| In recent years, terrorist attacks and accidental explosion occurredfrequently, thus it has been a common concern for the analysis and designof anti-explosion of structures. The blast shock, with the characteristics ofintensive impact, short duration and local effect, is destructive to thestructure. Some members and connections of the structures may yield anddamage under the blast load, leading to failure of the whole structure.Therefore, it is vital important to study the behavior of the connectionsunder blast load.In this paper, the non-linear explicit FEM software,LS-DYNA is usedto study the explosion propagation in the air.Based on the analysis resultsof the response of the structure under blast wave, the beam-to-columnconnection model is established. The dynamic response characteristics aswell as failure modes of the beam-to-column connections subjected to thetypical blast loads is investigated.The main research work include thefollowing parts:(1) The propagation of blast wave in the air is simulated by the methodof fluid-structure interaction with LS-DYNA It is observed that thediffraction flow overpressure behind the wall about1.5~2.5times wall ofthe wall height is higher.(2) The appropriate material constitutive model and explosive model isselected. The numerical simulation is carried out to study thedynamic response of steel frame under blast load near the ground surface.The development of the variation of displacement, speed, acceleration, different location of the structure under blast load is studied.Theacceleration and lateral deformation of the steel frame is extremely high.According to analysis results, an appropriate simplified model ofbeam-to-column connections is selected for further study.(3) Taken strain rate effect of the steel into consideration, thedynamic response of beam-to-column connections under blast load isanalyzed.Shear failure of column flange near connection is occurred,andthe fracture develops quickly.In addition,the stress concentration nearwelding access hole is obvious. Parameters such as explosion shockwave,the thickness of steel column flange,the transverse stiffener,thedimension of weld access hole,axial compression ratio and so on, influenceon the performance of the beam-to-column connections is conducted.Theanalysis results show local fracture occurred in the steel members andstress concentration appeared at weld access hole.In the case of thecolumn flange is thin,shear failure of flange plate with web occurred anddeveloped quickly under impact,which leads to connection failure. Inaddition, the influence of axial compression ratio on theexplosion-resistance behavior of of beam to column connections is notsignificant. Methods to improve the explosion-resistance capacity ofbeam-to-column connections are suggested. |
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