Study On Nonlinear Mechanical Behavior Of Assembled Group Studs

The development of assembly has promoted the research and application of assembled bundled nail group composite beams.The studs in the cluster nail group are discretely arranged along the beam,and the post-cast concrete slabs are reserved for the group of nails to realize the assembly of the composite beam.The assembly bundle group and the conventional stud group are significantly different in construction and construction,resulting in differences in analysis methods and mechanical behavior.This paper relies on the Chongqing Natural Science Foundation "Assembly combined beam double non-coupling structure behavior and computational theory research"(cstc2018jcyjAX0509).The whole process of mechanical behavior analysis and multi-parameter influence research is based on the existing experimental results by using the finite element.And extended the research to the assembled composite beam,analyzed the mechanical performance of the nail group in the composite beam,and obtained the following main results:(1)The main influence of assembled nail group is proposed by analysing 65 peg push-out test and beam test data and failure mode.And it is based on the research status of assembled group nails and the difference with conventional nail group.The factors are: post-concrete concrete strength,age difference of successive concrete pouring,pre-formed concrete reserved hole shape,nail group size and nail group arrangement.(2)The finite element analysis method of the cluster nail group using the cohesive behavior to simulate the concrete successive pouring interface,the penalty function interface contact simulation steel-mixed contact interface and the time-varying temperature method to simulate the concrete successive pouring age difference is proposed.The nail group launched the whole process stress model,which is in good agreement with the experimental data.This method can be used for finite element analysis of similar fabricated composite structures.(3)The influence analysis of the clustering nail group parameters of successive concrete pouring age,group stud spacing,nail group spacing and reserved hole shape was carried out,and the damage accumulation,bearing capacity and failure mode of each group were proposed.The relationship equation between the age difference of successively poured concrete and the area of interface damage is proposed.It is found that with the increase of studs spacing,the bearing capacity of the nail group increases,the stiffness and ductility decrease.The shape of the concrete hole and the arrangement of the studs in the hole both affect the bearing capacity and the ductility,and the rectangular reserved holes are superior to the circular shape in two aspects.(4)The whole process of loading of the typical bundled nail group composite beam is analyzed.The interface shear force of the composite beam is mainly assumed by the shear force of the root of the stud and the frictional force of the steel-mixed interface,wherein the stud bears about 90% of the total shear force.The root shear force distribution of the beam is the mid-span smaller than the support.When loading to the stage of plastic failure,the nail group gradually yields from the support to the middle(5)The clustering degree ? index which characterizes the degree of stud dispersion is proposed.The mechanical behavior comparison analysis of the uniform composite beam with l=0 and the bundled composite beam with l=0.167 is carried out: there is no significant difference between the bearing capacity of the two.However,the stiffness of the former is slightly lower than that of the latter;the bundle of composite beams is increased from 0 to 16.7%,and the bearing capacity of the steel-mixed interface is reduced by about 16.8%.