Joint Failure Research Articles

Seismic performance of full-scale prefabricated semi-rigid bolted connection between RC column and composite beam

This paper presents a novel proposal for an assembled bolted joint between precast reinforced concrete (RC) column and steel-concrete composite beams, focusing on its seismic performance. To evaluate the joint's behavior, a comprehensive experimental investigation was conducted on a full-scale RC column to composite beam joint specimen subjected to pseudo-static loading. The study aimed to analyze the joint's failure mode, bearing capacity, ductility, and energy dissipation characteristics. The joint stiffness was assessed by analyzing the bending moment-rotation (M-θ) curve of the beam in accordance with the European standard BS EN 1993-1-8:2005. The experimental results demonstrate that the proposed assembled bolted joint exhibits semi-rigid behavior under positive moments and approaches rigidity under negative moments. To further enhance our understanding of the joint's performance, a finite element model was developed using ABAQUS. The stress distribution in each joint component, as well as the failure mode and ultimate bearing capacity, were analyzed in conjunction with the experimental results. Based on the findings from both the experimental and finite element analyses, an improved joint design is proposed. Additionally, parametric analysis was conducted on the enhanced joint configuration. The study findings indicate that the improved joint exhibits superior damage resistance, seismic performance, and enhanced assembly efficiency compared to the original design. This research contributes to the advancement of assembled bolted joints between precast RC columns and steel-concrete composite beams, offering valuable insights for practical applications in seismic regions.

Climate change impact on the compound flood risk in a coastal city

Compound flooding caused by a combination of rainfall and water level may occur in coastal cities. Under the influence of climate change, compound flooding is likely to be intensified. In this paper, using the main urban area of Haikou City as an example, we developed an event-based statistical-numerical hybrid framework to investigate the effects of sea level rise (SLR) and future rainfall changes on compound flood risk. Future rainfall was predicted by using five global climate models (GCMs) in CMIP5. A combination of GCMs and IPCC AR5 was used to predict the future SLR. The copula was then used to calculate the probabilistic risk of compound flooding (OR joint probability and failure probability) for historical and future scenarios, and the numerical model was utilized to evaluate the risk of inundation under historical and future scenarios. The probabilistic risk results show that both the probability and the failure probability of compound flooding will increase in the future. Output from GCMs indicate that when the OR event of the 5-year event (the compound flooding when at least one of the 5-year rainfall and the 5-year water level happens) occurs, the joint probability of future compound flooding will likely increase to 37.5%. The numerical model results indicate that the flood extent, flood depth and flood duration will increase under the influence of future rainfall and SLR. Under the impact of climate change, the flood depth in the FS5 case will increase by 22.85% and the flood extent in the FS5 case will increase by 41.42% compared to HS5. By controlling for variables, we also find that the combined impact of future changes in rainfall and water level on the magnitude of flooding is greater than the sum of their individual impacts. Finally, we find that water storage facilities and tide gates could be set up to mitigate compound flooding under climate change.

Mechanical characterization of short Curauá/glass fiber-reinforced interlaminar hybrid composite adhesive joints

This paper presents a study on the mechanical characterization of novel short curauá/glass fibre reinforced interlaminar hybrid composite adhesive joints. The study aims to optimize the performance of these joints by analysing their mechanical properties as a function of the number of external synthetic layers and the architectural symmetry. Short curauá fibres and glass fibre bidirectional fabrics were used with a bi-component epoxy matrix in order to fabricate the hybrid composite adherends. The glass fibre bidirectional fabrics were placed on the outer layers, while the short curauá fibres were used as the core of the hybrid composites. The mechanical properties of the composites used as adherends, including tensile strength, flexural strength, and impact resistance, were determined through mechanical testing. Single lap joints bonded with a structural ductile bi-component epoxy automotive adhesive were fabricated and tested for each case. The results show that the failure mode of the bonded joints is strongly influenced by the composition and configuration of the adherends’ composite layers. It was found that the effect of the number of synthetic layers is highly significant for bonded joint failure load, while no significant variation was observed as a function of architecture symmetry. This study provides valuable insights into the mechanical properties of adhesively bonded joints in hybrid curauá/glass fibre reinforced composites, which can be useful in the design and optimization of these materials for various engineering applications.

Fire and post-fire performance of blind-bolted concrete-filled steel tubular joints with restrained steel beams: Experiment and simulation

Blind-bolted connection is a type of new developed prefabricated beam-column connection, which can be used to connect the concrete filled steel tubular (CFST) columns and the steel beams easily. The static and dynamic performance of CFST column to steel beam joints with blind-bolted connections have been well explored, but limited research has been conducted to investigate the fire and post-fire performance of this type of composite joint. In this paper, a series of reversed T-shaped joint fire tests were conducted to investigate the fire and post-fire performance of blind-bolted CFST joints with axially restrained steel beams. The influence of restrained effect from adjacent members in the entire frame structure on the response of blind-bolted joints in and after fire could be reasonably considered by the reversed T-shaped joint fire test. The joint temperature, failure modes, beam and column displacements and temperature internal force development during the entire loading and fire stage were recorded and discussed. The test results indicated that the blind-bolted connections showed very good working performance in and after fire, and no bolt shank fracture or bolt pull-out failure was observed. Finite element analysis (FEA) models were established to simulate the fire and post-fire performance of blind-bolted CFST T-shaped joints with axially restrained steel beams, and the joint moment versus relative rotation angle relationship curves of the blind-bolted joints during the entire fire and loading process were extracted and discussed based on the FEA models. The results indicated that the joint negative moment generated by the axially restrained beam boundary in the heating and cooling phases could go up to around 1.4 times the joint negative moment at ambient temperature.

Seismic design and experimental testing of precast tolerance concrete shear wall subject to cyclic load

A precast tolerance concrete shear wall (PTCW) characterized by proper-length steel connectors is proposed to adjust the tolerance and improve the joint failure model of the precast wall. The design method for this wall is also presented in this study and verified by test results. Four full-scale walls, including two cast-in-situ walls (RCWs) and two precast walls (PCWs) with axial compression ratios of 0.2 and 0.3, respectively, were tested under lateral loading. The seismic behavior of the panels, including the failure modes, hysteretic behavior, strength envelope curves, stiffness degradation, energy dissipation, and steel strains, was analyzed and discussed herein. The test results showed that all four walls were in a flexural-shear failure mode, and the PCWs showed better performance in terms of hysteretic behavior, strength envelope, stiffness, and energy dissipation, particularly under an axial compression ratio of 0.3. Furthermore, the peak load of PCW1 (axial compression ratio is 0.2) and PCW2 (axial compression ratio is 0.3) increased by 5.93% and 15.51%, and the yield load increased by 12.1% and 11.39% compared with those of RCW1 (axial compression ratio of 0.2) and RCW2 (axial compression ratio of 0.3), respectively. The equivalent viscous damping coefficients of all four panels were higher than 0.05. The lateral bearing capacity of the walls increased with an increase in the axial compression ratio. Moreover, no visible damage or slippage was observed when the PCWs were demolished after testing. The main nonlinear strain was concentrated on the vertical bar and not on the connectors, indicating that the plastic hinge position was transferred from the joint interface to the wall panel. The results indicated that the use of steel connectors to strengthen the joints can achieve the seismic design concept of strong joints and weak members.

Impact of standard and unexpected bolt-hole-washer tolerances on the performance of pinned and torqued joints in CFRP composites

This study aimed to investigate the impact of some practical assembly errors on the performance of composite joints with M6 bolts in quasi-isotropic CFRP laminates with stacking sequence of [±45/0/90]2S, which are increasingly used in aerospace and automotive industries. The detailed experimental explanations of the behaviors of the bolted joints in CFRP composites with standard and unexpected joining parameters, exhibited a vital impact on the bearing and ultimate joint strength, stiffness, energy absorption, and failure mechanisms. The joining parameters include tightening torque (0-16Nm), bolt-hole clearance (0–240 μm), and washer-to-bolt hole clearance (0–500 μm) with different offset arrangements. The bolt axial force is monitored during the testing of double-lap bolted composite joints. The maximum performance of the bolted joints was observed at tightening torque of 12Nm, bolt-hole clearance up to 60 μm, washer-to-bolt hole neat-fit or with negative clearance arrangement. The first peak, 2 % offset, and ultimate strengths are increased, respectively, by 55.9 %, 56.4 % and 52.4 % compared to those of the pinned joints. The 2 % offset strength and stiffness of bolted joints with negative washer-to-bolt hole clearance arrangements is improved by 26.8 % and 57 % respectively compared to those having positive arrangements. Energy absorption increase almost linearly with bearing load with correlation coefficient of 0.982.

Experimental Investigation on the Seismic Behavior of Precast Concrete Beam-Column Joints with Five-Spiral Stirrups

Precast concrete structure is a low-carbon building system that has been attracting extensive attention in recent decades. Beam–column joints are the weak links in precast concrete structures. Past studies showed that the five-spiral stirrups had excellent confinement effects and had the potential to enhance the seismic performance of concrete structures. This study proposed the reinforcement of precast concrete beam–column joints by using five-spiral stirrups and investigated their seismic performance. Considering the influences of the joint failure mode, joint type, construction method, and stirrup type, low-cycle loading tests were conducted on six full-scale precast concrete beam–column joint specimens. Various seismic behavior indicators, such as failure modes, hysteresis curves, skeleton curves, ductility, and energy dissipation, were obtained. The results indicated that the deformation capacity of the precast joints with five-spiral stirrups was comparable to that of cast-in-place joints. Under different failure design criteria, the seismic performance of the precast joints was superior to that of cast-in-place joints. Furthermore, the experimental capacities of the precast joints, using five-spiral stirrups, were higher than the calculated values according to the design code, demonstrating an adequate safety margin. This research contributes to the development of low-carbon and sustainable construction practices in the field of precast concrete structures.

Microstructure evolution and mechanical properties of Sn-9Zn-2.5Bi-1.5In solder joints with aging treatment under various conditions

Sn-Zn system solder has been considered promising lead-free solder materials to replace Sn-Pb and Sn-Ag-Cu systems in various conditions, due to the performance characteristics of low melting point and high reliabilities. This study investigates the microstructure evolution and mechanical properties of Sn-9Zn-2.5Bi-1.5In (Sn-Zn) solder paste joints on Cu substrates with aging treatment, which are under various conditions of different paste thicknesses and reflow times. It is concluded that the intermetallic compounds (IMC) of Sn-Zn/Cu solder joints are Cu5Zn8 layers at all stages of aging. The microstructure of before-aging joints and evolution during aging is significantly affected by the reflow times, while slightly affected by the paste thicknesses. In all experimental conditions, the IMC layers gradually thicken and reach 4-5 μm when aging for 720 h. While Cu5Zn8 products are generated at the position of the original Zn phases or along the Sn grain boundaries in the solder matrix with the aging process. The unequal diffusion rates of Cu and Zn atoms create two types of joint voids which are accumulated by Zn vacancies in the solder and accumulated by Cu vacancies at the interface between the solder and IMC layer. The interface voids and coarsened crystal structure are identified as the main factor for joint failure during aging. Finally, the shear strength of the joints with the initial 3.5 μm thickness IMC layers can maintain at high values above 45 MPa, exhibiting satisfactory reliability, which indicates that the soldering process determines the initial IMC structure, and affects the joint reliability more than the aging process.

Investigations on the diffusion bonding of titanium alloy and aluminum alloy using copper at low bonding pressure

This research investigates the diffusion bonding of hybrid aluminum (Al)–titanium (Ti) joints using a copper (Cu) interlayer in a vacuum environment. At 610 °C and 1 MPa pressure, partial melting of Al caused deformation and misalignment, while 520 °C showed no melting of Al–Cu at the interface. A rod-shaped precipitate with primarily Al was observed at 550 °C, and grain coarsening occurred at 580 °C at the interface, accompanied by increased Cu diffusion within the Al matrix for a bonding time of 45 min. A Ti–Al-based intermetallic layer formed on the Ti side, but voids and cracks were present in the Al–Cu diffusion region at 580 °C. Hardness variation resulted from microstructural changes due to bonding temperature, particularly near the bond line due to hard intermetallic compounds. Shear strength averaged 41 MPa at 550 °C and decreased to 33 MPa at 580 °C due to grain growth, voids, and crack propagation, causing brittle joint failure at the interface. X-ray diffraction on the fracture surfaces revealed that the failure of diffusion-bonded joints is attributed to fractures through the Ti–Al-based intermetallic compounds at the interface and unbonded region.

Microstructural Evolution, Intermetallic Formation, and Mechanical Performance of Dissimilar Al6061–Ti6Al4V Static Shoulder Friction Stir Welds

The present study focuses on achieving microstructural uniformity in dissimilar Al–Ti joints through static shoulder friction stir welding (SSFSW). This method restricts material mixing at the Al–Ti interface due to reduced shoulder action, resulting in peak temperatures of 317 °C (SSFSW) and 491 °C in conventional friction stir welding (CFSW). This reduction in heat input during SSFSW leads to decreased mechanical mixing, resulting in a thinner 2.169 μm intermetallic layer at interface of SSFSW compared to 5.485 μm in CFSW. The resulting weld nugget (WN) microstructure reveals the presence of Ti particles, intermetallic compounds, and fine Al‐associated grains. Rearrangement of dislocations through slip‐and‐climb mechanisms, along with distinct recrystallization processes in SSFSW, significantly reduces grain size within WN. The kernel average misorientation map highlights the presence of nonuniform dislocation concentrations at the interface of CFSW, attributed to the large Ti particles that impede the mobility of dislocations. As a result, the interface of CFSW is found to be the weakest among all the zones, eventually leading to the failure of the CFSW joint near the Ti interface after reaching an ultimate tensile strength of 259 MPa. In contrast, SSFSW welds achieve a higher tensile strength of 289 MPa.

Effect of welding parameters on the microstructure and mechanical behavior of dissimilar AISI 304/AISI 430 thin plates welded by gas Tungsten arc welding

In this work, the microstructure and mechanical behavior of dissimilar AISI 430 and AISI 304 thin sheets welded by Gas Tungsten Arc Welding using AISI 304 and AISI 316L as filler metals were studied. The obtained joints were characterized by optical and scanning electronic microscopy, Energy-dispersive X-ray spectroscopy and fluorescence, tensile tests and the Vickers microhardness test. Measurements carried out by energy dispersion X-ray spectrometry in the melting zone indicated a slightly heterogeneous distribution of nickel and iron. It was observed that the beginning of solidification of the zone fusion occurred through epitaxial growth. The WM solidification morphology was basically cellular influenced by temperature gradient, solidification rate and chemical composition. Variations in chemical composition and solidification morphology did not significantly alter the Vickers microhardness values in the melting zone. Results obtained in tensile tests indicated adequate mechanical behavior for the joints using AISI 304 as filler rod; those exhibited a ductile fracture behavior with the presence of dimples. However, the AISI 316L joints failure prematurely resulting in a fragile behavior.

Influence of process parameters and heat treatment on self-piercing riveting of high-strength steel and die-casting aluminium

The application of steel/die-casting aluminum alloy is an inevitable trend in the development of automotive lightweight technology. The joining process of self-piercing riveting (SPR) is the key technology to guarantee the collision safety for the body. However, the crackings on joint button can be easily found owing to the low ductility of die-casting aluminum. This paper aims to investigate cracking mechanism and improve the SPR joinability by exploring methods of cracking inhibition. Parametric study is performed to explore the effects of heat treatment, process parameters on crack inhibition and forming quality of SPR with steel/die aluminum alloy. The results show that SPR joinability can be improved by larger elongation and lower yield strength by proper heat treatments, i.e., AlSi10MnMg-T6 and AlSi10MnMg-T7. Meanwhile, the depth and diameter of the die are the main factors affecting cracking generation and forming quality. Similar to the upsetting process, tangential tensile stress is generated on the bottom surface in the riveting process, it leads to cracking generation on the bottom surface. This paper further studies the effects of heat treatment and stack direction on joint quality and mechanical response of SPR joints. Tearing failure of the lower sheet is the main factor causing failure of steel-aluminium joint (steel is the top sheet). The heat treatment mainly affects the energy absorption value and has a relatively small effect on the peak force. The mechanical properties of the steel-aluminium joints are superior to those of aluminium-steel joints (aluminium is the top sheet).

A Review on Effect of Stirrups in Beam under Seismic Loading

In many seismically active regions worldwide, massive Reinforced Concrete (RC) structures built before the 1970s existed. These older RC buildings, in countries having seismic history, were designed for gravity loads only. Anyway, the beam-column connections influence the structures where the functions of connection shortage by transport the forces like shear, moment, and torsion through the beam to the column. Also, it could behave in a ductile manner to help the structure resist the seismic, as simulate the seismic loading. Due to the failure of external joints more than the internal beam-column joints, this review focuses on the behavior of vulnerable beam under seismic loading, consequently simulated the behavior under an earthquake and the reinforcement detailed. Key Words: RC beam, Earthquake, Collapse, Stirrups, Buckling, Shear Failure.

Recent progress in computational predictions on fatigue and fracture resistance of steel connection joints

AbstractSteel structures are often subjected to cyclic loads, and sometimes to monotonic overloads, during the technical lifetime, which causes their performance degradation. Incidentally, they undergo progressive collapse, especially due to local failure of connections or joints. To ensure the overall integrity of the steel structures and to make sure the efficient transfer of the load between different components, it is necessary to evaluate the ultimate capacity and fatigue resistance of steel connections. Advances in material modelling and well‐controlled experiments at various scales in recent years have increased confidence in the finite element method as an effective way to predict the ultimate resistance and fatigue life. On examples of two common steel connections: bolted connection and welded connection, the recent progress will be presented in ductile fracture and fatigue crack initiation and propagation simulation.

The influence of lubricant temperature on the wear of total knee replacements

AbstractExperimental in vitro simulation can be used to predict the wear performance of total knee replacements. The in vitro simulation should aim to replicate the in vivo loading, motion and environment experienced by the joint, predicting wear and potential failure whilst minimising test artefacts. Experimental wear simulation can be sensitive to environmental conditions; the environment temperature is one variable which should be controlled and was the focus of this investigation. In this study, the wear of an all‐polymer (PEEK‐OPTIMA™ polymer‐on‐UHMWPE) total knee replacement and a conventional cobalt chrome‐on‐UHMWPE implant of similar initial surface topography and geometry were investigated under elevated temperature conditions. The wear was compared to a previous study of the same implants under simulator running temperature (i.e. without heating the test environment). Under elevated temperature conditions, the wear rate of the UHMWPE tibial inserts was low against both femoral component materials (mean <2 mm3/million cycles) and significantly lower (p < 0.05) than for investigations at simulator running temperature. Protein precipitation from the lubricant onto the component articulating surfaces is a possible explanation for the lower wear. This study highlights the need to understand the influence of different variables including environmental temperature to minimise the test artefacts during wear simulation which may affect the wear rates.

Experimental test setup design for ultimate limit state evaluation of ductile wrapped composite KK‐joints

AbstractComplex circular hollow section double KK‐joints are widely used in, e.g. offshore wind turbine jackets. As an alternative to conventional welded joints of the CHS multi‐membered structures, wrapped composite joints have shown superior structural performance in previous pilot tests. Experimentally characterizing the joint behaviour under uniplanar loading can be complicated, because of the ductile failure mechanisms of wrapped composite joints and second‐order bending moments. This paper presents the design of a test frame in combination with a conventional tensile 2.5 MN test rig. Ductile joint failure, joint imperfections and second‐order effects are considered in the design. Structural finite element software SOFiSTiK is used to analyse the effects of wrapped joint behaviour and imperfections on the test system and interaction of joint, frame and loading rig behaviours. Non‐linear joint behaviour and misalignments of the braces increased the second‐order effects significantly. Mitigation strategies have been explored to reduce additional bending moments in the KK‐joint. A complete test setup is proposed to perform static experiments on double KK‐joints in uniplanar axial loading conditions.

Alternative Fiber-Based Paperboard Adhesion Evaluation with T- and Y-Peel Testing

Due to increased pressure on the availability of wood biomass in the EU and the regulatory attempts to lower CO2 values, where wood-based biomass plays a crucial role in carbon sequestration, the use of cellulose derived from alternative sources is gaining increased interest in the pulp and paper industry as well as in other industries. The processing properties of alternative fiber-based packaging need to be checked in current processing operations with other types of materials and recycling workflows. For example, in the production of folding boxes, after printing other converting properties such as glueability are also of great importance. The adhesive absorption and bonding strength of materials are important as adhesive joints of packaging can interfere with the protective function. In the presented research, three different paperboards produced on a pilot scale from alternative raw material sources were tested. Two paperboards were produced from the alien invasive plants Japanese knotweed and black locust, and one from residual sawdust. The basic paperboard properties were tested regarding paperboard porosity, roughness, z-directional tensile strength, and dynamical behavior regarding liquid interaction (contact angle and liquid penetration dynamic), as water-based adhesives were used in the research. For adhesive joint strength testing, Y- and T-peel adhesion testing was performed on the joint paperboard samples, as still there is no fully standardized method for the evaluation of such fiber-based material properties. The results indicate differences in the penetration dynamics of liquids. This parameter had the highest influence on the peel adhesion strength, while porosity, roughness, and dynamic contact angle were not so significant. Regarding the two adhesive joint tests, the differences in separate materials regarding peel adhesion curves show similar results. However, the Y-peel maximum force values are higher due to the testing setup (in comparison to the T-peel test). The paperboards made from invasive plants showed adhesive joint failures which are more suitable for tamper-proof packaging due to their low surface strength and crack propagation into the fiber structure.

Failure and fracture in adhesively bonded 3D-printed joints: An overview on the current trends

Additive manufacturing (AM) as an innovative technique with favourable and unique solutions in fabricating complex products, is being widely used in diverse applications. AM, also known as three-dimensional (3D) printing technology was introduced for fabrication of prototypes, and currently its applications have been widely extended to production of end-used products too. As a result, mechanical strength of 3D-printed parts, and specially joints with 3D-printed substrates (adherends) gain considerable significance. This review attempts to comprehensively summarise recent advancements in failure and fracture of adhesively bonded joints with 3D-printed polymeric adherends. To this aim, we have reviewed experimental studies, which investigate effects of adhesive and printing parameters on the failure of 3D-printed adhesive joints. In addition, different approaches to strength improvement of 3D-printed adhesive joints are reviewed and discussed. Since computational finite element models (FEM) can provide a profound knowledge about the stress and force transition between adhesive layers and 3D-printed adherends, an overview on different FEM approaches in the field has been presented. The documented data can be used not only for comparison, failure analysis, and improvement of 3D-printed adhesive joints, but also is beneficial for the future research and further studies in fabrication of a 3D-printed joint with a superior structural performance and integrity.

Morphological Characterization and Failure Analysis of the Ultrasonic Welded Single-Lap Joints.

Ultrasonic welding technology represents an advanced method for joining thermoplastic composites. However, there exists a scarcity of systematic investigations into welding parameters and their influence on the morphological characteristics and quality of the welded regions. Furthermore, a comprehensive experimental understanding of the welded joint failure mechanisms remains deficient. A robust model for simulating the failure behavior of welded joints under loading has yet to be formulated. In this study, ultrasonic welded specimens were fabricated using distinct welding control methods and varied parameter combinations. Diverse experimental methodologies are employed to assess the morphological features of the welded areas, ascertain specimen strength, and observe welding interface failure modes. Based on a cohesive model, a finite element model is developed to predict the strength of the ultrasonic welded joints and elucidate the failure mechanisms. The results showed that, under identical welding parameters, the specimens welded with a high amplitude and low welding force exhibit superior welding quality. The specimens produced under displacement control exhibit minimal dispersion in strength. The proposed finite element model effectively prognosticates both welded joint strength and failure modes.

Analisis Kinerja Seismik Gedung dengan Pushover Analysis (Studi Kasus: Gedung Perkantoran Tiga Tingkat yang Runtuh Akibat Gempa Palu 2018)

Indonesia is an earthquake-prone country. The 2018 earthquake in Palu, Sulawesi, caused significant damage or collapse of the buildings. This research is aimed to evaluate the seismic performance of a three-story office building at Tadulako University and to evaluate what caused the collapse of the building. Evaluation of seismic performance was conducted using the default plastic hinge in SAP2000. The analysis results showed that the plastic hinge occurred first at the end of the beam, followed by the plastic hinge at the end of the column. The performance point from the intersection of the capacity curve and capacity spectrum based on ATC-40 indicated that the performance level of the building was damage control, which means that the building can resist seismic force and has a low risk of human death. These results did not represent the post-earthquake condition in which the building collapsed due to failure of the beam-column joint because the shear reinforcement was not installed in the beam-column joints. Further studies are necessary in order to develop an analysis model, including the failure model of the beam-column joint.