Adjacent buildings subjected to seismic excitations collide against each other when the separation distance is not large enough to accommodate the displacement response of the structures relative to one another. As shown by field observations and by numerical models, seismic pounding can cause severe damage on the affected structures. While these undesirable effects can be prevented by providing adequate separation distances, implementation of generous separations is not possible in metropolitan areas because of maximization of land usage. First, an extensive review of the current state-of-the-art on pounding and on mitigation with a connector linking adjacent structures is made. The only conclusion shared by the researchers is that the effect of pounding on the response of the structure is a very complex one, depending on various parameters of the structures and the characteristics of the ground motion. Due to high complexities of the pounding problems, assumptions have to be made. Most of the researchers have used single-degree-of-freedom systems but this model cannot represent the formation of a storey mechanism or the impact between slab and column. Another assumption generally made is to model linear structure. However, the author found that when pounding occurs, a structure entering in the plastic domain cannot generally be adequately represented by an elastic model. Various assumptions and restrictions are applied to these models. Non-linear direct time history analyses are realized with three artificial accelerograms. The problem has been reduced to a two-dimensional one. The interaction between soil and structure has been neglected. The structures studied have been designed according to Eurocodes [EC8, EC2] for a peak ground acceleration of 0,4g, 0,25g and 0,10g. Beams and columns are idealized as distinct elements and all inelastic deformations are considered concentrated at their two ends (point hinge models). Contact points are known a priori and located at each slab of the buildings. The Kelvin model, a spring and a dashpot used in combination with a gap element, is used in SAP 2000 program to simulate the pounding phenomenon. The pounding effects are first studied. The study concerns adjacent structures having same and different total height and (non)aligned floor levels. It was found difficult to give rules to anticipate the response of the adjacent buildings. This is due to the complex but necessary non-linear behaviour of pounding and structures. In short, pounding amplifies the displacements and the shear action effects of the impacted buildings. These effects can lead to serious damage caused by P-Delta effects or by shear brittle failure. As expected, pounding phenomenon is found to be very dangerous for buildings having non-aligned floor levels. The second part of the work studied the use of connections between adjacent buildings. The study consists in exploring problems and solutions in order to provide guidance to designers. Following the numerical simulations, a practical guide is presented to assist engineers in the choice of the adequate type and properties for the reconnection with reference to the characteristics of the structures submitted to pounding and to their stand-off distances.

Building pounding is a recognised phenomenon where adjacent buildings collide under lateral loading due to insufficient provision of building separation. The consequences of this interaction are known to be complex, and both buildings’ responses can be significantly affected. In the absence of extensive experimental data, numerical modelling has been frequently adopted as a means of evaluating building pounding risk during earthquakes. In performing numerical analysis, it becomes necessary to create specialised ‘contact’ elements to simulate building contact. While many contact elements have been previously proposed, detailed consideration of their inherent assumptions has frequently been overlooked. This thesis considers the significance and consequences of using the Kelvin contact element for a variety of pounding situations and with varying levels of model detail. Pounding between two adjacent floors (floor/floor collision) is considered as a one dimensional wave propagation problem. By modelling each floor as a flexible rod (termed distributed mass modelling), theoretical relationships for collision force, collision duration and post-collision velocity are derived. This theory is then compared to the predictions made when using the traditionally adopted assumptions of fully rigid colliding floors (termed lumped mass modelling). The post-collision velocities obtained from each method are found to agree only when the axial period of both floors is identical. Relationships between lumped mass and distributed mass models are formed, and an ‘equivalent lumped mass’ method is developed where distributed mass effects can be emulated without explicit modelling of floor flexibility. The theoretical solution method is then adapted for use in Non-Linear Time History Analysis (NLTHA) software to model specific pounding situations. Numerical modelling of a single collision is performed to compare these results to the theoretical predictions. Good agreement is found, and the model’s complexity is simplified until a sufficiently accurate simulation is performed without overly onerous computational requirements. Five methods are detailed that incorporate energy loss during collision into the distributed mass models and a calibration method is developed that enables researchers to define the level of energy loss that occurs during a single collision. Using the developed modelling methods, the pounding response of two existing Wellington buildings is predicted. This is first performed using 2D analysis of the stiffest frame from each building. The predicted building pounding damage is categorised into local damage (damageresulting from the magnitude of the force applied during contact) and global damage (damage due to the change in dynamic building properties resulting from momentum transfer during collision). Local and global damage effects are found to be fundamentally different consequences of collision, with the two categories responding differently to changes in the modelled system. The effects of building separation, scaling of input motion, modelling of soil-structure-interaction, collision damping, and floor rigidity are investigated for the considered system. 3D analysis of the building configuration is then investigated. Additional complications arising from the transverse movement of buildings prior to and during collision are identified and refined modelling methods are developed. The 3D configuration of these buildings causes torsional interaction, despite both buildings being perfectly symmetrical. This torsion is due to the eccentric positioning of the buildings relative to each other, which causes an eccentric contact load when pounding occurs. The 3D models are used to test the effects of building separation, 2D vs. 3D modelling, collision damping, floor rigidity, and the significance of the torsional interactions. Attention is then focused on collisions between a building’s floors and an adjacent building’s columns (floor/column collision). Due to the high frequency content of pounding impacts, the significance of using Timoshenko beam theory instead of Euler-Bernoulli theory is assessed. The shear stiffness in the Timoshenko formulation is found to significantly affect the columns’ predicted performance, and is used in subsequent modelling. An appropriately accurate method of modelling that minimises computational effort is then developed. The simplified model is used to predict the performance of two three-storey buildings that experience floor/column collision. The effects of floor/column impact are predicted for collisions at mid-height, and near the support of the impacted column. Each of these scenarios investigates the effect of building separation on local damage and global damage. Finally, a method to model collision between two adjacent walls that collide out-of-plane is developed (wall/wall contact). The adopted contact element properties are selected using analogous situations that have been previously investigated. The method is used to investigate a single collision between two different wall configurations. In the conclusions, the developed modelling methods from all the considered collision configurations are collected and presented in a summary table. It is intended that these recommendations will assist other researchers in selecting appropriate building pounding modelling properties.

The Georgia Department of Transportation has been installing steel pedestals on bridges, ranging in height up to 33½” (0.85m) to increase the vertical clearance of many multi-span simply-supported and multi-span continuous bridges in Georgia. But there is a concern about the performance of these steel pedestals as they are designed without seismic consideration and may perform poorly compared to high-type steel “rocker” bearings, which were found to be unstable supports in previous earthquakes. This research models a candidate bridge using experimental data that captures the force-displacement hysteretic behavior of the steel pedestals. The results show how these steel pedestals behave when subjected to a range of ground motions. Nonlinear time history analysis is conducted using SAP 2000 software on a three-dimensional model of the candidate bridge. In addition, parametric studies of various critical parameters that can affect the seismic performance of the bridge are investigated, such as 1) varying the mass of the structure, 2) varying the stiffness of the deck joint, 3) varying column heights, and 4) seismic retrofitting using cable restrainers. The results show that these pedestals should not be used in regions of high seismicity, and in regions of low seismicity, it is likely that they need to be retrofitted. They can, although, be used safely in regions of low seismicity. In addition, it was shown that the mass of a superstructure and height of the columns significantly affect the behavior of these steel pedestals, and should be given a careful consideration before usage. It was also shown that the stiffness of the expansion joints does not significantly affect the displacement of the steel pedestals and the forces transmitted to them. However, if the expansion joints are too stiff compared to the adjacent bridge components, then the forces transferred during pounding of superstructure is increased significantly.

The problem of investigating the possibilities of direct design transfer from plant to fabric and paper was divided into two parts. The first part is concerned with the exploration of the mechanics of the transfer. Invloved in this process are the technique of manipulating tools, of selecting suitable fabrics and paper, of determining chemicals that would facilitate the printing process and of experimenting with ways to preserve the finished design. The evaluation of the usability and durability of the finished print was based on a series of color fastness tests. The second part of this problem is concerned with the exploration of the design possibilities of the medium. The plants were tested and rated according to their visual attributes relative to the elements of design. Combinations of the successful plant prints were used to produce variations of pattern and texture. The results of the investigation were evaluated to determine the versatility of the medium as a design tool and the usefulness of the technique as a practical printing method

As the cost of land in cities increases, the need to build multistory buildings in close proximity to each other also increases. Sometimes, construction materials, other objects and any projections from a building may also decrease the spacing provided between the buildings. This leads to the problem of pounding of these closely placed buildings when responding to earthquake ground motion. The recent advent of base isolation systems and their use as an efficient earthquake force resisting mechanism has led to their increased use in civil engineering structures. At the same time, building codes that reflect best design practice are also evolving. The movement of these base isolated buildings can also result in building pounding. Since base isolation is itself a relatively new technique, pounding phenomenon in base isolated buildings have not been adequately investigated to date. This study looks at the base isolated response of a single two story building and adjacent two story building systems. Four earthquakes with increasing intensity were used in this study. It was found that it is difficult to anticipate the response of the adjacent buildings due to non- linear behavior of pounding and base isolation. The worst case for pounding was found to occur when a fixed base and base isolated buildings were adjacent to each other.

Earthquake ground motion can induce out-of-phase vibrations between adjacent structures due to differences in dynamic characteristics, which can result in impact or pounding of the structures if the at-rest separation is insufficient to accommodate the relative displacements. In bridges, seismic pounding between adjacent decks or between deck and abutment can result in localized deck damage, bearing failure, damage to shear keys and abutments, and even contribute to the collapse of bridge spans. This study investigates pounding in bridges from an analytical perspective. A simplified nonlinear model of a multiple-frame bridge is developed in MATLAB incorporating the effects of inelastic frame action, nonlinear hinge behavior and abutments. The equations of motion of the bridge response to longitudinal ground excitation are assembled and solved using the fourth-order Runge-Kutta method. Pounding is simulated using contact force-based models such as the linear spring, Kelvin and Hertz models, as well as the momentum-based stereomechanical method. In addition, a Hertz contact model with nonlinear damping (Hertzdamp model) is also introduced to model impact. The primary factors controlling the pounding response are identified as the frame period ratio, ground motion effective period ratio, restrainer stiffness ratio and frame ductility ratio. Pounding is most critical for highly out-of-phase frames. Impact models without energy dissipation overestimate the stiff system displacements by 15%-25% for highly out-of-phase, elastic systems experiencing moderate to strong ground excitation. The Hertzdamp model is found to be the most effective in representing impact. Traditional column hysteresis models such as the elasto-plastic and bilinear models underestimate the stiff system amplification and overestimate the flexible system amplification due to impact, when compared with stiffness and strength degrading models. Strength degradation and pounding are critical on the stiff system response to near field ground motions, for highly out-of-phase systems. Current design procedures are adequate in capturing the nonlinear hinge response when the bridge columns are elastic, but require revisions such as the introduction of time dependent reduction factors, and a frame design period to work for inelastic situations. Finally, a bilinear truss element with a gap is proposed for implementing energy dissipating impact models in commercial structural software.

As the cost of land in cities increases, the need to build multistory buildings in close proximity to each other also increases. Sometimes, construction materials, other objects and any projections from a building may also decrease the spacing provided between the buildings. This leads to the problem of pounding of these closely placed buildings when responding to earthquake ground motion. The recent advent of base isolation systems and their use as an efficient earthquake force resisting mechanism has led to their increased use in civil engineering structures. At the same time, building codes that reflect best design practice are also evolving. The movement of these base isolated buildings can also result in building pounding. Since base isolation is itself a relatively new technique, pounding phenomenon in base isolated buildings have not been adequately investigated to date. This study looks at the base isolated response of a single two story building and adjacent two story building systems. Four earthquakes with increasing intensity were used in this study. It was found that it is difficult to anticipate the response of the adjacent buildings due to non- linear behavior of pounding and base isolation. The worst case for pounding was found to occur when a fixed base and base isolated buildings were adjacent to each other.

This dissertation studied the structural identification and damage detection of civil engineering structures. Several issues regarding structural health monitoring were addressed. The data-driven subspace identification algorithm was investigated for modal identification of bridges using output-only data. This algorithm was tested through a numerical truss bridge with abrupt damage as well as a real concrete highway bridge with actual measurements. Stabilization diagrams were used to analyze the identified results and determine the modal characteristics. The identification results showed that this identification method is quite effective and accurate. The influence of temperature fluctuation on the frequencies of a highway concrete bridge was investigated using ambient vibration data over a one-year period of a highway bridge under health monitoring. The data were fitted by nonlinear and linear regression models, which were then analyzed. The substructure identification by using an adaptive Kalman filter was investigated by applying numerical studies of a shear building, a frame structure, and a truss structure. The stiffness and damping were identified successfully from limited acceleration responses, while the abrupt damages were identified as well. Wavelet analysis was also proposed for damage detection of substructures, and was shown to be able to approximately locate such damages. Delamination detection of concrete slabs by modal identification from the output-only data was proposed and carried out through numerical studies and experimental modal testing. It was concluded that the changes in modal characteristics can indicate the presence and severity of delamination. Finite element models of concrete decks with different delamination sizes and locations were established and proven to be reasonable. Pounding identification can provide useful early warning information regarding the potential damage of structures. This thesis proposed to use wavelet scalograms of dynamic response to identify the occurrence of pounding. Its applications in a numerical example as well as shaking table tests of a bridge showed that the scalograms can detect the occurrence of pounding very well. These studies are very useful for vibration-based structural health monitoring.