Strategy of anti-buckling design of transverse reinforcement
This paper presents a strategy to enhance the current provision for antibuckling design of lateral ties. The resulting design method will restrict the buckling-induced reduction of average compressive stress of main bars to an allowable limit until the desired level of ductility is attained. First, a method to determine the maximum compressive strain likely to be experienced by the main bars is described. Based on an average compressive stress-strain relationship of reinforcing bars, evaluation of bar buckling parameter (a function of slenderness ratio and yield strength of the bar) required to restrict the loss of compressive stress at the maximum compressive strain to a tolerable limit is then explained. For a bar of known diameter and yield strength, the maximum allowable tie spacing can then be determined. Next, lateral stiffness required to restrain the buckling tendency of the main bars at the tie locations is expressed as a function of the geometrical and mechanical properties of the main bars. Similarly, the anti-buckling stiffness of the lateral ties is also derived as a function of the mechanical and geometrical properties of the lateral ties. Finally, a design framework to decide the spacing, amount and arrangement of lateral ties is established.