<p>Free-form and bionic spatial shells are popular in the area of spatial structures. Scallop-shaped surface is the product of evolution and a kind of spatial shells that can satisfy the mechanical requirements. Based on the scallop-shaped lattice shells, this paper focused on the optimization of geometric parameters. The principle of minimum strain energy was applied to conclude the influence law of the geometric parameters on mechanical properties. Finally the optimal values of geometric parameters were obtained. The results show that the optimization of geometric parameters presents the integrated significance to improve scallop-shaped lattice shells.</p>

Free-form reticulated shells should not only satisfy the requirement of a specific geometric configuration but also have rational mechanical properties. This article introduced two form-finding methods of free-form configuration. The first method was a reverse realization method that is based on hanging fabric with a given boundary condition; the second method was a numerical simulation method that is based on the equilibrium characteristics of a natural tension membrane combined with a geometrical characteristics analysis and a mechanical properties optimization. The article then discusses the conducted beneficial comparison. The analytical results demonstrate that both these form-finding methods are feasible for obtaining rational free-form shells, and the numerical simulation method is more convenient for obtaining the surface family.

The precise edges of forging should be extracted from the image when measuring the dimensions of high temperature forging based on the non-contact image measurement technique. It is difficult to distinguish the forging boundary precisely due to the continuous variation of the air temperature near the forging. The two-dimensional simplified cross-section models, including the squaring, chamfering and rounding models, were established by the symmetrical modeling method. The air-cooling process from 1200°C to 800°C of high temperature long-shaft heavy forging was simulated based on ANSYS software. The variation regularities of temperature with the distance and time were obtained, which provides a theoretical basis to determine the edges of high temperature objects in non-contact measurement.

In view of the phenomenon that the curved duct in anchorage zone of cable-stayed bridges result in non-uniformity of each of steel strand, we analyzed the position change law of the prestressed steel strand in curved duct. Simulating real bridge design, a simple method was proposed to compute non-uniformity level of prestressed steel strand in the process of tensioning. Results showed that the rearrangement caused the additional length difference result in stress non-uniformity of each steel strand. Because each of steel strand cannot participate in force at the same time, the actual elongation value of the tendon is greater than theoretical value.

Non-contact measuring method based on CCD camera is desirable for product quality of high temperature long-shaft heavy forgings. In the light of the characteristics of RGB primary color and halation in forging image, the mean red gray value in the high temperature area is proposed as the dynamic threshold to acquire external contours. Internal edges in the image of the hot forging are blurry and discontinuous. For these characteristics, a method based on quadratic B-spline curve is employed to extract and fit the internal contours. Experiments show that this method can effectively remove pseudo features and extract accurate internal and external contours for images of high temperature squaring and chamfering forgings of 900 0C to 1050 0C.