D8.G.4 Beam Design
Beams are designed for flexure, shear and torsion. If required the effect of the axial force may be taken into consideration. For all these forces, all active beam loadings are prescanned to identify the critical load cases at different sections of the beams. The total number of sections considered is 13. All of these sections are scanned to determine the design force envelopes.
For design to be performed as per IS:13920 the width of the member shall not be less than 200 mm(Clause 6.1.3). Also the member shall preferably have a width-to depth ratio of more than 0.3 (Clause 6.1.2).
The factored axial stress on the member should not exceed 0.1fck (Clause 6.1.1) for all active load cases. If it exceeds allowable axial stress no design will be performed.
D8.G.4.1 Design for Flexure
Design procedure is same as that for IS 456. However while designing following criteria are satisfied as per IS-13920:
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The minimum grade of concrete shall preferably be M20. (Clause 5.2)
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Steel reinforcements of grade Fe415 or less only shall be used. (Clause 5.3)
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The minimum tension steel ratio on any face, at any section, is given by (Clause 6.2.1b)
ρmin = 0.24Öfck/fy
The maximum steel ratio on any face, at any section, is given by (Clause 6.2.2)
ρmax = 0.025
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The positive steel ratio at a joint face must be at least equal to half the negative steel at that face. (Clause 6.2.3)
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The steel provided at each of the top and bottom face, at any section, shall at least be equal to one-fourth of the maximum negative moment steel provided at the face of either joint. (Clause 6.2.4)
D8.G.4.2 Design for Shear
The shear force to be resisted by vertical hoops is guided by the Clause 6.3.3 of IS 13920:1993 revision. Elastic sagging and hogging moments of resistance of the beam section at ends are considered while calculating shear force. Plastic sagging and hogging moments of resistance can also be considered for shear design if PLASTIC parameter is mentioned in the input file. (Refer Table 8A1.1)
Shear reinforcement is calculated to resist both shear forces and torsional moments. Procedure is same as that of IS 456.
The following criteria are satisfied while performing design for shear as per Cl. 6.3.5 of IS-13920:
The spacing of vertical hoops over a length of 2d at either end of the beam shall not exceed
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d/4
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8 times the diameter of the longitudinal bars
In no case this spacing is less than 100 mm.
The spacing calculated from above, if less than that calculated from IS 456 consideration is provided.
D8.G.4.3 Beam Design Output
The default design output of the beam contains flexural and shear reinforcement provided at 5 equally spaced sections along the length of the beam. User has option to get a more detail output. All beam design outputs are given in IS units. An example of rectangular beam design output with the TRACK 2.0 is presented below:
B E A M N O. 1 D E S I G N R E S U L T S
M20 Fe415 (Main) Fe250 (Sec.)
LENGTH: 6400.0 mm SIZE: 300.0 mm X 400.0 mm COVER: 25.0 mm
DESIGN LOAD SUMMARY (KN MET)
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SECTION |FLEXURE (Maxm. Sagging/Hogging moments)| SHEAR
(in mm) | P MZ MX Load Case | VY MX Load Case
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0.0 | 0.00 0.00 0.00 1 | 60.61 0.00 1
| 0.00 0.00 0.00 1 |
533.3 | 0.00 29.63 0.00 1 | 50.51 0.00 1
| 0.00 0.00 0.00 1 |
1066.7 | 0.00 53.88 0.00 1 | 40.41 0.00 1
| 0.00 0.00 0.00 1 |
1600.0 | 0.00 72.73 0.00 1 | 30.31 0.00 1
| 0.00 0.00 0.00 1 |
2133.3 | 0.00 86.20 0.00 1 | 20.20 0.00 1
| 0.00 0.00 0.00 1 |
2666.7 | 0.00 94.28 0.00 1 | 10.10 0.00 1
| 0.00 0.00 0.00 1 |
3200.0 | 0.00 96.98 0.00 1 | 0.00 0.00 1
| 0.00 0.00 0.00 1 |
3733.3 | 0.00 94.28 0.00 1 | -10.10 0.00 1
| 0.00 0.00 0.00 1 |
4266.7 | 0.00 86.20 0.00 1 | -20.20 0.00 1
| 0.00 0.00 0.00 1 |
4800.0 | 0.00 72.73 0.00 1 | -30.31 0.00 1
| 0.00 0.00 0.00 1 |
5333.3 | 0.00 53.88 0.00 1 | -40.41 0.00 1
| 0.00 0.00 0.00 1 |
5866.7 | 0.00 29.63 0.00 1 | -50.51 0.00 1
| 0.00 0.00 0.00 1 |
6400.0 | 0.00 0.00 0.00 1 | -60.61 0.00 1
| 0.00 0.00 0.00 1 |
*** DESIGN SHEAR FORCE AT SECTION 0.0 IS 60.61 KN.
- CLAUSE 6.3.3 OF IS-13920
*** DESIGN SHEAR FORCE AT SECTION 6400.0 IS 60.61 KN.
- CLAUSE 6.3.3 OF IS-13920
NOTE :
MOMENT OF RESISTANCE IS CALCULATED BASED ON THE AREA OF STEEL PROVIDED.
IF AREA OF STEEL PROVIDED IS MUCH HIGHER COMPARED TO AREA OF STEEL
REQUIRED MOMENT OF RESISTANCE WILL INCREASE WHICH MAY INCREASE DESIGN
SHEAR FORCE.
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STAAD SPACE -- PAGE NO. 7
0.0 | 0.00/ 402.12( 2-16í )| 0.00/ 981.75( 2-25í )| 8í @ 100 mm
533.3 | 0.00/ 402.12( 2-16í )| 281.26/1472.62( 3-25í )| 8í @ 180 mm
1066.7 | 0.00/ 402.12( 2-16í )| 450.84/1472.62( 3-25í )| 8í @ 180 mm
1600.0 | 0.00/ 402.12( 2-16í )| 632.82/1472.62( 3-25í )| 8í @ 180 mm
2133.3 | 0.00/ 402.12( 2-16í )| 773.83/1472.62( 3-25í )| 8í @ 180 mm
2666.7 | 0.00/ 402.12( 2-16í )| 863.91/1472.62( 3-25í )| 8í @ 180 mm
3200.0 | 0.00/ 402.12( 2-16í )| 894.99/1472.62( 3-25í )| 8í @ 180 mm
3733.3 | 0.00/ 402.12( 2-16í )| 863.91/1472.62( 3-25í )| 8í @ 180 mm
4266.7 | 0.00/ 402.12( 2-16í )| 773.83/1472.62( 3-25í )| 8í @ 180 mm
4800.0 | 0.00/ 402.12( 2-16í )| 632.82/1472.62( 3-25í )| 8í @ 180 mm
5333.3 | 0.00/ 402.12( 2-16í )| 450.84/1472.62( 3-25í )| 8í @ 180 mm
5866.7 | 0.00/ 402.12( 2-16í )| 281.26/1472.62( 3-25í )| 8í @ 180 mm
6400.0 | 0.00/ 402.12( 2-16í )| 0.00/ 981.75( 2-25í )| 8í @ 100 mm
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