Column Load Balancing in Prestressed Concrete Building

Architectural and structural considerations in the design of the 27-story Wisma Dharmala office complex in Jakarta lead to the deployment of twin-column clusters around the perimeter and interior of the tower block. Due to the large difference in axial loads between the twin columns, excessive differential axial shortening between the columns and high shear stresses in the connecting horizontal structural components are expected. To mitigate this condition, the column load balancing method is proposed, in which the cable profiles in the prestressed girders are designed not only for moment balancing but also to transfer evenly the shear forces in the girders to the twin columns in each cluster. The effect of load balancing is examined in this paper with the use of a simple analytical model. The predicted loads on the columns are also checked against field measurements taken from three pairs of twin columns from the time the columns are cast until the casting of the helipad floor.