Numerical Simulation And Analysis On Shear Failure Of Prestressed Concrete Beams

There has been more than one hundred years for the research on shear behavior ofprestressed concrete Beams. However, in the operational phase, there will lead to structuralfailure because of the inclined section crack and the insufficiency shear bearing capacity ofthe inclined section.Now, no unified strength theories for rationally interpreting shearmechanisms have been obtained due to the complexity of shear mechanisms and themultiplicity of influencing factors. As a result, deep research of shear failure mechanisms andthe main factors influencing the shear failure is necessary. Based on this, in this paper,numerical simulation analysis and research have been done, just as follows:(1) Review several shear mechanisms which are higher approval at present. In addition,list several typical domestic and foreign design code about shear bearing capacity ofreinforced concrete structure and analyze these formulas and parameters.(2) Based on the orthogonal experiment design method, taking the shear span ratio,longitudinal reinforcement ratio and the bending angle of prestressed steel,design test beamsand find that the influence of shear span ratio against the shear bearing capacity is larger.With the increase of shear span ratio, shear bearing capacity decreases significantly. With theincrease of bending angle of prestressed steel, longitudinal preloading effect weakens. Ifcontinuing to increase the bending angle, the vertical component of the curve prestressed steelis increased. So that the shear bearing capacity will be increased. Besides, the increase oflongitudinal reinforcement ratio will increase the shear bearing capacity.(3) Study the method of creating prestressed steel such as equivalent load method, nodecoupling method, constrained equation method and entity segmentation method.Find thatentity segmentation method can effectively solve the problems of calculation convergence andthe great local stress caused by the tension forces of prestressed reinforcement. Thecalculation results of this paper also match the experimental values of reference [55].Comparing the simulation value with national design code value, learn that design codevalue is more close to the simulation calculation value when the shear span ratio is3.But atthis situation,the simulation beams will happen diagonal tension failure. So for practicalengineering, we should adjust the reinforcement ratio of the bridge to avoid diagonal tensionfailure. When the shear span ratio is2, the ratio of simulated value with national design codeis between1.54and1.91. So national design code actually reflect the shear capacity ofconcrete beam which happen the shear compression failure. The beams that the shear span ratio is small are prone to baroclinic destruction.The design code calculation value can notreflect the shear performance because it is smaller than actual value.(4) Because our country design code do not consider the influence of longitudinalreinforcement ratio and the predicted value is smaller than other countries design code,so thispaper put forward improvement opinions to the China design code.(5) Based on the research of the stirrups and the size of the prestressed steel,find thatunder a certain longitudinal reinforcement ratio and a certain bending angle of prestressedsteel, it can maximize the shear bearing capacity of the structure if the value of stirrups ratioand the size of the prestressed steel is reasonable.