Control of Tensile Stress in Prestressed Concrete Members Under Service Loads

In current design codes, crack control design criterion for prestressed concrete (PSC) members is stricter than conventional reinforced concrete (RC) members. In particular, it is stipulated that the net tensile stress of prestressing strands should be controlled under 250 MPa in the serviceability design of PSC members belonging to the Class C category section that is expected to be cracked due to flexure under service load conditions as defined in ACI318 code. Thus, the cracked section analysis is essentially required to estimate the tensile stress of the prestressing strands under the service loads, which requires very complex iterative calculations, thereby causing many difficulties in the applications of the Class C PSC members in practice. Thus, this study proposed a simple method to estimate the net tensile stress of the prestressing strands (Δf ps ) under the service load conditions, and also provided a summary table to be used for checking whether the net tensile stress (Δf ps ) exceeds the stress limit (250 or 350 MPa) with respect to the magnitude of effective prestress (f se ).