<p>A finite element method that utilizes boundary conditions from wave propagation considerations is given for predicting the seismic response of a pile embedded in soil. The response of the system and the stress distribution in the soil adjacent to and beneath the pile are resolved, and these provide a means of appraising the behaviour of a soil-pile system during an earthquake. The three directional components of the earthquake excitation are considered. The soil-pile system is idealized as an axisymmetric structure subjected to nonsymmetric loading to simplify the computations.</p> <p>Records of ground motions during recent earthquakes have clearly demonstrated the significance of local soil conditions on the amplitude and frequency characteristics of seismic motions. For large epicentral distances, the usual assumption of energy transfer by means of vertically propagating shear waves is valid. However, for sites nearer to the source the direction of shear wave propagation may be inclined and surface waves also contribute to the ground motions. These aspects of the seismic motions are considered.</p> <p>The spatial variations in seismic motions are computed using wave propagation theory and assuming that the earthquake energy is transferred through the soil layers by shear waves and Rayleigh waves. Spatial variations in motion are compared for various epicentral distances and wave propagation assumptions. It is shown that the surface wave makes a significant contribution to the response at near sites, while the effect of inclining the shear wave propagation is of secondary importance. The method and programs are general so that they can be used for a variety of problems. Dimensions of the soil-pile system are adopted so that "free field" conditions can be assumed at the boundary. The seismic motion record for each boundary node of the discretized structure is computed and used as the input for the full finite element dynamic analysis which utilizes a step-by-step procedure.</p> <p>It was found that the single pile foundation considerably reduced the responses transferred to the structure. The method of analysis was used to consider the pore pressures developed in the case of saturated soils around a single pile. The behaviour of a pile-saturated sand system during the San Fernando Earthquake showed that the sand around the pile liquefied. When a pile-saturated clay system was subjected to the same earthquake, there was no sign of liquefaction. These results are in qualitative agreement with field observations.</p> / Doctor of Philosophy (PhD)

<p>This thesis deals with the modelling of the circulation and pollutant transport in the nearshore areas of lakes and their tributaries. An integrated hydrodynamic/pollutant transport model was developed which operates in an interactive environment and is equipped with powerful graphics. The model can predict: (a) the horizontal and vertical current structure in the lake under isothermal and stratified conditions for steady and variable wind conditions, (b) the spatial and temporal pollutant concentration distributions in the lake from multiple input pollutant sources such as creeks, sewer treatment plant outfalls (STPs) and combined sewer outfalls (CSOs) discharging in the lake, and (c) the particle trajectories released in different locations in the lake. The model was calibrated with extant laboratory data. The water level set-up and current structure in the Great Lakes were obtained under various wind conditions and in two cases, in Lake St. Clair and Lake Ontario, the model was verified with current meter and water elevation measurements, respectively. The model was successfully applied to the St. Clair River in Sarnia for a number of storm cases and was proven to be an effective tool in screening remedial options for mitigation of bacteriological pollution in the Bay. The field data collected during the 1990-1991 field season in Hamilton Harbour was analyzed and used to verify the model. The seiches of Lake Ontario and Hamilton Harbour were revealed for the first time in the water level data in the Harbour. The simulated and measured currents and drogue trajectories were in good agreement, indicating the presence of topographical eddies and mixing zones in the Harbour. Finally, a nested-grid model was developed and successfully applied in three nearshore areas of Hamilton Harbour to examine the impact of artificial islands by studying the changes in current patterns and concentration peak, exposure, and flushing time in different locations of concern.</p> / Doctor of Philosophy (PhD)

<p>Although hollow structural sections (HSS) are an efficient structural member and have attractive architectural appearance, their use as columns in low or medium-rise moment-resisting steel frames has been limited. Some of the difficulties are due to the lack of a simple and practical field-bolted moment connection between a W-shape beam and an HSS column.</p> <p>The objectives of this research study are to develop a practical bolted moment connection between a W-shape beam and a square HSS column and to evaluate its behaviour experimentally under monotonic and cyclic loading. In addition, it is of interest to evaluate the effect of the developed connection response on the frame's overall behaviour, and provide guidelines and design rules for detailing the connection. In this research study, attention is focused on investigating the behaviour of bolted end-plate connections developed by blind fasteners. An experimental-analytical approach was used in this research program.</p> <p>The experimental program which was carried out on full scale beam-to-column connections involved three phases. First, three monotonic tests were conducted to examine the behaviour of such a connection using blind fasteners and to compare their response with a similar connection using high strength A325 bolts. Second, four tests were conducted on connections utilizing larger HSS columns and with different stiffening conditions to reveal different modes of failure. Third, two cyclic tests were performed to examine the effect of cyclic loading on such a connection.</p> <p>Based on the observations and results of the experimental program, an analytical model to predict the behaviour of the connection was developed. The sensitivity of the model was checked by comparing its predictions with the experimental results. The model was then incorporated into "Drain-2DX" computer program to be used in analyzing moment resisting frames. Based on both experimental and analytical results, a design procedure for the connection was proposed.</p> <p>The effect of connection flexibility on the response of a 4-storey steel moment frame was evaluated by comparing the response to that of a similar frame with rigid connections. The frames were analyzed statically under monotonically increasing loading and dynamically under two earthquake ground motions. It was concluded that, the flexibility of semi-rigid connections should be included in both static and dynamic analyses to determine a frame's structural response more realistically.</p> / Doctor of Philosophy (PhD)

<p>The central focus of research undertaken concerned the strength and behaviour of separated double chord rectangular hollow section (RHS) K-joints. Peripherally the concepts of the twin member shear beam is introduced as a simple and inexpensive bridging for revealing the intrinsic structural properties of such joints.</p> <p>The finite element method has been used to investigate the stiffness characteristics of the separated joint. The RHS chord member is idealized by a thin plate representing the inner web and a channel representing the top and bottom flanges and the outer web. The stiffening effect by the channel is incorporated through its condensation into a boundary stiffness matrix to be added to the inner web stiffness matrix.</p> <p>The proposed finite element formulation includes rectangular plate elements in the inner web plate and a variety of beam elements in the channel forming grillage. The formulation considers both bending and in-plane actions. Material nonlinearities of the joint are assumed to be adequately represented by the Von Mises yield criterion and the associated plastic flow rule. While geometric nonlinearities have been excluded, this was deemed reasonable for the range of displacements considered in this study.</p> <p>To verify the finite element model, a number of experiments were conducted on twin shear beams with the objective of making definitive statements about the joint performance to be anticipated for the finite element model. Twenty-four specimens were tested in the Applied Dynamics Laboratory of McMaster University. Test results showed a definite improvement in structural performances for both increased depth and a decrease in the gap.</p> <p>From experimental result, a local deflection limit criterion was suggested to define a range of permissible displacements in double chord joints. Such a criterion was based upon that presented in the literature for single chord joints.</p> <p>A verification of the finite element model was made using the experimental data of the twin shear beams and it exhibited good correlation. A model of sensitivity analysis was then carried out with the objective of furthering understanding of the behaviour of such structural components.</p> <p>The model was extended to the general model called EPAC-RHS (Elasto-Plastic Analysis of RHS Connections). In the process of this extension, triangular plane stress-plate bending elements were introduced to accommodate an arbitrary joint assembly of K and N configuration. In addition, member preloads were accounted for in EPAC-RHS.</p> <p>Theoretical results of simulated K-joint models were compared with experimental data of K-joints obtained from the literature. While strength predictions were somewhat conservative, very good agreement of elastic response was observed for all tests.</p> <p>A yield line theory was developed for which two strength models, trapezoidal and conical were proposed. Their predicted strengths were compared with experimental loads at the limiting deflections suggested. Good agreement with the tests was found particularly for the trapezoidal model. The twin shear beam models were then extended to be applicable to K-joints by taking into account both the reduction in strength due to chord axial preload and the horizontal component of the diagonal force. Theoretical results were compared with previous experiments on K-joints and exhibited reasonable correlation.</p> / Doctor of Philosophy (PhD)

<p>Equipment can be mounted on rigid floors by placing the equipment freely on the floor without fastening, fixing it tightly to the floor. This study investigates the rocking response of equipment resting freely on rigid floors and also the effect of restrained rocking on the response of partially fixed equipment under seismic excitations.</p> <p>Equipment which rests freely on rigid floors is simulated as a rigid rectangular block. The overturning of rigid blocks is studied under the effects of three types of base motion, namely, pulsive, critical, and harmonic excitations.</p> <p>When the effect of pulse shapes on the overturning potential of rigid blocks under pulsive excitations is examined. It is found that the rectangular pulse will require the least peak acceleration for a specified duration. Under critical excitations, it is found that the extent of response amplification depends on the coefficient of restitution and the initial angle of rotation in addition to the peak acceleration of the pulses. TO amplify the motion by a specified ratio, pulses with lower peak acceleration are required for cases of large initial angles and for cases with large values of the coefficient of restitution. Under harmonic excitation, the conditions for steady-state periodic motion is derived. It is also found that as the coefficient of restitution decreases, the system becomes more stable against overturning and can withstand higher accelerations.</p> <p>Also in this research, the response of partially fixed equipment resting on rigid floors under the effect of harmonic and earthquake excitations is investigated. For systems restrained by non-yielding bolts, it is found that the existence of gaps has the effect of decreasing the deformation of the mounted equipment relative to the base compares to the case of complete fixation. The existence of gaps also decreases the natural frequency of the system. In systems with yielding bolts, the presence of the gaps affects the deformation of the equipment more than is systems with non-yielding bolts. In the latter, the total rocking angle after all stretching takes place is not sensitive to the initial gap size and depends only on the level of excitation.</p> <p>Based on this study, it is recommended hat equipment systems be allowed to rock on their bases by providing gaps in their anchorage systems. This kind of mounting has the advantage of allowing the equipment to rock with out the rock without the risk of overturning. Also, larger gaps are recommended for higher floor acceleration levels.</p> / Doctor of Philosophy (PhD)

<p>Electric power transmission lines have been traditionally designed for wind and ice loads. The earthquake load has not been considered in the analysis of transmission lines. During recent earthquakes, there have been indications of damage to transmission lines. Due to the complex nature of the problem, there is a lack of research work in the area of seismic analysis of transmission lines. The objective of this study is to evaluate the response of transmission lines to earthquake ground motion in order to evaluate the current design code methodology. The scope of this research program includes: (1) Modelling of different parts of the transmission line to analyze its seismic response, (2) comparison between the forces generated in the transmission tower members by wind, ice and earthquake loads, and (3) analyzing the probabilistic characteristics of the cable response to earthquake ground motion in order to establish a seismic design procedure for transmission lines. An intermediate span of a typical transmission line is chosen for the analysis. The tower members are modelled as truss elements. The cables are modelled by two node elements that retain their geometric nonlinearity. The dynamic characteristics of different components of the line (towers and cables) are determined in order to obtain a better understanding of the line behaviour. The in-plane and out-of-plane vibrations of the line are analyzed. The transmission line response to multiple support as well as uniform support excitations is evaluated. A closed form analytical solution for the cable vibration is carried out for a more detailed study of the cable nonlinear behaviour. It is concluded from the analysis that earthquake ground motion may cause substantial displacements and internal forces in the transmission line elements. The forces in transmission tower members due to the earthquake load may exceed those caused by the wind loads specified by the National Electrical Safety Code (NESC, 1993). Seismic ground motion may cause large displacement in the transmission line cables. This suggests that the cable motion during earthquakes should be included in the design of the line clearances to avoid having cables touch each other, which may cause power failure.</p> / Doctor of Philosophy (PhD)

<p>Many multi-story reinforced concrete frame structures were designed before the availability of current seismic design codes. The lateral load resistance of these structures may not be adequate even for a moderate earthquake due to the non-ductile reinforcement details of this type of structures. Recent post-earthquake investigations indicated that extensive damage occurs as a result of excessive shear deformation of the beam-column joints in the non-ductile frames, thus leading to full collapse of structures. The objectives of this study are to investigate the seismic behaviour of existing reinforced concrete frames under simulated seismic loading; as well as develop a rehabilitation technique for strengthening non-ductile frames. The first major part of the study is an experimental program conducted to: (i) investigate the inelastic behaviour of the non-ductile beam-column connections under cyclic loading; (ii) compare the response of the non-ductile beam-column connections with the response of beam-column connections designed according to the current concrete design code; and (iii) propose a practical method of rehabilitating existing connections and investigate their cyclic behaviour. The tested connections represent one-third scale model of existing connections. Six beam-column connections were tested under cyclic loading. The variables in the test specimens included the amount of joint and column transverse reinforcement and jacketing of the column only or both the column and the beam. Based on the test results, a design procedure is proposed for the rehabilitation of beam-column connections using corrugated steel jackets. The second major part of the study is to develop a suitable analytical procedure to simulate the behaviour of existing reinforced concrete joints so as to predict the proper behaviour of the non-ductile frames and develop a strategy for rehabilitation of such frames. Two joint elements are developed to represent the joint shear deformation and the beam reinforcing bar bond slip. The two elements are introduced into a non-linear dynamic analysis program which is used to simulate existing and rehabilitated frames. From the experimental and analytical research findings, recommendations for the design and detailing of the corrugated steel jacketing system for existing reinforced concrete frames are developed. In addition, a rehabilitation strategy is proposed to improve the performance of existing structures. The effects of the rehabilitation system on the confinement of beam-column connections, the provision of adequate development length for the positive bottom beam bars and the provision of full joint shear capacity are assessed and quantified. Test results indicated that corrugated steel jacketing system was found to be efficient in the rehabilitation of existing structures which do not meet the current seismic code requirements. A method is proposed for the design of the corrugated steel jacket to enhance the shear strength and ductility of the beam-column joint.</p> / Doctor of Philosophy (PhD)

<p>Dam safety is an important issue of current interest. In seismic regions, dynamic forces on the dam may be significant and may lead to crack initiation and propagation in the dam. A significant component of the dynamic forces is due to the hydrodynamic effects of the impounded water in the reservoir. The developed hydrodynamic force on the dam is highly dependent on the physical characteristics of the boundaries surrounding the reservoir including the reservoir bottom and sides. In this study, the effects of the reservoir boundary conditions on the seismic response of the dam are investigated. This study consists of four components. First, a mathematical model is proposed to account for the absorption effect of a sedimented reservoir bottom on the seismic response of the dam-reservoir system. Secondly, a study is conducted to examine the possibility of reducing the earthquake response of concrete gravity dams using hydrodynamic isolation at the dam-reservoir boundary. Thirdly, an analytical procedure is developed to compute the response of the hydrodynamic pressure and the seismic response of the dam impounding a reservoir of general shape and boundary conditions. Finally, the earthquake response of the dam was studied with special attention to the stresses in the dam. An index for the evaluation of the overall state of stress in the dam subjected to different load combinations is proposed. The dynamic component of stress and the proposed index in the dam are computed when the dam-reservoir system is subjected to different ground motion records. The effect of the reflected waves from underlying reservoir foundation rock on the calculated response of the dam when subjected to earthquake ground motion was found to be very important. It is concluded that the effect of the stiffness of a semi-infinite reservoir foundation on the reduction of the dam seismic response is more significant as compared to the dissipation effect of the sedimentation layer. It is shown that the isolation layer needs to be very soft and with sufficient thickness so as to effectively reduce the hydrodynamic pressure acting on the dam. The effects of the reservoir length and the type of boundary condition at the truncated reservoir boundary on the calculated response of hydrodynamic pressure were found significant. The proposed index for the stress in the dam (Stress Factor) was shown to have an acceptable correlation with the intensity of the input ground motion and can be used as a complementary design factor for seismic design of concrete gravity dams.</p> / Doctor of Philosophy (PhD)

<p>A study was conducted to investigate the dam-reservoir interaction effect on the linear and nonlinear seismic response of concrete gravity dams. A mathematical approach was developed for the solution of the coupled dam-reservoir interaction problem which can be implemented in the nonlinear seismic analysis of concrete gravity dams. Two methods of staggered solution procedures are proposed for the dam-reservoir interaction. Using Routh-Hurwitz criteria, both methods are shown to be unconditionally stable when the two differential equations of the fluid and structure include damping terms. The staggered pressure method was modified for use when the equation of motion includes a lumped (diagonal) mass matrix. A finite element program was developed to include the staggered solution schemes for seismic analysis of concrete gravity dams. The program considers the dam-reservoir interaction. The reservoir can be considered as infinite in which an appropriate boundary condition can be applied at the desired distance from the upstream face of the dam. The finite reservoir condition is also an option that can be included in the analysis. The effect of the travelling wave where nonuniform earthquake ground motion is applied to the boundary of the reservoir can be evaluated. The nonlinear analysis of the concrete gravity dam was considered based on nonlinear fracture mechanics crack propagation criterion. Seismic response of a concrete gravity dam subjected to travelling seismic excitation is investigated. The analysis is applied to the case of a gravity dam with infinite and finite reservoirs of different lengths to evaluate the effect of the travelling seismic wave on the dam crest displacement. Various wave speeds representing the speed of wave travel in the reservoir foundation, are used in the analysis. Earthquake waves are considered to travel in the upstream or the downstream directions. The nonlinear seismic fracture response of the Pine Flat dam is investigated under the effect of reservoir interaction. Smeared crack analysis model based on a nonlinear fracture mechanics crack propagation criterion was used to study the cracking behaviour of a concrete gravity dam. The staggered method is used to solve the dam-reservoir interaction problem and results of the analysis were compared with the case when the added mass was used to represent the interaction effects. An experimental program was conducted on small scale models of the concrete dam. A loading mechanism with two actuators was designed to apply four concentrated loads on the upstream face of the dam model. Dynamic load was applied cyclically by an actuator to represent the effects of the earthquake loadings. The static load which represent the hydrostatic pressure was kept constant. The material properties of the model was maintained the same as the prototype. In the proposed approach, the stress distribution at the top part of the dam model and prototype of the same material properties are found to be in close agreement.</p> / Doctor of Philosophy (PhD)

<p>This thesis deals with numerical modelling of the behaviour of soils infiltrated with fluids. The main objectives are to study the effect of viscosity of the fluid on the response of particulate media under static and dynamic loadings, and to examine the influence of partial saturation on the behaviour under undrained conditions. The latter study is relevant to low as well as high degrees of saturation.</p> <p>In the formulation incorporating the effect of viscous fluid, the effective stress principle is modified by including the shear stress developed in the fluid phase. As this shear stress depends on the rate of shear strains the overall response is rate dependent. The formulation is implemented in a finite element algorithm and a number of numerical examples, including dynamic creep at low and high stress levels, are provided.</p> <p>In the next part of this thesis, the liquefaction of saturated soils is investigated. In these studies the effect of viscosity of liquefied material on the stability of the soil-foundation systems under earthquake excitation is examined. Furthermore, the stability theory is reviewed and a simplified stability criterion is introduced. The problems of stability of a strip foundation and a soil column are analyzed.</p> <p>In the last pan, a mathematical formulation for the behaviour of partially saturated soils is implemented in the finite element algorithm and some boundary-value problems are solved. In order to examine the performance of the constitutive model, a series of experimental tests are carried out. Subsequently, the effect of partial saturation on the stability of soil-foundation systems is examined. The liquefaction phenomenon under earthquake loading is studied for the case of high degrees of saturation, while the bearing capacity of fine grained soils is analyzed for the case of low degrees of saturation.</p> / Doctor of Philosophy (PhD)