Seismic Behavior of Top-weld Bottom-bolt Joints between CFST Columns and H-beams

In recent decades, connections between concrete-filled steel tubular columns (CFST) and H-steel beams have been well designed and implemented. However, owing to poor construction quality, brittle failure often occurs at weld seams. In this study, an innovative joint was developed to connect CFST columns and H-steel beams using a top-weld bottom-bolt (TWBB) connection to minimize the effect of welding quality on the seismic resistance of joints. Six specimens were designed for cycle-reversed loading tests to discuss the seismic performance of this joint. Four configurations, including different connection methods, beam heights, column forms, and stiffener thicknesses, were considered in the test. The impacts of different configuration forms on the failure mode, strength, stiffness, ductility, and energy dissipation of the specimens were evaluated. The test results demonstrated that the columns with or without concrete had a significant effect on the deformation capacity. However, a smaller effect was observed on other indicators. The replacement of the through-diaphragm and an increase in the beam height adversely influenced the ductility of the joint. Moreover, changing the stiffener thickness and using a full-bolted connection affected the failure mode. The joint type analyzed in this study satisfies the strong column–weak beam design criterion and the related seismic provisions.

Development and test of a self-centering fluidic viscous damper

This research presents a novel self-centering fluidic viscous damper that incorporates preloaded ring springs to offer self-centering capability and a fluidic viscous damper for energy dissipation. A full-scale self-centering fluidic viscous damper was developed and subjected to low-cyclic reversed loading tests. The test results show the self-centering fluidic viscous damper has both displacement-dependent and velocity-dependent hysteric responses with self-centering capability. Fatigue tests further show that the self-centering fluidic viscous damper maintains a stable hysteretic response under reversed loading. An analytical model and a numerical model are developed for the proposed self-centering fluidic viscous damper and analyzed. Comparisons of test results and the numerical and analytical models show similar hysteric responses, thereby validating the accuracy of the numerical and analytical models to simulate the behavior of the proposed damper.

Seismic performance of semi-tenon joints reinforced by steel angle in traditional timber buildings

This article presents an experimental and numerical study on seismic performance of semi-tenon joints reinforced by steel angle in traditional timber buildings. Five specimens with two different reinforced connections and one unreinforced connection subjected to low-cyclic reversed loading on the bending moment are examined. The unreinforced connection consists of left and right beams inserted into the column that has been used in setting up the mortise before assembly. The first type of reinforced connection is formed by bottom steel angles bolted to the column and jointed to the beam by means of bolts. The second type of reinforced connection is made up of top and bottom steel angles bolted to the column and connected to the beam relying on vertical and transverse bolts. Moreover, two reinforcement techniques aimed at enhancing the seismic performance of semi-tenon joints are investigated, including the change of steel angle limb length and the variation of steel angle limb thickness. The test setup, joint connection, reinforced conditions, and material properties are introduced through detailed account of the experimental results and observations. The key behavioral patterns are identified from the experiments and the main response characteristics such as hysteresis, stiffness, flexural capacity, energy dissipation, and the failure mechanism. This article demonstrates that the steel angle can enhance the flexural capacity of the semi-tenon joints significantly. Besides, the use of greater limb thickness steel angle is shown to be an effective detail for adequately increasing the flexural capacity and rotation stiffness of the joints. Finite element simulations of experiments are also conducted, together with a detailed description of the modeling methods, so as to gain further insight into the influence of various factors on the behavior of joints.

Experimental study and numerical simulation of reinforced concrete walls with lightened blocks connected with bolts

To verify the feasibility and mechanical properties of assembled composite walls, three assembled composite walls were designed. Two bolted connection specimens in horizontal joints were tested under low-cycle reversed loading and monotonic loading, respectively. Then, the failure mechanism, hysteretic behaviour, ductility, energy dissipation capacity, slip and stress distribution of the connectors were studied. A specimen with grouting sleeve connection was tested under low-cycle reversed loading as a contrast specimen. In addition, a specimen with bolted connection under monotonic loading was simulated by the finite element method to study the effects on structural performance of the connectors and walls. The results show that the bolted connection is feasible, and compared with the grouting sleeve connection, the bearing capacity of the bolted connection specimen decreases by 17%, the displacement ductility coefficient increases by 52% and the cumulative energy consumption increases by 62%. Slippage between the connectors and the wallboard occurs mainly between the yield point and the peak point of the specimens. With the increase in plate thickness, the bearing capacity and initial stiffness increased, but there was no obvious effect on the appearance of the slip section. The larger the bolt diameter, the later the slip section forms. However, the bolt diameter does not have an obvious effect on the bearing capacity of the specimens.