Strength of Concrete Beams and Pipes at First Crack--A Strain Limit Design Method


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Title: Strength of Concrete Beams and Pipes at First Crack--A Strain Limit Design Method

Author(s): P. Aagren and N. L. Harrison

Publication: Journal Proceedings

Volume: 83

Issue: 1

Appears on pages(s): 156-161

Keywords: beams (supports); bend tests; concrete pipes; flexural strength; cracking (fracturing); limit design method; prestressed concrete; railroad ties; reinforced concrete; strains; strength; structural design; tensile strength.

Date: 1/1/1986

A method is developed for calculating the bending moment at first crack of concrete beams or in the walls of pipes, whether unreinforced, reinforced, or prestressed, taking into account the nonlinear stress-strain behavior of concrete in tension. The effect of the concrete in tension is characterized by the mean tensile stress in the tensile zone and a dimensionless factor that determines the location of its centroid. The method gives good agreement with experimental results and accounts quantitatively for long-standing anomalies in structural concrete design, namely, that the modulus of rupture of unreinforced concrete (that is, the tensile strength in bending) is always higher than the direct tensile strength and that the apparent tensile strength of concrete tends to increase as the level of reinforcement or prestress increases.