几何尺寸与公差论坛------致力于产品几何量公差标准GD&T (GDT:ASME)|New GPS(ISO)研究/CAD设计/CAM加工/CMM测量  


返回   几何尺寸与公差论坛------致力于产品几何量公差标准GD&T (GDT:ASME)|New GPS(ISO)研究/CAD设计/CAM加工/CMM测量 » 三维空间:产品设计或CAX软件使用 » CAD设计 » 产品功能分析
用户名
密码
注册 帮助 会员 日历 银行 搜索 今日新帖 标记论坛为已读


 
 
主题工具 搜索本主题 显示模式
旧 2009-09-10, 03:17 PM   #1
huangyhg
超级版主
 
huangyhg的头像
 
注册日期: 04-03
帖子: 18592
精华: 36
现金: 249466 标准币
资产: 1080358888 标准币
huangyhg 向着好的方向发展
默认 most economical reinforced concrete beams and columns

most economical reinforced concrete beams and columns
i have a question guys. is there any combination of f'c and fy that would give the most economical section and reinforcement for reinforced concrete beams and columns? if not, how to design the most economical beams and columns for multi-storey buildings? what are the factors to be consider?
f'c and fy don't affect the economy that much - in fact usually in the us you have f'c = 4000 psi and fy = 60,000 psi on the steel. sometimes higher f'c values are specified, especially for columns.
the economy in concrete construction is usually affected more by the beam depth, beam/joist spacing, slab thickness, forming layouts of beam widths, etc. than the material strengths.

my approach is to use the same size columns as much as possible, limit the reinforcement quantity to 1% or a little more, and adjust the concrete strength according to the load. in australia, we customarily use concrete strengths of 32, 40, 50, 60, and 70 mpa for building columns. beams and floor slabs are normally 32 or 40 mpa.
rlc32681,
you must be a student, otherwise you would most likely realise that this is not a meaningful question. no offence intended.
steel and concrete are both only available at certain grades.
a higher steel stress grade would be of advantage for strength but would be no help for deflection/shrinkage. it therefore often does not make much difference on the overall steel volume.
concrete grades tend to be dictated by a other considerations such as durability.
material costs are only about a third of the total cost for concrete construction. at best you could shave 5 or 10% off the material costs it would be much more productive to focus your efforts on constructability where potentially larger savings can be made.
thanks for your opinion guys, but i have a follow-up question. assuming i am free to choose the sizes of the beams and columns, that is no predefined sizes as dictated by architectural considerations, how is the procedure to yield the most economical reinforced concrete beams and columns. most economical considering cost (materilas, labor, equipment.
rlc,
sounds like the same question to me. i suggest you get this type assistance from your mentor. consulting engineering firms typically have guidelines for preliminary design.
csd,
i think it is a valid and meaningful question. however, he may be a student, as this is his first post.
rlc32681,
apologies for my very opinionated post.
column sizes are generally dictated by fire rating requirements with a minimum size of 300mm(1 foot) being the minimum that i would recommend for any column due to compacting and detailing issues.
the actual cost of the columns is not really an issue (generally being only 1 or 2% of most projects) but the loss of usable space often is. for this reason most columns are kept as small as possible.
for taller buildings the concrete strength is generally the issue, so you should keep it as small as possible using standard strength grades even if the lower columns are at a different strength than the upper ones. i would only use high strength concrete where necessary.
hope this helps.
i agree that cost of column is negligible as compared to the total cost but my concern why asking how to design the most economical rc column and beam is that i am comparing what kind of structural frame (whether reinforced concrete or steel) to used in multistorey frame. i am given a task to make a study what kind of framing system (either steel and reinforced concrete) to use in multi storey building. i have in mind 3 criterion; 1. cost 2. construction time frame and 3. story drift. i am planning to compare these by considering a model structural frame and design it using reinforced concrete and steel and compare base on the criterion above. any comment is highly appreciated.
can you describe the project in more detail? how many stories, is it in a high seismic area? what location is it in as this might affect the relative economies of concrete vs. steel (some areas have more concrete frames than steel due to lower labor costs, etc.).

worth a read:
i am currently doing some preliminary design research this just happens to show up, not perfect some good points
__________________
借用达朗贝尔的名言:前进吧,你会得到信心!
[url="http://www.dimcax.com"]几何尺寸与公差标准[/url]
huangyhg离线中   回复时引用此帖
GDT自动化论坛(仅游客可见)
 


主题工具 搜索本主题
搜索本主题:

高级搜索
显示模式

发帖规则
不可以发表新主题
不可以回复主题
不可以上传附件
不可以编辑您的帖子

vB 代码开启
[IMG]代码开启
HTML代码关闭

相似的主题
主题 主题发起者 论坛 回复 最后发表
effective width of concrete flange with radial steel beams huangyhg 产品功能分析 0 2009-09-08 09:44 PM
designing columns for concrete buildings huangyhg 产品功能分析 0 2009-09-08 06:12 PM
demolition of 5-story reinforced concrete building huangyhg 产品功能分析 0 2009-09-08 05:07 PM
coninuous steel beams over columns huangyhg 产品功能分析 0 2009-09-08 01:09 PM
chapter 4 preliminary design properties of concrete huangyhg 产品功能分析 0 2009-09-07 11:23 PM


所有的时间均为北京时间。 现在的时间是 08:01 AM.


于2004年创办,几何尺寸与公差论坛"致力于产品几何量公差标准GD&T | GPS研究/CAD设计/CAM加工/CMM测量"。免责声明:论坛严禁发布色情反动言论及有关违反国家法律法规内容!情节严重者提供其IP,并配合相关部门进行严厉查处,若內容有涉及侵权,请立即联系我们QQ:44671734。注:此论坛须管理员验证方可发帖。
沪ICP备06057009号-2
更多