Hat Section Research Articles

Plastic Mechanism Models for use in DSM Localised Loading Design of Hat Sections

The Direct Strength Method (DSM) of design has been recently developed for the design of cold-formed steel members under localised loading. The method requires a yield load (Py) and an elastic buckling load (Pcr) as input variables to the DSM design equations. This paper summarises test results used to develop plastic mechanism models for calculating Py for hat sections subject to practical loading cases. All four loading cases, including Interior Two Flange (ITF), End Two Flange (ETF), Interior One Flange (IOF) and End One Flange (EOF) loading cases were investigated. The yield/plastic mechanism behaviour of multiple web sections is not yet fully understood, while several publications in the literature have discussed the mechanical behaviour of hat sections under localised loading. Hence, this paper explains and proposes a plastic mechanism model based on the experimental data for calculating the yield load (Py) to be used in the DSM for localised loading design of hat sections in conjunction with the elastic buckling load Pcr.

Moment capacity of cold-formed steel trusses with Howick Rivet Connectors: Tests, modelling and design

Cold-formed steel (CFS) trusses are increasingly used in lightweight building construction. A new type of pin-jointed connector, known as the Howick Rivet Connectors (HRCs), has been developed for CFS trusses. Previous studies focused on testing T-stub connections and shear strengths of CFS trusses with HRCs, providing insights into their structural performance and shear capacity. This paper extends the research by testing ten new CFS trusses with HRCs to determine their moment capacity. The study involved two different cross-sections: lipped channel sections and hat sections, used as truss chords. Variations in the number and locations of lateral supports were introduced to simulate different boundary conditions. A parametric study explored the effects of span-height ratio and variability in lateral support locations on truss strength and failure modes. Finally, the trusses with lipped section chords were designed according to the American Iron and Steel Institute (AISI 2016) and Australia/New Zealand standards (AS/NZS 2018), achieving an average test-to-design strength ratio of 0.86.

Investigation on bending collapse behavior of similar and dissimilar Aluminum-Steel hat-section sandwich beams jointed by structural adhesive: An experimental, numerical and theoretical study

A significant feature about the application of adhesive joints in various structures is their ability to join dissimilar materials, thus effectively maintaining the structural integrity regardless varying loads. In this paper, the bending collapse behavior of adhesively bonded hat section sandwich beam (HSSB) structures with using of aluminum and steel were investigated. Four configurations of HSSB with different materials for the upper hat beam and lower plate were subjected to quasi-static three-point bending tests as part of the experimental investigation. In comparing the specific absorbed energy (SEA) of the beams, a sample of a hat section sandwich beam with a steel upper hat and an aluminum lower plate had a higher SEA value despite the load-displacement and bending collapse behavior similar to the hat section sandwich beam with a steel upper hat and a steel lower plate. subsequently, a finite element model was developed for bending collapse analysis and a theoretical prediction based on the Kecman model was presented to investigate the hinge moment on HSSB. Based on this, the findings of the numerical study and the predicted theoretical model were in good agreement with the experimental results. The effect of adhesive thickness, the identical mass, and the thickness of the upper hat and lower plate were examined for the purpose of performing an in-depth analysis of the influencing parameters in HSSB structures.

Experimental and numerical investigation on the crashworthiness performance of double hat‐section Al‐CFRP beam subjected to quasi‐static bending test

AbstractNowadays, hybrid structures, which combine low‐density composites with low‐cost thin‐walled metals, have shown great effect in enhancing the performance of automotive body structures, especially the energy absorber components. This study focuses on the experimental and numerical investigation of the bending energy absorption behavior of CFRP/aluminum hybrid double hat‐section beams used in the side part of the car body. In the experimental section, two types of double hat‐section beams were fabricated: aluminum and Al/CFRP. These beams were then subjected to quasi‐static three‐point bending tests. The results demonstrated that the hybrid beam exhibited superior energy absorption capabilities compared to the single beam. Subsequently, a finite element model was developed using LS‐Dyna software and was validated by comparing the experimental and numerical load–displacement results. In‐depth numerical analyses were conducted to investigate the influence of various design parameters, including CFRP‐reinforcement configuration, numbers of CFRP layers, CFRP ply‐angle, CFRP reinforced length, and aluminum/CFRP mass, on crashworthiness indicators. The numerical findings indicate that the hybrid beam with , ply‐angles exhibited better crash force efficiency (CFE) and specific energy absorption (SEA) compared to other ply‐angles, respectively. Furthermore, increasing the number of CFRP layers within the total beam's mass improved its energy absorption capacity. It was also revealed that the CFRP length on the upper and lower hats could be considered as 42.5% of the total aluminum beam length, as opposed to the full CFRP length, providing enhanced energy absorption capabilities.Highlights Bending behavior of the Al and Al/CFRP double hat section beams. Effects of variable thickness and identical mass on the double hat section beam. Effects of variable ply angle and number of CFRP layers on the hybrid beams. Discrete effect of CFRP reinforcement configurations and inner CFRP lengths.

Experimental study and numerical modelling of a novel two-way steel-concrete composite slab

This study proposes a new innovative two-way steel-concrete composite slab system. The experimental work investigates the structural capacity, shear behaviour and two-way load distribution of the proposed composite slabs consisting of a new profiled steel deck and concrete. The innovative deck is developed by providing 90° bends in corrugated steel sheets to form hat sections, which then are placed on a corrugated base sheet in the perpendicular direction. Five composite slabs were tested under uniform loading, in which three slabs contained shear studs, and the remaining two were tested without shear studs. The slabs failed by flexural failure and shear bond failure, and the composite slabs with and without studs showed comparable load-carrying capacity and two-way action. The unique geometry of the deck profile provides good longitudinal shear capacity in the main direction. The slip is absent in the main longitudinal direction of the slab due to the corrugated top-hats. The provided shear studs further complement the role of the top-hats by resisting interface shear failure in the perpendicular direction. Therefore, the new deck type can be used effectively in two-way composite slabs for shear and load capacity by reducing the quantity of additional shear connectors, which is a significant advantage of the proposed deck compared to conventional deck types. A finite element (FE) model of the composite slabs with and without shear connectors is developed and validated against the experimental results and then used to investigate the slab's performance in two-way load distribution.

Elastic critical local buckling stress in cold-formed lipped channel and hat sections under uniform compression

The classical design approach for the elastic critical local buckling load of the cold-formed open section (CFOS) neglects the plate element interaction at the cross-section, which compromises the benefits of CFOSs designed for high performance. To derive a novel formula for the local buckling coefficient, taking into account the plate element interaction at the cross-section, a series of displacement functions for expressing the buckling deformations of the web, flanges, and lips caused by local buckling in CFOSs is proposed in this paper. The effect of cross-sectional geometry on the buckling coefficient was investigated using the proposed formula derived from Timoshenko’s plate buckling theory. Further, simplified formulae were proposed for the buckling coefficient and half wavelength of the elastic critical local buckling for practical use. The reliabilities of the proposed formulae were verified by comparing the results obtained from the proposed formulae with the analysis results based on the finite element method and finite strip method.

An experimental and numerical study on the behaviors of adhesively-bonded steel double-hat section components under axial impact loading

A significant consideration in the deployment of adhesively-bonded joints in applications such as automotive body structures is their performance under impact loading. Due to the distinct behaviors of an epoxy-based structural adhesive under normal and shear loads combined with its propensity to undergo brittle fracture in cohesion and adhesion, special care needs to be taken in the constitutive modeling of such an adhesive as traditional Von Mises type yielding and elastoplastic material behavior do not seem to be applicable. In the current study, to start with, experimental load-displacement behaviors till failure of single lap shear and T-peel joints with steel substrates are predicted with the aid of a cohesive zone material model using LS-DYNA, an explicit nonlinear finite element analysis solver. With confidence established on cohesive zone modeling of the joints mentioned, the procedure is extended to robust prediction of the load-displacement responses and deformed shapes of steel double-hat section components subjected to axial impact loading. Three variants of steel hat section components have been considered from the viewpoint of joining of flanges with conventional discrete spot-welds, only continuous adhesive bonding, and a hybrid configuration with a combination of adhesive bonding and sparse spot-welds. The study reported here provides insights into mechanical behaviors of adhesively-bonded steel double-hat sections under impact loading, and demonstrates an efficient finite element modeling approach for adhesively-bonded steel hat sections using cohesive zone elements with fracture mechanics-based criteria for failure.

Experimental investigation of CFRP-AA structures joined by ultrasonic additive manufacturing (UAM) and resistance spot welding (RSW)

Implementation of carbon fiber reinforced polymer (CFRP) composites in vehicle structures requires improved CFRP-metal joints. Aluminum alloy (AA) is joined to CFRP using ultrasonic additive manufacturing (UAM). To quantify the mechanical performance of UAM CFRP-AA joints, top-hat and double-hat CFRP-AA hybrid structures are prepared by joining aluminum flanges of CFRP hat sections to AA sheet or to another CFRP hat using resistance spot welding (RSW). Top-hat structures are tested in four-point bending; double-hat structures are tested in dynamic axial crush and quasi-static torsion. The structures with UAM CFRP-AA joints achieve higher energy absorption efficiency than the benchmark in all test modalities.

Experimental investigation on post-flexural–torsional buckling strength of CFS compression members

Recent studies have indicated that cold-formed steel (CFS) members could have strength above the global elastic flexural–torsional buckling (FTB) load. No test result demonstrating the post-buckling strength of channel compression members undergoing only FTB before failure is reported in the literature. Test results on a total of 25 CFS specimens, which included 19 channels (hat section, lipped channel, and plain channel) and 6 angles which experience only FTB under axial compression, carried out in this study, are presented. The interaction of other modes (flexural, local, and distortional) with FTB, which may reduce the ultimate strength of the member, was eliminated in this study by choosing the geometry of test specimens having elastic FTB load much smaller than the elastic buckling loads corresponding to other modes. The global buckling strength equations in the design standards and the modified equations reported in the literature are evaluated using the results generated in this study. The modified procedures proposed by Dinis et al. (2020), and Dinis and Camotim (2019) are found to be the most accurate for channel and angle compression members failing under FTB mode, respectively.

Numerical Investigation on Structural Behaviour of Cold Formed Steel Double Channel Hat Section with Two Plates

Numerical Investigation on Structural Behaviour of Cold Formed Steel Double Channel Hat Section with Two Plates

Friction stir lap joining techniques effects on microstructure and tensile properties of high-strength automotive steel top hat sections

Dual Phase (DP) steel, a type of Advanced High Strength Steel (AHSS) with a thickness of 1.7 mm, is used to fabricate single-hat components that are then joined to the base plate using two friction stir welding processes: friction stir lap welding (FSLW) and friction stir spot lap welding (FSSLW). It is difficult to join this assembly using fusion welding techniques. The welding variables for the FSLW process, tool rotation speed (TRS), tool traverse speed (TTS), and plunge depth (PD), were optimized using the design of an experiments-based response surface method by experimentally measured tensile shear failure load (TFL) of top hat assembly. For the FSSLW process, the welding variable TTS was replaced by dwell time (DT). Peak temperature, microstructure at different zones, microhardness mapping, and energy absorption capacity of both processes were evaluated under optimal welding conditions. For both processes, the stir zone and the heat-affected zone had the highest and lowest microhardness, which can be correlated with the level of martensite tempering, martensite lath spacing, polygonal ferrite volume, and precipitated carbides. Under optimum welding conditions, the TSL and energy absorption of FSLW joints were 14 kN and 170 J, respectively, which is 20% and 47 higher than the TSL and energy absorption of FSSLW joints.

Experiment on the Flexural Functioning of Cold-Formed Steel Built-Up Complex Hat Section

Abstract: Cold-formed steel members are comprehensively utilized in the building construction industry, especially in residential, commercial, and industrial buildings. Thin sheet steel products are widely noticed in the building industry and range from purlins to roof sheeting and floor decking. Generally, these are used for basic building elements for the congregation at the site or as prefabricated frames or panels. They obtained the generic title ‘ Cold-Formed Steel Sections. The uses of these products are many and varied, ranging from “tin” cans to structural piling, from keyboard switches to mainframe building members. This paper dispenses an experimental and software analysis of the flexural behavior of cold-formed steel built-up sections. The experimental results are also verified with finite element analysis using Manual Designs and ANSYS Software. The analytical results obtained are better exposure to the experimental results.

Parametric finite element study of novel corrugated steel deck for two-way action in steel-concrete composite floors

Composite construction using steel and concrete is a widely adopted flooring construction technique. Past literature has reported ample research in the development of composite one-way slabs. However, there is a lack of understanding of two-way action in these composite slabs. It has prevented the applicability of two-way steel-concrete composite slabs in floor construction. The performance of a novel deck composed of corrugated hat sections placed orthogonally at equal spacing on a corrugated base sheet has been investigated for achieving two-way action in steel-concrete composite slab construction. Non-linear finite element (FE) models were developed and researched for feasibility in two-way action using the commercial FE package ABAQUS. The decks were analyzed in the construction stage, that is, in the absence of concrete, to isolate the properties of the new steel deck. Various parameters such as depth and spacing of hat section, angle of hat section webs and aspect ratio of the decks were investigated to establish a suitable configuration for two-way action. The effect of the parameters on the load-deflection relationship and distribution of load in two directions were studied to optimize the two-way action. Decks were also analyzed for one-way action to benchmark the change in behavior of the corresponding two-way decks. Obtained numerical results showed that the proposed corrugated deck is efficient in two-way action and could be adopted in two-way steel-concrete composite slabs. The distribution of loads in both directions improved with a decrease in hat-section spacing but increased aspect ratio and depth.

Linear, nonlinear and post buckling analysis of a stiffened panel with cutouts

Stiffeners are typically used to strengthen structures that rely on plates for load bearing. Such structures are subjected to various kinds of in-plane and out-of-plane loading over its lifespan. Furthermore, cutouts in aerospace structures are considered for practical and design reasons. In the present paper, finite element method is used for the analysis of a flat rectangular stiffened plate. Static analysis is performed on three panels with different stiffener cross sections (I section, hat section and rectangular section), and the panel with the least deformation and stress is chosen for further buckling analysis. Linear, non-linear and post buckling analysis of the selected stiffened panel under in-plane compression is carried out and its load and end – shortening response is evaluated till collapse. Furthermore, the effect of rectangular and circular central cutouts on the buckling behaviour of the stiffened panel is investigated. By varying the dimensions of the cutouts, a parametric study on buckling and ultimate collapse strength is performed. The study takes into account an aluminium alloy with isotropic material properties and a carbon fibre reinforced polymer (CFRP) with orthotropic material properties.

Formability of roll-formed carbon fibre reinforced metal hybrid components and its experimental validation

Carbon Fibre Reinforced Metal Hybrid (CFRMH) materials that combine a sheet metal substrate with a reinforcing carbon fibre patch represent a promising solution to reduce weight while increasing the structural and crash performance of future automotive vehicles. CFRMHs cannot be formed with conventional stamping processes and at high volumes. This currently reduces their widespread application. Roll forming is increasingly used in the automobile industry for the forming of lightweight and high-strength metal structural components. The major deformation mode in roll forming is simple bending and this reduces interlaminar shear and compressive stresses that lead to fibre failure and delamination issues when stamping CFRMH sheet materials. This work analyses the potential of applying the conventional roll forming process for the manufacture of a simple top hat section shape from CFRMH sheet. For this, first, the material is produced in a hot press and then formed to shape in a laboratory roll forming facility at room temperature. Different layup sequences are tested, and component quality is analysed after roll forming by visual inspection. The results suggest that roll forming presents a promising manufacturing method for the production of automotive components from CFRMH sheets. The roll formed open shells are joined to produce crash box structure and tested in 3-point bending. The results show that depending on the fibre orientation a significant increase in weight specific strength is achieved.

Experimental and Analytical Investigation of Axial Compression Behavior of Hat Section Stiffener Composed of Discontinuous Carbon Fiber Reinforced Thermoplastic Composites Stiffened using Thermoplastic Matrix Prepreg

Experimental and Analytical Investigation of Axial Compression Behavior of Hat Section Stiffener Composed of Discontinuous Carbon Fiber Reinforced Thermoplastic Composites Stiffened using Thermoplastic Matrix Prepreg

Tests and Finite Element Modelling of Cold-Formed Steel Zed and Hat Section Columns Under Axial Compression

Tests and Finite Element Modelling of Cold-Formed Steel Zed and Hat Section Columns Under Axial Compression

A Sequential Approach for Simulation of Thermoforming and Squeeze Flow of Glass Mat Thermoplastics

In this study, a sequential thermoforming and squeeze flow simulation approach for Glass Mat Thermoplastic (GMT) material is proposed and applied to a hat section geometry using input properties based upon Tepex flowcore, a long glass fiber reinforced polyamide (PA/GF) mat manufactured by Lanxess. First, a fully-coupled thermomechanical simulation is conducted based on a purely Lagrangian description, to efficiently capture thermoforming. Subsequently, relevant state variables are mapped and initialized for a Coupled-Eulerian-Lagrangian (CEL) approach. The CEL approach is adopted to accurately capture squeeze flow, which is not possible by a purely Lagrangian description. While numerical techniques differ, both approaches use the same three-dimensional and thermomechanical constitutive equations including an equation of state, a nonlinear viscosity model, and crystallization kinetics, implemented through a material user-subroutine (VUMAT) for the commercially available simulation software package ABAQUS/Explicit.

Analysis of the crushing behaviors of woven carbon fiber reinforced plastic hat section component under dynamic bending and axial crushing loading

In current work, the crashworthiness of woven carbon fiber reinforced plastic (CFRP) hat section component is investigated under two types of loading experimentally and numerically, i.e., axial crushing and dynamic three-point bending. The crushing characteristics of woven CFRP hat section sample are evaluated at various impact velocities and layup orientations which exhibit different effects under two types of loading. With impact velocity/energy increasing, the bending behaviors illustrate different evolutions with distinct stages which are affected by the damage development. Layup orientation shows a little effect on the bending behaviors, while it exerts remarkable effects on the axial crushing which leads to different crushing modes and thus different energy absorption capabilities. The finite element model with multiple layers of thick shell element and cohesive element is shown to capture the crushing behaviors reasonably well in both axial crushing and dynamic bending. The corresponding damage evolutions are also analyzed with simulations to explain the crushing behaviors.

Numerical modeling of mechanical properties of UAM reinforced aluminum hat sections for automotive applications

Structural lightweighting is a key initiative in the automotive sector due to regulatory, customer, and powertrain demands. This research focuses on reinforcing aluminum sheet metal in strategic locations using ultrasonic additive manufacturing (UAM), as guided through an iterative optimization and simulation process. Among the three models used, the most successful is the multi-step model (MSM) which simulates the forming of tailored blanks and the unloading processes to accurately map the hardening and the residual stress in hat and reinforcement sections. The MSM shows that approximately 65% of the mass can be saved by replacing a large gauged sheet metal hat section with a discretely reinforced hat section. Further increases in specific energy absorption (SEA) and additional mass savings can be expected when utilizing higher specific strength and specific stiffness materials for reinforcement such as titanium alloys, composites, or ceramic materials, all of which have been demonstrated with UAM.