Effect of inclination on the strength of struts

In strut-and-tie modelling of structural concrete, the strength of a strut is known to be significantly influenced by its inclination with the adjoining ties. An inclination factor derived on the basis of strain compatibility which conservatively accounts for the effect of inclination on the strength of struts is proposed. The inclination factor takes the form of a linear scaling parameter and has been incorporated into the efficiency factor model suggested by the authors in an earlier study on the basis of isolated strut tests. This analytical investigation indicates that for strut inclination angles lower than 54°, the strength predictions in current design codes such as ACI 318-08 and Eurocode 2 could be unconservative. The apparent unconservatism with reference to ACI 318-08 is similar to the conclusion of an experimental investigation reported in the literature.