By using the computer program SAFIR for analysis of reinforced concrete structures in fire

a comparison between the fire endurance of frame columns and that of independent column has been conducted

and the numerical model of the column with sideway is verified.Then

the influences of lateral-displacement factor

sectional dimensions of column

axial load ratio

and reinforcement ratio on the fire resistance reduction coefficient（FRRC）of square column with sideway have been numerically studied

and a regressive formula is proposed to determine the FRRC.It is found that:（a）when the column’s sideway is large

the fire endurance of frame column is remarkable lower than that of independent column;（b）with the increasing of the lateral-displacement factor

the FRRC decreases gradually

especially when the sectional dimensions of the column is bigger

the effect of the lateral-displacement factor is more significant;（c）the FRRC reduces gradually with the increasing of the sectional dimensions of the column

and the greater the lateral-displacement factor

the faster the rate of reduction of the FRRC;and（d）with the increasing of the axial load ratio

the FRRC decreases gradually on the whole

but the effect of the reinforcement ratio on the FRRC is relatively negligible.