Study On The Pull-out Performance Of PSCC Connector For Prefabricated Steel-concrete Composite Beam

The prefabricated steel-concrete composite beam is one of the hot research topics in bridge engineering,and the shear connector is the key structure to transfer the shear force and vertical pull-out force.This study proposes a new prefabricated PSCC shear connector based on the National Natural Science Foundation of China(NSFC)project "Study on corrosion-fatigue coupled damage mechanism of post-cast UHPC-stud connection system for prefabricated composite beams"(52278147).PSCC connector consists of welded studs and side baffles on the flange of the steel girder and pre-buried shear connection steel in the prefabricated bridge deck.After the bridge decks are in place on the steel girders,the connection between the steel girder and the bridge decks is achieved by filling the bonding cavity concrete.PSCC connector has the advantages of easy factory fabrication,easy field assembly,and efficient,reliable,and integral connection.In this study,experimental and theoretical research was carried out on the static pull-out performance of PSCC connectors,and the main research contents and conclusions are as follows:(1)Four groups of 8 PSCC pull-out specimens were designed and fabricated with the parameters of stud height-to-diameter ratio and lateral spacing,and monotonic static pull-out tests were carried out using a self-balancing loading device,and the test results showed that: the failure modes of PSCC connector are mainly stud failure and UHPC cone damage,both of which are ductile damage;the load-deformation curve goes through the elastic phase,the elastoplastic phase,the yield phase,and the damage phase;increasing the height-to-diameter ratio will improve the pull-out capacity of the connector,but the pull-out stiffness will be significantly reduced;reducing the spacing between studs and shear rebars will improve both the load capacity and pull-out stiffness.(2)Based on the cohesive zone model,a finite element numerical model of the PSCC connector was established by applying ABAQUS software,and the analysis of the pullout bearing mechanism and parameters of the connector were carried out to study the effects of factors such as stud height-to-diameter ratio,stud strength,bonding material properties and width of steel bar at the end of shear rebar on the pull-out performance of the connector,and the results showed that: the critical value of stud height-to-diameter ratio that leads to the change of damage mode of the connector is about 5.0;stud strength,stud burial depth and UHPC tensile strength are the main factors affecting the failure mode and pull-out load capacity of PSCC connector;the reduction of transverse spacing between studs and shear rebars improves the load capacity;it is suggested that the width of steel bar at the end of shear rebar should be larger than 2.0 times of shear rebar diameter in practical engineering to prevent the anchorage failure.(3)Based on the pull-out test results and the existing theory of calculating the anchorage bearing capacity of stud connector,the theoretical model and calculation formula of the pull-out bearing capacity of the PSCC connector is proposed,taking into account the side baffle steel-UHPC interface bonding friction and the difference of cone breaking surface inclination between UHPC and normal concrete.A finite element model of a 40 m spans steel-concrete composite simple-supported girder bridge in Tibet was established,and the results showed that the pull-out force of the stud in the PSCC connector was less than 10% of the design pull-out load capacity from loading to the elastic limit state,and its pull-out performance met the requirements.