Therefore, the self-stressing concrete-filled steel tubes (SSCFSTs) were proposed as they have higher axial strength than CFSTs.
This paper gives a theoretical model for obtaining the axial compressive capacity of FCFSTs, in which the effect of self-stressing was considered.
Since the concrete in the steel tube is under triaxial compression, the axial compressive strength of concrete [[sigma].sub.cl] which considered both the self-stressing and axial compression can be expressed as 
where [f.sub.ck] is the standard compressive strength of the concrete, or the lateral pressure of the concrete, [[sigma].sub.cr] the lateral stress of the concrete core caused by axial compression, [[sigma].sub.ss] the initial lateral stress caused by expansion of the self-stressing concrete, and k the lateral stress coefficient.
[[sigma]'.sub.st] is the hoop tensile stress of steel tube that caused by self-stressing and [f.sub.y] is the yield strength of the steel tube.
Parametric analysis was performed to investigate the effects of the number of FRP layers and the self-stressing on the axial compressive capacity.
Figure 3 plots the axial compressive capacity versus self-stressing level of the filled concrete.
Theoretical study was presented to predict the nominal axial compressive strength of FCFSTs, in which the effect of self-stressing concrete was considered.
Correlation is not necessarily causation, though - other factors associated with being Type A, like smoking and having high cholesterol, could be the key, rather than the Type A's self-stressing
Kikas and coworkers  studying the influence of OSA on the properties of self-stressing shale ash cement concluded that the concrete made with burnt shale possesses high strength, high frost resistance, and low permeability.
Influence of ash content of Kukeriste oil shale on the properties of self-stressing shale ash cement.