Design Of Composite Joints Research Articles

Finite Element Modeling of Beam-to-Column Steel Timber Composite Joints with Different Parameters

This study presents a comprehensive three-dimensional finite element modeling and parametric analysis of composite beam-to-column joints in steel–timber composite structures. The investigation encompassed a variety of shear connector configurations, end plate designs, and bolt dimensions, aiming to elucidate their respective influences on the structural performance and behavior of these joints. Through meticulous numerical simulation, this research sought to enhance the understanding of the interactions and load transfer mechanisms within composite connections, thereby contributing to the optimization of design practices in the field of structural engineering. The load–displacement relationship for timber–steel composite joints subjected to monotonic loading was investigated using ABAQUS 6.14 software. This study systematically analyzed the effects of various parameters, including different configurations of shear connectors, end plate thicknesses, and bolt dimensions, on the overall performance of the joints. Through this comprehensive numerical analysis, the research aimed to provide deeper insights into the mechanical behavior and structural integrity of these composite connections under the applied loading conditions. A non-linear finite element model of timber was developed and verified with the results of the experiment in this study. The findings are discussed in detail, highlighting the intricate relationships between the selected parameters and their respective effects on the performance and overall stability of the composite connections. This thorough evaluation aimed to enhance the understanding of how these variables interact within the context of composite joint design and behavior. Finally, design recommendations for composite structures, such as the dimensions of the bolt, end plate thickness, and different sizes of shear connectors are provided.

Full‐Scale Composite Moment‐Resisting Frame with Dissipative Bolted Connections under Monotonic Loads: Experimental versus Numerical Results

AbstractThe detailing of typical semi‐rigid beam‐to‐column joints in Germany was based on the assumption of low seismic actions, thus design could be covered by wind and gravity actions. Given the recent seismic hazard assessment of the national territory, in which the seismic risk was proved to be higher than formerly considered, questions have been raised about the approach to steel and composite joint design and detailing. Answers to the effect of increased seismic demands on semi‐rigid connections and to joint performance are provided in new studies of the authors. The performance (insufficient bending resistance and stiffness, brittle failures) and detailing deficiencies (small weld sizes, weak web panel) require improvements in order for joints to transfer higher bending moments and to conform to prEN 1998‐1‐2. Pre‐test analyses showed that, in comparison with current typical joints, improved solutions have 40% / 70% higher sagging / hogging bending resistance and sustain plastic deformations within connections prior to failure. Thus, the performance of joints designed for moderate‐low seismicity is experimentally assessed through monotonic and cyclic tests on composite frame specimens. The focus of the paper is on the monotonic response.

Design of Composite Joint with Precast Bolted Shear Connectors for The Fabricated Structure

Because of the serious impact on the seismic performance, the joint connection form becomes a critical problem in the prefabricated building. Built on the dry connection, this paper proposes a detachable and recyclable bolt-steel plate connection design for the fabricated structure. Compared to the cast-in-situ method, the biggest advantage of the proposed design scheme lies in convenient construction. The construction process shows that the joint devices both are detachable and recyclable. Adopting a supported beam, the proposed form is simulated with the finite element method (FEM). The deformation results verify the effectiveness of the proposed connection design. The work provides a novel idea for further test research on the fabricated structure.

Effect of reinforced concrete slab on the flexural behavior of composite beam to column joints: Parameter study and evaluation formulae

This paper presents a comprehensive numerical and theoretical investigation into the flexural capacities of composite joints with reinforced concrete (RC) slab. The improved 3D (three-dimensional) numerical models were established by MSC. Marc (2012) and calibrated by the experimental observations presented in the companion paper (Mou et al., 2019a [1]). Supplementary parametric studies were then undertaken to examine the effect of concrete slab, size effect (H), axial-force ratio (n), slab thickness (hs), concrete compressive strength (fc’), and the width-to-thickness ratio of column (D/t) on the flexural capacities of the composite joints. Employing the yield line mechanism theory, a calculation method incorporating the effect of the RC slab for the composite joint was proposed. The proposed formulae were featured with a favorable accuracy and suggested to be applied for the design of composite joints in the steel structural systems.

EXPERIMENTAL STUDY ON BEHAVIOUR OF SHEAR CONNECTORS IN MOMENT RESISTANCE OF STEEL COMPOSITE JOINTS

AbstractThis paper presents an experimental investigation on the behavior of steel stud connectors in steel composite joints with precast hollowcore slabs in resisting the static bending moment. An experimental program including 5 flexural tests was carried out, and the failure modes of the studs, as well as the shear capacity of stud connectors are investigated. Their contribution to the overall joint moment capacity were studied in depth. The pertinent design recommendation in shear stud design for enhance the moment capacity of the composite joints are also proposed. The testing results and design recommendations presented in this paper can provide basic for future design of composite joints using shear stud connectors with precast slabs

Fabrication and tensile testing of composite hybrid joints

Abstract The composite joint strength to weight ratio was found based on actual joint arrangements in the aircraft structure and the test results were helped to the research to composite joint design and analysis. The experimental study, conventional hybrid and hybrid joints with curved attachments of different angles (12°, 16°, 24°) are designed fabricated and tested using UTM Machine which has the maximum capacity of 600 kN until the catastrophic failure of the joints. The results obtained tensile strength and failure modes are compared to find the better joint configuration. The joint has 117% more strength than the conventional joints.

Failure Mode and Failure Load of Adhesively Bonded Composite Joints Made by Glass Fiber-Reinforced Polymer

Failure mode and failure load of composite joint design has become a very vital research area for being a weak part of composite structures in aircraft segments. So the objective of this study is to investigate the effect of different parameters on the shear strength and failure mode of adhesively bonded single-lap and scarf joints. The parameters included the overlap length, adherend thickness, and adhesive thickness of single-lap joints, and also the effect of single and double scarf angles of scarf joints. The results showed that in single-lap joints, the increasing overlap length led to increase shear strength until the length-to-width ratio becomes same value. The final failure mode of most tested thin adherends bonded joints with similar specimens was the delamination, while the interfacial failure mode occurred in thick adherends bonded joints. The shear strength increased when the adhesive thickness was reduced. On the other hand, in scarf joints, the ultimate shear strength was obtained when the scarf angle was around θ = 18°, while when scarf angle reached θ = 75°, the shear strength was decreased. The failure mode of scarf joints occurred at the interfaces between the scarf angles.

Multi-objective and multi-constraint design optimization for hat-shaped composite T-joints in automobiles

This study presents a multi-objective design optimization methodology on geometry and lay-ups for carbon fiber reinforced plastics (CFRP) T-joints in automobiles to achieve car body lightweight design. The CFRP T-joint was subjected to out-of-plane bending load using experimental method, and a finite element analysis (FEA) method was developed to simulate full failure procedure in the hat-shaped composite T-joint. A multi-objective and multi-constraint design optimization problem was then formulated to find optimum geometry and lay-ups of the composite T-joint. The non-dominated sorting genetic algorithm II (NSGA-II) was introduced to search for global optimum solution, and radial basis function (RBF) approximations for the objective functions were applied to reduce the computational cost. An original method was proposed for the initialization of the optimization that significantly accelerates the search for the Pareto front. The proposed method was validated by an obtained optimum design of a composite T-joint with reduced weight and improved overall stiffness and strength behavior, and can thus provide a guidance in practical vehicle composite joint design.

Scale and manufacturing effects on tensile strength of marine grade sandwich composite panel joints

In this article, scale and manufacturing effects on the tensile strength of marine grade sandwich composite panels and joints are investigated to aid in the fabrication of large modular ship hulls. This is done by researching transverse sandwich composite joint design, experimental tension methods, and scale and manufacturing effects on tensile strength. Three scales are utilized in this investigation of tension characteristics: coupon scale, table-top single panel fabrication scale, and in position mock-up full-size fabrication scale. First, material properties are gathered through industry standard coupon scale fabrication and testing. Next, a single-infusion baseline panel along with two ship hull transverse joint designs are chosen, fabricated, tested, and compared at single panel scale. These tests include individually fabricated hull panels, as well as secondary structural stiffener sandwich composite web panels, and stiffener flange components. The highest performing joint design is then utilized in a mock-up full-size fabrication scale structure. This structure includes both a transverse hull joint, as well as joints in the secondary structural stiffener web and flange. This mock-up fabrication scale component was then cut apart and tested in tension. The novel sandwich composite panel joint tension experimentation methods used indicate the methods studied are reliable for determination of characteristic tensile properties, and that the joints selected are effective. Investigations concerning scale effects comparing baseline fiber failure mode tension results from the coupon scale to the single panel scale, and manufacturing effects comparing joint interlaminar shear failure mode from the single panel scale to the mock-up fabrication scale, show decreased ultimate tensile strength with increased overall part size and manufacturing complexity. These factors, applied to a reference strength to achieve a nominal strength, were found to range from 0.796 to 0.846.

Cyclic Testing of Concrete‐Filled Double‐Skin Steel Tubular Column to Steel Beam Joint with RC Slab

The design of composite joints for connecting concrete‐filled double‐skin tubular (CFDST) columns to steel beams supporting reinforced concrete (RC) slabs is presented in this paper. Five half‐scale specimens were designed, including four composite joints with RC slab and one bare steel beam joint, and were tested under a constant axially compressive force and lateral cyclic loading at the top end of the column to evaluate their seismic behavior. The main experimental parameters were the construction of the joint and the type of the column. The seismic behaviors, including the failure modes, hysteresis curves, ductility, strength and stiffness degradation, and energy dissipation, were investigated. The failure modes of the composite joints depended on the joint construction and on the stiffness ratio of beams to columns. Joints of stiffening type had significantly higher load‐bearing and deformation capacities than joints of nonstiffening type. Compared with the bare steel beam joint, the bearing capacities of the composite joints with RC slabs were markedly increased. The composite action was remarkable under sagging moments, resulting in larger deformation on the bottom flanges of the beams. Overall, most specimens exhibited full hysteresis loops, and the equivalent viscous damping coefficients were 0.282∼0.311. The interstory drift ratios satisfied the requirements specified by technical regulations. Composite connections of this type exhibit excellent ductility and favorable energy dissipation and can be effectively utilized in superhigh‐rise buildings erected in earthquake zones.

Sustainable and Deconstructable Semi-Rigid Flush End Plate Composite Joints

Composite construction is a popular and effective method of construction, exploiting the strengths of both reinforced concrete and structural steel in building construction in a complementary fashion. Within paradigms related to minimisation of emissions and maximisation of product recycling, these composite systems are problematic on a number of fronts. Firstly, common and traditional composite systems utilise ordinary Portland cement, which is known to be a very large contributor to atmospheric CO2 emissions. Secondly, for typical construction practices for steel-concrete composite systems, casting of the concrete onto profiled steel decking and conventional reinforcement placing are undertaken on-site, which is time consuming and labour intensive, and which can increase the cost of construction. Thirdly, composite action between the steel beam and the concrete slab is usually achieved by using headed shear studs. The headed shear studs connect these two elements permanently, which leads to much waste at the end of the service life of the building when it is demolished. This paper models a sustainable semi-rigid beam-to-column composite blind bolted connection with deconstructable bolted shear connectors using ABAQUS finite element (FE) software. In this “green” system, precast geopolymer concrete (GPC) slabs are attached compositely to the steel beam via pretensioned bolted shear connectors and the composite beam is connected to GPC-filled square columns using blind bolts. Non-linear material properties and non-linear geometric effects are considered in the simulation of a connection in hogging bending. Based on the FE modelling, using pretensioned bolts as shear connectors with GPC can improve the behaviour of semi-rigid flush end plate composite joints in terms of ductility and load capacity. Moreover, the behaviour of the bolted shear connectors should be considered in composite joint design as being very different to headed stud connectors.

Numerical Investigation on Bending Stiffnes of Several Composite Joints

With the weight-reduction requirement for transportation tools, more and more plastics and composite materials will be applied. However, the connection between plastics, polymer-based composite and traditional metal, such as steel or aluminum, possibly become the weakest region and thus decrease the structural safety, therefore, its mechanical properties should be investigated. In this paper, a typical single-lap joint was analyzed experimentally and numerically under the three-point-bending loads, and the results were compared and finite element model was updated. Based on the validated simulation technology, three other joints were simulated and all joints were compared, and suggestion for design of composite joints was provided.

L-형 보강재를 가진 복합재 패널의 제작과 평가

복합재 구조물에서 체결부위는 매우 취약한 부분이므로 복합재료 체결부에 대한 설계는 중요한 연구분야로 대두되고 있다. 본 논문에서는 L-형 보강구조를 가진 복합재 구조를 이차접착의 공법으로 제작하여 하중 방향을 달리하여, 접착두께(0.2 mm, 0.6 mm, 4 mm)에 따른 접착강도 실험을 수행하였다. 또한 이를 유한요소해석을 수행하여 파손지수값을 실험값과 상호 비교하였다. The design of composite joint is important research area because they are often the weakest areas in composite structures. In this paper, the specimens with three paste thickness (0.2 mm, 0.6 mm, 4 mm) were manufactured in secondary bonding method and tested in two different loading direction condition. Also, the failure index of the L-type stiffener was calculated by the finite element method and compared with experimental results.

기계 가공된 복합재료 키 조인트의 강도 연구

복합재료가 기계부품, 항공기 구조물에 폭 넓게 적용됨에 따라, 복합재료 구조물에서 가장 취약한 복합재료 체결부의 설계는 매우 중요한 연구 분야로 대두되고 있다. 본 논문에서는 기계적 체결방법의 문제점으로 발생하는 원공주위의 높은 응력집중현상을 감소시키기 위하여, 복합재료 키 조인트(composite key joint)를 제안하였고 파손강도를 평가하였다. 제안된 복합재료키 조인트 체결부의 파손 판정을 위해서 파손지수(failure index)와 파손영역법(damage area theory)이 각각 적용되었다. 실험 결과로부터 복합재료 키 조인트는 기계적 체결부의 파손강도보다 93% 높은 값을 가짐을 볼 수 있었고, 복합재료 키 홈 깊이(key slot depth)가 0.88 mm이고 끝단 길이(edge length)가 20 mm일 때 가장 높은 파손하중 나타내었다. The comparison of the numerical results with those measured by the experiment showed good agreement. The design of composite joint which is the weakest part in the composite structures has become a very important research area since the composite materials are widely used in the aircraft and machine structure. In this paper, the new composite key joints that minimize the fiber discontinuity and strength degradation of adherend were proposed and their failure loads were evaluated. The failure index and damage area method were used for the failure prediction of the composite key joint. From the tests, the failure load of the composite key joint was 93% larger than that of a mechanical joint and the key joint whose slot depth and edge length were 0.88mm and 20mm had the largest failure load. Also, the analytic failure modes by the failure index and damage area were compared with experimental failure modes.

Fire performance of concrete filled steel tubular (CFST) column to RC beam joints

The performance of concrete filled steel tubular—(CFST) column to reinforced concrete (RC) beam joints under fire is investigated in this paper. A three-dimensional finite element analysis (FEA) model is developed for sequentially coupled heat transfer and structural analysis. Four tests on circular CFST column to RC beam joints subjected to the ISO 834 standard fire performed earlier by the authors' research group are reviewed and used to verify the model. The FEA model is then used to construct the model of a typical full-scale CFST column to RC beam joint and perform analysis to the behavior of this joint in fire with respect to effects of parameters such as beam load ratio, column load ratio and beam to column linear stiffness ratio. Failure criteria in the International Standard ISO 834-1 are adopted to investigate the fire resistance and the failure modes. Extensive studies are also performed to the internal force redistribution, the joint stiffness degradation and typical failure modes in the joint. The results indicate that three typical failure modes of beam failure, column failure, and simultaneous beam and column failure should be considered in the design of composite joints under fire loading.

Static strength of a composite butt joint configuration with different attachments

The static failure behaviour of a composite single-strap joint configuration using three different attachments was studied experimentally. The attachments used were: adhesive bonding; mechanical bolting; and bonded-bolted joining. The dimensions of the composite butt joint used were determined based on actual joint configurations in aircraft structures, such that the test results would be beneficial to both the academic exploration and practical engineering application for advanced composite joint design and analysis. A damage evolution process was presented for the bonded-bolted butt joints based on the observed stress versus displacement curves and associated failure modes from all the related butt joints with the three attachments. An approach was then proposed for estimating the ultimate tensile strength in the bonded-bolted joints.

Recent developments in composite connections

AbstractEurocode 4 [1] suggests design rules for the evaluation of the mechanical properties of steel‐concrete beam‐to‐column composite joints (rotational stiffness, resistance and ductility). These rules cover situations where the joints are subjected to moments and shear forces, but in hogging regions only (negative bending moments). Recently, researches have been conducted on the behaviour of composite joints (Fig. 1) subjected to positive bending moments (called “sagging moments” in the following) and combined bending moments and axial loads; for instance, these loading situations may appear in composite sway frames under conventional loading and exceptional actions (impact, explosion …) leading to the loss of a structural column [2].In the present paper, the Eurocode 4 design rules are extended to joints in sagging regions and to joints subjected to combined bending moments and axial loads and the proposed methods are validated through comparisons with experimental test results. An easy‐to‐use and freely available software for the design of composite joints according to the Eurocode 4 principles is also described.

Failure Load Prediction of Composite Joints using Linear Analysis

With the wide application of fiber-reinforced composite materials in aero-structures, robotic arms, and mechanical parts, the design of composite joints has become a very important research area. In this article, linear finite element analyses in which the pin of the composite joint is assumed to be a frictionless rigid body are performed and the failure load of the mechanically fastened composite joint is predicted by the failure area index (FAI) method. From these analyses, it has been found that the FAI method can predict the failure loads of composite joints to within 20.1%.

Strength of Quasi-Isotropic Co-Cured Composite Joints Under Quasi-static and Fatigue Loading

Abstract Three composite joint configurations, namely, the straight laminate (SL), the single lap, and the single nested overlap (SNO) joints are investigated to ascertain the improvement of the SNO joint over the single lap joint under quasi-static and cyclic loading. The SNO joint is a co-cured composite joint design proposed previously, while the SL represents a perfect joint and serves as an upper bound for static strength and fatigue life comparisons. Stress-number curves are generated based on constant amplitude tension-tension cyclic loading at a frequency of 5 Hz and stress ratio (R) of 0.1 for quasi-isotropic graphite/epoxy (IM7/8551-7) joints. The maximum fatigue load is varied between an average of 70-90 % UTS for SL, 20–80 % ultimate tensile strength (UTS) for single lap joints and 40–95 % UTS for SNO joints. Fatigue run-out is defined at 1×106 cycles. The fatigue strength improvement of SNO joint is ascertained quantitatively through two indicators. Three quasi-static acoustic emission (AE) count peaks were identified during monotonic loading before eventually reaching a maximum at ultimate failure. The cumulative AE count peaks are used as a collective measurement of the significant damage event incurred under specific loading and subsequently correlated to the fatigue performance of each of these three joint configurations.

Strength of Composite Laminated Bolted Joint Subjected to a Clamping Force

As these composites have become more popular, composite joint design has become a very important research area, as these joints are often the weakest parts of composite structures. In this paper, the strength of a composite laminated bolted joint being subjected to a clamping force was tested and predicted using the FAI (Failure Area Index) method. The strengths of composite joints subjected to clamping forces on different geometric shapes and dimensions were predicted using the FAI method, and the results were compared with experimental results. From the tests and analyses, the strength of a given composite laminated bolted joint subjected to a clamping force could be predicted within 22.5% via the FAI method.