Effect of arrangement of tensile reinforcement on flexural stiffness and cracking

• Beams with different arrangement of tensile reinforcement bars were tested.
• Number of reinforcement layers correlates with tension stiffening.
• Maximum crack opening and crack spacing do not necessarily correlate.

Due to the highly complex cracking behaviour of reinforced concrete structures, their design for serviceability is one of the most challenging tasks of engineering practice. Existing test data support a general inference that the deformation behaviour of concrete elements is affected by the arrangement of reinforcement in the tensile zone. Most of the current design approaches are based on the experimental data of laboratory specimens with simplified arrangement of the reinforcement. Consequently, the corresponding models are often inadequate to predict deformations and cracking of elements with non-conventional distribution of the bars. In the current study, the number of the reinforcement layers is found to correlate with the flexural stiffness. The paper also compares the crack width and crack spacing experimentally determined in the beams with different numbers of reinforcement layers. The results to some extent seem to be in conflict with the generally accepted concept relating crack widths to the cracking distances. Although the observed crack distances of the beams with three layers of bars were larger, their maximum crack openings were smaller than in the conventionally reinforced specimens with the same reinforcement ratio.

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