Similarly, in Tehrani and Mitchell , the seismic performance of 15 continuous four- span bridges with different arrangements of column heights and diameters was studied using incremental dynamic analysis IDA.
The IDA procedure has been adopted by some guidelines to determine the seismic performance, collapse capacity, and fragility of buildings. Similar concepts can be used for the seismic assessment of bridges.
Fragility curves can be devel- oped using the IDA results to predict the conditional probability that a certain damage state is exceeded at a given intensity measure value. Assuming that the IDA data are lognormally distributed, it is possible to develop the fragility curves at collapse or any other damage state by computing only the median collapse capacity and the logarithmic standard deviation of the IDA results for any given damage state.
A simple BN. Literature Review and Synthesis 27 The seismic risk associated with exceeding different damage states in the columns, includ- ing yielding, cover spalling, bar buckling, and structural collapse i. Some simplified equations were derived for Montreal, Quebec, Canada, to estimate the mean annual probability of exceeding different damage states in the columns using the IDA results. Zimmerman et al.
The study focused on the analysis method of nonlinear trusses and the retrofit option known as supplemental gravity columns, which is an example of how loss prediction and the analysis process are linked and should be iterated through PBSD. For both standard and nonstandard bridges, Caltrans is also categorizing their inventory in terms of Ordinary Bridges, Recovery Bridges, and Important Bridges.
Some states have had issues with terms like Important or Essential, as a bridge is considered important to those that utilize each bridge. Caltrans SDC revisions will also provide updates to the design parameters in Chapter 3 of the SDC and updates to both the analysis methods and displacement ductility demand values in Chapter 4 of the SDC.
The adjustments to the displacement ductility demand values are revised to limit the bridge displacements beyond the initial yielding point of the ERE, specifically if a recovery standard bridge is being designed. A synopsis of the revisions is provided in Kuwabara et al. The revisions are based on improvements in terms of safety,. Based on those lessons, design earthquake ground motions corresponding to the subduction-type earthquake were revised, and the requirements for easy and secure maintenance inspection and repair works for the bridges were clearly specified.
The JRA revisions also address connection failures between reinforced concrete steel piles and the pile-supported spread footing to improve structural detailing and performance at the head of the piles. This is similar to research performed by the University of Washington, see Stephens et al.
Caltrans also funded a study by Saini and Saiidi to address probabilistic seismic design of bridge columns using a probabilistic damage control approach and reliability analysis. Source: Caltrans.
Caltrans draft proposed seismic design bridge performance criteria. Limit state of bridge is serviceability limit state. Negligible structural damage and nonstructural damage are allowed.
Table 7. Seismic performance of bridge and limit states of conventionally reinforced concrete bridge column. Literature Review and Synthesis 29 The probabilistic damage control approach uses the extent of lateral displacement nonlinearity defined by Damage Index DI to measure the performance of bridge columns. DI is a measure of damage from the lower measure of zero damage to the ultimate measure of a collapse mecha- nism for an element that has been subjected to base excitations.
A statistical analysis of the demand damage index DIL was performed to develop fragility curves load model and to determine the reliability index for each DS. The results of the reliability analyses were analyzed, and a direct probabilistic damage control approach was developed to calibrate design DI to obtain a desired reliability index against failure.
The calculated reliability indices and fragility curves showed that the proposed method could be effectively used in seismic design of new bridges, as well as in seismic assessment of existing bridges. Figure 14 shows a fragility curve using lognormal distribution. Figure 15 shows both the fragility curves upper two graphs and reliability indices lower two graphs for four column bents FCBs , with 4-foot diameter columns that are 30 feet in length in Site D for both the year and year seismic events.
Design performance levels. Correlation between DS and DI. Fragility curve. The Oregon DOT The Oregon DOT is developing a global plan for addressing resiliency in order to improve recovery for the next Cascadia Earthquake and Tsunami, using PBSD in terms of applying applicable hazards, identifying critical services, developing a comprehensive assessment of structures and systems, and updating public policies.
The resilience goals are similar to those discussed at the beginning of this chapter, with the following statement: Oregon citizens will not only be protected from life-threatening physical harm, but because of risk reduction measures and pre-disaster planning, communities will recover more quickly and with less continuing vulnerability following a Cascadia subduction zone earthquake and tsunami. Literature Review and Synthesis 31 Research has shown that the next great magnitude 9.
This comparison of historical subduction zone earthquakes in northern California, Oregon, and Washington covers years of seismic history. The evidence of a pending event has made decision makers and the public take notice and put forth resources to develop strategies revolving around PBSD.
Design of new bridges on and west of US 97 references two levels of perfor- mance criteria: life safety and operational. Design of new bridges east of US 97 requires life safety criteria only. Seismic design criteria for life safety and operational criteria are described as follows. The CSZE is a deterministic event, and a deterministic design response spectrum must be generated. To allow for consistency and efficiency in design for the CSZE, an application for generating the design response spectra has been developed by Portland State University Nako et al.
Table 3. For seismic retrofit projects, the lower level ground motion is modified to be the CSZE with full rupture, as seen in Table 9. Performance levels, including performance level zero PL0 , are specified based on bridge importance and the anticipated service life ASL category required.
Cascadia earthquake timeline. Chapters 12, 13, and 14 for geo technical seismic analysis, hazard, and design, respectively, have been updated to current practices and research, including incorporation of PBSD hazard prediction. Note that with the revisions, South Carolina DOT issued a design memorandum in November that revised the substructure unit quantitative damage criteria maximum ductility demand table Table 7. See Table There is an emphasis on differences between deterministic and performance-based procedures for assessing liquefaction hazards and how the output can vary significantly with these two methodologies, especially in areas of low seismicity.
Guidance is provided regarding when to use each of the two methodologies and how to bind the analysis effort. Additionally, a simplified performance-based procedure for assessment of liquefaction triggering using liquefaction loading maps was developed with this research. The components of this tool, as well as step-by-step procedures for the liquefaction initiation and lateral spread displacement models, are provided. The tool incorporates the simplified performance-based procedures determined with this research.
National Highway Institute Marsh et al. Other similar courses are also being offered to industry and are improving the understanding of practicing engineers. Modifications to minimum performance levels for retrofitted bridges. A step-by-step methodology and explanation of implementation are provided for an intensity-based assessment and for a time-based assess- ment.
The process of identifying and developing appropriate fragility curves is demonstrated. Japan Road Association The Japan Road Association JRA Design Specifications have been revised based on the performance-based design code concept in response to the international harmonization of design codes and the flexible employment of new structures and new construction methods. The performance matrix is based on a two-level ground motion Earthquakes 1 and 2 , with the first one based on an interpolate-type earthquake and magnitude of around 8, and the second one with a magnitude of around 7 with a short distance to the structure.
Kuwabara et al. These revisions include, but are not limited to, the ductility design method of reinforced concrete bridges, plastic hinge length equation, evaluation of hollow columns, and the introduction of high-strength steel reinforcement. South Carolina DOT substructure unit quantitative damage criteria maximum ductility demand ld. There is still a perception that the bridge industry could better predict likely performance in large, damaging earthquakes than is being done at the present, and there are still gaps in that knowledge base that need to be closed.
Most of the knowledge gaps listed in Marsh and Stringer are still applicable today; see Table The technology readiness levels represent what has been developed and used; what research is done, ongoing, and being discussed; and what only exists in concept. Code structure for seismic design using JRA design specifications. Technology readiness levels for PBSD. Literature Review and Synthesis 35 Gaps related to structural analysis can include minimum and expected properties for reinforcing greater than Grade 80, stainless steel, and other materials that can improve serviceability and in some conditions performance.
Oregon DOT has been using stainless steel in their bridges located along the coastline and other highly corrosive environments to extend the service life of the bridge; however, many of these locations are also prone to large CSZE and the use of these materials in earthquake resisting elements is still being developed.
This is a knowledge gap given what we know structurally and what this report is suggesting as a desired goal for post-earthquake recovery. Gaps related to decision makers can include bridge collapse. It is not intended that the PBSD guide specifications will address tsunami events, but the JRA specifications do address tsunami as well as landslide effects. Figures 18 and 19 are examples of these other types of failure systems and show the collapse of bridges caused by effects other than ground motion Kuwabara et al.
The decision to combine these types of effects with a seismic hazard, even combining liquefaction, down drag, and lateral spreading effects, needs additional clarification and is currently left up to the owner to assess implications of probability, safety, and cost ramifications. Liang and Lee summarized that in order to update the extreme event design limit states in the AASHTO , combinations of all nonextreme and extreme loads need to be formulated on the same probability-based platform.
Accounting for more than one-time variable load creates a complex situation, in which all of the possible load combinations, even many that are not needed for the purpose of bridge design, have to be determined. A formulation of a criterion to determine if a specific term is necessary to be included or rejected is described, and a comparison of the value of a given failure probability to the total pre-set permissible design failure probability can be chosen as this criterion.
Collapse of bridge due to landslide. Department of Commerce. Not copyrightable in the United States. Source: Kuwabara et al. This issue is not specific to PBSD; like all seismic design methods, PBSD is reliant on a full understanding of the hazard definition for proper implementation. Many of these knowledge gaps will become evident to both engineers and decision makers as the PBSD guidelines are developed.
Overall, the baseline information to develop PBSD guide specifica- tions are in place. Collapse of bridge due to tsunami. Performance-based seismic design PBSD for infrastructure in the United States is a developing field, with new research, design, and repair technologies; definitions; and methodologies being advanced every year.
The methodology is presented as proposed AASHTO guidelines for performance-based seismic bridge design with ground motion maps and detailed design examples illustrating the application of the proposed guidelines and maps. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.
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Get This Book. Unfortunately, this book can't be printed from the OpenBook. If you need to print pages from this book, we recommend downloading it as a PDF. Visit NAP. Looking for other ways to read this? Signs, Luminaires, and Traffic. Published by AASHTO on January 1, These methods of test are intended for determining the relation between the moisture content and density of soils compacted in a mold of a given size with a 2.
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Conference Registration Regency Foyer a. SCOPE 1. Provide PDF Format. Page 1 of This is why we give the books compilations in this website. The design truck is identical to HS Design Example for a Two-Span Bridge. This comprises mm thick RC deck slab, 50 mm wearing course and cast in situ railing is considered. Existing Specifications. Example 10 was designed with a geotechnical investigation performed on the soil. The substructure consists of three-column piers and abutment bents supported directly by drilled shafts.
All analyses undertaken dealt only with the external stability of the wall, i. The maximum moment from each analysis is then combined using Tables 3. The minimum foundation element length shall be 10 ft.
Both shallow e. A lagging material is placed between the soldier piles to complete the shoring system. Please scroll down to see the full erratum. The pile cap has normal-weight concrete with a compressive strength of psi and Grade 60 reinforcement.
Column size: 18"x18" concrete column. However, with approval, falsework pads may be used when underground utilities preclude the use of driven piling. The above referenced IDOT document is particularly useful for designers. Center for Transportation Research Collaborate. This example served as a benchmark.
Design lane load. Anderson1, G. What is an eBook? Why is an eBook better than a PDF? Where do I get eBook files? Overview Contents Rights Stats. There are approximately 1, movable highway bridges in the U. National Academies of Sciences, Engineering, and Medicine. You may request permission to: Republish or display in another publication, presentation, or other media Use in print or electronic course materials and dissertations Share electronically via secure intranet or extranet And more For most Academic and Educational uses no royalties will be charged although you are required to obtain a license and comply with the license terms and conditions.
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