Search Results (770)

Digital construction implementation has not yet realized its promised potential after three decades. Across the entire project lifecycle, adoption has encountered difficulties from high-level standard guidance, a lack of strategies, fragmented delivery approaches, and insufficient digital delivery competency. Establishing digital workflows tailored to organizations’ contexts is an essential linkage of the information layer to synthesize the business and technology layers to address these challenges within the ISO 19650 framework. The uneven implementation of building information modelling (BIM) in the Architecture, Engineering, Construction, and Operation (AECO) industry provides a holistic perspective to consider the digitalization workflow dynamics. This report performs a case study through a parallel approach to examining multiple projects’ digital construction implementation of an organization in the Forest City development. Applying an observation research method and real-world data of project records, it analyses its workflows’ digitalization and process digitization, combining with its organization’s structure and overall project strategy. Moreover, it highlights bespoke digital construction ecosystems and relevant stakeholders to streamline workflows. The digital construction implementation results and project benefits as project context indicators verify that fundamental digital workflows of design quality checking, project optimization, asset data collection, and defect management have significant applicability compared with the advanced workflows of integrated 5D cost management and precast design and production. Their adoptability keeps consistency with those of applicability using the extra cost, application complexity, and disruption level indicators from the technology–organization–environment (TOE) framework to measure. These multiple project studies reveal the feasibility for organizations to achieve lifecycle digital construction implementation competency. The feasibility is underpinned by introducing an in-house digital engineering team to organization structure, cultivating applicable digital delivery capabilities through workflows digitalization and process digitization, and synthesizing ISO 19650 with workflows to enable more contextualized digital construction implementation. Full article

Since a significant part of the Italian territory was not seismically classified until 2003, most existing bridges have been designed—for decades—disregarding earthquake-induced excitations. In fact, this means that load-bearing devices and shear keys of presently in-service infrastructures may not be up to current codes, both in terms of resistance and displacement capacity. Robust investigations are hence required for verifications and possible retrofit. In this study, the seismic behaviour of a case study post-tensioned concrete bridge built in the 1980s is numerically analysed. The examined structure is 440 m long and composed of nine spans, built with precast segments using the balance cantilever construction method. The deck is divided into two parts connected by a hinged joint in the middle of the central span, obtained with three shear keys and originally designed to allow for thermal expansion only. Most importantly, the mid-span hinge, the end joints and the bearing devices were originally designed without considering the effects of seismic action. In order to preliminarily investigate the performance of devices and joints, the case study bridge is analysed by means of non-linear dynamic time history simulations, formulating different hypotheses about the non-linear behaviour of the load bearings. Forces and displacements over time are obtained for a set of seven accelerograms, and maximum values are compared to the capacity of the bridge devices. Results are then critically discussed. Full article

This paper reviews the current state of research on the seismic behavior of precast segmental bridge piers, systematically elucidating their performance under different connection configurations in the context of accelerated bridge construction and resilience demands. Additionally, it compiles commonly used research methodologies and strategies for enhancing seismic performance. The evidence indicates that emulative precast segmental piers can closely match monolithic cast-in-place structures, with reported peak lateral strengths typically within about 10% and comparable yield and peak displacements, whereas non-emulative systems generally provide superior self-centering with smaller residual displacements. Experimental studies, theoretical analyses, and numerical simulations have all proven effective in characterizing the mechanical behavior of these piers; each approach has distinct advantages, and a synergistic integration of methods is recommended for comprehensive evaluation. Measurable improvements in seismic performance have been reported through hybrid connection systems, innovative detailing, supplementary energy-dissipating devices, and the use of high-performance materials such as ultra-high-performance concrete (UHPC), engineered cementitious composites (ECC), fiber-reinforced polymers (FRP), and shape memory alloys (SMA); for example, representative tests reported about a 30% increase in energy dissipation at drift ratios exceeding 3%, and SMA-based reinforcement has been reported to reduce residual drift by roughly 67% relative to steel reinforcement. Finally, future research directions are proposed to support the wider adoption of precast bridge piers in high-seismicity regions, including addressing challenges related to performance degradation under multi-hazard coupling conditions, insufficient design criteria for connections, and the need for rapid post-earthquake repair and resilience. Full article

Construction of precast reinforced concrete (PRC) industrial halls in seismically active areas has been increasing in recent decades. As connections are one of the most sensitive and vulnerable zones of PRC structures, there is a need to pay special attention to their investigation and modeling in seismic analysis. Knowing that each PRC system is specific and unique, this study aims to evaluate the actual seismic performances of PRC industrial halls built in the AMONT system, which represent a significant portion of the existing industrial building stock in Italy, the Balkans, and Turkey. As there is a lack of published research data on its specific joints, the results of the quasi-static full-scale experiments carried out up to failure on the models of four characteristic connections are presented. Since the implementation of nonlinear dynamic analysis in everyday engineering practice can be demanding, a simplified model of the structure considering the effects of the connections’ stiffness is proposed in this paper. The differences in the roof top displacements between the proposed model and the model with the rigid joints of the analyzed frames are in the range from 16.53% to 66.93%. The values of inter-story drift ratios are larger by 10–100% when the real stiffness of connections is considered, which is above the limit value provided by standard EN 1998-1. These results confirm the necessity of considering the nonlinear behavior and stiffness of connections in precast frame structures when determining displacements, which is particularly important for the verification of the serviceability limit state of structures in seismic regions. Full article

Sustainable development is crucial worldwide. Under the Paris Agreement, countries commit to Nationally Determined Contributions (NDCs) assessed every five years. China, a major contributor to global warming, has made significant efforts to reduce carbon emissions and achieve carbon neutrality, a key strategy for sustainable development. However, there is a lack of adequate attention to embodied emission reduction in rural residential construction, despite a surge in building to improve living standards. This paper evaluated the feasibility of applying a multi-ribbed composite wall structure (MRCWS) in rural China through a village service project. A full-scale shaking table test was conducted to study its seismic performance. Carbon emissions were analyzed using process-based life cycle assessment (P-LCA) and the emission-factor approach (EFA), while costs were estimated using life cycle costing (LCC) and the direct cost method (DCM). These analyses focused on sub-projects and specific structural members to validate the superiority of this prefabricated structure over common brick masonry. MRCWS blocks were prefabricated by mixing wheat straw with aerocrete, utilizing agricultural by-products from local farmlands, thus reducing both construction-related carbon emissions and agricultural waste treatment costs. Results show that this novel precast masonry structure exhibits strong seismic resistance, complying with fortification limitations. Its application can reduce embodied carbon emissions and costs by approximately 6% and 10%, respectively, during materialization phases compared to common brick masonry. This new prefabricated building product has significant potential for reducing carbon emissions and costs in rural housing construction while meeting seismic requirements. The recycling of agricultural waste highlights its adaptability, especially in rural areas. Full article

The accelerated carbonation of fresh concrete and recycled aggregates is one of the safest methods of CO₂ sequestration as it mineralizes CO₂, preventing its escape into the atmosphere. CO₂ injection during batching of concrete improves its strength and may partially replace Portland cement, as with supplementary cementitious materials (SCMs). The curing of concrete by incorporation of CO₂ also accelerates early strength development, which may enable early stripping of formwork/moulds for precast and in situ construction. The carbonation process may also be used for the beneficiation of recycled aggregates sourced from demolition waste. The CO₂ mineralization technique may also be used for producing low-carbon, carbon-neutral, or carbon-negative concrete constituents via the carbonation of mineral feedstock, including industrial wastes like steel slag, mine tailings, or raw quarried minerals. This research paper analyses various available technologies for CO₂ storage in concrete, CO₂ curing and mixing of concrete, and CO₂ injection for improving the properties of recycled aggregates. Carbon dioxide can be incorporated into concrete both through reaction with hydrating cement and through incorporation in recycled aggregates, giving a product of similar properties to concrete made from virgin materials. In this contribution we explore the various methodologies available to incorporate CO₂ in both hydrating cement and recycled aggregates and develop a protocol for best practice. We find that the loss of concrete strength due to the incorporation of recycled aggregates can be mitigated by CO₂ curing of the aggregates and the hydrating concrete, giving no negative strength consequences and sequestering around 30 kg of CO₂ per cubic metre of concrete. Full article

This study presents a comprehensive numerical investigation into the dynamic response of railway precast concrete slab track (PST) systems subjected to various interlayer gap conditions. Key parameters including gap width, depth, and location were examined, along with the geometric configuration of the grouting layer, comparing current (as-is) and earlier (as-was) models. A conservative modeling approach was adopted, assuming fully unbonded interfaces and delamination gap depths extending to the shear key, with dynamic loading applied. Results showed that the maximum principal stress in both the slab and grouting layer increased with larger gap widths but stabilize beyond specific thresholds. In the as-is model, stress levels remained below reference flexural tensile strength, indicating a low risk of cracking. However, the as-was model exhibited grouting layer stresses exceeding the allowable limit at the gap widths near 4 mm and approaching critical levels even at 1.5 mm. Stress responses also varied depending on whether gaps were located at the slab–grouting layer or grouting layer–hydraulic stabilized basecourse (HSB) interfaces. Based on the examinations, allowable interlayer gap width criteria were proposed to support maintenance decisions. The study provides a rational framework for monitoring and managing interlayer gaps, enhancing resistance to early fatigue cracking and structural integrity of PST systems under dynamic railway loads. Full article

To study the crack resistance of UHPC precast composite slabs, this paper conducts flexural performance tests on one UHPC monolithic slab and four UHPC precast composite slabs, investigating the influence of structural form, loading method, and shear reinforcement on the failure mode and crack resistance of UHPC precast composite slabs. The test results showed that UHPC precast composite slabs do not experience shear failure along the composite interface. They exhibit extensive microcracks and do not fail due to the immediate appearance of a single wide crack, demonstrating good plasticity and toughness. The cracking load of the monolithic slab is 6.6% to 12.5% higher than that of the composite slabs. However, the yield load and ultimate load of composite slabs equipped with shear reinforcement are 19.5% to 26.5% and 24.5% to 29.5% higher than those of the monolithic slab, respectively. These composite slabs are also characterized by extensive, dense microcracks with high quantity, small width, small spacing, short length, and dense distribution. Shear reinforcement can effectively improve the bearing capacity and crack resistance of UHPC precast composite slabs, with truss reinforcement showing a better effect in enhancing bearing capacity and inhibiting cracks. The comparison between positive and reverse loading methods better explains the “strain lag” of concrete and “stress advance” of reinforcement in composite slabs. Based on the section internal force equilibrium and the bond stress transfer principle between reinforcement and concrete, considering the enhancement effect of UHPC on bond stress, the calculation formulas for average crack spacing and maximum crack width in existing codes are modified. The calculated values are in good agreement with the test results. Full article

This study proposes a high-strength bottom-bar interlocking and anchorage precast beam–column joint (HSRU-PBCJ), which utilizes high-strength longitudinal reinforcement combined with U-shaped anchorage at the beam bottom. Low-cycle reversed loading tests were conducted on two precast specimens and one cast-in-place specimen to evaluate their seismic performance. Based on these results, parametric analyses were conducted through numerical simulations to investigate the effects of axial compression ratio, concrete strength, beam-end longitudinal reinforcement strength, and beam-end longitudinal reinforcement ratio on the seismic performance. The results indicate that the proposed joint exhibits stable and full hysteresis loops, cumulative energy dissipation comparable to that of the cast-in-place joint, and a 23.94–26.39% increase in equivalent viscous damping after yielding, achieving a displacement ductility coefficient of 4.14, which confirms its substantially improved seismic performance. The parametric study shows that maintaining a moderate axial compression ratio (≤0.6) enhances both load-bearing capacity and energy dissipation, whereas excessive values result in strength reduction. Increasing the beam-end longitudinal reinforcement strength significantly improves load-bearing capacity but may reduce energy dissipation. In addition, improving concrete strength and appropriately increasing the reinforcement ratio can further enhance both load-bearing capacity and energy dissipation, although a balance between seismic performance and economic considerations is recommended. Full article

In this paper, the synergistic strengthening mechanism of a new type of prefabricated knee brace to semi-rigid steel frame lateral resistance was experimentally and numerically analyzed. Five full-scale specimens with a control steel frame and four knee-braced configurations were tested under pseudo-static cyclic loading in order to understand the stiffness evolution, failure mode, and energy dissipation characteristics of the specimens. Results show the following: (1) The innovative integrated knee braces increase initial lateral stiffness and yield capacity by 184–242% and 91–154% compared to conventional semi-rigid frames with acceptable ductility; (2) Three different failure modes coupled brace-joint yielding (Type I), brace dominated instability (Type II) and beam buckling brace connections (Type III) are identified; (3) Finite element simulations using ABAQUS with isotropic/kinetic hardening models show good agreement with experiments for their hysteretic responses confirming In particular the ultimate failure location is identified at the lateral screw holes of beam flanges located near brace supports where the local stress is greater than 1.8f_y. The study further proposes a BIM-integrated design workflow. These results give a theoretical basis and some practical recommendations for the application of knee-braced semi-rigid systems in earthquake-resistant steel buildings. 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

In accelerated bridge construction, precast concrete girders are connected to cast-in-place concrete slab using shear transfer reinforcement across the interface plane to ensure the composite action. The steel transverse reinforcement is prone to severe corrosion due to the extensive use of de-icing salts and severe environmental conditions. As glass fiber-reinforced polymer (GFRP) reinforcement has shown to be an effective alternative to conventional steel rebars as flexural and shear reinforcement, the present research work is exploring the performance of GFRP reinforcements as shear transfer reinforcement between precast and cast-in-place concretes. Experimental testing was carried out on forty large-scale push-off specimens. Each specimen consists of two L-shaped concrete blocks cast at different times, cold joints, where GFRP reinforcement was used as shear friction reinforcement across the interface with no special treatment applied to the concrete surface at the interface. The investigated parameters included the GFRP reinforcement shape (stirrups and headed bars), reinforcement ratio, axial stiffness, and the concrete compressive strength. The relative slip, reinforcement strain, ultimate strength, and failure modes were reported. The test results showed the effectiveness and competitive shear transfer performance of GFRP compared to steel rebars. A shear friction model for predicting the shear capacity of as-cast, cold concrete joints reinforced by GFRP reinforcement is introduced. Full article

To address the dual challenges of improving precast cable trench joint performance and promoting solid waste recycling for carbon neutrality, this study developed a jute fiber-reinforced recycled aggregate concrete (JFRAC) and established a complete technical chain via experiments and numerical simulations. Compressive strength tests were conducted on JFRAC with varying jute fiber volume content and recycled coarse aggregate (RCA) replacement ratio to obtain their influence on the stress–strain relationship. A modified Concrete Damaged Plasticity (CDP) model was proposed by introducing correction coefficients for compressive strength and elastic modulus, achieving over 95% agreement with experimental data. Finite element simulations of cable trench joints showed that JFRAC outperforms C30 concrete, with the same compressive strength, in ultimate bearing capacity (↑4.17%), peak displacement (↑18.78%), and ductility (↑14.66%). JFRAC provides substantial environmental and economic advantages by reducing carbon emissions by 2.29% and saving costs of CNY 62.43 per meter of precast cable trench. Parametric studies indicated bolt grade and number are the primary performance influencers. Bolt grade’s impact diminishes as it increases from 8.8 to 10.9, while bolt number linearly enhances load-bearing capacity. This study provides a feasible path for JFRAC to replace conventional concrete in cable trenches, realizing both economic and environmental benefits. Full article

This study introduces a digital fabrication process for producing recyclable, closed-loop wax formwork for architectural concrete applications with visually rich surface articulation while drastically reducing formwork milling time. As such, this paper presents (a) a circular large-scale production method for wax blocks via a single casting process; (b) four machine-time-optimized surface articulation strategies through CNC toolpath-driven design; (c) the investigation of different coating systems to improve architectural concrete surface quality and to ease demolding; and (d) the integration of robotic concrete shotcreting using a low-CO₂ fine-grain concrete. For the first time, wax formwork technology, characterized by its waste-free approach, has been combined with robotic shotcreting in a digital and automated workflow to fabricate fiber-reinforced, geometrically complex thin-shell concrete elements with distinct surface articulations. To evaluate the process, a series of four thin-shell concrete elements was produced, employing four distinct parametric toolpath-driven designs: linear surface articulation, crossed surface articulation, topology-adapted curve flow surface articulation, and robotic drill topology-adapted surface articulation. Results revealed a possible reduction in milling time of between 77% and 94% compared to traditional milling methods. The optimized toolpaths and design-driven milling strategies achieved a high degree of visual richness, showcasing the potential of this integrated approach for the production of high-quality architectural concrete elements. Full article

This study evaluates the shear strength of precast concrete beam–column joints using a Combined Model based on the ACI code, with implications for sustainable structural design. A database of 87 specimens from the existing literature was compiled and classified by prestressing condition and failure mode to examine key variables affecting prediction accuracy. The model demonstrated high reliability, with average predicted-to-test shear strength ratios (V_test/V_cal) of 1.12 for non-prestressed joints and 0.99 for prestressed joints, supporting more efficient and reliable use of precast systems. By identifying cross-sectional geometry as the dominant factor governing shear strength and failure mode, the study highlights opportunities to optimize material use, enhance structural safety, and reduce overdesign, thereby contributing to resource-efficient and sustainable construction practices. Full article