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  • 1.  Concrete Question

    Posted 10-14-2018 09:04 AM
    Edited by Tirza Austin 10-14-2018 09:03 AM
    What its the difference between flexural and tensile modulus in concrete? And how these can be calculated?

    Praveen Anand S.M.ASCE
    Chennai TN

  • 2.  RE: Concrete Question

    Posted 10-15-2018 07:55 AM
    Edited by Tirza Austin 10-15-2018 07:54 AM
    The bending elastic modulus of the concrete is determined by the flexural strength of the concrete piece. Its application is in the design of concrete surfaces design.

    Ali Agakhanloo S.E., Aff.M.ASCE
    Civil Enginner
    (98)41347 5433

  • 3.  RE: Concrete Question

    Posted 10-15-2018 09:49 AM
    Edited by Tirza Austin 10-15-2018 09:49 AM
    For concrete, the elastic modulus is defined similarly with other materials even for steel. The larger difference is that the concrete has relatively very low tensile capacity. Most of the practical design of the concrete members, concrete tensile stress is considered to zero. This means the modulus in tension in not considered. When required for elastic analysis, the same value can be used for both compression and tension.

    For a concrete member, if it is simulated with 3D solid elements in elastic analysis. The elastic modulus, Ec, is used with poison's ration. The effects of reinforcement can be considered either by uniform contribution or independent frame elements. Due to its complexity of reinforced concrete, elastic model is normally impossible to have more accurate simulations.

    Flexural stiffness of a concrete member, frame or shell elements, is provided by I*Ec or D*Ec for frames or shells. For reinforced members, Ec is normally reduced by considering concrete cracks. Normally, on concrete in tension is considered.

    Yours Sincerely,

    Hengfeng Wang A.M.ASCE
    Struct Engr
    New York NY

  • 4.  RE: Concrete Question

    Posted 11-15-2018 07:04 AM
    Edited by Tirza Austin 11-15-2018 07:04 AM
    Dear Praveen, the flexural modulus corresponds to the tendency of a material to resist bending in a flexural test. Teorethically, if you perform a test according to ASTM C78 ("Standard Test Method for Flexural Strength of Concrete (Using Simple Beam with Third-Point Loading"), you have to derivate the flexural stress (sigma = M*(h/2)/Inertia for a rectangular section) and plot it against the corresponding longitudinal strain (dx/dL), epsilon. The flexural modulus will be the proportional constant of the equation sigma = E*epsilon. Nevertheless, for this test, is common to plot just M vs Theta (rotation).
    The tensile modulus for concrete is the tendency of the concrete to avoid elongation (slope for the plot of normal stress vs longitudinal strain). It is a quantity harder to determine because of the tests are mostly indirect (i.e. splitting test, flexural test), and the direct test has bias associated (e.g. grip failure). For practical effects, the E for the direct test should be the same for the flexural modulus, but I don't know if there is a study associated to those two measures (I am developing one regarding a new test to assess concrete tensile strength:



    Andres Guzman Ing., M.ASCE