Concrete Sandwich Panels Research Articles

In-plane shear behaviour of concrete sandwich panels reinforced with various geogrids

Seismic occurrences have caused severe damage and even the collapse of fragile unreinforced masonry structures. New technologies are replacing these conventional methods of construction; concrete sandwich panels (CSP) are one such technique gaining popularity. In-plane diagonal shear strength of concrete sandwich panels is studied experimentally, and the effect of incorporating geogrids on the deformation capability and load-bearing capacity is reported. Two forms of geogrid material, plastic uniaxial geogrid (PUG) and polyester biaxial geogrids (PBG2 and PBG3) are used to improve the strength and ductility of concrete sandwich panels. Diagonal compression tests have been carried out better to understand the behavior of CSP under in-plane strength. This paper also discusses the effect of the different mixes, the effect of geogrids, load-deformation behaviour, shear capacity, deflection ductility factor, mode of failure, shear strength, and energy dissipation. In contrast to the control specimen, specimens cast with plastic geogrid had a 13.7% and 26% improvement in shear capacity and load-bearing capability for the two types of micro-concrete mixes used in this study. The conclusion reached is that plastic uniaxial geogrid is effective in improving the concrete sandwich panels’ load-bearing capacity, shear capacity, and deformation ability. Polyester biaxial geogrids enhanced the ductility of the concrete sandwich panels.

Study of the flexural performance and a novel calculation formula for the degree of composite action for precast concrete sandwich panels

SummaryThis study investigates the flexural performance and degree of composite action (DCA) of precast concrete sandwich panels (PCSPs) with four types of connectors. Five full‐scale specimens were designed, and 4‐point bending tests were performed. The specimens included four PCSPs utilizing glass fiber reinforced polymer (GFRP) truss connectors, steel truss connectors, concrete rib connectors, and GFRP pin connectors, respectively, along with a solid panel (SP). The results indicated that the flexural performance and DCA provided by the four types of connectors followed an ascending order as follows: GFRP pin‐type connectors, GFRP truss connectors, steel truss connectors, and concrete rib‐type connectors. Moreover, the study presented a novel method for calculating DCA, namely, the neutral axis method, which was compared with the displacement and strain methods. The reasonableness and accuracy of the neutral axis method in calculating DCA during the linear elastic stage were verified. Results indicated that the neutral axis method provided more precise and reasonable DCA that closely matched the experimental results compared with the displacement and strain methods. Additionally, the neutral axis method was simpler to calculate DCA and had a broader range of applications. Finally, the study provided recommendations for the optimal application scenarios of each calculation method.

Experimental analysis on the out-of-plane structural performance of single-face superposed shear walls with different horizontal connections

Single-face superposed (SFS) shear wall is a novel precast concrete sandwich panel (PCSP) wall that can be used as load-bearing walls in high-rise buildings and underground structures in seismic zones. This paper investigates the out-of-plane structural performance of SFS shear walls with different horizontal connections. Three SFS shear walls with different lap-spliced rebar connection configurations at the horizontal connections were designed and tested to compare their out-of-plane structural performance with that of a cast-in-place specimen, in terms of failure modes, cracking patterns, load-displacement curves, stiffness degradation curves, ductility, and force transfer mechanism of lap-spliced rebar connections. The test results showed that the SFS shear wall specimens exhibited and maintained a high level of composite action until failure, and the studied three different horizontal connections can allow effective force transfer between the upper shear walls and the lower. The stiffness, ductility, and ultimate bearing capacities of SFS shear walls under out-of-plane monotonic loading were significantly higher than those of cast-in-place shear walls. The bearing capacity was found to depend to a large extent on the location of additional vertical connecting rebar, the displacement mainly caused by rigid body rotation and related to crack width at joint. A calculation method of the ultimate bearing capacity of a SFS shear wall under out-of-plane horizontal loads was proposed. Finally, some suggestions on the setting of the vertical connecting bar are put forward.

Behaviour of Innovative Concrete Sandwich Panels with Pervious Concrete Core under Flexural Bending

Research studies investigating the possibility of using new core material (other than polystyrene) in concrete sandwich panels are being reported in the literature. In this paper, lightweight pervious concrete core is proposed as a new alternative. In this paper, the flexural behaviour of concrete sandwich panels with pervious concrete core is investigated under three-point and four-point bending conditions. The geometrical variables considered are core thickness and number of shear connector lines. Test results showed that, sandwich panels without shear connector trusses failed due to separation of wythes, and the panels with shear connector trusses achieved composite action. The variables considered were found to influence the initial stiffness, cracking moment, ultimate moment, load-deflection behaviour and load-strain behaviour of the panels. Analytical study indicated that the equation given in ACI 318 underestimated the strength of the tested panels. The equation have to be modified by explicitly including the shear connector details in the equation for predicting the flexural strength with reasonable accuracy. Further experimental and analytical studies on prototype concrete sandwich panels with pervious concrete core produced using lightweight aggregates are required in view of developing design guidelines for practical applications.

Flexural performance of novel ECC-RC composite sandwich panels

To address the shortcomings of precast concrete sandwich panels (PCSPs) such as insufficient load-bearing capacity, poor ductility behavior, and susceptibility to cracking under temperature stress, this study reinforced the face layer of PCSP with engineered cementitious composite (ECC), resulting in the development of novel ECC-RC composite sandwich panels (ECSPs). The flexural performance of ECSP was revealed by way of a four-point bending test and finite element analysis. Test results showed that incorporating ECC into the wythes substantially improved the flexural performance of PCSP, and the maximum crack width of ECSP was well below the corresponding limit requirement when the mid-span deformation reached the serviceability limit state of the panel. ECSP presented a long load-hardening phase owing to the excellent tensile toughness of ECC, and the properties of the reinforcement could be fully utilized in ECSP without causing “over reinforced” damage as seen in PCSP. Finite element analysis demonstrated that the initial cracks of ECSP did not occur at the tensile edge of the panel, indicating excellent durability of ECSP. Based on the test results and finite element analysis, a formula for the flexural carrying capacity of ECSP was proposed, and the corresponding calculation model demonstrated better applicability. It is recommended to use 20 mm thick ECC to reinforce the face layer of ECSP for optimal economic benefits in practical engineering, while paying attention to the interface problem between ECC and concrete.

Design equations for thermal bowing and composite degree of concrete sandwich panels

Concrete sandwich panels (CSPs) are oftentimes subjected to extreme exterior temperatures, causing thermal gradients between inner and outer surfaces, and eventually bowing. In addition, the composite degree (kp) of CSPs has been conventionally estimated using methods that require costly and time-consuming experimental tests or rigorous numerical models. The lack of research and understanding on the effects of kp and bowing oftentimes result in overly conservative and uneconomic design, particularly for partially composite (PC) panels. This study develops simple design equations for thermal bowing and kp in CSPs based on a comprehensive parametric study using a transient thermal-structural coupled finite element (FE) model developed earlier by the authors. Key parameters considered are span (L); connector configuration, material, and reinforcement ratio; wythe and insulation thicknesses; concrete strength and thermal differential (ΔT) on both sides. In panels with L larger than 13 m, particularly those featuring steel and CFRP truss connectors and subjected to temperature gradients (ΔT) higher than 30 °C, bowing was larger than the deflection serviceability limit of L/360. Cracking in concrete wythes and yielding of steel connectors were also observed and were mainly dependent on ΔT and kp. Two existing theoretical models were evaluated using results of the parametric analysis and were found to overestimate thermal bow, particularly for panels with low kp. A proposed bowing model is presented which incorporates the effects of composite degree and yields much better predictions than these from literature.

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.

Thermal properties of multiple-wythe masonry overlayed with textile reinforced concrete sandwich panels

Thermal properties of multiple-wythe masonry overlayed with textile reinforced concrete sandwich panels

Flexural behaviors of sandwich panels with AR-glass textile reinforced concrete under low-velocity impact

Textile reinforced concrete（TRC）can be used as the face-sheet for sandwich panels due to its lightweight, excellent tensile strength, high energy absorption, and ductility. This study investigates the flexural behavior of alkali-resistant glass-textile reinforced concrete (ARG-TRC) sandwich panels with different textile layers, core thicknesses, and interface forms under various impact velocities. A new manufacturing technique for ARG-TRC sandwich panels is proposed. The sandwich panels with four textile layers have superior load-carrying capability and impact resistance than those with two layers. The impact load can be transferred more effectively for panels with a core thickness of 40mm, allowing the top and bottom face-sheets to bear the load simultaneously for better impact resistance. Ribbed panels can reduce the possibility of side core tensile fracture and core crushing while improving flexural stiffness. It was also found that TRC sandwich panels typically exhibit four failure modes under the impact load, including face-sheet fracture, core shear fracture, side core tensile fracture, and core crushing fracture. The findings of this study can provide some insights into promoting the design and application of TRC sandwich panels in residential and industrial structures.

A Review on Textile Products for Reinforcing Concrete Sandwich Panels

Concrete sandwich panels have gained considerable popularity in the construction industry. Based on their structural and thermal performance, sandwich panels have been employed in industrial, residential, and commercial structures. Two concrete outer layers are connected by connections that run through the interior insulating material, which is isolated from the exterior layers by an insulating stiff foam core to increase thermal effectiveness. There are numerous issues with the steel used for reinforcement including corrosion, high cost, heavy weight, increased thickness, and thermal bridges. Textile reinforcing concrete (TRC) is a solution for these issues, for that; researchers have attempted to replace steel with various textile goods to improve the quality of sandwich panels. Many researchers used textile’ grides for enhancing sandwich panels’ thermal isolation and reinforcing properties as nets or as a connector. This article reviews and observes methods of reinforcing concrete sandwich panels with TRC with different materials, constructions, behavior and application of textiles for investigating sandwich panels’ performance as well as textile reinforcing of concrete and discussing differences between these applications. It was found that TRC can be used for reinforcing concrete sandwich panels as core, as grid or as a connector, All these shapes of TRC effect on the performance of concrete sandwich panels positively.

A review on Textile Products for Reinforcing Concrete Sandwich Panels

A review on Textile Products for Reinforcing Concrete Sandwich Panels

Experimental study on seismic behaviour of an unreinforced precast wall-slab structure based on UHPC sandwich panels

Heavy prefabricated components and complex reinforcement arrangements are regarded as main problems affecting the construction efficiency of traditional precast concrete structures. This study proposes a new wall-slab structure based on prefabricated ultra-high performance concrete (UHPC) sandwich panels, which features with light weight, no reinforcement, fast bolt-based dry connection and insulation system integrated. A large-scale two-story substructure is prefabricated and assembled, which consists of eight sandwich walls and four sandwich slabs. Vertical load test and lateral cyclic load test are conducted to investigate the mechanical behavior of the wall-slab structure. The cracking patterns, failure modes, bearing capacity, stiffness, energy dissipation capacity, and strain distribution are analyzed. Test results demonstrate that the maximum and cracking base shear forces are about 10 and 7 times the sum of gravity and live load of the specimen, respectively. The various connections between precast panels are all reliable without obvious damage during the test. Therefore, the new wall-slab structure has excellent seismic performance, which can even avoid cracking under severe earthquake. In addition, design suggestions are proposed based on the test results, regarding the design principle, inter-story drift ratio limit and panel connections.

A Review on Textile Products for Reinforcing Concrete Sandwich Panels

A Review on Textile Products for Reinforcing Concrete Sandwich Panels

Shaking table tests and seismic assessment of a full-scale precast concrete sandwich wall panel structure with bolt connections

A novel, light-weight, sustainable, repairable and cost-effective precast concrete sandwich wall panel structure system is proposed in this paper, including the dry bolt connections and the precast concrete sandwich panels. To evaluate the seismic performance of precast structure system, a sequence of shaking table tests is carried on the full-scale precast concrete sandwich wall panel structure, and the dynamic characteristics, damage pattern, dynamic responses and seismic fragility are investigated and analyzed by the test results under service level earthquake, design based earthquake, and maximum considered earthquake. The seismic fragility curves and failure probability curves are analyzed by the shaking table test results, which quantitatively describes the seismic performanceexpressed by probability. The results show that the precast concrete sandwich wall panel structure performs high lateral stiffness, large safety margins and high strength reserves. The precast concrete sandwich wall panel structure system presents a good seismic performance. The damage of the structure is slight under maximum considered earthquakes, and the structure has begun to enter the plastic stage. The light-weight characteristic reduces the dynamic responses, and the mild sliding between precast components consumes a fraction of seismic energy.

Experimental study on the in-plane response of cast-in-situ reinforced concrete sandwich walls under combined vertical and horizontal load

Cast-in-situ Reinforced Concrete Sandwich Panel (cRCSP) technology represents a viable and increasingly popular solution for the construction sector to face recent crucial challenges, such as great housing demand or environmental sustainability. Recently, cRCSP-based buildings are being widely used also in earthquake-prone countries, like Italy. Nevertheless, so far, the available studies in the literature studies focused on the seismic response of this structural typology are not-exhaustive and, besides, relevant structural technical codes do not provide specific design rules. The present study deals with an experimental campaign carried out on four full-scale cRCSP walls subjected to increasing in-plane cyclic lateral loading. Two wall configurations have been considered different for shape and openings: the first has no openings and a squat profile; the second has a central door-type opening and a square profile. Two levels of uniformly distributed vertical load have been applied and kept constant during the test. Materials, specimens, and test set-up are described. The main experimental outcomes in terms of recorded force-displacement curves and observed damage states are discussed in detail. In particular, different failure modes and seismic performances have been observed.

Structural performance of a façade precast concrete sandwich panel enabled by a bar-type basalt fiber-reinforced polymer connector

Structural performance of a façade precast concrete sandwich panel enabled by a bar-type basalt fiber-reinforced polymer connector

Study on impact resistance of precast light-weight concrete sandwich panels

To investigate the dynamic impact resistance of precast lightweight sandwich panels (PLCSP) composed of non-sintered coal ash ceramsite concrete and self-developed thermal blocking shear connectors, drop hammer impact tests with different impact energy were carried out in the central area of the exterior wythe. The dynamic response of PLCSP under different steel fibers content, wythe thickness, and the different number of shear connectors was compared and analyzed. The numerical simulation was carried out by LS-DYNA. The results show that 2% volume fraction of steel fibers enhance the stiffness of the panel by improving the overall impact toughness, while the increase in wythe thickness slows down the panel amplitude to enhance the stiffness. The exterior wythe of the PLCSP has penetrated failure, and the failure mode of the interior wythe changes from bending failure to collapse failure with the increase of the number of shear connectors. Therefore, the arrangement spacing of shear connectors can be appropriately reduced to reduce the risk of collapse failure. The ratio of maximum displacement and residual displacement of the panel under different impact energies ranged from 3.37 to 5.94, and the maximum erosion depth of the hammer was twice the displacement of the bottom of the panel, indicating that the unique sandwich structure and material of the PLCSP have good impact resistance. The research results can provide reference for the design and application of PLCSP.

Retrofit of Building Façade Using Precast Sandwich Panel: An Integrated Thermal and Environmental Assessment on BIM-Based LCA

The study conducts a comprehensive life cycle assessment (LCA) of precast sandwich panels by integrating operational and embodied phases detailing thermal efficiency and environmental impacts. The analytical regression model is developed for climatic diversity and design variables using the energy rating tool FirstRate5 to compare with a conventional brick veneer construction. LCA is performed on the building information modeling (BIM) platform to connect operational energy and express the relative embodied impacts of insulation constituents, compressive strength, reinforcement, and mix design. Monte Carlo simulation shows significant advantages of concrete sandwich panels in reducing operational H/C loads over building service life. LCA reveals a 100 mm thick external precast concrete wall with 50% fly ash reduces CO2 emission and energy demand by 54.7% and 75.9% consecutively against the benchmark. Moreover, it comprises 84.31% of the total building mass, accountable for only 53.27% of total CO2 emission and 27.25% of energy demand, which is comparatively lower than other materials. In the case of selecting lining insulation, a broader benefit is identified for extruded polystyrene (XPS) and expanded polystyrene (EPS) boards due to their relative weight, thickness, and environmental impacts. Representative equations of energy efficiency and impact assessment will assist in adopting sandwich panels for new construction and refurbishment with relative dimensions.

Flexural Behavior of Insulated Concrete Sandwich Panels using FRP-Jacketed Steel-Composite Connectors

This study presented the experimental and theoretical results of insulated concrete Sandwich panels with innovative dumbbell-shaped steel fiber-reinforced polymer (FRP) composite bar (SFCB) connectors under flexural load. The influences of FRP thickness and raised thickness of dumbbell ends of connectors, axial compression ratio, the content of vitrified microspheres in the wythes, and loading direction were discussed. The increase in thickness of a glass FRP (GFRP) jacket on the hybrid bar from 2 to 3 mm led to increased initial cracking load, ultimate load, and flexural stiffness of the Sandwich panels by 75, 49, and 16%, respectively. The increase in the thickness of dumbbell ends from 4 to 6 mm led to increased initial cracking load, ultimate load, and flexural stiffness of the Sandwich panels of 18, 46, and 9%, respectively. The incorporation of vitrified microspheres in concrete wythes resulted in a significant increase in the load-carrying capacity of Sandwich panels but decreased ductility. Increased axial compression ratio from 0/1 to 0.2/1 contributed in improving the crack resistance and ultimate loads of Sandwich panels. Further increase of the axial compression ratio to 0.4/1 led to crushing failure of concrete wythe ends. Specimens under negative loads had higher ultimate loads than the counterparts under positive loads. Three-dimensional finite-element (FE) models were developed to simulate Sandwich panel flexural behavior and numerical results compared with the test data. Then, the verified FE model was used to analyze the influence of the arrangement of dumbbell-shaped SFCB connectors. Increased connector spacing from 550 to 650 mm was found to have an insignificant influence on load-deflection responses. Moreover, analytical solutions for deflection of Sandwich panels under combined axial-flexural load were obtained, in which the effect of slipping between the facade and structural wythes and shear deflection were considered. The predicted deflection at the ultimate load agreed well with the test results. This study provided a theoretical basis and design reference for FRP-jacketed steel-composite connectors in applications of Sandwich wall panels with large insulation layer thickness.

Mechanical and Thermal Properties of Composite Precast Concrete Sandwich Panels: A Review

Precast concrete sandwich panels (PCSPs) are utilized for the external cladding of structures (i.e., residential, and commercial) due to their high thermal efficiency and adequate composite action that resist applied loads. PCSPs are composed of an insulating layer with high thermal resistance that is mechanically connected to the concrete. In the recent decades, PCSPs have been a viable alternative for the fast deployment of structures due to the low fabrication and maintenance cost. Furthermore, the construction of light and thin concrete wythes that can transfer and resist shear loads has been achieved with the utilization of high-performance cementitious composites. As a result, engineers prefer PCSPs for building construction. PCSP design and use have been examined to guarantee that a building is energy efficient, has structural integrity, is sustainable, is comfortable, and is safe. Hence, this paper reviews the expanding knowledge regarding the current development of the mechanical and thermal properties of the PCSPs components; subsequently, future potential research directions are suggested.