Research On Dynamic Stability Of Steel Arches Under Impact

Steel arches are widely used in engineering construction,and the calculation of the stability isusually vital in design of steel arches.Until recently,researches involving stability of arches are mostly concentrated on their static stability,but quite rare when relating to dynamic stability.Existing works about dynamic issues of arches usually focus on their dynamic behaviors,while studies on the critical state of the dynamic stability are not sufficient.In this paper,the dynamic in-plane buckling of steel arches is studied based on an energy principle.Analytical solution and numerical simulation methodare used to obtain dynamic buckling load and relating energies.The analyses and comparison between results from two methods show the rationality of the energy principle.Firstly,the dynamic stability of elastic arches is studied.The method of conservation of energy is used to establish the criterion of dynamic buckling of arches.And analytical solution for the dynamic buckling load is obtained by studying the energy feature of arches under a sudden central concentrated load,and assuming the kinetic energy vanish in a critical state of dynamic stability.At the same time,the dynamic stability of arches is also studied using finite element method.FEM result of the dynamic buckling load is obtained through trials trying to approach the critical state.The comparison shows that results from two methods agree very well.And the results also verify that kinetic energy is indeed quite small compared to stain energy in a critical state of the dynamic stability.Secondly,FEM contact model is built to investigate the dynamic behavior of an elastic steel arch under impact.By assuming a similarity between stain energies from an arch in critical state of dynamic stability and in specific position of static equilibrium state,put forward that the dynamic buckling stain energy of elastic arches under impact should be nearly equal to that of the zero-point state on the unstable static equilibrium path.The theory is confirmed by the numerical analysis results.Works in this part,on the one hand,verify the validity of the energy approach,and on the other hand,provide a feasible method to judge if dynamic buckling occurs or not by calculating the energy imported to the arch.Thirdly,the energy theory is taken advantage in the study on the dynamic stability of elastic-plastic steel arches.Cases study shows:when a concentrated load is suddenly applied to the arch,the elastic strain energy obtained using energy approach from a static analysis can be a rather precise estimation for the dynamic buckling elastic strain energy.In the impact study,the occurrence of side plastic hinges is considered as the beginning of dynamic buckling,and the comparison shows that the elastic strain energy obtained by the energy method from a static analysis agrees well with the dynamic buckling elastic strain energy of an arch under impact.Fourthly,the sensitivity for dynamic incentive of latticed arches is studied by analyzing the strain energy features of the whole model and local bars.And the influence of failure of local bars is also investigated.Finally,the impact tests are conducted for scaled specimens of latticed arches and single arches.And the test results are compared with that from numerical simulations in material yield position,buckling shape and displacement of the vault,et al.The agreement implies that the numerical model used in this paper is appropriate.