Powell's optimal identification of material constants of thin-walled box girders based on Fibonacci series search method

A dynamic Bayesian error function of material constants of the structure is developed for thin-walled curve box girders. Combined with the automatic search scheme with an optimal step length for the one-dimensional Fibonacci series, Powell＇s optimization theory is used to perform the stochastic identification of material constants of the thin-walled curve box. Then, the steps in the parameter identification are presented. Powell＇s identification procedure for material constants of the thin-walled curve box is compiled, in which the mechanical analysis of the thin-walled curve box is completed based on the finite curve strip element （FCSE） method. Some classical examples show that Powell＇s identification is numerically stable and convergent, indicating that the present method and the compiled procedure are correct and reliable. During the parameter iterative processes, Powell＇s theory is irrelevant with the calculation of the FCSE partial differentiation, which proves the high computation efficiency of the studied methods. The stochastic performances of the system parameters and responses axe simultaneously considered in the dynamic Bayesian error function. The one-dimensional optimization problem of the optimal step length is solved by adopting the Fibonacci series search method without the need of determining the region, in which the optimized step length lies.

THE APPROXIMATE ANALYTICAL SOLUTION FOR THE BUCKLING LOADS OF A THIN-WALLED BOX COLUMN WITH VARIABLE CROSS-SECTION

For a thin-walled box column with variable cross-section, the three governing equations for torsional-flexural buckling are ordinary differential equations of the second or fourth order with variable coefficients, so it is very difficult to solve them by means of an analytic method. In this paper, polynomials are used to approximate the geometric properties of cross-section and certain coefficients of the differential equations. Based on the energy principle and the Galerkin's method, the approximate formulas for calculating the flexural and torsional buckling loads of this kind of columns are developed respectively, and numerical examples are used to verify the correctness of the solutions obtained. The results calculated in this paper provide the basis for demonstrating the stability of thin-walled box columns with variable cross-section. This paper is of practical value.

GRC异形内模预应力箱梁受力性能的试验研究

通过对12 m跨GRC异形内模折线形预应力筋箱梁受力性能的试验研究,测定箱梁的最大承载力,分析箱梁在各级荷载下裂缝和挠度的发展情况,及其破坏形态和破坏特点,并将试验结果与按现行规范计算的结果进行对比.结果表明:试验梁的受力性能良好,内模与梁形成统一的受力整体共同工作,当荷载达到设计破坏荷载的207%时,仍未发生破坏,有足够的安全储备;按照现行桥梁设计规范进行设计可满足工程要求.GRC薄壁筒芯是一种有发展前景的应用于小跨度桥梁的内模.

非金属(GRC)材料箱变外壳

分析了箱式变电站箱体外壳材料,介绍了非金属"GRC"材料特点、性能参数及其应用。

Shear deformable finite beam elements for composite box beams

The shear deformable thin-walled composite beams with closed cross-sections have been developed for coupled flexural, torsional, and buckling analyses. A theoretical model applicable to the thin-walled laminated composite box beams is presented by taking into account all the structural couplings coming from the material anisotropy and the shear deformation effects. The current composite beam includes the transverse shear and the restrained warping induced shear deformation by using the first-order shear deformation beam theory. Seven governing equations are derived for the coupled axial-flexural-torsional-shearing buckling based on the principle of minimum total potential energy. Based on the present analytical model, three different types of finite composite beam elements, namely, linear, quadratic and cubic elements are developed to analyze the flexural, torsional, and buckling problems. In order to demonstrate the accuracy and superiority of the beam theory and the finite beam elements developed by this study,numerical solutions are presented and compared with the results obtained by other researchers and the detailed threedimensional analysis results using the shell elements of ABAQUS. Especially, the influences of the modulus ratio and the simplified assumptions in stress-strain relations on the deflection, twisting angle, and critical buckling loads of composite box beams are investigated.

GRC空心楼盖在地下车库应用中的技术经济比较

GRC薄壁箱体是目前国内一种新型高强轻质薄壁箱体,针对该新型材料在地下车库现浇空心楼盖设计中的应用,对其设计、加工制作与采购、施工等方面进行了归纳总结与探讨,并结合地下车库的传统设计方案,与新方案进行了全面经济技术分析与比较,为该新型材料在类似项目中的应用提供借鉴与参考。

GRC薄壁盒现浇混凝土空心楼板施工技术

生产楼工程应用GRC高强薄壁盒现浇混凝土空心板施工技术,通过对GRC薄壁盒按设计排列图、采用专用定位卡具、抗浮拉结螺栓等措施,保证现浇混凝土空心楼板的施工质量,并总结出了一套可行的施工方法。

GRC薄壁空心箱现浇混凝土空心楼盖施工工法

本文介绍了GRC薄壁空心箱体混凝土结构在大跨度、大空间的建筑,保证结构强度、刚度和整体性能的基础上,大幅度减少钢材、水泥、混凝土高能耗产品用量的工艺特点及工艺流程。

Mechanics analysis of thin-walled box continuous girder with variable cross-sections in considering effect of large deflection and shear lag

In order to study the mechanics behavior of a thin-walled box continuous girder with variable crosssections,using potential variation theories,considering the effect of shear lag of flange’s stress and the nonlinear geometry of vertical displacement,and evolving five generalized displacements with the spline function,the large deflection problem of the thin-walled box continuous girder with variable cross-section was transformed to a nonlinear algebraic equation,which was solved using the Newton-Raphon iterative method.The results of the calculation show that different shear lag warp functions to the cantilever,top and bottom plate should be taken to analyze the mechanics behavior of the thin-walled box continuous girder reliably.The thin-walled box continuous girder with variable cross-sections has more reasonable stress state and is more adaptable for the longitudinal change of internal forces than that with equal crosssections.The effect of large deflection on the stress and displacement of the thin-walled box continuous girder with variable cross-sections depends on the values of the load.