Trusses are frameworks of bars connected by pins, used in bridges, electrical towers, and roofs. Truss analysis determines forces and structural integrity, using joint, section, or graphical methods. Analysis assumes no friction and equal stress on each component. Joint analysis uses free body diagrams and trigonometry, while section analysis focuses on the part with the greatest force. Graphical analysis uses force polygons and Maxwell diagrams. Truss analysis is used to measure mechanics before construction.
Often used in bridges, electrical towers, and some types of roofs, trusses typically consist of bars connected together in a framework. Bar components are usually connected via pins. Truss analysis can be used to determine the compressive and tensile forces acting throughout the structure. The structural integrity of the truss can be calculated using mathematical formulas and scientific evaluations. In truss engineering, the main methods of analysis often focus on joints, sections or through the graphical representation of the structure.
For truss analysis, the rules usually dictate that the bars are connected by pins and that there is no friction at the joints. Typically it is assumed that each component experiences the same amount of stress along its entire length, with structural loads affecting only the truss joints. Analysts usually observe the reactions of different forces on various parts. Truss analysis is typically performed by applying the equilibrium equations.
The joint method is a way to analyze a lattice structure. Typically, assuming that each piece is in tension, meaning that both ends of a rod are subjected to tensile forces, the analysis is performed on a portion of the truss represented on a free body diagram. Often two equations are used for each joint; the number of calculations is twice as many joints there are in the structure. Various steps lead to determining whether each member is in tension or in compression. This approach to truss analysis often involves the use of trigonometric functions for angle measurements as well.
Using the section method, you typically need the part of the truss design with the greatest force acting on it. Calculations are performed on either side of a dividing line through the truss, relying on the balance to guide the calculations. This line can pass up to three bars on the trellis. The tension and compression of each joint is also calculated with this truss analysis method. Components such as rods that carry no load, those that transmit forces to the opposite side, and curved parts sometimes need to be considered differently to get the most accurate analysis.
Graphical truss analysis often uses a minimum number of lines using force polygons. The result can be a simplified drawing called a Maxwell Diagram, which looks like a triangle on which forces and angles can be measured. Calculations are usually performed clockwise around the drawing. Truss analysis is often used to measure the mechanics of such systems before they are built. The complexity of the structure is sometimes a limitation, in which case accounting for joints in the calculations is usually more effective.
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