DESIGN OF PPC BEAMS ACCORDING TO CRACK WIDTH REGULATIONS IN CHINESE CODE GB50010

摘要

Partially prestressed concrete (PPC),which combines the advantages of fully prestressed concrete and reinforced concrete,has now been accepted and become normal practice in many regions.There are no accurate design procedures for PPC beams presently.In the design of PPC beams,one of the main issues is how to reasonably estimate the amount of non-prestressed reinforcement and prestressed reinforcement to satisfy the requirements of the cracking control provisions.In this paper,a method is established to determine the combination of these two types of reinforcements,which is mainly based on the serviceability limitations and especially on the maximum allowable crack width given by the Chinese Code GB50010.The stress of the non-prestressed reinforcement is estimated,and a cubic equation for the depth of compression zone in the crucial section is formulated.Then,the maximum value for the cross-sectional area of the prestressed reinforcement can be calculated and partial prestressing requirements can be estimated.The calculation of the partial prestressing requirements must abide by the assumption that plane sections remain plane.Finally the minimum required amount of steel according to the code will be evaluated.Helpful design procedures and a design example is presented in this paper.The presented design method is easy-to-apply on a flexural partially prestressed reinforcement concrete beam.