Biaxial bending moment magnifier method

This paper proposes a simplified method to design slender rectangular reinforced concrete columns with doubly symmetric reinforcement subjected to combined axial loads and biaxial bending, which is valid for short-time and sustained loads and for both normal and high strength concretes. The method is based on the so-called moment magnifier method (ACI-318-02) and EuroCode-2 (draft for stage 49) and it is only suitable for columns with equal effective buckling lengths in the two principal bending planes. A new equation of the column stiffness EI is proposed with which to obtain the moment magnification factor for single and double curvature. The method was compared with 371 experimental tests from the literature and a good degree of accuracy was obtained. Precision for sustained loads was improved in comparison with the method proposed by the American ACI-318 (02) and the European EC-2 (September 2003). The method allows slender reinforced concrete columns to be both checked and designed with enough accuracy for practice engineering.

[1]  Y. J. Kang.  Nonlinear geometric, material and time dependent analysis of reinforced and prestressed concrete frames , 1977 .

[2]  John E. Breen,et al.  LONG CANTILEVER COLUMNS SUBJECT TO LATERAL FORCES , 1969 .

[3]  Jin-Keun Kim,et al.  Buckling behaviour of slender high-strength concrete columns , 1995 .

[4]  Phil M. Ferguson,et al.  Long-Hinged Reinforced Concrete Columns , 1963 .

[5]  Stephen J. Foster,et al.  Experimental tests on eccentrically loaded high-strength concrete columns , 1997 .

[6]  S. Ali Mirza,et al.  Flexural Stiffness of Composite Columns Subjected to Major Axis Bending , 1999 .

[7]  Robert G. Drysdale,et al.  Sustained Biaxial Load on Slender Concrete Columns , 1971 .

[8]  W. H. Taso,et al.  Behaviour of biaxially loaded square and L-shaped slender reinforced concrete columns , 1994 .

[9]  C.-T. T. Hsu,et al.  Biaxially loaded slender high-strength reinforced concrete columns with and without steel fibres , 1995 .

[10]  B. V. Rangan,et al.  Studies on High-Strength Concrete Columns under Eccentric Compression , 1996 .

[11]  B. Bresler.  Design Criteria for Reinforced Columns under Axial Load and Biaxial Bending , 1960 .

[12]  S. Ali Mirza,et al.  FLEXURAL STIFFNESS OF COMPOSITE COLUMNS SUBJECTED TO BENDING ABOUT MINOR AXIS OF STRUCTURAL STEEL SECTION CORE , 1999 .

[13]  Kent Gylltoft,et al.  Slender Concrete Columns Subjected to Sustained and Short-Term Eccentric Loading , 2000 .

[14]  Wen Hu Tsao.  Behavior of square and L-shaped slender reinforced concrete columns under combined biaxial bending and axial compression , 1991 .

[15]  Manuel L. Romero,et al.  Analytical Approach to Failure Surfaces in Reinforced Concrete Sections Subjected to Axial Loads and Biaxial Bending , 2004 .

[16]  E. Hognestad,et al.  Sustained Load Strength of Eccentrically Loaded Short Reinforced Concrete Columns , 1956 .

[17]  R W Furlong,et al.  STRENGTH AND STIFFNESS OF REINFORCED CONCRETE COLUMNS UNDER BIAXIAL BENDING , 1976 .

[18]  P. Aitcin.  High Performance Concrete , 1998 .

[19]  Kent Gylltoft,et al.  SLENDER HIGH-STRENGTH CONCRETE COLUMNS SUBJECTED TO ECCENTRIC LOADING , 1998 .

[20]  Jin-Keun Kim,et al.  The Behavior of Reinforced Concrete Columns Subjected to Axial Force and Biaxial Bending , 2000 .

[21]  Wenliang Zhou,et al.  MODELING ERROR OF STRENGTH OF SHORT REINFORCED CONCRETE COLUMNS , 2000 .

[22]  J. D. Todd,et al.  Buckling and instability , 2000 .

[23]  John E. Breen,et al.  Eccentrically Loaded Concrete Columns Under Sustained Load , 1969 .

[24]  Sher Ali Mirza,et al.  FLEXURAL STIFFNESS OF RECTANGULAR REINFORCED CONCRETE COLUMNS , 1990 .