Seismic Analysis of Retaining Walls, Buried Structures, Embankments, and Integral Abutments
Author: McLean, David I | Size: 2.11 MB | Format:PDF | Quality:Unspecified | Publisher: Washington State Transportation Center | Year: 2005 | pages: 82
Experimental tests were conducted on seven 1/3-scale specimens to define the vulnerabilities of existing outrigger bents under in-plane and out-of-plane seismic loading and to develop appropriate retrofit measures that address the identified vulnerabilities. The specimens represented bents with short and long outrigger beams in the SR-99 Spokane Street Overcrossing in western Washington State. The as-built specimens failed at low ductility levels due to shear distress, low torsional strength of the beam, and reinforcement bond failures within the joint. Circular and D-shaped steel jackets were used to retrofit the regular and split as-built specimens, respectively. The retrofitted specimens developed plastic hinging in the column, with enhanced strength, energy and ductility capacities. Threshold principal tension stress values describing the expected condition of the joints were established and compared to values obtained by other researchers. Design and detailing guidelines for retrofitting outrigger bents were proposed. The guidelines include equations for the jacket thickness required to form a stable force transfer mechanism between the beam and the column reinforcement as well as to prevent joint failure.
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This study evaluates the impact of the newly recommended seismic design guidelines from NCHRP 12-49 on seismic design of bridges in New Jersey. It also provides seismic design criteria and guidelines for integral abutments, retaining walls, embankments, and buried structures. The study provides an overall review of the recommended guidelines and compares them to the current AASHTO LRFD specifications. It provides recommendations on seismic hazard and performance objectives and soil site factors for New Jersey that incorporate design criteria from NCHRP 12-49 guidelines, AASHTO LRFD specifications, South Carolina seismic design criteria, and NYCDOT seismic design guidelines. The study also includes two design examples based on the NCHRP 12-49 guidelines and current AASHTO LRFD specifications. Research results showed that: (1) the MCE ground motion level adopted by NCHRP 12-49 which has a 2500-year return is acceptable for safety evaluation of 'critical bridges' in New Jersey, (2) a reduced (2/3 MCE) ground motion is acceptable for safety evaluation of 'non-critical' bridges; (3) soil-site factors have increased dramatically for soft soils subjected to small ground motions which will have an impact on seismic design in Southern Jersey, (4) the USGS National Seismic Hazard Maps adopted by NCHRP 12-49 for ground motion accelerations may not necessarily reflect the actual geological soil conditions and realistic hazard levels in New Jersey, (5) NCHRP 12-49 SDAP E (pushover analysis) is preferable for the seismic analysis and design of bridges in New Jersey, and (6) NCHRP 12-49 SDAP C is a relatively simplified design procedure for many bridges and should be used when applicable. Recommendations from this study include adoption of NCHRP 12-49 subject to the above conclusions. However, there is a need to: (1) predict extreme earthquake events for New Jersey and the Northeast United States, (2) prepare Seismic Hazard Maps for bridge design in New Jersey and re-evaluate NCHRP 12-49 soil-site factors proposed for New Jersey, and (3) quantify damage level by using structural capacity and demand.
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Condition Indexing and Hazards Analysis for Communications Towers
Author: Likos, William J Salim, Hani | Size: 5.23 MB | Format:PDF | Quality:Unspecified | Publisher: University of Missouri, Columbia | Year: 2005 | pages: 118
Design and construction of the Missouri Department of Transportation (MoDOT) two-way radio network was initiated in the 1950’s and 60’s and was motivated primarily by the need to provide a statewide communication system for civil defense related issues. Today, the system is one of the largest networks in the state for providing voice and data communications associated with daily field operations as well as during times of emergency. Increasing reliance on the network is envisioned in the future to support wireless interoperability (e.g., with police and fire) and to support an increasing load of data communications for intelligent transportations system (ITS) infrastructure. Growing concern regarding the network’s performance during natural hazard events, most notably the possibility for significant earthquakes originating from the New Madrid Seismological Zone, has stimulated the desire for a comprehensive analysis of the network and the development of systematic asset management tools. A recent statewide emergency preparedness exercise involving a mock 6.7 magnitude earthquake revealed that the chief obstacle encountered as field crews attempted to communicate with each other was failure of the radio towers. Many of the towers are over 40 years old and in relatively poor physical condition. The primary objectives of this project were (1) to develop a rational condition indexing (CI) system as an asset management tool that may be used to systematically quantify the physical condition of towers in the network; (2) to conduct detailed dynamic and static structural analyses of key towers under seismic, wind and ice loading; (3) to evaluate the general effects of physical deterioration (e.g., corrosion related to aging) on tower dynamic response and stability; and (4) to develop a centralized electronic database. A CI system has been developed to quantify the physical condition of guyed communications towers. Use of the proposed system is demonstrated for two towers (Taum Sauk and Ashland) selected to represent towers in relatively poor and relatively good condition, respectively. Results from structural analysis indicate that the Taum Sauk tower (as built condition) is not loaded to near its capacity under simulated seismic loading. The Taum Sauk tower is shown to pass TIA-222-F code specifications with respect to wind and ice loading. Deterioration to the Taum Sauk tower was simulated by reducing the cross sectional areas of the guy cables, diagonal braces, and axial leg members. A free standing tower in Kansas City was also analyzed and is shown to be loaded to 2% over capacity according to TIA-222-C but meets the more recent 222-F code requirements. An electronic web-based database was developed for implementation into management of the tower network. General recommendations for implementing the results of these efforts are provided, which includes a recommendation to consider the proposed CI approach for a wide range of infrastructure managed by MoDOT.
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Development of Nondestructive Methods for Measurement of Slab Thickness and Modulus of Rupture in Concrete Pavements
Author: Popovics, John S University of Illinois, Urbana-Champaign Gibson, Alex Gallo, Gonzalo | Size: 1.09 MB | Format:PDF | Quality:Unspecified | Publisher: Virginia Transportation Research Council | Year: 2005 | pages: 72
This report describes work to develop non-destructive testing methods for concrete pavements. Two methods, for pavement thickness and in-place strength estimation, respectively, were developed and evaluated. The thickness estimation method is based on a new hybrid approach that combines frequency domain (impact-echo) and time domain (seismic) data. This new method makes use of a fuller understanding of the dynamic wave phenomenon, which was developed during the course of the work. The effects of material property gradients (due to aggregate segregation and moisture variation) through the slab thickness are compensated for in the method. A field testing method is proposed, described, and experimentally verified. Verification tests carried out on full-scale concrete slabs cast on granular base show that the new method provides more accurate thickness estimates than those obtained by the standard impact-echo procedure. On average, the error between predicted thickness and actual thickness determined by cores is less than 6 mm, although some individual estimates exceed this error value. However, the new method does not work on concrete over asphalt or cement-treated base (which accounts for most concrete pavements) or on full-depth asphalt concrete pavements. The in-place strength estimation method is based on ultrasonic surface wave measurements. A field test method is proposed, described, and experimentally verified. Verification tests carried out on a range of concrete mixtures with varying aggregate type and cementitious material, all of which satisfy the requirements of “A3” concrete as specified by the Virginia Department of Transportation. Two data analysis procedures are proposed. One procedure predicts flexural strength within 50 psi of actual strength determined by direct strength measurement of beams, although the procedure requires 1-day strength and ultrasonic values to be known. The second procedure is more flexible but provides strength estimates with lower accuracy. Field tests, which were carried out at two pavement sites in Virginia, are reported for both methods. Finally, a detailed description of the required testing equipment and experimental and analytical procedures for both methods are included in the Appendix. Cost savings from implementing the methods are not obvious, since the methods cannot be used to measure the thickness of most concrete pavements for acceptance and payment. The methods can be used to nondestructively evaluate the modulus of rupture of pavements for analysis purposes, but savings would depend on the nature of the analysis.
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Design of Precast Concrete Piers for Rapid Bridge Construction in Seismic Regions
Author: Wacker, Jonathan M Hieber, David G Stanton, John F Eberhard, Marc O | Size: 4.41 MB | Format:PDF | Quality:Unspecified | Publisher: Washington State Transportation Center | Year: 2005 | pages: 256
Incorporating precast concrete components in bridge piers has the potential to accelerate bridge construction and reduce the negative impacts that construction operations have on traffic flow. As part of this project, methodologies were developed to design economical and safe bridge piers out of precast concrete components. This research developed force-based and displacement-based procedures for the design of both cast-in-place emulation and hybrid precast concrete piers. The design procedures were developed so that they require no nonlinear analysis making them practical for use in a design office. The expected level of damage to piers designed using the proposed procedures was estimated. The evaluation considered three types of damage to the columns of a pier: cover concrete spalling, longitudinal reinforcing bar buckling, and fracture of the longitudinal reinforcing bars. Both the force-based and displacement-based design procedures were found to produce bridge designs expected to experience an acceptable amount of damage in a design-level earthquake.
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Precast Concrete Pier Systems for Rapid Construction of Bridges in Seismic Regions
Author: Hieber, David G Wacker, Jonathan M Eberhard, Marc O Stanton, John F | Size: 4.36 MB | Format:PDF | Quality:Unspecified | Publisher: Washington State Transportation Center | Year: 2005 | pages: 308
Increasing traffic volumes and a deteriorating transportation infrastructure have stimulated the development of new systems and methods to accelerate the construction of highway bridges. Precast concrete bridge components offer a potential alternative to conventional reinforced, cast-in-place concrete components. The use of precast components has the potential to minimize traffic disruptions, improve work zone safety, reduce environmental impacts, improve constructability, increase quality, and lower life-cycle costs. This study compared two precast concrete bridge pier systems for rapid construction of bridges in seismic regions. One was a reinforced concrete system, in which mild steel deformed bars connect the precast concrete components. The other was a hybrid system, which uses a combination of unbonded post-tensioning and mild steel deformed bars to make the connections. A parametric study was conducted using nonlinear finite element models to investigate the global response and likelihood of damage for various configurations of the two systems subjected to a design level earthquake. A practical method was developed to estimate the maximum seismic displacement of a frame from the cracked section properties of the columns and the base-shear strength ratio. The results of the parametric study suggest that the systems have the potential for good seismic performance. Further analytical and experimental research is needed to investigate the constructability and seismic performance of the connection details.
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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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