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A structure formed by connecting rods with hinges at both ends. The truss is composed of straight rods and generally has a plane or space structure with triangular members. The truss members mainly bear axial tension or pressure, so that the strength of the material can be fully utilized. When the span is large, the material can be saved compared with the solid web beam, and the weight and can be reduced but increase stiffness. Common trusses shapes are: triangular trusses, trapezoidal trusses, polygonal trusses, hollow trusses, and truss bridges.