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Chapter 2.11 Deep Beams and Diaphragms

Deep beams are, in essence, plates turned on their sides; a crude analogy but a visual aide in picturing the action of deep beams.

Figure 2.11.2 Deep Beam Section

Sometimes walls on the upper floors of buildings, or over basements, may be designed as dual action deep beams.

This chapter reviews a concrete deep beam, a SIP wall spanning over a void and floor diaphragms; all examples of deep beam action.

Approximation of End Strut Force (C) – ref. figure 2.6.6

Calculate Bar Area Tension in bars = M/deff = 400/1.24 = 324kN

Bar strength (tension) = 500N/mm²

Therefore, bar area needed = 324×10³/500 = 648mm²

A 16mm diameter reinforcement bar has an area of 201mm², so to provide this area of bar: Number of 20mm bars needed = 648/201 = 3.2 (round up to 4 bars)

 

 

Figure 2.11.5 Diaphragm Floor
Deep beams are, in essence, plates turned on their sides; a crude analogy but a visual aide in picturing the action of deep beams. Sometimes walls on the upper floors of buildings, or over basements, may be designed as dual action deep beams.

This chapter reviews a concrete deep beam, a SIP wall spanning over a void and floor diaphragms; all examples of deep beam action. In other words, like the previous example, the floor is a deep beam on its side. It transfers the wind force P by means of its nailed joints into the joists. At the other end of the floor is a ground floor cross wall. This cross wall collects the load P and transfers it into the foundations (like a deep beam).