The Force Mechanism Analysis Of The Hollow Beam Based On The Pure Shear Damage Constitutive Model Of The Shear Bond

The open-web sandwich plate structure is one of structural systems,which are suitable for large-span and wide-opening.The open-web beam is a member of the open-web sandwich plate,which has great significance in studying its mechanical performance.However,the current constitutive relationship does not reflect well the shear characteristics of the shear key.In order to explore the more suitable damage constitutive model and apply it to the analysis of mechanical characteristic of the open-web beam,the research work is following:(1)The basic theory of thermodynamics is summarized,what's more,the basic framework of analysizing problem with the damage mechanics are established.Several common equivalence hypotheses are introduced in detail,and the evolution rule of shear damage is given,which lays a theoretical foundation for the derivation of the subsequent damage constitutive.(2)Referring to the related literature,the double scalar elastic damage constitutive considering the inequality of tension and compression is deduced(tested)and compiled into a subroutine for debugging in the UMAT interface of ABAQUS.The finite element simulation of uniaxial tension and uniaxial compression was used to determine the relevant damage evolution parameters.The results show that the double scalar elastic damage constitutive relation has certain reliability in uniaxial loading.When the top rib adopts the above constitutive relation,the shear bearing capacity of the shear key is slightly smaller.(3)The double scalar elastic damage constitutive theory considering shear damage is deduced.According to the relationship between the two damage variables under the pure shear state,the two types of damage constitutive relations dominated by tensile(compressive)damage and shear damage are derived and the corresponding subroutines are compiled.The stress-strain development in three cases of uniaxial tension,uniaxial compression and pure shear state,is simulated;in addition,the following three situations: the upper rib adopts damage constitutive or the upper rib and shear key adopt damage constitutive relation or the shaer key adopts damage constitutive relation,are analysized.The results show that the pure shear constitutive theory has certain reliability in uniaxial loading of the shear key.Although the pure shear stress is slightly different from the related literature,it can still be used to analyze the shear key considering the mechanical characteristics of shear key.What's more,the shear bearing capacity of the shear key calculated by the pure shear damage constitutive relation is more about 11% than calculated by the constitutive value of the concrete code.(4)In the analysis of the open-web beam,whether the vertical uniform load or the horizontal uniform load is used,the shear stress value calculated by the pure shear damage constitutive relation exceeds the value calculated by elastoplastic damage constitutive relation of the concrete code by more than 10%,indicating the pure shear damage constitutive relation,to some extent,reflects the mechanical characteristics of the shear key.When adopting the vertical uniform load and the vertical restraint force reaches the peak value,the compressive stress value of the top rib and tensile stress value of the bottom rib calculated by the pure shear damage constitutive are more than the values calculated by concrete code;When the restraint force reaches the first minimum value,the compressive stress value of the top rib calculated by the pure shear damage constitutive are relatively larger and tensile stress value of the bottom rib calculated by the pure shear damage constitutive structure are relatively smaller.When adopting the horizontal uniform load,regardless of the horizontal restraint force of the bearing(the sum of the shear bearing force of the shear key),the compressive stress value of the top rib calculated by the pure shear damage constitutive is relatively larger and the tensile stress of the bottom rib is relatively smaller.(5)In the analysis of the open-web beam,adopting the vertical uniform load,when the vertical restraint force reaches the peak value,the bottom rib of the open-web beam has been cracked,and the cracking position is within a certain area of the two three-point points of the rib;when the vertical restraining force reaches the first minimum point,the top rib calculated by the pure shear damage constitutive theory has been cracked,the crack appears at a lateral surface between less than two three-points.(6)In the analysis of the open-web beam,adopting the horizontal uniform load,when the horizontal restraint force(the sum of the shear bearing capacity of the shear key)reaches the peak value,the bottom rib has been cracked and the position is from the left end to the quarter position;when the horizontal restraint force reaches the first minimum point,the top rib calculated by the pure shear damage constitutive relation is about to be cracked,and the crack will appear at the lateral surface of a certain area at the left end of the rib.