To promote greater acceptance and use of composite RCS systems, a two-bay two-story frame specimen with improved composite RCS joint details was tested in the laboratory under reversed cyclic loading. The test revealed superior seismic performance with stable load versus story drift response and excellent deformation capacity for an inter-story drift ratio up to 1/25. It was found that the failure process of the frame meets the strong-column weak-beam criterion. Furthermore, cracking inter-story drift ratio and ultimate inter-story drift ratio both satisfy the limitation prescribed by the design code. Additionally, inter-story drift ratios at yielding and peak load stage provide reference data for Performance-Based Seismic Design (PBSD) approaches for composite RCS frames. An advantage over conventional reinforced concrete and steel moment frame systems is that the displacement ductility coefficient of the RCS frame system is much larger. To conclude, the test results prove that composite RCS frame systems perform satisfactorily under simulated earthquake action, which further validates the reliability of this innovative system. Based on the test result, some suggestions are presented for the design of composite RCS frame systems.

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The procedure to obtain the inelastic demand curves for the multi-degree-of-freedom system, composed of inter-story shear versus inter-story displacement curve is introduced. The demand curves are established by using mode spectrum method, and the dynamical characteristic of structure under different earthquake hazard levels is taken into account. The relation of structure performance object and displacement ductility is adopted to deduce the relation of structure performance object and inter-story demand curve. Therefore, the inter-story demand curves take into account the inelastic behavior of structure under earthquake action adequately. Then, considering the seismic responding characteristic and the capacity curve of the frame structure, a new method named Inter-Story Capacity Spectrum (ISCS) is put forward for the performance-based seismic design of vertically irregular frame structures. Examples are presented to demonstrate the applicability and the utility of the proposed method. It is concluded that the new method can control the inter-story drift, the order and position of hinges of vertically irregular structures under different earthquake hazard levels. Comparing with time-history analysis method, it leans to safe and is superior to direct displacement-based design method.

Summary Application of recycled coarse aggregate concrete (RAC) will generate considerable environmental benefits. However, the properties of RAC must be studied before being adopted in structures. In this research, the failure process and damage assessment of RAC under compression were investigated by applying acoustic emission (AE) technology. The variables include loading rates, maximum coarse aggregate sizes, and water–cement ratios (w/c). Meanwhile, an innovative approach called stage cumulative proportion (SCP) analysis of AE result was put forward. Subsequently, the damage of RAC under compression was evaluated based on the rate process theory. The results demonstrated that void compaction and original crack expansion occurred first in the test and then the stable microcracking in interfacial transition zone (ITZ) and unstable cracking in mortar, and finally, there is the macrocrack expansion followed by the fracture. It was found that AE counts and energy were mainly produced before the peak stress was reached. The increase in loading rate caused the AE counts and energy to increase in stable microcracking of ITZ but decreased in unstable cracking of mortar. Increasing the w/c would also affect the AE results in these stages, but the effect was the opposite to the loading rate. Besides, an increase in coarse aggregate sizes would increase the AE counts and energy in unstable cracking of mortar and decrease in macrocrack expansion. In addition, a polynomial expression of the relationship between AE parameters and stress level was established. Then, an evaluation criterion was proposed based on the expressions and the rate process theory.

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The box-plate steel structure residence is a box structure with stiffened steel plates directly used as load-bearing walls and floors. In practical engineering, due to the functional requirements of the building, it is necessary to open door or window openings on the box-plate steel structure walls. To study the seismic performance of the box-plate steel structure with openings system, two three-story single-compartment box-plate steel structures with openings modular units were designed and fabricated according to the 1:3 reduced scale. Through the quasi-static loading test, numerical simulation, and theoretical analysis, the failure process, failure mode, lateral force resistant capacity, and hysteresis performance of the specimens were studied. The impact of the different opening areas and opening position on the seismic performance of the box-plate steel structure was emphatically analyzed. The results of the test indicated that the openings on the steel wall plate would reduce the initial stiffness and the lateral force resistant capacity of the specimen; the destruction of the box-plate steel structure with openings modular unit under the low cyclic loading effect started with the tear in the corner of the openings and ended with the tear in the corner steel wall plate. Then, the finite element analysis (FEA) models were developed to supplement the experimental study, and the comparisons were made between measured and simulated results on load versus displacement relationships and failure modes. On the basis of the stressing mechanism of the box-plate structure modular unit, the calculation equation of the lateral force resistant capacity of the box-plate structure with openings modular unit was put forward. Then, the proved finite element analysis (FEA) models were used for parameter analysis of different influence parameters to verify the proposed calculation equation. The results showed that the proposed calculation equation had high accuracy and could be used as a design basis for practical engineering.

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