Anna University, B. ARCH. DEGREE EXAMINATION
FIFTH SEMESTER, DESIGN OF STRUCTURES –II
Yield stress for Fe 415 grade reinforcement is 415 N/mm2 and for working stress method permissible tensile stress in reinforcement is 0.55 times the yield stress and permissible compressive stress in bending is one- third of the characteristic compressive strength of concrete. For the limit state of strength a load factor of 1.5 shall be used.
PART- A (10 x 2 = 20 marks)
Answer all Questions
1. Define the characteristic strength of materials and characteristic loads.
2. What are the different grades of concrete and reinforcement bars recommended for
reinforced concrete structural members?
3. What are the assumptions made in the working stress method of analysis of reinforced
4. Determine the ratio between the depth of neutral axis and the effective depth of
reinforced concrete rectangular beams with Fe 415 grade tensile reinforcement for
5. What are the partial safety factors for strength of concrete and reinforcement bars?
6. Determine the limiting value of the ratio between the neutral axis depth and the
effective depth of reinforced concrete beams with Fe 415 grade tensile bars for limit
state of collapse.
7. What are the maximum and minimum percentages of tensile reinforcement
recommended for reinforced concrete beams?
8. What are the factors governing the permissible shear stress in concrete and what is the
distance of critical section for the design of shear reinforcement in beams generally
carrying uniformly distributed load.
9. What are the span to effective depth ratios recommended for cantilever slabs, simply
supported and continuous slabs to satisfy their approximate stiffness?
10. What are the minimum percentage and maximum spacing recommended for non-
structural reinforcement for temperature and shrinkage and structural tensile
reinforcement in reinforced concrete slabs.
PART – B (5 x 16 = 80 marks)
11. For the limit state strength design of a single reinforced concrete section derive the
equation for xu/d, and limiting moment Mu, limit in terms of pt, fy, fck, where xu, is
the actual depth of neutral axis, fy, and fck, are the characteristic strengths of tensile
reinforcement and concrete, respectively, and pt, = As / b d, As is the area of tensile
reinforcement, b and d are the width and effective depth, respectively, of the beam.
12.a) A simply supported single reinforced concrete rectangular beam of 250 m, width
and 500 mm total depth with effective cover of 30 mm and effective span of 6 m
carries uniformly distributed service load of 8 kN/m in addition to self weight.
Determine the following using working stress method with M 20grade concrete and Fe 415 grade reinforcement: i) total design working load per metre, ii) Effective depth required for balanced section, iii) Area of tensile reinforcement for balanced section.
12.b) A simply supported single reinforced rectangular beam of 300 mm, width x 600
mm depth with an effective span of 8 m carries two concentrated loads of 15 kN at
the one–third points in the span. Determine the following using working stress
method of design with M 20 grade concrete and Fe 415 grade reinforcement: i)
maximum design moment due to concentrated loads and the self weight of the
beam, ii) depth and area of tension reinforcement for the balanced section.
13.a) A cantilever R.C. beam of 4m span having 300 mm width and total depth of 600
mm contain four Fe 415 grade reinforcing bars of 20 mm diameter. Using working
stress method of design with M 20 grade concrete and an effective cover of 35 mm
calculate the maximum uniformly distributed service load carried by the beam if
reinforcement and concrete are fully stressed to their permissible values.
13.b) A T beam floor slab of 125 mm flange thickness with 250 mm web width and 500
mm total depth contains four Fe 415 grade reinforcement bars of 16 mm diameter.
The centre to center distance of T beams is 4 m. Using working stress method of
design with M 20 grade concrete and an effective cover of 35 mm calculate the
following if the effective span of the T beam is 6m: i) effective width of
compression flange of the T beam; ii) actual depth of neutral axis; balanced depth
of neutral axis; iii) compressive force C above the neutral axis; iv) resisting moment
of the section.
14.a) A reinforced concrete rectangular cantilever beam of 3 m span carries an imposed
service load of 30 kN/m in addition to self weight. The width and total depth of the
beam are 250.0 mm and 500 mm, respectively. Draw the shear force diagram
indicating maximum shear force and its location from the support. Determine the
following using limit state method with an effective cover of 35 mm for tensile
reinforcement: i) the distance of the critical section for the design shear force from the edge of the support, ii) spacing of 8 mm diameter two legged stirrups of Fe 415 grade if the permissible shear stress in concrete is 0.4 Mpa., iii) maximum permissible spacing of vertical stirrups.
14.b) A simply supported reinforced concrete beam of 6 m effective span carries 25
kN/m, in additional to its self weight. The width and overall depth of the beam are
250 mm and 450 mm, respectively. Draw the shear force diagram and determine
the following using limit state method with an effective cover of 35 mm: i) the
distance of the critical section for design shear force, ii) design shear force if the
permissible shear stress in concrete in 0.5 Mpa., and iii) spacing of 8 mm diameter
Fe 415 grade vertical stirrups, minimum area of vertical stirrups.
15.a) A cantilever roof slab of 2.5 m span and 3.5 m width carries a total load of 10.0 kPa
including its self weight. Using limits state method with M 20 grade concrete and
Fe 415 grade reinforcing bars determine the following: i) effective depth
recommended from span to effective depth ratio for cantilever slabs, ii) effective
depth required for ultimate limiting moment, and iii) spacing of 10 diameter Fe 415
grade reinforcement bars at support, maximum permissible spacing of tensile
15.b) A rectangular R.C. floor slab of effective spans 10 m x 4 m carries an imposed
working load of 7 kPa. Using limit state method of design with M 20 grade concrete
and Fe 415 grade reinforcement determine the following: i) effective depth required
using the recommended span depth ratio without modification factor for tensile
reinforcement, ii) ultimate load intensity on the slab assuming effective cover of 25
mm and load factor of 1.5, iii) spacing of 10 mm diameter rod of Fe 415 at the
center of the slab in both directions. Use moment coefficients of 0.122 and 0.02 for
short and long spans respectively.