Weiming Yan

Experimental Investigation on the Seismic Performance of Large-Scale Interior Beam-Column Joints with Composite Slab

The experimental and analytical investigations carried out on large-scale interior precast beam to column joints with composite slab are presented in this paper. Four specimens were tested under reversed cyclic loading that simulated earthquake-type motions. The most relevant feature of the joint is that the beam reinforcement on the bottom was formed and installed with anchor head, rather than bent to form stand 90-degree hooks or closed loops. The performance of the precast concrete connection was compared with that of the monolithic connection, and the failure pattern, hysteretic characteristic, skeleton curve, displacement ductility and energy dissipation, were analyzed. The test results provided some information about the seismic behavior of the large-scale joint. In general, the performance of the joint was satisfactory. No bond problem and obvious pinching effect were observed in the test, and specimen behavior was ductile and joint strength was almost equal to that of monolithic reinforced concrete construction, however, the ductility of the specimens was affected by the ratio of column to beam flexural strength, and the scope of application was recommended.

Experimental study and analysis on the collapse behavior of an interior column in a steel structure under local fire

This article describes the experimental and analytical results of tests on two medium-scale steel frames to investigate the collapse behavior of a heated interior column in steel-framed structures and the fire-induced collapse mechanism of the structures. Because the heated column in the structure was under realistic inelastic end constraints (inelastic effects from the surrounding cool structures) as opposed to an idealized column in a furnace, the tests were designed to investigate the effect of inelastic end constraints and different load ratios. The interior column subjected to fire in the first story was connected with a force-measuring bearing, which was developed to measure the axial force in the heated column. This article presents the observations and analysis results of structural fire behavior, including the temperature distribution of the column, the development of deflection and axial forces, and the column failure modes. The results show that the effect of realistic inelastic end constraint is not significant for the column behavior during the pre-buckling stage, compared with the elastic constraint, but it is significant during the post-buckling stage. An analytical model was adopted to analyze the behavior of the column with inelastic end constraint under fire. Comparison of the theoretical and experimental results shows that the simplified analytical model can be used to predict the collapse behavior of the interior column in steel-framed structures under fire.

Experimental investigation of typical connections for fabricated cold-formed steel structures

This article presents a comparative investigation on mechanical behavior and construction characteristics of some typical connections in cold-formed thin-walled steel. The lap shear tests of 96 specimens considering four typical connections with a self-piercing rivet, clinching, self-drilling screw, and blind rivet were conducted. The effects of sheet thickness and thickness ratio on failure modes and mechanical behavior of the four types of connections were investigated. Through analyzing the feasibility of mechanic and construction, the applicability of the four types of connections in fabricated cold-formed steel structures was comprehensively evaluated. The result of the research shows that compared with the other three connections, self-piercing rivet connections are more suitable for modularly fabricated cold-formed steel structures because of its superior mechanical properties, well-formed quality, high efficiency, and potential industrialization. Based on the design methods of fasteners in North American (AISI S100-16) and European standards (prEN1999-1-4) on cold-formed steel structures, an appropriate design method is proposed for self-piercing riveting connections.

A novel energy dissipation outrigger system with rotational inertia damper

Rotational inertia damper, a novel damper, possessing the advantage of displacement amplification, has been employed in outrigger system for seismic mitigation. The equivalent analysis model composed by a uniform cantilever beam and an equivalent spring was proposed to simulate the rotational inertia damper outrigger system, by which the corresponding dynamic characteristic equation was derived based on numerical assembly technique. To gain the response of the damped system, finite element method and state space method have been utilized. Finally, the results show that the pseudo-undamped natural frequency ratios and system modal damping ratios are significantly influenced by stiffness parameter of the exterior column, while the mass parameter of the rotational inertia damper has little effect on them. The optimal damping ratio can be acquired for one mode, but it may be worse for the other mode in the same position equipping rotational inertia damper. Furthermore, numerical simulation results for the typical earthquake records have verified that the rotational inertia damper outrigger has excellent control performance in displacement as well as acceleration. A good agreement between damping force and equivalent force also suggests that the damping force of rotational inertia damper is predominant and the inertial force has no significant effect on the structure.

Mechanical performance of space sandwich joints under bidirectional cyclic loading

In high-rise buildings with high-strength concrete column and normal-strength concrete floor, the beams and slabs are usually cast in a continuous fashion through the beam–column joint to simplify construction, and this results in the lower strength concrete at the beam–column joint core (sandwich joint). It will influence the capacity of the joint. In this article, three groups of three-dimensional specimens consisting of sandwich joint specimens and corresponding traditional joint specimens were tested under bidirectional reversed cyclic loads to investigate seismic performance, including the failure mode, ductility, energy dissipation, and deformation. The test results show that the beam–column joint core can be cast with normal-strength concrete when the column concrete strength is less than 1.5 times that of the beam. However, when the ratio exceeds 1.5, the failure mode of the joint may change from beams flexural failure to joint shear failure and additional strengthening measures should be taken. Finally, the formula for calculating shear capacity of the three-dimensional sandwich joints is presented, and the predictions are compared to the experimental results.

Shear Strength Prediction of RC Beam-column Sandwich Interior Joints Based on Simplified Softened Strut-and- Tie

Due to the scarcity of rational models for predicting the strength of RC beam-column sandwich joints, a modified simplified softened strut-and-tie model suggests a more rational calculation method for the effective compressive strength and the height of the joint concrete based on the simplified softened strut-and-tie. The shear strength of existing tested 15 sandwich interior joints is calculated by using the modified simplified softened strut-and-tie model. Furthermore, the theory results are compared with those of the code method and those of the simplified softened strut-and-tie model.

Simplified Method for Critical Elastic Distortional Buckling of Cold-Formed Steel C and Z Sections:

The Direct Strength Method (DSM) is a recently adopted design approach by the North American Specifications for Cold-Formed Steel Structural Members (AISI S100) for calculating the nominal strength of cold-formed steel (CFS) sections. The critical elastic buckling load shall be obtained in order to employ the DSM in computing the nominal strength of CFS members. The AISI S100 provides simplified methods for determining the critical elastic distortional buckling load. However it is found that the AISI S100 simplified methods are over conservative for the industrial standard C and Z sections in the U.S. This paper presents revised simplified methods for calculating the critical elastic distortional buckling loads of typical CFS C and Z sections in bending and axial compression loading respectively. The new methods yield more accurate results but similar computation cost compared to the existing methods. The new methods can be added to the DSM methodologies for designing CFS members.