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原文传递 FIELD TESTING AND LOAD RATING PROCEDURES FOR STEEL GIRDER BRIDGES

题名：	FIELD TESTING AND LOAD RATING PROCEDURES FOR STEEL GIRDER BRIDGES
作者：	Michael G. Barker. Cory M. Imhoff, W. Travis McDaniel, and Troy L. Frederick
关键词：	Load Rating , Field testing, Bridge Evaluation, Posting
摘要：	Many of the nation’s bridges are posted for restricted truck loading. Analytical capacity rating procedures tend to underestimate the true stiffness and overestimate the response of bridges. Research has shown that in most cases, bridges exhibit capacities higher than analytical load capacity rating predictions. These rating procedures are based on conservative design assumptions that do not always represent the true bridge behavior. Testing bridges in the field has demonstrated this additional capacity and bridge field testing has become an acceptable means to determine a more accurate estimate of a bridge’s safe capacity. Many factors not considered in the design process contribute to the response of a tested bridge. Several of these, like the actual load distribution and additional system stiffness from curbs and railings, are welcome benefits and can be used to increase weight limits on bridges. However, there are also contributions from bearing restraint forces and unintended composite action that may not be reliable during the service life of the structure. Determining how much of the increase in capacity is acceptable is difficult. This report presents systematic field test rating procedures that separate and quantify these contributing factors so that owners may remove unwanted contributors and retain the reliable benefits. An efficient test plan is applied to a three span steel girder bridge to demonstrate the procedures. The bridge is currently posted for restricted lanes and loads using allowable stress rating procedures. Field test results show that the posted capacity can safely be raised near (opening the bridge to two lanes of traffic) or above (maintaining a single lane) legal AASHTO H20 truck loads. Even though field testing has become an acceptable means to determine a more accurate estimate of a bridge’s safe capacity, field testing can be a time consuming and expensive endeavor. This report presents an efficient modular field testing system and the application of the system to a steel girder bridge. The “plug-and-play” data acquisition vehicle and supporting equipment has great potential for economical field testing.
报告类型：	科技报告