Introduction to the Project
Description
The intent of this project is to design and build an articulating bridge which can be raised and lowered constructed from balsa wood. Bridges are intended to support large loads typically to cross over into an area that would otherwise be inaccessible. In order to withstand these large loads a bridge must be designed with toughness, areas of stress, and material in mind. Engineering design can account for all of these aspects in order to design a bridge that will not fail under the loads that may be placed on a bridge. By analyzing forces on the bridge, stresses within the material, and load distribution between beam members an engineer can accurately assess the strength of a bridge to determine if the bridge will be able to handle its working load.
Motivation
This project was motivated by a need for a device that would function as a bridge resting on abutments in order to meet predetermined specifications for loading force, weight, ability to be traversed, as well as being able to articulate 50% of the bridge length vertically 280mm. This motivation comes from the current state of the world surrounding the COVID-19 pandemic in which a project that could be built from home while socially distancing was required.
Function Statement
The function of this bridge is threefold, first, the bridge must span a divide while supporting a load. Secondly, the bridge must act as a means of passage for a moving structure horizontally. And finally, the bridge must be able to be under a load while still maintaining its rigidity.
Requirements
For this Project, a bridge is to be designed to meet specific requirements. These requirements are as follows.
will support at minimum between 18.9-20kg of mass.
This bridge must be within the specific dimensions as listed,
the overall length must be at minimum 400mm long
House a 38mm wide road deck that extends the entire length of the bridge with no openings except for an 8mm wide hole for loading
The road deck must also be within 12mm of the abutment level either at the outside edge of the abutment or the ends of the bridge (whichever is closer)
The road deck may either be flat or have a smooth curve, if the deck is curved the difference between the low point and high point may not exceed 25mm
The bridge must allow passage of a rectangular object that is 32mm wide by 25mm in height.
the bridge also must be able to articulate in the vertical direction such that 50% of the overall length of the bridge is raised a minimum of 200mm.
While at rest the bridge should rest evenly on both abutments so that there is no gap between the bridge and the abutments on both sides.
Applying 10g of force to the lifting mechanism should allow for a 20lb piece of paper to slip between the abutment and the bridge at minimum.
Engineering Merit
This project has engineering merit because it is a culmination of many different principles of engineering and mathematics. While designing a bridge you must look at what forces are being applied to which direction and locations, analyze the stresses placed on individual components as well as the overall structure, determine material dimensions while sticking to the previously mentioned weight and dimensional requirements of the project, and finally designing a strong and durable device that will easily actuate the vertical motion of the bridge without compromising the overall structure of the bridge itself. All of these factors lead to a large engineering challenge.
Scope of Effort
The scope of this project is to construct a truss that will be mirrored on both sides of the bridge as well as to design and build a device that will actuate the articulating portion of the bridge.
Success Criteria
This project will be determined as a success if the bridge matches the required dimensions while carrying a load and allowing passage to an over height structure.