Steel sheet piles exposed to fire. Experimental tests and numerical modelling

This paper deals with the behaviour under fire of vertical walls made of steel sheet piles in retaining walls close to, for example, a traffic road or an industrial facility or in underground structures such as car parks or cut and cover tunnels. For the later situation, the sheet pile walls support not only the horizontal pressure from the ground but also the vertical loads induced by the different floors.
Four experimental tests have been performed in the fire lab of ULiege on a test setup where different soils were located at the back of a heated sheet pile wall, namely sand and clay, either saturated with water or not. Equivalent thermal properties have been derived that allow reproducing in a simple conductive model the temperature distributions measured on the steel piles.
Modelling the whole sequence of events from erection of the structure to failure under fire requires the successive application of 2 different software, RIDO that reproduces the evolution of the displacements and force distribution in the wall during the successive sequences of construction and SAFIR® that models the behaviour of the structure when it is subjected to fire. The links that have been established to transfer the results of the first simulation to be taken as initial conditions for the second software are described.
Finally, a specialised one node finite element that has been introduced in SAFIR to model the elasto-plastic behaviour of soil is described and an application example is briefly discussed