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

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 between 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.