Research On Ultimate Bearing Capacity For Web Plates In I-girders Subjected To Patch Loading

In recent decades, more and more steel structures were used in buildings, bridges and hydraulic structures. Plate girders were extensively used in steel structures, because their cross-section can be self-selected according to design needs and they have many advantages which they do not suffer the restriction of profile steel specification, their manufacture is very easy, the costs are economical, the structures are reasonable and the applicability is powerful. Over the past few decades, many scholars have studied the ultimate bearing capacity of I-girder web subjected to patch loading, but their results are mainly for single-block rectangular flange plate, and are usually limited for the complex flange structure. Therefore, this paper aims to get a kind of calculation method of ultimate bearing capacity which can also be used for I-girder with complex flange.There are many factors that influence the ultimate bearing capacity of web subjected to patch loading, such as web geometry, flange restraints and material properties, etc. Firstly, this paper verified the feasibility by using ABAQUS software on the analysis of the problem, and the results show that ultimate bearing capacity which is calculated by ABAQUS is close to experimental data and the error is also under a reasonable limits. Based on the feasible analysis, hundreds of models with different sections and material strengths were analyzed by using nonlinear process. On the basis of the results, the influence of the constraint effect of upper and lower flange, material yield strength of web and flange and web height on the ultimate bearing capacity was analyzed. And the whole post-buckling process of web from initial state to failure was also simulated.The results show that, for slender plate girders, the influence of web height can be neglected; bottom flange have little impact on the ultimate bearing capacity; and the ultimate bearing force is proportional to 0.7 power of web yield strength. In addition, because the method using the flange width and thickness as parameters to calculate the ultimate bearing capacity has some limitations, this paper reoriented the influence parameters of flange as moment of inertia and the polar moment of inertia. Based on the nonlinear analysis of 80 numerical models, we summed up the influence of moment of inertia and polar moment of inertia and summarized a set of new methods of calculating the ultimate bearing capacity at the help of origin. An example analysis and error analysis revealed that, by comparing with traditional methods, results obtained by the above method are closer to the experimental data and more stable. More importantly, this method can be applied to I-girder with complex flange structures and expanded the range of use in greater degree, which has the good theoretical significance and engineering application value.