Alper Turan

THE NUMERICAL AND EMPIRICAL EVALUATION OF STRUCTURAL PERFORMANCE OF ELEVATED TANKS CONSIDERING SOIL–STRUCTURE INTERACTION EFFECTS

Water tanks are an essential lifeline whose continuing availability and serviceability immediately after earthquake events are crucial for providing undisrupted emergency services. Their seismic performance is, therefore, of paramount importance. The seismic response of an elevated liquid tank situated on a soft soil deposit was studied by means of field vibration tests and numerical simulations. The ambient and forced vibration tests were conducted to identify the soil–structure interaction (SSI) effects on the small strain dynamic behavior of the structure. A series of time domain numerical analyses were performed to evaluate the seismic performance of these structures from a performance based design point of view. The results showed that consideration of SSI increased the displacement demand significantly. Thus, the calculated maximum displacement demand for supporting frame components of the tank may be underestimated significantly when the SSI effects are neglected. In addition, the seismic induced shear forces considering SSI effects were much smaller than the seismic shear forces for the fixed based case. For some soil types, the effect of this reduction on the overall response may become more prominent than the structural ductility mechanism. This resulted in the failure mechanism being initiated by a coupled compression — bending moment effect, rather than shear failure. Finally, the sloshing response is significantly increased due to the SSI.

Influence of Pore Fluid Viscosity on the Dynamic Properties of an Artificial Clay

This paper presents the results of vane shear, laboratory compaction, isotropic consolidation, cyclic triaxial, bender element, and resonant-column tests that were performed to characterize the dynamic properties of an artificial soil called modified glyben. Modified glyben comprises a mixture of glycerin, water, and bentonite that can be used in scaled model tests performed at 1 G or  n G in a centrifuge to study seismic soil–structure interaction. The results described in this paper show that the vane shear strength, coefficient of consolidation, dynamic modulus, and damping ratio are strongly influenced by the viscosity of the pore fluid which can be varied by altering the ratio of glycerin-to-water. In addition, the properties of modified glyben are stable during prolonged exposure to air and multiple largestrain load cycles making it a suitable model soil for scaled model tests involving seismic soil–structure interaction.

Lateral earth pressures acting on circular shafts considering soil-structure interaction

Abstract Nowadays, there is a significant demand on developing and expanding the existing infrastructure which necessitates the implementation of fast and cost effective construction methods such as the secant pile walls. The secant pile walls constructed in a circular plan layout to form a vertical shaft provide unique advantages such as compression ring behaviour. Compression rings act as a single-unit system in resisting lateral earth pressure and converting loads from all directions to compressive forces which can be resisted only by low concrete strength. Secant pile walls require stringent drilling tolerances to be achieved in order to behave as a compression ring and to perform as an effective groundwater cut-off wall. This paper presents a parametric study that investigates various aspects of the behaviour of circular shafts constructed using secant pile walls. The aspects that are studied include the identification of the magnitude and distribution of earth pressures exerted on circular shafts by the retained material. The distribution of surcharge pressures on the shaft walls is also studied. The results showed that the surcharge pressures on the wall increased with increasing width of surcharge area; for example, the maximum surcharge pressure increased by at least 60% when surcharge width increased from W = 3 m to W = 48 m. In addition, the results indicated a decrease of the maximum surcharge pressure on the wall by almost 22% when shaft radius decreased from R = 5 m to R = 3 m for Soil 1. Unlike what is observed in plane strain conditions, distance between the surcharge and shaft wall was seen to have a small effect on the magnitude of maximum pressures. The results also showed that the theoretical estimate of pressures underestimated the calculated values at larger depths and that the horizontal extent of the spread of pressure around the shaft was significantly influenced by the type of soil as well as width of surcharge. The outcomes of this study address practical design concerns and are considered to be of interest to those involved in design and construction of vertical shafts.