Design of Prestressed
Design of Prestressed
Design of Prestressed
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Abstract: The concept of pre-stressed concrete appeared in the year 1888. In this present engineering technology Durable and
sustainable bridges play an important role for the socio-economic development of the nation. Owners and designers have long
recognized the low initial cost, low maintenance needs and long life expectancy of pre-stressed concrete bridges. This is reflected in the
increasing market share of pre-stressed concrete, which has grown from zero in 1950 to more than 55 percent today. This growth
continues very rapidly, not only for bridges in the short span range, but also for long spans in excess of length which, here therefore, has
been nearly the exclusive domain of structural steel. Many bridge designers are surprised to learn that precast, pre-stressed concrete
bridges are usually lower in first cost than all other types of bridges coupled with savings in maintenance, precast bridges offer
maximum economy. The precast pre-stressed bridge system offered two principal advantages: it is economical and it provides minimum
downtime for construction. Pre-stressing is the application of an initial load on the structure so as to enable the structure to counteract
the stresses arising during its service period. In this present project I am going to know the behavior of pre-stressed concrete beam, how
they stressed, percentage of elongation, pressure applied to make beam stressed. This thesis completely going to do in a practical
approach that on a major bridge having 299 mts span, 36 no’s of PSC Beams & 8 no’s of RCC Beams. My attempt is on PSC Beams,
where the Beam post tensioning values, rate of elongation & behavior can be defined after stressing. The main code that I follow in this
course is IS: 1343 – 2012. The title is Code of Practice for Pre-stressed Concrete. It is published by the Bureau of Indian Standards.
Remembering that am expected to know IS: 456 - 2000 which is the Code of Practice for Structural Concrete. Some of the provisions of
IS: 456 are also applicable for Pre-stressed Concrete.
Keywords: PSC T-Beam, IRC: 1343-2012, IRC: 5-1998, IRC: 6-2000, IRC: 18-2000, IRC: 21-2000, IS: 6006-1980.
a) The Lubha bidge24, the nation's longest single-span 6. Materials for Pre-Stressed Concrete
172mlongpre-stressedconcretebox-girder-
typecontinuous Bridge built across a 30 m deep gorge of 5.1 High-Strength Concrete Mixes
the Lubha river in Assam.
b) Gomti aqueduct, which is the longest and the biggest Pre-stressed concrete requires concrete which has a high
aqueduct in India comprising 9.9 m deep pre-stressed compressive strength at a reasonably early age, with
concrete girders each weighing as much as 5500 kN comparatively higher tensile strength than ordinary concrete.
over a span of 31.8 m, located in Uttar Pradesh. Low shrinkage, minimum creep characteristics and a high
c) Ball tank, Tom bay, Maharashtra, consisting of a pre- value of Young's modulus age generally deemed necessary
stressed concrete, tank of 4 million liter capacity for the for concrete used for possessed members. Many desirable
department of atomic energy. properties, such as durability, impermeability and abrasion
d) The Boeing hanger at Santa Cruz airport with a hoof resistance, age highly influenced by the strength of concrete.
consisting of barrel shells supported on pre-stressed
concrete edge beams spanning over 45.73 m. With the development of vibration techniques in 1930, it
became possible to produce, without much difficulty, high-
strength concrete having 28-day cube compressive strength
5. Principle of Pre-Stressing
in the range of 30-70 Nmm2. The minimum 28-day cube
compressive strength prescribed in the Indian standard code
The function of pre-stressing is to place the concrete
IS: 1343-1980 is 40 N/mm2 for pre-tensioned members and
structure under compression in those regions where load
30 N/mm2 for post tensioned members. The ratio of standard
causes tensile stress. Tension caused by applied loads will
cylinder to cube strength may be assumed to be 0.8 in the
first have to cancel the compression induced by the pre-
absence of any elegant test data. A minimum cement content
stressing before it can crack the concrete. Figure shows a
of 300 to 360 kg/m3 is prescribed mainly to cater to the
plainly reinforced concrete simple span beam and fixed
durability equipments. In high-strength concrete mixes, the
cantilever beam cracked under applied load. Figure shows
water content should be as low as possible with due egad to
the same unloaded beams with pre-stressing forces applied
adequate workability, and the concrete should be suitable for
by stressing post-tensioning tendons. By placing the pre-
compaction by the means available at the site. It is a general
stressing low in the simple-span beam and high in the
practice to adopt vibration to achieve thorough compaction
cantilever beam, compression is induced in the tension
of concrete used for possessed members.
zones; creating upward camber.
⁄− 0.4
6.3 IRC Class AA Loading
11.1mm 7-ply 11.1 69.7 1,20,100 102300
0.15
6.4 IRC Class 70 R Loading
References
[1] Krishna Raju, N., Design of Concrete Mixes (4th
Edition), C.B.S. Publishers New Delhi, 2002.
[2] Freysssinet, E., the Birth of Pre-stressing, Cement &
Concrete Association, London, Translation.
[3] Reynolds, C.E and Steedman, J., Reinforced Concrete
Designers Hand Book, Concrete Publications Ltd.,
London, 1974.
[4] IS: 10262 - 1982. Indian Standard Guide Lines for
Concrete Mix Design, Indian Standards Institution, New
Delhi. 1983.
[5] IS: 1343 - 1980 Indian Standard Code of Practice for
Pre-stressed Concrete (First revision). Indian Standards
Institute, New Delhi, 1981,
[6] IS:456 - 1978. Indian Standard Code of Practice for
Plain and Reinforced Concrete (third revision). Indian
Standards Institution, New Delhi, 1979
[7] IS: 1785 (Part II) - 1983, Indian Standard Specification
for Plain Hard-Drawn Steel Wire for Pre-stressed
Concrete. Part II as drawn wire, (2*1 revision), Indian
Standards Institution. New Delhi, 1983
[8] IS: 1785 (Part I) - 1983. Indian Standard Specification
for Plain Hard-drawn Steel Wire for Pre-stressed
Concrete. Part I cold-drawn stress relieved wire. (Dnd
revision), Indian Standards Institution. 1983.
[9] IS:6003-1983, Indian Standard Specification for
Indented Stress-Relieved Wire for Pre-stressed
Concrete. (1st revision), Indian Standards Institution,
New Delhi, (1strepint). April 1990.
[10] IS: 6006-1983, Indian Standard Specification for
Uncoated Stress Relieved Strand for Pre-stressed
Concrete (First revision), Indian Standards Institution,
New Delhi, first reprint. October 1989.
[11] Surya Prakash as a Designer in Sheladia Associates Inc
and Sew Infrastructure Limited