chapter 6 highway curves and volumes

[PEin2010]

Chapter 6, Reza problem #6: I can't figure out how part V was calculated. For the other parts I through IV looks like irrespective of instrument location they are just using F.S. length to calculate angle. Help!

 

[henryf]

While we're at it

I can't figure out what was going through Reza's head when showing the answer to 3.56

 

[PEin2010]

where's 3.56? example 3.56? do you know page number?

While we're at it
I can't figure out what was going through Reza's head when showing the answer to 3.56

 

[henryf]

where's 3.56? example 3.56? do you know page number?

Page 73 Spring 2010 printing

 

[henryf]

where's 3.56? example 3.56? do you know page number?

Page 73 Spring 2010 printing

BTW for 6.6-5

The answer is that the deflection angle to the point being staked is equal to:

(length of curve to point being spotted/total length of curve) * (alpha/2)

Reza uses delta instead of alpha in his notation. This is a problem for me since there seems to be 2 or 3 terms for every item in surveying (alpha = delta = I or PC=BC .. I'm sure that you have noticed this also)

In this case we are interested in .75 * the length so the equation becomes:

(.75L/L) * (alpha/2) where L is the total curve length

this reduces to (.75/2) times alpha or 3/8 alpha

 

[EnvEngineer]

When you sight back to PC from your point on the station you will turn the deflection angle for that point (PC to Point or Point to PC is the same), now you turn to new point on curve such as the midpoint, and will turn the same df as you would from the PC, so for the full curve the df is I/2 so the df for the mid point is I/4.

 

[lucky101]

where's 3.56? example 3.56? do you know page number?

Page 73 Spring 2010 printing

BTW for 6.6-5

The answer is that the deflection angle to the point being staked is equal to:

(length of curve to point being spotted/total length of curve) * (alpha/2)

Reza uses delta instead of alpha in his notation. This is a problem for me since there seems to be 2 or 3 terms for every item in surveying (alpha = delta = I or PC=BC .. I'm sure that you have noticed this also)

In this case we are interested in .75 * the length so the equation becomes:

(.75L/L) * (alpha/2) where L is the total curve length

this reduces to (.75/2) times alpha or 3/8 alpha

I think the question is about part 5. I also have trouble with that. The question is how much did the instrument turn to stake out 3/4 length. and answer is 5delta/16. Can somebody explain this?

 

[henryf]

I think the question is about part 5. I also have trouble with that. The question is how much did the instrument turn to stake out 3/4 length. and answer is 5delta/16. Can somebody explain this?

You are being asked to calculate a deflection angle in terms of the central angle for a horizontal curve stakeout.

The formula is:

((length along curve to point being staked)/(total length of curve)) x (central angle/2)

.75L/L x delta/2

which reduces to .375 x delta

While we are at it, you probably want to know how to calculate the straight line distance (ie chord length) from the BC to the point being staked:

C=2R(sin alpha) where R is the curve radius and alpha is the deflection angle from the BC to the point on the curve being staked. This was calculated above. It is not the central angle.

Now you have a deflection angle and a chord distance so you should be good to go for horizontal curve staking

Man..I sure hope that I can remember this for the test

 

[lucky101]

I think the question is about part 5. I also have trouble with that. The question is how much did the instrument turn to stake out 3/4 length. and answer is 5delta/16. Can somebody explain this?

You are being asked to calculate a deflection angle in terms of the central angle for a horizontal curve stakeout.

The formula is:

((length along curve to point being staked)/(total length of curve)) x (central angle/2)

.75L/L x delta/2

which reduces to .375 x delta

While we are at it, you probably want to know how to calculate the straight line distance (ie chord length) from the BC to the point being staked:

C=2R(sin alpha) where R is the curve radius and alpha is the deflection angle from the BC to the point on the curve being staked. This was calculated above. It is not the central angle.

Now you have a deflection angle and a chord distance so you should be good to go for horizontal curve staking

Man..I sure hope that I can remember this for the test

Can you please elaborate last step? Appreciate it

 

[henryf]

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