Nonlinear simulation of lattice girder segment tests

• In these experiments, the lattice girders fail with lower arc bars buckling.
• Both in-plane and out of plane buckling failure was observed.
• 2nd Order plastic FE models adequately evaluate the ultimate load capacity.
• Such models may also be used to evaluate the deflections and the mode of failure.

Lattice girders often replace conventional steel rib arches as a means of temporary support in tunnels and often have a comparative advantage over the latter mainly due to their lighter weight. Their use is directly related to the application of a shotcrete layer, in which they are encased, forming thus a composite structure that has been proved successful over numerous projects worldwide. However, any loads from the surrounding rock before shotcrete placement or hardening, have to be carried out by the lattice girder itself. Such loads may be concentrated in parts of the girder, due to sliding or falling blocks, detaching strata, reacting ground, etc. Their effects on it, which are nonlinear, necessitate analysis with detailed models; their adequacy should be experimentally validated. Therefore, a series of loading tests is conducted on simply supported arched lattice girder segments, in which the load is induced horizontally at the roller support. These tests are then simulated numerically with various 3D models. The appropriateness of the latter is thus checked by comparing the ultimate loads and deflections, which were found to be limited by buckling.