CALCULATION METHOD AND MODIFICATION OF SHEARING CAPACITY OF LIGHTWEIGHT AGGREGATE CONCRETE BEAMS UNDER CONCENTRATED LOAD

Different formulas have different ways to consider the factors of concrete strength, shear span ratio, reinforcement ratio and section size. Based on the test data of lightweight aggregate concrete (LAC) beams under concentrated load, the formula and model are compared and analyzed according to the method of variable separation. The results show that both the formulas (JGJ/T 12−2019, ACI 318-19, BS 8110:1997) and the models (Bazant-Sun, Kim-Park, Rebeiz, Vecchio-Collins) are not safe. According to the results, the influence of various factors on the shear capacity of LAC beams without web reinforcement is investigated. Referring to the form of Vecchio Collins model, the shear span ratio λ is introduced. With the cubic compressive strength as the representative value of various mechanical indexes of concrete in China, the nonlinear fitting of test data is carried out, and then the modified formula is put forward. The modified formula is checked from the aspects of crack width control and bearing capacity of beams with web reinforcement, and the results show that the modified formula can meet the requirements well. According to the design habit of China, the modified formula is converted into the form of design value expression, and according to the test parameter interval of the database, the corresponding provisions of material strength are made, so as to be used in engineering design.