Bolt Connection Research Articles

Bolt looseness localization with connection-stiffness-varying flange

Electromechanical impedance analysis is a traditional method to identify the occurrence of bolt looseness, but accurate localization of blot looseness is hard to realize on the flange. In this study, a flange model with bolt connection stiffness varying with position is proposed. The location of bolt looseness can be then determined from the impedance spectrum of the model since the uniformity and symmetry of the flange are broken. The analytic model is established to reveal the distinguishability of the eigenfrequency shifting characteristics when the connection stiffness at different positions changes. The frequency shifting sequence is extracted from the coupling impedance spectrum as a feature, and the correlation between the sequences corresponding to bolt looseness at different positions is low. The relationship between the sequence and the degree of looseness is highly related so that the unknown degree of looseness can be matched with the calibrated sequence to realize the localization of the looseness. Based on the distinguishability of the frequency shifting sequence, the connection-stiffness-varying model shows great potential in the field of flanges or other connecting structures for structural health monitoring and damage localization.

Ultimate in-plane shear capacity of 3-panel frameless cold-form steel corrugated walls under axial compression

The Frameless building system, developed by BEHLEN Industries LP, is a structural system that incorporates Cold Form Steel Corrugated Wall (CFSCW) components. These include walls, ceilings, and roofs formed by Frameless panels, along with footings, boundary columns, and an optional convex truss. The system employs simple bolt connections, enabling rapid construction without the need for heavy machinery. It is particularly cost-effective and is often utilized in regions with low seismic activity. In high seismic zones, the structural performance of The Frameless building system under combined compression and lateral loads has not been systematically examined. In this study, four full-scale 3-panel Frameless CFSCWs, were tested under combined axial and shear loads. A generic finite element model was proposed to simulate the force-deformation responses and deformed shapes of the 3-panel Frameless CFSCWs. The numerical simulation results were verified using the experimental results. The verified numerical model was then used in parameter study to examine the ultimate shear capacity of 3-panel Frameless CFSCW of different wall thickness, with the presence of axial compression. The results of the study revealed the ultimate shear capacity of 3-panel Frameless CFSCW is linearly correlated with gauge thickness of the wall panel.

Flexural behavior of laminated H-beams in modular constructions: Numerical and analytical studies

Modular steel construction (MSC) has become an important development direction of the construction industry thanks to the faster construction speed and recyclability. The laminated steel beam is one of the key structure characteristics of MSC, which can enhance the structural integrity by strengthening the interaction between the adjacent beams in vertically stacked modules. In this study, numerical and analytical studies were carried out to explore the flexural behavior and design method of the laminated H-beams in MSC. Firstly, finite element models were established and verified based on the previous experimental study on flexural behavior of the laminated square steel tube beams and laminated channel steel beams. Afterwards, finite element analysis was conducted on flexural behavior of the laminated H-beams with different connecting bolts. The results showed that the flexural capacity and stiffnesses of the laminated H-beams were significantly improved by increasing the number of the connecting bolts in the bending-shear sector. The flexural behavior of the laminated H-beams was discussed including the failure mode, load-deflection curves and slippage of the superimposed surface to reveal the co-bending mechanism. In addition, parametric analysis was performed to reveal the influence of the position, number and diameter of the connecting bolts on flexural behavior of the laminated H-beams. Finally, a theoretical model on flexural capacity of the laminated H-beams was developed to determine the neutral axis and derive the flexural capacity of the laminated H-beams. The calculation formulas were verified to be reliable by comparing the theoretical analysis results with the numerical ones. The present study is beneficial to consummating the mechanical behavior and design method of MSC.

Comparative assessment of load-bearing capacities in bolted laminated bamboo lumber connections: A study on diverse reinforcement techniques

Laminated bamboo lumber (LBL), a renowned engineered bamboo composite known for its outstanding performance and sustainability, is extensively used in modern bamboo structured buildings. This study focuses on examining the effects of diverse reinforcement techniques, particularly self-tapping screws and tension control bolts, on the load-bearing capacity of bolted LBL connections with steel plates. In total, 24 specimens were categorized into 8 groups and subjected to monotonic loading tests. The test results demonstrate that the non-reinforced group clearly shows longitudinal splitting failure at the bolt position, followed by a decrease in load-bearing capacity after failure. In contrast, the group with self-tapping screws (ST) and tension control bolts (BT) exhibited fiber tearing at the lower part of the midspan, accompanied by section bending and damage. The final load-bearing capacity of the groups reinforced with single-row three-bolt self-tapping screws and tension control bolts showed an increase of 67.30 % and 52.95 %, respectively. Likewise, the groups with single-row four-bolt configurations also demonstrated significant reinforcement effects, with increases of 40.52 % and 29.66 %, respectively. Furthermore, DIC-3D analysis was employed to examine the displacement of the connection bolts, and the van der Put model was utilized to estimate the load-bearing capacity of bolted LBL connections under splitting conditions. Subsequently, finite element models were established and calibrated based on the experimental data. The results confirm that self-tapping screws and tension control bolts can serve as structural enhancements in the design of bolted LBL connections, providing effective reinforcement for existing engineering structures.

OPTIMIZATION OF STEEL PROFILE DIMENSIONS AND BOLT CONNECTIONS IN INTAKE STRUCTURES FOR ENHANCED STRUCTURAL INTEGRITY

Intake structures are facilities for clean water supply situated along riverbanks. These structures are reinforced concrete with pile foundations, and the intake structure comprises a profiled steel frame serving as the upper column-beam framework. The implementation of steel structures demands a high level of precision, particularly in designing connections between sectional steel beams and columns. This study, therefore, aims to determine the optimal dimensions for steel profiles by referring to the design of bolt connections as specified in SNI 1729-2020, particularly for steel beam columns subjected to pump loads and load combinations. The analysis concludes that all three material types meet the safety criteria, with a structural ratio value of ≤ 1 and structural deflection within the allowable limits. Additionally, after assessing the steel column and beam sections' capacity to bear pump loads, it was determined that the optimal bolt connection involved 8 bolts of 24 mm diameter. The ideal supplementary steel plate connection required a plate thickness of 13 mm.

SensorDisc - a novel approach to in-situ assessment of bolt load and condition.

While Structural Health Monitoring has become widespread and well-accepted for ensuring safety and longevity of buildings and facilities, the condition of fasteners in said structures is oftentimes not considered for holistic condition assessment. This is not representative of the role fixings (in particular, bolt connections) play, as they experience high loads, fatigue, and corrosion, with the potential for causing costly consequences in case of failure. In practice, the condition assessment of bolts is usually carried out by periodic re-tightening and manual documentation of the torque and apparent condition. This procedure is not only labor-intensive but also fails to provide deeper insights into the condition of the bolted connection itself. Furthermore, in many cases, the inspection intervals are not tailored to the specific needs of projects and structures but are based on general assumptions, which necessarily represent a compromise between costly over-caution and accepting blind spots. One possible reason for not making more widespread use of monitoring technology in this case is the high cost and complexity of conventional bolt monitoring, where individual bolts are manually fitted with load sensors, and data processing is performed by highly skilled professionals. A solution for this dilemma is presented in the form of the fischer SensorDisc, which offers a fully integrated, robust, and convenient option for bolt load assessment. One of the key features that distinguish the SensorDisc is its dedicated design for use in industrial and construction environments. Not only can it be used in a variety of bolt connections, either as original equipment or as a retrofit, but it also does not require special tools for readout, as this can be accomplished with a common smartphone. For maximized ease of use, data and device management are all offered through a cloud-based service that can be accessed via an app, browser, or API.

Improve the impact property in a novel butt joint of Ti/Al dissimilar metals

The dissimilar metal welding joint is connected by the metallurgical bond of intermetallic compounds at the interface, which easily causes stress concentration at the interface and cracks continuously along the interface, resulting in low reliability in impact environments. A novel multi-layer plug and bolt connection for TC4/7A52 dissimilar metal butt joints is proposed in this manuscript and analyzes the influence mechanism of the structural design on impact toughness. The impact toughness of the Ti/Al composite butt joint is 30.3 J/cm2, which is 2.6 times that of the 7A52 BM. The layered toughening design significantly reduces stress concentrations for the butt joint at impact for the Ti/Al composite butt joint. Upon impact, the Ti/Al composite butt joint does not fracture continuously at the V-notch and exhibits significant macroscopic plastic deformation. For the microstructure of each TC4 and 7A52 layer in the impact fracture, more intragranular slip systems are activated and show a higher dislocation density. Therefore, this structural design can enable dissimilar metals to absorb more impact energy during the impact process.

Mitigation of rockfall geohazards: Full-scale investigation of the performance of a practical baffle design for direct use in the field

To arrest rockfall boulders, baffles are constructed as steel members affixed on top of a concrete footing. Existing designs aim to prevent any footing rotation and steel member bending. As such, existing baffle designs require massive reinforced concrete footings and complex bolt and weld connections. Such designs have limited constructability and result in complex failure mechanisms (i.e., tensile failure of concrete foundation at connections). In this paper, we introduce a new baffle design concept that optimizes the balance between steel member bending and footing rotation to enable a compact design. Full-scale pendulum experiments are conducted to evaluate the proposed easy-to-construct and design baffle under successive boulder impacts of 50 kJ. It is demonstrated that by considering the effects of steel member deflection and concrete foundation rotation, the maximum impact force on baffles is reduced by up to two times when compared with those on a rigid barrier and the failure modes are simplified to either overturning failure of the footing or buckling failure of the steel member. A ratio that defines the flexural capacity of the steel member to the overturning capacity of the shallow concrete foundation is proposed to control the failure mode. The optimized baffle configuration for an impact energy of 50 kJ, with minimum residual deflection, has a target capacity ratio of 2.0.

Seismic performance of an assembled monolithic concrete column

A prefabricated concrete column-to-column structure connected by high-strength bolts is proposed. To explore the seismic performance and failure form of the structure, the finite element analysis software is used to simulate the low-cycle repeated load test. The hysteretic curve and skeleton curve of the structure are obtained, and the stiffness degradation law, ductility and energy dissipation capacity of the structure are quantitatively analyzed to evaluate the seismic performance of the structure. The results show that the ductility coefficient of the structure is basically between 2.19 and 4.97, and the ductility coefficient of most specimens is greater than 3.0, indicating that the structure has good ductility and deformation capacity. The equivalent viscous damping coefficients of the specimens are in the range of 0.21–0.29, indicating that the structure has good energy dissipation capacity. In a certain range, increasing the thickness of the end plate has no significant impact on the energy consumption capacity of the structure. The compressive strength of the concrete in the core area is greatly improved under the constraint of the end plate bolts, and end plate bolt connection can well realize the transmission of force and give full play to the performance of materials.

Rapid assembly bolt connection design method for TBM disc cutter box based on AHP

With the TBM disc cutter box as the subject of investigation, this study addresses the intricate and labor-intensive nature of the assembly process in TBM disc cutter box welding assembly. In order to expedite the assembly of the cutter-head and disc cutter box, an alternative approach utilizing combined bolt connections is implemented in place of welding assembly. Therefore, this article proposes a TBM disc cutter combination bolt connection design method based on AHP. Initially, a hierarchical analysis model is constructed, taking into account the actual conditions of the TBM disc cutter box combined bolt connections. Subsequently, from the array of factors influencing bolted connection performance, five experimental variables were chosen, and an orthogonal experimental layout was devised to examine the stress dispersion in the TBM disc cutter box under conditions of bolted assembly, employing finite element analysis. By conducting extreme difference analysis, the study examined the effects of each experimental factor on the bolt connection performance, and determined the order of importance of each factor more objectively. Thus, the comprehensive weights of each factor were calculated, and the optimal solution of the bolt connection scheme was selected by synthesizing the effects of multiple factors.

Development of component stiffness equations for thread-fixed one-side bolt connections to an enclosed rectangular hollow section column under tension

Development of component stiffness equations for thread-fixed one-side bolt connections to an enclosed rectangular hollow section column under tension

Vibration Response of Metal Plate and Shell Structure under Multi-Source Excitation with Welding and Bolt Connection

There are many excitation sources and complex vibration environments in combine harvesters. The coupling and superposition of different vibration signals on the plate and shell seriously affect the working parts of the body. This also reduces the reliability of the whole machine. At present, domestic and foreign research on existing harvesters mainly focuses on harvesting performance, with less research on vibration characteristics. Therefore, in this paper, the vibration response of the metal plate–shell under the two connection modes of bolt connection and welding is studied, in order to optimize the design and structure of the plate–shell structure of the combine harvester and improve the overall performance. First, the welded and bolted plates are numerically modeled using Hypermesh pre-processing functions. Then, the boundary conditions are simulated by continuous variable stiffness elastic constraint experiments. Finally, the intrinsic vibration dynamic model of the four-sided simply supported plate and four-sided solidly supported plate is established using the modal superposition method. By analyzing the modal frequencies and vibration patterns, the following results are obtained. The connection method between the plate and the frame has a significant impact on the inherent vibration characteristics of the plate. The bolt connection will make the plate’s intrinsic vibration frequency higher than that of the welding method, but the effect on the plate’s intrinsic vibration pattern is more minor. At the same time, in order to verify the accuracy of the model, the actual modal vibration patterns and frequencies of the same proportion of plates in the modal test are compared with the results of modal vibration patterns and frequencies obtained by Ansys. The errors of the two dynamic model analytical methods are within 1% and 3%, respectively. This result verifies the accuracy of the dynamic model of the metal plate and shell structure under different connection methods.

A Vision-Based Bolt Looseness Detection Method for a Multi-Bolt Connection

Many vision-based bolt looseness detection methods that directly observe the bolts have been developed. However, these methods have many limitations in terms of the conditions and processes of their implementation. To address these problems, this paper proposed a fully automated vision-based bolt looseness detection method for a rigid multi-bolt connection. The proposed method combines digital shearing speckle pattern interferometry (DSSPI) and recurrent neural network (RNN) and involves capturing speckle fringe patterns under various looseness cases using the DSSPI system and classifying these patterns with an RNN model to detect the loose bolts. The proposed method can detect all the bolts within the measured surface at one time, which is efficient. On the other hand, it eliminates the need for prior information such as the initial angle and position of each bolt. It can even detect unseen bolts in multi-bolt connections, making it applicable for connections in complex structures in which occlusion often occurs. Additionally, the method eliminates the complex process of distortion rectification. These features make the method achieve a single-judgment time (four bolts at one detection) of only 4.70 millisecond with a detection accuracy over 99%, which has potential for the real-time detection of loose bolts in multi-bolt connections.

Design method of prestressed anchor bolt system for wind turbine foundation

SummaryThe prestressed anchor bolt system is a reasonable connection mode between the upper steel tower and the bottom concrete foundation for multi‐megawatt wind turbines. This prestressed anchor bolt connection with forged flanges has a similar form to the prestressed high‐strength bolt connection with forged flanges between steel tubes for the tower. However, their mechanical performances have a great difference because of the influence of the stiffness of the anchorage zone in the concrete foundation. Based on the Petersen's method, the engineering calculation method of the prestressed anchor bolt system for wind turbine foundation is derived. The tensile force of the anchor bolt, the anchorage stiffness and clamping force of the base are all deduced according to the theories of mechanics of materials. The numerical models of the segment foundation with the unfavorable anchor bolt and the overall foundation with all anchor bolts are developed for researching the influence of the spatial effect of adjacent segments on the restraint stiffness of the concrete foundation. The numerical analyses of four engineering cases designed by engineering calculation method are carried out for verifying the effectiveness of engineering calculation method. The analysis results show the spatial effect of adjacent segments can be neglected and the Petersen's method can be directly applied for the design of the prestressed anchor bolt system for wind turbine foundation in engineering practice. The engineering calculation method meets the accuracy requirements in engineering practice and can be used to design the prestressed anchor bolt system of wind turbine foundation.

A novel anti-loosening bolt looseness diagnosis of bolt connections using a vision-based technique

Bolt looseness detection is a common problem in engineering. Most vision-based detection techniques focus on diagnosing ordinary bolt looseness, i.e., the methods used for diagnosis are based only on the sidelines of nuts. These methods cannot be used for anti-loosening bolt looseness diagnosis because of the simultaneous rotation of screws and nuts. Therefore, a novel anti-loosening bolt looseness diagnosis method based on a vision-based technique is proposed in this paper. First, a regular hexagonal cap was installed on the screw, which can be used as a reference for the nut. Then, to automatically distinguish the hexagonal borders of the screw cap and nut, a new hexagonal border reconstruction algorithm is proposed. Furthermore, the relative rotation angles of the screw cap and nut hexagons can be determined using the sidelines of the reconstructed hexagonal borders of the screw cap and nut. Finally, a novel anti-loosening bolt looseness diagnosis method is established by using the relative rotation angle of the regular hexagonal borders of the screw cap and nut under initial status and loose status. A prototype flange node of the transmission tower was used for experimental verification. The results show that the proposed method can effectively detect the loosening angle of anti-loosening bolts.

Progress in Theoretical Modelling of Macroscopic and Microscopic Dynamics of Bolted Joints in Complex Equipment

Bolt connection structure is a common form of connecting large and complex equipment. Its object contact surfaces under normal and tangential loads will appear in the form of slip and adhesion, which affects the service life of mechanical equipment. Bolted connection structures cause changes in stiffness and damping, which have great impacts on the dynamic characteristics. Experimental studies and numerical simulations have difficulty predicting the overall performance of bolts in a timely manner, hence cannot ensure the reliability and safety of complex equipment. In order to improve the overall performance of complex equipment, it is necessary to study the contact theory model of bolt connection structures. Based on the relationship between friction force and velocity in the classical friction model, the mathematical expressions of restoring force and tangential displacement in the kinetic theory model are deduced to predict the stiffness degradation of the bolted structure and to characterise the kinetic properties and laws of the bolted structure. From the perspective of theoretical calculation, it makes up for the situation in which it is difficult to measure the performance of bolts due to the existence of spanning scale and provides theoretical support for the reliability of connecting complex equipment. This paper summarises and analyses the contact theory model of bolt connection structures, ranging from macroscopic to microscopic; describes the static friction model, kinetic friction model, statistical summation contact model, fractal contact model; and analyses the influencing factors of the microscopic contact mechanism. The advantages and disadvantages of the kinetic theoretical models are described, the manifestation of friction and the relationship between tangential force–displacement are discussed, and the key research directions of the kinetic theoretical models of bolted structures in the future are elucidated.

Finite element analysis of precast concrete beam‐column joint based on bolt connection

SummaryA novel proposal for an assembled bolted joint between a precast reinforced concrete beam and column is presented in this paper. In order to evaluate the behavior of the joint, a comprehensive experiment was carried out on a full‐scale precast concrete beam‐column joint based on bolted connection subjected to pseudo‐static loading. The experiment aims to investigate the failure mode, load carrying capacity, and energy dissipation characteristics of the joint. To further understand the performance of the joint, a finite element model was developed using ABAQUS. The difference in failure mode and ultimate bearing capacity between the bolted joints and cast‐in‐situ joints were analyzed in conjunction with the experimental results. Moreover, the impact of various parameters on the performance of the bolted joints was quantified. The characteristics of the bolted joints, such as the span‐depth ratio, reinforcement ratio of the beam, the stirrup ratio at the beam‐column junction, T‐end length, and the bolt strength grade, were meticulously analyzed through an examination of bearing capacity curve, stiffness degradation patterns, and energy dissipation capability. The results show that, in comparison with the traditional cast‐in‐situ joints, the damage failure extent exhibited by the bolted joints is notably smaller, thereby rendering it more advantageous for seismic restoration and replacement. Furthermore, the span‐depth ratio, reinforcement ratio of the beam, and the stirrup ratio have a greater influence on the seismic performance of bolted joints than the T‐end length and bolt strength grade.

Enhancing the interfacial bond performance of engineered cementitious composites and concrete

This study aims to investigate the influence of different surface treatments, including smooth interface, rough interface, anchor bolt connection, and epoxy bonding agent, on the shear resistance of Engineered Cementitious Composites (ECC)-concrete interface through bi-surface shear testing. The experimental results show that the interfacial shear strength between ECC and concrete is significantly enhanced by the implementation of the three interface treatment methods, as opposed to the smooth interface. Among these methods, the anchor bolt connection exhibits the greatest improvement in interfacial bonding performance. Notably, cohesive failure is observed in the anchor bolt connection method, while the other three methods result in adhesive failure, with only the anchor bolt connection method displaying ductile failure behavior. Following a comprehensive review of relevant studies and the outcomes of this experiment, three distinct interface bonding mechanisms were identified and the forces contributing to the bond were analyzed. Results indicated that the interfacial bond strength is notably influenced by the surface roughness. These research findings substantiate the viability of utilizing the anchor bolt connection method, particularly in applications where ductility requirements in the repair layer are essential for structural integrity.

Effect of connection methods on hygrothermal performance of prefabricated concrete building walls

With the ongoing surge in global energy demand and the escalating environmental concerns, attention has turned to building energy consumption in numerous countries. According to a 2019 report by the International Energy Agency (IEA), the global building industry is responsible for 36 % of energy consumption, ranking first among all industries. The 2022 China Building Energy Consumption and Carbon Emissions Research Report highlighted that in 2020, China's building energy consumption and carbon emissions represented 45.5 % and 50.9 % of the national total, respectively. Achieving carbon neutrality now hinges on decarbonizing buildings. Prefabricated buildings, as a prime example of industrialized construction, aid in reducing carbon emissions through standardized, factory-based production. However, unlike conventional construction, prefabricated concrete buildings (the dominant form of prefabricated buildings) employ metal connectors to join the prefabricated components. These metal connectors generate thermal bridges that can influence heat and moisture transfer through the walls. In this study, a coupled heat and moisture transfer model will be established to analyze the influence of different connection methods on the hygrothermal performance in prefabricated concrete building envelopes. Two typical connection methods for prefabricated buildings are mainly investigated: the grouted sleeve connection and the bolted connection. The findings indicate that different connection methods for prefabricated building connectors increase both the heat and moisture transfer rates in prefabricated concrete structures. Compared to the grouted sleeve connection method, the bolt connection method has a more significant impact on the thermal and moisture performance of the wall. In the tests on the T-shaped structure, the grouted sleeve connections increase heat transfer by 9%–10 %, while the bolt connections increase it by 52%–55 %. During summer, the bolt connections show a 7.42 % higher moisture transfer than the grouted sleeve connections, whereas, in winter, the bolt connections reduce moisture transfer by 12.4 % more than the grouted sleeve connections.

Modeling and vibration analysis of bolted composite conical-conical shells with flanges

This paper proposes a general semi-analytical modeling method of bolted composite conical-conical shells with flanges based on the first-order shear deformation theory. The coupling connections between conical shells and flanges are achieved by using the penalty function method. A bolted joint model that considers the non-uniform distribution of interface pressure is proposed, which can efficiently simulate any number of bolt connections between flanges and boundaries and between flanges and flanges. The correctness and effectiveness of the proposed modeling method are confirmed through step-by-step comparisons with finite element analysis and experimental testing. Then, the influence of various parameters on the frequency trajectories and modal shapes of bolted composite conical-conical shells with flanges is analyzed, with a particular focus on frequency veering and modal coupling vibration behaviors in these structures. The analyses indicate that the proposed modeling method can flexibly adjust structural geometric parameters, material parameters, bolt parameters, fiber layer parameters, and so on, which can efficiently guide the dynamic design of bolted composite conical shell structures with flanges.