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1
Jaafar, Kamal Rachid. "Spiral shear reinforcement for concrete structures under static and seismic loads." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.616166.
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Abbasiverki, Roghayeh. "Analysis of underground concrete pipelines subjected to seismic high-frequency loads." Licentiate thesis, KTH, Betongbyggnad, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-194076.
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Buried pipelines are tubular structures that are used for transportation of important liquid materials and gas in order to provide safety for human life. During an earthquake, imposed loads from soil deformations on concrete pipelines may cause severe damages, possibly causing disturbance in vital systems, such as cooling of nuclear power facilities. The high level of safety has caused a demand for reliable seismic analyses, also for structures built in the regions that have not traditionally been considered as highly seismically active. The focus in this study is on areas with seismic and geological conditions corresponding to those in Sweden and Northern Europe. Earthquakes in Sweden for regions with hard rock dominated by high-frequency ground vibrations, Propagation of such high-frequency waves through the rock mass and soil medium affect underground structures such as pipelines. The aim of this project is investigating parameters that affect response of buried pipelines due to high-frequency seismic excitations. The main focus of the study is on reinforced concrete pipelines. Steel pipelines are also studied for comparison purposes. The effects of water mass, burial depth, soil layer thickness and non-uniform ground thickness caused by inclined bedrock are studied. The results are compared to those obtained for low-frequency earthquakes and the relationship between strong ground motion parameters and pipelines response is investigated. It is shown that, especially for high frequency earthquake excitations, non-uniform ground thickness due to inclined bedrock significantly increase stresses in the pipelines. For the conditions studied, it is clear that high-frequency seismic excitation is less likely to cause damage to buried concrete pipelines. However, the main conclusion is that seismic analysis is motivated also for pipelines in high-frequency earthquake areas since local variation in the ground conditions can have a significant effect on the safety.Nedgrävda rörledningar (pipelines) är rörformiga strukturer som används för transport av viktiga flytande material och gas för att säkerhetsställa samhälleliga funktioner. Denna typ av infrastruktursystem korsar stora områden med olika geologiska förhållanden. Under en jordbävning kan markdeformationer påverka rörledningar av betong vilka kan få allvarliga skador som i sin tur kan leda till störningar i vitala system, såsom till exempel kylning av kärnkraftsanläggningar. Den höga säkerhetsnivå som eftersträvas ger upphov till ett behov av tillförlitliga seismiska analyser, även för strukturer som byggs i regioner som traditionellt inte har ansetts som seismiskt aktiva. Fokus i denna licentiatuppsats ligger på områden med seismiska och geologiska villkor som motsvarar de i Sverige och norra Europa. Jordbävningar i Sverige klassas som händelser inom en tektonisk platta som för regioner med hårt berg kan resultera i jordbävningar som domineras av högfrekventa markvibrationer. Sådana högfrekventa vågor propagerar genom bergmassa och jordmaterial och kan där påverka underjordiska strukturer såsom rörledningar. Syftet med detta projekt är att undersöka vilka parametrar som har stor påverkan på nedgrävda rörledningar som utsätts för högfrekventa seismiska vibrationer. Tyngdpunkten i studien är på rörledningar av armerad betong men stålledningar studeras också i jämförande syfte. Två-dimensionella finita elementmodeller används, utvecklade för dynamisk analys av rörledningar belastas av seismiska vågor som propagerar från berggrunden genom jorden. Modellerna beskriver båda längsgående och tvärgående snitt av rörledningar. Samspelet mellan rörledningar och omgivande jord beskrivs av en icke-linjär modell. De studerade rörledningarna antas vara omgivna av friktionsjord med stor, medel eller liten styvhet. Effekterna av vattenmassa i rören, grundläggningsdjup, jordlagrens tjocklek och varierande jordtjocklek på grund av lutande berggrund studeras. Det visas hur två-dimensionella modellerbaserade på plan töjning kan användas för seismisk analys av rörledningar med cirkulära tvärsnitt. Resultaten jämförs med de som erhållits för lågfrekventa jordbävningar och förhållandet mellan markrörelseparametrar och responsen hos rörledningar undersöks. Det visas att den naturliga frekvensen för modellerna beror av jordtyp, tjocklek och variation hos jordlagret. Det visas att, särskilt för högfrekventa jordbävningar, olikformigt varierande markdjup på grund av lutande berggrund avsevärt ökar spänningarna i rörledningarna. För de förhållanden som studerats är det klart att det är mindre sannolikt att högfrekvent seismisk belastning ska orsaka skador på nedgrävda rörledningar av betong. Dock är den viktigaste slutsatsen att seismisk analys ändå motiveras, även för rörledningar i områden där jordbävningar med högt frekvensinnehåll förekommer eftersom lokala variationer i markförhållanden kan ha en betydande inverkan på säkerheten.
QC 20161014
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Kim, Hongjin. "WAVELET-BASED ADAPTIVE CONTROL OF STRUCTURES UNDER SEISMIC AND WIND LOADS." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1039128747.
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Huaco, G., G. Huaco, and J. Jirsa. "Mechanical Splices for Seismic Retrofitting of Concrete Structures." Institute of Physics Publishing, 2020. http://hdl.handle.net/10757/651837.
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As an alternative to lap splicing, mechanical splices can be used for retrofit purposes. They are generally most economical than traditional lap splices when available spacing or length makes laps difficult to utilize. Mechanical splices are frequently used in new construction. However, their use is limited and not practical for use in retrofitted structures. However, if the bars to be joined do not need to be threaded in order to be connected with a special mechanical splice, such mechanical splices can be useful. It is presented a proposal of using two types of mechanical splices for retrofit purposes. Cycle Tension and cycle tension-compression tests are presented and discussed. It was found that mechanical splices are suitable and have acceptable response under seismic loads.
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Hite, Monique C. "Evaluation of the Performance of Bridge Steel Pedestals under Low Seismic Loads." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14485.
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Many bridges are damaged by collisions from over-height vehicles resulting in significant impact to the transportation network. To reduce the likelihood of impact from over-height vehicles, steel pedestals have been used as a cost-effective, efficient means to increase bridge clearance heights. However, these steel pedestals installed on more than 50 bridges in Georgia have been designed with no consideration of seismic loads and may behave in a similar fashion to high-type steel bearings. Past earthquakes have revealed the susceptibility of high-type bearings to damage, resulting in the collapse of several bridges. Although Georgia is located in a low-to-moderate region of seismicity, earthquake design loads for steel pedestals should not be ignored. In this study, the potential vulnerabilities of steel pedestals having limited strength and deformation capacity and lack of adequate connection details for anchor bolts is assessed experimentally and analytically. Full-scale reversed cyclic quasi-static experimental tests are conducted on a 40' bridge specimen rehabilitated with 19" and 33" steel pedestals to determine the modes of deformation and mechanisms that can lead to modes of failure. The inelastic force-deformation hysteretic behavior of the steel pedestals obtained from experimental test results is used to calibrate an analytical bridge model developed in OpenSees. The analytical bridge model is idealized based on a multi-span continuous bridge in Georgia that has been rehabilitated with steel pedestals. The analytical bridge model is subjected to a suite of ground motions to evaluate the performance of the steel pedestals and the overall bridge system. Recommendations are made to the Georgia Department of Transportation (GDOT) for the design and construction of steel pedestals. The results of this research are useful for Georgia and other states in low-to-moderate seismic zones considering the use of steel pedestals to elevate bridges and therefore reduce the likelihood of over-height vehicle collisions.
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Erhan, Semih. "Effect Of Vehicular And Seismic Loads On The Performance Of Integral Bridges." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613739/index.pdf.
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Integral bridges (IBs) are defined as a class of rigid frame bridges with a single row of piles at the abutments cast monolithically with the superstructure. In the last decade, IBs have become very popular in North America and Europe as they provide many economical and functional advantages. However, standard design methods for IBs have not been established yet. Therefore, most bridge engineers depend on the knowledge acquired from performance of previously constructed IBs and the design codes developed for conventional jointed bridges to design these types of bridges. This include the live load distribution factors used to account for the effect of truck loads on bridge components in the design as well as issues related to the seismic design of such bridges. Accordingly in this study issues related to live load effects as well as seismic effects on IB components are addressed in two separate parts.
In the first part of this study, live load distribution formulae for IB components are developed and verified. For this purpose, numerous there dimensional and corresponding two dimensional finite element models (FEMs) of IBs are built and analyzed under live load. The results from the analyses of two and three dimensional FEMs are then used to calculate the live load distribution factors (LLDFs) for the components of IBs (girders, abutments and piles) as a function of some substructure, superstructure and soil properties. Then, live load distribution formulae for the determination of LLDFs are developed to estimate to the live load moments and shears in the girders, abutments and piles of IBs. It is observed that the developed formulae yield a reasonably good estimate of live load effects in IB girders, abutments and piles.
In the second part of this study, seismic performance of IBs in comparison to that of conventional bridges is studied. In addition, the effect of several structural and geotechnical parameters on the performance of IBs is assessed. For this purpose, three existing IBs and conventional bridges with similar properties are considered. FEMs of these IBs are built to perform nonlinear time history analyses of these bridges. The analyses results revealed that IBs have a better overall seismic performance compared to that of conventional bridges. Moreover, IBs with thick, stub abutments supported by steel H piles oriented to bend about their strong axis driven in loose to medium dense sand are observed to have better seismic performance. The level of backfill compaction is found to have no influence on the seismic performance of IBs.
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Saldivar-Moguel, Emilio Enrique. "Investigation into the behaviour of displacement piles under cyclic and seismic loads." Thesis, Imperial College London, 2002. http://hdl.handle.net/10044/1/7589.
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Dechka, David Charles. "Response of shear-stud-reinforced continuous slab-column frames to seismic loads." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq64854.pdf.
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Rydell, Cecilia. "Seismic high-frequency content loads on structures and components within nuclear facilities." Licentiate thesis, KTH, Betongbyggnad, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-145403.
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Sweden is generally considered to be a low seismicity area, but for structures within nuclear power facilities, the safety level demand with respect to seismic events are high and thus, these structures are required to be earthquake-resistant. The seismic hazard is here primarily considered to be associated with near-field earthquakes. The nuclear power plants are further founded on hard rock and the expected ground motions are dominated by high frequencies. The design earthquake considered for the nuclear facilities has an annual probability of 10-5 events, that is, the probability of occurrence is once per 100 000 years. The focus of the study is the seismic response of large concrete structures for the nuclear power industry, with regard not only to the structure itself but also to non-structural components attached to the primary structure, and with emphasis on Swedish conditions. The aim of this licentiate thesis is to summarize and demonstrate some important aspects when the seismic load is dominated by high frequencies. Additionally, an overview of laws, regulations, codes, standards, and guidelines important for seismic analysis and design of nuclear power structures is provided. The thesis includes two case studies investigating the effect of seismic high-frequency content loads. The first study investigates the influence of gaps in the piping supports on the response of a steel piping system subjected to a seismic load dominated by high amplitudes at high frequencies. The gaps are found in the joints of the strut supports or are gaps between the rigid box supports and the pipe. The piping system is assessed to be susceptible to high-frequency loads and is located within the reactor containment building of a nuclear power plant. The stress response of the pipe and the acceleration response of the valves are evaluated. The second study investigates the effect of fluid-structure interaction (FSI) on the response of an elevated rectangular water-containing concrete pool subjected to a seismic load with dominating low and high frequencies, respectively. The pool is located within the reactor containment building of a boiling water reactor at a nuclear power plant. The hydrodynamic pressure distribution is evaluated together with the stress distribution in the walls of the tank. From the two case studies, it is evident that the response due to a seismic load dominated by high frequencies and low frequencies, respectively, is different. Although the seismic high-frequency load may be considered non-damaging for the structure, the effect may not be negligible for non-structural components attached to the primary structure. Including geometrical non-linear effects such as gaps may however reduce the response. It was shown that the stress response for most of the pipe elements in the first case study was reduced due to the gaps. It may also be that the inclusion of fluid-structure interaction effects changes the dynamic properties of a structural system so that it responds significantly in the high frequency range, thus making it more vulnerable to seismic loads dominated by high frequencies. In the second case study, it was shown that even for a seismic load with small amplitudes and short duration, but with dominating high-frequency content, as the Swedish 10-5 design earthquake, the increase of the dynamic response as fluid-structure interaction is accounted for is significant.QC 20150519
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Bouchard, Keith M. (Keith Michael). "A performance-based approach to retrofitting unreinforced masonry structures for seismic loads." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/38944.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2007.Includes bibliographical references (leaves 58-59).
The structural inadequacy of existing unreinforced masonry (URM) buildings to resist possible seismic loading is a serious problem in many parts of the United States, including the Northeast and Midwest. The fact that many of these buildings are deemed historic structures or house critical facilities, like firehouses, emphasizes the need for an effective retrofitting program. The Federal Emergency Management Agency published a performance-based design code - FEMA 356 - in 2000 to use for analyzing and retrofitting existing structures. This code includes procedures for URM buildings. This paper applies these performance-based analysis procedures to a URM shear wall and compares the results to a modified analysis proposed by researchers. The wall is then rehabilitated using two common retrofit methods and again analyzed using the code. Recommendations are made for practicing engineers when evaluating URM structures for seismic loads.
by Keith M. Bouchard.
M.Eng.
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Fourie, Johanna Aletta. "Effect of seismic loads on water-retaining structures in areas of moderate seismicity." Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/2061.
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Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: Water-retaining structures are commonly used in South Africa for the storage of potable water and waste water. However, a South African code pertaining to the design of concrete water-retaining structures do not currently exist and therefore use is made of the British Standard BS 8007 (1987). For the design of concrete water-retaining structures in South Africa, only the hydrostatic loads are considered while forces due to seismic activity are often neglected even though seismic excitations of moderate magnitude occur within some regions of the country. Hence, the primary aim of this study was to determine whether seismic activity, as it occurs in South Africa, has a significant influence on water-retaining structures and whether it should be considered as a critical load case. In order to assess the influence of seismic activity on the design of water-retaining structures the internal forces in the wall and the required area of reinforcement were compared. Comparisons were made between the seismic analyses and static analyses for both the ultimate and serviceability limit states. In order to obtain the internal forces in the wall use was made of an appropriate Finite element model. Three Finite element models were investigated in this study and the accuracy of each model was assessed based on the fundamental frequency, base shear force and overturning moment. These values were compared to the values obtained with the numerical method presented by Veletsos (1997) which was verified with Eurocode 8: Part 4 (2006). The results obtained indicated that seismic excitations of moderate magnitude do have a significant influence on the reinforcement required in concrete water-retaining structures. For both the ultimate limit state and serviceability limit state the required reinforcement increased significantly when seismic loads were considered in the design. As in the case for static design of water-retaining structures, the serviceability limit state also dominated the design of these structures under seismic loading.
AFRIKAANSE OPSOMMING: Beton waterhoudende strukture in Suid-Afrika word op ‘n gereelde basis gebruik vir die stoor van drink- sowel as afvalwater. ‘n Suid-Afrikaanse kode vir die ontwerp van hierdie strukture bestaan egter nie en dus word die Britse kode BS 8007 (1987) hiervoor gebruik. Vir ontwerp doeleindes word soms slegs die hidrostatiese kragte beskou terwyl kragte as gevolg van seismiese aktiwiteite nie noodwendig in berekening gebring word nie. Seismiese aktiwiteite van gematigde grootte kom egter wel voor in sekere dele van Suid-Afrika. Die hoofdoel van hierdie studie was dus om die invloed van seismiese aktiwiteite, soos voorgeskryf vir Suid-Afrikaanse toestande, op beton waterhoudende strukture te evalueer asook om te bepaal of dit ‘n kritiese lasgevalle sal wees. Vir hierdie doel is die interne kragte asook die area staal bewapening vir elk van die statiese en dinamiese lasgevalle vergelyk. Vergelykings is getref tussen die dinamiese en statiese resultate vir beide die swigtoestand en die diensbaarheidstoestand. Vir die bepaling van die interne kragte is gebruik gemaak van eindige element modelle. Tydens hierdie studie was drie eindige element modelle ondersoek en die akkuraatheid van elk geëvalueer op grond van die fundamentele frekwensie, die fondasie skuifkrag en die omkeermoment. Hierdie waardes was ondermeer bereken met twee numeriese metodes soos uiteengesit in Veletsos (1997) en Eurocode 8: Part 4 (2006). Die resultate dui daarop dat die invloed van seismiese aktiwiteite op beton waterhoudende strukture in Suid-Afrika nie weglaatbaar klein is nie en wel in berekening gebring behoort te word tydens die ontwerp. Die interne kragte vir beide die swigtoestand en diensbaarheidstoestand is aansienlik hoër vir die seismiese lasgeval as vir die statiese geval. Die diensbaarheidstoestand het deurentyd die ontwerp van beton waterhoudende strukture vir seismiese toestande oorheers.
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Kou, Yan. "Wedge failure analysis of anchored rock slopes subjected to surcharge and seismic loads." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2015. https://ro.ecu.edu.au/theses/1736.
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Slope stability in mining and civil engineering projects is always a problem of great concern. Because the rock mass behavior is significantly governed by the presence of joints or other discontinuities, several types of slope failure, such as plane failure, wedge failure, toppling failure, buckling failure and circular failure, are often observed. The present work focuses on the study of the wedge failure, which occurs as sliding of a mass of rock on two intersecting planes, generally discontinuity planes.
Recently, the factor of safety of rock slopes against the wedge failure has been studied in a number of investigations under static and/or dynamic conditions by different methods such as the limit equilibrium method, numerical modeling method, reliability method and stereographic method. However, the anchored rock slope against the wedge failure subjected to surcharge and seismic load has not yet been studied in detail in earlier studies. In this thesis, the rock slope subjected to the generalized loads such as surcharge and seismic/dynamic loads is analyzed against the wedge failure by the limit equilibrium method. The expression for the factor of safety was derived for the cases with anchors and without anchors separately. In addition, a parametric study is carried out to demonstrate the effects of the most relevant governing parameters on the stability of rock slope. The parameters include geometrical parameters, joint material properties, unit weight of rock, anchor inclination and hydraulic parameters. Several special cases of the developed generalized expression result in the expressions for the factor of safety for simplified field situations as reported in the literature.
The parametric study shows that most parameters as mentioned above affect the factor of safety ( FS ) of the rock slope against the wedge failure significantly. In order to find an easy way to work on the parametric analysis, the “ * ” indicates dimensionless parameters. It is observed that the surcharge would always be a destabilizing force when the cohesion (c* ) is not zero; the FS decreases with an increase in surcharge. However, when c* = 0, the FS increases slightly with an increase in surcharge. The anchor forces (T* ) would always be a stabilizing force that makes the FS increase with an increase in T*. As the angle of inclination of the joint plane/failure plane to the horizontal ( p y ) increases, the FS increases nonlinearly; it increase sharply by 60% from 42° to 45° while it deceases nonlinearly by 67% with an increase in the slope angle (yf ) from 40° to 60°. It is also observed that the FS decreases with an increase in horizontal seismic acceleration coefficient (k h ) and the vertical seismic acceleration coefficient (k v ), separately, while it increases linearly with an increase in the following parameters: the cohesion (c* ) and the angle of shearing resistance ( f ), separately. The FS increases with an increase in inclination of stabilizing force to the normal at the failure plane (a ); it becomes maximum when a increases to 80°. However, the unit weight of rock (g* ) does not affect the FS significantly.
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Penubothu, Naga Nataraja Satyanarayana Kumar. "Development of a phenomenological model for beam-to-column connections in moment resisting frames subjected to seismic loads." Cincinnati, Ohio : University of Cincinnati, 2006. http://www.ohiolink.edu/etd/view.cgi?acc%5Fnum=ucin1152583558.
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Thesis (M.S.)--University of Cincinnati, 2006.Title from electronic thesis title page (viewed Nov. 28, 2006). Includes abstract. Keywords: Connections, Moment Resisting Frames, Phenomenological Model, Cyclic; Loads, Seismic loads. Includes bibliographical references.
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Hossain, Md M. "Stability analysis of anchored rock slopes against plane failure subjected to surcharge and seismic loads." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2011. https://ro.ecu.edu.au/theses/139.
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The stability analysis of rock slopes has been a challenging task for engineers
because the rock mass constituting the slope often has discontinuities in various
forms, resulting in different types of slope failures. The plane failure is one of the
rock slope failures observed in field situations when the discontinuity is in the form
of joint planes. There are several parameters including surcharge and seismic loads
that govern the stability of the rock slope against plane failure in field projects. The
limit equilibrium approach for the estimation of the factor of safety of the rock slope
against plane failure has been well accepted by the engineers in the past. Very
recently, attempts have been made to present analytical expressions for the factor of
safety of the of the rock slopes against plane failure, which are not in a generalised
form because they do incorporate most field parameters. Therefore, in the present
work, the analytical expression for the factor of safety of a single-directional
anchored rock slope (SDARS) is derived, along with a discussion of its special cases
in view of different practical situations. Parametric studies and design charts for the
stability of the SDARS are presented, and an illustrative example is included to
explain the calculation steps for the factor of safety. In order to investigate the effect
of multi-directional rock anchors on the factor of safety, an analytical expression for
a multi-directional anchored rock slope (MDARS) is also presented.
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Ryan, Keri Lynn Chopra Anil K. "Estimating the seismic response of base-isolated buildings including torsion, rocking, and axial-load effects /." Berkeley : Earthquake Engineering Research Center, University of California, 2005. http://nisee.berkeley.edu/elibrary/.
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Previously published as first author's thesis (Ph. D. in Engineering--University of California, Berkeley, 2004)."June 2005." Includes bibliographical references. Also available as an electronic document from the Earthquake Engineering Online Archive Earthquake: http://nisee.berkeley.edu/elibrary.
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Marziale, Stephen. "Analysis of Brick Veneer on Concrete Masonry Wall Subjected to In-plane Loads." University of Dayton / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1407153177.
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Dicleli, Murat. "Effects of extreme gravity and seismic loads on short to medium span slab-on-girder steel highway bridges." Thesis, University of Ottawa (Canada), 1993. http://hdl.handle.net/10393/6730.
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This study addresses two separate but related problems. They are detrimental effects of extreme gravity and seismic loadings, which were not considered in the original design, on slab-on-girder steel bridges. In the first part of this thesis the effect of extreme gravity loads on slab-on-girder steel bridges is studied. Currently, in many jurisdictions of North America, special permits are issued to extra-heavy vehicles considering only the ultimate capacity of the bridges. Based on this, a large number of special permits have been issued to extra-heavy vehicles, and therefore concerns have been raised since the cumulative effect of such overloads have never been assessed. In this perspective, the ultimate and cumulative effect of such overloads on bridge components is studied. Typical heavy permit-truck configurations are selected to investigate their effect on steel bridges. As a first step, influence line analyses are conducted to find the ranges of spans of simply supported and continuous bridges for which heavy permit-trucks have the most detrimental effects. In the light of these observations, a number of actual bridges within the estimated span length limits are analyzed to find the bridge members largely affected by such overloads. Next, a literature review is conducted to appraise the state-of-knowledge on the impact of infrequent stress-range excursions produced by heavy loads on fatigue life of bridge members. The effect of variable amplitude loading due to both Ontario truck traffic and heavy permit trucks on fatigue life of bridge members is investigated. Analytical expressions to calculate the fatigue life and the reduction in fatigue life of bridges due to heavy permit-trucks, without the need for a detailed analysis of each bridge, are derived and presented, along with a fatigue-based methodology to assess the reduction in service life of bridges attributable to heavy-permit trucks. Finally, using the derived equations, a sample permit-policy is presented assuming that a two percent reduction in fatigue life due to heavy permit-trucks is acceptable. In the second part, the response of bridge superstructure components to seismic excitations is investigated. Single span simply supported, continuous and multi-span simply supported bridges are studied by varying their geometric and structural properties. Linear and nonlinear dynamic analyses of these bridges are conducted for earthquakes of different characteristic and intensity considering only the superstructure. The forces and displacements of superstructure components which significantly affect the response, are determined as a function of the selected properties and earthquake types. Then, using these results, a methodology is developed for ranking and rapid seismic evaluation of existing steel bridges. Bearing forces due to seismic excitation in both transverse and longitudinal direction are found to be proportional to the mass of the bridge, span length, and bearings' stiffness. The effect of span length, number of spans, column size and steel strength on the seismic response of continuous and multi-span simply supported bridges are studied. Next, sliding of bridges after the bearings are severed is investigated. High intensity earthquakes are required to slide multi-span simply supported bridges when the bearings at the abutments are severed but single span simply supported and continuous bridges may have considerable sliding displacements depending on the $A\sb{p}/V\sb{p}$ ratio of earthquakes. The effect of cross-bracing as a retrofitting element for continuous and multi-span simply supported bridges is investigated. (Abstract shortened by UMI.)
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Chen, Xianghui M. Eng Massachusetts Institute of Technology. "A comparative study : the dynamic behavior of tall buildings with diagrid and hexagrid structural systems subjected to seismic loads." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/119314.
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Thesis: M. Eng., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 66-67).
Most advancements in achieving new structural heights for tall buildings are not possible without the innovation in structural systems. One type of tubular shell structural system, diagrids, like the one used in Hearst Tower, have gained much popularity in high-rise constructions over the past decade due to its high efficiency by resolving both gravity and lateral loads with the same elements. A new iteration of such tubular shell system named hexagrid was examined in this paper. The aim of the study is to evaluate the dynamic response and behavior of such systems when they are subjected to seismic loads, and to compare their efficiency to the better understood diagrid system. Three 60-story and three 36-story models using diagrid and hexagrid exoskeleton systems designed to control the governing wind drift requirements were constructed in commercial software ETABS. For each height, one benchmark diagrid structure and two hexagrid structures using horizontal and vertical configurations were modeled. ASCE 7-10 Code based linear dynamic Modal Response Spectrum Analyses and modal analyses were then carried out for two locations, San Francisco and San Diego, to study the seismic performance based on the dynamic response and modal properties. The results from hexagrid architype models were compared against those of benchmark diagrid models to study the difference in dynamic behavior and relative efficiency. The analysis results showed similar mode shapes across different systems, which was attributed to the similar geometry and load-resisting mechanism of tubular shell structures. However, neither of the hexagrid configurations are as stiff as the diagrid system, resulting in larger seismic-induced lateral displacements and acceleration. An efficiency analysis shows, from the perspective of structural weight, that neither one of the two hexagrid configurations are as efficient as diagrids in controlling lateral drifts, but vertical hexagrids are comparable to diagrids in controlling lateral acceleration. It was also concluded that the studied vertical hexagrid configuration is stiffer and more efficient than the studied horizontal hexagrid configuration. The results of the study could be used by design professionals, architects and structural engineers alike, to make a more informed decision in system selection.
by Xianghui Chen.
M. Eng.
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Moharrami, Gargari Mohammadreza. "Development of Novel Computational Simulation Tools to Capture the Hysteretic Response and Failure of Reinforced Concrete Structures under Seismic Loads." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/71864.
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Reinforced concrete (RC) structures constitute a significant portion of the building inventory in earthquake-prone regions of the United States. Accurate analysis tools are necessary to allow the quantitative assessment of the performance and safety offered by RC structures. Currently available analytical approaches are not deemed adequate, because they either rely on overly simplified models or are restricted to monotonic loading. The present study is aimed to establish analytical tools for the accurate simulation of RC structures under earthquake loads. The tools are also applicable to the simulation of reinforced masonry (RM) structures.
A new material model is formulated for concrete under multiaxial, cyclic loading conditions. An elastoplastic formulation, with a non-associative flow rule to capture compression-dominated response, is combined with a rotating smeared-crack model to capture the damage associated with tensile cracking. The proposed model resolves issues which characterize existing concrete material laws. Specifically, the newly proposed formulation accurately describes the crack opening/closing behavior and the effect of confinement on the strength and ductility under compressive stress states. The model formulation is validated with analyses both at the material level and at the component level. Parametric analyses on RC columns subjected to quasi-static cyclic loading are presented to demonstrate the need to regularize the softening laws due to the spurious mesh size effect and the importance of accounting for the increased ductility in confined concrete. The impact of the shape of the yield surface on the results is also investigated.
Subsequently, a three-dimensional analysis framework, based on the explicit finite element method, is presented for the simulation of RC and RM components under cyclic static and dynamic loading. The triaxial constitutive model for concrete is combined with a material model for reinforcing steel which can account for the material hysteretic response and for rupture due to low-cycle fatigue. The reinforcing steel bars are represented with geometrically nonlinear beam elements to explicitly account for buckling of the reinforcement. The strain penetration effect is also accounted for in the models. The modeling scheme is validated with the results of experimental static and dynamic tests on RC columns and RC/RM walls. The analyses are supplemented with a sensitivity study and with calibration guidelines for the proposed modeling scheme.
Given the computational cost and complexity of three-dimensional finite element models in the simulation of shear-dominated structures, the development of a conceptually simpler and computationally more efficient method is also pursued. Specifically, the nonlinear truss analogy is employed to capture the response of shear-dominated RC columns and RM walls subjected to cyclic loading. A step-by-step procedure to establish the truss geometry is described. The uniaxial material laws for the concrete and masonry are calibrated to account for the contribution of aggregate interlock resistance across inclined shear cracks. Validation analyses are presented, for quasi-static and dynamic tests on RC columns and RM walls.Ph. D.
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Quezada, Eder, Yaneth Serrano, and Guillermo Huaco. "Dynamic Amplification Factor Proposal for Seismic Resistant Design of Tall Buildings with Rigid Core Structural System." Smart Innovation, Systems and Technologies, 2021. http://hdl.handle.net/10757/653773.
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El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado.Currently, there is an increase in the demand for tall buildings in the city of Lima. This research proposes to reduce the dynamic amplification factor through the seismic design of tall buildings based on the requirements of Peruvian code considering that they are regular in plan and height. Minimum base shear values according to the comparison of static seismic shear and dynamic shear from the spectral modal analysis were reviewed for cases of buildings larger than 120 m. The study of 28 reinforced concrete buildings was proposed, with different heights - varying from 24 to 36 floors, with different floor configurations, as well as the arrangement of the walls considering as a rigid core structural system. Additionally, the characteristics of the materials, the loads and combinations were defined. The responses of these buildings were determined by the response spectrum analysis (RSA) and then compared with those obtained by the lineal response history analysis (LRHA), for the last analysis, five Peruvian seismic records were used and scaled to 0.45 g. The seismic responses of the LRHA procedure were taken as a benchmark. The result of this study is the analysis and proposal of the C/R factor for high-rise buildings, as well as obtaining the base shear and drift verification. Minimum base shear values can be reduced for high or long-term buildings, being regular in plan and height.
Revisión por pares
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Papagiannis, Michail. "WIND TURBINE FOUNDATIONS IN CLAY : Technical and economic considerations for proposals for wind turbine foundations." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-353397.
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This thesis approaches the problem of the cost-efficient wind turbine foundation on an onshore site of clayey soil characteristics. The given soil stratigraphy includes a layer of clay and two sands of different density. The characteristics of the soil and the water level that were used as input come from a site in Peloponissos, Greece. The applied wind, static and seismic loads on this study were resolved with the German DIN standards, and other related research and European standards. The safety factors were adjusted for wind turbines. For the pile solution, after the bearing and overturning adequacy against the horizontal and vertical loads was proven with the calculation of the DIN equations, then the model was inserted in the Pfahl program using DIN 4017 equations to calculate settlements. Firstly, a shallow foundation of various dimensions in the clay layer over the water level with all the necessary checks was considered. Afterward, a deep foundation solution of a single bored pile, with reinforcement steel casing, of various diameters was investigated. The different foundation solutions were assessed and compared on a technical and economic basis. As a conclusion, the 0.70 meter diameter single pile was chosen as the best solution because it needs only a few days for construction, and it is the most cost-efficient. The chosen circular footing was of a diameter of 10 meters and 1.5 meter raft thickness, but proved unfeasible because of high excavations costs. The checks on the DIN standards and Eurocode that set the boundaries for the design in the two cases were recognised and possible future work goals were discussed.
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Fatima, Tabassum. "Optimisation of lateral load-resisting systems in composite high-rise buildings." Thesis, Queensland University of Technology, 2014. https://eprints.qut.edu.au/67563/2/Tabassum_Fatima_Thesis.pdf.
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This research is carried out by using finite element modelling of building prototypes with three different layouts (rectangular, octagonal and L-shaped) for three different heights (98.0 m, 147.0 m and 199.5 m) for the optimization of lateral load-resisting systems in composite high-rise buildings. Variations of lateral bracings (different number and varied placement along model height of belt-truss and outrigger floors) with RCC (reinforced cement concrete) core wall are used in composite high-rise building models. Prototypes of composite buildings are analysed for dynamic wind and seismic loads. The effects on serviceability (deflection and frequency) of models are studied and conclusions are deduced.
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Kandaz, Murat. "Computer Aided Design And Structural Analysis Of Pressure Vessels." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/2/12607261/index.pdf.
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This study is conducted for the design and analysis of pressure vessels and associated pressurized equipment using various codes and methods. A computer software is developed as the main outcome of this study, which provides a quick and comprehensive analysis by using various methods utilized in codes and standards together with theoretical and empirical methods which are widely accepted throughout the world.
Pressure vessels are analyzed using ASME Boiler and Pressure Vessel Code, whereas auxiliary codes, especially ASCE and AISC codes are utilized for structural analyses of these equipment. Effect of wind, seismic, and other types of loadings are also taken into consideration in detail, with dynamic analyses. Support structures and their auxiliary components are also items of analysis.
Apart from pressure vessels, many pressurized process equipments that are commonly used in the industy are also included in the scope of the study. They include safety valves which are an integral part of those kinds of pressurized or enclosed systems, two of the heat exchanger components with great importance -tubesheets and expansion joints-, and API 650 tanks for oil or water storage.
The computer software called as VESSELAID is written in Microsoft Visual Basic 6.0 using SI units. Design and analysis methods of VESSELAID are based on various code rules, recommended design practices and alternative approaches.
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Widjaja, Matius Andy. "The Influence of the Recommended LRFD Guidelines for the Seismic Design of Highway Bridges on Virginia Bridges." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/31453.
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The influence of the recommended LRFD Guidelines for the seismic design of highway bridges in Virginia was investigated by analyzing two existing bridges. The first bridge has prestressed concrete girders and is located in the Richmond area. The second bridge has steel girders and is located in the Bristol area. The analysis procedure for both bridges is similar. First the material and section properties were calculated. Then the bridge was modeled in RISA 3D. Live and dead load were imposed on the bridge to calculate the cracked section properties of the bridge. The period of vibration of the bridge was also calculated. After the soil class of the bridge was determined, the design response spectrum curve of the bridge was drawn. The spectral acceleration obtained from the design spectrum curve was used to calculate the equivalent earthquake loads, which were applied to the superstructure of the bridge to obtain the earthquake load effects. Live and dead loads were also applied to get the live and dead load effects. The combined effects of the dead, live and earthquake loads were compared to the interaction diagram of the columns and moment strength of the columns. The details of the bridge design were also checked with the corresponding seismic design requirement.A parametric study was performed to explore the effects of different column heights and superstructure heights in different parts of Virginia. The column longitudinal reinforcing was increased to satisfy the bridge axial loads and moments that are not within the column interaction diagram.Master of Science
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Šulerová, Zdeňka. "Dynamická analýza konstrukce zatížená seismickým zatížením." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-226647.
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This thesis deals with the calculation of response of reinforced concrete construction on the effect of seismic tension. Time and spectral analysis were made. They are mentioned as possible ways of calculation in EN 1998 - 1:2004 norm. Final figures of global deformations and stress on selected beam from the time and spectral analysis were firstly compared for the horizontal components of seismic stress affecting only in one direction. Subsequently comparison of time progress to combination of these effects mentioned in relevant norm was made. In the conclusion the results of used analysis are appraised.
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MOROTE, CARLOS HUGO SOTO. "STABILITY AND DEFORMATION OF SOIL SLOPES UNDER SEISMIC LOAD." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2006. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=9532@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOO comportamento sísmico de taludes tem sido um tópico de grande interesse da engenharia geotécnica nos últimos 40 anos. Durante este período, a prática da engenharia nesta área evoluiu do emprego de técnicas elementares para procedimentos numéricos bastante complexos. A abordagem mais simples é a análise pseudo-estática na qual o carregamento do terremoto é simulado por uma aceleração horizontal estática equivalente atuando na massa de solo deslizante, utilizando-se um procedimento de equilíbrio limite (método das fatias), geralmente conservativo. O parâmetro que descreve o comportamento dinâmico do solo é referido como coeficiente sísmico k, e sua seleção depende fortemente da experiência e normas técnicas locais, porque não há maneira simples e segura de se escolher um valor adequado. O segundo procedimento é conhecido como método de Newmark, que envolve o cálculo de uma aceleração de escoamento, definida como a força inercial necessária para o fator de segurança atingir 1 em uma análise pseudo-estática pelo método de equilíbrio limite. O procedimento então usa os registros de aceleração do terremoto de projeto e o integra duplamente no tempo para calcular os deslocamentos permanentes acumulados. O terceiro método é referido como análise de Makdisi- Seed, que procura definir a estabilidade sísmica do talude em termos de deslocamentos aceitáveis em vez de um fator de segurança tradicional através de uma versão modificada do método de Newmark. Esta técnica apresenta uma maneira racional de calcular uma aceleração de escoamento média, necessária para produzir um valor do coeficiente de segurança do talude igual a 1. Gráficos específicos foram também desenvolvidos para estimativa dos deslocamentos permanentes, tendo sido bastante aplicados em aterros rodoviários, barragens e aterros sanitários. Finalmente, o mais sofisticado método para análise de estabilidade sísmica de taludes é conhecido como análise dinâmica, que normalmente incorpora modelos de elementos finitos e relações tensão x deformação complexas numa tentativa de obter melhores representações para o comportamento mecânico de taludes sob cargas cíclicas Os resultados destas análises podem incluir a história no tempo dos deslocamentos e tensões, bem como das freqüências naturais, efeitos de amortecimento, etc. Este trabalho apresenta uma comparação entre os métodos mencionados anteriormente, analisando o comportamento sísmico dos taludes da estrutura de contenção dos resíduos de lixiviação de minério de urânio, na Bahia, e dos taludes do bota-fora sul da mina de cobre Toquepala, situada no Peru.
The seismic stability of slopes has been a topic of considerable interest in geotechnical engineering for the past 40 years. During that period, the state of practice has moved from simples techniques to more complicated numerical procedures. The simplest approach is the pseudo-static analysis in which the earthquake load is simulated by an equivalent static horizontal acceleration acting on the mass of the landslide, according to a generally conservative limit equilibrium analysis. The ground motion parameter used in a pseudo-static analysis is referred to as the seismic coefficient k, and its selection has relied heavily on engineering judgment and local code requirements because there is no simple method for determining an appropriate value. The second main procedure is known as the Newmark displacement analysis which involves the calculation of the yield acceleration, defined as the inertial force required to cause the static factor of safety to reach 1 from the traditional limit equilibrium slope stability analysis. The procedure then uses a design earthquake strong-motion record which is numerically integrated twice for the amplitude of the acceleration above the yield acceleration to calculate the cumulative displacements. These displacements are then evaluated in light of the slope material properties and the requirements of the proposed development. The third method is referred to as the Makdisi-Seed analysis sought to define seismic embankment stability in terms of acceptable deformation instead of conventional factors of safety, using a modified Newmark analysis. Their method presents a rational means to determine yield acceleration, or the average acceleration required to produce a factor of safety of unity. Design curves were developed to estimate the permanent earthquake- induced deformations of embankments, which have since been applied to sanitary landfill and highway embankments. Finally, the most sophisticated method for seismic slope stability calculations is known as the dynamic analysis, which normally incorporates a finite element model and a rather complex stress-strain behavior for geological materials in an attempt to obtain a better representation of the behavior of soils under cyclic loading. The results of the analysis can include a time history of displacements and stresses, as well as natural frequencies, effects of damping, etc. This work presents a comparison of the results obtained by the aforementioned approaches, considering the seismic behavior of the slopes of an uranium lixiviation pad situated in Bahia, Brazil, and the South embankment of the waste landfill of the Toquepala Mine, Peru.
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Hsiaw, Jennifer S. (Jennifer Sing-Yee). "Seismic load-resisting capacity of plastered straw bale walls." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/60773.
Full textAbstract:
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 57-58).
Straw bales have been incorporated into buildings for centuries, but only recently have they been explored in academic settings for their structural potential. Straw bale building is encountering a growing audience due to its social and economic benefits. Plastered and reinforced straw bale wall assemblies have been found comparable to wood frame construction in resisting vertical and lateral loads. A number of straw bale residences have been constructed in the highly seismic state of California, while recent efforts have expanded its presence to quake-prone areas in developing countries like Pakistan and China. As this is a burgeoning arena of research, only empirical tests have been conducted. This thesis introduces a computer simulation of a wall assembly under lateral loading, using two techniques: a multi-layer shell element and an equivalent compression strut frame in SAP2000. The models assume homogeneity, and based on the results, areas for improvement and further research are suggested.
by Jennifer S. Hsiaw.
M.Eng.
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Včelný, Michal. "Seismická analýza konstrukce s využitím residuálních tvarů." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2021. http://www.nusl.cz/ntk/nusl-433399.
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This thesis deals with the possibility of using the residual shape with help of the structural analysis software SCIA Engineer in the calculation of seismic load. Residual shape will be used in combination with CQC and SRSS calculation method, including different numbers of own shapes and the oscillated mass. In the last step, the results will be compared with each other.
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Li, Xinrong. "Reinforced concrete columns under seismic lateral force and varying axial load." Thesis, University of Canterbury. Civil Engineering, 1994. http://hdl.handle.net/10092/7593.
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The project is carried out with the intention to study the strength and ductility of reinforced concrete columns subjected to simulated seismic horizontal loading and varying axial load.
First, an extensive review of previous research on the behaviour of reinforced concrete members and hysteretic modelling is provided.
Then, the experimentally investigation which involves testing a total of nine reinforced concrete specimens under simultaneously cyclic lateral loading and varying axial load is carried out. The first series of six reinforced concrete column units were tested to obtain the variations in flexural hysteretic behaviour with fluctuation in axial load level. In the second phase of experimental investigation, three specimens were tested to study the shear strength of reinforced concrete columns subjected to cyclic lateral loading and varying axial load with emphasis placed on the study of degrading concrete shear resisting mechanisms and comparisons with the present design code equations for shear strength.
Following the experimental program, the mechanisms of shear resistance and the factors affecting the shear strength are considered. In particular, the effects of alternating tension and compression axial load on the shear resisting mechanisms are studied. On the basis of experimental results, proposals are made for predicting shear strength of reinforced concrete column of ductility and limited ductility.
Next, the theoretical work was undertaken to investigate the elastic and post-yield flexural rigidities of reinforced concrete sections. The equations for determining the elastic and post-yield flexural regidities are presented. Also, a moment-curvature hysteretic model including varying axial loading effect is proposed. The theoretical predictions for the moment-curvature hysteresis relationship were found to compare well with the experimental results.
Finally, an example is given of inelastic dynamic response analysis of reinforced concrete frame using the proposed moment-curvature model which includes the effects of varying axial load on the yield moment, and loading and unloading stiffness of the structural members.
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Wong, Sze-man. "Seismic performance of reinforced concrete wall structures under high axial load with particular application to low-to moderate seismic regions." Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B34739531.
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Bazargani, Poureya. "Seismic demands on gravity-load columns of reinforced concrete shear wall buildings." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/46651.
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In shear wall buildings, walls serve as the seismic force resisting system while the gravity-load system consists of columns that are primarily designed to carry the weight of the building through frame action and are not detailed for seismic ductility. Design codes require the gravity-load system to be checked for deformation compatibility as the building deforms laterally. The process of checking the columns for adequate deformability still requires more work.
In addition to flexural deformations, components such as shear strain and rotation of the foundation contribute significantly to lateral deformations in the wall plastic hinge zone. Shear strains in flexural shear walls are analytically shown to be a result of large vertical tensile strains in areas with inclined cracks. Based on this theory, a simple design-oriented method for estimating shear strain profile of flexural shear walls is formulated, the accuracy of which is verified against experimental results from works of other researchers.
Rotation of shear wall foundations is studied through performing about 2000 Nonlinear Time-History Analysis (NTHA) considering the nonlinear interaction between the foundation and the underlying soil. Behaviour of shear walls accounting for foundation rotation is explained with emphasis on relative wall to foundation strengths. A simple method for obtaining the monotonic foundation moment-rotation response is formulated which is then used in a simple step-by-step method for estimating foundation rotation in a given shear wall building.
Curvature demand on columns pushed to a given wall deformation profile is studied using a structural analysis algorithm specifically designed for the task. In the absence of wall shear strain or significant foundation rotation, column curvature demand is found to remain close to the wall maximum curvature. Wall shear strain and foundation rotation are found to cause severe increase to column curvature demand. In a parametric study on column curvature demand, parameters including wall length, column length, height of column plastic hinge zone, first storey height, fixity of the column at grade level, and the effect of members framing into the column are studied. Several simple expressions for estimating column curvature demand are derived that can be implemented in design.
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Arifuzzaman, Shah. "Seismic Retrofit of Load Bearing Masonry Walls with Surface Bonded FRP Sheets." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24233.
Full textAbstract:
A large inventory of low rise masonry buildings in Canada and elsewhere in the world were built using unreinforced or partially reinforced load bearing wall. The majority of existing masonry structures is deficient in resisting seismic force demands specified in current building codes. Therefore, they pose significant risk to life safety and economic wellbeing of any major metropolitan centre. Because it is not economically feasible to replace the existing substandard buildings with new and improved structures, seismic retrofitting remains to be an economically viable option.
The effectiveness of surface bonded carbon fiber-reinforced polymer (CFRP) sheets in retrofitting low-rise load bearing masonry walls was investigated in the current research project. The retrofit technique included the enhancements in wall capacity in shear and flexure, as well as anchoring the walls to the supporting elements through appropriate anchorage systems. Both FRP fan type anchors and steel sheet anchors were investigated for elastic and inelastic wall response. One partially reinforced masonry (PRM) wall and one unreinforced masonry (URM) wall were built, instrumented and tested under simulated seismic loading to develop the retrofit technique. The walls were retrofitted with CFRP sheets applied only on one side to represent a frequently encountered constraint in practice. FRP fan anchors and stainless steel sheet anchors were used to connect the vertical FRP sheets to the wall foundation. The walls were tested under constant gravity load and incrementally increasing in-plane deformation reversals. The lateral load capacities of both walls were enhanced significantly. The steel sheet anchors also resulted in some ductility. In addition, some small-scale tests were performed to select appropriate anchor materials. It was concluded that ductile stainless steel sheet anchors would be the best option for brittle URM walls.
Analytical research was conducted to assess the applicability of truss analogy to retrofitted walls. An analytical model was developed and load displacement relationships were generated for the two walls that were retrofitted. The analytical results were compared with those obtained experimentally, indicating good agreement in force resistance for use as a design tool.
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Nguyen, Tan. "Load transfer mechanisms and seismic stability of embankments subjected to basal subsidence." Kyoto University, 2018. http://hdl.handle.net/2433/235077.
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Guidi, Giovanni. "Displacement Capacity of Load-Bearing Masonry as a Basis for Seismic Design." Doctoral thesis, University of Trento, 2011. http://eprints-phd.biblio.unitn.it/588/1/Giovanni_Guidi_-_PhD_Thesis_-_2011.pdf.
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The masonry still one of the widespread construction system for low-rise residential buildings even for countries prone to seismic risk. Seismic design methods yet in use are based on idea that controlling forces is better way to control earthquake induced damages. In recent decades, however, was highlighted as the differences in strength between two levels of damage is low, and therefore as the damage is better correlated to the displacement. Also, in recent years, has arose a widespread expectation for being able to control the damage based on the probability of occurrence of an earthquake or being able to base the design on different performance levels ("performance-based design").
In this context, the design of masonry buildings needs to develop these design methods. The results of experimental tests performed at the University of Padua in the recent years on different masonry systems both reinforced and unreinforced with different horizontal and vertical joints typologies, which were aimed to characterization under combined in-plane vertical and horizontal cyclic loading, were used to make different strategies of finite element modeling that reproduce and extend the experimental results using parametric analyses. These analyses allow a comparison and a validation of an analytical model which was then developed. This model is able to reproduce the envelope curves of the cyclic shear-compression tests and it is able to interpret the performances of panels linking them with limit states resulting from integration of cross-section equilibrium equations. Finally, it was applied a model able to reproduce the hysteretic behavior of masonry and were carried out dynamic analyses using the input data derived from the envelope curves. The data thus collected can be used as database and as input for displacement-based design methods.
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Taghinezhadbilondy, Ramin. "Extending Use of Simple for Dead Load and Continuous for Live Load (SDCL) Steel Bridge System to Seismic Areas." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/2986.
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The steel bridge system referred to as Simple for Dead load and Continuous for Live load (SDCL) has gained popularity in non-seismic areas of the country. Accordingly, it results in many advantages including enhanced service life and lower inspection and maintenance costs as compared to conventional steel systems. To-date, no research studies have been carried out to evaluate the behavior of the SDCL steel bridge system in seismic areas. The main objective of this research was to extend the application of SDCL to seismic areas.
The concept of the SDCL system was developed at the University of Nebraska-Lincoln and a complete summary of the research is provided in five AISC Engineering Journal papers. The SDCL system is providing steel bridges with new horizons and opportunities for developing economical bridge systems, especially in cases for which accelerating the construction process is a priority. The SDCL steel bridge system also provides an attractive alternative for use in seismic areas.
The SDCL concept for seismic areas needed a suitable connection between the girder and pier. In this research, an integral SDCL bridge system was considered for further investigation. The structural behavior and force resistance mechanism of the proposed seismic detail considered through analytical study. The proposed connection evaluated under push-up, push-down, inverse and axial loading to find the sequence of failure modes. The global and local behavior of the system under push-down forces was mainly similar to non-seismic detail. The nonlinear time history analysis indicated that there is a high probability that bottom flange sustains tension forces under seismic events. The finite element model subjected to push-up forces to simulate the response of the system under the vertical component of seismic loads. However, the demand-capacity ratio was low for vertical excitation of seismic loads. Besides finite element results showed that continuity of bottom flange increased ductility and capacity of the system. While the bottom flange was not continuous, tie bars helped the system to increase the ultimate moment capacity. To model the longitudinal effect of earthquake loads, the model subjected under inverse forces as well as axial forces at one end. In this case scenario, dowel bars were most critical elements of the system. Several finite element analyses performed to investigate the role of each component of preliminary and revised detail. All the results demonstrated that continuity of the bottom flange, bolts area (in the preliminary detail), tie bars over the bottom flange (in the revised detail) were not able to provide more moment capacity for the system. The only component increased the moment capacity was dowel bars. In fact, increasing the volume ratio of dowel bars could be able to increase the moment capacity and prevent premature failure of the system.
This project was Phase I of an envisioned effort that culminated in the development of a set of details and associated design provisions to develop a version of the SDCL steel bridge system, suitable for the seismic application. Phase II of this project is an ongoing project and currently the component specimen design and test setup are under consideration. The test specimen is going to be constructed and tested in the structures lab of Florida International University. A cyclic loading will be applied to the specimen to investigate the possible damages and load resistance mechanism. These results will be compared with the analysis results. In the next step, as phase III, a complete bridge with all the components will be constructed in the structures lab at the University of Nevada-Reno. The connection between steel girders will be an SDCL connection and the bridge will be subjected to a shake table test to study the real performance of the connection due to earthquake excitation.
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Tola, Adrian Patricio. "Development of a Comprehensive Linear Response History Analysis Procedure for Seismic Load Analysis." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/36106.
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This thesis reviews the parameters required to perform linear response history analysis according to Chapter 16 of the American Standard ASCE 7-10. A careful analysis is presented about the selection of ground motions using real records and using artificial records generated such that their response spectrum matches with a defined target spectrum; three different techniques are studied for the generation of these artificial records. Also, this document revises the scaling of ground motion techniques in the American Standard ASCE-7 as well as in other seismic codes. It presents a detailed analysis of the variables influencing the scaling of ground motions, and it suggests a new scaling technique for linear response history analysis. The assumptions made establishing the flexibility of the diaphragms are also analyzed as well as dynamic methods to include accidental torsion when doing a linear response history analysis. Other modeling issues such as the orientation of the ground motion axis, scaling of element forces and displacements, orthogonal loading, solution techniques, P-Delta effects, modeling of the basement, and calculation of drifts are also studied in the context of linear response history analysis. The thesis concludes with suggested code language for linear response history analysis intended to be considered in future editions of the American Standard ASCE 7.Master of Science
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Park, Kyungha. "Lateral load patterns for the conceptual seismic design of moment-resisting frame structures." College Park, Md.: University of Maryland, 2007. http://hdl.handle.net/1903/7731.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2007.Thesis research directed by: Dept. of Civil and Environmental Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Kunwar, Sushil. "Comprehensive Evaluation of Composite Core Walls for Low-Seismic Force and Wind Load Applications." University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1613750905724949.
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De, la Harpe Charles William Henry. "The development of a seismic risk reduction procedure for the prioritization of low cost, load bearing masonry buildings." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/97014.
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Thesis (MEng)--Stellenbosch University, 2015.ENGLISH ABSTRACT: The Western Cape is one of the most seismically active regions in South Africa. It features geological properties which can develop earthquakes as large as 6.87 on the Richter scale. This poses a serious threat to all of the buildings that are currently located within this region. A recent study has found that typical three-storey Unreinforced Masonry (URM) buildings in the Cape Town area shows a high probability of failure or damage if subjected to such a large earthquake. Many of these buildings can be found in an area of Cape Town called the Cape Flats, housing approximately 11 000 individuals. The structural integrity of these buildings are of concern to engineers since it houses a number of individuals. The purpose of the study was to develop a risk assessment procedure that could be used to assess low-rise multi-storey (2, 3 and 4 storeys) URM buildings in order to determine where the risk of earthquake related damage would be the highest. The risk assessment procedure compared various characteristics regarding the buildings, residents, seismic attributes of the region and the recovery capability of the residents. The result, in the form of a risk rating, enabled the buildings to be prioritized according to their seismic risk. The aim was to develop a comparative model which could be applied to a range of buildings, indicating where the impact of an earthquake would be greatest. This result could then be used for further remedial action (such as retrofitting) where it is needed the most. The risk assessment procedure used an Earthquake Risk Assessment Model (ERAM) which was specifically developed to assess the earthquake risk of each building with the use of 26 factors. These factors would each be individually scored and through the ERAM model would produce a risk rating. The buildings' can then be ranked (prioritized) according to it's risk rating to determine where remedial actions or procedures are needed first.
AFRIKAANSE OPSOMMING: Die Wes-Kaap is een van die mees seismiese aktiewe streke in Suid-Afrika. Dit bevat geologiese eienskappe wat aardbewings met groottes van 6,87 op die Richterskaal kan laat ontwikkel (1 in 475 jaar herhaal periode). Dit hou 'n bedreiging vir baie die geboue wat tans in hierdie streek geleë is. 'n Onlangse studie het bevind dat tipiese drie-verdieping lasdraende steengeboue in die omgewing van Kaapstad 'n hoë waarskynlikheid van faling of skade toon as dit blootgestel word aan 'n groot aardbewing. Baie van hierdie geboue kan gevind word in 'n gebied van Kaapstad genaamd die Kaapse Vlakte, wat vir ongeveer 11 000 individue behuising bied. Die strukturele integriteit van hierdie geboue is van belang aangesien dit 'n groot aantal individue huisves. Die doel van die studie was om 'n risiko-evaluerings proses te ontwikkel wat gebruik kan word om multi-verdieping (2, 3 en 4 verdiepings) lasdraende steengeboue te evalueer ten opsigte van aardbewing verwante skade. Die risiko-evaluering proses vergelyk verskeie kenmerke van die geboue, die inwoners, seismiese eienskappe van die streek en die vermoë van die inwoners om terug te keer na hul alledaagse leefstyl. Die resultaat is in die vorm van 'n risiko-gradering, wat die gebruiker in staat stel om die geboue te prioritiseer volgens hul aardbewings risiko. Die doel was om 'n vergelykende model te ontwikkel wat toegepas kan word om 'n verskeidenheid van geboue te evalueer, en aan te dui waar die impak van 'n aardbewing die grootste sal wees. Hierdie resultaat kan dan gebruik word vir verdere remediërende optrede of prosedures soos versterkings. Die risiko-evaluerings proses gebruik 'n "Earthquake Risk Assessment Model" (ERAM) wat spesifiek ontwikkel is om die aardbewings-risiko van elke gebou te evalueer met die gebruik van 26 faktore. Hierdie faktore word elkeen individueel beoordeel en 'n risiko-gradering word verkry met behulp van die ERAM model. Die geboue kan dan geprioritiseer word volgens elkeen se risiko-gradering om te bepaal waar daar remediërende optrede nodig is.
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Allington, Christopher James. "Seismic Performance of Moment Resisting Frame Members Produced from Lightweight Aggregate Concrete." Thesis, University of Canterbury. Civil Engineering, 2003. http://hdl.handle.net/10092/1254.
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A total of 47 lightweight aggregate concrete columns were constructed from four different types of lightweight aggregate and provided with different quantities of transverse reinforcement. The specimens were tested under a monotonically increasing level of compressive axial load. The rate of load application was varied from pseudo-static to the rate of dynamic loading expected during a major seismic excitation. The results from the experimental testing of the column members were used to derive a theoretical stress-strain model to predict the behaviour of lightweight aggregate concrete members under imposed loads. The stress-strain model was derived to predict the response of both lightweight aggregate and conventional weight concretes with compressive strengths up to and including 100 MPa. The model was calibrate against the experimental results obtained in this study and previously tested lightweight aggregate and conventional weight concrete columns. A series of pseudo-cyclic moment-curvature analyse were undertaking using the derived stress-strain model, to predict the behaviour of the lightweight aggregate concrete members when subjected to axial load and flexure. The results were compared to the confinement requirements in the potential plastic hinge regions of column elements required by the New Zealand Concrete Structures Standard, NZS3101: 1995. It was determined that the confinement requirements of NZS3101: 1995 were could be used to accurately determine the required quantity of transverse reinforcement for lightweight aggregate concrete members with a concrete density greater than 1700 kg/m3. A total of four lightweight aggregate concrete beam column subassemblies were constructed and tested under reversed cyclic lateral loading. The results from the specimen indicate that cyclic behaviour of the lightweight aggregate concrete was similar to conventional weight concrete. However the bond capacity between the longitudinal reinforcement and the surrounding concrete was weaker than previously tested conventional weight concrete members.
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Wrzesniak, Daniela. "Connection systems in multi storey timber buildings under seismic action." Doctoral thesis, Università degli studi di Trieste, 2014. http://hdl.handle.net/10077/10121.
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2012/2013Timber structures are currently experiencing a significant upturn. Reason for this are their distinct advantages concerning environmental and seismic aspects compared to steel and concrete structures. “Open space” and “multi-story” are no longer attributes which are exclusively used in connection with concrete and steel structures. Key aspects are the connection systems. Finding a high strength and ductile connection solution is especially challenging when seismic loads are considered. Designing a connection which does not undergo damage in a seismic event is another characteristic aimed for. This study presents a numerical investigation on the ductile behaviour of high strength tube type fasteners for post and beam joints. This new type of connection was developed at the University of Delft, the Netherlands. Different types of multi-story frames and a portal frame, made of glulam, were subjected to a set of different ground motion. The conducted incremental dynamic analysis revealed that q-factor of 2.5 and a high q-factor of 3.0 can be applied for portal frames and multi-story timber frames respectively. Although damage to timber parts is mostly avoided, the fasteners have to be replaced after a seismic event. The feasibility and behaviour of a conventional bolted connection for glulam walls subjected to high, seismic loads were experimentally studied. Both, the dynamic tests on timber walls with bolted anchorage and complementary tests on single dowelled connections showed, that brittle failure mechanisms can be delayed by applying simple design rules; such as increased spacing and distances. Utilizing reinforcement, ductile connection behaviour can be achieved. Irreversible damage to both timber and fasteners has to be anticipated when using this connection type. The applicability and response of an innovative viscous type damper in a glue laminated (Glulam) timber wall was numerically and experimentally studied. The high-force-to-volume (HF2V) viscous damper was developed at the University of Canterbury, New Zealand. The interaction between the devices and the flexibility properties of the timber wall and its connecting elements were investigated. The influence of additional weight on the self-centring behaviour of the damping devices was studied. The tests revealed that utilizing the HF2V devices in a timber wall, a damage-free system is achieved. The tests were completed without damage occurring to the dampers, the damper to wall connection and damper to foundation connection. Utilizing these devices result in high-strength, ductile and damage free design solutions for timber structures under seismic loads. The mathematical model which was developed based on the experimental findings can be used to determine the displacement time-history and structural reaction forces for a timber wall with HF2V viscous damping devices. This study contributes to the on-going research on suitable damage avoidance connection systems for multi-story, open plan timber structures under seismic loads. Advantages and disadvantages concerning the behaviour of the different systems under repetitive cyclic loading are highlighted as well as some specific areas that could benefit from further research. The presented results contribute to the understanding of the behaviour of connection systems which have so far not or not sufficiently been studied in timber elements subjected to seismic loading.
XXVI Ciclo
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Doherty, Kevin Thomas. "An investigation of the weak links in the seismic load path of unreinforced masonary buildings /." Title page, table of contents and abstract only, 2000. http://web4.library.adelaide.edu.au/theses/09PH/09phd655.pdf.
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Drivas, Georgios Valdemar. "Cost Evaluation of Seismic Load Resistant Structures Based on the Ductility Classes in Eurocode 8." Thesis, KTH, Betongbyggnad, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-157137.
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Most people do not associate Scandinavia with seismic activity and earthquakes; however, there is in fact seismic activity in the region. Although in comparison with southern Europe the return periods of earthquakes with large magnitudes are quite long, itis critical to consider earthquake impact when designing structures. Earthquake impact is difficult to predict, but building standards provide guidance to safely designstructures based on statistical and empirical data specific to regional conditions andcircumstances. Crucial for the final impact and response of a structure is not only theground acceleration, but also the ground type, which can amplify seismic vibrationsand ultimately cause unfortunate damage to the structural elements. Since 2010 Eurocode 8, the European standards for seismic design has been in effectfor building structures in Norway. The main difference with the application of thestandards in Norway compared to Southern Europe is the choice between elastic andductile design in some cases. Presumably, the same design regulations are applicablefor design of structures in Sweden, because parts of Sweden share similar conditionsas in Norway. This master thesis examines the results of selecting between elastic andductile design based on an arbitrary finite element model, and ultimately, presentsthe differences in cost efficiency in both quantitative and qualitative measures. In the arbitrary structure that is analyzed, the lateral bearing system contains a concrete wall shaft. In order to evaluate profitability, the cost development of reinforcement in the walls, is analyzed based on ground acceleration and ductility class. Thestudy ultimately implies a breaking point when structures in ductility class mediumare more cost efficient than structures in ductility class low and vice versa, with thecondition that the governing lateral force is the seismic vibration and that the normalized axial force is less than 15%Skandinavien förknippas inte i första hand med seismisk aktivitet och jordbävningar.I regionen förekommer seismisk aktivitet, dock är returperioderna för jordbävningarmed stor magnitud förhållandevis lång i relation till södra Europa. Jordbävningslasterär svåra att förutse, men byggnormerna vägleder till säkert utformande och dimensionering mot dess påverkan, baserat på statistiska och empiriska data för regionala förutsättningar och omständigheter. En avgörande faktor för konstruktioners inverkan och respons är inte endast markaccelerationen utan även marktypen som kanförstärka de seismiska vibrationerna och eventuellt orsaka skada på byggnader. I Norge används sedan 2010 de europeiska normerna för jordbävningsdimensionering, Eurokod 8. Den väsentliga skillnaden jämfört med utförandet av konstruktioneri södra Europa är att valet mellan elastiska och duktila utformanden ges i vissa fall.Hypotetiskt kan samma normer användas för dimensionering av byggnader i Sverige,eftersom vissa regioner i Sverige har samma förutsättningar som i Norge. I detta examensarbete undersöks valet mellan elastisk och duktil dimensionering medhjälp av finita element modellering av en godtycklig konstruktion samt en jämförelseav de två fallen som slutligen leder till en analys av kostnadseffektiviteten, både kvantitativt och kvalitativt. Det horisontella bärsystemet i den använda modellen är ett schakt bestående av betongväggar. För att kunna uppskatta lönsamheten analyseras kostnadsutvecklingenav armeringsinnehållet, beroende av markacceleration och duktilitetsklass. Studienhar resulterat i definitionen av en brytpunkt som anger när dimensionering enligtduktilitetsklass medium är effektivare än dimensionering enligt duktilitetsklass lågoch vice versa, under förutsättning att jordbävningslasten är dimensionerande ochden normaliserade axialkraften är lägre än 15%.
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Tubaldi, Enrico. "Probabilistic seismic response and fragility assessment of steel-concrete composite bridges with dual load path." Doctoral thesis, Università Politecnica delle Marche, 2010. http://hdl.handle.net/11566/242260.
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Paparo, Maria Ausilia <1983>. "Evaluation of slope stability under water and seismic load through the Minimum Lithostatic Deviation method." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6602/1/Paparo_Maria_Ausilia_tesi.pdf.
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The main objective of this thesis is to obtain a better understanding of the methods to assess the stability of a slope.
We have illustrated the principal variants of the Limit Equilibrium (LE) method found in literature, focalizing our attention on the Minimum Lithostatic Deviation (MLD) method, developed by Prof. Tinti and his collaborators (e.g. Tinti and Manucci, 2006, 2008).
We had two main goals: the first was to test the MLD method on some real cases. We have selected the case of the Vajont landslide with the objective to reconstruct the conditions that caused the destabilization of Mount Toc, and two sites in the Norwegian margin, where failures has not occurred recently, with the aim to evaluate the present stability state and to assess under which conditions they might be mobilized.
The second goal was to study the stability charts by Taylor and by Michalowski, and to use the MLD method to investigate the correctness and adequacy of this engineering tool.
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Paparo, Maria Ausilia <1983>. "Evaluation of slope stability under water and seismic load through the Minimum Lithostatic Deviation method." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6602/.
Full textAbstract:
The main objective of this thesis is to obtain a better understanding of the methods to assess the stability of a slope.
We have illustrated the principal variants of the Limit Equilibrium (LE) method found in literature, focalizing our attention on the Minimum Lithostatic Deviation (MLD) method, developed by Prof. Tinti and his collaborators (e.g. Tinti and Manucci, 2006, 2008).
We had two main goals: the first was to test the MLD method on some real cases. We have selected the case of the Vajont landslide with the objective to reconstruct the conditions that caused the destabilization of Mount Toc, and two sites in the Norwegian margin, where failures has not occurred recently, with the aim to evaluate the present stability state and to assess under which conditions they might be mobilized.
The second goal was to study the stability charts by Taylor and by Michalowski, and to use the MLD method to investigate the correctness and adequacy of this engineering tool.
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Otten, Zachary David. "Seismic Retrofitting of a Historic Structure with Limited Construction Documentation." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016.
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Many buildings constructed during the middle of the 20th century were constructed with criteria that fall short of current requirements. Although shortcomings are possible in all aspects of the design, the inadequacies in terms of seismic design present a more pressing issue to human life. This risk has been seen in various earthquakes that have struck Italy recently, and subsequently, the codes have been altered to account for this underestimated danger. Structures built after these changes remain at risk and must be retrofitted depending on their use. This report centers around the Giovanni Michelucci Institute of Mathematics at the University of Bologna and the work required to modify the building so that it can withstand 60% of the current design requirements.
The goal of this particular report is to verify the previous reports written in Italian and present an accurate analysis along with intervention suggestions for this particular building. The work began with an investigation into the previous sources and work to find out how the structure had been interpreted. After understanding the building, corrections were made where required, and the failing elements were organized graphically to more easily show where the building needed the most work. Once the critical zones were mapped, remediation techniques were tested on the top floor, and the modeling techniques and effects of the interventions were presented to assist in further work on the structure.
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Sabri, Amirreza. "Seismic Retrofit of Load Bearing URM Walls with Internally Placed Reinforcement and Surface-Bonded FRP Sheets." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/40675.
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Concrete block masonry is a common building material used worldwide, including Canada. Reinforced masonry buildings, designed according to the requirements of recent building codes, may result in seismically safe structures. However, unreinforced masonry (URM) buildings designed and constructed prior to the development of modern seismic design codes are extremely vulnerable to seismic induced damage. Replacement of older seismically deficient buildings with new and seismically designed structures is economically not feasible in most cases. Therefore, seismic retrofitting of deficient buildings remains to be a viable seismic risk mitigation strategy. Masonry load bearing walls are the most important elements of such buildings, potentially serving as lateral force resisting systems.
A seismic retrofit research program is currently underway at the University of Ottawa, consisting of experimental and analytical components for developing new seismic retrofit systems for unreinforced masonry walls. The research project presented in this thesis forms part of the same overall research program. The experimental component includes design, construction, retrofit and testing of large-scale load bearing masonry walls. Two approaches were developed as retrofit methodologies, both involving reinforcing the walls for strength and deformability. The first approach involves the use of ordinary deformed steel reinforcement as internally added reinforcement to attain reinforced masonry behaviour. The second approach involves the use of internally placed post-tensioning tendons to attain prestressed masonry behaviour. The analytical component of research consists of constructing a Finite Element computer model for nonlinear analysis of walls and conducting a parametric study to assess the significance of retrofit design parameters. The results have led to the development of a conceptual retrofit design framework for the new techniques developed, while utilizing the seismic provisions of the National Building Code of Canada and the relevant CSA material standards.
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Acun, Bora. "Energy Based Seismic Performance Assessment Of Reinforced Concrete Columns." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12611728/index.pdf.
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Severe seismic events in urban regions during the last two decades revealed that the structures constructed before the development of modern seismic codes are the most vulnerable to earthquakes. Sub-standard reinforced concrete buildings constitute an important part of this highly vulnerable urban building stock. There is urgent need for the development and improvement of methods for seismic performance assessment of existing reinforced concrete structures.
As an alternative to current conventional force-based assessment methods, a performance evaluation procedure for structural members, mainly reinforced concrete columns is proposed in this study, by using an energy-based approach combined with the low cycle fatigue concept. An energy-based hysteresis model is further introduced for representing the inelastic response of column members under severe seismic excitations. The shape of the hysteresis loops are controlled by the dissipated cumulative energy whereas the ultimate strength is governed by the low cycle fatigue behavior. These two basic characteristics are obtained experimentally from full scale specimens tested under constant and variable amplitude
displacement cycles.
The first phase of the experimental program presented in the study constitutes of testing sub-standard non-conforming column specimens. The second phase of testing was conducted on standard, code compliant reinforced concrete columns. A
total number of 13 specimens were tested. The behavior of these specimens was observed individually and comparatively according to the performance based objectives. The results obtained from the experiments were employed for developing relations between the energy dissipation capacity of specimens, the specimen properties as well as the imposed displacement history. Moreover, the measured rotation capacities at the plastic regions are evaluated comparatively with the limits proposed by modern displacement-based seismic design and assessment provisions.
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Longo, Francesco. "Numerical Modelling of Unreinforced Masonry Infill Walls under Seismic Load Considering In-Plane / Out-Of-Plane Interaction." Doctoral thesis, Università degli studi di Trento, 2016. https://hdl.handle.net/11572/368465.
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Many studies and post-earthquake investigations have recognized that masonry infill walls play a major role in the seismic response of structures. Although their effect may be beneficial in some situations, the walls are also susceptible to high levels of damage, including collapse that can be life-threatening because of the heavy debris. Despite the critical importance of infill walls for life safety, infill walls are often neglected in numerical models and analyses implemented by designers because they are traditionally considered to be non-structural elements. Moreover, the majority of experimental studies and numerical models include only the in-plane behaviour of the panels: indeed, until recently, only sophisticated micro-models incorporated the out-of-plane response of unreinforced masonry infill walls. Recently, however, researchers have started to advance proposals for simplified macro-models that are capable of modelling in-plane/out-of-plane interaction, paving the way for the consideration of the associated issues in design practice. However, very few studies have applied these models to the dynamic seismic response history analysis of realistic structures.
In this context, this thesis focuses on the numerical modelling of unreinforced masonry (URM) infill walls, with particular attention to the combined in-plane/out-of-plane response of panels in reinforced concrete (RC) frame buildings during seismic events.
In the first part of this research, existing studies for URM masonry infill walls are reviewed, with an emphasis on the out-of-plane response of the panels. Significant experimental tests, modeling strategies and post-earthquake surveys are presented, stressing the parameters that influence the behaviour of the infills. An in-depth description is dedicated to the infill wall macro-model that is adopted for the analyses performed in this work, emphasizing its capabilities and limitations. This model consists of a single diagonal formed by two beam elements representing the wall; lumped modal mass is concentrated at the midpoint node of the diagonal. In-plane axial force and out-of-plane bending of the equivalent element interact by means of two fibre sections located adjacent to the central node. User defined domains limit axial/bending strengths and in-plane/out-of-plane ultimate displacements of the wall. When the response of an element exceeds these domains, the model simulates the collapse of this infill wall by removing it from the analysis.
Next, the numerical model is calibrated in the OpenSees software framework by comparing existing experimental results with numerical outputs. The laboratory tests comprise in-plane cyclic and out-of-plane quasi-static results on 1-bay and 1-storey frame specimens with two different types of clay URM infill walls that are frequently found in Italian and other Mediterranean countries. The calibrated model is then applied to the static pushover analysis of a set of planar frames, while the wall elements are simultaneously loaded in both orthogonal directions.
The nucleus of present study is the application of the calibrated model to the dynamic response history analysis of planar RC frames. Frame dimensions, number of stories, design and infill configurations are selected to be representative of the Italian building stock. Acceleration time histories consist of a suite of a bidirectional ground motions that are scaled to be compatible with Eurocode 8 elastic spectra. Cracking and collapse of the infill walls are monitored during the analysis. The infill walls reach their ultimate displacement capacity by a combination of in-plane and out-of-plane displacements, with the out-of-plane component usually playing the dominant role. The intensity of seismic load that is required to fail the infill walls, as well as the patterns of failure, are shown to be consistent with observed damage to URM infill walls in similar buildings during recent earthquakes.
This research suggests that simplified macro-elements are suitable for design-oriented models of URM infill walls in RC framed structures, capturing the critical interaction between in-plane and out-of-plane response of the infill walls but without making the models excessively complex.