Pounding response of concrete rods with rough impacting surfaces

This paper presents theoretical research that is supported by experimental data, aiming at investigating and explaining unexpected experimental results that were obtained on low velocity pounding response of adjacent concrete rods. The experimental results indicate inelastic response expressed by the post-impact relative velocity and coefficient of restitution that is smaller than one, although elastic response is expected. This research conjectures that the inspected response is due to the roughness of the impacting surfaces. A theoretical analytical and a following numerical investigation examined the behavior of the surface roughness represented by small size asperities in an idealized model. Analysis of the asperity behavior clarified its inelastic behavior that affects major parameters on the response. An integrated parameter has been identified, which includes major parameters of the asperity affecting the dynamic behavior and helping to relate the geometrical parameters of an asperity with the measured pounding data. It was found that asperities may explain the energy absorption during low velocity pounding. This explains the lower coefficient of restitution than expected even at low velocity pounding. An effective and simple analytical approach is developed to simulate the rods collision with an idealized surface asperity and demonstrates the role of the asperities on a realistic simulation of the experimental result.