally-induced spalling. Dynamic loading conditions are also extended to include seismic loading, in addition to blast and impact loading. Advancing the mechanisms considered, VecTor3 is developed to include the Disturbed Stress Field Model (DSFM), dowel action and buckling of steel reinforcement bars, geometric nonlinearity effects, strain rate effects for dynamic loading conditions, and the deterioration of mechanical properties at elevated temperatures for fire loading conditions. Finally, the newly-developed Simplified Diverse Embedment Model (SDEM) is implemented in VecTor3 to add analysis capability for steel fibre-reinforced concrete (SFRC). Various analyses covering a wide range of different structural members and loading conditions are carried out using VecTor3, showing good agreement with experimental results available in the literature. These analyses verify the reliability of the models, mechanisms, and algorithms incorporated in VecTor3.

Os Sismos podem provocar uma cadeia de eventos, sendo que um deles pode ser a ocorrência de um incêndio. Os efeitos do incêndio após um sismo em áreas urbanas podem ser mais severos que os efeitos diretos do próprio sismo. Os edifícios podem não estar adequadamente dimensionados para a ação de incêndio após um sismo visto que a maioria dos regulamentos ignora essa possibilidade. O objetivo deste trabalho é perceber as consequências que o dano introduzido pela ação sísmica pode causar na resistência ao fogo em vários elementos de betão armado. Foram desenvolvidas várias análises numéricas com o programa SAFIR, considerando a análise térmica e mecânica da estrutura, tanto ao nível da secção como em elementos isolados (pilares, vigas e pórticos). As principais variáveis nas análises foram o tipo de dano nos elementos. As análises numéricas foram realizadas usando a curva de incêndio padrão ISO 834. Os resultados mostram que o dano nos elementos de betão armado reduz a resistência ao fogo, especialmente quando as armaduras ficam expostas ao fogo. Após um sismo, e dado o elevado número de ocorrências, as equipas de socorro vão ser muito solicitadas, pelo que os tempos de resposta serão consequente mais elevados. Esta situação associada a uma redução na resistência ao fogo dos elementos de betão armado pode originar a perda de vidas e o colapso de estruturas. Assim, é importante uma melhor compreensão sobre o comportamento em incêndio após um sismo, em particular em estruturas de maior importância, para que seja possível implementar algumas medidas prescritivas que possam garantir melhor desempenho das estruturas nestas circunstâncias.

碩士
義守大學
土木與生態工程學系碩士班
99
The purpose of this study is to investigate the Earthquake Energy Dissipation Effects for Reinforced Concrete Structural Systems with Non-stiffness Shear Wall and Advanced Damping Mechanism. In damping, the energy of the vibrating system is dissipated by various mechanisms. As a result, the damping in actual structures is usually represented in a highly idealized manner. For multiple purposes the actual damping can be idealized satisfactorily by a linear viscous damper or dashpot. The damping coefficient is selected so that the vibration energy dissipated is equivalent to the energy dissipated in all the damping mechanisms, combined, present in the actual structure. The equivalent viscous damper is intended to model the energy dissipation at deformation amplitudes within the linear elastic limit of the overall structure. Over this range of deformations, the damping coefficient c determined from experiments may vary with the deformation amplitude. This nonlinearity of the damping property is usually not considered explicitly in dynamic analyses. It may be handled indirectly by selecting a value for the damping coefficient that is appropriate for the expected deformation amplitude, usually taken as the deformation associated with the linearly elastic limit of the structure. The larger deformation related with the more energy dissipated can be assumed. New damping equipments have been generated to amplify the deformation of the structure. For the original structure does notchangethe natural frequency of the system shall be equipped with non-shear wall stiffness in the original structure of the system, the non-shear wall stiffness is also easy to install high-performance organizations and damping energy dissipation corresponding damper. The new damping equipments could be implemented efficiently to the reinforced concrete structures for earthquake energy dissipation.

This thesis examines the development of a superstructure for a slab-on-girder wood-concrete composite highway bridge. Wood-concrete composite bridges have existed since the 1930's. Historically, they have been limited to spans of less than 10 m. Renewed research interest over the past two decades has shown great potential for longer span capabilities. Through composite action and suitable detailing, improvements in strength, stiffness, and durability can be achieved versus conventional wood bridges. The bridge makes use of a slender ultra-high performance fibre-reinforced concrete (UHPFRC) deck made partially-composite in longitudinal bending with glued-laminated wood girders. Longitudinal external unbonded post-tensioning is utilized to increase span capabilities. Prefabrication using double-T modules minimizes the need for cast-in-place concrete on-site. Durability is realized through the highly impermeable deck slab that protects the girders from moisture. Results show that the system can span up to 30 m while achieving span-to-depth ratios equivalent or better than competing slab-on-girder bridges.