Mid-America Transportation Center


Date of this Version


Document Type



Report # MATC-KSU: 110 Final Report


A Cooperative Research Project sponsored by the U.S. Department of Transportation Research and Innovative Technology Administration

A Report on Research Sponsored By Mid-America Transportation Center University of Nebraska-Lincoln


When evaluating the condition of existing bridges determining in situ stresses in the members provides valuable information about the condition of the structures. In this study, a method of surface strain relief was investigated whereby the change in strain at the surface of concrete members is used to determine the in situ stress. The method involved mounting a linear electrical-resistance strain gage along the axis of maximum stress, coring around the gage, and then relating the change in strain to the corresponding stress in the member. Members were fabricated and varying stresses were applied in order to determine the accuracy of the method. Results were then compared to the global stresses and to the theoretical local stresses predicted by two different finite element models. In order to improve the accuracy of the surface-strain relief method, a procedure was introduced whereby the core was fractured along its base and subsequently removed from the member. This served to eliminate possible shear stresses between the core and surrounding member, allowing for the full release of strains.

PowerPoint presentation attached below as Related File.

Link to webinar video: http://vimeo.com/38526445