Strut angle formula given in Eurocode? (concrete beam)

[Pretty Girl7]

The following strut angle calculation equation for a beam, it is from a book. I'm trying to calculate shear r/f. So I need to know the strut angle.
However I didn't notice that it's in the Eurocode. Is it available in the Eurocode or any other proper british standard etc?

 

[centondollar]

The strut angle is assumed in design. Theory gives the lower bound (22 something degrees), but the upper bound is obtained from experiments. Accordingly, Eurocode provides a range and the designer should choose from that. If you choose smaller angle, less anchorage and more stirrups is required and vice versa for larger angle.

 

[Pretty Girl7]

The strut angle is assumed in design. Theory gives the lower bound (22 something degrees), but the upper bound is obtained from experiments. Accordingly, Eurocode provides a range and the designer should choose from that. If you choose smaller angle, less anchorage and more stirrups is required and vice versa for larger angle.

Thank you for the reply. Yeah the lower bound for strut is 21.8 degrees and I'm aware of it. However I was asking if this formula, or a formula which would output similar results, is stated in Eurocode? As I did not see it in the Eurocode.

Which formula the Eurocode recommends us to calculate the strut angle? Which official formula to use if not above?

 

[bkal]

As centondollar has stated, you chose the angle. Eurocode 2 puts the limit on the value in eq. 6.7 but it does not state how you select it.

 

[centondollar]

As a correction to my previous post, the lower bound is experimental and the upper recommended value (45 degrees) is based on strut-and-tie model and mathematics. Another correction concerns the angle: smaller angles require more anchorage and less stirrups, while larger angle requires less anchorage and more stirrups.

 

[HTURKAK]

The expression for θ that you have posted is derived from the code EN 1992, formula (6.9) for VRd,max ( which is the design value of the maximum shear force which can be sustained by the member, limited by crushing of the compression struts.)..
VRd,max = αcw *bw* z *ν1* fcd/(cotθ + tanθ )

You can obtain θ from this expression mit mathematical operations assuming αcw=1.0 and z = 0.9d..

Steps for shear reinf . design using the mentioned formula for θ;

- Calculate shear capacity assuming cotθ = 2.5 Vmin=0.15d* bw*SQRT( fck)

- Calculate θ ( If there is no solution , cot θ <1 that means the strut failed , resize the beam or increase fck )

- If cot θ ≥ 2.5 , assume cot θ = 2.5 and calculate the shear reinf.

- If cot θ ≥ 1.0 und cot θ < 2.5, calculate shear reinforcement required at z*cot θ from end of beam..

I hope this respond answers to your question ..







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