Lab 12: The Truss

The Problem
The problem is to optimize one of the given truss forms through computer aided analysis.

The Objectives
The objective is to deepen the understanding of the behavior of the truss and to further exercise the utilization of computer tools in design.

The Process
Each team within the lab will select a unique truss to investigate. The truss options for this exercise are as indicated in the illustration to the right. The process during the lab should be as follows:

• confirm truss selection with lab TA
• build the truss in MultiFrame assuming a 150 meter total span
• assume an initial total truss depth at midspan of 10 meters
• assume initially that all members are W18x60 steel elements
• calculate the total joint load if a road deck was 3 meters wide and loaded with 100 KN/m² total load (ignore self-weight)
• apply the joint loads as appropriate for an evenly distributed load
• analyze the truss
• check for accuracy of model by ensuring ABSENCE of moment forces in truss elements
• describe the relative magnitude and sense of the Normal forces acting in the truss
• color identification of elements that are in tension or compression
• describe the relative magnitude of the Normal, or Direct, Stress in the elements of the truss
• optimize your truss for this loading scenerio by changing the weight of the sections. maintain the 18 inch depth.
• describe what was the greatest suprise during the analysis

• replace the evenly distributed load with an oversized truck load of 3000 KN. Do this by placing TWO 1500KN point loads at two adjacent panel points of the truss. These panel points should be on the RIGHT side of the truss. This is so that the asymmetrical load and resulting stress pattern can be observed and compared to the other groups.
• describe the relative magnitude and sense of the Normal forces acting in the truss
• color identification of elements that are in tension or compression
• describe the relative magnitude of the Normal, or Direct, Stress in the elements of the truss
• optimize your truss for this load by changing the wight of the W18 sections.
• describe what was the greatest suprise during the analysis

• drawings of the elevation
• print-outs of deflections
• descriptions as indicated above

The Evaluation
The evaluation for grades will be based upon the clarity and degree of completion of the lab report.