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# In the design of corbel beams in a pumping station, why are shear links designed in the top 2/3 of the section? What is the general advice on the design?

Corbel beams are defined as z/d<0.6 where z is the distance of bearing load to the beams’ fixed end (or called shear span) and d is depth of beams. The design philosophy is based on strut and tie system. To establish the design model, it is firstly assumed the failure surface, i.e. shear cracks extending to 2/3 of depth of beam. Experiment results verified that the failure cracks extended only to 2/3 of beam while the remaining 1/3 depth of concrete contributed as concrete strut to provide compressive strut force to the bearing loading. Horizontal links are normally provided to corbel beams because experimental results indicated that horizontal links were more effective than vertical links when shear span/depth is less than 0.6. For shear span/depth>0.6, it should be not considered as corbel beams but as cantilevers.

In designing corbel beams, care should be taken to avoid bearing load to extend beyond the straight portion of tie bars, otherwise the corners of corbel beams are likely to shear off. Reference is made to L. A. Clark (1983).

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

### Kanwarjot Singh

Kanwarjot Singh is the founder of Civil Engineering Portal, a leading civil engineering website which has been awarded as the best online publication by CIDC. He did his BE civil from Thapar University, Patiala and has been working on this website with his team of Civil Engineers.

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## 2 comments on "In the design of corbel beams in a pumping station, why are shear links designed in the top 2/3 of the section? What is the general advice on the design?"

Ashok says:

Calculation of Ground Pressure for Crawler Crane and Mobile Crane
Temporary bund to comprise of loose sand with SPT N value = 10
(To assess the ground bearing pressure below 70 t Crawler crane and 100 t mobile crane outriggers and to compare with allowable bearing capacity for un-compacted fill material of the temporary bund Sheet piling duties, e.g. Moving sheet pile; heaviest lift is movement of Hydraulic power pack.)

submitter says:

is there difference if we design the steel for corbel using bending moment, instead of strut and tie (tension force)?