EXPERIMENTAL STUDY AND FINITE ELEMENT ANALYSIS ON FLEXURAL PERFORMANCE OF HIGH-STRENGTH STEEL REINFORCED ULTRA-HIGH PERFORMANCE CONCRETE BEAM

In order to study the flexural performance of high-strength steel reinforced ultra-high performance concrete (UHPC) beams, six specimens were designed and tested under static loads, with the variation parameters being the steel ratio, position of steel and volume fraction of steel fiber. The failure patterns and curves between load and mid-span deflection of specimens were obtained. The bearing capacity, deformation capacity and strain variation laws of steel, longitudinal reinforcements and UHPC were analyzed. Based on experimental study, the finite element analysis model of flexural performance of high-strength steel reinforced UHPC beams was established, and the calculated results were in consistence with experimental results. Then parametric analysis was carried out. The results showed that the appropriate reinforcement failure occurred for all specimens, and longitudinal tensile reinforcements and bottom flange of steel yielded first and then UHPC of compression zone was crushed. At the failure stage, the load experienced four stages, including sudden drop, fluctuation, slow rise and slow decline. The deformation capacity coefficients of specimens were larger than 5, showing strong deformation capacity. The strain of UHPC conformed to plane section assumption before cracking of specimen; but only the strain of UHPC at the compression zone and a small part of the tensile zone near the neutral axis distributed linearly after cracking. Higher steel ratio and steel strength lead to larger bearing capacity and deformation capacity of specimens. When the compression strength of UHPC increased and the position of steel moved down, the bearing capacity of specimens increased but the deformation capacity decreased. When the volume fraction of steel fiber increased, the crack resistance and deformation capacity increased, but the bearing capacity changed insignificantly.