Geologists have indicated that the question is not if a catastrophic earthquake will occur in Oregon but when one will occur. Scientists estimate that there is close to 40 percent conditional probability that a Cascadia subduction zone earthquake of magnitude 8.0 or above will strike Oregon in the next 50 years. In addition, the majority of Oregon's bridge inventory was built prior to the current understanding of bridge response and prior to current understanding of the expected earthquake demands. In order to minimize potential bridge damage in the case of an earthquake, one approach is to retrofit seismically deficient bridges. However, often times the decision maker is faced with the difficulty of selecting only a few bridges within the inadequate ones. Hence, the issue of prioritizing upgrading naturally arises. The goal of this study is to assess and refine bridge prioritization methodology to be utilized for ranking Oregon's bridge inventory. CFRP retrofit has been experimentally and analytically evaluated to demonstrate the effectiveness of the technique and was found to be an efficient and economical option. A vulnerability assessment estimates that close to 30 percent of Oregon's highway bridge inventory will sustain moderate damage to collapse. However, retrofitting two most common bridge types in the inventory will reduce the number of damaged bridges by about 70 percent. A cost-benefit assessment that takes into consideration direct and indirect costs associated with damaged bridges and retrofitting of bridges shows that the benefit is up to three times the cost to retrofit. The same principle was applied to rank twelve highway segments for seismic retrofit considered important by Oregon Department of Transportation. One selected segment was considered to be retrofitted and vulnerability assessed. The benefit to cost ratios for each assessment was compared and the highway segments were ranked accordingly. The top five segments in the ranking happen to be located in the East-West corridor connecting I-5 to US-101.

A large magnitude, long duration subduction earthquake is impending in the Pacific Northwest, which lies near the Cascadia Subduction Zone (CSZ). Great subduction zone earthquakes are the largest earthquakes in the world and are the sole source zones that can produce earthquakes greater than M8.5. Additionally, the increased duration of a CSZ earthquake may result in more structural damage than expected. Given such seismic hazard, the assessment of reinforced concrete substructures has become crucial in order to prioritize the bridges that may need to be retrofitted and to maintain the highway network operable after a major seismic event. Recent long duration subduction earthquakes occurred in Maule, Chile (Mw 8.8, 2010) and Tohoku, Japan (Mw 9.0, 2011) are a reminder of the importance of studying the effect of subduction ground motions on structural performance. For this purpose, the seismic performance of substandard circular reinforced concrete bridge columns was experimentally evaluated using shake table tests by comparing the column response from crustal and subduction ground motions. Three continuous reinforced columns and three lap-spliced columns were tested using records from 1989 Loma Prieta, 2010 Maule and 2011 Tohoku. The results of the large-scale experiments and numerical studies demonstrated that the increased duration of subduction ground motions affects the displacement capacity and can influence the failure mode of bridge columns. Furthermore, more damage was recorded under the subduction ground motions as compared to similar maximum deformations under the crustal ground motion. The larger number of plastic strain cycles imposed by subduction ground motions influence occurrence of reinforcement bar buckling at lower displacement compared to crustal ground motions. Moreover, based on the experimental and numerical results, subduction zone ground motion effects are considered to have a significant effect on the performance of bridge columns. Therefore, it is recommended to consider the effects of subduction zone earthquakes in the performance assessment of substandard bridges, or when choosing ground motions for nonlinear time-history analysis, especially in regions prone to subduction zone mega earthquakes. Finally, for substandard bridges not yet retrofitted or upgraded seismically, the following performance limit recommendation is proposed: for the damage state of collapse, which is related to the ODOT's Life Safety performance level, the maximum strain in the longitudinal reinforcement should be reduced from 0.09 (in./in.) to a value of 0.032 (in./in.) for locations where subduction zone earthquakes are expected, to take into consideration the occurrence of bar buckling.

The catastrophic damage to the infrastructure due to the most recent major earthquakes around the world demonstrated the seismic vulnerability of many existing reinforced concrete buildings. Accordingly, this thesis is focused on a proposed seismic retrofitting system (PSRS) configured to upgrade the performance of seismically vulnerable reinforced concrete buildings. The proposed system is composed of a rigid steel frame with chevron braces and a conventional energy dissipating shear link. The retrofitting system is installed within the bays of a reinforced concrete building frame. A retrofitting design procedure using the proposed seismic retrofitting system is also developed as part of this study. The developed design methodology is based on performance-based design procedure. The retrofitting design procedure is configured to provide a uniform dissipation of earthquake input energy along the height of the reinforced concrete building. The PSRS and a conventional retrofitting system using squat infill shear panels are applied to an existing school and an office building. Nonlinear time history analyses of the buildings in the original and retrofitted conditions are conducted to assess the efficiency of the PSRS. The analyses results revealed that the PSRS can efficiently alleviate the detrimental effects of earthquakes on the buildings. The building retrofitted with PSRS has a more stable lateral force-deformation behavior with enhanced energy dissipation capability than that of the one retrofitted with squat infill shear panels. For small intensity ground motions, the maximum inter-story drift of the building retrofitted with the PSRS is comparable to that of the one retrofitted with squat infill shear panels. But for moderate to high intensity ground motions, the maximum inter-story drift of the building retrofitted with the PSRS is considerably smaller than that of the one retrofitted with squat infill shear panels.

Deficient concrete structures are serious danger in seismic zones. In order to minimize economical and human loss, these structures should be retrofitted. Selecting suitable retrofitting schemes requires detailed investigation of these systems. Considering these facts, this study aims to calibrate analytical models of systems with chevron braces and internal steel frames / and evaluate their seismic performances. First, analytical models of the frames with braces and internal steel frames were prepared and then their responses were compared with cyclic responses of experimental studies. Results of these models were used to determine performance limits by the methods proposed by TEC2007 and ASCE/SEI-41. Then, calibrated models were employed for time history analyses with various scales of Duzce ground motion and analytical results were compared with experimental findings. Seismic performance of these systems was also evaluated by using aforementioned codes. Finally, evaluated retrofitting schemes were applied to a 4-story 3-bay reinforced concrete frame that was obtained from an existing deficient structure and effectiveness of applied retrofitting schemes was investigated in detail.

Modular construction is a relatively new technique where prefabricated units are assembled on-site to produce a complete building. Due to detailing requirements for the assembly of the modules, these systems are prone to undesirable failure mechanisms during large earthquakes. Specifically, for multi-story Modular Steel Buildings (MSBs), inelasticity concentration in vertical connections can be an area of concern. Diaphragm interaction, relative displacements between modules and the forces in the horizontal connections need to be investigated. In this study, two 4-story MSBs with two different structural configurations were chosen to be analyzed. In the first model which was introduced in a study by Annan et al. (2009 a), some of the unrealistic detailing assumptions were challenged. To have a more accurate assessment of the structural capacity, in the second model, a more realistic MSB model was proposed. Using OpenSees, Incremental Dynamic Analyses (IDA) have been performed and conclusions were made.

Modular construction is a relatively new technique where prefabricated units are assembled on-site to produce a complete building. Due to detailing requirements for the assembly of the modules, these systems are prone to undesirable failure mechanisms during large earthquakes. Specifically, for multi-story Modular Steel Buildings (MSBs), inelasticity concentration in vertical connections can be an area of concern. Diaphragm interaction, relative displacements between modules and the forces in the horizontal connections need to be investigated. In this study, two 4-story MSBs with two different structural configurations were chosen to be analyzed. In the first model which was introduced in a study by Annan et al. (2009 a), some of the unrealistic detailing assumptions were challenged. To have a more accurate assessment of the structural capacity, in the second model, a more realistic MSB model was proposed. Using OpenSees, Incremental Dynamic Analyses (IDA) have been performed and conclusions were made.

During the evaluation of the seismic retrofitting option for risk reduction/mitigation measures to be applied over buildings, Benefit Cost Analysis is an often-used method. During this study of Benefit Cost Analysis, the condition that the earthquake can happen just after or sometime after retrofitting will be taken into consideration rather than some approaches that focus on the benefits and costs regarding the annual probability of the occurrence for possible earthquakes. The analysis will use conditional probability such that the earthquake will be assumed to occur at different periods of time (5, 10, 20 years etc.) after the mitigation measures are taken so that benefit-cost ratios and net social benefits can be observed over time using the results at these periods. Also during this study the indirect effects of earthquake such as business disruption, social disturbance will also be taken into consideration. As a final step, it is aimed to conclude with convincing financial results regarding the direct and indirect effects of the earthquake in terms of benefits and costs to encourage people and the public officials to reduce the potential vulnerability of the housing units people live by taking the necessary precautions against the earthquake.

Retrofitting the UK domestic built environment presents an excellent opportunity to improve its energy performance. However, retrofitting homes is a complex challenge conflated by multiple factors. Due to this complexity, a shortfall exists between the full potential and realised adoption of energy efficiency measures in the UK, a phenomenon termed the ‘Energy Efficiency Gap’. While a number of technical or economic factors may help explain this gap, difficult to quantify factors, such as social motivations, barriers, and viewpoints towards energy are also significant and often under-emphasised in public policy. As such, in order to improve the understanding of the Energy Efficiency Gap and the uptake of future retrofit initiatives, this research adopted a socio-technical approach that considered social and technical retrofit factors together. Specifically, this research collected data from interviews, questionnaires, and a Q Study in the cities of Manchester and Cardiff, alongside a questionnaire that measured energy efficiency technology and behaviour preferences. An original contribution to knowledge was using the data to empirically identify motivations and barriers to adopting energy efficient technologies, as well as identifying household viewpoints towards energy use and linking them to retrofit technology and energy efficiency behaviour preferences. As a result of this research, specific policy recommendations are presented to help promote energy efficiency retrofits in the UK. This research was carried out as part of the Engineering & Physical Science Research Council and Sustainable Urban Environment research programme, “Re-Engineering the City 2020-2050 Urban Foresight and Transition Management (RETROFIT 2050)”.

The effectiveness of a new structural material, namely textilereinforced mortar (TRM), was investigated experimentally in this study as a means of confining old-type reinforced concrete columns with limited capacity due to bar buckling or due to bond failure at lap splice regions. Comparisons with equal stiffness and strength fiber-reinforced polymer (FRP) jackets allow for the evaluation of the effectiveness of TRM versus FRP. Tests were carried out on full scale non-seismically detailed RC columns subjected to cyclic uniaxial flexure under constant axial load. Thirteen cantilever-type specimens with either continuous longitudinal reinforcement (smooth or deformed) or lap splicing of longitudinal bars at the floor level were constructed and tested. Experimental results indicated that TRM jacketing is quite effective as a means of increasing the cyclic deformation capacity of old-type RC columns with poor detailing, by delaying bar buckling and by preventing splitting bond failures in columns with lap spliced bars. Compared with their FRP counterparts, TRM jackets used in this study were found to be equally effective in terms of increasing both the strength and deformation capacity of the retrofitted columns. From the response of specimens tested in this study, it can be concluded that TRM jacketing is an extremely promising solution for the confinement of reinforced concrete columns, including poorly detailed ones with or without lap splices in seismic regions.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20760号 / 工博第4412号 / 新制||工||1686(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 杉浦 邦征, 教授 白土 博通, 教授 清野 純史 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM