C-shaped Sections Research Articles

Finite element analysis of hysteretic characteristics of steel member under cyclic loading

Abstract In this paper, the square, H-shaped and C-shaped steel members with three cross-section forms are selected. Considering the cross-section form, slenderness ratio and constraints at both ends, the force-displacement curve and single-ring energy consumption of steel members under cyclic loading are simulated and analysed. The buckling performance and hysteresis characteristics of steel members with different properties are compared. The results show that the section form has the greatest influence on the energy dissipation level of the component. The hysteretic performance of H-shaped section member is the best, followed by C-shaped section member and square section member. The energy consumption level of the component is negatively correlated with the slenderness ratio, and the single-cycle energy consumption of the steel component decreases with the increase of the slenderness ratio. The constraint condition has the smallest influence on the energy consumption level of the component, and the energy consumption of the component under the end solid-solid constraint and solid-hinge constraint is similar.

Control effect and optimization scheme of combined rockbolt–cable support for a tunnel in horizontally layered limestone: A case study

This study focused on the mechanical behavior of a deep-buried tunnel constructed in horizontally layered limestone, and investigated the effect of a new combined rockbolt–cable support system on the tunnel response. The Yujingshan Tunnel, excavated through a giant karst cave, was used as a case study. Firstly, a multi-objective optimization model for the rockbolt–cable support was proposed by using fuzzy mathematics and multi-objective comprehensive decision-making principles. Subsequently, the parameters of the surrounding rock were calibrated by comparing the simulation results obtained by the discrete element method (DEM) with the field monitoring data to obtain an optimized support scheme based on the optimization model. Finally, the optimization scheme was applied to the karst cave section, which was divided into the B- and C-shaped sections. The distribution range of the rockbolt–cable support in the C-shaped section was larger than that in the B-shaped section. The field monitoring results, including tunnel crown settlement, horizontal convergence, and axial force of the rockbolt–cable system, were analyzed to assess the effectiveness of the optimization scheme. The maximum crown settlement and horizontal convergence were measured to be 25.9 mm and 35 mm, accounting for 0.1% and 0.2% of the tunnel height and span, respectively. Although the C-shaped section had poorer rock properties than the B-shaped section, the crown settlement and horizontal convergence in the C-shaped section ranged from 46% to 97% of those observed in the B-shaped section. The cable axial force in the B-shaped section was approximately 60% of that in the C-shaped section. The axial force in the crown rockbolt was much smaller than that in the sidewall rockbolt. Field monitoring results demonstrated that the optimized scheme effectively controlled the deformation of the layered surrounding rock, ensuring that it remained within a safe range. These results provide valuable references for the design of support systems in deep-buried tunnels situated in layered rock masses.

Structural fire design of load-bearing cold-formed steel assemblies from a prototype metal building

This paper describes a procedure to complete the structural fire design of cold-formed steel structures and applies it to column assemblies taken from a prototype one-story metal building designed following U.S. building codes. The fire design procedure includes the definition of performance objectives, design fires, heat transfer analyses by the finite element method, and structural analyses using both the Direct Strength Method and finite element modeling. The results show that the design by analysis achieves the required performance while enabling flexibility and efficiency in design. Thermal analyses provide steel temperatures consistent with prescriptive fire ratings and are also used to demonstrate adequacy of unrated assemblies such as protected double C-shaped sections. The finite element model confirms the applicability of the Direct Strength Method with appropriate retention factors to evaluate the elevated temperature response. The cold-formed steel columns maintain stability well beyond their prescriptive rating owing to the low applied load resulting from the ASCE/SEI 7 load combination in the fire situation, which does not include wind. Therefore, for structures which are lightly loaded in the fire situation, such as these metal building columns, analysis methods can be used to demonstrate superior performance compared to the applied fire resistance rating.

Applied Element Modelling of Warping Effects in Thin-Walled C-Shaped Steel Sections

The Applied Element Method (AEM) is a relatively recent numerical technique, originally conceived for simulating the large displacement nonlinear response of reinforced concrete, masonry and steel structures, and successful applications have been presented by various researchers. Recently, AEM was used to model the mechanical behaviour of steel storage pallet racks, i.e., particular cold-formed steel structures typically employed for storing goods and materials. Such systems are often subjected to peculiar displacements and stresses due to warping effects, which are inherent and often govern their behaviour, increasing the peak strength and ultimate displacement demand. This phenomenon has not been studied through AEM yet; hence, this work investigates the capabilities of AEM in simulating the warping effects in typical steel rack members, i.e., thin-walled C-shaped sections. Preliminary results and comparison against established modelling approaches indicate that AEM can accurately simulate this phenomenon, both in terms of displacements and stresses.

Failure analysis of GFRP columns subjected to axial compression manufactured under various curing-process conditions

Fibre reinforced polymers are one of the most used materials in the manufacturing of thin-walled structures due to their favourable mechanical properties in terms of strength-to-weight ratios. The curing-process conditions of polymer-based composites can be a source of the residual stresses which can play the main role in failure mechanisms of a composite. The work presents a comparative failure analysis following the post-buckling state of thin-walled composite columns made by autoclave methods with various curing parameters and geometrical concepts. The study inspected the compression of thin-walled composite profiles with C-shaped sections and square cross-sections made of unidirectional preimpregnated tapes of glass/epoxy. It was presented that the boundaries of the halfwaves of the composite flanges are the initiation point of local but catastrophic damage (out-of-plane buckling and plies split) of the composite. These regions are stress concentration points in columns. However, the dominant form of damage is delamination. Delamination is the propagation stage of failure of composite, which propagates from initiation points. The progress of delamination occurs because of increasing load, halfwave deformation and column stiffness reduction. Depending on the curing parameters and geometrical concepts some additional, important failure initiation mechanisms, such as stepped cracks and fibre rupture, were noticed.

ㄷ형강 부재로 구성된 모듈 간 접합부의 보강 상세에 대한 해석적 연구

ㄷ형강 부재로 구성된 모듈 간 접합부의 보강 상세에 대한 해석적 연구

CFD computation of the hydrodynamic torque due to free-surface antiroll tanks with 3D dynamics

ABSTRACT The aim of this work is to simulate the complex 3D hydrodynamics inside free-surface anti-roll tanks with obstacles and side sub-compartments. The case studies comprise a rectangular tank, a tank with a C-shaped section and a rectangular tank with baffles, for which experimental results are provided. The simulations have been performed for 3 and 6 degrees of roll, and for various filling levels. The Open Source Computational Fluid Dynamics (CFD) tool OpenFOAM has been used to carry out the simulations. Various turbulence models and boundary condition implementations have been used. It is shown in the paper that the k-ω SST model with slip boundary condition is the one that provides the best trade-off between accuracy and computational efficiency. In order for present results to be easily reproducible, the simulations files, also including the geometrical ones, are provided as supplementary material.

Assessment of web crippling design provisions for application to proprietary soldier beams

Structures used for temporary works are lightweight so that they are easy to transport, erect and dismantle. Particular care should be taken in their design as local instabilities could arise due to their thin-walled nature. This article presents 12 tests on proprietary soldier beams subjected to two concentrate opposing loads applied simultaneously. The geometry of the proprietary beams feature cold-formed C-shaped sections with web holes connected back to back with internal spacers. In the absence of design rules for application to such members, the experimental results are used in the present investigation to assess the suitability of the provisions for the web crippling design of cold-formed steel members as well as existing design methods from the literature, which account for the effect of perforations in the web. Experimental and predicted resistances are compared and design recommendations are provided.

Experiment and Design Method on Cold-Formed Thin-Walled Steel Lipped Channel Columns with Slotted Web Holes Under Axial Compression

Background: Cold-formed steel structural sections used in the walls of residential buildings and agricultural facilities are commonly C-shaped sections with web holes. These holes located in the web of sections can alter the elastic stiffness and the ultimate strength of a structural member. The objective of this paper is to study the buckling mode and load-carrying capacity of cold-formed thin-walled steel column with slotted web holes. Methods: Compression tests were conducted on 26 intermediate length columns with and without holes. The tested compressive members included four different kinds of holes. For each specimen, a shell finite element Eigen-buckling analysis and nonlinear analysis were also conducted. The influence of the slotted web hole on local and distortional buckling response had also been studied. The comparison on ultimate strength between test results and calculated results using Chinese cold-formed steel specification GB50018-2002, North American cold-formed steel specification AISI S100-2016, and nonlinear Finite Element method was made. Result: Test results showed that the distortional buckling occurred for intermediate columns with slotted holes and the ultimate strength of columns with holes was less than that of columns without holes. The ultimate strength of columns decreased with the increase in transverse width of hole in the cross-section of member. The Finite element analysis results showed that the web holes could influence on the elastic buckling stress of columns. The shell finite element could be used to model the buckling modes and analysis the ultimate strength of members with slotted web holes. The calculated ultimate strength shows that results predicted with AISI S100-2016 and analyzed using finite element method are close to test results. The calculated results using Chinese code are higher than the test results because Chinese code has no provision to calculate the ultimate strength of members with slotted web holes. Conclusion: The calculated method for cold-formed thin-walled steel columns with slotted web holes are proposed based on effective width method in Chinese code. The results calculated using the proposed method show good agreement with test results and can be used in engineering design for some specific cold-formed steel columns with slotted web holes studied in this paper.

Cold‐formed members – comparison between tests and a unified design method for beam‐columns

AbstractIn [1] a unified method for the design of steel beam‐columns is presented. The method has been checked for rolled steel beam‐columns and extruded aluminium beam‐columns. It is included in Eurocode 9 [19] for aluminium members and it is proposed to be included also in Eurocode 3 Part 1‐3 [16] as well, but then it needs to be checked for typical cold‐formed sections.Cold‐formed sections are usually un‐symmetric and thin‐walled, for instance channel sections or C‐shaped sections (lipped channels). When used as compression members, local buckling causes a redistribution of the longitudinal stress which leads to a shift of the effective centroid. The shift causes overall bending and reduces the column strength when the member is compressed between pinned ends. In fixed‐ended columns, however, the shift of the effective centroid is balanced by a shift of the applied force and bending is not introduced [6]. As a result, the strength of fixed‐ended channel column exceeds that of a pin‐ended column of the same effective length [7].Using effective width for the flanges of channels e.g. according to EN 1993‐1‐5 [17] gives conservative result as the centroid of the effective section is too close to the web. The mixed effective width/effective thickness method for outstand elements given in Annex D of EN 1993‐1‐3 [16] is the basis in the following interpretations.

Seismic Behavior Prediction of Flanged Unreinforced Masonry (FURM) Walls

In most available studies, unreinforced masonry (URM) walls are idealized as rectangular sections, while in reality walls have effective sectional shapes such as C, I, T, and L. In this article, the results of experimental and analytical assessment of flange effects on the behavior of I- and C-shaped URM walls are reported. Four clay brick walls at half scale were tested. Two specimens were designed with I- and C-shaped sections, and for comparison, two additional specimens were designed without flanges. The tests showed that under constant axial load the strength of the I-shaped wall increases, but that of the C-shaped wall decreases, because of out-of-plane distortion effects. Despite the loss of strength, both flanged walls indicated almost similar initial stiffness, deformation capacity, and mode of failure in comparison with walls without flanges. A mixed-mode analytical model is proposed to predict the lateral force displacement curve of flanged URM (FURM) walls. The proposed analytical model is based on section analysis of the walls and shows good agreement with previous experimental results.

On the shear centre in Saint-Venant beam theory

The notion of shear centre in Saint-Venant beam theory was introduced by Robert Maillart who envisaged it to explain the results of experimental tests on beams with C-shaped sections. In literature, the location of the shear centre is provided in terms of flexure functions. The new result is a formula for the shear centre, based on the knowledge of the sole twist warping function of the cross-section.

2-Seam 냉간성형 각형 CFT 기둥-보 내다이아프램 접합부의 구조성능에 관한 연구

The construction of a moment connection for a rectangular hollow section (RHS) column and a H-shaped beam is difficult because the RHS is a closed section. When a inner diaphragm is used for such a connection, in general, it is installed after cutting the HSS columns, which results in increased construction work. This paper suggests a new fabrication method to overcome such problems: An inner diaphragm is welded to inside a C-shaped section first, and then a column is fabricated by welding two C-shaped sections. This fabrication method is superior to a classic method in terms of constructibility. An experimental and a numerical study using Ansys 9.0 were performed in order to compare the strength of connections with respect to the presence of concrete, the corner shape of diaphragm, and the axis of loading. The experimental results including initial stiffness and ultimate loads are reported and the analytical results including load transfer mechanism, degree of stress concentration, and strain distribution are also reported.

Better connection details for strap-braced CFS stud walls in seismic regions

Buildings composed of cold-formed steel (CFS) framing systems have become popular in many parts of the world. Light-gauge CFS frames can be built up from C-shaped sections and laterally braced with tension-only thin strap members. Recent research has raised many concerns about the lateral performance of these light wall systems in regions of high seismic activity. This paper focuses on the failure modes of different systems and on the main factors contributing to the ductile response of the CFS walls. The aim is to ensure that the diagonal straps yield and respond plastically with a significant drift, thereby preventing any risk of brittle failure such as connection failure or column buckling. Several superior connection details are then proposed, which provide a reliable lateral performance even in large lateral deformations by using perforated straps and/or bracket members in four corners of the wall. Performance of the proposed systems is evaluated by experimental tests on full-scale 2.4 m×2.4 m and 1.2 m×2.4 m specimens under a particular cyclic load regime. Method B of ASTM E2126-05 standard was selected as lateral loading regime, which introduces a progressively increasing cyclic loading with two stabilized cycles at each displacement amplitude. In order to maximize the precision of the result, each specimen was connected to the testing rig by high strength bolt. The tests showed that all of the new proposed systems can provide reliable response with good ductility and maintain their lateral and vertical load-bearing abilities up to a relative lateral displacements of 3.3%, which was the limit of the testing rig.

Recent research and developments in cold-formed steel framing

Recent research studies at the University of Missouri-Rolla (UMR) have focused on developing a better understanding of the behavior of cold-formed steel members and truss assemblies. This research was initiated by the more widespread use of cold-formed steel in the residential construction market, and the need to provide structurally reliable, as well as highly economical design solutions. Steel trusses are commonly assembled using C-shaped sections and self-drilling screws. Based on UMR findings, appropriate design recommendations have been proposed for the web and chord members of a truss. Also of concern is the introduction of large holes in the webs of floor joists. To assess the effect of the web opening, a multi-phased research effort has recently been concluded. This paper summarizes the UMR studies, and the suggested design recommendations.