The roof of South Shanghai railway station is a long-span beam-cable hybrid steel structure. The essential role of cables
pretension between and under steel beams is to keep whole roof stable under possible load conditions. Using finite element
analysis computer program ANSYS, the time-history analysis of seismic response and the stability behavior of the steel roof
is calculated. Based on the numerical results, the optimal tension force of cables and reasonable pretension sequence are
obtained.
Combined with a time-history analysis and a buckling analysis, the tension forces of prestressed steel rods are optimized
on the basis of guaranteeing no cable slack. Then four kinds of steel rod pretension schemes are proposed. An optimal one
is chosen to enssuring cable stress value uniformity. Subsequently, beginning with the ideal state of completed roof, the
counter-pretension procedure, in which cables are disassembled in the opposite direction of pretension, is modeled stepwise,
and the initial cable force values are obtained to insure a successful pretension process.