deep beams final

8/3/2019 Deep Beams Final

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Prepared by

NILESH B. APTE

112040014

M-tech. structures

Department of StructuralEngineering

VJTI Matunga,Mumbai 19


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Deep beams are structuralelements loaded as beams inwhich a significant amount ofthe load is transferred to thesupports by a compressionthrust joining the load and the

reaction. As a result, the strain

distribution is no longerconsidered linear, and theshear deformations becomesignificant when compared topure flexure.

E.g. :- Floor slabs underhorizontal load, short spanbeams carrying heavy loads,and transfer girders


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Stresses in deep beam can be determined by:

Finite Element Method Strut and Tie Mechanism

Plane stress approach (stress function approach)

photoelasticity


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A beam may be classified as adeep beam depending onthe ratio L/D ratio given below

1. Simply supported beam L/D< or = 2

2. Continuous beam L/D < or =2.5

Where D = overall depth of thebeam sectionL= effective span

The effective span shall takenby the lesser of the following

1. Centre to centre distancebetween supports

2. 1.15 times the clear span


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Positive reinforcement: the tensile reinforcement required toresist positive bending moment in any span of deep beam.

1. Shall extend without curtailment between the supports.

2. Shall be embedded beyond the face each support, so that theforce of the support it shall have a development length not lessthan 0.8 times the development length for the design stress in

reinforcement. Negative reinforcement :

1. Termination of reinforcement: half of the reinforcement may beterminated at a distance of 0.5D from face of the support. Theremainder shall extend over the whole span.

2. Distribution : when ratio of clear span to overall depth is 1.0 to 2.5,

tensile reinforcement over a support of a deep beam shall beplaced in two zones comprising;

3. Zone of depth 0.2D adjacent to the tension face which is contain0.5(L/D 0.5 ) times the negative reinforcement


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Zone of depth 0.2D adjacentto the tension face which iscontain 0.5(L/D 0.5 ) timesthe negative reinforcement.

Vertical reinforcement: Ifforces are applied to a deepbeam in such a way thathanging action is required,bars or suspension stirrups shallbe provided to carry all theforces concerned.

Side face reinforcement :shall be provided vertically &horizontally. The spacing ofsuch reinforcement shall notexceed 3 times the width ofthe beam. It shall not alsoexceed 450 mm


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For flexural design, ACI Code 31883(revised 1986) defines a deepbeam as a beam in which theratio of the clear span (lo) to theoverall depth (h) is less than thelimits in

simple spans: lo/h


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ACI Section 10.7.1 For Deep Beam:

1. L/d < 5/2 for continuous span;

deep beams final

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