An extensive research program is on-going at the University of Canterbury, New Zealand to develop new technologies to permit the construction of multi-storey timber buildings in earthquake prone areas. The system combines engineered timber beams, columns and walls with ductile moment resisting connections using post-tensioned tendons and eventually energy dissipaters. The extensive experimental testing on post-tensioned timber building systems has proved a remarkable lateral response of the proposed solutions. A wide number of post-tensioned timber subassemblies, including beam-column connections, single or coupled walls and column-foundation connections, have been analysed in static or quasi-static tests. This contribution presents the results of the first dynamic tests carried out with a shake-table. Model frame buildings (3-storey and 5-storey) on one-quarter scale were tested on the shake-table to quantify the response of post-tensioned timber frames during real-time earthquake loading. Equivalent viscous damping values were computed for post-tensioned timber frames in order to properly predict their response using numerical models. The dynamic tests were then complemented with quasi-static push and pull tests performed to a 3-storey post-tensioned timber frame. Numerical models were included to compare empirical estimations versus dynamic and quasi-static experimental results. Different techniques to model the dynamic behaviour of post-tensioned timber frames were explored. A sensitivity analysis of alternative damping models and an examination of the influence of designer choices for the post-tensioning force and utilization of column armouring were made. The design procedure for post-tensioned timber frames was summarized and it was applied to two examples. Inter-storey drift, base shear and overturning moments were compared between numerical modelling and predicted/targeted design values.

Reinforcement of soil enables a soil slope or wall to be retained at angles steeper than the soil material’s angle of repose. Geosynthetic Reinforced Soil (GRS) systems enable shortened construction time, lower cost, increased seismic performance and potentially improve aesthetic benefits over their conventional retaining wall counterparts such as gravity and cantilever type retaining walls. Experience in previous earthquakes such as Northridge (1994), Kobe (1995), and Ji-Ji (1999) indicate good performance of reinforced soil retaining walls under high seismic loads. However, this good performance is not necessarily due to advanced understanding of their behaviour, rather this highlights the inherent stability of reinforced soil against high seismic loads and conservatism in static design practices. This is an experimental study on a series of seven reduced-scale GRS model walls with FHR facing under seismic excitation conducted using a shake-table. The models were 900 mm high, reinforced by five layers of stiff Microgrid reinforcement, and were founded on a rigid foundation. The soil deposit backfill was constructed of dry dense Albany sand, compacted by vibration (average Dr = 90%). The influence of the L/H ratio and wall inclination on seismic performance was investigated by varying these important design parameters throughout the testing programme. The L/H ratio ranged from 0.6 – 0.9, and the walls were primarily vertical except for one test inclined at 70o to the horizontal. During testing, facing displacements and accelerations within the backfill were recorded at varying levels of shaking intensity. Mechanisms of deformation, in particular, were of interest in this study. Global and local deformations within the backfill were investigated using two methods. The first utilised coloured horizontal and vertical sand markers placed within the backfill. The second utilised high-speed camera imaging for subsequent analysis using Geotechnical Particle Image Velocimetry (GeoPIV) software. GeoPIV enabled shear strains to be identified within the soil at far smaller strain levels than that rendered visible by eye using the coloured sand markers. The complementary methods allowed the complete spatial and temporal development of deformation within the backfill to be visualised. Failure was predominantly by overturning, with some small sliding component. All models displayed a characteristic bi-linear displacement-acceleration curve, with the existence of a critical acceleration, below which deformations were minor, and above which ultimate failure occurs. During failure, the rate of sliding increased significantly. An increase in the L/H ratio from 0.6 to 0.9 caused the displacement-acceleration curve to be shallower, and hence the wall to deform less at low levels of acceleration. Accelerations at failure also increased, from 0.5g to 0.7g, respectively. A similar trend of increased seismic performance was observed for the wall inclined at 70o to the horizontal, when compared to the other vertical walls. Overturning was accompanied by the progressive development of multiple inclined shear surfaces from the wall crest to the back of the reinforced soil block. Failure of the models occurred when an inclined failure surface developed from the lowest layer of reinforcement to the wall crest. Deformations largely confirmed the two-wedge failure mechanism proposed by Horii et al. (2004). For all tests, the reinforced soil block was observed to demonstrate non-rigid behaviour, with simple shearing along horizontal planes as well as strain localisations at the reinforcement or within the back of the reinforced soil block. This observation is contrary to design, which assumes the reinforced soil block to behave rigidly.

In recent years the public expectation of what is acceptable in seismic resisting construction has changed significantly. Engineers today live under demands which are far more intensive than their historical counterparts and recent seismic events have shown that preserving life is no longer sufficient, and a preservation of livelihood is now the minimum. This means that after a major seismic event a building should not only be intact but be usable with no or minimal post-quake intervention. In addition to this already high expectation these demands must be met in a green and sustainable fashion with minimal (or even negative) environmental impact. This doctoral project looks to further advance the research into a new and innovative method of timber construction which satisfies (and exceeds) these demands. In response to these higher expectations recent developments in the field of seismic design have led to the development of damage control design philosophies and innovative seismic resistant systems. Jointed ductile connections for precast concrete structures have been implemented and successfully validated. One of these systems, referred to as the hybrid system, combines the use of unbonded post-tensioned tendons with grouted longitudinal mild steel bars or any other form of dissipation reinforcing device. During the controlled rocking of the system under seismic loading the post-tensioning provides desirable recentering properties, while the devices allow adequate energy dissipation from the system as well as increased moment resistance at column bases and beam-column connections. The hybrid concept is material independent and in 2004 an extensive campaign was begun to investigate the performance of the hybrid system when applied to large engineered timber members. Numerous small and large scale tests on both subassemblies and full buildings were performed showing that post-tensioned timber meets the seismic resilience demands now imposed by society. Recently this technology has also been applied in practice with over ten structures now using post-tensioned timber walls or frames, or a combination of the two, in New Zealand. In-spite of the extensive research effort and the acceptance and adoption in practice of post-tensioned timber as a structural system, significant work was still required in the review and refinement of both the system itself and the analytical and numerical methods used to predict and analyse structural performance. The objectives of this research were to review and refine comprehension of the static and dynamic response, analytical and numerical modelling, and design of post-tensioned timber frames under lateral loading. In order to do this a three phase experimental testing campaign was devised and performed including quasi-static testing of an angle dissipative reinforcing device, quasi-static testing of a full-scale beam-column joint and the mono-directional dynamic testing of a 2/3rd scale three storey frame. All testing used glue laminated timber, which had not been previously used in post-tensioned timber structures. Insight gained from the experimental testing was used to analyse and refine existing analytical modelling techniques. These techniques were split into two categories: 1) modelling of the local behaviour of a post-tensioned timber beam-column joint, with particular focus on stiffness and energy dissipation capacity, and 2) evaluation of the seismic demand (in the form of design base shear) on post-tensioned timber frames looking at current Force Based (FBD) and Displacement Based (DBD) design methods. This analysis led to the development of recommended alterations in the existing beam-column joint analytical procedure enabling the procedure to provide better prediction of initial and post-yield stiffness. Analysis of the FBD and DBD procedures showed that both methods are capable of providing accurate prediction of seismic demand provided correct assumptions are made regarding system ductility and damping characteristics. Recommendations have been made on how designers can ensure that assumptions are either sufficiently accurate in the beginning of a design or require minimal iteration to be performed. Current numerical modelling techniques have also been compared against the quasi-static and dynamic testing results providing confidence in their accuracy when applied to post-tensioned timber frames. Modelling techniques were also extended to the widely used SAP2000 modelling programme which had not been previously used in post-tensioned timber research. Although many observations and conclusions were made, a common theme continued throughout this research. This was the importance of the deep understanding of displacements within a post-tensioned timber frame and the impact of these displacements on frame performance. Displacements occur throughout a frame in dissipative reinforcing devices, in the connection of these devices, in beams, columns and joint panels as well as at the interfaces between members. When these displacements are allowed for through proper design excellent seismic performance, possible using this innovative system, is obtained.

Underground structures perform an important role in transportation systems in many seismically active regions around the world, but empirical data regarding the seismic behavior of these structures is limited. This research works towards filling that empirical gap through the use of scale model shake table testing. Underground seismic soil-structure interaction (USSSI) effects were investigated for a stiff rectangular tunnel cross-section embedded within soft clay. San Francisco Young Bay Mud was used as a prototype soil for developing a scale model soil mixture consisting of kaolinite, bentonite, class C fly ash, and water. A single cell Bay Area Rapid Transit (BART) cut-and-cover subway tunnel was used as the prototype for the 10th scale model subway cross-section. A flexible walled test container originally developed for a pile study at UC Berkeley was modified for use at Cal Poly, San Luis Obispo. The flexible container allows for close approximation of one-dimensional (1D) free-field site response by significantly limiting the rigidity of the boundary conditions and allowing the soil to deform under simple shear. The study was conducted over two shake table testing phases: Phase I consisted of shaking a model soil column to evaluate the ability of the test container to produce adequate 1D free-field site response, and Phase II tests explored the horizontal racking distortion of a shallow rectangular tunnel cross-section subjected to strong transverse ground shaking. Phase I test results and comparison with SHAKE models indicate that the test container can sufficiently mimic 1D free-field conditions, specifically for the primary shear deformation mode. Similarly, the equivalent linear soil-structure interaction code FLUSH was found to adequately model site response for the Phase II soil-structure system. Comparison of recorded horizontal racking distortions of the model structure with those from numerical modeling suggest that current simplified design methods may overestimate distortions to some degree for cases similar to those examined in this research. Overall, the flexible wall testing container shows promise as a viable means for gaining further insight into USSSI topics, as well as various other geotechnical and soil-structure interaction problems.

This thesis presents the details of designing and commissioning the multi-use static/dynamic large-scale soil testing table. The table was developed with the intention of creating a large scale testing apparatus versatile enough to carry out several different types of testing on a large scale. This report describes the background research done to develop the testing table concept and the thinking that went into each component. The apparatus itself consists of a shake table with a laminar soil container (inside dimensions L:100cm W:50cm H:65cm) and a top which can be lowered to apply overburden pressures on specimens. It is set up to run both static and cyclic tests on large soil samples. The final design allows for performing shaking tests with a non-fixed top, static and dynamic simple shear tests, and direst shear tests with minimal changes to the table configuration. The table has separate control and data acquisition systems which are necessary to run and record tests. All components of the table will be explained thoroughly within the thesis. Preliminary testing was done with the table to determine how well it is functioning and what needs to be done to further improve it. Static simple shear and cyclic simple shear tests were both run, and while the table showed some flaws, the results seem promising. It is determined that with proper instrumentation and after addressing some small issues, the testing table can be a useful and versatile tool in the future. This thesis will outline the strengths and flaws of the table as currently constructed and determine what the future applications for this testing apparatus will be. / text

This research involves shake table testing of 1g scale models that mimic the coupled seismic response of a structure on a shallow mat foundation and foundation soil (known as soil-foundation-structural-interaction or SFSI). In previous research, SFSI effects have been quantified through analytical models, numerical analyses, and limited field data. This research works towards increasing the amount of empirical data through scale model shake table testing. A suite of earthquake time histories is considered in evaluating a nominal 10th scale soil-structure model using a flexible wall barrel on a 1-D shake table. San Francisco Young Bay Mud (YBM) is used as the prototype soil and long period narrow building as the prototype structure. Foundation embedment depth, fundamental mode of the structure, and seismic loading function are varied to generate a large database of SFSI results under controlled conditions. The foundation level response is compared to free-field responses to determine the magnitude of the SFSI. The results confirm the effects of foundation embedment on the peak ground motion and the spectral acceleration at the predominant period of the structure. The foundation level accelerations are deamplified compared to free-field results. Results also confirm the legitimacy of the testing platform and program by comparing the data to previous experimental study.

Real-time structural health monitoring is a well established tool for post-earthquake damage estimation. A key component in the monitoring campaign is the approach used for processing the data from the structural health monitoring system. There is a large body of literature on signal processing approaches aimed at identifying ground-motion induced damage in civil engineering structures. This dissertation expands on a specific subgroup of processing approaches dealing with the identification of damage induced high-frequency transients in the monitoring data. The underlying intuition guiding the current research can be formulated in the following hypothesis - the time difference between the occurrence of a high-frequency transient and the closest deformation extremum forward in time is proportional to the degree of damage. A mathematical deduction is provided in support of the above hypothesis followed by a set of shaking table tests. For the purposes of this research two shaking table tests of reinforced concrete bridge piers were performed. Data from a shaking table test performed by another research group was also analyzed. The cases in which the proposed procedure could find a practical application are examined along with the present limitations.

Container cranes represent one of the most critical components of ports worldwide. Despite their importance to port operations, the seismic behavior of cranes has been largely ignored. Since the 1960s, industry experts have recommended allowing cranes to uplift, believing that it would limit the amount of seismic loading. However, modern cranes have become larger and more stable, and the industry experts are now questioning the seismic performance of modern jumbo cranes. The main goal of this research was to experimentally investigate the seismic behavior of container cranes from the general elastic behavior through collapse, including non-linear behavior such as buckling and cross section yielding, utilizing the 6 degree-of-freedom shake tables at the University at Buffalo. The testing was divided into two phases. The first phase of testing was conducted on a 1/20th scale model. The second phase of testing was conducted on a 1/10th scale model, which was designed such that no inelastic action would develop prior to uplift (as is the common design practice). In support of the experiments, finite element models were created to determine what simplifications could be made to the structure to aid in testing. The data collected from the testing has been used to validate finite element models, to give a better understanding of the behavior of container cranes under seismic excitations, validate fragility models, and to develop recommendations and guidelines for the design and testing of container cranes.

Based upon the upper bound limit analysis, the stability numbers have been developed for a two-layered soil slope both for an associated flow rule material and for a homogeneous slope with non-associated flow rule material. The failure surface was assumed to be an arc of logarithmic spiral and it automatically ensures the kinematics admissibility of the failure mechanism with respect to the rigid rotation of the soil mass about the focus of the logarithmic spiral. The effect of the pore water pressure and horizontal earthquake body forces was also included m the analysis. For a non-associated flow rule material, the stress distribution along the failure surface was developed with the assumption of interslice forces given by Fellenius and Bishop. The stability numbers have been found to reduce appreciably with increases m the (i) horizontal inclination (β) of slope, (ii) pore water pressure coefficient, ru and (iii) horizontal earthquake acceleration coefficient (kh). The values of the stability numbers for a non-associated co-axial flow rule, with dilatancy angle ψ =0, have been found to be considerably lower as compared to the associated flow rule material. For a given height of the slope, with associated flow rule, the values of the stability numbers have been found to increase with increase in the thickness of a layer with greater value of the friction angle Φ. The results have been given in the form of non-dimensional stability charts, which can be used for readily obtaining either the value of the critical height or the factor of safety The methodology can be easily extended even for multi-layered soil slopes with different values of cohesion (c), bulk unit weight (γ) and friction angle (Φ). An attempt has also been made in this thesis to study experimentally the effect of the frequency of the excitation and the addition of non-plastic fines on the liquefaction resistance of the material Shake table studies, generating uni-axial sinusoidal horizontal vibrations, were earned out for this purpose. During the period of excitation of the material, the settlement at the surface of the sample increases continuously with time up to a certain peak value and thereafter, it becomes almost constant. For the excitation of the material with higher frequency, more number of cycles was seen to reach the final settlement. With the continuous excitation of the material, the magnitude of the pore water pressures increases up to a certain peak value and there after, its magnitude decreases till it again becomes the hydrostatic pressure as it was before the excitation of the material. The peak magnitude of the pore water pressure tends to be higher for the excitation with smaller frequency especially at greater depths from the ground surface. The addition of non-plastic fines tends to increase the magnitude of the settlement as well as the increase in the pore water pressure.

Several studies were undertaken by various investigators during the last five decades to better understand the engineering behaviour of unsaturated soils. These studies are justified as more than 33% of soils worldwide are found in either arid or semi-arid regions with evaporation losses exceeding water infiltration. Due to this reason, the natural ground water table in these regions is typically at a greater depth and the soil above it is in a state of unsaturated conditions. Foundations of structures such as the housing subdivisions, multi-storey buildings, bridges, retaining walls, silos, and other infrastructure constructed in these regions in sandy soils are usually built within the unsaturated zone (i.e., vadose zone). Limited studies are reported in the literature to understand the influence of capillary stresses (i.e., matric suction) on the bearing capacity, settlement and liquefaction potential of unsaturated sands. The influence of matric suction in the unsaturated zone of the sandy soils is ignored while estimating or evaluating bearing capacity, settlement and liquefaction resistance in conventional engineering practice. The focus of the research presented in the thesis has been directed towards better understanding of these aspects and providing rational and yet simple tools for the design of shallow foundations (i.e., footings) in sands under both static and dynamic loading conditions. Terzaghi (1943) or Meyerhof (1951) equations for bearing capacity and Schmertmann et al. (1978) equation for settlement are routinely used by practicing engineers for sandy soils based on saturated soil properties. The assumption of saturated conditions leads to conservative estimates for bearing capacity; however, neglecting the influence of capillary stresses contributes to unreliable estimates of settlement or differential settlement of footings in unsaturated sands. There are no studies reported in the literature on how capillary stresses influence liquefaction, bearing capacity and settlement behavior in earthquake prone regions under dynamic loading conditions. An extensive experimental program has been undertaken to study these parameters using several specially designed and constructed equipment at the University of Ottawa. The influence of matric suction, confinement and dilation on the bearing capacity of model footings in unsaturated sand was determined using the University of Ottawa Bearing Capacity Equipment (UOBCE-2011). Several series of plate load tests (PLTs) were carried out on a sandy soil both under saturated and unsaturated conditions. Based on these studies, a semi-empirical equation has been proposed for estimating the variation of bearing capacity with respect to matric suction. The saturated shear strength parameters and the soil water characteristic curve (SWCC) are required for using the proposed equation. This equation is consistent with the bearing capacity equation originally proposed by Terzaghi (1943) and later extended by Meyerhof (1951) for saturated soils. Chapter 2 provides the details of these studies. The cone penetration test (CPT) is conventionally used for estimating the bearing capacity of foundations because it is simple and quick, while providing continuous records with depth. In this research program, a cone penetrometer was specially designed to investigate the influence of matric suction on the cone resistance in a controlled laboratory environment. Several series of CPTs were conducted in sand under both saturated and unsaturated conditions. Simple correlations were proposed from CPTs data to relate the bearing capacity of shallow foundations to cone resistance in saturated and unsaturated sands. The details of these studies are presented and summarized in Chapter 3. Standard penetration tests (SPTs) and PLTs were conducted in-situ sand deposit at Carp region in Ottawa under both saturated and unsaturated conditions. The test results from the SPTs and PLTs at Carp were used along with other data from the literature for developing correlations for estimating the bearing capacity of both saturated and unsaturated sands. The proposed SPT-CPT-based technique is simple and reliable for estimation of the bearing capacity of footings in sands. Chapter 4 summarizes the details of these investigations. Empirical relationships were proposed using the CPTs data to estimate the modulus of elasticity of sands for settlement estimation of footings in both saturated and unsaturated sands. This was achieved by modifying the Schmertmann et al. (1978) equation, which is conventionally used for settlement estimations in practice. Comparisons are provided between the three CPT-based methods that are commonly used for settlement estimations in practice and the proposed method for seven large scale footings in sandy soils. The results of the comparisons show that the proposed method provides better estimations for both saturated and unsaturated sands. Chapter 5 summarizes the details of these studies. A Flexible Laminar Shear Box (FLSB of 800-mm3 in size) was specially designed and constructed to simulate and better understand the behaviour of model surface footing under seismic loads taking account of the influence of matric suction in an unsaturated sandy soil. The main purpose of using the FLSB is to simulate realistic in-situ soils behaviour during earthquake ground shaking. The FLSB test setup with model footing was placed on unidirectional 1-g shake table (aluminum platform of 1000-mm2 in size) during testing. The resistance of unsaturated sand to deformations and liquefaction under seismic loads was investigated. The results of the study show that matric suction offers significant resistance to liquefaction and settlement of footings in sand. Details of the equipment setup, test procedure and results of this study are presented in Chapter 6. Simple techniques are provided in this thesis for estimating the bearing capacity and settlement behaviour of sandy soils taking account of the influence of capillary stresses (i.e., matric suction). These techniques are consistent with the methods used in conventional geotechnical engineering practice. The studies show that even low values of capillary stresses (i.e., 0 to 5 kPa) increases the bearing capacity by two to four folds, and the settlement of footings not only decreases significantly but also offers resistance to liquefaction in sands. These studies are promising and encouraging to use ground improvement techniques; such as capillary barrier techniques to maintain capillary stresses within the zone of influence below shallow foundations. Such techniques, not only contribute to the increase of bearing capacity, they reduce settlement and alleviate problems associated with earthquake effects in sandy soils.