Question

Consider a slab that is part of the floor system shown in the Figure. The slab extends by 100 mm beyond the exterior edges of edge and corner columns to support the exterior wall panels. The slab is subjected to a specified superimposed dead load of 2.0 kPa (in addition to its own weight) and a specified live load (LL) of 4.8 kPa. The weight of the exterior panel is 3 kN/m. Use 15M bars for flexural reinforcement and 25 mm clear cover. All columns are 400 x 400 mm. Assume f'c = 25 MPa and fy=400 MPa. a- Assume that the slab is supported by beams in both directions (along all grid lines). The overall depth of the beams are 600 mm (includes slab thickness) and width, b=350 mm. i) Determine the minimum slab thickness for the most critical panel. ii) Assuming a slab thickness of 200 mm, design the slab in the E-W direction (for grid line 1). iii) Determine the design moments in the beams and the slab. Determine the amount and distribution of reinforcement in the slab. Show the details of your design on a neat sketch. b) Assume the slab is supported on columns only with the slab extending by 100 mm beyond the column lines around the perimeter of the slab. Assume the slab thickness is 250 mm. Determine the slab-ve and +ve moments within the column and middle strips for a slab strip along gridline 1. At this stage, assume the slab thickness is adequate to carry the applied shear (both one-way and two-way). i) Determine the amount and size of reinforcement for the slab. ii) Determine whether the slab meets the one-way shear requirements including corner column A1. iii) Determine whether the slab can carry two-way shear around the interior column B2. Include the effect of unbalanced shear-moment transfer in your design. c) Determine the slab moments and reinforcement for both slabs in parts a) and b) (with beams, h=200 mm and without beams, h=250 mm) using the SAFE ETABS computer program. Compare the computer solution with the Direct Design Method. Comment on your results.