Simplified Guidelines for Checking Single Steel I-Girder Stability under Erection through AASHTO LRFD and FEA

摘要

For a long time, erectors have been using simplified rules of thumb to assess the stability of single cantilevers or simply-supported girders under erection by the L/b ratio, where L is the unbraced length and b is the compression flange width. Certain limits on the L/b ratio exist, which determine if a girder under erection with a specific L/b ratio would remain stable, need temporary support or need stability check. Those rules of thumb, although convenient for on site check, were purely based on experiences and therefore need to be checked for accuracy and applicability with the current design code.Formulae for the maximum allowable girder span Lraax as well as the maximum (L/b) ratio have been developed following the current AASHTO LRFD code. Parametric studies were conducted on various girder sections in order to 1) calculate the maximum L/b ratio for each girder section and check the rules of thumb; 2) determine the dominant section parameters on girder stability under erection. Finite element analyses (FEA) were also conducted in order to 1) further understand the behavior of girder instability; 2) compared the maximum L/b ratio obtained from FEA with the ratio obtained from AASHTO LRFD code.