Hamid Reza Tabatabaiefar

Performance Based Assessment of Dynamic Soil-Structure Interaction Effects on Seismic Response of Building Frames

Soil-Structure Interaction (SSI) has progressed rapidly in the second half of 20th century stimulated mainly by requirements of the nuclear power and offshore industries to improve the seismic safety. In this study, a fifteen storey moment resisting building frame is selected in conjunction with three different soil deposits with shear wave velocity less than 600m/s. The design sections are defined after applying dynamic nonlinear time history analysis based on inelastic design procedure using elastic-perfectly plastic behaviour of structural elements. These frames are modelled and analysed employing Finite Difference approach using FLAC 2D software under two different boundary conditions, namely fixed-base (no soil-structure interaction), and considering soil-structure interaction. Fully nonlinear dynamic analyses under the influence of different earthquake records are conducted and the results of inelastic behaviour of the structural model are compared. Variations of the shear modulus ratio with the shear strain are included in the nonlinear dynamic analysis. The results indicate that the inter-storey drifts of the structural model resting on soil types De and Ee (according to the Australian standard) substantially increase when soil-structure interaction is considered for the above mentioned soil types. Performance levels of the structures change from life safe to near collapse when dynamic soil-structure interaction is incorporated. Therefore, the conventional inelastic design procedure excluding SSI is no longer adequate to guarantee the structural safety for the building frames resting on soft soil deposits. Design engineers need to address the effects of dynamic SSI precisely in their design especially for construction projects on soft soils.

Mechanical properties of sandwich panels constructed from polystyrene/cement mixed cores and thin cement sheet facings

Sandwich panels are made of two materials that are relatively weak in their separated state, but are improved when they are constructed together in a sandwich panel. Sandwich panels can be used for almost any section of a building including roofs, walls and floors. These building components are regularly required to provide insulation properties, weatherproofing properties and durability in addition to providing structural load bearing characteristics. Polystyrene/cement mixed cores and thin cement sheet facings sandwich panels are Australian products made of cement-polystyrene beaded mixture encapsulated between two thick cement board sheets. The structural properties of sandwich panels constructed of polystyrene/cement cores and thin cement sheet facings are relatively unknown. Therefore, in this study, to understand the mechanical behaviour and properties of those sandwich panels, a series of experimental tests have been performed and the outcomes have been explained and discussed. Based on the results of this study, values for modulus of elasticity and ultimate strength of the sandwich panels in dry and saturated conditions have been determined and proposed for practical applications.

Detail design and construction procedure of laminar soil containers for experimental shaking table tests

In this study, a comprehensive procedure for detail design and construction of laminar soil containers has been developed and presented for practical applications in shaking table tests. A laminar soil container is a flexible container that can be placed on a shaking table to simulate vertical shear-wave propagation during earthquakes through a soil layer of finite thickness and can realistically simulate the free field conditions in comparison with other types of soil containers. The presented laminar soil container consists of aluminum frames and rubber layers in alternating pattern as the container main construction materials. The aluminum frames provide lateral confinement of the soil, while the rubber layers allow the container to deform in a shear beam manner. The designed and constructed container satisfies the conditions required to authentically capture free field ground motion. The lateral movements of the container in shaking table tests expected to be almost identical to the free field movements in reality. In addition, natural frequency of the constructed soil container, measured from Sine Sweep tests, matches the targeted natural frequency with acceptable accuracy.

Development of synthetic soil mixture for experimental shaking table tests on building frames resting on soft soils

ABSTRACT In this study, a synthetic soil mixture has been developed and proposed for experimental soil-structure interaction shaking table tests on building frames with shallow foundations resting on soft soil deposits. The proposed mix provides adequate undrained shear strength to mobilise the required shallow foundation bearing capacity underneath the structural model while meeting both criteria of dynamic similarity between the model and the prototype to model soft soils in shaking table tests. To find the most appropriate mixture, different mixes with different proportions of mix components were examined in the soils laboratory. Performing bender element tests, the shear wave velocity of the soil specimens was acquired at different cure ages and the results were examined and compared. Based on the test results, a synthetic clay mixture consisting of kaolinite clay, bentonite, fly ash, lime and water has been proposed for experimental shaking table tests.

Application Of Sustainable Design Principles To Increase Energy Efficiency Of Existing Buildings

Abstract This study investigates the effectiveness of different energy retrofitting techniques and examines the impact of employing those methods on energy consumption of existing residential buildings. Based on the research findings, the most effective and practical method of retrofitting has been proposed in order to improve energy efficiency of existing buildings. In order to achieve this goal, an existing residential building has been simulated in FirstRate 5 software so as to determine the existing thermal performance of the building. Afterwards, considering sustainable design principles, different insulation layers, glazing, and construction materials have been employed to conduct a comprehensive thermal performance study. Based on the research outcomes, the best technique for increasing energy efficiency of existing buildings and reducing their environmental impact and footprint has been identified and proposed for practical purposes.

Comparing of Normal Stress Distribution in Static and Dynamic Soil‐Structure Interaction Analyses

It is important to consider the vertical component of earthquake loading and inertia force in soil‐structure interaction analyses. In most circumstances, design engineers are primarily concerned about the analysis of behavior of foundations subjected to earthquake‐induced forces transmitted from the bedrock. In this research, a single rigid foundation with designated geometrical parameters located on sandy‐clay soil has been modeled in FLAC software with Finite Different Method and subjected to three different vertical components of earthquake records. In these cases, it is important to evaluate effect of footing on underlying soil and to consider normal stress in soil with and without footing. The distribution of normal stress under the footing in static and dynamic states has been studied and compared. This Comparison indicated that, increasing in normal stress under the footing caused by vertical component of ground excitations, has decreased dynamic vertical settlement in comparison with static state.