Concrete Sandwich Research Articles

Thermal performance of concrete sandwich panels incorporating phase change materials: An experimental study

The employment of phase change materials (PCMs) in the construction of concrete building components has engaged many researchers’ interest. In this study, a novel reduced-scale experiment is employed to perform a parametric investigation of the thermal performance of PCM-integrated wall specimens considering two types of concrete, two types of PCM, and different thicknesses of the concrete and PCM layers. Moreover, three different ambient temperature profiles of a summer day in three different cities were considered as the outside ambient temperature to evaluate the performance of each PCM under different temperature conditions. The test procedure is capable of evaluating the thermal performance of different wall configurations under various temperature conditions. The inside temperature variations of the wall specimens were monitored as the thermal performance criteria. In consequence, integrating the PCM layer with normal concrete or with slimmer concrete layers resulted in better thermal performance of PCM in absorbing heat in comparison to lightweight concrete or thicker specimens due to the considerable effect of density and specific heat capacity of different types of concrete. Moreover, the compatibility of the melting temperature of PCMs with the ambient temperature of the considered cities in summer is assessed and discussed.

Structural performance and section optimization of precast concrete sandwich panels with pin-type GFRP connectors

A precast concrete sandwich panel (PCSP) offers a good potential in the application of façade wall due to the improved energy efficiency. In this study, the structural performance of PCSP with pin-type glass fiber reinforced polymer (GFRP) connectors was investigated, and an optimization characterized by ribbed structural wythe was proposed and studied. Firstly, the pull-out and shear capacity of the pin-type connector were evaluated through direct tensile test and direct shear test, respectively. Thereafter, seven PCSP specimens were fabricated and tested under four points flexural load. The investigating parameters included the structural wythe thickness, loading direction, insulation bond, and section type of the structural wythe. The load-deflection relationship, crack pattern, failure mode, load-strain relationship, and degree of composite action of the PCSP were studied and compared. It was concluded that: (1) the tested PCSPs presented ductile failures; (2) the structural wythe thickness, loading direction and insulation bond would influence the cracking, yielding, and peak loads of the tested PCSP; (3) the PCSP with pin-type GFRP connectors could be designed as non-composite type owing to the low composite action; and (4) the proposed ribbed structural wythe could achieve a lightweight PCSP while considerable flexural stiffness and capacity could be retained.

Structural performance of concrete sandwich panels under fire

This paper investigates the structural performance of load-bearing precast concrete sandwich panels subjected to one-sided fire. It focuses on panels made with FRP diagonal-bar connectors. Heat transfer analysis is conducted for characterizing the temperature gradient within the panel and a structural model is developed. The model considers the composite action between the reinforced concrete (RC) wythes, the transient creep of concrete under fire, strain softening in compression, cracking and tension stiffening, yielding of the steel reinforcement and geometric nonlinearity. The heat transfer analysis is conducted using a finite element approximation, and the governing differential equations of the structural model are solved using the nonlinear shooting method following an iterative procedure. The model is validated through comparisons with test results and other models in the literature. A numerical example and a parametric study that show the capabilities of the proposed model and clarify the structural behavior are presented. The results reveal progressive failures of the FRP-bar connectors and buckling failures of the panels under fire. It is revealed that the load eccentricity of the applied load greatly affects both the structural performance and the fire resistance of the panels. The diameter of FRP bars, the thickness of insulation layer and the load level are also found to play key roles in the fire resistance of the panels.

Impact behaviour of crushed-brick lightweight RC sandwich slabs

In recent construction practice, sandwich panels have been increasingly adopted due to the fact that they are lightweight, energy efficient, aesthetically attractive, and easy to handle and erect. This study examines the impact behaviour of lightweight reinforced concrete (RC) sandwich slabs produced from local lightweight coarse aggregate. The experimental program included testing two slabs produced with normal coarse aggregate (solid slab + sandwich slab) and six concrete sandwich slabs (CSSs) produced using crushed clay bricks as lightweight coarse aggregate with various shear connecter configurations and types and steel fibre volume fractions (VF%). The impact load was applied at the midpoint of each slab using an 8 kg drop-weight from a height of 2 m. The test results showed CSS behaviour variation with different VF% and the optimum layout and location of shear connectors.

An experimental and numerical study on the in-plane axial and shear behavior of sprayed in-situ concrete sandwich panels

The paper deals with the experimental and numerical characterization of the in-plane axial and shear mechanical behavior of sprayed in-situ reinforced concrete (RC) sandwich panels, used as structural walls. Axial compression tests were carried out on specimens with different slenderness ratios to study their behavior under axial vertical loads. While the diagonal compression test and shear load with constant compression test were respectively performed on squared panels, analyzing their response to in-plane horizontal lateral forces. Ultimate axial and shear loads have been experimentally determined and the most significant load–displacement diagrams have been reported. The obtained results have been compared with other experimental campaigns on RC sandwich panels and with conventional RC walls equations, available in codes of practice and literature. The structural potentialities of RC sandwich panels as load-bearing and shear walls are highlighted. The experimental investigation is corroborated by a 3D nonlinear finite element (FE) numerical analysis, considering the influence of the insulation layer, the efficiency of steel connectors, and the involved material nonlinearities.

Low-Velocity Impact Experiments and Modeling of TRC Skin-Aerated Concrete Core Sandwich Composites.

Mechanical response of textile-reinforced aerated concrete sandwich panels was investigated using instrumented three-point bending tests under quasi-static and low-velocity impact loads. Two types of core material were compared in the sandwich composite consisting of plain autoclaved aerated concrete (AAC) and fiber-reinforced aerated concrete (FRAC), and the stress skins were alkali-resistant glass (ARG) and textile reinforced concrete (TRC). The textile-reinforced layer promoted distributed cracking mechanisms and resulted in significant improvement in the flexural strength and ductility. Digital Image Correlation (DIC) was used to study the distributed cracking mechanism and obtain impact force-crack width response at different drop heights. A constitutive material model was also developed based on a multi-linear tension/compression strain hardening model for the stress-skin and an elastic, perfectly plastic compression model for the core. A detailed parametric study was used to address the effect of model parameters on the flexural response. The model was further applied to simulate the experimental flexural data from the static and impact tests on the plain aerated concrete and sandwich composite beams.

Shaking table test on insulated sandwich concrete wall building structure

To solve the problems of concrete sandwich panels such as cold bridge, weak connection, and poor ductility, a new configuration, namely the insulated sandwich concrete wall (ISCW) is proposed in this paper. Shaking table test is performed on a 1:3 scaled model of 3-storey ISCW building structure to study the seismic behavior of an ISCW structure. Results indicate the ISCW building structure has large stiffness and can work in elastic state under small earthquakes. The stiffness degrades continuously and the structure arrives in a plastic state as the PGA increases, but the degradation process is relatively slow. The cracks or damages mainly occur on the wall with big opening of floor one, but they do not spread through the walls and no collapse happens. With a rational arrangement of the cold-formed thin-walled steel tube columns, the structural integrity and ductility are significantly improved. Three types of seismic waves were input in the test, and significantly different structural responses were caused. Hence the ground motion spectrum characteristics cannot be ignored when the seismic response of an ISCW building structure is analyzed.

High Temperature Performance of a prefabricated concrete sandwich panel

The innovative sandwich wall panel studied in this paper can be used as the load-bearing member of the structure. In addition to the traditional sandwich panel structure, the new panel system also has the characteristics of spiral stirrups along the section of the core column, 650mm column spacing, foam concrete for insulation layer and self-compacting concrete for outer layer. In addition, in order to improve the overall strength and stiffness of the panel, a unique wire system consisting of two vertical wire mesh connected by a short horizontal steel bar is adopted in the concrete layer. In order to study the mechanical properties of the new panel system at high temperature, ABAQUS simulation was carried out. The simulation results show that the new precast concrete sandwich wall system has good resistance to high temperature and still has good bearing capacity after high temperature.

Design and production of sustainable lightweight concrete precast sandwich panels for non-load bearing partition walls

The trend for utilizing sustainable products is becoming increasingly important in the construction industry. Precast concrete sandwich systems containing expanded polystyrene (EPS) is gradually re...

Long-term behavior of precast, prestressed concrete sandwich panels reinforced with carbon-fiber-reinforced polymer shear grid

Long-term behavior of precast, prestressed concrete sandwich panels reinforced with carbon-fiber-reinforced polymer shear grid

Structural performance of textile reinforced concrete sandwich panels under axial and transverse load

AbstractThe performance of textile reinforced concrete composite panels (TRCCPs) under the action of pseudo-static load up to collapse was evaluated. The test of TRCCPs under axial and transverse loading was conducted, and the results were compared with those for steel wire mesh reinforced-concrete composite panels (SMRCCPs). Ceram-site concrete was utilized as the panel matrix owing to its lightweight and insulation characteristics. The ultimate load bearing capacity, load-deformation and load-strain relationships, and failure modes were discussed and investigated in comparison with the findings of non-linear finite-element-model (FEM) analysis and the analytic method on the basis of the reinforced concrete (RC) theory. The analysis results indicate that TRCCP is suitable for use as a potential structural member for a wall or slab system of buildings, and the typical RC theory can be applied to predict the ultimate load bearing capacity if modified suitably.

In-plane behaviour of expanded polystyrene core reinforced concrete sandwich panels

The structural behavior of Expanded Polystyrene (EPS) core Reinforced Concrete Sandwich Panels (RCSP) under axial and in-plane shear loading is studied, experimentally. An experimental study is conducted on RCSP consisting of factory made corrugated EPS core, welded wire mesh, and orthogonal shear connectors. Total 14 specimens (six of axial compression and eight of diagonal compression) are constructed and tested. The specimens are tested in displacement control mode with Digital Image Correlation (DIC) to measure displacements and strains. The mode of failure, propagation of cracks, ultimate axial load carrying capacity, in-plane shear strength, and stress–strain curves are presented in this article. The experimentally obtained axial load capacity and shear strength are also compared with those calculated analytically. The axial load capacity obtained analytically is in good agreement with experimental results, but the shear strength obtained from experiment is much higher than that estimated using the design codes for reinforced concrete.

Development Length of Small-Diameter Basalt FRP Bars in Normal- and High-Strength Concrete

Abstract Small-diameter fiber-reinforced polymer (FRP) bars have great potential in certain applications, such as concrete sandwich panels, ties, and shear connectors. In this study, the developmen...

Bond between concrete and rigid foam in precast concrete sandwich construction

AbstractIn precast concrete sandwich construction mechanical connectors are used to transfer loads between the two concrete shells. Omitting these connectors seems economically interesting for realizing novel sandwich elements with lightweight facings made of textile‐reinforced concrete or other materials. Then, the adhesion between the isolating layer and the cover layers becomes the decisive parameter. In order to evaluate the basic influence of surface texture and type of concrete on the bond strength, an experimental study including different rigid foams and ordinary performance concrete (OPC) as well as ultra‐high performance concrete (UHPC) was carried out. The results of 120 tensile bond tests and 30 shear tests on concrete‐rigid foam composites show that technically relevant bond strengths can be achieved by pouring the concrete onto the rigid foam. For OPC, the tensile bond strength is 50% higher than the minimum value required for external thermal insulation composite systems without mechanical connectors. For UHPC significantly higher bond strengths are obtained, which can be attributed to a better micromechanical interlock. In some cases, the strength of the composite was limited by the strength of the foam. The results are valuable for identifying promising rigid foam‐concrete configurations.

Behavior of Steel–Concrete–Sandwiched Beam with Steel Fiber Reinforced Concrete Core and X-Form Shear Connectors

Steel–concrete–sandwich (S–C–S) construction has its applications in protection against fatigue, impact and blast loads. In blast-resistant construction, concrete is the most predominantly used building material. Due to the impact of blast loads, the structural and material integrity of concrete gets deteriorated due to spalling, cracking, etc. Recent studies have showed that steel–concrete–sandwich structures exhibited better ductility, structural integrity and blast-resistant capacity. The paper presents a numerical study on steel–concrete–sandwiched beam with through–through shear connectors (S–C–S-TT) after validation from previous experimental tests. Also, the shear connector of the S–C–S-TT beam was modified to X-form shear connectors (S–C–S-X) and its behavior due to the configuration change was studied. The performance of the S–C–S-X beam was found to be superior in terms load carrying capacity and deflection capacity than the S–C–S-TT beam. In order to understand the role of fiber reinforced concrete in S–C–S construction, a new S–C–S-X beam with steel fiber reinforced concrete core (S–C–S-X-SFRC) was modeled and its performance was comparatively studied with S–C–S-TT beam and S–C–S-X beam. The results showed that the S–C–S-X-SFRC beam exhibited enhanced deflection capacity as well as high load carrying capacity than S–C–S-TT beam and S–C–S-X beam. A parametric study was carried out by varying the diameter of connectors, thickness of cover plates and spacing of connectors of S–C–S-X-SFRC beam. From the study, the deflection capacity, which is considered as an important factor for absorbing energy and for designing structures against explosion induced forces, of S–C–S-X-SFRC was found to be high, and thus, it can be used as an alternative to conventional concrete in areas subjected to extreme loading.

Precast Concrete Sandwich Panels for Mass Housing Systems: Plan and Design Strength Requirements

Ambitious mission mode project ‘Affordable Housing for All’ proposed by the Government of India requires an innovative technology for speedy construction of cost-effective residential housing systems. Precast concrete sandwich panels with reinforced concrete wythes, expanded polystyrene core and truss shear connectors can be considered as a suitable alternative to conventional brick masonry walls and reinforced concrete floors. In this paper, a typical plan for mass housing systems is arrived and concrete sandwich panels are proposed to be used in the mass housing systems. In the proposed housing plan, the dimension of each room was selected based on length and width of the concrete sandwich panels (achieving dimensional co-ordination). The design strength of concrete sandwich panels is obtained from the experimental studies available in the literature and compared with actual loading effects on the mass housing system with the proposed plan. The study shows that concrete sandwich panels can be used for acting as load bearing walls and floors in housing systems. The study also indicates that dead weight of the housing systems could be reduced significantly by using concrete sandwich panels. Further experimental and analytical studies are required for assessing the structural behavior of the housing systems with concrete sandwich panels under lateral loads.

Experimental Study on Shear Behavior of Reinforced Concrete Sandwich Deep Beam

In present making of construction industry at a high pace. The tendency of world influenced the high raised buildings. In modern days one of the most common element is deep beam, constructed a small span to depth ratio. The transfer girders most of used in deep beams. In an experimental program consists of 12 deep beam specimens are carried out for shear strength behavior investigation of Reinforced Concrete sandwich deep beam concealed with insulation pad in various depths 200mm and 300mm and 400mm. in the experimental program effective length, depth, the width of the specimens, width of bearing plates, longitudinal reinforcement as 1% to maintain constantly and horizontal reinforcement as varies as 0.15% and 0.25% and 0.35%. We are considered shear span to depth ratio of deep beam is 0.95. The main aim of the experimental study the influence of longitudinal shear reinforcement along with vertical and horizontal shear reinforcement on the shear strength, shear ductility of RC sandwich deep beams of insulation pads placed at different depths.

Experimental and numerical investigation of the creep response of precast concrete sandwich panels

A numerical model is developed in this paper for investigating the time-dependent creep and shrinkage response of precast concrete sandwich panels made with diagonal-bar shear connectors. The material model uses the fixed smeared cracking approach and the modified principle of superposition in its integral form. It is incorporated into the finite element package ABAQUS to build a structural model that considers concrete cracking, tension stiffening, aging, creep, shrinkage and geometric nonlinearity. The time-dependent behaviour is described via a time-stepping analysis. An experimental study that includes testing of four panels under sustained loading for a period of four months is reported. Two panels were subjected to 4-point bending and the other two were loaded under eccentric axial compression. The test results show that creep has led to a reduction of up to 27% in the residual capacity of the axially loaded panels. A good correlation between the numerical model and the experimental results is obtained. The numerical model is further used for conducting parametric studies. The results provide an insight into the critical parameters that govern the time-dependent behaviour of concrete sandwich panels, which include the diameter of the shear connectors, sustained load level, loading eccentricity and concrete strength. It was found that global creep buckling of the investigated panels can occur under eccentric axial load levels that are as low as 60% the load carrying capacity.

Review of thermal and environmental performance of prefabricated buildings: Implications to emission reductions in China

Prefabricated buildings recently became more prominent providing significant benefits including contribution to emission reductions at scale and the manufacturing of building components to high accuracy. However, in China, the proportion of prefabrication is lower than that in many developed countries. The prefabricated wall is one of the most important precast elements and its thermal performance has significant impacts on buildings' energy consumption and environmental performance. This work reviews the thermal performance of prefabricated walls encompassing survey of two common structures, precast concrete sandwich walls and lightweight steel-framed walls. The applicability and limitations of methods frequently used to determine the thermal resistances of these two walls are presented. This article also shows a literature review on the implications of prefabricated buildings to China's emission reductions. Compared to conventional buildings, the contribution of prefabricated buildings on China's emission reduction has been recognized. The potentials on building energy efficient and waste minimisation were also acknowledged. It is concluded that the prefabrication has been generally considered to be a more sustainable method in building sector. The energy-saving potential of prefabrication was demonstrated based on life cycle analysis and thermal performance evaluation. It was found the thermal performance of buildings has multiplied by adopting prefabricated façade elements for building retrofitting. More studies related to thermal performance of prefabricated walls with different structures shall be covered in future research. It is also suggested to develop a more representative result of energy performance by adopting prefabrication, with all dimensions of prefabricated buildings' feature considered.

Blast behaviors of precast concrete sandwich EPS panels: FEM and theoretical analysis

Precast concrete sandwich panel (PCSP) is widely used as the component of the precast concrete structure (PCS). Various numerical studies on PCSPs have been conducted to investigate their blast behavior. At first, a three-dimensional finite element model was established to study the blast resistance of PCSPs. An explosion tests were adopted to validate the accuracy and reliability of the numerical model developed in this study. Secondly, parametric analyses were carried out to investigate the influence of the thickness of expanded polystyrene (EPS) insulation layer, the spacing of connectors, layouts of connectors and the force transfer mechanism of connectors on maximum deflection and the effective plastic strain of PCSPs. Finally, a simplified numerical model is proposed to validate the derivation and simplify the calculation of the dynamic response of PCSPs under blast loads. Moreover, the comparisons of the anti-blast performance between the reinforced concrete (RC) slab and PCSP were also carried out. The results showed that the blast resistance of PCSP is weaker than the conventional RC slab.