Precast Concrete Panels Research Articles

Towards Sustainable Construction: Evaluating Thermal Conductivity in Advanced Foam Concrete Mixtures

Traditional concrete structures are frequently linked to poor energy efficiency and substantial heat loss, which pose significant environmental issues. To enhance thermal insulation and reduce heat loss, the use of precast insulated walls is suggested. This research introduces a new energy-efficient precast concrete panel (PCP). We explored various material combinations, including air bubbles, nano microsilica compound (NMC), nano microsilica powder (NMP), and latex, to determine the most effective formulation. A total of 99 tests were performed to assess the compressive strength of the samples, with 28 tests selected for thermal conductivity evaluations at temperatures of 300 °C and 400 °C based on satisfactory compressive strength results. The results indicated that the optimal mix of 4% air bubbles and 13% NMC achieved the lowest thermal conductivities of 1.31 W/m·K and 1.20 W/m·K at 300 °C and 400 °C, respectively, showing improvement ratios of 7% and 15.5% compared to the baseline tests. Additionally, the tests that included latex did not meet the thermal conductivity standards. The optimal combinations identified in this research can be effectively utilized in PCPs, resulting in significant energy savings. It is expected that stakeholders in the green building sector will recognize these proposed PCPs as a practical energy-efficient solution to advance sustainable and environmentally friendly construction practices.

Evaluation of the flexural stiffness of a lattice girder composite slab at the construction stage according to the lattice girder shape

Lattice girder composite slabs (LGCS) for use in construction stages are structures in which part of the lattice girder is embedded in precast concrete panels with a thickness of less than 100 mm. they serve as a permanent formwork supporting the casting loads of on-site concrete while constituting a portion of the RC slab. In this study, analytical research was conducted to evaluate the flexural stiffness of LGCS effectively and simply considering a range of variables. Based on the results, an Euler-Bernoulli beam-theory-based equivalent sectional analysis method is proposed. To achieve this, the study extracted the second moments of area (Iexp) from the experimental results of previous researchers and compared them with the second moments of area (Ibeam) calculated using the Euler-Bernoulli beam-theory-based sectional analysis, analyzing how the ratio (Ibeam/Iexp) varies according to the design parameters. Variable analyses over a wide range were conducted by expanding the types and ranges of variables, and the effects of different variables and ranges were analyzed by comparing the second moments of area based on an FE analysis of LGCS (IFEM) with those based on a beam analysis (Ibeam). Furthermore, to apply the equivalent sectional analysis method to LGCS, equivalent second-moment-of-area formulas were proposed through the equivalent neutral axis and equivalent arm length for each sectional element.

Experimental Analysis of the Mechanical Behavior of Shear Connectors for Precast Sandwich Wall Panels When Subjected to the Push-Out Tests

Precast concrete sandwich panels consist of two outer layers connected by a central connector and an inner insulating layer that enhances thermal and acoustic performance. A key challenge with these panels is eliminating thermal bridges caused by metallic connectors, which reduce energy efficiency. PERFOFRP connectors, made from perforated glass fiber-reinforced polymer (GFRP) sheets, have been proposed to address this issue. These connectors feature holes that allow concrete to pass through, creating anchoring pins that enhance shear resistance and prevent the separation of the concrete layers. This research aimed to evaluate the effect of the diameter and number of holes on the mechanical strength of PERFOFRP connectors. Three diameters not previously reported in the literature were selected: 12.70 mm, 15.88 mm, and 19.05 mm. A total of 18 specimens, encompassing 6 different configurations with varying numbers of holes, underwent push-out tests. The most significant resistance increase was a 15% gain over non-perforated connectors, observed in the configuration featuring three holes of 19.05 mm. The connections exhibited rigid and nearly linear behavior until failure.

Influence of diagonal reinforcement in grouted vertical joints between precast concrete wall panels, part I: Experimental investigation

AbstractMulti‐storeyed buildings are constructed using precast concrete large panels. Although the resistance to lateral loads during an earthquake can be provided by the walls, the vertical joints between the panels remain the weak links. Conventionally, a grouted vertical joint between precast panels is achieved using minimum number of overlapping transverse horizontal U‐bars or looped wire ropes from the adjacent panels, with a holder bar at the overlap, and subsequent grouting of the gap. It was observed that under in‐plane lateral loads, the shear behavior of such joints, especially those with looped wire ropes, is brittle. This paper presents a study to improve the behavior of conventional joints by introducing diagonal reinforcement (DR). Toward this, 13 specimens were tested under monotonic loading and 2 specimens were tested under quasi‐static cyclic loading. The parameters investigated were the types of transverse joint reinforcement, types and strengths of diagonal reinforcement. The compressive strengths of panel concrete and joint grout were kept similar to industry practice. The specimens with DR showed substantial increase of the shear strength and load retention beyond the peak. The presence of conventional transverse joint reinforcement in addition to DR, increases the retention capacity of the joint. Thus, the behavior of a joint with DR was found to be stronger and more ductile.

Structural performance of precast concrete sandwich panels with bolt-steel plate connection subjected to axial loading

A new precast concrete sandwich panel with glass fiber-reinforced polymer connectors was proposed, utilizing bolt-steel plate connections. A compressive experiment was carried out to investigate the performance. The main damage was concrete crushing in the bolt connection region, at the panel bottom, and above the joint. The connector type, solid concrete rib, slenderness ratio, and thickness affected the failure mode and bearing capacity. The use of GFRP connectors and solid concrete ribs enhanced the ultimate bearing capacity and stiffness of the panels while reducing the lateral deflection. Higher slenderness ratios leading to reduced axial bearing capacity and increased lateral deflection. Finally, the results of the existing empirical calculation formulae were compared with experimental ones, and they were overly conservative. A new formula for predicting the bearing capacity was proposed, and the difference percentages between the proposed formula and experimental results were −0.4 %–2.8 %, which was the most accurate prediction formula.

Thermal Performance and Building Energy Simulation of Precast Insulation Walls in Two Climate Zones

Traditional concrete buildings exhibit low energy consumption and high heat loss, which results in a larger environmental problem. Precast insulation walls are proposed for strengthening thermal insulation efficiency and mitigating heat loss. Numerous studies have investigated the thermal performance of insulation walls over the past decades. However, gaps remain in practical engineering applications. This study aims to bridge these gaps by providing practical design recommendations based on experimental research. Nine different types of precast insulation walls were tested to examine the thermal performance, and the parameters of the insulation material, insulation form, insulation layer thickness, and concrete rib width were investigated. Then, numerical models of these walls were developed for simulating the thermal performance of the tested specimens. Finally, a six-story student apartment model using designed walls was developed to assess energy consumption in two distinct climate zones: the hot summer and cold winter zone of Changsha City, and the cold zone of Harbin City. The results indicate that the precast insulation wall with external insulation form shows better thermal performance than the sandwich insulation form. It is recommended to use precast insulation walls with 50 mm extruded polystyrene (XPS) external thermal insulation form in Changsha City and 80 mm XPS external thermal insulation form in Harbin City. Furthermore, buildings using precast insulation walls can significantly reduce energy consumption by 49.25% in Changsha and 49.38% in Harbin compared to traditional concrete wall buildings. Based on these findings, suitable design suggestions for this precast concrete wall panel building composed of insulation walls are given.

A self-centering multilevel rocking wall-frame system for mitigating seismic damage in precast concrete buildings

In order to improve seismic resilience and reparability of precast concrete buildings, different forms of rocking wall building systems have been proposed in recent decades. The base-rocking single wall-panel system incurs limited damage under lateral loading, but it experiences high floor acceleration and storey forces for mid- and high-rise buildings due to the effect of higher vibration modes. A multiple-rocking wall system has been proposed to reduce the effect of higher modes in storey forces, but this system leads to larger drifts, thereby increasing the damage to drift-sensitive non-structural elements. To overcome these limitations, the present study proposes a Self-centering Multilevel Rocking Wall-frame (SMRW) system that simultaneously reduces all forms of seismic demands. The SMRW system consists of multiple small rocking wall units, semi-rigid horizontal precast concrete panels and post-tensioned base-rocking boundary columns at each floor level. To enhance the energy dissipation capacity of the proposed system, external tension-compression yield steel dampers are provided across each rocking interface. Superior seismic behaviour of the proposed SMRW system is validated by comparing the seismic performance of 3, 9, 15 and 21-storey building models with the proposed SMRW system together with the base-rocking, multiple-rocking and conventional cantilever structural wall systems. For this purpose, nonlinear static and dynamic (time-history) numerical analyses are conducted on the building models using finite-element and fiber-element modelling, which are validated using experimental results. As the numerical results demonstrate, the proposed SMRW system, while being a low-damage system, can simultaneously mitigate the inter-storey drift, floor acceleration and storey forces/moments compared to other systems. Therefore, the proposed SMRW system can significantly reduce seismic damage to a building’s structural and non-structural elements, and can offer a truly low-damage option for mid and high-rise buildings in seismic regions.

Improving sustainability of precast concrete sandwich wall panels through stone waste aggregates and supplementary

Precast concrete sandwich wall panels offer advantages such as design flexibility, ease of installation, cost-effectiveness, and energy efficiency due to the incorporated insulation layer, but regular concrete production has sustainability issues. This study aims to improve the sustainability of these panels by utilizing stone waste aggregates as a replacement for natural aggregates and supplementary cementitious materials as a partial replacement for cement. The panels were made with two concrete wythes reinforced with steel fibers and joined using basalt fiber-reinforced polymer (BFRP) connectors, with high-density expanded polystyrene (EPS) insulation (30 kg/m3) in between. Self-compacting concrete mixes with varying proportions of stone waste aggregates and supplementary cementitious materials were used. Full-scale wall panels were cast and subjected to flexural tests per ASTM standards, analyzing load-displacement curves, ultimate bearing capacity, and failure modes. The incorporation of steel fibers and stone waste aggregates resulted in substantial increases in failure load and flexural strength compared to controlled concrete panels, with the stone waste steel fiber panels exhibiting significantly higher maximum cracking loads and improved energy absorption and ductility. The inclusion of these sustainable materials, along with basalt fiber connectors and grooves in the EPS layer for mechanical interlock, prevented brittle failure modes and enhanced the composite action, leading to more ductile behavior under flexural loading. Utilizing sustainable materials like stone waste aggregates (100% replacement) and supplementary cementitious materials (30% replacement) in these panels can contribute to eco-friendly and efficient construction practices while maintaining adequate structural performance, paving the way for more sustainable building systems

Experimental and numerical investigations on the axial compression performance of precast geopolymer concrete sandwich wall panel

This paper investigated a novel precast concrete sandwich panel (PCSP) which made by the geopolymer concrete and enabled by the glass fiber reinforced polymer (GFRP) hexagonal tube connector. Six precast geopolymer concrete sandwich wall panel (PGCSP) specimens were fabricated and tested under axial compression load. The investigating parameters included the connector spacing, panel height, and panel thickness. The failure mode, axial load capacity, load-axial deflection relationship, and load-concrete strain relationship were studied and discussed. Moreover, two-dimensional (2D) finite-element (FE) analysis was conducted to reproduce the test. Parameter analysis was then performed to modify the axial load capacity formula in the Chinese code GB50010-2010. The results indicated that: all specimens exhibited large eccentric compression failure due to the second-order effect, which was caused by concrete crushing and horizontal cracking in the two wythes, respectively; with the decrease of the connector spacing, the crushing area of the specimens would be enlarged, the out-of-plane lateral deformation would be decreased, and the axial load capacity decreased by 17 % and 42 % when the connector spacing changed from 300 mm to 600 mm and 900 mm, respectively; with the decrease of the panel height and the increase of concrete wythes thickness, the axial load capacity of the specimens almost presented a linear increase; the established 2D FE model and the modified formula effectively reflected the axial load capacity of the specimens.

ANALYSIS OF DESTRUCTIONS AND STRENGTHENING METHODS OF PRECAST REINFORCED CONCRETE FLOOR PANELS

Currently, there is a high demand in Ukraine for the rapid restoration of buildings destroyed and damaged as a result of Russian armed aggression, as most people, despite active shelling of cities (especially those close to combat zones) and consequent constant danger, want to return to their homes. Due to military aggression to over 160,000 buildings in Ukraine got extensive damage, with nearly 20,000 high-rise residential structures being built using large-panel construction. The challenges of restoration include unpredictable structural failures and the economic feasibility of repair methods.Recent studies on building restoration in Ukraine due to military damage have emerged only in recent years, with a focus on panel buildings being notably absent in international literature. Given the current situation, domestic research primarily addresses the inspection methodologies and classification of war-related damages, offering preliminary assessments but limited restoration recommendations. In this paper, the authors focused on the panel construction of Kharkiv city, as these buildings account for the most destruction among residential buildings. The assessment of damage to panel slabs of multi-story residential buildings focusing on the heavily affected North Saltivka district due to artillery shelling and rocket strikes is discussed. Despite occupying only 9 % of the area, residential buildings in North Saltivka sustained significant damage, with 70 % affected. Construction in the area consists mainly of precast concrete panel buildings of various heights and designs. Damage severity varies, ranging from minor cracks to complete structural failure, influencing repair and reinforcement strategies. The assessment involves on-site inspections and categorizes damage levels to determine the buildings' suitability for repair or replacement. Based on numerous inspections of panel buildings, in which the authors of the article directly participated, it was possible to identify a gradation of the degree of damage to the panels of multi-storey buildings. As a result of summarizing the obtained information, three categories of panels with acceptable damage for restoration were identified. An analysis of existing methods for reinforcing such structures allowed the selection of a prototype for detailed development of a structural solution to restore the load-bearing capacity of such panels. In the future, the authors of the article will focus on improving the described structural solution and developing a step-by-step technology for its implementation.

Full scale testing of ultra-high performance concrete closure joint for prefabricated full-depth precast concrete bridge deck panel system

The main objective of the transverse joint between prefabricated full-depth precast concrete deck panels is to prevent the relative vertical movement between the panels and to transfer the loads between adjacent panels without cracking. The most common failure mode for these types of joints during their service life are the interface cracks. Such cracks serve as a conduit for ingress of water into the superstructure, leading to further deterioration requiring frequent maintenance. UHPC is known for its high tensile and bond strengths and is often considered as a joint fill material that has the potential to make this connection more durable. This research has been initiated to investigate if closure joints cast using UHPC material can compete with the performance of monolithic deck systems. The experimental program consisted of two full-scale concrete bridge decks that were statically tested until failure. One bridge deck was a jointed panel deck (JPD) consisting of two half-size panels connected by UHPC closure joint, while the control deck was a full panel deck (FPD) cast as one monolithic specimen. Both decks were connected to the steel girders with UHPC shear pockets that contained four to six shear studs welded to the girder flange. The JPD had rectangular tapered shear pockets and the FPD had circular shaped pockets. The results indicated that the JPD and FPD reached the same ultimate loads, and both failed via concrete punching at the load point situated adjacent to the closure joint of JPD. The results demonstrated that using UHPC closure joint resulted in similar performance and behaviour under loading as the monolithic deck. The interfacial failure was not indicated even at ultimate loads. This confirms the ability of the UHPC closure joint to transfer the load to the adjacent panel. The results also indicated the use of circular or rectangular pockets led to similar behaviours.

Experimental and numerical study on the shear performance of stainless steel-GFRP connectors for use in precast concrete sandwich panels

Precast Concrete Sandwich Panel (PCSP) is composed of concrete load-bearing panels, thermal insulation panels, and decorative panels, which are assembled through connectors, integrating load-bearing, thermal insulation, and decorative functions. The connector bears the main shear force between the wall panels, and the shear resistance and insulation performance of the connector largely determine the mechanical stability and insulation effect of the wall panels, which is a key component in PCSPs. The current common practice is to cross assemble stainless steel insulation (SSI) connectors and Glass-Fiber-Reinforced Plastic (GFRP) connectors into PCSPs, which can reduce building energy consumption and save resources while meeting strength and insulation requirements. A large-scale pull-out test on a PCSP with intersecting SSI-GFRP connectors was conducted in this paper. The damage process and damage pattern of PCSP were observed and the shear performance of SSI-GFRP connectors was analyzed. Secondly, a numerical analysis model of the test PCSP was built using ABAQUS finite element software and its validity was verified through the test data. In addition, parameters such as connector diameter, connector number ratio and concrete strength were analyzed for their effect on the shear performance of SSI-GFRP connectors and it was found that connector diameter and connector number ratio had a significant effect. Finally, it is found that there are some differences between the classical theory for calculating the shear performance of SSI-GFRP connectors and the actual results. A theoretical correction factor (ζ) is given to improve the accuracy of the calculation of the classical theory, and its influencing factors and changing rules are investigated.

Optimization of Shear Resistance in Precast Concrete Sandwich Wall Panels Using an S-Type Shear Connector

Precast concrete sandwich wall panels (PCSPs) are popular for building exteriors due to their high thermal efficiency, composite performance, and low manufacturing and maintenance costs. Researchers have investigated the possibility of reducing the panel thickness while maintaining the cladding components’ thermal efficiency and strength to further improve efficiency and to reduce material consumption. However, limited research has been conducted on the shear bonding of steel plates, which is critical to ensuring durability and energy efficiency. This study investigated the shear behaviour of PCSPs with an S-type shear connector (SSC) through nine push-off tests and non-linear finite element modelling using Abaqus. Parametric studies were carried out to investigate the influence of the geometric properties of the SSC, the yield strength of the steel and the insulation thickness. The results suggest that the maximum secant stiffness for SSCs was achieved at a width of 101.4 mm and a thickness of 2 mm. Therefore, it is recommended that the width of the SSCs be limited to this value or less. Furthermore, the study found that increasing the yield strength of the steel beyond a thickness of 2 mm and a width of 101.4 mm did not improve the results and had a negative impact on the secant stiffness of the SSCs.

In-plane shear performance and damage evolution of FRP connectors for composite sandwich panels

This study investigated the in-plane shear responses of four types of connectors (single-strand truss, double-strand truss, grid-type, and I-shaped) in precast concrete sandwich panels (PCSPs). The influence of connector type, connector arrangement, and wythe material on the shear performance was discussed through in-plane shear tests and finite element analysis. The failure modes and test results of the four types of connectors were closely related to their shear resistance mechanisms. Changing the connector arrangement method from continuous along the length to discrete arrangement improved connector damage extent and toughness index (TI). The substitution of ordinary concrete with ECC or UHPC in wythes can prevent the wythes failure and enhance peak load (Pm). The finite element (FE) model using the Hashin damage model and randomly generated fibers can accurately capture the shear response of the connectors within PCSP. The damage factor was introduced for quantitative analysis of the damage processes in connectors and wythes and corresponding damage evolution model was developed. Furthermore, the damage evolution model was applied to characterize the degradation of shear stiffness in the load-slip curve, and a load-slip theoretical model that accounted for the progressive development of damage was established.

Assessment of a Simplified Methodology for Preliminary Blast-Resistant Design of Insulated Precast Concrete Wall Panels

Abstract A Blast loading history can be represented by the peak pressure value and the impulse. Combinations of pressure and impulse of various blast loading scenarios can be collected to draw a pressure-impulse (P-I) curve that corresponds to a level of damage of a blast-resistant structural component. The P-I curve is typically used for a preliminary design or assessment of blast resistance structural components. Generating a P I curve for a given structural component and level of protection requires repeatedly ru nning a single degree of freedom system (SDOF) model, which can be tedious for early design stages. Hence, a simplified approach (i.e., the normalization approach) was utilized to promptly generate the P- I curve for insulated precast concrete wall panels, which relies on shifting a control P I curve using normalization factors. The generated P-I curves using the normalization approach are validated with the traditional SDOF approach curves; 95% of the examined insulted panel configurations have an error between +/-7%. As a result of the reached low error percentages, a spreadsheet- design tool was developed using this approach. The tool can further enable rapid evaluation of the performance of insulated precast concrete panels under blast loading during the preliminary design phase.

In-plane seismic performance of precast concrete hollow-core slab panels for basement walls

In building structures, exterior basement walls should resist the soil pressure type earthquake load transmitted by the ground. Thus, the structural performance of the exterior basement walls is affected by in-plane seismic performance as well as out-of-plane load resistance. In the present study, for better constructability and cost-effectiveness of the exterior basement walls, conventional reinforced concrete walls were replaced with precast hollow core slab (HCS) panels. To investigate the in-plane earthquake load resistance of HCS for exterior basement walls, cyclic lateral loading test and numerical analysis were performed on four HCS panels with in-plane double curvature. The test and analysis results showed that the structural behavior of the HCS panels was significantly affected by the panel layout. In the test specimens using a single panel, flexural compression failure occurred at the bottom of the panel, and shear friction damage occurred at the upper and lower parts of the panel. In the test specimens using double panels, failure mode was governed by direct shear. The load-carrying capacity of the test specimens using double panels was greater than two times that of the test specimens using a single panel, because the load transfer changed from flexure into direct shear in the wall specimens using double panels. Further, to use HCS panels for exterior basement walls, a design method for prediction of in-plane seismic performance and yield displacement of HCS panels was proposed.

Advancements in precast concrete sandwich panels for load bearing structures

Concrete sandwich panels consist of two concrete layers separated by an insulating foam core, offering thermal insulation, structural strength, and fire resistance. This study investigates sustainable precast concrete sandwich panels made with industrial waste materials like limestone slurry, quarry waste, and basalt fiber as shear connectors. The research evaluates the flexural and axial strength behavior of these panels and explores strategies to improve their structural performance. The panels were fabricated with outer concrete layers, an expanded polystyrene (EPS) insulation core, and basalt fiber connectors. Flexural tests using four-point bending and axial compression tests were conducted on panels with varying concrete layer thicknesses and basalt fiber widths. Findings revealed panels with thicker outer concrete layers (35mm) and wider basalt fiber connectors (11.5mm) exhibited higher cracking loads, load-hardening behavior, and increased ductility compared to thinner layers and narrower connectors. The axial test showed premature failure at the top and bottom quarters. Thicker concrete layers and wider basalt fiber connectors enhanced crack control, load distribution, and ductile behavior under flexural loading. Strengthening measures like additional reinforcement, proper anchorage detailing, and increased shear reinforcement at the end regions are recommended to improve axial load-bearing capacity and prevent premature end failures. The PCSP demonstrated up to 40% cost savings over commercial products while providing better thermal insulation than conventional brick masonry due to the EPS core. Overall, the study promotes developing sustainable, energy-efficient, and cost-effective load-bearing sandwich panel systems.

Design parameter study based on nonlinear analysis of a bolt-connected precast concrete composite wall panel structure

Design parameter study based on nonlinear analysis of a bolt-connected precast concrete composite wall panel structure

Flexural performance of UHPC-filled narrow joints between precast concrete bridge slabs

The deck slabs narrow joints in concrete bridges filled with Ultra-high performance concrete (UHPC) have the potential for wide application and high-efficiency promotion, but there is limited research available on this topic. This paper conducted flexural tests on the new joints. Ten precast concrete deck panels were designed and manufactured for concrete bridges. These panels were connected using UHPC-filled narrow joints. Combined with stress analysis, this study investigates the influence and mechanism of various factors on the mechanical performance of UHPC joints. These factors include the geometric shape of the joint, the roughness of the joint interface, the filling material used in the joint, the width of the joint, and the configuration of joint reinforcement (including the shape and length of lap reinforcement). The test results show that the panel with the UHPC joint filled with steel fibers has excellent flexural and bonding capacity. The jointed panel with a lap length of 140 mm and 120 mm has better flexural performance than the one with a lap length of 90 mm. The straight-jointed panel has a higher flexural capacity compared to the complex triangular-jointed panel. Additionally, reducing the joint width can achieve similar mechanical properties as before. A method has been proposed for calculating the flexural capacity of a jointed panel, utilizing the strut-and-tie model (STM). This method can accurately predict experimental results.

Seismic behavior of horizontally spliced single-side superposed shear wall using a concealed column

The single-side superposed (SSS) shear wall is an innovative precast concrete sandwich panel that better meets the requirements of building industrialization. However, the seismic behavior of SSS shear walls remains inadequately understood. In this paper, a full-scaled horizontally spliced SSS shear wall using a concealed column and an integral SSS shear wall of the same dimensions were tested. The seismic behavior was investigated considering various aspects including hysteresis performance, bearing capacity, ductility performance, energy dissipation capacity, and stiffness degradation curve. The simulation models were established by the Abaqus, which provided the verification and further research for the test. Furthermore, two innovative splicing forms were proposed to optimize the existing specimens through the Abaqus. The experimental results indicated that implementing the vertical joint would lead to a decrease in the yield-bearing capacity by 24%, but it would also enhance the ultimate bearing capacity by 12.7%. Meanwhile, the deformation capacity would improve by 9.7%. The numerical simulations demonstrated that the suggested splicing methods effectively meet the demands of building industrialization.