Design Procedure for Reinforced Concrete Beams and Reinforcement Replacement by Bamboo

Abstract

The use of non-renewable resources by the construction industry has several environmental consequences, contributing to excessive energy consumption and loss of materials. So, the construction sector is always in search of improvement and methods that innovate the existing techniques, aiming at the use of alternative and sustainable materials. Bamboo is a perennial plant with fast growth rate and low cost that has great physical and mechanical characteristics that assure its performance in the building environment. The use of beams with total or partial replacement of steel by bamboo has been well studied, due to the possibility of using the same design methods used in reinforced concrete beams, since the bamboo-reinforced beams meet the Bernoulli-Kirchoff bending theory. The objective of the work was to adapt a design procedure into an electronic spreadsheet for bamboo reinforced concrete beams subjected to four-point bending, with rectangular section, according to Brazilian Standard NBR 6118 (2014). The spreadsheet was tested based on other authors taking into consideration a steel double reinforcement. The resulting values were equivalents to those obtained by the authors, validating the efficiency of the worksheet. This methodology aims to optimize the design process of beams and enable the substitution of steel by bamboo, highlighting the validation, from the structural point of view, obtained by the authors.

Flexural Strength of Bamboo and Steel Reinforced Concrete Beam

“…For equilibrium, the ultimate design moment, 𝑀, must be equal to the tensile force 𝐹 𝑠𝑡 in the reinforcing bar and the concrete compressive force 𝐹 𝑐𝑐 that passes via the midpoint of the actual area of concrete in compression, at a distance of (z). Figure 1 illustrations the balanced state of a section of singly reinforced concrete beam (Tokuda et al, 2020;Mosley et al, 2012;BS 8110, 1997). The is calculated from Equation ( 1)…”

“…Imposed load: The imposed load 𝑃 is given in Equation ( 6 where: 𝑀 = bending moment (MPa); 𝑓 𝑐𝑘 = Concrete compressive strength (N/mm 2 ); 𝑏 𝑤 = breadth of concrete beam (mm); x = distance from beam's top to neutral axis (mm); d = effective dept (mm); 𝐹 𝑐𝑐 = compressive force in concrete (KN); 𝑓 𝑦𝑘 = characteristic yield stress (N/mm 2 ); 𝐹 𝑠𝑡 = resultant tensile force in concrete; 𝑀 𝑘 = service bending moment (MPa); 𝑀 = bending moment (MPa); 𝑃 = imposed load (KN); 𝑎 = distance between load 𝑃 and support (mm); 𝑞 = beam's distributed load (KN/mm); 𝑙 = element length (mm); 𝐴 𝑠 = area of steel reinforcement (mm 2 ); 𝜎 𝑠𝑡𝑒𝑒𝑙 = steel tensile stress (N/mm 2 ); 𝐹 = load on the bamboo/steel reinforcement (KN); 𝜎 𝑏𝑎𝑚𝑏𝑜𝑜 = bamboo tensile stress (N/mm 2 ); 𝐴 𝑏 = equivalent bamboo area (mm 2 ); 𝐷 𝑚𝑎𝑥 = deflection (mm); (Tokuda et al, 2020;Mosley et al, 2012).…”