Abstract:

With the cross section of special-shaped reinforced concrete column subjected to elevated temperature as the research object , this paper investigates the characteristics of its temperature field , the generalized neutral-axis position , the ultimate bearing capacity , the point position corresponding to the maximum bearing capacity as well as the N-M and M-M envelop diagrams , and reveals the bearing property of the column at elevated temperature. The results show that: (a) the axial compression columns with T -shaped and L-shaped cross sections at room temperature change to eccentric ones at elevated temperature; (b) when the load does not act on the symmetry axis , the angle between the normal of sectional generalized neutral axis and the plane exerted by a bending moment varies with the increase of temperature , and the maximum angle at elevated temperature reaching 29°; (c) the differences of ultimate bearing capacity between square and special-shaped cross sections increase with fire-exposure time ，the former possibly being about 20% larger than the average of 出e later after being heated for 180 min; (d) the points corresponding to the maximum bearing capacity of T -shaped and L-shaped cross sections with equal limb offset along the sectional symmetry axis during the heating process; and (e) the limit eccentricity between large and small eccentric compressions of the special-shaped cross section mostly decreases with the increase in fire-exposure time.

Key words: reinforced concrete, special-shaped column, elevated temperature, bearing property, ultimate bearing capaclty