Question CE 415 Repaired

8/20/2019 Question CE 415 Repaired

http://slidepdf.com/reader/full/question-ce-415-repaired 1/15

Question: (Ex- 5.3)

A posttensioned beam has a midspan cross section with a duct of 50 mm by 75 mm to house the

wires, as shown in fig, It’s prestressed with 520 mm2 of steel to an initial stress of 1035 pa!

Immediately after transfer the stress is reduced by 5" owing to anchorage loss and elastic

shortening of concrete! #ompute the stresses in the concrete at transfer!

Question: (Ex- 5.4)



A posttensioned bonded concrete beam in fig, has a prestress of 1575 $% in the steel

immediately after prestressing, which e&entually reduces to 1350 $% due to losses! 'he beam

carries two li&e loads of (5 $% each in addition to it’s own weight of (!5 $%)m!

#ompute the e*treme fiber stress in midspan

+a -nder the initial condition with full prestressand no li&e load

+b-nder the final condition, after the losses ha&e ta.en lace, and with full li&e load

Question: (Ex- 5.6)



A posttensioned simple beam on a span of 12 m is shown in fig, It carries a superimposed load

of 11 $%)m in addition t its own weight of (!5 $%)m! 'he initial prestress in the steel is /50

a, reducing to 20 pa after deducting all losses and assuming no bending of the beam! 'he

parabolic cable has an area of 100 mm2, n,

#ompute the stress in the steel at midspan, assuming

+1'he steel is bonded by grouting+2'he steel is unbonded and entirely free to slip

Question: (Ex- 5.8)



An I4shaped beam is prestressed eith A ps 1750 mm2 as prestressing ateel with an effecti&e

stress, f se, of 1100 a! 'he c!g!s! of the strands which supply the prestress is 115 mm abo&e

the bottom of the beam as shown in fig, along with the shape of the concrete cross section!

aterial properties are f pu 10 a, f c’ ( a!

6ind the ultimate resisting moment of the section for design following the A#I code!

Question: (Ex- 5.9)



'he same I4shaped prestressed concrete beam as e*45! but the steel area is increased to A p

2350 mm2 ! 'he effecti&e steel stress remains 1100 a! 'he c!g!s! of the strands is 115 mm

abo&e the bottom of the beam as shown in fig, along with the shape of the cross section

material properties are same as e*45!!

6ind the ultimate resisting moment fr the section for design following the A#I code

Question: (Ex- 5.12)



'he midspan section of composite beam is shown in fig, 'he precast stem 300 mm by /20 mm

deep is posttensioned with an initial force of 2(50 $%, 'he effecti&e prestress after losses is

ta.en as 2150 $%! oment due to weight of that precast section is 270 $%4m at midspan! After

it is erected in place, the top slab of 150 mm by /20 mm wide is to be cast in place producing a

moment of 135 $%4m, After the slab concrete has hardened, the composite section is to carry a

ma*imum li&e load moment of 750 $%4m!

#ompute stresses in the section at &arious stages, A ps 2(00 mm2, f pu 150 a, f c’ 3( a

8stimate the ultimate moment!

Question: (Ex- 6.1)



a.e a preliminary design for section of a prestressed4concrete beam to resist a total moment

of (35 $%4m! 'he o&erall depth of the section is gi&en as /20 mm! 'he effecti&e prestress for

steel is 0 a, ad allowable stress for concrete under wor.ing load is 411 a

Question: (Ex- 6.2)



a.e a preliminary design for the beam section in e*4!1 with ' (35 $%4m, 9 55 $%4m,

h /20 mm , f se 0 a, and f c 411 a

Question: (Ex- 6.3)



6or the preliminary section obtained in e*ample !2, ma.e a final design, allowing

f b 412!5 a, f 0 1035 a! :ther gi&en &alues were ' (35 $%4m, 9 55 $%4m, f se

0 a, and f t 411 a; 62 $%! And the preliminary section is the same as in 6ig,

Question: (Ex- 6.4)



a.e final design for the preliminary section obtained in e*4!1, , 9 25 $%4m, allowing

f b 412!5 a, f 0 1035 a! :ther &alues are gi&en were ' (35 $%4m, f se 0 a,

and f t 411 a; h /20 mm! 'he preliminary section is shown in fig, with Ac 12/ <103 mm2,

#t 3(5 mm, # b 575 mm, I 10!7<10/ mm(, $ t 1( mm, . b2(mm, 6 727 $%,

6o 727+1035)0 75 $%

Question: (Ex- 6.5)



=edesign the beam section in e*4!3, allowing and considering tension in concrete! 6t’2!1 a

f b’ 1!5 a! :ther gi&en &alues were ' (35 $%4m, 9 55 $%4m, f t 411 a;

60( $%, f b 412!5 a, f 0 / $%

Question: (Ex- 7.3)



#hec. shear strength for the beam shown in fig, at station 141 which is h)2 from support! 9i&en

that this section is ade>uate for wu70 $%)m on the basis of its fle*ural strength computed in

e*4 5!! f c’ (/ a

Question: (Ex- 7.4)



#hec. the shear strength for station 242 for the beam shown in fig, 'he I4shaped noncomposite

section spans 15 m, and the c!g!s is as 113 mm from the bottom fiber at station 242, :ther

information is gi&en in fig, for this beam 6e 1// $%, e 337 mm, d 77 mm, f c’ (/ a,

wd 5!5 $%)m +beam wt!

Question: (Ex- 8.1)



A concrete beam of 10m simple span, fig, is posttensioned with 70 mm2 of high tensile steel to

an initial prestress of /5 a immediately after prestressing!

#ompute the initial deflection at midspan due to prestress and the beam’s own weight, assuming

8c 2<103 a! 8stimate the deflection after 1!5 months, assuming a creep coefficient of #c

1! and an effecti&e prestress of 25 pa at that time!

Question: (Ex- 8.2)



6or the beam in e*4!1,

#ompute the center deflection due to a (5 $% concentrated load applied at midspan, when the

beam is 1!5 months old after prestressing, Assume camber is 10!7 mm at this time prior to

application of the (5 $% load as computed in e*4!1

Documents

Question CE 415 Repaired