The central focus of this dissertation is a seismic vulnerability assessment of retrofitted bridges. The objective of this work is to establish a methodology for the development of system level fragility curves for typical classes of retrofitted bridges using a probabilistic framework. These tools could provide valuable support for risk mitigation efforts in the region by quantifying the impact of retrofit on potential levels of damage over a range of earthquake intensities. The performance evaluation includes the development of high-fidelity three-dimensional nonlinear analytical models of bridges retrofit with a range of retrofit measures, and characterization of the response under seismic loading. Sensitivity analyses were performed to establish an understanding of the appropriate level of uncertainty treatment to model, assess, and propagate sources of uncertainty inherent to a seismic performance evaluation for portfolios of structures. Seismic fragility curves are developed to depict the impact of various retrofit devices on the seismic vulnerability of bridge systems. This work provides the first set of fragility curves for a range of bridge types and retrofit measures. Framework for their use in decision making for identification of viable retrofit measures, performance-based retrofit of bridges, and cost-benefit analyses are illustrated. The fragility curves developed as a part of this research will fill a major gap in existing seismic risk assessment software, and enable decision makers to quantify the benefits of various retrofits.

Cities in Turkey are great risk pools. Underqualified building stocks are the major components of such risk pools. For the mitigation of risks, &#039 / engineering approach offers retrofitting of individual buildings as an ultimate method. However, this proposition has economic and legal difficulties. Instead, it is essential to develop new policies to focus on areas of high earthquake risk as comprehensive urban regeneration activities. This new policy requires new tools to monitor urban regeneration processes. It is obligatory to make comprehensive plans for high risk areas and to take low income groups into consideration in mitigation action plans. Comprehensive regeneration in existing districts could provide means and standards of safety not necessarily maintained by the retrofitting of individual buildings. Potentials of regeneration processes are readily observed and practiced in Turkey as means of regulating urban regeneration processes, even if for purposes other than safety. Analysis of a set of regeneration projects selected from world experience indicates that current regeneration practice in Turkey is far from a comprehensive approach. Municipalities are fully empowered to designate regeneration areas and carry out redevelopment activities often providing increased dentsities on compensate for the costs. This has been reinstated in the new draft law. Rather than a separate law, general regulation of regeneration could be accommodated in the Development Law 3194. A special Law concerning regeneration could instead focus only on risk reduction issues in cities throughout Turkey. The identification of priorities for such regeneration processes could be made by the Ministry of Public Works and Settlement as the central authority, clarifying the scale and timing of each project. The implementation tools of urban regeneration and issues like authorization, responsibility, funding, and auditing could be determined in this special law. A new approach for urban regeneration is needed to describe organizational, participatory, financial framework.

The goal of this study is to design and evaluate economic and rapid seismic retrofit strategies for relatively small rehabilitation projects for steel structures consistent with the tenets of sustainable design. The need to retrofit existing structures in earthquake prone regions may arise directly from the problem of aging and deteriorating conditions, recognition of the vulnerability of existing infrastructure, from updates in seismic code requirements, or changes in building performance objectives. Traditional approaches to seismic hazard mitigation have focused reducing the failure probabilities, consequences from failures, and time to recovery. Such paradigms had been established with little regard to the impact of their rehabilitation measures on the environment and disruptions to occupants. The rapid rehabilitation strategies proposed here have sustainability benefits in terms of providing a more resilient building stock for our communities as well as minimizing environmental and economical impacts and social consequences during the rehabilitation project. To achieve these goals, a unique approach to design supplemental systems using tension-only elements is proposed. In this design approach undesirable global and local buckling are eliminated. Two rapid rehabilitation strategies are presented. The first is a bracing system consisting of cables and a central energy dissipating device (CORE Damper). The second is a shear wall system with the combined use of thin steel plate and tension-only bracing. Analytical studies using both advanced and simplified models and proof-of-concept testing were carried out for the two devices. The results demonstrated stable, highly efficient performance of the devices under seismic load. Preliminary applications of the CORE damper to the retrofitting of a braced steel frame showed the ability of the system to minimize soft story failures. Both techniques can be implemented within a sustainability framework, as these interventions reduce the seismic vulnerability of infrastructure, are low cost, utilize materials and fabrication processes widely available throughout the world, can be handled by unskilled labor and carried out with minimal disruptions to the environment. The approach taken in this study can provide a road map for future development of sustainability-based rehabilitation strategies.

While site effects are accounted for in most modern U.S. seismic design codes for building structures, there exist no standardized procedures for the computationally efficient integration of nonlinear ground response analyses in broadband ground motion simulations. In turn, the lack of a unified methodology affects the prediction accuracy of site-specific ground motion intensity measures, the evaluation of site amplification factors when broadband simulations are used for the development of hybrid attenuation relations and the estimation of inelastic structural performance when strong motion records are used as input in aseismic structural design procedures. In this study, a set of criteria is established, which quantifies how strong nonlinear effects are anticipated to manifest at a site by investigating the empirical relation between nonlinear soil response, soil properties, and ground motion characteristics. More specifically, the modeling variability and parametric uncertainty of nonlinear soil response predictions are studied, along with the uncertainty propagation of site response analyses to the estimation of inelastic structural performance. Due to the scarcity of design level ground motion recording, the geotechnical information at 24 downhole arrays is used and the profiles are subjected to broadband ground motion synthetics. For the modeling variability study, the site response models are validated against available downhole array observations. The site and ground motion parameters that govern the intensity of nonlinear effects are next identified, and an empirical relationship is established, which may be used to estimate to a first approximation the error introduced in ground motion predictions if nonlinear effects are not accounted for. The soil parameter uncertainty in site response predictions is next evaluated as a function of the same measures of soil properties and ground motion characteristics. It is shown that the effects of nonlinear soil property uncertainties on the ground-motion variability strongly depend on the seismic motion intensity, and this dependency is more pronounced for soft soil profiles. By contrast, the effects of velocity profile uncertainties are less intensity dependent and more sensitive to the velocity impedance in the near surface that governs the maximum site amplification. Finally, a series of bilinear single degree of freedom oscillators are subjected to the synthetic ground motions computed using the alternative soil models, and evaluate the consequent variability in structural response. Results show high bias and uncertainty of the inelastic structural displacement ratio predicted using the linear site response model for periods close to the fundamental period of the soil profile. The amount of bias and the period range where the structural performance uncertainty manifests are shown to be a function of both input motion and site parameters.

Concrete-filled buckling restrained braces (BRBs) was first developed in 1988 in Tokyo, Japan, to prevent the steel plates in the core portion from buckling, leading the steel core to exhibiting a more stable and fully hysteretic loop than conventional steel braces. However, past studies have shown that buckling restrained braced frames (BRBFs) have a large residual deformation after a median or high seismic event due to steel’s residual strain. In order to address this issue, innovative self-centering SMA braces are proposed and installed in the originally unbraced bays in existing BRBFs to become a hybrid frame system where the existing steel BRBs dissipate energy induced by external forces and the newly added self-centering SMA braces restore the building configuration after the steel BRBs yield. A case study of conventional three-story BRBF retrofitted by the proposed self-centering SMA braces is carried out to develop systematic retrofit strategies, to investigate the structural behavior, and to probabilistically assess their seismic performance in terms of interstory drifts, residual drifts, and brace deformation, as compared to the original steel BRB frames. Finally, the developed brace component fragility curves and system fragility curves will be further used for the assessment of downtime and repair cost.

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This study presents information on the design procedure of seismic base isolation systems. Analysis of the seismic responses of isolated structures, which is oriented to give a clear understanding of the effect of base isolation on the nature of the structure / and discussion of various isolator types are involved in this work. Seismic isolation consists essentially of the installation of mechanisms, which decouple the structure, and its contents, from potentially damaging earthquake induced ground motions. This decoupling is achieved by increasing the horizontal flexibility of the system, together with providing appropriate damping. The isolator increases the natural period of the overall structure and hence decreases its acceleration response to earthquake-generated vibrations. This increase in period,together with damping, can reduce the effect of the earthquakes, so that smaller loads and deformations are imposed on the structure and its components. The key references that are used in this study are the related chapters of FEMA and IBC2000 codes for seismic isolated structures. In this work, these codes are used for the design examples of elastomeric bearings. Furthermore, the internal forces develop in the superstructure during a ground motion is determined / and the different approaches defined by the codes towards the &lsquo / scaling factor&rsquo / concept is compared in this perspective.

Denna rapport beskriver framtagandet av Katastrofsjukhus, robustare fältsjukhus med förbättrad standard. Jämförelse görs mellan det framtagna Katastrofsjukhuset och uppblåsbara tältsjukhus samt standarden i svenska sjukhus. En färdig produkt finns ännu inte framtagen och rapporten lämnar en hel del lösa trådar, men är en bra grund för mer omfattande utveckling av konceptet och som en idéstudie till en vetenskaplig avhandling eller annan fortsatt forskning. Problemet med befintliga fältsjukhus är främst miljön i operationsavdelningen. Detta är något det lagts stor vikt vid och en strävan att uppnå svensk standard har genomsyrat hela processen. En annan viktig punkt vid framtagandet av Katastrofsjukhus har varit konstruktionens vikt, vilket är tältsjukhusens största fördel. Vikten är av stor betydelse vid både transport och uppbyggnad. Katastrofsjukhusets konstruktion utgår ifrån standardcontainrar för att skapa goda transportmöjligheter. Containrarna är en del av konstruktionen och de rymmer prefabricerade element som utgör Katastrofsjukhusets huvudmodul. Konstruktionen är dimensionerad för att klara kraftiga snö- och vindlaster. Trots detta har elementen gjorts så lätta att det är möjligt att bygga upp hela sjukhuset för hand. Dimensionering efter laster som verkar under en jordbävning har också beräknats redovisas inte i detta arbete då de ej är fullständiga. Utformningen av Katastrofsjukhuset har gjorts för att på bästa sätt fylla det stora behov som finns av sterila operationssalar, samtidigt som planlösningen är anpassningsbar för att Katastrofsjukhuset ska kunna erbjuda olika typer av vård. Rapporten ger även rekommendationer för fortsatt utveckling av Katastrofsjukhuset. / This report describes the development of Emergency Hospital, a robust field hospital with an improved standard. Comparison is made between the developed Emergency Hospital and inflatable tent hospitals and with the standard in Swedish hospitals. A completed product is not presented in this report and it leaves a lot of loose ends, but is a good basis for more extensive development of the concept and as a conceptual study of a scientific treatise, or other continued research. The problem with existing field hospitals is mainly the environment in the operating theater. This is something that has been a strong focus, and a desire to achieve the Swedish standard has permeated the entire process. Another important point in the development of Emergency Hospital has been the mass of the structure, which is the tent hospitals' greatest advantage. The weight is of great importance in both transportation and construction. The Emergency Hospital's design is based on standard containers to provide good transportation possibilities. The containers are a part of the design and they also contain all the prefabricated elements which create the Emergency Hospital's main module. The structure is dimensioned to handle heavy snow and wind loads. Nevertheless, the elements made ​​so light that it is possible to build up the hospital by hand. The design for loads acting during an earthquake has been calculated, but is not included in this report since they are not complete. The hospital has been designed to fill the large needs for sterile operating room, but at the same time the layout is adaptable for different types of care needs. The report also gives recommendations for further development of the Emergency Hospital.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering; and, (M.S.)--Massachusetts Institute of Technology, Dept. of Architecture, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: p. 175-178. / by Joseph Gilmary Burns. / M.S.

No description available.