With the advancement in knowledge of inelastic response of structures, the design and construction practices of reinforced concrete buildings have been changing worldwide. Most of the codes are incorporating the near-fault factors and performance based designs in the seismic codes. However, further investigation is needed to identify the physical behaviour of multi-storey buildings to near-fault ground motions. At present, quantitative evaluation of response and its mitigation to near field ground motions is a popular topic in earthquake engineering field. The present study discusses the inelastic response of symmetric and asymmetric multi-storey buildings to near-fault ground motions. The possibility of design approach is based on ‘expendable top storey’ for the multi-storey RC- buildings to near field records. If such behaviour is feasible one can conceive of a structure whose top storey is permitted and designed to undergo large inelastic deformations while reducing damage in the lower storey. The concept was first proposed in an earlier research (RaghuPrasad, 1977). Such a concept juxtaposes the often-mentioned ‘soft first storey’ concept. Further in this report, the performance evaluation of multi-storey buildings near Chiplun fault in Mumbai, India is also discussed. The thesis is organized in the following chapters: Introduction in Chapter-1 contains detailed literature review on inelastic response of symmetric and asymmetric buildings, response of buildings to near-fault records, elastic and inelastic vibration absorber concepts and performance based designs. The literature reveals that considerable amount of research has been carried out on the elastic, inelastic response of structures and vibration absorber concepts to ordinary ground motions. Recently, the effect of near field ground motions on the response of multi-storey buildings is gaining much importance. Most of the research publications are available on response of symmetric buildings subjected to near field ground motions. But many problems are yet to be investigated. They are, identification of important ground motion parameters in near fault records, vibration absorber concepts and torsional response of structures subjected to pulse type ground motions. These problems are clearly mentioned in the recently published state-of-the-art review by Shuang and Li-Li (2007). In this report an attempt has been made to solve these problems. Effect of near-fault ground motions on symmetric multi-storey buildings in Chapter-2, describes simplified non-dimensionalized equations of motion to study the response behaviour of multi-storey buildings to near fault records. The non-dimensionalized equations of motion are expressed in terms of near fault ground motion parameters. The objective is to find a relation between ductility demand and near field ground motion parameters through neural network approach. For this a neural network modeling was done to predict the ductility demand in terms of peak ground acceleration, peak ground velocity, epicentral distance and pulse period of the near field ground motion. A thorough sensitive analysis is carried out, to ascertain which parameters are having maximum influence on ductility demand. In this chapter further, a comparative study is made on the inelastic seismic response of multi-storey buildings to pulse type and non pulse type ground motions. The study shows that, it is necessary to consider the effect of near fault ground motions separately and make provisions for the design in the codes of practice accordingly. Vibration absorber effect in multi-storey buildings in chapter-3, discusses the behaviour of top storey as a vibration absorber during near field ground motions. For this purpose, a five storey symmetric building model is considered as an example problem to demonstrate the effectiveness of the proposed concept. Response of the structure is obtained for the various combinations of absorber storey parameters such as mass ratio, frequency ratio and yield displacement ratio. Here mass ratio means mass of the absorber storey to that of the bottom storey and similarly for the frequency and yield displacement ratios. Observing the storey-wise variation of these responses, we can say that for a range of mass ratios, frequency ratios and yield displacement ratios, the inelastic response of top storey is large compared to the lower storeys. This range is termed as ‘effective range’. Further, in this range the top storey absorbs the vibration energy of the structure by keeping the lower storeys in elastic state i.e. acts as a vibration absorber. The top storey can also be termed as ‘expendable top storey’. Effect of near-fault ground motions on asymmetric multi-storey buildings in Chapter-4, discusses the inelastic response of asymmetric buildings to single horizontal component and two horizontal components of near fault ground motions viz., fault normal and fault parallel components. For numerical investigations eight building models are considered. Eccentricity has been created by keeping the stiffness and mass centre separately. The building models are subjected to strong motion records of Imperial Valley Array-5 (1979) and Northridge-Sylmar (1994). A detailed study on the effect of base shear strength, eccentricity and pulse period of near fault ground motions on the response is investigated. Performance of multi-Storey buildings in Chapter-5, reported a detailed procedure for the performance evaluation of structures. The procedure is applied to find the performance evaluation of multi-storeyed buildings located in near fault region. Chiplun fault in Mumbai, India has been chosen for the study because several features of that fault are clearly published (RaghuKanth and Iyengar, 2006). Results of performance evaluation of five and ten storeyed symmetric buildings with and without infill panels are studied. Ground motion records consistent with the hazard spectrum for the design are considered. The performance of the building near the Chiplun fault in Mumbai, India shows operational under UHS-500 (uniform hazard spectrum) event and it collapses when the building is exposed to UHS-2500 record. The thesis is concluded in Chapter-6 with an overall summary of the report and suggestions for further scope of the work.

Nuclear power plays a crucial role in energy supply in the world: around 15% of the electricity generated worldwide is provided from nuclear stations avoiding around 2.5 billion tonnes of CO2 emissions. As of January 2016, 442 reactors that generated 380+ GW were in operation and 66 new reactors were under construction. The seismic design of new nuclear power plants (NPPs) has gained much interest after the high-profile Fukushima Dai-ichi accident. In the UK, a tectonically stable continental region that possesses medium-to-low seismic activity, strong earthquakes capable of jeopardising the structural integrity of NPPs, although infrequent, can still occur. Despite that no NPP has been built in Great Britain after 1995, a New Build Programme intended to build 16 GW of new nuclear capacity by 2030 is currently under way. This PhD project provides a state-of-the-art framework for seismic probabilistic safety assessment and risk control of NPPs in Northwest Europe with particular application to the British Isles. It includes three progressive levels: (i) seismic input, (ii) seismic risk analysis, and (iii) seismic risk control. For seismic input, a suitable model to rationally define inputs in the context of risk assessments is proposed. Such a model is based on the stochastic simulation of accelerograms that are compatible with seismic scenarios defined by magnitude 4 < Mw < 6.5, epicentral distance 10 km < Repi < 100 km, and different types of soil (rock, stiff soil and soft soil). It was found to be a rational approach that streamlines the simulation of accelerograms to conduct nonlinear dynamic analyses for safety assessments. The model is a function of a few variables customarily known in structural engineering projects. In terms of PGA, PGV and spectral accelerations, the simulated accelerograms were validated by GMPEs calibrated for the UK, Europe and the Middle East, and other stable continental regions. For seismic risk analysis, a straightforward and logical approach to probabilistically assess the risk of NPPs based on the stochastic simulation of accelerograms is studied. It effectively simplifies traditional approaches: for seismic inputs, it avoids the use of selecting/scaling procedures and GMPEs; for structural outputs, it does not use Monte Carlo algorithms to simulate the damage state. However, it demands more expensive computational resources as a large number of nonlinear dynamic analyses are needed. For seismic risk control, strategies to control the risk using seismic protection systems are analysed. This is based on recent experience reported elsewhere of seismically protected nuclear reactor buildings in other areas of medium-to-low seismic activity. Finally, a scenario-based incremental dynamic analysis (IDA) is proposed aimed at the generation of surfaces for unacceptable performance of NPPs as function of earthquake magnitude and distance. It was found that viscous-based devices are more efficient than hysteretic-based devices in controlling the seismic risk of NPPs in the UK. Finally, using the proposed scenario-based IDA, it was found that when considering all controlling scenarios for a representative UK nuclear site, the risk is significantly reduced ranging from 3 to 5 orders of magnitude when using viscous-based devices.

La Norma E.030 y gran parte de los códigos de diseño sismorresistente consideran el análisis unidireccional para cada uno de los ejes principales de manera independiente. A comparación de ello, en realidad los eventos sísmicos tienen un comportamiento bastante aleatorio. Además, imponen solicitaciones bidireccionales en diferentes orientaciones a las edificaciones. Se realizó el estudio de la respuesta en edificaciones sujetas a solicitaciones de carga sísmica con irregularidades de esquina entrante y de piso blando. Para ello, se ha realizado el análisis tiempo historia lineal (ATHL) de éstas imponiendo solicitaciones sísmicas en dos direcciones ortogonales simultáneas. Así, se obtiene la respuesta estructural con variaciones de ángulos de incidencia de 10° y se compara con la respuesta derivada del análisis unidireccional. Los resultados obtenidos muestran que el análisis tradicional subestima las respuestas de las estructuras. Se obtuvieron variaciones de hasta 50% en el modelo de esquina entrante y hasta 72% en el modelo de piso blando. En las edificaciones con irregularidad de piso blando extremo existen variaciones de hasta el 90%. Estos resultados confirman la necesidad de considerar la bidireccionalidad sísmica en el análisis y diseño sismorresistente. / Standard E.030 and most of the seismic-resistant design codes consider the unidirectional analysis for each of the main axes independently. By comparison, seismic events actually behave quite randomly. In addition, they impose bidirectional solicitations in different orientations to the buildings. The study of the response in structures subjects to earthquake loads with irregularity of l-shaped plan and soft story is carried out. For this, the linear time-story analysis (LTHA) of these has been carried out imposing seismic solicitations in two perpendicular directions at the same time. Thus, the structural response with incidence angle variations of 10° is obtained and compared with the response derived from the unidirectional analysis. Variations of up to 50 were obtained in the l-shaped plan model and up to 72% in the soft story model. In structures with extreme soft story variations of up to 90%. These results confirm the need to consider seismic bidirectionality in earthquake analysis and design. / Tesis

One of the most difficult tasks towards designing earthquake resistant structures is the determination of critical earthquakes. Conceptually, these are the ground motions that would induce the critical response in the structures being designed. The quantification of this concept, however, is not easy. Unlike the linear response of a structure, which can often be obtained by using a single spectrally modified ground acceleration history, the nonlinear response is strongly dependent on the phasing of ground motion and the detailed shape of its spectrum. This necessitates the use of a suite (bin) of ground acceleration histories having phasing and spectral shapes appropriate for the characteristics of the earthquake source, wave propagation path, and site conditions that control the design spectrum. Further, these suites of records may have to be scaled to match the design spectrum over a period range of interest, rotated into strike-normal and strike-parallel directions for near-fault effects, and modified for local site conditions before they can be input into time-domain nonlinear analysis of structures. The generation of these acceleration histories is cumbersome and daunting. This is especially so due to the sheer magnitude of the data processing involved. The purpose of this thesis is the development and documentation of PC-based computational tools (hereinafter called EQTools) to provide a rapid and consistent means towards systematic assembly of representative strong ground motions and their characterization, evaluation, and modification within a performance-based seismic design framework. The application is graphics-intensive and every effort has been made to make it as user-friendly as possible. The application seeks to provide processed data which will help the user address the problem of determination of the critical earthquakes. The various computational tools developed in EQTools facilitate the identification of severity and damage potential of more than 700 components of recorded earthquake ground motions. The application also includes computational tools to estimate the ground motion parameters for different geographical and tectonic environments, and perform one-dimensional linear/nonlinear site response analysis as a means to predict ground surface motions at sites where soft soils overlay the bedrock. While EQTools may be used for professional practice or academic research, the fundamental purpose behind the development of the software is to make available a classroom/laboratory tool that provides a visual basis for learning the principles behind the selection of ground motion histories and their scaling/modification for input into time domain nonlinear (or linear) analysis of structures. EQTools, in association with NONLIN, a Microsoft Windows based application for the dynamic analysis of single- and multi-degree-of-freedom structural systems (Charney, 2003), may be used for learning the concepts of earthquake engineering, particularly as related to structural dynamics, damping, ductility, and energy dissipation. / Master of Science

A major concern for geotechnical engineers is the ability to predict how a soil will react to large ground motions produced by earthquakes. Of all the different types of soil, liquefiable soils present some of the greatest challenges. The ability to quantify the degradation of a soil's shear modulus as it undergoes liquefaction would help engineers design more reliably and economically. This thesis uses ground motions recorded by an array of downhole accelerometers on Port Island, Japan, during the 1995 Kobe Earthquake, to quantify the shear modulus of sand as it liquefies. It has been shown that the shear modulus of sand decreases significantly as it liquefies, apparently decreasing in proportion to the increasing excess pore water pressure ratio (Ru). When completely liquefied, the shear modulus of sand (Ru = 1.0) for a relative density of 40 to 50% is approximately 15% of the high-strain modulus of the sand in its non-liquefied state, or 1% of its initial low-strain value. Presented in this thesis is an approach to modeling the shear modulus degradation of sand as it liquefies. This approach, called the "degrading shear modulus backbone curve method" reasonably predicts the hysteretic shear stress behavior of the liquefied sand. The shear stresses and ground accelerations computed using this method reasonably matches those recorded at the Port Island Downhole Array (PIDA) site. The degrading shear modulus backbone method is recommended as a possible method for conducting ground response analyses at sites with potentially liquefiable soils.