A flexible insulated wall solar greenhouse (FIWSG) can represent an upgraded improvement over conventional soil-walled ones. However, structural stability is often caused by insufficient stiffness, particularly towards larger spans, due to the replacement of thick soil walls by steel tubes with a large slenderness ratio. In this study, a Y-type braced multi-form arch was proposed in the FIWSGs, according to the mechanical properties of existing diagonal and strut brace systems. The stability was enhanced to reduce steel consumption via the local stiffness and internal force transmission paths of FIWSG. A static analysis was conducted on the Y-type braced solid-web FIWSG. Subsequently, a variable-stiffness truss arch in FIWSG was proposed to arrange the upper chord, lower chord, and web members according to the bending moment and deformation distribution diagrams. According to elastoplastic mechanics and nonlinear finite element (FE) theory, the Beam188 element was selected from its element library to simulate the greenhouse members using ANSYS software. The member base and the foundation were related to a fixed constraint. The arclength was employed to consider geometric nonlinearity in the descending branch of the equilibrium path. Additionally, the constitutive equation was adopted for the material nonlinearity parameters in a bilinear model, the von Mises yield, and the BKIN bilinear kinematic hardening model. Refined FE analysis models were established for FIWSGs with different brace types (no brace, diagonal, strut, 3/4-2.2Y-type, 27/40-2.2Y-type, 3/5-2.2Y-type, 3/5-2.7Y-type, and 3/5-3.2Y-type braces) and different arch forms (solid-web and truss). Elastoplastic stability analysis and parametric studies were conducted to compare the performances, including stability and steel consumption indicators, of the critical span applicable for arch selection in FIWSGs. The results indicated that: (1) The Y-type brace significantly improved the performance of the arch, compared with the brace types. Bifurcation heights and front roof support point position were compared to determine the 3/5-2.2Y- and 27/40-2.2Y-type braces. The maximum stability increased, with the 27/40-2.2Y-type brace superior overall performance. (2) The overall displacement of the 3/5-2.2Y-type brace was reduced by 10.3%, 19.8%, and 30.4%, compared with the scenarios with no brace, only diagonal brace, and only strut brace, respectively. The instability of the location gradually shifted toward the front wall. Arch stiffness and internal force transmission were obtained among the diagonal, strut, and Y-type braces. (3) The critical span between solid-web and truss arches was determined for the high stability and low steel consumption of FIWSGs with the spans of 10, 12, 14, 16, 18, and 20 m and different arch forms. Specifically, when the span was within 14 m, greater advantages were found for solid-web arches; on the contrary, more advantages were observed for truss types. The finding can provide the theoretical and technical reference for performance enhancement, arch selection, and engineering practice of FIWSGs.

Solar greenhouses have been widely used in the vast western and northern regions of China, due mainly to the convenient construction and installation, low economic cost, and outstanding environmental adaptability. The slender steel can be the load-bearing components of the section-steel arched solar greenhouse to resist external loads, such as wind and snow. There are the prominent instability and disaster that caused by insufficient stiffness of solar greenhouse under extreme weather conditions, such as snowstorms. In this study, the nonlinear stability analysis was conducted on the commonly-used section-steel arched solar greenhouse in Hebei using elastic-plastic mechanics and nonlinear finite element (FE). A refined FE model was established for the section-steel arched solar greenhouse. The greenhouse arch roof and the vertical sections on both sides were simulated using the Beam188 element in the element library of the universal FE analysis program ANSYS. The linear elements were used to fit the circular arc segments. Diagonal tension bars, vertical brace struts, and longitudinal tie bars were all simulated using Link10 element. The bottom of the vertical sections on both sides of the arch was assumed to be consolidated with the foundation. The steel was made of Q235, with an elastic modulus of 206 GPa, a Poisson's ratio of 0.3, and a density of 7 850 kg/m³. Geometric and material nonlinearity was considered to simulate the constitutive relationship of steel using an ideal elastic-plastic model, followed by von Mises yield criterion and bilinear kinematic hardening model BKIN. The stability performance and parameter analysis of solar greenhouse structure were carried out under snow loads. The stability capacity of solar greenhouse was determined under different parameters, such as steel-section type (flat elliptical, hollow rectangular and hat-shaped cross-section), greenhouse span (8, 10, and 12 m), and snow load distribution pattern (non-uniform distribution thickness and asymmetric distribution area). There was the quantitative influence of snow load distribution on the stability capacity of solar greenhouses. The load factor-displacement curves were combined with the deformation, stress, axial, and bending moment at different points of loading time. The static instability of solar greenhouses was explored from two aspects: intuitive phenomena and intrinsic essence. The conclusions were obtained as follows: The stability capacity of the steel component with a flat elliptical section in the solar greenhouse was increased by 21.0% and 44.2%, respectively, compared with the box and hat-shaped section. There was no out of plane instability in the same cross-sectional area and flange width of the steel component. The stability capacity of solar greenhouse was rapidly reduced with the increase of span. The stability capacity of solar greenhouse under non-uniform distribution of snow loads was reduced by the maximum of 63.8%, compared with the uniform. The maximum stability capacity of a solar greenhouse increased by 9.0% and 66.8% with only tension bars and brace struts, respectively. The findings can provide the technical guidance and theoretical reference for the anti-snow loads, stability and disaster prevention in the section-steel arch solar greenhouses.