Simplified structural design and LCA of reinforced concrete beams strengthening techniques

Abstract

This work provides the Life Cycle Assessment (LCA) of four commonly used strengthening techniques of reinforced concrete beams. Firstly, it provides a simplified methodology to size the strengthening, overcoming the need of extensive knowledge in structures. Secondly, it provides the application of LCA to the selected techniques. The method improves the applicability of LCA to buildings, analyzes the environmental differences between techniques, and reveals the importance of the anchoring method as well as the enormous benefit in reusing building structures. Results obtained for conventional beams are displayed in tables ready to use in LCAs with broader boundary systems. NOMENCLATURE Variables and units:Latin upper-case letters ∆C: increase of the bending capacity Ar: Area of the added strengthening piece M0: Original beam bending capacity MT: Required bending moment N p c: Axial force in concrete considering a parabolic distribution M p c: Bending moment in concrete considering a parabolic distribution N r c: Axial force in concrete considering a rectangular distribution M r c: Bending moment in concrete considering a rectangular distribution MJ-Eq: MJ of non-renewable primary energy Er: Young modulus of the new strengthening material (steel or CFRP) Es: Young modulus of the existing rebars steel L: Length of the beam LT: Total length of the reinforcement Ls: Length of the part of the beam with insufficient bearing capacity La: Anchorage length Vrd,anch: Design shear stress of the anchorage Tsd: Required shear stress Greek lower-case letters εc max : Maximum strain in concrete εs1: Strain in the tensile rebar εs2 : Strain in the compression rebar εr: Strain in the strengthening material Latin lower-case letters b: overall width of a beam cross-section d: distance between the most compressed concrete fiber and the most tensioned rebar d': rebar cover fdr: yielding stress of the new strengthening material (steel or CFRP) fcd: design value of concrete compressive strength f yd: yielding stress of the existing rebars steel h: overall depth of a beam cross-section h/b: relation between depth and width of a cross-section beam kgCO2-eq: kilograms of CO2 equivalent s1: Tensile rebars s2: Compressive rebars x: neutral axis depth z: distance between the most compressed concrete fiber and the reinforcement axis position Acronyms:

Environmental effects of using different construction codes applied to reinforced concrete beam designs based on Model Code 2010 and Spanish Standard EHE-08

“…This trend also applies in the remaining impact indicators (see Appendix A2). Previous literature on RC structures also reported on similar patterns (e.g., [32,37,38,39,40,41]). In this sense, in cases with L = 8.0 m the maximum impacts of reinforcing steel have a larger contribution to the total environmental impacts of the beam, representing up to 50-90 % of the life cycle impacts.…”

Sustainability assessment of refurbishment vs. new constructions by means of LCA and durability-based estimations of buildings lifespans: A new approach

“…This paper reveals the importance of the lifespan to get economic and environmental benefits and render cost-effectiveness in the long term to the building sector. In the case of the existing buildings an important objective should be to extend their lifespan by means of improving their structure, as suggested in [3]. In the case of new buildings, the objective should be to ensure their potential durability by changing current human tendencies of early substitution.…”

“…One question recently posed in the field of buildings LCA is whether or not it is more sustainable to refurbish than to rebuild [3]. Most of the literature on LCA focuses on new construction [4][5][6][7][8], whereas refurbishment is dealt with at a lower extent [9][10][11][12].…”

Evaluation of anchor bolt effects on the thermal performance of building insulation materials

“…The energy demand for cooling and heating buildings is increasing greatly, especially in developing countries [1]. According to existing literatures, buildings can contribute to up to 40% of the whole energy consumption of our society [1][2].…”

“…The energy demand for cooling and heating buildings is increasing greatly, especially in developing countries [1]. According to existing literatures, buildings can contribute to up to 40% of the whole energy consumption of our society [1][2]. Many studies have shown that promoting thermal performance of building envelopes, especially external walls, can significantly decrease buildings' energy demand [3][4][5].…”