The significant increase in legal load limits allowed on the Nation and 039;s highways is raising concerns on the load-carrying capacity of the aged reinforced concrete bridges (i.e., arch, slab and T-beam bridges). Many State Highway Agencies are being forced to post load limits on such bridges, a decision for the most part based on information obtained through visual inspection and/or from traditional rating manuals. There have been many instances where data from controlled field-testing has shown the bridges exhibiting strengths and stiffness characteristics beyond traditional codified parameters and beyond calculated standard load-rating manuals. The use of such load testing is being accepted by public agencies increasingly for determining load rating of deficient bridges. This can be credited to advancements in analytical tools, sensing technologies and commercial equipments, which have simplified the process of testing, modeling, and rating bridges.

The main objectives of this study are as follows; 1. Evaluate current/emerging technology for reliable, expedient and feasible controlled load testing of highway bridges, 2. Develop a methodology that can be employed by the State Highway Agencies to assess the actual behavior and predict the long-term repeated overload capacity of aged reinforced concrete bridges (i.e., arch, slab and T-beam bridges) by controlled load testing in conjunction with advanced analytical techniques, 3. Establish standard procedures for load testing and load rating on the basis of load test results, 4. Demonstrate the application of these procedures by conducting load tests on 2 bridges of concern, 5. Assist in training/educating State Highway engineers in both the basic theory and application of procedures so that they can conduct tests and evaluate test results.

The scope consists of both analytical and controlled diagnostic field tests on 2 bridges of concern to determine their load carrying capacity. It is envisioned that this work will consist of, at the minimum, following tasks: Task 1 - Selection of 2 Concrete Bridge(s) of Concern Select bridges for study based on location, condition, age, and current NBI rating factor of `structurally deficient and no.039;. In addition to evaluating maximum load capacity rating and long-term load capacity rating for repeated overloads, these bridges will serve to demonstrate the experimental and analytical tools that may be used for testing and rating other types of bridges, Task 2 - Literature Review Conduct a literature search on all current and emerging technology focusing on proven commercially available (off-the-shelf) sensors, data acquisition and communication hardware. Task 3 - Initial Inspection Conduct detailed field evaluations of selected bridges. This shall include documenting the condition of the bridges, measuring geometry, obtaining material sampling, evaluating the reinforcement detailing at critical areas by NDE techniques, etc. It is also recommended to conduct an impact modal testing, by using a drop-hammer and limited number of accelerometer, to determine dynamic characteristics of the bridges. Such inspection is necessary as engineering plans and drawings are not normally available for aged bridges. Task 4 - Analytical Study Utilizing commercially available software, analyze the behavior of the bridges through finite element analysis. The models shall be calibrated based on the current bridge conditions observed at the sites, material test results and the observed dynamic characteristics. Task 5 - Development of Instrumentation System Utilizing analytical results, design instrumentation systems to capture relevant data during load testing of the reinforced concrete bridges. Evaluate the feasibility of low cost wireless monitoring and data acquisition systems (DAQ) identified in Task 2. The system shall be designed to interrogate major stresses and strains, rotations and deflections felt by the structures during load testing. Task 6 - Controlled Field Load Testing Conduct controlled load tests of the selected bridges under proof-load levels. Bridge owners shall provide traffic control and safe access to the underside of the bridges for installing sensors. They shall also provide loading vehicles for conducting the tests. Task 7 - Data Analysis The load-test results shall be processed and evaluated. The findings shall serve for updating the calibrated FE models to incorporate bridge behavior under proof-load level. Analyses shall be carried out to reach a final evaluation of the long-term load carrying capacity of each bridge under repeated overloads. Task 8 - Draft Report and Executive Summary Prepare a draft report and a draft executive summary on the findings of this study for review and comment. The report shall include the current and emerging technologies for load testing and evaluation and a methodology for load testing and rating reinforced concrete bridges including ideal instrumentation plan for these bridges. Task 9 - Final Report and Executive Summary Prepare a final report and a final executive summary incorporating all comments from reviewers.