基于正交试验设计的间断式砼护栏研究

RESEARCH ON INTERRUPTED TYPE OF CONCRETE GUARDRAILS USING ORTHOGONAL DESIGN

为设计出能满足碰撞安全要求的山区公路间断式砼护栏,联合应用正交试验设计方法及动态显式有限元方法,以乘员头部伤害指数HIC值为考核指标,对间断式砼护栏的设计参数进行了优化。采用正交试验表L25(56),对间断式砼护栏的6个设计变量进行了研究,其中,每个设计变量安排了5个水平,基于eta/VPG及ls-dyna软件平台及“汽车-护栏-乘员-座椅-安全带”一体化模型,共进行了25次仿真试验。模型中,汽车采用总重10000kg、重心高1212mm的大货车,其长×宽×高为8575mm×2445mm×3278mm,驾驶室内置自重78kg的50百分位成年男性假人,并配置1.2mm厚的三点式安全带。大货车以60km/h的速度、行驶方向与护栏纵向平面成20°的角度撞击砼护栏。最后,应用SPSS统计软件包,对仿真试验结果进行了方差分析,并据此确定了间断式砼护栏设计参数的最优结果。发现间断式砼护栏的6个设计变量中,只有砼墩长度、砼墩间距、下斜坡高度这3个变量为显著变量,应该选择其最好的水平,因为水平的变化会造成指标的显著不同,而对不显著的另外3个变量,则可根据工程需要来考虑其水平的选择。结果表明,只要设计参数合理,间断式砼护栏也可以在有较强吸能能力的同时,具有一定的引导失控车辆返回正确行驶方向的导向能力。

In order to design interrupted type of concrete guardrails for highway in mountain area to satisfy collision safety request,using the method of orthogonal design(MOD)and the dynamic explicit finite element method(EFEM),taking passenger's head injury criterion(HIC)value as a check index,design parameters for the interrupted type of concrete guardrails are optimized.An orthogonal design table L25(56)is used,6 design variables and 5 levels for each variable are considered.Based on eta/VPG and LS-DYNA software and a integrated model of “automobile-guardrail-passenger-seat-safety belt”,total 25 simulation tests are carried on.In the integrated model established here,a big truck with length of 8575 mm,width of 2445 mm,height of 3278 mm,weight of 10 000 kg and height of 1212 mm for its gravity center is used.At the driver seat inside the truck,a 50 percent adulthood male dummy with weight of 78 kg is put on,a safety belt with thickness of 1.2 mm and three-point fixed is used.The truck with speed of 60km/h,in the direction with a 20°angle to the lengthwise of the guardrail crashes the concrete guardrail.The analysis of variance for the results of the 25 simulation tests is done by using the statistical package for social sciences(SPSS)and the optimal design parameters for the interrupted type of concrete guardrails are given.It is found that only 3 design variables of all 6 ones are significant,i.e.,the length of the concrete frustum,the distance between two concrete frusta and the slope down height of infrastructure.For these 3 design variables,their best levels should be selected because the level changes will make the check index be obviously different.For the other 3 nonsignificant variables,their levels can be selected according to the engineering requirement.The results indicate that if the design parameters are reasonable,then the interrupted type of concrete guardrails can have stronger energy-absorbing ability and a certain steerable ability to lead to the vehicle lost control to return the right running direction.