Two Way Slab MCQ Quiz in తెలుగు - Objective Question with Answer for Two Way Slab - ముఫ్త్ [PDF] డౌన్‌లోడ్ కరెన్

Explanation

For two way slab of shorter span (up to 3.5 m) with mild steel reinforcement, the span to overall depth ratios is given below may generally be assumed to satisfy vertical deflection limits for loading class up to 3 kN/m2

Note:

For slabs spanning in two directions, the shorter of the two spans should be used for calculating the span to effective depth ratio.

For high strength deformed bars of grade Fe 415, the value given in the column of mild steel should be multiplied by 0.8 (as mentioned in the third column for HYSD bars).

In Rankine's Grashoff method, the effect of restraint against the lifting of the corners and the effect of torsion in the slab were neglected.

Marcus has given an approximate method for determining BM in slabs, simply supported on four edges with corners prevented from being lifted and considering torsion in the slab.

In this method thickness of the slab is generally taken to be 1/30 of a shorter span.

2) Pigeaud's Method for Design of Two-Way Slabs: Pigeaud's method is a classical approach used in the design of two-way slabs subjected to uniformly distributed loads. This method simplifies the analysis of two-way slabs by providing coefficients for calculating bending moments in both directions.

Key Concepts of Pigeaud's Method:

• Coefficient Tables: Pigeaud's method uses coefficient tables to determine the distribution of moments in two-way slabs. These tables provide coefficients based on the aspect ratio (ratio of the longer span to the shorter span) of the slab.
• Moment Calculation: The moments in the slab are calculated using the coefficients from Pigeaud's tables. The total moment is distributed between the shorter span (Mx) and the longer span (My) based on these coefficients.
• Load Distribution: The method assumes that the load is distributed between the two directions of the slab according to the aspect ratio and the support conditions.

Explanation:

Table: Area of reinforcement per metre width of spacing:

So, by the interpolation:

For 400mm²/m and 10 mm diameter, corresponding spacing:

Spacing = 200 + \(\frac{175-200}{448-397} \times \) (400-397)

Spacing = 200 - 1.47

Spacing = 198.53 = 63.2 π mm

Concept:

The design moments for a two way slab torsion ally restrained at corners are given as:

M_x = α_x W l_x²

and

M_y = α_y W l_x²

Where

M_x and M_y are bending moments spanning l_x and l_y

W is the design factored load

Calculation

For Panel 5:

It is an interior panel, with ℓ_x = 2.5 m & L_y = nm

\(r = \frac{{{\ell _y}}}{{{\ell _x}}} = \frac{4}{{2.5}} = \frac{8}{5} = 1.6\)

For r = 1.6, from the given lable : d_x = 0.032, d_y = 0.032

Negative B.M spanning ℓ_x at continuous edge is (GF O₂ GI, FK or JK)

\({M_x} = {d_x}W\ell _x^2\)

M_x = 0.032 × 100 × (2.5)² = 20 kN.m/m

For Panel 4:

One edge (HI) is Discontinuous & ℓ_y = 5 m, ℓ_x = 2.5 m

\(r = \frac{{{\ell _y}}}{{{\ell _x}}} = \frac{5}{{2.5}} = 2 \Rightarrow {d_x} = 0.068\)

Therefore, M_x = .068 × 100 × (2.5)² = 42.5 kN/m

For panel 8:

Over edge (ON) is Discontinuous. It can be treated as longer or starter (any one)

ℓ_x = 4m & ℓ_y = 4m

\(r = \frac{{{\ell _y}}}{{{\ell _x}}} = 1 \Rightarrow {d_x} = .037\)

M_x = .037 × 100 × 4² = 59.2 kN.m/m

For Panel 7:

Two adjacent edges (IP & PO) are discontinuous,

ℓ_x = 4m, ℓ_y = 5m

\( \Rightarrow r = \frac{{{\ell _y}}}{{{\ell _x}}} = \frac{5}{4} = 1.25 \Rightarrow {d_x} = 0.065\)