Design Theory And Methodology Based On The Seismic Damage Mechanism Control For Frame Structures Using FRC In The Expected Damage Position

One of the effective measures for seismic security of the structure is the damage mechanism control.The reinforced concrete?RC?frame structures are applied widely in multi-story and high-rise buildings.During earthquakes,the behaviors of RC frame structures are affected by various factors.The seismic damage mechanism,damage degree and seismic performance of the RC frame structures were controlled by using the fiber reinforced concrete?FRC?in the expected damage positions?the beam end and its flange slab,the column end and the joint?.On this basis,the seismic performances,the influence factors of damage mechanism control and the evaluation index of the frame structures,of which the FRC was used in the expected damage position,were investigated through test,simulation and mechanical analysis.The major achievements of the dissertation are as follows:?1?Quasi-static cyclic lateral tests were conducted on seven one-half scaled beam-column subassemblies with the flange slab and horizontal beam,six of which used FRC at the expected damage position,and one used normal RC completely.The seismic behaviors and the influencing factors of damage mechanism control were analyzed.It is found that,compared with the RC beam-column-slab subassemblies,the horizontal bearing capacity,deformability and energy dissipation capacity of the FRC beam-column-slab subassemblies were improved,as well as the damage tolerance.The subassemblies of which the FRC was used in the expected damage positions were prone to reach the“strong column–weak beam”damage mechanism.?2?The column-to-beam flexural strength ratio and the effective flange width are the controlling parameters of damage mechanism of the beam-column-slab subassemblies.They were investigated through the test and simulation.The results showed that the designed FRC beam-column-slab subassemblies which were equipped with 6 times the slab thickness flange widths on each side of the beam could reached the“strong column–weak beam”failure mechanism when the column-to-beam flexural strength ratio was 1.4.The subassemblies with a flange width of 8 times the slab thickness on each side of the beam reached the‘strong column–weak beam'failure mechanism whether the column-to-beam flexural strength ratio was 1.2 or 1.4.?3?The Bayesian parameter estimation was applied to predict the joint shear capacity.Mechanical analysis was conducted to establish the moment–curvature model of the beam end and column end.Based on the theoretical analysis and test data statistics,a complete model applicable to the FRC beam-column-slab subassemblies is proposed according to the stress characteristics of FRC beam-column-slab subassemblies and the strain-hardening behavior of FRC material.?3?In order to further realize the control of frame structures'damage mechanism,finite element analysis was used to investigate the influence factors and mechanism of damage mechanism of FRC space frame structures.21 space frame structures,using the FRC in the expected damage positions,were simulated to analysis the stress and strain distribution of reinforcement in beam,column and slab,as well as the influence of FRC material,column-to-beam flexural strength ratio,flange width and axial compression ratio on the damage mechanism and the contribution of slab reinforcement to the beam flexural capacity.By using the FRC material in the expected damage positions,the drift ratio of the beam longitudinal bars yielding decreased,and the yielding of column longitudinal bars and slab longitudinal bars was postponed,the range and the strain amplitude of the slab longitudinal bars which contribute to the beam flexural strength were also decreased.Thus the frame structures of which FRC was used in the expected damage positions were prone to“strong column-weak beam”mechanism.Along with the increasing of the column-to-beam flexural strength ratio and the effective flange width,the drift ratio of the beam longitudinal bars yielding decreased,and the yielding of column longitudinal bars and slab longitudinal bars was also postponed,and the strain amplitude of the slab longitudinal bars was decreased as well.But the range of the slab longitudinal bars which participated the beam bearing was little varied.The drift ratio of the beam longitudinal bars yielding also decreased along with the increasing of axial compression ratio,but the drift ratios of the column and slab bars increased with the increment of axial compression ratio when the ratio was less than 0.6.?5?The parameters,including drift,residual deformation and rotation of column section,were chosen as the damage indices.The damage limit values at each performance levels of the frame structures using the FRC in the expected damage position were based on the test data.The relation between the damage degree and the indices was investigated.The damage mechanism control was studied through the dynamic history analysis on 8 horizontal frame structures with slabs on both side of the longitudinal beam.When using the FRC material in the expected damage positions,both the damage degree of the whole structure and the element were lightened.And the occurrence of the plastic hinge on column was postponed.When the imputing seismic precautionary intensity reached 8,the FRC frame structures of which the column-to-beam flexural strength ratio was 1.2,with 8 times the slab thickness on each side of the beam,reached deformation limit of the 4^th performance level.When the rare earthquake of magnitude of 8 was inputted,the FRC frame structures could reach the deformation limit of the 5^th performance level.When the frequency earthquake of magnitude of 8 was inputted,the FRC frame structures could reach the deformation limit of the 1^th performance level.