Sandwich Composite Wall Research Articles

Compressive performance of full-scale GFRP composite sandwich wall panels with wood core

This paper investigated the compressive behaviors of sandwich wall panels consisting of glass fiber-reinforced polymer (GFRP) face sheets and Paulownia wood core experimentally and numerically. Vacuum-assisted resin infusion molding (VARIM) process was used to produce GFRP sandwich wall panel specimens. Four full-scale wall panels with different heights were tested under axial loading to study their failure modes and load-bearing capacities. The results revealed that buckling was the main failure mode of GFRP wall panels under the axial compression and the ultimate load-bearing capacities of specimens were improved the decrease of the height-to-thickness ratio. Experiments showed that decreasing the height-to-thickness ratio from 51.5 to 38.6 can effectively improve the ultimate load-bearing capacities of the wall panels by 124%. The experimental results were compared with finite element analysis (FEA) and analytical results were in good agreement. In addition, an equation was used to predict the load-bearing capacities of the wall panels suitable for the specimens with smaller height-to-thickness ratio.

Study on the post-fire axial compressive performance of the lightweight ceramsite foamed concrete sandwich composite shear wall

This study is carried out to develop a new lightweight ceramsite foamed concrete sandwich composite shear wall, which is a new and affordable building system. The shear wall consists of two ordinary concrete wythes and a ceramsite foamed concrete intermediate sandwich layer between the wythes. Experimental investigation on five shear wall specimens is conducted by varying the parameters such as thickness of the ordinary concrete wythes and the insulation layer, reinforcement pattern and constrained component. Besides, by conducting fire test and axial compressive load test, the results are obtained, including the apparent phenomenon after fire, crack pattern and failure modes, load capacity, load-out of plane curve, strain distribution of the composite sandwich shear wall. The results show that sandwich ceramsite foamed concrete has good thermal insulation performance, and the compositeness of wythes and sandwich layer has reached in a certain degree. However, the compositeness of specimen using truss bars is weaken in the late loading stage and truss bars are advised to be used with the horizontal tie bars in practical engineering application. Compared with other specimens, the experiment ultimate strength has been increased by approximately 75 % by arranging the constrained component on the wall. Finite Element (FE) analysis is also conducted by ABAQUS and the results shows good agreement with experiment results, indicating that the FE model can be used to predict the behavior of the sandwich composite shear wall. Based on the existing methods, a modified method to calculate ultimate compressive bearing capacity after fire is proposed, with the maximum calculation error of 19 %, which shows that all methods can be applied to the practical engineering design.

Behavior of novel steel-concrete-steel sandwich walls under low-velocity impact loading

This paper reported experimental and analytical studies on impact behaviors of steel-concrete-steel sandwich composite (SCSSC) walls using enhanced C-channels (ECs). Six SCSSC walls, designed with variations in impact energy levels and boundary columns, were tested by drop hammer and simulated by LS-DYNA. The main failure modes of the specimens after impact loading were global flexure and flexure-shear mode. As direct-link connections, the ECs provided strong interfacial shear and tensile resistances, which prevented local failure of SCSSC walls. Under three impact energy levels, boundary CSFT columns increased the ultimate impact resistance of SCSSC walls, and effectively reduces their peak displacements. Refined finite element (FE) models considering the effect of strain rate were established, and verified by reported impact test results. In addition, this study adopted modified two-degree-of-freedom (TDOF) model to estimate the impact force and displacement responses of this type of SCSSC walls. Validations against reported test results confirmed that the TDOF model provided reasonable predictions.

Evaluation of a strengthening approach for existing RC buildings in terms of resilience and cost efficiency

The aim of the present study is to assess the performance of a reinforced concrete (RC) building been retrofitted with a new precast insulated steel and concrete composite sandwich wall. The applied retrofitting method, as well as the selection of the performance level for design have been studied with reference to their impact on the retrofit cost and the estimated cost due to possible earthquake losses. As a case study an existing 8-story RC building has been selected that is strengthened with inverted-V steel bracings as well as with the application of the proposed insulated composite walls, respectively. By applying inelastic dynamic analyses with artificial accelerograms scaled to represent earthquake scenarios with specific probabilities of recurrence, the seismic response of the strengthened structure is defined for each scenario. The results of the aforementioned analyses are being correlated with the earthquake losses based on an established methodology. Eventually, the performance of each retrofit method is determined and then compared with the respective performance of the existing building. The most efficient method is defined by considering both the construction cost and the earthquake losses cost of each earthquake scenario.

Numerical analysis on fire performance of sandwich composite wall with truss connectors

Based on the previous experimental study on sandwich composite walls with truss connectors under axial loads and one-side fire, finite element analysis was conducted on the fire performance of the novel wall in this paper. Firstly, a thermal coupling analysis model was established for the sandwich composite wall by the finite element software ANSYS, and simulation of test results was performed. The comparison between the predicted results and the test results showed that this model could accurately simulate behaviors of sandwich composite walls under fire. The validated finite element analysis model was utilized to carry out parametric analysis on the fire performance of the sandwich composite walls under one-side fire and two-side fire, respectively. Results showed that wall thickness is a major parameter affecting the fire resistance of the wall under one-side fire. The axial compression ratio, the height-thickness ratio and the wall thickness are major parameters influencing the fire resistance of the wall under two-side fire. Equations for predicting the fire endurance of sandwich composite walls were obtained, by fitting with the major affecting parameters. The calculated results from the equations were in good agreement with the results from the finite element simulation, and the equations can be used as a reference for the fire-resistant design of sandwich composite walls.

Study on seismic behavior of oblique CFRP corrugated plate-steel plate light weight sandwich composite shear wall

To improve the seismic behavior of the thin steel plate shear wall (SPSW), carbon fiber reinforced polymer (CFRP) is introduced into the thin SPSW, and polyethylene terephthalate (PET) foam is filled between CFRP corrugated plates and steel plate. An oblique CFRP corrugated plate-steel plate lightweight sandwich composite shear wall specimen (hereinafter: sandwich composite plate specimen) is designed. Furthermore, this paper compares the failure mechanism and hysteresis performance of the sandwich composite plate specimen and traditional non-stiffened SPSW specimen under the quasi-static test, and explores the influence of sandwich composite plate on the performance of wallboard. Finally, a simplified finite element model is established and its accuracy is verified by experiments. The results show that compared with the non-stiffened SPSW structure, the initial stiffness of the sandwich composite plate structure is increased by 34.0%, the energy dissipation capacity is increased by 38.44% when loads to 2% drift, and the maximum out-of-plane deformation is reduced by 93.24%. The sandwich composite plate structure shows obvious four-stage stress characteristics, and has good cooperative working performance before the CFRP corrugated plates debond in a large area, also plays a great role in anti-buckling.

Seismic behaviors of T-shaped steel-concrete-steel sandwich composite walls using enhanced C-channels

This paper developed the T-shaped steel-concrete-steel sandwich composite (TSCSSC) walls using enhanced C-channels, and investigated their seismic behaviors through three cyclic loading tests. The parameters studied in the cyclic loading test programme included wall thickness of the steel tube in boundary CFST columns and aspect ratio of TSCSSC wall specimens. The test results showed that TSCSSC walls exhibited flexural failure modes characterized by infilled-concrete crushing, tensile fracture of steel tubes, weld seams, and local buckling of steel faceplates and tubes. The skeleton hysteretic P-Δ curves of TSCSSC walls exhibited a typical three-stage working mechanism, i.e., elastic, nonlinear development, and recession stage. Increasing the thickness of steel tubes in the web wall improved the strength and energy dissipation capacities. Reducing the aspect ratio of TSCSSC walls improved strength and stiffness, but exhibited lower peak bending resistance owing to the effect of acting shear force on wall-base cross section. Finally, prediction equations were developed to estimate the peak bending resistance of TSCSSC walls. Validations against reported test results confirmed their limited prediction errors (≤10%). • T-shaped steel-concrete-steel sandwich composite (TSCSSC) walls with enhanced C-channels is proposed. • TSCSSC walls exhibited flexural failure and plump hysteretic load-drift behavior. • Increasing the wall-thickness of boundary steel tube improves seismic behaviors of TSCSSC walls. • TSCSSC walls with low aspect ratio failed in combined flexure and shear mode. • Developed prediction equations predict well the bending resistance of TSCSSC walls.

Comparing Testing Methods of Partially Composite Sandwich Wall Panel Glass Fiber–Reinforced Polymer Connectors

Precast concrete insulated sandwich wall panels have been commonly used as exterior load bearing or cladding wall panels on building structures. These panels are usually designed as composite, partially composite, or noncomposite, depending on the strength of the shear connectors connecting the two exterior concrete wythes. Various proprietary available shear connectors are used to achieve the required degree of composite action. The design information of the shear connectors is provided by the connector supplier based on testing results. Currently, there is no universally accepted method of testing composite shear connectors in practice or in the literature, however, connector suppliers usually use one of two testing methodologies recommended by the International Code Council–Evaluation Service, namely, AC320 or AC422, respectively. It is not known which test provides a better measurement of design values such as strength and stiffness, and there is no such comparison in the literature. In this study, 68 pushoff experiments were presented to evaluate the difference between these two testing methodologies. The testing program consisted of 20 single shear specimens and 48 double shear specimens. Three different commercially available shear connectors were used as well as variable insulation wythe thicknesses. The results were statistically analyzed. Large differences in the measured connectors’ shear strengths and stiffness were observed between the two testing methods, with AC422 providing consistently larger ultimate shear and secant stiffness, but considerably more variability. Large-scale flexural specimens from the literature were modeled using AC320 and AC422 as-measured results, and AC422 tests were found to predict deflections, cracking, and strength more accurately. It was concluded that AC422 produces a more accurate measure of connector properties, but suffers from large variability, resulting in a recommendation that further investigation into changing testing parameters and/or methods is warranted to reduce this variability.

Experimental investigation on fire resistance of sandwich composite walls with truss connectors

The sandwich composite wall with truss connectors is a new type of double-steel-plate composite wall, which consists of two external steel plates, square steel tubes at both ends, and in-fill concrete. The external steel plates are constrained by the steel trusses, thereby possessing superior mechanical performance. In order to study the fire resistance of the sandwich composite wall, 4 full-scaled walls were tested under one-side ISO-834 standard fire, aiming to investigate the effects of axial compression ratio, truss spacing to thickness ratio, and steel plate thickness on the fire resistance of the walls. The temperature, axial displacement and transverse displacement of key parts of the walls were measured. Experimental results indicate that, the walls could maintain sufficient load-bearing capacity as specified by the Class I fire resistance rating of Chinese Code. The fire endurance of the wall was controlled by its thermal insulation. The deformation pattern of the walls under the fire was overall deflection toward the unexposed surface, and the steel plate exposed to the fire experienced obvious local buckling. The axial compression ratio and the truss spacing to thickness ratio had great effects on the deformation behavior of the walls. When the axial compression ratio was reduced from 0.5 to 0.3, the axial deformation of the wall was changed from compression-predominant to expansion-predominant deformation. A larger truss spacing to thickness ratio led to more obvious buckling of the steel plate exposed to the fire. It is recommended to restrict the truss spacing to thickness ratio of the wall in engineering design.

Performance of dovetail profiled steel concrete composite sandwich walls under axial compression

Using dovetail profiled steel sheets (DPSs) as exterior faceplates of composite sandwich walls, an innovative thin-walled walling system with potential as bearing members in low and medium-rise building structures, namely dovetail profiled steel concrete composite sandwich wall (DSCW), is formed. The dovetailed ribs of DPS not only enhance the stability performance of steel sheets, but can also be used as the inherent connector to achieve the composite action between steel sheets and infilled concrete. This paper presents the results of experimental and numerical investigations on DSCWs under axial compression. Fourteen DSCW specimens are tested to failure, the variables considered included the types of DPS, the thickness of DPS, concrete grade and wall thickness. The effects of these variables on the steel sheet buckling, specimen failure mode, axial load vs. deformation responses, initial stiffness and DPS' strain development and distribution around the buckling wave are critically evaluated. The results show that the dovetailed ribs can function as solid anchorage to DPS and separate the DPS into multiple strips, only local buckling occurred on the strips between dovetailed ribs. Both the strain measurement and VIC-3D imaging results confirmed the specimen failed by infill concrete crushing while DPSs were in the post-buckling stage. The width to thickness ratio of the strip and corrugations on strips are the key factors affecting the DPS buckling behavior. Furthermore, the finite element analysis model using the commercial software package ABAQUS is established to perform work mechanism analysis of DSCW, including the axial load vs. strain response, failure mode, buckling behavior of DPS and composite interaction between DPS and concrete. In addition, the critical buckling strength of DPS was derived by using orthotropic plate theory based on energy methods, and the effect of the corrugation height on the critical buckling strength of DPS was also discussed. Finally, suggestions for predicting the axial load capacity of DSCW are proposed, in which the post-buckling strength of DPS' strip can be calculated by the effective width method suggested in AISI S201-2007 and GB50018-2013.

Thermal insulation performance evaluation of autoclaved aerated concrete panels and sandwich panels based on temperature fields: Experiments and simulations

The thermal performance of wall materials has a profound influence on the energy consumption and thermal comfort of the buildings. The thermal performance can be evaluated by various indexes, such as thermal conductivity, decrement factor, delay time lag, etc., which are obtained by different methods. To more comprehensively characterize the thermal insulation performance of wall materials, a thermal inertia factor was proposed in this study based on the temperature fields of the wall materials. The autoclaved aerated concrete (AAC) panels with different densities and thicknesses were prepared, and also a kind of AAC - calcium silicate board (CSB) composite sandwich wall panels were designed to be compared. It was found that the low density (i.e. low thermal conductivity) alone did not equivalent to high thermal inertia, that is, both the decrement factor and the time lag were proportional to the density of the panels. Thickening of the AAC panels significantly hindered the heat transfer, and the designed sandwich structure also had this enhanced hindering effect. The thermal inertia factor was calculated based on the simulations of temperature fields by ANSYS software. It was concluded that the comprehensive thermal inertia of AAC panels was favorable when the density of AAC was in the range of 700–900 kg/m3. The heat flux through the AAC panels reached equilibrium at a position of 55%–75% panel thickness away from the high-temperature surface facing the hot box. These achievements contribute to better understanding of the thermal insulation performance of AAC and are desirable for proper modeling and design of AAC or other insulation materials.

Axial compressive behaviours of steel–concrete-steel sandwich composite walls with novel enhanced C-channels

This paper developed novel steel–concrete-steel sandwich composite walls (SCSSCWs) with enhanced C-channels (SCSSCW-ECs), and studied their compressive behaviours through seven axial compression tests. The studied parameters include layout of C-channels in SCSSCWs, faceplate thickness, strength of concrete core, vertical and horizontal spacing of C-channels. Test results exhibited a three-stage working mechanism for SCSSCW-ECs under compression. Experimental observations also showed that under axial compression SCSSCW-ECs failed in concrete core crushing and local buckling of faceplate. The test results also offer useful information on the mechanism and influences of these studied parameters on axial compressive behaviours of SCSSCW-ECs. The layout of novel ECs in SCSSCW-ECs was finally optimized including layout of C-channels as well as their spacings. This paper also developed theoretical models and modified code equations in AISC, CECS, and Eurocode 4 to estimate ultimate compressive resistance of SCSSCW-ECs. These models have been validated by reported 11 test results. The validations showed that developed theoretical models offered the most accurate predictions on ultimate compressive resistance of SCSSCW-ECs.

Compressive behaviours of steel-UHPC-steel sandwich composite walls using novel EC connectors

This paper reports the developments of steel-UHPC-steel sandwich composite walls with novel EC connectors (SUSSCW-ECs). The ECs in SUSSCW-ECs directly linked the two faceplates that enhance the composite action of the composite wall. Axial compression tests on 11 SUSSCW-ECs to investigate their compressive behaviours, and the selected key influencing parameters in the testing program included layout of C-channels, steel faceplate thickness, horizontal and vertical spacing of ECs, and strength of core. Under compression, the SUSSCW-ECs exhibited an elastic-plastic-recession three-stage working mechanism. Tests results show that major local buckling of faceplates ended the elastic stage, and UHPC crushing occurred at the peak compression resistance of SUSSCW-ECs. Installing the ECs with horizontal webs exhibited larger axial compression resistance of SUSSCW-ECs than those with V-web ECs. Increasing the steel faceplate thickness improved compressive behaviours of SUSSCW-ECs. Increasing horizontal and vertical spacing of EC connectors resulted in reduced ultimate compressive resistance of SUSSCW-ECs. Using UHPC improves both peak resistance and elastic stiffness of sandwich composite walls. Finally, this paper developed theoretical models to predict ultimate compressive resistance of SUSSCW-ECs, and validations against 11 test results showed their reasonable estimations.

Structural behavior of sandwich composite wall with truss connectors under compression

Sandwich composite wall consists of concrete core attached by two external steel faceplates. It combines the advantage of steel and concrete. The appropriate composite action between steel faceplate and concrete core is achieved by using adequate mechanical connectors. This research studied the compressive behavior of the sandwich composite walls using steel trusses to bond the steel faceplates to concrete infill. Four short specimens with different wall width and thickness of steel faceplate were designed and tested under axial compression. The test results were comprehensively evaluated in terms of failure modes, load versus axial and lateral deformation responses, resistance, stiffness, ductility, strength index, and strain distribution. The test results showed that all specimens exhibited high resistance and good ductility. Truss connectors offer better restraint to walls with thinner faceplates and smaller wall width. In addition, increasing faceplate thickness is more effective in improving the ultimate resistance and axial stiffness of the wall.

Behavior of T-shaped sandwich composite walls with truss connectors under eccentric compression

Sandwich composite walls are composed of two external steel faceplates and concrete infill and have been increasingly applied in infrastructure to resist either gravity or lateral loads. They combine the advantages of both steel and concrete and offer excellent structural behavior. In this paper, the performance of a new type of T-shaped sandwich composite walls with truss connectors was studied. Three full-scaled specimens with T-section were tested under eccentric compression. The failure mode was identified as the sectional strength failure. Load versus axial and out-of-plane displacement responses, buckling stress, axial stiffness, ductility, and strength utilization were discussed. Based on CECS 159, the interaction model between the compression and bending moment was proposed to estimate the sectional strength of sandwich composite walls under eccentric compression. The comparison between the test data and the proposed curve shows that the proposed method offers reasonable and conservative predictions on the strength of sandwich composite walls.

Mechanics-Based model for elastic Bending, Axial, thermal Deformations, and asymmetry of concrete composite sandwich wall panels

Engineers must design load-bearing panels to handle gravity loads, out-of-plane loads and deformations due to thermal bowing. Outside of finite element analysis (FEA), there is currently no codified or well-accepted design or analysis method within the literature that can perform these calculations within the same framework. This paper describes the theory, development, and validation of a new mechanics-based model (MBM) for partially composite concrete sandwich wall panels in the elastic range. Most concrete sandwich wall panels in the United States are designed exclusively in the elastic range. The MBM is suitable for incorporation into a spreadsheet (provided) or computer program and can provide analysis information suitable for practical design. The model is validated based on available experiments with an average measured-to-predicted ratio of 0.98 for deflections in out-of-plane loading and 1.08 for thermal bowing estimation. A parametric study and comparison to FEA is performed to illustrate the robustness of the MBM to handle different situations including openings, eccentric dead loads and asymmetric panels.

Cyclic tests on novel steel-concrete-steel sandwich shear walls with boundary CFST columns

Firstly, this paper proposed a type of steel-concrete-steel (SCS) sandwich composite shear wall with J-hook connectors (SCSSWJ) and boundary concrete-filled-steel-tube (CFST) columns. Five full-scale cyclic tests were performed to study seismic performances of SCSSWJs. The studied parameters were connectors’ spacing and axial force ratio. Test results showed that flexure failure occurred to these five SCSSWJs with boundary CFST columns, which is characterized by tensile fracture of boundary steel tube, local buckling in the edge tube and faceplates, and concrete crushing. The test results revealed that increasing the spacing of J-hook connectors from 100mm to 160mm and 200mm firstly slightly improves but then compromised the seismic behaviour of SCSSWJ due to early buckling of steel faceplate; increasing the axial force ratio significantly compromised the seismic behaviours of SCSSWJ. This paper also developed theoretical models to evaluate lateral peak shear resistance of SCSSWJ. The validations proved that the developed models predicted well lateral peak shear resistance of SCSSWJ with boundary CFST columns.

Generalized beam–spring model for predicting elastic behavior of partially composite concrete sandwich wall panels

Partially composite sandwich wall panels (SWP) have been used in the construction industry for at least twenty years. Currently there is limited codified guidance for designers of partially composite concrete SWP, but they are being designed safely and routinely. Design is often guided by the composite connector manufacturers who sell proprietary composite connectors often using a variation of truss-type matrix methods for prediction of elastic behavior of SWPs. The purpose of this paper is to quantify the accuracy of such a model in a uniform manner by developing a generalized version of these matrix models called the beam-spring model (BSM). The primary benefits of the model are its simplicity and versatility making it suitable for design and variations of this model are already in use today. Its accuracy was established in this paper by comparing to 51 specimens from the literature and found to be similar to that of other methods related to strength and cracking of concrete members in the literature. These results indicate that this BSM, or the very similar methods that are already standard practice, provides an adequately safe elastic analysis. On average, the BSM predicted cracking load within 2% with a coefficient of variation (COV) of 7%, out-of-plane panel stiffness within 3% with a COV of 17%, and cracking deflection within 2% with a COV of 18%. These results also indicate that the United States precast industry’s use of 7.5fc' for predicting the cracking moment is acceptable for partially composite precast panels. A parametric study performed with the BSM presents several different design situations and can be used as a rudimentary design tool for preliminary behavior and arbitrary connectors.

Compressive behaviours of novel SCS sandwich composite walls with normal weight concrete

Novel steel-concrete-steel (SCS) sandwich composite walls with normal weight concrete (NWC) and J-hook connectors have been proposed for shear walls in buildings and protective walls in Arctic offshore platforms. Eight SCS sandwich walls with J-hook connectors and NWC were tested under monotonic compression. Investigated parameters in this testing programme included thickness of steel faceplate, spacing of J-hook connectors, strength of NWC core, and different types of connectors. Based on the reported test results, the influences of these parameters were analysed and discussed. Theoretical models were developed to predict compressive resistance of SCS sandwich walls with different types of connectors. The developed analytical models considered the confinement of steel faceplate on compressive strength of concrete core and proposed new buckling length coefficient for steel faceplate in SCS sandwich wall. The accuracies of the proposed analytical models were checked through validations against 50 test results reported by authors and other researchers. Finally, step-by-step design procedures were proposed to determine compressive resistance of SCS sandwich walls with different types of shear connectors.

Compressive behaviours of steel-concrete-steel sandwich walls with J-hooks at low temperatures

Abstract Recently, gravity base offshore platforms consisting of novel steel-concrete-steel (SCS) sandwich ice-resistant walls with J-hook connectors have been developed for the Arctic oil & gas production. This paper made pioneer studies on compressive behaviours of SCS sandwich composite walls with J-hook connectors (SCSSWJ) at the Arctic low temperatures through a nine-specimen testing program. The low temperatures ranging from 20 to −80 °C, thickness of steel faceplate, spacing of connectors, and concrete strength were selected as key parameters in this experimental study. The test results revealed the failure modes and load versus shortening/strain behaviours of the SCSSWJ at low temperatures. These studied parameters were found to have significant influences on the compressive behaviours of this novel SCSSWJ. Including experimental studies, this paper also developed theoretical models to predict the ultimate compressive resistance of SCSSWJ at the low temperature environment. The validations of predictions against results of nine reported tests confirmed that the theoretical models were capable of provide reasonable but conservative estimations on the compressive resistance of such novel SCSSWJ.