Improved Equivalent Single Degree Of Freedom Method For Blast Analysis Of Reinforced Concrete Beams

The frequent terrorist attacks and accidental explosion may cause the structural component destruction or even collapse in succession,causing heavy personnel casualties and huge property damage.It is important to analyze the dynamic response of reinforced concrete(RC)components under blast load.Equivalent SDOF method is widely used in design and analysis because of its clear concept and simple using.According to experiment and FE analysis,RC components may suffer from different failure modes subject to blast loads,mainly about flexural failure,direct shear failure and flexural and shear failure.Different failure modes have different dynamic response.it is necessary to summarize different equivalent SDOF models for different failure modes.This paper takes RC beam components as the research object and studies the possible failure modes and dynamic response of components.Further considering direct shear failure mode,direct shear SDOF is presented based on Biggs' s equivalent SDOF model and Krauthammer's direct shear resistance function.The dynamic response including response time,dynamic shear force and direct slip can be determined by this model.Then consider diagonal shear failure,the dynamic response can be determined by flexural SDOF mode.And principle tensile stress near the support can be used to determine the diagonal crack of the beams.When considering different failure modes,assumption of flexural failure mode,direct failure mode and diagonal shear failure,a method for determining failure modes of RC beam components under blast loading is proposed.On this basis,an equivalent SDOF method for blast analysis method of RC components based on failure modes is proposed.And the analysis step of this is summarized base this method.The results of equivalent SDOF models are compared with the results of FE analysis and theoretical analysis.The validity of the proposed method is verified.The equivalent SDOF system considering different failure modes in article is simple in model and clear in concept.It can explain the dynamic response of direct shear failure modes of components.And it can quickly and accurately determine the failure modes of components and carry out dynamic analysis.