New Bridge Synthesis Reports
REDARS Validation Report
By S. Cho, C.K. Huyck, S. Ghosh and
August 8, 2006, 150 pages, $30.00
This report presents the results of an extensive review and evaluation of the Seismic Risk Assessment (SRA) methodology for highway systems, as documented in “A Risk-Based Methodology for Assessing the Seismic Performance of Highway Systems,” by Werner et al., MCEER-00-0014.
The efficacy of all key modules in the REDARS (Risk of Earthquake Damage for Roadway Systems) software program was evaluated. The modules included: bridge damage or fragility module, post-earthquake traffic state module, transportation module and economic loss module. The results from this review were evaluated by the REDARS development team and subsequently used to update the REDARS software program.
The REDARS methodology and software for seismic risk analysis of highway systems is presented in a companion MCEER special report, “REDARS 2 Methodology and Software for Seismic Risk Analysis of Highway Systems,” by Werner et al., MCEER-06-SP08.
Review of Current NDE Technologies for Post-Earthquake Assessment of Retrofitted Bridge Columns
By J. Song, Z. Liang, and G.C. Lee, MCEER-06-0008, August 21, 2006, 108 pages, $25.00
This report presents an evaluation of various nondestructive testing/evaluation (NDE) technologies for use on bridge columns that have been retrofitted with FRP-type jackets. Suitable and/or potentially suitable techniques for practical applications are identified, and promising techniques that could benefit from additional research are assessed. For each technology, the inherent physical principles and application characteristics are analyzed to determine whether they could be used to detect damage and defects in the jacketed bridge columns. The most promising NDE methods (impact echo and electromagnetic method) are identified and corresponding application procedures are presented. This report focuses solely on the application of NDE technologies to bridge columns, and therefore, the recommendations and conclusions may differ from those discovered for other applications. Furthermore, this is a rapidly advancing field, so some applications and conclusions may change in the coming years.
Liquefaction Remediation in Silty Soils Using Dynamic Compaction and Stone Columns
By S. Thevanayagam, G.R. Martin, R. Nashed, T. Shenthan, T. Kanagalingam and N. Ecemis, MCEER-06-0009, August 28, 2000, 114 pages, $25.00
This report introduces a rational analysis procedure and design guidelines for liquefaction hazards mitigation in saturated sands and non-plastic silty sands using Dynamic Compaction (DC) and Vibro-Stone Columns (SC). A numerical model was developed to simulate the densification processes by quantifying pore pressure generation due to vibrations caused by successive impacts on the ground or repeated insertions of a vibratory probe. Site-specific conditions such as hydraulic conductivity, fines content, etc. were quantified for a range of energy contents delivered to the soil at specific spacing. The effects of field operational parameters such as energy per impact, number of impacts, time cycle between impacts, impact grid spacing, impact grid pattern, and wick drain spacing, in the case of DC, or area replacement ratio and wick drains spacing in the case of SC, on post-improvement resistance to liquefaction were included. Based on the results, design charts, guidelines, procedures and examples are provided.