Visit Concrete.Com

Visit Concrete.Com | Advertising | Contact Us | Concrete Calculators

Topic Options
#10258 - 05/06/01 03:50 PM Tensile Strength of "unreinforced" concrete
Matthew Offline
Junior Member

Registered: 05/06/01
Posts: 1
Loc: England
I am working at home on a little problem of assessing the affects of a dynamic load from a basement explosion (which I am treating as a quasi-static imposed force) on a concrete floor slab in a 1898 building. The explosion reverses the loading on the floor slab, so ineffect I am assessing it as unreinforecd, their is no steel in the top face. I will be grateful for some guidance on the likely tensile strength of one hundred year old concrete that gives an Fcu of 42-48 N/mm2 during on-site NDT. A response to would be even better and worthy of a big thank you!

#10259 - 05/14/01 12:46 PM Re: Tensile Strength of "unreinforced" concrete
bulldog Offline

Registered: 05/08/01
Posts: 79
Loc: San Antonio, Texas
The tensile strength, known as the modulus of rupture (fr), of concrete is low (typically 10-15% of compressive, and may vary depending on aggregates, etc.). The ACI Building Code (318) estimates the fr as 0.62 * square root of compressive strength (SI). The modulus of rupture (ASTM C-78 for 3rd point) may be tested and determined from the following: fr = Mc/I where M is moment, c is distance to extreme tensile fiber, and I is moment of inertia. The shear or moment capacity of a concrete beam should be determined by a structural engineer and requires some degree of judgement.