Behavior Of Joints Research Articles

Fracture and Fatigue Crack Growth Behaviour of A516 Gr 60 Steel Welded Joints

The facture and fatigue behaviour of welded joints made of A516 Gr 60 was analysed, bearing in mind their susceptibility to cracking, especially in the case of components which had been in service for a long time period. With respect to fracture, the fracture toughness was determined for all three zones of a welded joint, the base metal (BM), heat-affected zone (HAZ) and weld metal (WM), by applying a standard procedure to evaluate KIc via based on JIc values (ASTM E1820). With respect to fatigue, the fatigue crack growth rates were determined according to the Paris law by the standard procedure (ASTM E647) to evaluate the behaviour of different welded joint zones under amplitude loading. The results obtained for A516 Gr. 60 structural steel showed why it is widely used in the case of static loads, since the minimum value of fracture toughness (185 MPa√m) provides relatively large critical crack lengths, whereas its behaviour under amplitude loading indicated a need for further improvement in WM and HAZ, since the crack growth rate reached values as high as 4.58 × 10−4 mm/cycle. In addition, risk-based analysis was applied to assess the structural integrity of a pressure vessel, including comparison with the high-strength low-alloy (HSLA) steel NIOVAL 50, proving once again its superior behaviour under static loading.

Numerical investigation of existing RC exterior beam-column joints under cyclic loading: case study of 1971 algerian building

Many reinforced concrete (RC) buildings constructed in Algeria before the 1980s may have serious structural deficiencies and are considered substandard according to the Algerian seismic code. Specifically, the failure of the beam-column joints has been the cause of building collapse in many earthquakes in the past: Alasnam October 10, 1980 and Boumerdes May 21, 2003. In this work, the behavior of RC exterior beam-column joints under quasi-static cyclic loading is studied by 3D nonlinear finite element analysis using ANSYS software. To perform the non-linear analysis, the load was applied step by step and the modified Newton-Raphson method was used for the solution. In order to prove that the program successfully captures the necessary response parameters without any modifications to the structure details, some available experimental works were modeled and non-linearly analyzed using ANSYS. Moment-rotation and load-displacement relationships were compared with the experimental data. It was observed that the results are quite similar to each other. Thereafter, a typical RC exterior beam-column joint belonging to a building constructed for residential use in Algeria in 1971 was modeled using ANSYS. The joint was subjected to quasi-static cyclic loading, and its performance was examined in terms of load resistance and failure. The moment-rotation hysteresis curve has been established. The hysteretic loops of the joint, representing the existing structure, showed stiffness degradation and strength deterioration.

Finite element analysis of the behaviour of double-row bolted fin-plate connections

Fin-plate connections are among the most prevalent shear connections in the United States and Australia due to their simplicity in manufacturing and erection. Eurocode 3 Part 1-8 (Eurocode 3, 2005) classifies fin-plates as connection components that can transmit significant moments despite being classified as pinned connections. This study aims to investigate fin-plate connections with double rows of bolts and their effect on joint behaviour and strength, including the effect of plate thickness on the Torsional Moment-Angle of Twist and Moment-Rotation relationship. The results were analysed to determine the influence of these factors on behaviour and joint strength, and they were utilized to assess the efficacy of the Eurocode 3 Part 1-8 design approach. To fulfil the study's objective, finite element models were developed using the finite element analysis software Abaqus. The modelling considers material and geometric non-linearity to evaluate the overall behaviour of the connection and the individual components involved in this type of connection. The results were compared with those obtained from experimental testing to validate the finite element models.

Studies on Strength Properties of RC Beam Column joint With Basalt Reinforcement

In recent earthquakes it Is observed that the beam column joint is more exposed to lateral loads due to which the joints undergoes severe deformations leading to yielding of the joints and the overall structure. . Poor design practices for beam-column joints are compounded by the high demand imposed by adjacent flexural members (beams and columns) as they mobilize their inelastic capabilities to dissipate load energy. Unsafe design and details in the joint region put the entire structure at risk, even if other structural elements meet the design requirements. Therefore the new material that is basalt rebar is used as reinforcement to observe the structural behaviour of the beam column joint. The experiment is conducted and the results are taken. The comparative study is done by using both steel specimens and basalt reinforced specimens. The detailing is done as per the seismic codes. The results are tabulated and graph is plotted.

An Experimental Study on Industrial Concete Pile Foundation in Soft Soil: Comparison of Monolithic and Pile with Welded Joints

This study presents an experimental investigation into the industrial foundation piles. The research carried out employed both destructive and non-destructive testing methods to evaluate the concrete compressive strength and flexural strength capacity of the piles under monotonic loading. The Destructive Test (DT) involves a 28-day cylinder concrete compressive test, while the Non-Destructive Test (NDT) utilizes the Ultrasonic Pulse Velocity (UPV) and Rebound Hammer (RH) tests. The flexural strength test is conducted using a loading frame, and the results are compared to the GeoPIV-RG, which measures the displacement during the test. The experimental investigations provide insights into the behavior of pile joints when subjected to monotonic load in soft and loose soil. The results indicate a significant difference between the compressive strength obtained from the DT and NDT, with a ratio of 0.64-0.74. Furthermore, the failure occurred at the joints, rather than the welded area, with the ratio of the initial stiffness of the piles with joints to the monolithic pile being 0.15 for zig-zag welded and 0.30 for circular welded, and reaching an average value of 0.225. According to the GeoPIV-RG result, the displacement is similar to the flexural strength test result.

Mechanical behavior of en-echelon joints under cyclic shear loading conditions: Roles of joint persistence and loading conditions

Studying the mechanical response of en-echelon joints under cyclic shear loading conditions can provide novel insights into the instability of jointed rock masses under seismic conditions. To investigate the effects of joint persistence, normal stress, cyclic distance, and shear velocity on the cyclic shear behavior of en-echelon joints, a series of cyclic shear tests in the laboratory was performed. Findings revealed that the failure morphography of en-echelon joints manifested through brecciated shear zones and abraded rupture surfaces, resulting in notable reductions in shear strength and significant compressibility. The degradation factor of shear strength ranged from 0.363 to 0.708 after ten cycles. The shear strength degradation factor showed an inverse relationship with joint persistence and normal stress while exhibiting a direct correlation with cyclic distance over ten cycles. En-echelon joints characterized by moderate joint persistence, high normal stress, small cyclic distance, and low shear velocity demonstrated increased cyclic friction strength. Moreover, normal stress and joint persistence exerted a more significant influence on shear strength compared to cyclic distance and shear velocity. For en-echelon joints, shear stiffness increased during small shear displacements with cycle number while decreased during large shear displacements; shear stiffness was inversely proportional to the cyclic distance and joint persistence, and directly proportional to the normal stress. Compressibility of en-echelon joints correlated directly with joint persistence, normal stress, cyclic distance, and shear velocity. Compared to normal stress and cyclic distance, joint persistence and shear velocity exhibited less influence on compressibility

Study on the effects of hole diameter and sheet thickness on quasi-static and fatigue behaviors of pre-holed self-piercing riveted steel-aluminium joints

Study on the effects of hole diameter and sheet thickness on quasi-static and fatigue behaviors of pre-holed self-piercing riveted steel-aluminium joints

Shear behavior of rock joints reinforced with fully-grouted and energy-absorbing bolts subjected to shear cycles

Shear behavior of rock joints reinforced with fully-grouted and energy-absorbing bolts subjected to shear cycles

Design model for shear keys used as thermal break systems in balcony-slab joints under combined shear and bending loads

Balcony-slab joints (BSs) are common in residential buildings. Integrating thermal break systems (TBSs) can reduce the energy loss resulting from thermal bridging. However, the mechanical performance of BSs equipped with TBSs against shear and bending remains hardly explored in design and experimentation. The aim of this study is to evaluate the mechanical behavior of BS joints under combined shear and bending actions, taking into account the presence of TBSs. Seven large-scale balcony-slab specimens were fabricated and tested under vertical loading with different moment-shear ratios (M/V). The BSs are equipped with TBSs comprising steel bars and shear profiles. A simplified finite element (FE) model was then developed using the ABAQUS software. The FE model employs spring-like elements to simulate the bond and contact behavior between concrete and steel, reproducing both the resistance and stiffness of the tested specimens. On the basis of the experimental and FE results, a resistance model consistent with the Eurocode design guidelines was drawn. Finally, moment-shear (M-V) interaction curves for balcony-slab joints were generated at the ultimate (ULS) and serviceability (SLS) levels, considering the impact of horizontal loading to achieve comprehensive design insights. The tests and FE results showed that the moment-shear ratio (M/V) significantly influences the shear capacity of the BS joints. The steel profiles effectively acted as shear keys connecting the balcony and the slab. A strength reduction coefficient of 0.701 was introduced for the design.

Experimental study on the post-fire seismic behavior of exterior beam-column joints in reinforced concrete frames

This study outlines the post-fire seismic behavior of reinforced concrete beam-column joints. Due to the lack of sufficient research data regarding the seismic vulnerability of exterior reinforced concrete beam-column joints after fire exposure, experimental investigations were carried out to assess variations in the seismic performance of these joints after experiencing high temperatures. In this way, five scaled beam-column joints were considered for examinations and were designed according to the seismic provisions of ordinary moment frames. One benchmark specimen was subjected to reverse cyclic loading at ambient temperature without prior fire exposure. Four others were exposed to the heating regimes with various target temperatures and then examined by reverse cyclic loading after cooling to the ambient temperature. Damage patterns were exhibited with substantial alterations from flexural beam-end hinging for the benchmark specimen to the shear ruptures for the fired specimens exposed to the high temperatures of 400°C, 600°C, and 800°C. The quantitative results indicated minor changes in the load-bearing capacity, ductility factor, and energy dissipation by the effect of the 200°C heating regime. On the other hand, other three heating regimes led to noticeable reductions of 16–62% in the load-bearing capacity, 25–65% in the cumulative energy dissipation, and 14–42% in the ductility factor by propagating diagonal cracks and developing shear ruptures inside the joint core. Trends in variations of investigated parameters were also discussed, and novel findings were presented in this regard. The results and observations in this study can be employed as the applicable data for retrofitting decisions of fired exterior beam-column joints in reinforced concrete ordinary moment frame buildings.

Influence of diffusion bonding temperature on the interfacial evolution behaviors of GH4169 joints produced by solid-state diffusion bonding additive manufacturing

Influence of diffusion bonding temperature on the interfacial evolution behaviors of GH4169 joints produced by solid-state diffusion bonding additive manufacturing

A machine learning-based method for predicting the shear behaviors of rock joints

In this study, machine learning prediction models (MLPMs), including artificial neural network (ANN), support vector regression (SVR), K-nearest neighbors (KNN), and random forest (RF) algorithms, were developed to predict the peak shear stress values and shear stress-displacement curves of rock joints. The database used contained 693 records of peak shear stress and 162 original shear stress-displacement curves derived from direct shear tests. The results demonstrated that the MLPMs provided reliable predictions for shear stress, with the mean squared errors (MSEs) between their predicted and measured shear stress varying from 0.003 to 0.069 and the coefficients of determination (R2 values) varying from 0.964 to 0.998. The feature importance values indicate that the joint surface roughness coefficient (JRC) is the most important influential factor in determining the peak shear stress, followed by the joint wall compressive strength (JCS), basic friction angle (φb), and shear surface area (As). Similarly, for the shear stress-displacement curve, the JRC is the dominant factor, followed by As, φb, and JCS. Additional direct shear tests were conducted for model validation. The validation shows that the MLPM predictions demonstrate improved consistency with the experimental results in relation to both the peak shear stress and peak shear displacement.

Eccentric load bearing performance of high bolt screw (HBS) active joints for prestressed internal supports in the subway excavation

This study introduces a novel High Bolt-Screw (HBS) active joint for enhancing the load-bearing performance of steel support systems used in subway foundation pits. The HBS joint addresses the limitations of traditional steel wedge joints, particularly in handling eccentric loads and tensile forces. Experimental and numerical analyses were conducted on specimens with different screw diameters to evaluate the mechanical behavior of the HBS joint under eccentric compression. Load-strain curves, load-displacement curves, and failure modes were documented to compare the performance of the HBS joint with an equal length steel support (ELSS) and a traditional wedge joint. The data and results obtained from numerical simulations exhibited a high degree of concordance with those derived from laboratory tests. Finite Element Analysis (FEA) was employed to perform parametric studies, examining the effects of key design factors such as screw diameter and eccentricity. The results indicate that the HBS joint provides superior preloaded axial force retention. Additionally, the HBS joint exhibited a yield load 1.35 times greater than that of traditional wedge joints, with an initial compressive stiffness 3.5 times higher, enhancing its resistance to deformation under eccentric loads. Parametric analysis indicated that the yield load is influenced by the eccentric distance but unaffected by the eccentric angle, with screw diameter, barrel nut height, and extension length identified as key factors. A yield load formula was derived through rigorous theoretical analysis and validated against experimental data, showing a relative error of less than 10 %. These findings emphasize the exceptional eccentric load-bearing capacity and stiffness of HBS joints, providing valuable insights for designing and implementing advanced support systems in subway foundation pit construction.

Performance of hinge joints in hollow-core slab bridges reinforced with iron-based shape memory alloy U-bars

The mechanical behavior of hinge joints has an important influence on the hollow-core slab bridges. However, hinge joints are prone to cracking. This study proposed a new hinge joint reinforced by locally prestressed iron-based shape memory alloy (Fe-SMA) U-bars for the new hollow-core slab bridge. To verify the effectiveness of this hinge joint, six test specimens were prepared, encompassing two spans (10 m and 20 m), and three working conditions (nonactivation, activation before cracking, and repair and activation after cracking). The load transfer mechanism under flexural-shear load was investigated, and the validity was verified using a proposed simplified analytical model. The results indicated that the failure mode of the new hinge joint under flexural-shear load can be divided into three stages. The new hinge joint can effectively apply local prestressing by heating activation of the Fe-SMA U-bars, thus increasing the crack penetration load. In addition, the damaged new hinge joints can be repaired and further reinforced by pressure injection of adhesive and heating activation of the Fe-SMA U-bars. Load transfer is affected by the development of cracks, and the ultimate load of the new hinge joint is controlled by the splitting tensile strength of the concrete in the hinge joint.

Coupling mechanism of bioinspired artificial composite synovial fluid on tribological behavior of artificial joints

Coupling mechanism of bioinspired artificial composite synovial fluid on tribological behavior of artificial joints

Effect of high-strength SCC with and without steel fibres on the shear behaviour of dry joints in PCSBs

The structural behaviour of precast concrete segmental bridges (PCSBs) heavily relies on the strength of the joints between segments. Multi-keyed dry joints are currently the most commonly used solution in these discontinuity zones. Employing high-strength concrete is becoming increasingly common in civil engineering given its higher strength and improved durability. It specifically allows higher prestressing levels in PCSBs. Using self-compacting concrete enhances workability and adding steel fibres improves mechanical properties. The existing scientific literature includes experimental tests to analyse the shear behaviour of castellated dry joints in different concrete types. However, no experimental tests appear specifically for the castellated dry joints made with high-strength self-compacting concrete (HS-SCC) with and without steel fibres. Therefore, this experimental study conducted 31 push-off-type tests to analyse the behaviour and shear capacity of dry joints made of HS-SCC by investigating the influence of adding steel fibres to the concrete mix. The study examined crack patterns, load-displacement behaviour, failure modes and different (cracking, ultimate and residual) loads. The addition of steel fibres improved joints’ shear capacity. However, brittle behaviour was observed after reaching ultimate load when using HS-SCC, even when steel fibres were added to the concrete mix. Finally, the adequacy of existing formulations was analysed. Standard AASHTO proved to be on the unsafe side for the castellated dry joints specimens made of HS-SCC without steel fibres, and provided a good approximation for the specimens with steel fibres.

The development of a component-based model for extended endplate joints in fire-induced progressive collapse scenarios

This paper develops a generalized component-based model (CBM) for extended endplate (EP) joints designed to be applicable in progressive collapse scenarios induced by fire, which is capable of capturing the nonlinear full-range behavior of EP joints from initial yielding to ultimate failure. Based on refined FE modeling established in preceding studies, a simplified CBM method is established to simulate the collapse resistance of EP joints subjected to fire-induced column removal scenarios. For panel zones of fire-exposed EP joints, a trilinear model is applied to characterize the three-phase force-deformation behaviors of “linear-hardening-unloading” for axial springs, while a relatively large shear stiffness is used to characterize the minor shear deformation at the panel zones. For connecting zones of fire-exposed EP joints, the respective constitutive models and corresponding spring parameters for diverse spring components are established based on the strain distributions and loading transmission mechanisms of equivalent T-stub components. The proposed simplified CBMs with detailed spring parameters as well as their constitutive laws were incorporated into the ABAQUS program to validate against both experimental results and refined FE modeling. A comparative study with test data manifests that the proposed CBM method can precisely capture the collapse response of EP joints at elevated temperatures with high computing efficiency.

A slope-based J-integral approach and advanced image processing for assessment of the cyclic fatigue delamination behavior of adhesive joints

A fatigue fracture mechanics methodology was developed and established, employing a slope-based J-integral approach combined with advanced image processing techniques. Adhesively bonded double cantilever beam (DCB) specimens were tested under constant displacement amplitude loading. The beam rotation was tracked by affixing a repetitive pattern on the DCB specimens and capturing images at the maximum displacement amplitude. Using a custom-developed image processing procedure, the beam rotation was deduced. To validate the methodology, DCB fatigue experiments were conducted at 23, 60 and 75 °C on aluminum adherends bonded with a structural 2-K epoxy adhesive. The J-based approach was compared with a conventional, compliance-based linear elastic fracture mechanics (LEFM) method. The epoxy was a rather brittle, high-modulus adhesive with a bond line thickness of 0.25 mm, resulting in predominantly linear elastic material behavior. By analyzing the images taken during fatigue testing, a stiffening effect of the steel load blocks was observed. Excluding pattern elements directly below the load block yielded the best agreement between J-integral and LEFM data. Both approaches were in excellent agreement within the investigated temperature range. The investigated adhesive exhibited a highly temperature-dependent behavior, which was associated with higher crack propagation rates and a lower fatigue threshold at 60 and 75 °C.

Statistical Shape Modeling to Determine Poromechanics of the Human Knee Joint.

Subject-specific knee joint models are widely used to predict joint contact mechanics for individuals but may not capture the variance in knee joint geometry across a population. Statistical shape modeling uses the dataset of a cohort to encapsulate population-wide variability. The present study aimed to develop a shape modeling procedure for poromechanical finite element models of knee joint to account for population diversity in the creep response of knees. Shape models of right knee joints were created from MRI of 31 healthy male subjects using principal component analysis. Creep analysis was performed for 13 shape models in total, i.e., the average model, plus six models for both the first and second principal modes. For a given loading, the contact and fluid pressures varied substantially within these mathematically produced models but compared reasonably well to that of three subject-specific models that were constructed from individual knees, representing approximately the smallest, median and largest knees of the 31 right knees. While the joint size variation, generally represented by the first principal component, predominantly influenced the magnitudes of contact and fluid pressures, the joint shape variation characterized by the second principal component further affected the pressure distribution, and load sharing between the lateral and medial compartments. The present study evaluated a workflow for the statistical shape modeling of poromechanical behavior of knee joints with sample results based on a small population. However, the workflow can be readily used for a large population to address the challenge of interpatient variability in joint contact mechanics, particularly in contact and fluid pressures in articular cartilage, and variable creep behaviors of the joint associated with individual anatomical variations.

Numerical Study on Welding Residual Stress and Microstructure in Gas Metal Arc Welding Square Tube–Plate Y-Shaped Joints

Welding residual stresses significantly influence the mechanical behavior of hollow section joints, especially in the pivotal connection zones of steel structures employed in construction. The research object of this study is the Q355 steel square tube–plate Y-joint welded using Gas Metal Arc Welding (GMAW) with CO2 Shielding. The thermodynamic sequence coupling method was employed to simulate the temperature field, microstructure distribution, and welding residual stresses in square tube–plate Y-joints. Based on the monitored temperature field data and the cross-sectional dimensions of the weld pool, this study calibrated the finite element model. Subsequently, the calibrated finite element model was employed to analyze the influence of microstructural phase transformations and welding sequences on the welding residual stresses in square tube–plate Y-joints. The research findings indicate that the peak transverse welding residual stresses in the branch pipes of the four joint zones were lower when considering the phase transformation effect than when not accounting for it in the calculations. There was no significant difference in the transverse and longitudinal welding residual stresses on the surface of branch pipes under the three welding sequences. However, there were certain differences in the microstructural content of the weld zones under the three welding sequences, with the martensite content in the third welding sequence being significantly lower than that in the other two sequences.