Abstract:The deflection value of the gantry crane girder is the most important inspection index in the overall test under rated loadFor the overall test of large tonnage gantry crane,the preparation of the experimental weight at the site is often very difficult,or even the overall test is impossible to performConsidering the effects of the leg bending moment on the girder deflection,the girder deflection curve equation of hinged gantry structure was deduced when the concentrated load was applied to the position of the girder midspanThrough measuring the girder deflection values when exerting three small loads at the girder midspan,the coefficients of gantry frame girder flexural equation were obtained,and the deflection of the large tonnage gantry crane was predictedThe three small loads method provides a practical and effective method for the prediction of the girder deflection of large tonnage gantry structure.