My only problem with this question was the LRFD vs ASD. I automatically go for LRFD. Other than that I don’t really rely on that reference for any structural questions. It has almost nothing in it. Anyway, thanks for the question!
I think the formula comes from ACI- SP-4 Table 7.1 p 7-5 ; but honestly can just use the 3 span formula with load across only 2 of the spans: Continous Beam - Three Equal Spans - One End Span Unloaded (this is in the civil reference manual and aisc (diagram 37)). It is so similar to the real 2 span one doesn't matter on test . 3 span = 1.20wL while 2 span = 1.25wl . The correct way to do it though using the AISC: TABLE 3-22C (CONTINUOUS BEAMS MOMENTS AND SHEAR COEFFICIENTS): You will see a equal span equally loaded uniform load table. You will notice a "number" "arrow up" "number" divided by a "number" in the shear visual part under the reactions. These are the shears at the reaction points (they can be different positive and negative directions). To get total reaction at that point you should be adding these shear numbers up then dividing by the number under it then multiplying vs wL. L should not be the total length of continuous beam, only the span. For example (using ^ as up arrow): 4 span beam has 17^15 /(28) from the table. Negative shear = 17/28 * w * L (span only) which matches the diagrams in table 3-23 btw. The positive shear at that point is also 15/28 * w * L. To get the reaction it is ((17+15) / 28) * w * L (span only). For example in the video: It is "5" arrow up "5" divided by 8 in AISC TABLE 3-22C. ((5+5)/8) * w * L = correct answer. It just so happened the shears at the mid point are equivalent so multiplying by 2 for total length it just worked out, but in other situations it will get wrong answer.
Hi Smoke - Really great explanation! The only additional context I'll add is that at 6:19 I state that the equation used from AISC table 3-22c is for equal spans and equal loading. this means that the reaction at mid point will always be 2 times the shear value from each span or just double the span length like I did - it shold get you the same thing every time, BUT it must be equal spans and equal loading. next time ill stick with 10/8wl instead of 5/8w(2l) - I made it confusing!
You can also use superposition i.e. take the value of (5/8)wl which is given in the reference book for R2 and multiply it by 2 to account for the adjacent span, which is basically the same formula you showed.
I spoke with NCEES in my state and they said depending on your depth is what you will be given for references. Structural and Construction. If you are Water, Geotechnical, or Transportation you will NOT have access to these resources and only the Design Standards provided by NCEES for that specific depth. I would email or chat with your state board to verify this as well just to get full clarification.
Jeffrey this is really great info! I'll give them a call and see what the deal is. I had no idea that some test takers may not get the reference manual.
@@Kestava_Engineering everyone will have the pe reference handbook, but not AISC, ACI, NDS etc. Is what I was told. For example, water will have the three references, PE Handbook and the two references they have now, transportation will have pe reference and their depth reference, structural pe reference and their respective depth references, etc.
Hopefully the breadth and depth portions will contain questions appropriate for what is provided... if the question in the video was in the breadth section of a water exam, which will not have the steel manual reference, that would be concerning. Likewise for any water questions that require our standards ending up on a structural exam's breadth portion.
@@Jeff29E6 spoke to ncees and confirm what you have stated here. i am water and will have 3 refs. already got them in pdf and am learning to search them efficiently.
Thanks so much for pointing it out. I do not know really why they this kind of Manuel . They have elaborated slot on water section and geotechnical that what required in addition they have taken out the import part of construction and structures . What is your opinion?
I'm taking the computer based exam in october. a little worried about everything being computer based. Mainly worried about not being able to tab anything. Any tips on how to overcome this? Or should I plan on just remembering where to look and searching certain keywords?
yeah this is a tough one. its like a whole new strategy - I would start creating a list of keywords and cross check it with your paper codes that your studying from.
very good point Jefe. Just wanted to point out that the reference manual doesnt include things like that, where as a typical paper back reference manual traditionally has a lot more info
Thanks. However, I don't see any equation for continuous beam - Two equal spans - distributed load in AISC. The 5wl/8 is for when the load is on only one span!
Look at Table 3-22c. Moment and shear coefficients are given for continuous beams with equal spans uniformly loaded. Refer to the two span beam figure (its the second beam from the top). From there on you can get the reaction at mid support = 5wl/8 + 5wl/8 = 10wl/8 where l = 5ft for this question. Hope it helps.
Excellent, I feel this way with geotech that some statistical factors are referenced somewhere else and you have to know them by memory or know how to get them somehow
I assume that the PE reference manual thought you would use superposition for the load case where one span has weight and the other doesn't. By using superposition you would get an R2 of 5/4*w*L where w is as calculated and L is 5 ft giving the same answer.
started seeing discrepancies in my old paper/pen notes for water and the ncees hb 1.1. there are items which are missing in ncees hb 1.1. i think that this is fine AS LONG AS you make the hb 1.1 your bible and know what IS in it and what is NOT. study it assiduously. you cannot be allowed to become surprised, to be knocked off your feet during a time which is naturally already stressful. make it your best friend by practicing w it constantly. good luck!
Hi Rich! Thanks for great content. Are you familiar with sfrc desings? If so, it would be good subject for a video. Ps. Hieno nimi ja logo! Greetings from Finland.
JaffFree im seeing that sfrc is steel fiber reinforced concrete? I have used this system before back in massachusetts for a slab and have watched a few lectures on the subject but im not the most well versed. Is that becoming big in Finland?? and kiitos!
Yeah thats what I ment. I think sfrc is becoming more and more popular all around the world and in many different structures, so it would be nice to hear how did the structures turn out etc. experiences in general.
Result is correct, but I believe L=5, then it has to be multiplied by 2. Refer to 39 on Table 3-23 on AISC 15th edition (RB=1.1wl= 0.500wl+0.600wl). Hope someone can confirm. Amazing content btw!
Could have used the virtual work method to solve for the unknown reaction, in the lieu of having to search through the steel manual. good content however!
My only problem with this question was the LRFD vs ASD. I automatically go for LRFD. Other than that I don’t really rely on that reference for any structural questions. It has almost nothing in it.
Anyway, thanks for the question!
I think the formula comes from ACI- SP-4 Table 7.1 p 7-5 ; but honestly can just use the 3 span formula with load across only 2 of the spans: Continous Beam - Three Equal Spans - One End Span Unloaded (this is in the civil reference manual and aisc (diagram 37)). It is so similar to the real 2 span one doesn't matter on test . 3 span = 1.20wL while 2 span = 1.25wl .
The correct way to do it though using the AISC: TABLE 3-22C (CONTINUOUS BEAMS MOMENTS AND SHEAR COEFFICIENTS): You will see a equal span equally loaded uniform load table. You will notice a "number" "arrow up" "number" divided by a "number" in the shear visual part under the reactions. These are the shears at the reaction points (they can be different positive and negative directions). To get total reaction at that point you should be adding these shear numbers up then dividing by the number under it then multiplying vs wL. L should not be the total length of continuous beam, only the span.
For example (using ^ as up arrow): 4 span beam has 17^15 /(28) from the table. Negative shear = 17/28 * w * L (span only) which matches the diagrams in table 3-23 btw. The positive shear at that point is also 15/28 * w * L. To get the reaction it is ((17+15) / 28) * w * L (span only).
For example in the video: It is "5" arrow up "5" divided by 8 in AISC TABLE 3-22C. ((5+5)/8) * w * L = correct answer. It just so happened the shears at the mid point are equivalent so multiplying by 2 for total length it just worked out, but in other situations it will get wrong answer.
Hi Smoke - Really great explanation! The only additional context I'll add is that at 6:19 I state that the equation used from AISC table 3-22c is for equal spans and equal loading. this means that the reaction at mid point will always be 2 times the shear value from each span or just double the span length like I did - it shold get you the same thing every time, BUT it must be equal spans and equal loading. next time ill stick with 10/8wl instead of 5/8w(2l) - I made it confusing!
@@Kestava_Engineering ahhh gotcha. Thanks for content btw, good stuff =]
You can also use superposition i.e. take the value of (5/8)wl which is given in the reference book for R2 and multiply it by 2 to account for the adjacent span, which is basically the same formula you showed.
Very helpful. I will say those continuous span tables like the tables from the steel manual are also in the PE reference manual.
I spoke with NCEES in my state and they said depending on your depth is what you will be given for references. Structural and Construction. If you are Water, Geotechnical, or Transportation you will NOT have access to these resources and only the Design Standards provided by NCEES for that specific depth. I would email or chat with your state board to verify this as well just to get full clarification.
Jeffrey this is really great info! I'll give them a call and see what the deal is. I had no idea that some test takers may not get the reference manual.
@@Kestava_Engineering everyone will have the pe reference handbook, but not AISC, ACI, NDS etc. Is what I was told. For example, water will have the three references, PE Handbook and the two references they have now, transportation will have pe reference and their depth reference, structural pe reference and their respective depth references, etc.
Hopefully the breadth and depth portions will contain questions appropriate for what is provided... if the question in the video was in the breadth section of a water exam, which will not have the steel manual reference, that would be concerning. Likewise for any water questions that require our standards ending up on a structural exam's breadth portion.
@@Jeff29E6 spoke to ncees and confirm what you have stated here. i am water and will have 3 refs. already got them in pdf and am learning to search them efficiently.
Thanks so much for pointing it out. I do not know really why they this kind of Manuel . They have elaborated slot on water section and geotechnical that what required in addition they have taken out the import part of construction and structures . What is your opinion?
I'm taking the computer based exam in october. a little worried about everything being computer based. Mainly worried about not being able to tab anything. Any tips on how to overcome this? Or should I plan on just remembering where to look and searching certain keywords?
yeah this is a tough one. its like a whole new strategy - I would start creating a list of keywords and cross check it with your paper codes that your studying from.
Do you have the steel maul available to you during the computer-based PE exam?
It's not allowed.
AISC is provided on the exam so all of the beam equations are there...
very good point Jefe. Just wanted to point out that the reference manual doesnt include things like that, where as a typical paper back reference manual traditionally has a lot more info
We could still use the PE reference manual by using supersposition, since it is symmetric. Just assume another udl on the right span
Thanks. However, I don't see any equation for continuous beam - Two equal spans - distributed load in AISC. The 5wl/8 is for when the load is on only one span!
Look at Table 3-22c. Moment and shear coefficients are given for continuous beams with equal spans uniformly loaded. Refer to the two span beam figure (its the second beam from the top). From there on you can get the reaction at mid support = 5wl/8 + 5wl/8 = 10wl/8 where l = 5ft for this question. Hope it helps.
Thank you for sharing good explanation! can you share some examples for Geotechnical depth foundation design?
Was their intent with not including that diagram to see if you know how to use superposition?
likely the case.
don't you need to multiply 5/8 by 2 for being equal shear on both side of the support?
Excellent, I feel this way with geotech that some statistical factors are referenced somewhere else and you have to know them by memory or know how to get them somehow
I assume that the PE reference manual thought you would use superposition for the load case where one span has weight and the other doesn't. By using superposition you would get an R2 of 5/4*w*L where w is as calculated and L is 5 ft giving the same answer.
You can find Rb=1.25wl in ACI SP-4 Table 7.1
started seeing discrepancies in my old paper/pen notes for water and the ncees hb 1.1. there are items which are missing in ncees hb 1.1. i think that this is fine AS LONG AS you make the hb 1.1 your bible and know what IS in it and what is NOT. study it assiduously. you cannot be allowed to become surprised, to be knocked off your feet during a time which is naturally already stressful. make it your best friend by practicing w it constantly. good luck!
very nicely put
Hi Rich! Thanks for great content. Are you familiar with sfrc desings? If so, it would be good subject for a video. Ps. Hieno nimi ja logo! Greetings from Finland.
JaffFree im seeing that sfrc is steel fiber reinforced concrete? I have used this system before back in massachusetts for a slab and have watched a few lectures on the subject but im not the most well versed. Is that becoming big in Finland?? and kiitos!
Yeah thats what I ment. I think sfrc is becoming more and more popular all around the world and in many different structures, so it would be nice to hear how did the structures turn out etc. experiences in general.
Where do I find the LRFD load cases? I usually use AASHTO LRFD Table 3.4.1-1
Result is correct, but I believe L=5, then it has to be multiplied by 2. Refer to 39 on Table 3-23 on AISC 15th edition (RB=1.1wl= 0.500wl+0.600wl). Hope someone can confirm. Amazing content btw!
I'm not finding the diagram for 2 span with a uniform load all the way across in the steel manual either.
Hi Christiane - I use the 14th edition and have them available in Table 3-22c page 3-212, does the 15th edition not have this anymore???
@@Kestava_Engineering The 15th edition does not include this diagram unfortunately. Only has the one that you showed in the reference manual.
Could have used the virtual work method to solve for the unknown reaction, in the lieu of having to search through the steel manual. good content however!
Great suggestion!
You need to disturb the loads triangle and trapezoidal
Thank you Rich
Damn, I thought the answer was D
Me too….I still feel like it is 😅
You are doing wrong !!!
Then what is the right way to do it????