BALANCED VECTOR BASED GENERALIZED PLASTIC HINGE METHOD FOR ULTIMATE BEARING CAPACITY OF FRAME STRUCTURES

Generalized plastic hinge method can maintain the proportional characteristics of traditional plastic hinge method and obtain the ultimate bearing capacity of frame structures efficiently, which overcomes the limitations of the traditional plastic hinge method and the refined plastic hinge method. However, the effect of axial force increment of the formed plastic hinges on the structure equilibrium state is not considered, which affects the calculation accuracy of the ultimate bearing capacity of partial frame structures. Therefore, the generalized plastic hinge method was modified according to the balanced vector presented, which eliminated the negative influence of the unbalance state caused by axial force increment on the calculation accuracy. Based on the modified section strength of each component under the action of multiple internal forces determined by the strength reduced factor, the element bearing ratio was defined by the homogeneous generalized yield function. The position and load increment of the new plastic hinge were determined according to the maximum element bearing ratio and its proportional relation with external load. Additionally, the balanced vector was established by using the generalized yield criterion and the slope-deflection equation; according to which the position of plastic hinge and load increment of the current loading step were modified. A comparison of different methods verified that the proposed method was much more efficient and accurate.