Dynamic Response Of Kiewitt Single-layer Reticulated Dome Under Aircraft Impact

As one of the main representative forms of long-span spatial structures,the reticulated shells are often used in large public buildings which have important significance in politics,economy and culture.While researches on anti-seism and anti-wind of reticulated shell are relatively mature,researches concern anti-impact and anti-explosion are still at an early stage.Although the aircraft impact is an accidental event,yet its damage to the buildings,the great economic loss and the negative social impact cannot be ignored.The impact properties of reticulated shells are studied mainly by numerical simulation and accompanied by experiment method at present.The ANSYS/LS-DYNA which is a kind of finite element analysis software is often used in previous numerical simulation.The beam elements were usually chosen for the shells’ members and a piecewise linear plastic material model which apply to beam element was used to simplify the calculation.When beam elements were used,the ball nodes were simplified to the intersections of the beams.When the effect of temperature is not obvious under medium-low velocity impact,this method is feasible.However,when it subjected to high-speed impact or super high-speed impact,especially under the high speed impact of aircrafts,such as missile,the temperature effect cannot be ignored and there will be a large error if the model mentioned above is still chosen.Therefore,in order to acquire the structure’s mechanics response under impact accurately,both the character of strain hardening of material and the effect of high strain rate,high temperature,large strain,change of stress state and loading history on the mechanical properties of material should be taken into consideration[1].So the S-J modeling method is presented in this thesis.The Johnson-Cook material model which can consider the temperature effect and the SHELL 163 were used in the building of the numerical model.In this thesis,a numerical model of reticulated dome with ball nodes was built based on the S-J method,and the dynamic response of reticulated shell under aircraft impact was studied;the main works are as following:1.Numerical analysis methods of reticulated dome under aircraft impactNumerical model of reticulated dome under aircraft impact was built by using ANSYS/ LS-DYNA.And the SHELL 163 and Johnson-Cook material model were chosen for the shell’s bars,ball nodes and roof plate.The applicability of this material model on the study of impact problem was verified by the circular steel tube’s drop weight impact test.The connection of bars and ball nodes was determined and the type of contact-impact was compared and selected.2.Numerical analysis on dynamic response of reticulated dome under drop-hamper impactNumerical models of the reticulated dome was built with the method of S-J,and it took the existence of roof panel or not into consideration.The peak stress,impact duration,time-interval and other dynamic response under elastic impact or destructive impact were analyzed.The tests of reticulated dome under drop-hammer impact conducted by Fan Feng,Lin Li and other scholars in Harbin Institute of Technology were simulated,and the results of numerical simulation(obtained with the models made by S-J method and B-P method,respectively.The piecewise linear plastic material model and BEAM 161 were used in the B-P modeling method)and tests were compared,which verified the correctness and advantage of the S-J numerical modeling method.3.Study on dynamic response of reticulated dome under airplane impactBased on the method of S-J,the numerical model of reticulated dome was built.The numerical model of the bombardier challenger 850 air minibus was built,too.The dynamic response,such as node displacement,change of the members’ stress and energy in impact area under the plane’s horizontal impact at a velocity of 120m/s were researched.4.Study on dynamic response of reticulated dome under high speed impact of missileThe numerical models of reticulated dome were built with the method of S-J and B-P,respectively.And the missiles’ numerical models of militia-3 intercontinental ballistic missile and trident-2 submarine-launched ballistic missile were built.The dynamic response,such as failure mode,bar stress in impact area,node displacement and energy change of the two models under two kinds of dud high-speed impact were compared and analyzed.From the point of energy,the effect of temperature under high speed impact was analyzed.