Seismic Response of Multiple Span Steel Bridges in Central and Southeastern United States. I: As Built (original) (raw)
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2020
Considering the spatial variations of ground motions in the design of extended structures, especially bridges, is of importance. In this paper, the effect of spatial variations of the ground motions on bridges regarding the horizontal and vertical components of the earthquake was investigated. A five spans bridge is modeled in OpenSees and 3D nonlinear dynamic time history analysis is performed. The generation of acceleration time histories is in accordance to the spectral-representation-based simulation algorithm which has been presented in previous studies. Seismic performance of the bridge was studied by considering the identical and differential support ground motions. Shear force, bending moment, displacement of bridge piers in identical and differential excitation supports with different soil conditions were analyzed. The results showed that by considering the spatial variations of ground motions, internal forces made significant changes at the piers of the bridge. Based on th...
Seismic Behavior of Steel Girder Bridge Superstructures
Journal of Bridge Engineering, 2004
Recent earthquakes exposed the vulnerabilities of steel plate girder bridges when subjected to ground shaking. This paper discusses the behavior of steel plate girder bridges during recent earthquakes such as Petrolia, Northridge, and Kobe. The paper also discusses the recent experimental and analytical investigations that were conducted on steel plate girder bridges and their components. Results of these investigations showed the importance of shear connectors in distributing and transferring the lateral forces to the end and intermediate cross frames. Also, these investigations showed the potential of using end cross frames as ductile elements that can be used to dissipate the earthquake input energy. The paper also gives an update on specifications and guidelines for the seismic design of steel plate girder bridges in the United States.
Seismic fragility of typical bridges in moderate seismic zones
Engineering Structures, 2004
A set of fragility curves for the bridges commonly found in the Central and Southeastern United States (CSUS) is presented. Using the results of an inventory analysis of the typical bridges in the CSUS, four typical bridge types are identified. Using nonlinear analytical models, and a suite of synthetic ground motions, analytical fragility curves are developed for the four bridge types. The fragility curves were first generated for the individual components of each of the bridge types and then, they were combined into fragility curves that represent the entire bridge system using first-order reliability principles. The fragility curves show that the peak ground acceleration for a 50% probability of exceeding slight damage ranges from approximately 0.19 to 0.24 g for the four bridge types. Comparison of the fragility curves shows that the most vulnerable bridge types are the multi-span simply supported and multi-span continuous steel-girder bridges. The least vulnerable bridge is the multi-span continuous pre-stressed concrete-girder bridge. The developed fragility curves can be used for economic loss estimation as well as a basis for assigning retrofit prioritization for bridges. This is particularly useful in the Central and Southeastern United States where seismic retrofit of bridges is becoming more prevalent. #
Simplified seismic analysis of a class of regular steel bridges
Engineering Structures, 2002
AASHTO's (American Association State Highway and Transportation Officials) simplified method of analysis for multiple-span regular bridges requires modeling and analysis of the structures and it is not less time-consuming than performing a computeraided response spectrum analysis. Furthermore, for single-span bridges, AASHTO specifications do not require a seismic analysis. The connections between the superstructure and substructure are designed for a minimum load calculated as the product of site coefficient, the acceleration coefficient and the tributary permanent load. This may result in underestimation of seismically induced forces in connections. To overcome such problems, analytical equations are derived to calculate the fundamental period and seismically induced forces and displacements in the structural components of a class of regular steel bridges. The equations are derived considering the effect of deck width, number and length of spans, bearing types and their stiffness, on the dynamic behavior of bridges. The results from multi-mode response spectrum analysis and those obtained from the derived equations have shown good agreement. Thus, these equations may be used in lieu of AASHTO's simplified analysis method for the seismic analysis of regular steel bridges. It was also observed that AASHTO's simplified analysis method for single-span bridges underestimates the seismically induced forces in fixed bearings.
Earthquake Spectra, 2007
Seismic fragility curves for classes of highway bridges are essential for risk assessment of highway transportation networks exposed to seismic hazards. This study develops seismic fragility curves for nine classes of bridges (common three-span, zero-skew bridges with non-integral abutments) common to the central and southeastern United States. The methodology adopted uses 3-D analytical models and nonlinear time-history analyses. An important aspect of the selected methodology is that it considers the contribution of multiple bridge components. The results show that multispan steel girder bridges are the most vulnerable of the considered bridge classes while single-span bridges tend to be the least vulnerable. A comparison of the proposed fragility curves with those currently found in HAZUS-MH shows a strong agreement for the multispan simply supported steel girder bridge class. However, for other simply supported bridge classes (concrete girder, slab), the proposed fragility curves suggest a lower vulnerability level than presented in
1998
This paper presents an investigation into the behavior of reinforced concrete slabs, steel girders, and concrete columns of a two span steel girder bridge under the influence of different combtn auon of earthquake dtrections and intensities. The beam-column elements were used to represent the composite bridge deck (concrete slab and steel girder) and also the concrete columns. T ht s clement type has the nonlinear material capability. The free vibration analysis was performed to detect th e fi rst four mode shapes of the bridge models. Time history analysts was implemented on th e bndgc when subject to San Fernando Earthquake, 1971. Various fat lure patterns were detec ted by cxamming the maximum displacement patterns, and the maximum forces (or stresses) of th e bridge components. Stgnificant amplification of the bridge response occured in all directions, longitudinall y, transversely, and vertically as a result of the combination effect of earthquake in the other directions.
CCEER Report 13 15 Seismic Design and Nonlinear Evaluation of Steel I Girder Bridges
This study introduces analytical fragility curves for horizontally curved steel girder highway bridges. A large number of benchmark bridges were developed following a statistical evaluation of typical bridges commonly used in the US. Both seismically and non-seismically designed bridges are considered that present differences primarily in column confinement, type of bearings and abutment support length. Columns and bearings were found to be the most seismically vulnerable components for both categories. Non-seismically designed bridges are significantly more vulnerable than seismically designed bridges due to their inadequate column confinement and abutment support length. Curvature was identified to be an important factor that adversely affects the seismic vulnerability. Consistent with the central angle-dependent fragility curves, a set of more generic fragility curves were introduced for cases when central angle is not specified such as the case in the National Bridge Inventory. It was shown that HAZUS-MH damage functions underpredict the seismic vulnerability.
Seismic Performance of bridges; Lesson Learned From Past
Lifeline systems consist of Bridges, Roads, Tunnels, Communication networks, Water and Gas Transmissions, Airports, etc, are known as a general parameter for all cities especially Megacities survival. Any trouble in their operation particularly in times of crisis (earthquake, flood, tempest, war, etc) will increase irreparable losses of life and property. Large lifeline systems such as bridges are susceptible to earthquake damages, and their performance, integrity and stability according to their special application in current-day transportation, during and after an earthquake have significant implications on public safety. Bridges are one of the most importance lines to control rescue operations during and after earthquake. So, there is an urgent need to recognition the effective factors on bridge damages in an unforeseen exigency. Hence, their vulnerability significantly should be under continual surveillance and bridges stability has to be controlled by retrofitting and rehabilitating. In this study the seismic performance of various types of bridges during the past earthquakes is presented. The objective of this study is to present typical failure modes of bridges and providing some clues in order to reduce the seismic vulnerability of such structures. Results of this study demonstrated that there are some typical failure modes in bridges. Hence, by considering some special practical consideration the seismic vulnerability of bridges may decrease.
Effects of near-fault earthquakes on existing bridge performances
Journal of Civil Structural Health Monitoring, 2020
The vertical component of seismic acceleration, often overlooked in ordinary structures, plays a role of primary importance in the case of bridges and viaducts. In particular, it induces both the appearance of uncommon stress conditions on vertical structures, and in some cases, it is a really important factor for bearing device capacity of girders. In fact, seismic excitations may give rise to great relative displacement between deck and piers or abutment in bridges. Among many structural damages of bridges during past earthquakes, the unseating failure is one of the most severe and recurring damages of girder bridges. When relative displacements exceed a pre-assigned seating length, the unseating of span will then take place. Therefore, for seismic design of new bridges or for a check of existing bridge, to take into account the vertical component due to seismic acceleration is an important issue. This paper presents a numerical analyses about damage effects of near-fault seismic events on existing bridge performances. The near-fault earthquakes are characterised by own some fundamental characteristics, such as forward-directivity phenomena, relatively high acceleration amplitudes and elastic response spectra, which are very different with respect to the reference ones defined in the codes. With this background, the purpose of this paper is to highlight the role of this kind of analysis of understanding the response behavior of girder bridges subjected to near-fault earthquakes. Furthermore, a case study and parameter studies are performed to evaluate its effectiveness in preventing bridge spans from unseating failure and protecting the piers and the abutment of bridges from damage.
Transverse and Longitudinal Seismic Effects on Soil-Steel Bridges
2020
Soil-steel bridges and culverts, typically ranging from 3 to 25 m, can be used as an effective alternative for short-span bridges. They can meet the design and safety requirements of traditional bridges but at lower costs and with shorter erection time. For these reasons, soil-steel bridges are more and more often used in road and railway projects in many parts of the world. The purpose of present analysis is more advanced. Respective FEM models of a large soil steel bridge were prepared and eigen problem solved applying SAP 2000 and DIANA programs. Next the dynamic response was computed using time history response analysis with El Centro 1940 record. Two basic cases of seismic loads were analysed, i.e. “XZ” and “YZ” (seismic excitations were induced simultaneously at directions: transversal (X) and vertical (Z), and longitudinal (Y) and vertical (Z)). The totally different way of response of the large soil-steel bridges along and perpendicular to them generates key irregularity eff...