Article

Biaxial Seismic Performance of a Two-Span Concrete Bridge Model with Six ABC Connections

Authors:
If you want to read the PDF, try requesting it from the authors.

Abstract

A prerequisite to the implementation of accelerated bridge construction (ABC) in moderate and high seismic regions is reliable data proving that bridges constructed by assembling precast elements can emulate the seismic performance of cast-in-place bridges. Previous seismic studies have not provided sufficient information about the interaction of conventionally reinforced precast concrete elements and connections when they are integrated within a bridge system. This paper addresses this knowledge gap by conducting biaxial shake table tests on a 0.35-scale, two-span bridge model that incorporated 38 precast reinforced and prestressed concrete elements. The elements were joined by using six connection types joining column to footing, column to cap beam, girder to cap beam, deck panels (two types), and deck to girder. The bridge and the connections performed well even under earthquake motions beyond the design-level earthquake and combined large drift ratio demands and substantial in-plane rotation. Although the load path was affected by the interaction among different components, no adverse effect was observed.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

ResearchGate has not been able to resolve any citations for this publication.
Article
Full-text available
There have been significant research efforts on seismic-resistant precast bridge columns; however, the research results have not been transformed into the industry to achieve their full potential. This review provides a summary of the research development and challenges for both researchers and practitioners. Applications of new materials in rocking columns are briefly discussed. Three types of rocking columns are reviewed: emulative column, simple rocking column, and hybrid rocking column. It is believed that hybrid rocking columns are the most prominent option comparing with the other two types. Its design recommendations with respect to energy dissipating bars, axial load ratios and tendons are concluded based on the review data. The amount of energy dissipating bars should be such that its contribution to total bending moment capacity is less than 50%. In most of the cases, the energy-dissipating bar ratios are less than 1.7% of the column sectional area. Upon a careful review of existing experimental test results, an effective stiffness ratio of 20% to 40% can be suggested for design. To further facilitate engineering designs, regression equations predicting residual drift to maximum drift ratios, as well as viscous damping ratios are also proposed.
Article
Full-text available
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.
Article
Full-text available
This paper presents a novel, bridge-dependent approach for quantifying the increase of design quantities due to spatially variable earthquake ground motion (SVEGM). Contrary to the existing methods for multiple support bridge excitation analysis that are either too complicated to be applied by most practitioners or oversimplied (e. g. Eurocode 8, Annex D provisions), this method aims to strike a balance between simplicity, accuracy and computational efficiency. The method deliberately avoids generating support-dependent, acceleration or displacement, asynchronous inputs for the prediction of bridge response. The reasons behind this decision are twofold: (a) first, the uncertainty associated with the generation of asynchronous motion scenarios, as well as the exact soil properties, stratification and topography is high while, (b) the response of a bridge is particularly sensitive to the above due to the large number of natural modes involved. It is therefore prohibitive to address SVEGM effects deterministically in the framework of a design code. Instead, this new method is based on two important and well-documented observations: (a) that SVEGM is typically globally beneficial but locally detri-mental [1], and (b) that the local seismic demand increase is very closely correlated with the excitation of higher modes, which are not normally activated in the case of uniform ground motion [2,3]. Along these lines, a set of static analyses are specified herein to complement the standard, code-based response spectrum analysis. These static analyses apply spatially distributed lateral forces, whose patterns match the shape of potentially excited anti-symmetric modes. The amplitude of those forces is derived as a function of the expected amplification of these modes according to the process initially proposed by Price et al. [4]. Two real bridges with different structural configurations are used as a test-bed to demonstrate the effectiveness of the new method. Comparison of the results with those obtained through rigorous response history analysis using partially correlated, spatially variable, spectrum-compatible input motions [5] shows that, the simplified method presented herein provides a reasonably accurate estimation of the SVEGM impact on the response of the bridges examined at a highly reduced computational cost. This is essentially an elastic method that is found to be simple, yet precise enough to consist an attractive alternative for the design and assessment of long and/or important bridge structures in earthquake-prone regions. Download fulltext: https://authors.elsevier.com/c/1aTYdytxOFGx~
Article
Full-text available
In this paper, a novel precast concrete segmental bridge system is introduced and experimentally investigated. The system consists of segmental members incorporating hybrid sliding-rocking (HSR) joints and internal unbonded posttensioning (PT). The HSR joints are plane interfaces that are oriented normal to the member axis and do not include shear keys or epoxy adhesives. The HSR joints are designed to exhibit sliding (slip-dominant, SD) or rocking (rocking-dominant, RD) to mitigate the applied seismic loading and reduce damage. The joint response is affected by the PT system, which can include straight or curved tendons. Two types of HSR members are developed and investigated: (1) members with SD joints and straight tendons, intended for substructure columns (HSR-SD columns), and (2) members with RD joints and curved tendons, intended for superstructure girders (HSR-RD girders). The SD joints are shown to offer energy dissipation with low damage through sliding in addition to moderate self-centering. The RD joints, albeit offering low energy dissipation, are shown to provide high self-centering. A series of shake table tests on a large-scale bridge specimen demonstrates the successful integrated response of the HSR-SD substructure and the HSR-RD superstructure for intense horizontal and vertical seismic excitations.
Article
Full-text available
The latest version of the ACI Building Code requires five equations to prescribe the limiting horizontal shear stress for differing amounts of reinforcing steel. The test results from the 16 beams tested in this study indicate that a more consistent limit can be obtained by replacing four of the present equations with a parabolic equation modified from the one used in the PCI Design Handbook. The proposed equation combines the effect of concrete strength and clamping stress. It is equally applicable for lightweight and semi-lightweight concrete. The test results indicate that an as-cast surface with the coarse aggregate left protruding for the surface, but without special efforts to produce a rough surface, can develop adequate shear resistance and simplify production of the precast concrete beams. Also, the tests show that stirrups are typically unstressed and ineffective until horizontal shear stresses exceed 1.5 to 2 MPa (220 to 290 psi).
Article
Full-text available
The torsional effects on short-span highway bridges are investigated for two situations: post-design asymmetric bridges and nominally symmetric bridges subject to seismically induced torque. The study indicates that for post-design asymmetric bridges the presence of accidental post-design asymmetric factors significantly influences the dynamic response of bridges having a small rotational to translational frequency ratio. For nominally symmetric bridges, the seismically induced torque often triggers rotational motions, which tend to aggravate the bridge deck displacements and magnify the shear forces of the supporting columns. If necessary, this torsional effect should be considered in the seismic design of bridges.
Article
Girder unseating in skewed bridges with seat-type abutments has been frequently observed in past earthquakes. This has been attributed to excessive in-plane rotation of the superstructure and a handful of numerical studies have been conducted to investigate the cause of this rotation. The most common explanation has been pounding between the superstructure and abutment back wall, but this phenomenon has not been verified by experimental testing. Accordingly, this paper describes an experimental investigation into the behavior of skewed bridges with special attention being given to the interaction between the superstructure and abutment. Shake table experiments are described on a family of four, single-span, simply supported bridge models with skew angles of 0º, 30º, 45º, and 60º, and five different expansion gaps. These models were subjected to a suite of ground motions that varied by type (near-field and far-field), intensity, and input direction. In total, 876 experiments were conducted. Data collected included superstructure displacements and accelerations, and impact forces at the abutments. The results confirm that a skew bridge experiences large in-plane rotation when the obtuse corner of the span impacts the adjacent back wall with or without slippage along the face of the wall. As a consequence, these bridges can experience large in-plane displacements normal to the back wall at their acute corners, and larger support lengths are required to prevent unseating than for straight bridges. The comprehensive data set obtained in these experiments may be used in future studies to validate numerical models for skew bridges and improve the empirically-based, minimum support length requirements that are specified for skew bridges in many bridge design codes.
Article
This paper investigates the seismic response of skewed bridges using the comprehensive dataset obtained from a family of shake table experiments conducted by the authors. To begin, the influence of friction along the abutment on the in-plane rotation of skewed bridges is evaluated. Then the influence of expansion gap size, type of ground motion (near-field and far field), and input direction on seismic response is described. It is shown that once impact occurs between the bridge and abutment back wall, significant forces can be generated normal to the back wall due to impact, and in the plane of the back wall through friction. These forces cause in-plane rotation of otherwise symmetric skewed bridges. Both impact and friction should therefore be included in numerical models used to compute in-plane displacements of the superstructure. Moreover, it is shown that bridges with very small or very large gaps experience lower response. It is also shown that numerical models that do not include the gap, could give non-conservative results, especially for moderate-sized gaps. Furthermore, skew bridges are more vulnerable to near-field ground motions than far-field motions. Finally, if the major component of the ground motion is applied in the transverse direction alone, comparable maximum displacements and in-plane rotations are obtained as for biaxial excitations. But it produces significantly smaller impact forces than for biaxial input, due to the contribution of the minor component in the longitudinal direction.
Technical Report
The Nevada Department of Transportation (NDOT) has used to a limited extent prefabricated bridge elements for accelerated construction of single-span bridges. For NDOT to expand its accelerated bridge construction (ABC) program, reliable and practical earthquake-resistant elements and connections need to be developed for bridges with two or more spans. The main objective of the present study was to address this need utilizing a comprehensive literature search on different types of ABC connections, a rating system for evaluation of available connections, and experimental and analytical studies. Various types of bridge column moment and pin connections and superstructure-cap beam-column connections suitable for use in ABC were identified and reviewed in detail. To evaluate the ABC bridge column connections suiting the needs of NDOT, a rating system was developed taking into account the level of development, seismic performance, and non-seismic parameters associated with each connection type. All the connections were rated compared to reference cast-in-place connections. The seismic performance of the top-rated connections was investigated in shake table testing of a one-third scale, two-column pier model. Columns were connected to the footing using moment pocket connections and to the cap beam using a combination of the rebar hinge and pocket detail for one column, and a new generation of pipe pins (labeled as one-piece pipe pin) and pocket detail for the other. The one-piece pipe pin connection is composed of an in-filled steel pipe with welded studs on the surface embedded in the column and the adjoining member. The pier model was tested to failure under increasing amplitudes of the Sylmar convertor station ground motion record simulated on a shake table. The proposed pocket connections, pipe pin, and rebar hinge were found to be successful even under high drift ratios. Moreover, the precast cap beam remained elastic and damage free during the entire testing. To investigate the effects of important variables on the response and behavior of pipe pins, a comprehensive parametric study was conducted analytically on a reference subsystem using OpenSees. The reference subsystem was a fixed-fixed single-column pier in which the column was connected to the cap beam using a one-piece pipe pin. The parameters included in the study were: the axial load index, debonded length of the pipe in the column and adjoining member, pipe diameter, embedment length of the pipe in the column and the adjoining member, and the compressive strength of the material around the pipe. It was found that limiting the minimum plastic moment capacity of the infilled-pipe and debonding of the pipe either in the column alone or in the column and the adjoining member can effectively reduce the strain demand in the pipe. The analytical results were utilized to develop a simple and practical analytical method for modeling pipe pins. Results of the parametric studies together with the experimental observations led to a method for seismic design of pipe pins followed by several detailing recommendations and an illustrative example.
Article
A continuous bridge in high-speed railway is close to several known faults in China. Those faults, respectively at different distances from the bridge site, will produce different ground motions with the different ratios of vertical component to the horizontal component at the bridge site. It is necessary to identify the influence of vertical ground motions on the seismic responses and vulnerabilities of the track-bridge system. This paper solved this problem by carrying out an incremental dynamic analysis (IDA) and a further seismic fragility analysis on a widely used continuous bridge in China. The results show that the damage probabilities of most bridge and track components increase along with the increase of vertical part in ground motions. This trend is significant for the sliding layer of track part in the longitudinal direction and the piers of bridge part in any direction, however, insignificant for the bearings of bridge part in any direction. Moreover, this trend is more significant for the track part across the girder gap due to the different seismic responses of adjacent bridges. The seismic design of track-bridge system should rigorously take the vertical part of ground motions into account.
Article
The 2010 Maule and 2015 Illapel earthquakes recently affected the highway infrastructure in Chile. Deck rotation in straight and skewed bridges, damage to the connection between the superstructure and substructure, and even collapse of bridges were observed in these events. However, deck rotation in straight bridges has been identified as an unusual failure mode. The main objective of this research is to evaluate if potential asymmetries in the bridge characteristics can be a probable reason that explain deck rotation observed in straight bridges. The second objective is to assess the effect of transverse diaphragms on the seismic behavior of these bridges. In order to achieve these objectives, the Chada underpass, which suffered deck rotation, damage to lateral stoppers and prestressed concrete girders during the Maule earthquake, is used as a case study. The asymmetries considered in this study are related to the variation of the strength of the lateral stoppers, the coefficient of friction of the elastomeric bearings, and the gap distance between the lateral stoppers and prestressed concrete girders. The induced asymmetries are evaluated with a three-dimensional model of the bridge developed in Opensees. The seismic response of the bridge is obtained from nonlinear dynamic analyses considering seven seismic records applying both horizontal components simultaneously. From the results of this study, it is concluded that the studied asymmetries induce deck rotations that can explain only part of the observed deck rotation in the studied straight bridge. A maximum relative horizontal displacement of the deck of 58.2 cm was estimated for the case with asymmetric strength of lateral stoppers, which is only 41% of the residual relative displacement measured in Chada bridge after the Maule earthquake. Additionally, it is concluded that the incorporation of transverse diaphragms, which is required by current Chilean bridge design code, improved the seismic behavior of the studied bridge.
Article
The strain rate effect can inevitably impact the seismic responses of reinforced concrete (RC) structures because the dynamic properties of RC materials under earthquakes change significantly with the time-varying loading rates. This paper carries out systematic experimental tests and numerical simulations to investigate the effects of strain rates on the seismic responses of RC structures. The dynamic properties of micro-concrete and iron wire used in the shaking table specimen are firstly tested under seismic loading rates and the corresponding dynamic increase factors (DIFs) are estimated based on the test data. The shaking table test of a 1/5 scaled RC structure is performed to realistically reproduce the dynamic responses of RC structures with strain rate effect. Moreover, a three-dimensional rate-dependent fiber beam-column element is developed in the ABAQUS platform to establish the finite element (FE) model of the shaking table specimen, in which the estimated DIFs for the key parameters of micro-concrete and iron wire are employed to consider the strain rate effect. Besides, the rate-independent structural FE model is also developed using the traditional beam-column element with the static RC material constitutive models. The numerical results demonstrate that the seismic responses of RC structures are overestimated when the strain rate effect is neglected. As validated by the experimental data of the shaking table test, the FE model developed using the proposed rate-dependent fiber beam-column element can yield better structural seismic response predictions in comparison with the rate-independent model.
Article
Precast concrete facilitates a construction method using durable and rapidly erectable prefabricated members to create cost-effective and high-quality structures. In this method, the connections between the precast members as well as between the members and the foundation require special attention to ensure good seismic performance. Extensive research conducted since the 1980s has led to new precast concrete structural systems, designs, details, and techniques that are particularly suited for use in regions of high seismic hazard. This paper reviews the state of the art of these advances, including code developments and practical applications, related to four different systems: (1) moment frames; (2) structural walls; (3) floor diaphragms; and (4) bridges. It is concluded from this review that the widespread use of precast concrete in seismic regions is feasible today and that the jointed connection innovation introduced through precast research leads to improved seismic performance of building and bridge structures.
Article
Shake-table studies were conducted on a ¼-scale, 2-span bridge model incorporating a newly-developed concept of replaceable plastic hinges and columns that can be easily assembled and disassembled. The plastic hinges are made of engineered cementitious composite or shimmed flexural elastomeric bearings reinforced with superelastic alloy bars, which allow the bridge to undergo intense seismic shaking and remain fully operational when most reinforced concrete bridges would warrant demolition. Designed to be disassembled, the column components have the potential to be reused, which is intended to help mitigate the environmental impact from material extraction and manufacture. The concept feasibility was demonstrated by assembling, testing, and disassembling the bridge model twice. It was found that the plastic hinge elements successfully eliminated or minimized damage, led to negligible permanent drift, and prevented distress in connections and other capacity-protected elements. The detachable connections allowed for disassembly and reassembly of the bridge as intended. The results further showed that the seismic performance of the reassembled bridge utilizing reused components was comparable to that of the original bridge with pristine components.
Article
A new bridge bent system has been developed to reduce on-site construction time, minimize residual displacements even after a large earthquake, and reduce seismic damage in comparison with conventional cast-in-place construction. Accelerated construction is achieved through the use of precast columns and cap beams that can be assembled quickly. Postearthquake residual displacements are reduced by pretensioning the columns with partially unbonded tendons. Damage in the columns is nearly eliminated by concentrating flexural deformations to specially detailed regions at the top and bottom of the columns. In this study, the seismic performance of the new system was evaluated with a multi-shaking table test of a quarter scale, two-span bridge at the Network for Earthquake Engineering Simulation (NEES) Earthquake Engineering Laboratory at the University of Nevada, Reno. The maximum displacements of the bents were similar to those expected for a conventional bridge through the 100% design-level event [peak ground acceleration (PGA) = 0.75 g]. Residual drift ratios never exceeded 0.2% up to the 221% design-level motion (PGA = 1.66 g). Damage to the column concrete was negligible; the columns would not need any repair after being subjected to the 100% design-level motion. The only structural damage to the bridge was the eventual fracture of the column's longitudinal reinforcement and bulging of the column's confining tube, both of which occurred at drift ratios of approximately 6%. These damage states could be delayed by increasing the debonded length of the deformed bar reinforcement at the ends of the columns and by using a thicker steel tube for the confining detail.
Article
Ultra-high-performance concrete (UHPC) is a relatively new class of advanced cementitious composite materials, which exhibits high compressive (above 21.7 ksi [150 MPa]) and tensile (above 0.72 ksi [5 MPa]) strengths. The discrete steel fiber reinforcement included in UHPC allows the concrete to maintain tensile capacity beyond cracking of the cementitious matrix. The combination of the matrix and fiber performance allow for a reduction on the development length of reinforcing steel bar, thus providing the potential for a redesign of some structural systems such as field-cast connections between prefabricated bridge elements. The bond behavior of deformed steel reinforcing bar in UHPC is investigated in this study by conducting direct tension pullout tests. Over 200 tests were completed and the effect of embedment length, concrete cover, bar spacing, concrete strength, bar size, bar type, and yielding strength on bond strength were investigated. It was found that the bond behavior of deformed reinforcing steel in UHPC is different from that in traditional concrete in many aspects. In general, the reinforcing steel development length in UHPC can be significantly reduced. Guidance on the embedment of deformed reinforcing bars into UHPC is provided.
Article
Detailed data from 30 bridge column models, mostly tested on shake tables, were evaluated to determine the correlation between the apparent damage and internal and external seismic response parameters. The majority of the columns were of circular cross section. The columns were divided into five categories based on seismic design, shear demand, and ground motion type. Five distinct damage states were proposed based on the apparent damage. Six response parameters were also defined in terms of drift, frequency, strains, yielding, and ultimate displacements. The correlation between damage states and the response parameters were determined for each column category. The results demonstrate a general trend relating damage states to response parameters. Using the observed damage and the data presented in this article it was shown that an estimate of a non-dimensionalized push over curve may be made.
Article
A closed-loop servohydraulic testing machine was used to conduct high rate tests on reinforced concrete beams. Seven pairs of singly reinforced beams (without shear reinforcement) were tested under displacement control. From each pair, one beam was tested at a "static" rate (piston velocity = 0.00071 cm/sec) and the other at a "high" rate (piston velocity = 38 cm/ sec). The total number of cracks reduced significantly at the high rate. Peak load and energy absorption capacity were found to increase with the rate of straining. The load-deflection curves for beams failing in flexure at the high rate did not show a sharp "yield point" or a "yield plateau." A standard sectional analysis using rate-dependent constitutive relationships does not adequately predict the shape of the high-rate load-deflection curve. Localized yielding of steel at higher strain rates is believed to be a cause for this. Computations to support this hypothesis are presented. For three of the pairs tested, final failure mode shifted from shear failure at the static rate to flexural failure at the high rate. This phenomenon is the opposite of the brittle transition in the mode of failure reported by some other researchers. It is tentatively proposed herein that this apparent contradiction can be explained on the basis of the rate sensitivity of the different steels used in these studies.
Article
Through an in-depth review of previous work complemented by an experimental study, the nature of shear-friction behavior is studied. It is shown that the ACI 318-08 and AASHTO approaches to shear friction do not capture the actual behavior and imply incorrect limit states. A simple explanatory model and modifcations to the form of empirical design equations are proposed. A large number of parameters affect shear-friction performance. This study does not attempt to address them all but rather illustrates the fundamental shear-friction behavior. This study does, however, consider the use of high-yield-strength reinforcing steel (ASTM A1035/A1035M). In doing so, the serious limitations of the design equations are illustrated. Additionally, this study is the only known study of shear-friction behavior to include high-strength steel.
Conference Paper
Precast, post-tensioned segmental bridge construction has been widely used in non-seismic regions in the U.S. for the objectives of accelerated bridge construction (ABC), higher quality control, less traffic disruption, and better workman safety. However, use of segmental bridges in moderate and high seismic regions is limited due to insufficient understanding of its behavior. This paper presents the results of a series of shake table tests on large-scale bridges with pre-cast, post-tensioned, concrete segmental columns. The seismic behavior of segmental columns was observed, segmental joint opening and closing were studied, and the self-center capability of segmental bridge was analyzed. This research is a U.S.-PRC international cooperative project established by the Multidisciplinary Center for Earthquake Engineering Research, University at Buffalo, the State University of New York, under contract with the Federal Highway Administration (Contract No. DTFH61-07-C-00020), and the Chongqing Communication Research and Design Institute, State Key Laboratory of Bridge Structural Dynamics, Chongqing, China, with the International Science & Technology Cooperation Program of China (Project No.: 2011DFA83300).
Article
SUMMARY Different levels of model sophistication have recently emerged to support seismic risk assessment of bridges, but mostly at the expense of neglecting the influence of vertical ground motions (VGMs). In this paper, the influence of VGMs on bridge seismic response is presented and the results are compared with the case of horizontal-only excitations. An advanced finite element model that accounts for VGMs is first developed. Then, to investigate the effect of soil–structure interaction (SSI) including liquefaction potential, the same bridge with soil-foundation and fixed boundary conditions is also analyzed. Results show that the inclusion of the VGMs has a significant influence on the seismic response, especially for the axial force in columns, normal force of bearings, and the vertical deck bending moments. However, VGMs do not have as much influence on the seismic demand of the pile cap displacements or pile maximum axial forces. Also, the significant fluctuation of the column axial force can reduce its shear and flexural capacity, and a heightened reversal of flexural effects may induce damage in the deck. In addition, relative to the fixed base case, SSI effects tend to reduce response quantities for certain ground motions while increasing demands for others. This phenomenon is explained as a function of the frequency content of the ground motions, the shift in natural vertical periods, and the VGM spectral accelerations at higher modes. Moreover, the mechanisms of liquefaction are isolated relative to SSI effects in nonliquefiable soils, revealing the influence of liquefaction on bridge response under VGMs. Copyright © 2012 John Wiley & Sons, Ltd.
Article
This paper examines the role of shear keys at bridge abutments in the seismic behavior of “ordinary” bridges. The seismic responses of bridges subjected to spatially uniform and spatially varying ground motions for three shear-key conditions—nonlinear shear keys that break off and cease to provide transverse restraint if deformed beyond a certain limit; elastic shear keys that do not break off and continue to provide transverse restraint throughout the ground shaking; and no shear keys—are examined. Results show that seismic demands for a bridge with nonlinear shear keys can generally be bounded by the demands of a bridge with elastic shear keys and a bridge with no shear keys for both types of ground motions. While ignoring shear keys provides conservative estimates of seismic demands in bridges subjected to spatially uniform ground motion, such a practice may lead to underestimation of some seismic demands in bridges in fault-rupture zones that are subjected to spatially varying ground motion. Therefore, estimating the upper bounds of seismic demands in bridges crossing fault-rupture zones requires analysis for two shear-key conditions: no shear keys and elastic shear keys.
Article
In order to utilize results obtained from quasi-static cyclic load tests on structural components for a general performance evaluation, the need exists to establish loading histories that capture critical issues of component capacity as well as seismic demands. In inelastic seismic problems capacity and demands cannot be separated since one may strongly depend on the other. Because of cumulative damage issues the capacity depends on the number of inelastic excursions and the magnitude of each excursion (not just the largest one). These two parameters depend on the frequency content of the ground motion, the period(s) of the structure, and the strength and inelastic deformation characteristics of the structure. The paper presents procedures how these characteristics can be considered in the selection of suitable loading histories.
Article
Results of comprehensive nonlinear response history analyses on a range of configurations representing typical highway overcrossings subjected to combined effects of vertical and horizontal components of near-fault ground motions are reported. Current seismic design guidelines in California neglect the vertical components of ground motions for peak ground accelerations less than 0.6 g and provide rather simplistic measures to account for vertical effects when they need to be incorporated in the design. Results from the numerical simulations show that the vertical components of ground motions cause significant amplification in the axial force demand in the columns and moment demands in the girder at both the midspan and at the face of the bent cap. Axial capacity of the columns and moment capacity of the girder at the face of the bent cap were generally found to be sufficient to resist the amplification in the respective demands due to vertical effects. However, midspan moments in negative bending due to vertical motions are found to exceed the capacity of the girder. The amplified midspan moments lead to yielding of the top reinforcement resulting in average peak strains on the order of 1%. It is concluded that seismic demand analysis of ordinary highway bridges in general and overcrossings in particular should incorporate provisions for considering the adverse vertical effects of near-fault ground motions.
Shake table test videos (Calt-Bridge 1).” Accessed
  • J Benjumea
Experimental and analytical seismic studies of a two-span bridge system with precast concrete elements and ABC connections
  • J Benjumea
Laurel street overcrossing-Caltrans’ first multi-span precast accelerated bridge construction pilot project
  • D Mellon
  • Mellon D.
Estimating the construction cost of accelerated bridge construction (ABC)
  • W Orabi
  • A Mostafavidarani
  • M Ibrahim
  • Orabi W.