Steel Connections Research Articles

Numerical design calculation of bolted lap joints at elevated temperatures

This paper presents experimental and numerical studies to investigate the mechanical behaviour of bolted lap joints at elevated temperatures. The load-deformation curves, failure modes, and resistance values of the specimens were obtained from experimental studies. A solid finite element model generated using ABAQUS software was validated and verified by the experimental results and analytical models to investigate the different failure modes and predict the fire resistance of bolted lap joints at elevated temperatures, respectively. Then, the component-based finite element model (CBFEM) was prepared to analyse the fire behaviour of bolted lap joints as an alternative to design specifications for structural fire engineers. The CBFEM was verified by the validated solid model and analytical models in terms of load-deformation curve, fire resistance, and failure modes. Parametric studies were performed to investigate the influence of several parameters on the fire response of bolted lap joints. The study shows that the CBFEM may be used to design bolted lap joints at elevated temperatures and the 5 % limit strain for plates proposed in EN 1993-1-5 can be applicable for predicting the fire resistance of steel connections.

Push-out performance of stud/channel steel connectors in UHPC for new precast concrete beam-slab connections

Push-out performance of stud/channel steel connectors in UHPC for new precast concrete beam-slab connections

Response Modification Factor of High-Strength Steel Frames with D-Eccentric Brace Using the IDA Method

The design innovation of high-strength steel frames paired with D-eccentric bracing exhibits remarkable resistance to plastic deformation during seismic events. This method strategically combines regular steel connections (with yield strengths below 345 MPa) and high-strength steel beams and columns (such as Q460 or Q690, with yield strengths over 460 MPa), effectively reducing cross-sectional sizes while preserving the elasticity of non-energy-dissipating members. This configuration results in substantial ductility and superior energy dissipation capabilities. The response modification factor (R) is vital for achieving both effective and economical seismic resilience, particularly in the development of efficient and cost-effective seismic designs. However, the 2016 edition of the Code for Seismic Design of Buildings (GB50011-2010) fails to incorporate the concept of R, opting instead to apply a uniform value to all structural systems. This oversight is fundamentally flawed, necessitating a comprehensive investigation into the R value specifically for the high-strength steel frame with a D-eccentric brace. This research primarily aims to improve structural performance design, provide guidance for future projects, and encourage the adoption of this advanced seismic performance structure in earthquake-prone areas. To achieve these objectives, a performance-based seismic design approach is employed. This method involves designing structures with varying numbers of stories (4, 8, and 12), different link lengths (900, 1000, and 1100 mm), and various steel strengths (Q460 and Q690). This study uses the Incremental Dynamic Analysis (IDA) method to determine the R values for each prototype. The derived performance coefficients act as crucial references for the development of future innovative structural designs. This research greatly enhances seismic design practices and facilitates the wider adoption of high-strength steel frames with D-eccentric braces due to their outstanding seismic performance.

Topology optimisation of steel connections under compression assisted by physical and geometrical nonlinear finite element analysis and its application to an industrial case study

Topology optimisation of steel connections under compression assisted by physical and geometrical nonlinear finite element analysis and its application to an industrial case study

Microstructures and properties of 7075 aluminum alloy and CP780 steel resistance spot welded joint assisted by magnetic field

Joining steel and aluminum is vital for lightweight automobile but still challenging due to their different physical properties. Herein, resistance spot welding tests were performed on CP780 high-strength steel (thickness 1 mm) and 7075 aluminum alloy (thickness 1.5 mm) dissimilar metals under steady-state magnetic field. The influences of magnetic field (B = 40 mT) on the structure of welded joints, the phase composition/content of intermetallic compounds, and tensile properties of welded joints were analyzed under different welding current conditions (I = 9 kA,10 kA, 11 kA, and 12 kA). At the same welding current, the Lorentz force generated by the additional magnetic field promoted the outward circumferential movement of the molten metal in the weld along the horizontal surface , as well as increased the diameter of the Fe/Al contact interface in the weld nugget along the horizontal direction, conducive to the effective utilization of heat of the resistance spot welding. Except under (11 kA-0 mT) and (11 kA-40 mT), welded joints under other welding parameters displayed a few welding defects, such as incomplete fusion and shrinkage cavity formed at the cross-section of the welded joints. Therefore, the synergism between the magnetic field and appropriate welding current held important roles in the formation of welded joints without obvious welding defects. The intermetallic compounds of all the welds were mainly composed of (Fe, Si)Al2 and (Fe, Si)Al5. Meanwhile, the thickness and content of the intermetallic compounds layer reduced under a magnetic field at the same welding current, significantly improving the tensile properties of the welded joints. The comprehensive properties of welded joints were the best under 11 kA-40 mT, with an average shear force increase from 3.02 kN to 3.49 kN (15.56%) and an average displacement increase from 1.01 mm to 1.22 mm (20.79%). Overall, the proposed dissimilar aluminum/steel resistance spot welded joint assisted by magnetic field looks promising for lightweight automobile use.

Numerical Simulation Analysis of the Bending Performance of T-Beams Strengthened with Ultra-High-Performance Concrete Based on the CDP Model

Numerical Simulation Analysis of the Bending Performance of T-Beams Strengthened with Ultra-High-Performance Concrete Based on the CDP Model

COMPARATIVE STUDY OF STEEL CONNECTION USING US AND IS CODE ON TEKLA STRUCTURE

This paper presents a comprehensive comparative study of steel connections implemented in Tekla Structures software, employing both the US and IS (Indian Standards) codes. The investigation focuses on analyzing the differences in design criteria, detailing requirements, and fabrication practices between the two codes. Specifically, the study explores variations in bolt sizing, beam and column dimensions, as well as detailing specifications for bolted connections. Through detailed examination and comparison, significant disparities are identified, highlighting the importance of adhering to specific standards to ensure structural integrity and compatibility in construction projects. Additionally, the study addresses the implications of these differences on material estimation, cost evaluation, and overall project outcomes. By providing insights into the utilization of US and IS codes within Tekla Structures, this research contributes to enhancing the understanding and implementation of international standards in structural engineering practices. Keyword- Tekla Structure, Steel Structure, Us and Is Codes

Tensile Capacity of Self-Piercing Rivet Connections in Thin-Walled Steel and Concrete Composite Structures

Tensile Capacity of Self-Piercing Rivet Connections in Thin-Walled Steel and Concrete Composite Structures

Investigating the Effects of Adhesive on the Shear Capacity of Bolted Steel Connections

Recently, there has been a particular emphasis on the use of structural adhesives in steel connection systems. Applying adhesives that possess both high strength and flexibility would be highly advantageous for structural purposes. In this study, experimental tests are conducted on two main different types of steel-plate connections; namely, bolted connections and bolted connections with glue. The number of bolts ranged from one to eight for each connection type, such that a total of seven specimens of each type are tested. Additionally, one specimen with only glue is also tested for comparison. The findings indicated that the inclusion of up to four bolts with glue along the connection does not significantly increase the ultimate stress. This can be attributed to the non-uniform distribution of normal stresses, induced by the tightening of the small number of bolts that are not arranged across the entire connection region, on the capacity of the connection in the perpendicular direction. Thus, the connection could have been adequately established the same capacity through the use of adhesive alone. In contrast, the capacity is increased up to 60% and 100% when six or eight bolts are added, respectively, compared to the use of the connection with glue only. A three-dimensional finite-element analysis is developed based on the tested connections using ABAQUS/Explicit software. The glued interface between two steel plates is modelled using cohesive and damage criteria. The results are demonstrated to be consistent with the experimental findings. Keywords: ABAQUS, Adhesive, Bolts, Finite-element analysis, Shear, Steel connections

The Influence of Shear Connector Numbers on The Flexural Characteristics of Composite Geopolymer Reinforced Concrete Beams With Small Transverse Web Openings

Geopolymer concrete is a sustainable alternative to conventional Portland cement-based concrete, utilizes industrial by-products like fly ash and slag. Renowned for its reduced carbon footprint and exceptional durability, geopolymer concrete is gaining global recognition in eco-friendly construction practices. Steel composite reinforced geopolymer concrete beams combine the strength of steel with the sustainability of geopolymer concrete, offering a sturdy structural solution. This collaborative approach results in a composite material with excellent crack resistance and durability, harnessing the advantageous properties of both steel and geopolymer concrete. These beams present a promising option in construction by striking a balance between structural performance and environmental considerations through the incorporation of geopolymer technology. The focus of the current study is to investigate the impact of steel connectors on the flexural behavior of composite reinforced geopolymer concrete beams that have transverse web opening through experimental methods. The experimental program involves casting four geopolymer beams, with one being a traditional geopolymer-reinforced concrete beam (Control). The remaining three specimens are composite reinforced geopolymer concrete beams, each featuring a bottom 5 mm steel plate with six, twelve, and eighteen connectors near each support. The beams share common dimensions, with a total length of 1600mm, a height of 250mm, and a width of 180mm. The results showed that increasing the number of connectors near supports increased the resulted flexural behavior of beams. Such connectors increased the first crack load from 6.67% to 42.22% while the service load increased from 16.22% to 36.20%. the load carrying capacity was also increased from 12.00% to 24.80%. Finally, the mode of failure was moved from traditional tension failure to concrete crushing.

A novel framework for set-based steel connection design automation

Existing computational design tools for steel connection design predominantly employ a point-based design (PBD) approach, which requires iterative re-evaluation whenever there are changes in design specifications. This paper introduces a new framework that adopts a set-based design (SBD) approach, aiming to substantially reduce the iteration and time cost associated with steel connection design and rework. The framework integrates a component-set connection design model with a database storage and query-based data retrieval method. The first method enables the flexible and efficient generation of a large connection design space from all possible component combinations, and automated identification of valid connection configurations within it. The latter method allows for automated design space refinement from preference-based evaluation of connection design efficiency and high-speed comparison and selection of optimal connection designs. To evaluate the relative performance of SBD and PBD approaches, the framework is applied to a steel floor system design case study with 62 connections. Results showed that the SBD approach achieved near-instantaneous connection design automation, with a total execution time of fewer than 55 milliseconds, making it over 10 times faster than the corresponding PBD approach.

Numerical investigation of cold formed steel sleeve connection for channel sections subjected to combined bending and shear

This study focuses on the behaviour of the sleeve connection to ensure proper distribution of moment at the location of discontinuity between two channel sections subjected to combined bending and shear using finite element (FE) modelling. The FE model was validated with the experimental data from previous authors studies and was found. A total of 180 simulations were carried out as part of the parametric study, by varying the depth, thickness, length of sleeve connector, length of the test specimen, and bolt configuration. Two modes of failure were identified based on sleeve length (Ls) and combination of sleeve length and channel thicknesses. The Ls/D ratios were suggested to achieve a similar strength and stiffness of sleeve specimen when compared with control specimen. The influence of sleeve length on the ultimate moment resistance was studied for combination of sleeve length and channel thickness. The increase in the channel thickness from 2 mm to 2.5 mm led to as significant increase in the ultimate moment resistance. An equation was proposed to calculate the nominal moment capacity of sleeved specimens and reliability analysis of this equation was carried out. The conservativeness of the proposed design procedure was checked by comparing it with the AISI S100 [1] interaction curve.

Investigation of the Post-Fire Behavior of Different End-Plated Beam–Column Connections

Heat affects the mechanical properties of steel and the bearing capacity of steel structures, with joints being a crucial factor in determining their behavior. Steel can regain its mechanical properties that are lost owing to heat if the temperature remains below 600 °C, allowing for the possibility of reusing steel after cooling. In such cases, it becomes essential to assess the damage caused by heat exposure to decide whether to demolish the structure or continue using it. However, continuing its usage requires anticipating the potential negative effects of heat. To achieve this, it is necessary to determine the behavior of steel joining tools experimentally or numerically after exposure to heat. This study aims to ascertain the post-fire behavior of various end-plated beam and column connections, providing a cost-effective alternative to expensive fire experiments. Three different end-plated combination models were heated to a specified temperature, and steel frames were constructed after the elements cooled. Six three-point bending tests were conducted, and the experimental data obtained were validated using finite element models. The results indicate that the temperature causes a reduction in the bearing capacity of the joint, and the length of the end plate has a significant effect on the connection behavior. The finite element model validated by experiments is expected to facilitate numerical studies with different characteristics.

Post-fire performance evaluation of steel connections under a column-loss scenario

This study evaluates the post-fire performance of steel connections under a column-loss scenario. A series of fire tests, coupon tests and cyclic loading tests were carried out on 5 sets of 1/3-scaled SN400YB steel H-beam-to-H-column connections. After exposure to temperatures reaching 800 °C, the connections do not indicate any beam residual deformations or column drifts, and the steel properties, such as yield strength, tensile strength, and elongation, still meet the design requirements for room temperature. Under cyclic loading testing, fracture occurs in the base metal of beam flanges near the column faces of the connections subjected to high temperature and room temperature. Moreover, all the connections developed a moment strength greater than the 80% of nominal plastic moment strength of the beam after the first loading cycle with a drift angle of 0.04 rad. Finite element analyses were also conducted to simulate the test results, showing the severity of a column-loss scenario and the minor effect of initial heating rates. The results obtained from this work show the structural robustness of steel connections against earthquake shaking following a fire accident.

Prevention of brittle failure for steel connections utilizing special devices

The present paper proposes the use of a special design procedure devoted to the prevention of brittle failure for welded steel connections. In particular, reference is made to steel frame structures made up of beam elements with I-shaped cross-sections where the connections between columns and beams are usually welded and/or bolted. The proposed new design procedure consists of four subsequent analysis steps; it is based on the identification and analytical definition of new appropriate brittle safe domains defined in the N,V,M space and on the use of suitably designed devices (LRPD), recently proposed by the authors, belonging to the class of the RBS connections. The latter are able to impose prefixed values of internal forces on selected beam element cross-sections, avoiding any modification of the elastic stiffness features of the involved beam. The main novelties of the present study consist in the introduction of new brittle safe domains for I-shaped cross-sections, in the specialization of the LRPD optimal design to the present context and in the definition of a special design strategy which allows to contextually obtain structures safe from the risk of brittle failure as well as being able to dissipate an appropriate amount of plastic strain energy. The numerical application, devoted to plane steel frames, confirms the sound reliability of the procedure and the great flexibility of the utilized LRPDs.

Experimental and numerical investigation of the hysteretic behavior of reinforced concrete column-steel beam interior joints under low seismic intensity levels

For the composite frame structure of concrete column and steel beam, a connection structure based on ribbed angle steel connector (RASC) is proposed, and the hysteresis performance and force transmission mechanism of this new type of composite joint are studied. Through quasi-static experimental research, the influence of beam and column cross-sectional dimensions on the bearing capacity, energy dissipation capacity, stiffness degradation, ductility, and failure form of the frame structure was analyzed. The results of experimental and finite element analysis show that the failure forms of this joint under low-cycle repeated loading are mainly manifested as the shear failure of concrete in the core area of beams and columns and sliding failure between angle steel connectors and steel beams, and the hysteresis curves of the joints are similar to those of frame beams and columns, respectively.

GIS-BASED REAL-TIME GAS LEAK DETECTION SYSTEM AT BASKENT NATURAL GAS DISTRIBUTION COMPANY

Abstract. Natural gas has been used for heating and production purposes in Turkey since 1987, and every passing year, the natural gas pipeline network continues to expand with investments. The distribution of natural gas within urban areas is achieved through a complex network structure formed by the joining of Polyethylene (PE) and Steel (ST) pipes using various connection elements. This complex structure is susceptible to deformation over time due to various reasons such as corrosion in steel lines, manufacturing errors in connection elements in PE lines, and other factors. As a result, natural gas leaks occasionally occur in these pipelines. The leakage control process in natural gas pipelines is carried out using specially designed equipment and vehicles equipped for this purpose. However, while these systems may be sufficient for collecting the necessary data for leak detection, the complex structure of the distribution network and the necessary data for leak detection, the complex structure of the distribution network and the necessity of performing this process with multiple teams bring about many challenges in terms of tracking, management, and reliability of the operation. At this point, the advancement of GIS (Geographic Information System), mobile, and communication technologies has made it possible to overcome these challenges. In this study, a real-time GIS-supported leak detection system developed using these technologies for Başkent Natural Gas Distrubition Inc. (Başkentgaz), which provides natural gas distribution services in Ankara, has been described. The study discusses the benefits brought by this system to the natural gas leak detection process.

Comparative Study of Friction Stir, Stud and Seam Welding of Aluminium Alloys Using Different Grades

Friction stud welding is an innovative and efficient welding process used to create strong and reliable bonds between studs or fasteners and workpieces, particularly in applications where rapid and secure fastening is critical. This welding technique involves generating friction and heat between the stud and workpiece to forge a strong joint. The process consists of several key steps, including preparation, rotation, weld formation, and cooling. Friction stud welding offers numerous advantages, such as speed, consistency, minimal distortion, and the elimination of the need for additional filler materials. It is widely employed in various industries, including construction, automotive, and aerospace, for applications ranging from structural steel connections to automotive component assembly. However, successful friction stud welding necessitates careful selection of materials, welding parameters, and skilled operators to ensure durable and dependable welded joints. This abstract provides a concise overview of the friction stud welding process and its essential features.

Finite element analysis on composite steel-concrete shear walls with centered and staggered openings

Present paper presents a comparative study made on the seismic performance of composite steel-concrete shear walls with rectangular openings, by performing numerical analyses using ATENA 3D software. Two specimens were designed at a reduced scale 1:3 having similar arrangements in the cross-section and the same geometry. First element was conceived with centered openings while the second one was designed with staggered openings. Steel connectors disposed as horizontal stiffeners were used to design and to assure the full connection between the structural steel profiles embedded in the edges and the concrete core. The openings that were considered on each story of the walls, were having the dimension of a common architectural door. A part of the results recorded from the experimental tests were used to calibrate the numerical models. This study aims to establish the seismic performance and to investigate the influence of the openings and the geometric position on the overall seismic behavior of the composite shear walls. Key parameters which describe the seismic performance of structural elements such: bearing capacity, deformation capacity, stiffness degradation, cracks and strain development are compared between the specimens and discussed. The results showed that different arrangements of the openings could significantly modify or increase the seismic performance of the composite structural walls.

Advancing Modular Steel Structures: An Innovative Paradigm in Corner Connections for Enhanced Stability and Efficiency

This research addresses the structural challenges inherent in modular steel connections, exploring innovative approaches beyond traditional methods. Pre-fabricated modular steel structure connections normally incorporate a combination of welding, bolts, plates, and innovative methods, including post-tensioning and corner box inter-locking techniques. These connections are usually tested in a cantilever beam setup to assess their strength and structural behavior. As the load increases, the connection's resistance decreases, materials weaken, and deflection grows steadily until structural failure occurs. This often results in a low slip resistance within the connection corner, highlighting the need for upgrading and enhancing corner connections in pre-fabricated modular steel structures. Previous studies have mainly focused on variations of traditional techniques, such as different bolt setups and plate thicknesses for square sections of hollow steel members. This research proposes and analyzes a novel corner fitting connection applicable for connecting four modular units, forming an inter-sliding box design. The proposed connection, secured by bolts, significantly reduces construction time, eliminates the need for expert labor, and minimizes human error. The static finite element analysis demonstrates that the performance of the proposed inter-modular connection consistently falls within the rigid of both Eurocode and UK standards for service load, transitioning to semi-rigid towards the ultimate. Additionally, substantial improvements in displacement along the X, Y, and Z directions at the connection point and an increase in the initial rotation from 18.3 KN.m to 85 KN.m highlight the effectiveness of the proposed technique in enhancing pre-fabricated modular steel connections.