Shear Capacity Model And Construction Error Analysis Of RC Beams With Large-Scale Rectangular Openings

In practice,it is possible to encounter situations where larger diameter equipment ducts(such as air conditioning ducts)pass through RC beams.However,beams with large openings may have different force mechanisms than beams with small ones.Statistically,the percentage of structural damage due to construction errors resulting in reduced structural performance is generally high.Therefore,it seems necessary to study the mechanical properties of RC beams with large openings in the abdomen,clarify their force mechanisms,analyze the stochastic response of various indices of RC beams with large openings under several common construction errors,and propose a more general design method.Based on static loading tests and a refined nonlinear numerical model,this paper presents a nonlinear analysis of the shear performance of RC large-opening beams and a stochastic analysis considering several common construction errors,accomplishing the following.(1)By testing eight RC simple supported beams under concentrated load,the effects of the horizontal position of the hole,the vertical position of the hole,chord hoop rate,and hole side hoop rate on the shear performance of RC beams with large openings were analyzed.The results show that the horizontal position of the hole has little effect on the shear bearing capacity of the beams with large openings where diagonal tensile damage at the hole angle occurs.The change of shear bearing capacity is also tiny when the holes are eccentric upward and downward by the same distance,respectively.(2)Based on 40 refined nonlinear finite element numerical models,the effects of hole geometry,hole location,chord hoop reinforcement,and hole side reinforcement on the shear performance of RC beams with large openings are analyzed for chord shear damage and hole side shear damage.The shear bearing capacity equation of RC beams with large openings in the abdomen is proposed,the effects of different reinforcement forms around the holes on the crack initiation and damage modes are compared,and the differences in shear damage mechanisms between RC beams with large openings and small openings are discussed and compared.The results show that the shear resistance mechanism of the trusses of RC beams with large holes in the web will fail,the hollow web effect becomes significant,and the upper and lower chords are regarded as independent member bars to transfer the load.As the length and height of the hole increase,the shear performance of RC beams with large openings gradually decreases,and the damage pattern gradually changes from hole-side shear damage to chord shear damage.(3)Using the Latin hypercube sampling technique and the sampling method based on the Sobol sequence,considering the construction errors such as hole length,hole height,concrete strength,and hoop spacing,random analyses were conducted for two different damage types of beams with large openings.The probabilistic statistical characteristics of crack width,deflection,and reinforcement strain at peak load and bearing capacity were analyzed.The results show that the indicators of bearing capacity,deflection,crack width,and steel strain of RC large-opening beams with two different damage types obey normal distribution.It is recommended that at least 10% redundancy be left when using the shear bearing capacity formula of RC beams with large openings proposed in this paper.