<p> This dissertation presents a new development of the wave method for structural health monitoring (SHM) of buildings. Robust and reliable SHM methods help save lives and reduce economic losses caused by earthquakes and other extreme events. Previously, in system identification and health monitoring, it was assumed that waves of different frequency propagate with constant velocity and the identification was based on the non-dispersive shear beam model of the structure. This study presents the first effort to consider dispersive wave propagation in system identification and health monitoring by the wave method. To consider dispersion due to bending deformation in buildings a Timoshenko beam model is used. Although buildings as a whole deform primarily in shear, bending deformation is always present to some degree especially for shear wall buildings. To identify allowable ranges of important parameters of the model parametric studies are performed. The model is further generalized to a non-uniform Timoshenko beam model which can take into account variation of properties with height and be used for higher resolution structural health monitoring. The models together with the suggested method to estimate initial values were validated on three full scale buildings. They were used to identify two full scale building from earthquake records and also to monitor the changes in a full-scale 7-story slice of shear wall building which was progressively damaged on UCSD-NEES shake table. It was shown that the model is robust for structural identification and health monitoring of a wide range of building systems and can successfully model dispersion due to bending deformation. </p>

<p> In rural parts of the world, lack of access to roads that are useable year-round significantly contributes to poverty. Suspended footbridges can improve access at locations that require medium span crossings (15 m to 64 m). This dissertation challenges the idea that modern bridges of this type must use steel rope, a well-established material for this application. Polyester rope, an unconventional bridge material, is investigated as an alternative to steel rope for rural suspended footbridges. The specific goals of this research are to: (i) characterize the static and dynamic behavior of polyester-rope bridges and (ii) determine which design criteria and system parameters will influence future design guidelines for these structures. </p><p> Numerical and analytical, static, natural frequency, and pedestrian excitation computations are performed to investigate the influence of polyester rope's material stiffness on the static and dynamic response of polyester-rope suspended footbridges. Polyester rope's low stiffness leads to larger static bridge deflections than occur for steel-rope structures. These deflections are accompanied by a nonlinear increase in a bridge's geometric stiffness and lead to high levels of safety against overloading. Polyester rope's low stiffness also requires that these bridges be prestressed to meet static and dynamic serviceability (pedestrian comfort) limits specified in footbridge guidelines. The damping ratios that are utilized in the pedestrian excitation analyses follow from the first set of full-scale physical tests that have been performed on a medium-span polyester-rope bridge. </p><p> Multi-objective optimization is utilized to find minimum volume polyester-rope and steel-rope suspended footbridge designs across the medium span range when subject to in-plane static and dynamic strength and serviceability constraints. The optimization problems are evaluated with a novel methodology that combines a genetic algorithm with static, natural frequency, and pedestrian excitation analyses. The impact of cross-sectional area, material stiffness, prestress, damping, mass, and stiffening stay elements on rope volume requirements for these bridges are investigated. Minimum volume results are presented graphically as functions of span to provide visual design aids that can be included in future bridge guidelines to facilitate comparisons between different systems under a range of constraint combinations.</p>

The purpose of a water distribution system (WDS) is to deliver the required amount of water to the customer under the desired pressure and quality. However, demand change and component failure result in low pressures at customer taps and make it difficult to achieve the goal. To mitigate the impact of the disturbances, system performance measure such as robustness and resilience can be considered in the WDS design and operation. Robustness is generally defined as an ability of the systems to maintain its function under a defined set of disturbance. On the other hand, Resilience is a system's ability to prepare and recover from a failure. The goal of this dissertation is to develop methodologies to enhance WDS robustness and resilience. In robustness-based design, reliability has been considered. Reliability is generally defined as the system's ability to provide an adequate service to customers under uncertain system condition and measured by the probability that stochastic nodal pressures are greater than or equal to a prescribed minimum pressure. However, although improving reliability will improve system robustness, the question is how the reliability index will improve system robustness. Robustness incorporates the variation of system performance; an additional aspect of system performance that reliability does not encompass. Pipe bursts are the most common failure in WDS. Therefore, promptly detecting and locating bursts will decrease the failure duration and increase system resilience. While many burst detection methods are available, identifying the method with the highest detectability is important to system owners/operators. However, to date, no cross comparisons of these methods have been completed for burst detection using a common data set. In addition, most traditional burst detection methods do not have a mechanism to include system operational changes. This dissertation is composed of three journal manuscripts that address these three key issues on WDS robustness and resilience. For WDS robustness improvement, a new robustness index is developed and used for multi-objective robustness-based design. The robustness-based design is compared to conventional reliability-based design. For WDS resilience improvement, the best method among six Statistical Process Control (SPC) methods is identified in terms of detection effectiveness and efficiency. Finally, a burst detection method applicable under system operational condition change is posed.

Nondestructive measurement of the concrete strength is an important topic of research. Among different nondestructive testing (NDT) methods the ultrasonic pulse velocity (UPV) technique is the most popular method for concrete strength estimation. The device which is commonly used for finding this property is called "PUNDIT". Many studies have been conducted to find the relationship between the concrete strength and its UPV (ultrasonic pulse velocity) using this device. The purpose of this study is to gain a better understanding of nondestructive evaluation of plain and polymer concretes to determine their properties using a new method. To achieve this goal, instead of using PUNDIT an alternative method has been used to generate the ultrasonic waves. The main difference of this new method in comparison to the earlier methods followed by other researchers is that in this method a linear chirp signal with different frequencies is transmitted through the material unlike the single frequency signal as PUNDIT does. This new method is applied to both plain and polymer concrete samples. While measuring concrete strengths by the UPV method almost all researchers have neglected the effect of applied stress or load on the concrete member. When the specimen is tested under stress, its behavior is quite different from when it is tested without any load. In this investigation attempts have been made to properly incorporate the effect of the applied load on the strength prediction of plain and polymer concrete specimens from the UPV generated values. After applying the load on the specimen in multiple steps - at 20%, 40%, 60% and 80% of its failure strength - the time of flight (TOF) was measured for every loading step. From regression analyses the best equations which can be used to find the applied stress on the structure from the velocity values have been derived. Under cyclic loadings pre-existing cracks inside both conventional concrete and polymer concrete may grow and cause catastrophic failure of the structure. Structural failure under cyclic loading is also known as the fatigue failure. Another aim of this study is to investigate the behavior of plain and polymer concretes under the cyclic loading or fatigue. The specimens used for this study were subjected to compressive loads for different numbers of cycles. The applied load was gradually increased. After the loading- unloading cycles, nonlinear impact resonance acoustic spectroscopy (NIRAS) test was carried out on the samples using instrumented impact hammer. The degree of nonlinearity in the concrete specimens was measured by recording the shift in the resonance frequency as the impact energy increased. Experimental results from the conventional plain concrete and polymer concrete specimens were compared to investigate which type of concrete exhibits more nonlinear behavior under fatigue.

A modular plastic hinge seismic special detail has been developed for use in steel special moment frames (SMFs). The aim of the special detail design is to dissipate seismic energy through stable yielding of a beam "link" in plastic hinge region. Reliable and repeatable energy dissipation at high ductility is assured through the elimination of weld failure modes, and the mitigation of local buckling and high multi-axis restraint. A casting process is used to configure the modular detail directly to meet these performance objectives. The primary features of the link region are an isolated flange with an integrally cast stiffener and a reduced section isolated web. Two forms of the detail exist: a plastic hinge modular node (PH-MN) and a bolted alternative, the bolted plastic hinge connector (BPHC). The PH-MN, a "node" occupying the entire beam-to-column joint, was used to develop the concept. The PH-MN configuration removes the field weld from the critical cross-section, reduces triaxiality and eliminates through-thickness failure modes at the beam/column interface. The BPHC preserves the primary features of the PH-MN and provides performance at nearly the same efficiency, but, as a replaceable field-bolted component, is significantly more economical, improves modularity, and has certain practical advantages. A design procedure was developed to create a family of modular designs.

Principles of similitude are derived, applying to prestressed concrete in flexure. The principles are proved experimentally to apply not only in the elastic but also in the inelastic range and on to ultimate strength with good precision. [...]

Fatigue durability, damage tolerance and strength evaluations of cracked structural components require accurate determination of stress intensity factors (SIF). Most practical crack configurations are embedded and surface breaking planar cracks subjected to complex two-dimensional stress fields. The only cracked body configuration which has been studied analytically for all types of applied stress fields is a circular crack in an infinite elastic solid. However, this model is suitable only for a narrow class of practical applications. Much wider class of practical problems can be solved using the model of an elliptical crack. The exact analytical SIF solutions for an elliptical crack were obtained only for some particular cases of polynomial applied stress fields. In the present work the exact analytical SIF solution has been obtained for an elliptical crack embedded in an infinite elastic body and subjected to an arbitrary applied normal stress field (Mode I). The most effective method of evaluating the stress intensity factor induced by an applied stress field is by using the weight function for a given cracked body. The weight function represents the SIF induced by a unit concentrated load. The only exact analytical weight function for a planar crack was obtained for a circular one. In the present research the exact analytical weight function has been derived for an elliptical crack embedded in an infinite elastic solid. The weight function for an elliptical crack was subsequently employed in the alternating method to obtain the unique SIF solution for a surface breaking semi-elliptical crack in a semi-infinite body subjected to an arbitrary applied stress field. The solutions obtained in the present work can be used in various practical applications, such as cracks in pressure vessels, welded structures and mechanical engineering components subjected to cyclic loading.

This Thesis is primarily concerned with Water Intakes. These structures, which are an elementary part of any self-sufficient watersupply system, are necessary wherever the source of raw-water is a stream, river, lake or impounding reservoir. In comparison to the more complex units of a water-supply system, such as pumping stations and treatment plants, the water intake has been the subject of very little research. Even a summary reading of some of the published reference material on water intakes will serve to establish this statement. [...]

This investigation deals primarily with the examination of the distribution of stress in the haunch of a glued laminated wood arch, and the comparison of test data and theoretical values based on the results of tests conducted on a simple beam of similar glued laminated wood construction.

Technical Report. Structural Engineering Series No. 2012-15 / The author and her supervisor, Prof. Ghyslaine McClure, recently worked on a research aimed at validating computational seismic response predictions of a guyed telecommunication mast with ambient vibration measurements. This report summarizes telecommunication towers damages due to recent earthquakes (from 1999 to 2011) as reported in damage reconnaissance accounts openly accessible.