Shear capacity of rectangular RC beams with continuous spiral shear reinforcement

The use of continuous spiral shear reinforcement in Reinforced Concrete (RC) elements can substantially increase the load bearing capacity and the ductility of structural elements. Also it is generally accepted that total seismic response of structural elements will be improved by the use of spiral reinforcement. Up to now spiral reinforcement is mostly used in concrete columns with circular cross section. Advantages by using continuous spiral shear reinforcement in rectangular reinforced concrete beams under shear loading are also expected. In this study the behavior of continuous spiral transversal reinforcement as shear reinforcement in rectangular RC beams instead of conventional independent stirrups is experimentally investigated. The test program consists of three point shear tests with static loading. The load was applied with a shear span ratio a/d of 3.0. All specimen of the test program had the same volume of shear reinforcement. In the tests three different shapes of spiral shear reinforcement were used. The specimen were loaded up to failure and compared to the performance of a reference beam with common stirrups. To get detailed information about failure behavior and crack development an optical 3-D measurement system was used. In all tests could be seen that the use of continuous spirals leads to an increase of shear capacity and ductility in comparison to beams with stirrups.