Effect Of Additional Deformation Of RC Shaft Floor Beam On Internal Stress Of Slab

The research in this paper is based on the analysis of an engineering example.The engineering structure is a reinforced concrete frame floor with a well shaped structure.After the main body of the structure is completed,the deflection deformation of the beam members is large,vertical cracks appear on the side of the beam,and the corners of the floor members are inclined to 45° cracks.Based on this background,this paper studies the influence factors of beam stiffness,the influence of beam stiffness on its deformation,and the change rule of internal stress in the plate when the beam has deflection deformation.This paper mainly does the following work:1)due to the change of use of the structure,the safety of the structure under 3kn/m2 load is judged by load test.The deflection and crack development of the structure are measured and the safety of the structure is judged by grading load;2)the design index of the structure is checked by PKPM software,and the calculated results are compared with the measured parameters;the influence of the effective section on the rigidity of the beam is studied and analyzed,and the corresponding rigidity reduction coefficient is taken,and the reduced rigidity of the beam is input through SAP2000,and the measured deflection and the calculated deflection are compared and analyzed;3)based on SAP2000 model analysis of the whole structure,the peak value of the slab internal stress of the floor member is analyzed under the condition that the beam has the same degree of deformation as the actual deflection of the structure;4)the simplified and extended analysis of the structure is carried out.The engineering model is simplified to a general single-layer 3 × 3-span and 4 × 4-span floor structure of the well shaped beam.The influence of the additional deformation of the RC well shaped floor covering beam on the internal stress of the slab under the influence factors of different spans,the size of the well shaped beam grid interval,the thickness of the floor,the side beam and the cross-section size of the well shaped beam is analyzed;The research results show that the structural design meets the requirements of the current design code,and the bearing capacity of the structure meets the design requirements.The reduction of the effective section caused by the surface shrinkage crack has little impact on the rigidity of the beam.Under the same deflection,the internal stress of the beam slab structure with a span of 9m is the minimum.When the deflection is 1.5 ‰,the internal stress of the slab is less than the standard value of its tensile strength,and the slab is in an uncracked state.When the structural plate thickness h＝L/30,the internal stress of the plate is the minimum.In 3 × 3 cross well floor structure,the critical cracking deflection is 1.58 ‰ when the plate thickness is L/30,and 1.78 ‰ when the plate thickness is L/30 in 4 × 4 cross well floor structure.When the section height of the side beam is L/10,the internal stress of the slab is relatively small.In the 3 × 3 cross well floor structure,the critical cracking deflection is 2.2 ‰ when the side beam is L/10,and 2.73 ‰ when the side beam is L/10 in the 4 × 4 cross well floor structure.When the cross-section height of the beam is L/17.5,the internal stress of the slab is relatively small.In the 3 × 3 span slab structure,the critical cracking deflection is 2.01 ‰ when the beam is L/17.5,and 2.78 ‰ when the beam is L/17.5 in the 4× 4 span slab structure.