Steel Sandwich Research Articles

Ultimate strength of steel–concrete–steel sandwich panels under lateral pressure loading

The response behavior of steel–concrete–steel (SCS) sandwich panels without shear connectors was experimentally studied under lateral pressure loading in this paper. The loading was applied by a hydraulic actuator on an inflated airbag to assert lateral pressure on the SCS panels. The failure modes and maximum resistance of the SCS panels were obtained from the test and compared with the numerical analysis results. It was found from the experimental and numerical studies that the end plates could function as shear connectors to achieve the composite action between face plates and concrete core. Based on the experimental and numerical observations, the formulae to predict the bending resistance and transverse shear resistance of SCS panel without shear connectors were developed and the accuracy of the proposed formulae was verified by comparing with the experimental and numerical results.

Punching shear behavior of steel–concrete–steel sandwich composite plate under patch loads

This paper studied the structural behaviors of steel–concrete–steel sandwich composite plates under patch loads. Ten SCS sandwich plates, adopting an ultra-lightweight cement composite (ULCC) and overlapped headed studs as the bonding measures at the steel–concrete interface, were simply supported and subjected to patch loads till failure. The investigated parameters included spacing of the connectors, strength of the ULCC core, thickness of the steel skin, volume fraction of the fiber, and depth of the cross section. Test results estimated the size of the punching cone and showed that load-defection behaviors of the SCS sandwich plate contained five stages. The influences of the different parameters have been discussed and analyzed. Analytical models have been developed to predict the ultimate resistances of the SCS sandwich plate under patch loads through modifying the code equations. These innovations and modifications included developing models to predict the tensile resistance of the connectors, incorporating the contribution of the top steel skin on the punching shear resistance, consideration of the tensile resistance of the connectors on the second peak resistance of the structure, and adopting a proper critical perimeter. The validations of the predictions against the test results showed that the code provisions overestimated ultimate resistances of the SCS sandwich plates and the developed analytical models offered reasonably good agreements. Design recommendations were finally given based on these validations and discussions.

Eigenfrequency analyses of laser-welded web–core sandwich panels

A web–core steel sandwich panel is a lightweight structure where thin plates are welded together by laser-welding technique. The plates form a T-joint which has in the center a weld thinner than the plates themselves. Thus the rotational stiffness of the joint is not infinite. The paper investigates the influence of T-joint rotational stiffness on the lowest natural vibration frequency of the panel. The methods used in the study have different kinematic assumptions. Equivalent single-layer (ESL) theory is used to obtain the frequency of the global vibration. The local vibrations are predicted using an isolated part of the panel, the I-beam model. In addition, three-dimensional model of a sandwich panel is analyzed. Finite element method (FEM) and analytical solution are used to obtain the frequencies. First-order shear deformation theory (FSDT) is used. The joint is considered through its rotational stiffness whose quantitative values are presented in the literature. Four different cross-sections with industrial relevancy are considered. The rotational stiffness of the T-joint affects the transverse shear stiffness of the panels. The results show up to 22% reduction of the fundamental frequency when compared with the case of the rigid joint for the global vibration mode. The effect on local vibrations is up to 11% in the case of asymmetric rotation in the T-joint and is otherwise insignificant. The study furthermore outlined the limitations of the ESL approach for assessment of natural frequencies in web–core sandwich panels depending on the vibration mode shape. The results show that the rotational stiffness of the T-joint has to be considered in the conceptual design of these structures.

Experimental study on shear performance of steel–concrete–steel sandwich beams

This paper studies the shear performance of steel–concrete–steel (SCS) sandwich slender beams inter-connected with round steel bars and headed studs. Nine beams with shear span/depth ratio from 2.5 to 3.5 were tested under static loads. Other experimental parameters include the diameter and spacing of the vertical tie bars and stud connectors. All beams failed by vertical shear with the failure patterns differing slightly due to stud arrangement and shear reinforcement ratios. Test results show that the shear resistance after critical cracking is dependent on the strength of vertical reinforcement, steel plate and stud connectors. Based on the observed failure modes, an analytical expression is derived for the shear resistance after critical cracking. The mechanical model considers the contribution of the vertical reinforcement and the dowel resistance resulting from the composite action between the steel plate and concrete. The stud spacing value is recommended to maintain a full composite behavior in shear span, and if it is exceeded, the dowel action should be revised accordingly. Accuracy of the proposed method is ascertained by comparing with the test results.

Experimental and analytical studies of curved steel–concrete–steel sandwich panels under patch loads

The paper proposes a novel curved steel–concrete–steel (SCS) sandwich panel for Arctic offshore platform to resist the ice loads due to ice floes in Arctic region. The SCS sandwich panel consists of two curved steel plates infilled with a type of novel ultra-lightweight cement composite (ULCC) with a compressive strength of 60MPa and a density less than 1400kg/m3. Headed shear studs working in pairs with overlapped lengths are used to achieve composite action between the core material and steel face plates. This paper investigates the performance of curved SCS sandwich composite panel experimentally and analytically. Ten quasi-static tests on the curved sandwich composite panels subjected to patch loads are carried out to explore their failure modes, ultimate strength and load–defection behaviour. The main failure modes of the tests are identified as flexural failure, diagonal concrete strut crushing and shear tension failure. Based on the failure mechanism, a unified deep beam model is constructed to estimate the shear resistance of flat and curved SCS sandwich panels by considering equilibrium status, material yielding criteria and boundary conditions. The validations show that the modified model can provide close and conservative estimations on shear resistance for SCS sandwich composite panel.

Steel–concrete–steel sandwich system in Arctic offshore structure: Materials, experiments, and design

The gravity based structure (GBS) with external Steel–Concrete–Steel (SCS) sandwich ice-resistant wall has been developed for the Arctic oil and gas drilling. This paper firstly reported the experimental studies on the mechanical properties of steel and concretes under Arctic low temperature. With the test data, design equations were developed to incorporate the influences of the low temperature on these mechanical properties. Two types of Arctic GBS structure with flower-conical SCS sandwich shell type and plate type of ice-resistant wall have been developed for the Arctic offshore structure. Besides the studies on the materials, two SCS sandwich prototype shells and plates were, respectively, prepared and tested under patch loading that simulated the localized ice-contact pressure. The structural behaviors of the SCS sandwich structure under patch loading were reported and discussions were made on the influences of different parameters on the structural behavior of the structure. Analytical models were developed to predict the punching shear resistances of the SCS sandwich structure through modifying the code provisions. The accuracies of the developed analytical models were checked through validations against 27 tests in the literature. Corresponding design procedures on resistances of SCS sandwich structure were recommended based on these discussions and validations.

Non-linear Dynamic Analysis of Steel Hollow I-core Sandwich Panel under Air Blast Loading

In this paper, the non-linear dynamic response of novel steel sandwich panel with hollow I-core subjected to blast loading was studied. Special emphasis is placed on the evaluation of midpoint displacements and energy dissipation of the models. Several parameters such as boundary conditions, strain rate, mesh dependency and asymmetrical loading are considered in this study. The material and geometric non-linearities are also considered in the numerical simulation. The results obtained are compared with available experimental data to verify the developed FE model. Modeling techniques are described in detail. According to the results, sandwich panels with hollow I-core allowed more plastic deformation and energy dissipation and less midpoint displacement than conventional I-core sandwich panels and also equivalent solid plate with the same weight and material.

Damping strategies for steel lattice sandwich constructions

A square steel sandwich plate with lattice corrugated core is explored for damping improvement. A range of damping materials are filled inside the openings provided by the corrugated core, or are applied on the surfaces of the facesheets. The dynamic properties such as natural frequency and damping factor are experimentally measured for the sandwich plate with each filling solution. The relative performance of each insertion is compared in terms of damping capacity and added mass.

Structural behaviour of steel–concrete–steel sandwich composite wall subjected to compression and end moment

Steel–concrete–steel (SCS) sandwich wall infilled with ultra-lightweight cement composite has been developed and proposed for applications in offshore and building constructions. A new form of J-hook connector is introduced to connect the external plates to improve the composite action between the steel face plates and cement composite core to form an integrated unit which is capable of resisting extreme loads. This research experimentally investigates the structural behaviour of SCS sandwich composite wall based on a series of combined compression and uniaxial bending tests on short SCS sandwich composite wall with interlocking J-hook connectors. From the tests, it is found that the SCS sandwich wall exhibits good ductility behaviour with a bending failure mode. Nonlinear finite element (FE) model is also developed to simulate the mechanical behaviour of sandwich wall in terms of ultimate strength and load-deflection curves. Analytical studies show that the N–M interaction model based on Eurocode 4 may over-predict the combined resistance of the SCS sandwich walls subjected to eccentric compression. Therefore, a new approach is proposed to evaluate the resistance of sandwich wall. The axial force versus moment capacity interaction diagrams of sandwich wall are calculated. The validation against the test and FE results shows a reasonable and conservative estimation on the combined resistance of SCS sandwich wall.

Tool for life cycle analysis of facade-systems for industrial buildings

Minimal investment cost, flexibility and expandability of the construction have been the highest priorities in the design of industrial facilities. With the sharpening of building codes and the upcoming polices on energy efficiency, life cycle optimisation is starting to gain importance among industrial investors. On the case study of an energy efficient industrial facility, a decision-support tool was developed for analysing life cycle economic and environmental impacts of facade-systems. The tool was tested by analysing three different facade-systems (steel liner tray, steel sandwich panels, cross laminated timber panels) of the proposed building model. The construction cost of the tested facade-systems are largely differing (up to 27%), however after a period of 35 years, the life cycle costs are diverging by only 6%. In terms of ecology (Global Warming Potential) the cross laminated timber facade, with the highest initial costs, features the best performance by 80% less emissions. The test underlines the large impact the design stage has on the life cycle performance, when determining facade elements and shading concepts. The tool has large implementation potential as a relatively easily applicable decision-support instrument for designers and investors, when studying and determining sustainable construction and facade systems; thus improving the traditional decision-making process, still based on the choice of the lowest costing construction.

Ultimate strength behavior of curved steel–concrete–steel sandwich composite beams

A concept of using curved steel–concrete–steel (SCS) sandwich structure as the ice-resistant wall has been proposed for Arctic oil and gas drilling platform. In the developed curved SCS sandwich structure, ultra-lightweight cement composite (ULCC) and overlapped headed studs were used as the core material and bonding measures at the steel-concrete interface, respectively. In this paper, quasi-static tests on ten curved SCS sandwich beams have been carried out to investigate their ultimate strength behaviors under patch loading that considers the critical local ice-contact pressure. The test results reported the failure mode and shear resistances of structures, studied the influences of thickness of the steel skin shell, curvature, spacing of the connectors, depth of the cross section, strength of core materials, and boundary conditions on the ultimate strength behavior of the curved SCS sandwich beam. Extensive discussions and analysis were also carried out to provide information for the development of the analytical models. Analytical models were developed through modifying design code provisions. These innovative modifications in the analytical models included redefining the inclination angle of shear failure surface, redefining the effective depth of the section, considering the influence of the thickness of steel skin, and developing analytical models on tensile resistance of the overlapped headed studs. The accuracy of the predictions by the analytical models was checked by the test data. All these efforts were made to provide better predictions on the shear resistance of the curved SCS sandwich beam.

Measuring and modelling of linear water vapour transmittance of steel sandwich panels with mineral wool

AbstractNowadays the measurement of water vapour diffusion resistance factor of building components is performed according to EN ISO 12572 or EN 12086. Both these standards use cup methods. However, measuring vapour transmission in this way by means of linear or point water vapour bridges would be difficult because of the limited sample size and shape. Therefore in this study water vapour pressure equipment with twin chambers, according to the old Slovenian standard JUS U.J5.024 standard were used, enhanced with a guard chamber. 15 cm thick sandwich panels composed of 2 steel sheets with a mineral wool core and 5 types of joints were measured. The type of sealant used between the steel sheets (outer and inner pair) and mineral wool differs: without it, with a PUR or with an EPDM sealant. Due to the slow process of water vapour diffusion through such panels, measurements were stopped well before steady state was reached. Experimental results were modelled to obtain linear water vapour transmittance. Our modelling function contains 2 fit‐parameters. Due to the vapour‐guard, final results improve systematically. Modelling procedure works on panels, which are faster than standardised steady‐state ones.Messung und Simulation der linearen Wasserdampftransmission durch Stahl‐Sandwichpaneele mit Mineralwolledämmung. Die Messung des Wasserdampfdiffusions‐Durchlasskoeffizienten von Baukomponenten erfolgt nach EN ISO 12572 oder EN 12086. Beide Verfahren arbeiten mit Probenschalen. Die Messung der Dampftransmission auf diese Weise mittels linearer oder punktueller Wasserdampfbrücken ist aufgrund der Einschränkungen der Probengröße und ‐form jedoch schwierig. Deshalb wurde in der vorliegenden Studie ein 2‐Kammern‐Wasserdampfdruck‐Versuchsaufbau nach der alten Norm JUS U.J5.024 verwendet und mit einer Abschirmkammer verbessert. Gemessen wurden 15 cm starke Sandwichpaneelen bestehend aus 2 Stahlblechen mit MW‐Kern und 5 Arten von Fugen. Es wurden unterschiedliche Arten von Dichtstoffen zwischen den Stahlblechen (äußeres und inneres Paar) und der Mineralwolle verwendet: ohne Dichtstoff, mit einem PUR‐ oder mit einem EPDM‐Dichtstoff. Aufgrund des langsamen Voranschreitens der Wasserdampfdiffusion durch derartige Paneelen wurden die Messungen lange vor Erreichen des stabilen Zustands beendet. Die Ergebnisse des Experiments wurden simuliert, um die lineare Wasserdampftransmission zu erhalten. Unsere Simulationsfunktion enthält 2 Fit‐Parameter. Die Dampfabschirmung sorgt für eine systematische Verbesserung des Endergebnisses. Das Simulationsverfahren arbeitet mit Paneelen und ist hierdurch schneller als das Normverfahren im stationären Zustand.

Lumped models for transient thermal analysis of multilayered composite pipeline with active heating

In this study, improved lumped parameter models were proposed for transient thermal analysis of multilayered composite pipeline with active heating, which is essential for flow assurance design and operating strategies of deepwater subsea pipelines. Improved lumped models for transient heat conduction in multilayered composite pipelines were based on two-points Hermite approximations for integrals. The transient energy equation for the bulk temperature of the produced fluid was transformed into a set of ordinary differential equations in time by using a finite difference method. The coupled system of ordinary differential equations for average temperatures in the solids and bulk temperature of the fluid at each longitudinal discretization point along the pipeline was solved by using an ODE solver. With the proposed method, we analyzed the transient heat transfer in stainless steel-polypropylene-stainless steel sandwich pipes (SP) with active electrical heating. Convergence behaviors of the average temperature of each layer and the bulk temperature of the produced fluid calculated by using the improved lumped models (H0,0/H1,1 and H1,1/H1,1 approximations) against the number of grid points along the pipelines were presented. Case studies were performed to investigate the effect of the linear rate of power input and the average velocity on the bulk temperature distribution of the produced fluid.

Lightweight steel–concrete–steel sandwich composite shell subject to punching shear

The development of Arctic oil and gas fields requires high strength structures that can resist critical loads in extreme environment. A novel conical caisson structure constructed by lightweight steel–concrete–steel (SCS) sandwich shell is proposed for withstanding ice pressure imposed thereon by impinging sheet ice in Arctic region. This paper mainly investigates the ultimate strength behaviour of SCS sandwich shell experimentally and analytically. Two pilot quasi-static tests on the lightweight SCS sandwich composite shells subject to patch loading are carried out. The failure mode of composite shell is punching shear. Tests show that the punching shear resistance depends on the control perimeter of punched concrete frustum and shear connectors. The membrane action of the outer steel plates provides post-hardening strength. On the basis of the experimental failure mechanism, an analytical model is developed to explain the force transfer mechanism and predict the punching shear resistance of SCS sandwich composite shell. The verification of the model shows that the predictions are in good agreement with the test results. It is also shown that the SCS sandwich shell, in accord with the ISO ice load design, is capable of resisting the localised contact and punching loads.

Experimental and numerical studies of non-composite Steel–Concrete–Steel sandwich panels under impulsive loading

Abstract The performance of non-composite Steel–Concrete–Steel (SCS) sandwich panels under impact-induced impulsive loading was experimentally and numerically studied in this paper. Two SCS sandwich panels with different core depths were tested and the impulsive loading was applied in the laboratory by utilizing an inflated high pressure airbag to transfer the impact load from dropped projectile onto the panels. The deformation modes, applied pressures, displacement and strain responses of the panels were determined in the test. A combination of bending and shear deformation mode was observed in the SCS panel with thinner core while there was minimal visible deformation in the thicker panel. The maximum and permanent deformations of the panel with thicker panel were significantly reduced due to the increase in resistance and mass. Debonding between grout core and bottom plate was also noted in both panels during impact from the strain–time histories. Following the test, Finite Element (FE) models were constructed and verified against the test data to simulate the tests. It was shown in the FE analysis that the steel plates absorbed more energy due to its higher strength and ductility as compared to the grout core under the impact-induced impulsive pressure loading.

Numerical modelling of lightweight Steel‐Concrete‐Steel sandwich composite beams subjected to impact

This paper presents the numerical and analytical models to predict the response behaviour of Steel–Concrete–Steel (SCS) sandwich composite beams subjected to drop-weight impact loading. The sandwich composite beam has an ultra-lightweight concrete core of density 1440kg/m3 sandwiched between two thin steel face plates which are interconnected by J-hook connectors. Explicit nonlinear finite element analysis was carried out and the results obtained are verified against the impact test data to establish its accuracy in predicting the permanent deformation, vertical displacement–time history and impact force–time history of the sandwich beams. The numerical analysis also shows that the J-hook connectors are subjected to tension force during impact in addition to shear force due to flexural action in the beam. This signifies the important role of J-hook connectors in preventing tensile separation of the steel face plates when subjected to impact load. An analytical approach based on energy balance model was also developed to predict the impact response of SCS sandwich beams. A good agreement was observed between the analytical solution and the experimental data indicating that the approach provides a reasonable and conservative estimation of the impact resistance of the sandwich beams.

FEM modelling of stress and strain distribution in weld joints of steel sandwich panels

The development of laser welding technology has enabled the mass production of thin-walled structures, including steel sandwich panels. The technology of joining plating panels with stiffeners by welding allows us to create joints with a specific geometry and material properties. In comparison with other types of joints, laser welds are characterized by their specific behaviour under cyclic load and, as a consequence, a different model of fatigue damage. The basis of fatigue analysis of laser-welded joints was the determination of stress concentrations in the notches. For this purpose, a numerical finite element method model of a laser-welded joint was created. The article presents the main aspects of the numerical model and the results concerning the influence of the modelling method on the strain and stress distribution in the notches. For the weld root notch, the theoretical results have been compared with experimental data of strain distributions obtained by the laser extensometry grid technique.

The dynamic indentation response of sandwich panels with a corrugated or Y-frame core

The dynamic indentation response of stainless steel sandwich panels with a corrugated core or a Y-frame core has been explored using the finite element method to gain insight into the potential of the cores to mitigate against collisions over a wide range of impact velocities pertinent to land and sea-borne vehicles. Back-supported sandwich panels were impacted on the front face by a flat-bottomed or a circular punch at constant velocity ranging from quasi-static loading to 100m/s. At velocities below 10m/s the forces on the front and back faces are equal but inertia stabilisation raises the peak load above its quasi-static value. This strength elevation is greater for the corrugated core than for the Y-frame core, and more pronounced for the flat-bottomed punch than for the circular punch. For velocities greater than 10m/s, the indentation force applied to the front face exceeds the force transmitted to the back face due to plastic-shock effects. In this regime, the force transmitted to the back face by the Y-frame core is markedly less than for the corrugated core, and this brings a performance benefit to the Y-frame, i.e. it protects the underlying structure in the event of a collision.

Failure mechanism and shear strength of steel–concrete–steel sandwich deep beams

In steel–concrete–steel (SCS11SCS: steel–concrete–steel.) sandwich deep structural members the shear performance becomes rather critical. This paper describes an experimental study on the shear behavior of SCS continuous deep beams. Three beams with different shear spans were tested under anti-symmetric concentrate loads, and the failure pattern is found to be different from reinforced concrete members. Tests show that the shear capacity depends strongly on the steel plates and the shear connectors, and the membrane action of the outer steel plates provides the beams with excellent strength and ductile performance. On the basis of the experimental observations (both the continuous beam tests in this paper and the simple beam tests conducted earlier), a plastic limit analytical model is developed to explain the force transfer mechanism and predict the shear strength of both simple and continuous members. Considering equilibrium and boundary conditions, the lower bound approach shows satisfactory predictions for the shear performance of SCS deep beams.

The Influence of Modelling Material Zones on Strains and Stresses at Weld Toe Notch

The latest development in the field of welding technology enabled prefabrication of thinwalled sandwich structures in an industrial scale. Sandwich structures fabricated of steel, or aluminium alloy plates and stiffeners are welded with the use of hipower CO2 lasers. Strength analysis of such structures with the use of finite element method needs proper material modelling. In this paper the material model of steel sandwich panel tee-joint is analysed. The influence of including different material zones on strains and stresses at the weld notch area is presented. The analysis shows that material changes outside the weld notch area do not influence the results of strains and stresses. The impact of the geometrical notch is very local and it does not interfere with material property changes at neighbouring weld zones. For the purpose of determination of maximum values of stresses and strains at weld toe notch, the analysed laser weld can be modelled with the use of one material property for all weld zones.