BRIDGE TRUSS ANALYSIS
The aim is to understand truss deflections better under particular loadings, which will be done by the analysis of a simple pin jointed frame using equilibrium equations. The collection of data will be in the form of a compilation of truss properties, member cross-section area, Young’s modulus of material, the electric strain gage factor and loads that are used for analysis of the truss stress. For every member, data is presented in a table to show calculated member strain.
Using the basic equilibrium calculations from statics and mechanics of materials, the forces in every member can be found. Hence, stress will be found in each member by dividing its force by the area (remains constant throughout the truss). Then strain is calculated by the division of stress by Young’s modulus.
The agenda of this lab was analysis of a simple pin-jointed frame by use of equilibrium equations and also check whether or not analysis by experimental measures is valid.
BRIDGE TRUSS ANALYSIS-Experimental setup/introduction
The aim of experiment is to find the displacements and deformations that arise due to the stress. This also aids in the acquisition of information pertaining to electric strain gages, study its functionality and analyze our data from it. The experimental form of truss lab entailed a small bridge truss model made from aluminum tubing. It was fixed on one end then supported by rollers on the other and two loading hangers mounted. Multiple strain gages were placed on different beams in pairs for the measuring of tensile strength. Strain readings were made by adding weights on the two hangers alternatively.
BRIDGE TRUSS ANALYSIS-Discussion
- How well do the analytical and experimental results compare.
As stated earlier, experimental results were quite close to calculated ones, an mean percentage error of 2.13%, the largest being 9.02% and the least 2.37%
- What are the reasons of difference in analytical and experimental results
The margin in the strain values might have originated from stiffness in the joints resulting to a moment in the truss thus creating varied forces in members of interest.
Also the modulus of elasticity in the actual truss was not precisely 10*E6psi
- Does it appear that bending loads are present in any member?
It seems that some bending moment may be in the truss as some of the amount of error varies a bit from member to member, indicating that some joints are functioning well while others aren’t. Such an error may also be contributed to tolerance error resulting due to construction techniques.