published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Civil Engineering / Master / Master of Science in Engineering

published_or_final_version / Civil Engineering / Master / Master of Science in Engineering

published_or_final_version / Mechanical Engineering / Master / Master of Science in Engineering

published_or_final_version / Civil Engineering / Master / Master of Philosophy

published_or_final_version / Civil Engineering / Master / Master of Philosophy

No description available.

The interface normal behavior between Ottawa sand and concrete for static and cyclic loading has been studied using Cyclic Multi Degree-of-Freedom test device. The static force controlled test for the interface showed exponential relation between normal stress and strain during initial loading, hyperbolic relation during unloading and linear relation during reloading. A series of cyclic force controlled interface tests are described for normal behavior and the interface behavior is found to be a function of the applied initial normal stress, the amplitude of the stress and the number of loading cycles. The reloading modulus is shown to increase with number of loading cycle. Also, a series of combined normal (force controlled) and shear (displacement controlled) tests are described in which the shear stress for given amplitude of shear displacement is found to increase as normal stress and number of loading cycles increases. The results of the laboratory tests for normal behavior are used to determine the parameters to describe the interface stress-strain response. The model is shown to describe the hysteresis behavior of the interface as a function of amplitude of normal stress and number of loading cycles. The model is used to predict the results of cyclic normal tests and combined normal and shear tests, and was found to yield satisfactory results. The interface model is implemented in a 2D nonlinear soil-structure interaction finite element procedure. The finite element procedure is verified with respect to simple problems for which close form solution or laboratory results are available. The response of the force controlled cyclic test and combined normal and shear test is then predicted using the FE procedure and reasonable results are obtained. A pier foundation subjected to base displacement is then analysed for different combinations of soil and interface behavior. Computer results are qualitatively compared with displacement and contact stresses and the effect of including the interface behavior is identified with respect to debonding and rebonding of the interface. The results of this research have provided understanding of the cyclic behavior of sand-concrete interface subjected to normal and combined normal and shear loading. The interface behavior has been represented by simple mathematical model for which parameters can be easily determined from static and cyclic tests. The model is also defined for general loading to incorporate debonding and rebonding and it is easy to implement into a FE procedure.

The control of stresses and liquid pressure surges in pipes is an important problem in the design of hydraulic pipe networks. The method of characteristics has been used to solve the transient stresses and pressures in liquid-filled piping systems. The friction force is included in the equations of motion for the fluid and the pipe wall. The maximum pressure and maximum stress at any point along the length of the pipe are evaluated for the entire simulation time. A nonlinear search technique has been developed using the simplex method. The optimal valve closure is sought, that will minimize the maximum pressure and/or stresses. A continuous optimal valve closure policy is specified using spline functions. Numerical examples are presented showing the reduction of the dynamic pressure and the dynamic stress from linear valve closure to optimal valve closure for a simple pipeline and a complex pipeline. Also, a method for choosing the shortest time of closure which will keep the stresses below specified allowable stresses is presented.

A finite element formulation, based on assumed stress functions, is developed for the linear elastic analysis of the stresses in two-dimensional elasticity problems, including multiply-connected regions and flat plate bending. For planar analysis the Airy stress function is utilized. The physical significance of the Airy stress function and its normal derivatives are brought out. A new technique is introduced to account for traction type boundary conditions. A family of rectangular finite elements, which enables the direct insertion of stress type boundary conditions, and two higher-order rectangular elements which enable continuous stress variations along the interelement boundaries are constructed using blending function interpolants. In addition, a C° continuous triangular plate bending element is adapted for use as a plate stretching element. The Southwell stress function is employed for the analysis of flat plates in bending. A computer program is developed to substantiate the proposed methodology. The formulations are evaluated through the comparison of solutions obtained from the proposed method with classical solutions and solutions obtained from the assumed displacement finite element method. The elements are evaluated by solving the same example problem with different element types. Extensions of the proposed method to account for body forces, initial stresses, material nonlinearities, and shells are briefly discussed. It is demonstrated that the proposed method can directly be integrated with minimal modifications into existing general purpose finite element programs.