| The flexibility and convenience of reinforced concrete (RC) frame with special-shaped columns in structure design and its fuction make it widely used in construction industry. Studies of fire performance of special-shaped columns are only limited to structure members. So, it is necessary to study the behaviour of frames with special-shaped column in fire.Based on test and numerical simulation, the paper investigates the failure mode of frames and the influence of the bracing and fire exposure case to the performance of the frames in fire, presents a guide to judge the dangerour parts of frames in fire and presents a method to calculate the horizontal displacement of beam-column joint of frames.1. Three full-scale RC frame with special-shaped columns were experimentally investigated in fire following ISO834 standard heating process. The loading ratio and beam-column stiffness ratio were analyzed. The experimental results show: (1) Similar catenary action were found when frame beams fails. (2) Increasing beam-column stiffness ratio will increase the deformation rate of verticale displacement of frame beams at the final stage and will make the rotation of beam-column joint decrease, even inverse. (3) When failure appears in frame beams, load ratio has great impact on the fire resistance of the frames, while the beam-column stiffness ratio has little.2. Through parameters study, their influence to the fire performance of frames with special-shaped columns were discussed. Results shows: (1) Beam failure mode has ductility characteristic,while column failure mode, fragility. (2) Parameters like beam length, number of beam spans, beam load, section dimension of beam and section reinforced ratio of beam has great influence to beam failure mode, while parameters correlated to column has little influence. Parameters correlated to beam and column, except beam load and heighth of beam section, has great impact on column failure mode. (3) Decreasing the restrain to the frame beam will accelerate its the failure. (4) Increasing horizontal displacement of beam-column joint will enhance the second-order effect of axial force of column.3. Four L-shaped sections, three T-shaped sections, four +-shaped sections and fourteen rectanglar sections were investigated by temperature analysis. The ratio of the area of the zone with temperatures larger than 500℃to the whole sectional area, axial rigidity and flexural rigidity were studied. Through structure analysis in fire, the difference of fire permance of frames with rectanglar and specially-shaped columns were analyzed. Results shows: (1) As a whole, sectional high temperature area ratio and decreasing rate of axial rigidity and flexural rigidity of specially-shaped section are generally larger than rectanglar sections, because of larger fire exposure area, while the flexural rigidity may be opposite. (2) In beam mode, there is little difference between frames with rectanglar and specially-shaped columns, while in column mode, the behaviour of frame has relation with sectional axial rigidity of column sections. (3) The horizontal displacement of beam-column joint of frames with specially-shaped columns is generally larger than frames with rectanglar columns.4. Frame with specially-shaped columns and bracings were investigated in numerical study. The effect of position, section size, reinforced ratio and fire exposure case of bracings were considered. Results show: (1) It is advantageous to fire performance of frames, when the bracing appears in two-ends beam spans or mid-span, while opposite when appears only in one-end beam span. (2) When bracing appears only in one-end beam span or mid-span, the axial force ratio of beam span closed to bracing span will be larger than other spans. (3) While, when the bracing appears in two-ends beam spans, there is little difference of axial force ratio among non-bracing spans. (4) Section size, reinforced ratio and fire exposure case of bracing have little influence to deformation of frames in beam or column mode.5. Subject to fixed fire exposure case and fire spread mode, frames with specially-shaped columns were investigated by numerical analysis, and associate with the analysis results in previours chapters, a method to judge dangerous parts in frames subjected to fire was presented. Results show: (1) Fire spread mode has great impact on temperature field distribution of columns, and the temperature field distribution gradually changes from dissymmetry to symmetry. (2) Subjected to fire spread mode, behaviour of frames has the characteristic of regular time-delay, and tends to all-fire mode. (3) On horizontal displacement and rotation of beam-column joints, fire zone can only influence adjacent span or store, less effects on other parts of frames. (4) To the frames subjected to dissymmetry fire exposure case, when fire appears in one side of the frame and continuous fire spans exceed half of all spans, the horizontal displacement of the frame joints in fire zone is larger than frame in all-fire mode6. Based on the principle of internal force balance, a simplified method to calculate horizontal displacement of beam-column joints is presented for two types of structure model. Results shows good agreement with analysis results by finite element program.
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