Search Results (169)

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

As one of the most important sources of carbon emissions, the construction industry consumes approximately 30% to 40% of global energy and emits about 30% of global greenhouse gases. Therefore, low-carbon emission reduction in the construction industry is an important means for China to achieve its “3060” strategic goals. In this context, prefabricated buildings have become a development direction for the transformation and upgrading of the construction industry due to their green, low-carbon, and efficient characteristics. Jiangsu Province in China has taken the lead in promoting the application of “three slabs”. Currently, the precast concrete floor slabs in the province mainly use two types: laminated slabs and prestressed hollow slabs. This article takes three types of slab systems (laminated slabs, prestressed hollow slabs, cast in-site slabs) as the research objects, compares and analyzes the construction process of the three in the materialization stage, establishes a calculation model for carbon emissions and comprehensive costs in the materialization stages, and conducts a comparative analysis of carbon emissions and economics from both environmental and economic perspectives. Research has shown that during the materialization stage, cast in-site slabs have the highest carbon emissions per unit area, with an increase of approximately 71.3% and 74.3% compared to laminated slabs and prestressed hollow slabs, respectively. The highest construction and installation cost per unit area is also for cast in-site slabs, which are increased by about 113.8% and 64.9%, respectively, compared to laminated slabs and prestressed hollow slabs. Among them, material costs are the most significant factor affecting construction and installation costs. The comprehensive cost per unit area of cast in-site slabs is much higher than that of laminated slabs and prestressed hollow slabs, with the construction and installation costs being the most important factors affecting the comprehensive cost. Therefore, compared with cast in-site slabs, laminated slabs and prestressed hollow slabs have significant advantages in carbon emissions and economics and thus have practical significance for carbon reduction in the construction industry and are worth promoting and further developing. Full article

Against the backdrop of the ongoing implementation of the “dual-carbon” strategy and green building policies, this study concentrates on the production stage of precast concrete (PC) components. A composite analytical framework that integrates the structural equation model (SEM) with the system dynamics model (SD) is developed, through which a systematic and dynamically responsive model for the joint optimization of carbon emissions and costs is proposed. The results demonstrate that (1) when investment in green policies is maintained within the range of 10–20%, a 4.2% reduction in carbon emissions can be achieved by 2030, while costs remain optimized; (2) under the scenario of moderate green policy investment (10–20%) combined with a carbon tax of CNY 100/ton, carbon emissions can be reduced by 7.52%, with costs also reaching an optimal level; and (3) among the multi-path emission reduction strategies, the technology optimization pathway and energy structure optimization pathway achieve reductions of 9.68% and 8.97%, respectively. These findings provide theoretical support for the coordinated control of carbon emissions and costs during the production stage of PC components, while also offering empirical evidence and practical guidance for governments in formulating green building policies and for enterprises in advancing low-carbon transitions. Full article

Structural Concrete Insulated Panels (SCIPs) offer a precast, lightweight, and off-site option for several types of construction including residential, commercial, and industrial structures. This study addresses a critical gap in the existing literature by investigating the flexural behavior of Structural Concrete Insulated Panels (SCIPs) under pinned-ended conditions—unlike prior research that focused primarily on fixed-ended configurations. It further introduces original variations in reinforcement placement and spacing, offering a novel perspective on enhancing composite action and deflection performance in floor slab applications. By experimentally evaluating four distinct SCIP configurations using four-point bending tests, the research contributes new empirical data to inform optimized structural design. The findings reveal ultimate moment capacities ranging from 2.84 to 5.70 kN m, and degrees of composite action between 6.5% and 28.2%. Notably, SCIP-2 and SCIP-3 satisfied ACI 318-19 deflection criteria, demonstrating their viability for structural flooring systems. The findings emphasize the capacity of SCIPs to transform the building sector by providing practical and sustainable solutions for floor systems. Full article

Construction and demolition waste (CDW) is the most significant portion of solid waste generated throughout the European Union (EU). CDW represents more than a third of the waste generated, considering the waste generated by all economic activities and household waste. The central reuse of CDW is as a base for roads, and in specific cases, it can be reused as recycled coarse aggregates (RA) in the manufacture of precast concrete, new building blocks, bricks, and as RA on new concrete formulations, among other activities. This work aims to enable the concentration of the aggregates mixed in the CDW with the jigging process. The recovered RA was replaced in the concrete, and four different replacement levels (25%, 50%, 75%, and 100%) were analyzed for reuse in new C30/40 concretes. Physical characterization of the material was performed, and compressive strength tests were conducted to verify the RA replacement’s influence on the concrete. The work tests allowed us to observe the positive variation of the material’s physical properties according to the jigging processing and the efficiency of recovering the aggregates. After analyzing the results obtained in the strength force tests, it is possible to conclude that the RA generated can be a substitute for natural aggregates (NA) in new C30/40 concrete formulations. When 100% RJA is used as a replacement, the 28-day compressive strength reaches 33.2 MPa, which is only 6% lower than that of the NA group, reducing the environmental liabilities inherent in the aggregate mining process and generating an economically viable material. Full article

Many existing reinforced concrete (RC) frames with brick infill walls are vulnerable to earthquake damage, particularly when the walls contain window openings that reduce the lateral resistance. This study aims to examine the seismic performance of RC frames strengthened with U-shaped precast concrete (PC) wall panels. In the proposed method, the window-containing brick infill walls within the RC frames are replaced with factory-fabricated U-shaped PC wall panels, thereby converting the infill into a strong and rigid structural element while preserving the openings. The panels are anchored to the RC frame using post-installed anchors inserted through predrilled holes, allowing for rapid and secure installation with minimal on-site work. To validate the method, five full-scale, one-bay, one-story RC frames were constructed and tested under reversed cyclic lateral loading. Three frames were strengthened with U-shaped PC wall panels of varying thicknesses and large openings. Displacement-controlled cycles following ACI 374.1-05 (R7.0) were applied, with three cycles at each drift ratio stage, and no axial load was applied to the columns. Compared with the reference specimen with a U-shaped brick wall, the strengthened frames exhibited up to 3.29 times higher lateral strength, 4.39 times higher initial stiffness, and 4.33 times greater energy dissipation capacity. These findings demonstrate that the proposed strengthening technique significantly enhances seismic resistance while maintaining the architectural openings, offering a practical and efficient solution for upgrading low-rise RC buildings. Full article

Digital twin (DT) technology, integrated with building information modeling (BIM), enables real-time feedback and predictive analytics in construction. This study presents a BIM-enabled DT framework to optimize in situ production and yard-stock management of precast concrete (PC) components with a focus on minimizing CO₂ emissions. Using Oracle Crystal Ball, scenario-based simulations revealed up to an 8.9% reduction in environmental impact. Distinct from prior research that largely emphasized cost or off-site strategies, this study uniquely addresses on-site sustainability by embedding carbon metrics into the decision-making process. The framework was validated through a large-scale logistics warehouse project that showcased its practical utility. This research contributes a replicable method for enhancing sustainability in precast construction through digital technologies. Full article

Alkali-activated building materials have attracted the interest of many researchers due to their low cost and eco-efficiency. Different binders with different chemical compositions can be used for their production, so the reaction mechanism can become complex and the results of studies can vary widely. In this work, several alkali-activated mortars based on marginal by-products as binders, such as high calcium fly ash and ladle furnace slag, are investigated. Their mechanical (flexural and compressive strength, ultrasonic pulse velocity, and modulus of elasticity) and physical (porosity, absorption, specific gravity, and pH) properties were determined. After evaluating the mechanical performance of the mortars, the optimum mixture containing fly ash, which reached 15 MPa under compression at 90 days, was selected for the production of precast compressed slabs. Steel or glass fibers were also incorporated to improve their ductility. To reduce the density of the slabs, 60% of the siliceous sand aggregate was also replaced with recycled polyethylene terephthalate (PET) plastic aggregate. The homogeneity, density, porosity, and capillary absorption of the slabs were measured, as well as their flexural strength and fracture energy. The results showed that alkali activation can be used to improve the mechanical properties of weak secondary binders such as ladle furnace slag and hydrated fly ash. The incorporation of recycled PET aggregates produced slabs that could be classified as lightweight, with similar porosity and capillary absorption values, and over 65% achieved strength compared to the normal weight slabs. Full article

The seismic risk assessment of large building stocks is crucial for informed asset management in earthquake-prone regions, providing decision-support for retrofit intervention planning. Many existing methodologies focus on a single structural typology or asset class (e.g., ordinary buildings or industrial facilities), thus limiting their applicability to mixed portfolios. This study proposes a comprehensive and adaptable methodology for the seismic assessment of diverse building stocks—a cross-typology approach encompassing masonry, reinforced concrete (r.c.), precast r.c., and steel structures. The approach integrates deficiency-based qualitative evaluations with simplified mechanical models tailored for each building class. Where validated methodologies were unavailable, new assessment tools were developed. The proposed framework was applied to an industrial-oriented building stock comprising 79 structural units at regional scale, demonstrating its capability to identify priority structures for retrofitting interventions. By overcoming the constraints of typology- or asset-specific approaches, this methodology enables a more comprehensive and scalable assessment. This ultimately contributes to effective risk mitigation planning and seismic resilience enhancing. Full article

Epoxy adhesives derived from bisphenol A diglycidyl ether (BADGE) are widely utilized in segmental construction—particularly in precast concrete structures—and in building structural strengthening, owing to their outstanding adhesion properties and long-term durability. These materials constitute a significant class of polymeric adhesives in structural engineering applications. However, BADGE-based epoxy adhesives are susceptible to aging under service conditions, primarily due to environmental stressors such as thermal cycling, oxygen exposure, moisture ingress, ultraviolet radiation, and interaction with corrosive media. These aging processes lead to irreversible physicochemical changes, manifested as degradation of microstructure, mechanical properties, and dynamic mechanical properties to varying degrees, with performance deterioration becoming increasingly significant over time. Notably, for the mechanical properties of concern, the decline can exceed 40% in accelerated aging tests. A comprehensive understanding of the aging behavior of BADGE-based epoxy resin under realistic environmental conditions is essential for predicting long-term performance and ensuring structural safety. This paper provides a critical review of existing studies on the aging behavior of BADGE-based epoxy resins. This paper summarizes the findings of various aging tests involving different influencing factors, identifies the main degradation mechanisms, and evaluates current methods for predicting long-term durability (such as the Arrhenius method, Eyring model, etc.). Furthermore, this review provides recommendations for future research, including investigating multifactorial aging, conducting natural exposure tests, and establishing correlations between laboratory-based accelerated aging and field-exposed conditions. These recommendations aim to advance the understanding of long-term aging mechanisms and enhance the reliability of BADGE-based epoxy resins in structural applications. Full article

Construction costs have increased significantly since the COVID-19 pandemic due to supply chain disruption, labour shortages, and construction material price hikes. The market is increasingly demanding innovative construction methods that can save construction costs, reduce construction time, and minimise waste and carbon emission. The prefabrication system has been used for years in industrial construction, resulting in better performance in regard to structure stability, the control of wastage, and the optimisation of construction time and cost. In addition, prefabrication has had a positive contribution on resource utilisation in the construction industry. There are various types of prefabricated wall systems. However, the majority of comparative studies have focused on comparing each prefabrication wall system against the conventional construction system, while limited research has been conducted to compare different prefabrication structures. This study examined four prominent prefabricated wall systems, i.e., precast walls, tilt-up walls, prefabricated steel-frame walls, and on-site-cut steel-frame walls, to determine which one is more suitable for the construction of industrial buildings to minimise cost, time delay, and labourer utilisation on construction sites, as well as to enhance structure durability, construction efficiency, and sustainability. One primary case project and five additional projects were included in this study. For the primary case project, data were collected and analysed; for example, a subcontractor cost comparison for supply and installation was conducted, and shop drawings, construction procedures, timelines, and site photos were collected. For the additional five projects, the overall cost data were compared. The main research finding of this study is that factory-made precast walls and tilt-up wall panels require similar construction time. However, on average, tilt-up prefabrication construction can reduce the cost by around 23.55%. It was also found that prefabricated frame walls provide cost and time savings of around 39% and 10.5%, respectively. These findings can provide architects, developers, builders, suppliers, regulators, and other stakeholders with a comprehensive insight into selecting a method of wall construction that can achieve greater efficiency, cost savings, and environmental sustainability in the construction of industrial and commercial buildings. Full article

To improve the post-earthquake resilience evaluation of concrete buildings with various construction types, this study presents a generalized recovery-based framework that ext-ends the FEMA P-58 methodology. The proposed method introduces a dynamic repair scheduling approach that incorporates two key construction-related parameters: the prefabrication ratio and the types of prefabricated components. These inputs govern the allocation of parallel or sequential repairs, enabling a more accurate estimation of recovery trajectories and downtime. Functional loss over time is modeled through component-level repair sequencing combined with mobilization delays. A case study involving three four-story prestressed concrete frame buildings (cast-in situ, partially prefabricated, and fully precast prestressed concrete (PCaPC) with mortise–tenon (MT) connections) demonstrated the framework’s applicability. The results show that higher prefabrication levels lead to significantly shorter median repair times, with up to a 97-day reduction observed for the fully prefabricated frame. Additionally, recovery differences emerge even between buildings with the same prefabrication ratio but different component configurations. Compared to conventional assessment methods, the proposed framework avoids the overestimation of mobilization and repair duration, offering a practical tool for the design and performance assessment of resilient precast and hybrid concrete building systems. Full article

Self-compacting concrete (SCC) is an innovative building material that is distinguished by its ability to flow and fill forms without the need for mechanical vibration. The aim of this research was to determine the effect of different types of fibres—steel, glass, and polypropylene—on the properties of both the fresh mix (consistency, density, air content, and viscosity) and the hardened concrete (compressive strength, tensile strength in bending, density, water absorption, and frost resistance). Attention was also paid to CO₂ emissions associated with cement production and the potential of their reduction by using alternative materials. The results of the conducted research demonstrate that, in terms of enhancing the mechanical properties of self-compacting concrete (SCC), the incorporation of glass fibres (GFs) leads to the most significant improvements in compressive and flexural strength—by 1.6% and 29.2%, respectively. Therefore, these fibres can be recommended for use in high-performance structural applications, such as precast elements, load-bearing components, and structures subjected to dynamic loading. Polypropylene fibres (PPFs), owing to their ability to reduce water absorption by 7.3%, may be suitable for elements exposed to high humidity and shrinkage risk, such as tunnels, fire-resistant barriers, or insulating layers. Steel fibres (SFs), in turn, have proven particularly effective in SCC used for industrial flooring and other elements exposed to cyclic dynamic loads. Full article

The eccentrically braced frame (EBF) is a typical structural system used in high-rise buildings. Current related design methods focus on the concrete and steel structures rather than on the complex composite structure. In addition, they tend to overlook the contribution of the energy-dissipation unit and its corresponding additional influence on the structure. In this study, a precast composite EBF structure is selected as a case study, including the partially steel-reinforced concrete (PSRC) beam and the concrete-filled steel tubular (CFST) column. A modified energy-based design method is proposed to leverage the excellent seismic performance of the precast composite EBF structure. The multi-stage energy-dissipation mechanism and the additional influence of the eccentric braces are systematically considered through the energy distribution coefficient and the layout of dampers. A case study of a 12-floor, three-bay precast composite EBF structure is conducted using a series of nonlinear time-history analyses. Critical seismic responses, including the maximum inter-story drift ratio, residual inter-story drift ratio, and peak acceleration, are systematically analyzed to evaluate the effectiveness of the proposed design theory. The distribution coefficient is recommended to range from 0.70 to 0.80 to balance the energy-dissipation contribution between the frame and the eccentric braces. In terms of the damper layout, the energy-dissipation contribution of the eccentric brace should differ among the lower, middle, and upper floors. Full article

Precast concrete structures have become increasingly popular in the construction industry due to their ability to enhance efficiency, structural soundness, quality, and sustainability. Among these, modular construction has emerged as a transformative approach that fully leverages precast technology by manufacturing 3D modules off-site and assembling them on-site using inter-module connections. This study reviewed current literature trends on precast concrete structures and modular construction, analysing how modular construction distinguishes itself from other precast systems. This review further emphasises the role of composite connections—grouted, bolted, and hybrid systems—critical in ensuring structural integrity, efficiency in load transfer, and seismic resilience in modular construction. Advancements in composite connections have demonstrated significant promise, particularly in seismic performance, with reported energy dissipation improvements of up to 30% in hybrid connection systems. Yet limitations still exist, necessitating improvements in load transfer efficiency, ductility, and reliability under dynamic loads. Additionally, design considerations for modular construction, such as modular configurations, handling stresses, and transportation challenges, are explored to highlight their influence on system performance. This review underscores the feasibility and potential of modular construction in fostering sustainable and resilient infrastructure, as studies indicate that modular construction can reduce project timelines by up to 50% while minimising material waste by approximately 30%. The role of Non-Destructive Evaluation (NDE) techniques and intelligent monitoring systems in assessing and enhancing the lifecycle performance of composite connections is also emphasised. This review further advocates for continued research to refine composite connections and support the broader adoption of modular construction in modern building practices. Full article