钢管混凝土框架柱耐火性能研究

Study on fire performance of concrete filled steel tubular frame columns

建立了火灾下钢管混凝土柱-钢梁平面框架的有限元模型,对不同火灾工况、不同位置的钢管混凝土框架柱的破坏形态、受力机理、内力重分布规律、耐火极限等进行了系统的分析。分析表明,火灾下钢管混凝土框架柱出现了两种典型的破坏形态：当框架柱位于非顶层时,由于柱顶转动约束较大,框架柱出现3个塑性铰成为机构而发生破坏;当框架柱位于顶层时,由于柱上端的转动约束较小,框架柱在中上部出现1个塑性铰而发生破坏。非顶层、同层火灾工况下,当框架柱受火情况相同时,随受火范围的扩大,由于内力重分布,火灾中破坏柱所受的压力较大,耐火极限较小。非顶层、同跨火灾工况下,随楼层增高,框架柱的轴压比减小,耐火极限增加。

A finite element model of concrete filled steel tubular（ CFST） column and steel beam plane frame under fire was established. The failure modes,stress mechanism,redistribution law of internal force and fire performance of concrete filled steel tubular columns under different fire conditions and locations were systematically analyzed. The analysis shows that there are 2 typical failure modes in CFST columns under fire. When the frame column is not in top floors,3 plastic hinges appear in frame column and the frame columm becomes a mechanism to damage because the top rotational restraint is large.When the frame column is located on the top floor,1 plastic hinge appears in the upper part of the frame column to become a mechanism to damage because the upper rotational restraint is small. Under the condition of non-top layer and same-layer fire,when the frame column is under same fire condition,with the extension of fire range,the pressure of the damaged column in fire is large and the fire resistance is small because of the redistribution of internal force. With the increase of story,the axial compression ratio of frame columns decreases and the fire resistance increases.