American Society of Civil Engineers

Determination of Actual Design Moment in Ultradeep Reinforced Concrete Rafts

by Muhammad Tariq Amin Chaudhary, Ph.D., P.E., M.ASCE, (3942 Acorn Crescent, Windsor, ON N8W 5R4, Canada. E-mail:

Practice Periodical on Structural Design and Construction, Vol. 13, No. 4, November 2008, pp. 186-188, (doi:

     Access full text
     Purchase Subscription
     Permissions for Reuse  

Document type: Journal Paper
Abstract: This paper deals with determination of actual design moment in the flexural design of ultradeep reinforced concrete rafts. Due to diagonal crack in concrete, the workpoint of the internal tension-compression couple resisting the applied moment is shifted by a distance equal to the effective depth of the member. This shift in the workpoint necessitates that the design moment at a particular section shall also be shifted accordingly. The case is highlighted with the example of a 9.0 m (29.5 ft) deep circular raft that is acted upon by upward buoyant forces as well as downward gravity loads. Design moments in various regions of the raft increased by 1.3 to 248% after application of the moment shift rule described in the paper. The substantial increase in moment values signifies the importance of the phenomena for ultradeep reinforced concrete rafts.

ASCE Subject Headings:
Reinforced concrete
Finite element method
Concrete structures