Precast Concrete Sandwich Panels Research Articles

Structural Behavior of Precast Foamed Concrete Sandwich Panel Subjected to Vertical In-Plane Shear Loading

Experimental and analytical studies were accomplished to examine the structural behavior of precast foamed concrete sandwich panel (PFCSP) under vertical in-plane shear load. PFCSP full-scale specimens with total number of six were developed with varying heights to study an important parameter slenderness ratio (H/t). The production technique of PFCSP and the procedure of test setup were described. The results obtained from the experimental tests were analysed in the context of in-plane shear strength capacity, load-deflection profile, load-strain relationship, slenderness ratio, shear cracking patterns and mode of failure. Analytical study of finite element analysis was implemented and the theoretical calculations of the ultimate in-plane shear strengths using the adopted ACI318 equation for reinforced concrete wall were determined aimed at predicting the in-plane shear strength of PFCSP. The decrease in slenderness ratio from 24 to 14 showed an increase of 26.51% and 21.91% on the ultimate in-plane shear strength capacity as obtained experimentally and in FEA models, respectively. The experimental test results, FEA models data and theoretical calculation values were compared and provided a significant agreement with high degree of accuracy. Therefore, on the basis of the results obtained, PFCSP wall has the potential use as an alternative to the conventional load-bearing wall system.

Modeling, Analysis, and Behavior of Load-Carrying Precast Concrete Sandwich Panels

AbstractThis paper investigates the behavior of precast concrete sandwich panels (PCSPs) made with truss shear connectors, which accounts for partial shear interaction. A theoretical model is developed based on variational principles and equations of equilibrium that account for the axial and bending rigidities of reinforced concrete (RC) layers and their potential cracking, the shear and normal rigidities of the insulation layer, and the elastic flexibility of the diagonal truss connectors. This layered modeling approach is general and can be used to describe the structural behavior under various loading patterns and boundary conditions, with the influence of the partial shear interaction as an automatic outcome of the analysis. As such, it provides a better and a more reliable tool than other existing simplified models in the literature for describing the complex structural behavior of PCSPs. A parametric study is presented, which investigates key parameters in the design of concrete sandwich panels, su...

Structural behavior of axially loaded precast foamed concrete sandwich panels

This paper presents results from an experimental and analytical study of precast foamed concrete sandwich panels (PFCSPs). Full-scale experimental tests of six PFCSPs were conducted to study the behavior of the panels under axial loads. Foamed concrete (FC) was used to cast PFCSP concrete wythes. The axial load-bearing capacity, load–deflection profiles, load–strain relationships, slenderness ratio, load–displacement, load–deformation, failure and collapse modes, cracking patterns, and propagations under constant increments of axial loads were recorded and discussed. The properties and use of FC were briefly reviewed. Results of the experimental test and finite element analysis were compared with the theoretical values calculated based on the American Concrete Institute (ACI) design equation for a solid concrete wall and other empirical formulas developed by antecedent researchers which might be applicable to predict the ultimate load-bearing capacity of sandwich panels. A semi-empirical formula was proposed based on the laboratory test and finite element analysis results.

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

EXPERIMENTAL AND NUMERICAL STUDY ON THE FLEXURAL BEHAVIOR OF PRECAST LIGHT-WEIGHT CONCRETE SANDWICH PANELS

Use of light-weight structural elements in buildings is becoming popular in the recent years. This paper presents the experimental and numerical studies carried out to understand the flexural behavior of prototype precast light-weight concrete sandwich panels under four-point bending. In the experimental study, two prototype panels were cast and tested. Transverse deflections of the panels were recorded during testing and the results are presented and discussed. Numerical studies were carried out using the general purpose finite element software ABAQUS. 8-noded linear brick element and 2-noded linear truss element were used to model the wythes and mesh reinforcements, respectively. Saenz model is used to model the behavior of concrete in compression. It is observed from the tests that, the panels behaved as composite elements until failure. Experiments indicate that the thickness of the panel affect the load carrying capacity of the concrete sandwich panel significantly. The load-deflection curves of the panels determined using numerical studies are comparable to that of the experimental results.

Durability and long term behavior of FRP/foam shear transfer mechanism for concrete sandwich panels

This paper presents an experimental program to evaluate the effect of sustained loading and outdoor exposure on the shear strength of precast concrete sandwich panels connected with FRP grid/rigid foam insulation as shear transfer mechanism. CFRP and GFRP grids were considered in this study along with EPS and XPS foam. The experimental program is comprised of three different studies with a total of 26 test panels using different combinations of FRP grid and foam insulation.

Cost optimization of load carrying thin-walled precast high performance concrete sandwich panels

The paper describes a procedure to find the structurally and thermally efficient design of load-carrying thin-walled precast High Performance Concrete Sandwich Panels (HPCSP) with an optimal economical solution. A systematic optimization approach is based on the selection of material's performances and HPCSP's geometrical parameters as well as on material cost function in the HPCSP design. Cost functions are presented for High Performance Concrete (HPC), insulation layer, reinforcement and include labour-related costs. The present study reports the economic data corresponding to specific manufacturing process and actual financial parameters for the Danish prefabrication industry. The strength based design of HPCSP is in competence with the format of Eurocode 2 and takes into account failure modes related to flexure, shear, HPCSP buckling/slenderness, local HPC plate buckling and maximum deflections. The solution of the optimization problem is performed in the computer package software Matlab® with SQPlab package and integrates the processes of HPCSP design, quantity take-off and cost estimation. The proposed optimization process outcomes in complex HPCSP design proposals to achieve minimum cost of HPCSP.

Numerical simulation of hollow steel profiles for lightweight concrete sandwich panels

The focus of the present study is to investigate both local and global behaviour of a precast concrete sandwich panel. The selected prototype consists of two reinforced concrete layers coupled by a system of cold-drawn steel profiles and one intermediate layer of insulating material. High-definition nonlinear finite element (FE) models,based on 3D brick and 2D interface elements, are used to assess the capacity of this technology under shear, tension and compression. Geometrical nonlinearities are accounted via large displacement-large strain formulation, whilst material nonlinearities are included, in the series of simulations, by means of Von Mises yielding criterion for steel elements and a classical total strain crack model for concrete; a bond-slip constitutive law is additionally adopted to reproduce steel profile-concrete layer interaction. First, constitutive models are calibrated on the basis of preliminary pull and pull-out tests for steel and concrete, respectively. Geometrically and materially nonlinear FE simulations are performed, in compliance with experimental tests, to validate the proposed modeling approach and characterize shear,compressive and tensile response of this system, in terms of global capacity curves and local stress/strain distributions. Based on these experimental and numerical data, the structural performance is then quantified under various loading conditions, aimed to reproduce the behaviour of this solution during production, transport, construction and service conditions.

In-plane shear behavior of insulated precast concrete sandwich panels reinforced with corrugated GFRP shear connectors

Precast concrete sandwich panels often are used for the exterior cladding of residential and commercial buildings due to their thermal efficiency. Precast concrete sandwich panel systems consist of two precast reinforced concrete walls that are separated by a layer of insulation and joined by connectors that penetrate the insulation layer and are anchored to two precast concrete wythes. This paper presents push-out test results of concrete sandwich panels with and without corrugated shear connectors to investigate in-plane shear performance. The variables in this study are two types of insulation materials and the width, pitch, and embedment length of shear connectors. The test results indicate that the type of insulation material that is used in the system considerably affects the bond strength between the concrete walls and the insulation layer. A design equation adopted in ICC-ES is revised to determine the shear design capacity of precast concrete sandwich panels with various configurations of shear connectors.

Experimental and Numerical Investigation of the FRP Shear Mechanism for Concrete Sandwich Panels

AbstractThis paper investigates the composite action of 46 segments representing precast concrete sandwich panels (PCSPs) using a fiber-reinforced polymer [FRP; specifically, a carbon fiber–reinforced polymer (CFRP)] grid/rigid foam as a shear mechanism. The experimental aspect of the research reported in this paper examined the effect of various parameters believed to affect the shear flow strength for this CFRP grid/foam system. The parameters that were considered are the spacing between vertical lines of CFRP grids and the thickness of the rigid foam. Results of the experimental aspect of the research reported in this paper indicated that increasing the spacing between vertical lines of CFRP grid increase the overall shear flow strengths due to the increase of the bonded contact area of the rigid foam to the concrete surface. However, the overall shear stresses were decreased due to the increase of this interface surface area. Test results also indicated that increasing the rigid foam thickness decreas...

Computation of linear transmittance of thermal bridges in precast concrete sandwich panels

Precast concrete lightened sandwich panels are widely used building elements. They are 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 wythe and act as thermal bridges.Computation of thermal transmittance of sandwich panels is clearly described in European Standards, but in many cases it requires numerical simulations to determine the linear transmittance ψ associated with lightweight material-concrete interfaces in the inhomogeneous layer. Although simple, these simulations represent a critical issue for many panel manufacturers and they would much rather prefer correlations to compute ψ.In this work we present a correlation based on an artificial neural network (ANN) to estimate linear trasmittauce values for current Italian sandwich panel production. Five input parameters are considered: rib width, lightweight material conductivity, and thickness of the three panel layers. To obtain the data which are necessary to train and test the ANN, a fast and accurate Spectral Element Method is used to solve Laplace equation in the neighborhood of a rib. 5460 ψ values are collected which ensure an accurate network response.

Facilitating the incorporation of VIP into precast concrete sandwich panels

This research focuses on the development of thin, load bearing, composite concrete façade elements containing high performance thermal insulation. A pilot project involving the construction of a detached house has been completed resolving issues related to the construction, production and economic requirements of utilizing vacuum insulated panels (VIPs) within prefabricated concrete façade elements. During the project planning process it was discovered that particular VIP dimensions were necessary for avoiding wasted material and thermal bridging. VIPs produced for façade elements with widths corresponding to architectural modules of 15, 30, and 60cm and lengths corresponding to 1/3rd of the project height would alleviate these issues. Within the building industry, VIPs are viewed as a viable solution for optimizing the space saving attributes of high performance walls. By correctly sizing mass-produced VIP elements for façade measurement modules, rather than expecting insulation along the border of each sandwich panel to be cut-to-fit, architects can more easily take advantage of the efficiency that VIPs offer when designing prefabricated façade panels. Currently, there is a demand for a new market catering to VIP inclusion within façade strategies that would facilitate the use of VIPs by architects and planners in building large-scale urban planning strategies.

Structural Behavior of Precast Lightweight Foam Concrete Sandwich Panel with Double Shear Truss Connectors under Flexural Load

This paper presents the structural behaviour of precast lightweight foam concrete sandwich panel (PFLP) under flexure, studied experimentally and theoretically. Four (4) full scale specimens with a double shear steel connector of 6 mm diameter and steel reinforcement of 9 mm diameter were cast and tested. The panel’s structural behavior was studied in the context of its ultimate flexure load, crack pattern, load-deflection profile, and efficiency of shear connectors. Results showed that the ultimate flexure load obtained from the experiment is influenced by the panel’s compressive strength and thickness. The crack pattern recorded in each panel showed the emergence of initial cracks at the midspan which later spread toward the left and right zones of the slab. The theoretical ultimate load for fully composite and noncomposite panels was obtained from the classical equations. All panel specimens were found to behave in a partially composite manner. Panels PLFP-3 and PLFP-4 with higher compressive strength and total thickness managed to obtain a higher degree of compositeness which is 30 and 32.6 percent, respectively.

Structural Behaviour of Precast Lightweight Foamed Concrete Sandwich Panel (PLFP) with Double Shear Truss Connectors under Eccentric Load: Preliminary Result

Recent years in Malaysia, precast concrete sandwich panel gained its popularity in building industries due to its economic advantages, superior thermal and structural efficiency. This paper studied the structural behaviour of precast lightweight foamed concrete sandwich panel (PLFP) with double shear truss connectors under eccentric load. Preliminary results were analysed and studied to obtain the ultimate load carrying capacity, load-deflection profiles and strain distribution across the panel thickness at mid depth. The achieved ultimate load carrying capacity of PLFP due to eccentric load from the experimental work was compared with values calculated from classical formulas (if it is more than 1 comparison) developed by previous researchers. Preliminary results showed that, the use of double shear truss connectors in PLFP was able to improve its ultimate load carrying capacity to sustain eccentric load and achieve certain compositeness reaction in between the wythes.

Testing and Acceptance Criteria for Fiber-Reinforced Composite Grid Connectors Used in Concrete Sandwich Panels

Precast concrete sandwich panels have been used in building construction since the 1960s. These sandwich wall panels are constructed with two wythes of concrete separated by a layer of thermal foam plastic insulation and a shear connector mechanism between concrete wythes. Recently, more research is focused on fiber-reinforced composite grids as shear connectors due to their superior thermal performance compared to other connectors such as steel or solid concrete. However, while there are guidelines for design of concrete sandwich panels, there is no standardized guidance that provides testing and capacity determination for composite shear connectors. Therefore, testing and acceptance criteria were developed to evaluate the shear transfer capacities of fiber-reinforced composite grid connectors used in combination with rigid insulation in concrete sandwich panel construction. The criteria are intended to standardize testing and evaluation of the interaction between concrete and composite shear connectors so manufacturers can provide consistent results, and the data pool generated by standardized testing can support the formulation of design assumptions.

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...

Insulation Type Effect on the Direct Shear Behavior of Concrete Sandwich Panel (CSP) with Non-Shear Connectors

Precast concrete sandwich panels (PCSP) are often used as exterior cladding of residential buildings due to thermal efficiency. PCSP systems consist of two precast reinforced concrete walls separated by a layer of insulation and connected with connectors which penetrate the insulation layer and are anchored at two precast walls. This paper provides the pull-out test results of concrete sandwich panel (CSP) with non-shear connectors. The variables in this study were the casting direction of reinforced concrete walls and types of insulation. Test results indicated that the types of insulations and casting direction have a significant effect on the bond strength between concrete wall and insulation. The effect of insulation type is notable for CSP cast horizontally concrete walls.

Effect of GFRP Shear Ties on Shear Behavior of Interfaces between Precast Concrete Panel and Extruded Polystyrene Special Insulation

This paper describes the test results on the direct shear behavior of glass-fiber reinforced polymer (GFRP) shear tie reinforced interfaces between precast concrete sandwich panels (PCSP) and extruded polystyrene (XPS) insulations. The insulated PCSP consists of two concrete panels with 100mm or 80mm thick insulation between inner/outer concrete panel layers. In order to achieve composite action concrete panels are connected by corrugated GFRP shear connector. In this study, three types of couple replicate insulated PCSP with different embedment length of GFRP shear connector were made and loaded in push-out. The test results indicated that the reinforcement of GFRP shear ties for interface between PCSP and XPS insulation improves initial and post-peak shear performance of insulated PCSPs. These phenomena are remarkable for XPS insulated PCSPs with larger embedment length of GFRP shear connectors.

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.

Revised zone method R-value calculation for precast concrete sandwich panels containing metal wythe connectors

Metal wythe connectors are used in a typical precast concrete sandwich panel to tie concrete wythes together and to keep the panel intact during handling and in service. Connectors interrupt the continuous insulation layer, reducing the effectiveness of the insulation. In current practice, thermal resistance (R-value) of such a panel is calculated from the zone method. However, the zone width parameter W used in the zone method was originally developed for metal-frame structures and an accurate R-value cannot be estimated for precast concrete sandwich panels containing metal wythe connectors. This paper proposes a new zone-width equation for use in the current zone method to compute the R-value of precast concrete sandwich panels containing the metal wythe connectors. The proposed zone width W n was derived from the results of a series of finite element heat-transfer analyses intended to quantify the influence of several key parameters on W n . It was found that the zone method with the proposed zone-width equation can accurately estimate R-value of a precast concrete sandwich panel containing metal wythe connectors. Also the proposed zone-width equation can effectively consider the effects of metal wythe connector sizes and spacing, material conductivities, and panel thicknesses in the zone method of R-value computation.