LOAD DISTRIBUTION TESTS ON PRECAST PRESTRESSED HOLLOW-CORE SLAB CONSTRUCTION

Abstract

The only available authoritative source concerning the distribution of concentrated loads on a floor or roof construction composed of precast hollow-core slabs is ACI Standard 711-58, Minimum Standard Requirements for Precast Concrete Floor and Roof Units. This ACI Standard has now been superceded by ACI 512-67, Recommended Practice for Manufactured Reinforced Concrete Floor and Roof Units. However, prestressed concrete units and units whose length exceeds 35 ft. are not covered in ACI 512-67. Because of this gap in the ACI Standards, it is common practice among hollow-core slab manufacturers to refer to ACI 711-58 for criteria concerning the load distribution of concentrated loads. ACI 71158 states: Where a hollow-core (closed section) system supports partition walls parallel to the unit, or where heavy concentrated loads are to be expected, such loads may be considered to be uniformly distributed over not more than identical units on each side thereof but never over a greater total width than 0.4 of the clear span distance. Since the width of precast hollowcore units has greatly increased since the writing of the provision for three identical units on each side, it was felt that this provision would no longer be applicable. However, it was felt that a design width of 0.4 of the span was still an adequate conservative provision. Therefore, these tests were conducted to demonstrate the ability of grouted shear keys to transfer concentrated loads to adjacent slabs. Two load distribution tests were devised, conducted and reported by The Flexicore Co., Inc. The tests were witnessed and test data recorded by a commercial testing laboratory.