Bolted End Plate Research Articles

Moment Capacity of Bolted-Side Plate for the Eaves Joint of Nested Tapered Box Beam Portal Frame

The joints of cold-formed steel (CFS) portal frames with box sections are primarily formed either through stiffened welded connections or by bolted end plates, which typically involve costly full penetration butt welds. In New Zealand, CFS portal frames with nested tapered box beam (NTBB) sections are popular, and the joints of these portal frames are also formed through a bolted end plate system. In literature, it was found that welds in these joints are prone to cracking in the heat-affected zone (HAZ) under bearing opening moments (tension). Therefore, this paper focuses on proposing an alternative connection system (bolted-side plate) for eaves joints without any weld, aiming to reduce the overall cost of construction and increase construction speed. The performance (strength and stiffness) of these joints is mainly dependent on the geometric details of the bolted-side plate, which is limited in Australia/New Zealand standards (AS/NZ 4600). Herein, a non-linear finite element (FE) model was developed for the NTBB portal frame and validated against the experimental test results from the literature. Firstly, the validated FE model was used to investigate the feasibility of using bolted-side plates for NTBB portal frames and found that the bolted-side plate can increase the ultimate capacity of NTBB portal frame by 9%. A parametric study was then conducted by considering different geometric details of the bolted-side plates under both closing (gravity) and opening (wind uplift) moments. Finally, unified design equations for the moment capacity of bolted-side plates were proposed based on the results of the parametric study, and their accuracy was assessed through reliability analysis.

Experimental, numerical, and analytical studies of asymmetric bolted square hollow section splices in bending

The flexural behaviour of two types of asymmetric bolted square hollow section (SHS) splices is investigated in this paper. The asymmetric bolted SHS splices are derived from the traditional bolted end plate SHS joints but with the end plate flushed to the SHS surface on one side or two adjacent sides, where a cover plate connects two SHSs. Firstly, four-point bending tests are conducted for two configurations under different loading conditions. Next, finite element (FE) analysis is carried out to simulate the experiments. To reduce the computational time, a simplified FE model is developed, which is further employed for a parametric study. Finally, the component method, which was extended for the asymmetric bolted SHS splices under tensile load, is verified against the FE models in the parametric study. The results show that the extended component method could effectively predict the stiffness and the resistance of bolted asymmetric SHS splices under different bending loads.

Experimental and numerical investigation of the bending behavior in nontraditional steel beam-to-beam tip connections

This study aimed to conduct combined experimental testing and numerical studies on the static performance of tip beam-to-beam flush endplate moment connections. The research parameters considered were bolt layout, diameters, and end plate thickness. Three specimens consisting of two IPE 300 beams connected to a beam of section HEA 300 using two end plates were designed and assembled with different bolt configurations. The grade of the steel elements was S235, while that of the bolts was 8.8. A monotonic load was applied to the specimen during testing, revealing failure modes such as fractures in bolts, end plate bending, and necking loosening of bolts. The study presented and discussed the moment rotation relationship, rotation capacity, and initial stiffness for the three specimens. A finite element (FE) model was constructed based on the moment-rotation curves of the tested connections, and the numerical and experimental results showed good agreement. An extensive parametric study was conducted to investigate the effect of different end plate thicknesses and bolts of various diameters and configurations on the connection's behavior. The study revealed that increasing the bolts' row number in tension rather than increasing the number of bolts in a row significantly affects the ultimate capacity and ductility of the connection. A thick end plate increases the connection's rotation capacity but decreases its ductility. The study also introduced a simple approach based on virtual work to predict the connections' bending stiffness using load and deflection results.

Numerical analysis of a prefabricated concrete beam-to-column connection with bolted end plates

Precast concrete structures have been widely used in China in recent years because of the obvious advantages in construction speed, labor saving and quality control. Many experimental and numerical studies have been performed to investigate the seismic behavior of the precast concrete structures. However, the numerical analysis on prefabricated concrete beam-to-column connection with bolted end plates (PCC) under cyclic loading is still limited. Therefore, in this paper, the developed finite element models (FEM) were established to further study the seismic performance of the PCC specimens. The sensitivity analysis were conducted to ensure the reliability and validity of the FEM. Then, the FE models of the typical specimens were validated by test data such as failure modes, hysteresis curves and steel strain. Parametric analysis was carried out to investigate the effect of the end plate thickness, preload of bolt, concrete strength, etc. The key parameters affecting the seismic behavior of the connections were obtained. Eventually, based on the numerical simulation results, the law between the responses of the connections and the key parameters was determined quantitatively by response surface methodology. According to the yield line theory, the theoretical formula on the bending capacity of the connection with thin end plate was derived. Meanwhile, the formulas on the bending capacity of the unbonded prestressed concrete beam were also obtained. The results indicated that the bearing capacity and initial stiffness of the connection were improved with the increase of end plate thickness and bolt preload. The steel box significantly enhanced the shear capacity of joint region of the PCC specimens. Although the bending capacity of the beam can be improved by increasing the concrete strength, high strength concrete significantly reduced the ductility. The calculated value of the connection matched well with the test or simulation data which may provide a reference for predicting the bending capacity of specimens with different failure modes in subsequent studies.

Component method for bolted SHS end plate splice joints loaded in tension

Bolted end plate connections are traditional solutions for splice joints with square hollow sections (SHS). A cover plate could be used on one side or two adjacent sides of SHS where the end plate is flushed, resulting in two types of asymmetric splice joints. The advantage of the asymmetric joints is that no space is required between the façade panel and the member surface whilst the easy assembly feature remains. The component method is used to design the bolted end plate connection, as stipulated in prEN 1993–1–8. However, the design rule is only available for connections with open cross-sections. In this paper, a modified component method for predicting the tensile resistance (end plate fails with failure mode 1 according to prEN 1993–1–8) and stiffness of the asymmetric bolted SHS end plate splice joints is proposed. First, a parametric study is carried out to develop the component method for the traditional symmetric bolted SHS end plate splices based on the validated finite element (FE) model. Next, a simplified two-dimensional FE model is employed to evaluate the effect of the asymmetric feature on the stiffness of the joint. Finally, a parametric study is carried out on two types of asymmetric joints to validate the interaction model of individual components. The resistance and stiffness of the asymmetric end plate splice joints are well predicted using the modified component method.

Seismic behaviour of precast concrete beam-column connections with bolted end plates

This paper presents the seismic behaviour of a dry beam-column connection with bolted end plates for precast concrete structures. Experimental tests were carried out on one cast-in-situ connection and three precast concrete connections with bolted end plates to study the behaviour under reversed cyclic loading. The load resistance, failure mode, ductility and energy dissipation capacity were determined from experimental results. Comparisons were made among different connections to show the influence of end plates and stiffeners on the connection behaviour. Test results showed that precast concrete connections with bolted end plates mainly dissipated energy through bending of the end plate and deformation of steel bolts. The final failure of connection resulted from the yielding of the end plate or crushing of concrete in the compression zone of beams, depending on the thickness of the end plate and the presence of stiffeners. The connection with bolted end plates could achieve good ductility and energy dissipation. Moreover, failure of columns and the joint core was prevented through the use of end plates. An analytical method was also proposed to evaluate the moment-rotation relationship of connections. The contributions of joint core, steel bolts and the end plate to rotational stiffness and moment resistance were quantified in the analytical method. Comparisons with test results showed that the analytical method can estimate the moment-rotation curve of connections with bolted end plates with good accuracy when failure of connection was dominated by steel bolts or the end plate. Design recommendations were also proposed for connections with bolted end plates.

Semirigid Bolted Endplate Moment Connections: Review and Experimental-Based Assessment of Available Predictive Models

Semirigid Bolted Endplate Moment Connections: Review and Experimental-Based Assessment of Available Predictive Models

Cyclic behavior of a novel bolted beam-to-box column connection with reduced beam section

The present research investigates the seismic performance of innovative subassemblages in built-up box columns with reduced beam sections (RBS) technique through the finite element (FE) analysis method. The configuration of the subassemblages additionally benefits from having an extended endplate connection, which allows the subassemblages to be erected quickly and at a lower cost. So far, there has been very little detailed research on RBS moment connections in box columns with extended bolted endplates due to the closed shape of box columns and difficulty of accessing the column inside for developing a reliable load path. To solve these complexities, a novel configuration called “Reduced Bolted Extended Endplate accompanied by Stub Beam (Reduced BEEP-SB)” is introduced. The new load transfer mechanism of the subassemblages is described. Furthermore, 35 various exterior beam-to-column subassemblages are modelled in ABAQUS/STANDARD FE analysis software and tested under the connection qualification cyclic loading conditions. The results indicate that the proposed subassemblages can push away plastic hinge formation at an appropriate distance from the column endplate interface. Also, the flexural capacity of subassemblages is approximately 10–20% higher than the beam plastic moment capacity. Moreover, the results in terms of moment-rotation curves and strain in critical sections show that the models without continuity plates could satisfy the connection qualification criteria. It is noteworthy that the accuracy of the introduced models was validated via two experimental models.

Cyclic behavior and mechanical model of a novel endplate connection to double-skin composite wall with slip-critical blind bolts

This paper presents an assembled bolted endplate joint for connecting steel beams and double-skin composite walls (DSCWs). The slip-critical blind bolts (SCBBs) were utilized in this novel joint to decrease welding work on-site. In order to investigate the seismic performance of this novel joint, two full-scale beam-to-wall SCBB endplate connection specimens with different design parameters were tested under incremental cyclic loading. Two failure modes of the specimens, namely beam bucking (mode I) and column wall damage (mode II), were finally observed. Analyses of test results indicated that a properly designed SCBB endplate connection with failure mode I could exhibit stable load-bearing capacity and satisfactory energy dissipating capacity. On the contrary, failure mode II should be avoided in engineering due to its unacceptable performance. Finite element models (FEMs) were developed and validated subsequently to further investigate the interior stress and damage distribution. The parametric analysis was also conducted using the FEMs. Based on the experimental results and numerical analyses, an alternative mechanical model was proposed to predict the bending resistance capacity of the column wall. The segmentation method was adopted in the model to eliminate the dependency on a specific pattern of yield line without reducing the accuracy. The reliability of the strength-prediction model of the column wall was validated through the results of the parametric analysis. The design methods and specifications for the components of the joint were finally summarized to make the SCBB endplate connection effectively used in practical applications.

Design and cyclic testing of bolted end plate connections between steel link beams and cross-laminated timber for coupled shear walls

Coupled cross-laminated timber (CLT) wall systems with ductile steel link beams offer an efficient, high-capacity lateral load resisting system for buildings in earthquake-prone regions. This study proposes a type of beam to CLT wall connection using a bolted end plate in a notched CLT panel edge to create a semi-rigid joint. A simplified analytical method is proposed to predict the connection strength and is compared against the results of full-scale experiments. The experimental strength values were all greater than the predictions from the proposed method. Therefore, the strength method seems conservative and is suitable for the capacity design of similar connections in coupled wall systems. The final specimen in the test programme was capacity designed and its cyclic test results demonstrated adequate connection strength and relatively high stiffness were achieved for a 200 mm-deep wide flange link beam. The specimen’s link beam yielded at an applied shear load of 180kN and reached a maximum strength of 278kN while dissipating a large amount of energy through steel yielding. The bolted end plate connection appears to be a practical solution for application in coupled CLT shear walls.

Behavior of end plate connection for steel angles

This study investigated the behavior of bolted end plate connection for structural angle sections. For the splice of angles under tensile loading, thick end plates attached to the end of angles are connected by one single high-tension bolt. To improve connection performance and reduce required plate thickness, plate washers made of the same material as that of the end plates are used under the bolt head and nut. Tensile tests of twenty-two specimens with different connection details were conducted. The tests showed that the governing failure mode was bolt rupture and the connection performance was affected by the thickness of the plates. The minimum thickness of end plate and plate washer determined by the yield line theory was conservative. Due to prying action, the connection strength (i.e., the tensile load of angles) was reduced to about 85% of the tensile strength of high-tension bolt. The force transfer behavior of the end plate connection with and without plate washer was investigated in detail through finite element analysis.

Experimental study on the seismic performance of steel–concrete beam–column connections for prefabricated concrete frames

A novel type of prefabricated steel–concrete beam–column connection with different configurations for moment-resisting frames was developed for better constructability . Five beam–column connections, four prefabricated steel–concrete specimens, and one reference monolithic joint were tested under reversed cyclic load–displacement controlled conditions. The main variables were the steel form in beams and columns, fabrication method , and use of steel fiber reinforced concrete (SFRC) in the joint and connection parts. The cracking patterns and load–displacement hysteresis curves were recorded during the test. The efficiency of the developed connection was compared based on bearing capacity, energy dissipation , ductility, and stiffness. The results revealed that the prefabricated specimens with welded reinforcement connection exhibited flexural failure at the prefabricated beam, whereas the specimens with bolted end plates or weld-bolted H-steel beam connecting method failed through joint shear failure. The proposed prefabricated H-steel concrete connection with bolted end plates and SFRC had higher strengths and stiffnesses, more stable load–displacement cycles, and better energy dissipation capabilities. Moreover, the concrete spalling in the joint was adequately controlled, and shear deformation was also reduced. The H-steel beam connector in the proposed connection could effectively transfer loads under earthquakes. • A new prefabricated concrete beam–column connection connected with variable steel configurations is developed. • Cyclic loading tests performed on four prefabricated connections and one monolithic connection. • The prefabricated connection with welded reinforcements to H–steel flange fails in flexural failure. • Connections with bolted end plates or weld-bolted H-steel connection shows shear failure. • The prefabricated connections demonstrate satisfactory strength, stiffness and energy dissipation capacity.

Experimental and theoretical modeling for predicting bending moment capacity of T-head square-neck one-side bolted endplate to tube column connection

One-side bolting technology is expected to play an important role in the bolted connection between H-beam and Hollow Section Steel Column (HSSC). By evaluating the possible defects of the existing one-side bolts in terms of cost, installation, and mechanical properties based on plentiful reported studies, a new type of T-head Square-neck One-side Bolt (TSOB) was proposed, which has a simple construction, can adapt to the rough installation manners in the construction site, and no additional auxiliary tools are required. The bending performance of four T-head Square-neck One-side Bolted Connections (TSOBCs) for a beam to a HSSC and a Standard Double-sides Bolted Connection (SDBC) for comparison was experimentally studied, in which two arrangement patterns for the slotted bolt holes and two strengthening measures of stiffeners on the endplate and inner concrete in the HSSC was explored. The results show that the TSOBC with vertical bolt holes has nearly the same yield moment, and the horizontal bolt holes have more excellent post-yield performance, compared with the SDBC. Besides, three yield line patterns and an analytical model for calculating the bending bearing capacity of the HSSC and the concrete strengthened HSSC are proposed, respectively. • Tests on beam-to-column connections using TSOBs under bending were conducted. • TSOBCs have no less than 85% of the bending moment capacity of the traditional SDBCs. • Three novel yield line patterns of tube column wall were proposed. • A novel bending moment capacity calculation model of CFST column was presented. • Design methods of TSOBC were recommended.

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.

Lateral‐torsional buckling of a stiffened beam with semi‐rigid joints

AbstractThe paper presents an experiment and a numerical analysis of a steel beam subjected to three‐point bending. The beam was connected to short column stubs by bolted end plates. The joints were designed as semi‐rigid and their influence on the lateral‐torsional buckling resistance of the beam was evaluated. The cross‐sections of the beams and the columns were IPE 180 and HEB 140, respectively. The columns were 1 m long and were rigidly connected to the loading frame at their ends. The beams were 3.3 m long and were loaded at midspan. 9 beams were tested in total, from which 3 beams were without any stiffeners, 3 beams had two inclined stiffeners welded prior to the test, and 3 beams upon which the stiffeners of the same geometry were welded under load equal to 50 % of the bending resistance of the unstiffened beam. The stiffeners were at one third and two thirds of the beam span. The experiment was modelled in software using Component‐based Finite Element Method. Shell elements were used for plates and special nonlinear springs and interpolation links for simulation of bolts and welds. Geometrically and materially nonlinear analysis with imperfections was used. The experimental results were compared to the model. A sensitivity study with various levels and kinds of initial imperfections was performed.

Meshless numerical simulation of steel connections: application to the T‐stub component

AbstractFinite element analysis is a widely used simulation technique in steel design to analyze the structural behavior of structural components, such as beams, columns or connections. The major steps involved in finite element simulations are the definition of the basic parameters and the discretization in elements of the component, also known as preprocessing; the analysis of the model and the post‐processing by the representation and the interpretation of the obtained results. On the particular case of bolted connections, the most time‐consuming of these three phases is that of preprocessing, because on traditional finite element technology is required that the real geometry of the CAD model is simplified to be meshed and analyzed; this task is specifically severe and requires paying close attention on the case of components affected to concentration stresses. Nowadays, different techniques have been proposed and developed with this objective: reduce costs in terms of time and specialized human resources because the workflow is easier and simpler. One of these methods are the known as the meshfree methods, that do not require connection between nodes and are based on the interaction of the points of the geometry with the neighbors, so the processor analyzes taken as base the real CAD geometry and no simplifications are needed.On this paper is exposed the meshless method based on the theory of external approximations as an alternative to the classic finite element method. This method is based on the theory where all parts of the assembly are considered as different elements, and the approximation of displacements inside is arbitrary and not only by polynomials. The convergence of the simulation model is based on the external equilibrium of the assembly. The method is applied to a practical case: the simulation of the T‐stub connection. The T‐stub component corresponds to one T‐shaped steel profile bolted through their flanges and loaded through their web until collapse, and its behavior is similar to the tension zone of beam to column bolted end plate connections. The analysis of strength, stiffness and ductility have been widely investigated experimentally, by simulation and theoretically, and they are obtained from the force‐displacement characteristic curve. Information presented by Bursi and Jaspart on the paper “Benchmarks for finite element modelling of bolted steel connections” are considered to elaborate the models and to compare the results.

Experimental studies on thread-fixed one-side bolted endplate connection with internal strengthening structure

The thread-fixed one-sided bolt has excellent potential application in engineering practice thanks to its low cost and easy installation. However, there must be a sufficient length of threads on the hollow square column wall to prevent the threads from premature failure. This paper proposed two novel internal strengthening structures to strengthen the thread-fixed one-sided bolted beam to hollow square column endplate connection and experimentally studied the behavior of this type of connection. A total of six specimens subjected to static bending moment were tested. The experimental results were analyzed in this paper to evaluate the structural performance of the strengthened connection and the efficiency of different strengthening structures. It was indicated that the double H-shaped stiffener could better improve the yielding bending moment of the connection, compare to polygonal steel tube stiffener. And the bolt hole threads failure and the column wall yielding failure could be avoided at the same time by utilizing strengthening structures moderately, which proved that this type of connection could meet the design criteria of “strong column - weak beam”. Moreover, based on the test results and theoretical analysis, the calculation methods for corresponding failure modes were proposed to predict the yielding bending moment capacity of the strengthened connection. And the calculated results were in good agreement with the test results.

Seismic behavior of thread-fixed one-side bolted endplate connection of steel beam to hollow square column

Experimental studies were conducted to investigate the seismic behavior of the Thread-fixed One-side Bolts bolted Endplate Connection (TOBEC) of a steel beam to a Hollow Square Column (HSC). Three forms of strengthening methods were applied to the TOBECs, including the infilled concrete of HSC, the small facing plates, and the big facing plate outside of HSC. In addition, one TOBEC with no strengthening structures and one traditional Standard Nut-fixed Bolted Endplate Connection (SNBEC) were tested for comparative analysis. Presented test results included failure modes, bending moment strength, rotation ability, ductility, strength and stiffness degradation, and energy dissipation capability of connection. Test results indicated that these strengthening methods could effectively improve the mechanical performance of TOBECs. The initial stiffness and ultimate bending moment of the strengthened TOBECs could reach or even exceed those of SNBECs. The strengthened TOBECs could satisfy the rotation limitation requirements specified in both GB50011-2010 and FEMA-350, which proved the applicability of TOBECs in moment-resisting framed structures.

Seismic behavior of double-HSS links for eccentrically braced frames

This study experimentally and analytically investigates an innovative double-HSS link (DHL) used as the active link in eccentrically braced frames (EBFs). Hollow structural sections (HSS) are mechanically efficient and are used in resisting compression, torsion, and bending. Their high torsional rigidity generally eliminates lateral-torsional buckling (LTB). As a result, the plastic rotational capacity and strength degradation rate are mainly governed by flange local buckling (FLB) and web local buckling (WLB). The proposed configuration consists of a double-HSS connected to braces or columns through a center gusset plate secured by flare-bevel groove welds. The advantages of the proposed configurations are: (1) They effectively reduce the width-thickness ratios (b/t) of the flanges by using two HSSs with much shorter flanges, which considerably increases the compactness thereby enabling a large rotational capacity. (2) They provide simple and practical connection details between the link and braces or columns. (3) Typically, double-HSS sections have an e/(Mp/Vp) ratio much larger than that of wide-flange sections due to the fact that double-HSS sections have four webs which significantly increase the shear capacity. Consequently, a DHL can yield in flexure even with a length similar to that of a wide-flange shear yielding link. This in turn eliminates the need for web stiffeners. (4) The welding requirement for DHLs is less than that of the conventional shear links since no stiffeners are required. (5) The overstrength factor due to strain hardening produced by flexural yielding links is generally less than that produced by shear yielding links leading to more economical designs for the elastic portion of the frame, and (6) the iteration design process is minimized by balancing the link length and rotational demand because of a single flexural yielding mode. Furthermore, experimental and analytical results indicated that the novel DHLs can sustain larger plastic rotations and meet AISC 341′s acceptance criterion for shear yielding links. In addition, DHLs can be potentially used in D-braced EBFs with links attached to columns because the link-to-column connection of DHL remains essentially elastic. DHLs can also be used as a replaceable link which is attached to the beam and column through bolted end plates.

Parametric study of steel flush and extended end-plate joints under column loss scenario

In steel-framed structures, joints play an essential role in providing a frame response to loading under persistence scenarios and especially in robustness analysis, which is very often executed in column loss scenarios. A type of joint used in framed structures is a bolted end-plate joint with extended and flush end plates. Experimental tests of six configurations of extended and flush end-plate joints were conducted to understand the actual joint behaviour under loading based on bending moment and tension force from catenary action. An advanced 3D FEM model of the joints was created using Abaqus software. Validated to own results of the experimental tests models were used in a wide parametric study to investigate the effect of the arrangement and thickness of the end plate, number, placement, and grade of bolts. The results provide practical recommendations for improving the joint characteristics required in accidental scenarios, for example, for enhanced resistance and rotation capacity under bending moment and tension force. The change from brittle to ductile failure mode was analysed as the second major parameter of joint ultimate behaviour. The thicker end plate and higher bolt diameter as the main component of the connection with the unstiffened column web was recommended to increase capacity in an accidental scenario. Finally, few proposals were presented to create innovative joints that demonstrate better performance in the column loss case: additional channels, saddles, and rings at bottom beam flanges. A significant increment in the load capacity and rotation capacity of the modified joints was achieved. The failure mode of the modified joints was changed moving the damage outside the joint zone. Further, the brittle destruction of bolts and end-plate fracture were avoided in the innovative models of joints.