Challenge 7

Ans of question- 1

SLS load combination=(1*DL+1.2*SIDL+1.1*LL*1.3)

Where, impact on live load=1.3, DL=100KN, SIDL= 80 KN, LL= 120 KN

= (1*100+ 1.2*80+ 1.1*120*1.3)

=367.6 KN

Reaction occurred 0.25 m from tip of cantilever.

So, distance between pier face and reaction= (4.5-0.25) =4.25 m

So, Moment= 367.6* 4.25=1562.3 kn-m.

Ans of question- 2

Differentiate between RC and PSC pier cap

RC pier cap	PSC pier cap
Thicker/heavy weight structure needed.	Thinner/light weight structure used.
RC structure is under continuous tension, so due to the effect of creep and shrinkage cracks seen in tensile zone, so it is less durable.	Prestress section are practically in no stress zone, so durability of concrete in PSC structure is more.
Unskilled labour also do the job with the help of site supervisor.	Skilled labour need for apply the prestressing forces.
More time taken to construct.	Less time taken to construct.

Ans of question- 3

Codal provision for design crack width depending on the various exposure conditions-

Exposure condition	Design crack width in mm
Moderate	0.20
Severe	0.10
Extreme	0.10

Ans of question- 4

Cantilever pier cap is preferred because we know that the metro alignment is curve in nature, so it is not possible to placed the pier cap bellow the rail because there could be a road running bellow the metro viaduct. We cannot construct the pier cap at middle of road , so that case we used the cantilever pier cap.

Limitations-

1. it can not take excessive load due to cantilever in nature.

2.if eccentricity ( the distance between pier and centre line of metro viaduct) is with in 2 meter then we used rc pier cap, and when the eccentricity is upto 3 meter we used the psc pier cap.