Minimum thickness requirement of CFRP in built- up timber columns in compression and flexure

Stochastic evaluation of the minimum thickness requirement of CFRP in built-up timber columns in compression and flexure is presented. It is carried out using the Box complex method for complex constraint problems. The critical load is obtained for pin ended columns made of circular built-up glulam timber which is also externally wrapped with CFRP. The critical load is used to find the constraint equation which is the difference between the critical load and the safe load of glulam for the four strength classes employed. The safe load is obtained from the relevant Eurocode. The constraint equation and critical loads are then considered using the Box method with the critical load as the objective function and variables such as: column diameters, CFRP thicknesses, and lengths of columns. The method is applied by varying one parameter at a time, while leaving the others constant. When CFRP thickness is varied, it is observed that for some increases in the CFRP thicknesses there are increases in the minimum function which is the measure of the strength or capacity of the column. Therefore, it is concluded herein, that increases in CFRP thicknesses are recommended up to an optimum value depending on the lengths or spans in order to strengthen structural members like columns beams, etc., as long as delamination or de-bonding does not occur; and the Box method can be safely used for analysing structural members. Also, it is clear that relevant Euro codes prove to be suitable and convenient design criteria.