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Influence of curing conditions on the shrinkage behavior of three-dimensional printed concrete formwork

Frontiers of structural and Civil engineering 2024年第8期18卷 1225-1236页

作者： M.BEKAERT K.van TITTELBOOM G.de SCHUTTER Magnel-Vandepitte Laboratory for structural Engineering and Building Materials Department of Structural Engineering and Building MaterialsFaculty of Engineering and ArchitectureGhent UniversityGhent 60 B-9052Belgium

The use of three-dimensional(3D)printed concrete as formwork is becoming more widely applied within the ***,the technology is still not optimized and there are many reports of preliminary cracking during the curing of cast *** is believed to result from differential shrinkage between the printed and cast *** cracks(in the printed concrete or at the interface between the infill and printed concrete)form a preferential path for aggressive substances and can reduce the durability of the combined concrete *** ensure the desired service life of the structure,it is important that the differential shrinkage between cast and printed concrete is *** study investigated the effect of curing conditions on the differential shrinkage behavior of 3D and cast *** influence of prewetting of the dry-cured 3D printed formwork was also *** the experimental program,a vibrated and self-compacting concrete were used as cast *** 3D printed formwork was produced and combined with cast concrete to simulate a concrete *** formwork was cured for 1,7,or 28 d exposed to the air(relative humidity:60%or 95%)or submerged in *** length change of the combined elements was observed over 56 d after concrete casting and throughout the thickness of the *** show that increasing the curing period in dry conditions of the printed concrete leads to an expansion of the formwork on the first day after *** expansion leads to a non-uniform strain evolution throughout the curing period of the combined *** concrete formwork stored in wet conditions does not expand after the casting process but tends to show a decreasing linear deformation within the whole elements.

关键词： 3D concrete printing formwork shrinkage curing

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structural build-up model for three-dimensional concrete printing based on kinetics theory

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Frontiers of structural and Civil engineering 2024年第7期18卷 998-1014页

作者： Prabhat Ranjan PREM P.S.AMBILY Shankar KUMAR Greeshma GIRIDHAR Dengwu JIAO Advanced Materials Laboratory CSIR-Structural Engineering Research CentreChennai 600113India Department of Architecture and Civil Engineering City University of Hong KongHong Kong 999077China

The thixotropic structural build-up is crucial in extrusion-based three-dimensional(3D)concrete *** paper uses a theoretical model to predict the evolution of static and dynamic yield stress for printed *** model employs a structural kinetics framework to create a time-independent constitutive link between shear stress and shear *** model considers flocculation,deflocculation,and chemical hydration to anticipate structural *** reversible and irreversible contributions that occur throughout the build-up,breakdown,and hydration are defined based on the proposed structural ***,detailed parametric studies are conducted to evaluate the impact of model *** is revealed that the proposed model is in good agreement with the experimental results,and it effectively characterizes the structural build-up of 3D printable concrete.

关键词： structural build-up rheology thixotropy 3D printable concrete kinetics theory ultra high performance concrete

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Enhancing ventilation in street canyons using adjustable roof-level wind flow deflectors

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Energy and Built Environment 2025年第2期6卷 201-218页

作者： Vasudevan, Madhavan Pilla, Francesco McNabola, Aonghus Department of Civil Structural and Environmental Engineering Trinity College Dublin Ireland School of Architecture Planning and Environmental Policy University College Dublin Ireland

Traffic emission impacts the air quality at both the road surface and in near road buildings. Previous research has examined the benefit of using roof-level wind catchers to reduce concentration along building facades in urban environments. Although roof-level interventions are more effective in improving the street canyon air quality in its entirety, localized re-distributions that detrimentally affect specific regions in and around the street canyons are unavoidable. In the current work, a deflector system that can adjust its position and orientation to changing ambient conditions is introduced to ensure that no particular region perpetually experiences compromised air quality. At optimal roof-level positions, the wind deflectors resulted in a local maximum and minimum of pollution removal through mean flow-induced fluxes and overall canyon concentrations respectively. In this study, the potential of the wind deflectors was first demonstrated using 2D Computational Fluid Dynamics (CFD) investigations. A maximum reduction in overall canyon concentration of 2.84 fold was predicted when the deflector was placed 2 m from the leeward walls. Subsequently, the benefit of the dynamic nature of the intervention and the efficacy of the same in a more realistic 3D city-type environment was demonstrated by considering two different pollution source conditions. The wind deflectors performed modestly for the Cross Road Pollution (CRP) source model by reducing 7%, 11% and 13% of CO exposure on the leeward wall, upwind side wall and downwind side wall without affecting the windward wall of the target street canyon. Whereas for the Side Road Pollution (SRP) source model, it reduced 91%, 32% and 34% on the same with a 17% reduction on the windward wall of the target street canyon. Finally, the concept of an adjustable deflector system was demonstrated to mitigate prolonged high exposure for building occupants exposed to changing traffic emission sources via all the surrounding buil

关键词： Roofs

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Aluminium nodes for timber gridshells: Parametric detailing of node principles

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International Journal of Space Structures 2023年第4期38卷 217-232页

作者： Dyvik, Steinar Hillersøy Haakonsen, Sverre Magnus Luczkowski, Marcin Komiyama, Yosuke Department of Architecture and Technology Norwegian University of Science and Technology Trondheim Norway Department of Structural Engineering Norwegian University of Science and Technology Trondheim Norway Department of Architecture and Architectural Engineering Kyoto University Kyoto Japan

Gridshell nodes are key elements regarding structural performance, visual appearance and assembly of any gridshell that have been given little attention in recent research. This paper explores aluminium as a material for timber gridshell nodes. First, existing gridshell nodes are categorised regarding bulk materials, gripper types and connection methods and based on this, a set of novel node principles in aluminium are deducted and proposed for a timber gridshell on the geometry of the British Museum Great Court. A finite element analysis is done on the proposals to increase the understanding of the node principles’ structural behaviour and feasibility. Together, the set of node principles, their evaluation and the utilised procedure can provide new options in the future design of gridshells and gridshell nodes. © The Author(s) 2023.

关键词： Timber

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Fundamental Issues Towards Unified Design Theory of Recycled and Natural Aggregate Concrete Components

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engineering 2023年第10期29卷 188-197页

作者： Jianzhuang Xiao Kaijian Zhang Tao Ding Qingtian Zhang Xuwen Xiao Department of Structural Engineering Tongji UniversityShanghai 200092China College of Civil Engineering and Architecture Guangxi UniversityNanning 530004China College of Civil Engineering Fuzhou UniversityFuzhou 350116China

In the past 20 years,recycled aggregate concrete(RAC),as a type of low-carbon concrete,has become a worldwide focus of ***,the design methodology for RAC structural components remains a ***,demands for a unified design of natural aggregate concrete(NAC)and RAC components have been ***,this study analyses the necessity of a unified design theory and provides an in-depth demonstration of the strength determination,compressive constitutive relationship,and design method of concrete *** coefficient of variation of RAC strength is found to be generally higher than that of NAC *** compressive and tensile strengths of RAC can be defined and determined using the same method as that used for *** uniaxial compressive constitutive relationship between NAC and RAC has a unified mathematical ***,the elastic modulus of RAC decreases,and its brittleness exhibits an increasing trend compared with that of ***,to unify the design formulae of RAC and NAC components for bearing capacity,modification factors for RAC components are proposed considering safety and ***,the feasibility of the proposed unified time-dependent design theory is demonstrated in terms of conceptual design and structural measures considering the effects of strength degradation and reinforcement *** is believed that this study enriches and develops the basic theory of concrete structures.

关键词： Recycled aggregate concrete(RAC) Natural aggregate concrete(NAC) Strength determination Constitutive relation Reliability Unified design theory

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Analysing user daylight preferences in heritage buildings using virtual reality

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Building Simulation 2022年第9期15卷 1561-1576页

作者： Mohamed Marzouk Maryam ElSharkawy Ayman Mahmoud Department of Structural Engineering Faculty of EngineeringCairo University12613GizaEgypt Department of Architecture Engineering Faculty of EngineeringCairo University12613GizaEgypt

Technology has always been creating effective ways to support human *** virtual reality(IVR)has emerged to engage users in a simulated world,and this has gained the interest of a wide variety of users in the heritage industry.A historical case study built in the early 19th century is considered for an adaptive reuse *** palace is located in Cairo,Egypt,and named after Prince Omar *** current palace state incorporates a smashed top-lit zone,which is being studied and analyzed for daylighting *** simulated distinct optimum skylight configurations are suggested for the redesign where the selection should not be based solely on simulation data,but should consider real-user *** daylight design criteria are previously based on simulation data that do not necessarily indicate the users'*** utilizing user interactive tools such as IVR to test daylight redesign options,a whole new dimension is *** this study,the VR users’survey data is statistically analyzed using Statistical Package for Social Sciences(SPSS),where results revealed that the assessment attributes succeeded in reflecting the users'preferences;which,motivated designers to consider potential users’daylight preferences in reused *** paper highlights the most significant emotional attributes that provide cost-effective and reliable information concerned with the performance of daylight in IVR before design *** study compares and analyzes the effect of three skylight designs(Cases A,B&C)on the users'perception before design implementation using(IVR)***-eight participants have contributed to the study,providing their feedback on six attributes namely:Pleasant,Contrasting,Brightness,Uniform Distribution,Visual Comfort,and *** attributes are evaluated for the three cases in space using five scale rating values to reveal that the"Pleasant"attribute is most reliable in the study to reflect th

关键词： daylight preferences heritage buildings rehabilitation immersive virtual reality statistical analysis

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Refined span-to-depth ratio expressions for one-way slabs aligned with ACI-318 deflection limits

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Journal of Umm Al-Qura University for engineering and architecture 2025年 1-9页

作者： Elgohary, Hamdy A. El Zareef, Mohamed A. Civil Engineering Department College of Engineering and Architecture Umm Al-Qura University Makkah Saudi Arabia Structural Engineering Department Faculty of Engineering Mansoura University Mansoura 35516 Egypt

The ACI-318 code presents span-to-depth ratio expressions for solid, non-prestressed one-way slabs to control deflection when the impact on nonstructural items is not significant. These expressions relate slab thickness to span length, incorporating adjustments for steel yield strength and concrete density. However, they do not account for key design factors such as live load and concrete compressive strength, often resulting in conservative slab thickness estimates where the minimum reinforcement ratio is used. The adoption of the Bischoff formula for the effective moment of inertia in ACI-318-19 has further increased predicted deflections compared to the previous Branson formula, necessitating a review of span-to-depth ratio accuracy for deflection control. This study evaluates the compatibility of existing span-to-depth limits with deflections predicted using the Bischoff formula and proposes a new, efficient span-to-depth ratio formula for one-way slab design. The proposed expression incorporates key design factors, including concrete compressive strength, live load, and span length. A parametric analysis was performed to assess the influence of these parameters, and the new formula was derived based on deflection calculations and ACI-318 deflection limits. The suggested span-to-depth ratio is advised for slabs that do not support or connect to elements vulnerable to damage due to excessive deflections. Verification through case studies demonstrates that the predicted deflections using the proposed formula remain within ACI-318 limits while achieving more efficient designs with reduced slab thickness. © The Author(s) 2025.

关键词： Deflection control Deflection limits One-way slab Span-to-depth ratio

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Probabilistic assessment of the moment-curvature response of PC beams with different corrosion scenarios 12th

Probabilistic assessment of the moment-curvature response of...

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12th International Conference on Bridge Maintenance, Safety and Management, IABMAS 2024

作者： Belletti, B. Ravasini, S. Sandrini, S. Caspeele, R. Botte, W. Department of Engineering and Architecture University of Parma Parma Italy Department of Structural Engineering and Building Materials Ghent University Belgium

ISBN: (纸本)9781032770406

Corrosion of the reinforcement significantly affects the resistance and ductility of concrete members. While various approaches have been proposed to study the sectional response of corroded reinforced concrete structures, the effects of corrosion on prestressed concrete (PC) members still poses significant challenges. Therefore, this study focuses on investigating the bending resistance of prestressed concrete sections with different corrosion scenarios through probabilistic assessment using Monte Carlo simulations based on preliminary results of previous work. First, the mechanical properties of the materials and the investigated pit depths have been established as input parameters of the cross-sectional model. To account for corrosion in the constitutive behaviour of the prestressing strands, the Simplified Model for Corroded Prestressing Strands (SCPS model) has been adopted. Furthermore, different statistical distributions of the pit depths are derived to represent different corrosion scenarios. Subsequently, Monte-Carlo simulations are utilized to capture the inherent randomness associated with the mechanical properties and pit depths in the sectional response of PC elements. Based on the outcome of these simulations, the influence of corrosion on the moment-curvature response as well as the expected failure mode are assessed. Finally, the latter results are investigated for different scenarios of corrosion, providing a comprehensive understanding of the effects of corrosion in PC elements and the associated uncertainties. These findings are relevant to researchers, engineers, and practitioners involved in the design, assessment, and maintenance of prestressed concrete structures. © 2024 The Author(s).

关键词： Prestressed concrete

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A simplified trilinear concrete stress–strain curve: energy-based modeling of experimental data compliant with various codes

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Journal of Umm Al-Qura University for engineering and architecture 2025年 1-11页

作者： Elgohary, Hamdy A. Civil Engineering Department College of Engineering and Architecture Umm Al-Qura University Mecca Saudi Arabia Structural Engineering Department Faculty of Engineering Mansoura University Mansoura 35516 Egypt

The stress–strain relationship of concrete is a key factor in structural engineering, helping to determine how concrete elements respond to loads in terms of strength and deformation. The accuracy of these evaluations depends on the shape of the stress–strain curve, the mathematical model used to represent it, the precise identification of the peak stress point, and the behavior of the material after reaching its peak strength. Energy-based modeling has gained recognition as a powerful and adaptable approach for analyzing concrete mechanical properties. By integrating the stress–strain curve, this method effectively captures energy dissipation and material behavior, providing valuable insights into performance. This study utilizes energy-based modeling to analyze experimental data and develop a more simple and precise stress–strain relationship for concrete. The proposed model is rigorously evaluated by comparing its predictions with experimental results and the idealized response curves from various structural design codes. The findings reveal that the new model aligns more closely with experimental data. This improved accuracy highlights its potential to enhance the reliability of concrete behavior predictions in structural applications. © The Author(s) 2025.

关键词： Concrete Energy modeling Stress–strain diagram

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A STUDY ON STRUCTURE OF WIND VELOCITY DISTRIBUTION AND CORRESPONDING PRESSURE DEFICIT CHARACTERISTICS UNDER THE TORNADO-LIKE WIND FLOW AFFECTED BY SURFACE ROUGHNESS

Journal of Structural and Construction Engineering

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Journal of structural and Construction engineering 2025年第827期90卷 15-26页

作者： Kikitsu, Hitomitsu Okuda, Yasuo Takadate, Yuki Building Department National Institute for Land and Infrastructure Management Japan Dept. of Architecture Faculty of Science and Engineering Setsunan University Japan Dept. of Structural Engineering Building Research Institute Japan

In this study, PIV and wind pressure experiments were carried out under tornado-like wind flow affected by surface roughness. The authors discussed the effects of swirl ratio and roughness density on the velocity field and the pressure deficit characteristics near the surface. It was confirmed that the velocity field structure gradually transitioned by changing swirl ratio and roughness density. Next, the pressure deficit characteristics showed that the measured pressure was the lowest when the roughness density was 0.014 at any swirl ratio. In the above discussion, the models on the radial velocity distribution and the pressure deficit distribution were proposed. © 2025 Architectural Institute of Japan. All rights reserved.

关键词： Wind stress

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