Parametric numerical study on service-load deflections of reinforced recycled aggregate concrete slabs and beams based on fib Model Code 2010

This is the peer reviewed version of the following article: [ Tošić, N, Kurama, Y. Parametric numerical study on service‐load deflections of reinforced recycled aggregate concrete slabs and beams based on fib Model Code 2010. Structural Concrete. 2020; 1– 15. https://doi-org.recursos.biblioteca.upc.edu/10.1002/suco.202000015], which has been published in final form at https://onlinelibrary.wiley.com/doi/abs/10.1002/suco.202000015. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-ArchivingRecycled aggregate concrete (RAC) is entering into structural design codes such as the new Eurocode 2. However, serviceability limit state (SLS) behavior of RAC, especially deflections, can be significantly greater than for natural aggregate concrete. Proposals for deflection control of RAC exist, but there still have not been significant studies on their implications for SLS design. In this paper, a comprehensive numerical parametric study on the sustained serviceload deflections of reinforced RAC slabs and beams is described. First, a concrete material model for the time-dependent analysis of reinforced concrete structures is described, validated, and calibrated, incorporating fib Model Code 2010 creep and shrinkage models in the OpenSees structural analysis program. Then, service-load deflection analyses are conducted on RAC one-way slabs and T-beams considering the amount of coarse recycled concrete aggregate (RCA), concrete strength class, element height, span, statical system, relative humidity, and quasi-permanent load-to-design load ratio. The results show that RCA begins to have an appreciable effect on deflections only for coarse aggregate replacement percentages above 25%. At 50% replacement, the maximum spans to satisfy deflection limits can be considerably reduced; however, these reductions are smaller for T-beams and higher class concrete. The results confirm the versatility of the numerical model, as well as the applicability and limitations of RAC in SLS design.This research was funded by the United States Department of State through a Fulbright Visiting Scholar Grant for the project “Optimization of Stratified Recycled Concrete Structures Based on Numerical Analyses and Life Cycle Assessment.” This support is gratefully acknowledged. The authors also express their gratitude for research assistance provided by Dr. Adam Knaack (Schaefer-Inc) and Dr. Seyed Alireza Jalali (Civil Soft Science). Any opinions, findings, conclusions, and/or recommendations in the paper are those of the authors and do not necessarily represent the views of the individuals or organizations acknowledged.Peer ReviewedPostprint (author's final draft

Improved serviceability and environmental performance of one-way slabs through the use of layered natural and recycled aggregate concrete

The following are available online at http://www.mdpi.com/2071-1050/12/24/10278/s1: Excel file with input data for the parametric numerical studyRecycled aggregate concrete (RAC), i.e., concrete produced with recycled concrete aggregate (RCA) has been heavily investigated recently, and the structural design of RAC is entering into design codes. Nonetheless, the service load deflection behavior of RAC remains a challenge due to its larger shrinkage and creep, and lower modulus of elasticity. A novel solution to this challenge is the use of layered concrete, i.e., casting of horizontal layers of different concretes. To investigate the potential benefits and limits of layered concrete, this study contains a numerical parametric assessment of the time-dependent sustained service load deflections and environmental impacts of homogeneous and layered NAC and RAC one-way slabs. Four types of reinforced concrete slabs were considered: homogeneous slabs with 0%, 50% and 100% of coarse RCA (NAC, RAC50 and RAC100, respectively) and layered L-RAC100 slabs with the bottom and top halves consisting of RAC100 and NAC, respectively. In the deflection study, different statical systems, concrete strength classes and relative humidity conditions were investigated. The results showed that the layered L-RAC100 slabs performed as well as, or even better than, the NAC slabs due to the differential shrinkage between the layers. In terms of environmental performance, evaluated using a “cradle-to-gate” Life Cycle Assessment approach, the L-RAC100 slabs also performed as well as, or slightly better than, the NAC slabs. Therefore, layered NAC and RAC slabs can be a potentially advantageous solution from both structural and environmental perspectives.This study has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 836270 and from the United States Department of State through the Fulbright Visiting Scholar Grant “Optimization of Stratified Recycled Concrete Structures Based on Numerical Analyses and Life Cycle Assessment.” Any opinions, findings, conclusions, and/or recommendations in the paper are those of the authors and do not necessarily represent the views of the funding organizations.Peer ReviewedPostprint (published version