Masonry Magazine June 1972 Page. 21
NCMA-TEK
An Information series from National Concrete Masonry Association
41
Introduction
Floor systems for use with modern loadbearing concrete masonry walls serve two primary functions: they transmit the vertical dead load and live load to the bearing walls; and they function as diaphragms, transmitting lateral wind and siesmic loading through the walls to the foundation. Stiffness of the floor system influences the distribution of lateral loads to the walls. For diaphragms with stiffness similar to the masonry walls, such as almost any type of concrete floor system, lateral loads are transmitted to the walls in proportion to their relative rigidities. With floor systems which are considered as flexible diaphragms, lateral loads are distributed to the walls in proportion to
Floor Systems for
Use With Loadbearing
Concrete Masonry Walls
the tributary area in the diaphragm depending on its shear and moment deformation. In addition to the structural functions the floor should provide a satisfactory barrier to the transmission of sound and fire. The many types of concrete floor systems in use today are designed to satisfy all of these requirements in an economical manner.
The multi-story building with loadbearing concrete masonry walls has experienced a dramatic increase in the past few years. This is due to several factors: advent of modern structural design criteria, speed of construction, and economy. The design criteria assumes that the floors will act as diaphragms. Economy and speed of construction depend, in most instances, on a type of floor system that can be erected quickly.
Filler Block with
Cast-in-Place Joists
One of the types of systems developed to accomodate these factors is the concrete joist-concrete filler block floor. Manufactured in a range of sizes from 4 inches to 12 inches deep, the filler block are applicable to floors having a correspondingly wide range of effective depths and of maximum span limits and load capacity. Since hollow concrete filler block are made with lightweight aggregate and contain hollow cores which total 40-60 percent of the gross volume, their use results in a substantial reduction in dead load as compared with a solid slab of equal load carrying capacity. Construc-
TEK 41 © 1972 National Concrete Masonry Association
C
Concrete Units