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Building fragility describes the likelihood of damage to a building due to random ground motions. Conventional methods for computing building fragilities are either based on statistical extrapolation of detailed analyses on one or two specific buildings or make use of Monte Carlo simulation with these models. However, the Monte Carlo technique usually requires a relatively large number of simulations in order to obtain a sufficiently reliable estimate of the fragilities, and it quickly becomes impractical to simulate the required thousands of dynamic time-history structural analyses for physics-based analytical models. An alternative approach for carrying out the structural simulation is explored in this work. The use of Response Surface Methodology in connection with the Monte Carlo simulations simplifies the process of fragility computation. More specifically, a response surface is sought to predict the structural response calculated from complex dynamic analyses. Computational cost required in a Monte Carlo simulation will be significantly reduced since the simulation is performed on a polynomial response surface function, rather than a complex dynamic model. The methodology is applied to the fragility computation of an unreinforced masonry (URM) building located in the New Madrid Seismic Zone. Different rehabilitation schemes for this structure are proposed and evaluated through fragility curves. Response surface equations for predicting peak drift are generated and used in the Monte Carlo simulation. Resulting fragility curves show that the URM building is less likely to be damaged from future earthquakes when rehabilitation is properly incorporated. The thesis concludes with a discussion of an extension of the methodology to the problem of computing fragilities for a collection of buildings of interest. Previous approaches have considered uncertainties in material properties, but this research incorporates building parameters such as geometry, stiffness, and strength variabilities as well as nonstructural parameters (age, design code) over an aggregation of buildings in the response surface models. Simulation on the response surface yields the likelihood of damage to a group of buildings under various earthquake intensity levels. This aspect is of interest to governmental agencies or building owners who are responsible for planning proper mitigation measures for collections of buildings.

Seismic provisions for steel buildings present limiting width-thickness and slenderness ratios for bracing members. Most of these limits were established based on experimental observations. The number of experimental studies is limited due to the costs associated with them. With the rapid increase in computing power / however, it is now possible to conduct finite element simulation of brace components using personal computers. A finite element study has been undertaken to evaluate the aforementioned limits for pin-ended pipe section steel braces. Fifty four tubular pipe brace models possessing different diameter-to-thickness ratios varying from 5 to 30 and slenderness ratios varying from 40 to 200 were analyzed. The effect of cyclic hardening modulus on the response of braces was explored. In all analysis, the models were subjected to reversed cyclic displacements up to ten times the yield displacement. Local buckling was traced during the loading history using a criterion based on local strains. Results are presented in terms of the ductility level attained by the member at the onset of local buckling. It is shown that local buckling of the section is influenced by the diameter-to-thickness and the slenderness ratios of the member. Moreover, the amount of hardening modulus was found to affect the local buckling response significantly. The need to include this material property into seismic provisions is demonstrated. Finally, the hysteretic energy dissipated by the member was quantified for each displacement excursion.

In this study, a new vector form intrinsic finite element (VFIFE) for the plate is developed and applied to study the responses of a traditional plate member applied to engineering structures. The VFIFE method is a solution procedure for the mechanic problems by adopting the traditional co-rotational explicit finite element method developed by Belyschko and Hsieh (1973). Three different shape-functions including the simplest polynomial form shape-function (Poly), non-conforming area coordinate shape-function (BCIZ) and the conforming area coordinate shape-function (BCIZC) are utilized to simulate the displacement field of the plate. For a system with nonzero rigid-body displacement, the equilibrium will be difficult to achieve in the global coordinate system when the traditional finite element method is applied. By separating the rigid-body motions from the deformed motions, this problem can be easily taken care. In numerical examples, the accuracy and efficiency of this new developed vector form intrinsic finite element for plate simulation are also examined. It is found that compared to the analytical solution, the accuracy is excellent, while compared to traditional finite element method, the efficiency is also encouraging. This new VIFIFE plate element was also applied to the analysis for the sheet plate members in the harbor structures such as the sheep-pile wharf structural system. It was found that not only can the global behaviors of the pile be clearly observed but also local variations in deformations of the steel sheet are clearly shown.

The Woodford Shale is an important unconventional oil and gas resource. It can act as a source rock, seal and reservoir, and may have significant elastic anisotropy, which would greatly affect seismic response. Understanding how anisotropy may affect the seismic response of the Woodford Shale is important in processing and interpreting surface reflection seismic data. The objective of this study is to identify the differences between isotropic and anisotropic seismic responses in the Woodford Shale, and to understand how these anisotropy parameters and physical properties influence the resultant synthetic seismograms. I divide the Woodford Shale into three different units based on the data from the Pioneer Reliance Triple Crown #1 (RTC #1) borehole, which includes density, gamma ray, resistivity, sonic, dipole sonic logs, part of imaging (FMI) logs, elemental capture spectroscopy (ECS) and X-ray diffraction (XRD) data from core samples. Different elastic parameters based on the well log data are used as input models to generate synthetic seismograms. I use a vertical impulsive source, which generates P-P, P-SV and SV-SV waves, and three component receivers for synthetic modeling. Sensitivity study is performed by assuming different anisotropic scenarios in the Woodford Shale, including vertical transverse isotropy (VTI), horizontal transverse isotropy (HTI) and orthorhombic anisotropy. Through the simulation, I demonstrate that there are notable differences in the seismic response between isotropic and anisotropic models. Three different types of elastic waves, i.e., P-P, P-SV and SV-SV waves respond differently to anisotropy parameter changes. Results suggest that multicomponent data might be useful in analyzing the anisotropy for the surface seismic data. Results also indicate the sensitivity offset range might be helpful in determining the location for prestack seismic amplitude analysis. All these findings demonstrate the potentially useful sensitivity parameters to the seismic data. The paucity of data resources limits the evaluation of the anisotropy in the Woodford. However, the seismic modeling with different type of anisotropy assumptions leads to understand what type of anisotropy and how this anisotropy affects the change of seismic data. / text

Η εργασία αυτή ασχολείται με τον υπολογισμό της δυναμικής απόκρισης επίπεδων μεταλλικών πλαισίων που υποβάλλονται σε σεισμική διέγερση, λαμβάνοντας υπόψη την επίδραση του ρυθμού παραμόρφωσης στις ιδιότητες του υλικού κατασκευής.Από την έρευνα προέκυψαν πολύ χρήσιμα συμπεράσματα που αιτιολογούν, σε ικανοποιητικό βαθμό, την απρόβλεπτη συμπεριφορά μεταλλικών κατασκευών κατά τη διάρκεια ισχυρών σεισμικών γεγονότων στο παρελθόν. / This work elaborates with the calculation of the dynamic response of plane steel frames subjected to earthquake motions taking care of strain rate effect on material properties. The obtained results justify, in a satisfactory way, the unpredictable behavior of steel structures observed in the past due to severe earthquake ground motions.

This thesis explores the creation and assessment of semi-active control algorithms for both squat shear buildings and tall flexible structures. If cost-effective, practicable, semi-active structural control systems can be developed, the potential reduction in loss of both property and lives due to seismic events is significant. Semi-active controllers offer many of the benefits of active systems, but have power requirements orders of magnitude smaller, and do not introduce energy to the structural system. Previous research into semi-active controllers has shown their potential in linear simulations with single earthquake excitations. The distinguishing feature of this investigation is the use of appropriate non-linear modelling techniques and realistic suites of seismic excitations in the statistical assessment of the semi-active control systems developed. Finite element time-history analysis techniques are used in the performance assessment of the control algorithms developed for three and nine story structural models. The models include non-linear effects due to structural plasticity, yielding, hysteretic behaviour, and P-delta effects. Realistic suites of earthquake records, representing seismic excitations with specific return period probability, are utilised, with lognormal statistical analysis used to represent the response distribution. In addition to displacement focused control laws, acceleration and jerk regulation control methods are developed, showing that potential damage reduction benefits can be obtained from these new control approaches. A statistical assessment of control architecture is developed and undertaken, examining the distribution of constant maximum actuator authority for both squat shear buildings, and tall slender structures, highlighting the need to consider non-linear structural response characteristics when implementing semi-active control systems. Finally, statistical analysis of all results and normalised values shows the efficacy of each control law and actuator type relative to different magnitude seismic events. As a result, this research clearly presents, for the first time, explicit tradeoffs between control law, architecture type, non-linear structural effects, and seismic input characteristics for the semi-active control of civil structures.

The main purpose of this research is to investigate the effectiveness and feasibility of semi-active control systems for structural protection during severe earthquake loading. However, the research reported herein also involves analytical studies on the effect of adding viscous damping to the second and fourth quadrants of the force-displacement curve, and laboratory and field testing of a fibre-optic gyroscope (FOG) for measuring rotations in civil engineering structures. The concept of the 2-4 viscous damping is introduced to reduce the response of single-degree-of-freedom (SDOF) systems subjected to harmonic and earthquake excitations. This concept involves the addition of structural viscous damping to the second and fourth quadrants of the force-displacement graph. Time-history analyses and response spectra for various SDOF systems are carried out to assess the effect of adding 2-4 viscous damping. The analytical results indicate that the addition of 2-4 viscous damping is beneficial for reducing the harmonic and seismic response of a wide range of SDOF systems. A newly developed semi-active resettable device is proposed to reduce the seismic response of a one-fifth scale structure. The device is investigated as part of a resettable tendon system installed in the structure. Nonlinear dynamic analyses are performed to determine the optimal configuration of the resettable tendon in the structure. Several shake table tests are performed on the structure equipped with two resettable devices. The dynamic characteristics of the structure and the devices are described. Various earthquake records at different levels of intensity are used during the seismic testing. Different control laws are employed to manipulate the hysteretic behaviour of the devices. The results of the shake table tests validate the effectiveness of the resettable devices to reduce the seismic response of structures. Analytical studies are performed to determine the optimal utilization of the resettable devices in a twelve-storey reinforced concrete building. The seismic performance of the structure is discussed in relation to the number and distribution of the devices. Inelastic time-history analyses are carried out to assess the effectiveness of the devices to reduce the seismic response of the building. The impact of various tendon arrangements and different control laws on the earthquake response is investigated. Relevant issues for the implementation of the resettable devices in actual building systems are identified. Finally, a new measurement concept based on the use of the fibre-optic gyroscope is proposed to measure rotation rates, rotations, displacements and inter-storey drifts of civil engineering structures. FOGs are compact, easy to install and, unlike conventional linear potentiometers, do not require a fixed reference frame to operate. Measurements recorded during the seismic testing of the one-fifth scale structure and displacement measurements at the Sky Tower in Auckland validate the suitability of the FOGs for applications in civil engineering.

Earthquake safety engineering of nuclear power plant structures poses several challenges to the analyst and designer. These problems are characterized by highly transient and dynamic nature of earthquake induced excitations, random nature of details of support motions (in terms of duration, frequency content, amplitude modulation, multiple components, and spatial variability), nonlinear nature of structural behavior, geometrical complexity of the primary and a large number of secondary systems (such as, for example, piping, rotors, and machine panels), soil-structure interactions, demands on high level of safety expected of these structures, and general paucity of recorded data on strong ground motions appropriate for the given site. Probabilistic methods offer the most rational framework to base design decisions for this class of problems. The work reported in the present thesis belongs to this broad area of research. We focus attention on studying two classes of nuclear power plant components, namely, a pipework in the heat exchanger segment, and, control and safety rod drive mechanism (CSRDM) and investigate their performance by taking into account complicating features such as differential seismic support motions across multiple supports, nonlinearities at support locations, random nature of dynamic loads and uncertainties in system parameters. Response measures include peak responses, reliability against specified performance criterion, measures of uncertainties in response variables of interest. Chapter-1 provides the functional details of nuclear power plant structures that includes reactor assembly and heat transport system assembly, CSRDM, heat transfer piping networks, and nonlinear supporting devices (such as rod, spring, guide supports, limiters, and snubbers). The discussion brings out the structural mechanics issues that need attention while analyzing seismic response of some of these components. Chapter-2 provides a brief review of literature covering the following topics: Monte Carlo simulation based methods for static and dynamic reliability analysis problems, digital simulation of random variables and processes, treatment of non-Gaussianity in simulations, strategies for variance reduction, models for uncertainty in response using limited samples, data based extreme value analysis, studies on multi-supported piping networks under differential seismic inputs and seismic performance of CRDM structures. The study identifies specific issues related to numerical simulation of nonlinear dynamic response of multisupported pipeworks to differential seismic inputs, uncertainty propagation and reliability modeling in seismic response of pipeworks and CSRDM using Monte Carlo simulations with variance reduction, data based extreme value analysis, and uncertainty propagation using limited samples as topics requiring further research. The problems of numerical simulation of nonlinear multisupported piping systems subjected to differential seismic support motions and drop time characterization of CSRDM structure during a seismic event are considered in Chapter-3. It is noted that commercially available professional finite element analysis (FEA) softwares do not offer a direct means to tackle this class of problems. On the other hand, FEA packages are best suited to produce acceptable FE models which take into account the geometrical complexities of the structures. Thus, the reasonable way to move forward would be to develop external interfaces that take advantage of FE modeling capabilities of professional packages and at the same time enable treatment of complexities associated with differential support motions, nonlinearities and axial rigid motions of subsystems as in CSRDM. The work reported in Chapter-3 describes the efforts expended in achieving this objective. Here the given built-up structure is divided in to a set of linear substructures each of which are modeled using FE analysis procedures. The proposed scheme allows for these FE models to reside in professional FE analysis codes. An iterative time domain scheme for modeling the interaction forces between these substructures is discussed. The set of governing equations of motion are developed in terms of normal modes of substructures in their uncoupled states. A suite of benchmark problems are first employed to validate the procedure developed. Subsequently, the earthquake induced dynamic response of CSRDM structure and the pipeline running between IHX and secondary sodium pump in a typical fast breeder reactor is simulated. The algorithm for simulation of dynamic response of CSRDM and multi-supported pipelines under differential support motions developed in Chapter-3 is employed in Chapter-4 to investigate the questions concerning influence of uncertainties in specifying the loads and the system parameters on the system response. Specifically, the study focuses on quantifying uncertainty in system response characteristics based on limited number of Monte Carlo simulations of the response. For this purpose we draw upon an earlier work by Wilks which specifies the number of samples needed to estimate γ th percentile point of a random variable with β level of confidence. We explore in this Chapter, the application of this idea in the analysis of nonlinear, randomly parametered, dynamical systems under stochastic excitations. In Chapter-5 we turn our attention to the modeling of aseismic reliability of the nonlinear pipework under differential support motions and the CSRDM structure. The performance functions considered for the piping structure are in terms of highest displacements and stresses over a specified time durations while for CSRDM, the performance function is in terms of scram time being less than a specified time duration. We tackle the first problem by using theory of data based extreme value analysis while the second problem is addressed using an adaptive importance sampling strategy. The contributions here pertain to the exploration of data based extreme values analysis as applied to an industrial scale structure and improvisation of algorithmic modifications in the development of adaptive importance sampling density functions. This improvisation consists of selection of sampling points as a judicious mix of points from both safe and unsafe regions. This is shown to reduce the strong correlations that otherwise would be present if samples are taken only from the unsafe region. These studies demonstrate how Monte Carlo simulations with limited samples can be utilized to draw useful conclusions on structural reliability. Chapter-6 summarizes the main contributions made in the thesis and makes a few suggestions for further research. There are five annexures in the thesis. Annexure-1 contains listing of Matlab m-files used for solving illustrative problems in Chapter-2. The details of FE modeling of multisupported system under differential support motions and the details of substructuring scheme used in modeling of such systems with local nonlinearities are provide in Annexure-2. The details of material and geometry of CSRDM structure are provided in Annexure-3. Annexure-4 summarizes the main details of hypothesis tests used in data based extreme value analysis. The algorithms used for converting response spectra into compatible power spectral density functions are described in Annexure-5.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20346号 / 工博第4283号 / 新制||工||1663(附属図書館) / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 清野 純史, 教授 高橋 良和, 准教授 古川 愛子 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM