Research on Axial Compression Stability of Partially Encased Composite Wall

Partially encased composite walls(PEC walls) have been widely used in the field of prefabricated buildings. In recent years, it has been gradually applied in building structures. However, the researches on the stability performance of PEC remain to be improved. In this paper, the stability performance of PEC wall under axial compression is studied. Based on the existing experiments, a finite element model is established. The influence of parameters such as calculation length, material strength, main steel section thickness and, section size of components on the wall stability is investigated, and the calculation formula of the PEC wall axial compression stability curve is proposed. The research shows that the calculated values of the formula are in good agreement with the finite element results. In this paper, the finite element software ABAQUS is used to establish a finite element analysis model, and the accuracy of the model is verified by existing experimental data. Then, this paper analyzes the the axial compression stability performance of PEC wall under parameters, and investigates the influence of different parameters on the stability performance of components, including calculated length, material strength, steel section thickness of the main steel parts, and the cross-sectional size of the components. The parameter analysis process adopts the control variable method to study the influence of each parameter on the stability performance of PEC wall, and summarize the mechanical characteristics and regulations. Then, based on the stability theory of the composite structure, the equivalent strength f_EQ and equivalent elastic modulus E_EQ of the composite section are comprehensively determined according to the composition of concrete and main steel parts in the composite section, and the regularized slenderness ratio λn of the PEC wall components is derived. Then, based on the results of finite element analysis, the axial stability curve of PEC wall is drawn, and the stability curves of four types of sections of steel structure are compared with the stability curve of PEC wall, the regulation is summarized, and the calculation method suitable for the stability curve of PEC wall components is found. Finally, based on the parameter analysis results, the influence of each component parameter on the stability curve of PEC wall is summarized, and the key component parameters are introduced as control variables in the calculation formula of the axial compression stability curve of PEC wall, and the calculation formula of the axial compression stability curve of the "three-stage" PEC wall is proposed based on the characteristics of the failure mode of the components under different calculated lengths. The results show that: 1) the calculated length l₀ of the component has a great influence on the destruction form of PEC wall, and with the increase of l₀, the destruction form of the component and its ultimate bearing capacity change from material strength control to overall stability control; 2) among the parameters of each component of PEC wall, the flange thickness and the section thickness of the main steel parts had significant effects on the stability performance, and the material strength, web thickness of the main steel parts, and the cross-sectional height of the components had relatively little effect on the stability performance; 3) the relevant specifications for PEC wall design have not been promulgated at home and abroad, and the four types of section stability curves provided by China′s current design code Steel Structure Design Standard(GB 50017—2017) are not applicable to the determination of the axial compressive stability coefficient of PEC wall; 4) the calculation formula of the axial compressive stability coefficient of PEC wall proposed in this paper is "three-stage". The calculated value of the formula is in good agreement with the finite element results, and can maintain high accuracy for PEC walls of different materials and sizes, which can be used to determine the axial compressive stability coefficient of PEC walls.