Question Regarding Span

nicolas

Hi Everybody,

I am looking for an information regarding the recommended span between 150x150 RCC Columns reinforced with 4 Nos. Y 12 and having RCC Beams of the same section reinforced also with 4 Y12. The Stirrups are made up of Mild Steel Bars 6mm spaced 150mm. c/c. The whole is designed for a basement foundation+groundfloor level+first floor level with plinth area about 1500 square feet. How do you calculate the span? Supposed I increased the section of the columns/beams from 150x150 to 200x200, even increasing replacing the Y12 with Y16, how much then is the recommended span? The Flat RCC slabs are 125mm thick, grade 25, each.

Thank you in advance, a prompt and detailed answer will be much welcomed.

Nicolas.

Driftwood

And You're going to build it ,based on info on the net??

You need an Eng.

nicolas

Hi,

The usual normative span here is 3m from 150x150 columns or 200x200 columns reinforced with 4 nos. Y12mm dia. with stirrups made of R06 150 c/c. However, I am looking for a simplified exposition of span between columns/beam.

Thank in advance.

Nicolas.

concretemasonry

You really should have a local engineer look at precisely what you want.

There is the possibility that increasing the span could effect the slab thickness and reinforcement if you get to 4 meters or more.

When you have a concrete post and beam type structure, increasing the column or beam dimensions will also include increasing the finished wall thickness from the 150 (6") to 200 (8") unless you are willing the have exposed columns projecting.

If this is for residential use with many 3 to 4 meter spans, loadbearing concrete masonry would be very economical even up to 20 stories. - 150 mm (6" block) loadbearing block walls, no columns and 100m (4") or 125 mm (5") concrete slabs bearing on 4 sides. With this system, the lower level could be built with columns and beams, changing over to loadbearing masonry above (Brazil is the best example). - This is common in many other countries. Even with the weak masonry in India, it is common on the ground plus 3, 4 or 5 buildings.

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Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

nicolas

Hi,

Thank you for the answer provided. However it would be great if you can please help me a little understanding the meaning of load bearing wall. As far as I understand, all wall is more or less "load bearing" and the blocks that we use (100mm., 150mm., 200mm. different widths x 450 Long x 200 High) are hollow block. We sometimes infilled concrete within the 2-3 gaps provided to solidify it as well as putting a Y10 every 600mm in the blocks infilled with concrete.

Hope to hear from you.

Nicolas.

concretemasonry

What you describe would be a loadbearing wall. What load it will take depends on the strength of the block and construction methods. The mortar strength and grout strength have little to do with the compressive strength of the wall.

I have seem masonry construction in 37 countries, but not in yours and I have little knowlwdge of what the block manufacturing equipment and raw materials are, so I cannot comment on the strength. Making some assumptions, based on other similar areas, you may have some older European (probably German or older French) manufacturing equipment and have to deal with aggregates that are somewhat variable and not fully processed. This will produce a very adequate masonry unit, but may have some problems if you try to rely on getting the higher strengths seen in the U.S., South America and some areas.

You mentioned filling 2 or 3 gaps (cores?). If you used mortar, that helps little. If you used grout (much wetter with some stome up to 10mm), that would help on the strength.

I recognize that you have some local building methods that are acceptable and adequate. One you start changing dimensions and materials, you need assistance from an engineer since all parts of a building work together.

You do a lot with 150 mm (6") block if you have the right design AND construction techniques. - In south america, they can go 20 stories with 150 mm concrete masonry and NO steel or concrete columns.

An engineer could help you.

Good luck!!

Dick

__________________
Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.