concise & clear primer. thank you so much! may i add? it wasn't stated in the ncees hb 1.1 that for a problem such as this the L = L_1 + L_2, thought this seems intuitive once you are an expert in a non-compound/simple hor-curve concept.
I have no evidence to support a confident answer to this question, however, this content uses 2 full pages, so I would expect this content to be included.
are we allowed to carry into the pe exam room 2 identical calculators? 1 is the main machine and the other is backup. and what about 3 machines ? for new cbt format exam.
From the NCEES EXAMINEE GUIDE December 10, 2021: You are allowed to bring one NCEES-approved calculator into the testing room. You may store spare calculators and covers with your personal belongings.
Hi Sir. What superelevation should you use on these curves. If you want to maintain your speed, must you apply different superelevations on the different curves? Or should you rather apply one superelevation throughout?
Excellent question! You would use different superelevation rates that are sufficient for each curve's radius and design speed. Below is some useful guidance from the Illinois DOT about tying those superelevation rates together. The image on Page 32-3.28 is particularly helpful also. www.idot.illinois.gov/Assets/uploads/files/Doing-Business/Manuals-Split/Design-And-Environment/BDE-Manual/Chapter%2032%20Horizontal%20Alignment.pdf 32-3.05 Compound Curves Superelevation development for compound curves requires the consideration of several factors. For two-lane roadways, these are discussed in the following sections for two Cases: Case I: The distance between the PC and PCC is 300 ft (90 m) or less. Case II: The distance between the PC and PCC is greater than 300 ft (90 m). 32-3.05(a) Case I For Case I, superelevation development for compound curvature on two-lane roadways should meet the following objectives: 1. Relative Longitudinal Gradient (RS). A uniform RS should be provided throughout the superelevation transition (from normal crown section to design superelevation rate at the PCC). 2. Superelevation at PC. Section 32-3.02 will yield the design superelevation rate (e1) for the first curve. At the PC, 67% e1 should be reached. 3. Superelevation at PCC. The criteria in Section 32-3.02 will yield the design superelevation rate (e2) for the second curve; e2 should be reached at the PCC. 4. Superelevation Runoff Length. Section 32-3.02 will yield the superelevation runoff (L1) for the first curve. The superelevation should be developed such that 67% of L1 is reached at the PC. 5. Tangent Runout Length. TR will be determined as described in Section 32-3.02. To meet all or most of these objectives, the designer may need to try several combinations of curve lengths, curve radii, and longitudinal gradients to find the most practical design. Section 32-3.08 presents a typical figure for Case I superelevation development for a compound curve. 32-3.05(b) Case II For Case II, the distance between the PC and PCC (> 300 ft (90 m)) is normally large enough to allow the two curves to be evaluated individually. Therefore, the superelevation development on two-lane roadways should meet the following objectives for Case II: 1. First Curve. Superelevation should be developed assuming the curve is an independent simple curve. Therefore, the criteria in Section 32-3 for superelevation rate, transition length, and distribution between tangent and curve apply. 2. Intermediate Treatment. Superelevation for the first curve (e1) is reached a distance of 33% of the superelevation runoff length beyond the PC. e1 is maintained until it is necessary to develop the needed superelevation rate (e2) for the second curve. 3. Second Curve. Assuming the second curvature has a sharper radius of curve than the first curve, a higher rate of superelevation will be required (e2 > e1). e2 should be reached at the PCC. The distance needed for the additional superelevation development is not specified, except that the maximum RS for the highway design speed should not be exceeded. One logical treatment would be to apply the same RS used for the superelevation transition of the first curve. This would provide a uniform change in gradient for the driver negotiating the compound curve. Section 32-3.08 presents a typical figure for Case II superelevation development for a compound curve.
Thank you for this😊
concise & clear primer. thank you so much!
may i add? it wasn't stated in the ncees hb 1.1 that for a problem such as this the L = L_1 + L_2, thought this seems intuitive once you are an expert in a non-compound/simple hor-curve concept.
what are odds of seeing the 2- and 3-centered compound curves on the civil pe, am section ?
I have no evidence to support a confident answer to this question, however, this content uses 2 full pages, so I would expect this content to be included.
are we allowed to carry into the pe exam room 2 identical calculators? 1 is the main machine and the other is backup. and what about 3 machines ? for new cbt format exam.
From the NCEES EXAMINEE GUIDE December 10, 2021: You are allowed to bring one NCEES-approved calculator into the testing room. You may store spare calculators and covers with your personal belongings.
@@FindleyDaniel verified with the ncees via email, today. they told me the same exact thing.
@@oleopathic Thanks for confirming
Hi Sir.
What superelevation should you use on these curves. If you want to maintain your speed, must you apply different superelevations on the different curves? Or should you rather apply one superelevation throughout?
Excellent question! You would use different superelevation rates that are sufficient for each curve's radius and design speed.
Below is some useful guidance from the Illinois DOT about tying those superelevation rates together.
The image on Page 32-3.28 is particularly helpful also.
www.idot.illinois.gov/Assets/uploads/files/Doing-Business/Manuals-Split/Design-And-Environment/BDE-Manual/Chapter%2032%20Horizontal%20Alignment.pdf
32-3.05 Compound Curves
Superelevation development for compound curves requires the consideration of several factors.
For two-lane roadways, these are discussed in the following sections for two Cases:
Case I: The distance between the PC and PCC is 300 ft (90 m) or less.
Case II: The distance between the PC and PCC is greater than 300 ft (90 m).
32-3.05(a) Case I
For Case I, superelevation development for compound curvature on two-lane roadways should
meet the following objectives:
1. Relative Longitudinal Gradient (RS). A uniform RS should be provided throughout the superelevation transition (from normal crown section to design superelevation rate at the PCC).
2. Superelevation at PC. Section 32-3.02 will yield the design superelevation rate (e1) for the first curve. At the PC, 67% e1 should be reached.
3. Superelevation at PCC. The criteria in Section 32-3.02 will yield the design
superelevation rate (e2) for the second curve; e2 should be reached at the PCC.
4. Superelevation Runoff Length. Section 32-3.02 will yield the superelevation runoff (L1) for the first curve. The superelevation should be developed such that 67% of L1 is reached at the PC.
5. Tangent Runout Length. TR will be determined as described in Section 32-3.02.
To meet all or most of these objectives, the designer may need to try several combinations of curve lengths, curve radii, and longitudinal gradients to find the most practical design. Section 32-3.08 presents a typical figure for Case I superelevation development for a compound curve.
32-3.05(b) Case II
For Case II, the distance between the PC and PCC (> 300 ft (90 m)) is normally large enough to allow the two curves to be evaluated individually. Therefore, the superelevation development on two-lane roadways should meet the following objectives for Case II:
1. First Curve. Superelevation should be developed assuming the curve is an independent simple curve. Therefore, the criteria in Section 32-3 for superelevation rate, transition length, and distribution between tangent and curve apply.
2. Intermediate Treatment. Superelevation for the first curve (e1) is reached a distance of 33% of the superelevation runoff length beyond the PC. e1 is maintained until it is necessary to develop the needed superelevation rate (e2) for the second curve.
3. Second Curve. Assuming the second curvature has a sharper radius of curve than the first curve, a higher rate of superelevation will be required (e2 > e1). e2 should be reached at the PCC. The distance needed for the additional superelevation development is not specified, except that the maximum RS for the highway design speed should not be exceeded. One logical treatment would be to apply the same RS used for the superelevation transition of the first curve. This would provide a uniform change in gradient for the driver negotiating the compound curve.
Section 32-3.08 presents a typical figure for Case II superelevation development for a
compound curve.
@@FindleyDaniel thank you so much. I really appreciate this information.
ncees hb 1.1, page 274.
would we use T_1 and T_2, as indicated by the ncees hb, instead of the T_a and T_b indicated this is video ?
Yes, that's correct - you should get the same answer I show in the video using the NCEES equations.
Sir, how to find the Ta formula? Thanks!
The equation is about 2 minutes into this video - ua-cam.com/video/gcEzjuXZa1U/v-deo.html
The derivation of the equation is available here - ua-cam.com/video/6HgVfR24vqw/v-deo.html