Dynamic Behavior Of CHS-SHS Steel Tubular T-joints Subjected To Low-velocity Axial Impact

Steel structures in practical engineering,due to accidental collisions caused by earthquakes,explosions,erroneous operations and other accidents,often suffer huge damage and meanwhile cause huge losses to people's lives and property safety.At those regions with high latitudes,the impact load(ice load)is one of the dangerous loads to which offshore platforms are subjected.Therefore,study on the anti-collision performance of tubular joints is becoming a hot topic in the field of structural and disaster prevention engineering.So far,research overseas on the dynamic performance of steel structure under impact loading is mainly based on a single pipe as the research object,whilst the tubular joints have rarely been studied.Domestic scholars have carried out experimental research on steel tubular joints subjected to impact load,but those joints were comprised of either circular or rectangle tubes.No joints made up of a combination of circular and rectangle tubes,or say circular hollow section to square hollow section(CHS-SHS)tubular T-joints,have been experimentally investigated yet.To study the anti-impact performance of CHS-SHS steel tubular T-joints,a large drop hammer impact test machine was used to investigate that of seven joint specimens of the type.A preliminary analysis was made on the influence of the brace to chord width ratio(d/B),impact velocity and boundary conditions on the dynamic performance,such as impact bearing capacity,joint deformation,failure modes and energy dissipation capacity.Based on the plastic hinge line theory,the impact bearing capacity of the T-joints was evaluated,and the validity of the plastic hinges method was verified.Then,the finite element analysis software ABAQUS was used to model the 1/4 structure of the specimen,with numerical results compared with the experimental ones.The two agreed well with each other,verifying that the numerical model was efficient and accurate in simulating experimental results..Due to the verification of the reliability of the finite element(FE)model,comprehensive parameter analyses,with a wider range of values of influential factors like impact mass,impact velocity,impact energy and d/B ratio,were carried out on the influence on dynamic performance of the joint.Finally,based on the theory of virtual beam elements subjected to axial compression,a new method concerning virtual beam elements that is subjected to flexural compression was developed to simplify the aforementioned solid element model,resulting in improved computational accuracy and efficiency.