RF-CONCRETE Members – Online Manual Version 5

Online manuals, introductory examples, tutorials, and other documentation.

RF-CONCRETE Members – Online Manual Version 5

Switch to Fullscreen Mode Exit Fullscreen Mode

2.4.3.1 Model: Tensile Strength of Concrete

Model: Tensile Strength of Concrete

This model that is used to determine the effectiveness of concrete on tension between cracks is based on a defined stress-strain curve of concrete in the tension zone (parabola-rectangle diagram). The mathematical tensile strength is no fixed value but refers to the given strain in the governing steel (tension) fiber. The approach has been taken up in accordance with the specifications in [7] to the effect that the maximum tensile strength fctR decreases linearly to zero, starting at the defined crack strain until a yield strain εsy is reached in the governing steel fiber.

In several research projects (i.a. [8]), efforts were made to refine or modify the approach of Quast and adjust it on the basis of evaluated experiments.

The following figure illustrates the schematic approach.

Figure 2.23 Calculation of residual tensile strength for Tension-Stiffening model according to Quast

The parabola-rectangle diagram for the tensile zone is determined according to the following formal relations:

fct,R = αred · fct,grund

v = fctfct,R 

εcr = εc1v 

nct=1.05·Ectm·εcrfct,R

σct = fct,R · εsy - εs2εsy - εcr        mit  εcr  εs2  εsy 

where

    • αred : reduction factor of basic value of tensile strength
    • fct,basic : basic value of tensile strength (e.g. fctm)
    • fct,R : calculational tensile strength
    • v : ratio of compressive to tensile strength
    • εcr : calculational strain when fcr,R is reached
    • nct : exponent of parabola in tension zone
    • σct,R : calculational stress depending on governing strain of steel fibre
    • εsy : calculational yield strain
    • εs2 : strain of governing steel fiber
Literatur
[7] Deutscher Ausschuss für Stahlbetonbau (Hrsg.) Heft 415 – Programmgesteuerte Berechnung beliebiger Massivbauquerschnitte unter zweiachsiger Biegung mit Längskraft. Beuth Verlag GmbH, Berlin, 1990.
[8] Pfeiffer, Uwe. Die nichtlineare Berechnung ebener Rahmen aus Stahl- oder Spannbeton mit Berücksichtigung der durch das Aufreißen bedingten Achsendehnung. Cuviller Verlag, Göttingen, 2004.

Quick Overview of this Section