Bolt Line Research Articles

Response of Embedded Plates in Reinforced Concrete Loaded in Eccentric Shear towards an Edge

Embedded plates (EPs) are commonly used to connect steel to reinforced concrete elements. Due to a lack of industry-wide standard designs, EPs are custom designed for every instance in each project. This leads to many inefficiencies in the construction process and introduces susceptibilities to error. North American design standards based on the concrete capacity design (CCD) philosophy require many assumptions to predict EP capacity, which then lead to inconsistencies in their application. CCD is also well suited for analysis as it depends on a considerable numbers of variables (e.g., edge distances, anchor size, number, and length) to check capacity. The sheer number of variables makes it difficult for designers to come up with a trial design to fit a situation. This study aims to improve the efficiency of this process by proposing standard EPs. A subset of these proposed standard EPs are then experimentally tested to verify predicted capacities and evaluate design assumptions using existing CCD approaches in North America. Four- and six-anchor proposed standard EPs with shear tab connections were placed at four distances from the concrete edge (75–250 mm) and tested in shear towards the edge. North American provisions for concrete anchorage were adequate in predicting the failure loads if connection eccentricity, caused by the gap between the shear tab bolt line and the exposed surface of the plate, is considered in capacity predictions. Mean test-to-predicted ratios of 0.92 and 1.05 were obtained, respectively, when not considering and considering this eccentricity. Rotations of these connections during testing (0.01 to 0.02 rad at peak load with further rotations post-peak) and signs of secondary tension breakout cones suggest that connection eccentricity significantly affects the behavior of EPs and should be considered in design.

Experimental and analytical performance of replaceable shear fuse connections for heavy beams

Experimental testing and finite element analysis were used to quantify the inelastic rotation capacity of replaceable shear fuse connections that exceed the current prequalification limits in AISC 358–22. Three experimental specimens with W1000 × 591 beams were tested per the procedures in AISC 341 Chapter K. Fuse plate geometry and the number of fuse plate bolts varied between specimens. All three specimens completed at least one cycle at 0.04 rad, with one specimen completing a cycle at 0.06 rad under the standard AISC special moment frame connection loading protocol. Using extra bolts on the fuse plate to match the bolts at the top flange in one configuration resulted in higher strains in the fuse yielding regions. Finite element models confirmed that about 90% of the moment at the face of the column was transmitted by the horizontal couple at the beam flange levels and that bolt lines should be more centered on the external connection plates. The connections had high post-yield stiffness and had strain hardening factors of up to 1.52. A more transparent procedure for addressing strain hardening in design was developed.

Behavior of Gusset Plates Connecting Angle Sections in Compression

This paper contains experimental and numerical study on the behavior of the gusset plate in compression. Gusset plate connections are usually used for the transfer of load from one member to another, they are generally used in bridge trusses and steel braced frames. However, due to lack of technical information regarding the behavior of the gusset plate under compression, these have been under research focus. It has been seen that the gusset plate shows a buckling failure by swaying on one side as there is no out of plane restraint. In this paper, a study is initiated aimed at the gusset plate connected with the angle section on a single side. Key items that were investigated in the study were strain, strength, and displacement. A total of 5 specimens were used for the experimental investigation. The parameters which were considered for the study, the number of bolt lines and the thickness of the gusset plate. Based on the experimental results of load and strain, a numerical model was developed and compared with experimental load-carrying capacity of plate and displacements. After going through the study unpredicted behavior was observed for the two-bolt line and suggestions were given accordingly.

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...

Damage detection in composite aircraft wing-like test-box using distributed fiber optic sensors

Structural Health Monitoring Systems for the aircraft structures are intended to detect the location and size of the damage with minimum downtime of the aircraft. As the damage produces localized strain changes, a sensor network of many sensors bonded/embedded throughout the structure is required for damage diagnosis. This paper describes a distributed fiber optic sensor's demonstration to detect the disbond damage in a typical aircraft wing-like structure where a single optical fiber can cover a large area. Distributed fiber optic sensor is being bonded along the bolt line of the test-box. Controlled disbond are created by the removal of the bolts. In the pristine state, the strain signature/map is measured under applied load, which act as a reference in this case. In this approach, localized strain signature difference between the reference and disbond-structure is used to detect the damage. A non-dimensional quantity damage index (DI) is calculated based on the normalized sum of the square magnitude of strain difference of all sensors to indicate the damage severity. We have found that the DI value greater than or equal to 0.2 indicates the damage region through the iterative approach. Further, the algorithm is validated by loading the structure with disbond at different load levels. The maximum error in the disbond estimation is found to be ∼11 mm. This system and methodology hold immense promise for a ground-based method for detecting damage (disbond) in the aircraft/unmanned aerial vehicle structures (UAV).

Effectiveness of CFS web cleat bolted connections between beam–to–column

This paper aims to study the experimental behavior of web cleat, bolted between beam–to–column in terms of strength, relative rotation, and failure mechanism of web cleat leg attached to the column web. The study was carried out to understand the effect of 230 mm depth (B) of web cleat primarily subjected to a shear load. Three different parameters were considered for the study namely (i) aspect ratio (L/B = 0.15–0.42) of web cleat leg attached to the column, (ii) thicknesses of web cleat (TC = 1.5 mm, 2.0 mm and 2.5 mm), and (iii) bolt configuration (Bn = 2 and 3 numbers). The aspect ratio (L/B) was taken as the ratio of the flat distance (between the folded line and bolt line) to the depth of the clip angle. A total of thirty-eight specimens of different configurations were tested under a four-point bending test. The test results indicate an increase in the ultimate strength with the reduction in aspect ratio. Similarly, the ultimate strength increased for the specimens with a three-bolt configuration when compared to the corresponding specimens with a two-bolt configuration. A majority of the tested specimens failed due to local buckling except few specimens which exhibited shearing of bolts and bearing of the beam under the loading points. A comparison of test results with the literature indicates that the test results are un-conservative for two–bolted specimens with slenderness ratio (λ) of the web cleat lesser than 0.6. The reliability studies were performed for the design of bolted web cleat configuration with limitation.

Cyclic Behavior and Modeling of Bolted Glulam Joint with Cracks Loaded Parallel to Grain

Under varying humidity and temperature conditions, with the constraint of metal fasteners to wood shrinkage, cracks along the bolt lines are generally observed in bolted glulam joints. A three-dimensional (3D) numerical model was established in software package ANSYS to investigate the cyclic behavior of bolted glulam joints with local cracks. A reversed cyclic loading was applied in the parallel-to-grain direction. The accuracy of numerical simulation was proved by comparison with full-scale experimental results. Typical failure modes were reproduced in the numerical analysis with the application of wood foundation zone material model and cohesive zone material model. The effect of crack number and length on the hysteretic behavior of bolted glulam joints was quantified by a parametric study. It was found that initial cracks impair the peak capacity and elastic stiffness of bolted glulam joints significantly. More decrease in capacity was observed in joints with more cracks, and longer cracks affect elastic stiffness more dramatically. Moreover, with the existence of initial cracks, the energy dissipated and equivalent viscous damping ratio of bolted joints are reduced by 24% and 13.3%, respectively.

Preloaded Bolted Joint Made with a Single Row of Fasteners

Abstract The purpose of this technical note is to present a method of analysis of a joint made using a single row of bolts, typical of a bolts around the edge of a closure plat or a simple bracket. Classical analysis methods are applied to the joint subjected to combinations of both in-plane and out-of-plane loads and moments. An analysis of loads and stresses in a single bolt is developed. The note brings together a number of concepts and links them into a practical design analysis process that is applicable for many cases of joints made with a single bolt or a single line of bolts and are adequate to demonstrate the structural integrity of the joint. In some cases finite element methods may be more appropriate, and the methods discussed can be used in the validation process.

Bearing behavior of multi-bolt high strength steel connections

This paper presents an experimental and numerical investigation on the bearing behavior of multi-bolt high strength steel connections in single bolt line. Three grades of high strength steel with nominal yield stress of 550 MPa, 690 MPa and 890 MPa were used to fabricate thirty lap connections with two or three bolts. It is found that the deformation capability of high strength steel plate near bolt hole is sufficient to meet the deformation demand of compatibility in multi-bolt connection even with an intended bolt hole misalignment of 2 mm for M24 high strength bolt. The comparison with Eurocode3 and AISC 360-16 is conducted. When no partial or safety factors are considered, the original formulae of Eurocode3 already has sufficient safety while AISC 360-16 gives unsafe predictions. Numerical models were established and verified by test results. With the obtained results, the full-range distribution of internal load among different bolts can be divided into four stages. Features for each stage are summarized and the effect of bolt hole misalignment on the distribution pattern is evaluated. Numerical analysis results indicate that, behavior of an individual bolt in multi-bolt connection may be influenced by surrounding bolts. The formation of critical yielding band between different bolts may explain this influence. Based on the experimental and numerical analyses, this paper proposed a new ultimate bearing resistance model for multi-bolt connections. The proposed model is capable of describing the nonlinearity in the ultimate bearing resistance of multi-bolt connection and achieves improved predicting accuracy compared to classical models.

Experimental study on mechanical properties of laminated bamboo beam-to-column connections

Moment-rotation behavior of three types of beam-to-column connections intended for laminated bamboo structures are presented: (a) conventional bolted connections with slotted-in steel plates; (b) T-shaped extended end plate connections with side plates that confine the beam; and, (c) an L-shaped end bracket connection which partially confines both the beam and column. Each connection was tested under monotonic and reversed cyclic loads and the influence of bolt arrangement and the local inclusion of cross-laminated laminae locally in the connection region were investigated. Specimens having cross-laminated laminae did not exhibit parallel-to-grain splitting initiating at the bolt lines which was prevalent otherwise. Connections fabricated with slotted-in steel plates clearly exhibited slip deformation and lower stiffness and capacities than the T-connections and L-connections. Load-carrying capacities calculated according to Eurocode 5 were found to conservatively estimate the capacities of the T-connections and L-connections. For the I-connections, the safety margin was considerably lower.

フィラープレートによる 2 列配置高力ボルト引張継手の高強度化に関する検討

フィラープレートによる 2 列配置高力ボルト引張継手の高強度化に関する検討

Full-scale testing of stiffened extended shear tab connections under combined axial and shear forces

Owing to the lack of a comprehensive published procedure for the design of stiffened extended shear tabs, practicing engineers usually follow design guides for unstiffened shear tabs. The results of recent laboratory experiments and numerical analyses have demonstrated that improvements to this approach are warranted. Furthermore, design methods for this connection type under combined axial and shear forces are not well established. To address these shortcomings, full-scale laboratory tests were carried out on the double-sided configuration of stiffened extended beam-to-girder shear tab connections with full depth shear plates. These experiments were complemented by a continuum finite element (CFE) study, with which the axial force demands along with other critical parameters that affect the connection behaviour were further examined. The experiments supported by the CFE findings indicated that the primary connection damage states are mainly associated with yielding and fracture of the shear plate due to the interaction of flexural, shear, and axial force. The study demonstrated that the direction and magnitude of the applied axial force significantly affected the shear and axial demands along the centerline of the interior bolt line. The current design practice for the double-sided configuration of the full-depth extended beam-to-girder shear tab was also evaluated; a significant underestimation was observed in the prediction of a connection’s ultimate resistance.

Parametric Study on Effect of Adding Stiffener to Post-tensioned Steel Connection

Beam-to-column connections with post-tensioned (PT) elements are used in steel moment-resisting frames to provide adequate stiffness, strength, and ductility and to eliminate residual displacements under seismic loads. A steel PT connection has recently been developed with top and seat angles. In this connection, angles are used to dissipate energy under cyclic loading. This paper aims to investigate the influence of adding stiffeners to the top and seat angles on the cyclic responses of PT connections. To this end, a parametric study is performed to compare the effectiveness of stiffeners and some design parameters in the cyclic behavior of the PT connections. The design parameters are the angle thickness, the distance between the bolt line passing through the column and the heel of the angle (g2), the PT force of the strands, and number of strands. First, the results of finite element analyses are compared to previously conducted experiments on PT connections with top and seat angles through a verification study. In this way, finite element models of 23 PT connections are developed and analyzed under cyclic loading. Results indicate that adding the stiffeners to the angles, enhances the energy dissipation capacity, moment capacity, stiffness and ductility of the PT connection much higher than improving other design parameters.

Deformation and Control Countermeasure of Surrounding Rocks for Water-Dripping Roadway Below a Contiguous Seam Goaf

To solve the technical problem of supporting a water-dripping roadway below contiguous seams at the Tuanbai coal mine, the deformation law of surrounding rocks for the roadway was studied using Fast Lagrangian Analysis of Continua in Three Dimensions (FLAC3D) numerical simulation. Then, a mechanical model of water-dripping rock using a bolt support was established, and further, technical countermeasures to control the deformation of the roadway with a bolt and cable support are proposed. The results show that the erosion of the water dripping on the roadway was substantial and showed notable changes over time during roadway excavation and mining work. These effects caused the road to heave slightly, but it tended to be stable during roadway excavation. Moreover, the erosion of the roof and two ribs increased exponentially, and the floor heave increased with significant displacement oscillation during mining. The anchoring length of bolts and the rock weakening from water dripping had noticeable effects on the surrounding rocks of the roadway. The logical parameters of the bolt spacing and tightening force (the bolt line spacing was 0.7–0.9 m and the tightening force exceeded 40 kN) of the bolt supports were studied and optimized. Finally, a support scheme for water dripping on the roadway at the Tuanbai coal mine is proposed. The observation data regarding the deformation of the surrounding rocks, monitoring of bolt and cable stress, endoscopy results of roof failure, and roof bed separation monitoring were used to verify the reasonableness of the scheme and ensure the requirements for support were met. The study results can serve as a reference regarding the support for water dripping on a roadway under similar conditions.

03.36: Skewed extended shear tab connections: Behavior, analysis and parametric study

ABSTRACTThe objective of this study is to investigate the behavior of skewed extended shear tab connections with different support conditions: In which plate (shear tab) is welded to supporting member webs (flexible supports). And with the plate is welded to the supporting member flanges (rigid supports). The finite element analysis software ABAQUS was used to model different configurations for these connections. It was concluded that the connection orientation have significant effect on the connection torsional stability for the case with flexible supports. And there is a need to develop a unique design procedure for these connections. A parametric study was performed to develop a design procedure for skewed extended shear tab connections based on results obtained from finite element analysis for 300 models with different configurations. The variable parameters used for this study are: plate thickness, the a‐distance between the weld line and the bolt line, skewed angle, and number of bolts. These parameters were investigated in terms of the connection vertical displacement, plate twist along the bolt line, plate twist along the weld line, and the connection shear capacity. Modifications to the current connection lateral stability checks in the literature will also be addressed. The proposed design procedure on this study is specific procedure for the skewed extended shear tab connections. This procedure is compared with the current design procedure in the AISC Manual 14th edition.

03.18: Anchor bolt tensile load distribution: Effects of the column base‐plate design: Wide flange column bases – loading on additional line of bolts

ABSTRACTThe designer of column base elements usually considers that the uplift force existing in the column member is equally distributed on its anchor bolts. While this simplified approach may be used for the most common cases of a steel structures (for instance, when only 4 equally spaced anchor bolts exist in the column base design), it may lead the designer to overlook that the distribution of uplift loads is highly influenced by factors such as the rigidity of the base plate, the positioning of its stiffeners and the number and geometric arrangement of the anchor bolts. This unequal distribution of uplift loads on the anchor bolts may cause overloading on some of the anchor bolts, leading to diverting failure. This paper analyses through finite element several different wide‐flange column base elements, with varying plate thicknesses and geometry. The conclusion summarizes that the distribution of the loads on the anchor bolts largely depend on the typology of the base plate and suggests a revision of the codes to be more precise on when unequal axial tensile loads may arise on the anchor bolts and recommend more refined methods for the estimation of those unequally distributed loads.

07.34: Influence of semi‐rigid sleeve joints on the multi‐span purlin design

ABSTRACTThe sleeve joint is a bolted connection frequently employed in the purlins assembly of secondary structure in industrial building, because it facilitates the assembly of the structure. The joint behaviour determines the purlin structural behaviour.Recently, authors have proposed a simple approach to predict the stiffness and strength of the sleeve connection, depending on the lap length to depth ratio [1]. It includes rotational springs on the joint bolt lines, actuating in a coordinated way.In the present paper, multi‐span purlin models including the semi‐rigid nature of the joints are developed. They consist on beam and rotational spring finite elements, based on the previous approach. The joint behaviour influences the stresses and deformations developed by the purlin, which can be analysed, allowing for safety design in elastic range.The multi‐span purlin design with sleeve joints are studied, employing a model that includes the realistic behaviour of joints. The objective is to address the minimum lap length to depth ratio of the sleeve joints, needed for a confidence purlin design. This work is proposed in the framework of the optimized multi‐span purlin design with cold formed profiles, according to the European standards.

Mechanical model and finite element analyses of the T-stub joint component in fire

This article presents a mechanical model, based on thin plate theory and which incorporates the thermal degradation of material properties, to investigate the behavior of T-stub assembly, in terms of resistance, stiffness, deformation capacity, and failure modes at different temperatures. Also, a three-dimensional finite element model is developed to simulate the performance of T-stub. The proposed two models are validated against T-stub experiment available in other literature, and it is shown that the models proposed in this article satisfactorily predict the behavior of a T-stub assembly exposed to fire. Then, a thorough parametric study is conducted. The key variables include flange thickness, bolt grade, the distance from bolt line to flange root, and the temperature of the T-stub. Two kinds of loading paths, namely, “loading under constant temperature” and “heating under constant load,” are also adopted. The parametric study provides some valuable suggestions to improve the performance of T-stub and to refine the T-stub configurations.

Full-scale Tests of Stabilized and Unstabilized Extended Single-plate Connections

Little guidance is available in the literature that is suitable for use in the design of extended single-plate connections. In particular, these connections have not been studied sufficiently for scenarios that involve axial load, which is relatively common in industrial applications. To address this shortcoming, an investigation into the behaviour of extended single-plate connections was completed by testing 23 full-scale specimens. Connections with and without stabilizer plates were tested that varied in plate thickness, plate depth, and the number of horizontal bolt lines. Horizontal loads varied from 500kN in compression to 200kN in tension. The influences of the test variables on connection behaviour, capacity, and failure mode are discussed. Among the findings of this research are that despite their slenderness these connections tend to be quite ductile, and the capacities of the unstabilized connections without axial load were much larger than those predicted by available design provisions.

Investigation of Structural Steel Webs for Punching Shear

Shear tab connections or simple connections are widely used in structural steel structures. There are several limit states associated with these connections such bolt shear, bolt bearing, block shear, shear yielding and shear rupture. A modified version of the shear tab has been developed during the last decade, which is extended shear tab connections. In developing design provisions for the extended shear tab connections, experimental work showed that there are additional limit states other than those mentioned above that limit the capacity of the extended shear connection. Extended shear tab connections could be used to frame beam-to-column or beam-to-girder. In the case where a beam is framed into girder, a new limit state develops in the web of the supporting girder. This limit state is punching shear of the supporting girder web which is due to a higher moment. The higher moment in extended shear tab connections is due to the larger moment arm (eccentricity) from the bolt line, the location of the shear force, to the support, which is in this case the girder's web. This study investigates the supporting girder web using experimental work, finite element analysis, and yield line theory. This paper shows the result of this investigation and proposes an evaluation of the web capacity equation which should be used when calculating the beam-to-girder connection capacity.