Thin-walled Square Research Articles

Experimental and numerical studies on failure and energy absorption of composite thin-walled square tubes under quasi-static compression loading

Abstract To analysis the failure and energy absorption of carbon fiber reinforced polymer (CFRP) thin-walled square tube, the quasi-static axial compression loading tests are conducted for [±45]3s square tube, and the square tube after test is scanned to further investigate the failure mechanism. Three different finite element models, i.e. single-layer shell model, multi-layer shell model and stacked shell mode, are developed by using the Puck 2000 matrix failure criterion and Yamada Sun fiber failure criterion, and three models are verified and compared according to the experimental energy absorption metrics. The experimental and simulation results show that the failure mode of [±45]3s square tube is the local buckling failure mode, and the energy are absorbed mainly by intralaminar and interlaminar delamination, fiber elastic deformation, fiber debonding and fracture, matrix deformation cracking and longitudinal crack propagation. Three different finite element models can reproduce the collapse behaviours of [±45]3s square tube to some extent, but the stacked shell model can better reproduce the failure mode, and the difference of specific energy absorption (SEA) is minimum, which shows the numerical simulation results are in better agreement with the test results.

The reinforcement optimization of thin-walled square tubes for bending crashworthiness

Thin-walled structures have an inherent shortcoming that their cross sections are likely to flatten when subjected to transverse loading. In the paper, four simple novel reinforcement configurations into the thin-walled square tubes are put forward, and their bending resistance under three-point bending is investigated using the ABAQUS/Explicit code. The numerical results indicate that the reinforcements considerably enhance the structural bending resistance by effectively restricting the flattening of the upper compressive region of the cross sections. The variational characteristic of the maximum loads and the mean loads with the variables for the four reinforcing configurations is analyzed. The two key indicators SEA (specific energy absorption) and CLE (crash load efficiency) are introduced to further evaluate their energy absorbing and safeguard performance. It is found that one of the suggested reinforcement configurations significantly improve the values of SEA and CLE by 93.5%, 68.1% respectively, compared with the conventional empty tube.

Compressive behaviour of thin-walled square tubular columns filled with high-strength steel section and precast compound concrete segments

Abstract Different from small-scale recycled aggregates (≤31.5 mm) in recycled aggregate concrete, recycling waste concrete in structural members in the form of compound concrete, constructed with large-scale (60–200 mm) demolished concrete lumps (DCLs) and fresh concrete, provides a viable option to designers. Such DCLs can be mixed with fresh concrete in shop to produce precast concrete segments (PS-DCLs), which can be transported to construction site to expedite construction process of the structural members with the PS-DCLs. In this paper, an innovative thin-walled square tubular column filled with I-shaped high-strength steel (HSS) section and PS-DCLs is proposed to enable easy application of the DCLs into vertical structural members and address the shortcomings of the HSS section. The PS-DCLs are placed into the gap between the outer tube and the inner HSS section, using in-filled grout as bonding among them, to produce composite column. A new precasting procedure for fabricating such columns is proposed. Axial compression tests were conducted to investigate the effects of fabrication procedure, yield strength of the inner steel section, replacement ratio of the DCLs, and configuration of the PS-DCLs on the compressive behaviour of the proposed columns. The test results show that the precast columns constructed using the proposed procedure had axial compression capacities comparable to those cast in place. A practical method for predicting the load-bearing capacity of such columns is proposed and validated against the experiments and published data from previous studies. It shows better agreement with the experimental data than the existing approaches. An effective strength index is proposed for utilizing the strength contribution of steel section in the proposed columns, and recommendations for practical selection of appropriate materials for the steel section are presented.

Cyclic loading tests of thin-walled square steel tube beam-column joint with different joint details

To study the seismic performance of a thin-walled square steel tube beam-column joint of a light steel frame, 8 kinds of thin-walled square-hollow structural steel (HSS) and concrete-filled steel tube (CFST) beam-column joints with different joint details were designed and manufactured. The joint details were divided mainly into welded joint, plate joint, angle joint and angle with stiffener joint. A total of 14 specimens of beam-column joint specimens were tested using a low reversed cyclic loading test. The failure characteristic, load-bearing capacity, hysteretic property, stiffness degradation and energy dissipation were compared. The results showed that the different joint details had a great influence on the seismic performance of the beam-column joint. The bearing capacity and failure rotation of the welded joint were poor. The bearing capacity of the plate joint was close to that of the welded joint, but it showed improved bearing capacity, failure rotation and energy dissipation capacity of the joint. The bearing capacity of the angle joint was poor. With the angle welded stiffener, the bearing capacity, stiffness and energy dissipation capacity of the joints were significantly improved. The number and height of the stiffener can improve the seismic performance of the joint. The stiffness and energy dissipation capacity of the CFST beam-column joint was better than that of the HSS beam-column joint with the same joint detail. The classification of the joint is discussed, and a simplified M-R calculation model is proposed.

Nonlinear analysis of square concrete-filled double steel tubular slender columns incorporating preload effects

Thin-walled square and circular hollow steel tubes are designed to support the permanent and construction loads of several upper composite floors before filling the concrete into the tubes to form concrete-filled double steel tubular (CFDST) columns. The influences of preloads acting on the steel tubes on the structural responses of slender square CFDST columns have not been investigated either experimentally or numerically. This paper presents a fiber-based computational model for the determination of the interaction behavior of local and global buckling in axially and eccentrically loaded CFDST thin-walled square slender columns including preload effects. The computational modeling method accounts for the influences of the deformations induced by preloads, local-global interaction buckling, geometric imperfections, second-order, and geometric and material nonlinearities. The accuracy of the computational algorithms developed is validated by comparing computations with test data on concrete-filled steel tubular (CFST) columns and finite element results of double-skin CFST (DCFST) columns with preload effects. The computer algorithms are employed to quantify the influences of preloads on the local-global interaction buckling responses of CFDST columns with various important parameters. Proposed is a design method for calculating the ultimate loads of concentrically loaded slender square CFDST columns considering preloads. The computational and design models developed are shown to be efficient modeling and design tools for square CFDST slender columns taking into account the construction method of high-rise composite buildings.

Effect of Ridgeline Radius on the Maximum Bending Moment of Thin-walled Square Tubes

Effect of Ridgeline Radius on the Maximum Bending Moment of Thin-walled Square Tubes

Crashworthiness topology optimization of thin-walled square tubes, using modified Bidirectional Evolutionary Structural Optimization approach

Abstract In this study, topology optimization of a thin-walled square tube subjected to an axial crushing load was carried out to enhance its crashworthiness performance, utilizing the modified Bidirectional Evolutionary Structural Optimization (BESO) procedure. In this way, by systematic searching, topology optimization finds the best material layout for the structure to satisfy the objective function. In each iteration, a new pattern of material-void through the tube walls can trigger various folding mechanisms. Thus, the energy absorption history trend might not be smooth and the ultimate pattern proposed by the algorithm is less likely to be the optimal one. With an emphasis on the BESO hypothesis regarding direct removal and addition of elements, the modified BESO algorithm excavated the optimal design in two steps. First, material-void patterns were produced, considering specific energy absorption as the element efficiency criterion. Then, the pattern with the least material usage which satisfies an energy absorption constraint was selected as the optimal design. Such an optimum layout also boosts the tube performance respecting peak crushing force, since the embedded voids through the structure serve as a crush initiator. The optimization code was developed in MATLAB, which was automatically integrated with ABAQUS software performing the nonlinear crushing analysis. To validate the finite element model, an experimental investigation was carried out on a simple square tube. Having performed the topology optimization and some fine-tuning process, the topologically optimized tube was constructed and experimentally tested. Results showed 16.21% weight reduction enriched with 36.57% enhancement in the peak crushing force by sacrificing less than 3.5% energy absorption, which represents substantial improvements from a crashworthiness viewpoint. The obtained interesting results showed the high potential of the BESO algorithm for the design of thin-walled structures under large deformation and out-of-plane buckling.

Axially Loaded Thin-Walled Square Concrete-Filled Steel Tubes Stiffened with Diagonal Binding Ribs

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Energy absorption properties of thin-walled square tube with lateral piecewise variable thickness under axial crashing

Purpose This paper aims to study the energy absorption properties of the thin-walled square tube with lateral piecewise variable thickness under axial crashing and the influence of the tube parameters on energy absorption. Design/methodology/approach In this work, the energy absorption properties of the thin-walled square tube were analyzed by theoretical, numerical and experimental approach. The numerical results are obtained based on the finite element method. The explicit formulation for predicting the mean crushing force of the tube with lateral piecewise variable thickness was derived based on Super Folding Element method. The limitation of the prediction formulation was analyzed by numerical calculation. The numerical calculation was also used to compare the energy absorption between the tube with lateral piecewise variable thickness and other tubes, and to carry out the parametric analysis. Findings Results indicate that the thin-walled tube with lateral piecewise variable thickness has higher energy absorption properties than the uniform thickness tubes and the tubes with lateral linear variable thickness. The thickness of the corner is the key factor for the energy absorption of the tubes. The thickness of the non-corner region is the secondary factor. Increasing the corner thickness and decreasing the non-corner thickness can make the energy absorption improved. It is also found that the prediction formulation of the mean crushing force given in this paper can quickly and accurately predict the energy absorption of the square tube. Originality/value The outcome of the present research provides a design idea to improve the energy absorption of thin-walled tube by designing cross-section thickness and gives an explicit formulation for predicting the mean crushing force quickly and accurately.

Numerical, theoretical, and experimental studies on the energy absorption of the thin-walled structures with bio-inspired constituent element

Nowadays, more bio-inspired structures were proposed and adapted in structural designs to improve their energy absorbing performance. In this paper, a bio-inspired constituent element (BCE) consisting of a hollow cylindrical tube with four panels was studied. Quasi-static tests were conducted to evaluate its energy-absorbing performance using specimens with a thin-walled square tube. A FE model was developed and validated in favorable agreement with the experimental data. Using the FE model, a parametric study of the energy absorbing capability and deformed pattern of the BCE was conducted. The specific energy absorption (SEA) of the BCE is higher than that of traditional angle elements and significantly affected by the wall thickness, radius of cylindrical tube and number of intersecting panels. Finally, analytical (or theoretical) formulae for estimating the mean crushing force of the BCE was derived and correlated favorably with the experimental data.

Study on crushing behaviors of foam-filled thin-walled square tubes with different types and number of initiators under multiple angle loads

Abstract A finite element model of a thin-walled foam-filled square tube is developed for estimating its energy absorption characteristics. The crush behavior of the foam-filled tube is experimentally evaluated under axial loading and the measured force-deflection properties are used to examine validity of the model. The validated model is subsequently applied to study the effects of types and number of crush initiators on the energy absorption characteristics of the foam-filled thin-walled square tubes subjected to loading at different angles. It is shown that initiators can yield improved collision performance of the foam-filled thin-walled square tubes, when a reasonable number of crushing initiators are introduced. The energy absorption performances of the foam-filled structure with different types and quantities of crushing initiators are calculated and ranked. The results showed best performance when a set of four-corner-holes along the axial direction of the tubes is added. Based on the model results, a multi-objective optimization method is proposed for deriving an optimal design of the tube with a set of four-corner-holes for enhanced crashworthiness performance.

Stability of thin-walled square tubes with intermediate stiffeners under torsion

The present paper deals with the buckling of thin-walled square tubes with intermediate stiffeners under torsion when the shear lag phenomenon and distortional deformations are taken into account. A plate model (2D) was adopted for the tube. The tubes were assumed to be simply supported at their ends. The values of critical loads of the tubes were determined with three methods, namely: analytical-numerical method (ANM), finite difference method (FDM) and finite element method (FEM).

Crashworthiness of extruded magnesium thin-walled square tubes

Abstract Axial compression tests were conducted on AZ31B magnesium and A6063 aluminum thin-walled square tubes with varied lengths and induced features at different compression rates. In compression, the magnesium tubes exhibited a “local buckling and fracture” mode, with three fracture patterns, i.e. “horizontal”, “double-oblique”, and “spiral” fractures. In general, the magnesium tube showed an inferior crashworthiness to the aluminum square tube. In addition, the effects of L/W ratio, strain rate and induced features on the crashworthiness of thin-walled square tubes were investigated. With an increase in the L/W ratio (L and W represent the tube length and width, respectively) from 1 to 4, the maximal force and global specific energy absorption decreased in a power-law trend for the magnesium tubes, while they remained approximately constant for the aluminum tubes. Furthermore, as the compression rate increased from 5×10−5 to 10 m/s, the primary crashworthiness parameters of the magnesium tubes increased in an approximately exponential manner, while for the aluminum tubes, they changed slightly. Finally, the involved induced features were proven to be not an effective method to improve the specific energy absorption of magnesium tubes, thus, more trigger types, locations, and sizes will be evaluated in future to improve the energy-absorption ability.

Crashworthiness performance of thin-walled prismatic tubes with corner dents under axial impact - Numerical and experimental study

The paper presents results of the numerical and experimental study into crashworthiness performance and energy absorption capability of thin-walled square section columns with dents, subjected to axial impact load. Thin-walled aluminum tubes with four dents in the corners are under investigation. Energy absorption effectiveness of energy absorbing thin-walled structures is discussed. Finite Element parametric study into energy absorption capacity of structures under investigation is performed. Crushing behavior and some crashworthiness indicators are examined. Results of experimental impact tests carried out on aluminum tubes with dents of selected shape and position are presented. FE theoretical model and numerical results are confronted with those obtained from experimental tests. Some conclusions concerning optimal dent shape and position are derived.

Energy absorption of thin-walled square tubes designed by kirigami approach

Thin-walled tubes are extensively employed as energy absorption devices. The extensional mode (EM) of collapse in thin-walled square tube is desirable in terms of energy absorption while facing impact loading. In this paper, a novel tube known as the kirigami crash box (KCB) that is designed by kirigami approach, is proposed to improve the crashworthiness of the tubular structures by collapsing in EM. The experimental and numerical results show that kirigami pattern in KCB serves as both geometric imperfection to reduce the initial peak force Fmax and mode inducer to trigger the desired EM while collapsing. Numerical simulation indicates that the ideal EM is successfully triggered with a 39.7% reduction of initial peak force Fmax and 33.9% increase of mean crushing force Fm comparing to conventional square tube (N-CST). Parametric study shows that the collapse mode of KCBs deformed in EM is independent of aspect ratio b/t within the range of b/t ≤ 81.3, while for CST, the corresponding range is b/t ≤ 7.5. KCB inclines to collapse in EM when the dihedral angle θ or the number of modules M decrease. The Fmax, Fm and CFEs of KCBs with identical M increase with the increasing θ. Whereas, the effect of M on energy absorption is relatively less important while θ remains the same. Moreover, the superiority of energy absorption for KCB subjected to dynamic loading is more significant comparing to quasi-static axial crushing.

Axial crush performance of polymer-aluminium alloy hybrid foam filled tubes

The paper presents the findings of a pioneering study investigating the newly developed polymer-aluminium alloy hybrid foam as fillers of thin-walled square tubes made of aluminium alloy, as an alternative to the conventional closed-cell aluminium foams. The hybrid foam filled structures were prepared by infiltrating an aluminium alloy open-cell foam with silicone or epoxy inside the thin-walled tubes. Quasi-static and dynamic crush compressive response, deformation and failure modes and energy absorption characteristics of the hybrid foam filled structures were evaluated and compared to the empty tubes and tubes filled with conventional aluminium alloy open-cell foam (with voids). Results show that the deformation of the square thin-walled is improved due to the open-cell foam filler. It stabilises the tube and prevents the unstable global bending mode or a mixed buckling mode that is considered as an inefficient mode from the crashworthiness point of view. The deformation of the hybrid foam filled tubes was accompanied with a progressive folding mode. It was also observed that the polymer fillers caused the rupture of the outer tube at the corners, which results in higher energy apportion but might limit their application. However, it was found that the most efficient hybrid foam filled structures studied, in terms of crashworthiness, were the tubes filled with the epoxy-aluminium alloy hybrid foam. An increase of 610% and 300% in energy absorption and 78% and 51% in specific energy absorption of hybrid foam filled structures with length of 25 mm and 50 mm in comparison to the empty tubes (at strain of 0.7) was noted, respectively.

A three-hinge-line method for calculating the deformation process of thin plates under quasi-static axial loading

This paper presents a modified calculation method for the crushing deformation of sheet metals, which is called the three-hinge-line method (THLM). Through developing the folding mechanism of a thin-walled square tube, the effect of the buckling curvature on thin plates is approximately considered by improving the original single hinge to three hinges, and a method for calculating the distance between the hinges is given. A program is designed for the solution of this problem. In addition to solving for the average force and energy, the deformation process and force-displacement curves are also included. The accuracy of the THLM can be checked by the finite element method (FEM). The good agreement between the methods shows that the compressive forces are predicted satisfactorily from the results of the proposed uniaxial crushing.

Energy absorption investigation of square CFRP honeycomb reinforced by PMI foam fillers under quasi-static compressive load

A type of hybrid core made up of thin-walled square carbon fiber reinforced polymer (CFRP) honeycomb and Polymethacrylimide (PMI) foam fillers was proposed and prepared. Numerical model of the core under quasi static compression was established and validated by corresponding experimental results. The compressive properties of the core with different configurations were analyzed through numerical simulations. The effect of the geometrical parameters and foam fillers on the compressive response and energy absorption of the core were analyzed. The results show that the PMI foam fillers can significantly improve the compressive strength and energy absorption capacity of the square CFRP honeycomb. The geometrical parameters have marked effects on the compressive properties of the core. The research can give a reference for the application of PMI foam materials in energy absorbing structures and guide the design and optimization of lightweight and energy efficient cores of sandwiches.

Seismic Behavior Tests of Square Reinforced Concrete–Filled Steel Tube Columns Connected to RC Beam Joints

AbstractThis paper proposes a joint system that connects the thin-walled square reinforced concrete–filled steel tube (RCFST) column to RC beams at both sides of the joint. In order to delay the lo...

Crashworthiness of Thin-Walled Square Steel Columns Reinforced Based on Fractal Geometries

In this paper, the crashworthiness of steel thin-walled square columns was investigated. These structures were reinforced with three types of reinforcers. The first type was aluminum shells which were placed inside the steel columns based on a specific fractal geometry, and two other types were aluminum and polyurethane foams. All samples were placed under axial loading, and fractals were thinned out up to three stages. At each stage, the effectiveness of aluminum shells alone and also in the presence of polyurethane and aluminum foams has been investigated. Also, the effect of foams' location and in or out of fractal geometry, was studied. The results showed that the presence of reinforcers with different geometries and materials improved the energy absorption. As the fractal geometry of the reinforcers becomes smaller, the energy absorption capacity increases. The presence of the foams well compensated the load–displacement diagram drop after the initial peak and made the energy absorption behavior more ideal. On the other hand, polyurethane foam showed a significant effect on buckling control so that in one of the samples it prevented buckling. Comparison of the studied samples showed that the energy absorption was better when polyurethane foam prevailed. The effect of the second-stage fractal geometry was almost twice the fractal geometry of the first stage. The best choice among the discussed examples was an absorbent in the second stage with foam, in which the polyurethane foam predominated. Finally, some results were validated.