Nonlinear Finite Element Analysis of Strengthened Reinforced Concrete Columns

Abstract

The demand for strengthening structures became necessary when an increase in load was inevitable. Columns are an important element that needs strengthening because the degradation of these columns causes total failure of structures. This research studied the behavior of nonlinear analysis of strengthening reinforced concrete column by finite element method used ANSYS package. The verification models in this research consist of eight specimens; three of these specimens subjected to short-term loading, and other five remained specimens subjected to long-term loading. A three-dimensional finite element model has been used in this work. SOLID65 element used for modeling concrete and LINK8 element for steel reinforcement modeling in the analysis of reinforced concrete columns under short-term loading. In the analysis of concrete columns under long-term loading used VISCO89 element for concrete modeling and SHELL41 element for FRP modeling. This study achieved a good agreement between numerical and available experimental results, it was found that the percentage of error of specimens which subject to short-term loading between (0.5-5.7)% for displacement and about (1.1-7.7)% for ultimate load, while the percentage of error of the other specimens that subjected to long-term loading between (2.3-5.9)% based on creep strain. Also, this research studied the effect of some important parameters on the behavior of strengthening circular section of concrete columns. Five parameters are studied in this research the magnitude of sustained load (7%Pu -28%Pu - 72%Pu)kN, e/h ratio (0-0.26-0.46), length-diameter ratio (8-15-30), compressive strength (30-40-50)MPa and FRP type (glass or carbon). A 162 models were analyzed and discussed and then noticed from studying the effect of these III parameters that creep strain decreased about 13.2% and 10.4%when increased the compressive strength from (30-40)MPa and (40-50)MPa, respectively, but creep strain increased about 300% and 150% when the magnitude of sustained load increased from (7%Pu to 28%Pu)kN and (28%Pu to 72%Pu)kN respectively, while the effect of eccentricity magnitude and length - diameter ratio was very little on the creep strain. Finally, notice that strengthened concrete columns with CFRP give a high creep strain more than thirteen times of other concrete columns which strengthened with GFRP. However, that the studied model can be represent more efficient tool for simulating long term behavior of strengthened RC column.