Supported End Conditions Research Articles

Bending response of cover-plated CFS built-up sections: Testing, numerical parametric analysis and design

This study investigates the bending response of cover-plated cold-formed steel (CPCFS) built-up sections comprising of plain channel members under pure bending achieved through four-point loading, both experimentally and numerically. Channels were appropriately spaced back-to-back and screw-fastened at the flanges using cover-plates on the tension and compression sides. This novel design for the CPCFS built-up section combines the benefits of box-profile (closed sections) and I-profile (open sections), including high strength-to-weight ratio, simplified fabrication, and enhanced torsional rigidity. Eight CPCFS built-up sections with different cross-sectional aspect ratios were tested for bending about the major axis under simply supported end conditions. Flexural strengths, failure modes, and moment-curvature plots were discussed. Subsequently, a finite element model was developed in ABAQUS and validated against the test response obtained. Afterwards, an extensive parametric analysis was conducted to assess the variational effect of aspect ratios, cross-sectional slenderness, and plate slenderness on the ultimate moment capacity of the CPCFS built-up beams. Finally, the adequacy of the codified Continuous Strength Method (CSM) and Direct Strength Method (DSM) for CPCFS built-up beams was evaluated. Generally, it was observed that the flexural strengths predicted by the codified CSM and DSM for CPCFS built-up beams were unconservative and conservative, respectively. Suitable modifications were proposed to both DSM and CSM to accurately predict the flexural strength of CPCFS built-up beams, which were eventually verified through a reliability analysis.

Lateral-Torsional Failure and DSM Design of CFS Lipped Channel Beams at Room and Elevated Temperatures

About a decade ago, in-depth investigations on the behaviour of cold-formed steel (CFS) single-span simply supported lipped channel beams failing in lateral-torsional modes at both room and elevated temperatures were reported at QUT (Queensland Technical University). They revealed a significant underestimation of the lateral-torsional (LT) failure moments by the Direct Strength Method (DSM) global design curve at room temperature, then codified in the Australian/New Zealand and North American specifications. In order to remedy this situation, these authors proposed two novel DSM-based beam strength curve sets, which were found to substantially improve the LT failure moment prediction quality, both at room and elevated temperatures. This work aims at extending the scope of the above investigations, by analysing a visibly larger set of CFS lipped channel beams at elevated temperatures (up to 800 °C), exhibiting (i) various cross-section dimensions and yield stresses, selected to cover wider LT slenderness ranges, (ii) two end support conditions, differing only in the end cross-section wall displacement/rotation and warping restraints (either fully free or fully prevented), and (iii) temperature-dependent steel material properties according with the model prescribed in Part 1-2 of Eurocode 3. The results presented and discussed consist of beam LT post-buckling equilibrium paths and failure moments, obtained through Abaqus shell finite element GMNIA that include critical-mode (LT) initial geometrical imperfections. Lastly, the numerical failure moment data obtained in this work and reported in the literature are used to develop and propose a new unified set of DSM-based strength curves capable of adequately handling beam LT failures at room or elevated temperatures. Since it is shown that the proposed strength curve set provides a quite good LT failure moment prediction quality, it is fair to argue that it constitutes a good starting point to search for an efficient general DSM-based design approach for CFS beams failing in LT modes at room and elevated temperatures.

Analysis of free vibration characteristics of non-uniform graphene-reinforced axially functionally graded nanocomposite beam

This paper presents the changing effect on the free vibration behaviour of graphene-reinforced axially functionally graded nanocomposite (Gr-AFG) beam with non-uniform geometry. A generalized finite element method (GFEM) and Euler Bernoulli’s theory have been used for parametric analysis and the subsequent formulation of governing differential equations. The proposed approach (for uniform geometry) has been compared with the existing gradation schemes, e.g. ‘X’, ‘O’, ‘UD’, ‘A’, and ‘V’, and found to be well in agreement. Furthermore, a new harmonic ‘M’ function has been introduced in the current analysis, and the non-uniformity in the geometry has been implemented by varying the cross-section along the axial direction of the beam. The ‘M’ gradation in the axial direction results in an increase in the natural frequency with an increase in the slenderness ratio for the first four modes. Compared to uniform geometry, the non-uniform AFG-M beam with exponential geometry variation shows a lower fundamental frequency for all values of the slenderness ratio of the beam with an increase in the value of the exponent under C–S and C–C end support conditions.

DSM design of cold-formed steel fixed-ended lipped channel columns undergoing distortional-global interaction

This work reports a numerical investigation dealing with the post-buckling behaviour, strength, and Direct Strength Method (DSM) design of cold-formed steel fixed-ended lipped channel columns experiencing coupling between distortional and global (flexural-torsional) buckling − distortional-global (D–G) interaction. Various cross-section dimensions and lengths are considered, to ensure that the columns selected undergo different levels and types (“true”, “secondary-bifurcation distortional” or “secondary-bifurcation global”) of D–G interaction. The results presented and discussed, determined by means of Abaqus shell finite element geometrically and materially non-linear analyses, consist of elastic and elastic-plastic post-buckling equilibrium paths, failure loads and collapse modes. The steel material behaviour is deemed elastic-perfectly plastic and several yield stresses are considered, thus making it possible to cover a wide column D–G slenderness range. Particular attention is devoted to identifying the most detrimental initial geometrical imperfection shapes, in the sense that they lead to the lowest column failure loads. The numerical failure load data gathered are subsequently used to assess the merits of the available DSM-based design approaches developed to handle cold-formed steel columns undergoing D–G interaction. Since these design approaches are shown to be either inefficient and/or improvable, the above failure load data are also used to propose modifications/improvements aimed at achieving an efficient failure load prediction in the specific context of fixed-ended lipped channel columns. The success of this endeavour provides encouragement to the authors in their search for a safe, accurate and reliable DSM-based design approach capable of handling cold-formed steel columns with arbitrary cross-section shapes and/or end support conditions that fail in D–G interactive modes.

Buckling strengths of cold-formed built-up cruciform section columns under axial compression

This paper describes experiments addressing the buckling and collapse behaviour of cold-formed stainless steel cruciform section columns. Doubly symmetrical flanged cruciform section columns were built using six individual press-braked plain channels made of austenitic grade EN 1.4307 assembled back-to-back. Three different column lengths were tested – namely, short (600 mm), intermediate (1200 mm) and long (2400 mm) lengths, and two channel geometries were used in all tests – with cross-section depths of 200 mm and 100 mm. Tests were carried out under pure axial compression and with fixed end support conditions. Tests were repeated two times for each length. It was observed that the buckling patterns were affected both by the global slenderness and by the spacing between the fasteners. Stocky columns experienced local buckling of the individual channel sections. The plastic failure mechanism was dependent on the fasteners spacing. Intermediate slenderness columns were characterised by interaction between global torsional buckling and local buckling whereas more slender columns failed predominantly through torsional buckling. For the latter, the spacing between the fasteners had a minor influence on the ultimate capacity.

CFS lipped channel beams buckling in distortional modes at elevated temperatures: Behaviour, failure and DSM design

This work reports the findings of a comprehensive numerical investigation on the post-buckling behaviour, failure and Direct Strength Method (DSM) design of cold-formed steel (CFS) single-span simply supported lipped channel beams buckling in distortional modes at elevated temperatures (up to 800 °C) due to fire conditions. It extends the scope of a previous investigation carried out by Landesmann and Camotim [1], by analysing a substantially larger lipped channel beam set, exhibiting various cross-section dimensions and yield stresses, selected to cover wider distortional slenderness ranges. As done before, (i) the beams analysed display two end support conditions, (ii) the Eurocode 3 (part 1.2) model to describe the temperature-dependence of the CFS material properties is adopted and (iii) the results are obtained by means of Abaqus shell finite element GMNIA. After presenting and discussing the main features of the beam distortional post-buckling behaviour, extensive beam failure moment sets are gathered and used to develop and validate DSM-based design approaches. The methodology followed consists of modifying the most performant available DSM-based design curves (developed for beams at ambient temperature [2]), which naturally involves the temperature-dependant reduction factors of the CFS model. A merit assessment procedure shows that the modified DSM-based strength curves predict the lipped channel beam distortional failure moments with remarkable accuracy and reliability, thus constituting an excellent starting point to search for a DSM-based design approach capable of handling arbitrary CFS beams failing in distortional modes at elevated temperatures.

Contact behaviors involving a nanobeam with surface effect by a rigid indenter

In this study, we present a novel surface model that utilizes surface energy density to predict the surface effect in nanobeam contact problems. To address the issue of a finite-length elastic nanobeam being indented by a rigid cylindrical indenter, we propose an equivalent substitution method. This method allows us to formulate analytical relations between the load and contact half-width for two different boundary cases. The explicit expressions of the contact-zone width, the pressure distribution in the contact zone, the deflection outside the contact zone, and the load–displacement relation are obtained for the nanobeam with surface effect and are compared with classical results in detail. The results show that the influence of the surface effect is very significant for nanobeam contact behavior, especially when the half-width of the contact zone increases and the contact zone becomes two independent symmetric strips. It is also found that the length-height ratio of nanobeam and the end support conditions have a fairly obvious effect on the normalized pressure distribution, which deviates significantly from the one predicted by the classical results due to the surface effect. However, for a given beam length and indenter radius, the ratio of the width of the contact zone to the beam thickness is almost constant, independent of the indenter load and beam boundary conditions. Meanwhile, the model predicts that the contact pressure distribution after the normalization of the average indentation pressure is almost independent of the indentation load and beam boundary conditions, but obviously depends on the surface effect parameters. The present method and result should be helpful not only to the measurement of mechanical properties of the indentation nanobeam but also to the design of the nanobeam-based devices.

Computational modelling of built-up cold-formed steel columns and parametric studies

The paper develops a detailed finite-element model for the reliable nonlinear collapse analysis of built-up cold-formed steel columns with discrete fastener connections. First, the main components of the computational model are discussed, including their available options and comparison between their results, followed by a rational justification for the options chosen in this study. Specifically, a detailed theoretical background is provided with conclusive comparisons of the options for enforcing end support conditions, applying contact conditions between the constituent plates, selecting connection elements for representing intermediate screw fasteners, and finally, the incremental load stepping and nonlinear solution schemes. The accuracy and performance of the proposed FE modelling strategy are verified against the experimental data, contributing to the calibration of the influencing parameters. The predictions of the proposed methodology are shown to be in excellent agreement with the test data in terms of the failure mode and the inelastic capacity curve up to ultimate capacity and beyond. Upon its successful calibration, the FE model is utilised to perform extensive parametric studies into the effects of various design parameters on the ultimate strength of built-up columns. This includes practical variations of cross-section dimensions, sectional slenderness, built-up section geometry, and fastener spacing. The parametric study results suggest a meaningful dependency of the ultimate capacity of built-up sections on the fastener spacing ratio, the critical buckling half-wavelength of the built-up section and the relative number of restrained components in the built-up configuration undergoing sectional buckling.

Free Vibrational Analysis of Non-uniform Double Eulerbernoulli Beams on a Winkler Foundation Using Laplace Differential Transform Method

In this study, the free vibrational analysis of non-uniform Euler-Bernoulli double beams on a Winkler foundation under simply supported and fixed-fixed boundary conditions is examined. The governing equation is solved using the Laplace Differential Transform Method, the combined form of the Laplace transform and differential transform technique (DTM). The accuracy of the method used is demonstrated by comparing the natural frequencies obtained using LDTM with previously published results available in the literature. It is discovered that for non-uniform double Euler-Bernoulli beams on a Winkler foundation with fixed-fixed end conditions, the natural frequencies are higher than those of simply supported end conditions. It is also observed that as the non-uniformity of the cross section of the beam increases, the natural frequencies reduce. Hence, it is suggested that the non-uniformity of the cross-section of the beam for a simply supported end condition be between 0 and less than 0.8. While the fixed-fixed end condition should have a value between 0 and 0.95. Journal of Engineering Science 14(1), 2023, 111-121

Nonlocal couple stress-based meshless collocation model for nonlinear dynamic performance of microbeam-type piezoelectric energy harvesters

The prime aim of the current exploration is that to analyze the size-dependent nonlinear dynamics of microsize laminated bridge-type piezoelectric energy harvesters containing a passive core made of an agglomerated nanocomposite and piezoelectric surface layers under a time-dependent mechanical load. For this purpose, the both nonlocal and couple stress tensors are incorporated to the classical quasi-3D shear flexible beam theory to model microsize beam-type laminated energy harvesters. After that, a numerical solution methodology based on the meshless collocation method is employed to discretize the obtained size-dependent nonlinear equations via using a coalesce basis function including polynomial and multiquadric parts on the basis of the Chebyshev node distribution scheme to remove any possible singularity. The nonlinear time histories relevant to the induced lateral deflection and extracted voltage are plotted in the presence and absence of the nonlocal and couple stress tensors as well as various values of the agglomeration constants relevant to the nanocomposite passive core of microsize energy harvesters. One can find that by increasing the cluster volume fraction, the effect of the nonlocal stress tensor on the extracted voltage from the microsize energy harvester increases from +16.50% to +17.53% in the case of simply supported end conditions, and from +21.84% to +22.99% in the case of clamped end conditions. In addition, the effect of the couple stress tensor enhances from −22.21% to −23.09% in the case of simply supported end conditions, and from −27.15% to −27.94% in the case of clamped end conditions.

On transient responses of sandwich plate with cutout using FEM

In the present research work, time-dependent transverse deflection responses of a sandwich composite plate with cutout have been analyzed by using lower-order theory in conjunction with the finite element approach. Initially, the sandwich structure with the cutout (square, pentagonal, hexagonal, and circular) is developed in the ANSYS platform using ANSYS parametric design language (APDL) code. The necessary material properties of the sandwich structure (face sheet and core) are assigned. The developed model has been discretized using 8 noded shell element (Shell 281). The structure is now assigned a simply supported end condition and uniformly distributed loading (UDL). Now, the numerical model’s accuracy is evaluated by comparing the simulated results to previously published literature’s results. The developed simulation model has been used further to investigate the effect of cutout ratios, cutout shape (square, pentagon, hexagon and circle) and core to face thickness ratio on the transient response of a square sandwich panel via new examples. The findings of the examples are analyzed and discussed in detail.

Nonlinear dynamics of traveling beam with longitudinally varying axial tension and variable velocity under parametric and internal resonances

In this investigation, the nonlinear dynamics of an axially accelerating viscoelastic beam on a pully mounting system have been analyzed. The axial tension of the beam is modeled as a function of the traveling velocity, support stiffness parameter as well as spatial coordinate. Geometric cubic nonlinearity in the equation of motion is due to elongation in the neutral axis of the beam. The integro-partial differential equation of motion of the axially accelerating beam associated with the simply supported end conditions is solved analytically by adopting the direct perturbation method of multiple time scales. As a result, a set of complex variable modulation equations is generated, which governs the modulation of amplitude and phase. This set of modulated equations is numerically solved to explore the influence of the support stiffness parameter upon the stability and bifurcation of the beam which has not been addressed in the existing literature. Apart from this, the impact of fluctuating velocity component, viscoelastic coefficient, longitudinal stiffness parameter, internal and parametric frequency detuning parameters on the stability and bifurcation analysis is studied, revealing significant dynamic characteristics of the traveling system. The fourth-order Runge–Kutta method is applied is to find the dynamic solution of the system. The system displays stable periodic, quasi-periodic, and mixed-mode dynamic responses along with the unstable chaotic behavior for a specific set of system parameters. The results obtained through an analytical–numerical approach may help the design and operation of an axially moving beam.

Investigation of flexural and shear failure modes of tapered castellated steel beams using expansion plates

Using modern technologies for fabricating steel, I-beams can be easily made by welding, and hot-rolled beams can often be produced at an economical price with slender webs and equal flanges. Experimental and theoretical studies of the behavior of tapered castellated steel beams were carried out. Due to the cost reductions associated with tapered castellated steel beams, they are a feasible alternative to prismatic components. This study assessed the influence of tapered castellation on the bending capacity and flexural stiffness of tapered castellated steel beams (TCBs) with simply supported end conditions experimentally and theoretically. Four three-point bending tests on TCBs with H/h values of 1, 1.2, 1.4 and 1.6 were conducted utilizing a standard parent I-section beam (IPE140) as the control specimen. The test findings include the ultimate load vs. mid-span deflection response curves and failure mechanisms. The testing findings indicated that the TCBs' ultimate load capacity might be up to 140 percent of that of the parent section. The Abaqus program was used to conduct a finite element (FE) analysis of TCB, which allows for material and geometric nonlinearity. The derived finite element models exhibit excellent agreement with the experimental results in terms of ultimate load capacity vs. mid-span deflection response and failure mechanisms. Based on the results of the work, TCBs can be used for increasing the strength and stiffness of the I-section parent beam with adding expansion plates. The maximum load capacity of TCBs can be enhanced when adding expansion plates up to 40 % above that of the parent beam. A TCB has lower ductility than its parent beam. Moreover, a TCB fulfills serviceability requirements since its mid-span depth exceeds that of its parent beam.

Effect of Design Parameters on the Flexural Strength of Reinforced Concrete Sandwich Beams

Sandwich beams are preferable for aerostructure and marine structures due to their high mechanical strength, durability, stiffness, and fatigue resistance. This paper presents a study on the flexural behavior of sandwich beams made of self-compacting concrete comprising a polystyrene inner core with wire mesh reinforcement. The effect of the design parameters such as the inner core area, percentage of tension reinforcement, and wire mesh on the moment carrying capacity and failure modes of sandwich beams was analyzed. Ten beams were cast and tested to failure with simply supported end conditions and they were classified into three different groups. The longitudinal section of the inner core area was varied by 0% (control beam), 25%, 50%, and 75% of the gross area. The tension reinforcement ratio varied between 0.6 and 1.5%. In addition, the effect of the wire mesh in shear and flexural resistance was studied. The load-carrying capacity of sandwich beams increased with flexural reinforcement. In addition, the welded wire mesh improved the sandwich beams’ flexural and shear performance. The conventional expressions for the moment of resistance were valid for sandwich beams, whereas the shear strength expressions overestimated the capacity; therefore, modifications were suggested. The refined models had a significant agreement with the experimental results.

Global–global interaction in cold-formed steel plain and lipped channel columns

While investigating how accurately the current Direct Strength Method (DSM) global strength curve predicts the major-axis flexural–torsional failures of cold-formed steel columns, the authors (Dinis et al., 2019; 2020) found strong evidence that, for some column lengths and end support conditions, the ultimate strength is eroded by the coupling between major-axis flexural–torsional (FMT - critical) and minor-axis flexural (Fm) bucking (the first two global buckling modes) - i.e, a global–global (G–G) coupling/interaction. This finding is at the root and provided the motivation for the ongoing numerical investigation whose first results are reported in this work. The paper presents and discusses results concerning the behaviour and DSM design of cold-formed steel (CFS) fixed-ended plain and lipped channel columns that buckle in FMT modes and undergo G–G interaction. After a brief review of the DSM-based design approach that was proposed to handle column FMT failures (Dinis et al., 2020), attention is turned to investigating the column (i) buckling behaviour, essential for the selection of column geometries susceptible to G–G interaction, and (ii) FMT non-linear (post-buckling) behaviour — special care is devoted to the identification of the most detrimental initial geometrical imperfection shape. Then, the FMT failure loads of the selected columns are obtained for five yield stresses (to cover wide slenderness ranges) and the gathered failure load data are used (i) to clearly show that the existing DSM-based design approach cannot adequately predict them and (ii) as guidance for its modification, which brings about the Fm-to-FMT buckling load ratio and enables the adequate handling of also G–G interactive failures. The excellent failure load prediction quality exhibited by this modified design approach is very encouraging and makes the authors believe that its domain of application can be extended to CFS columns with other cross-sections and/or end support conditions — research is under way to assess whether this belief is well founded.

Nonlinear Finite Element Analysis and Comparison of In‐Plane Strength of Circular and Parabolic Arched I‐Section Cellular Steel Beam

The advancement in steel fabrication technology extends the structural and constructional advantages of cellular steel beams into arched cellular steel structure members. However, less attention is given to understanding the in‐plane and out‐of‐plane structural behavior and performance of arched cellular steel beams. This article presents a numerical study using the finite element package ABAQUS to investigate the effect of arch axis geometry (circular and parabolic) and the impact of end support types on the in‐plane inelastic buckling strength and buckling mode of I‐section arched cellular steel beams. In the nonlinear finite element analysis of the model material nonlinearity, a second‐order effect due to large deformation and initial geometric imperfection was incorporated in predicting inelastic buckling load and buckling mode. Furthermore, finite element analysis results were verified by comparing them to the existing experimental work. Test models covering shallow to deep arches of subtended angle in a range of 45–180 were investigated under uniformly distributed vertical loads and mid‐span point loads. It was found that nonlinear finite element results fairly replicate the experimental work in predicting inelastic buckling load and post‐buckling behavior. From the parametric investigation, it was found that deep parabolic arched cellular steel beams are structurally more efficient than their equivalent circular arched cellular steel beams. Pinned in‐plane and free out‐of‐plane end support conditions result in a reduced inelastic ultimate buckling load capacity of arched cellular steel members when compared to other possible end support types. The geometry of an arch axis has no noticeable impact on the buckling mode of arched cellular steel beams.

Nonlinear eigenfrequency prediction of functionally graded porous structure with different grading patterns

The effect of full-scale geometrical nonlinearity on the eigenfrequencies of the porous graded curved panel structure is examined in this current work, considering the configurational variation due to curvature (single/doubly). A nonlinear isoparametric finite element formulation has been derived using the Green-Lagrange nonlinear strain and the higher-order deformation kinematics. Additionally, each mid-plane strain is incorporated within the model to count the exact structural flexure due to the large deformation. Further, the equation of motion has been converted to a set of algebraic forms through a nine-noded quadrilateral element and solved computationally (via MATLAB code) in association with the direct iterative method. The comparison and convergence tests are carried out to check the accuracy of the mathematical model by solving different sets of examples as same as the references. Afterwards, the model has been used to compute the nonlinear frequency (NLF) data to examine the influence of various structural input parameters, i.e. porosity, grading pattern, amplitude ratio, power-law exponent, curvature ratio, end-support conditions, geometrical shapes, thickness ratio and aspect ratio.

Testing and modelling of hot-rolled steel castellated hollow tubular beams

Researchers and design engineers are increasingly interested in castellated beams because of their ability to provide greater flexural strength with lower dead loads, as well as provide services and cost-effective structures. The influence of castellation on the bending strength and stiffness of the hot-rolled steel Square Tubular Beams (STBs) and Castellated Tubular Beams (CTBs) with simply supported end conditions were investigated in this study. Totally eight bending tests were carried out on hollow tubular beams with and without castellation under three point bending. The STBs with a nominal steel tube thickness of 2.5 mm are castellated in a hexagonal pattern. The ultimate moments, moment versus mid-span deflection response curves, and failure patterns are provided as part of the test results. The bending tests show that the flexural capacities and stiffness of the hollow tubular sections significantly increased due to the castellation process. Finite element (FE) models of STBs and CTBs were established by including the material and geometric nonlinearity as well as the measured geometric imperfections. The FE models established show good agreement with the experimental test in terms of ultimate bending strength, moment vs. mid-span deflection response, and failure modes.

Analytical and numerical investigation of the free vibration of functionally graded materials sandwich beams

Purpose: In this study, the free vibration analysis of functionally graded materials (FGMs) sandwich beams having different core metals and thicknesses is considered. The variation of material through the thickness of functionally graded beams follows the power-law distribution. The displacement field is based on the classical beam theory. The wide applications of functionally graded materials (FGMs) sandwich structures in automotive, marine construction, transportation, and aerospace industries have attracted much attention, because of its excellent bending rigidity, low specific weight, and distinguished vibration characteristics. Design/methodology/approach: A mathematical formulation for a sandwich beam comprised of FG core with two layers of ceramic and metal, while the face sheets are made of homogenous material has been derived based on the Euler–Bernoulli beam theory. Findings: The main objective of this work is to obtain the natural frequencies of the FG sandwich beam considering different parameters. Research limitations/implications: The important parameters are the gradient index, slenderness ratio, core metal type, and end support conditions. The finite element analysis (FEA), combined with commercial Ansys software 2021 R1, is used to verify the accuracy of the obtained analytical solution results. Practical implications: It was found that the natural frequency parameters, the mode shapes, and the dynamic response are considerably affected by the index of volume fraction, the ratio as well as face FGM core constituents. Finally, the beam thickness was dividing into frequent numbers of layers to examine the impact of many layers' effect on the obtained results. Originality/value: It is concluded, that the increase in the number of layers prompts an increment within the frequency parameter results' accuracy for the selected models. Numerical results are compared to those obtained from the analytical solution. It is found that the dimensionless fundamental frequency decreases as the material gradient index increases, and there is a good agreement between two solutions with a maximum error percentage of no more than 5%.

EXPERIMENTAL AND ANALYTICAL STUDY ON THE IMPACT BEHAVIOR OF STEEL–CONCRETE COMPOSITE SLAB

Concrete structures have been widely used for many years to resist impact loads. Steel–concrete composite structures may be considered efficient structures in the emerging modern construction field. Hence, the main objective of this research was to study the impact behavior of steel concrete composite slabs with different shear connectors and compare them with conventional slabs. Seven specimens of dimensions 500 × 500 × 50 mm were cast, which included plain cement concrete slabs, two reinforced cement concrete slabs with steel mesh and steel rebars as reinforcement, and four steel-concrete composite slabs with four different shear connectors: stud, tee, angle, and channel connectors. The composite action was achieved using a steel decking sheet welded with connectors on which the concrete layer was poured at the top. The test setup was fabricated with slots provided for specimens with simply supported end conditions and a mild steel drop weight. The specimens were impacted at the center of the span by dropping a steel mass from a free fall height of 1 m. The number of blows corresponding to the initial cracking and ultimate failure stages was recorded. The parameters that were used to compare the specimens were the impact energy absorbed, crack pattern, crack width, and increase in impact energy from the first blow to the last blow. The experimental results were very close to the analytical results obtained using ANSYS. The experimental and analytical results showed that the composite slabs with channel connectors performed better than the others, and it was proven that the composite slabs performed better under impact loading than conventional slabs.