Nondestructive load testing of bridges has been used primarily as a research tool to provide better understanding of the way in which loads are carried by, and distributed through, the bridge structure. In some cases, load testing has been used to assist in the determination of bridge load-carrying capacity. From such tests, some structures have been found to possess greater load-carrying capacity than predicted by conventional analytical load-rating procedures. Load-rating procedures that incorporate load test results have potential for demonstrating higher load capacity for many structures that would otherwise be determined to require load-posting based on conventional analysis alone.
NCHRP Project 12-28(13), Nondestructive Load Testing for Bridge Evaluation and Rating, was initiated in 1987 with the objective of developing guidelines for nondestructive load testing of highway bridges in order to augment the analytical rating process. The project included a comprehensive review of literature related to bridge load testing and resulted in a report summarizing the present status of load-test technology. In addition, the project produced a draft procedure for performing some of the more common nondestructive load tests. However, the project report does not completely cover all steps necessary for developing a load-rating procedure. Specifically, procedures are required for post-test data review and calculations, and for incorporation of the load-test results into the bridge rating process.
In order to allow bridge owners to take advantage of load testing in bridge load rating, a procedure for integrating test results into strength evaluations must be developed in detail. A step-by-step methodology is needed to conduct the load test and translate the test results into a rational bridge load-rating. After this has been done, bridge owners and bridge engineers can be introduced to the advantages of load testing and educated in the methods of bridge evaluation and rating through load testing.
Research was needed to broaden the draft load-test procedures developed in NCHRP Project 12-28(13), to develop a detailed methodology for bridge evaluation and rating based on the results of load testing, and to prepare materials for a training program for bridge owners and bridge engineers that demonstrates the bridge evaluation and rating process through load testing.
The objective of this project was to develop a manual of recommended procedures for performing bridge load tests and for incorporating load test results into the bridge rating process. Based on the manual, course curriculum and all necessary training materials for a 2-day workshop were developed to demonstrate and explain bridge load-rating by means of bridge load testing.
The project is complete. A manual for bridge rating through nondestructive load testing, a technical report, a student workshop notebook, and an instructor's notebook have been submitted. Additionally, a video and pamphlet on the concept of nondestructive load testing of bridges were received. The workshop materials have been turned over to the Federal Highway Administration for a training course which may be offered through the National Highway Institute. The manual and the technical report have been published as Research Results Digest Number 234.