向量式有限元法是將連續體近似成質點的組合,質點運動遵循牛頓運動定律。藉由虛擬逆向轉動分離剛體運動,並搭配變形座標系統定義變形,進而計算元素的內力以作用於質點之上。因此,向量式有限元法能夠有效模擬連續體同時具有大的剛體運動和大的幾何變形行為。本文即是利用向量式有限元的特性模擬含溫度效應下平面構架之行為,並加入材料非線性分析,利用彎矩-曲率的關係考慮含溫度效應下彈塑性行為,在彈塑性分析時假設塑性變形不因溫度改變而改變。材料強度會因為溫度升高而有所折減,此部分根據國外常用規範如EC3(EUROCODE 3)、ECCS等建議公式計算, 再利用內力折減而相對於抵抗外力能力降低之概念,計算出含溫度之變形。
The vector form intrinsic finite element (VFIFE) method, in contrast to traditional finite element approaches which is based on the variational principles, the analyzed structure is simulated by a group of particles, and Netown’s second law is applied to describe each particle’s motion. The deformation coordinate system is used to separate the rigid body motion and pure deformation to evaluate the internal force on the node. Thus the VFIFE method can effectively simulate overall dynamic motions, either rigid body motion or deformation of continua. The main purpose of this paper is to use the characteristic of VFIFE to simulation planar frames with the effect of fire, and adding nonlinear analysis. Using moment-curve relation to reflect the elastic-plastic behavior, in elastic-plastic analysis assume that plastic strain doesn’t change with thermal change. Material properties of steel structure will decrease rapidly as the temperature increase, this part base on EC3 and ECCS in common use overseas code to calculate, and using the internal force decrease is to represent the ability of resisting external force comparatively decrease to calculate deformation with thermal effect.