A Review-Behavior of Reinforced Concrete Exterior Beam-Column Connections under Cyclic Loading

In many seismically active regions worldwide, massive reinforced concrete (RC) structures built before the 1970s existed. These older RC buildings, in countries having seismic history, were designed for gravity loads only. Anyway, the beam-column connections influence the structures where the functions of connection shortage by transport the forces like shear, moment, and torsion through the beam to the column. Also, it could behave in a ductile manner to help the structure resist the seismic, as simulate the seismic loading by high and low cyclic loading. Due to the failure of external joints more than the internal beam-column joints, this review focuses on the behavior of exterior beam-column joints under cyclic loading, consequently simulated the behavior under an earthquake and the reinforcement detailed.

Low-Cyclic Loading Tests of Self-Centering Variable Friction (SCVF) Brace

A novel assembled self-centering variable friction (SCVF) brace is proposed which is composed of an energy dissipation system, a self-centering system, and a set of force transmission devices. The hysteretic characteristics and energy dissipation of the SCVF brace with various parameters from low-cyclic loading tests are presented. A finite element model was constructed and tested under simulated examination for comparative analysis. The results indicate that the brace shows an atypical flag-type hysteresis curve. The SCVF brace showed its stable self-centering ability and dissipation energy capacity within the permitted axial deformation under different spring and friction plates. A larger deflection of the friction plate will make the variable friction of this SCVF brace more obvious. A higher friction coefficient will make the energy dissipation capacity of the SCVF brace stronger, but the actual friction coefficient will be lower than the design value after repeated cycles. The results of the fatigue tests showed that the energy dissipation system formed by the ceramic fiber friction blocks and the friction steel plates in the SCVF brace has a certain stability. The finite element simulation results are essentially consistent with the obtained test results, which is conducive to the use of finite element software for calculation and structural analysis in actual engineering design.

Experimental test for mechanical properties of new tenon composite wall using thermal self-insulation block

Concrete hollow blocks have the advantages of simplified construction, reduced construction time, and better thermal performance, and can thereby achieve energy conservation in building engineering and significantly improved thermal and mechanical performance. A new tenon composite block is presented to achieve better self-thermal insulation and mechanical performance by integrating thermal materials into blocks. The tenon composite block application requires satisfying mechanical and seismic performance. Therefore, to prove the mechanical and seismic performance of the tenon composite block, a low cyclic loading test was performed on two self-thermal insulation wall specimens: the tenon composite block and the “Martha” block (used as the comparison specimen). The crack distributions, failure modes, force–displacement data expressed using hysteresis and skeleton curves, mechanical parameters of strengths, displacements, ductility coefficients, stiffness degradations, and equivalent viscous damping coefficients of the two specimens were analyzed in the low cyclic loading test. By analyzing the specimen crack distributions and failure modes, the tenon composite block was proven capable of effectively connecting the heat insulation and loading bearing parts. The differences in the force–displacement data and the mechanical parameters between the tenon composite block and “Martha” block specimens, such as the higher strength and stiffness of the tenon composite block specimen and similar ductility performance with the widely applied “Martha” specimen, were mainly caused by the size differences between the tenon composite block and “Martha” specimens. Finally, suggestions for tenon composite block applications are proposed to overcome the limitations of the tenon composite block’s ability to consume seismic energy.

Experimental study on the seismic behavior of precast concrete column with grouted corrugated sleeves and debonded longitudinal reinforcements

The seismic performance and the influence of debonded longitudinal reinforcements at the footing on the precast concrete columns connected with the embedded grouted corrugated sleeve were investigated experimentally in this research. Low cyclic loading tests were carried out on eight bending columns and four shear columns, considering the designed parameters of the partial debonding of the longitudinal reinforcements above the column–foundation interface, the axial load index, and the strength of the stirrups. Experimental results indicate that the partial debonding of the longitudinal reinforcements heavily influenced the damage spreading of the bending columns, but does not affect the damages of the shear columns. Compared to the columns without debonded longitudinal reinforcements, the seismic behaviors in terms of the ductility and energy dissipation can be improved clearly by the partial debonding of the longitudinal reinforcements for bending columns, but there was no clear improvement for shear columns. In addition, with the decrease of the axial load index or the increase of the strength of the stirrups, the seismic behaviors of the precast columns with the partial debonding of the longitudinal reinforcements are improved largely.

Application of Energy-Based Damage Model to Simulate Ductile Fracture Under Cyclic Loading and Validation Against Piping System Test Data

In this paper, a method to predict ductile fracture under low cyclic loading condition is proposed. Then it is compared with test results of surface cracked pipes which is conducted by Battelle Institute. A&F nonlinear kinematic hardening model is adopted to describe material behavior under cyclic loading condition and energy-based damage model is applied to simulate ductile crack growth. The energy-based damaged model is depending on multi-axial fracture strain energy. To apply this model, two parameters should be determined from tensile and C(T) test results under monotonic loading condition. One is multi-axial fracture strain energy Wf and the other is critical damage value ωc. From the determined damaged model, it is enable to simulate surface cracked pipe tests under low cyclic loading condition.