Sandwich Wall Panels Research Articles

Synthesis and characterization of 3D-printable geopolymeric foams for thermally efficient building envelope materials

Synthesis and characterization of 3D-printable foamed fly ash-based geopolymer matrices for thermal insulation is the focus of this paper. A surfactant-based foaming process, multi-step mixing that ensures foam jamming transition and thus a dry foam, and microstructural packing to ensure adequate skeletal density are implemented to develop foamed suspensions amenable to 3D-printing. The foamed suspensions show lower yield stress with increasing surfactant contents, especially above the foam jamming transition. The mixtures demonstrate adequate extrudability, shape retention, and buildability. The geopolymeric foams show porosities ranging from 55 to 75% and bulk densities from 0.6 to 1.0 g/cm3, and these properties are similar irrespective of whether the mixtures are extruded or conventionally cast. The thermal conductivities of the foamed matrices range from 0.15 to 0.25 W/m-K. It is shown that designed architectures that minimize heat transfer can be printed using foamed matrices to obtain sandwich wall panels with thermal insulation properties comparable to or better than those of currently available insulated concrete wall panels. This positions 3D-printing as a strategy to develop composite systems with previously unattainable thermal performance.

Numerical analysis on seismic behavior of a novel sandwich wall system

Concrete sandwich panel is a kind of building element with the characteristics of light weight, high strength, suitability for standardized production, meanwhile it has the multi-function of heat preservation and sound insulation which can be used not only as enclosure components, but also as structural components for multi-story residential buildings. A novel sandwich wall system has been presented in this work with an innovative design concept. Compared with traditional steel wire sandwich panel, this sandwich panel wall system has unique features such as prefabricated steel system, core column with spiral stirrup, foamed concrete as insulation layer. This wall system also meets the national policy requirements in energy-saving and has potential application and development prospects. In this paper, Finite element method is used to simulate and analyze the seismic performance of this new sandwich wall panel. The results show that the panel with 3D steel wire has greater stiffness and better earthquake resistance than panel with planar steel wire mesh.

Flexural behavior of precast insulated sandwich wall panels: Full-scale tests and design implications

This paper focuses on a new type of precast sandwich wall panels in which the expanded polystyrene (known as EPS) insulation layers are inserted between exterior reinforced concrete panels. The exterior reinforced concrete panels are held through diagonal steel bars to allow the sandwich panel to form the composite action to resist the bending moment demands. To investigate flexural behavior of the sandwich wall panels, four specimens with representative geometries and typical materials were designed. The four specimens included one with the flat exterior reinforced concrete panels and three with the ribbed exterior reinforced concrete panels. The specimens were tested using gradually increased uniformly distributed loads. It is found that all the specimens developed the composite action when resisting the bending moment demands and exhibited the same failure mode. Test results show that the specimens consisting of the ribbed exterior reinforced concrete panels (which had lower mass per unit volume) exhibited reduced flexural resistances at the cracking limit state and the ultimate limit state in comparison with the one with flat exterior reinforced concrete panels. This paper develops a set of analytical models based on the test data and simplified strain/stress diagrams for analyzing flexural behavior of the proposed sandwich wall panel. Result comparisons show that the models can provide reasonable predictions and they can be used for future practice.

Point Thermal Transmittance of Rib Intersections in Concrete Sandwich Wall Panels

ABSTRACTConcrete sandwich panels are building elements made by two concrete wythes separated by a layer of lightweight material: the central layer is inhomogeneous due to the presence of concrete ribs which tie the external wythes and act as thermal bridges. This paper deals with the problem of determining point thermal transmittance associated with rib intersections. Together with previous results by the authors, it allows accurate calculation of thermal transmittance of sandwich panels according to current International Standards. A dataset of 1080 point transmittance values is obtained upon use of a spectral element method, varying systematically material conductivities and thickness of panel layers, for the most common pairs of rib widths in current panel production. To limit the computational cost, a solution strategy based on the use of low-order polynomials on three grids of increasing refinement, coupled with Richardson extrapolation is adopted. Finally, a power law correlation is proposed that allows to estimate point transmittance within a relative error of 10%.

Axial Compression Behavior of a New Type of Prefabricated Concrete Sandwich Wall Panel

A novel type of prefabricated concrete sandwich wall panel which could be used as a load-bearing structural element in buildings has been presented in this paper. Compared with the traditional sandwich panels, there are several typical characteristics for this wall system, including core columns confined by spiral stirrup along the cross-section of panel with 600mm spacing, precast foamed concrete block between two structural layers as internal insulation part, and a three-dimensional (3D) steel wire skeleton in each layer which is composed of two vertical steel wire meshes connected by horizontally short steel bar. All steel segments in the panel are automatically prefabricated in factory and then are assembled to form steel system in site. In order to investigate the structural behavior of this wall panel, two full-scale panels have been experimentally studied under axial compressive load. The test results show that the wall panel presents good load-bearing capacity and integral stiffness without out-of-plane flexural failure. Compared to the panel with planar steel wire mesh in concrete layer, the panel with 3D steel wire skeleton presents higher strength and better rigidity even in the condition of same steel ratio in panels which verifies that the 3D steel skeleton could greatly enhance the structural behavior of sandwich panel.

Evaluating Elastic Behavior for Partially Composite Precast Concrete Sandwich Wall Panels

Evaluating Elastic Behavior for Partially Composite Precast Concrete Sandwich Wall Panels

Investigation on Wall Panel Sandwiched With Lightweight Concrete

The rapid population growth and urbanization have made a massive demand for the shelter and construction materials. Masonry walls are the major component in the housing sector and it has brittle characteristics and exhibit poor performance against the uncertain loads. Further, the structure requires heavier sections for carrying the dead weight of masonry walls. The present investigations are carried out to develop a simple, lightweight and cost effective technology for replacing the existing wall systems. The lightweight concrete is developed for the construction of sandwich wall panel. The EPS (Expanded Polystyrene) beads of 3 mm diameter size are mixed with concrete and developed a lightweight concrete with a density 9 kN/m3. The lightweight sandwich panel is cast with a lightweight concrete inner core and ferrocement outer skins. This lightweight wall panel is tested for in-plane compression loading. A nonlinear finite element analysis with damaged plasticity model is carried out with both material and geometrical nonlinearities. The experimental and analytical results were compared. The finite element study predicted the ultimate load carrying capacity of the sandwich panel with reasonable accuracy. The present study showed that the lightweight concrete is well suitable for the lightweight sandwich wall panels.

EXPERIMENTAL STUDY ON SHEAR PERFORMANCE OF COMPOSITE CONNECTOR FOR PRECAST CONCRETE SANDWICH PANELS

In order to ensure desirable overall performance between interior panel and exterior panel for precast concrete sandwich panels, the shear performance of a new composite connector is investigated in this paper through the experiment of shear specimens, including 4 groups of bilateral shear test specimens and 8 groups of unilateral shear test specimens. The connector’s shear capability and shear failure process phenomenon of destruction of all specimens are obtained. Then the effect rule on shear performance of connector from positional relation of connector and distribution reinforcement and concrete strength are gained. The experimental results and analysis show that the shear failure model is bending shear failure of connector’s reinforcing steel bar, which is brittle failure; the measured value of shear force of experiment compared to the measures values for the actual project, the new composite connector provides an enough safety reserve; The relative position of connector and distribution reinforcement and concrete strength have no influence on the ultimate bearing shear capability; The shear performance of the new composite connector could satisfy the use requirement of sandwich wall panels based on the text results. Furthermore, the connectors perform superb anchoring bond and deformation capability. According to the results and analysis, the new composite connector could be popularly used in engineering practice.

Structural feasibility of Expanded Polystyrene (EPS) based lightweight concrete sandwich wall panels

In a global context where the need for quality housing is increasing with improved standard of living and growing population, the over exploitation of natural resources as building materials is becoming a serious problem. In this context, the conversion of non-bio degradable waste materials to quality building products would be extremely useful. In this research, the use of mechanically recycled Expanded Polystyrene as 50% of the total EPS used in a composite foam concrete panel has been assessed experimentally. The results of the experimental program have been interpreted with respect to various useful structural behaviors in compression and flexure. It is shown that the use of this foam concrete along with cement fiber boards produces a lightweight wall panel that can be used very effectively for load-bearing walls of single storey houses and non-loadbearing walls of multi-storey buildings. These lightweight panels can allow rapid construction while reducing the overall weight of the building.

Axial Performance of Jointed Sandwich Wall Panels

AbstractThroughout this paper, a new system for connecting composite sandwich wall panels is proposed. The relevant structural components are investigated with the aim of utilizing these panels as ...

Experimental evaluation of precast concrete sandwich wall panels with steel–glass fiber–reinforced polymer shear connectors

A new shear connector is proposed in this article. The shear connector is made of steel–glass fiber–reinforced polymer material. Twelve full-scale precast insulated concrete sandwich panels were tested under flexure to analyze their flexural behavior subjected to pressure. The test program was composed of eight sandwich panels with steel–glass fiber–reinforced polymer connectors and four panels for comparison that were panels using stainless steel truss connectors, pure glass fiber–reinforced polymer pin connectors, and no connectors, respectively. Their load–deflection relationships, load–slip relationships, concrete strain profiles along the wythes cross section, as well as the strains in the steel–glass fiber–reinforced polymer W-shaped connectors were investigated in this article. The panels exhibited a composite action in terms of strength exceeding 85% with steel–glass fiber–reinforced polymer connectors and 40 mm insulation thickness. In addition, the other panels with more than 40 mm insulation layer and different diameter connectors only exhibited 26%–62% composite action. When evaluating the degree of the composite action in terms of stiffness, all sandwich panel values ranged from 6% to 26%. But the compared specimens with pure glass fiber–reinforced polymer connector and smaller diameter steel truss connector had lower level composite action less than 10%. Reasonable design of steel–glass fiber–reinforced polymer W-shaped connectors may provide high composite action for panels and prevent the strength from dropping rapidly due to the steel inner core in the connectors.

Structural behavior of load-bearing sandwich wall panels with GFRP skin and a foam-web core

Abstract An innovative load-bearing sandwich wall panel with glass fiber-reinforced polymer (GFRP) skins and a foam-GFRP web core (GSFW wall panels, where “GS” denotes GFRP skin and “FW” denotes foam-GFRP web core), which was manufactured using a vacuum-assisted resin infusion process, was developed in this paper. An experimental study involving nine specimens was conducted to validate the effectiveness of this panel for increasing the axial strength under edgewise compression loading. The effects of web thickness, web spacing, web height, and skin thickness on axial stiffness, displacement ductility, and energy dissipation were also investigated. The test results demonstrated that axial strength, axial stiffness, displacement ductility, and energy dissipation could be improved by increasing the web thickness, web height, and skin thickness. An analytical model that considers the confinement effect of foam and the local buckling of GFRP skin was proposed to predict the ultimate axial strength of GSFW panels. A comparison of the analytical and experimental results showed that the analytical model accurately predicted the ultimate axial strength of GSFW wall panels under edgewise compression loading. To simulate the low velocity impact by blindings that are rolled by the wind, an impact test was conducted and the residual axial strength of the wall panels after impact was also investigated.

Effect of cyclic loading on composite behavior of insulated concrete sandwich wall panels with GFRP shear connectors

Abstract A full-scale experiment was conducted to investigate the composite behavior of insulated concrete sandwich wall panels (ICSWPs) under monotonic loads and wind-induced cyclic loads. The experimental program consists of two groups, according to the applied loading type and the type of insulation, with the same configurations of glass-fiber-reinforced polymer (GFRP) grids. The degree of composite action in terms of the initial stiffness and ultimate strength were compared at the global level, and the degree of composite action in terms of the shear flow were compared at the local level (in accordance with the variables). The test results showed that the adhesive bonds based on the insulation absorptiveness and the mechanical bonds based on the insulation surface roughness and groove treatment were effective for inducing the desired composite behavior of ICSWPs in both monotonic loading and cyclic loading tests. The cyclic test group showed a lower degree of composite action compared to the monotonic test group at a constant rate. This is the case because cumulative fatigue loading damaged the GFRP strands and debonded the interface between the concrete and insulation. These results indicated that the adhesive and mechanical bonds between the insulation and concrete wythes can be used to estimate the design strength of ICSWPs with GFRP shear grids. Additionally, the reduction factor for the design strength by the fatigue effect should be considered in estimation of design strength.

Experimental characterisation of cork agglomerate core sandwich panels for wall assemblies in buildings

In recent times, the construction market has seen a very significant increase in the demand of prefabricated solutions of nonstructural elements, such as sandwich panels for buildings walls. Due to the inherent low weight, good mechanical behaviour, ease of assembly and cost-effectiveness, these types of wall assemblies are especially competitive in construction of single-family houses or one unit dwelling structures.However, the low fire resistance of many of these solutions, such as sandwich panels with expanded polystyrene core or polyethylene terephthalate foam core, precludes their use in buildings with more than one floor. The substandard fire resistance is generally due to the fact that the constituent materials are combustible or, at least, their properties are extremely sensible when subjected to high temperatures or flame.Given the isolation properties, good mechanical damping and fire resistance, cork agglomerate can be used as the core material for sandwich panels. However, this material is heavier than the other materials commonly used as core for sandwich panels. In order to deal with this drawback, it is necessary to choose a material for the panel facings that could fulfil the mechanical requirements and the condition not excessively increase the panel weight. The use of a glass fibre reinforced polymer seemed a suitable solution for the facing component. Therefore, the proposed wall assembly solution consists in a sandwich panel with cork agglomerate core and glass fibre reinforced polymer facings.The scope of this work was the assessment of the feasibility of a new configuration of vertical (wall) sandwich panels that could, not only be a cost effective solution for prefabricated construction, but also provide good mechanical performance and fire resistance. This sandwich wall panel configuration was tested for characterisation of its mechanical behaviour, resistance to impact and to fire. The results of the experimental campaign carried out are presented in this manuscript along with some conclusions about the suitability of this solution as sandwich wall panel for buildings façades.

Reliability-based flexural design models for concrete sandwich wall panels with continuous GFRP shear connectors

This paper proposes design models for insulated concrete sandwich wall panels (SWPs) with GFRP grids against a flexural failure. The design models are developed by considering both ultimate and serviceability limit states. First, mean-prediction models for evaluating ultimate moments and cracking moments of SWPs are proposed, and second, they are further developed into design models by adding capacity factors (or safety factors). The capacity factors are statistically determined using the method provided in Eurocode 1990: 2002 [1]; this method considers the random distribution of resistance defined by evaluating both modeling and parametric uncertainties. Two capacity factors are calibrated for an ultimate limit state function and a serviceability limit state function. For a more convenient design process, a unified capacity factor is determined by combining both factors into a function of a nominal ultimate moment. The unified factor can be applied to achieve the ultimate limit state requirement, and at the same time it automatically achieves the serviceability requirement.

Precast Concrete Sandwich Wall Panels with Bolted Angle Connections Tested in Flexure Under Simulated Wind Pressure and Suction

Precast Concrete Sandwich Wall Panels with Bolted Angle Connections Tested in Flexure Under Simulated Wind Pressure and Suction

Flexural strength for insulated concrete sandwich wall panel reinforced with glass-fiber-reinforced polymer shear grids: roughness-induced mechanical bonding

Insulated concrete sandwich wall panel systems proposed in this paper were reinforced with glass-fiber-reinforced polymer (GFRP) grids as continuous shear connectors. This continuous shear grid connecting inner/outer concrete wythes is advantageous to induce mechanical bond between concrete and insulation. Three different surface roughness was adopted to investigate the effect of mechanical bonding on flexural strength of extruded polystyrene-insulated concrete sandwich wall panels. An experimental programme is organised to conduct full-scale bending tests with three groups of original surface, mechanically roughened surface and traction-free surface of extruded polystyrne (XPS) foams. The load–deflection behaviour was investigated at different number of shear grids in terms of strength, stiffness and deformation capacity. Mechanical bond dependence on the flexural strength could be quantified at different surface treatment and should be considered in design of continuous shear grids for insulated concrete sandwich wall panel systems.

Flexural behavior of precast concrete sandwich wall panels with basalt FRP and steel reinforcement

Flexural behavior of precast concrete sandwich wall panels with basalt FRP and steel reinforcement

Composite Behavior of Insulated Concrete Sandwich Wall Panels Subjected to Wind Pressure and Suction.

A full-scale experimental test was conducted to analyze the composite behavior of insulated concrete sandwich wall panels (ICSWPs) subjected to wind pressure and suction. The experimental program was composed of three groups of ICSWP specimens, each with a different type of insulation and number of glass-fiber-reinforced polymer (GFRP) shear grids. The degree of composite action of each specimen was analyzed according to the load direction, type of the insulation, and number of GFRP shear grids by comparing the theoretical and experimental values. The failure modes of the ICSWPs were compared to investigate the effect of bonds according to the load direction and type of insulation. Bonds based on insulation absorptiveness were effective to result in the composite behavior of ICSWP under positive loading tests only, while bonds based on insulation surface roughness were effective under both positive and negative loading tests. Therefore, the composite behavior based on surface roughness can be applied to the calculation of the design strength of ICSWPs with continuous GFRP shear connectors.

Composite Behavior of a Novel Insulated Concrete Sandwich Wall Panel Reinforced with GFRP Shear Grids: Effects of Insulation Types.

A full-scale experimental program was used in this study to investigate the structural behavior of novel insulated concrete sandwich wall panels (SWPs) reinforced with grid-type glass-fiber-reinforced polymer (GFRP) shear connectors. Two kinds of insulation-expanded polystyrene (EPS) and extruded polystyrene (XPS) with 100 mm thickness were incased between the two concrete wythes to meet the increasing demand for the insulation performance of building envelope. One to four GFRP shear grids were used to examine the degree of composite action of the two concrete wythes. Ten specimens of SWPs were tested under displacement control subjected to four-point concentrated loads. The test results showed that the SWPs reinforced with GFRP grids as shear connectors developed a high degree of composite action resulting in high flexural strength. The specimens with EPS foam exhibited an enhanced load-displacement behavior compared with the specimens with XPS because of the relatively stronger bond between insulation and concrete. In addition, the ultimate strength of the test results was compared to the analytical prediction with the mechanical properties of only GRFP grids. The specimens with EPS insulation presented higher strength-based composite action than the ones with XPS insulation.