Strength and deformability under short-term static load

Analytical models of cement-based composite materials were initially based on the theory of elasticity with additional simplifying assumptions. The following notions were applied  

That system is neither coherent nor experimentally verified, but it is simple enough for large applications and safe enough when combined with an imposed system of safety coefficients. These coefficients help to keep structures and elements made of concrete-like composites far away from ultimate states. Therefore, the inconsistencies of the system are only taken under consideration when they become unacceptable for various reasons for example, stress concentrations, structure of ITZ, etc. 

A compressive concrete strength may be examined as an example of such inconsistencies. According to the rules that have been established since the beginning of the twentieth century, the compressive strength was tested on specimens of various shapes and dimensions, always subjected to axial compression and calculated assuming that stress was distributed uniformly over the cross-section and that its value corresponded to the failure of the specimen. The main discrepancies between such procedures and reality are  

2 Nobody ever has seen a concrete specimen loaded by an axial compression 

Another simple example is the direct tension test in which the load is again divided by the cross-sectional area, even though it is well known that a failure at tension is initiated at the weakest point, e.g. an initial crack or other defect. 

---

Strength and deformability under short-term static load... 

Strength and deformability under short-term static load Table 8.1 Directional efficiency coefficient for short fibres... 

---