Weak-axis Connections Research Articles

Exterior weak-axis beam-to-column bolted connections between GFRP I-shaped pultruded profiles using stainless steel cleats

This paper presents an experimental investigation on the mechanical behaviour of bolted GFRP pultruded profiles beam-to-column connections, using I-shaped profiles and stainless-steel cleats, rotating around the weak-axis of the column. Using metallic cleats increases resistance, by comparison with composite cleats, using straightforward connection systems, unlike cuff connections, that can be readily used in construction. The campaign included web-cleated and flange-cleated connections, using different cleat thicknesses (4 mm, 6 mm and 8 mm), investigating the influence of the edge end distance (w.r.t. the beam end). The specimens were tested under monotonic and cyclic loads. The results show that the thickness of the cleats influences the behaviour of the flange-cleated configuration, but not that of the web-cleated connections. Additionally, while the former configuration can be considered as semi-rigid, for design, web-cleated connections should be considered as pinned. Both configurations presented significant resistance and rotation capacity, unlike connections using GFRP cleats, reported in previous research. On the other hand, the cyclic tests indicate that these connections present limited energy dissipation capacity, therefore they are not expected to contribute to dissipate energy under seismic actions. Overall, the results show that these weak-axis connections can support load bearing beams, although global structural design must avoid their (brittle) column failure modes.

Experiment and numerical analysis of multi-story coupled steel plate shear wall with weak-axis connections

As an extension of the steel plate shear wall (SPSW), the coupled steel plate shear wall (CSPSW) usually needs to be placed around the perimeter forming a core tube to resist seismic lateral forces. Therefore, the beam-to- column web connection (i.e., the weak-axis connection) is often inevitable. To develop the benefits of the CSPSW and increase prefabricated flexibility, the cyclic behavior was detailed experimentally and numerically. A 1/3 scaled four-story CSPSW specimen with weak-axis connections was tested under cyclic loading. The test results show that the specimen exhibits a desirable failure sequence and has stable lateral resistance and energy dissipation capacity due to the contribution of coupling beams and weak-axis connections. Based on this test, multiscale model and strip model were developed for simplifying analysis. To balance the accuracy and calculation cost, we further proposed the solution strategy of submodel and substructure for the CSPSW, and examined the effect of coupling beam's length using this substructure strategy by software ABAQUS. The numerical results show that the CSPSW with weak-axis connections exhibits good out-of-plane stability in bottom columns and has excellent properties in energy dissipation and ductility. The proposed multiscale model and strip model as well as the substructure solution strategy are proved to be effective and feasible, which substantially promotes the efficiency of numerical analysis. Besides, the length ratio of coupling beams should better no greater than 1.5, and the length ratio of 0.8 would be the optimal to ensure that the structure can enjoy excellent stiffness, ductility, energy dissipation and material efficiency.

Seismic performance of a narrow flange H-beam-to-column full-bolt end-plate weak-axis connection

This study proposes a full-bolted end-plate weak-axis connection T-shape joint based on a narrow flange H-beam-to-column section. A quasi-static test was conducted to solve the problems of large steel cross-section and high steel utilization, as well as the decline in space utilization and aesthetics caused by convex beam-to-column components in low-rise and multi-story steel frame residential buildings. The failure mode, hysteresis curve, and bearing capacity of the specimens were discussed and investigated. The test results show that the stiffness of the joints of the specimens are relatively high, the failure mode is the beam hinge failure mechanism, the hysteresis curves of the joints are full fusiform, and the seismic performance is good. An experimental numerical model was established using the ABAQUS software to determine the factors that affect the performance of the joint. The effects of skin thickness, bolt diameter, beam end-plate thickness, stiffener thickness and rid slope on the seismic performance of the T-shape joint were analyzed. The numerical simulation results indicate that when the thickness of the skin plate increases, the energy dissipation capacity of the joint significantly increases, whereas the ductility decreases. a moment–rotation formula that can be used as a reference in the control design of the key parameters of the joint was obtained, which is useful in practical engineering applications.

Cyclic tests and performance of weak-axis connected uncoupled and coupled steel plate shear wall with novel infill plate configuration

Steel plate shear wall is usually in the form of a tube as the lateral force-resisting component in high-rise buildings. In addition to the connection between the column flange and beam section, the connection between the column web and beam section (i.e. the weak-axis connection) is also required. Therefore, the hysteretic behavior of uncoupled and coupled steel plate shear walls with this connection form was studied. Cyclic loading tests were carried out on two 1/3 scaled four-story specimens consisting of the uncoupled and coupled steel plate shear wall specimens (S4RN and C4RN). The test results show that the weak-axis connected form makes the column avoid premature out-of-plane deformation; the coupled specimen has better performance than the uncoupled specimen with a higher ductility of 4.31, and both specimens tend to a similar angle of 45° in the direction of the tension band; the coupling beam can effectively enhance the bearing capacity, improve the pinch of the hysteresis loop, and its rotation exhibits a similar tendency to that inter-story rotation while hitting the max of 0.07rad. A numerical method to simulate the behavior of S4RN and C4RN, and the submodel solution strategy to investigate the improvement of infill plates, are proposed and implemented using the ABAQUS. The specimens’ shear distribution and partially slotted infill plate configuration were examined after the numerical modeling method was validated against the test results. The numerical results show that approximately 60% of the total lateral force can be shared by the infill plates, and the coupling beams can further reduce the lateral force resisted by the infill plates. The coupling beams can effectively reduce the overturning moment of each wall pier and adjust the axial pressure between the inner and outer column. The partially slotted CSPSW exhibits a plump spindle-shaped hysteretic curve with a great ductility of 5.88, so the measurement for replacing ordinary infill plates with partially slotted infill plates has a good application prospect.

Determining the effective slab width of composite joint with the weak-axis connection for ultimate bearing capacity

Extensive brittle failures on the weld zone of beam bottom flange in composite joints of SMRFs were observed during the Northridge earthquake. One of the main reasons is the sizeable tensile strain demand generated at the beam bottom flange zone under sagging bending. The key to accurately understanding the mechanical properties of composite joints is the effective width of the slab. However, the previous research is all aimed at the I-section composited joints with column strong-axis connection or CFST column connection. Therefore, the research conclusions may not suit the composited joint with the weak-axis connection. Beam column weak axis connection is as universal as the strong axis connection. Therefore, this paper used ABAQUS software to investigate the effective width of the slab in composited joints with the weak-axis connection. Firstly, it defines the ultimate state of bearing capacity corresponding to the analysis in this paper. Secondly, it investigates the influence factor on the effective width of the slab under the ultimate sagging moment and hogging moment. Thirdly, it uses Gray Correlation Theory and MATLAB to fit the calculation formula of the effective width of the slab under the ultimate sagging moment and hogging moment. Fourthly, it compares the slab's effective flange width in the previous experiment and the formula presented in the paper. Finally, analyze the applicability of the fitting formula to the strong axis rigid composite joints and T-shaped rigid composite joints of the I-shaped column and H-beams.

Biaxial cyclic behavior of bolted end-plate connection to I-column reformed by box-plates

In the research study, different 3D joint concepts of a frame formed by an I-column subjected to the biaxial cyclic load were simulated. Non-linear finite element models using the Ansys software were developed to evaluate the biaxial cyclic behaviors of the joints. After verification via five existing experimental tested beam-to-column connections, six different representative finite element models of the joints, including a 3D corner joint, two 3D edge joints, and two 3D interior joints with the biaxial cyclic load as well as a 2D corner joint as a base specimen with uniaxial cyclic load, were established with and without under axial compression force on the column. A newly developed weak-axis connection detail was implemented to connect the beam to the weak-axis of the column. Two box-plates parallel to the web of the column connected between the flange tips of the I-shaped column were used to reform the region of the I-column corresponding to the beam connection. The four-bolted unstiffened end-plate connection specified in AISC 358-16 was used as the beam-to-column connection in both the strong-axis and the weak-axis directions of the I-shaped column. The results indicate that biaxial loading causes a loss of strength in the early loading cycles compared to uniaxial loading. The strong-axis connection of the 3D corner joint has less ultimate connection rotation and a greater value of rotational stiffness than that of the 2D corner. Moreover, all the connections of the joints possessed good hysteretic curves satisfying the limits given in the ANSI/AISC 341-16. Axial compression force on the column reduced performance parameters of the connections such as plastic rotation capacity, energy dissipation ability, and hysteretic equivalent viscous damping ratio. By the way, the weak-axis connections of the joints are acceptable to consider as partially restrained connections, while the strong-axis connections are fully-restrained.

Seismic performance of spatial beam-column connections in steel frame

This paper presents a developed spatial beam-column connection in steel frame which is suitable for widely used H-section column and beam. To provide a first insight into the hysteretic responses of the proposed spatial connections, a numerical comparative analysis was conducted for the proposed connections and also the traditional connections after verifying the validity of the finite element methods. The normalized moment versus the story drift rotation hysteretic loops, energy dissipation capacity, failure modes, Mises index (MI), triaxiality index (TI) and rupture index (RI) distribution at the beam flange welds were discussed in detail. The proposed connection could significantly improve the hysteretic performance of the strong–axis connections and also the weak-axis connections in terms of the stiffness, strength, energy dissipation capacity, and could effectively move the beam plastic hinges away from the beam-column interface. The proposed spatial connection has the characteristics of “strong connection and weak member”. The spatial loading exerted negligible effects on the structural behavior of the beam-column connections for the considered sizes and loading methods. It is recommended that the anti-lamellar tearing steel plate could be used for the side plates in the proposed connections to prevent the tearing fracture.

Effect of anchors on the seismic performance of exposed column-base plate weak-axis connections

The number and magnitude of earthcorrquakes are increasing in South Korea. However, unreliable exposed column-base plate connections of low-rise steel buildings are still easily found in the field. Therefore, based on intensive field inspection, six large-scale exposed column-base plate weak-axis connection specimens were examined, under both axial compression and lateral cyclic loading, to develop stable and reliable column-base plate joints in the weak-axis direction. From the test results of the first set of specimens, it was found that the seismic performance of field-representative specimens was quite poor due to a “rocking” phenomenon observed between the base plate and concrete foundation because of the severe residual plastic deformation of round-section anchor bolts. To reduce the rocking phenomenon, a second set of specimens was fabricated and evaluated. By using an eight threaded anchor-layout, the rocking phenomenon was substantially reduced. Therefore, it is strongly recommended to use eight threaded anchors in three rows in order to enhance seismic performance, rather than four in two rows, for exposed column-base plate weak-axis connections.

Mechanical performance of a new I-section weak-axis column bending connection

This paper reports a novel steel beam-to-column connection suitable for use in the weak axis of I-section column. Monotonic and cyclic loading experimental investigations and numerical analysis of the proposed weak-axis connection were conducted, and the calculation procedure of the beam-column relative rotation angle and plastic rotation angle was developed and described in details. A comparative analysis of mechanical property and steel consumption were employed for the proposed I-section column weak-axis connection and box-section column bending connection. The result showed that no signs of fracturing were observed and the plastic hinge formed reliably in the beam section away from the skin plate under the beam end monotonic loading, and the plastic hinge formed much closer to the skin plate under the beam end cyclic loading. The fracture of welds between diaphragm and skin plate would cause an unstable hysteretic response under the column top horizontal cyclic loading. The proposed weak-axis connection system could not only simplify the design calculation progress when I-section column is adopted in frame structural design but also effectively satisfy the requirements of \'strong joint and weak member\', as well as lower steel consumption.

Cyclic performance and design recommendations of a novel weak-axis reduced beam section connection

In previous weak-axis moment connection tests, brittle fracture always initiated near the edge of the beam flange groove weld due to force flow towards the stiffer column flanges, which is the opposite pattern as strong-axis moment connections. As part of the China NSFC (51278061) study, this paper tested two full-scale novel weak-axis reduced beam section moment connections, including one exterior frame connection specimen SJ-1 under beam end monotonic loading and one interior frame joint specimen SJ-2 under column top cyclic loading. Test results showed that these two specimens were able to satisfy the demands of FEMA-267 (1995) or ANSI/AISC 341-10 (2010) without experiencing brittle fracture. A parametric analysis using the finite element software ABAQUS was carried out to better understand the cyclic performance of the novel weak-axis reduced beam section moment connections, and the influence of the distance between skin plate and reduced beam section, a, the length of the reduced beam section, b, and the cutting depth of the reduced beam section, c, on the cyclic performance was analyzed. It was found that increasing three parametric values reasonably is beneficial to forming beam plastic hinges, and increasing the parameter a is conducive to reducing stress concentration of beam flange groove welds while increasing the parameters b and c can only reduce the peak stress of beam flange groove welds. The rules recommended by FEMA350 (2000) are suitable for designing the proposed weak-axis RBS moment connection, and a proven calculation formulation is given to determine the thickness of skin plate, the key components in the proposed weak-axis connections. Based on the experimental and numerical results, a design procedure for the proposed weak-axis RBS moment connections was developed.

Cyclic loading tests on exposed column-base plate weak-axis connections of small-size steel structures

Research on evaluating the seismic performance of exposed column-base plate weak-axis connections of small-size steel structures is substantially limited. Therefore, in this study, six exposed column-base plate weak-axis connection specimens with L-shaped anchor bolts under cyclic loading were tested. The primary test variables were the thickness of base plates, the presence of rib plates, and the number and embedment length of anchor bolts. Furthermore, round and threaded rods with L-shape were used as anchor bolts to assess the effect of bond performance. It was found that the structural performance of the connections was influenced by the thickness of base plate and the bond performance of anchor bolts. It should be noted that although base plate meets the minimum thickness requirements by the current design code, if the base plate yields before the moment capacity of steel column reaches the plastic moment, the structural performance of the connection will decrease. The connection details in this study can be considered semi-rigid connections. Threaded anchor bolts with L-shape are more preferred over the smooth round anchors for increased bond strength. Furthermore, equations for required tensile capacity and cross-sectional area for anchor bolts were derived in this study.

Seismic Evaluation of Exposed Column-base Plate Weak-axis Connections Using L-shaped Hooked Anchor Bolts

Seismic Evaluation of Exposed Column-base Plate Weak-axis Connections Using L-shaped Hooked Anchor Bolts

Investigation of composite action on seismic performance of weak-axis column bending connections

This paper presents a developed beam-to-column connection which is suitable for weak axis of I-section column and H-shaped beam. Ten cruciform joint specimens, including five bare steel joint specimens (SJ) and five composite joint specimens (CJ) reinforced with partial shear connection, were tested under reversal of loads to evaluate the effect of composite action on the developed weak-axis connections. The beam ends were designed with standard, RBS, cover-plate, taper flange, and welded haunch respectively. The experimental results are analyzed and the composite action is discussed based on the test data. Overall, most joints failed due to welding fracture at the conjunction of diaphragm, skin plate and beam-end flange. But relatively speaking, the composite specimens performed well and achieved the story drift ratios of 0.04rad before experiencing 20% strength degradation because only slight strength degradation occurred in the composite joints compared to bare steel joints, thus the composite joints have a more stable bearing capacity. The test data clearly illustrate that the neutral axis shifted upward significantly under positive bending, resulting in larger strains on beam bottom flange. The reinforcing bars in concrete slab did not work well, but remained in elastic state. The slab slippage was negligible even in 50% degree partial shear connection. The welding quality is an important guarantee to avoid the brittle failure of the connections, and lamellar tearing resistant steel is suggested to be used in skin plate.

Experimental study on structural performance of the new shaped weak-axis connection in full-scale test

The bracket-type connection is often used for the weak-axis steel connection of H-shaped beam-to-column. However it lead to weakness of competitiveness in steel structure due to difficulty in production and installation of connection. Consequently, new shaped weak-axis connection was developed. It has a simple shape with less spot of welding points, and has advantage about showing the obvious power flow in connection points. In this study, monotonic and cyclic loading tests in full-scale were performed to evaluate structural behavior and examine on-site application. Therefore, 12 specimens (9 specimens for monotonic loading test and 3 specimens for cyclic loading test) were manufactured for the variables which are overlap length of beam end and column flange. As the results, new shaped weak-axis connection is appeared Special Moment Frame (SMF) and have excellent structural performance and workability when the parameter is over 50 mm.

실물대 실험을 통한 H형강 기둥의 신형상 약축접합부 성능평가에 관한 연구

The bracket-type connection is often used for the weak axis steel connection of H-shape beam-to-column. However it leads to weakness of competitiveness in steel structure due to difficulty in production and installation of connection. Consequently, new shape weak-axis was developed. It has a simple shape with the less spot of welding points, and has advantage about showing the obvious power flow in connection points. In this study, monotonic and cyclic loading test in full-scale was performed to evaluate structural behavior and examine on-site application. Therefore, 12 specimens(9 specimens for monotonic loading test and 3 specimens for cyclic loading test) were built for the variables which are overlap length of beam-end and column flange. As the result, new shape of weak-axis connection appeared special Moment Frame(SMF) and had excellent structural performance and constructablility when the parameter is over 50mm.

Behavior and Design Recommendations of Splice Connection in Weak-Axis Column-Tree Steel Moment Frames

The main objectives of this paper was to investigate the cyclic performance of splice connection in weak-axis column-tree connections with the formation of plastic hinge assumed at splice connection and provide some design recommendations. By reducing the cross-sectional area of the splice plates, the splice connection in this test are designed as a weaken component to utilize the ductility capacity and energy dissipation. The results showed that it could develop the plastic rotation capacity in the beam splice connection and portion in the link beam but not increase the energy dissipation capacity during the same story drift ratio.

Seismic Performance Evaluation on Cyclic Testing of Weak-Axis Column-Tree Connections

The objective of this paper is to research seismic performance of the weak-axis column-tree connections. For this purpose, two specimens CTY600 and CTY900 were fabricated and tested in this experiment. From the test results, the CTY specimen successfully achieved a 5% rad story drift ratio without brittle fracture and the total plastic rotation reached over 0.04rad.

ㅍ형강 기둥구조시스템 개발 및 신형상 약축접합부 구조성능평가

The importance of composite structure systems such as CFT in the building structure is being highlighted which led high-rise buildings, enlarged and long spanning. CFT is difficult to apply to the field due to the installation of the internal and external diaphragm. Therefore, this study developed concrete filled ㅍ-section column structure systems to solve the problem in accordance with conventional systems for CFT and evaluated structural performance of ㅍ-section steel column New shape weak-axis connection. Five specimens are built to test variables that thickness of welding plates and monotonic loading tests are performed. As the result, new shape weak-axis connection can adjust the strength and rigidity according to welding plate thickness.

Development and performance evaluation of weak-axis column bending connections for advanced constructability

This paper reports a new beam-to-column connection that is suitable for use in the weak axis of a column. The proposed system mainly uses bolts, and it minimizes the use of welding, which is generally difficult to perform onsite. In this system, an H-shaped steel beam is joined to an H-shaped steel column by bolted splices at the top flange and without a scallop at the web. Eight specimens were tested to verify the structural performance of the developed connection; in doing so, the effects of geometry and arrangement of the plate were also considered. The connection materials required and CO2 emissions were estimated to evaluate the cost-effectiveness of the proposed system. The obtained results showed that this system was suitable had better structural performance than standard weak-axis connections and excellent constructability, making it suitable for replacing existing bracket-type weak-axis connections.

시공성을 고려한 H형강 기둥의 신형상 약축접합부 내진성능평가

H형강 기둥에 대한 신형상 약축접합부를 개발하여 단조가력실험을 통해 구조성능평가에 관한 연구를 수행하였으며, 선행연구결과를 바탕으로 본 연구는 시공성을 고려한 신형상 약축접합부의 내진성능을 평가하기 위해 반복가력실험을 실시하였다. 신형상 약축접합부는 접합개소 및 용접량이 적고 접합상세가 단순하며, 접합부에 작용하는 힘의 흐름이 명확하다는 장점이 있다. 이에 따라 H형강 기둥플랜지와 보 단부의 겹침길이를 실험변수로 한 신형상 약축접합부(WPL-WK-FC2, WPL-WK-FC3)와 건축강구조 표준접합상세지침에 근거한 표준 약축접합부(HH-WK-FC4) 총 3개의 실험체를 실물대 사이즈(Full-scale)로 제작하였다. 실험결과, 신형상 약축접합부는 0.04 rad 이상의 층간변위각에서 보 소성모멘트(<TEX>$M_P$</TEX>)의 80%이상을 유지하는 특수모멘트골조(SMF)의 내진성능을 확보하였으며, H형강 기둥플랜지와 보 단부의 겹침길이가 50 mm 이상이면 시공성 뿐만 아니라 구조적으로 우수한 것으로 나타났다. H-section steel column new shape weak-axis was developed and performed through monotonic loading test regarding basic structural performance evaluation. In this study cyclic loading test was followed up in order to evaluate seismic performance through the full-scale of new shape weak-axis connection for constructabilitiy. New shape weak-axis connection has a simple shape with the less spot of welding points, and it has advantage about showing the obvious flow of strength in connection points. Therefore, three specimens are built for the variables which are overlap length of beam-end and column flange. As the result, New shape of weak-axis connection is appeared special Moment Frame(SMF) and have excellent structural performance and constructablility when the parameter is over 50 mm.