Alaa Taqi Abdnoor Alisawi

Abstract The probability of extreme events such as an earthquake, fire or blast occurring during the lifetime of a structure is relatively low but these events can cause serious damage to the structure as well as to human life. Due to the significant consequences for occupant and structural safety, an accurate analysis of the response of structures exposed to these events is required for their design. Some extreme events may occur as a consequence of another hazard, for example, a fire may occur due to the failure of the electrical system of a structure following an earthquake. In such circumstances, the structure is subjected to a multi-hazard loading scenario. A post-earthquake fire (PEF) is one of the major multi-hazard events that is reasonably likely to occur but has been the subject of relatively little research in the available literature. In most international design codes, structures exposed to multi-hazards scenarios such as earthquakes, which are then followed by fires are only analysed and designed for as separate events, even though structures subjected to an earthquake may experience partial damage resulting in a more severe response to a subsequent fire. Most available analysis procedures and design codes do not address the association of the two hazards. Thus, the design of structures based on existing standards may contribute to a significant risk of structural failure. Indeed, a suitable method of analysis is required to investigate the behaviour of structures when exposed to sequential hazards. In this paper, a multi-hazard analysis approach is developed, which considers the damage caused to structures during and after an earthquake through a subsequent thermal analysis. A methodology is developed and employed to study the nonlinear behaviour of a steel framed structure under post-earthquake fire conditions. A three-dimensional nonlinear finite element model of an unprotected steel frame is developed and outlined

Abstract Dynamic response records of pile performance during earthquakes are limited mainly due to the challenges of recording the seismic soil–pile response. This limitation has led to an inadequacy in providing a standardized basis for the calibration and validation of the available analytical and numerical methods developed for seismic soil–pile superstructure interaction problems. To bridge this gap, a series of numerical simulations of scaled, shaking table tests of model piles in soft clay has been developed in the current study. This paper aims to accurately identify all aspects and critical parameters in the numerical simulation and propose the most suitable soil constitutive model. Three soil constitutive models are selected as advanced models for soft soil, namely, the modified Mohr–Coulomb, Drucker–Prager/cap plasticity, and Cam–clay models. Similar to the physical test case study, this numerical analysis uses dimensional analysis techniques to identify scale modelling criteria and develop a scaled soil and pile-supported structure model correctly. The 3D nonlinear numerical models are developed using the Abaqus software.

ABSTRACT There are a significant number of studies into the failure of pile-supported structures exposed to earthquakes, however, there remain a difficulties with the in situ examination of pile response and performance during seismic excitation. A flexible wall barrel, shaking table test method is suitable for investigating pile behavior during an earthquake. Cost, time, and difficulties in identifying soil properties accurately in physical models, in addition to the effects of test conditions, have led to the current research where the physical test is replaced by numerical simulation. Many researchers have experienced difficulties in the validation of numerical models and have found that there is a lack of available information in the literature. Thus, developing a practical approach will extend the soil-structure interaction (SSI) database and promote the validation opportunities for studies into pile performance during strong excitations. This study provides an insight into a set of SSI problems and proposes a procedure for calibration of the advanced SSI analysis. A framework is performed to simulate a shaking table test of a model pile-foundation superstructure on soft clay. A variety of model scaling relationships are used to develop an approach that allows observation of the inherent dynamic and non-linear nature of SSI behavior. The three-dimensional, non-linear dynamic response and elastoplastic analysis are included in the simulation. Through the development of finite element analysis (FEA) using ABAQUS software, fully non-linear unidirectional input excitations, which are amplified from the base to the top and are capable of including all of the possible degrees of freedom, are applied to the model. The inertial, kinematic, and damping interaction components of the response are also examined. The gap-slap mechanism between soil and pile is a significant aspect to the model. The results are validated using physical test results.

Analysis and design methods of piles can be categorised based on their levels of sophistication and accuracy. Such methods have demonstrated progressive development from empirical methods towards procedures with a robust theoretical basis. Amongst these methods, numerical techniques have emerged as advanced tools for the enhancement of the analysis and design procedures of piles. A systematic literature review concluded that piles experience settlements that must be controlled. Therefore, this study aimed to predict the behaviour of a single pile and a group of piles under in situ load conditions and a single pile model in a laboratory scale. Results of this study will help predict the bearing capacity of a system and the stress– strain state of subsoil for all cases mentioned above. Aims and objectives This study focused on problems concerning static axial loading. Both load capacity and deformation were considered. Consequently, the main objectives of the study were as follows: • configure an adaptable analytical framework that can associate several methods of analysis, • examine the characteristics of the behaviour of single piles and pile groups under static axial loading, • assess approaches that determine the soil parameters required for prediction, • present a procedure of using CPT data for theoretical analysis and characteristic soil parameters linked to finite element numerical analysis, • compare the applications of theoretical, practical and numerical methods, and • analyse the sensitivity of pile performance predictions to a variety of factors over which the geotechnical analyst has control, including the purpose of analysis and the geotechnical characterisation of the site.