Strengthening Slender Reinforced Concrete Columns Using High-Modulus Bonded Longitudinal Reinforcement for Buckling Control

This paper introduces a model for strengthening slender reinforced concrete columns. The proposed technique aims at controlling second-order lateral deflections using longitudinal high-modulus bonded reinforcement, thereby altering the loading path to intercept the axial load-bending moment (P-M) interaction curve at a higher axial capacity. With the availability of high and ultra-high-modulus carbon fiber-reinforced polymer (CFRP) plates, this approach should be quite efficient according to Euler's buckling rule, in which column strength is stiffness-controlled. This approach is different from the classical transverse-wrapping method for confinement, a technique that achieves strengthening by enlarging the (P-M) diagram in the compression-controlled region. The proposed model accounts for concrete nonlinearity in compression, cracking in tension, steel rebar plasticity, and certainly geometric nonlinearity, in addition to the possibility of premature CFRP-debonding failure in tension and the lower CFRP strength in compression than tension. The model is validated against experimental results and used in a parametric study to assess the effects of slenderness ratio., axial load initial eccentricity ratio e(0)/h, CFRP reinforcement ratio rho(f), and modulus E-f. It was shown that significant gains in axial strength, ranging from 17 to 90%, occur as the magnitudes of lambda, rho(f), E-f and e(0)/h increase. (C) 2014 American Society of Civil Engineers.

本文介绍了一种加固细长钢筋混凝土柱的模型。所提出的技术旨在利用纵向高模量粘结钢筋控制二阶侧向挠度，从而改变加载路径，在更高的轴向承载力下与轴力 - 弯矩（P - M）相互作用曲线相交。随着高模量和超高模量碳纤维增强聚合物（CFRP）板的出现，根据欧拉屈曲准则（柱的强度由刚度控制），这种方法应该是非常有效的。这种方法不同于用于约束的经典横向包裹方法，横向包裹方法是通过扩大受压控制区域的（P - M）图来实现加固的。所提出的模型考虑了混凝土受压的非线性、受拉开裂、钢筋的塑性，当然还有几何非线性，以及CFRP在受拉时过早脱粘破坏的可能性以及CFRP受压强度低于受拉强度的情况。该模型通过实验结果进行了验证，并用于参数研究以评估长细比、轴力初始偏心距比e(0)/h、CFRP配筋率ρ(f)和模量E - f的影响。结果表明，随着λ、ρ(f)、E - f和e(0)/h数值的增加，轴向强度有显著提高，提高幅度在17%到90%之间。（C）2014美国土木工程师协会。