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Quantitative and qualitative assessment of the seismic risk to highway bridges is crucial in pre-earthquake planning, and post-earthquake response of transportation systems. Such assessments provide valuable knowledge about a number of principal effects of earthquakes such as traffic disruption of the overall highway system, impact on the regions' economy and post-earthquake response and recovery, and more recently serve as measures to quantify resilience. Unlike previous work, this study captures unique bridge design attributes specific to California bridge classes along with their evolution over three significant design eras, separated by the historic 1971 San Fernando and 1989 Loma Prieta earthquakes (these events affected changes in bridge seismic design philosophy). This research developed next-generation fragility curves for four multispan concrete bridge classes by synthesizing new knowledge and emerging modeling capabilities, and by closely coordinating new and ongoing national research initiatives with expertise from bridge designers. A multi-phase framework was developed for generating fragility curves, which provides decision makers with essential tools for emergency response, design, planning, policy support, and maximizing investments in bridge retrofit. This framework encompasses generational changes in bridge design and construction details. Parameterized high-fidelity three-dimensional nonlinear analytical models are developed for the portfolios of bridge classes within different design eras. These models incorporate a wide range of geometric and material uncertainties, and their responses are characterized under seismic loadings. Fragility curves were then developed considering the vulnerability of multiple components and thereby help to quantify the performance of highway bridge networks and to study the impact of seismic design principles on the performance within a bridge class. This not only leads to the development of fragility relations that are unique and better suited for bridges in California, but also leads to the creation of better bridge classes and sub-bins that have more consistent performance characteristics than those currently provided by the National Bridge Inventory. Another important feature of this research is associated with the development of damage state definitions and grouping of bridge components in a way that they have similar consequences in terms of repair and traffic implications following a seismic event. These definitions are in alignment with the California Department of Transportation's design and operational experience, thereby enabling better performance assessment, emergency response, and management in the aftermath of a seismic event. The fragility curves developed as a part of this research will be employed in ShakeCast, a web-based post-earthquake situational awareness application that automatically retrieves earthquake shaking data and generates potential damage assessment notifications for emergency managers and responders. / Errata added at request of advisor and approved by Graduate Office, March 15 2016.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: In regions of moderate seismicity it has been shown that a suitable structural system is created when designing the shear wall with a plastic hinge zone at the lower part of the wall, with the shear walls resisting lateral loads and all other structural elements designed to resist gravity loads. A suitably stiff foundation is required for the assumption of plastic hinge zones to hold true. This foundation should have limited rotation and should remain elastic when lateral loads are applied to the structure. Ensuring a foundation with a greater capacity than the shear wall results in excessively large shear wall foundations being required in areas of moderate seismicity for buildings with no basement level. This study aims to investigate the feasibility of reducing the size of shear wall foundations in areas of moderate seismicity for buildings with no basement level. The investigation is aimed at allowing shear wall foundation rocking and taking into account the contribution of structural frames to the lateral stiffness of the structure. An example building was chosen to investigate this possibility. Firstly, lateral force-displacement capacities were determined for a shear wall and an internal reinforced concrete frame of this investigated building. Nonlinear momentrotation behaviour was determined for the wall foundation size that would traditionally be required as well as for six other smaller foundations. The above capacity curves against lateral loads were then used to compile a simplified model of the structural systems assumed to contribute to the lateral stiffness of the building. This simplified model therefore combined the effect of the shear wall, internal frame and wall foundation. Nonlinear time-history analyses were performed on this simplified model to investigate the dynamic response of the structure with different wall foundation sizes. By assessing response results on a global and local scale, it was observed that significantly smaller shear wall foundations are possible when allowing foundation rocking and taking into account the contribution of other structural elements to the lateral stiffness of the building. / AFRIKAANSE OPSOMMING: Daar is reeds getoon dat ʼn voldoende strukturele sisteem verkry word in gebiede van gematigde seismiese risiko indien ʼn skuifmuur ontwerp word met ʼn plastiese skarnier sone naby die ondersteuning van die muur. Skuifmure word dan ontwerp om weerstand te bied teen laterale kragte met alle ander strukturele elemente ontwerp om gravitasie kragte te weerstaan. Vir die aanname van plastiese skarnier sones om geldig te wees word ʼn fondasie met voldoende styfheid benodig. Só ʼn fondasie moet beperkte rotasie toelaat en moet elasties bly wanneer laterale kragte aan die struktuur aangewend word. ʼn Fondasie met ʼn groter kapasiteit as dié van die skuifmuur lei daartoe dat uitermate groot fondasies benodig word in gebiede van gematigde seismiese risiko vir geboue met geen kelder vlak. Hierdie studie is daarop gemik om die moontlikheid van kleiner skuifmuur fondasies te ondersoek vir geboue met geen kelder vlak in gebiede van gematigde seismiese risiko. Die ondersoek het ten doel om skuifmuur fondasie wieg aksie toe te laat en die bydrae van strukturele rame tot die laterale styfheid van die struktuur in ag te neem. Eerstens is die laterale krag-verplasing kapasiteit van ʼn skuifmuur en ʼn interne gewapende beton raam van die gekose gebou bepaal. Nie-lineêre moment-rotasie gedrag is bepaal vir die skuifmuur fondasie grootte wat tradisioneel benodig sou word asook vir ses ander kleiner fondasie grotes. Die bogenoemde kapasiteit kurwes is gebruik om ʼn vereenvoudigde model van die strukturele sisteme wat aanvaar word om laterale styfheid tot die gebou te verleen, op te stel. Hierdie vereenvoudigde model kombineer gevolglik die effek van die skuifmuur, interne raam en skuifmuur fondasie. Nie-lineêre tydgeskiedenis analises is uitgevoer op die vereenvoudigde model ten einde die dinamiese reaksie van die struktuur te ondersoek vir verskillende fondasie grotes. Resultate is beoordeel op ʼn globale en lokale vlak. Daar is waargeneem dat aansienlik kleiner skuifmuur fondasies moontlik is deur wieg aksie van die fondasie toe te laat en die bydrae van ander strukturele elemente tot die laterale styfheid van die gebou in ag te neem.

Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: South Africa has some regions which are susceptible to moderate seismic activity. A peak ground acceleration of between 0.1g and 0.15g can be expected in the southern parts of the Western Cape. Unreinforced Masonry (URM) is commonly used as a construction material for 2 to 4 storey buildings in underprivileged areas in and around Cape Town. URM is typically regarded as the material most vulnerable to damage when subjected to earthquake excitation. In this study, a three-storey URM building was analysed by applying seven earthquake time-histories, that can be expected to occur in South Africa, to a finite element model. Experimental data was used to calibrate the in- and out-of-plane stiffness of the URM. A linear modal dynamic analysis and non-linear implicit dynamic analysis were performed. The results indicated that tensile cracking of the in-plane piers was the dominant failure mode. The building relied on the postcracking capacity to resist the 0.15g magnitude earthquake. It is concluded that URM buildings of this type are at risk of failure especially if sufficient ductility is not provided. The results also showed that connection failure must be investigated further. Construction and material quality will have a large effect on the ability of typical URM buildings to withstand moderate magnitude earthquakes in South Africa. / AFRIKAANSE OPSOMMING: Sekere gebiede in Suid-Afrika het ’n risiko van matige seismiese aktiwiteit. Aardbewings met maksimum grondversnellings van tussen 0.1g en 0.15g kan in die suidelike gedeeltes van die Wes- Kaap voorkom. Twee- tot vier-verdieping onbewapende messelwerkgeboue kom algemeen voor in die lae sosio-ekonomiese gebiede van Kaapstad. Oor die algemeen word onbewapende messelwerkgeboue as die gebou-tipe beskou wat die maklikste skade opdoen tydens aardbewings. In hierdie studie is sewe aardbewings, wat tipies in Kaapstad verwag kan word, identifiseer en gebruik om ’n tipiese drie-verdieping onbewapende messelwerkgebou te analiseer. Eksperimentele data is gebruik om die materiaaleienskappe in die in-vlak asook uit-vlak rigtings te kalibreer. Beide ’n liniêre modale en nie-liniˆere implisiete dinamiese analises is uitgevoer. Die resultate dui daarop dat die dominante falingsmode die kraak van in-vlak messelwerk-tussenkolomme is. Die gebou moes sy plastiese kapasiteit benut om die 0.15g aardbewing te kan weerstaan. Die gevolgtrekking is dat dié tipe onbewapende messelwerkgeboue ’n risiko inhou om mee te gee, veral as genoegsame vervormbaarheid nie verskaf word nie. Die resultate toon ook dat konneksie-faling verder ondersoek moet word. Kwaliteit van vakmanskap en van materiaal het ’n groot invoed op die vermoë van onbewapende messelwerkgeboue om aardbewings van matige intensiteit in Suid-Afrika te weerstaan.

Past earthquake events have shown that seismic damage to electrical power systems in commercial buildings, hospitals, and other systems such as public service facilities can cause serious economic losses as well as operational problems. A methodology for evaluation of the seismic vulnerability of electrical power systems is needed and all essential components of the system must be included. A key system component is the switchboard cabinet which houses many different elements which control and monitor electrical power usage and distribution within a building. Switchboard cabinets vary in size and complexity and are manufactured by a number of different suppliers; a typical cabinet design was chosen for detailed evaluation in this investigation. This study presents a comprehensive framework for the evaluation of the seismic performance of electrical switchboard cabinets. This framework begins with the introduction and description of the essential equipment in building electrical power systems and explains possible seismic damage to this equipment. The shortcomings of previous studies are highlighted and advanced finite element models are developed to aid in their vulnerability estimation. Unlike previous research in this area, this study proposes practical, computationally efficient, and versatile numerical models, which can capture the critical nonlinear behavior of switchboard cabinets subjected to seismic excitations. A major goal of the current study was the development of nonlinear numerical models that can accommodate various support boundary conditions ranging from fixed, elasto-plastic to free. Using both linear and nonlinear dynamic analyses, this study presents an enhanced evaluation of the seismic behavior of switchboard cabinets. First the dynamic characteristics of switchboard cabinets are determined and then their seismic performance is assessed through nonlinear time history analysis using an expanded suite of ground motions. The seismic responses and associated ground motions are described and analyzed using probabilistic seismic demand models (PSDMs). Based on the PSDMs, the effectiveness and practicality of common intensity measures are discussed for different components. Correlation of intensity measures and seismic responses are then estimated for each component, and their seismic performance and uncertainties are quantified in terms of engineering demand parameters. The results of this study are intended for use in the seismic vulnerability assessment of essential electrical equipment in order to achieve more reliable electrical power systems resulting in reduced overall risk of both physical and operational failures of this important class of nonstructural components.

The California Department of Transportation (Caltrans) seismic bridge design process for an Ordinary Bridge described in the Seismic Design Criteria (SDC) directs the design engineer to meet minimum requirements resulting in the design of a bridge that should remain standing in the event of a Design Seismic Hazard. A bridge can be designed to sustain significant damage; however it should avoid the collapse limit state, where the bridge is unable to resist loads due to self-weight. Seismic hazards, in the form of a design spectrum or ground motion time histories, are used to determine the demands of the bridge components and bridge system. These demands are compared to the capacity of the components to ensure that the bridge meets key performance criteria. The SDC also specifies design detailing of various components, including abutments, foundations, hinge seats and bent caps. The expectation of following the guidelines set forth by the SDC during the design process is that the resulting bridge design will avoid collapse under anticipated seismic loads. While the code provisions provide different analyses to follow and component detailing to adhere to in order to ensure a proper bridge design, the SDC does not provide a way to quantitatively determine whether the bridge design has met the requirement of no-collapse. The objectives of this research are to introduce probabilistic fragility analysis into the Caltrans design process and address the gap of information in the current design process, namely the determination of whether the bridge design meets the performance criteria of no-collapse at the design hazard level. The motivation for this project is to improve the designer's understanding of the probabilistic performance of their bridge design as a function of important design details. To accomplish these goals, a new bridge fragility method is presented as well as a design support tool that provides design engineers with instant access to fragility information during the design process. These products were developed for one specific bridge type that is common in California, the two-span concrete box girder bridge. The end product, the design support tool, is a bridge-specific fragility generator that provides probabilistic performance information on the bridge design. With this tool, a designer can check the bridge design, after going through the SDC design process, to determine the performance of the bridge and its components at any hazard level. The design support tool can provide the user with the probability of failure or collapse for the specific bridge design, which will give insight to the user about whether the bridge design has achieved the performance objective set out in the SDC. The designer would also be able to determine the effect of a change in various design details on the performance and therefore make more informed design decisions.

Shape Memory Alloys (SMAs) exhibit the ability to undergo large deformations but can recover permanent strains via heating (shape memory effect) or when stress is removed (superelastic effect). This study evaluates the comparative seismic performance of steel moment resisting frames (SMRFs) with innovative beam-to-column connections that use SMA bars as connecting elements. The performance evaluation studies are based on two types of SMA beam-to-column connections: (1) superelastic SMA connections with recentering capability; (2) martensitic SMA connections with high energy dissipation capacity. Fiber models for these SMA connections are implemented in the OpenSees finite element framework, and are verified against data from full-scale experimental tests that were performed on a prototype SMA connection in previous research at Georgia Tech. Three- and a nine-story model buildings with partially-restrained (PR) moment frames are selected from the SAC Phase II Project as case studies. Non-linear time history analyses on these model buildings, with and without SMA connections, are conducted using suites of ground acceleration records from the SAC Phase II project that represent different seismic hazard levels. Several SMA connections are designed for each structure, and their effect on peak and residual inter-story drift angles, connection rotations, and normalized dissipated hysteretic energy demands are investigated to determine the most suitable design. Finally, the seismic demands on the model buildings with conventional PR and selected SMA connections are evaluated in a probabilistic framework. The resulting seismic demand relationships are used to assess the effectiveness of the SMA connections in enhancing the building performance over a range of demand levels. The results of this performance evaluation show that the SMA connections are most effective in controlling structural response under high levels of seismic intensity leading to large deformation demands. In particular, the energy dissipating SMA connections are found to be effective in reducing maximum deformation demands, while the recentering SMA connections are more suitable for controlling residual deformations in the structure.