Search Results (65)

Steel-concrete-steel composite (SCS) panels have been extensively utilized in structural engineering and are vulnerable to impact loading during their service life. Therefore, this work numerically and theoretically investigated the low-velocity impact performance of SCS panels. Firstly, based on the existing drop-hammer impact experiments, three-dimensional finite element (FE) models incorporating material failure and strain-rate effect were constructed using ABAQUS and employed to predict the dynamic responses of SCS panels subjected to impact loading. After verifying the reliability of numerical models with test results, the impact-resistant mechanism of these members was analyzed. Then, a parameter analysis was carried out to systematically explore the influences of essential parameters on the impact responses of SCS panels. Results indicated the sandwiched concrete played a predominant role in absorbing impact energy. The proportion of plastic energy absorbed by the concrete reduced by approximately 11% with increasing impact height from 3.0 m to 4.5 m. The steel plate ratio had a marginal effect on the impact response under the constant panel thickness, while the variations in impact velocities, boundary conditions, and axial-load levels significantly affected it. As the axial load ratio reached 0.6, the instability occurred due to severe buckling of steel faceplates. Finally, an empirical formula for calculating the local bulging stiffness of bottom steel faceplate was proposed. The revised calculation method was able to accurately predict the post-peak mean force and the mid-span deflection of bottom steel faceplate. Full article

To achieve the same service life of glass fiber reinforced polymer (GFRP) connectors and precast concrete sandwich panels, ensuring the structural stability and safety of the walls during long-term service, it is necessary to research the durability of GFRP connectors. In accordance with the ACI 440.3R-12 test method, an accelerated aging study was conducted by immersing 90 GFRP connectors in a simulated concrete pore solution at temperatures of 40 °C, 60 °C, and 80 °C for durations of 3.65, 18, 36.5, 92, and 183 days. This investigation aimed to analyze the effects of temperature and exposure time on the shear strength of the GFRP connectors. Scanning Electron Microscopy (SEM) was employed to analyze the micro-morphology of the specimens before and after exposure. The SEM observations revealed that after 183 days at 40 °C, the fiber-matrix interface remained relatively intact without significant debonding. However, at 60 °C, noticeable degradation occurred, characterized by corrosion of fibers and evident debonding from the surrounding matrix. At 80 °C, the GFRP specimens were severely damaged, precluding the extraction of viable samples for SEM analysis. The results further indicated that the most rapid decline in the shear strength occurred within the initial 3.65 days of exposure, with reductions of 8.62%, 10.12%, and 10.77% at 40 °C, 60 °C, and 80 °C, respectively. The degradation rate subsequently decelerated with prolonged exposure. After 183 days, the residual shear strength retention rates decreased by 21.03% and 26.89% at 40 °C and 60 °C, respectively. This behavior is primarily attributed to a high moisture absorption rate driven by a significant humidity gradient between the surface and the interior, leading to rapid swelling and plasticization of the vinyl ester resin matrix, which consequently reduced the stiffness and strength of the GFRP connectors. Finally, a predictive model for the time-dependent shear strength of GFRP connectors under various temperature conditions was developed based on Fick’s law. Full article

This paper presents an experimental investigation of the shear connection between outer layers of lightweight precast concrete sandwich panels (PCSP) made of high-performance concrete (HPC). The shear-transfer mechanism is based on reinforcing ribs composed of rigid polymer-based thermal insulation combined with carbon-fibre-reinforced polymer (CFRP) shear reinforcement. A total of seven full-scale sandwich panels were tested in four-point bending. This study compares three types of rigid thermal insulation used in the shear ribs—Purenit, Compacfoam CF400, and Foamglass F—and investigates the influence of the amount of CFRP shear reinforcement on the structural behavior of the panels. Additional specimens were used to evaluate the effect of reinforcing ribs and of polymer-based thermal insulation placed between the ribs. The experimental results show that panels with shear ribs made of Purenit and Compacfoam CF400 achieved significantly higher load-bearing capacities compared to Foamglass F, which proved unsuitable due to its brittle behavior. Increasing the amount of CFRP shear reinforcement increased the load-bearing capacity but had a limited effect on panel stiffness. The experimentally determined composite interaction coefficient ranged around α ≈ 0.03, indicating partial shear interaction between the outer concrete layers. A simplified strut-and-tie model was applied to predict the load-bearing capacity and showed conservative agreement with experimental results. The findings demonstrate that polymer-based materials, particularly CFRP reinforcement combined with rigid polymer insulation, enable efficient shear transfer without thermal bridging, making them suitable for lightweight and thermally efficient precast concrete sandwich panels. Full article

A precast concrete sandwich panel (PCSP), consisting of inner and outer wythes, an insulation layer, and connectors, relies heavily on the shear behavior of these connectors, which governs the structural performance of the entire system. Owing to their low thermal conductivity, excellent durability, and high strength, fiber-reinforced polymer (FRP) connectors offer strong potential for widespread application. This study introduces a novel cross-shaped FRP rod connector designed to provide improved anchorage performance, bidirectional shear resistance, and ease of installation. However, concern remains about the specific influence of embedment depth, outer-wythe thickness, and insulation-layer thickness on its shear performance. Moreover, no calculation model for shear capacity or shear–slip model has been established considering the shear-bending interaction within the connector. To evaluate its shear behavior, six groups of push-out tests were conducted, with key parameters including embedment depth, outer-wythe thickness, and insulation-layer thickness. The specimens exhibited two primary failure modes: connector fracture and concrete anchorage failure. The measured shear capacity per connector ranged from 5.63 kN to 14.19 kN, increasing with longer embedment depths, decreasing with increasing insulation thickness, and showing no clear dependence on outer-wythe thickness. Guided by test results and the Hashin failure criterion for composite materials, analytical formulas to estimate the shear capacity of FRP connectors were developed. The mean ratio of calculated to experimental values is 0.97, with a standard deviation of 0.06, indicating good agreement between the predicted and measured shear capacities. Furthermore, a theoretical shear–slip model was established. The correlation coefficients between the experimental and calculated load–slip curves for all specimens are greater than 0.98, indicating a high consistency in curve shape and variation trend. Full article

Textile-reinforced concrete (TRC) sandwich panels with lightweight cores are a promising solution for sustainable and slender building envelopes. However, their structural performance depends strongly on the shear connection between the outer shells. This study investigates the flexural behavior of TRC sandwich panels with glass fiber-reinforced polymer (GFRP) rod connectors under four-point bending. Three full-scale specimens were manufactured with high-performance concrete (HPC) face layers, an expanded polystyrene (EPS) core, and 12 mm GFRP rods as shear connectors. The panels were tested up to failure, with measurements of load–deflection behavior, crack development, and interlayer slip. Additionally, a linear-elastic finite element model was developed to complement the experimental campaign, capturing the global stiffness of the system and providing complementary insight into the internal stress distribution. The experimental results revealed stable load-bearing behavior with ductile post-cracking response. A degree of composite interaction of γ = 0.33 was obtained, indicating partially composite action. Slip measurements confirmed effective shear transfer by the GFRP connectors, while no brittle failure or connector rupture was observed. The numerical analysis confirmed the elastic response observed in the tests and highlighted the key role of the GFRP connectors in coupling the TRC shells, extending the interpretation beyond experimental results. Overall, the study demonstrates the potential of TRC sandwich panels with mechanical connectors as a safe and reliable structural solution. Full article

Precast concrete sandwich panels (PCSPs) have been widely adopted for constructing exterior walls in prefabricated residential buildings, but they face threats from impact loads such as natural disasters, terrorist attacks, and runaway vehicles. Their impact performance directly affects the overall safety and durability of the structure. However, research on the impact performance of such exterior walls remains limited. In this study, LS-DYNA R11 software is employed to establish a numerical model of PCSPs. The proposed numerical simulation method is validated by comparing the results with existing experimental data. On the basis of this numerical method and adopting an actual prefabricated residential building project as the background, the damage behavior of three distinct types of PCSPs in a bedroom is numerically investigated under varying impact location and energy conditions. The results demonstrate that the interior wythe of the PCSPs studied in this work exhibit excellent stability under external impact loading, with the most of damage absorbed by the exterior wythe, which provides effective protection to the interior wythe. Compared with windowed PCSPs subjected to impact, loads at the same energy level exhibit concrete spalling and a more pronounced dynamic response. Additionally, the windowed surface of L-shaped PCSPs is more susceptible to generating significant dynamic responses, with the non-windowed side exhibiting at least 13.2% lower maximum displacement under impact compared to the windowed side. Full article

Reinforced concrete walls (RC walls) are widely used in transportation, building structures, and civil air defence engineering. RC walls are vulnerable to low-velocity impact, such as the fall of components caused by earthquakes or explosions, for example, and the impact from road objects, such as vehicles, during their service life. When subjected to instantaneous high-energy impact, RC walls at key positions are prone to severe damage, which can further lead to structural collapse. Therefore, it is necessary to consider improving the impact resistance of key RC walls in a structure. Using a porous honeycomb structure with excellent energy absorption performance to provide impact protection for key RC walls is an effective way to reduce the damage of RC walls and thereby enhance the impact resistance of a structure. Therefore, based on the author’s previous series of experimental and numerical studies on the impact resistance of RC walls, as well as the high-mass pendulum impact experimental study on the honeycomb sandwich panel composite RC wall (HSP-RC wall), this paper adopts a multi-scale modelling method in micro-mechanics and macro-mechanics to establish a pendulum impact finite element model (FEM) for the HSP-RC wall. The representative volume element (RVE) and periodic boundary condition (PBC) are used to calculate the elastic property parameters of the honeycomb, which guide the establishment of the FEMs for the HSP-RC wall. The FEMs can avoid the computational difficulty caused by refined simulation, analyse the impact damage of the HSP-RC walls more accurately, quantify the impact protection effect of the honeycomb sandwich panel, and thus facilitate the parametric analysis of the impact resistance of HSP-RC walls with different honeycomb panel structural parameters in subsequent studies. Full article

This study examines the dynamic response of autoclaved aerated concrete (AAC) under solar radiation and ambient temperature coupling. A comparative analysis is conducted between traditional sintered bricks (brick), AAC, and autoclaved aerated concrete sandwich insulated wall panels (ATIM), using three thermal engineering models. The experimental group focuses on the south wall, with differentiated designs: Model A (brick), Model B (AAC), and Model C (ATIM). Temperature data collectors assess heat transfer and internal temperature regulation in winter. The results show that the AAC sandwich system significantly reduces thermal fluctuations, with a 26% and 14.8% attenuation in temperature amplitude compared to brick and AAC. The thermal inertia index of the AAC sandwich structure system is 51.5% and 14.58% higher than that of traditional brick walls and AAC walls, respectively. The heat consumption index of ATIM is, on average, 14% lower than that of AAC and 74.5% lower than that of the brick system. The study confirms that the AAC sandwich rock wool wall structure enhances temperature stability and energy efficiency, supporting green building and low-carbon energy-saving goals. Full article

In order to explore new wall panel materials and structural systems suitable for prefabricated buildings, this study proposes a polypropylene fiber-reinforced concrete sandwich wall panel (PFRC sandwich wall panel) and a polypropylene fiber-reinforced concrete sandwich wall panel with glass fiber grid (G-PFRC sandwich wall panel). A comparative investigation was conducted using finite element analysis to numerically simulate the mechanical response of these composite wall panels under impact loads. The simulation results were compared with those of an unreinforced concrete sandwich wall panel with glass fiber grid (G-UC sandwich wall panel). Key findings include: (1) Compared with the G-UC sandwich wall panel, the G-PFRC sandwich wall panel exhibited 19.3% lower peak deformation and 23.7% reduced residual deformation; (2) Relative to the standard PFRC sandwich wall panel, the G-PFRC sandwich wall panel demonstrated 16.5% smaller peak deformation and 27.9% less residual deformation under impact loads; (3) Damage analysis revealed that the G-PFRC sandwich wall panel developed fewer cracks with lower damage severity compared to both the PFRC and G-UC sandwich wall panels. Parametric studies further indicated that the G-PFRC sandwich wall panel maintains superior deformation resistance and impact performance across varying impact heights and impact masses. The synergistic combination of polypropylene fiber with a glass fiber grid significantly enhances the impact resistance of composite sandwich panels, providing valuable theoretical insights for engineering applications of these novel wall systems in prefabricated construction. Full article

The global construction industry faces pressing challenges in enhancing building energy efficiency standards. To address this critical issue, facilitate worldwide green and low-carbon transformation in construction practices and improve the thermal performance of building wall panels to achieve optimal levels, a novel polypropylene fiber-reinforced concrete wall panel has been developed and investigated. A three-dimensional steady-state heat transfer finite element model of the wall panel was established to simulate its thermal performance. Key parameters, including the thickness of the inner and outer concrete layers, insulation layer thickness, connector spacing, and connector arrangement patterns, were analyzed to evaluate the thermal performance of the fiber-reinforced concrete composite sandwich wall panel. The results indicate that the heat transfer coefficients of the G-FCSP and FCSP wall panels were 0.768 W/m² · K and 0.767 W/m² · K, respectively, suggesting that the glass fiber grid had a negligible impact on the thermal performance of the panels. The embedded insulation layer was crucial for enhancing the thermal insulation performance of the wall panel, effectively preventing heat exchange between the two sides. Increasing the thickness of the concrete layers had a very limited effect on reducing the heat transfer coefficient. Reducing the spacing of the connectors improved the load-bearing capacity of the composite wall panel to some extent but had minimal influence on the heat transfer coefficient; to achieve optimal performance by balancing structural load distribution and thermal damage resistance, a connector spacing ranging from 200 mm to 500 mm is recommended. The variation in heat transfer coefficients among the four different connector arrangement patterns demonstrated that reducing the thermal conduction media within the wall panel should be prioritized while ensuring mechanical performance. It is also recommended that the connectors are arranged in a continuous layout. Full article

Straw as a building material alternative is in line with sustainable development goals. To make effective use of straw resources such as rice and corn stalks in rural areas, a kind of steel wire mesh-reinforced straw concrete sandwich panel (SCSP) was developed. The SCSP was composed of cold-drawn low-carbon steel-wire mesh (SWM), fine gravel concrete (FGC), and straw. The used type of FGC was shotcrete. A cold-drawn low-carbon SWM was arranged on the upper and lower sides of the SCSP, and a vertical wire tie was arranged between the upper and lower cold-drawn low-carbon SWMs. The FGC was sprayed on the SWM to make the SCSP layer work together. The loading process of the SCSP could be divided into three stages: elastic working state, cracking state, and failure state. The results of the four-point loading test show that the maximum flexural moment of the SCSP can be up to 7.5 kN·m in the elastic range. The ultimate bearing capacity of SCSP reaches 10.9 kN·m, and the maximum crack width can reach 3~4 mm. At the same time, based on the assumption of the flexural section of SCSP, two simplified calculation models of SCSP bearing capacity were established. The average error was 2.99% and 9.41%, respectively, by comparing the experimental values with the two calculated values. The results obtained by using the two models were in good agreement with the experimental results. Full article

Concrete sandwich wall panels (CSWPs) have been constructed since the early 1900s using various wythe connectors, panel geometries, and construction methods to create a structurally and thermally efficient system. Initially, thermal bridging hindered thermal efficiency due to the concrete connections and steel bars used to transfer interface forces between the concrete wythes. This issue was mitigated with the advent of polymer connectors, now widely used in the precast and tilt-up industries. As a result, CSWPs now offer buildings an efficient envelope, aiding in energy savings and reducing the need for additional construction materials and therefore contributing to the construction industry’s sustainability goals. This paper examines the current state of the practice in CSWP construction, focusing on CSWP’s construction methods, sustainability, material selection, and design processes. This manuscript delves into the history of CSWPs and showcases projects ranging from housing to industrial applications. Moreover, the materials and hardware popularly used in their construction are reviewed from the practicing engineer and researcher’s point of view and other aspects, such as environmental, architectural, and structural design, are presented. The most popular construction methods and approaches when precasting these panels on- or off-site and their associated challenges are also presented. Lastly, current deficiencies in CSWP design and construction are outlined and future directions for research and practice are suggested to advance this field further. Full article

The development of sustainable and energy-efficient construction materials is crucial for mitigating the growing environmental impact of the building sector. This study introduces a new lightweight sandwich panel, featuring a core made of lightweight concrete with rice husk bio-aggregate (RHB) and faces constructed from foamed cementitious composites. The innovative design aims to promote sustainability by utilizing agro-industrial waste while maintaining satisfactory mechanical performance. Composites were produced with 4% short sisal fibers and matrices containing 15%, 20%, and 30% foaming agent. These composites were evaluated for density, direct compression, and four-point bending. It was found that the mixture with 20% foam volume demonstrated the highest efficiency for use in the production of sandwich panels. Concrete mixtures containing 50%, 60%, and 70% rice husk bio-aggregates were tested for density and compressive strength and used in the production of lightweight sandwich panels with densities ranging from 670 to 1000 kg/m³. Mechanical evaluation under flexion and shear indicated that the presence of fibers inhibited crack propagation in the face, enabling the creation of lightweight sandwich panels with deflection-hardening behavior. On the other hand, the increase in RHB content led to a reduction in the ultimate stress on the face, the core shear ultimate stress, and the toughness of the sandwich panels. Full article

This study investigates the shear-bending performance of GFRP (Glass Fiber Reinforced Polymer) connectors in sandwich insulation composite wall panels following tension–compression fatigue damage. A total of 24 specimens, divided into 11 groups, were prepared for experimental analysis. Three distinct load amplitudes (5.4 kN, 4.0 kN, 2.7 kN) and three fatigue loading cycles (30,000, 50,000, 80,000) were established as loading conditions. The experimental protocol included out-of-plane tension–compression fatigue tests followed by post-fatigue shear-bending tests. The influence of varying load amplitudes and fatigue loading cycles on failure modes, load–displacement relationships, and bearing capacity alterations was systematically examined. A two-factor analysis of variance (ANOVA) was utilized to evaluate the statistical significance of these factors. The findings reveal that the predominant shear-bending failure modes post-fatigue damage are connector fracture and concrete crushing in the anchorage zone. Specifically, under a load amplitude of 2.7 kN and 30,000 cycles, the shear-bending capacity of the specimens exhibited a minimal reduction of 1.82% compared to the ultimate capacity of undamaged specimens. Conversely, at a load amplitude of 5.4 kN and 80,000 cycles, the shear-bending capacity experienced a substantial decline of 37.11%. Both load amplitude and fatigue loading cycles were found to significantly impact the shear-bending capacity, with fatigue loading cycles demonstrating a more pronounced effect. This research provides critical insights for the design and assessment of sandwich insulation composite wall panels, particularly in the context of long-term fatigue damage and its implications on structural performance, thereby contributing valuable theoretical and practical knowledge to the field. Full article