Research On Mechanical Performance Of Hollow-Core Partially Encased Concrete Composite Beams

A new type of partially encased concrete composite beam,hollow-core partially-encased concrete composite beam(referred to as HPEC beam),is proposed in this paper,which has good overall working performance and light weight,which can save some steel under the premise of ensuring bearing capacity and rigidity.The four-point static loading test study and digital image correlation(DIC)of this composite beam were carried out to observe crack and deformation,and the bending failure mechanism of the positive bending moment region of HPEC beam was investigated.Based on the results of experiments and finite element analysis,the design method of bending bearing capacity of HPEC beam is put forward on the basis of the results of experiments and finite element analysis,considering the influence of section steel flange width and thickness,web height and thickness and concrete filling thickness on the bending performance and failure mechanism of HPEC beam.The main contents of this article are as follows:(1)The four-point loading static tests of four HPEC beams,one PEC beam and one pure steel beams were accomplished.And the bending failure mode,load-deflection curve,stress-strain distribution and development of HPEC beams were analyzed.And the bending mechanism of HPEC beam was discussed.(2)Digital image correlation(DIC)technology was employed to analyze the process of the deformation and cracking of the pure bending section of HPEC beams.And the changes of deflection and the crack development law of the pure bending section were given in detail during the whole loading process.(3)Based on the experiment,the finite element analysis software ABAQUS was used to conduct orthogonal analysis of the numerical simulation model on the width and thickness of flange of section steel,height and thickness of web of section steel,concrete filling thickness of HPEC beam.And the influence of each parameter on the bending performance of HPEC beam was explored,and it was found that the web height was the most influential factor on the bending performance of HPEC beam,followed by concrete filling thickness.The research recommendations of the web height to thickness ratio is no longer than 105.4εa,and the concrete thickness in the bearing part is not more than one-third of the beam height,and not less than 60mm.(4)Combined with the experiment,DIC analysis and finite element simulation results,the calculation formula of the bending bearing capacity of HPEC beam was proposed,based on slip theory and structural stability theory,the theoretical formula of crack width,crack spacing and deflection of HPEC beam is derived,the stability of flange and web was analyzed,and the design method and structural measures of HPEC beam were proposed.