Browsing by Subject "Earthquake"
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Item A comparative study of housing reconstruction after two major earthquakes: The 1994 Northridge earthquake in the United States and the 1999 Chi-Chi earthquake in Taiwan(Texas A&M University, 2004-09-30) Wu, Jie YingThough the idea of pre-impact recovery preparedness planning has recently been promoted by federal and state governments, very little research has been done to evaluate how it affects the process of disaster recovery. This research attempts to understand how pre-impact recovery planning affects housing reconstruction by examining the relationship of pre-impact recovery planning with housing reconstruction speed and the use of mitigation techniques during housing reconstruction. This study was conducted by comparing two cases, the City of Los Angeles, California and Taichung County in Taiwan. This study finds that having a pre-impact preparedness recovery plan increases the speed of housing reconstruction. The relationship between having a pre-impact recovery preparedness plan and the extent to which hazard mitigation is integrated into the recovery process is not very clear, but the experience of the City of Los Angeles suggests that having a pre-impact recovery plan allows local officials to make more effective use of the ?window of opportunity? after disaster.Item Analysis of soil-structure system response with adjustments to soil properties by perturbation method(2014-05) Patta, Sang Putra Pasca Rante; Tassoulas, John LambrosThe research described in this dissertation undertakes a computational study of wave motion due to ground excitation in layered soil media. Adjustments of soil properties consistent with the level of deformation is applied using an equivalent linear approach. The finite element method provides the basis of the numerical procedure for soil-structure system response calculation in conjunction with a first-order perturbation scheme. Available experimental data are employed for shear-modulus and damping adjustments. The findings of the research are expected to lead to efficient calculation of structural response to earthquake ground motion.Item Direct in-situ evaluation of liquefaction susceptibility(2014-05) Roberts, Julia Nicole; Stokoe, Kenneth H.Earthquake-induced soil liquefaction that occurs within the built environment is responsible for billions of dollars of damage to infrastructure and loss of economic productivity. There is an acute need to accurately predict the risk of soil liquefaction as well as to quantify the effectiveness of soil improvement techniques that are meant to decrease the risk of soil liquefaction. Current methods indirectly measure the risk of soil liquefaction by empirically correlating certain soil characteristics to known instances of surficial evidence of soil liquefaction, but these methods tend to overpredict the risk in sands with silts, to poorly predict instances of soil liquefaction without surface manifestations, and fail to adequately quantify the effectiveness of soil improvement techniques. Direct in-situ evaluation of liquefaction susceptibility was performed at a single site at the Wildlife Liquefaction Array (WLA) in Imperial Valley, California, in March 2012. The project included a CPT sounding, crosshole testing, and liquefaction testing. The liquefaction testing involved the measurement of water pressure and ground particle motion under earthquake-simulating cyclic loading conditions. The objective of this testing technique is to observe the relationship between shear strain in the soil and the resulting generation of excess pore water pressure. This fundamental relationship dictates whether or not a soil will liquefy during an earthquake event. The direct in-situ evaluation of liquefaction susceptibility approach provides a more accurate and comprehensive analysis of the risks of soil liquefaction. It also has the ability to test large-scale soil improvements in-situ, providing researchers an accurate representation of how the improved soil will perform during a real earthquake event. The most important results in this thesis include the identification of the cyclic threshold strain around 0.02% for the WLA sand, which is very similar to results achieved by other researchers (Vucetic and Dobry, 1986, and Cox, 2006) and is a characteristic of liquefiable soils. Another key characteristic is the 440 to 480 ft/sec (134 to 146 m/s) shear wave velocity of the soil, which are well below the upper limit 656 ft/sec (200 m/s) and an indication that the soil is loose enough for soil liquefaction to occur. The third significant point is that the compression wave velocity of the sand is greater than 4,500 ft/sec (1,370 m/s), indicating that it is at least 99.9% saturated and capable of generating large pore water pressure due to cyclic loading. These three conditions (cyclic threshold strain, shear wave velocity, and compression wave velocity) are among the most important parameters for characterizing a soil liquefaction risk and must all be met in order for soil liquefaction to occur.Item Discrete conformal approximation of complex earthquake maps(Texas Tech University, 2005-08) Murphy, Eric Michael; Williams, G. Brock; Barnard, Roger W.; Pearce, Kent; Allen, Edward J.Using the techniques of circle packing, we construct discrete conformal approximations for complex earthquake maps on the Teichmüller spaces of compact, hyperbolic Riemann surfaces developed by William Thurston and Curtis McMullen, and we show that these approximations are convergent. We then describe earthquake maps on the Teichmüller spaces of compact, Euclidean Riemann surfaces, extending the work of Thurston and McMullen. Using the discrete conformal approximations developed for hyperbolic surfaces, we approximate the action of these new maps with circle packing.Item Discrete conformal approximation of complex earthquake maps(2005-08) Murphy, Eric Michael; Williams, G. Brock; Barnard, Roger W.; Pearce, Kent; Allen, Edward J.Using the techniques of circle packing, we construct discrete conformal approximations for complex earthquake maps on the Teichmüller spaces of compact, hyperbolic Riemann surfaces developed by William Thurston and Curtis McMullen, and we show that these approximations are convergent. We then describe earthquake maps on the Teichmüller spaces of compact, Euclidean Riemann surfaces, extending the work of Thurston and McMullen. Using the discrete conformal approximations developed for hyperbolic surfaces, we approximate the action of these new maps with circle packing.Item The influence of earthquake ground motion on wind turbine loads(2011-05) Arora, Himanshu; Manuel, Lance; Civil, Architectural, and Environmental Engineering; Kallivokas, Loukas F.The design of wind turbines installed in various regions of the world where earthquakes are likely must take into account loads imposed on the turbine due to ground shaking. Currently, design standards such as the International Electrotechnical Commission’s standard, IEC 61400-1, do not provide detailed guidelines for assessing loads on wind turbines due to seismic input excitation. In regions of high seismic hazard, it is extremely important to perform a thorough seismic analysis. Various simplified and full-system wind turbine models have been published and used for seismic analysis of turbine loads in recent years. Among these models, the open-source software, FAST, allows for full-system simulation of the response of wind turbines subjected to earthquake ground motion along with other sources of loading such as from the mean wind field and turbulence. This study employs this open-source software to simulate seismic loads and presents statistical and spectral summaries resulting from extensive analyses undertaken by simulating turbine response to various input motions from Western U.S. earthquakes. A total of 150 different earthquake ground motion records with varying magnitude and distance from fault rupture are selected and normalized/scaled to selected target levels prior to response simulation using a utility-scale 5-MW wind turbine model. The records selected are divided into six groups of 25 records each; the groups consist of different magnitude and distance-to-rupture values. The records in each bin are scaled to have similar demand levels as the average of the demand of the unscaled records in that bin. Two different normalization options are considered—in one, the scaling is at the rotor rotation rate (or the once-per-rev or 1P frequency); in the other, the scaling is done at the tower fore-aft first mode frequency. A study of various turbine load measures is conducted. It is found that turbine tower loads, in particular, are especially influenced by the earthquake excitation.Item Measuring liquefaction-induced deformation from optical satellite imagery(2014-05) Martin, Jonathan Grant; Rathje, Ellen M.Liquefaction-induced deformations associated with lateral spreading represent a significant hazard that can cause substantial damage during earthquakes. The ability to accurately predict lateral-spreading displacement is hampered by a lack of field data from previous earthquakes. Remote sensing via optical image correlation can fill this gap and provide data regarding liquefaction-induced lateral spreading displacements. In this thesis, deformations from three earthquakes (2010 Darfield, February 2011 Christchurch, and 2011 Tohoku Earthquakes) are measured using optical image correlation applied to 0.5-m resolution satellite imagery. The resulting deformations from optical image correlation are compared to the geologic conditions, as well as field observations and measurements of liquefaction. Measurements from optical image correlation are found to have a precision within 0.40 m in all three cases, and results agree well with field measurements.Item Seismic retrofit of RC columns with FRP composites and anchorage system(2015-05) Psaros Andriopoulos, Apostolos; Jirsa, J. O. (James Otis); Hrynyk, TrevorResearch on the use of composite materials in structural applications started more than 30 years ago but still remains active. The challenges that accompany those applications are diverse and seem to increase as the variety of applications grows. There are several fiber-reinforced polymer (FRP) systems that have been introduced through the years for strengthening reinforced concrete (RC) structures. Those systems focus on strengthening of slabs, beams and columns. The present study pertains to seismic retrofit of rectangular RC columns. The typical FRP materials used in structural applications are introduced, as well as, how FRP materials become an integral part of the force-resisting system. In addition, analysis work pertaining to a series of strengthened RC columns was conducted and the results were compared to the experimental data. Moreover, deficiencies of typical material models were highlighted. Design guidelines are discussed and recommendations about current design practices are provided. Finally, research gaps and future research recommendations are identified.Item Seismic retrofit of RC columns with FRP composites and anchorage system(2015-05) Psaros Andriopoulos, Apostolos; Jirsa, J. O. (James Otis); Hrynyk, TrevorResearch on the use of composite materials in structural applications started more than 30 years ago but still remains active. The challenges that accompany those applications are diverse and seem to increase as the variety of applications grows. There are several fiber-reinforced polymer (FRP) systems that have been introduced through the years for strengthening reinforced concrete (RC) structures. Those systems focus on strengthening of slabs, beams and columns. The present study pertains to seismic retrofit of rectangular RC columns. The typical FRP materials used in structural applications are introduced, as well as, how FRP materials become an integral part of the force-resisting system. In addition, analysis work pertaining to a series of strengthened RC columns was conducted and the results were compared to the experimental data. Moreover, deficiencies of typical material models were highlighted. Design guidelines are discussed and recommendations about current design practices are provided. Finally, research gaps and future research recommendations are identified.Item Strength, stiffness, and damage of reinforced concrete buildings subjected to seismic motions(2016-05) Kwon, Jinhan; Ghannoum, Wassim M.; Jirsa, James O.; Bayrak, Oguzhan; Hrynyk, Trevor; Sen, Mrinal K.Current analytical tools were calibrated mainly using pseudo-static experimental investigations of individual structural components. Relatively few tests have been performed on reinforced concrete structural systems under realistic boundary conditions and even fewer exist that were conducted dynamically due to the high costs and experimental challenges. Thus, the structural engineering field has resorted to a number of extrapolations from limited test data to form analytical models of structural systems they design. It is therefore no surprise that blind prediction contest results for structural strength and deformation are typically several times higher and lower than those from experiments. A complete system of a full-scale, four-story, reinforced concrete structure was tested under increasing seismic excitations, to near collapse damage states, one the National Research Institute for Earth Science and Disaster Prevention (NIED)/E-Defense shaking table in Japan. A moment frame system was adopted in one direction and a pair of shear walls incorporated in the exterior frames in the other direction. Wherever possible, minor adjustments to the designs were made to bring the final structures closer to U.S. seismic design provisions. No other tests currently exist that provide behavioral data about a complete, seismically detailed, reinforced concrete structural system tested under such realistic boundary conditions. Comprehensive and in-depth analyses were performed in light of the NIED/E-Defense test data to 1) assess the validity of current behavioral knowledge and design codes; 2) to assess the accuracy of current analytical methods for this common type of structure; 3) to recommend improvements and ways forward on both fronts. Implications of test results to U.S. seismic provisions and recommendations for estimating structural strength and stiffness of reinforced concrete buildings were made based on comparison between the estimates from the current analytical methods and the actual seismic behavior of the NIED/E-Defense test data.