M.TECH. DEGREE EXAMINATION
Model Question Paper
Branch: Civil Engineering
Computer Aided Structural Engineering
E 106.1 PRESTRESSED CONCRETE (Elective
Time: Three Hours
Maximum: 100 marks
Note: i) Answer
i) Reference to IS:
) Assume suitable data wherever necessary
Briefly explain basic concept of prestressing.
cracking and post
what is " Pressure line or Thrust line" ? explain its significance.
A prestressed concrete beam 500 mm wide and 750 mm deep has a simply supported
span of 7m. It is prestressed with a linearly bent tendon with zero eccentricity attends
and an ecce
ntricity of 150 mm below the beam axis at mid span. The beam carries a
concentrated load of 250 kN at centre besides its self
weight. Compute the stresses at
Differentiate between post
tensioning system and pre
Distinguish clearly between short
term and long
term deflections of prestressed
concrete beam , 200mm wide and 300mm deep is prestressed with
) located at a constant eccentricity of 50mm a
nd carrying an
tial stress of 1000N/mm
. The span of beam is 10 m. Calculate the percentage loss
of stress in wires if (a) the beam is pre
(b) the beam is post
using the following data:
steel stress = 5
per cent of the initial stress
Shrinkage of concrete = 300
tensioning and 200×10
Slip at anchorage=1
Frictional coefficient for wave effect =0.0015
what are the
different types of flexural failure modes observed in prestressed
concrete beams ?
Explain the term (a) minimum section modulus (b) Maximum eccentricity
Explain the importance of anchorage zone in prestressed members.
The end block of a prestressed concret
e beam is 200 mm wide by 400 mm deep.
Two cables carrying an effective force of 1000kN, each are anchored by Freyssinet
anchorages of 150 mm diameter and 150 mm long with their centers @ 100 mm
the axis of the beam, using steel of Fe 415 grade, design suit
able anchorage zone
reinforcement using IS: 1343 provisions and sketch the details of the reinforcement
in the end block.
Explain the tensile stress distribution in an end block of a post
tensioned beam with
riefly explain the limi
ting zone for prestressing force
tensioned bonded prestressed concrete beam of rectangular cross
400mm wide by 500mm deep, is subjected to a service
load bending moment of
166.6 kN m, torsional moment of 46.6 kN m and shear force of 66.6 k
has an effective prestressing force , determined from service load requirements, of
magnitude 500 kN at an eccentricity of 150 mm, provide 5 numbers of 12.5mm
relieved strands of cross
sectional area 506 mm
with an ultimate tensile
trength of 1820 N/mm
. If the cube strength of concrete is 40 N/mm
, design suitable
longitudinal and transverse reinforcement in the beam using IS:1343
Design of pre
tensioned roof purlin to suit the data below:
Effective span=6 m
For dead load =1.4
For live load =1.6
Concrete cube strength,
Cube strength at transfer,
Tensile strength of concrete
Modulus of elasticity of concrete,
Loss ratio , µ=0.8
At working load :
= 17 N/mm
7mm high tensile steel wires having an ultimate tens
ile strength ,
= 1600 N/mm
What are the advantages of continuous members in prestressed concrete structures?
What are cap cables? Where are they used?
A continuous beam ABC
(AB=BC=10m) is prestressed by a parabolic cable profile
carrying an eff
ective force of 200kN. The cable profile shown in the fig below. The
beam supports a dead and live load of 0.24 kN/m and 2.36 kN/m respectively.
Calculate the resultant moments developed in the beam and locate the pressure line
Outline the design princ
iples of prestressed compression members and its application
in the design of flag mast.
What are the advantages of using composite construction with prestressed and
concrete in structural members?
en propped and un
struction methods in composite
construction using stress diagrams at various stages of construction.
What is differential shrinkage?
its importance in composite construction.
Design a composite slab for the bridge deck using
standard inverted T
top flange is 250mm wide and 100mm thick. The bottom flange is 500mm wide and
250mm thick. The web thickness is 100mm and the overall depth of the inverted T
section is 655mm. the bridge deck has to support a
imposed load of 50
over an effective span of 12 m. Grade
40 concrete is specified for the precast
with a compressive strength at transfer of 36 N/mm
. Concrete of
30 is used for the
part. Determine the minimum prestress necessary and
for safety under serviceability limit state.
What are the advantages of prestressing in the design
of concrete members subjected
to axial tension? What are the load factors generally specified against cracking and
collapse in such members?
n a suitable section for the tie member of a truss to supporta maximum design
tensile force of 500 kN. The permissible compressive stress in concrete at transfer is
and no tension is permitted under working loads. The loss ratio is 0.8 7mm
r wires of ultimate tensile strength of 1700 N/mm
with an intial stress of 950
may be used. The direct tensile strength of concrete is 3 N/mm
factor of 2 at the limit state of collapse and 1.25 against cracking is required.
Explain the des
ign procedure of prestressed folded plates.
How do you compute the shrinkage and resultant stresses in composite members?