Numerical Analysis Of Reduced Beam Section Steel Structure Behavior Subject To Impact Load

Lots of investigations and researches have been made on the brittle fractures of traditional beam-to-column connections since the earthquakes in Northridge (1994) and Kobe (1995). Meanwhile a new kind of moment-resisting frame connection containing the reduced beam section (RBS) connections and the strengthened connections is devised and greatly developed according to the strong column-weak beam criteria which can effectively reduce brittle fractures of connections, improve their ductility and survive steel structures in violent earthquakes. So far, this kind of connection especially the RBS connections has been or is being applied in many tall structures or even skyscrapers such as Taipei101building. However, the study of these connections in other areas is underway such as in explosion and impact field which is severe lack of relevant data and researches yet at home. Additionally the shaved beam may decrease the strengthen and stiffness of structures, so further investigations in other fields is more than ever important.After9.11terrorist attacks, performance of structures on impact resistance once again aroused people’s attention and some researches show that improving the ductility of structures can to some extent enhance the impact fracture resistance of structures which happens to be an coincidence with the reduced beam section connections.To meet the two aspects discussed above, in this paper, a brief presentation of the new ductile connections and some influencing factors is given, and great attention will be paid to the resistance to impact. Then several kinds of steel frames including traditional frames and the RBS moment-resisting frames are established using ANSYS/LS-DYNA finite element software to verify whether this connection can be used in impact-resistance structures from impact force, energy distribution, frame stiffness and stress distribution of the whole frame, beam-to-column connection and the bottom of columns. In addition, the constitutive relationship model of steel including the effect of strain rate is also given. The conclusions are as follows:●The deeper the depth of the flange is cut, the higher the energy dissipation capacity and the less the rigidity of frames. Yet the depth of the flange cut has little influence on both of them.●The impact load is linear to the increasing impact speed and almost do not change with the beam span. ●Energy propagates along with the path below:impact object, beam, beam-to-column connection, column and bottom of the column. Similarly, the higher the speed is, the more energy dissipated, during which the beam take larger possession than the column.●The reduced beam section connection can to some extent transfer the plastic hinge from the joint weld to a certain position in the beam which obviously improve the ductility, and of course can be used in impact-resistance structures. Nevertheless, the ductility improvement of the new shaved connections under impact is not as effective as under earthquakes.●The beam should be replaced when the velocity is or more than20m/s.Finally, based on analyses above, some suggestions are put forward for the impact resistance design of steel moment-resisting frames.