Guide to Long-Span Concrete Floors

Course Summary:

Concrete floor systems offer the designer a wide variety of options from which to choose a floor system for a particular project. All of these systems incorporate the many advantages which concrete bestows. Most importantly it is a plastic material when fresh and can be molded into any shape the designer chooses. Thus, it imposes almost no restriction on the plan of the floor although individual systems may impose limitations. Further, concrete allows a variety of surface finish, color and texture to be used. Concrete is non-combustible and possesses good insulating qualities, concrete floor systems can thus be designed to meet the requirements for fire resistance. Concrete is also a durable material and can easily be designed to meet the durability requirements for the particular exposure location, while the abrasion resistance of the floor surface can be adjusted to meet the most demanding requirements. This Guide concentrates on the structural design of the floor system and the designer should consult other manuals for advice on how to specify the concrete mix and construction practices to achieve the desired performance (see Bibliography).

The permission of the National Precast Concrete Association to use material from its Precast Concrete Handbook in the section on precast floor systems is gratefully acknowledged.

The charts for the insitu floors have been prepared using the computer program RAPT version 5.41 as licensed by the Prestressed Concrete Design Consultants (PCDC) to the Cement and Concrete Association.

Learning Objective:

The online PDH or CE course below is for improving and expand in engineering knowledge and technical science in the construction industry. It should not be used as Code course in the United States.

Concrete structures have, for many years, dominated the multi-story commercial and residential building scene. Landmark projects such as MLC building and Rialto rank among the tallest reinforced concrete buildings in the world and testify to the skills of designers, builders and tradesmen.

Traditionally, column spacings and floor spans in these buildings have been in the range of 6 to 9 meters, to both contain costs and simplify construction. However, recently there is an increasing preference by building owners and tenants for large floor areas with column-free space and spans from 9 to 16 meters. This has focused the interest of designers and builders on methods of reducing costs and speeding construction of long-span floors. For the purposes of this Guide, long-span floor systems are generally spanning greater than six meters for reinforced concrete systems or eight meters for prestressed systems. Some systems are effective below these arbitrary limits and their full range is included herein for completeness.

The aim of this Guide is to provide designers with an appreciation of the factors that should be taken into account in selecting a floor system for a particular building. A section on the major architectural considerations is followed by another on the major structural design considerations and one on construction considerations. These are followed by a description of the various floor systems, photographs/ sketches of each showing the appearance of the soffit and a chart indicating the economical spans and load capacities to aid in their selection.

The Guide provides discussion on only the common factors to be considered in the choice of a floor system. Designers are responsible for identifying and designing for all the requirements specific to their particular project, ex. attack by chemicals to be used in the manufacturing process to be carried out in the building or specific limits required on deflections or vibration.

It is emphasized that the graphs are not design charts but aids to enable designers to quickly identify appropriate floor systems to carry the applied loading for the desired span, and thus provide approximate dimensions for the preliminary design.

Review the quiz before studying the course.

Course Content

Course Author: CCA