Spacing Of Connectors Research Articles

Equation for the simplified calculation of the horizontal shear stress in composite beams of rectangular cross-section with considerable width

The theory of elasticity allows describing the law of variation of shear stresses Τzy and Tzx for a beam of rectangular cross-section, however, the expressions are extensive and complex. For beams with a width/depth ratio equal to 0.25, it is allowed to calculate approximately the maximum shear stress Tzy, with the Collignon-Zhuravski equation. Depending on the width/depth ratio of the beam, it will depend on the percentage of error made. Unfortunately, for the shear stress Tzx there is no approximate formula available to determine the value of the shear stress. Using a simplified procedure, a differential beam element was analyzed in the elastic field for different width/depth ratios and a very simple expression was obtained. The results of the approximate formula were compared with the values obtained from the application of the exact formula and the results of a linear numerical analysis using the finite element method. For cross-sections of homogeneous beams and composite beams of considerable width, it is essential to determine the horizontal shear stresses Tzx in particular in the case of vertical planks, arranged side by side, connected solidly by horizontally arranged mechanical connectors, since the shear stresses Tzx developed across the width of the cross-section may considerably exceed the vertical shear stresses Tzy and furthermore govern the pattern, spacing and cross-section of the mechanical connectors. The validity of the approximate expression for calculating the maximum value of the shear stress Tzx was limited to beams with a width/depth ratio between 0.25 and 10.0.

Experimental and numerical investigations on the axial compression performance of precast geopolymer concrete sandwich wall panel

This paper investigated a novel precast concrete sandwich panel (PCSP) which made by the geopolymer concrete and enabled by the glass fiber reinforced polymer (GFRP) hexagonal tube connector. Six precast geopolymer concrete sandwich wall panel (PGCSP) specimens were fabricated and tested under axial compression load. The investigating parameters included the connector spacing, panel height, and panel thickness. The failure mode, axial load capacity, load-axial deflection relationship, and load-concrete strain relationship were studied and discussed. Moreover, two-dimensional (2D) finite-element (FE) analysis was conducted to reproduce the test. Parameter analysis was then performed to modify the axial load capacity formula in the Chinese code GB50010-2010. The results indicated that: all specimens exhibited large eccentric compression failure due to the second-order effect, which was caused by concrete crushing and horizontal cracking in the two wythes, respectively; with the decrease of the connector spacing, the crushing area of the specimens would be enlarged, the out-of-plane lateral deformation would be decreased, and the axial load capacity decreased by 17 % and 42 % when the connector spacing changed from 300 mm to 600 mm and 900 mm, respectively; with the decrease of the panel height and the increase of concrete wythes thickness, the axial load capacity of the specimens almost presented a linear increase; the established 2D FE model and the modified formula effectively reflected the axial load capacity of the specimens.

A Critical Review of Cold-Formed Steel Built-Up Composite Columns with Geopolymer Concrete Infill

Concrete-filled built-up cold-formed steel (CFS) columns offer enhanced load-carrying capacity, improved strength-to-weight ratios, and delayed buckling through providing internal resistance and stiffness due to the concrete infill. Integrating sustainable alternatives like self-compacting geopolymer concrete (SCGC) with low carbon emissions is increasingly favoured for addressing environmental concerns in construction. This review aims to explore the current knowledge regarding CFS built-up composite columns and the performance of SCGC within them. While research on geopolymer concrete-filled steel tubes (GPCFSTs) under various loads has demonstrated high strength and ductility, investigations into built-up sections remain limited. The literature suggests that geopolymer concrete’s superior compressive strength, fire resistance, and minimal shrinkage render it highly compatible with steel tubular columns, providing robust load-bearing capacity and gradual post-ultimate strength, attributed to the confinement effect of the outer steel tubes, thereby preventing brittle failure. Additionally, in built-up sections, connector penetration depth and spacing, particularly at the ends, enhances structural performance through composite action in CFS structures. Consequently, understanding the importance of using a sustainable and superior infill like SCGC, the cross-sectional efficiency of CFS sections, and optimal shear connections in built-up CFS columns is crucial. Moreover, there is a potential for developing environmentally sustainable built-up CFS composite columns using SCGC cured at ambient temperatures as infill.

Large rectangular cross-section tunnel undercrossing urban road by micro pipe jacking and joint assembly structure (MPJ & JAS) method in soft soils

With the continuous construction of urban traffic roads, more and more new roads are cut off by existing roads to form “dead end roads”. There is an urgent need for a trenchless method suitable for urban ultra-shallow overburden to build the undercrossing tunnel. To solve this problem, this paper proposed the micro pipe jacking and joint assembly structure (MPJ & JAS) method, which has the characteristics of shallow burial depth, low cost, short construction time, flexible cross-section setting and high space utilization. The MPJ & JAS method construct a large cross-section tunnel through assembling small cross-section elements, quite different from traditional methods. Therefore, this paper designed a CT-shaped integrated joint, the mechanical performance of which was verified and clarified by tensile test. The bending test and finite element (FE) analysis proved the reliability of MPJ & JAS tunnel structure, and confirmed the structure performances such as the failure models, crack behaviors, load–deflection response and stress–strain distribution. Moreover, the influences of the steel plate thickness, concrete strength and shear connector spacing were determined by the FE analysis. On the basis of test results and reasonable assumptions, a theoretical design method considering the influence of the CT-shaped integrated joint was proposed, which can effectively predict the bending strength of the MPJ & JAS tunnel structure with an error of less than 10%. Finally, in view of the characteristics of the MPJ & JAS method, the suitable micro pipe jacking machine, soil reinforcement measure, hydraulic traction construction technology, high-precision guidance system and concrete construction quality detection method based on the phased array ultrasonic imaging technology were developed, supporting the accurate and efficient construction of the MPJ & JAS tunnel.

Ultimate bearing capacity of T-shaped retrofitting diagonal members for angle steel transmission towers

Collapse of steel latticed transmission towers under strong winds is a significant safety concern for power systems. Attaching additional members to the tower members can enhance the wind resistance of transmission towers. To establish systematic retrofitting schemes and methods for predicting the ultimate bearing capacity of T-shaped retrofitting diagonal members, static experiments and finite element analysis on various cross-sectional dimensions and member lengths were utilized in this study. The experimental results indicate that retrofitting can effectively increase the bearing capacity of diagonal members. Finite element models are developed and verified based on the discussion of load-displacement curves and failure modes. The finite element analysis reveals that the increase in capacity achieved by reducing connector spacing is relatively small when compared to the ultimate bearing capacity obtained with the spacing of two connectors, and the arrangement of connectors at both ends meets the requirement of connector spacing. The relationship between the retrofitting bearing capacity and the slenderness ratio of diagonal members can be divided into two linear stages, which correspond to different failure modes. Furthermore, a λk coefficient method based on the axial compression equation is proposed to predict the ultimate bearing capacity of T-shaped retrofitting members. The bearing capacity based on the λk method shows agreement with finite element analysis results.

Push-out tests on steel composite sections with engineered cementitious composite

This paper investigates the shear strength and failure modes of steel-concrete-steel (SCS) sandwich composite member with Engineered Cementitious Concrete (ECC) and explores the influences of various shear connectors such as headed stud and bolt on shear behavior of SCS sandwich composite member by carrying out push-out testing program. Based on the test results in this study, the failure modes and the load-slip behavior of the specimens are investigated. In addition, the experimental results on the shear resistance of the headed stud connector with various connector spacing and numbers of connector is compared and explored.

Design method for masonry structures retrofitted with steel reinforced plaster

In this paper an analytical approach for the design and assessment of masonry structures retrofitted with steel reinforced plaster (SRP) is proposed. The aim of the proposed method is to consider the main parameters affecting the performance of the strengthened wall (such as masonry properties, plaster properties, spacing and number of connectors) and provide a general formulation for practitioners to use in the design of SRP retrofitting interventions in place of the common empirically-based numerical coefficients proposed by the Italian Standard. The approach is developed starting from the experimental results of diagonal compression tests performed on clay brick walls retrofitted with SRP presented by the authors in previous studies. The maximum load is analytically predicted considering that the plaster and masonry layers work in parallel. A validation is conducted using additional experimental data available in literature. The obtained formulation is able to approximate the experimental values, being on the safe side against them in most of the cases. It is important to note that the method has been developed and validated using a limited number of experimental results. For this reason, adjustments may be needed for different types of masonry, plaster or anchor configurations.

Experimental and numerical study on the blast resistance of C-shaped doubled steel concrete slab (C-DSCS) with L-shaped connectors

This study aims to explore the blast resistance of C-shaped doubled steel concrete slabs (C-DSCS) with L-shaped connectors. These slabs utilize the superior compressive strength of concrete and enhance the load-bearing capacity by following a load path similar to that of arch structures. The dynamic behaviors and energy dissipation of the C-DSCS with L-shaped connectors were experimentally and numerically investigated under near-field explosion. Firstly, the pressure–time curve of the explosion was obtained by the pressure sensor in the test. Then, a finite element model (FEM) of the C-DSCS specimen was established through the LBE algorithm, and the accuracy of the finite element model was experimentally validated. Finally, parametric analyses was carried out to investigate the steel plate thickness, explosion distance and spacing of connectors on the dynamic response of the C-DSCS. The results indicated that the C-DSCS specimen had good integrity without failing or severe destruction under the explosion. A small number of oblique cracks appeared in the concrete infill near the free side of L-shaped connectors, which can effectively exert the compressive strength of the concrete. Concrete and bottom steel plate were the main energy-consuming component for C-DSCS and dissipated more than 78% of the explosive energy. In addition, L-shaped connectors also played a certain role in absorbing explosive energy, which can effectively reduce the maximum deflection of the specimens by decreasing the spacing of connectors. This paper provides a basis for theoretical analysis of dynamic response of C-DSCS subjected to close-in explosion, laying a foundation for further design methods.

Finite Element Analyses of Demountable Shear Connection in Cold‐Formed Steel‐Concrete Composite Beam Based on Experimental Data

AbstractThere is a surging demand for innovations that would increase the value of construction elements and materials in their life cycle. Therefore, the subject of this research is the shear connection in the floor composite system of cold‐formed steel and concrete slab. Composite systems can be further improved by a demountable type of shear connection, which shows good performance compared to traditional solutions but also allow for system demountability, fulfilling some sustainability policy aspects. Here, two configurations of CFS‐concrete composite systems with bolted shear connections were considered. The first configuration considers two directly connected back‐to‐back CFS profiles, while the second considers two back‐to‐back CFS profiles spaced apart simulating the presence of a corrugated web in between. Based on the experimental results of the second configuration, the numerical model in ABAQUS was developed and calibrated. A detailed comparison of the two configurations has been carried out. Additionally, the behaviour of considered configurations was also analysed regarding the number of bolts within the rib of the concrete slab. The obtained results show that close spacing of the shear connectors can prevent the development of their full bearing capacity.

Structural response of hybrid timber ‐ cold formed steel floors

AbstractThe paper examines the composite performance of hybrid steel‐timber lightweight floor assemblies incorporating cold‐formed steel (CFS) profiles and plywood (PW) flooring panels with varying degrees of shear connection achieved by means of self‐drilling screws. Material, push‐out, and three‐point short‐span floor tests with or without web openings were carried out. The results and observations from the tests provide a detailed insight into the inelastic properties and ultimate response of such floor systems. Push‐out tests indicate that denser connector arrangements increase connection stiffness, while push‐out and short beam tests suggest an optimum connector spacing equal to the beam depth for a balance between structural performance and constructability. The experimental observations indicate that the ultimate condition of the short composite beams was characterized by CFS web crippling under the load application point, followed by a pull‐through of the self‐drilling screws. Web openings reduced the strength of the floor elements compared to the members with full webs. Complementary numerical studies are undertaken using nonlinear finite element procedures which were validated against the beam tests, offering a detailed insight into the stress levels in the timber, steel, and connectors. Codified procedures for determining the capacity of composite CFS sections are compared with the test results, and guidance for the practical design and construction of such systems is given.

Design Methodology of U-Shaped Infilled Composite Beams with Angled Shear Connectors Using Finite Element Analysis

A composite beam is a structural member that behaves as a single unit by using shear connectors between a concrete slab and an I-shaped steel girder. The composite ratio is crucial and is determined by the shear connectors’ ability to withstand the horizontal shear forces between the concrete and steel girder. In this study, a U-shaped composite beam was designed, which differs from conventional composite beams as it allows the use of a steel girder as a formwork. Moreover, angle-type shear connectors, instead of stud-type connectors, were employed. Based on this design, large-scale U-shaped composite beams with angle-type shear connectors were fabricated, and load tests were conducted to analyze the behavior after composite action and the influence of shear connector spacing. Additionally, the strength of the angle-type shear connectors used in this paper was evaluated through finite element analysis. Finally, a strength evaluation method for composite beams of this configuration is proposed.

Numerical investigation of steel-timber composite floors with flush end-plate connection

Steel-timber composite floors have received much attention in the past years due to their lightweight, high construction and dismantling speed, low pollution and energy consumption. These floors consist of timber slab that is connected to steel beam by shear connectors. This paper investigates the behavior of steel-timber composite floors, which have flush end-plate beam-to-column connections. To achieve this, three-dimensional finite element models were prepared from several laboratory specimens and then validated against each other. The numerical and laboratory results were compared and validated, which shows the appropriate accuracy of the assumptions used for modeling specimens. In the following, parametric studies were conducted to investigate the factors affecting stiffness, strength, and rotational capacity such as type, diameter, and spacing of shear connectors, thickness and width of timber slab, the thickness of flush end-plate, and beam-to-column bolt size. Lastly, several mathematical formulas were presented to estimate the moment-rotation response of semi-rigid steel-timber composite connections.

Behaviour of Steel-Concrete-Steel Sandwich Beams with Novel Enhanced C-Channels

As the load increases, most composite beams generally experience failure in both shear and flexural behavior. This outcome highlights the critical challenges of achieving sufficient strength and structural integrity in such beams. The proposed study has used the cold-formed behavior of an Enhanced C-channel (EC) shear connectors and Light Weight Concrete (LWC) to examine the new Steel-Lightweight Concrete-Steel sandwich Beams (SLCSB). The ECs have provided significant shear resistance at the faceplate-LWC interfacial interface and the tension separation resistance for faceplates (cold form steel) from the LWC core. Cold Form Steel (CFS) is the most often used substitute because of its high productivity and practicality in the field. Four different composite beams are examined in the proposed research with different ECs spacing. The beams’ top and bottom face plates are covered using CFS (1.6 mm). In addition to that, two different types of shear connectors are used. Two unique longitudinal spacing of 100 mm and 150 mm are also used for one with lipped ECs and without lipped ECs. Importantly, self-tapping screws are used to secure ECs in place between the top and bottom of the face plates. The effectiveness of the composite beams with various shear connector spacing subjected to a two-point load test is assessed through a series of experiments.

Structural behavior of steel-concrete-steel and steel-ultra-high-performance-concrete-steel composite panels subjected to near-field blast load

In this paper, field blast tests and numerical simulations were conducted to investigate the structural behavior of steel-concrete-steel (SCS) composite panels with shear studs and tie bars as connectors under near-field blast load. Four specimens, including two SCS panels, one steel-ultra-high-performance-concrete-steel (S-UHPC-S) and one normal reinforced concrete (NRC) panel, were fabricated with the same geometric dimensions and tested in the field with cylinder charges under the scaled distances of 0.4 m/kg1/3 and 0.6 m/kg1/3. Finite element models with the implementation of multi-material Arbitary-Lagrangian-Eulerian (MM-ALE) algorithm were built to demonstrate the spatial distribution of shock waves with adequate validation, and the calculated blast load was then simplified and used to compute the dynamic response and the failure mode of SCS and S-UHPC-S panels. After validation of the numerical models, the parametric studies were conducted to investigate the effects of thickness and yield strength of faceplates, ratio of shear connector spacing to the faceplate thickness, section depth of the panels and scaled distance on the structural behavior of SCS and S-UHPC-S panels against near-field blast load. The results indicate that the structural response of SCS and S-UHPC-S panels under the near-field blast load is dominated by global flexural response with the scaled distance (Z) ranging from 0.3 m/kg1/3 to 0.6 m/kg1/3, but shear cracks form near the supports and local damage occurs at Z = 0.3 m/kg1/3. Replacing normal concrete core with UHPC or enlarging the section depth is an effective way to mitigate shear cracking and potential shear failure. In addition, the blast resistance of SCS panel is much superior to that of NRC panel with the same geometric dimensions and is also much greater than that of NRC panel with the similar section strength under close-in scaled distance.

Flexural behavior of large-scale U-shaped steel-concrete infilled composite beams with flat and embossed webs

Most popular shape of steel-composite beams is the exposed type in which wide-flange steel sections are connected to the reinforced concrete (RC) slab through shear connectors. However, recently innovative U-shaped steel–concrete infilled type composite beam sections are introduced which demonstrated promising structural performance. In these composite beams, the U-shaped steel section filled with concrete serves as formwork in fresh state of concrete while it behaves as main reinforcement during the service life of the structures. Although, active research has been conducted on former type, but research on the later infilled type beams seems insufficient. There exist several research questions which need to be addressed for optimized and efficient design of these innovative composite sections. In this paper, six large-scale U-shaped steel–concrete infilled composite beams with flat and embossed webs were tested to investigate their flexural behavior. The tested composite beams were designed with angle shear connectors which provide efficient shear transfer mechanism with economy. The main parameters of the tests were the shape of web and the spacing of the shear connectors. The effects of embossed web on horizontal shear transfer and its contribution to the flexural capacity were mainly focused. In addition, a detailed section analysis was conducted to comprehend the experimental observations.

Numerical modelling of cold-formed steel built-up columns

Built-up cold-formed steel structural members can provide technically and economically advantageous solutions in cold-formed steel construction. However, there is a need for a deeper understanding of their stability behaviour, and this paper demonstrates that detailed, accurate and reliable finite element models provide an excellent means to achieve this. Apart from the typical issues to be considered in the high-fidelity modelling of thin-walled members, which include geometric and material nonlinearity, element type, mesh density, and the modelling of imperfections and boundary conditions, the paper focuses on two additional complications which arise in built-up members: the modelling of connectors, and contact between constituent parts. A number of alternative techniques to model connector behaviour are investigated and their effect on the predictions of the ultimate capacity quantified by benchmarking against experimental data. Various successful strategies to mitigate stubborn convergence problems, which almost inevitable originate when modelling complex contact problems, are also presented. It is demonstrated, however, that the inclusion of contact as a model feature does not have a significant effect on the predicted capacity in the majority of the considered cases, with its influence typically remaining limited below 10%. The validated models were further used in parametric studies which showed that once the connector spacing is short enough to prevent global instabilities of the component sections between connector points, its effect on the ultimate capacity of the built-up column is very small within the practical range of connector spacings. Modelling connector lines as continuous longitudinal constraints tying surfaces together, on the other hand, is bound to significantly overestimate the capacity.

Experimental studying structural behavior of shear connector in cold-formed steel - concrete composite beam

An experimental push-out test was carried out on 12 specimens in 6 groups to investigate the mechanical behavior of shear connectors in cold-formed steel-concrete composite beams. Specimen groups have differences in rivet spacing, shear connector spacing, tab aspect, and rebar through shear connectors. The mechanical behavior was evaluated through quantities such as shear resistance, relative slip between the steel beam and concrete slab, and failure modes. The results show that screw significantly affects the mechanical behavior of shear connectors in cold-formed steel-concrete composite beams.

Full-scale push-out testing of headed stud-steel block connectors in prefabricated steel-concrete composite beams

Full-scale push-out tests of 13specimens were conducted to study the shear behavior of the headed stud-steel block connectors (HSBCs) in prefabricated steel-concrete composite bridge beams, where the key parameters of steel block height, longitudinal connector spacing, presence of oblique rebars in the precast slab, and grouting material were considered. The objective was to develop large shear stiffness, high shear capacity, and sufficient deformability of the connectors in prefabricated steel-concrete composite bridge beams. The results from the push-out tests reveal: two main failure modes the compression failure in the concrete slab and the shear failure in the grouting material and concrete slab; and the HSBC has large shear stiffness, high shear capacity (≈1500kN), and sufficient deformability. Based on the analysis of the shear extrusion dimension of the grouting material and concrete slab, the shear inclination ratio was found approximately to be 1:5, which agrees well with the stipulation specified in the EC4. The height and spacing of HSBCs are the two principal parameters affecting the shear capacity and failure mode of the specimens. By comparing the measured shear capacities of the HSBCs with those calculated by the design formulas for steel blocks and headed studs as specified in the EC4, it is shown that the steel block and headed studs can work together to resist the force between the precast concrete slab and the steel beam.

Structural performance of orthotropic Steel-Concrete continuous composite decks with larger U-ribs and PBL shear connectors

This study investigates the structural performance of the OSCCCDs with larger U-ribs and PBL shear connectors. Four OSCCCDs with larger U-ribs and PBL shear connector specimens were fabricated and tested under a static load, in which the experimental parameters were the spacing of the PBL shear connector and the spacing of the holes of the PBL shear connectors. Parametric analysis via finite element models was also carried out to explore the effects of the reinforcement ratio, the thickness of the steel plate, the thickness of the U-ribs, the thickness of the concrete slab, and the hole diameter of the PBL shear connector on the structural performance. It can be concluded from the experimental and numerical results that the OSCCCDs exhibited higher bearing capacity and better ductility. The OSCCCDs exhibited flexure failure at the mid-span and diagonal tension failure at the intermediate supports. The thickness of the U-ribs and the thickness of the concrete slab showed the highest impact on the initial stiffness and ultimate load of the OSCCCDs, followed by the spacing of the PBL shear connectors and the spacing of holes in the PBL shear connectors. The reinforcement ratio, the thickness of the steel plate, and the hole diameter of the PBL shear connector had little influence on the initial stiffness and ultimate load of the OSCCCDs. Finally, a simplified flexural analysis method can be proposed to accurately predict the elastic deflection and ultimate bending moment of the OSCCCDs under the service loads, respectively. The maximum absolute discrepancies of the elastic deflection and ultimate bending moment of the theoretical results are 8.2% and 12.0% by validating against the experimental and numerical results within the investigated ranges of parameters, respectively.

Flexural behavior of different types of steel-concrete composite decks with perfobond rib or head stud shear connectors

With the advent of long-span bridges, steel-concrete composite decks are increasingly concerning structures to address the fatigue problem, wear of the surfacing, and corrosion of the steel decks. The different types of ribs result in the variety of the cross-sections of the composite decks. Thus, the flexural behavior of different types of steel-concrete composite decks with perfobond rib (PBL) or head stud shear connectors was investigated in this study. The different types of composite decks included steel-concrete composite decks (SCCDs), open-rib stiffened steel-concrete composite decks (OSCCDs), and U-rib stiffened steel-concrete composite decks (USCCDs). For this purpose, the static flexural tests of two USCCDs with PBL or head stud shear connectors were conducted. Parametric analyses were also carried out via finite element models to investigate the effects of the number of ribs, the thickness of the ribs, the thickness of the steel plate, the thickness of the concrete slab, and the spacing of the shear connectors on the flexural behavior of the SCCDs, OSCCDs, and USCCDs with PBL or head stud shear connectors. The results indicated that the types of ribs showed significant influence on the flexural behavior of the composite decks. For the same type of shear connector, the flexural behavior of the USCCDs was significantly higher than that of the SCCDs and OSCCDs. Compared with the SCCDs with PBL or head stud shear connectors, the initial stiffness and ultimate load of the USCCDs with PBL or head stud shear connectors were increased by 314.2% and 354.5%, 62.2%, and 89.3%, respectively. The flexural behavior of the composite decks with PBL connections was larger than that of the composite decks with head stud shear connectors for one type of composite deck. The thickness of the concrete slab showed the highest impact on the flexural behavior of the composite decks, followed by the thickness of the rib, the number of ribs, and the spacing of the shear connector. The thickness of the steel plate showed a slight influence on the flexural behavior of the composite decks. The ultimate load of three types of composite decks with PBL or head stud shear connectors was increased by more than 46.5% when the thickness of the concrete slab increased from 80 mm to 120 mm. The reduction stiffness method considering the slip effect was proposed to accurately predict the elastic deflections of three types of composite decks. This study can provide some reference for the design and engineering application of the different types of composite decks.