Test 18 - Isolated and Combined RCC Footings

Question 1 ప్రశ్న 1

Which situation most commonly justifies providing a combined RCC footing instead of two separate isolated footings?

A The columns are very far apart and each isolated footing is small B Individual footings would overlap, or an exterior column near a property line cannot be provided with a suitably concentric isolated footing C The soil has infinite bearing capacity D Only one column is present and it is centrally loaded

Question 2 ప్రశ్న 2

Under the conventional rigid-footing assumption, what condition permits a combined footing to develop a uniform soil-pressure distribution under vertical column loads?

A The larger column load must always be located at the geometric centre B Both column loads must be numerically equal C The centroid of the footing area should coincide with the line of action of the resultant vertical load D The footing width must equal the spacing between the columns

Question 3 ప్రశ్న 3

Two columns C1 and C2 carry service loads of 600 kN and 900 kN respectively and are 4.0 m apart. Neglecting other loads for locating the resultant, how far from C1 does the resultant of the two column loads act?

A 2.40 m B 2.00 m C 1.60 m D 3.00 m

Question 4 ప్రశ్న 4

For the columns in the previous question, the left edge of a proposed rectangular combined footing is fixed by a property line 0.50 m to the left of C1. What footing length will place the centroid of the rectangular footing at the resultant of the column loads?

A 4.80 m B 5.20 m C 5.40 m D 5.80 m

Question 5 ప్రశ్న 5

For the same two columns, assume the required service-level footing area is based on the 1500 kN total column load plus an estimated 10 percent allowance for footing and backfill weight. If the allowable soil pressure is 200 kN/m² and the footing length is 5.80 m, what constant footing width is required approximately?

A 1.20 m B 1.42 m C 1.75 m D 2.10 m

Question 6 ప్రశ్న 6

Why may a trapezoidal combined footing be preferred to a rectangular combined footing in some two-column foundation layouts?

A Because a trapezoidal footing always requires zero reinforcement B Because it eliminates one-way and punching shear checks C Because varying the footing width can shift the centroid of area to coincide with an eccentric load resultant when site geometry or unequal column loads make a suitable rectangle inconvenient D Because trapezoidal footings always produce triangular soil pressure

Question 7 ప్రశ్న 7

A trapezoidal combined footing has length L and end widths B1 and B2. What is its plan area?

A A = L(B1 + B2)/2 B A = LB1B2 C A = L(B1 - B2)/2 D A = (B1 + B2)/(2L)

Question 8 ప్రశ్న 8

For a trapezoidal footing whose width varies linearly from B1 at x = 0 to B2 at x = L, which expression gives the centroid distance measured from the B1 end?

A x̄ = L(B1 + B2)/(2B1) B x̄ = L(B1 + B2)/(3B2) C x̄ = L(B2 - B1)/(B1 + B2) D x̄ = L(B1 + 2B2)/[3(B1 + B2)]

Question 9 ప్రశ్న 9

A trapezoidal combined footing is 6.0 m long and has a required area of 18 m². Its centroid must be 3.5 m from the end of width B1. What end widths B1 and B2 satisfy these requirements?

A B1 = 2.0 m and B2 = 4.0 m B B1 = 1.5 m and B2 = 4.5 m C B1 = 3.0 m and B2 = 3.0 m D B1 = 1.0 m and B2 = 5.0 m

Question 10 ప్రశ్న 10

The trapezoidal combined footing in the previous question supports a total service vertical load of 1800 kN, and its centroid coincides with the load resultant. What uniform service soil pressure results?

A 75 kN/m² B 90 kN/m² C 100 kN/m² D 120 kN/m²

Question 11 ప్రశ్న 11

For a rigid rectangular isolated footing of area A subjected to a vertical load P with eccentricity e about one centroidal axis, and with full soil contact maintained over a footing dimension L in the eccentricity direction, which expression gives the extreme pressures?

A qmax,min = (P/A)(1 ± 6e/L) B qmax,min = (P/A)(1 ± e/6L) C qmax,min = P/(A ± 6eL) D qmax,min = P/A ± PL/e

Question 12 ప్రశ్న 12

For a rectangular footing subjected to eccentricity e in one direction, what condition ensures that the resultant remains within the middle third so that the conventional linear pressure distribution has no tensile soil pressure?

A e ≤ L/3 B e ≤ L/4 C e ≤ L/5 D e ≤ L/6

Question 13 ప్రశ్న 13

A 3.0 m × 2.0 m isolated footing carries a vertical load of 1200 kN with eccentricity 0.20 m along the 3.0 m footing dimension. Assuming full contact and a linear pressure distribution, what are qmax and qmin?

A 300 kN/m² and 100 kN/m² B 280 kN/m² and 120 kN/m² C 240 kN/m² and 160 kN/m² D 320 kN/m² and 80 kN/m²

Question 14 ప్రశ్న 14

For the same 3.0 m × 2.0 m footing and 1200 kN vertical load, what pressure distribution results when the eccentricity along the 3.0 m dimension is exactly L/6 = 0.50 m?

A Uniform pressure of 200 kN/m² B qmax = 300 kN/m² and qmin = 100 kN/m² C A triangular distribution with qmax = 400 kN/m² and qmin = 0 D A uniform tensile pressure of 400 kN/m²

Question 15 ప్రశ్న 15

What is the correct interpretation if the resultant eccentricity of a footing exceeds L/6 in one direction?

A The soil pressure becomes more uniform B The full-base linear formula remains valid even if it predicts tension C The footing automatically becomes a combined footing D Part of the base tends to lose contact because soil tension is not normally relied upon, so a compression-only contact distribution must be considered

Question 16 ప్రశ్న 16

A centrally loaded rectangular isolated footing is 3.0 m × 2.4 m in plan and supports a 0.40 m × 0.40 m column placed at its centre. What are the footing projections beyond the column faces in the 3.0 m and 2.4 m directions respectively?

A 1.30 m and 1.00 m B 1.50 m and 1.20 m C 1.10 m and 0.80 m D 1.20 m and 1.00 m

Question 17 ప్రశ్న 17

The footing in the previous question carries a uniform factored soil pressure of 250 kN/m². What is the design bending moment per metre width at the column face for cantilever action in the direction having the 1.30 m projection?

A 125.0 kN·m/m B 162.5 kN·m/m C 211.25 kN·m/m D 325.0 kN·m/m

Question 18 ప్రశ్న 18

An M25 footing strip 1000 mm wide has effective depth d = 500 mm and must resist Mu = 211.25 kN·m/m using Fe500 reinforcement. Using the singly reinforced Limit State equations, what flexural tension-steel area is required approximately, before any separate minimum-reinforcement check?

A 780 mm²/m B 1013 mm²/m C 1250 mm²/m D 1680 mm²/m

Question 19 ప్రశ్న 19

For longitudinal analysis, how is a conventional combined footing commonly idealized structurally?

A As a continuous or beam-like member subjected to upward distributed soil reaction and downward concentrated column loads B As an axially loaded column carrying no flexure C As a pure membrane with zero shear and bending moment D As two unrelated isolated footings even though they share one common slab

Question 20 ప్రశ్న 20

A 6.0 m long rectangular combined footing is 2.0 m wide and carries a uniform factored soil pressure of 200 kN/m². Two factored column loads of 1200 kN each act at x = 1.0 m and x = 5.0 m from the left edge. Taking upward soil reaction as positive, what is the shear force immediately to the right of the first column?

A +400 kN B -400 kN C +800 kN D -800 kN

Question 21 ప్రశ్న 21

For the combined footing described in the previous question, what is the longitudinal shear at x = 3.0 m from the left edge?

A -800 kN B -400 kN C 0 kN D +400 kN

Question 22 ప్రశ్న 22

For the same combined footing, what is the magnitude of the longitudinal bending moment at x = 3.0 m obtained from the forces to the left of the section?

A 400 kN·m B 600 kN·m C 800 kN·m D 1200 kN·m

Question 23 ప్రశ్న 23

For local transverse bending of an RCC footing adjacent to a concrete column, where is the critical section for the greatest design bending moment taken under IS 456?

A At a distance d from the column face B At a distance d/2 from the column face C At the footing edge D At the face of the concrete column

Question 24 ప్రశ్న 24

For an interior column of a combined footing on soil, sufficiently far from footing edges, which statement correctly distinguishes the ordinary one-way and punching-shear critical locations?

A One-way shear is checked at distance d from the column face, while the basic punching-shear perimeter is at distance d/2 from the column periphery B Both checks are made only at the column face C One-way shear is checked at d/2 and punching shear at 2d D Both checks are made at the footing edge

Question 25 ప్రశ్న 25

Which reinforcement interpretation is most appropriate for a combined footing whose longitudinal bending-moment diagram changes sign along its length?

A All longitudinal reinforcement must be placed only at the bottom regardless of moment sign B All longitudinal reinforcement must be placed only at the top regardless of moment sign C Longitudinal reinforcement should be provided on the appropriate tension face in the positive- and negative-moment regions, with adequate anchorage and development length D Longitudinal reinforcement may be omitted because soil pressure supports the entire footing

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