Pushover analysis involves certain approximations and simplifications that some amount of variation is always expected to exist in seismic demand prediction of pushover analysis. In literature, some improved pushover procedures have been proposed to overcome the certain limitations of traditional pushover procedures. The effects and the accuracy of invariant lateral load patterns utilised in pushover analysis to predict the behavior imposed on the structure due to randomly selected individual ground motions causing elastic and various levels of nonlinear response were evaluated in this study. For this purpose, pushover analyses using various invariant lateral load patterns and Modal Pushover Analysis were performed on reinforced concrete and steel moment resisting frames covering a broad range of fundamental periods. Certain response parameters predicted by each pushover procedure were compared with the &#039 / exact&#039 / results obtained from nonlinear dynamic analysis. The primary observations from the study showed that the accuracy of the pushover results depends strongly on the load path, properties of the structure and the characteristics of the ground motion. Pushover analyses were performed by both DRAIN-2DX and SAP2000. Similar pushover results were obtained from the two different softwares employed in the study provided that similar approach is used in modeling the nonlinear properties of members as well as their structural features. The accuracy of approximate procedures utilised to estimate target displacement was also studied on frame structures. The accuracy of the predictions was observed to depend on the approximations involved in the theory of the procedures, structural properties and ground motion characteristics.

This thesis investigates the torsional performance of steel structures with and without rigid diaphragm constraints through numerical simulations and evaluates the appropriateness of relevant design provisions in current seismic design codes. In the first part of the work, six theme structures with different (1) in-plane stiffness of diaphragm, and (2) horizontal configurations of vertical braced frames were designed and their performance evaluated through both nonlinear static and dynamic analyses. Comparisons of the analytical results between the structures with and without rigid diaphragm constraints indicate that the in-plane rigidity of the diaphragms affects the efficiency of in-plane force transfer mechanisms, resulting in different global ductility and strength demands. Rigid diaphragm structures exhibit higher global strengths as well as higher torsional rotation capacity because of the infinite in-plane stiffness of the diaphragm. Semi-rigid diaphragm structures have higher ductility demands due to the finite in-plane diaphragm stiffness. The inclusion of bi-axial forces in the analyses reduces the structural strength and increases the ductility demands on the peripheral frames. The axial forces in the collectors and chords that make up the diaphragm depend on (1) the sequence of brace buckling and (2) vertical configuration of the braced frames. The results show higher axial forces in collectors in the roof diaphragms, and higher chord axial forces in the third floor diaphragms. The shear connections in the beams that make up both the collectors and chords are susceptible to failure due to the significant increment of axial forces in those members. The conventional beam analogy used in design can severely underestimate the axial forces in chords and collectors when the structures step into the inelastic stage. / Ph. D.

The main objective of this investigation is to examine how various material properties, governed by code specification, affect the seismic response of a twelve- story reinforced concrete building. This study incorporates the pushover and response history analysis to examine how varying steel yield strength (Fy), 28 day nominal compressive concrete strength (f’c), modes, and ground motions may affect the base shear capacity and displacements of a reinforced concrete structure. Different steel and concrete strengths were found to have minimal impact on the initial stiffness of the structure. However, during the post-yielding phase, higher steel and concrete compressive strengths resulted in larger base shear capacities of up to 22%. The base shear capacity geometric median increased as f’c or Fy increased, and the base shear capacity dispersion measure decreased as f’c or Fy increased. Higher mode results were neglected in this study due to non-convergent pushover analyses results. According to the response history analysis, larger yield and concrete compressive strengths result in lower roof displacement. The difference in roof displacement was less than 12% throughout. This displays the robustness of both analysis methods because material properties have insignificant impact on seismic response. Therefore, acceptable yield and compressive strengths governed by seismic code will result in acceptable building performance.

Nonlinear response history analysis is accepted as the most accurate analytical tool for seismic response determination. However, accurate estimation of displacement responses using conceptually simple, approximate analysis procedures is preferable, since there are shortcomings in the application of nonlinear response history analysis resulting from its complexity. An equivalent linearization procedure, which utilizes the familiar response spectrum analysis as the analysis tool and benefits from the capacity principles, is developed in this thesis study as an approximate method for predicting the inelastic seismic displacement response of MDOF systems under earthquake excitations. The procedure mainly consists of the construction of an equivalent linear system by reducing the stiffness of structural members which are expected to respond in the inelastic range. Different from similar studies in literature, equivalent damping is not explicitly employed in this study. Instead, predetermined spectral displacement demands are utilized in each mode of the equivalent linear system for the determination of global displacement demands. Response predictions of the equivalent linearization procedure are comparatively evaluated by using the benchmark nonlinear response history analysis results and other approximate methods including conventional pushover analysis and modal pushover analysis (MPA). It is observed that the proposed procedure results in similar accuracy with approximate methods which employ nonlinear analysis. Considering the conceptual simplicity of the procedure and the conventional analysis tools used in its application, presented equivalent linearization procedure can be suggested as a practically applicable method for the prediction of inelastic seismic displacement response parameters with sufficient accuracy.

Dans le cadre de l'analyse et de la gestion intégrée des risques sismiques, deux approches sont proposées. La première, une méthode pseudo - adaptative de réponse modale (PSA), qui estime la réponse sismique des bâtiments à portiques, avec une précision acceptable et un temps de calcul et d'analyse réduit. En effet, dans le cadre de l'analyse de pushover multimodale (MPA), la courbe de capacité se construit sur la base d'une approche énergétique et le changement des propriétés modales après plastification est évalué à partir des vecteurs de déplacement pendant l'analyse de pushover. L'estimation des réponses en termes de déplacements absolus et relatifs, forces de cisaillement et rotations est satisfaisante comparativement aux résultats d'analyses non linéaires complètes. La seconde approche porte sur l'évaluation post-sismique des dommages structuraux à partir de dommages locaux observés. Elle est fondée sur une relation postulée entre le dommage et la probabilité résiduelle de ruine, à deux niveaux : l'étage et le bâtiment complet. Quatre portiques sont analysés et les résultats sont comparés à une approche mécanique qui estime l'endommagement du système à partir de la perte de raideur de la courbe de capacité. Les résultats obtenus montrent de bonnes estimations du niveau de dommage global. Ainsi, cette approche pourrait bien faire partie d'un outil d'aide à la décision dans le cadre des programmes d'évaluation urbaine des dommages qui requièrent des estimations simultanément rapides et précises / Within the overall framework of seismic risk analysis and management two approaches are presented. First, the Pseudo-Adaptive Uncoupled Modal Response Analysis (PSA) aims to provide improved estimates of seismic response for framed buildings, with an acceptable accuracy and a reduced calculation time duration. It relies on an energy-based equivalent displacement to develop the capacity curve and a pseudo-adaptive feature that considers changes in modal shapes after yielding, within the framework of the widely used Modal Pushover Analysis. According to the results, PSA is able to provide good estimates of structural responses such as displacements, storey drifts, shear forces and rotations, in comparison to a complete Nonlinear Time History Analysis. Second, a strategy for post-seismic evaluation of structural global damage is proposed on the basis of observed local damages and the postulation of adequate relationships between damage and residual probability of failure at two levels: a storey level prior to a building level. Three factors are proposed to reflect the influence of components damage at each of those levels. The obtained results appear as good predictions of the global damage. Accordingly, this strategy has the potential for being a first step within the implementation framework of a decision-making tool for rapid and accurate estimates of structural damages

Taiwan is located in a highly seismic zone and the historical “Dieh-Dou” timber buildings, constructed without following any code or standard, are prone to collapse under earthquake. These buildings are unique and represent the culture, heritage and art of Taiwan, therefore need to be preserved while minimizing unnecessary intervention that could damage their authenticity. <br /> This research comprises a thorough investigation on the parameters influencing the seismic vulnerability of the Dieh-Dou timber frames in Taiwan, and propose a methodology of assessment and a strategy for strengthening validated through experimental testing and numerical analysis. <br /> After review existing literature and post-earthquake surveys, the failure modes of the buildings are identified, showing that the dislocation of the elements of the frame from the joints is the primary source of damage. An experimental investigation is carried out comprising both rotational and translational tests on full scale joint specimens which, together with a parametric study undertaken with an appropriate FE simulation, demonstrates how both the rotational and translational stiffness of the joints play a key role in defining the behaviour of these structures. <br /> Lateral force, response spectrum, and step-by-step pushover analyses are performed and compared with the post-earthquake survey of two Dieh-Dou buildings seriously affected by the 1999 Chi-Chi earthquake. The results show that the proposed FE modelling can successfully be employed to assess the vulnerability of the frames. <br /> Based on a damage level approach, an assessment methodology is suggested that would allow to optimisation of the strengthening strategy, permitting protection these precious structures from future earthquakes while avoiding unnecessary interventions.

Contemporary approach performance based engineering generally relies on the approximate procedures that are based on the use of capacity curve derived from pushover analysis. The most important parameter in the displacement-based approach is the inelastic displacement demand computed under a given seismic effect and the most common procedures employed for this estimation / the Capacity Spectrum Method and the Displacement Coefficient Method are based on bi-linearization of the capacity curve. Although there are some recommendations for this approximation, there is a vital need for rational guidelines towards the selection of the most appropriate method among several alternatives. A comprehensive research has been undertaken to evaluate the influence of several existing alternatives used for approximating the capacity curve on seismic demands. A number of frames were analyzed under a set of 100 ground motions employing OpenSees. In addition, the pushover curves obtained from nonlinear static analyses were approximated using several alternatives and the resulting curves were assigned as the force-deformation relationships of corresponding equivalent single-degree-of-freedom systems. These simplified systems were later analyzed to compute the approximate seismic response parameters. Using the results of the complex and simplified analyses, the performance of each approximation method was evaluated in estimating the &amp / #8216 / exact&amp / #8217 / inelastic deformations of the multi-degree-of-freedom systems at various degrees of inelasticity. Dependency of the errors on ductility, strength reduction factor and period was also investigated. The interpretations made and the conclusions drawn in this study is believed to clarify the rationality and accuracy of selecting the appropriate idealization of the capacity curve.

Nonlinear response history analysis is considered as the most accurate analytical tool for estimating seismic response. However, there are several shortcomings in the application of nonlinear response history analysis, resulting from its complexity. Accordingly, simpler approximate nonlinear analysis procedures are preferred in practice. These procedures are called nonlinear static analysis or pushover analysis in general. The recently developed Generalized Pushover Analysis (GPA) is one of them. In this thesis study, GPA is presented and evaluated comparatively with the nonlinear time history analysis and modal pushover analysis. A generalized pushover analysis procedure was developed for estimating the inelastic seismic response of structures under earthquake ground excitations (Sucuoglu and G&uuml / nay, 2011). In this procedure, different load vectors are applied separately to the structure in the incremental form until the predefined seismic demand is obtained for each force vector. These force vectors are named as generalized force vectors. A generalized force vector is a combination of modal forces, and simulates the instantaneous force distribution on the system when a given response parameter reaches its maximum value during the dynamic response. In this method, the maximum interstory drift parameters are selected as target demand parameters and used for the derivation of generalized force vectors. The maximum value of any other response parameter is then obtained from the analysis results of each generalized force vector. In this way, this procedure does do not suffer from the statistical combination of inelastic modal responses. It is further shown in this study that the results obtained by using the mean spectrum of a set of ground motions are almost identical to the mean of the results obtained from separate generalized pushover analyses under each ground motion in the set. These results are also very close to the mean results of nonlinear response history analyses. A practical implementation of the proposed generalized pushover analysis is also developed in this thesis study where the number of pushovers is reduced in view of the number of significant modes contributing to seismic response. It has been demonstrated that the reduced generalized pushover analysis is equally successful in estimating maximum member deformations and member forces as the full GPA under a ground excitation, and sufficiently accurate with reference to nonlinear response history analysis.

Nonlinear response history analysis is regarded as the most accurate analysis procedure for estimating seismic response. Approximate analysis procedures are also available for the determination of seismic response and they are preferred over nonlinear response history analysis since much less computational effort is required and good response prediction is achieved by employing rather simple concepts. A generalized pushover analysis procedure is developed in this thesis study as an approximate analysis tool for estimating the inelastic seismic response of structures under earthquake ground excitations. The procedure consists of applying generalized force vectors to the structure in an incremental form until a prescribed target interstory drift demand is achieved. Corresponding generalized force vectors are derived according to this target drift parameter and include the contribution of all modes. Unlike many approximate analysis procedures, response of the structure is directly obtained from generalized pushover analysis results without employing a modal combination rule, eliminating the errors cultivating from these methods. Compared to nonlinear response history analysis, generalized pushover analysis is less demanding in computational effort and its implementation is simpler relative to other approximate analysis procedures. It is observed that the proposed analysis procedure yields results accurately in comparison to the other nonlinear pushover analysis methods. Accordingly it can be suggested as a convenient and sound analysis tool.

SOFTWARE DEVELOPMENT FOR R/C BUILDING VULNERABILITY INDEX AND MEMBER IMPORTANCE CALCULATION Turkey has many active faults which have the potential to generate large earthquakes. Recent earthquakes showed that the buildings in Turkey are not well designed and vulnerable to earthquakes. Previous studies on the subject showed that many structures in Turkey need to be strengthened before the next major earthquake to minimize property loss and casualties. A number of fast and approximate (mostly empirical) methods have been developed in the past to process large building stock. However, there are some important and special structures that do not fit with the general building stock and needs special consideration (e.g., disaster management center, governmental buildings, hospitals, tall structures, etc.). This study targets to evaluate those important and special structures in a detailed, fast, and correct manner. The developed software, which constitutes an important part of this study, does process the building information several times to determine member-based importance factors. The vulnerability index of the building will be determined using the importance of each load-carrying member and how much each member is forced with respect to its capacity. In order to augment user perception, a functional graphical user-interface is designed. Software is equipped with modules that generate input files for SAP2000 analysis program, conduct dynamic and static analysis automatically, and postprocess the generated analysis results which enable the engineer to make a decision on the vulnerability of the structure. Program is written in C++, using object-oriented programming technique. The main difference between this and similar studies is the generator program which automatically generates 3D-FE models and post-processes nonlinear analysis results for an effective decision mechanism. In this way, more realistic results can be obtained much faster. As future studies, new routines are planned to be implemented to the graphical user interface of the program which will suggest smart and engineered retrofit/strengthening alternatives to the user.