Development of a New Test Facility to Examine Reinforced Concrete Panels Under Uniaxial and Biaxial Direct Tension

摘要

There is a definite and growing interest in using fiber reinforced polymers (FRP) reinforcing bars as an alternative for traditional steel in several structural applications. Nevertheless, little information is available about the behavior of FRP reinforced concrete (RC) members subjected to direct tension. Testing concrete members subjected to direct tension is considered an important approach in understanding important features of concrete, such as cracking characteristics, stress-strain relationships, etc. These features have been considered an important design aspect of FRP-RC. This paper presents a new experimental technique that can be used to test both FRP- and steel-RC panels under uniaxial and biaxial direct tension. A new testing facility is designed and constructed at Memorial University of Newfoundland. The testing facility is specially designed to test RC panels subjected to direct tension. The tension loads can be applied in either a uniaxial or biaxial direction. The unique aspect of this test setup is that it can accommodate FRP reinforcing bars. FRP reinforcing bars have a major problem of gripping under a tension load. Several research workers have developed elaborate and expensive techniques to provide adequate grip for FRP bars by using steel pipes and epoxy injection. The proposed design provides a simple solution to the gripping problem and can accommodate different specimen sizes, bar diameters, various bar spacing, and loading conditions. This paper presents the design, details, construction stages, and testing capabilities of this new testing facility. Descriptions of the experimental equipment, the instrumentation, and the data acquisition system are provided. The paper also presents a sample of the test results of a recent experimental investigation that has been carried out on concrete panels reinforced with steel and glass-FRP (GFRP) bars. Test results demonstrate that the testing facility is successfully capable in overcoming the difficulties of testing RC panels under direct tension. The test results also show significant differences in behavior between steel and GFRP-RC panels with respect to cracking characteristics, stress-strain relations, and failure loads.