Beam Connections Research Articles

Innovative self-centering systems using shape memory alloy bolts and energy dissipating devices

In conventional eccentrically braced frames (EBFs), earthquake input energy is mainly dissipated by plastic deformation of link beams. However, the plastic deformation of link beams can cause extensive structural damage during severe seismic events. The self-centering eccentrically braced frames (SEBFs) are one of the strategies that have been proposed to address this problem. This paper presents two new SEBF systems incorporating shape memory alloy (SMA) bolts and energy dissipation devices, consisting of shear tabs and web hourglass pins (WHPs). SMA bolts are employed in collector beams-to-link beam connections to dissipate energy and recenter the frame with negligible residual drift after an earthquake, while shear tabs and WHPs are utilized in both ends of the link beam web to enhance the seismic performance of the frame. Detailed finite element simulations are performed to assess the cyclic performance of the proposed self-centering systems using experimentally validated models. The results indicate the excellent efficiency of the proposed systems in terms of recentering and energy dissipation capacity. It is shown that the application of shear tabs and WHPs can improve the ultimate strength, equivalent damping and energy dissipation capacity of the system by up to 20%, 35% and 60%, respectively. The experimentally validated models are then used to investigate the effects of key design parameters such as initial prestress of SMA and shear tab bolts, friction coefficient, and the diameter and clear length of the hourglass pins. The results of this study should prove useful in the practical design of the SMA-based self-centering systems.

Fire performance of hybrid mass timber beam-end connections with perpendicular-to-wood grain reinforcement

PurposeThe fire resistance of timber structures is heavily dependent on the fire behaviour of the connections between its structural elements. The experimental study presented in this paper aimed to investigate the fire performance of glued-laminated timber beam connections reinforced perpendicular-to-wood grain with self-tapping screws (STS).Design/methodology/approachTwo full-size fire experiments were conducted on glulam beam-end connections loaded in flexure bending. Two connection configurations, each utilizing four steel bolts arranged in two different patterns, were reinforced perpendicular to wood grain using STS. The bolt heads and nuts and the steel plate top and bottom edges were fire protected using wood plugs and strips, respectively. Each connection configuration was loaded to 100% of the ultimate design load of the weakest unreinforced configuration. The test assemblies were exposed to elevated temperatures that followed the CAN/ULC-S101 standard fire time–temperature curve.FindingsThe experimental results show that the influence of the STS was significant as it prevented the occurrence of wood splitting and row shear-out and as a result, increased the fire resistance time of the connections. The time to failure of both connection configurations exceeded the minimum fire resistance rating specified as 45 min for combustible construction in applicable building codes.Originality/valueThe experimental data show the effectiveness of a simple fire protection system (i.e. wood plugs and strips) along with the utilization of STS on the rotational behaviour, charring rate, fire resistance time and failure mode of the proposed hybrid mass timber beam-end connection configurations.

Reverse Cyclic Loading Effect on RCC Wall‐Floor Slab‐Deep Beam Connection

High‐rise structures are more vulnerable when subjected to lateral loading. Generally, the shear walls function as the main lateral load resistant system in high‐rise structures. In the case of high‐rise structures with an open ground story, the shear wall‐floor slab‐deep beam acts together as a rigid jointed frame connection to withstand gravity and lateral force induced by external loadings like earthquakes and wind. The wall‐floor slab‐deep beam connection will be subjected to a higher concentration of stresses, which is a more vulnerable area in any high‐rise structure. Hence, it is necessary to design this connection with more ductility. This article presents the experimental investigations carried out to study the behavior of three different reinforcement detailing in RCC wall‐floor slab‐deep beam connections, such as (1) 90° bend up bars connection as per Indian Standard Code (Conventional connection), (2) U‐hooks connecting the core region as per Euro code 2, and (3) proposed U‐hooks with additional reinforcement in the core region transverse to the beam orientation. The additional reinforcement is provided at a distance of 50 mm from the face of the shear wall. The parameters considered for this study are load‐carrying capacity, energy dissipation, ductility, and stiffness. The results were then compared with that of the conventional connection. It was found that the proposed U‐hook with additional reinforcement performed better than that of the conventional connection and type 2 connection.

Block Shear Strength of Coped Beam Connections with Double Bolt Lines

AbstractCoped beam connections are commonly used in the construction of steel structures. Existing block shear provisions for these connections, with multiple bolt lines, account for the presence o...

Precast Concrete Column Beam Connection Using Dowels Due to Cyclic Load

The beam-column connection plays an important role in the building structure, especially when the load is cyclic. The main problem that must be solved is the beam and column connection panels. The purpose of this study was to analyze the characteristics of the hysteresis loop of the displacement load relationship with the control displacement of the precast beam-column connection due to cyclic loading. The research method used is the experimental method with a measurable object design test and a special testing method. The results of this study indicate that normal concrete has a compressive strength of 26.43 MPa, while grouted concrete has a compressive strength of 36.97 MPa. The findings of this study also show that the bond stress grouted concrete increases by 102.4% from normal concrete for D13 diameter screw reinforcement, while for D16 diameter, the adhesive stress increases by 51.63%. The findings of this study also show that in the ultimate condition, the load obtained in the tensile load is 13.58 kN with a displacement of 87.58 mm, while the compressive load is 12.62 kN with a displacement of 88.30 mm. This study concludes that the behavior of precast beam-column joints with dowels is stronger in resisting cyclic loads.

Filtering and Enhancement Method of Ancient Architectural Decoration Image based on Neural Network

Due to poor ambient light or uneven lighting, the old decoration image acquisition methods are easy to cause the image blur. To solve this problem, this paper proposes a neural network-based filtering enhancement method for ancient architectural decoration images, which preserves image details by enhancing contrast, smoothing noise reduction and edge sharpening. Based on the convolutional neural network which is composed of encoder, decoder and layer hop connection, the residual network and hole convolution are introduced, and the hole U-Net neural network is constructed to fuse the pixel feature blocks of different levels. This method enhanced the image contrast according to the gray level and frequency histogram, and aiming at the gray value of the pixel to be processed in the image. And the middle value of the gray value of the neighborhood pixel is used to filter the noise of the ancient building decoration image. The paper also analyzes the joint strength of beams and columns in ancient buildings, and calculates the elastic constants of beams and columns and the stress at the joint of them, considering the image texture characteristics of the wood in ancient buildings with the mortise and tenon connection of beams and columns. Experimental results show that the proposed method has good noise suppression performance, can effectively obtain image detail features, and significantly improve the subjective visual effect of ancient architectural decoration images.

Seismic performance of welded flange plate (WFP) connections in composite steel structures

This paper studies the seismic behavior of welded flange plate (WFP) connections of steel beams to H-shaped columns with composite floors. Nonlinear finite element models of exterior beam-column connections under monotonic and quasi-static cyclic loadings are developed in ABAQUS commercial software. Geometric, material, and contact nonlinearities are considered in the models, and the specimens are loaded up to the final failure point. The von-Mises J2-plasticity model with bilinear kinematic hardening and ductile damage parameter is employed to simulate steel constitutive behavior, and reinforced concrete is modeled by the Concrete Damage Plasticity (CDP) model enhanced with embedded steel rebars. Load-carrying capacity, ductility, failure modes, strain distribution, and energy dissipation capacity of the specimens are compared, and various effects of composite action are studied. The research represents the importance of considering the composite action in the design process, which contrasts with the common practice. Based on these observations, a novel reduced beam section detailing is proposed, which circumvents the issues with current design configurations, and provides an optimal seismic behavior for WFP composite connections.

Broadband energy harvester for low-frequency rotations utilizing centrifugal softening piezoelectric beam array

Harvesting the rotational energy has drawn great attention in the past decade with its abundance in our living environment and its great potential to power the wireless transmitter. However, issues exist that small-scale and resonant-frequency-based linear harvesters typically have high natural frequencies and narrow operating frequency bandwidth. Therefore, to design a broadband energy harvester for low-frequency rotations, this paper proposes the centrifugal softening beam array harvester. The broad bandwidth is achieved by arranging groups of inverted piezoelectric beams at different rotational radii in a straight array, which results in different centrifugal softening coefficients. This eliminates the tedious work of pre-designing and manufacturing beams with different geometries in a conventional beam array harvester. Furthermore, the centrifugal softening effect can decrease the resonant frequency of the harvester, leading to the higher energy output under low-frequency rotations. In addition, the analytical model of such centrifugal softening beam array with different interface circuits is firstly proposed based on the equivalent impedance method. Results show that for both parallel and series connections of piezoelectric beams, the output power is highest and the bandwidth is broadest with the parallel-SSHI circuit compared with those with the standard AC/DC and series-SSHI circuits. Despite that both the parallel-SSHI and series-SSHI circuits can significantly improve the output power compared with the standard circuit, the series-SSHI circuit has a degradation on the frequency bandwidth compared with the other two circuits. Specifically, when attached to the parallel-SSHI circuit, for ten identical parallel-connected beams with decreasing centrifugal softening coefficients, the 3 dB bandwidth can be broadened by up to 1240.7% within the frequencies lower than 20 Hz compared with that of a single beam.

Optimization of through-bolt steel beam connection to CFST column reinforced with rib plates using RSM method and MCEO algorithm

Optimization of through-bolt steel beam connection to CFST column reinforced with rib plates using RSM method and MCEO algorithm

PERILAKU SAMBUNGAN BALOK I DAN KOLOM TABUNG BAJA AKIBAT BEBAN SIKLIK

Using Concrete-Filled Steel Tube (CSFT) as a column component provides many advantages over steel columns and reinforced concrete columns. Steel tube serve as reinforcement as well as formwork for concrete filler material. Besides, restrain effect of steel tube prevent crack in the concrete. The concrete-filler on steel tube prevent local buckling and increases the strength and stiffness of the column. The lack of experience and complexity of the beam-column connection system becomes an obstacle to use the CFST as a column. In addition, strength and stiffness of the connection system on CFST should be sufficient to endure the earthquake loads. This research purpose to find alternate connection of CFST column beams and also to know hysterestis behavior, strength, stiffness and pattern of connection collapse due to cyclic loading. There are two specimens in this research, continuous joint of beam-column steel tube with concrete filler (BKM-T) and continuous joint of beam-column steel tube without concrete filler (BKM-K). BKM-K as a comparator to show an increasing strength and stiffness due to the concrete core. Load cycle of specimens refer to ACI 374.1-05. The test results showed the average maximum load (P peak ) of 32.59 kN on BKM-K increased to 34.08 kN on BKM-T. Elastic stiffness (K e ) at BKM-K of 0.78 kN/mm increased to 1.08 kN/mm on BKM-T. BKM-T also has a larger hysteretic loop than BKM-K. In addition, BKM-K and BKM-T adequate the strong column weak beam criteria with partial ductility.

Seismic behavior of innovation steel-embedded precast concrete beam-to-column joints

This study proposes a novel joint using embedded steel connections in columns and beams to further improve the seismic performance and assembly efficiency of hybrid precast concrete joints. Five joint specimens, comprising four newly designed prefabricated joints and one monolithic joint, were subjected to axial and cyclic loads to evaluate their seismic performance. In this investigation, the effects of various configurations of steel connectors and steel fiber-reinforced concrete (SFRC) in the core area and the connecting portion on the joint performance were considered. Recorded failure modes and hysteresis curves were used to analyze the seismic parameters, including strength, stiffness, ductility, and energy dissipation. The proposed joints were found to be reliable, depending on the test results. The novel precast concrete beam-to-column joints exhibited significant advantages over cast-in-place joints in terms of several performance characteristics. The use of SFRC in the panel zone and the connecting portion can inhibit the development of cracks. The embedded square steel tube may reduce the shear deformation owing to its restraining effect on the concrete. The inclusion of horizontal–vertical connecting plates benefits the internal force transfer and improves the bearing capacity and ductility of the joints. Hence, these novel joints with steel connectors in columns such as specimen PC3 or PC4 and H-steel in beams could be preferred for precast concrete beams after further improvement.

Finite Element Analysis of Overlapped Z-Purlins Restrained by Sheeting

Cold-formed steel Z-purlins with overlapping at the intermediate supports ensures the continuity of the bending moment. A continuous beam with two equal spans of 6 m is investigated under gravity loading using the finite element method. The numerical model includes the beneficial interaction between the Z-purlins and the trapezoidal sheeting. Finite element results show that the screw spacing and sheeting thickness has a limited influence on the resistance of the member. The effect of the overlapping length and detailing of the connection is studied through a parametric study. Six overlaps varying from 100mm to 1200mm (1.6% to 20% of one span) capture the change of the failure mode from the overlap edge to the support region of the purlin. The connection detailing is studied considering multiple bolt/screw patterns. The detailing and length of the overlap connection has a major influence on the moment distribution and consequently on the failure mode. The detailed finite element analysis shows that assuming the beam connection as continuous in 1D beam models lead to an unrealistic bending moment distribution and failure mode. Connecting the bottom flange using screws improves the overall load carrying capacity of the beam especially for short overlap lengths. The increase in resistance is attributed to the restraining effect on the free flange which fails due to distortional buckling.

Design Method for End-Plate Bolted Connections

The design of buildings envelopes is more elaborate than it has ever been. Starting from the design method of nodal space frames made of one layer of structure and covered in glass, this paper presents e new type of end-plate beam to beam connection. Specific to this is the fact that both end-plates are welded inside of the tubes, having a minimum gap between them of 2 mm. This will reduce considerably the in-surface and welding-induced end plates tolerances which appear at classical end-plate connections. Through the pre-tensioning of the bolts, a continuous contact surface is assured along the cross-sections of the hollow profiles. Several tests were run with the software Gas Win in order to establish the maximum capacity of the connection. This condition is achieved when the neutral axis goes out of the crosssection and the entire cross-section is compressed. Installation hand-holes were also considered. In order to get a better understanding about the force flow, an FEM analysis was run using the Abaqus software. A comparison between the results followed.

Seismic tests and nonlinear model of beam-CFDST column joints with blind fasteners

In recent years, substantial research efforts have turned towards concrete filled double skin steel tubular (CFDST) column due to its superior mechanical performance. However, an effective and convenient connection method between a CFDST column and a beam still needs to be investigated in depth. This paper tried to adopt the blind bolting technology in a CFDST column to beam connection. A series of joint specimens were prefabricated and designed with different end plate types, column hollow ratios and beam types to carry out pseudo-dynamic tests. Excellent seismic performance was detected for all test specimens. It was observed that increasing the column hollow ratio could moderately increase the ultimate strength and the specimen with extended end plate had higher ultimate strength stiffness compared with that with flush end plate. To accurately capture the dynamic response for this type of joint, an analytical model was developed considering the shear performance of panel zone and moment-rotation behavior of connection. Shear strength of CFDST column panel zone was modified from that of CFST column panel zone based on the yield line method for including the contribution of confined compression strut. It indicated that two potential yield mechanism might appear depending on the column hollow ration (χ). The analytical model could well predict the test results. The research and analytical results provided an effective connection method to assemble a CFDST column to a beam and supply a feasible analytical model to predict the joint performance.

Improved calculation of the rigidity of double-row piles and double-beam composite support and displacement analysis under different soil properties

As a new type of cantilever-type supporting structure, the double-row pile supporting combination system can improve the overall rigidity to maintain the safety and stability of the side of the foundation pit. The case of a double-row pile foundation pit support project in the Wanquan District of Zhangjiakou is taken as an example. Based on the existing double-row pile crown beam stiffness coefficient calculation method, the effect coefficient of the crown beam and the coupling beam is introduced to optimize and improve the effect of the coupling beam and the crown beam. The results show that (1) in the calculation of the double-row pile structure, the common lateral restraint effect of the crown beam and the connecting beam on the double-row supporting piles should be considered, and the rigid connection of the crown beam and the connecting beam should be taken as a whole to improve the rigidity coefficient of the double beam lateral support of a rectangular double-row pile. (2) The combined stiffness of the double-beam combined support system has a greater impact on the displacement of the pile top, and the displacement under a combined stiffness of 40-50 MN/m are close to the observed value. The calculated length of the crown beam and the introduced crown beam and connecting beam effect coefficient have a great influence on the combined stiffness of the double-beam composite support system. The combined stiffness decreases with the increase of the calculated length, and increases with the decrease of the effect coefficient. (3) The lateral support stiffness of the double-row piles under the double-beam composite support system is affected by the difference between the vertical and lateral displacements of the front and rear piles. The maximum lateral displacement of the front and rear piles is affected by the friction angle of the soil, the cohesion and the proportional coefficient of the horizontal resistance of the soil. Changing the tensile strength will not affect the displacement and deformation of the double-row piles. There is a displacement inflection point below the buried depth of the foundation pit and within the scope of the pile bottom. The displacement at the inflection point is equal under different friction angles and different cohesive forces.

Nonlinear Finite-Element Analysis of the Seismic Behavior of RC Column–Steel Beam Connections with Shear Failure Mode

RC column–steel beam (RCS) systems, a novel type of hybrid structure, have been used widely in recent decades owing to their excellent seismic performance and simple fabrication process. However, due to the effects of variable strengthening configurations on force-transfer mechanisms, the mechanical behavior of RCS connections has not been fully understood by existing experimental studies. This paper proposes a reliable finite-element model of RCS connections and investigated the effects of different strengthening configurations and design parameters on the seismic performance and shear mechanism. A detailed three-dimensional finite-element model was developed and validated against previously obtained experimental results, including load–displacement relationships and cracking patterns. Parametric studies based on the validated model were conducted. The studies showed that the axial load ratio significantly affects the failure mode and ductility of the connection. The load-carrying capacity of the connection is enhanced significantly when the concrete strength is increased. Furthermore, additional yield capacity of steel plates and transverse reinforcements has limited effects on crack propagation and strain state when adequate resistance can be provided.

Experimental investigation of a simple shear connection to concrete-filled FRP tube (CFFT) columns

The concrete-filled fiber-reinforced polymer (FRP) tube (CFFT) system has been widely studied as a robust alternative to conventional reinforced concrete (RC) for column construction. Despite the superior structural performance of this column system in terms of durability, strength and ductility, its application in building construction is limited due to a lack of viable designs for beams-to-column connections. To address this gap, this study proposes a simple connection for a circular CFFT column and a steel I-shape beam. The connection consists of a curved end plate with a shear tab that is attached to the finished CFFT using commercially available concrete anchors. In this study, three connection assemblies with adhesive and expansion anchors were tested under half-cyclic loading. The connection assemblies varied based on the type of the anchors and installation torque. The performance was evaluated in terms of ease of construction, shear capacity, moment-rotation relationship, and observable damage. The FRP shell eliminated concrete breakout failure and the anchors exceeded the theoretical pullout capacity noted by the manufacturer. A methodology for estimating the proof load of the proposed connection detail is presented. The proposed connection provides a viable option for simple connection of steel beams to circular CFFT columns. The findings may inform future research on beam-column connections for CFFTs and lead to an increased use of CFFT systems in building construction.

Seismic performance of self-centering circular concrete-filled steel tubular column to steel beam connection with web friction device

A novel self-centering circular concrete-filled steel tubular (CFST) column to steel beam connection is developed. The connection has a beam web friction device (WFD) that provides energy dissipation and post-tensioned (PT) high-strength steel strands running parallel to the beam. The PT strands provide self-centering behavior to the connection. The mechanical behavior of the connection was analyzed theoretically. Three full-scale specimens were tested to investigate the mechanical characteristics of the connections under low-cyclic reversed loading. And the effects of the parameters including the initial posttensioning force, the pretension force in the friction bolts though WFD and the number of PT strands on the performance of the connection were examined experimentally and numerically. Both the experiment and simulation results show that the self-centering capacity increased with the increase of initial PT force or the number of PT strands, however, decreased with an increase in the pretension force in the friction bolts; while the energy dissipation increased with an increase in the pretension force in the friction bolts. The beam and column remained elastic under 5% inter-story drift; the PT strands and WFD can provide excellent self-centering and reasonable energy dissipating capacities for the connection, respectively.

Energy dissipation capacity of precast concrete beam-column joint connected by double notch subjected to cyclic lateral loading

This paper presents the experimental investigation of full-scale precast concrete beam-column connections subjected to cyclic lateral loading. The specimen consists of three models. Two of which are precast beam-column connections and one is monolith. The precast and monolith specimen were designed for the same strength. The cross-sectional dimensions of the beam 250 mm x 300 mm and column 300 mm x 300 mm. Connections are placed in plastic hinge area, with a distance of h (beam height) from the face of the column which is expected to occur first destruction. Precast construction joints are distinguished, with 3 different models, namely monolith, double notch type 1 (STR-1), and double notch type 2 (STR-2). Maximum load capacity, hysterical behavior and energy dissipation are measured, and capacity is compared. The results showed that beam-column joint STR-2 are better able to absorb energy than beam column joint monolith and beam-column joint STR-1. Kumulative energy dissipation of monolith about 9333.07 kN-mm, STR-1 is 8336.76 kN-mm, and STR-2 is 10162.52 kN-mm. The use of dual notch connections (STR-1 and STR-2) provides satisfactory performance, which is marked by meeting the minimum relative energy dissipation ratio at a 3.5% drift according to the ACI Committee 374.1-05. The results show that the STR-2 beam-column connection is more capable of absorbing energy than the monolith beam-column connection and STR-1 beam connection. the value of monolithic cumulative energy dissipation is around 9333.07 kN-mm, STR-1 is 8336.76 kN-mm, and STR-2 is 10162.52 kN-mm. in principle, all three test specimens, monoliths, STR-1 and STR-2 provide satisfactory stability performance under lateral cyclic loads, because they still meet the minimum relative energy dissipation ratio at a deviation of 3.5% according to the ACI Committee 374.1 -05

Seismic response on T-head square-neck one-side bolted endplate connection of beam to square tubular column

Totally four T-head square-neck one-side bolted connections (TSOBCs) for H-beam to hollow section steel column (HSSC) and a standard double-sides bolted connection (SDBC) for comparison were tested under cyclic load to evaluate the seismic performance of TSOBC. Two arrangement patterns of the slotted bolt holes and two strengthening measures for the connections were studied in the tests, especially the comparison between the TSOBCs and the SDBC. The test results show that the failure mode of the TSOBCs is the same as that of the SDBC, which is endplate fracture. The TSOBC with Type-V bolt holes has higher rigidity, bending moment capacity, and energy dissipation capacity than the TSOBC with Type-H bolt holes. Overall, the TSOBCs have no less than 85% of the bending moment capacity and more than 130% of the ductility coefficient, and 145% of the energy dissipation capacity of the SDBC in whole cycle life, which indicates that TSOBC can replace SDBC under certain conditions. Moreover, the strengthening measures of endplate stiffener and concrete filled in the HSSC can significantly improve the yield bending moment of TSOBC by 13.2% and 50.8%, respectively, but the latter will weaken the ductility coefficient of the joint by 35.2%. Test results on the bending moment capacity and failure mode of TSOBC under static and cyclic loads agreed well with calculated results by currently available computational models.