Safety and serviceability of highway bridges, during and after an earthquake, is a prerequisite to ensure continuous transport facilities, emergency and evacuation routes. Recently, fragility curves have emerged as important decision support tools to identify the potential seismic risk and consequences during and after an earthquake. There has been a substantial increase in interest among researchers in the topic of seismic fragility assessment of highway bridges as evidenced by the growing number of published literature. Advanced computational techniques and available resources have led to the development of different methodologies for fragility assessment. This study presents a review of the different methodologies developed for seismic fragility assessment of highway bridges along with their features, limitations and applications. This study presents a review of available methodologies and identifies opportunities for future development. This study mainly focuses on the key features of different method...

Seismic fragility assessment of highway bridges: a state-of-the-art review

Seismic performance of ordinary RC frames retrofitted at joints by FRP sheets

Response modification factors of chevron-braced frames

The optimal decisions to maintain or improve the reliability and functionality of structures and infrastructure systems can only be achieved through proper integrated management planning in a life-cycle comprehensive framework. Structure and Infrastructure Engineering (SIE) is an international journal dedicated to recent advances inmaintenance, management, and life-cycle performance of a wide range of infrastructures. The purpose of this article is to provide a brief review of the recent research accomplishments in the field of design, maintenance, life-cycle management, and optimisation of structures and infrastructures reported in papers published in SIE during the period 2005–2011. The papers are categorised under main topics and very briefly discussed.

Maintenance, management, life-cycle design and performance of structures and infrastructures: a brief review

This paper presents a numerical investigation of buckling restrained brace (BRB) frames (BRBF) and a comparison with concentrically braced frames (CBF). A simplified core-spring finite element model was used to model BRB elements. Four types of CBF (X, V, inverted V, and two-story X) and four types of BRBF (diagonal, V, inverted V, and two-story X) were modeled in ABAQUS. A static nonlinear pushover analysis considering two cyclic loading protocols showed that the buckling restraint allows the BRB elements to undergo significant plasticity without forming plastic hinges , thereby dissipating a proportionally larger amount of energy and delaying yielding in the frame elements. Results indicated dramatic improvements in energy dissipation and ductility in BRBF models as compared to equivalent CBF models. Seismic response modification factors for BRBF models also showed greater values over CBF models. Time-history analysis evaluated the performance of CBF and BRBF under historical earthquake loadings and supported the same conclusions. The best performance was observed for V, inverted V, and two-story X BRBF configurations; the diagonal BRBF configuration performed better than equivalent CBF models, but did not perform nearly as well as the other BRBF models.

Numerical evaluation of the hysteretic behavior of concentrically braced frames and buckling restrained brace frame systems

Seismic behaviour factor, r, for steel x-braced and knee-braced rc buildings

This paper presents the results of an inspection campaign as well as condition evaluation and replacement of more than 1000 elastomeric bridge bearings under service on the Isfahan state highway bridges constructed before 1990. It is the first comprehensive survey of this kind. The research was accomplished through inspection surveys, analysis of existing bridge maintenance data, condition evaluation and replacement of a significant portion of the inspected bearings and expert interviews. Inspection surveys and analysis of extracted data identified the problems and their causes and the merits and potential improvement of performance of each one of the inspected elastomeric bearings. Replacement of the damaged bearings with new ones was performed based on the results of this stage. The expert interviews investigated the practices of Isfahan and surrounding states regarding the selection of bearing manufacturers, the performance and the quality control of elastomeric bearings.

Inspection, condition evaluation and replacement of elastomeric bearings in road bridges

A set of fragility curves of a class of reinforced concrete bridges with different degrees of irregularity has been generated Eighteen bridge configurations have been identified, from regular to so-called highly irregular models The geometric irregularity in this class of bridges is assumed to vary with the height of the piers Using non-linear analytical models and an appropriate suite of 60 ground motions, analytical fragility curves have been generated for the individual piers of each of these 18 bridge models Discussions have been made about the imposition of the displacement ductility demand of the piers versus the earthquake intensity as well as the bridge regularity Comparison of the fragility curves shows that the most vulnerable bridges are the irregular bridges and high damage probability is expected for the short piers of this class of bridges It was found that the fragility curves may be used for categorisation of regular and irregular bridges

Seismic fragility analysis of reinforced concrete continuous span bridges with irregular configuration

Several definitions have been used concerning structural regularity. A structure is considered here as regular, if its responses obtained from different well recognized analysis methods do not show significant differences. In this paper, the effects of the inclusion of higher modes on the response of a class of reinforced concrete viaducts with different degrees of irregularity have been investigated. The seismic responses of continuous span single-column-bent viaducts have been studied through the comparison of the results obtained from different pushover-based analysis methods. Commonly used single and multi-mode pushover-based analysis methods have been utilized and their corresponding results have been compared with the results obtained from simpler methods such as the so-called uniform load procedure, as well as the more sophisticated inelastic time history analysis methods. For the class of the bridges under consideration, those configurations for which the effects of the higher modes are considerable have been identified and categorized as irregular, for which the minimum analysis requirements have been indicated in order to achieve a reliable bridge response. In contrast, the conditions in which a configuration may be classified as regular have been demonstrated and the adequacy of the simplified methods for the analysis of such models has been examined. The regularity issue has been discussed initially based on an expression developed by other researchers. Another index has also been introduced here for the attainment of a more realistic representation of the structural particulars of such bridges consist with the analysis methods specified in the AASHTO Specifications.

Adequacy of the Seismic Analysis Methods for Single-column-bent Viaducts Considering Regularity and Higher Modes Effects

A structure is considered to be irregular in this paper if its response is influenced considerably by higher modes. Herein, the effects of the higher modes on the geometric regularity of single-column-bent viaducts have been investigated by comparing modal parameters resulting from the elastic eigenvalue modal analysis with transverse displacements obtained from static modal pushover analyses. A class of bridges with equal span lengths, but with different pier heights, has been considered in this study. For a better identification of the modal behavior of this class of bridges, several regularity indices are discussed. Some of these indices were used previously in model updating, model validation, and the determination of modal correlations in the field of experimental vibration analysis (modal testing) of mechanical and structural systems. Certain modifications have been applied to previous works in order to improve bridge regularity indices. New indices have also been proposed for the attainment of a more realistic representation of the structural particulars of such bridges to be consistent with the analytical methods addressed in the AASHTO Specifications, for practical design purposes. The results calculated with the aid of various indices are reported and compared.

Reza Akbari

Papers

Seismic behaviour factor, r, for steel x-braced and knee-braced rc buildings

Inspection, condition evaluation and replacement of elastomeric bearings in road bridges

Seismic fragility analysis of reinforced concrete continuous span bridges with irregular configuration

Adequacy of the Seismic Analysis Methods for Single-column-bent Viaducts Considering Regularity and Higher Modes Effects

The effect of higher modes on the regularity of single-column-bent highway viaducts