Narrow Results

The seismic performance of monopiled offshore wind turbine (OWT) structures was evaluated numerically. The aim was to analyze offshore wind farm sites on complicated layered seabed with high seismicity. Following pile soil analysis (PISA) model, three-dimensional (3D) numerical evaluations were undertaken for two separate locations under two independent seismic events. The effects of pile diameter, depth, site impact owing to transverse soil layering, uni-directional and multi-directional seismic loading and seismic acceleration magnitude are presented. Dynamic impedance depth variation and site response analysis via lateral displacement, lateral soil response and Fourier response amplitude are explored in frequency and time domain. In a seismic zone with stratified soil, pile diameter has a greater influence. Variations in soil profile affect wind turbine performance and seismic sensitivity. This research will give a strong platform for later studies to recommend a safe wind farm site based on simulation results.

The United States Nuclear Regulatory Commission issued requests for licensees to re-evaluate the seismic hazards at their sites after the accident at the Fukushima Daiichi Nuclear Power Plant in Japan on March 11 in 2011 and to identify and address any site-specific vulnerabilities associated with seismic hazards. The primary guidance for performing those evaluations is provided in the Electric Power Research Institute EPRI-1025287 report, which also provides guidance for evaluating spent fuel pool (SFP) integrity. In addition, the EPRI-3002009564 report also provides evaluation approaches regarding the effects of seismic ground motions on SFPs that supplement the guidance provided in EPRI-1025287. SFP integrity has become increasingly important for active and decommissioned nuclear power plants. According to EPRI-1025287, the SFP integrity evaluation emphasizes failure modes of the SFP that could result in “rapid drain-down.” The definition of “rapid drain-down” is a failure that could lead to the uncovering of irradiated fuel stored in the SFP within 72h of an earthquake. Possible failures can be classified into two categories: failures relevant to the SFP structure and failures relevant to non-structural elements. This paper aims to study the approaches of implementing seismic evaluation of an SFP structure. EPRI-3002009564 provides separate seismic evaluation approaches for plants with a ground motion response spectrum (GMRS) peak $\mathrm{\text{Sa}}\le 0.8$g and for plants with a GMRS peak $\mathrm{\text{Sa}}>0.8$g. Structural dynamic analysis is also a common approach for implementing seismic evaluation if a detailed finite element model is available. In this paper, a sample SFP structure was evaluated using the two approaches, structural dynamic analysis and structural analysis criteria. The results indicate that shear failure controlled the failure mode of the SFP structure for both approaches. This shows that the two approaches drew the same conclusion regarding the failure mode. Furthermore, a smaller seismic margin was obtained using the structural analysis criteria, which means this evaluative approach is more conservative.

This study is focused on the effects of the new standard of the building design under seismic loading in Thailand (DPT 1302-52) on cost estimates and the seismic performance of nine-story reinforced concrete apartment buildings with various ductility in moderate seismic zone and a gravity load designed (GLD) building. Both the nonlinear static pushover and nonlinear dynamic analyses are applied. Comparisons of performance point (PF) evaluation of studied frames are investigated by three different methods, namely, capacity spectrum method (CSM), inelastic demand diagram method (IDDM), and nonlinear time history analysis (NTHA) method. Five selected ground motion records are investigated in the analyses. In order to examine the influence of design ductility classes, the seismic forces on moment resisting frame buildings are defined according to the new standard of the building design under seismic loading in Thailand with ductility from 8, 5, and 3, corresponding to special ductile frame (SDF), intermediate ductile frame (IDF), and ordinary ductile frames (ODF), respectively. For the cost estimates, ODF is the most expensive among ODF, IDF, and SDF. Costs of SDF and IDF in Chiang Mai are quite similar. The results show that SDF is more ductile than that of ODF, however, the strength of SDF is less than ODF. The results indicate that all frames including GLD are able to withstand a design earthquake. The study also found that the average ductilities at the failure state for SDF, IDF, ODF, and GLD are 1.45, 1.42, 1.28, and 1.17, respectively. The average PGAs at the failure state for SDF, IDF, ODF, and GLD are 0.85 g, 0.83 g, 0.63 g, and 0.35 g, respectively when these buildings have the volumetric ratio of horizontal confinement within joint panel greater than 0.003. Moreover, at the failure state of GLD with volumetric ratio of horizontal confinement within joint panel less than 0.003, the average PGA is only 0.17 g which is lower than the design earthquake of PGA of 0.39 g in the draft DPT. The SDF and IDF are the two best options in consideration of cost and seismic performance.

This paper describes the development of a web-based system for seismic performance evaluation and preliminary design of inelastic structures. The core of system includes a simple yet accurate performance-based earthquake engineering procedure based on the Capacity-Spectrum Method. The present system allows authenticated users to carry out seismic performance evaluation, preliminary design for inelastic, bridge column as well as searching previous data and results from their offices or directly from the field. Accuracy of the procedure is verified by comparing with published data. The architecture and functions of system are given. Example of the present system is presented.