Static Analysis of Prestressed Floor Slabs HC500 with Changes in Tendon Adhesion to Concrete Induced by Penetration of Chloride Ions

摘要

Prestressed hollow-core slabs are suitable for various span applications in different types of buildings.Such structures are quick to mount and do not require boarding system or assembly supports reducing deflection,which is an economic asset.The performed analysis included HC-500 slabs made of C50/6Q concrete with w/c ratio of 0.31,with Portland cement CEM II 52.5 R.Strength of such structures is determined by,among other things,chloride ion concentration at the interface between the surface of prestressing tendons and concrete.Corrosion products,induced by chloride ions,will certainly reduce stress of adhesion to concrete,and consequently,second-order momentum in the structure.It may be difficult to draw firm conclusions about the predicted strength of analysed slabs on the basis of the obtained results.Therefore,we performed the static analysis including the changes in tendon adhesion to concrete caused by corrosion.We also analysed the bearing capacity of slabs according to concrete cover thickness of upper and lower tendons.The analyses included results from the accelerated tests on chloride ion penetration to cylindrical elements drilled directly from the top surface of prefabricated prestressed floor slabs HC500-19/R120.Those results were used to determine the diffusion coefficient of chloride ions into concrete,from which the analysed slabs were made. The value of diffusion coefficient D 0.72-10 m~2/s for the tested concrete was used to illustrate results for changes in the bearing capacity over time.We determined times,after which those tendons could corrode,assuming that penetration of chloride ions is observed only at the surface of the upper floor slab.The obtained results were used to develop recommendations and draw conclusions for further tests.