Experimental Study of an Alternative Precast Concrete Beam–Column Connection with Embedded Steel Block Detail

Seismic behaviors of precast sidewall-bottom slab joints of U-bar connections with UHPC permanent formwork in precast subway station structures

ABSTRACT Precast concrete cladding systems are not only vulnerable to seismic damage but also pose a life-safety hazard due to the potential for panel detachment and falling during earthquakes. However, research assessing seismic response of the cladding systems installed on full-scale buildings under dynamic loading is limited. To address this gap, an experimental programme was undertaken as part of the RObust BUilding SysTem (ROBUST) project. In this study, rocking cladding panels were installed on the upper two storeys of a full-scale, three-storey steel frame building specimen. The building was subjected to unidirectional and bidirectional horizontal ground motions, inducing peak inter-storey drift ratios of up to 1.71% and peak floor accelerations of up to 0.95 g at the storeys where the cladding panels were installed. This paper presents the experimental findings on the seismic response of the rocking cladding system, including peak rocking displacements and component acceleration amplification factors. Physical damage observations are categorised by severity and correlated with inter-storey drift ratios. Damage to the sealant was first observed at a peak inter-storey drift ratio of 0.51% in one of the cladding systems, while the remaining eleven cladding systems sustained drift levels up to 1% without any damage. Additionally, vibration modes and corresponding frequencies are identified. The results demonstrate that the rocking cladding system effectively accommodated the imposed seismic demands without severe damage or collapse, highlighting the rocking mechanism as a low-damage solution for precast concrete cladding systems.

This study experimentally evaluates the mechanical healing performance of precast concrete incorporating hybrid capsules under load reapplication conditions. Hybrid capsule systems are defined as self-healing systems that combine solid capsules (SCs) and liquid capsules (LCs), to enable multi-scale crack healing. In this study, four mix proportions (HC-0, HC-1, HC-3, and HC-5), corresponding to 0%, 1%, 3%, and 5% replacement of fine aggregate by volume with hybrid capsules, were prepared. The hybrid capsules consisted of SCs and LCs in a fixed ratio of 7:3. Among the mixtures, a representative intermediate content (3%) was selected to examine the feasibility of mechanical recovery compared to plain concrete, rather than to determine an optimal dosage. Mechanical recovery was evaluated through compressive and flexural strength tests after preloading and healing periods. The results confirm that the incorporation of hybrid capsules enables partial recovery of mechanical properties after damage. These findings provide preliminary experimental evidence of the feasibility of hybrid capsule systems in precast concrete. Further studies are required to investigate the influence of capsule content and to establish optimal mixture conditions.

To ensure the prefabrication quality of concrete segmental beams for assembled railway bridges, this study investigates the main factors affecting the casting and curing of such beams. Using the Zheng-Xu regional railway bridge as a case study, this study analyzes the impact of environmental temperature, formwork materials, formwork thickness, pouring temperature, wind speed, and prestressed ducts on the thermal-structural coupled stresses in the beams, based on meteorological conditions at the prefabrication yard. A detailed concrete curing control plan is proposed. The research results show that formwork materials and pouring temperature have a significantly greater influence on the early thermal effects of prefabricated concrete segmental beams than other factors. Formwork materials exhibit the highest sensitivity to temperature and temperature stress, with sensitivities of 17.8% and 36.1%, respectively, followed by pouring temperature, which has sensitivities of 12.7% and 21.7% to temperature and temperature stress, respectively, and is positively correlated with peak temperature and peak stress. Wind speed and prestressed ducts are sensitive to temperature stress, with their sensitivities being less than 5%. Prestressed ducts promote internal heat dissipation in concrete segmental beams, reducing the internal peak temperature and the temperature difference between the interior and exterior, thereby lowering the risk of cracking. The better the thermal insulation performance of the formwork materials, the later and higher the temperature peak. Additionally, the thickness of the formwork materials has a greater impact on the temperature and stress of the segmental beam concrete. Based on the identified temperature field and thermal stress patterns for each significant factor, this study proposes detailed curing plans, including winter steam curing and summer spray curing. These strategies effectively reduce the internal-external temperature difference, minimize surface stresses, and mitigate the risk of cracking. The quality of prefabricated concrete segmental beams confirms the scientificity and rationality of the fine-curing control plan, which can serve as a reference for the detailed control of prefabrication and curing.

Study on Flexural Performance of Non-Prestressed Concrete Precast Slab with Perforated Steel Ribs and Cross-Shaped Steel Shear Keys

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.

Precast concrete (PC) component production scheduling is essential to the efficiency and reliability of industrialized construction. Although intelligent algorithms have been widely applied in this field, the relationships among research evolution, collaboration patterns, and industrial applicability remain insufficiently understood. To address this issue, this study presents a bibliometric review of 1272 publications indexed in the Web of Science Core Collection from 1990 to 2025. CiteSpace was employed to analyze publication trends, collaboration networks, co-citation structures, keyword co-occurrence, and burst terms. On this basis, a technology adaptability evaluation framework was developed to assess the alignment between algorithmic advances and industrial implementation in terms of dynamic adaptability, verification completeness, and technological generation gap. The results indicate that the field has evolved through four broad stages, from early static optimization to multi-objective coordination, digital twin-enabled dynamic scheduling, and emerging human-centric intelligent autonomous systems. The analysis also shows an increasing convergence of operations research, computer science, and civil engineering. However, a gap remains between academic output and industrial application. Specifically, 32% of the retrieved studies focused on genetic algorithms, whereas only 6% reported full-process industrial validation. In addition, Gen 4.0-related studies showed a technological generation gap of 82.5%, indicating that many frontier technologies have not yet reached broad industrial implementation. The collaboration network further reveals a “high-output, low-synergy” pattern, in which major publishing countries contribute substantially to the literature but exhibit limited cross-institutional integration. This study provides a structured overview of the development of PC component production scheduling research and highlights future directions for digital twin integration, human–robot collaboration, and cross-sector validation platforms.

This study assesses the electrochemical compatibility of steel reinforcement with molten sulfur in Sulfur-Infiltrated Concrete (SIC) through integrated electrochemical and compositional analyses. Twelve cylindrical concrete specimens (100 mm × 200 mm) with 10-mm-diameter Fe550D steel reinforcement embedded in them were prepared: six with sulfur infiltration and six without. Half-cell potential measurements were conducted on triplicate specimens from each series at 1-day and 28-day curing ages according to ASTM C876-15. These measurements were complemented by Scanning Electron Microscopy and Energy Dispersive X-ray spectroscopy (SEM-EDX) characterization at 28 days. The results show that sulphur infiltration does not adversely affect the electrochemical state of embedded steel reinforcement. SIC specimens exhibited corrosion potentials of −181 mV (1-day) and −211 mV (28-day) versus −193 mV and −237 mV for conventional concrete. Both specimen types remained within the low corrosion probability range (more positive than −350 mV versus CSE) according to ASTM C876 criteria, confirming that exposure to molten sulphur at 140°C does not initiate corrosion. SEM imaging revealed a modified pore structure with a sulfur coating on cement particles. EDX analysis confirmed a fivefold higher sulfur content in SIC (2.6 wt%) than in conventional concrete (0.5 wt%). These findings establish the electrochemical compatibility of sulfur infiltration with steel reinforcement and validate that the SIC process does not compromise steel passivity, making it suitable for reinforced concrete precast applications.

Peeling coatings at a precast concrete warehouse prompt questions.

• Introducing a precast HPC slab-steel composite floor with grout as a wet shear key. • Testing nine different precast slabs to select the suitable precast slab design. • Performing a uniform stacking loading test on a full-scale two-span specimen. • 6.7 % less deflection of the proposed floor than an in-situ steel-concrete floor. • The proposed floor met the serviceability criteria for most occupancy classes. Lightweight and rapidly constructible floor systems are essential for modern steel structures, yet conventional composite floors still rely on steel decking, temporary formwork, and labor-intensive in-situ concreting. This study introduces an innovative steel-concrete composite floor that eliminates these limitations by utilizing thin precast High-Performance Concrete (HPC) slabs, steel beams with pre-welded shear studs, and high-strength expansive grout as a two-way shear key, thereby reducing structural self-weight and accelerating construction. To select a suitable precast slab design, first, nine slabs, varying in concrete type and reinforcement grade and ratio, were subjected to a four-point bending test. Results indicated that High-Strength Steel (HSS) reinforcement, compared to Normal-Strength Steel (NSS) reinforcement, increased flexural capacity by 10 %, but decreased ductility by 44 % in HPC and 87 % in normal-strength concrete. Using High-Performance Fiber-Reinforced Concrete (HPFRC) instead of HPC enhanced ductility by 60 % and flexural capacity by 30 %, but increased the cost 2.3 times. The HSS-reinforced HPFRC precast slab with 60 % of the maximum permissible reinforcement ratio demonstrated the best flexural performance. Considering these results, NSS-reinforced HPC precast slabs were selected for a full-scale two-span composite specimen, which, under uniform stacking loading, sustained a 15.2 kN/m² superimposed dead load without any plastic deformation and showed 6.7 % less deflection than an equal-sized cast-in-place steel-concrete composite floor. According to AISC 360–22 and ASCE/SEI 7–22, the composite specimen satisfies the serviceability deflection limit and minimum design loads for most residential and office uses. The proposed composite floor offers a reliable and efficient solution that expedites flooring in steel structures.

Precast concrete components, as one of the important structural systems in prefabricated buildings, have received widespread attention due to their efficient manufacturing characteristics on the production line. Their production sequence and layout on the mold table have a crucial impact on production energy consumption. However, a critical constraint is often overlooked in the first step of precast concrete manufacturing: the production sequence and layout of molds are planned without considering the limited availability of molds for each component type. Therefore, this article proposes a mixed-integer programming model for the production sequence and layout of precast concrete components under a limited number of molds, aiming to simultaneously minimize production energy consumption, fluctuation coefficients of mold table utilization, and mold switching time. To obtain high-quality solutions for production sequence and mold layout, a multi-objective genetic flatworm algorithm with a Tabu mapping mechanism is developed to efficiently determine the production sequence and the positions of molds on the mold tables. Through three production cases of precast concrete components with different scales, the proposed model and algorithm have been demonstrated to be highly effective in assisting decision-makers in quickly formulating the optimal production sequence and layout schemes for precast concrete components.

The utilization of intermediate diaphragms (IDs) in precast concrete (PC) I-girder bridges has been a topic of debate among researchers for decades, with its effectiveness remaining a subject of controversy. Nevertheless, the consideration of IDs is an essential aspect of engineering practice, making it crucial to explore their role in live load moment distribution. This study delves into the application of concrete IDs, examining the impact of various finite element modeling practices and key parameters on their effectiveness. A sensitivity study was conducted to compare the efficacy of grillage, planar, and solid models in determining the suitable modeling approach for straight, skewed, and curved deck bridges equipped with IDs. To optimize modeling practices, a further investigation was undertaken to evaluate the influence of different parameters on the role of IDs, including the presence of IDs, the rigidity of connections between IDs and girders, and several geometric parameters related to the bridge span layout. The live load moment envelope of girders was chosen as the response indicator to evaluate the role of IDs. The findings of the parametric study revealed that the removal of IDs leads to an increase in the midspan moment of the interior girders, while the midspan moment of the exterior girders decreases. Furthermore, it was found that the rigidity of connections between IDs and girders, girder spacing, and span length significantly influence the role of IDs in PC I-girder bridges.

Abstract Building component reuse (BCR) has a high potential to mitigate the environmental impacts of the construction sector. However, while studies have explored BCR as an alternative to the highly linear practices of construction, a thorough understanding of what is needed for BCR to become feasible remains lacking. To bridge this research gap and accelerate the diffusion of reuse within the construction sector, our study aims to identify the constituents of BCR feasibility and elucidate how such constituents facilitate BCR practice. We conducted an in-depth multiple-case study on precast concrete element reuse in Finland, Germany, and the Netherlands, utilising 23 interviews, extensive ethnographic observation data, and secondary sources. We found that BCR feasibility has six main constituents (regulation, societal aspects, building component characteristics, technological and technical capabilities, organisation of actors, and business models), each with its own configurations and effects. Furthermore, we place the results within a framework that locates the constituents of BCR feasibility in societal, technical, and business domains. Our study contributes to the circular business, sustainability policy, and circular construction literature, providing managers with a comprehensive understanding of BCR.

Shipping services play a crucial role in ensuring smooth operational processes and cost efficiency. This is particularly relevant for one of the manufacturing companies in Riau, a company engaged in the production of precast concrete using a make-to-order system. However, the selection of shipping services has so far been based solely on the experience of the purchasing department, without the application of clear criteria or prioritization systems. This has led to delays in material delivery, resulting in increased operational costs and failure to meet production targets. This study aims to provide the company with a method and relevant information for selecting an efficient and timely shipping service. This research will be using hybrid methods with Interpretive Structural Modeling (ISM) and the Simple Multi Attribute Rating Technique (SMART). Through the ISM method, four key influential criteria were identified: cost, availability of delivery units (trucks), timeliness, and delivery coverage area. These criteria were then used in the SMART method to assess 11 shipping service providers. The analysis shows that the most recommended shipping service is Lancar Jaya, with a score of 97.09, while the least recommended is Cakra, with a score of 40.15. These findings are expected to serve as a reference for one of the manufacturing companies in Riau in determining effective shipping service providers.

Synergistic utilization of bauxite residue (red mud) and multiple solid wastes for low carbon precast concrete materials: Mechanical performance, mechanism and sustainability assessment

Existing hollow‐core floors are vulnerable to nonductile failure and potential collapse under earthquake loading. This study presents the development and experimental evaluation of novel comprehensive seismic retrofits for hollow‐core floors. These retrofits include a strongback‐type retrofit that provides an alternative gravity load path through steel beams positioned underneath the hollow‐core unit close to the support. In addition, a cable catch retrofit was developed to catch the floor in case it collapses. The retrofits were tested as part of a full‐scale super‐assembly experiment on a reinforced concrete moment frame structure with hollow‐core floors. Both retrofits prevented floor collapse throughout the experiment, which reached a peak inter‐story drift of 4.9%. The strongback retrofit effectively limited vertical deformation of the floor even when subjected to approximately twice the design gravity load. Despite the satisfactory performance of the cable catch retrofit, design and installation challenges are likely to make this retrofit option less desirable. The test also provided insights into the floor–retrofit interaction with broader implications beyond these specific retrofits. This research introduces new versatile retrofit options that can substantially enhance the hollow‐core floor performance and thereby improve life safety during earthquakes.

Mortise-and-tenon precast concrete (MTPC) beam–column joints utilize a mortise–tenon structure with longitudinal prestressing to secure their connections. This approach offers advantages such as dry construction, easy assembly, a short construction period, and the possibility of disassembly. To meet the “strong joint” requirement, this study enhances the core areas of the joints through ultra-high–performance concrete (UHPC) reinforcement and rebar enhancement. First, the structure and assembly method for MTPC joints are introduced. Subsequently, five distinct specimens are fabricated for testing: two UHPC-reinforced models, one rebar-enhanced model, one standard MTPC joint model, and one cast-in-place joint model. All specimens are then subjected to monotonic axial compression tests. The results show that the optimized MTPC joints exhibit significantly improved axial compressive strength, reaching 90% to 100% of the capacity of the cast-in-place joint. With regard to the optimization methods, whereas increasing rebar ratios enhances axial strength, it does not fully achieve the “strong joint” criterion. By contrast, UHPC reinforcement significantly boosts axial compressive capacity, achieving the desired “strong joint” standard. After axial load is used to compact the assembly gaps in MTPC joints, the overall integrity is made strong, axial stiffness remains stable, and the load transfer path becomes clear. With UHPC reinforcement, force transmission through the MTPC joint components becomes more reliable, with the tenon bearing more axial load; however, the tenon should not be used as the main vertical force transmission section. Finally, it is found that the axial compressive load capacity calculation method recommended by the Chinese code can accurately and safely predict the axial compressive load capacities of MTPC joints.

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.

ABSTRACT Grouted sleeves serve as critical load-transfer components in precast concrete structures, and their reliable connections are decisive for ensuring structural integrity. However, the inherent structural complexity of precast concrete leads to severe ultrasonic wave scattering and mode conversion during testing, significantly degrading the imaging accuracy of the Synthetic Aperture Focusing Technique (SAFT) due to signal contamination. To address this challenge, we propose a noise-suppression-enhanced SAFT algorithm that significantly improves detection performance by applying advanced filtering techniques to the raw signals.Through systematic evaluation of four filtering methods – elliptic bandpass filtering, wavelet transform filtering, Wiener filtering, and Butterworth bandpass filtering – an optimized hybrid filtering strategy combining time-frequency decomposition and adaptive noise cancellation was established. Experimental validation on precast concrete columns with embedded grouted sleeves demonstrated the superiority of our enhanced algorithm. Compared to conventional SAFT processing, it achieved a 48.6% higher signal-to-noise ratio (SNR), a 170% increase in contrast-to-noise ratio (CNR), and a 381.5% improvement in contrast ratio (CR). Quantitative comparison with physical measurements revealed a positional assessment error of less than 1.5 cm.This study marks the first successful application of noise-suppressed SAFT technology for grouted sleeve characterization, establishing a novel methodological framework for quality assurance in modular construction through enhanced nondestructive testing capabilities.