Steel-concrete-steel Sandwich Research Articles

Impact response of SCS sandwich slabs with ultra-high performance concrete: Failure mechanism and influence of shear connector configuration

In the typical steel-concrete-steel (SCS) sandwich structure, the normal-strength concrete core fills the external steel skeleton. This paper describes a program of drop-weight tests and finite element investigations on reduced-scale SCS sandwich slabs with ultra-high performance concrete (UHPC) core material as a novel protective layer construction. Test results demonstrated that the steel-ultra-high performance concrete-steel (SUHPCS) sandwich slabs were adequate for forming enhanced dynamic resistance through the high strength of UHPC and tensile stiffening membrane of the steel skins. Also, this construction was found to perform a highly ductile behavior and sustain obvious bulges without penetration through the whole slab. Precise finite element models for sandwich slabs under impact loading conditions were established and the simulated time histories were verified against the test data. Furthermore, a parametric study of sandwich slabs designed with different configurations of shear connectors was subjected to a spherical hammer weighing 540 kg dropping from the height of 5 m. The simulation results showed that the failure mode of SUHPCS sandwich slab changed with various degrees of composite interaction. Moreover, a theoretical methodology was proposed to classify the failure mode involving stiffness, flexural and punching resistances. SUHPCS sandwich slabs with a reasonable layout of shear connectors were found to provide a means for effective energy absorption against severe impact attacks.

Push-out tests on steel composite sections with engineered cementitious composite

This paper investigates the shear strength and failure modes of steel-concrete-steel (SCS) sandwich composite member with Engineered Cementitious Concrete (ECC) and explores the influences of various shear connectors such as headed stud and bolt on shear behavior of SCS sandwich composite member by carrying out push-out testing program. Based on the test results in this study, the failure modes and the load-slip behavior of the specimens are investigated. In addition, the experimental results on the shear resistance of the headed stud connector with various connector spacing and numbers of connector is compared and explored.

Structural behavior of steel-concrete-steel sandwich slender and deep beams considering different connectors

Steel-concrete-steel (SCS) sandwich deep beams, with a shear span ratio of less than 2.0, are commonly employed in high-rise buildings and bridges. However, their failure mechanism differs from that of SCS sandwich slender beams, which have a shear span ratio greater than 2.0. This study systematically investigates the failure mechanisms of SCS sandwich deep beams and compares them with those of SCS sandwich slender beams. To improve their structural performance, ultra-high performance concrete (UHPC) was utilized as the core material to form S-UHPC-S sandwich deep beams, with shear studs serving as the sole shear connectors. The influence of these shear connectors was explored in comparison to cross ties. Three S-UHPC-S sandwich deep beams were subjected to static loading, and their performance was compared with ten existing SCS sandwich deep and slender beams. The analysis focused on failure modes, mechanical behaviors, and contributions of each component, including the steel plate (SP), core concrete (CC), and shear connectors. The results revealed distinctions in force transferring models, load-displacement curves, and the contributions of cross ties in deep beams compared to slender beams. Additionally, finite element (FE) analyses were employed to examine the force transferring mechanism of shear connectors. Based on both experimental and FE simulation analyses, theoretical models for predicting the ultimate capacity of S-UHPC-S sandwich deep beams and slender beams were proposed, accounting for different shear connectors. These models offer valuable insights for practical structural design and application.

Flexural performance of steel-concrete-steel sandwich beams with lightweight fiber-reinforced concrete and corrugated-strip connectors: Experimental tests and numerical modeling

The present paper experimentally investigates the flexural behavior of steel-concrete-steel (SCS) composite beams with lightweight polypropylene fiber-reinforced concrete core and corrugated-strip shear connectors. For this purpose, the four-point bending tests have been performed on 11 specimens. This aims to investigate the influence of lightweight concrete core on the performance of the beams, and therefore all the parameters in the tested beams are kept constant except the type of concrete core. Based on the results of the performed quasi-static loading tests, the observed failure modes and force-displacement curves are reported and analyzed to achieve a deeper understanding of the influence of lightweight fiber-reinforced concrete on the flexural behavior of SCS beams. It was found that the utilization of polypropylene fiber has an improving influence on the performance of SCS beams, and especially enhances their toughness and ultimate deflection. A positive linear relationship between the fiber content (up to 2 %) with the specimen’s toughness was detected. It was also found that the addition of micro-silica to the lightweight fiber-reinforced concrete core results in considerable improvement in the flexural load capacity of the tested SCS beams. In addition, numerical finite element models including detailed material and geometric modeling of SCS beams are developed using the general software package ABAQUS. The accuracy of the developed models is validated using the attained experimental results. The numerical models can be used to simulate the load-deflection behavior and ultimate strength of SCS sandwich beams.

Finite element analysis of steel-concrete-steel sandwich beams with novel interlocked angle connectors subjected to impact loading

The steel–concrete–steel (SCS) sandwich structures are increasingly adopted to improve the impact resistance of the buildings or infrastructures owing to their good structural performances. Recently, the SCS sandwich beams with interlocked angle connectors (SCSSB-IACs) have been developed, and their performances under impact loading have been experimentally studied. This paper presents detailed numerical analyses of the SCSSB-IACs subjected to impact loading and reveals its response mechanisms. The Finite Element (FE) models of the SCSSB-IACs were established using LS-DYNA, and the FE predictions showed a good agreement with the impact test data. The impact process as well as distribution and evolution of bending moment and shear force, stress and strain were discussed. Furthermore, the internal energy histories of the SCSSB-IACs were revealed by FE analyses. Numerical results indicated that the majority of impact energy was absorbed by the concrete and bottom faceplate, and the deformation of the SCSSB-IACs was dominated by a flexural manner. Finally, parametric studies were performed to reveal the effects of impact momentum, energy and location on the response of the SCSSB-IACs.

Assessment on interface slip of steel-concrete-steel sandwich panels with ribbed bar connectors

Steel-concrete-steel (SCS) sandwich structure is widely used because of its excellent mechanical properties. A SCS sandwich panel with ribbed bar connectors (B-SCS) was developed. Experiments were carried out on seven specimens where the faceplate thickness, loading mode, connectors spacing and connector type were varied. Test results reported the failure mode and crack distribution of the B-SCS structure. The bearing capacity of the structure with the ribbed bars was 36% higher than that with studs (the length is 60 mm). At the same time, the bottom faceplate determined the resistance limit and ductility of the B-SCS sandwich panel. The proposed interface slip model can accurately predict the relative displacement between the steel plate and the concrete. Under the peak load, the sliding amount of the top plate was less than 12% of that of the bottom plate.

Impact response of SCS sandwich panel with energy absorption connectors: Experimental and numerical studies

This paper developed a new steel-concrete-steel sandwich panel with energy absorption connectors (SCS-EC) for resisting impact load, and the impact responses of the SCS-EC were studied by conducting impact tests and Finite Element (FE) simulations. The failure modes of the SCS-EC under impact loading could be categorized into two types based on the crushing magnitude of the energy absorption connector (EC). The EC was found to effectively dissipate impact energy via the plastic deformation of pleated steel plates and the compression of aluminum foam fillers. The steel-concrete-steel (SCS) panel showed the combination of global and local deformation under impact loading. Moreover, the influences of pleated plate thickness (tp) and angle (θp), aluminum foam filler and initial momentum on the impact performances of the SCS-EC were studied quantitatively. The results showed that the SCS-EC exhibited enhanced impact resistance via increasing initial momentum of the impactor as well as filling aluminum foam in the EC and assuring the maximum crushing displacement of the EC being equal to its densification displacement.

INVESTIGATION ON CONCRETE FILLED SKINNED BEAMS

Steel-Concrete-Steel Sandwich (SCSS) beam is a relatively new and innovated form of construction consisting of a layer of concrete, sandwiched between two relatively thin plates of steel which are connected to the concrete by shear connectors. In this project we investigated the difference between conventional Beam strength & concrete filled skinned beams strength. These skinned beams consist 1.5mm thick Steel plate and 1m in length, welded with 4 nos of 8mm diameter bar using shear connector consists of 12mm dia bar placed at spacing of 150mm in two rows of longitudinal section. It is a composite sandwich concrete section. Key Words: 1.5mm Steel plate 1m, 4 nos of 8mm diameter, M25 concrete.

Experimental and analytical studies on impact behaviours of a steel–concrete–steel sandwich beam with novel interlocked angle connectors

The dynamic responses of steel–concrete–steel (SCS) sandwich beams with novel interlocked angle connectors (IACs) under low-velocity impact were studied and presented in this paper. The impact tests on the SCS sandwich beams were first implemented using a drop-weight impact test machine, and the failure modes, displacement, and impact responses were obtained from the tests. The varying parameters considered in the tests included the thicknesses of the concrete and steel faceplates, as well as the spacing and type of IACs. The test results indicated that nine specimens experienced flexural failure, and one specimen exhibited shear failure. Moreover, local buckling of the top steel faceplate occurred in four specimens with a relatively larger spacing of IACs. A two-degree-of-freedom (TDOF) analytical model considering the strain rate effect was proposed for the SCS sandwich beam to obtain their impact forces and mid-span displacements. The analytically-predicted responses of the SCS sandwich beam with IACs agreed well with the test data.

The behavior of steel-concrete-steel sandwich beams with different depths effect

This research studies the effect of beam depth on the behavior of steel-concrete-steel (SCS) sandwich beams. Four SCS sandwich beams measuring 100 mm wide and 1200 mm length were cast and tested up to failure under three-point flexural loading. The depths in the tested beams ranged from 150 to 300 mm in regular increments of 50 mm. All beams had top and bottom steel skin plates with thickness 4 mm. The shear connector configuration of the Truss using 10 mm diameter steel bars was used to directly connect the two external steel skin plates. The test results confirmed that increasing the depth of the SCS beams from 150 to 300 mm led to an increase in the first cracking load and the ultimate load by 33.5 to 66.5% and 59.2 to 64.2%, respectively. In addition to improving the mechanical properties, when the SCS beams depth was raised to 50%, the service stiffness and secant stiffness both improved by 226.9 and 190.4%, respectively. Moreover, the flexural toughness increased by 101.1% with the SCS sandwich beams depth rising by 25%.

Experimental and numerical studies on novel stiffener-enhanced steel-concrete-steel sandwich panels subjected to impact loading

In this study, a new stiffener-enhanced steel-concrete-steel (SESCS) sandwich panel was proposed with the aim of improving the impact resistance of the traditional steel-concrete-steel (SCS) sandwich panel. The drop-weight impact tests on the SESCS sandwich panels were conducted to obtain their failure modes, impact force and displacement responses. The effects of concrete core thickness, steel plate thickness, presence of stiffeners, and drop height on the dynamic responses of SESCS sandwich panels were experimentally revealed. All the tested panels exhibited the combined failure mode of global flexure and local indentation, and the SESCS sandwich panel demonstrated improved impact resistance. As compared to the SCS sandwich panel without stiffeners, the peak impact force and post-peak mean force of the SESCS sandwich panel were enhanced by 41.56% and 31.7%, respectively, while the maximum displacement was reduced by 30.21%. In addition, the impact resistance of the SESCS sandwich panel was found to be improved by increasing the thickness of steel plate and concrete core. The Finite Element (FE) models of the SESCS sandwich panels under impact loading were developed and validated with the experimental results. The FE analyses were subsequently conducted to reveal the damage evolution of concrete core during impact, and the concrete core exhibited punching shear failure at the impact zone and flexural failure at the free side of the panel, respectively. Furthermore, parametric studies were conducted to investigate the influences of impact velocity, hammer mass, impact energy and momentum of the hammer on the impact responses of SESCS sandwich panels.

Blast behavior of steel-concrete-steel sandwich panel: Experiment and numerical simulation

As a lateral resisting element, the steel–concrete composite structure has been gradually employed in the anti-seismic and the anti-explosion design of structures due to the favorable capacity of energy dissipation and impact resistance. The blast capacities of steel–concrete-steel (SCS) sandwich, concrete-steel–concrete (CSC), and reinforced concrete (RC) slabs were investigated by experiment and numerical simulation. The effects of the explosive charge, concrete grade, steel plate thickness, and length of shear studs on the blast behaviors of the composite slabs were studied by parametric analysis. The failure modes and dynamic responses of the specimens were investigated and compared. Simultaneously, the empirical formulas for mid-span deflection of the SCS and CSC slabs were proposed by using a multiple nonlinear regression analysis method. The results indicated that the three specimens exhibit different failure modes, in terms of local damage, spallation of concrete, and punching failure. And the steel plate takes a dominant role against the blast loads, which can provide a robust protective capacity to prevent the slab from damage due to the high tensile strength of steel. The SCS sandwich slab has the smallest damaged area on the front steel plate with a smaller mid-span displacement, maintains the integrity, and owns bearing capacity after the blast test compared with the CSC and RC members. The proposed empirical formula can well fit the relation among the deflection of the composite slabs, explosive charge, and thickness of steel plate, which can reasonably predict the midspan displacements of the composite slabs.

Behavior of steel-concrete-steel sandwich beams with blot connectors under off-center impact load

The structural performance of the Steel-Concrete-Steel (SCS) sandwich beams with bolt connectors subjected to off-center impact load was investigated in this paper. Nine SCS sandwich beams were tested under impact loading by employing a drop hammer impact test system. The influences of concrete core depth, steel plate thickenss, top to bottom steel plate thickness ratio, and impact location on the responses of SCS sandwich beams were experimentally studied. The experiments revealed three failure modes of the SCS sandwich beams, i.e., flexure, flexure-shear, and fracture of the bottom steel plate. The separation of steel plates was prevented, and the structural integrity of the SCS sandwich beams was maintained despite the impact near the support, owing to the presence of bolt connectors. An analytical model was developed to predict the displacement–time histories of the SCS sandwich beams subjected to impact load. The predicted displacement responses showed a good match with the experimental results. Moreover, the force–displacement curves obtained from the analytical model and impact tests were compared, and good agreement between them could be observed.

Dynamic response of dry cask storage systems for spent nuclear fuel to near field blast loading

Dry storage casks are the most common form of spent nuclear fuel (SNF) storage in the United States. An explosion near a spent nuclear storage facility poses a serious public risk due to the potential of radioactive leakage. In this study, for the first time, the structural performance of vertical steel–concrete-steel sandwich (SCSS) and reinforced concrete (RC) casks under blast loading scenarios is studied using explicit finite element simulations considering material and geometric nonlinearity and strain rate effects. The response of the cask is investigated in terms of stress levels, deformations, and peak accelerations. The conventional weapons (CONWEP) model was used to induce a blast load on the structure at varying blast charges. The accelerations experienced by the canister and the fuel assemblies, which are critical for design are estimated. The inherent vibration damping characteristics of the cask are evaluated, and a novel damper configuration is proposed to improve the energy dissipation capacity of the system. The results showed that the general integrity of the cask could be preserved in the presence of a thick reinforced concrete layer. However, due to the lack of a damping mechanism, the blast wave can propagate through the system and result in very large accelerations in the canister and the fuel assemblies. Results also revealed that the SCSS configuration has a more ductile response compared to the RC design. The results of this study could be used for the safety evaluation and design optimization of current casks in service and other cylindrical composite containment structures.

Developments of steel-concrete-steel sandwich composite structures with novel EC connectors: Members

This paper developed new steel-concrete-steel (SCS) sandwich composite structures using novel enhanced C-channels (ECs) for civil engineering infrastructures as shear walls, bridge decks, and protective structures. Their structural behaviours have been studied through a series of tests from the component to structural member level. Push-out tests on ECs, two-point loading tests on SCS sandwich beams with ECs (SCSSB-ECs), axial compression tests on SCS sandwich walls with ECs (SCSSW-ECs), in-plane cyclic shear tests and out-of-plane punching shear tests on SCSSW-ECs were carried out to investigate the shear behaviour of ECs, flexural and shear behaviour of SCSSB-ECs, compression behaviour, in-plane seismic behaviour, and out-of-plane punching shear behaviour of SCSSW-ECs, respectively. These studies offered comprehensive information of structural behaviours of SCS sandwich structural members with ECs. Including these experimental studies, corresponding prediction equations were also proposed for ultimate shear resistance and shear-slip behaviour of ECs, flexural and shear resistances of SCSSB-ECs, axial compression resistance, in-plane lateral shear resistance, and out-of-plane punching shear resistance of SCSSW-ECs. Through validations against reported test results, accuracies of these developed prediction equations were confirmed.

Modeling and Dynamic Response of Curved Steel–Concrete–Steel Sandwich Shells Under Blast Loading

The steel–concrete–steel sandwich structures are usually composed of concrete core and face steel plates. This paper presented the dynamic response of the curved steel–concrete–steel (SCS) sandwich shells subjected to blast loading. The bolts were employed to connect the face steel plates and the concrete. Numerical model was established based on LS-DYNA and the accuracy of the modelling method was verified against existing blast test. The displacement histories, damage of concrete and energy absorption capability of the shell were obtained from the numerical calculations and discussed. Different failure modes of the curved SCS sandwich shell under various loads were obtained from numerical results, i.e., local deformation of the shell for the case of close-in detonations and buckling of steel plates for the case of far-field detonations. It was noted that the concrete debris can be restrained by the face steel plates with good ductility. Numerical results showed that the energy absorption from concrete is higher under close-in detonations on the ground. The effects of charge weight, steel plate thickness, concrete thickness and rise height on the dynamic response of curved SCS sandwich shells were also analyzed and discussed in detail. The curved SCS sandwich shell with thicker back steel plate showed better blast resistant performance. Moreover, the damage of curved shell was more serious if the rise height to span ratio (Rr-s) is beyond the range of 0.16–0.25.

Numerical and analytical investigations on projectile perforation on steel–concrete–steel sandwich panels

Steel–concrete–steel (SCS) sandwich panels have been achieving increasing attention due to its good impact resistant performance, but there still lacks related research concerning analytical model for SCS perforation. In this paper, numerical and analytical investigations were performed to study the impact resistance of SCS sandwich panels against rigid projectile penetration. FE simulations of concrete-steel perforation were conducted to validate the numerical model in terms of projectile residual velocity and damage mode. With same concrete core, five thickness combinations of front and rear steel plates were numerically studied to explore the sandwich structural effect on the perforation responses. Utilizing spherical cavity expansion analysis and plates petalling theory, a semi-empirical analytical model was developed to describe the perforation on SCS sandwich panels, which was characterized with 7 penetration stages. Agreement was reached between numerical simulation and theoretical model in terms of both projectile deceleration history and residual velocity. On the perspective of structurally absorbed energy, the thickness combinations of front and rear steel plate were further analyzed and discussed. For the same thickness, the rear steel plate was found to consume more energy than the front plate, which provides better protection against projectile impact loadings.

Investigation of shear strength correlations and reliability assessments of sandwich structures by kriging method

Steel-concrete-steel (SCS) sandwich composite structure with corrugated-strip connectors (CSC) is the promising structure which is applied in offshore and building structures. The behavior prediction of shear connections is of major importance in SCS structures. The present study evaluated the existing shear strength correlations of SCS sandwich structures exploiting experimental data and Finite Element Analysis (FEA). The considered system is a double steel skin sandwich structure with CSC (DSCS). Due to the limitation of the literature regarding CSC development, some new correlations were proposed and studied relying on several FEA results through the Genetic Programming method. The accuracy of the estimated shear strength predicted by the existing and proposed equations was evaluated using the FEA data and push-out test results. The FE models were verified through experimental data. Moreover, the correlations were investigated based on reliability assessment due to the high importance of the reliability analysis of such structures. Given that high accuracy in estimating the shear strength fails to necessarily lead to acceptable results in structural reliability analysis, the reliability of the existing and proposed equations was evaluated using the Kriging model by considering experimental data. This meta-model could predict accurate values with a limited number of initial training samples.

Behavior of Steel-Coconut Shell Concrete-Steel Composite Beam without and with Shear Studs under Flexural Load.

In this study, we investigated using coconut shell concrete (CSC) in double-skin steel plate sandwich beams, i.e., steel–concrete–steel (SCS) under flexure. Two cases—without and with shear studs to interconnect the bottom tension and top compression plates—were considered. Conventional concrete (CC) was used for comparison purposes. The effect of quarry dust (QD) in place of river sand (RS) was considered. Therefore, four mixes named as CC, conventional concrete produced using QD (CCQ), CSC and coconut shell concrete produced using QD (CSCQ) were used. Three different steel plate thicknesses were considered (4 mm, 6 mm and 8 mm). In total, twelve SCS specimens were tested to evaluate the flexural performance under two-point static loads. Study parameters include: partial and fully composite, ultimate moment and failures, deflection characteristics, ductility property, cracking behavior and strains in both tension and compression plates. It was found that the moment carrying capacity of the SCS sandwich beams increased when the thickness of the steel plate increased. Our results provided evidence that using QD in place of RS augmented the strength of beams. Theoretical deflections were underestimated the experimental deflection, except in one case. The SCS beams showed good ductility behavior. The SCS beams exhibited crack widths at yielding well below guideline values.

Numerical and parametric studies on SCS sandwich walls subjected to in-plane shear

Steel-concrete-steel (SCS) sandwich walls with J-hooks (SCSSWJs) exhibit wide potential applications in both civil and offshore constructions. This paper firstly developed nonlinear finite element models (NFEMs) for SCSSWJs. Two different NFEMs, namely FEM-I and FEM-II, were developed that adopted different simplifying methods on modelling complex J-hooks. Accuracies of these two NFEMs were validated by 11 tests on SCSSWJs under in-plane shear. The validations showed that these two NFEMs were capable of simulating structural behaviours of SCSSWJs subjected to in-plane shear. The FEM-II was finally adopted for the parametric studies considering both numerical accuracy and simulation efficiency. The studied parameters in the parametric studies included concrete core strength, J-hook spacing, thickness of faceplate, wall thickness of steel tube in edge column, and axial force ratio. The effects of these parameters on ultimate lateral shear resistance of SCSSWJs were detailed reported and discussed. Theoretical models have also been proposed to predict the ultimate lateral shear resistance of SCSSWJs. Their capabilities on the predictions of ultimate lateral shear resistance of SCSSWJs have been checked through validations against 22 test results and 60 FE simulated results.