Research On Strong Column-weak Beam Demand Coefficients Of RC Frame Structure Based On Preset Failure Mode

Seismic collapse capacity of the frame structure is closely related to failure mode, beam hinge failure mode and mixed hinge failure mode can guide the large The redistribution of internal force and energy consumption ability. the anti collapse ability is strong. It means the failure mode of beam hinge is relatively safe, This requires the actual bending capacity of column is greater than the bending capacity of beam. In Chinese Seismic Code, the fixed "strong column weak beam" coefficient is used for the same earthquake grade to guide the failure mode of beam hinge. Unfortunately, the Wenchuan earthquake failed to achieve the goal. although code(2010 edition) has improved the coefficient. Although the analysis shows that the effect has improved, column hinge still generated, Because of the internal force redistribution and the seismic structure measures, different height structure and different floors of the same structure have different "strong column weak beam " demand coefficient. "strong column weak beam" coefficient given by New Zealand standard vary with the structural period is more economical and reasonable. Therefore, to provide a reference for more reasonable varied "strong column weak beam" coefficient, It is necessary to study the distribution of "strong column weak beam" coefficient under the standard system of China,.In this paper, a series of typical plane frames located in different intensity region(7 degree 0.15 g area、8 degree 0.2g area and 8 degree 0.3g area), different height(5story、8story、10story and 13 story model) and different axial compression ratio(large axial compression ratio and small axial compression ratio) are design according to the current code. The "strong column weak beam" coefficient demand law is obtained by combining longitudinal reinforcements determineinternal by the force of column under the storng earthquake based on beam hinge failure mode and mixed hinge failure mode, and the column axial force under small earthquakes. Contrasting the change law with different structural parameters and failure mode, and compare with the current code value, Finally, there is a preliminary discussion on how the slab reinforced、the ground motion intensity and vertical ground motion influence the "strong column and weak beam" coefficient demand.Through the above work, the following conclusions are obtained:① "Strong column and weak beam" coefficient of side column in mixed hinge failure mode is greater than the beam hinge failure mode, the difference between two failure mode gradually decreases with the increase in the number of story.The difference of the upper floors is larger than the lower floors.② In each seismic area, the demand coefficient is different in different height models. The coefficient of the same intensity area have large scatter in the lower part of the structure, this shows that "Strong column and weak beam" demand coefficient have a relationship with the number of storys and axial compression ratio. The coefficient of high-story models is large, but reinforcement is smaller than detailing reintorcement, coefficient calculated by detailing reintorcement is larger than the coefficient calculated by calculation reinforcement.③ "Strong column and weak beam" demand coefficient of Low axial compression ratio model is larger than large axial pressure. In the same axial compression ratio, "Strong column and weak beam" demand coefficient increases along with the increase of the number of floors, coefficients have a relationship with the basic period which have same conclusion in New Zealand Norm.④ slab reinforcement、the ground motion intensity and vertical ground motion have a enhanced effect on the "strong column and weak beam" coefficient demand especially in the upper floors.