How to work out least bar spacing for bundle bars in cast-in place concrete
In this construction article, you will learn the process for working out the minimum bar spacing for bundle bars in Cast-in Place Concrete with adherence to AASHTO provisions.
Minimum Bar Spacing: With adherence to AASHTO LRFD, section 5.10, the lowest bar spacing for bundled bars should be computed on the basis of the originated diameter rather than measuring from individual diameters.
Computation Example: As for instance if 2 nos. 32 mm dia bars are utilized, the similar diameter in line with 2×32 is 45mm. Therefore, 45 should be employed to utilize the following clauses from AASHTO.
For 2×32 dia bars, clear spacing should be provided as ~68mm for Cast-in Place concrete and 60mm for precast concrete.
Assign the Clauses given below from AASHTO LRFD 5th Edition 2010.
For cast-in-place concrete, the clear distance among parallel bars in a layer should not be kept under the followings:
• 5 times the nominal diameter of the bars,
• 5 times the maximum size of the coarse aggregate, or 1.5 in.
For precast concrete that is developed under plant control conditions, the clear distance among parallel bars in a layer should not be kept under the followings:
• The nominal diameter of the bars,
• 33 times the maximum size of the coarse aggregate, or 1.0 in.
The number of equivalent reinforcing bars bundled in contact to function as a unit shall not be over four numbers in any one bundle, apart from in flexural members, the number of bars greater than No. 11 shall not be over two numbers in any one bundle.
Bundled bars should be surrounded inside stirrups or ties. Separate bars in a bundle, cut off inside the extent of a member, should be concluded at various points with minimum 40-bar diameter stagger.
Where spacing restraints are created on the basis of bar size, a unit of bundled bars shall be considered as a single bar of a diameter resulting from the corresponding total area.