EXPERIMENTAL STUDY ON LONGITUDINAL NEGATIVE BENDING PERFORMANCE OF FLAT STEEL PLATE-UHPC COMPOSITE BRIDGE DECK

The main girder of the secondary span and middle span of a bridge is steel-UHPC composite beam, and the bridge deck of which adopts a new type of composite bridge deck system for the first time with 8 mm flat steel plate being connected with 15 cm UHPC layer by PBL shear key. In order to explore the performance and safety of negative bending moment resistance of the new steel-UHPC composite bridge deck of the bridge, the static performance tests of two full-scale models were completed, and the overall force of the bridge and the local force of the bridge deck were calculated. The composition analysis of the ultimate bearing capacity of the negative bending moment resistance of the bridge deck was also performed. The results show that the nominal cracking strength of UHPC is above 8.90 MPa, which is much larger than the maximum longitudinal tensile stress of the upper edge of UHPC under real bridge load. The negative bending moment crack resistance of composite bridge deck is good, which can meet the engineering requirements. For the calculation of the bearing capacity of the composite bridge deck, the trilinear model is suitable for the tension structure of UHPC. The equivalent uniform stress reduction coefficient of the UHPC tension zone calculated by the simplified calculation of the bearing capacity of the negative bending is 0.76, and the compressed steel plate under the negative bending is still in the linear elastic stage. The failure mode of negative bending is significantly different from that of positive bending, which is tensile fracture of tensile reinforcement. The PBL shear key can ensure the overall joint force of steel plate and UHPC plate. The ductility of composite bridge deck under negative bending moment is good with the crack width increasing slowly and the nominal ultimate strength of UHPC being more than 4.1 times of the nominal cracking strength. After reaching the ultimate load, the bearing capacity of the composite deck does not decrease significantly.