Chinese design code for slender reinforced concrete columns
How, Wei Min.
Date of Issue2013
School of Civil and Environmental Engineering
The purpose of this report is to study the behaviour of slender reinforced concrete columns based on design code of practice GB50010-2010, EC2, BS8110, and theoretical analytical methods of transformation concept and P-delta method to analyse the failure load capacity of the slender reinforced column. Assumed pin-ended slender columns subjected to short term uniaxial bending and axial loading are evaluated using analytical and experimental methods. In this study, the author familiarizes the concept of slender reinforced concrete columns in terms of design and analysis methods in accordance to GB50010-2010, EC2, BS8110 and theoretical analytical methods of transformation concept and P-delta method. The analysis method, GB50010-2010 will be the main focus of this paper. A total of 152 columns have been analysed with 79 test columns from appendix 2 of Cranston and 73 columns from past FYP students. Variables such as slenderness ratio, material strength, eccentricity ratio and steel reinforcement ratio will be used to evaluate the data from the various codes of practice. The test data comprises slenderness ratio (L/h) ranging from 14.7 to 50.0, ratio of load eccentricity to depth (e/h) of 0 to 0.75, compressive strength of concrete of 16.7N/mm^2 to 106.7N/mm^2, yield strength of steel of 206N/mm^2 to 625N/mm^2, and steel ratio (A_s/bh) of 0.005 to 0.524. Analysis report and discussion showed that a decrease in slenderness ratio, a decrease in eccentricities of load, an increase in concrete strength and an increase in the steel reinforcement ratio will result in an increase in the failure loads of slender columns. The results of theoretical methods and analysis methods are slightly different. The analysis methods based on GB50010-2010 give the least conservative predictions. GB50010-2010 gives unsafe and inaccurate results, compromising on the safety margin of design standards. This report also shows that GB50010-2010 is inadequate for the design of slender columns with high strength concrete and normal strength concrete for short term loading. Both codes of practices and theoretical methods have their own merits and demerits in the design of slender columns. P delta method and transformation method provides good predictions of failure load capacity and is conservative with safety margin as high as 1.51 for normal strength concrete. Both analytical methods also provide an acceptable safety factor of 1.10 for high strength concrete. Design codes GB50010, EC2 show a higher safety factor for higher concrete strength slender columns, BS8110 displays a high safety margin of 1.65. On the other hand, GB50010 displays the least conservative with safety margin below 1 and is not ideal for design standards of slender reinforced concrete columns. GB50010-2010 is a new design code which requires a period of time to materialise and design equations for slender reinforced concrete columns requires further research. Demand for the use of slender reinforced concrete columns is increasing. The development and advancement in design of slender columns requires more research to be carried out in order to study the behaviour of slender reinforced concrete columns.
Final Year Project (FYP)
Nanyang Technological University