Concrete Beam
Q2. Prestressed Beam and One Way Slab – Schematic Design of Beam and Slab Sizea) Depth of BeamsSince 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/26.0Therefore, the conservative case for the beam would be (which is to obtain the largest depth), L/D = L/25.5Since, the beams would normally span in the N/S direction, the Depth of the beam would beCase 1Two internal columns & no perimeter columnsCase 2One internal column & two perimeter columnsL = 15m[pic 11]L = 12m[pic 12]Therefore, the depth of the beam would be Case 1:D = 590 mmCase 2:D = 475 mmb) Depth of slabsSince 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/36.6Therefore, the conservative case for the beam would be (which is to obtain the largest depth), L/D = L/35.8Since, the slab is one-way slab, the length for the slab would be the grid spacing.Hence, the Depth of the slab would beCase 1Two internal columns & no perimeter columnsCase 2One internal column & two perimeter columnsL = 8.4-1.8 = 6.6 m  [pic 23]L = 8.4-1.8 = 6.6 m [pic 24]