Research On The Robust Multi-objective Optimization Of New Combined Median Barrier

Accidents that vehicles cross median and enter opposite lane are occurred frequently,the existing median barrier has weak anti-collision strength.Chinese median is narrower than the western countries’,the secondary crash event is caused by the large deformation of median barrier.In order to enhance the anti-collision strength of the median barrier and decrease its deformation,a new combined median barrier(NCMB)consisted of reinforced concrete structure and w-guardrail is proposed in this paper.However,the initial design of the structure is in poor safety performance,and there are some uncertainties in the design process.So optimization design of the structure is further carried out.In this paper,the nonlinear finite element method(FEM)is used to simulate the process that vehicles impact on the NCMB.Hypermesh and LS-DYNA are applied for establishing the FE model of NCMB,LS-DYNA is used for collision simulation analysis of evaluating the contained performance,buffering performance and anti-collision strength.The simulation of crashworthiness of NCMB structure is conducted.Results show that the tires of sedan and medium truck are snagging,and the centroid acceleration of sedan is more than 20g.The safety performance does not meet the regulation requirement.Aiming at the deficiencies of the initial design of the NCMB structure,the parameters of the concrete structure are optimized.Firstly,the interval between two concrete slabs is optimized by dichotomy,and the suitable interval between two concrete slabs is determined.Then the cross-section parameters of concrete structure are optimized by orthogonal experimental design method and the optimal parameters of cross section are determined.Considering the influence of uncertainties,combined with the Taguchi method and grey relational analysis,a robust multi-objective design model based on Signal-noise ratio(SNR)and grey relational degree is established,and then the established model is used to realize the robust multi-objective optimization design of SBm level NCMB.Results show that the acceleration and the maximum dynamic lateral deformation are greatly reduced when the vehicle impacts the optimized guardrail,the crashworthiness is improved;Meanwhile,the mean and standard deviation of the target response are reduced,and the SNR is improved,robustness is enhanced.The crashworthiness topology method based on hybrid cellular automata(HCA)and SIMP is used to optimize the crash cushion,and the topological configuration of the energy absorbing box is obtained.A robust multi-objective optimization model based on SNR and satisfaction is established by combining Taguchi method with the satisfaction function,and the robust multi-objective optimization design of the energy absorbing box of crash cushion is carried out,results show that after robust multi-objective optimization design,crashworthiness and robustness of crash cushion are significantly improved at the same time.