Application of genetic algorithms in the optimisation of steel rib supports

•Use of the genetic algorithms for the optimization of the steel rib support of circular tunnels.•Analysis of the law of displacements: symmetric and asymmetric radial displacements.•Calculus of the stresses on the support due to the displacements and the heat.•Optimization of one steel rib support and analysis of the results. One of the most critical aspects in the design of tunnels or mine galleries is their support. This one not only must be able to withstand the stresses to which it is subjected, but also that its deformations must allow the functionality of the structure, both in the construction phase and in the operation phase. In order to meet these two requirements (resistance and functionality), the tendency is to obtain oversized supports. This implies not only a greater weight but also a greater cost. This paper analyses and optimises the steel rib support to ensure that with the minimum weight, it can withstand the stresses arising during excavation process. The optimisation process has been established using genetic algorithms, based on the evolutionary theory of Eugenics. For making the rib support Omega profiles have been adopted due to their robustness (ratio of resistant modules Wx / Wy approximately equal to unity). The study has been implemented for tunnels with circular section. Previously, the efforts that act on the steel rib support are analysed, considering two hypotheses: radial symmetrical displacements and radial asymmetrical displacements. Also the stresses caused by the possibility of a fire inside the tunnel have been analysed. From the optimization, it is obtained for different depths: the size of the profiles of the steel rib supports, their weight and total cost, the radial displacements of the nodes of the rib, the temperature and critical depth or temperature and depth where the generalized failure of the elements is produced. The stresses on the steel rib support caused by the possibility of a fire inside the tunnel have also been analysed based on a constant increase in temperature throughout the beam elements of the steel rib support.