Author: Joseph Wieser
Publisher:
ISBN:
Category : Electronic books
Languages : en
Pages : 1040
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Book Description
Seat-type bridge abutments are most commonly used to support the end spans of curved highway bridges. This type of abutment is often selected to eliminate unbalanced stresses in the superstructure under service loads, in particular thermal expansion and contraction. However, depending on the width of the expansion gap, large earthquakes may cause the expansion gap to close which results in bridge-abutment interaction. This phenomenon was studied in a federally-funded research project examining the seismic performance of curved highway bridges at the University of Nevada, Reno. As a part of this research a 2/5 th scale model of a 3-span curved steel girder bridge was constructed on four multi-degree-of-freedom shake tables. Two configurations of the bridge one without bridge-abutment interaction and one with nonlinear bridge-abutment interaction were tested. The purpose of these tests was to: (i) identify the influence of bridge-abutment interaction on the global seismic response of the bridge, (ii) characterize the force-deformation characteristics of dynamic bridge-abutment interaction, and (iii) provide experimental data used to calibrate numerical models of bridges including bridge abutment interaction. Based on the experimental investigation it was concluded that bridge-abutment interaction shortens the effective period of vibration of the bridge, which results in decreased deck displacement and increased total base shear demands. However, the increase in base shear demand is resisted by the abutments which results in a net reduction in column shear demand. Though the deck displacement is reduced at the mid-span of the bridge, the active displacement of the deck at the abutments is increased due to the increased in-plane deck rotation generated as a result of the sudden changes in eccentricity between the center of mass and center of stiffness. The amount of in-plane rotation is shown to depend on the phasing and intensity of the ground motion. Interaction between the bridge and abutment backwall can generate significant radial shear forces through contact friction. These radial forces limit the radial displacement of the bridge while in contact with the backwall particularly after the radial shear keys have failed. However, depending on the details of the abutment backwall local damage may occur. In general, engaging the passive resistance of the backfill soil was able to improve the seismic response of the bridge by reducing damage to the columns and adding an additional form of energy dissipation. Both rigorous 3D finite element and simplified grillage models of the experimental model were validated using available software. Good agreement between the numerical models and the experimental data were obtained using both models however the computational effort was greatly reduced using the simplified grillage model. A grossly simplified 3DOF model of the bridge analyzed using the linear multi-modal response spectrum method was shown to give a prediction of the peak displacement response with minimal complexity. Finally, a parameter study determined that the degree of curvature, size of expansion gap, column diameter, and abutment backfill soil type all influence the response of the bridge. Based on the small scale parameter study conducted herein, bridge designers are encouraged to optimize the combination of expansion gap width with the selection of column diameter to minimize the column and/or abutment soil ductility demands.
Author: Hartanto Wibowo
Publisher:
ISBN:
Category : Electronic books
Languages : en
Pages : 1572
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Book Description
Current bridge design specifications have few requirements concerning the inclusion of live load in the seismic design of bridges for perhaps two reasons: 1) the likelihood of the full design live load occurring at the same time as the design earthquake is deemed to be very low, and 2) adverse behavior in an earthquake due to live load has not been observed in practice. However, with increasing congestion in major cities, the occurrence of the design earthquake at the same time as the design live load is now more likely than in the past. But little is known about the effect of live load on seismic response and this dissertation describes an experimental and analytical project that investigates this behavior. The experimental work included shake table testing of a 2/5th -scale model of a three-span, horizontally curved, steel girder bridge loaded with a series of representative trucks. The model spanned four shake tables each synchronously excited with scaled ground motions from the 1994 Northridge Earthquake. Observations from the experimental work show the presence of the live load had a beneficial effect on performance of this bridge, but this effect diminished with increasing amplitude of shaking. During the design earthquake, the bridge with live load was essentially elastic whereas the bridge without live load suffered some yielding and the maximum displacement at the top of the column was approximately 35% less in the live load case. Parameters used to measure performance included column displacement, abutment shear force, and degree of concrete spalling in the plastic hinge zones. Results obtained from nonlinear finite element analyses of the bridge with and without trucks confirm this behavior, that live load reduces the dynamic response of the bridge. The most likely explanation for this phenomenon is that the trucks act as a set of nonlinear multiple mass dampers, a variation of tuned mass dampers that are known to be effective at controlling wind vibrations in buildings. Parameter studies have also been conducted and show the above beneficial effect is generally true for other earthquake ground motions and vehicles with different dynamic properties. Exceptions exist, but adverse effects are usually within 10-15% of the no-live load case. Although the above results were obtained for a particular bridge, earthquake loading, and vehicle configuration, they may also apply to other bridges. Further work is required to confirm this observation.
Author: Carlos Alonso Cruz-Noguez
Publisher:
ISBN:
Category :
Languages : en
Pages : 1524
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Book Description
As part of a multi-university project utilizing the NSF Network for Earthquake Engineering Simulation (NEES), a quarter-scale model of a four-span bridge incorporating plastic hinges with different advanced materials was tested to failure on the three shake table system at the University of Nevada, Reno (UNR). The bridge was the second test model in a series of three 4-span bridges, with the first model being a conventional reinforced-concrete (RC) structure. The purpose of incorporating advanced materials was to improve the seismic performance of the bridge with respect to two damage indicators: (1) column damage and (2) permanent deformations. The goals of the study presented in this document were to (1) evaluate the seismic performance of a 4-span bridge system incorporating SMA/ECC and built-in rubber pad plastic hinges as well as post-tensioned piers, (2) quantify the relative merit of these advanced materials and details compared to each other and to conventional reinforced concrete plastic hinges, (3) determine the influence of abutment-superstructure interaction on the response, (4) examine the ability of available elaborate analytical modeling techniques to model the performance of advanced materials and details, and (5) conduct an extensive parametric study of different variations of the bridge model to study several important issues in bridge earthquake engineering. The bridge model included six columns, each pair of which utilized a different advanced detail at bottom plastic hinges: shape memory alloys (SMA), special engineered cementitious composites (ECC), elastomeric pads embedded into columns, and post-tensioning tendons. The design of the columns, location of the bents, and selection of the loading protocol were based on pre-test analyses conducted using computer program OpenSees. The bridge model was subjected to two-horizontal components of simulated earthquake records of the 1994 Northridge earthquake. Over 340 channels of data were collected. The test results showed the effectiveness of the advanced materials in reducing damage and permanent displacements. The damage was minimal in plastic hinges with SMA/ECC and those with built-in elastomeric pads. Conventional RC plastic hinges were severely damaged due to spalling of concrete and rupture of the longitudinal and transverse reinforcement. Extensive post-test analytical studies were conducted and it was determined that a computational model of the bridge that included bridge-abutment interaction using OpenSees was able to provide satisfactory estimations of key structural parameters such as superstructure displacements and base shears. The analytical model was also used to conduct parametric studies on single-column and bridge-system response under near-fault ground motions. The effects of vertical excitations and transverse shear-keys at the bridge abutments on the superstructure displacement and column drifts were also explored.
Author: Nathan W. Harrison
Publisher:
ISBN: 9781124682358
Category : Columns
Languages : en
Pages : 542
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Book Description
As part of a Federal Highway Administration (FHWA) sponsored research project to study highway system resilience, a 40 percent scale curved steel plate girder bridge is to be constructed and subjected to earthquake simulation at the Large Scale Structures Laboratory on the University of Nevada, Reno (UNR) campus. The 145 foot long bridge model is to have three-spans, supported on two single-column bents with hammer-head pier caps, and have a subtended angle of 104°. The purpose of the shake table testing is to study the seismic system behavior of the bridge as well as additional bridge components including; conventional columns, isolation, ductile-cross frames, abutment behavior, and the seismic behavior of bridges including the effects of live load. Ultimately design recommendations will be developed from this research. The research presented in this document is the results of preliminary analysis and design of conventional reinforced concrete bridge columns and substructure elements as part of the larger project to examine global seismic behavior of the scaled bridge model. In order to prepare for seismic testing of the scaled bridge model, extensive pre-experimental numerical analysis was performed. Finite element models were developed using SAP2000 and non-linear time-history analysis was performed to investigate the seismic response of the bridge model. Analytical bridge models were analyzed using both 16-inch and 20-inch column diameters and various abutment support conditions. The models were subjected to two levels of horizontal bidirectional earthquake excitation representing a design level earthquake and a large amplitude earthquake intended to cause column failure. Using the results from the analysis, preliminary construction plans were prepared for one set of columns and the adjacent substructure components using the provisions from the AASHTO Guide Specifications for LRFD Seismic Bridge Design. In addition to the investigation into column performance, a parametric study was performed to determine axial response of the bearings at both the abutments and piers when subjected to seismic loading. The numerical analysis showed that system effects due to superstructure-substructure interaction can cause column flexural response that is typically not observed with stand-alone column tests. The effects of bridge horizontal curvature was shown to have a significant impact on the axial performance of the bearings in which the response was not uniform for all bearing at one support location. As a component of the analysis and design, two strut-and-tie models were developed to provide adequate joint detailing in order to ensure capacity protection of the column-to-bentcap connection under multiple cycles of seismic loading.
Author: Fatemeh Kavianipour
Publisher:
ISBN:
Category : Electronic books
Languages : en
Pages : 1350
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Book Description
Funded by the National Science Foundation through the Network for Earthquake Engineering Simulation (NEES) research program, a major multi-university research project has been in progress at the University of Nevada, Reno. This study describes the study of one of the three large-scale bridge models that were tested to failure on three shake tables system. This model was supported on fiber-reinforced polymer (FRP) composite piers implementing accelerated bridge construction (ABC) techniques. The bridge was a quarter scale model of a 4-span bridge with continuous reinforced concrete superstructure and a drop cap, two-column pier design. Each pier utilized different unconventional FRP details. The purpose of using these innovative details was to improve the seismic performance of the bridge. The first pier consisted of cast-in-place concrete-filled glass FRP tubes with ±55 degree fibers. The second pier consisted of two segmental reinforced concrete columns wrapped with layers of unidirectional carbon FRP sheets to provide confinement and shear reinforcement. Only nominal hoops were used to hold the longitudinal reinforcement, as FRP jacket and tube were sufficient in providing confinement and shear required reinforcement. The third pier had the same configuration as that of pier 1 but the columns and footing were precast. The top connections in piers 1 and 3 consisted of pipe-pin joints to facilitate ABC and provide hinge behavior. The objectives of the study presented in this document were to evaluate the biaxial seismic performance of this bridge system incorporating composite piers, investigate the performance of each detail and compared them to each other and to conventional ones, determine the influence of abutment-superstructure interaction on the response, assess the performance of a bridge model incorporating ABC techniques, evaluate sufficiency of analytical modeling of the performance of composite material and details, and to conduct parametric study of different variations of the bridge model to study the effect of several important factors such as near-fault earthquake effects and the variations in the configuration of the bridge model. large-scale 4-span bridge model was designed, constructed, and subjected to simulated earthquake loading on three shake tables. The simulated shake table motions were the modified 1994 Northridge, CA ground motion recorded in Century City and were applied to the bridge model in ten runs with increasing amplitudes. Over 380 channels of data were collected. Compared to conventional reinforced concrete bridges, experimental results showed superior performance under extreme seismic loading even under lateral drift ratios exceeding 9%. Extensive post-test analytical studies were conducted and it was determined that a computational model of the bridge that included bridge-abutment interaction using OpenSees was able to provide satisfactory estimations of key structural response parameters such as superstructure displacements. The analytical model was also used to conduct parametric studies on response of the bridge model and its variations under near-fault excitations. The effects of changing the column section properties were also explored. It was found that concrete-filled FRP tube piers and CFRP wrapped post-tensioned segmental piers reduce residual displacements compared to their conventional reinforced concrete counter parts even under impulsive near-fault motions.
Author: Kazuhiko Kawashima
Publisher:
ISBN:
Category : Bridges
Languages : en
Pages : 214
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Book Description
This report describes correlations between analytical and experimental seismic responses of a model bridge structure which was constructed to have the same features as the typical full-scale high curved highway bridge structure. Modifications of the previously reported mathematical procedures for simulating the nonlinear behavior of expansion joints are presented. These include subdividing the time interval of integration and applying an equilibrium correction at the end of each interval and each subinterval. Correlations of displacement response of the bridge model carried out for three different excitations are described. Parameter studies conducted to assist in the interpretation of correlation results are presented, and the characteristics of the dynamic behavior of the bridge model are discussed. General conclusions are summarized.
Author: Wai-Fah Chen
Publisher: CRC Press
ISBN: 1482255030
Category : Technology & Engineering
Languages : en
Pages : 3130
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Book Description
Over 140 experts, 14 countries, and 89 chapters are represented in the second edition of the Bridge Engineering Handbook. This extensive collection provides detailed information on bridge engineering, and thoroughly explains the concepts and practical applications surrounding the subject, and also highlights bridges from around the world.Published
Author: United States. Federal Highway Administration. Structures and Applied Mechanics Division
Publisher:
ISBN:
Category : Bridges
Languages : en
Pages : 54
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Book Description
Author: Andres Oscar Espinoza
Publisher:
ISBN:
Category :
Languages : en
Pages : 666
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Book Description
Abstract Seismic Performance of Reinforced Concrete Bridges Allowed to Uplift During Multi-Directional Excitation by Andres Oscar Espinoza Doctor of Philosophy in Engineering - Civil and Environmental Engineering University of California, Berkeley Professor Stephen A. Mahin, Chair The behavior of bridges subjected to recent moderate and large earthquakes has led to bridge design detailed for better seismic performance, particularly through wider bridge foundations to handle larger expected design forces. Foundation uplift, which is not employed in conventional bridge design, has been identified as an important mechanism, in conjunction with structural yielding and soil-structure interaction that may dissipate energy during earthquakes. Preventing uplift through wider foundations looks past the technical and economical feasibility of allowing foundation uplift during seismic events. The research presented in this thesis is part of a larger experimental and analytical investigation to develop and validate design methods for bridge piers on shallow foundations allowed to uplift during seismic events. Several analytical and some experimental studies have been performed to assess rocking and or uplift of shallow foundation systems, however they have evaluated systems with a limited range of footing dimensions and seismic excitations. As such, there is an uncertainty in the information needed to base a performance evaluation and develop design methods. The purpose of this study is to investigate, through experimental and analytical studies, the seismic performance of uplifting bridge piers on shallow foundations when considering different ground motions and footing dimensions. As well as to identify key differences in performance evaluation criteria for conventional and uplifting bridge pier systems. The experimental study dynamically tested a single reinforced concrete bridge column specimen with three adjustable footing configurations grouped by footing dimension, and tested for various combinations of one, two, and three components of seismic excitation. Groups one and two evaluated uplifting systems where the column was limited to elastic loading levels while group three considered inelastic column loading levels. All test groups remained stable and exhibited some rocking and or uplift during testing. Analytical models were developed and validated using the experimental testing results to predict local and global footing and column response. Reliable estimates of forces and displacements during elastic and inelastic response were achieved. To assess the seismic performance of a range of bridge pier systems allowed to uplift a parametric investigation using the validated analytical models was performed in which the column was modeled per conventional design criteria to ensure adequate strength and flexural ductility. The parameters varied include footing width, ground motion excitation, and elastic or inelastic column response. Response of the uplifting bridge pier systems was found to be sensitive to the structural periods, magnitude of excitation, and footing width.
Author: Wai-Fah Chen
Publisher: CRC Press
ISBN: 1439852294
Category : Technology & Engineering
Languages : en
Pages : 734
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Book Description
Over 140 experts, 14 countries, and 89 chapters are represented in the second edition of the Bridge Engineering Handbook. This extensive collection highlights bridge engineering specimens from around the world, contains detailed information on bridge engineering, and thoroughly explains the concepts and practical applications surrounding the subjec
