Seismic Behavior Of Connection Research Articles

Seismic behaviour of connections between replaceable coupling beam and double skin composite shear wall

In order to optimize the performance of hybrid coupled wall system, a novel of connections between replaceable coupling beam (RCB) and double skin composite shear walls (DSCSWs) are proposed. The seismic design of RCB-to-DSCSW connection is very important for structural safety. This study investigates the seismic behaviour of RCB-to-DSCSW connections. Two specimens with different layout schemes of embedded rebars and one with embedded steel I-beam were subjected to reversed cyclic loading. The failure process of all the specimens was basically the same, mainly by steel faceplate local buckling, weld tensile fracturing and the concrete crushing at both ends of the joint. The strength and ductility of connections were highly affected by the weld tensile fracturing and concrete crushing. At the current loading level or the next loading level of weld tensile fractured, the connection specimens reached its peak loading capacity, and then the concrete rapidly crushed. The ductility coefficients of all the specimens were smaller than those of RC structures. In addition, the mechanical properties of these two kinds of embedded rebar connections were similar. The steel I-beam connection exhibited higher initial stiffness. Under the same rotation of loading, the cumulative energy consumption of the steel beam was higher. Finally, according to the stress pattern of each component, the simplified mechanical model and calculation formulae of the connection bearing capacity were developed.

Seismic performance of TFOSBs bolted endplate connection to CFSST with repaired threaded holes

This paper evaluates the seismic behavior of short thread-fixed one-sided bolts (TFOSBs) bolted connection of an I-section beam to concrete-filled square steel tube (CFSST) with repaired threaded holes by enlarging threaded holes through cyclic tests. The parameters investigated were endplate thickness, inner stiffener type, thread anchored length and bolt installation sequence. The test results are presented in terms of strength, rigidity, ductility and energy dissipation capacity. Based on the experimental results: 1) the failure modes of the connections with repaired threaded holes by enlarging threaded holes were similar to the failure modes of the connections having intact hole threads; 2) the connections with repaired threaded holes exhibited 1.8% ∼ 23.8% higher ductility and 3.9% ∼ 46.6% higher energy dissipation capacity compared with the connections having intact hole threads, and the ultimate bearing capacity of those two types of joints were comparable; and 3) the bolt installation sequence has a negligible influence on the failure modes and seismic behavior of connections with repaired threaded holes. In addition, the existing calculation methods of yield moment capacity for TFOSBs bolted endplate connections under various failure modes were still suitable for connections with repaired threaded holes, and the theoretical values and test results were well-matched with errors no greater than 15%.

Experimental and theoretical study on seismic behavior of connection between prefabricated steel-reinforced concrete column and base

This paper presents the seismic behavior of the prefabricated steel-reinforced concrete (PSRC) column. An experimental program was first performed on five full-scale specimens, varying by axial compression ratio (n) and shear span ratio (λ). Finite element analysis program was then carried out to calibrate the accuracy of the FEA models. Both experimental and numerical results revealed that PSRC column exhibited high energy dissipation and good plastic deformation. The calculational method to assess the bearing capacity of PSRC column was proposed and provided a reference for the actual engineering design and application of the PSRC column.

Seismic behavior of connections between H-beams and L-shaped column composed of concrete-filled steel tube mono-columns connected by double vertical plates

L-shaped column composed of concrete-filled steel tube mono-columns connected by double vertical plates (LCFST-D) is widely used in high-rise buildings because it can be embedded into walls and is flexible for architectural design. Due to the asymmetrical cross-section of the LCFST-D, the traditional form of one side of the H-beam and LCFST-D connection is the widen-flange plate joint and other sides are vertical stiffener joints. However, the strength and stiffness of the former are relatively low. Thus, in this study, the π-shaped joint was introduced to make the flexural capacity of both sides of the connection are close. Five full-scale specimens were casted for pseudo-static tests, and finite element models (FEM) calculation by Abaqus was introduced to provide a supplementary calculation. The results showed that the whole connection had a good seismic performance. The strength and stiffness of the vertical stiffener joint and the π-shaped joint were closed. Subsequently, parameter analysis was performed for further study of the factors of the flexural capacity. Finally, the calculation formulas for the flexural strength of the connection were derived, and the formulas of the shear strength were quoted. The calculation results were conservative and the errors were acceptable, thus, these calculation methods could be used in actual projects.

Study on the seismic behavior of connection via welding strengthening under load

This study proposed a reinforced connection with an outer annular stiffener for square hollow section (SHS) columns and H–beams. Low-cyclic-load tests were designed for three strengthening specimens and one common specimen. The verified finite element model was used to study the impact of the welding thermal effect, axial compression ratio, and vertical stiffener size on the seismic performance of joints. The results showed that joints reinforced with an outer annular stiffener for SHS columns and H–beams can effectively transfer loads. Compared to common joints, their moment resistance increased by 75%–113%, the energy dissipation coefficient increased by 5.5%–20.4%, and the moment resistance of the strengthened joints was significantly different in the positive and negative directions. In the process of welding strengthening, the influence of the welding thermal effect can be ignored. When the axial compression ratio was greater than 0.7, the moment resistance decreased by more than 14%. The strengthening was optimal when the vertical stiffener thickness was not less than 40% of the column wall thickness or 6 mm, the enlarged flange connection plate was completely wrapped, and the lap length was within 10–20 mm of the upper and lower steel angles

Experimental investigation of seismic behavior of UHPC-filled socket precast bridge column-foundation connection with shear keys

Accelerated bridge construction (ABC) has been paid great attention in China for the significant advantages compared with cast-in-place (CIP), such as higher construction speed, less environmental impact and structural members of higher quality. However, the reliability, durability and seismic behavior of the connection between prefabricated bridge column and the rest of the structure are primary factors that limit the application of the ABC in the moderate and high seismic zones. In this study, quasi-static experimental investigation of seismic performance of three 1:3-scale ultra-high performance concrete (UHPC)-filled socket reinforced concrete (RC) column-foundation connection specimens were conducted. A fiber-based finite element model is developed considering the rotation effect of the column embedded in the footing. The seismic behavior of the precast column specimens with UHPC-filled socket connection type was compared with that of CIP specimen. The experimental and numerical results show that the damage evolution, failure modes and hysteretic responses of the precast bridge column are equivalent with those of the CIP bridge column. Numerical analysis also validated that the finite element model(FEM) in this paper is adequate to predict seismic response of the precast column with UHPC-filled socket connection. The UHPC-filled socket connection is a reliable connection type in prefabricated column-foundation connection joint which is suitable for moderate and high seismic regions.

Experimental tests of precast reinforced concrete beam-column connections

In the reinforced concrete (RC) precast industry there is great concern about the seismic behavior of connections that emulate monolithic ones. Therefore, an experimental program was developed to examine the seismic performance of a particular RC precast connection type frequently used in industrial applications in comparison to monolithic connections. Tests were conducted on full scale. This paper presents and discusses the main results. Comparisons of a benchmark monolithic connection and six precast beam-column joints are presented. Precast connections were fabricated using different detailing, various levels of joint confinement, and post-tensioning. Test results are compared in terms of strength and deformation capacity, energy dissipation, and stiffness degradation. A relation between effective beam stiffness and inter-storey drift is found and compared to cracked stiffness modification factors recommended by design codes. Two effective stiffness models for reinforced concrete beams are proposed. Conclusions relevant to the precast construction industry have been formulated. Results show an acceptable performance of the tested precast system for seismic applications.

Seismic behaviour of connections between prefabricated RC flat slabs and square steel tube columns

Reinforced concrete (RC) flat slab column structure is a typical vertical support system and is often used in regions of moderate seismicity. Additionally, a steel structure is easy to assemble and exhibits good mechanical property, ductility and energy dissipation performance. Thus, this study presents a new type of connection between a prefabricated RC flat slab and square steel tube column. The connection effectively improves seismic performance and stress mechanism and leads to plastic deformation in the cantilever beams that can be replaced after an earthquake. The connection consists of a column base with four cantilever beams, a channel steel connection, and an RC flat slab. A gap connected by four square crossing I-steel cantilever beams is left between the column and channel steel connection, and this forms an opening around the column. An experiment was performed to study the seismic behaviour of the prefabricated slab column connection. The effects of the key parameters including the I-steel web thickness of the cantilever beam and axial compression ratio were investigated. The failure modes, hysteretic curves, and stress–strain curves with respect to relevant components were presented. A numerical simulation verified by the tests was performed to analyse the section stress and bolt forces for making up the test deficiency. The results indicated that the prefabricated slab column connection exhibits a superior seismic performance, thereby leading to earthquake-resilience. Finally, design considerations were presented to guide engineering practice for the proposed prefabricated slab column connection.

Study on Seismic Behavior of Vertical Connection in Prefabricated Reinforced Concrete Structures

The paper attempts to research the seismic behavior and mechanical mechanisms under repeated low-cycle loading of vertical connections in prefabricated reinforced concrete structures. Eighteen specimens were designed and tested, the test process and the mechanical mechanisms are studied, the seismic behavior of connections is analyzed, and the shear resistance formulas are proposed. The theoretical values based on proposed formulas are good agreement with test results. Under repeated loading, the shear resistance decreases, the connection ductility increases with connecting bar, but decreases with connection width. However, all the connections fail crisply with poor ductility. At sudden-cracking, the shear resistance increases with connecting bar, but changes nonlinearly with connection width. The resistance is composed of attributions of mechanism of diagonal-compressive column (MDCC) and mechanism of compressive friction action (MCFA). After sudden-cracking, the shear resistance is provided by weakened MDCC and dowel action of connecting bars (DACB). It increases with connecting bar and connection width.

Parametric Analysis on Seismic Behavior of Connections to Concrete-Filled Square Steel Tubular Columns with Three Edges Welded Interior Diaphragm

In order to further understand the seismic behavior of connections to concrete-filled square steel tubular columns with three edges welded interior diaphragm, basic sample and corresponding finite element models are constructed and analyzed according to criterion; furthermore influences on seismic behavior of such connections from many factors such as axial load ratio, height of steel beam, strength of steel beam and interior diaphragm and so on are studied. Results show that the base sample has excellent seismic behavior; such factors as axial load ratio, height of steel beam, strength of steel beam and interior diaphragm have great influence on seismic behavior. Therefore, the feasibility of such connections at edge columns and corner columns is further validated.

Seismic behavior of steel reinforced ultra high strength concrete column and reinforced concrete beam connection

To investigate the seismic behavior of connections composed of steel reinforced ultra high strength concrete (SRUHSC) column and reinforced concrete (RC) beam, six interior strong-column-weak-beam connection specimens were tested subjected to reversal cyclic load. Effects of applied axial load ratio and volumetric stirrup ratio on ductility, energy dissipation capacity, strength degradation and rigidity degradation were discussed. It was found that all connection specimens failed in bending in a ductile manner with a beam plastic hinge. The ductility and energy dissipation capacity increased with the decrease of applied axial load ratio or increase of volumetric stirrup ratio. The displacement ductility coefficient and equivalent damping coefficient lay between those of steel reinforced ordinary concrete connection and those of reinforced concrete connection. The applied axial load ratio and volumetric stirrup ratio had less influence on the strength degradation and more influence on the stiffness degradation. The stiffness degraded sharply with the decrease of volumetric stirrup ratio or increase of applied axial load ratio. The experimental results indicate that SRUHSC column and RC beam connection exhibited better seismic performance and can provide reference for engineering application.