| The steel-UHPC composite structure is a newly developed structural system in recent years,which is used to replace the traditional orthotropic steel bridge deck and the steel-concrete composite deck system in the large bridge.With high compressive strength,tensile strength and durability,the steel-UHPC composite structure can significantly improve the bridge deck from the weight issue and the problem of negative bending zone cracking.At present,the research on steel-UHPC composite structure in China and abroad mainly includes force bending performance,fatigue performance,interface shear connection performance,etc.Less attention has been paid to the shear performance of steel-UHPC.In the steel-UHPC composite structure,the UHPC layer is relatively thin(usually 50mm),which may lead to the two-way shear failure occurs under the concentrated load of the member,that is,the punching failure.In this paper,the study object is steel-UHPC composite structure in the top of the steel plate and UHPC part of the composition of steel-UHPC composite panels.The fracture behavior of steel-UHPC composite slab was studied by methods of experiment,nonlinear finite element method and theoretical derivation.The main research work of this paper includes:1.This paper summarized the experimental and theoretical researches on the steel-UHPC composite structure in China and abroad,and the experimental and theoretical researches on the punching and failure of various types of structures.And then the research contents and research methods was suggested;2.The punching failure experiment of steel-UHPC composite slab under concentrated load was carried out by using the test device designed in this study.The whole experiment was completed in two batches.The first batch of test components was fabricated according to the steel-UHPC deck system components in a practical engineering project.UHPC was equipped with a steel mesh and the main variable parameters were peg arrangement,stud diameter and bearing condition.The second batch of test components was not equipped with steel mesh,and the main changes in the parameters was the pegs,UHPC layer thickness,steel plate thickness,loading area,etc.The destruction modes of the test components included bending failure and punching failure.The two failure modes formed a composite failure mode,rather than opposed to each other.Based on the experiment results,the factors influencing the punching failure performance were analyzed;3.In this study,the bending ultimate bearing capacity and the punching bearing capacity of steel-UHPC composite slabs were derived by plastic hinge and rigid-plastic analysis respectively.Combined the experiment phenomena with formal study results,the theoretical calculation formula consisting bending and punching bearing capacity was built.The results showed that the mechanism of the theoretical calculation formula is clear and the calculation results are in good agreement with the experiment results;4.The test components are modeled and analyzed by the general finite element software MSC.Marc(r2015).Moreover,the pincent constitutive mechanism consisting the descending section of the peg was suggested,which could be successfully applied in the whole force analysis process of steel-UHPC composite slab.The reliability and accuracy of the finite element model were verified by calculation;5.At last,this paper summarized main research results and limitations of the current studies,and put forward the direction of future research work. |
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