Experimental studies on horizontal shear capacity of prestressed beams casted in stages with multiple-stage tendon stressing as xompared to various codes

In concrete composite construction, the first cast and the second cast of the concrete must be effectively connected together so that the structure behaves in a monolithic manner as a whole. If the two casts are not bonded together, slips occur at the interface under flexure and each component slides against each other at the interface joint. This will cause each component of the composite subjected to bending about their own individual centroidal axis, and eventually result in substantial reduction in stiffness and structural strength of the section. To prevent this, various codes of practice include provisions for the design of the horizontal shear across the interfacing concrete joint of the two casts in order to ensure full composite action can be developed. For practical construction of thick prestressed members at site, the structures are normally casted in few layers in two or three stages. It is not uncommon that the first cast of the concrete is designed to be prestressed to support the wet concrete weight of the subsequent casts in order to reduce the burden of the formwork. This paper studies the effect of multiple-stage tendon stressing on the horizontal shear capacity of a prestressed beam specimens casted and stressed in stages. The experimental results obtained from the specimen testing are then compared with the interfacing shear capacity computed by various codes. The major international codes of practice, like Eurocode EC2:2004, American ACI318M-14, British BS8110:1997, Australian AS3600-2009, and Chinese GB50010:2010 are considered in this research [1–5].