•Better structural performance for HRC compared to fibres as unique reinforcement.•HRC led to global safety factors lower than those obtained for the FRC solutions.•The model proposed proved to be a ...reliable tool for safely design of real-scale slab.
The growing use of fibre reinforced concrete (FRC) for structural purposes has led several guidelines to include design-oriented models that allow the partial (and even total) substitution of the steel reinforcing bars. Among those, fibres as concrete reinforcement for elevated concrete flat slabs is gaining interest due to the identified technical and benefits and quantified sustainability enhancements. However, although this technology has already been used in buildings and its sufficient bearing capacity confirmed by real-scale experimental programs, its straightforward implementation is far from being consolidated. The latter is owing to the existence of several paramount aspects to be answered. One of those is the influence of the fib MC-2010 FRC post-cracking strength classification, including the combination of steel bars, on the mechanical response of these elements at ULS and SLS. In this context, a non-linear finite element model was implemented and validated by means of results from existing real-scale tests. Posteriorly, the model was used to design a new real-scale test to be performed within the context of the research project eFIB (from the Spanish, Optimization of Construction Processes of Structural Elements by using Fibre Reinforced Concretes). To this end, a parametric study was developed by considering several FRC post-cracking strength classes, using fibres as unique reinforcement or combined with steel meshes, to determine an optimum solution for flexure (which governs the main reinforcement requirements) based on the structural reliability index targeted for building construction. The model results and analysis permitted to derive relevant conclusions from the material design optimization point of view, which can be a reference for future similar experiences.
•Textile waste nonwoven fabric (TW) as reinforcement for cement-based composite.•Mechanical and durability material characterization.•6-layers of TW resulted the most flexural resistant solution.•TW ...Composite resulted satisfactory for non-structural building components.
Large amounts of nonrenewable resources are depleted by the construction industry in addition to the generation of million tons of mineral waste and carbon dioxide gas every year. For the sake of a more sustainable consumption pattern of building materials, as well as for reducing the waste flux to landfills, the use of recycled materials and wastes should be researched and motivated. In this sense, textile waste (TW) nonwoven fabric from residues of the garments and textile industries are investigated as internal reinforcement for cement-based matrices to enhance ductility and cracking control. To this end, an extensive experimental program was carried out to characterize both the mechanical and durability properties of the composite. The results were compared with those obtained from flax nonwoven fabric, taken as a reference (FNH and FH composites). All the composites showed a remarkable improvement in terms of toughness and post-cracking stress-bearing capacity, six being the optimum number of TW reinforcing layers. Through the analysis of the results obtained, the feasibility of using TW composite as a potential construction material in non-structural applications was confirmed. The extension to structural applications of low-medium responsibility is still required further research; nonetheless, the results are promising to this respect.
•Experimental results database of recycled aggregate concrete (RAC) creep compiled.•Differences between RAC and natural aggregate concrete (NAC) creep examined.•Application of fib Model Code 2010 ...creep model to RAC tested.•Correction factor for calculating RAC creep using the fib Model Code 2010 proposed.
Recycled aggregate concrete (RAC) is a promising solution to addressing the sustainability issues raised by concrete production. However, its long-term properties are not fully characterised, especially creep behaviour, which is significant for the design of RAC structures. This study presents the results of a meta-analysis of previously published research on the creep behaviour of recycled aggregate concrete (RAC). The main goal of the study is to formulate an analytic expression for the creep coefficient of RAC as an extension of the fib Model Code 2010 creep prediction model. A database of experimental results on the creep of RAC and companion natural aggregate concrete (NAC), produced with the same effective water-cement ratio, was compiled from available literature and using strict selection criteria. The database is comprised of results from 10 studies, 46 creep curves (14 NAC and 32 RAC) and 233 data points. Compared with companion NAC, RAC displays a larger creep coefficient; the difference between RAC and NAC increases with increasing recycled concrete aggregate (RCA) content and decreases with increasing RAC compressive strength. When predicting the creep coefficient of RAC using the fib Model Code 2010’s creep prediction model, relative to the model’s performance on companion NAC, the creep coefficient of RAC is underestimated. A correction coefficient for the creep coefficient of RAC, ξcc,RAC, is proposed for use with the fib Model Code 2010 model, dependent on RAC compressive strength and RCA replacement ratio.
Environmental and sustainability assessment tools have an important role in moving towards a better world, bringing knowledge and raising awareness. In the architecture and civil engineering sector, ...these assessment tools help in moving forward to constructions that have less economic, environmental and social impacts. At present, there are numerous assessment tools and methods with different approaches and scopes that have been analyzed in numerous technical reviews. However, there is no agreement about which method should be used for each evaluation case. This research paper synthetically analyzes the main sustainability assessment methods for the construction sector, comparing their strengths and weaknesses in order to present the challenges of the Spanish Integrated Value Model for Sustainability Assessment (MIVES). MIVES is a Multi-Criteria Decision Making method based on the value function concept and the Seminars of experts. Then, this article analyzes MIVES advantages and weak points by going through its methodology and two representative applications. At the end, the area of application of MIVES is described in detail along with the general application cases of the main types of assessment tools and methods.
This paper describes a meta-analysis of previously published studies on the shrinkage strain of recycled aggregate concrete (RAC). The study aims at providing an analytic expression for the shrinkage ...strain of RAC to be used in conjunction with the existing
fib
Model Code 2010 shrinkage prediction model. For this purpose, a database of experimental results on the shrinkage of RAC and companion natural aggregate concrete (NAC), produced with the same water-cement ratio, was compiled using strict selection criteria. Results from 19 studies entered into the database, consisting of 125 shrinkage curves (39 NAC and 86 RAC) with a total of 424 data points. A comparison of RAC and companion NAC revealed that, on average, RAC displays a larger shrinkage strain. This difference increases with increasing recycled concrete aggregate (RCA) content and with decreasing compressive strength. Applying the
fib
Model Code 2010 shrinkage prediction model revealed that, relative to its performance on NAC, the shrinkage strain of RAC is underestimated. Finally, a correction coefficient for the shrinkage strain of RAC,
ξ
cs
,
RAC
, to be used in conjunction with the
fib
Model Code 2010 model, was proposed in the form of a bivariate power function with RAC compressive strength and RCA replacement ratio as variables.
A multi-criteria decision-making system based on the MIVES method is presented as a model for assessing the global sustainability index scores of existing wind-turbine support systems. This model is ...specifically designed to discriminate between tower systems in order to minimize the subjectivity of the decision and, thus, facilitate the task of deciding which system is best for a given set of boundary conditions (e.g., height, turbine power, soil conditions) and economic, social and environmental requirements. The model's versatility is proven by assessing the sustainability index of an innovative new precast concrete tower alternative also described in this paper. As a result of this analysis, some points of improvement in the new system have been detected.
Temporary housing units (THUs), which are provided after disasters, are crucial in terms of sustainability pillars (economic, social, and environmental). In general, THUs, which are regular houses ...with minimum space and facilities, incorporate some negative aspects of the building industry. Additionally, as large numbers of THUs are usually provided in a short time and under emergency situations, some negative impacts of these units escalate. In this context, this study aims at reducing some negative impacts of THUs by applying a novel optimization model that maximises sustainability indexes by simulating the design of interior geometries for THUs. This method is based on the coupling of artificial intelligence and a multi-criteria decision-making model for sustainability assessment. The proposed model generates optimal solutions using a backtracking algorithm together with a binary search. To evaluate the sustainability indexes, an Integrated Value Model for Sustainability Assessment (MIVES) is applied. This novel method enables decision makers to automatically generate the most suitable alternative solutions for the early design stage of THUs. The results confirm that small changes in the interior geometric design can remarkably affect the sustainability indexes of THUs.
•Multi-objective MIVES-based approach for optimizing temporary housing units' layout.•Backtracking algorithm coupled to binary search to generate optimal solutions.•Economic and environmental performances were enhanced respect to the reference solutions used in Bam 2003 earthquake.
Within the building construction sector, fiber cement boards have attracted interest as facade cladding materials in the last ten years, especially those that incorporate –for reinforcing purposes– ...natural and/or recycled synthetic fibers (i.e, from the textile industry). So far, the design-governing parameters of facade cladding panels have been mechanical strength, durability, constructability, aesthetics, insulation capacity, and fire resistance. From the sustainability perspective, the impact of the facade on the economic and energy efficiency performance is most often the parameter that leads the decision-making process. Within this context, the quantification of the sustainability performance of the facade –accounting for economic, environmental, and social indicators– is unfrequently carried out in design and project phases, this being attributed to the lack of methodologies that allow considering and quantifying some relevant indicators representative of the facade sustainability performance. As consequence, decisions made based on solely economic and on some of the environmental indicators might lead to solutions with lower sustainability performance than that required (or expected). Recycled textile waste fabric-reinforced cement board as a facade-cladding material for building envelopes is the focus of this research. In order to characterize the fire resistance, and thermal and acoustic insulation –as relevant serviceability parameters– of this material, an experimental program was carried out. Likewise, the sustainability performance of this facade-cladding is assessed through a method based on the Integrated Value Model for Sustainability Assessment (MIVES). This multi-criteria decision making (MCDM) model relies on the value function concept and the multi-disciplinary participation of experts to identify and quantify the relevant indicators of the facade sustainability performance and the relative importance of indicators and requirements. The MIVES-based model generated for this research can be straightforwardly used for assessing the sustainability performance of facade-cladding techniques made of any material and for any type of building (and location). The application of the MIVES model led to the sustainability index of this new material for facade-cladding ranging from 0.68 to 0.71 (/1.00) for different weighting scenarios.
•Fire, thermal and acoustic experimental characterization of TWFRC panels.•Sustainability analysis of TWFRC panels by means of MIVES approach.•Sustainable index of TWFRC panels > 0.7 (/1.0).
A design-oriented numerical model for the analysis of RC, FRC, and RC-FRC tunnel sections exposed to fire with different spalling parameters is presented. The numerical model is conceived in two ...steps: the first is the determination of the temperature field in the cross-section exposed to fire according to the spalling parameters; and the second is the determination of the bearing capacity of sections based on the thermal field in the section. At last, a parametric study was conducted to evaluate the effect of the fire curve, the spalling parameters, the reinforcement type, and the rebar’s concrete cover on the bearing capacity of the sections. The results showed that the use of FRC as total or partial substitution to RC mitigates the fire-related reduction in the bearing capacity of the sections. Moreover, increasing the RC concrete cover is beneficial only if thermal spalling is avoided. When thermal spalling occurs, the FRC and RC-FRC solutions yielded the lowest reductions in the bearing capacity among the reinforcement solutions tested.
Fibre reinforced concrete (FRC) is increasingly used for structural purposes owing to its many benefits, especially in terms of improved overall sustainability of FRC structures relative to ...traditional reinforced concrete (RC). Such increased structural use of FRC requires safe and reliable models for its design in ultimate limit states (ULS). Particularly important are models for shear strength of FRC members without shear resistance due to the potential of brittle failure. The
fib
Model Code 2010 contains a model for the shear strength of FRC members without shear reinforcement and the same partial factor accepted for RC structures is accepted for FRC elements. This approach, however, is potentially on the unsafe side since the uncertainties of some design-determining mechanical properties of FRC (i.e., residual flexural strength) are larger than those for RC. Therefore, in this study, a comprehensive reliability-based calibration of the partial factor
γ
c
for the shear design of FRC members without shear reinforcement according to the
fib
Model Code 2010 model is performed. As a first step, the model error
δ
is assessed on 332 experimental results. Then, a parametric analysis of 700 cases is performed and a relationship between the target failure probability
β
R
and
γ
c
is established. The results demonstrate that the current model together with the prescribed value of
γ
c
= 1.50 does not comply with the failure probabilities accepted for the different consequences of failure of FRC members over a 50-year service life. Therefore, changes to the shear resistance model are proposed in order to achieve the target failure probabilities.
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