| In recent years,due to the rapid development in construction industry,the building scale continuous expansion.A large number of intelligent buildings appear with diversified functions,so various building auxiliary facilities suitable have become more and more huge.Opening in the web of reinforced concrete(RC)beams to ensure the building auxiliary facilities and equipment pipelines pass through,which can avoid occupying building space and keep the interior beauty.As is known to all,opening in the web of RC beam will destroy the integrity of the beam and weaken the mechanical properties of RC beam,such as the bearing capacity and the stiffness.However,the existing studies for opening RC beams have many restrictive conditions on the hole size,moreover,there is a lack of relatively well design theory and calculation method.Therefore,in order to study the shear performance of the web huge rectangular opening RC beams,explore their influencing factors and laws on the shear capacities and failure modes,reveal the mechanical mechanism of opening RC beams,and propose a calculation method of shear capacity of web huge rectangular opening RC beams.This dissertation mainly carried out the following work:(1)A total of 15 RC beams,including one ordinary RC beam and fourteen web huge rectangular opening RC beams,were tested by three-point static loading test.Took the hole position and stirrup around the hole as the parameter variables,analyzing the failure modes,ultimate bearing capacities and strain distributions of all specimens.The results show that the horizontal movement of the openings had little effect on the shear behavior of opening RC beams,but the vertical eccentricity of the opening led to the transference of the weak part of the RC beam specimens,which had a great influence on the failure modes of the specimens.Moreover,the reinforcement amount of the chord stirrup and hole-side stirrup had a certain influence on the ultimate bearing capacities and failure modes of opening RC beams,and the influence degree mainly depended on the opening size.(2)Established a total of 29 finite element models of web huge rectangular opening RC beams by using the finite element software ABAQUS to carry out the parametric analysis.Quantitatively analyzed the actual shear contribution of hole-side stirrup and the influence of opening position on the shear performance by comparing their stress nephogram and peak loads.The results show that the reinforcement amount of hole-side stirrup had a significant effect on the ultimate bearing capacities and failure modes in case of the model beam with small opening width,but the effect could be negligible for the model beam with large opening width.For the model beam with small opening height,as the chord stirrup gradually strengthened,the failure modes tended to occur shear failure near the hole side,and the ultimate bearing capacity was improved;Meanwhile,the horizontal movement of opening had little effect on the failure modes and ultimate bearing capacities of opening RC beams.(3)On the basis of experimental study and existing calculation model of shear capacity of RC beams with openings,parameters of stirrup around the openings were introduced to establish the calculation method of RC beam with huge rectangular openings.The results show that the fitting degrees of the existing calculation models to the failure modes and ultimate bearing capacities of the specimen with huge openings were poor,and the improved calculation model could accurately predict.Verifies the accuracy and applicability of the proposed calculation model by collecting the relevant test data of other scholars.Furthermore,given some design suggestions,such as it can improve the ultimate bearing capacities by strengthening the stirrup around the opening in case of the RC beams with a opening width no more than 0.25 times the shear span and hole height no more than 0.38 times the beam height. |
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