Precast concrete floor systems represent a major component of the cost and weight of precast concrete buildings. Hollow-core (HC)
planking is considered the most common precast concrete floor system for residential and commercial buildings because of their economy, light
weight, structural capacity, and ease of production and erection. However, the high thermal conductivity of HC planks hinders their use in radiant
heated floor and roof applications where thermal insulation is needed. This paper presents the development of a precast/prestressed concrete
sandwich floor panel that consists of an internal wythe of insulation and two external wythes of concrete similar to those used in sandwich
wall panels. The main difference between the sandwich floor and wall panels is the design of shear connectors between concrete wythes to
achieve full composite action under ultimate loads while simultaneously having an adequate creep resistance under sustained loads and acceptable
deflection under live loads. Truss-shaped glass fiber-reinforced polymer ties, known as NU ties, were used as shear connectors because of
their structural and thermal efficiency. The proposed floor panels have comparable weight and capacity to HC planks while being more thermally
efficient and can easily be fabricated in standard casting beds with typical equipment, thus eliminating the high initial investment required
for HC production. This paper presents the design, detailing, production, and testing of three 7.9-m-long (26-ft-long), 1.22-m-wide (4-ft-wide),
and 200-mm-thick (8-in.-thick) specimens with 50-mm-thick (2-in.-thick) composite topping. The three specimens represent two different
panel designs. One specimen has solid concrete ends and was designed for a total superimposed service load of 9.6 kPa (200 psf), whereas
two specimens are fully insulated and designed for a total superimposed service load of 4.8 kPa (100 psf). The performance of the three specimens
under flexure and shear loadings indicated that the proposed sandwich floor panels can achieve full composite action and have satisfactory
structural performance and acceptable deflection characteristics
تاريخ النشر
08/01/2014
الناشر
Practice Periodical on Structural Design and Construction Journal
ايليا عزت عشم حنين | Eliya Ezzat Asham Henin, Ph.D., P.E., S.E., PMP. | 5538