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A large-scale, two-span bridge model constructed by assembling precast elements was tested under a series of bi-axial ground motions simulated on a shake table at the Earthquake Engineering Laboratory at the University of Nevada, Reno. The response of the bridge was estimated before the tests using a three-dimensional computational model developed in OpenSees software. After the tests, key measured seismic responses were compared to those predicted by the computational model to assess the modeling assumptions. Relatively large errors for the displacements, base shears, and hysteretic response of the bridge were observed. The influence of the earthquake loading, materials, connectivity of the precast elements, and boundary conditions in the computational model on the errors are discussed in this paper. Future modeling directions are proposed to reduce these errors. [ABSTRACT FROM AUTHOR]

Next generation performance-based earthquake engineering involves the use of a probability framework, which incorporates the inherent uncertainty and variability in seismic hazard, structural and non-structural responses, damage states and economic and casualty losses. One key issue in seismic performance assessment is the scaling of ground motions for nonlinear response-history analysis. In this paper, the impact of ground-motion scaling procedures, including 1) geometric-mean scaling of pairs of ground motions, 2) spectrum-matching of ground-motions, 3) first-mode-based scaling to a target spectral acceleration and 4) maximum-minimum orientation scaling, on the distributions of floor acceleration, story drift and floor spectral acceleration of a sample high-rise building is investigated using a series of nonlinear response-history analyses of a 34-story moment-resisting frame building. The advantages and disadvantages of each ground-motion scaling method are discussed for seismic performance assessment of a 34-story building. [ABSTRACT FROM AUTHOR]

Shaking table testing is a common experimental method in earthquake engineering for performance assessment of structures subjected to dynamic excitations. As most shaking tables are driven by servo hydraulic actuators to meet the potentially significant force stroke demand, the review is restricted to hydraulic shaking tables. The purpose of the control systems of hydraulic shaking tables is to reproduce reference signals with low distortion. Accurate control of actuators is vital to the effectiveness of such apparatus. However, the system dynamics of a shaking table and the specimens to be tested on the shaking table are usually very complex and nonlinear. Achieving the control goal can prove to be challenging. A variety of closed- and open-loop control algorithms has been developed to solve different control problems. With the focus placed on the control schemes for hydraulic shaking tables, the paper reviews algorithms that are currently used in the testing industry, as well as those which are the subject of academic and industrial research. It is by no means a complete survey but provides key reference for further development. [ABSTRACT FROM AUTHOR]

In a medium-to-large earthquake, there are often reports of people being trapped or injured in elevators. This study investigates using an earthquake early warning (EEW) system, which provides seconds to tens of seconds warning before seismic waves arrive at a site, to help people escape from the elevators before a strong shaking arrives. However, such an application remains as a major engineering challenge due to the uncertainty of the EEW information and the short lead time available. A recent study presented an earthquake probability- based automated decision-making (ePAD) framework to address these issues. This paper focuses on studying the influence of two commonly ignored factors, uncertainty of warning and lead time, on the decision of stopping the elevators and opening the doors when an EEW message is received. Application of the ePAD framework requires using the performance-based earthquake engineering methodology for elevator damage prediction, making decision based on a cost-benefit model and reducing computational time with a surrogate model. The authors' results show that ePAD can provide rational decisions for elevator control based on EEW information under different amounts of lead time and uncertainty level of the warning. [ABSTRACT FROM AUTHOR]

Performance-based design in earthquake engineering is a structural optimization problem that has, as the objective, the determination of design parameters for the minimization of total costs, while at the same time satisfying minimum reliability levels for the specified performance criteria. Total costs include those for construction and structural damage repairs, those associated with non-structural components and the social costs of economic losses, injuries and fatalities. This paper presents a general framework to approach this problem, using a numerical optimization strategy and incorporating the use of neural networks for the evaluation of dynamic responses and the reliability levels achieved for a given set of design parameters. The strategy is applied to an example of a three-story office building. The results show the importance of considering the social costs, and the optimum failure probabilities when minimum reliability constraints are not taken into account. [ABSTRACT FROM AUTHOR]

The performance assessment and optimal design of fluid viscous dampers through life-cycle cost criteria is discussed in this paper. A probabilistic, simulation-based framework is described for estimating the life-cycle cost and a stochastic search approach is developed to support an efficient optimization under different design scenarios (corresponding to different seismicity characteristics). Earthquake losses are estimated using an assembly-based vulnerability approach utilizing the nonlinear dynamic response of the structure whereas a point source stochastic ground motion model, extended here to address near-fault pulse effects, is adopted to describe the seismic hazard. Stochastic simulation is utilized for estimation of all the necessary probabilistic quantities, and for reducing the computational burden a surrogate modeling methodology is integrated within the framework. Two simplified design approaches are also examined, the first considering the optimization of the stationary response, utilizing statistical linearization to address nonlinear damper characteristics, and the second adopting an equivalent lateral force procedure that defines a targeted damping ratio for the structure. These designs are compared against the optimal life-cycle cost one, whereas a compatible comparison is facilitated by establishing an appropriate connection between the seismic input required for the simplified designs and the probabilistic earthquake hazard model. As an illustrative example, the retrofitting of a three-story reinforced concrete office building with nonlinear dampers is considered. [ABSTRACT FROM AUTHOR]

Recent research efforts have focused on the development of performance based seismic design methodologies for structures. However, the seismic design rules prescribed in the current Canadian Highway Bridge Design Code (CHBDC) is based largely on force based design principles. Although a set of performance requirements (performance objectives) for different return period earthquake events have been specified, there is no explicit requirement in the CHBDC to check the attainment of such performance objectives for the designed bridges. Also, no engineering parameters have been assigned to the specified performance objectives. This paper correlates seismic performance objectives (both qualitative and quantitative) with engineering parameters, based on the data collected from published experimental investigations and field investigation reports of recent earthquakes. A simple method has been developed and validated with experimental results for assessing the performance of bridges designed according to CHBDC. It has been found that the design rules prescribed in CHBDC do not guarantee that specified multiple seismic performance objectives can be achieved. An implicit seismic design rule in the form of performance response modification factor has been outlined for the performance based seismic design of bridges. [ABSTRACT FROM AUTHOR]

Abstract: Structural reinforcement is an economical and ecological method of preventing damage caused by seismic loading. Indeed, it is estimated that two out of three buildings will become unsafe over the next 40years if no policy of treatment for existing constructions is adopted. FRP strengthening appears to be an advantageous method of structural strengthening due to the mechanical properties of the composite and the ease of application in the damage area. Various reinforcement systems have been presented in the literature, characterized by several parameters (FRP materials, configuration, reinforcement ratio, anchored bars etc.). This paper proposes the use of a performance index, based on a damage index, to assess the efficiency of external FRP reinforcement retrofitting using three experimental investigations. The influence of (i) axial compressive loading, (ii) the shape of the reinforced short column, (iii) the presence of FRP bars and (iv) FRP reinforcement on the performance index of the columns is determined. A parameter ξ is also defined to evaluate the performance of the columns according to the geometrical configuration and mechanical properties of the FRP reinforcement. [Copyright &y& Elsevier]

Abstract: Significant investments are undergoing internationally to develop earthquake early warning (EEW) systems. So far, reasonably, the most of the research in this field was lead by seismologists as the issues to determine essential feasibility of EEW were mainly related to the earthquake source. Many of them have been brilliantly solved, and the principles of this discipline are collected in the so-called real-time seismology. On the other hand, operating EEW systems rely on general-purpose intensity measures as proxies for the impending ground motion potential and are suitable for population alert. In fact, to date, comparatively little attention was given to EEW by earthquake engineering, and design approaches for structure-specific EEW are mostly lacking. Applications to site-specific systems have not been extensively investigated and EEW convenience is not yet proven except a few pioneering cases, although the topic is certainly worthwhile. For example, in structure-specific EEW the determination of appropriate alarm thresholds is important when the false alarm may induce significant losses; similarly, economic appeal with respect to other risk mitigation strategies as seismic upgrade should be assessed. In the paper the least issues to be faced in the design of engineering applications of EEW are reviewed and some work done in this direction is discussed. The review presented intends to summarize the work of the author and co-workers in this field illustrating a possible performance-based approach for the design of structure-specific applications of EEW. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the seismic performance of reinforced concrete exterior wide beam–column connections with shallow spandrel beams lightly reinforced for torsion and moderate levels of gravity loads was investigated experimentally. The study focuses on existing frames designed and detailed according to construction practices used over ten years ago in the moderate-seismicity Mediterranean area. The results can be useful for assessing the seismic vulnerability of older structures and orienting seismic retrofit alternatives. Two 3/5 scale test models representative of exterior sub-assemblages in a prototype six-story building were subjected to gravity-load levels typical of those acting during an earthquake, and quasi-static cyclic lateral loads until failure. The performance was studied in terms of strength, displacement, ductility and energy dissipation capacity. The data are analyzed in conjunction with the results of previous tests. The specimens exhibited a “strong column–weak beam” type of flexural yielding mechanism. The average drift ratios at first yielding of the wide beam longitudinal reinforcement, , and at failure, , were 2.2% and 4.5% respectively; the displacement ductility ratio was approximately 2.2. Comparison to similar connections without added gravity loads showed that moderate levels of gravity loading increased by about 40%, and decreased by a similar percentage the value of and the energy dissipated in each half cycle of displacement expressed in terms of an equivalent viscous damping ratio. Finally, two approaches for estimating the wide-beam flexural capacity are examined. [Copyright &y& Elsevier]

Abstract: Several studies have shown that the lateral response of concentrically-braced frames is dominated by the inelastic behavior of the bracing members. However, the overall performance of the entire frame depends on the frame configuration including its connections. In this study, the hysteretic characteristics of modular steel-braced frames under reversed cyclic loading are evaluated. The design and construction of the test specimen accounted for the unique detailing requirements of these frames. A regular concentrically-braced frame with similar physical characteristics was also tested for comparison. Both test specimens consisted of a one-storey X-braced system with tubular brace cross-section. This paper describes the behavior characteristics and provides a detailed comparison of the two systems to assess the strength, stiffness, inelastic force and deformation, and energy dissipation characteristics of the modular system. An analytical model capable of capturing the effect of the system’s unique detailing requirements is proposed and validated using the test results. [Copyright &y& Elsevier]

This paper presents a systematic evaluation approach that allows the design professional to estimate the performance of damaged buildings subjected to sets of ground motions representing different hazard levels. The performance of damaged buildings for a future seismic event prior to repair and/or rehabilitation was evaluated using an elastic model and stiffness of the structure. The linear static model using the damaged state of brittle fractured connections in steel moment resisting frame buildings provides a reasonable estimation of the interstory drift of the damaged buildings when compared to nonlinear time history analysis. Then, this result was incorporated in a reliability-based procedure that provides a degree of confidence that a building before and after the damage will exceed the given performance levels. Finally, examples of confidence level calculations are presented. The results showed that the linear static model and the performance evaluation procedure are very useful and allow the design professional to determine the level of safety of damaged buildings. [ABSTRACT FROM AUTHOR]