Precast Concrete Sandwich Wall Panels Research Articles

Thermal performance and reduced carbon footprint of precast concrete sandwich wall panels (PCSWPs) with composite shear connector – an experimental assessment

ABSTRACT The objective of the present work is to compare the thermal performance of precast-reinforced sandwich wall panels to that of precast-reinforced concrete wall panels. The variables used in this investigation are two different insulation materials (expanded polystyrene (EPS) and extruded polystyrene (XPS) and three different connectors (steel, glass fiber (GFRP)-wrapped steel, and aramid fiber (AFRP)-wrapped steel). A thermal analyzer setup was developed to investigate the heat transfer between the exterior and interior of the panels. The results showed that sandwich wall panels had better thermal resistance compared to the precast concrete wall panel. The temperature on the interior surface of the control specimen was 44°C after the stipulated test period. According to the experimental findings, inclusion of the insulation layer (no connectors) reduced heat transfer by 7.4°C for XPS and 6.7°C for EPS. The temperature on the interior surface was reduced only by 1.6°C and 3.6°C for sandwich panels with steel shear connectors and EPS and XPS as insulation material, respectively, indicating thermal bridging. Diminution of temperature on the interior surface of the sandwich panels with FRP-wrapped connectors varied between 5°C and 7.1°C compared to control specimen as the corrugated C-type fiber-wrapped shear connectors significantly decreased the thermal bridge between layers. In sandwich wall specimens, CO2 emissions from concrete were decreased up to 33%. Embodied carbon during the manufacturing of these panels was also compared, and it was found that the carbon emission was reduced up to 21% in the precast sandwich panels when compared to the precast reinforced wall panels.

Shear Transfer Mechanism between CFRP Grid and EPS Rigid Foam Insulation of Precast Concrete Sandwich Panels

An experimental program was implemented to investigate the shear transfer mechanism of carbon-fiber-reinforced polymer (CFRP) grids and expanded polystyrene (EPS) rigid foam insulation in three wythe precast concrete sandwich wall panels. The purpose of the research was to measure the shear flow capacity and to observe the failure mode(s) of precast concrete sandwich panels manufactured with a CFRP grid shear transfer mechanism between wythes. Six precast concrete sandwich panels were examined by push-out tests in which the center concrete wythe was pushed downward with respect to two outer concrete wythes. It was observed that the average shear flow capacity of the specimens having 2 in (51 mm) thick foam was higher than that of the specimens having 4 in (102 mm) thick foam. In addition, stiffness decreased significantly when the thickness of the EPS insulation increased. The failure mode for the panels included relative displacement between the center concrete wythe and the outer concrete wythes. Test results showed that panels tended to fail by CFRP grid rupture, CFRP grid pull-out, and loss of bond at the concrete/foam interface. Further tests should be performed to fully comprehend the nature of the shear transfer mechanism between the specific CFRP grid used and EPS rigid foam insulation.

Experimental and Numerical Investigation of Novel I-Shaped GFRP Connectors for Insulated Precast Concrete Sandwich Wall Panels

Abstract Insulated precast concrete sandwich wall panels (IPCSWPs) are widely used in the thermal resistance systems of buildings. This paper proposes a novel I-shaped glass fiber-reinforced plasti...

A comparative study of different methods to calculate degrees of composite action for insulated concrete sandwich panels

Precast concrete sandwich wall panels consist of two outer wythes of precast concrete separated by a middle layer of insulation. In recent years, Fiber-Reinforced Polymer (FRP) shear connectors have been increasingly used since they have lower thermal conductivity compared to traditional steel shear connectors, which can significantly reduce thermal bridging. However, FRP shear connectors have lower stiffness, resulting in partial Degree of Composite Action (DCA), which is an important parameter to describe the structural behavior of the panels. Different methods have been proposed to calculate DCAs, including displacement method, strain method, and load method. This paper will compare and evaluate the effectiveness of these methods. A bending test was conducted on a full size of 7 m × 3 m, precast, prestressed insulated concrete sandwich panel with FRP shear connectors. A non-linear Finite Element (FE) model is created, where good correlations can be achieved between the test and FE results. The FE model is further employed to conduct a parametric study by varying the stiffness of the shear connectors. DCAs for different stiffnesses are calculated using the aforementioned three methods and the applicability and limitation of each method are investigated.

Evaluating Elastic Behavior for Partially Composite Precast Concrete Sandwich Wall Panels

Evaluating Elastic Behavior for Partially Composite Precast Concrete Sandwich Wall Panels

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.

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 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

Investigation of Various GFRP Shear Connectors for Insulated Precast Concrete Sandwich Wall Panels

AbstractGlass fiber–reinforced polymer (GFRP) shear connectors provide much reduced thermal bridging in insulated concrete sandwich panels compared to steel connectors. In this study, 50 specimens with dimensions of 254×254×900 mm representing segments of a precast sandwich wall comprising two concrete wythes and a concrete stud surrounded by insulation foam have been tested in a double-shear configuration. Three types of GFRP connectors produced from available sand-coated and threaded rods were tested and compared to conventional steel and polymer connectors. GFRP connector diameters varied from 6 to 13 mm, and spacing varied from 80 to 300 mm. Both circular and rectangular cross sections were examined, along with various end treatments to compare with simple straight embedment. The shear strength of GFRP connectors, including the effect of friction between concrete and foam, ranged from 60 to 112 MPa, significantly higher than polymer connectors but lower than steel connectors. As the connectors bridge...

Performance and Characterization of Shear Ties for Use in Insulated Precast Concrete Sandwich Wall Panels

Insulated precast concrete sandwich wall panels are commonly used for exterior cladding on building structures. The insulation is sandwiched between exterior and interior concrete layers to reduce the heating and cooling costs for the structure. The panels can be designed as composite, partially composite, or noncomposite. Shear ties are used to achieve these varying degrees of composite action between the interior and exterior concrete layers. A variety of shear ties are available for domestic construction. An experimental study was conducted to assess the relative strength and response of these commercially available ties. Fourteen different shear tie types were examined, the failure modes and responses were quantified, and simplified engineer level multilinear strength curves were developed for each connection. The test results indicate that shear ties used in sandwich wall construction have considerable variation in strength, stiffness, and deformability. The maximum shear strength of the discrete ties averaged 9.3 kN (2,100 lbf) with a minimum of 3.2 kN (730 lbf) and maximum of 18.4 kN (4,138 lbf). The ties exhibited elastic-brittle, elastic-plastic, and plastic-hardening responses. The results were used to develop trilinear constitutive relationships, which were used to approximate the flexural response of sandwich wall panels.

Thermal performance evaluation of precast concrete three-wythe sandwich wall panels

Precast concrete sandwich wall panels are commonly constructed of two wythes of concrete separated by a layer of thermal insulation. In these two-wythe panels, solid concrete regions are often provided for embedded hardware for lifting, handling, and connections, or to provide composite action. These solid concrete regions can have a significant adverse impact on the thermal performance of the panels. This research was directed towards the development of precast concrete three-wythe sandwich wall panels with potential improved thermal and structural performance. A three-wythe panel has three concrete wythes and two insulation layers, and all three concrete wythes are connected by solid concrete regions. However, the connections between successive concrete wythes are staggered in location so that the total thermal path length through the concrete is extended. Practical panel configurations of the three-wythe panels were developed to reduce thermal bridge effects caused by regions of solid concrete. The thermal performance of the three-wythe panel was evaluated by estimating its thermal resistance ( R-value) using the finite element method. It was found that, in general, the thermal performance of three-wythe panels is better than that of two-wythe panels due to the increased thermal path length through the panel.

Analytical Investigation of Thermal Performance of Precast Concrete Three-Wythe Sandwich Wall Panels

Precast concrete sandwich wall panels are commonly constructed of two wythes of concrete separated by a layer of thermal insulation. In these two-wythe panels, solid concrete regions which extend directly through the entire thickness of the panel are often provided with embedded hardware for lifting, handling, and connections, or to provide composite action. These solid concrete regions have a significant adverse impact on the thermal performance of the panels. This research was directed towards the development of precast concrete three-wythe sandwich wall panels with improved thermal and structural performance. A three-wythe panel has three concrete wythes and two insulation layers, and all three concrete wythes are connected by solid concrete regions that are staggered in location so that no concrete path extends directly through the entire thickness of the panel. Practical panel configurations of three-wythe panels were developed, and their thermal performance was evaluated by estimating thermal resistance (R-value) using finite element method.

Experimental Evaluation of the Composite Behavior of Precast Concrete Sandwich Wall Panels

Lateral load tests were performed on four full-scale precast concrete sandwich wall panels. The first panel was a typical precast, prestressed concrete sandwich panel that had shear transfer provided by regions of solid concrete in the insulation wythe, metal wythe connectors (M-ties), and bond between the concrete wythes and the insulation wythe. The degree of composite action developed by each shear transfer mechanism (regions of solid concrete, wythe connectors, and bond) was then evaluated by testing three additional panels that included only one mechanism each. The panels were tested in a horizontal position with simple supports under the action of a uniform lateral pressure. It was found that, for the panel geometries and materials treated in this study, the solid concrete regions provide most of the strength and stiffness that contribute to composite behavior. Steel M-tie connectors and bond between the insulation and concrete contribute relatively little to composite behavior. For design purposes, it is recommended that solid concrete regions be proportioned to provide all of the required composite action in a precast sandwich wall panel.