钢筋混凝土箱梁近场爆炸响应的试验与数值模拟

Test and numerical study on the near-field explosion response of reinforced concrete box girder

为了研究近场爆炸作用下单箱三室混凝土箱梁的动力响应和破坏特征,开展了缩比试件爆炸试验和数值模拟。以原型桥梁主梁截面按1∶3缩比设计和制作了箱梁试件,测量了3 kg TNT药柱爆炸作用下试件的反射超压、钢筋应变、竖向位移及破洞形态;采用LS-DYNA软件进行了箱梁爆炸响应模拟,结合试验数据验证了数值模拟方法的可靠性;分析了TNT当量、起爆位置、混凝土强度、配筋率对箱梁抗爆性能的影响。结果表明:3 kg TNT药柱于箱梁中间箱室中心正上方0.4 m处起爆时,在中间箱室顶板中心形成一个椭圆形的贯穿破口,破口沿横、纵桥向长度分别为41.50、45.50 cm;中间箱室顶板底面的混凝土发生大面积剥落,呈现喇叭状冲切破坏特征;多室箱梁的超宽截面形式使得其爆炸响应沿横桥向分布不均匀;箱梁底板竖向位移峰值和钢筋应变峰值随药量的增大而增大,采用最小二乘法得到了对应的拟合曲线表达式;不同起爆位置下,中间箱室底板中心的竖向位移均大于两侧箱室中心的。

In order to study the dynamic response and failure characteristics of the concrete girder with single box and three chambers under near-field explosion,the explosion test and numerical simulation of a scaled specimen were carried out.The girder specimen was designed and manufactured by the scale of 1∶3 according to the prototype bridge girder.The bottom of the specimen was supported by six brick supports.The TNT grain was located at 0.4 m above the top plate center of the middle chamber with an equivalent of 3 kg and a proportional distance of 0.77 m/kg1/3.The reflected overpressure,reinforcement strain,vertical displacement and acceleration of bottom plate and the shape of breach were measured and analyzed.The effectiveness of the explosion load in the test was verified by comparing the measured reflection overpressure with the calculated value by the CONWEP empirical formula.The LS-DYNA software was used to simulate the explosion response of the box girder.The SOLIDWORKS software and HYPERMESH software were used to establish the finite element model of the specimen.The Solid 164 element was used to simulate the concrete,and Beam 188 element was used to simulate the steel rebar.The LOAD BLAST ENHANCED(LBE)method was used to apply explosive loads.The*MAT_CONCRETE_DAMAGE_REL3 material model and*MAT_PLASTIC_KINEMATIC model were used to simulate the concrete and rebar,respectively,to consider the effects caused by high strain and large deformation.The keyword*MAT_ADD_EROSION was used to define the failure of concrete.The reliability of numerical simulation method was verified with the test data.Finally,the effects of TNT equivalent,detonation location,concrete strength,and reinforcement ratio on the explosion resistance of the box girder were analyzed.The results show that when a TNT grain of 3 kg is detonated at 0.4 m above the center of the middle chamber of the box girder,an elliptical penetration breach is formed in the center of top plate of the middle chamber,with the length values along the transverse and longitudinal bridge directions being 41.50 and 45.50 cm,respectively.The concrete on the bottom surface of the top plate of the middle chamber peels off in a large area,presenting a trumpet-shaped punching failure feature.The extra-wide cross-section of multi-chamber box girder makes the explosive responses unevenly distributing along the transverse bridge direction.The peak values of vertical displacement and rebar strain of the bottom plate of the girder increase with the increase of the charge.Using the least square method,the corresponding fitting curve expressions are obtained.Under the working conditions of different detonation positions,the vertical displacement of the bottom plate center of the middle chamber is greater than those of the chamber centers on both sides.The results can provide a basis for the anti-explosive evaluation and protection of similar extra-wide concrete box girder.