Bearing Capacity Of Joints Research Articles

Performance of SRC unequal-depth beam-column irregular joint in NPP under progressive collapse

The prototype structure of this study is taken from the main shield building of nuclear power plant (NPP) conventional island facilities. Emphasis is on steel reinforced concrete (SRC) unequal-depth beam-column irregular joints, studying their resistance to progressive collapse via analysis of two 1/5 scale irregular joints. Vertical monotonic loading tests were conducted on the joints, followed by numerical simulations to analyze their mechanical properties, failure modes, and progressive collapse resistance. Experimental analyses focused on irregular joint failure modes, central column load changes with displacement, beam deformations, strain variations in critical sections, and resistance mechanism development. Finite element (FE) software modeled these behaviors and was validated against experimental data. Then, according to the various beam section depths of the connected beams, this research applied the validated numerical models to examine the load-bearing capacity of the irregular joints. The results indicate that the damage of the unequal-depth beam-column irregular joint exhibits significant asymmetric characteristics. In terms of load performance, the performance of the irregular joint depends on the component performance of the shallow beam section. Within a certain range, the greater the height difference between the various beams, the greater the joint bearing capacity, but the stability of the bearing performance deteriorates. The fracture yield of H-shaped steel significantly reduces the bearing capacity, and it is recommended to reinforce shallow beams. Providing data reference for the design of the irregular joints has important practical significance.

Influence of predrilled holes in the upper sheets on the formability and bearing capacity of self-piercing riveted bonded structural components

Self-piercing riveted bonded (SPRB) joints have been widely used in the automotive manufacturing industry, and it was interesting to find that the joint performance was greatly improved by predrilling holes in the upper sheets. The predrilled hole diameters (1.0 mm, 2.0 mm, 3.0 mm, 4.0 mm, and 5.4 mm) in the upper sheet of joints were prepared, and the corresponding joints were named PSPRB-D1, PSPRB-D2, PSPRB-D3, PSPRB-D4, and PSPRB-D5, respectively. Numerical and experimental results showed that the bonding area of joints increased due to the adhesive flowing into the rivet cavity through the predrilled holes. As the diameter of the predrilled hole increased, the stiffness of the trapped upper sheet gradually decreased. Rivets were easier to pierce the upper sheet and insert longer into the lower sheet, together with the supporting effect of the upper sheet trapped steel, resulting in the mechanical interlock of joints increasing, followed by decreasing. The mechanical properties of PSPRB-D3 joints were better than others under lap shear and pull-out loading conditions. The peak force and energy absorption of PSPRB-D3 joints were improved by 12.79 % and 35.71 % at most as compared with those of the SPRB joints, respectively. This was due to the increased mechanical interlock of the joint and the additional bonding reinforcement. However, the strength of PSPRB-D1 joints improved little due to the insufficient filling of adhesive, while the strength of PSPRB-D4 and D5 joints was significantly decreased due to the inadequate stiffness of the upper sheet trapped steel and the smaller mechanical interlocks. Moreover, two box-beam structural components containing SPRB and PSPRB-D3 joints were prepared. The one with PSPRB-D3 joints showed higher mechanical properties in the experimental test. The peak force and energy absorption increased by 15.21 %−22.42 % and 12.01 %−13.01 %, respectively, compared to those of the SPRB structural components. The proposed predrilling hole process improved the thickness distribution of the adhesive layer of the SPRB joints and provided guidance for the connection of structural components with high requirements for joint bearing capacity.

Seismic performance of earthquake-damaged HSRAC beam-column interior joints rehabilitated by bonding steel plates in the plastic hinge of beams

In order to investigate the seismic performance of earthquake-damaged high-strength recycled aggregate concrete (HSRAC) beam-column interior joints employing ultra-high strength bars (UHSB) in columns, four specimens were designed and manufactured. The research variables included whether the steel tube was encased in the column and whether beams were rehabilitated by bonding steel plates. Among them, the rehabilitated specimens were firstly loaded to 1.0 % drift ratio, and then loaded to failure after rehabilitating the plastic hinge of beams. The test results showed that the beam hinge failure mode occurred in the specimens loaded directly to failure. The damage of columns and joint cores was relatively slight, and the crack width satisfied the repairability limits before 2.0 % drift ratio. The shear failure of the joint core occurred in the rehabilitated specimen without steel tube, as shear deformation and stirrup strain in the joint core increased. The shear bearing capacity of joints increased after steel tubes were encased in columns, and the damage of joint cores was reduced. The bearing capacity and deformation capacity of specimens improved after rehabilitating. Finite element models were established and verified with experiment results. Parameter analysis was conducted for different pre-damage degrees, and the results indicated that as pre-damage degree increased, the bearing capacity of specimens decreased.

Design and application of a prefabricated structure for large-span arch open-cut highway tunnels

To enhance construction efficiency, improve lining quality, and reduce project costs, this study proposes a prefabricated arch structure scheme for large-span open-cut highway tunnels, specifically targeting the ongoing construction of an eight-lane open-cut tunnel on Chongqing’s Xinsen Avenue. By establishing a finite element “load-structure” integrated calculation model and adopting an iterative analysis method, the impact of joint stiffness variations on internal force distribution was determined. Combined with long-term field monitoring and measurements, a thorough analysis was conducted on the performance of the prefabricated arch structure during different construction stages. The results indicate that after assembly into a ring, the structure undergoes a self-adaptive adjustment phase, during which the joints experience significant stress and deformation. Following top-layer backfilling and water level restoration, the axial force on the joints increases, while stress and deformation decrease, exerting a positive effect on the joint bearing capacity. From the construction period to post-opening operations, the stress variation experienced by the joints remains within a controllable range, demonstrating substantial safety margins. This fully validates the safety and reliability of the prefabricated arch structure scheme.

Ultimate strength of multi-ring-stiffened tube-gusset joints with dual-function stiffeners under combined bending and compressive loads

Tube-gusset (TG) joints play a crucial role in connecting crossarm chords to tower bodies in steel-pipe power transmission towers, bearing the highest loads in the entire tower structure. This study investigated TG joints with five-ring stiffeners under combined bending and compressive loads, using the middle stiffener plate as the connecting plate. Through experimental studies, numerical simulations, and theoretical analyses, insights were obtained into the failure mechanism and mechanical characteristics of TG joints. This study identifies the key factors influencing the ultimate strength of TG joints under combined bending and compressive loads and proposes a method for determining the joint bearing capacity. Notably, the mechanical performance of multi-ring-stiffened tube-gusset joints was minimally affected by the initial geometric defects under combined compression and bending moments. The load exerted on the gusset plate was primarily supported by the stiffeners, with the gusset plate demonstrating minimal bending deformation, owing to its substantial in-plane stiffness. Consequently, the gusset plate underwent an overall rotation or translation under the combined effects of compression and the bending moment. The proposed method accurately predicted the joint bearing capacity, ensuring the safety of TG joints. These findings provide valuable insights into the meticulous design of joints in steel-pipe transmission towers, thereby ensuring the safety and stability of transmission lines in the field of civil engineering.

Experimental behavior of connection between composite columns and reinforced concrete flat slab

The combination of concrete-filled steel tube (CFST) columns and reinforced concrete flat slabs provides a suitable structural solution that can be used to replace traditional structures in high-rise buildings. The connection between the CFST column and the RC flat slab is an important factor for this construction system to operate efficiently. In this study, a new form for the connection between the CFST column and the RC flat slab has been proposed. This connection has more constructability, where the steel tube is cut at the level of the slab to prevent the separation between the slab and the concrete inside the steel tube as the slab reinforcement is allowed to continue in the connection zone. The joint zone is strengthened with rebar rings to compensate for the loss in confinement caused by cutting the steel tube at the slab level. In addition to using longitudinal rebar in the joint zone to bear part of the vertical load and to ensure bending rigidity. The behavior of the proposed connection was investigated by testing three sets of small-sized samples. In addition, an equation based on the outcomes of the second set of tests has been carried out to determine the joint bearing capacity for the vertical load.

Tunnel Assembly-Type Temporary Support Joint Bearing Capacity

Tunnel Assembly-Type Temporary Support Joint Bearing Capacity

Experimental study on seismic behavior of RCS joints with asymmetric friction connections and slabs

This paper introduces a new reinforced concrete column-steel beam (RCS) joint that employs asymmetric frictional connections (AFC) to improve energy dissipation and moment transfer, reducing stress concentrations within the joint’s core. Two RCS joint specimens with AFC and floor slabs were designed and tested under quasi-static loading to analyze the impact of bolt preload on seismic performance. The experimental results demonstrate that RCS joints with AFC and slabs exhibit favorable seismic behavior in terms of bearing capacity, energy dissipation, and stiffness degradation. Increasing bolt preload enhances the bearing capacity, stiffness, and energy dissipation capacity of the joints. The failure occurred at the steel beam splice connections, while only minor micro-cracks appeared in the reinforced concrete column when the joint's bearing capacity dropped below 80% of the peak load. Displacement at the column top was primarily influenced by steel beam and column deformation, with minimal contribution from joint core deformation. The use of AFC effectively reduced deformation in the joint core area, meeting seismic design code requirements for “strong columns-weak beams.”

Significant improvement in tensile shear properties of friction stir lap welded nano TiB2/2024 Al composite joints via a novel tool pin geometry design

A novel designed tool pin with two shoulders and pins (stepped pin, S-pin) was performed to fabricate the friction stir lap welded nano-TiB2/2024 Al composite joints for the interface migration optimization and tensile shear strength improvement purposes. Compared with the conventional tapered pin (T-pin) joints, broken and dispersedly distributed hook, significantly restrained cold lap were observed in the S-pin joints. Submicron or hundreds of nanometers grains were detected in the stir zone (SZ), which should be attributed to the existence of nano-TiB2 hindering the movement of grain boundaries and limiting the growth of recrystallized grains. A wedge-shaped microhardness distributions of the S-pin joints were found, which would be better for the joint bearing capacity. Tensile shear loads of the S-pin joints were much higher than those of the T-pin joints. The optimal average tensile shear strength, 7.3 kN or 484 N/mm, were obtained when the S-pin was performed, dominantly fracturing in the heat affected zone (HAZ) rather than the SZ.

Behavior of hybrid FRP-concrete-steel double-skin tubular member T-joints subjected to brace axial compression

Hybrid fiber reinforced polymer (FRP)-concrete-steel double-skin tubular members (DSTMs) are a novel form of structural members comprised of an outer FRP tube, an inner steel tube, and an annular concrete sandwiched between the two tubes. By leveraging the advantageous properties of each constituent material, DSTMs possess superior mechanical performance and exceptional durability, making them highly promising for applications in ocean structures. Despite extensive research highlighting the excellent performance of individual DSTMs such as beams and columns since their inception, investigations into the behavior of DSTM joints have been scarce. This critical knowledge gap presents a significant obstacle to the widespread practical application of DSTMs. To address this gap, the present study was proposed to investigate the behavior of circular DSTM T-joints subjected to brace axial compression. An experimental program was conducted to systematically examine the influence of key factors such as FRP/steel tube thickness, brace-to-chord diameter ratio, void ratio, and concrete strength on the performance of DSTM T-joints. The experimental results demonstrated that the DSTM T-joints exhibited a ductile behavior; FRP confinement was demonstrably effective in enhancing the joint bearing capacity; the brace-to-chord diameter ratio and void ratio were identified as two crucial factors influencing the joint bearing capacity. Finally, simple design equations capable of providing reasonably accurate and slightly conservative predictions for the bearing capacities of the test DSTM T-joint specimens were proposed.

Evaluation on structural characteristics of the spiral case influenced by external concrete

Abstract As hydropower is developing vigorously, hydraulic-turbine units have to experience higher head to balance the large power production and consumption on the grid. It requests for higher level of structural strength and stability during operation. Water-filled and pressure-retaining spiral case is commonly used in the power houses of large-scale hydropower stations, which has a good joint bearing capacity of internal water pressure. In this paper, finite element models of the water-filled and pressure-retaining spiral case with and without external concrete under preloading pressure are established, which are used to simulate the structural characteristics when the water-filling process and concrete pouring process are completed. The results show that the maximum stress and deformation of the spiral case are significantly reduced by almost 50% under the support of concrete. Both of them are located at the inner edge and are about 200.80 MPa and 0.60 mm, respectively. The reason why the maximum stress and deformation positions of the spiral case changes after the external concrete being poured is the structural characteristics of concrete, which determine its stress and deformation distribution, and then affect the restraint effect of the corresponding area on the spiral case. The concrete can share parts of the preloading pressure from the spiral case that greatly improves the joint bearing capacity and stability of the overall structure. The conclusions in this paper can also be applied to evaluate the influence of external concrete on the spiral case structural characteristics for similar spiral case structure.

Experimental study and numerical simulation analysis of RCS joint with asymmetric friction connection

Based on the seismic design principle of recoverable function and replaceable seismic design, a novel type of reinforced concrete column-steel beam (RCS) joint was proposed, incorporating an asymmetric friction connection in the lower flange of the steel beam. Subsequently, experimental tests, numerical simulations, and theoretical analyses were conducted to evaluate this joint. The test results indicate that the RCS joint with asymmetric friction connection can effectively exert friction slip energy dissipation characteristics, demonstrating good seismic performance in terms of bearing capacity and stiffness. The damage observed in the specimen is primarily focused on the spliced cover plate of the steel beam, with minimal deformation in the core area of the joint. Numerical simulation and parameter analysis were conducted using ABAQUS software. The results demonstrate that the finite element model accurately reproduces the observed phenomena in the test. The parameter analysis reveals that a 10 % increase in bolt preload or a 0.05 increase in friction coefficient can result in a 7 % or 13 % rise in joint bearing capacity, respectively. Finally, a calculation method for determining friction slip in RCS joints with asymmetric friction connection was developed, showing close agreement between the calculated results and finite element outcomes, indicating the accuracy of the formula.

Working mechanism evaluations of full-scale joints with bolted-cover plate connection for modular steel buildings

The force-reliability of the modular structural joints is crucial for ensuring the structural integrity of modular steel buildings. However, the welds connecting the beam and column within the module are susceptible to tear during seismic events. This mode of failure greatly undermines the ability of these joints to withstand seismic forces. Four full-scale modular structural joints with bolted-cover plate connection were designed and conducted for seismic performance testing, emphasizing the significance of methods such as reinforcing diagonal braces and strengthening flanges on the protective effect of beam–column welds in the module. The simplified modular structural joint and frame finite element model were proposed based on experimental data, refined finite element modeling, and theoretical analysis. The findings suggest that the seismic behavior of the modular structural joint remains unaffected by variations in axial compression ratio within the designed range of parameters. The beam–column weld of the module in the reinforced joint exhibits almost no weld tearing, and both strengthening methods demonstrate exceptional capacity for energy dissipation. The proposed simplified modeling method facilitates the efficient determination of the modular structural joint bearing capacity and the lateral stiffness of the modular frame. The research findings presented in this paper can serve as a valuable reference point for the engineering design of modular steel structures.

Finite Element Analysis of Corrosion Tubular T-Joint Repaired with Grouted Clamp

A finite element (FE) analysis of corroded circular hollow section T-joints repaired using grouted clamps is presented in this study. To ensure an accurate simulation, experiments on a T-joint with uniform corrosion and an intact T-joint with grouted clamp are reproduced separately using an FE model. The experimental and FE modeling results correlate closely, displaying similar failure behaviors and load–displacement responses. Subsequently, a total of 56 FE T-joint models with varying degrees of corrosion on the chord, repaired by grouted clamp, were then analyzed numerically. The corrosion was artificially applied to the chord’s outer surface at depths of 10%, 20%, and 30% of the chord’s thickness. The models also account for variations in joint geometry, dictated by parameters β and γ, which range from 0.565 to 0.678 and from 21 to 28, respectively. Furthermore, grouted clamp’s properties were examined, including sleeve length, thickness, strength, as well as the thickness and strength of the grout, in relation to the complexity of the repair. The grouted clamp demonstrated significant repair capability, increasing the ultimate strength of the corroded joint by up to 2.23 times. Reinforcements that are both thicker and longer substantially enhance the joint’s ultimate strength. However, inappropriate repair construction results in an abrupt termination of the load–displacement curve and a brittle failure phenomenon outside reinforced chord region. Additional weight from the grouted clamp requires reasonable control, and sleeve overlapping ratio should be guaranteed to be greater than 0.7. The joint bearing capacity can be efficiently increased by thicker grouts and sleeves only in ductile failure cases. The confinement effect and mechanism of the grouted clamp in joint deformation were visually analyzed as stress distribution from FE analysis results. Finally, a prediction equation is proposed to estimate the static strength of the repaired joint through regression analysis.

Analysis of the Joint Bearing Capacity of Composite Cushion-Spiral Case Structures for Hydropower Stations Considering the Damage Mechanisms of Surrounding Concrete

The spiral case structure is an essential part of a hydropower station. To accurately explore the joint load-bearing effect of the cushion-spiral case structure, a cushion-spiral case structure with a high HD value was selected, modeled, and analyzed in this study. The reliability of the model was verified through measured data. Given the contact relation between the spiral case and the cushion, the cushion laying range was used as the control parameter to investigate its impact on the joint bearing capacity of the structure. In addition, the concrete damage theory was introduced to probe the damage mechanism of the structure under assumed extreme working conditions. The steel spiral case bears most of the internal water pressure in the joint bearing system, and the bearing ratio of the surrounding concrete and reinforcement decreases with the increase in the cushion wrap angle. A 1.1–1.2 overload head is the main section that forms penetrating cracks. For the spiral case structure with a high HD value, a reasonable cushion can significantly reduce the damage level of the surrounding concrete and regulate the uneven lifting of the turbine pier and the shear strength of the stay ring. This study can provide reference points for the spiral case arrangement and range and the structural failure response under extreme working conditions.

Margin of bearing capacity of one-way straight mortise-tenon joints based on inspection of apparent damage and rotation angle

In essence, safety evaluation of damaged mortise-tenon joints (MJs) involves checking whether the joints have sufficient residual bearing capacity. However, the load, which is necessary in the calculation process, is difficult to observe in practice, resulting in insufficient reliability of the evaluation results. Thus, this study proposes the concept of a margin of bearing capacity (MBC) of an MJ and presents a calculation method for assessing the safety of one-way straight mortise-tenon joints (OSMJs). In the calculating process, the load was replaced with the observed apparent damage and rotation angle. First, the MBC includes the influence of joint damage and rotation angle on the residual moment bearing capacity of the joint. Second, the apparent damage to an OSMJ is simplified to average section loss rates in the height and width directions, which reduces the amount and difficulty of data acquisition. Third, the damage model of an OSMJ included in the proposed calculation method establishes the transforming relationship between the measured average section loss rate and the damage setting on the model, and avoids the influence of uneven distribution of the actual size reduction on the calculation of the residual moment bearing capacity. The results of unidirectional pushover tests of several damaged and intact OSMJ models showed that most absolute errors between the calculated and measured MBCs were less than 0.04, indicating the accuracy of the proposed method for practical safety assessment of damaged OSMJs.

Static behavior of multi-planar CFST chord-CHS brace TT joints

The static performance of the multi-planar concrete-filled steel tubular (CFST) chord-circular hollow section (CHS) brace TT (CFST-TT) joint is investigated using theoretical and finite element analysis (FEA). The joint ultimate bearing capacity is the minimum strength of each member to ensure that the joint will not fail under any loads. Accordingly, the strength calculation formulas for joints are proposed based on the failure mechanism. FEA models verified by experiments were established to obtain the joint bearing capacity and failure modes, and further analysis was done to find the effects of geometrical parameters, material strength, and the axial compression ratio. The results show that the joint bearing capacity increased with the increase of brace-to-chord diameter ratio (β) and steel yield strength of the chord (fy) but decreased with the increase of the chord diameter-to-thickness ratio (γ). However, the concrete compressive strength (fcu), the brace-to-chord thickness ratio (τ), the angle between two braces (Ф), and the axial compression ratio (n) almost have no effect on the joint bearing capacity. The proposed ultimate bearing capacity formula is validated using FEA. The optimized formula is proposed to simplify the theoretical calculation formula and make the results more consistent with the FEA results.

Study of the Seismic Behavior of Simplified RCS Joints via Nonlinear Finite Element Analysis

Compared to more complex structures, simply configured reinforced concrete column–steel beam (RCS) composite structures have more promising application prospects, especially in regions with moderate–high seismic levels, due to their ease of construction. However, the current understanding of the seismic performance of simplified RCS joints is not sufficient. Validated by experimental results, a nonlinear finite element analysis (FEA) model was developed in this study to reveal the seismic behavior of simplified RCS joints. Six vital design parameters, namely axial load ratio, concrete strength, yield strengths of steel webs and flanges, and diameters of transverse and longitudinal reinforcements, were comprehensively studied. Research has shown that the axial compression ratio has a significant impact on the failure mode and bearing capacity of joints. When the concrete strength increases, the load-bearing capacity of the joints significantly increases, while the brittleness of high-strength concrete leads to a decrease in its deformation capacity. In addition, when the steel beam strength is constant, higher flange and web yield strengths have a limited influence on crack propagation and strain development. The stirrup reinforcement ratio and longitudinal reinforcement ratio play a significant role in inhibiting crack propagation and improving the bearing capacity, respectively. With the help of the numerical results, six theoretical models introduced by national codes and other researchers were compared. Among them, the modified model proposed by Kanno demonstrated the highest accuracy and was the most suitable for simply configured RCS joints.

Analysis of mechanical performance of modular steel-concrete composite joints considering floor slab composite effects

This study establishes and verifies the finite element models (FEM) of MSCCJs to analyze the mechanical performance of modular steel–concrete composite joints (MSCCJs) under monotonic static load without considering the floor slab composite effect (FSCE). Subsequently, 12 MSCCJ models incorporating the FSCE are constructed using ABAQUS. The study evaluates the effects of varying column axial compression ratios (n = 0.15, 0.25, 0.4, 0.6), floor width (w = 800, 1200 mm), floor thickness (t = 90, 110, 120 mm), and floor reinforcement ratio (r = 6 %, 8 %, 12 %) on the bending moment, initial stiffness (k0), ductility, and stress transfer of the joints. The results indicated that as n increases, the shear stress concentration in the joint core module (JCM) and the steel framework at the lower column end become more pronounced. Concurrently, the bearing moment and k0 of the joint also increase. However, once n surpasses 0.4, the joint's plastic properties diminish upon damage. With an increment in w, the k0 and ductility deformation of the joint remain stable and then decline. At w = 1000 mm, the joint's bearing capacity, stress distribution, and deformation performance reach their optimum. Since it significantly impacts stress distribution, its effect on the joint's mechanical performance is minimal. Lastly, the value of r enhances the ductility of MSCCJs and the stress concentration in the reinforcement. It is advisable to maintain r between 1.1 % and 1.7 %.

Numerical simulation analysis of load-bearing capacity at joints of symmetrical cantilever-assembled bridges based on the logistic regression model

Abstract Bridge joint bearing capacity analysis is difficult to fit the requirements of the era of big data. The traditional way of bridge-bearing capacity numerical analysis exists in the wave of digital development of big data information, the Internet of Things, and artificial intelligence technology like a wild development. The traditional way of under the problem: is efficiency, engineering analysis is not accurate, data information paper, work responsibility is not in place, technical equipment, etc. This paper revolves around the numerical simulation analysis of the load-bearing capacity at the joints of symmetrical cantilever-assembled bridges based on the logistic regression model by finding literature to understand the concept and algorithm of the logistic regression model, construct logistic regression model based on dichotomous dependent variable logistic regression algorithm, logistic regression model parameter estimation, logistic regression. The three aspects of the model evaluation index are studied. The numerical simulation analysis of the load-bearing capacity at the symmetrical cantilever joint based on the logistic regression model, the shear strength calculation at the bridge joint, and the bridge longitudinal bar slip deformation are calculated, respectively, and then the actual value of the bridge load bearing capacity is derived. Simulation in the bridge bearing capacity at 0kN, 5kN, 10kN, 15kN, 20kN, 25kN, and 30kN, the model algorithm evaluation index under the three indicators of prediction rate, accuracy, deviation of the verification analysis. The results show that the prediction rate of the logistic regression model algorithm based on the load carrying capacity up to 30kN is 84%, the accuracy rate is 94%, and the deviation is 11%, and the three index values have better performance compared with the one-dimensional linear regression model algorithm and the multiple linear regression model algorithms. This study is beneficial to extend the bridge structural analysis function and make the bridge load capacity assessment more automatic; it can facilitate the comparison of historical data of bridge tests, longitudinal change of indicators at different testing time points, and grasp the current situation and change trend of bridges. Thus it is of great historical significance to the development of the Chinese bridge infrastructure industry.