Dynamic Analysis Of Protective Frame And Ultra High Limit Vehicle Collision With A Cushioning Device

The high limit protective frame is one of the most important safety facilities to protect the railway bridges. At present, the most widely used forms of protective frame are rigid, and the research and application of semi-rigid and flexible protective frame are very few. The research of the relevant specification is blank. The role of protective frame:when the over-high vehicle collides with the protective frame, it absorbs part of the collision energy in order to prevent the over-high vehicle from causing more disasters and accidents in the premise of avoiding its own destruction. As a result, the high limit protective frame must reach certain requirements of energy absorption and stability while meeting the requirements of strength and rigidity.The prominent advantage of rubber bumper is that it has good cushioning effect and energy absorption characteristic. Semi-rigid node has good energy dissipation ability under dynamic load. There may be potential economic benefits and broad application prospects if both of them are applied to the height limit protective frame.In this paper, the collision process of the height limit protective frame and the over-high vehicle was simulated and analyzed by using the ANSYS/LS-DYNA software. Multiple models using rigid node without adding rubber buffer and adding rubber buffer as well as rigid connection and semi-rigid connection etc. were carried out the finite element simulation and the comparative analysis of the dynamic response of the collision. The study shows that:(1) After adding rubber bumper to height limit protective frame, the stress of protective frame unit and the displacement, velocity, acceleration and impact force etc. response of protective frame node all were decreased; the time of each dynamic response index reaching the peak was increased; moreover, the plastic deformation energy of the protective frame and the over-high vehicle in the system were significantly decreased; part of the internal energy was transformed into the elastic deformation energy of the rubber bumper. So, the kinetic parameter peak of the whole collision was reduced.(2) After beam-column joints of the height limit protective frame were adopted semi-rigid connection, on the whole, the change of the dynamic response of protective frame tends to increase. After the collision, the internal energy absorbed by protective frame is more and more than half of the internal energy is the plastic strain energy of bolts of protective frame. This fully shows that energy dissipation property of semi-rigid nodes was convincing. Meanwhile, the plastic deformation energy of the over-high vehicle is less and the damage of the over-high vehicle is lesser; the peak of dynamic acceleration reduced and the damage of the people inside the vehicle decreased.(3) Through the analysis and the contrast research with the existing protective frame, it provides great reference value for the engineering design of the height limit protective frame of railway-bridge and highway-bridge. Meanwhile it is also very beneficial for establishment and perfection of related specifications.