Effect of Separation Distance between the Columns on Punching Pattern for Flat Plates with High Strength Concrete

Hussein Al-Shammari, Abeer

	Effect of Separation Distance between the Columns on Punching Pattern for Flat Plates with High Strength Concrete
Journal of Engineering and Sustainable Development
Article 1, Volume 14, Issue 3, 2010, Pages 162-177
Author
Abeer Hussein Al-Shammari
Abstract
When a reinforced concrete slab is supported by coupled columns, these columns may behave as one column or as separated two columns according to the separation distance between them. Therefore, this study investigates the effect of separation distance of the columns on punching pattern for flat plates with high strength concrete and compares their results with other results of flat plates with normal strength concrete. Eight reinforced concrete slab specimens with coupled columns are cast with dimensions (length, width and thickness) equal to (850,470 and 50mm) by using a single high strength concrete mix with average compressive strength (f`c) that equals (55MPa) supported by coupled circular cross-section columns (diameter=85mm), these columns are located at the centerline of the slab in long direction; while in the short direction ,the positions of the columns are variable with respect to the centerline of the slab. However, the problem remains symmetric about the two axes. The specimens are tested over a simply supported span at four edges. The variable of this study is the clear distance between columns which takes the values (0.05 ,0.5 ,1 ,1.5 ,3 ,5 ,7 and 9)d ,where d is the effective depth. The test results show that ,the ultimate load reaches the maximum value when the clear distance between columns equals 9d and decreases by about (17.3 to 44.5) % of the maximum ultimate load when the clear distance between columns decreases from 7d to 0.05d .Also it is noticed that when the clear distance between columns is in the range (0.05d to 7d) ,the failure zone behaves as one zone; while when the clear distance between columns is equal to 9d , the failure zone separates into two zones. When the test results are compared with other results of flat plates with normal strength concrete(f`c=24MPa),it is concluded that ;when the concrete compressive strength factor ( )is increased by about 50% (f`c is increased from 24 to 55MPa),the ultimate loads increase by (16,17.5,20.7,21.4,31.67,31.74 and 32.84) % for the specimens from 0.05d to 9d respectively. So this study investigates the effect of separation distance of the columns on punching pattern for flat plates with high strength concrete.
Keywords
punching shear; flat plate; coupled columns; High Strength Concrete

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