Buckling resistance of equal-leg hot-rolled angles: An improved imperfection factor

In recent years, the construction of increasingly taller and more efficient structures, especially in the field of towers and masts, has required the development of high-performance steel profiles that can withstand new loads. In response to this growing demand, high-strength hot-rolled angles up to S460 have been introduced to the steel market. However, despite the existence of evidence demonstrating that the detrimental influence of geometrical and material imperfections decreases with increasing yield strength, the same buckling curve is frequently recommended for different steel grades. For instance, in the forthcoming design specifications for hot-rolled sections in the next generation of Eurocodes, only the S460 grade benefits from a higher buckling curve while the same buckling curve is recommended for grades up to S420. In a first step, this paper illustrates the beneficial effect of the yield strength on the stability of steel angles subjected to pure compression and highlights the limitations of the current stepwise evolution of the imperfection factor in the design rules, based on a review of existing buckling tests and a series of numerical simulations on hot-rolled equal-leg angle members. In a second step, a new modified imperfection factor evolving with the steel grade is proposed and validated, in order to better reflect the beneficial effect of the yield strength on buckling resistance, for both existing and future emerging steel grades.