The self-centering energy dissipative (SCED) brace is an innovative cross-bracing system that eliminates residual building deformations after seismic events and prevents the progressive drifting that other inelastic systems are prone to experience under long-duration ground motions. This research improves upon the design and use of SCED braces through three large-scale experimental studies and an associated numerical building model study. The first experimental study increased the strength capacity of SCED braces and refined the design procedure through the design and testing of a new high-capacity full-scale SCED brace. This brace exhibited full self-centering behaviour and did not show significant degradation of response after multiple earthquake loadings. The second experimental study extended the elongation capacity of SCED braces through the design and testing of a new telescoping SCED (T-SCED) brace that provided self-centering behaviour over a deformation range that was two times the range that was achieved by the original SCED bracing system. It exhibited full self-centering in a single storey full-scale frame that was laterally deformed to 4% of its storey height. The third experimental study confirmed the dynamic behaviour of a multi-storey SCED-frame in different seismic environments and confirmed the ability of computer models of differing complexity to accurately predict the seismic response. To achieve these goals, a three-storey SCED-braced frame was designed, constructed, and tested on a shake table. Lastly, a numerical six-storey SCED-braced building model was constructed. This model used realistic brace properties that were determined using a new software tool that simulates the full detailed mechanics of SCED and T-SCED braces. The building model showed that initial SCED brace stiffness does not have a significant effect on SCED frame behaviour, that T-SCEDs generally perform better than traditional SCEDs, and that the addition of viscous dampers in parallel with SCED braces can significantly reduce drifts and accelerations while only causing a small increase in the base shear.

Substructure hybrid simulation has been actively investigated in recent years. The simulation method allows for the assessment of seismic performance of structures by representing critical components with physical specimens and the rest of the structure with numerical models. In this study the system level performance of a six-storey structure with self-centering energy dissipative (SCED) braces was validated through pseudo dynamic (PsD) hybrid simulation. Fragility curves are derived for the SCED system. The study presents the configuration of the hybrid simulation and discusses some of the practical intricacies in performing PsD hybrid simulations. In addition the study addresses some of the challenges associated with the substructuring process during a hybrid simulation. Two techniques, extensive analytical study and model updation, are discussed to improve the response from the hybrid simulation accounting for the variation in global response of a structural system depending on which structural element was represented as a physical specimen.

The self-centering energy dissipative (SCED) brace is an innovative cross-bracing system that eliminates residual building deformations after seismic events and prevents the progressive drifting that other inelastic systems are prone to experience under long-duration ground motions. This research improves upon the design and use of SCED braces through three large-scale experimental studies and an associated numerical building model study. The first experimental study increased the strength capacity of SCED braces and refined the design procedure through the design and testing of a new high-capacity full-scale SCED brace. This brace exhibited full self-centering behaviour and did not show significant degradation of response after multiple earthquake loadings. The second experimental study extended the elongation capacity of SCED braces through the design and testing of a new telescoping SCED (T-SCED) brace that provided self-centering behaviour over a deformation range that was two times the range that was achieved by the original SCED bracing system. It exhibited full self-centering in a single storey full-scale frame that was laterally deformed to 4% of its storey height. The third experimental study confirmed the dynamic behaviour of a multi-storey SCED-frame in different seismic environments and confirmed the ability of computer models of differing complexity to accurately predict the seismic response. To achieve these goals, a three-storey SCED-braced frame was designed, constructed, and tested on a shake table. Lastly, a numerical six-storey SCED-braced building model was constructed. This model used realistic brace properties that were determined using a new software tool that simulates the full detailed mechanics of SCED and T-SCED braces. The building model showed that initial SCED brace stiffness does not have a significant effect on SCED frame behaviour, that T-SCEDs generally perform better than traditional SCEDs, and that the addition of viscous dampers in parallel with SCED braces can significantly reduce drifts and accelerations while only causing a small increase in the base shear.

Substructure hybrid simulation has been actively investigated in recent years. The simulation method allows for the assessment of seismic performance of structures by representing critical components with physical specimens and the rest of the structure with numerical models. In this study the system level performance of a six-storey structure with self-centering energy dissipative (SCED) braces was validated through pseudo dynamic (PsD) hybrid simulation. Fragility curves are derived for the SCED system. The study presents the configuration of the hybrid simulation and discusses some of the practical intricacies in performing PsD hybrid simulations. In addition the study addresses some of the challenges associated with the substructuring process during a hybrid simulation. Two techniques, extensive analytical study and model updation, are discussed to improve the response from the hybrid simulation accounting for the variation in global response of a structural system depending on which structural element was represented as a physical specimen.

The structural damage after the Christchurch earthquake (2011) led to extensively damaged facilities that did not collapse but did require demolition, representing more than 70% of the building stock in the central business district. These severe economic losses that result from conventional seismic design clearly show the importance of moving towards resilience-based design approaches of structures. For instance, special reinforced masonry shear walls (SRMWs), which are fixed-base walls, are typically designed to dissipate energy through the yielding of bonded reinforcement while special detailing is maintained to fulfill ductility requirements. This comes at the expense of accepting residual drifts and permanent damage in potential plastic hinge zones. This design process hinders the overall resilience of such walls because of the costs and time associated with the loss of operation and service shutdown. In controlled rocking systems, an elastic gap opening mechanism (i.e., rocking joint) replaces the typical yielding of the main reinforcement in conventional fixed-base walls, hence reducing wall lateral stiffness without excessive yielding damage. Consequently, controlled rocking wall systems with limited damage and self-centering behavior under the control of unbonded post-tensioning (PT) are considered favorable for modern resilient cities because of the costs associated with service shutdown (i.e., for structural repairs or replacement) are minimized. However, the difficulty of PT implementation during construction is challenging in practical masonry applications. In addition, PT losses due to PT yielding and early strength degradation of masonry reduce the self-centering ability of controlled rocking masonry walls with unbonded post-tensioning (PT-CRMWs). Such challenges demonstrate the importance of considering an alternative source of self-centering. In this regard, the current study initially evaluates the seismic performance of PT-CRMWs compared to SRMWs. Next, a new controlled rocking system for masonry walls is proposed, namely Energy Dissipation-Controlled Rocking Masonry Walls (ED-CRMWs), which are designed to self-center through vertical gravity loads only, without the use of PT tendons. To control the rocking response, supplemental energy dissipation (ED) devices are included. This proposed system is evaluated experimentally in two phases. In Phase I of the experimental program, the focus is to ensure that the intended behavior of ED-CRMWs is achieved. This is followed by design guidance, validated through collapse risk analysis of a series of 20 ED-CRMW archetypes. Finally, Phase II of the experimental program evaluates a more resilient ED-CRMW is evaluated, which incorporates a readily replaceable externally mounted flexural arm ED device. Design guidance is also provided for ED-CRMWs incorporating such devices. / Thesis / Doctor of Philosophy (PhD)

M.A.Sc. Thesis / Most conventional seismic design intends for key structural members to yield in order to limit seismic forces, leading to structural damage after a major earthquake. To minimize this structural damage, self-centering systems are being developed. But how to estimate the peak seismic displacement of a self-centering system remains a problem for practical design. This thesis addresses this need by presenting a parametric study on the seismic displacement demands of single-degree-of-freedom (SDOF) systems with flag-shaped hysteresis considering 13,440,000 nonlinear time history analyses. Ground motion records that represent seismic hazards in active seismic regions with stiff soil and rock site conditions are used. The influences of the four independent parameters that define a flag-shaped hysteresis are presented in terms of median displacement ratios, facilitating the design-level estimation of nonlinear displacement demands on self-centering systems from the spectra displacements of elastic systems. The influence of initial period on self-centering systems is similar to its influence on traditional systems with elastoplastic hysteresis, but a much lower linear limit can be adopted for self-centering systems while achieving acceptable peak displacements. Supplemental energy dissipation suppresses the peak displacement but additional energy dissipation becomes less effective as more is added. The effect of nonlinear stiffness is small as long as it is positive and close to zero, but a negative nonlinear stiffness can lead to unstable response. Self-centering systems located on rock sites usually have smaller displacement demands than those on stiff soil sites. When the damping ratio is increased or decreased, the displacement ratios do not necessarily decrease or increase consistently. A tangent stiffness proportional damping model is considered, leading to a significant increase in displacement demands but similar overall trends. Based on the observations, regression analysis is used to develop a simplified equation that approximates the median inelastic displacement ratios of self-centering systems for design. / Thesis / Master of Applied Science (MASc)

This paper investigates the development, design and modeling of a human spine-inspired seismic lateral force resisting system. The overall goal is to create a design for a lateral force resisting system that reflects human spine behavior that is both practical and effective. The first phase of this project involved a literature review of the human spine and rocking structural systems. The goal of this phase was to identify concepts from the spine that could be transferred to a lateral force resisting system. The second phase involved creating a 3-dimensional model of the lumbar region of the spine in SAP2000 and using it to examine concepts that could be transferred to a lateral force resisting system. The third phase consisted of creating possible system designs using concepts and principles identified through phases one and two and identifying a final system design. The last phase involved modeling the final lateral force resisting system design in SAP2000, validating the model and testing the design's effectiveness. This paper shows that this system is a viable option to prevent permanent structural damage in buildings during a seismic event. / Master of Science

No description available.

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第14565号 / 工博第3033号 / 新制||工||1452(附属図書館) / 26917 / UT51-2009-D277 / 京都大学大学院工学研究科建築学専攻 / (主査)教授 井上 一朗, 教授 田中 仁史, 教授 西山 峰広 / 学位規則第4条第1項該当

No description available.