Bolt Arrangement Research Articles

Flexural strength of end-plate connection with several different bolt arrangements

Abstract An end-plate connection is one of the common connections implemented in beam-column joints. This connection used a combination of bolts and welds as the connectors, so it is also specified as a semi-rigid connection. In general, the end-plate connection is applied to withstand the bending moment and to enhance its bending capacity, the connection area of the end-plate is generally enlarged. So far, the studies carried out to obtain the contribution of bolt arrangements to flexural strength are very limited, so maximum flexural capacity has not yet been optimally achieved. This research aims to examine the flexural strength of end-plate connections varied by bolt arrangements and bolt connection areas. The study was first conducted by analytically modeling the end-plate connection in SAP 2000, where the internal forces, i.e., shear force and moment were obtained from this numerical study. The theoretical studies were also carried out by considering internal troops to discover the influence of the bolt configuration on the end-plate connection to the flexural strength. The height of the area connection was also assorted, i.e., 100 mm, 200 mm, and 300 mm. The study revealed that enlarging area connections and increasing the number of bolts, reduce the tensile and shear stress at the maximum rate of 97.6 and 50 %, respectively. However, it can increase the flexural strength up to the rate 15 times from the minimum flexural strength. This result revealed that enlarging the connection area and adding the number of bolts can be suggested to enhance the flexural capacity when the end plate connection deals with a strong bending moment.

Analytical model for cyclic behavior of cold-formed steel bolted connection frames considering local buckling

Cold-formed steel (CFS) structures are increasingly popular in the construction industry due to their high strength-to-weight ratio, ease of fabrication, and cost-effectiveness. This study focuses on the development of a detailed mathematical model to accurately simulate the cyclic behavior of CFS moment-resisting bolted connection frames, particularly considering the local buckling of connected frames. Bolted joints are preferred in thin-walled CFS structures over welded joints due to their ease of installation and adaptability in seismic design, relying on slip and bearing mechanisms of bolts to accommodate inelastic deformations and dissipate energy during seismic events. The proposed model incorporates these mechanisms and validates them against experimental data and refined finite element analyses. Significant findings highlight the importance of the balanced number and arrangement of bolts in preventing excessive bolt slip and premature buckling. This research provides a robust analytical tool for optimizing bolted joint designs in CFS bolted connection frames, contributing to safer and more resilient CFS structures in seismic regions. The model’s computational efficiency further enhances its practicality for engineers and researchers.

Progressive failure analysis of woven and non‐woven CFRP composite/steel bolted joints

AbstractDue to recent advancements in textile fabrication, woven fabric reinforcements are used in composite structures as an alternative to traditional unidirectional fiber reinforcing layups. In this paper, experimental work was performed to study the behavior of multiple bolt‐lapped joints under uniaxial tension. Different bolt numbers, composite layups, and fabric configurations were studied. Single‐ and double‐lap configurations were used to investigate the effect of secondary stresses. It was found that the P‐δ curves of lapped joints exhibit four primary stages: a linear elastic stage, followed by a nonlinear hardening stage, then linear hardening leading up to the peak, and finally a softening stage. For double‐lapped non‐woven joints, the curves encompass only the first three stages; however, for woven composites, the last stage is very small. In addition, among the laminates, the non‐woven laminate sustains the highest normalized failure load, except in the staggered case, where the quasi‐isotropic woven laminate exhibits higher strength. Conversely, the bidirectional woven laminate demonstrates the lowest loads and the highest deformation.Highlights A study compared bolted joint performance of woven and uni‐based composites. Lapped joints with different bolt arrangements were experimentally studied. P‐δ curves showed elastic, nonlinear, linear hardening, and softening stages. Woven laminates showed higher displacements compared to non‐woven laminates. Secondary bending induced additional stress with less impact on woven samples. Bearing failure predominated, with variations in extent of bearing damage.

Experimental investigation on an innovative built-up cold-formed steel I-section connection

Bolted connections for built-up cold-formed sections are studied using different section configurations, gusset plates, and bolt arrangements. This paper presents the study of a connection between beam and column in light-weight steel frames with spans ranging between 8.0 and 12.0 m and a maximum height of 6.0 m that are used in agricultural sheds. The cross section of the beam and column is a novel built-up cold-formed cross section. A total of eight connections were tested and studied. The purpose of the study is to determine the effect of serval factors on the moment capacity and failure modes of the connection. The experimental study considered the effects of different shapes of tie plates, numbers, and spacings of bolts, as well as the effect of strengthening angles with different numbers of bolts in the connections. The experimental results showed that the failure modes in all connection types were due to a local failure in the connecting parts. The experimental results revealed that the configuration type has a great influence on the moment capacity of the connection.

Numerical Investigation of Cold Formed Z Purlins with Lap Bolted Connection

Abstract The main aim of this paper is to investigate the flexural rigidity of lapped cold-formed steel (CFS) purlin connections under monotonic loading, using a numerical model developed with finite element software ABAQUS. The purlins are made up of CFS Z-section, while high strength bolts of diameter 12 mm and grade 8.8 have been used. The test setup consists of simply supported two Z-section that are connected together using overlap connection, where load is being applied at mid span. Furthermore, a parametric study has been conducted to investigate various parameters including, length of lapped connections, thickness, and depth of CFS section and arrangement of bolts, to end up with a total of 15 case specimens. All case specimens were examined in detail in terms of load carrying capacity and deflection characteristics. The results showed that overlap connection is capable of transmitting moment and acts as semi-rigid connection. Moreover, results proved that increasing the ratio of overlap length to beam span resulted in an increase in connection moment capacity. Additionally, decreasing the ratio of lap length to section thickness increases the flexural capacity. Finally, the specimens with bolts in both flange and web at the position of overlap connection were found to have the highest moment capacity.

Monitoring of interface separation damage in buckling-restrained steel plate shear walls using piezoelectric based smart aggregates under cyclic loading

Interface debonding damage is a critical issue for many prefabricated concrete components. Various studies have employed different methods to detect debonding behaviors and provided quantitative damage indexes. In this paper, we propose a novel monitoring approach for detecting interface debonding damage in Engineered Cementitious Composite (ECC) panel-restrained composite steel plate shear walls (SPSWs) using piezoelectric ceramics (PZT). Four SPSWs were designed with different types of concrete, steel plate thicknesses, and bolt arrangements for the cyclic loading experiment. Energy data was collected for time-domain and wavelet packet analysis. The root mean square deviation (RMSD) was then calculated to provide a quantitative damage index for the specimens. The highest damage indices for each specimen were 0.770, 0.963, 0.988, and 1, respectively, which corresponded well with the actual damage scenarios. The experiments verified that using PZT can accurately monitor debonding damage in SPSWs.

Flexural behaviour of shallow-embedded steel column bases

This paper investigated the flexural behaviour (the initial rotational stiffness and ultimate moment resistance, in particular) of the shallow-embedded column bases through experimental and numerical approaches. Three full-scale tests with different embedded depth ratios (i.e., 0.5, 1.0 and 1.5) were carried out, from which the moment-resisting mechanisms were identified and the effects of the embedded depth ratio on the initial stiffness, moment resistance and ductility were evaluated. The test results were further used to evaluate the accuracy of the available resistance and stiffness models for the shallow-embedded column bases. The resistance models codified in design codes GB 50017-2017 and AISC 341-16 are highly conservative, with an average prediction accuracy of 0.268 and 0.451, respectively; by contrast, the resistance models recently reported in the published articles show better accuracy. The stiffness models are fewer in number and are also inaccurate for the shallow-embedded column bases. Complementary finite-element models were developed and validated. Subsequently, systematic parametric finite-element analyses were performed to investigate the effects of axial force and shear force in the steel column, as well as those of the structural details such as the presence of base plate, arrangement of anchor bolts and width of concrete foundation. Shear force has an adverse effect on both the initial stiffness and moment resistance, and this effect becomes more significant with the increase in the embedded depth ratio; axial compression force leads to an increase in both the initial stiffness and moment resistance, which is more pronounced for embedded column bases with smaller η-values. Among all structural details, the presence of the base plate has the most notable influence on the flexural behaviour of the shallow-embedded column base, increasing both its initial stiffness and moment resistance; comparatively, the effects of the other structural details are minor or even could be ignored.

A new elastoplastic model for bolt-grouted fractured rock

Complexities in mechanical behaviours of rock masses mainly stem from inherent discontinuities, which calls for advanced bolt-grouting techniques for stability enhancement. Understanding the mechanical properties of bolt-grouted fractured rock mass (BGFR) and developing accurate prediction methods are crucial to optimize the BGFR support strategies. This paper establishes a new elastoplastic (E-P) model based on the orthotropic and the Mohr-Coulomb (M-C) plastic-yielding criteria. The elastic parameters of the model were derived through a meso-mechanical analysis of composite materials mechanics (CMM). Laboratory BGFR specimens were prepared and uniaxial compression test and variable-angle shear test considering different bolt arrangements were carried out to obtain the mechanical parameters of the specimens. Results showed that the anisotropy of BGFR mainly depends on the relative volume content of each component material in a certain direction. Moreover, the mechanical parameters deduced from the theory of composite materials which consider the short fibre effect are shown to be in good agreement with those determined by laboratory experiments, and the variation rules maintained good consistency. Last, a case study of a real tunnel project is provided to highlight the effectiveness, validity and robustness of the developed E-P model in prediction of stresses and deformations.

Novel steel connection for modular houses in indigenous communities: An experimental study

Remote Indigenous communities across Canada are facing housing shortages and the need for major repairs, which resulted from engineering challenges that obstructed the construction phases. Prefabricated steel moment-resisting frame modular houses are currently utilized as alternatives to typical conventical houses because of their technical advantages, such as better-quality control, lightweight structures, and ease of transportation to remote and rural regions. To explore the potential use of hollow structural sections (HSS) in panelized steel modular structures, this study presents a novel steel-bolted connection for connecting HSS beams to HSS columns using high-strength long bolts, indicating that the connections can be easily installed without requiring skilled workers and heavy machinery. Six specimens were fabricated and tested under monotonic load with a Digital Image correlation (DIC) camera to capture full-field 3D displacement and deformation until failure accurately. The impact of different geometric parameters such as bolt arrangement, extended plate thickness, number of bolts, and the existence of stiffener on the mechanical performance of the joint, stiffness, inelastic rotation, ductility, and failure modes were analyzed. Bolt arrangement with an aspect ratio of 1:1 was found to increase the connection capacity, initial stiffness, and ductility by 7%, 216%, and 26%, respectively. The yielding and rotation of the extended plate were eliminated using a stiffener. Increasing the number of bolts triggered the connection's ability to gain more capacity at earlier stages and reduced joint rotation by 60%.

Shear-bearing capacity prediction of concrete-infilled double steel corrugated-plate shear walls

The concrete-infilled double steel corrugated-plate shear wall (CDSCW), consisting of two corrugated plates, infilled concrete, and two boundary elements, is a highly efficient force-resistant structural component under axial compression, in-plane bending, and shear loading. Previous research has primarily focused on the structural performance of CDSCWs under axial compression and bending loads. However, there is still a lack of a sufficiently accurate design method for predicting the shear-carrying capacity of CDSCWs. This paper presents numerical investigations into the shear buckling behavior of corrugated plates and proposes the shear strength design method of CDSCWs. Firstly, the shear elastic bilateral buckling behavior of corrugated plates subjected to lateral constraints of high-strength bolts is explored, considering influences of the bolt arrangement, the bolt spacing, and the dimensions of the plates. The formulas involving various buckling modes are established as a foundation for the further elastoplastic buckling capacity prediction. Then, by applying the normalized slenderness ratio, this study suggests the shear-carrying capacity design of the corrugated plates considering the bolt constraints and unilateral concrete constraint on the plates. Moreover, the shear-carrying mechanism of the CDSCWs is revealed: when CDSCWs experiences shear failure, the corrugated plates are primarily subjected to the shear load, with the boundary elements acting as constraints on the corrugated plates. Finally, a design method is proposed for the CDSCWs’ shear-carrying capacity prediction, which shows good accuracy and offers foundations for the stability design of corrugated plates under shear loads.

Experimental and numerical characterization of column webs/faces loaded out-of-plane in steel joints

This paper presents a comprehensive investigation into the behavior of column webs/faces under out-of-plane loading within steel joints. The experimental component of the study involves testing five profiles, encompassing both open and closed sections with varying web slenderness and steel grade, subjected to direct out-of-plane tensile loads through bolted connections, utilizing both single and double rows of bolts. Concurrently, numerical simulations are conducted using finite element models, thoroughly calibrated with the experimental results. Drawing upon the calibrated numerical models, the paper systematically explores the influence of key parameters, including web slenderness, bolt arrangement, and analysis methods, through a parametric study involving 167 cases. A careful comparison of the observed behavior of the component from experimental tests, numerical models, and analytical models for initial stiffness is presented. Finally, the initial stiffness formulation derived from a recent model developed by the authors is improved to align with the observations from the experimental and numerical results.

Mechanical properties of multi-bolted Glulam connection with slotted-in steel plates

The Bolted Glulam Connection with Slotted-in Steel Plates (BGCSSP) is widely employed in modern timber structures due to its advantages of convenient installation and reliable force transmission. However, the current design methods lack rigorous mechanical derivation and fail to consider various influencing factors comprehensively. Furthermore, designing multiple dowel connections based on the behavior of individual dowels impedes optimization and limits the applicability of design rules. To systematically investigate the failure modes and mechanical characteristics of Multi-bolted Glulam Connection with Slotted-in Steel Plates (MGCSSP), specimens from 12 groups (6 specimens per group) were subjected to parallel grain tensile tests, considering four key influencing factors: bolt quantity, bolt arrangement, bolt diameter, and base material thickness. The experimental results indicate that as the number of bolts increases, the failure transitions from double-hinge failure to single-hinge failure. Additionally, there is an observable upward trend in both initial stiffness and peak load for the same type of specimen as the quantity of bolts increases, accompanied by a decreasing trend in the ductility coefficient. The analysis of experimental results reveals that both the quantity and diameter of bolts impact the initial stiffness and peak load of MGCSSP specimens. Based on experimental observations, dual-parameter calculation models for the initial stiffness and peak load of MGCSSP are proposed. The calculated results of the models align well with experimental data, providing references and convenience for the design of MGCSSP.

Structural Performance of Bolted Lateral Connections in Steel Beams under Bending Using the Component-Based Finite Element Method

Structures must provide strength, stability, and stiffness to buildings and at the same time be efficient. This study addressed the effect of design elements and parameters on the strength of bolted lateral connections in steel beams under bending using the component-based finite element method. The variables evaluated were plate thickness, horizontal and vertical spacing between bolts, and geometric arrangement of bolts. Finite element software was used to evaluate the stress state of the junction plate, its plastic deformation, and bolt shear. A sensitivity analysis was performed to determine which bolt arrangements result in safer and more efficient designs using the same components. Stress distribution within the junction plate and plastic deformation values were used to evaluate the structural performance of the joints according to EuroCode 3. The results showed that placing bolts near the edge of a plate affected the bolts’ utilization, especially with thinner plates. Additionally, introducing an offset between central and outer bolt rows is not recommended as it worsened the stress distribution and the structural performance.

Bolt loosening angle detection through arrangement shape-independent perspective transformation and corner point extraction based on semantic segmentation results

The identification of loosened bolts is crucial for the early warning of structural damage and maintaining the overall stability of the structure. Most existing two-dimensional computer vision-based bolt loosening detection methods need to rely on the bolt arrangement shape for perspective transformation, to overcome this limitation, this study proposes a bolt loosening angle detection method through arrangement shape-independent perspective transformation and corner point extraction based on semantic segmentation results. First, a dataset of 1748 images containing bolts is collected. Second, a bolt region of interest (RoI) detection is developed to extract the sub-image of the bolt. The results show that the training and validation accuracy of bolt RoI detector are 99.5%, and 99.4%, respectively. Then, the contour corner points are extracted, the automatic and arrangement shape-independent perspective transformation of the image is completed using the planar homography-based image processing algorithm and the regular hexagonal characteristics of the bolt. Finally, automatic estimation of the bolt angle is performed on the corrected bolt image. The proposed method is used to detect bolt images obtained from different shooting distances, perspective angles, and lighting conditions. The results demonstrate that the method can accurately detect the looseness of bolts in bolt connections, and the quantification error is mostly less than 3°, it has the potential for real-time bolt loosening monitoring of multi-type bolted connections.

Effects of off‐axis load direction on tensile properties of pultruded fiber‐reinforced polymer bolted joints with multi‐directional fiber lay‐ups

AbstractThe limited joint performance of unidirectional (UD) pultruded fiber‐reinforced polymer (FRP) composites poses a critical issue that constrains their application in structural engineering. Moreover, UD pultruded FRP joints display a notable reduction in strength and stiffness as the load angle diverges from the fiber pultrusion direction. This paper presents a numerical study of bolted pultruded FRP joints with different off‐axis loading directions. Two types of fiber lay‐ups, including UD and multi‐directional (MD), were investigated. Static tensile tests were conducted with the loading direction parallel to the pultrusion. A finite element model was validated by the test results. Studied geometric parameters includes the end‐to‐diameter (e/d) ratio, width‐to‐diameter (w/d) ratio, and bolt arrangement. Compared to UD joints, MD joints exhibited significant advantages in strength and stiffness under off‐axis loading with an increasing of 78.3% at a loading angle of 90°. Compared to the end distance, plate width has a more significant impact on the off‐axis behaviors of MD joints, especially between 30° and 75°. Multi‐bolted joints were more susceptible to net‐tension failure than single‐bolted joints. Furthermore, classical laminate theory and Hashin failure criterion were employed to predict the resistance of single‐bolted FRP joints with different loading angles, achieving high accuracy.Highlights Under increased off‐axis loading angles, compared with unidirectional (UD) joints, multi‐directional (MD) joints display a less reduction in both strength and stiffness. At a 90° angle UD joints displayed only 21.7% of the joint resistance of MD joints. Compared to the end distance, plate width has a more significant impact on the off‐axis behaviors of MD joints, especially between 30° and 75°. Classical Laminate Theory, Hashin failure criterion were effectively utilized to predict the ultimate strength of pultruded joints under various tensile loading angles, yielding high accuracy. The error between theoretical and simulated values is within 20%.

Experimental and theoretical investigation on seismic behavior of precast wall panel structures based on different bolt arrangements

Previous studies have shown that bolt-connected precast wall panel structures have good seismic behavior. However, the existing research lacked a complete calculation method for the bending capacity of horizontal seam. This paper proposed a novel method for calculating the bending capacity of horizontal seam. To validate the applicability and rationality of the calculation method, six precast wall panel specimens with bolt-connected joints were designed. Quasi-static tests were conducted to investigate the influence of parameters such as the number of bolts, arrangement, size, and type on the seismic performance of the wall panel structure. The main test results indicated that: (1) With an increasing number of bolts, the failure area of the specimens transitioned from the tensile joint to the bottom of the concrete compressive boundary. (2) There were obvious relative vertical slips between the wall panel and the connectors, which reduced the height of the concrete compressive zone. (3) The maximum bending capacity of the wall panel structure significantly decreased when high-strength bolts were replaced with ordinary bolts. Finally, considering the relative vertical slips between the connectors and the wall panel, the calculation method for the maximum bending capacity of the horizontal joint was improved and optimized. The results showed that the maximum bending capacity calculated using the improved method aligned well with the test results and can be applied to the study of horizontal joints in bolt-connected concrete wall panel structures.

Experimental and numerical studies on friction energy-dissipating combination chord of staggered truss

Staggered truss framing systems have the problem of insufficient energy dissipation capacity in high intensity areas. To improve this situation, this paper proposes to replace the top chord of the staggered truss with a combination chord for frictional energy dissipation. Two groups and a total of four 1:2 scaled friction energy-dissipating combination top chord specimens were designed and fabricated, and hysteretic performance tests were carried out on them under low cycle reciprocating loads. It was investigated how high-strength bolt pre-tightening force and bolt layout affected the capacity of the combination chord to dissipate energy. The experimental results show that the hysteresis curve of the combination top chord for friction energy dissipation almost presents an ideal rectangle, and its energy-dissipating capacity is very strong. The combination top chord's capacity for friction energy dissipation increases with the increasing pre-tightening force of the high-strength bolt, but its stability for energy dissipation decreases. When the bolt layout is the staggered arrangement of single and double bolts, the initial energy dissipation and cumulative energy dissipation are weaker than that of the uniform arrangement of double bolts. Then, the friction energy-dissipating staggered truss with a sliding bottom chord was proposed to improve the load state of the diagonal web member in the staggered truss. The numerical simulation results show that the overall energy dissipation capacity and lateral bearing capacity of the staggered truss with the bottom chord sliding are 4.0% and 24.5% higher than those of the staggered truss with the top chord sliding.

Seismic Performance of U-Shaped Connection for Prefabricated Steel Plate Shear Wall

In this investigation, a U-shaped connection (U-C) was introduced for a prefabricated steel plate shear wall with beam-only connections. This design replaces a portion of shear bolts with tension bolts to enhance bolt efficiency and reduce the overall bolt count, and it is suitable for a prefabricated high-rise steel structure. Four 1/3 scale specimens were designed, and an array of performance aspects including failure modes, hysteretic behavior, skeleton curves, energy dissipation capacity, stiffness degradation, and key performance indicators were systematically investigated through a combination of quasi-static tests and finite element analyses. The results showed that the combination arrangement of tensile and shear bolts in U-C effectively reduced the usage of bolts used and reduced installation costs; under low cycle reciprocating loads, the ultimate bearing capacity and energy dissipation capacity of a beam-only-connected prefabricated steel plate shear wall with U-shaped connection (BPSW-U) had slightly decreased compared with the prefabricated steel plate shear wall with discontinuous cover-plate connection (DCPC). Nevertheless, the BPSW-U excelled in preserving the integrity of the frame beams, channeling structural plastic deformations primarily into the infilled steel plate. This design feature ensures that post-earthquake functionality recovery can be achieved by simply replacing the infilled steel plate.

Experimental and numerical investigation on failure behavior of hybrid bonded/bolted GFRP single-lap joints under static shear loading

The mechanical performance of the GFRP (Glass Fiber Reinforced Polymer) hybrid bonded/bolted single-lap joints under static shear loading is investigated. Static loading tests considering the hybrid joints with one bolt, four bolts, and nine bolts were first conducted to study the failure mechanism of hybrid joints, where failure process, rigidity, failure load, and failure modes were focused. Finite element (FE) analysis involving the material degradation and failure laws was also carried out for exploring the internal mechanism of joints’ failure. Based on the verified FE model, the effects of plate thickness and bolt edge distance on the failure capacity and strength of the hybrid joints were further investigated by performing a numerical parametric analysis. Results show that, the failure process of the hybrid joints can be divided into two stages which correspond to the failures of adhesive layer and GFRP plates, respectively. The joint rigidity of joints increases by 98.9 %∼133.1 % comparing the second loading stage to the first stage, and it is found that the rigidity in the first stage is hardly affected by the number of fasten bolts, while it decreases with more bolts in the second stage due to the severe incompleteness of GFRP plates. The failure patterns of the hybrid joints mainly include the slippage between connected plates, the compressive failure and shear failure of GFRP material, and the inclination of bolts. A proper arrangement of bolts can lead to shear failure of GFRP which makes full use of the material property. The final failure loads of four-bolt and nine-bolt joints are respectively 14.5 % and 22.9 % higher than the single-bolt specimen. As the plate thickness getting greater, the shear bearing capacity of hybrid joint increases almost linearly, while it would increase first and then descend with increasing bolt edge distance. In general, the achievement of this work can provide references for the design and further study of the GFRP hybrid joints.

Behaviour and design of duplex stainless steel bolted connections failing in block shear

Duplex stainless steel (DSS) is an emerging construction material for structural engineering, which is featured with high mechanical strength and superior corrosion resistance. Compared with considerable research on DSS structural members, available research is relatively limited for structural joints/connections between these members. In line with this concern, this paper presents a comprehensive experimental and numerical study of duplex stainless steel bolted connections (DSSBCs), focusing on the behaviour and design related to block shear failure. Eleven specimens are tested to investigate the effect of different bolt arrangements on the block shear behaviour. Furthermore, a detailed numerical study was performed as a supplement to the experimental tests, where the anisotropic mechanical properties of DSS are considered in the finite element modelling. Based on the test and analysis results, it is found that the block shear failure mode of DSSBCs resembles that of carbon steel bolted connections, which can be characterised as necking of the tensile section and yielding of the shear sections. Using the experimental and numerical data obtained in this and previous studies, the applicability of various block shear design methods to stainless steel bolted connections is assessed. An updated design method is proposed for predicting the block shear capacity of duplex and austenitic stainless steel bolted connections. A proper partial safety factor/resistance factor is suggested for the proposed method based on the results of reliability analyses.