Behavior Of Beam-column Connections Research Articles

Seismic performance analysis of sleeve beam-column nodes under different reinforcement conditions based on Abaqus

This study investigates the effect of different reinforcement designs on the seismic performance of RC columns with beam-column joints connected using grouted sleeves. Through finite element analysis using ABAQUS software, various reinforcement configurations were simulated and their seismic performance was evaluated. 3 reinforcement configurations were simulated and their seismic performance was evaluated through finite element analysis using ABAQUS software. The results showed that the use of grouted sleeve connections with additional installed reinforcement and composite hoop configurations were effective in improving the seismic performance of prefabricated columns with grouted sleeve beam-column connection nodes. The stiffness reduction and displacement ductility of the specimens were analyzed, and it was found that the longitudinal reinforcement diameter had a negligible effect on the stiffness reduction, while the use of composite hoops was more effective in improving the displacement ductility compared to parallel hoops. These findings help to understand the behavior of beam-column connections and provide a reference for the design of seismic-resistant structures and future research.

Moment response of post-tensioned timber beam-column connections in fire – Experimental behaviour of a simple connection

Post-Tensioned Timber (PTT) frames combine high-strength tendons with heavy timber elements to create seismic low-damage or longer span timber structures. Although many aspects of structural performance, including seismic and long-term performance, have been investigated the behaviour of beam-column connections in fire has not been studied. Since it is the ductile rocking beam-column connections that give this system its advantageous response, the behaviour of these connections is key to evaluating the full-structural performance in fire. This paper presents the results of an experiment of a simple PTT beam-column subassembly under an applied load and exposed to an ISO 834 Standard Fire. The connection decompressed after 3 min and the beam rotation increased exponentially until it the applied moment was unable to be resisted at 20 min. Temperatures in the timber connection away from and at the connection are presented. Although the tendon force decreased from the effects of heating, the primary reduction in tendon force was due to crushing of timber under the anchorage.

Seismic Analysis of Basalt Fiber Reinforced Beam Column Joint under Cyclic Loading

Abstract: Beam-column joint assemblage in the RC moment-resisting framed structures is a critical seismic element because its behaviour under severe earthquake motions has a significant effect on failure mode , strength and deformation of the building structures. Basalt Fiber Reinforced Concrete (BFRC) is a concrete with short , discrete lengths of basalt fiber that randomly dispersed. Structures under seismic zone five are often badly damaged or can collapse during earthquakes. The observations from recent earthquakes show that many RC structures have failed in the brittle behaviour of beam-column connections due to the deficiency of seismic details in the joint regions. In this study, RC beam column specimen are modelled in the Ansys with excitation of cyclic loading. Attempts are made to study the performance of the test specimen by studying loop hysteresis, stiffness behaviour and energy dissipation. From the results it has shown that basalt fiber reinforced beam column joint produces less deformation and it act as crack arresters also it produces increase in joint core stiffness compared to conventional concrete beam column joint

Experimental investigation of the moment-rotation behaviour of beam-column connections produced using compressed wood connectors

The use of timber in construction in medium–high rise construction has increased in recent years largely due to the significant innovation in engineered wood products and connection technology coupled with a desire to utilise more environmentally sustainable construction materials. While engineered wood products offer a low-carbon solution to the construction industry, the widespread use of adhesive and metallic fasteners often limits the recyclability of the structural components at the end of life of the structure and it may be beneficial to reduce this where possible.To establish the possibility of an all-wood connection solution, this preliminary study examines a series of beam-column connections designs to evaluate the relative performance of the different designs, which are connected with modified or compressed wood (CW) connectors. The connection designs are formed between glued-laminated beam and column members in the first instance and later examined when connecting dowel-laminated timber (DLT) members.The results show that significant moment capacity and rotational stiffness can be achieved for connections solely connected using CW fasteners. Furthermore, the all-wood solution utilising CW fasteners to connect DLT members has also demonstrated significant moment capacity and rotational stiffness capacity without the use of adhesive and metallic components.

Rotational behavior of glulam moment-resisting connections with long self-tapping screws

The rotational behavior of beam-column connections plays an important role on the mechanical performance of timber frames. Recently, long self-tapping screws and threaded rods applied as fasteners by virtue of their advantageous withdrawal capacity and stiffness, provide promising technical solutions to achieve beam-column connections with high moment resistance and rotation stiffness. To investigate the rotational behavior of the glulam beam-column moment-resisting connections using self-tapping screws as fasteners, a series of monotonic and low-frequency cyclic loading tests are conducted on a total of ten full-scale specimens with screw inclination as the geometric configuration parameter in this paper. Based on the experimental campaign and results, the moment resistance, rotation stiffness, deformability and energy dissipation capacity of the connections are evaluated. The results indicate that this type of connection is characterized by a high moment resistance and rotation stiffness, but not very considerable deformability and energy dissipation capacity. When the connection fails in the tensile fracture of self-tapping screws, the screw inclination at the range of 15°∼30° has negligible influence on the moment resistance but significant influence on the rotation stiffness. Besides, the connections with 15° screw inclination show larger stiffness, lower ductility, faster degradation of secant stiffness and more rapid growth of equivalent viscous damping ratio compared with the connections with 30° screw inclination.

Cyclic Behavior of Beam-Column Connections in Precast Structures

The performance of precast concrete structures is greatly influenced by the response of beam–to-column connections. In this study, a new moment resisting precast concrete beam-column connection detail with post-tensioning bolts, made out of high yield strength spring steel, has been experimentally investigated as an alternative to the conventional precast moment resisting connections. Precast specimens and an aseismic monolithic reference specimen have been tested under reverse cycling loads. The contribution of the mild steel in the connection region to the flexural moment capacity, and to the initial pre-stressing force on post-tensioning bolt have been the main test variables. The moment capacity, stiffness, energy dissipation capacity and the residual displacement performance of the precast connections have been compared with those of the aseismically detailed monolithic connection. The conducted tests reveal that the connection detail with steel corbel along with the post-tensioning bolt and mild steel has superior performance properties as compared to the companion precast specimens.

Optimization of plane frame structure with consideration of semi-rigid connections

Beam-column connections play an important role in the load capacity of frame structures. In Vietnam, in the current design calculation standards for steel frame structures, to simplify calculations, the beam-column connections in the frame structures is considered as the two idealized extremes of either rigid connection or pinned connection. The actual behavior of beam-column connection is neglected. The paper presents the optimization calculation of steel frame structure taking into account the semi-rigid beam-column connections. The optimization problem is solved by Genetic algorithm method and the calculation procedure was implemented by Matlab programming software. Some numerical examples are conducted and from there the conclusions and recommendations of calculations and design of steel frames will be proposed.

Classification of failure modes in ductile and non-ductile concrete joints

In reinforced concrete structures, the behavior of beam-column connections has a significant effect on the overall behavior of the structure. Therefore, knowledge of the failure mode in these elements can be essential. In this article, two methods are proposed that can determine the failure mode type of the reinforced concrete joints, those with sufficient transverse reinforcement (ductile joints) and in concrete joints with no or little transverse reinforcement (non-ductile joints), in a probabilistic manner with high accuracy. For this purpose, two classification structures based on a number of classifiers for exterior and interiors concrete joints were utilized to determine the type of failure modes. A collection of laboratory tests were used to create and validate the classifications. It was concluded from the results that the models presented in this paper have the ability to determine the failure mode. The use of these models are simple and do not need any complex calculation. They also can be useful tools in structural engineering problems such as the initial investigation of damages in existing concrete structures or for retrofitting applications.

Considering Shear Behavior of Beam-Column Connections to Assess the Seismic Performance of RC Frames Subjected to Freeze-Thaw Cycles

ABSTRACT Freeze-thaw of concrete is significantly responsible for serious damage to RC buildings, which may result in premature failure with little warning. Therefore, it is necessary to consider the effects of freeze-thaw environment when assessing seismic performance for RC structures. In this study, pseudo-static experiments of interior beam-column joints were conducted in terms of different axial compression ratios and the number of freeze-thaw cycles (FTC). Based on the experimental results, the effects of freeze-thaw were mathematically modeled using a reduced envelope and a parameter of cyclic deterioration for the joint shear–strain relationships. The constitutive parameters of joint panels were defined by transforming the shear–strain relation into the moment–rotation relation of a shear spring. Finally, a numerical model of a beam-column joint was proposed in order to predict its shear behavior after being subjected to FTC. The numerical model was well validated by the experimental results of two RC beam-column joint test series. As an application to RC structures, model calculations were applied to five-story and three-bay RC frames of 0 and 30 years, respectively.

Nonlinear analysis of damaged RC beams strengthened with glass fiber reinforced polymer plate under symmetric loads

This study presents a new beam-column model comprising material nonlinearity and joint flexibility to predict the nonlinear response of reinforced concrete structures. The nonlinear behavior of connections has an outstanding role on the nonlinear response of reinforced concrete structures. In presented research, the joint flexibility is considered applying a rotational spring at each end of the member. To derive the moment-rotation behavior of beam-column connections, the relative rotations produced by the relative slip of flexural reinforcement in the joint and the flexural cracking of the beam end are taken into consideration. Furthermore, the considered spread plasticity model, unlike the previous models that have been developed based on the linear moment distribution subjected to lateral loads includes both lateral and gravity load effects, simultaneously. To confirm the accuracy of the proposed methodology, a simply-supported test beam and three reinforced concrete frames are considered. Pushover and nonlinear dynamic analysis of three numerical examples are performed. In these examples the nonlinear behavior of connections and the material nonlinearity using the proposed methodology and also linear flexibility model with different number of elements for each member and fiber based distributed plasticity model with different number of integration points are simulated. Comparing the results of the proposed methodology with those of the aforementioned models describes that suggested model that only uses one element for each member can appropriately estimate the nonlinear behavior of reinforced concrete structures.

Evaluating the accuracy of a new nonlinear reinforced concrete beam-column element comprising joint flexibility

This study presents a new beam-column model comprising material nonlinearity and joint flexibility to predict the nonlinear response of reinforced concrete structures. The nonlinear behavior of connections has an outstanding role on the nonlinear response of reinforced concrete structures. In presented research, the joint flexibility is considered applying a rotational spring at each end of the member. To derive the moment-rotation behavior of beam-column connections, the relative rotations produced by the relative slip of flexural reinforcement in the joint and the flexural cracking of the beam end are taken into consideration. Furthermore, the considered spread plasticity model, unlike the previous models that have been developed based on the linear moment distribution subjected to lateral loads includes both lateral and gravity load effects, simultaneously. To confirm the accuracy of the proposed methodology, a simply-supported test beam and three reinforced concrete frames are considered. Pushover and nonlinear dynamic analysis of three numerical examples are performed. In these examples the nonlinear behavior of connections and the material nonlinearity using the proposed methodology and also linear flexibility model with different number of elements for each member and fiber based distributed plasticity model with different number of integration points are simulated. Comparing the results of the proposed methodology with those of the aforementioned models describes that suggested model that only uses one element for each member can appropriately estimate the nonlinear behavior of reinforced concrete structures.

REPAIRING AND RETROFITTING OF EARTHQUAKE-AFFECTED EXTERIOR BEAM-COLUMN CONNECTION BY USING RESIN CONCRETE

Reinforced concrete structures may suffer a failure that caused by natural events such as earthquake. If the damaged buildingstill can be used, then a repair (retrofitting) on the damaged section is highly necessary. Retrofitting materials that can be used isthe polymer concrete. The purpose of this study was to determine the behavior of beam-column connections after repair(retrofitting) using polymer concrete. Test sample in the form of exterior beam-column connection with cross-sectional size ofthe column 30 x 30 cm, length of 3.5 m and the size of the beam cross-section of 17 x 30 cm, length 1.8 m, consists of 3 pieces.Experiment test method was based on ACI T1.1-01. All samples were tested in two stages, the first stage of the test until targeteddamaged level which controlled by crack width of 0.4 mm. Furthermore, the test object repaired using normal concrete (BKN-1N) and polymer concrete (BKN-2R and BKN-3R). The second phase of test is done to collapse. Lateral force, deflection, andstrain and crack pattern are observed. The data were processed to obtain the load-deflection relationship curve, stiffness,ductility ratio, energy dissipation and model of collapse. Beam-column joint behavior is compared with the acceptance criteria(ACI T1.1-01) to determine whether in accordance with the criteria required. Test results showed the value of the maximumlateral load test object BKN-1N, BKN-2R and BKN-3R,consecutively were 39.2 kN; 43.77 kN and 46.24 kN in the direction ofcurvature response (+) and the direction of curvature response (-), respectively for 59.1 kN; 62.73 kN and 69.91 kN. BKN-2Rtest objects have a greater ductility factor of 24.1% in the direction of curvature response (+) when compared with the test objectBKN-1N. At the direction of curvature response (-), BKN-2R sample has a greater ductility 39.3% of the sample BKN-1N.Based on ACI T1.1-01, all samples have the response modification factor of 8. From SAP2000 modeling, BKN-1N, BKN-2R,and BKN-3R consecutively showed ability to withstand earthquake forces 3.36 times greater; 3.77 times; and 3.97 times greaterthan the earthquake forces are designed based on SNI 1726:2012. An advantage of using a resin concrete repair materials is veryfast drying time.

Impact of Joint Modeling Approach on Performance Estimates of Older-Type RC Buildings

The behavior of beam-column connections has usually been ignored in the modeling process due to its complexity and relatively recent awareness of its possible impact on response. This study presents the features of modeling unreinforced beam-column joints in estimating seismic demands. A representative RC frame is subjected to strong ground motions. Through nonlinear dynamic analyses, base shear, roof displacement, inter-story drift and joint rotation are noted. The dynamic analyses are performed comparatively through two analytical models with rigid and flexible joint assumptions. In the flexible joint model, shear deformation at the beam-column joint and bond-slip deformation at the beam-column interface are simulated through a previously verified analytical representation. Results indicate that introducing unreinforced beam-column joint behavior to the model may lead to almost two times larger seismic demands compared to those obtained from rigid connection assumption. Thus, the performance assessment of such buildings may conclude erroneously with underestimated seismic demands and damage levels when inelastic actions in the joints are ignored. However, in some cases, lower seismic demands can also be obtained for the flexible joint model.

보-기둥 접합부의 방폭성능에 관한 해석적 연구

폭발사고나 테러 등이 증가함에 따라 구조물 방폭성능의 요구가 증가되고 있다. 국내에서도 폭발사고 등에 대비하기 위한 방폭구조물의 수요가 증가할 것이며, 이를 위해서는 다양한 측면의 관련 연구가 수행되어야 할 것이다. 본 연구에서는 철근상세가 보-기둥 접합부의 방폭성능에 미치는 영향에 대해 분석하였다. 표준 시험체는 보-기둥 설계매뉴얼을 바탕으로 정하중에 대해 설계되었으며 이 외에 철근상세에 따른 영향을 분석하기 위해 휨, 전단, Diagonal철근 등이 보강된 시험체와 비교하였다. 접합부의 방폭성능을 평가하기 위해 유한요소해석 프로그램인 LS-DYNA에 의한 해석적 연구가 수행되었다. 해석결과는 시험체의 파괴형상, 변형, 지점회전각 그리고 철근의 응력을 포함하고 있다. 추가적인 휨철근이 보강된 시험체의 방폭성능을 표준 시험체와 비교하여 큰 차이를 보이지 않았으나, Diagonal철근이 보강된 시험체는 보 영역에서 발생하는 소성힌지영역을 이동시켜 접합부의 안전성을 확보하는 등 방폭성능을 향상시켰다. 따라서 동일한 철근비에서 휨철근보다 Diagonal철근이 폭발하중에 더 효율적으로 저항하는 것을 확인하였다. 이에 더하여 전단철근이 배근된 시험체는 우수한 방폭성능을 보였으며, 이를 통해 폭발하중을 받는 콘크리트 구조에서 휨 성능과 함께 전단성능 역시 중요한 고려사항임을 확인할 수 있었다. As the increase of explosive accidents and terrorism, demands of blast-resistant capacity in structures would be increased to prevent those situation. Therefore, various studies on blast-resistant structures should be performed. In this study, behavior of beam-column connections is investigated. Base specimen was designed according to the design criterion of beam-column connections. To determine the effects of reinforcement details, flexure, shear and diagonal bar were considered as variables. LS-DYNA, nonlinear finite element program, is selected to the numerical analysis of specimens. The analysis results included failure shape of specimens, deflection, support rotation and stress of reinforcements. In conclusion, specimen which was reinforced with additional flexure bars did not show significant differences as contrasted with base specimen. The diagonal reinforcements are more effective to resist the blast loads than additional flexure reinforcements because safety of connection was enhanced due to the transfer of plastic hinge region in case of reinforcing diagonal bars. In the specimen which is reinforced with additional shear bars, outstanding behavior was observed. In the structures subjected to blast loads, therefore, it is should be considered to not only flexural performance but also shear forces.

Study on the behavior of beam-column connection in precast concrete structure

Due to the increase of the use of precast concrete structures in multistory buildings, this paper deals with the behavior of an specific type of beam-column connection used in this structural system. The connection is composed by concrete corbels, dowels and continuity bars passing through the column. The study was developed based on the experimental and numerical results. In the experimental analysis a full scale specimen was tested and for numerical study, a 3D computational model was created using a finite element analyze (FEA) software, called DIANA. The comparison of the results showed a satisfactory correlation between loading versus displacement curves.

The Effect of Splicing Area Parameters on Mechanical Behavior of Beam-Column Connection with Cantilever Beam Splicing

This paper deals with the effect of splicing area design parameters on the mechanical behavior of beam-column connection with cantilever beam splicing. A series of models are designed based on the change of parameters. The mechanical behavior of beam-column connection with cantilever beam splicing is systematically studied by using the finite element analysis. The analysis results show that the number and arrangement of web bolt will have a great influence on mechanical behavior of the splicing joint when the number of flange bolt is designed by the precise design method; the number and arrangement of web bolt will have a less influence when the number of flange bolt is designed by the equal strength design method; Splicing area design parameters have little effect on the ultimate load and the initial rotational stiffness of the splicing joint; the number and arrangement of bolt is sensitive parameter for yield load of the splicing joint and the rotational stiffness in the the splicing area.

Energy Absorption Capacity of Reinforced Concrete Beam-Column Connections, with Ductility Classes Low

Once the behaviour of reinforced concrete moment resisting frame structures is investigated, it is concluded that the performance of beam column connections is not satisfactory. In order to understand the complex mechanisms and satisfactory behaviour of beam column connections, lots of investigations have been done. The most critical zone in reinforced concrete moment resisting frames would be the beam column connection. The behaviour of beam column connection once it is subjected to large forces during earthquakes has a great impact on the response of the structure. The shear failure has a brittle nature which is not a desirable structural performance during earthquakes. Two new types of shear reinforcements design are introduced in this study for the purpose of reaching a higher performance and material capacity for the connection and hence, the structure. These two shear reinforcement designs working simultaneously with other reinforcement systems and concrete have a better performance compared to that of conventional methods. The first specimen is made according to conventional method of design as control specimens in conformance with Euro code EC2 & EC8. The second specimen introduces a continued shear resistance system against discontinued conventional shear resistance system (stirrups) which is called “Single Square Spring Shear Resistance System” (SSSSRS). The third specimen possesses two continued square spring systems twisting together and making a parallel system called “Double Square Spring Shear Resistance System” (DSSSRS). A comparison was made between the performances of the improved shear reinforcement systems of beam-column connections against the control specimens. It was concluded that a lower deflection along with higher energy absorption was achieved for “Single Square Spring Shear Resistance System” (SSSSRS) and “Double Square Spring Shear Resistance System” (DSSSRS) compared to control specimens.

A Trilinear Model for M - θ Curves of Semi-Rigid End-Plate Connections

The moment behavior of beam-column connections should be considered in advanced steel space frame analysis. A trilinear model and calculation method were presented. Based on the comparison with the FEM results, it has been proved that the M-θ relationship of semi-rigid end-plate connections can be accurately estimated by this simplified calculation method and satisfy the requirement of structural design. This calculation method is simple and ease of use, it benefits application of this kind of joint in actual structure engineering and provides the basis and reference for design of the semi-rigid connection.

A study on the behavior of beam-column connections in precast concrete structures: experimental analysis

Due to the large increase in the use of precast concrete structures in multistory buildings, this work covers a study on the behavior of beam-column connection with emphasis on the continuity provided by the slab reinforcement. Two prototypes were tested, each one with a different detail of the continuity reinforcement distribution. In both connections, the steel area used on the concrete cover of the hollow core slab was the same, varying the amount of bars that passed through the column and the ones that were placed adjacent to the column. The experimental results showed that the connection with bars adjacent to the column presented stiffness increase and a better cracking control. According to the classification the two tested connections can be considered semi-rigid.

Cyclic flexural analysis and behavior of beam-column connections with gusset plates

This research investigates the cyclic flexural behavior of double-angle concentrically braced frame beam-column connections using three-dimensional nonlinear finite element analysis. Prior experimental research demonstrated that such connections possess appreciable flexural stiffness, strength, and ductility. The reserve capacity provided by these connections plays a significant role in the seismic behavior of low-ductility concentrically braced frames, so knowledge about the impact of connection parameters on local limit states and global connection performance is needed for employing reserve capacity to design and assess concentrically braced frames. Finite element models were developed and validated against prior experiments with focus on the limit states of failure of the fillet weld between the gusset plate and beam, low-cycle fatigue fracture of the steel angles joining the beam and gusset plate to the column, and bolt fracture. The models were used to evaluate the flexural stiffness, strength, and ductility of braced frame connections with primary attention on the effects of beam depth, angle thickness, and a supplemental seat angle. The finite element analysis demonstrated that increasing beam depth and angle thickness and adding a supplemental seat angle all increased the stiffness and strength of the connection while maintaining deformation capacity. A procedure to estimate the flexural behavior of beam-column connections with gusset plates was developed based on the results of the numerical simulations.