Search

In order to investigate the effects of steel fiber, polyvinyl alcohol (PVA) fiber and mineral powder contnet on permeability resistance of steel-PVA hybrid fiber high performance concrete (HFHPC). The orthogonal experiment was designed to conduct the permeability resistance test of steel-PVA HFHPC, and the test results were analyzed through range analysis, variance analysis and regression analysis. The results show that the influence degree on the impermeability of HFHPC is steel fiber, mineral powder and PVA fiber from high to low. In the range of test level, the optimal horizontal combination of impermeability of concrete specimens is as follows: steel fiber volume fraction of 1.0%, PVA fiber volume fraction of 0.7% and slag powder mass replacement rate 20% . When the steel fiber volume fraction exceeds 1.0%, the impermeability of HFHPC decreases slightly, but it is still higher than that of standard plain concrete. Finally, multiple regression analysis is used to establish the prediction model of HFHPC permeability and steel fiber, PVA fiber and mineral powder. [ABSTRACT FROM AUTHOR]

The influence of various seismic parameters on the seismic performance of rectangular reinforced recycled concrete columns was comprehensively revealed through collecting and screening experimental data from 53 rectangular recycled aggregate concrete columns. The research results showed that the bearing capacity of the specimens decreased and the ductility performance increased, which were attributed to the following factors. a. The increase in the replacement ratio and slenderness ratio of recycled coarse aggregate, and b. the reduction in the axial compression ratio and the strength of recycled aggregate concrete. The seismic design limitations and boundary conditions of this study are γ ∈ [0, 100%], n0 ∈ [0, 0.9], λ0 ∈ [5.06, 18.479], λ ∈ [1.09, 3.93], ρsl ∈ [1.01%, 2.45%], ρsv ∈ [1.4%, 5.33%], and f ∈ [C30, C50]. Thus, it is recommended that for the seismic design value of rectangular recycled aggregate concrete columns, the optimal longitudinal reinforcement rate be set at 1.59%. [ABSTRACT FROM AUTHOR]

Carbon fiber reinforced polymer (CFRP) materials are important reinforcing substances which are widely used in the shear strengthening of seismic-damage steel reinforced concrete (SRC) frame structures. To investigate the shear strength of SRC frame columns strengthened with CFRP sheets, experimental observations on eight seismic-damaged SRC frame columns strengthened with CFRP sheets were conducted at Yangtze University and existing experimental data of 49 SRC columns are presented. Based on the existing experiments, the theories of damage degree, zoning analysis of concrete, and strengthening material of the column are adopted. To present the expression formula of the shear strength of SRC frame columns strengthened with CFRP sheets, the contributions of strengthening material and transverse reinforcement to shear strength in the truss model are considered, based on the truss-arch model. The contribution of arch action is also considered through the analysis of the whole concrete and that of the three zones of the concrete are also considered. The formula is verified, and the calculated results are found to match well with the experimental results. Results indicate that the proposed whole analysis model can improve the accuracy of shear strength predictions of shear seismic-damaged SRC frame columns reinforced with CFRP sheets. [ABSTRACT FROM AUTHOR]

• Influence of damage degrees and confinement materials on seismic behavior of joints. • FE models of strengthened joints are calibrated with test results. • The predicted models of the shear capacity are good agreement with test results. • The results provide useful information for the engineering application. The seismic behavior of reinforced concrete (RC) beam-steel-reinforced concrete (SRC) column composite joints strengthened with carbon fiber-reinforced polymer (CFRP) sheets and enveloped steel jackets (ESJ) was investigated. Based on the existing regulations, nine specimens were designed and built to simulate pre-damage loading, rehabilitation with CFRP sheets or ESJ, and destruction tests under lateral cyclic loading to determine the performance of the two reinforcement materials (CFRP sheets and ESJ) for different degrees of seismic damage. An analysis of the hysteretic curves, skeleton curves, ductility, energy dissipation, bearing capacity degradation, stiffness degradation, and strain-displacement curves of the specimens indicated that the two strengthening materials exhibited good reinforcement performance. The ESJ improved the bearing capacity and stiffness of the specimens and the CFRP sheets improved the ductility and energy dissipation of the specimens, thereby improving the seismic behavior of the specimens. The severely damaged specimen strengthened with the CFRP sheets or ESJ did not collapse in a simulated strong earthquake and was similar to or even exceeded the seismic performance of the original specimen; this result is important and applicable to engineering practice. The ductility and energy dissipation was lower for the ESJ-strengthened specimen than the CFRP-strengthened specimen. Therefore, the ESJ material is preferable when only one type of material is used for strengthening the specimen. The seismic performance of the RC beam-SRC column frame joints strengthened with the CFRP sheets and ESJ was simulated using the finite element analysis software ABAQUS. There was a good agreement between the simulation results and the experimental results. It was proved that the simulated and experimental results of the ultimate bearing capacity of the joints in the core zones were in good agreement, which meets the design principle of "strong joint, weak member". [ABSTRACT FROM AUTHOR]

Concrete-filled steel tubular columns have been studied extensively worldwide. Such columns provide stable energy dissipation, which is ideal for earthquake engineering application. However, most applications use rectangular steel tubular sections. In the location of wall intersections, these sections often create sharp corners, which are architecturally displeasing. In some facilities such as schools and correctional facilities, sharp corners are even prohibited due to their potential hazard to occupants. To resolve the issue, concrete-filled crisscross steel tubular columns (CCSTCs) have been proposed. Three half-scaled specimens were constructed and tested under cyclic displacement loading history. The experimental results were used to calibrate numerical models of the components and further used to examine the seismic behavior of a three-story prototype office building located in Los Angeles. The results showed the proposed CCSTC has excellent energy dissipation and postearthquake performance, and hence it can be used as an alternative lateral force resisting system for seismic applications. [ABSTRACT FROM AUTHOR]