An innovated structural system, namely the Shell-Slab Roofing System
(SSRS) of precast thin reinforced concrete cylindrical shell and flat slab has been
fabricated as a roof segmental unit. The flat slab rests on the cylindrical shell at the
crown and also connected to the shell by steel rod connections at each side. Steel
plate strips are fixed on the bottom surface of the slab and on the top and the
bottom surfaces of the shell as external tensile and shear steel reinforcement to
prevent punching shear around the steel rod connections. The ratio of the shell
height to the chord length was (0.1). The structural behavior of the roof system had
been investigated under uniformly distributed static load. Experimental work was
carried out by fabrication of six complete segments with scale-down simulation
factor equal to (0.25). The vertical deflections had been observed at selected
positions on the models. A water/cement ratio of (0.5) combined with a cement:
sand ratio of (1:2) had been employed. The influence of certain experimental
parameters had been studied. The model with only twelve rod connections and
minimum reinforcement volume ratio was adequate to resist the live loads for
buildings with large span roofing. The investigation showed that the combined unit
of thin concrete shell and flat slab with embedded small diameter steel
reinforcement was suitable for construction of such roofing system as large span
structures with lower ratio of shell height to chord length (h/c) equal to (0.1) .