### 1. Introduction

### 2. Finite Element Modeling

### 2.1 Development of FE Model

*x, y*, and

*z*directions and the rotation about the

*x*axis were restrained. While point B was assumed to have roller support, where the displacement in directions

*y, z*and the rotation about the

*x*axis are restrained. Lastly, lines W and F were restrained against

*y*and

*z*displacements, respectively.

^{3}regardless of the temperature.

*k*), yield strength (

_{p,θ}=f_{p},_{θ}/f_{p}*k*) and Young's modulus (

_{y,θ}=f_{y,θ}/f_{y}*k*) at elevated temperature, as shown in Fig. 4(d) In this figure,

_{E,θ}=E_{a,θ}/E*f*and

_{p,θ}, f_{y,θ}*E*represent the proportional limit, effective yield strength and slope of the linear elastic range, at a temperature θ, respectively. Lastly, Fig. 5 shows the stress-strain curve at elevated temperature for hot rolled steel taken from Eurocode 3 Part 1-2 (2005).

_{a,θ}### 2.2 Model Validation

*χ*and

_{LT}*χ*at ambient and elevated temperature, respectively) and different slenderness values (λLT and λL,fi at ambient and elevated temperature, respectively).

_{LT,fi}*χ*) and the non-dimensional slenderness (

_{LT}*M*is the design buckling resistance moment,

_{b,Rd}*M*is the design resistance for bending,

_{c,Rd}*W*is the plastic section modulus of the cross-section and

_{pl,y}*M*is the elastic critical moment for lateral-torsional buckling.

_{cr}*χ*) and the non-dimensional slenderness values (

_{LT,fi}*M*is the design lateral torsional buckling resistance moment and

_{b,fi,t,Rd}*M*is the fire design moment resistance.

_{fi,θ,Rd}### 3. Analysis Results

### 3.1 Critical buckling load

### 3.2 Flexural strength ratio at elevated temperature and buckling mode shape

*M*) and at ambient temperature (

_{T℃}*M*) with respect to the unbraced length.

_{20℃}