SLAB-ON-GRADE REINFORCING DESIGN
Matthew
Stuart, P.E., S.E., F.ASCE, SECB
Course Outline
Concrete
slabs-on-grade are highly susceptible to cracking due to shrinkage. Construction
and control joints are typically used to control crack location. Since it is
not always desirable or practical to use a large number of closely spaced joints,
reinforcing of the slab-on-grade allows for greater flexibility with joint spacing.
Welded wire mesh or deformed bar reinforcement normally used in slabs-on-grade
helps to control the width or growth of any cracks that may occur. This type
of steel is sometimes called distribution reinforcement to differentiate it
from structural reinforcement that is added to increase the load-carrying capacity
of the slab.
This
course includes a multiple choice quiz at the end.
Learning Objective
This course will enable the user to become familiar with the following methods of designing slab-on-grade "distribution" reinforcement;
1. Subgrade Drag
Theory
2. Temperature Method
3. Concrete-to-Steel Ratio Method
This course will also familiarize the users with the three principal methods of reinforcing slab-on-grades;
1. Welded wire
fabric
2. Deformed reinforcing bars
3. Post-tensioning cables
This course will
also enable the user to have a fundamental understanding of the limitations
of fiber reinforced concrete and the option to use shrinkage compensating concrete
for slab-on-grade construction.
Course Introduction
Course Content
The course content is contained in the following PDF file:
SLAB-ON-GRADE REINFORCING DESIGN
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In the absence of properly located control or contraction joints in slab-on-grade construction the concrete will crack randomly as a result of the shrinkage of the material. Providing sawn joints in the slab promotes cracking at the joint itself thereby preventing random cracking of the slab. Spacing requirements for sawn control joints in unreinforced slab-on-grades are available through the recommendations of PCA. However, it is possible through the introduction of "distribution" reinforcement to increase the spacing of the contraction joints. Reinforcement can be provided in the form of welded wire fabric, deformed bars or post-tensioning tendons. The use of fiber reinforcement is not recommended to help control cracking in the absence of conventional reinforcing. Shrinkage compensating concrete (Type K) can also be used to help minimize the number of required control joints.
Related Links
For
additional technical information related to this subject, please visit the following
websites or web pages:
American
Concrete Institute
Fiber
Reinforced Concrete
Post
Tensioned Slabs
Wire Reinforcement
Institute
Slab Works
http://www.greenstreak.com/specs_resources.asp?LitID=33
http://www.forconstructionpros.com/print/Concrete-Contractor/Features/Reinforcement-for-Crack--Width-Control/7FCP14576
https://www.structuremag.org/wp-content/uploads/2014/08/C-StructuralDesign-Azzi-Apr081.pdf
Quiz