Finite-element analysis on beam–column joints with replaceable energy-dissipation plates

A finite element analysis (FEA) model is established to investigate the concrete-encased concrete-filled steel tubular (CFST) column to reinforced concrete (RC) beam joints under cyclic loading. The feasibility of the FEA model is verified by a set of test results, consisting of the failure modes, the exposed view of connections, the crack distributions and development, and the hysteretic relationships. The full-range analysis is conducted to investigate the stress and strain development process in the composite joint by using this FEA model. The internal force distributions of different components, as well as the deformation distributions, are analyzed under different failure modes. The proposed connections are investigated under dimensional and material parameters, and the proper constructional details of the connections are recommended. Parameters of the beam-column joints, including material strength, confinement factor, reinforcement ratio, diameter of steel tube to sectional width ratio, beam to column linear bending stiffness ratio and beam shear span ratio are evaluated. Furthermore, the key parameters affecting the failure modes and the corresponding parameters ranges are proposed in this paper.

A new seismic energy dissipation shear wall structure is proposed in this paper. The new shear wall is one with purposely built-in vertical slits within the wall panel, and rubber belts as seismic energy dissipation devices are installed in the vertical slits. In order to verify this concept, shaking table tests of a 10-storey shear wall model with rubber belts filled in the vertical slits were carried out, and comparison of seismic behaviour was made between the new shear wall system and a shear wall with reinforced concrete connecting beams as energy dissipation. Furthermore, the seismic behaviour of this new shear wall is analysed by a finite element time history analysis method. The test and analysis show that the new shear wall system has a very good ability to dissipate seismic energy and is easy to use in engineering practice. Copyright © 2000 John Wiley & Sons, Ltd.

Cyclic behavior of interior RC beam-column joints strengthened with NSM-CFRP ropes

Shear strength of beam–column joint with enlarged joint area

The work presented in this study aimed to investigate the hysteretic behavior of composite partially restrained (PR) steel frame-reinforced concrete infill walls (PSRCW) with vertical slits, which consisted of a PR steel frame, a slit-reinforced concrete (RC) infill wall, and shear connectors. An experimental program at one-third scale of a one-bay by three-story PSRCW with vertical slits was tested under horizontal cyclic loading. The seismic behavior was examined in terms of the lateral load-carrying capacity, ductility, deformability, lateral stiffness, and energy dissipation. The results showed that this kind of structure exhibited superior ductility and deformability, as well as excellent energy-dissipation capacity. The slit RC infill walls exhibited flexure-dominated behavior and significantly increased the lateral load-carrying capacity. In contrast, the slit RC infill walls decreased the rotation demand on the PR connections from earthquake, which avoided the fracture failure of the beam-to-column connection. Additionally, the test results were verified, and relative parametric analyses of PSRCW with vertical slits were conducted by using a simplified macro fiber model to illustrate the factors that influence the structural hysteretic behavior.

A representative and most commonly used ballistic target system consisting of a 93W ball and Q235 steel plate is investigated for its ballistic limit fast calculation engineering model. The basic data on the material of the projectile target system was obtained through quasi-static compression tests on the mechanical properties of 93W ball and Q235 steel plate materials. Using a Φ12.7mm ballistic gun and the ten shot v50 ballistic limit method, tests were carried out with 93W balls positively penetrating Q235 steel target plates and v 50 was obtained for 3g of 93W balls penetrating 6mm and 8mm thick Q235 steel plates respectively. Based on the Autodyn platform, a numerical simulation model of a 93W ball intruding through a Q235 steel target plate was established and the accuracy of the simulation model was verified using test data. On this basis, the range was extended to obtain v 50 for a total of 34 working conditions with 93W ball masses between 1 and 6g and Q235 steel target plate thicknesses between 2 and 12mm, and the v 50 engineering calculation model for 93W ball intrusion into Q235 steel plate was obtained by multiple linear regression. Comparative analysis with other representative v 50 engineering models shows that the resulting v 50 calculation model has a greater range of applicable speeds, higher accuracy and greater practicality. The results of the research can provide basic methods and tools for the design of warhead power, target protection, and the assessment of the destructive effectiveness of weapons and ammunition.

This investigation aimed to determine the optimum percentage of crumb rubber (CR) in self-consolidating concrete (SCC) to enhance the structural behaviour of beam–column joints under reverse cyclic loading. The investigated mixtures were developed with percentages of CR ranging from 0% to 25%. The beam–column joint contained 2% flexural reinforcement and 0·6% shear reinforcement. The structural behaviour of the tested beam–column joints was evaluated based on load deflection, initial stiffness, rate of stiffness degradation, failure mode, cracking behaviour, displacement ductility, brittleness index, energy dissipation, first crack load and load-carrying capacity. The results indicated that the optimum percentage of CR to be used in beam–column joint mixtures is 15%. Although using this percentage slightly reduced the load-carrying capacity, it greatly enhanced the ductility, brittleness index, deformability and energy dissipation. The results also showed that further increase in the percentage of CR (above 15%) changed the failure mode of the tested specimens and limited the deformation capacity, which negatively affected the ductility, brittleness index and energy dissipation.

Online test of building frame with slit-wall dampers capable of condition assessment

Ductile structures have demonstrated the ability to withstand increased seismic intensity levels. Additionally, these structures can be restored to their operational state promptly following the replacement of damaged components post-earthquake. This capability has been a subject of considerable interest and focus in recent years. The study presented in this paper introduces an innovative beam-column connection that incorporates V-shaped steel as the replaceable energy-dissipating component. It delineates the structural configuration and design principles of this joint. Furthermore, the paper conducts a detailed analysis of the joint’s failure mode, stress distribution, and strain patterns using ABAQUS 2022 finite element software, thereby elucidating the failure mechanisms, load transfer pathways, and energy dissipation characteristics of the joint. In addition, the study investigates the impact of critical design parameters, including the strength, thickness, and weakening dimensions of the dog-bone energy-dissipating section, as well as the strength and thickness of the V-shaped plate, on the seismic behavior of the beam-column joint. The outcomes demonstrate that the incorporation of V-shaped steel with a configurable replaceable energy-dissipating component into the traditional dog-bone replaceable joint significantly improves the out-of-plane stability. Concurrently, the V-shaped steel undergoes a process of gradual flattening under load, which allows for a larger degree of deformation. In conclusion, the innovative joint design exhibits superior ductility and load-bearing capacity when contrasted with the conventional replaceable dog-bone energy-dissipating section joint. The joint’s equivalent viscous damping coefficient, ranging between 0.252 and 0.331, demonstrates its robust energy dissipation properties. The parametric analysis results indicate that the LY160 and Q235 steel grades are recommended for the dog-bone connector and V-shaped steel connector, respectively. The optimal thickness ranges are 6–10 mm for the dog-bone connector and 2–4 mm for the V-shaped steel connector, while the weakened dimension should preferably be selected within 15–20 mm.

Integration of FRP sheet as internal reinforcement in reinforced concrete beam-column joints exposed to sulfate damaged

This paper aims to investigate the seismic performance of the prestressed steel strips retrofitted RC beam-column joints. Two series of joint specimens were conducted under compression load and reversed cyclic loading through quasi-static tests. Based on the test results, the seismic behavior of the strengthened joints specimens in terms of the failure modes, hysteresis response, bearing capacity, ductility, stiffness degradation, energy dissipation performance and damage level were focused. Moreover, the effects of the amount of the prestressed steel strips and the axial compression ratio on seismic performance of retrofitted specimens were analyzed. It was shown that the prestressed steel strips retrofitting method could significantly improve the seismic behavior of the RC joint because of the large confinement provided by prestressed steel strips in beamcolumn joints. The decrease of the spacing and the increase of the layer number of the prestressed steel strips could result in a better seismic performance of the retrofitted joint specimens. Moreover, increasing the axial compression ration could enhance the peak load, stiffness and the energy performance of the joint specimens. Furthermore, by comparison with the specimens reinforced with CFRP sheets, the specimens reinforced with prestressed steel strips was slightly better in seismic performance and cost-saving in material and labor. Therefore, this prestressed steel strips retrofitting method is quite helpful to enhance the seismic behavior of the RC beam-column joints with reducing the cost and engineering time.

ABSTRACTIn this paper, five shear wall specimens were fabricated and tested under cyclic loading, including one conventional low‐rise shear wall, one conventional shear wall with vertical slits, two low‐rise shear walls with different amount of X‐shaped vertical steel band, and one low‐rise shear wall with X‐shaped vertical steel and lead composite energy dissipation band. The failure characteristics, hysteretic performance, strength, deformation, energy dissipation capacity, stiffness, and strain characteristics were studied. The results showed that the low‐rise shear walls with energy dissipating band exhibited a transition in failure mode from the shear failure of the conventional wall to bending failure. The strength of the shear wall with vertical energy dissipation band was increased by 20.3%, 25%, and 41.6% compared with the conventional vertical slit shear wall. The proposed shear walls with vertical energy dissipation bands exhibited stable hysteresis curves, and their ductility and energy dissipation behavior were significantly improved. The specimens with lead blocks exhibited the most significant improvement in energy dissipation capacity. Finally, an evaluation method for the ultimate strength of the shear walls with vertical energy dissipation bands was proposed and validated.

Glass fiber-reinforced polymer (GFRP) bars have been introduced as an effective alternative for the conventional steel reinforcement in concrete structures to mitigate the costly consequences of steel corrosion. However, despite the superior performance of these composite materials in terms of corrosion, the effect of replacing steel reinforcement with GFRP on the seismic performance of concrete structures is not fully covered yet. To address some of the key parameters in the seismic behavior of GFRP-reinforced concrete (RC) structures, two full-scale beam-column joints reinforced with GFRP bars and stirrups were constructed and tested under two phases of loading, each simulating a severe ground motion. The objective was to investigate the effect of damage due to earthquakes on the service and ultimate behavior of GFRP-RC moment-resisting frames. The main parameters under investigation were geometrical configuration (interior or exterior beam-column joint) and joint shear stress. The performance of the specimens was measured in terms of lateral load-drift response, energy dissipation, mode of failure and stress distribution. Moreover, the effect of concrete damage due to earthquake loading on the performance of beamcolumn joints under service loading was investigated and a modified damage index was proposed to quantify the magnitude of damage in GFRP-RC beam-column joints under dynamic loading. Test results indicated that the geometrical configuration significantly affects the level of concrete damage and energy dissipation. Moreover, the level of residual damage in GFRP-RC beam-column joints after undergoing lateral displacements was related to reinforcement ratio of the main beams.

Seismic performance of corroded reinforced concrete beam-column joints repaired with BFRP sheets

Over centuries, natural phenomena have claimed a large number of lives and caused large amounts of damage. However, they were the reason for the development of knowledge and science. In engineering, there is no doubt that earthquakes were the driving force behind many design philosophies and advanced technologies. In this regard, steel plate shear walls (SPSWs) represent one of the technologies employed in both new constructions and existing structures to bolster lateral load resistance. In addition to its high elastic stiffness and strength, SPSWs often experience significant pinching during their hysteretic response unless heavily stiffened. Thus, numerous investigations have been performed recently to enhance the seismic behavior of SPSWs during severe ground shaking. The shear walls of steel plates have been studied in various ways, including stiffened and unstiffened steel plates, low yield strength steel plates, SPSWs perforated with circular holes or vertical slits, steel walls with stiffened and unstiffened openings. A stiffened SPSW panel dissipates significantly more energy than an unstiffened panel, as well as exhibiting a ductile and stable behavior. In view of its high elongation, the SPSW with low yield point has the best damping capacity. It has been demonstrated that steel walls perforated with circular holes have improved energy dissipation, in addition to allowing utilities to pass through their openings. Vertical slits on steel plate shear walls produce an exceptionally full hysteresis loop with improved performances. Slit steel walls (SSWs) can sustain a drift of over 3% while experiencing minimal hysteresis degradation. Additionally, a frame with a SSW can endure up to 6% drift without significant damage, surpassing expected ductility levels of a special moment frame, particularly with efficient slit geometry.