| Infilled framework is one of the most widely used building structures in our country. Serious seismic damage of infilled frames in recent earthquake indicates that there is complicated interaction between the infill wall and frame, which influences the seismic behavior of structure significantly. Therefore, seismic design of infilled frame which does not consider the effect of infill wall cannot ensure the seismic behavior in earthquake. Under the background of performance-based seismic design, serious damage of infilled frames in Wenchuan earthquake and prohibitive use of clay bricks, research on working mechanism and performance-based seismic design of reinforced concrete (RC) frame infilled with new masonry was carried out in this paper, the following studies include:(1) Six one-storey, two-bay RC infilled frames were tested under cyclic loading to investigate the effects of masonry material and height-width ratio on the seismic behavior of specimens. The masonry material included concrete hollow blocks, aerated concrete block and solid clay bricks. The height-width ratio of infill wall varied from 1.5 to 2.0. Based on the test results, the damage characteristics, hysteretic curves, skeleton curves, displacement ductility, rigidity degradation, strength degradation and energy dissipation of the specimens were analyzed. The test results indicate that: Infill walls have strong stiffness effect on RC frames, and enhance the ultimate capacity and hysteretic energy-dissipating capacity of frames. Because the infill walls were damaged first, and the plastic hinges occurred at the end of column and beam, the five infilled frames meet the principle of"Strong frame and weak infill wall". Infilled frames should be designed as the type of"Strong frame and weak infill wall".(2) To the infilled frame meeting the principle of"Strong frame and weak infill wall", equivalent confined infill wall model was established. Based on the experiment results and theoretical analysis, restoring force model of equivalent confined infill wall was proposed, and the characteristic value of skeleton curve and hysteretic rule were presented. Then, the improved equivalent slant strut model was set up, and the width of equivalent slant strut and the transformation formula of restoring force model between equivalent confined infill wall and improved equivalent slant strut were suggested. (3) Three one-storey, two-bay RC infilled frames were tested under cyclic loading to investigate the effects of infill walls, infilled configuration and slab on the seismic behavior of RC frame structures. In the three specimens, one frame was comparative specimen without infill walls, and the other two frames had infill walls with different configurations which were two bays infilled with half-height wall and only one bay infilled with all-height wall, respectively. The test results show that: Infill walls have strong stiffness effect and restraint effect on RC frames. The configuration of infill walls has great effect on the seismic behavior of frames, and would change the failure mode of frames. Because of restraint effect, half-height infill walls induce short column failure. And because of dilatancy effect, shear failure also occurred in those columns connected with all-height infill wall. Because the failure mode of all the columns connected with infill walls is shear failure, the two infilled frames meet the principle of"Weak frame and strong infill wall". Infilled frames cannot be designed as the type of"Weak frame and strong infill wall".Based on the different damage characteristics of two batches of infilled frames, the judgement for"strong frame and weak infill wall"and"weak frame and strong infill wall"of infilled frame was proposed, and the calculation formula of ultimate capacity were presented.(4) The method and the principles of elasto-plastic analysis of infilled frame structure based on fiber model with PERFORM-3D program were introduced in detail. Nonlinear hysteretic simulation of the first six infilled frames tested in this paper was made with PERFORM-3D program. The simulation results showed good agreement with the experimental results, and the restoring force model of equivalent confined infill wall can be used in elasto-plastic analysis of infilled frame structure in consideration of infill wall.(5) Elastic-plastic analysis method for seismic responses of infilled RC frame is studied. To research the effect of vertical configuration of infill wall on RC frame structure, push-over analysis of 4, 8, 12 storey RC infilled frame were carried out. Based on the calculation results, the period-reduction factor, bearing capacity, distribution of plastic hinge, performance point and displacement of infilled frames were investigated.
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