6 minute solutions vs actual SE I exam?

[buening]

Look at the end of Chapter 4 in AASHTO for the Appendix A. It is a table of moments for the deck design based on the span.

 

[Jennifer]

Look at the end of Chapter 4 in AASHTO for the Appendix A. It is a table of moments for the deck design based on the span.

Oh...ok. The AASHTO stuff is a huge hole in my knowledge. I'm clueless here except what's in SERM and what little knowledge I've picked up doing practice problems.

 

[buening]

Now you know how I feel with the IBC, ASCE 7, ACI masonry, PCI, and many others :beerchug:

The AASHTO is enormous, but at least its all in one code. You might flag a few sections of AASHTO, like the effective flange width sections and the table I mentioned. Tab the load combination page as well. I've been tabbing quite a bit of stuff in the larger manuals.

Let me know about those two problems I question above. I could be wrong though.....like the wood problem

 

[Jennifer]

Now you know how I feel with the IBC, ASCE 7, ACI masonry, PCI, and many others :beerchug:
The AASHTO is enormous, but at least its all in one code. You might flag a few sections of AASHTO, like the effective flange width sections and the table I mentioned. Tab the load combination page as well. I've been tabbing quite a bit of stuff in the larger manuals.

Let me know about those two problems I question above. I could be wrong though.....like the wood problem

Yea...I'll check those tonight when I get home. I started to look at it this morning and got off into the errata of the NCEES sample exam. Wow...that's grown since I last checked it...which was before the exam in April. Guess I should keep up with that more.

As for the AASHTO...I tabbed the big general sections for the April exam. I'll add the sections you mentioned. Thanks for your help.

the PCI...I didn't use it very much last time, so I'm not very familiar with it...for the ASCE, tab the sections for the live loads, wind stuff, seismic sections. I would tab the tables in the wind section so you can easily find them and the wind speed map. AISC, i have tabs all over the place...all the tables I use regularly...connections split up by type, beam design charts, column charts...I also tabbed the first page of each of the section property sections.

 

[Shaker-PE]

Aw shoot, I was adding the three values together instead of multiplying them! :brickwall: Check the errata for the chord forces on those problems you question, the leader was pointing to the wrong line.
Got a few more questions with the same SE I practice exam, maybe you could help/clarify. The solution to 501 shows the L for the column as 13.67 ft. According to ACI, the L should be the clear distance between floors. Wouldn't that be 12ft then, not 13.67?

One other one that I think may be incorrect is the LRFD solution to #525. The section is doubly symmetric, so I think they should use section H1. You would then see if Pr/Pc > 0.2 I get Pr = 32k. The Pc = phi * Fcr * A = 0.9 * 23.7 * 15.6 = 332.75k. The ratio ends up being 0.096 < 0.2, therefore the second equation applies. Pr/(2Pc) + Mr/Mc <1. In their solution, they are finding the stress in the column (P/A) and then use an equation fa/Fa + Mr/Mc This equation lacks the 2 in the denominator of the axial portion. I end up getting 0.814 for the combined ratio compared to their 0.853

I did OK with the afternoon portion, just barely passing. The masonry expansion/contraction questions really threw me for a loop. Such an odd group of questions, and there were like 5 of them!

I noticed the same thing for #501. I think you use the center-to-center spacing in the determination of the Psi factor. You know EI/L over EI/L. But when it comes to finding the effective length (le = k * lu) you use the clear spacing for lu. Check out #65 in the 6 minute solutions. I'm not sure where it would verify this, if I am correct, in the code.

For #525, a W14x53 is singly symmetric. A tube or pipe would be doubly symmetric, right? For the answer, the AISC does say that H2 is permitted to be used instead of H1. And since the ASD question specifically talks about fbx and Fbx, it seems like they're moving you away from H1, which doesn't contain those terms, and into H2 which does contain them. They did change the ASD answer though.

http://www.ncees.org/exams/study_materials...truc_errata.pdf

As for the LRFD option, they make it confusing when switching to moments instead of stresses. However, kl/r is 93.75, so from Table 4-22 Fcr is 22.875 ksi, which makes Pc = 321 k. So I actually get 0.815 but LRFD is not my strength. Personally I do ASD and try to stay away from LRFD. I guess, just hope that the test doesn't present such opposing ideas. But yes, I do think their whole question/answer for LRFD is incorrect. I'd be curious to know how much the answers from H1 and H2 actually differ. What's the right answer? I'm not sure... :blink:

 

[Jennifer]

Aw shoot, I was adding the three values together instead of multiplying them! :brickwall: Check the errata for the chord forces on those problems you question, the leader was pointing to the wrong line.
Got a few more questions with the same SE I practice exam, maybe you could help/clarify. The solution to 501 shows the L for the column as 13.67 ft. According to ACI, the L should be the clear distance between floors. Wouldn't that be 12ft then, not 13.67?

One other one that I think may be incorrect is the LRFD solution to #525. The section is doubly symmetric, so I think they should use section H1. You would then see if Pr/Pc > 0.2 I get Pr = 32k. The Pc = phi * Fcr * A = 0.9 * 23.7 * 15.6 = 332.75k. The ratio ends up being 0.096 < 0.2, therefore the second equation applies. Pr/(2Pc) + Mr/Mc <1. In their solution, they are finding the stress in the column (P/A) and then use an equation fa/Fa + Mr/Mc This equation lacks the 2 in the denominator of the axial portion. I end up getting 0.814 for the combined ratio compared to their 0.853

I did OK with the afternoon portion, just barely passing. The masonry expansion/contraction questions really threw me for a loop. Such an odd group of questions, and there were like 5 of them!

On 501, I agree it should be 12'...ACI 10.11.3 says it's the clear distance.

I'm still trying to figure out 525.

 

[Jennifer]

on 525, I agree with you...it appears that you should be using eqn. H1-1b. However, with the information they are giving you, you don't have what you need to answer it. Other than that, i don't know what to tell you. It does say that you can use that section in lieu of H1. It would seem to me that M/Mn would be the same as f/F...but I'm not sure it works out that way. I would think the information provided would lead you to the H2 equation...but I'm not sure that's right.

 

[Jennifer]

Shaker, wouldn't an I shape be doubly symetric...you could fold it about both axis, doesn't that make it doubly symetric?

 

[buening]

Doubly symmetric is for all W shapes, HSS shapes, and others. They are a mirror image about each of the X and Y axis. A singly symmetric section would be a C-shape. It is symmetric about one axis, but not about the other axis.

Thanks for the confirmation Angela. I found the exact section of ACI that said it was the clear distance, but wasn't sure if there was a catch somewhere.

Regarding 525, can't you pull the φPn from the AISC tables since you know the KL? The axial force was given in the problem, so looking up the φPn should give you the first part of the H1 equation. It gives the Mu and φMn, so you have the second part of the question.

Thanks for the tips on the building manuals. I have tabs all over the friggin place. I have a feeling I may have too many things tabbed and will never find the sections I need. Oh well

Since I'll be taking the bridge portion of the SE II, I broke up the AASHTO manual into different binders. One binder has Chapters 1-5, another with Ch 6, another with Ch 7, and the last with the remaining chapters. The steel and concrete section are large enough for their own binders, and on the exam the problem will only involve one material.

There are tons of errors in the bridge portion of the SE II practice exam, yet none have been released for the bridge section. I will be submitting my full page of errors, ranging from them pulling the wrong equations to even using allowable stress without phi factors.

 

[Jennifer]

That's what I was thinking on the doubly symetric...tubes, W sections...the WT, Channels would be singly symetric.

On 525, I looked into the P/Pn from the tables, but it didn't give the correct answer. I meant to bring that book to work today to talk with someone over that problem, but I forgot it. I'll still see if I can describe it to him. Let you know what he says.

I thought about splitting my AASHTO up, but decided not to since I need the index to find most of it.

 

[Jennifer]

we looked into the old ASD manual and it only had the equations that are shown in H2. I had the older version of the sample test and all they did was rework the solutions for the new manuals (sometimes rather poorly), we think it's probably a carry over from the older code. I would think if they are writing the exam questions based on the new codes, they would be more likely to give M/Mn values...but I guess we'll see.

 

[buening]

That's what I was thinking on the doubly symetric...tubes, W sections...the WT, Channels would be singly symetric.
On 525, I looked into the P/Pn from the tables, but it didn't give the correct answer. I meant to bring that book to work today to talk with someone over that problem, but I forgot it. I'll still see if I can describe it to him. Let you know what he says.

I thought about splitting my AASHTO up, but decided not to since I need the index to find most of it.

Yeah I got a different answer then them using the P/Pn, which was why I wondered if combining ASD axial stresses and LRFD moments ends up throwing things off a bit.

In Illinois we aren't supposed to break up the AASHTO manual, but I did it anyways. I'm bringing the enormous empty binder just in case they give me grief. I copied the index and put it at the end of each binder :beerchug:

 

[Jennifer]

Yeah I got a different answer then them using the P/Pn, which was why I wondered if combining ASD axial stresses and LRFD moments ends up throwing things off a bit.
In Illinois we aren't supposed to break up the AASHTO manual, but I did it anyways. I'm bringing the enormous empty binder just in case they give me grief. I copied the index and put it at the end of each binder :beerchug:

If you are combining ASD and LRFD, you will get the wrong answer...look at the tables. The LRFD values are significantly higher.

 

[Shaker-PE]

That's what I was thinking on the doubly symetric...tubes, W sections...the WT, Channels would be singly symetric.
On 525, I looked into the P/Pn from the tables, but it didn't give the correct answer. I meant to bring that book to work today to talk with someone over that problem, but I forgot it. I'll still see if I can describe it to him. Let you know what he says.

I thought about splitting my AASHTO up, but decided not to since I need the index to find most of it.

Oops, I think you're right about the doubly symmetric thing. I'm always hesitant to even post things because I hate to give out incorrect information. Regardless, good luck on your exams 10940623:

 

[Shaker-PE]

One more question for you guys.... number 538 in the NCEES SE1 book. I understand that the net area is defined in 2.3.3.3.1 as the least of the center to center bar spacing, 6 times nominal wall thickness, or 72 inches. That makes sense, but the area of the steel is shown on page 136 as 0.8 square inches. How do they get that number? It seems to me like it should be a #5 area at 0.31 square inches since we're taking the net width at 4 feet. Do you think I'm missing something or is it a mistake?

 

[Jennifer]

One more question for you guys.... number 538 in the NCEES SE1 book. I understand that the net area is defined in 2.3.3.3.1 as the least of the center to center bar spacing, 6 times nominal wall thickness, or 72 inches. That makes sense, but the area of the steel is shown on page 136 as 0.8 square inches. How do they get that number? It seems to me like it should be a #5 area at 0.31 square inches since we're taking the net width at 4 feet. Do you think I'm missing something or is it a mistake?

I'll check into this when I get home...I don't have that here with me.

 

[Jennifer]

I'll check into this when I get home...I don't have that here with me.

honestly I don't think the steel should be included at all in this problem. You can only include the steel in masonry axial design if it is tied. However, I got Pa=12831 for the masonry only and I used .31 for the Ast and got Ast=.31...getting Pa for the steel equal to 1027...total of 13859...not the answer in the book either way. But...if I run their numbers, it doesn't add up in my calculator either way. My way gets me close to the answer. Don't know what to tell you other than I don't agree with it either way

for the steel thing I was talking about see 2.3.2.2.1 and 2.1.6.5. It never says the steel is tied...but I guess if it doesn't...you are supposed to assume it is tied.

 

[Shaker-PE]

honestly I don't think the steel should be included at all in this problem. You can only include the steel in masonry axial design if it is tied. However, I got Pa=12831 for the masonry only and I used .31 for the Ast and got Ast=.31...getting Pa for the steel equal to 1027...total of 13859...not the answer in the book either way. But...if I run their numbers, it doesn't add up in my calculator either way. My way gets me close to the answer. Don't know what to tell you other than I don't agree with it either way
for the steel thing I was talking about see 2.3.2.2.1 and 2.1.6.5. It never says the steel is tied...but I guess if it doesn't...you are supposed to assume it is tied.

I see what you're saying as far as the code goes for compression steel with the lateral tie requirement. Unfortunately I can't find any other examples that show how to deal with strictly axial loads on reinforced walls using ASD design. I think I'm just going to trust that the example solution is mostly correct, except for the Ast part.

 

[Jennifer]

I see what you're saying as far as the code goes for compression steel with the lateral tie requirement. Unfortunately I can't find any other examples that show how to deal with strictly axial loads on reinforced walls using ASD design. I think I'm just going to trust that the example solution is mostly correct, except for the Ast part.

It's just a matter of leaving out the part of the equation that includes the steel. I don't know what to think on that. Yes, though...other than the Ast and the fact that when I punch in their numbers I don't get the same answer, I think they have done the problem correctly...i just have to question whether you should be using the steel.