Concrete Beam
Autor: darrenbot • October 15, 2017 • Exam • 858 Words (4 Pages) • 505 Views
Q2. Prestressed Beam and One Way Slab – Schematic Design of Beam and Slab Size
a) Depth of Beams
Since the client is to build a typical office floor using the post-tensioned (P/T), the L/D ratio for ‘End Span’ would be L/27 for the typical applied load according to the table from tutorial 1.[pic 1]
For this design, the load applied would be [pic 2]
Therefore, the L/D ratio would be
-Depth for constant stress and span [pic 3] [pic 4] | -Depth for constant rate of deflection [pic 5] [pic 6] |
[pic 7] [pic 8] Hence, L/D = L/25.5 | [pic 9] [pic 10] Hence, L/D = L/26.0 |
Therefore, the conservative case for the beam would be (which is to obtain the largest depth),
L/D = L/25.5
Since, the beams would normally span in the N/S direction, the Depth of the beam would be
Case 1 Two internal columns & no perimeter columns | Case 2 One internal column & two perimeter columns |
L = 15m [pic 11] | L = 12m [pic 12] |
Therefore, the depth of the beam would be
Case 1:
D = 590 mm
Case 2:
D = 475 mm
b) Depth of slabs
Since the client is to build a typical office floor using the post-tensioned (P/T), the L/D ratio for slab would be L/38 for the typical applied load according to the table from tutorial 1.[pic 13]
For this design, the load applied would be [pic 14]
Therefore, the L/D ratio would be
-Depth for constant stress and span [pic 15] [pic 16] | -Depth for constant rate of deflection [pic 17] [pic 18] |
[pic 19] [pic 20] Hence, L/D = L/35.8 | [pic 21] 36.6[pic 22] Hence, L/D = L/36.6 |
Therefore, the conservative case for the beam would be (which is to obtain the largest depth),
L/D = L/35.8
Since, the slab is one-way slab, the length for the slab would be the grid spacing.
Hence, the Depth of the slab would be
Case 1 Two internal columns & no perimeter columns | Case 2 One internal column & two perimeter columns |
L = 8.4-1.8 = 6.6 m [pic 23] | L = 8.4-1.8 = 6.6 m [pic 24] |
...