Experimental research of a membrane roof with the membrane eccentrically fixed on a thin-walled open-profile supporting contour

Abstract

This paper presents experimental research about operation of a square-shaped membrane-type sag roof on a flat supporting contour. Membrane roofs include a thin metal shell (membrane) attached to the supporting contour. The membrane has the functions of structural support and protection, mainly resisting the stretching force. The supporting contour resists the compression force by bending in two planes. Eccentric fixing of the membrane in the contour gives rise to a torque. With torsion, the thin-walled open-profile contour develops additional normal tensions. Experiments were conducted on a test bench consisting of a base, a model and instrumentation. The membrane model is convertible: the same model can be used to represent four structural setups. The test have examined the effects of a load uniformly distributed over the surface of the roof, and of focused loads: vertical loads applied to the membrane (to emulate the effect of a suspension crane), and horizontal loads applied to the supporting contour (to emulate wind loads and loads created by support bridge cranes). Parameters of the test structure are such that they enable emulation of roofs spanning over 24 × 24 m and 36 × 36 m. The model's dimensions in plane are 3 × 3 m, with the supporting contour shaped as a channel bar welded of L-bar. The membrane roof model is manufactured of aluminum alloys. The paper places the main focus on the operation of a model with a membrane fixed eccentrically (to lower ledge of the channel bar) to the supporting contour. Performance of such roofs has been experimentally confirmed; the test revealed significant reserves of structural bearing capacity, small horizontal and vertical displacements of the supporting contour, and admissibility of plastic deformations in small sections of the contour. Experimental data are compared with calculated results from the computing system model. The calculations are carried out taking into account the constrained torsion of thin-walled open-profile rods.