I'm wondering Hand Calculation 2

[envc77]

First of all, I'm sorry that i can't speak english very well. I hope you to understand me.
I have done structural engineeing(mainly bridges) for about five years.
when i seen this forum, there are a lot of people say hand calculation is important.
I wnat to do calculation because my job was mainly to draw structures.

I think the calculation is to run special software.
I surprise that to do pre-design is possible by only hand.

And. I'm very wondering how to do hand calculation.

I would appreciate that you give me any suggestion or how to do hand cals.

 

[csd72]

envc77,

It concerns me that you may have been using spreadsheets to design things without understanding the theory behind it. As engineers is is critical that we not only know, but also that we understand.

If you have forgotten how to do hand calculations since university then this is not really the place to learn. The issue is far too complex and long winded to learn over a forum.

I would suggest that you obtain some good texts on the subject and go from there. What codes are you using?

csd

 

[KENAT]

envc77 as part of your bachelors did you not do basic stress analysis /statics/structure? Things like bending of a beam, Second Moment of Area, stress = Force/Area, Moores Circle etc. Classic linear static analysis is perhaps the term.

When people talk about doing hand calcs this is the kind of stuff they mean. There are books etc that give developed equations based on these, Roarkes is a big one for Mechanical, not sure for civil/structural.



KENAT, probably the least qualified checker you'll ever meet...

 

[KENAT]

Thinking about it part of the problem may be the language barrier and the OP just doesn’t know what we mean by hand calculations. We basically mean classical methods as I started explaining above.

The below may help a little.

http://www.ce.ufl.edu/~kgurl/Classes/syl_stsp03.pdf

http://www.chalice-engineering.com/Analysis_Basics/Stress_analysis.html

KENAT, probably the least qualified checker you'll ever meet...

 

[Gymmeh]

Free body Diagrams?
Ex. Simple supported beam
1/2L 1/2L
-------------------------
| ^ ^
V | |
F R1 R2

F=1000kg
R1=?
R2=?
Fx=R1+R2-F=0
MR2= F*L-R1*1/2L =0

 

[Gymmeh]

forgot one thing
L = 2m

 

[whyun]

envc77, GIGO.

If this doesn't ring a bell, Google the word. Ability to do hand calcs (rough analysis) to approximate the final design before using the computer software (refined analysis) is essential.

 

[envc77]

I didn't know meanning of han cals.
Just now I understand
From now, I will try to resolve my works by hand and read many books.

 

[shin25]

An engineer using a computer software without knowing the principle and theory behind it is, a quack treating a patient without knowing a single thing about the diseage.

 

[Kwan]

Shin, I give you a star for a great response.

Suppose the software analyzes pinned joints. However, the design has fixed joints. Garbage in, garbage out.

 

[Ussuri]

http://www.imbsen.com/Midas.htm

I guess this is the software you use to design your bridges. From the sales pitch it looks like a pretty useful package with a number of fairly advanced features.

You stated you spend 70% of your time drawing the bridge and only 30% doing the calcs. You didn't say however, if it is small bridges or really long span, multi million dollar, suspension bridges.

I would make sure I was up to speed with the process the package uses for each of the different aspects of the design. Only then can you be sure the package is doing what you think it is doing.

 

[csd72]

envc77,

I think what you refer to as 'hand calcs' is more what we refer to as 'preliminary design'.

Each person has their own methods of this based on experience.

The key is to take note of what usually controls the design for a particular type of structure and do a quick calculation based on this to get your preliminary size.

csd