Since curved bridges have become prevalent in urban areas, their seismic behavior needs to be und... more Since curved bridges have become prevalent in urban areas, their seismic behavior needs to be understood. A three-span, 0.4-scale curved bridge model was tested on the NEES Shake Table Array in the Large-Scale Structures Laboratory at University of Nevada, Reno and seismic analysis using finite element (FE) method was conducted to validate the numerical model. However, studies to develop modeling techniques to propose a model that can efficiently predict the seismic behavior are limited. This paper focuses on the modeling work, which used beam elements instead of shell elements for the superstructure to efficiently capture the bridge seismic behavior in the analysis. The bridge model has a steel plate I-girder superstructure, single-column reinforced concrete column substructure, and seat-type abutments. This study presents a comparison between a FE model and a simplified beam model. In the FE model, which was made in FE analysis software SAP2000, the superstructure is modeled as sh...
A 2/5th scale model of a three-span, seismically isolated, curved steel plate girder bridge was c... more A 2/5th scale model of a three-span, seismically isolated, curved steel plate girder bridge was constructed on multiple shake tables and subjected to extreme shaking. The isolation system consisted of 12 lead rubber bearings. The purpose of this experiment was to identify the limit states for an isolated curved bridge under large displacements and to determine the effect of instability on the isolator properties. It was observed that adequate vertical load capacity was maintained even at displacements exceeding the isolator diameter. Isolator instability occurred at an abutment and a pier at earthquake level equal to three times the Design Earthquake where the isolator displacement-to-diameter ratio was up to 150% and the shear strain was up to 400%. However, this instability did not cause bridge collapse because the isolators at other supports remain stable and the columns were elastic. During instability the seismic inertia force in the superstructure was sufficient to return the ...
Seismic isolation is an innovative design approach to minimize the effects of earthquakes on buil... more Seismic isolation is an innovative design approach to minimize the effects of earthquakes on buildings and bridges. The intent is to reduce the seismic demand on a structure rather than increase its capacity, thereby avoiding structural collapse and reducing human casualties. To assist the design of an isolated bridge, the Simplified Method of analysis is recommended in the American Association of State Highway and Transportation Officials (AASHTO) Guide Specifications for Seismic Isolation Design, for initial design and the optimization of various design parameters. It is a displacement-based methodology assuming a single degree of freedom model of the bridge and elastic substructures. This paper describes an extension of the methodology to ductile substructures while maintaining all the attractive features of the original method. The modified method is applied to the analysis of a seismically isolated, 3-span, curved highway bridge of total length 362.5 ft. The results are compared to a nonlinear time history solution using SAP2000 software for three levels of input motion: 0.475, 1.0 and 1.4 times the 3600 component of the Sylmar ground motion. Displacements and substructure shear forces were found to be within 13% for the lowest level motion improving to within 8% for the highest level motion.
Structures - A Structural Engineering Odyssey, Structures 2001 - Proceedings of the 2001 Structures Congress and Exposition, 2004
ABSTRACT: Elastomeric isolation bearings are required to be stable at high shear strains, which o... more ABSTRACT: Elastomeric isolation bearings are required to be stable at high shear strains, which occur during strong earthquakes. Hence, rigorous determination of the critical axial load during design is important. Currently the critical load is determined using small displacement Haringx theory and modified to account for large shear strains by an approximate correction factor. The objective of this study is to experimentally determine the effect of horizontal displacement or shear strain on critical load and to study the validity of ...
Ductile end cross frames have been proposed in the past as a seismic design and retrofit strategy... more Ductile end cross frames have been proposed in the past as a seismic design and retrofit strategy for steel plate girder bridges. In this paper it is shown that with good connection details, single angles are able to undergo large cyclic deformations in excess of 6% average axial strain before failure occurs. Large-scale shake table experiments were performed on a straight steel I-girder bridge model to evaluate the performance of a superstructure with ductile end cross frames using single angle X braces. The cross frames exhibited no apparent overall strength degradation, but also a comparatively low postyield stiffness, allowing the cross frames to act as effective structural fuses. The measured base shear was 61% of the elastic base shear in response to 2.0 times the El Centro earthquake at an average drift of 3.4%. Large girder drifts were achieved without distress in the deck slab by removing selected studs between the slab and top flange of the girders at the end cross frame locations, with axial deformations in the angles well below their deformation capacity based on component experiments.
... DOI: 10.1080/13632461003702910 Ian Buckle a * , Ahmad Itani a & Lyle Carden b ... where i... more ... DOI: 10.1080/13632461003702910 Ian Buckle a * , Ahmad Itani a & Lyle Carden b ... where it has been shown that the braces have a tendency towards strength and stiffness degradation due to buckling of the compression members when deformed inelastically [Jain et al., 1980 ...
Of the nearly 12,000 highway bridges in Chile, approximately 300 were damaged in this earthquake,... more Of the nearly 12,000 highway bridges in Chile, approximately 300 were damaged in this earthquake, including 20 with collapsed spans. Typical failure modes include damage to connections between super- and substructures, unseating of spans in skewed bridges due to in-plane rotation, and unseated spans with some column damage due to permanent ground movement. Unusual failure modes include unseating of spans in straight bridges due to in-plane rotation, plate girder rupture due to longitudinal forces, scour and pier damage due to tsunami action, and collapse of a historic masonry bridge. The most common damage mode was the failure of super-to-substructure connections (shear keys, steel stoppers, and seismic bars), which is the most likely reason for the low incidence of column damage. Whereas the fuse-like behavior of these components is believed to have protected the columns, the lack of adequate seat widths led to the collapse, or imminent collapse, of many superstructures.
Including minor nonstructural damage, over 1,500 highway bridges and numerous rail bridges were d... more Including minor nonstructural damage, over 1,500 highway bridges and numerous rail bridges were damaged during the Tohoku-oki earthquake of 11 March 2011. The causes of this damage can be broadly classified in two categories: ground shaking, including ground failure (liquefaction); and tsunami inundation. Damage included span unseating, column shear and flexural failures, approach fill erosion, liquefaction induced settlement, and failed steel and elastomeric bearings. Since many bridges in the north Miyagi-ken and south Iwate-ken suffered extensive damage during the 1978 Miyagi-ken-oki earthquake, bridge performance during the 2011 earthquake is of particular interest. Advances in design and retrofit may be assessed by looking at the performance of bridges designed to post-1990 codes and those retrofitted since the Kobe earthquake in 1995. In both categories, bridge damage due to ground shaking was minor, thus validating the provisions in the post-1990 codes and the Japan bridge re...
Seismic pounding at seat-type abutments has resulted in a wide range of damage to bridges in seve... more Seismic pounding at seat-type abutments has resulted in a wide range of damage to bridges in several recent earthquakes. Seat-type bridge abutments are commonly used in long span, skew, or curved bridges to relieve thermally induced stresses in the superstructure. However, during large seismic events the expansion gap between the superstructure and the abutment backwall is closed resulting in high amplitude, short duration impact loads. When seismic pounding occurs the boundary conditions of the bridge are instantaneously altered thus it is expected that the bridge response be significantly affected. Frequent observations of this type of bridge damage have inspired researchers to explore the effects of seismic pounding and bridge soil structure interaction on the seismic response of bridges. As this area of research is relatively young, little experimental data of bridge systems subjected to seismic pounding is available. As a part of a Federal Highway Administration funded research...
Since curved bridges have become prevalent in urban areas, their seismic behavior needs to be und... more Since curved bridges have become prevalent in urban areas, their seismic behavior needs to be understood. A three-span, 0.4-scale curved bridge model was tested on the NEES Shake Table Array in the Large-Scale Structures Laboratory at University of Nevada, Reno and seismic analysis using finite element (FE) method was conducted to validate the numerical model. However, studies to develop modeling techniques to propose a model that can efficiently predict the seismic behavior are limited. This paper focuses on the modeling work, which used beam elements instead of shell elements for the superstructure to efficiently capture the bridge seismic behavior in the analysis. The bridge model has a steel plate I-girder superstructure, single-column reinforced concrete column substructure, and seat-type abutments. This study presents a comparison between a FE model and a simplified beam model. In the FE model, which was made in FE analysis software SAP2000, the superstructure is modeled as sh...
A 2/5th scale model of a three-span, seismically isolated, curved steel plate girder bridge was c... more A 2/5th scale model of a three-span, seismically isolated, curved steel plate girder bridge was constructed on multiple shake tables and subjected to extreme shaking. The isolation system consisted of 12 lead rubber bearings. The purpose of this experiment was to identify the limit states for an isolated curved bridge under large displacements and to determine the effect of instability on the isolator properties. It was observed that adequate vertical load capacity was maintained even at displacements exceeding the isolator diameter. Isolator instability occurred at an abutment and a pier at earthquake level equal to three times the Design Earthquake where the isolator displacement-to-diameter ratio was up to 150% and the shear strain was up to 400%. However, this instability did not cause bridge collapse because the isolators at other supports remain stable and the columns were elastic. During instability the seismic inertia force in the superstructure was sufficient to return the ...
Seismic isolation is an innovative design approach to minimize the effects of earthquakes on buil... more Seismic isolation is an innovative design approach to minimize the effects of earthquakes on buildings and bridges. The intent is to reduce the seismic demand on a structure rather than increase its capacity, thereby avoiding structural collapse and reducing human casualties. To assist the design of an isolated bridge, the Simplified Method of analysis is recommended in the American Association of State Highway and Transportation Officials (AASHTO) Guide Specifications for Seismic Isolation Design, for initial design and the optimization of various design parameters. It is a displacement-based methodology assuming a single degree of freedom model of the bridge and elastic substructures. This paper describes an extension of the methodology to ductile substructures while maintaining all the attractive features of the original method. The modified method is applied to the analysis of a seismically isolated, 3-span, curved highway bridge of total length 362.5 ft. The results are compared to a nonlinear time history solution using SAP2000 software for three levels of input motion: 0.475, 1.0 and 1.4 times the 3600 component of the Sylmar ground motion. Displacements and substructure shear forces were found to be within 13% for the lowest level motion improving to within 8% for the highest level motion.
Structures - A Structural Engineering Odyssey, Structures 2001 - Proceedings of the 2001 Structures Congress and Exposition, 2004
ABSTRACT: Elastomeric isolation bearings are required to be stable at high shear strains, which o... more ABSTRACT: Elastomeric isolation bearings are required to be stable at high shear strains, which occur during strong earthquakes. Hence, rigorous determination of the critical axial load during design is important. Currently the critical load is determined using small displacement Haringx theory and modified to account for large shear strains by an approximate correction factor. The objective of this study is to experimentally determine the effect of horizontal displacement or shear strain on critical load and to study the validity of ...
Ductile end cross frames have been proposed in the past as a seismic design and retrofit strategy... more Ductile end cross frames have been proposed in the past as a seismic design and retrofit strategy for steel plate girder bridges. In this paper it is shown that with good connection details, single angles are able to undergo large cyclic deformations in excess of 6% average axial strain before failure occurs. Large-scale shake table experiments were performed on a straight steel I-girder bridge model to evaluate the performance of a superstructure with ductile end cross frames using single angle X braces. The cross frames exhibited no apparent overall strength degradation, but also a comparatively low postyield stiffness, allowing the cross frames to act as effective structural fuses. The measured base shear was 61% of the elastic base shear in response to 2.0 times the El Centro earthquake at an average drift of 3.4%. Large girder drifts were achieved without distress in the deck slab by removing selected studs between the slab and top flange of the girders at the end cross frame locations, with axial deformations in the angles well below their deformation capacity based on component experiments.
... DOI: 10.1080/13632461003702910 Ian Buckle a * , Ahmad Itani a & Lyle Carden b ... where i... more ... DOI: 10.1080/13632461003702910 Ian Buckle a * , Ahmad Itani a & Lyle Carden b ... where it has been shown that the braces have a tendency towards strength and stiffness degradation due to buckling of the compression members when deformed inelastically [Jain et al., 1980 ...
Of the nearly 12,000 highway bridges in Chile, approximately 300 were damaged in this earthquake,... more Of the nearly 12,000 highway bridges in Chile, approximately 300 were damaged in this earthquake, including 20 with collapsed spans. Typical failure modes include damage to connections between super- and substructures, unseating of spans in skewed bridges due to in-plane rotation, and unseated spans with some column damage due to permanent ground movement. Unusual failure modes include unseating of spans in straight bridges due to in-plane rotation, plate girder rupture due to longitudinal forces, scour and pier damage due to tsunami action, and collapse of a historic masonry bridge. The most common damage mode was the failure of super-to-substructure connections (shear keys, steel stoppers, and seismic bars), which is the most likely reason for the low incidence of column damage. Whereas the fuse-like behavior of these components is believed to have protected the columns, the lack of adequate seat widths led to the collapse, or imminent collapse, of many superstructures.
Including minor nonstructural damage, over 1,500 highway bridges and numerous rail bridges were d... more Including minor nonstructural damage, over 1,500 highway bridges and numerous rail bridges were damaged during the Tohoku-oki earthquake of 11 March 2011. The causes of this damage can be broadly classified in two categories: ground shaking, including ground failure (liquefaction); and tsunami inundation. Damage included span unseating, column shear and flexural failures, approach fill erosion, liquefaction induced settlement, and failed steel and elastomeric bearings. Since many bridges in the north Miyagi-ken and south Iwate-ken suffered extensive damage during the 1978 Miyagi-ken-oki earthquake, bridge performance during the 2011 earthquake is of particular interest. Advances in design and retrofit may be assessed by looking at the performance of bridges designed to post-1990 codes and those retrofitted since the Kobe earthquake in 1995. In both categories, bridge damage due to ground shaking was minor, thus validating the provisions in the post-1990 codes and the Japan bridge re...
Seismic pounding at seat-type abutments has resulted in a wide range of damage to bridges in seve... more Seismic pounding at seat-type abutments has resulted in a wide range of damage to bridges in several recent earthquakes. Seat-type bridge abutments are commonly used in long span, skew, or curved bridges to relieve thermally induced stresses in the superstructure. However, during large seismic events the expansion gap between the superstructure and the abutment backwall is closed resulting in high amplitude, short duration impact loads. When seismic pounding occurs the boundary conditions of the bridge are instantaneously altered thus it is expected that the bridge response be significantly affected. Frequent observations of this type of bridge damage have inspired researchers to explore the effects of seismic pounding and bridge soil structure interaction on the seismic response of bridges. As this area of research is relatively young, little experimental data of bridge systems subjected to seismic pounding is available. As a part of a Federal Highway Administration funded research...
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