1997

DoS(Concrete)

Qn- The cylinder strength of the concrete is less than the cube strength because of

A) The difference in the shape of cross section of the specimensB) The difference in the slenderness ratio of specimensC) The friction between the concrete specimens and the steel plate of testing machineD) The cubes are tested without capping but cylinders are tested with capping

Qn- The IS: 459-1978 recommends to provide certain minimum steel in RCC beam

A) To ensure compression failureB) To avid rupture of steel in case a flexural failure occursC) To hold the stirrup steel in positionD) To provide enough ductility to beam

Qn- Permissible bending tensile stress in high yield strength deformed bars of grade 415 N/mm2

in a beam is

A) 190 N/mm2

B) 230 N/mm2

C) 140 N/mm2

D) None of the above

Qn- A pre-stressed concrete rectangular beam of size 300 mm x 900 mm is pre-stressed with an initial pre-stressing force of 700 kN ata an eccentricity of 350 mm at mid-span. Stress at top of the due to pre-stress alone in N/mm2 is

A) -3.46 (tension)B) 2.59 (compression)C) ZeroD) 8.64 (compression)

Qn- Factor of safety adopted by IS: 800 -1984 while arriving at the permissible stress in axial compression is

A) 2B) 1C) 1.67D) 1.5

Qn- A hall is covered by a beam and slab system with beams placed at 3m centres. The effective span of the beam is 8.35 m. The thickness of slab is 120 mm. The size of beam below the slab is 230mm width and 380 mm depth. The beam is reinforced with two numbers of 32 mm diameter steel rods of grade 415 N/mm2. Compute the maximum total load/m run, the beam can carry, including its own weight at service stage. Grade of concrete is M25.

Qn- A) A simply supported beam of a beam and slab system, rests on a support of width 450 mm. The clear span of the beam is 10 m. The thickness of the slab is 120 mm. The depth of the beam below the slab is 480 mm and the width of the beam is 250 mm. The beam is reinforced with one row of 32 mm diameter steel rods. The total load including the super-imposed dead load, live load and its own weight is 25 kN/m at service stage. Compute the maximum nominal design shear stress in the concrete.

B) Design a square R. C. column to resist an axial load of 400 kN due to load and 240 kN due to live load at service stage. Design the section as a short axially loaded column. Use M25 concrete and steel of grade 415 N/mm2. Give a neat sketch of the cross section.

1998

DoS(Concrete)

Qn- An isolated T-beam is used as a walkway. The beam is simply supported with an effective span of 6m. The effective width of flange, for the cross-section shown in Figure, is

A) 900 mmB) 1000 mmC) 1259 mmD) 2200 mm

Qn- The plane of stairs supported at each end by landings spanning parallel with risers is shown in figure. The effective span of staircase slab is

A) 3000 mmB) 4600 mmC) 4750 mmD) 6400 mm

Qn- A reinforced concrete wall carrying vertical loads is generally designed as per recommendations given for columns. The ratio of minimum reinforcements in the vertical and horizontal directions is

A) 2:1B) 5:3C) 1:1D) 3:5

Qn- the cross-section of a pre-tensioned pre-stressed concrete beam is shown in fig. The reinforcement is placed concentrically. If the stress in steel at transfer is 1000 MPa, Compute the stress in steel immediately after transfer. The modular ratio is 6.

Qn- The cross-section of a simply supported plate girder is shown in fig. The bearing stiffeners at supports are the sole means of providing restraint against torsion. Design the bearing stiffeners at supports, with minimum moment of inertia about the centre line of web plate only as the sole design criterion. The flat section available are: 250 x 25, 250 x 32, 200 x 28 and 200 x 32 mm. Draw a sketch.

Qn- The diameter of a ring beam in water tank is 7.8m. It is subjected to an outward radial force of 15kN/m. Design the section using M 25 grade concrete and Fe 415 reinforcement. Sketch the cross-section.

1999

DoS(Concrete)

Qn- In reinforced concrete, pedestal is defined as compression member, whose effective length does not exceed its dimension by

(A) 12 times

(B) 3 times

(C) 16 times

(D) 8 times

Qn- The minimum area of tension reinforcement in a beam shall be greater than

(A) 0.85bD/fy(B) 0.04bD(C) 0.87fy/bD(D) 0.4bD/y

Qn- Maximum strain at the level of compression steel for a rectangular section having effective cover to compression steel as and neutral axis depth from compression face xu is

(A) 0.0035(1-(d’/xu))

(B) 0.002(1-(d’/xu))

(C) 0.0035(1-(xu/d’))

(D) 0.002(1-(xu/d’))

Qn- The width and depth of a reinforced concrete beam is 250 mm and 400 mm respectively. The beam is provided with 4 Number of 20 mm tor bars in the tension zone. The beam is subjected to a shear force of 150 kN (Factored). Check the requirement of shear reinforcement and provide if required. Grade of concrete is M 20 and that of steel is Fe 415. The shear strength of concrete for different percentages of tensile steel are as below.[Vus = 0.87fyAsvd/Sv and (Asv/Sv) ≥ 0.4 b/fy with the terms having usual meaning]

% of steel shear strength of concrete. (τc) in N/k

1.0 0.62

1.25 0.67

1.50 0.72

Qn- A beam with a rectangular cross section of size 250 mm wide and 350 mm deep is pre-stressed by a force of 400 kN using 8 number 7 mm φ steel cables located at an eccentricity of 75 mm. Determine the loss of pre-stress due to creep of concrete. Grade of concrete is M40; coefficient of creep is 2; Stress at transfer is 80%, Modulus of elasticity of steel (Es) is 2.0 × 105MPa.

Qn- Fig. 9 shows the section (non–overflow portion) of a straight gravity dam built with concrete. Considering water pressure and uplift pressure, and neglecting the other external forces acting on the dam, check whether the resultant passes through the middle third of the base for the reservoir full condition. In the figure, RL stands for Reduced Level in metres and MWL stands for Maximum Water Level. (Unit weight of water is 1000 kg/m3 and that of concrete is 2400 kg/m3)

2000

DoS(Concrete)

Qn- The following two statements are made with reference to a simply supported under-reinforced RCC beam:

I. Failure takes place by crushing of concrete before the steel has yielded.II. The neutral axis moves up as the load is increased.

With reference to the above statements, which of the following applies?

(A) Both the statements are false.

(B) I is true but II is false.

(C) Both the statements are true.

(D) I is false but II is true.

Qn- A simply supported rectangular pre-stressed concrete beam 200 mm wide and 400 mm deep has an effective span of 12 m. The pre-stressing cable has a triangular profile with zero eccentricity at ends and 70 mm at the mid-span as shown in the figure below. The effective pre-stress is 800 kN after all losses. Determine the value of a point load, the beam can support at the mid-span if the pressure line passes through the upper kern of the section. The weight density of the material of the beam can be taken to be 25kN/m3.

Qn- A continuous beam 250 mm×450 mm carries 6 number of 12 mm diameter longitudinal bars as shown. The factored shear force at the point of inflection is 200 kN. Check if the beam is safe in bond. Assume M15 mix with σck = 15 N/ and mild steel with σy = 250 N/. A clear cover of 25 mm can be assumed. The design bond stress for mild steel bars in M15 concrete is specified to be 1.0 N/mm2.

Qn- For the retaining wall shown in the figure below assume that the wall can yield sufficiently to develop active stage. Use Rankine’s active earth pressure theory and determine

(a) active force per meter of the wall, and

(b) the location of the resultant line of action.

2001

DoS(Concrete)

Qn- Identify the FALSE statement from the following, pertaining to the design of concrete structures.

(A) The assumption of a linear strain profile in flexure is made use of in working stress design, but not in ultimate limit state design.

(B) Torsional reinforcement is not required to be provided at the corners of simply supported rectangular slabs, if the corners are free to lift up.

(C) A rectangular slab, whose length exceeds twice its width, always behaves as a two way slab, regardless of the support conditions.

(D) The ‘load balancing’ concept can be applied to select the appropriate tendon profile in a pre-stressed concrete beam subject to a given pattern of load.

Qn- Consider the following two statements related to reinforced concrete design, and identify whether the y are TRUE or FALSE:

I. Curtailment to bars in the flexural tension zone in beams reduces the shear strength at the cut - off locations.

II. When a rectangular column section is subject to biaxially eccentric compression, the neutral axis will be parallel to the resultant axis of bending.

(A) Both statements I and II are TRUE.(B) Statement I is TRUE, and statement II is FALSE.(C) Statement I is FALSE, and statement II is TRUE.(D) Both statements I and II are FALSE.

Qn- The plan of a reinforced concrete column section, and the distribution of strains at the ultimate limit state are shown below. The concrete is of M20 grade and the steel of Fe 250 grade. Also sketched below, for convenience, are the concrete compression stress block and the design stress - strain curve for Fe 250, with all notations as per IS 456. Ignore the reduction in concrete area due to the embedded steel.

(A) Determine the ultimate axial compression capacity (in kN units).(B) Determine the corresponding eccentricity e (in mm units) of loading, with respect to the

centroidal axis at the ultimate limit state.

Qn- The effective spans for a simple one-way slab system, with an overhang, are indicated in the figure below. The specified ultimate design loads on the slab are 6.0 kN/ and 4.5 kN/ for dead loads and live loads respectively considering the possibility of live loads not occurring simultaneously on both spans, determine the maximum spacing (in mm units) of 8 mm diameter bars required as bottom reinforcement in the span AB, assuming an effective depth of 125 mm.Assume M20 concrete and Fe 415 steel.

Qn- A concrete gravity type retaining wall, shown below, retains granular soil having a friction angle of 35 and dry and saturated unit weights of 16 kN/m3 and 20 kN/m3. The unit weights of concrete and water are 24 kN/m3 and 10 kN/m3 respectively. The friction factor at the base of the wall against lateral sliding is 0.47. Calculate the following quantities for the retaining wall.

(i) Factor of safety against lateral sliding,(ii) Factor of safety against overturning, and(iii) Bearing pressure on foundation soil using Meyerhoffs method.

2002

DoS(Concrete)

Qn- Read the following two statements

I. Maximum strain in concrete at the outermost compression fibre is taken to be 0.0035 in bending

II. The maximum compressive strain in concrete in axial compression is taken as 0.002. Keeping the provisions of IS 456-2000 on limit state design in mind, which of the following is true?

(A) Statement I is true but II is false

(B) Statement I is false but II is true

(C) Both statements I and II are true

(D) Both statement I and II are false

Qn- As per the provisions of IS 456-2000, the (short term) modulus of elasticity of M25 grade concrete (in N/mm2) can be assumed to be

(A) 25000

(B) 28500

(C) 30000

(D) 36000

Qn- As per the provisions of IS 456-2000, in the limit state method for design of beams, the limiting value of the depth of neutral axis in a reinforced concrete beam of effective depth ’d’ is given as

(A) 0.53d

(B) 0.48d

(C) 0.46d

(D) Any of the above depending on the different grades of steel.

Qn- A schematic representation of a interaction diagram for the design of reinforced concrete columns is given in the following figure. Based on the given diagram, answer the following question: (1 + 1 + 2 + 1)

(A) What do the points A and C physically signify?(B) What is the basic difference between the portions AB and BC?(C) In the region BC, why does the moment capacity of the column increase even as the

axial load is also being increased?(D) Design codes often require the designer to ensure adequate strength for a minimum

eccentricity. How is such a provision incorporated into the interaction diagram?

Qn- A 10 m long pre-stressing bed is used to cast 4 (pre-tensioned) pre-stressed concrete e beams of 2.3 m each. A schematic representation of the bed is given in the following figure. The continuous pre-stressing reinforcement is pulled at the end ‘Y’ of the bed through a distance of 20 mm to introduce the required ‘pre-stress’, before the concrete is cast. After the concrete has hardened, the pre-stressing reinforcement is cut at points A, B, C, D and E.

Qn- Give reasons for the following in not more than 20 words:(1×5)

(A) A maximum permissible distance between ties in reinforced concrete columns is usually specified

(B) A concrete mix is targeted to give higher compressive strength than the required characteristic strength.

(C) In the limit state design of reinforced concrete beams, it is a requirement that the maximum strain in the tension reinforcement in the section at failure is not less than a given value.

(D) In the case of slabs running over supports, reinforcement needs to be provided on the top in the neighborhood of the supports.

(E) The load carrying capacity of an RC column with appropriate helical reinforcement can be taken to be slightly higher than that having lateral ties

2003

DoS(Concrete)

Qn- The effective length of a column in a reinforced concrete building frame, as per IS: 456-2000, is independent of the

(a) Frame type i.e., braced (no sway) or un-braced (with sway)

(b) Span of the beam

(c) Height of the column

(d) loads acting on the frame

Qn- The working stress method of design specifies the value of modular ratio, m = 280/ (3σcbc), where σcbc is the allowable stress in bending compression in concrete. To what extent does the above value of m make any allowance for the creep of concrete?

(a) No compensation

(b) Full compensation

(c) Partial compression

(d) The two are unrelated

Qn- Maximum strains in an extreme fibre in concrete and in the tension reinforcement (Fe-415 grade and Es=200 kN/mm2) in a balanced section at limit state of flexure are respectively.

(a) 0.0035 and 0.0038

(b) 0.002 and 0.0018

(c) 0.0035 and 0.0041

(d) 0.002 and 0.0031

Qn- A long structural column (length = L) with both ends hinged is acted upon by an axial compressive load, P. The differential equation governing the bending of column is given by (d2y/dx2) = -py, where y is the structural lateral deflection and EI is the flexural rigidity. The first critical load on column responsible for its buckling is given by

(a)π2EI/L2

(b) √2π2EI/L2

(c) 2 π2EI/L2

(d) 4 π2EI/L2

Qn- Top ring beam of an Intze tank carries a hoop tension of 120 kN. The beam cross-section is 250 mm wide and 400 mm deep and it is reinforced with 4 bars of 20 mm diameter of Fe 415 grade. Modular ratio of the concrete is 10. The tensile stress in N/mm2 in the concrete is

(a) 1.02 (b) 1.07 (c) 1.20 (d) 1.32

Qn- The state of two dimensional stress acting on a concrete lamina consists of a direct tensile stress, σx= 1.5 N/mm2 , and shear stress 1.20 N/mm2, which cause cracking of concrete. Then the tensile strength of the concrete in N/mm2 is

(a) 1.5 (b) 2.08 (c) 2.17 (d) 2.2

Qn- A concrete column caries an axial load of 450 kN and a bending moment of 60 kN m at its base. An isolated footing of size 2m by 3m, with 3m side along the plane of the bending moment, is provided under the column. Centers of gravity of column and footing coincide. The net maximum and the minimum pressures in kN/m2 on soil under the footing are respectively.

(a) 95 and 55 (b) 95 and 75 (c) 75 and 55 (d) 75 and 75

Qn- A reinforced concrete beam, size 200 mm wide and 300 mm deep overall is simply supported over a span of 3m. It is subjected to two point loads P of equal magnitude placed at middle third points. The two loads are gradually increased simultaneously. Beam is reinforced

with 2 HYSD bars of 16 mm diameter placed at an effective cover of 40 mm bottom face and nominal shear reinforcement. The characteristics compressive strength and the bending tensile strength of the concrete are 20.0 N/mm2 and 2.2N/mm2 respectively.

Qn- Ignoring the presence of tension reinforcement, find the value of load P in kN when the first flexure crack will develop in the beam.

(a) 4.5 (b) 5.0 (c) 6.6 (d) 7.5

Qn- The theoretical failure load of the beam for attainment of limit state of collapse in flexure is

(a) 23.7 kN (b) 25.6 kN (c) 28.7 kN (d) 31.6 kN

2004

DoS(Concrete)

Qn- In the limit state design method of concrete structures, the recommended partial material safety factor for steel according to IS:456-2000 is

(a) 1.5 (b) 1.15 (c) 1.00 (d) 0.8

Qn- For avoiding the limit state of collapse, the safety of R.C. structures is checked for appropriate combinations of dead load (DL), imposed load or live load (IL), wind load (WL) and earthquake load (EL). Which of the following load combinations is NOT considered?

(a) 0.9 DL + 1.5 WL

(b) 1.5 DL + 1.5 WL

(c) 1.5 DL + 1.5 WL + 1.5 EL

(d) 1.2 DL + 1.2 IL + 1.2 WL

Qn- an R.C. short column with 300 mmx300 mm square cross-section is made of M20 grade concrete and has 4 members, 20 mm diameter longitudinal bars of Fe 415 steel. It is under the action of a concentric axial compressive load. Ignoring the reduction in the area of concrete due to steel bars, the ultimate axial load carrying capacity of the column is

(a) 1659 kN (b) 1548 kN (c) 1198 kN (d) 1069 kN

Qn- An R.C. square footing of side length 2 m and uniform effective depth 200 mm is provided for a 300 mmx300 mm column. The line of action of the vertical compressive load passes through the centroid of the footing as well as of the column. If the magnitude of the load is 320 kN, the nominal transverse (one way) shear stress in the footing is

(a) 0.26 N/mm2

(b) 0.30 N/mm2

(c) 0.34 N/mm2

(d) 0.75 N/mm2

Qn- simply supported pre-stressed concrete beam is 6 m long and 300 mm wide. Its gross depth is 600 mm. It is pre-stressed by horizontal cable tendons at a uniform eccentricity of 100 mm. The pre-stressing tensile force in the cable tendons is 1000 kN. Neglect the self-weight of beam. The maximum normal compressive stress in the beam at transfer is

(a) Zero

(b) 5.55 N/mm2

(c) 11.11 N/mm2

(d) 15.68 N/mm2

Qn- At the limit state of collapse, an R.C. beam is subjected to flexural moment 200 kN-m, shear force 20 kN and torque 9 kN-m. The beam is 300 mm wide and has a gross depth of 425 mm, with an effective cover of 25 mm. The equivalent nominal shear stress (τve) as calculated by using the design code turns out to be lesser than the design shear strength (τc) of the concrete.

Qn- The equivalent shear force (Vc) is

(a) 20 kN (b) 54 kN (c) 56 kN (d) 68 kN

Qn- The equivalent flexural moment (Mel) for designing the longitudinal tension steel is

(a) 187 kN-m (b) 200 kN-m (c) 29 kN-m (d) 213 kN-m

2005

DoS (Concrete)

Qn- IS : 1343 – 1980 limits the minimum characteristic s strength of pre-stressed concrete for post tensioned works and pretension work as

(a) 25 MPa, 30 MPa respectively

(b) 25 MPa, 35 MPa respectively

(c) 30 MPa, 35 MPa respectively

(d) 30 MPa, 40 MPa respectively

Qn- The permissible stress in axial tension “sst” in steel member on the net effective area of the section shall not exceed the following value (fy is the yield stress)

(a) 0.80fy

(b) 0.75fy

(c) 0.60fy

(d) 0.50fy

Qn- The partial factor of safety for concrete as per IS : 456-2000 is

(a) 1.50 (b) 1.15 (c) 0.87 (d) 0.4

Qn- concrete beam of rectangular cross section of 200 mmx400 mm is pre-stressed with a force 400kN at eccentricity 100 m. The maximum compressive stress in the concrete is

(a) 12.5 N/mm2

(b) 7.5 N/mm2

(c) 5.0 N/mm2

(d) 2.5 N/mm2

Qn- Which one of the following is NOT correct for steel sections as per IS : 800-1984 ?

(a) The maximum bending stress in tension or in compression in extreme fibre calculated on the effective section of a beam shall not exceed 0.66fy

(b) The bearing stress in any part of a beam when calculated on the area shall not exceed 0.75fy.

(c) The direct stress in compression on the gross sectional area of axial loaded compression member shall not exceed 0.6 fy.

(d) None of above.

Qn- A cantilever beam of length I, width b and depth d is loaded with a concentrated vertical load at the tip. If yielding starts at a load P, the collapse load shall be

(a) 2.0 P (b) 1.5 P (c) 1.2 P (d) P

Qn- The flexural strength of M30 concrete as per IS: 456-2000 is

(a) 3.83 MPa (b) 5.47 MPa (c) 21.23 MPa (d) 30.0 MPa

Qn- rectangular column section of 250 mmx400 mm is reinforced with five steel bars of grade Fe 500, each of 20 mm diameters. Concrete mix is M 30.Axial load on the column section with minimum eccentricity as per IS : 456-2000 using limit state method can be applied up to

(a) 1707.37

(b) 1805.30

(c) 1806.40

(d) 1903.

Qn- Assume straight line instead of parabola for stress-strain curve of concrete as follows and partial factor of safety as 1.0.A rectangular under-reinforced concrete section of 300 mm width and 500 mm effective depth is reinforced with 3 bars of grade Fe415, each of 16 mm diameter. Concrete mix is M20.

Qn- The depth of the neutral axis from the compression fibre is

(a)76 mm (b) 81 mm (c) 87 mm (d) 100 mm

Qn- The depth of the neutral axis obtained as per IS: 456-2000 differs from the depth of neutral axis obtained in 83 by

(a) 15 mm (b) 20 mm (c) 25 mm (d) 32 mm

2006

DoS (Concrete)

Qn- Consider following statements:

1) The width to thickness ratio limitations on the plate elements under compression in steel members are imposed by IS 800-1984 in order to avoid fabrication difficulties.

2) In a doubly reinforced concrete beam, the strain in compressive reinforcement is higher than strain in adjoining concrete.

3) If a cantilever I-section supports slab construction all along its length with sufficient friction between them, the permissible bending stress in compression will be the same as that in tension.

The true statements are

A) Only 1 and 2

B) Only 2 and 3

C) Only 1 and 3

D) 1, 2 and 3

Qn- the characteristic strength of concrete fck is defined a the strength below which not more than 50% of the test results are expected to fall the expression for fck in terms of mean strength fm and standard deviation “S” would be

(a) fm-0.1645S

(b) fm-1.645S

(c) fm

(d) fm+1.645S

Qn- a beam of rectangular cross-section is subjected to a vertical shear force V, the shear force carried by the upper one-third of the cross-section is

(a) Zero

(b) 7V/27

(c) 8V/27

(d)V/3

Qn- Assuming concrete below the neutral axis to be cracked, the shear stress across the depth of a singly-reinforce rectangular beam section

(a) Increases parabolic ally to the neutral axis and then drops suddenly to zero value.

(b) Increases parabolically to the neutral axis and then remains constant over the remaining depth

(c) Increases linearly to the neutral axis and then remains constant up to the tension steel

(d) Increases parabolically to the neutral axis and then remains constant up to the tension steel.

Qn- As per IS : 456-2000, consider the following statements,-

I. The modular ratio considered in the working stress method depends on the type of steel used.

II. There is an upper limit on the nominal shear stress in beams (even with shear reinforcement) due to the possibility of crushing of concrete in diagonal compression.

III. A rectangular slab whose length is equal to its width may not be a two-way slab for some support conditions.

The TRUE statements are

(a) only I and II

(b) only II and III

(c) only I and III

(d)I , II and III

Qn- Consider the following statements:

I. The width-thickness ratio limitations on the plate elements under compression in steel members are imposed by IS: 800-1984 in order to avoid fabrication difficulties.

II. In a doubly reinforced concrete beam, the strain in compressive reinforcement is higher than the strain in the adjoining concrete.

III. If a cantilever I-section supports slab construction all along its length with sufficient friction between them, the permissible bending stress in compression will be the same as that in tension.

The TRUE statements are

(a) only I and II

(b) only II and III

(c) only I and III

(d) I, II and III

Qn- In the design of beams for the limit state of collapse in flexure as per IS : 456-2000, let the maximum strain in concrete be limited to 0.0025 (in place of 0.0035). For this situation, consider a rectangular beam section with breadth as 250 mm, effective depth as 350 mm, area of tension steel as 1500 mm2, and characteristics strengths of concrete and steel as 30Mpa and 250 MPa respectively.

Qn- The depth of neutral axis for the balanced failure is

(a) 140 mm (b) 156 mm (c) 168 mm (d) 185 mm

Qn- At the limiting state of collapse in flexure, the force acting on the compression zone of the section is

(a) 326 kN (b) 389 kN (c) 424 kN (d) 542 kN

2007

DoS (Concrete)

Qn- An axially loaded bar is subjected to a normal stress of 173 MPa. The shear stress in the bar is

(a) 75 MPa

(b) 86.5 MPa

(c) 100 MPa

(d) 122.3 MPa

Qn- For an isotropic material, the relationship between the Young’s modulus (E), shear modulus (G) and

Poisson’s ratio () is given by (A) G=E/2(1+)(B)) E=G/2(1+)(C) G=E/(1+2)(D) G=E/2(1-).

Qn- The vertical stress at some depth below the corner of a 2m x 3m rectangular footing due to certain load intensity is 100 kN/m2. What will be the vertical stress in kN/m2 below the Centre of a 4m x 6m rectangular footing at the same depth and same load intensity?

(a) 25 (b) 100 (c) 200 (d) 400

Qn- The percentage loss of pre-stress due to anchorage slip of 3 mm in a concrete beam of length 30 m which is post-tensioned by a tendon with an initial stress of 1200 N/mm2 and modulus of elasticity equal to 2.1 x 105 N/mm2 is

(a) 0.0175 (b) 0.175 (c) 1.75 (d) 17.

Qn- A concrete beam of rectangular cross-section of size 120 mm (width) and 200 mm (depth) is pre-stressed by a straight tendon to an effective force of 150 kN at an eccentricity of 20 mm (below the centroidal axis in the depth direction). The stresses at the top and bottom fibers of the section are

(a) 2.5 N/mm2 (compression), 10N/mm2 (compression), 10N/mm2 (compression).

(b) 10N/mm2 (tension), 2.5 N/mm2 (compression)

(c) 3.75 N/mm2 (tension), 3.75 N/mm2(compression)

(d) 2.75 N/mm2(compression), 3.75 N/mm2(compression)

Qn- A singly reinforced rectangular concrete beam has a width of 150 mm and an effective depth of 330 mm. The characteristics compressive strength of concrete is 20 MPa and the characteristics tensile strength of steel is 415 MPa. Adopt the stress block for concrete as given in IS 456-2000 and take limiting value of depth of neutral axis as 0.48 times the effective depth of the beam.

Qn.- The limiting value of the moment of resistance of the beam is kN.m is (A) 0.14 (B) 0.45 (C) 45.08 (D) 156.82

Qn.- The limiting area of tension steel in mm2 is (A) 473.9 (B) 412.3 (C) 373.9 (D) 312

2008

DoS (Concrete)

Qn- Un-factored maximum bending moments at a section of a reinforced concrete beam resulting from a frame analysis are 50, 80, 120 and 180kNm under dead, live, wind and earthquake loads respectively. The design moment (kNm) as per IS: 456- 2000 for the limit state of collapse (flexure) is

(A) 195

(B) 250

(C) 345

(D) 37

Qn- A reinforced concrete column contains longitudinal steel equal to 1 percent of net cross-sectional area of the column. Assume modular ration as 10. the loads carried (using the elastic theory) by the longitudinal steel and the net area of concrete, are Ps and Pc respectively. The ration Ps/Pc expressed as percent is

(A) 0.1

(B) 1

(C) 1.1

(D) 1

Qn- A pre-tensioned concrete member of section 200mm x 250mm contains tendons of area 500 mm2 at the Centre of gravity of the section. The pre-stress in tendons is 1000N/mm2 . Assuming modular ratio as 10, the stress (N/mm2) in concrete is

(A) 11

(B) 9

(C) 7

(D)5

Qn- A footing 2m 1m exerts a uniform pressure of 150kN/mm2 on the soil. Assuming a load dispersion of 2 vertical to 1 horizontal, the average vertical stress (kN/m2) at 1.0m below the footing is

(A) 50

(B) 75

(C) 80

(D) 10

Qn- A reinforced concrete beam of rectangular cross section of breadth 230 mm and effective depth 400 mm is subjected to a maximum factored shear force of 120 kN. The grade of concrete, mains steel and stirrup steel are M20, F415 and Feb 250 respectively. For the area of main steel provided, the design shear strength c as per IS : 456-2000 is 0.48N/mm2. The beam is designed for collapse limit state.

Qn- The spacing (mm) of 2-legged 8 mm stirrups to be provided is

(A) 40

(B) 115

(C) 250

(D) 400

Qn- In addition, the beam is subjected to a torque whose factored value is 10.90 kNm. The stirrups have to be provided to carry a shear (kN) equal to

(A) 50.42

(B) 130.56

(C) 151.67

(D) 200.

2009

DoS (Concrete)

Qn- A thin walled cylindrical pressure vessel having a radius of 0.5m and wall thickness of 25mm is subjected to an internal pressure of 700kPa. The hoop stress developed is

(A) 14MPa (B) 1.4MPa (C) 0.14MPa (D) 0.014M

Qn- For limit state of collapse, the partial safety factors recommended by IS 456:2000 for estimating the design strength of concrete and reinforcing steel are respectively

(A) 1.15 and 1.5

(B) 1.0 and 1.0

(C) 1.5 and 1.15

(D) 1.5 and 1.0

Qn- A rectangular concrete beam of width 120mm and depth 200mm is pre-stressed by pre-tensioning to a force of 150kN at an eccentricity of 20mm. The cross sectional area of the pre-stressing steel is 187.5mm2. Take modulus of elasticity of steel and concrete as 2.1 × 105 MPa and 3.0×104 MPa respectively. The percentage loss of stress in the pre-stressing steel due to elastic deformation of concrete is

(A) 8.75

(B) 6.125

(C) 4.81

(D) 2.

2010

DoS (Concrete)

Qn- As per India standard code of practice for pre stressed concrete (IS:1343-1980) the minimum grades of concrete to be used for post-tensioned and pre-tensioned structural elements are respectively

(A) M20 for both

(B) M40 and M30

(C) M15 and M20

(D) M30 and M40

Qn- A doubly reinforced rectangular concrete beam has a width of 300mm and an effective depth of 500mm. the beam is reinforced with 2200mm2 of steel in tension and 628mm2 of steel in compression. The effective cover for compression steel is 50mm. Assume that both tension and compression steel yield. The grades of concrete and steel used are M20 and Fe250 respectively. The stress lock parameters (rounded off to first two decimal places) for concrete shall be as per IS 456:200.

Qn- The depth of neutral axis is

(A) 205.30mm (B) 184.56mm (C) 160.91mm (D) 145.30mm

Qn- The moment of resistance of the section is

(A) 206.00kN-m (B) 209.20 kN-m (C) 236.80 kN-m (D) 251.90kN-m

Qn- If a square footing of size 4m x 4m is resting on the surface of a deposit of the above clay, the ultimate bearing capacity of the footing (as per Terzaghi’s equation) is

(A) 1600kPa (B) 315kPa (C) 27kPa (D) 54kPa

2011

DoS (Concrete)

Qn- Consider a bar of diameter ‘D’ embedded in a large concrete block as shown in the adjoining figure, C with a pull out force P being applied. Let σb and σst, be the bond strength (between the bar and concrete) and the tensile strength of the bar, respectively. If the block is held in position and it is assumed that the material of the block does not fail, which of the following options represents the maximum value of P?

A) Maximum of bb2D/4 and DLst B) Maximum of stD2/4 and DLb

C) Minimum of bD2/4 and DLst D) Maximum of stD2/4 and DLb

Qn- Consider two RCC beams, P and Q, each having the section 400 mmx750 mm (effective depth, d = 750 mm) made with concrete having a τcmax= 2.1 N/mm2. For the reinforcement provided and the grade of concrete used, it may be assumed that the τc= 0.75 N/mm2. The design shear in beam P is 400 kN and in beam Q is 750 kN. Considering the provisions of IS 456 2000, which of the following statements is TRUE?

(A) Shear reinforcement should be designed for 175 kN for beam P and the section for beam Q should be revised.

(B) Nominal shear reinforcement is required for beam P and the shear reinforcement should be designed for 120 kN for beam Q.

(C) Shear reinforcement should be should be designed for 175 kN for beam P and the shear reinforcement should be designed for 525 kN for beam Q.

(D) The sections for both beams P and Q need to be revised.

2012

DoS (Concrete)

Qn- Q - As per IS 456:2000, in the Limit State Design of a flexural member, the strain in reinforcing bars

under tension at ultimate state should not be less than

A. fy/Es

B. fy/Es + 0.002

C. fy/1.15Es

D. fy/1.15Es + 0.002

Qn- Which one of the following is categorized as a long-term loss of pre-stress in a pre-stressed concrete member?

(A) Loss due to elastic shortening

(B) Loss due to friction

(C) Loss due to relaxation of strands

(D) Loss due to anchorage slip

Qn- The ratio of the theoretical critical buckling load for a column with fixed ends to that of another column with the same dimensions and material, but with pinned ends, is equal to

(A) 0.5

(B) 1.0

(C) 2.0

(D) 4.0

Qn- A concrete beam pre-stressed with a parabolic tendon is shown in the sketch. The eccentricity of the tendon is measured from the centroid of the cross-section. The applied pre-stressing force at service is 1620 kN. The uniformly distributed load of 45 kN/m includes the self-weight.

(A) Tensile 2.90

(B) Compressive 2.90

(C) Tensile 4.32

(D) Compressive 4.32

Qn- The cross-section at mid-span of a beam at the edge of a slab is shown in the sketch. A portion of the slab is considered as the effective flange width for the beam. The grades of concrete and reinforcing steel are M25 and Fe415, respectively. The total area of reinforcing bars (As) is 4000 mm2. At the ultimate limit state, xu denotes the depth of the neutral axis from the top fiber. Treat the section as under-reinforced and flanged (xu > 100 mm).

Qn- The value of xu (in mm) computed as per the Limit State Method of IS 456:2000 is

(A) 200.0

(B) 223.3

(C) 236.3

(D) 273.6

Qn- The ultimate moment capacity (in kNm) of the section, as per the Limit State Method of IS 456:2000 is

(A) 475.2

(B) 717.0

(C) 756.4

(D) 762.5

2013

DoS (Concrete)

Qn- As per IS 800:2007, the cross-section in which the extreme fiber can reach the yield stress, but cannot develop the plastic moment of resistance due to failure by local buckling is classified as

(A) Plastic section

(B) Compact section

(C) Semi-compact section

(D) Slender section

Qn- The creep strains are

(A) Caused due to dead loads only

(B) Caused due to live loads only

(C) Caused due to cyclic loads only

(D) Independent of loads

Qn- As per IS 456:2000 for M20 grade concrete and plain bars in tension the design bond stress τbd= 1.2 MPa. Further, IS 456:2000 permits this design bond stress value to be increased by 60 % for HSD bars. The stress in the HSD reinforcing steel bars in tension, σs=360Mpa. Find the required development length, Ld, for HSD bars in terms of the bar diameter, Φ= __________

Qn- A rectangular concrete beam 250 mm wide and 600 mm deep is pre-stressed by means of 16 high tensile wires, each of 7 mm diameter, located at 200 mm from the bottom face of the beam at a given secton. If the effective pre-stress in the wires is 700 MPa, what is the maximum sagging bending moment (in kNm) (correct to 1-decimal place) due to live load that this section of beam can withstand without causing tensile stress at the bottom face of beam? Neglect the effect of dead load of beam.

2014

DoS (Concrete)

Qn- Match the information given in Group – I with those in Group - II.

Group – I

P. Factor to decrease ultimate strength to design strength

Q. Factor to increase working load to ultimate load for design

R. Statistical method of ultimate load analysis

S. Kinematical mechanism method of ultimate load analysis

Group – II

1. Upper bound on ultimate load

2. Lower bound on ultimate load

3 Material partial safety factor

4 Load factor

(A) P - 1; Q - 2; R - 3; S - 4

(B) P - 2; Q - 1; R - 4; S - 3

(C) P - 3; Q - 4; R - 2; S - 1

(D) P - 4; Q - 3; R - 2; S – 1

Qn- While designing, for a steel column of Fe250 grade, a base plate resting on a concrete pedestal of M20 grade, the bearing strength of concrete (in N/mm2) in limit state method of design as per IS:456-2000 is ________________

Qn- A rectangular beam of width (b) 230 mm and effective depth (d) 450 mm is reinforced with four bars of 12 mm diameter. The grade of concrete is M20 and grade of steel is Fe500. Given that for M20 grade of concrete the ultimate shear strength, τuc = 0.36 N/mm2 for steel

percentage, p = 0.25, and τuc = 0.48 N/mm2 for p = 0.50. For a factored shear force of 45 kN, the diameter (in mm) of Fe500 steel two legged stirrups to be used at spacing of 375 mm, should be

(A) 8

(B) 10

(C) 12

(D) 16

Qn- For a beam of cross-section, width = 230 mm and effective depth = 500 mm, the number of rebars of 12 mm diameter required to satisfy minimum tension reinforcement requirement specified by IS:456-2000 (assuming grade of steel reinforcement as Fe500) is _____________

Qn- In a reinforced concrete section, the stress at the extreme fibre in compression is 5.80 MPa. The depth of neutral axis in the section is 58 mm and the grade of concrete is M25. Assuming linear elastic behavior of the concrete, the effective curvature of the section (in per mm) is

(A) 2.0×10−6

(B) 3.0×10−6

(C) 4.0×10−6

(D) 5.0×10−6