| With the rapid development of social intelligence and information technology,the building auxiliary facilities in the building structure are gradually large and the pipelines are increasing.At present,most of the equipment pipelines are generally passed directly under the beam of the structure,occupying a large number of building space,resulting in the reduction of indoor floor height,which affects the use function of the building.If a circular hole is set up in the reinforced concrete(Reinforced Concrete,hereinafter referred to as RC beam)beam for the equipment and pipeline of the building,the net height of the building can be guaranteed to meet the needs of the use function to the maximum extent under the premise of constant layer height.In practical engineering,more and more large transport hub projects need to open large size holes on the beam to meet the passage of various equipment pipelines.Therefore,this paper takes the RC beams with web huge circular opening as the research object,adopts the method of model test,numerical simulation and theoretical calculation,studies the influence of hole location,stirrups and hole size on the shear performance of RC beam with web huge circular opening,analyzes the mechanical mechanism of RC beam with web huge circular opening,establishes the calculation formula of shear bearing capacity suitable for RC beam with web huge circular opening,and puts forward the design suggestions of RC beam with web huge circular opening.The main conclusions are as follows :(1)The opening of huge circular holes on reinforced concrete beams weakens the shear bearing capacity of the beams greatly,and the holes become the weak area of the beams.According to the location of the main crack passing through the final failure,the failure modes of RC beams with web huge circular opening can be mainly defined as three types : shear failure at the hole side,shear failure of chords and shear failure in non-encrypted areas.(2)The hole position has a great influence on the shear performance of web huge circular opening RC beams.The change of hole position will directly affect the effective action of hole side stirrups and the height of compression chord of web huge circular opening RC beams,thereby changing the failure modes and shear bearing capacity of beams.(3)The interaction between the hole side stirrups and the chord stirrups has a significant influence on the failure mode and shear bearing capacity of web huge circular opening RC beams.Increasing the stirrup ratio of the hole side can significantly improve the shear capacity of web huge circular opening RC beams,but the effect is not obvious when the stirrup ratio reaches a certain extent.When the hole side stirrups are appropriate and the chord stirrups are insufficient,the web huge circular opening RC beams are prone to chord shear failure.When the hole side stirrups and chord stirrups are sufficient,the most unfavorable position of the beams will be transferred to the non-encrypted area,and finally shear failure occurs at the weak position of the non-encrypted area.(4)The hole size has a great influence on the failure mode and shear capacity of web huge circular opening RC beams.With the increase of the hole size,the shear bearing capacity and the deflection below the loading point of web huge circular opening RC beams decrease continuously.When the hole diameter exceeds 0.5 times the beam height,the shear bearing capacity of web huge circular opening RC beams can not be restored by encrypting enough hole side stirrups and chord stirrups,so that the ideal shear failure in the non-encrypted area occurs.Therefore,it is recommended that the hole size of web huge circular opening RC beams should not be greater than 0.5 times the beam height.(5)By summarizing the existing related research of the opening beam,collecting the relevant test data,analyzing the existing shear calculation model of the opening beam,discussing the advantages and disadvantages of each calculation model and the applicability of web huge circular opening RC beam.On the basis of the existing model,based on the model test and finite element parametric analysis,the shear bearing capacity calculation formulas of the shear failure of the hole side and the shear failure of the chord of the web huge circular opening RC beams are established.The calculation results are in good agreement with the experimental results,and the failure mode can be predicted well,which can provide reference for engineering design. |
