Decreasing the Displacements of a Composite Saddle-Shaped Cable Roof

The structural possibilities of decreasing the compliance of a composite saddle-shaped cable roof having a compliant support contour are investigated. The use of a supporting contour consisting of cables joined together with tie-bars is considered as a structural method enabling one to decrease the compliance of the roof. Each cable of the support has its own initial flexure. The method is most efficient from the viewpoint of material consumption per unit of covered area relative to the increasing rigidity and prestress level of the cable net.The efficiency of the method was evaluated by a numerical experiment, which was carried out for a composite saddle-shaped cable roof 50 × 50 m in the plan. The roof was formed by two orthogonal cable groups joined with a compliant supporting contour. A hybrid composite cable based on a carbon-fiber-reinforced plastic, a glass-fiber-reinforced plastic, and steel was considered as a material for the cable net in combination with steel. The material consumption and the maximum vertical displacement of the cable net in relation to the initial geometrical characteristics of the supporting contour were obtained. A possibility of decreasing the maximum vertical displacements of the roof by 8% was established.     

Hygrothermomechanical behavior of composites under nonsymmetric environmental effects

The paper discusses analytical methods for the stimation of mechanical properties and the behavior of composite materials under unilateral environmental exposure. An advanced graphite/epoxy composite plate and a densified wooden strand board of different configurations were examined. It was found that midplane strains, curvatures, and warping at nonsymmetric moisture (or temperature) distribution depended on the moisture content profile, composite type, and configuration as well as stacking sequence of layers. The optimum configuration for hygrothermal response may not coincide with that of mechanical properties.Institute of Structural Engineering and Reconstruction, Riga Technical University, Riga, Latvia, LV-1048. Published in Mekhanika Kompozitnykh Materialov, Vol. 34, No. 4, pp. 507–518, July–August, 1997.     

Hygromechanics of composites with unsymmetric structure

Conclusions An analytical method is presented for estimation of midplane strains and curvatures of a 3D general composite. By using the multilayer model based on the laminate analogy, the effect of an unsymmetric distribution of moisture content and material structure on swelling and wrap as well as the stability in compression of a densified technological pressing wooden composite board has been estimated for a real composite production process.Published in Mekhanika Kompozitnykh Materialov, Vol. 30, No. 6, pp. 831–838, November–December, 1994.     

Formation of Saddle-Shaped Composite Sheets

Based on the deformation model of an unbalanced multilayer composite, changes in bending curvatures of sheet-type composites with nonsymmetric structure relative to the midplane of the sheet, depending on the moisture of layers, are predicted. The bending curvatures of saddle-shaped sheets of wood-based composites are calculated with regard to the physical and mechanical properties, geometrical dimensions, orientation, and distribution of layers. The analytical results are compared with the bending curvatures found experimentally for a four-layered unbalanced composite made of birch veneer. The applied calculation model enables us to determine the values of bending curvatures of saddle-shaped wood composite sheets, which can be used in elaborating the technological recommendations.     

Nonlinear moisture deformation of a composite with a densified reinforcement

Conclusion An analytical method is presented for estimation moisture deformation of densified in technological pressing wood-based composite material with nonlinear swelling properties. This includes modelling of the processing effects as well as interfacial bonding. By using the multilayer model supported on the laminate analogy the optimum particle alignment has been estimated for a real composite production process.Published in Mekhanika Kompozitnykh Materialov, Vol. 30, No. 3, pp. 314–320, May–June, 1994.     

Utilization of Composite Materials in Saddle-Shaped Cable Roofs

A saddle-shaped cable roof formed by two orthogonal groups of cables joined with a compliant support contour is considered. The kinematic invariability of the roof obtained by prestabilizing the cables makes it possible to avoid heavy slabs of reinforced concrete in the construction of roofs and to use light composite materials. The main geometric characteristics for a cable roof with CFRP load-carrying and contour cables and steel stabilizing cables are determined by a numerical experiment.     

Prestress Losses in the Stabilizing Cables of a Composite Saddle-Shaped Cable Roof

The paper deals with a square composite saddle-shaped cable roof 30 × 30 m in the plan, which is formed by two orthogonal cable groups joined with a compliant support contour. The kinematic invariability of the roof is achieved by prestressing the cable net. From the viewpoint of material consumption, the cable roof has rational geometrical characteristics. A hybrid composite cable on the basis of CFRP, GFRP, and steel is considered as a material for contour cables. The load-carrying and the stabilizing cables are made of steel. Prestress losses in the stabilizing cables are determined for three variants of prestressing. The possibility of reducing the consumption of cable materials by prestressing each cable of the net by an individual force is revealed.