In order to describe the bending property of sandwich beam with wood skin and binderless bamboo chips core, the effect of construction parameters and material type on bending normal stress and moment was analyzed systematically. It is shown that maximum bending normal stress of sandwich construction is bigger than homogeneous single layer beam with same cross section if the skin has higher modulus than the core. The bending moment can be taken almost by skin layer if the core modulus is much smaller than skin materials and core thickness should also be smaller to special point than total cross section. As for wood-bamboo sandwich composite, the core resistance to bending moment should be considered. The results can provide basic theory for design optimization of sandwich construction.
The effect of construction parameters and material type on bending shear stress and shear force was analyzed systematically. It is shown that maximum bending shear stress of sandwich construction is smaller than homogeneous single layer beam with same cross section if the skin has higher modulus than the core. Besides the effect of core or skin layer to shear force is almost identical for sandwich composite composed by different materials with same construction parameter. In addition, the shear force can be taken almost by the core of sandwich beam only if the ratio of core thickness to the whole is more than. Otherwise the resistance to shear force of skin layer should be considered to calculate the shear deformation. The results can provide basic theory for design optimization of sandwich construction.
The shear strength of soil refers to the ultimate resistance of the shear stress generated by the external load of the soil. The strength problem is one of the most important basic contents of soil mechanics, and shear failure is an important feature of strength damage. At present, the monitoring methods of the soil shear strength device, such as indoor direct shear test, triaxle compression test, large-scale direct shear test on site, and on-site cross shear test, cannot realize real-time measurement in situ in the long-term field. In this paper, a device for measuring the shear strength of soil based on shear wave velocity is proposed, and the shear strength of the soil in situ can be obtained in real time.
Epidermodysplasia verruciformis (EV) is a rare disease caused by human papillomavirus (HPV) infection. Part of skin lesions at the exposed site would become malignant, but few cases with squamous cell carcinoma (SCC) transformation at unexposed sites have been reported. In December 2016, one EV patient with squamous cell carcinoma transformation at unexposed sites (perianal region) were admitted and treated at our hospital. Here we reported the clinicopathological characteristics and our surgical management of the SCC skin lesion of this EV patient. We deem that once local malignant transformation occurs, early surgical resection should be performed, and skin without lesions at the unexposed sites should be selected as the donor site for skin graft or skin flap transplantation.
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