The design of detailing in discontinuity regions plays a crucial role both for the structure behaviour and for its safety [1,2]. The stress flow in the so-called D-regions, where the strain distribution over the cross-section is significantly non-linear, is well described by strut & tie model. In this work the behaviour of Steel Fiber Reinforced Concrete (SFRC) in a D-region has been investigated. The experimental program refers to the bottle-shaped stress field, that develops significant transverse compressive and tensile stresses, respectively in the bottle neck and far away along the vertical symmetry axis (bursting). The distribution of the high local stresses under the bearing plate causes transverse tensile stresses also along the horizontal upper border, there inducing concrete cracking (spalling). The experimental tests were performed on thin square slabs (270 x 270 x 60mm) made of either SFRC or plain concrete. One fiber type (hooked –end, low-carbon steel, lf = 60mm, df = 0.80mm) and one fiber content (25 kg/m3) were investigated. A uniform vertical displacement was imposed on the top region characterized by a variable depth. Several ratios  (1, 1.5, 2, 2.5 and 3) between the specimen size and the bearing plate width were considered for both SFRC and plain concrete specimens, with the only exception of  = 2.5 for the latter material. The analysis of crack propagation highlights some limits concerning the generally accepted assumptions for the bearing capacity design of these zones and allows us to quantify the related fiber benefits.

Steel-fiber role in the D-regions

COLOMBO, MATTEO;DI PRISCO, MARCO
2005-01-01

Abstract

The design of detailing in discontinuity regions plays a crucial role both for the structure behaviour and for its safety [1,2]. The stress flow in the so-called D-regions, where the strain distribution over the cross-section is significantly non-linear, is well described by strut & tie model. In this work the behaviour of Steel Fiber Reinforced Concrete (SFRC) in a D-region has been investigated. The experimental program refers to the bottle-shaped stress field, that develops significant transverse compressive and tensile stresses, respectively in the bottle neck and far away along the vertical symmetry axis (bursting). The distribution of the high local stresses under the bearing plate causes transverse tensile stresses also along the horizontal upper border, there inducing concrete cracking (spalling). The experimental tests were performed on thin square slabs (270 x 270 x 60mm) made of either SFRC or plain concrete. One fiber type (hooked –end, low-carbon steel, lf = 60mm, df = 0.80mm) and one fiber content (25 kg/m3) were investigated. A uniform vertical displacement was imposed on the top region characterized by a variable depth. Several ratios  (1, 1.5, 2, 2.5 and 3) between the specimen size and the bearing plate width were considered for both SFRC and plain concrete specimens, with the only exception of  = 2.5 for the latter material. The analysis of crack propagation highlights some limits concerning the generally accepted assumptions for the bearing capacity design of these zones and allows us to quantify the related fiber benefits.
2005
Construction Materials
9780888658104
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11311/535706
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