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Check of a solid brick wall under gravity load

Short answer

Using H_eff=0.75×3.2=2.4 m, SR=2400/230=10.43, k_s=0.879, k_a=1.0, f_c=0.879 N/mm². Self-weight 13.98 kN/m, total load 133.98 kN/m gives stress 0.583 N/mm² < 0.879, safe. Maximum total load capacity = 202 kN/m.

A single-storey load-bearing brick wall is 230 mm thick and 3.2 m high (clear height between floor and roof slab). The RC roof slab bears over the full wall thickness on both sides and gives lateral and rotational restraint at the top, and the wall is fixed at the base. The basic compressive stress is fb=1.0f_b = 1.0 N/mm². The slab transfers a working load of 120 kN per metre length of wall at the top, and the unit weight of masonry is 19 kN/m³. Using the IS 1905 method with ksk_s from the table (SR 10 → 0.89, SR 12 → 0.84), check the wall and find the maximum load per metre it can carry.

Step 1: Slenderness

Lateral and rotational restraint at both ends gives Heff=0.75HH_{eff} = 0.75H:

Heff=0.75×3200=2400 mmSR=2400230=10.43\begin{aligned} H_{eff} &= 0.75 \times 3200 = 2400\ \text{mm} \\ SR &= \frac{2400}{230} = 10.43 \end{aligned}

SR<27SR < 27, so OK.

Step 2: Stress reduction factor

Interpolate between SR=10SR = 10 (ks=0.89k_s = 0.89) and SR=12SR = 12 (ks=0.84k_s = 0.84):

ks=0.89−0.432×0.05=0.879k_s = 0.89 - \frac{0.43}{2}\times 0.05 = 0.879

Step 3: Permissible stress

Per metre length, area A=0.23×1.0=0.23A = 0.23 \times 1.0 = 0.23 m² >0.2> 0.2 m², so ka=1.0k_a = 1.0; for bricks kp=1.0k_p = 1.0.

fc=1.0×0.879×1.0×1.0=0.879 N/mm2f_c = 1.0 \times 0.879 \times 1.0 \times 1.0 = 0.879\ \text{N/mm}^2

Step 4: Actual stress at base

Wwall=19×0.23×3.2=13.98 kN/mP=120+13.98=133.98 kN/mf=133 980230×1000=0.583 N/mm2\begin{aligned} W_{wall} &= 19 \times 0.23 \times 3.2 = 13.98\ \text{kN/m} \\ P &= 120 + 13.98 = 133.98\ \text{kN/m} \\ f &= \frac{133\,980}{230 \times 1000} = 0.583\ \text{N/mm}^2 \end{aligned}

0.583<0.8790.583 < 0.879, so the wall is safe (utilisation 66 percent).

Step 5: Maximum load

Pmax=fc A=0.879×230×1000=202 170 N/m≈202 kN/mP_{max} = f_c\,A = 0.879 \times 230 \times 1000 = 202\,170\ \text{N/m} \approx 202\ \text{kN/m}

Allowable additional slab load =202.2−14.0=188 kN/m= 202.2 - 14.0 = 188\ \text{kN/m}.

Answer: Actual stress 0.58 N/mm² < 0.879 N/mm², safe. Maximum total load = 202 kN/m (slab load about 188 kN/m).

✓ Answer checked by Claude Sonnet 5.5

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