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-   -   reinforced concrete building design step-by-step (http://www.dimcax.com/hust/showthread.php?t=27912)

huangyhg 2009-09-15 05:12 PM

reinforced concrete building design step-by-step
 
reinforced concrete building design step-by-step
hello,
what book(s) would you recommend for learning the design process (emphasis on "designfff">") of low-rise/mid-rise reinforced concrete buildings?
for example, after the architect hands me the typical plan view of, say, a 6-story building and asks me to design the structure (see picture for illustration purposes, not from a real project)fff"> ... where do i begin?
in other words, what is the thought process that seasoned/senior structural engineers apply to arrive at the most satisfactory structural design?
how do they perform load analysis to begin with? how conservative is this process? how many combinations are tested? e.g. for a 3-span beam: loaded-loaded-loaded -or- loaded-loaded-unloaded -or loaded-unloaded-unloaded etc. etc.
secondly, how do they choose the locations, dimensions and thicknesses of all the elements that comprise the structure, namely footings, internal columns, edge columns, beams and slabs?
thirdly, what are the criteria for the design and inclusion (or not) of:
bracing: why/where/when and how ?
shearwalls: where and how many of them? when does wind start to be a concern? lateral forces... how do designers deal with wind/drift/vibrations?
fourthly, what is the common practice with regards to continuity in concrete elements? what's the relevance of workmanship in this decision? do they design the concrete skeleton as a framed structure or as a myriad of column-supported continuous beams with neglegible to null moment transmission at edge columns? what consideration is given to foundations settlement and the impact (read: cracking) on neighboring buildings?
fifthly, how do they do the detailing? manually? or is it computer-assisted? if so, what software do they use for detailing?
how do they choose as/ac for the concrete members? what's the tipping point that makes as/ac non-viable (read: anti-economic) and signals the designer to increase ac?
and last but not least, what are the things to watch out in a structural design? what can go wrong? what are the pitfalls to avoid?
this is what i don't want.
i don't want math-bloated volumes aimed at teaching structural analysis. i also don't want books that dissect the latest and greatest construction codes.
i want a book (or books) targeted at the practicing engineer, written with a "from mentor to mentoreefff">" spirit, aimed at teaching the timeless and code-immune(*)fff">fff"> craftfff"> that is the structural design of reinforced concrete buildings. the content should be straightforward and practical, preferably with worked and commented end-to-end examples.
can anyone give me a pointer or two?
thanks.
(*)fff">fff"> except for live load selection.

check out our whitepaper library.
design from the top down. make a list of loadings applicable to this structure. design roof, roof beams, top floor columns, top floor, top floor beams, etc. to the foundation. get approval from the architect and go back to detail all connections and the bracing systems. check original load assumptions with the now firm dead load calcs to see if you need to redo anything.
i don't know that such a book exists. university courses and textbooks deal with the technical issues, analysis, etc., but not how to be a structural engineer. i had to learn by working under experienced engineers, attending technical workshops, and reading whatever seemed applicable. always keep an open mind and don't accept advice that at first seems incorrect without thoughtful consideration.
good luck, and if you do find a book such as you described, let us all know.
hokie66 is right. the reason engineering is a professionfff"> and not a jobfff"> is that you just don't read it in a book and then do it.
apprenticeship is necessary.
that said, the steps i've done, in general, for concrete structures would be something like this:
1. as with any structure, conceptually determine the type of concrete system that best meets the layout, size, budget, fire-protection, loading,and expected durability.
2. with a framing concept in hand, do some preliminary sizing calculations to set structure depths and verify that the concept will adequately support the loads and meet serviceability criteria.
3. draw out the framing for each level.
4. identify joist or beam "runs" as i call them. these are individual lines of continuous joists or beams that share common spans and loadings.
5. for joists and beams, i usually do a continuous beam analysis using alternating live loads (live on even spans, ll on odd spans, ll on adjacent spans - three types, and ll on all spans.)
6. design the reinforcing for these beam runs.
7. for columns that are not part of the lateral force resisting system, do the design and detail them.
8. identify which beams might participate in lateral resistance (for moment frames) and create models to analyze the overall building for wind and seismic.
9. design the reinforcing for the lateral system beams and columns.
10. design any shearwalls that are used.
11. for beams acting as collectors, re-design with added tension or compression forces and supplement the reinforcement accordingly.
12. for unique situations, floor openings, special concentrated loads, floor drops, ramps and stairs, provide design efforts on these special areas and adjust supporting beams and columns as necessary.
12. design the footings.
i'm sure i left out some steps but this is a snapshot of what i've done. also, there may be times when you must iterate the design due to changing conditions, too-shallow depths, etc.
but i'd agree there is no book out there that will do you justice. the best "book" is one with skin, a pocket protector, and an old hp calculator that can teach you the concepts, teach you the pitfalls, and teach you how to respond to special extraordinary challenges....i.e. a good mentor.

jae's list is good, but somewhere along the way, when you are confident that your system will work, share it with the architect. don't take the chance of doing all the work and having to start over for some reason. projects normally evolve: schematic design, preliminary design, final design.
oh yes...good point.
thanks everybody for sharing insights.
i understand the value of good mentorship. unfortunately that has been elusive in my case. and like me, many many others.
it's somehow unfair that the professional growth for an (aspiring) structural engineer is sofff"> dependant on the availability of a resource that he cannot control: mentorshipfff">.
other professions put personal development mostly in the hands of the individual, not so much on third parties.

and last of all, especially for someone in your position, pay someone else who really does know what he is doing to check your work.
fa2070,
i share your concerns deeply about the availability of mentoring. many firms do a good job of leading young engineers through their apprenticeship, but unfortunately it is not universal. some posts on this forum seem almost in despair for help.
in your case, it may be a struggle, but you will prevail. the reason for my confidence is that you have the ability, as evidenced in this discussion, of formulating a systematic approach to a problem. solving the problem is the easy part.
i agree with mentoring, good mentoring is not universal and i would say that my assigned "mentors" didn't care about my career development (or their own professional development). i have the mindset to make sure when it becomes my turn to mentor, i am going to do a damn good job at it.
always consider patterned loading, i see too many guys not considering patterned loading in there designs.
actually do some design during the schematic and preliminary design phase. i had the task of completing a detailed design for a job where the senior engineer had a "gut" feel of what the sizes should be and they were way off.
set out the column grids and span lengths based on punching shear and deflection calculations during the preliminary design. if you consider these two aspects early, the design should go together smoothly.
if there is a bible of engineering out there with all the answers in it, then i haven't found it yet (pardon the christian reference). you need to accumulate a library of texts, papers, design aids, other technical info, notes from workshops, user manuals and professional relationships for your design expertise.
i think when you encounter one specific problem, you should throw the question up on eng-tips, someone will help you out.
fa2070 i feel your pain.
i agree there are no books describing the building engineering design & detailing process. i didn't get a lot of help coming out of school. i also looked for books, found some but nothing like you are looking for. i found that getting a complete set of drawings (str&arch) from a completed job that someone you trust in you firm has done in the recent past. i would take them home and study them to make sure you understood where every line & word on every plan & detail came from. feel free to ask questions from the original designer. also once you understand the complete set, see how you would approach the design. also try to see if you can improve any aspects of the design, there is no perfect job. i did this several times my first five years as a design engineer. it worked for me.


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