Seismic Retrofitting Manual for Highway Structures: Part 1 - Bridges
Author: Buckle, Ian University of Nevada, Reno Friedland, Ian Mander, John Martin, Geoffrey University of Southern California, Los Angeles Nutt, Richard Power, Maurice | Size: 15.45 MB | Format:PDF | Quality:Unspecified | Publisher: Multidisciplinary Center for Earthquake Engineering Research | Year: 2006 | pages: 656
The main objective of this research was to assess the seismic vulnerability of typical pre-1975 Washington State Department of Transportation (WSDOT) prestressed concrete multi-column bent bridges. Additional objectives included determining the influence of soil-structure-interaction on the bridge assessment and evaluating the effects of non-traditional retrofit schemes on the global response of the bridges. Overall this research highlighted the vulnerability of non-monolithic bridge decks and shear-dominated bridThis manual, which is comprised of two parts, represents the most current state-of-practice in assessing the vulnerability of highway structures to the effects of earthquakes, and implementing retrofit measures to improve performance. Part 1 of this manual focuses on highway bridges, and is a replacement for the Federal Highway Administration (FHWA) publication "Seismic Retrofitting Manual for Highway Bridges" which was published in 1995 as report FHWA-RD-94-052. Revisions have been made to include current advances in earthquake engineering, field experience with retrofitting highway bridges, and the performance of bridges in recent earthquakes. It is the result of several years of research with contributions from a multidisciplinary team of researchers and practitioners. In particular, a performance-based retrofit philosophy is introduced similar to that used for the performance-based design of new buildings and bridges. Performance criteria are given for two earthquake ground motions with different return periods, 100 and 1000 years. A higher level of performance is required for the event with the shorter return period (the lower level earthquake ground motion) than for the longer return period (the upper level earthquake ground motion). Criteria are recommended according to bridge importance and anticipated service life, with more rigorous performance being required for important, relatively new bridges, and a lesser level for standard bridges nearing the end of their useful life. Minimum recommendations are made for screening, evaluation and retrofitting according to an assigned Seismic Retrofit Category. Bridges in Category A need not be retrofitted whereas those in Categories B, C and D require successively more rigorous consideration and retrofitting as required. Various retrofit strategies are described and a range of related retrofit measures explained in detail, including restrainers, seat extensions, column jackets, footing overlays, and soil remediation.ge columns in pre-1975 WSDOT prestressed concrete multi-column bent bridges as well as the importance of including soil-structure-interaction, calibrating the force/displacement characterization of the columns to experimental test data and detailed modeling of the bridges such as expansion joint/girder interaction. In the end, the seismic assessment of bridges is a cost/efficiency issue. Each bridge is different, therefore, investing in improved analyses up front will enable an efficient use of the limited funds for bridge improvement, resulting in a significant savings overall.
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Seismic Assessment and Retrofit of Existing Multi-Column Bent Bridges
Author: McDaniel, Cole C | Size: 2.08 MB | Format:PDF | Quality:Unspecified | Publisher: Washington State University, Pullman | Year: 2006 | pages: 63
The main objective of this research was to assess the seismic vulnerability of typical pre-1975 Washington State Department of Transportation (WSDOT) prestressed concrete multi-column bent bridges. Additional objectives included determining the influence of soil-structure-interaction on the bridge assessment and evaluating the effects of non-traditional retrofit schemes on the global response of the bridges. Overall this research highlighted the vulnerability of non-monolithic bridge decks and shear-dominated bridge columns in pre-1975 WSDOT prestressed concrete multi-column bent bridges as well as the importance of including soil-structure-interaction, calibrating the force/displacement characterization of the columns to experimental test data and detailed modeling of the bridges such as expansion joint/girder interaction. In the end, the seismic assessment of bridges is a cost/efficiency issue. Each bridge is different, therefore, investing in improved analyses up front will enable an efficient use of the limited funds for bridge improvement, resulting in a significant savings overall.
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Seismic, Creep, and Tensile Testing of Various Epoxy Bonded Rebar Products in Hardened Concrete
Author: Meline, Robert J Gallaher, Malinda Duane, Jacob | Size: 2.32 MB | Format:PDF | Quality:Unspecified | Publisher: California Department of Transportation | Year: 2006 | pages: 110
The objective of this project was to evaluate the performance of currently specified epoxy adhesive anchor systems on various epoxy-coated rebar under seismic, creep and tensile loading. The epoxy-coated rebar was found to meet the requirements of ICBO-AC58, Section 5.3.7.2.4, for tension and seismic loading when bonded into hardened concrete using an epoxy adhesive but not the Caltrans Augmentation/Revisions for creep loading when bonded into hardened concrete. The rebar bonded with Covert Operations CIA-Gel 7000 was found to meet the creep requirements, whereas the rebar bonded with Simpson SET22 and Red Head Epcon C6 did not meet the conditions of acceptance for creep loading. It was also noticed that, when compared to the manufacturer test data, the epoxy-coated rebar outperformed uncoated rebar in allowable tensile loads for two of the three epoxies tested. Simpson SET22 adhesive under performed the manufacturer test data. In the Revision to this report in 2007, further review of the creep data for the rebar bonded with Simpson SET determined that the adhesive met the creep requirement. Due to the load fluctuations, only the first 26 days of data were used for the logarithmic curve fit.
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Seismic Response of Precast Segmental Bridge Superstructures
Author: Veletzos, Marc J | Size: 15.79 MB | Format:PDF | Quality:Original preprint | Publisher: University of California, San Diego | Year: 2006 | pages: 93
While precast segmental bridge construction can help accelerate construction and reduce construction costs in congested urban environments and environmentally sensitive regions, the use of precast segmental bridges in seismic regions of the U.S. has been limited. A primary obstacle to their use is the concern regarding seismic response of segment joints. This report summarizes recent research that has shown that segment joints can sustain very large rotation opening up gaps in the superstructure without significant loss of strength. Using models of precast segmental bridges similar to the Otay River Bridge in San Diego County and the San Francisco-Oakland Bay Bridge Skyway as case studies, the study also investigates the response of segment joints using detailed finite element analyses. A suite of ten near field earthquake records are used for determining the median joint response and for quantifying the effect of vertical motion on the joint response.
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Author: Dehler, William | Size: 15.79 MB | Format:PDF | Quality:Original preprint | Publisher: University of Minnesota, Twin Cities | Year: 2007 | pages: 116
The objective of this work was to show that cone penetration testing (CPT) can be used for pavement applications, specifically estimating resilient modulus and organic content. A series of undisturbed samples were obtained from borings directly adjacent to CPT soundings. These samples underwent both laboratory resilient modulus and bender element testing. A statistical analysis was then performed on these results in conjunction with the data obtained from the CPT soundings to determine the feasibility of developing correlations between field and laboratory measurements of moduli. A relationship was developed between Young’s modulus determined by bender element testing and that determined by resilient modulus testing. However, the correlation did not apply to the field-based seismic measurements of stiffness from the CPT soundings. The analysis presented with respect to the identification of highly organic soils via CPT testing shows that at this point the model identified using the discriminate analysis method is not currently sufficient to use in practice. The 10% increase in correctly classified soils, however, holds promise for the future, and the introduction of additional independent parameters within a significantly larger data set can be easily analyzed using the methods and tools presented here.
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Seismic Response of Telescopic Pipe Pin Connections
Author: Doyle, Kelly A | Size: 8.19 MB | Format:PDF | Quality:Original preprint | Publisher: University of Nevada | Year: 2008 | pages: 182
Two-way hinges are often used in reinforced concrete bridge columns to prevent excessive flexural stresses from entering the connection to the superstructure or the footing. A study was undertaken for Caltrans to understand the behavior of pipe pin connections to help develop a simple and reliable design method. Two 0.3 scale specimens were constructed and tested under cyclic loading to determine if the models behave in pure shear and to study the effect of rotation on the connection behavior and strength. Analytical studies of a simple method gave the foundation for the development of a design method. A sensitivity analysis of the equations revealed that using the ultimate stress of the pipe (rather than the yield stress) in calculations leads to a close estimate of the actual ultimate connection capacity. If yielding is to be avoided in the pin, however, the pipe yield stress should be used in the simple method.
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Seismic Behavior of Reinforced Concrete Bridge Columns at Sub-Freezing Temperatures
Author: Montejo, Luis A | Size: 12.00 MB | Format:PDF | Quality:Original preprint | Publisher: North Carolina State University, Raleigh | Year: 2008 | pages: 397
The final goal of this research was to develop recommendations for the future seismic design or assessment of reinforced concrete (RC) bridge bent structures in cold seismic regions. Ten large scale circular columns were constructed and tested under cyclic reversal of loads inside an environmental chamber in the North Carolina State University Constructed Facilities Laboratory (CFL). The columns were tested at freezing (-40°C, -40°F) and ambient (23°C, 74°F) temperatures. In order to characterize every aspect of the seismic response at low temperatures, the columns' design was governed by a desired behavior: shear dominated columns, flexural dominated columns and reinforced concrete filled steel tube columns. Results obtained show that RC members exposed to the combined effects of sub-freezing temperatures and cyclic loads undergo a gradual increase in strength and stiffness coupled with a reduction in displacement capacity. The experimental results were used to calibrate a fiber-based model and a series of static and inelastic analyses were performed to typical Alaska Department of Transportation and Public Facilities bent configurations. Based on the results obtained from the experimental tests, the non-linear simulations and a moment-curvature parametric analysis, a simple methodology was developed to account for the low temperature flexural overstrength and reduction in ductility capacity.
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Dynamic Response of Bridges to Near-Fault Forward Directivity Ground Motions
Author: Rodriguez-Marek, Adrian | Size: 2.82 MB | Format:PDF | Quality:Original preprint | Publisher: Washington State Transportation Center | Year: 2008 | pages: 84
Research over the last decade has shown that pulse-type earthquake ground motions that result from forward-directivity (FD) effects can result in significant damage to structures. Three typical post-1990 Washington State Department of Transportation (WSDOT) monolithic concrete bridges were chosen to investigate their nonlinear response to FD ground motions (FDGMs) and non-FDGMs. Results showed that significant seismic damage may occur if the structural response is in tune with the period of the velocity pulse of the FDGM. This velocity pulse is a result of fault propagation effects in the near-fault, and occurs when the direction of slip and rupture propagation coincide. The period of the velocity pulse is proportional to the magnitude of the earthquake. The severity of the demand is controlled by the ratio of the pulse period to bridge fundamental periods. As a consequence of this, damage in a bridge with moderate periods (T=0.1s to 1.0s) may be more significant in smaller magnitude earthquakes where the pulse period is closer to the fundamental period of the structure. This was the case for both the MDOF and SDOF analyses of all three bridges in this research. The results showed also that the occurrence of high PGA and/or PGV is only one of several conditions that can cause high demand on the bridges. Of the three bridges considered, all typical concrete overpasses ranging from 50 m to 91 m in length, all generally survived the earthquake motions with only minor damage to their columns. However, column flexural failure was predicted for one model when subjected to two of the forward directivity ground motions. SDOF bridge models for preliminary analyses were found to yield slightly unconservative base shears and displacements compared to that of the full bridge models under non-FDGM. For FDGM, the results of a simple SDOF bridge model ranged from very conservative to slightly unconservative. Therefore, nonlinear SDOF analyses are specifically not recommended in the case of FDGM since the results were not consistent. A more detailed MDOF model should be used to assess bridge seismic performance so that SSI and the interaction of the longitudinal and transverse responses of the bridges can be included, particularly if a performance based design or assessment of the bridge is required.
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Development of Guidelines for Incorporation of Vertical Ground Motion Effects in Seismic Design of Highway Bridges
Author: Kunnath, Sashi K | Size: 2.72 MB | Format:PDF | Quality:Original preprint | Publisher: California Department of Transportation | Year: 2008 | pages: 108
This report describes a study which was conducted in order to assess the current provisions in the California Department of Transportation's Standard Design Criteria 2006 (SDC-2006) for incorporating vertical effects of ground motions in seismic evaluation and design of ordinary highway bridges. A series of simulations was carried out on a range of typical bridge configurations for the purpose of isolating the effects of vertical motions. Results from the simulations reveal that vertical ground motions can have a significant effect on the axial force demand in columns, moment demands at the face of the bent cap, and moment demands at the middle of the span.
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Bridge abutments are designed to provide resistance to deformation and earthquake-induced inertial forces from the bridge superstructure. The passive earth pressure of the abutments' structure backfill is an integral part of the force-resistance mechanism of bridge abutments in the longitudinal direction. Current design practices by the California Department of Transportation (Caltrans) do not take into account the structure backfill properties of bridge abutments. This report describes an experimental and analytical research program that investigated the role that soil properties, abutment geometry, and structure backfill have on the ultimate capacity and stiffness of bridge abutments. Specifically, it examined the effects of structure backfill properties, area of structure backfill, backfill height, and vertical wall movement. In addition, the report evaluates the current design procedures by Caltrans, and also proposes an improved soil spring model for predicting the stiffness and capacity of bridge abutments in longitudinal direction for cases where post-peak softening behavior is important in system modeling efforts.
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