Engineering Projects/Truss Bridge Project

Group Members

Goal

The goal is to design and build a draw bridge that will use truss members.

Research

There are five different types of bridge designs.

Beam bridge

Steam Across Iowa River by Douglas W. Jones

Beam Bridge- is the easy bridge to design because they are made of piers that support the horizontal beams. Very basic type of bridges that are supported by several beams of various shapes and sizes. They can be inclined or V shaped. The strength is determined by the roadway and by adding additional piers increases the strength of the bridge. Compression acts on the top of the roadway and the beam of the bridge and though the piers. Tension is pulling apart the underside of the roadway as the loads passes over the bridge is pressing down

Pros: these bridge are easy to build, inexpensive and is used in urban and rural area.

Cons: these bridge’s span between the piers are limited to a certain length, large ships and boats cannot pass underneath and they do not have an interesting appearance.

Arch bridge

Arch bridges are one of the oldest types of bridges and have been around for thousands of years. Arch bridges have great natural strength. They were originally built of stone or brick but these days are built of reinforced concrete or steel. The introduction of these new materials allow arch bridges to be longer with lower spans. Instead of pushing straight down, the load of an arch bridge is carried outward along the curve of the arch to the supports at each end. The weight is transferred to the supports at either end. These supports, called the abutments, carry the load and keep the ends of the bridge from spreading out. Arch bridge the arch uses semicircle design that can reduce the compression forces throughout the structure of the bridge. If the semicircle of the arch is greater than there is a greater the effect of the tension on the underside of the bridge. The arch bridge strength is determine by the shape of the arch.

Pros: is that the bridge is very strong and can use many different materials to build.

Cons: the design is limited to certain sites and can be expensive.

Truss bridge

Truss bridges are one of the oldest types of modern bridges. Truss bridges are among a variety of bridge designs that are being used for road traffic. Truss bridges are made up of triangles that holds up the roadway and is set on two piers for support. Truss bridge are very strong and are support heavy loads. The triangle angle are used because they are rigid and are stable. Compression acts on the upper horizontal members of the truss structure and in the piers that support the bridge. Tension acts on the bottom horizontal members. The angular members shares both of the force.

Pros: very strong used for a draw bridge or used for railroad trains.

Cons: difficult to build and require high maintenance. Are different to widen the bridge.

Suspension bridge

Bridge with overhead cables supporting its roadway. One of the oldest of engineering forms, suspension bridges were constructed by primitive peoples using vines for cables and mounting the roadway directly on the cables Suspension bridges are one of the strongest bridges that can span for long distances. They require large amount of materials and takes a long time to build. They are usually located near harbors. Suspensions bridges commonly have cable that stretch from two towers and are attached to each end of the bridge. The smaller cables are attached to the main cable to the roadway. The compression in the bridge is carried through the cables to the two towers. Tension is always acting on the cable because the roadway is stretching them.

Pros: can span long distances, can allow large ships and bats to travel underneath.

Cons: Expensive and requires a long time to build. Requires a large amount of material.

Cable stayed bridge

Cable stayed bridge are similar to Suspension bridges but are cheaper in cost and materials. These bridges have one or more towers that have cable attached to the roadway. The tower of a cable-stayed bridge is responsible for absorbing and dealing with the compression forces. The cables attach to the roadway in various ways. Bridge that uses deck cables that are directly connected to one or more vertical columns. The compression is in the cables that are attached to the roadway and are transfer to the towers. The tension is always located in the cables because the roadway is stretching them.

Pros: can span medium distance of about 500-2800 feet, are less expensive and faster to build than suspension bridge.

Cons: are typically more expensive than the other type of bridges.

Draw Bridge design

|Basic types of truss bridges or other bridges

pdf file of an explanation of the 5 common bridges

Bridge design

Design

CAD design

This is a CAD design of the truss bridge that open at a 45 degree angle. To build the actual bridge the group will have to find the a way to operate the truss bridge to open. This truss bridge is design in autodesk inventor.

The is an assembly drawing with two parts the truss bridge and the holder. First made a sketched of half of the bridge and was able to put constraints on the bridge so that it was connected with the holder. Then mirror the whole assembly to make a complete bridge. Next the bridge move up and down because of a constraint function on the parts and using the inventor studio in the Autodesk. Next was able to animate the constraints so that the bridge can open and closed at 45 degrees. A video of the truss draw bridge that I design.

This is a simple bridge in openSCAD, these are the code that were used to design the bridge.

cube(size =[10,21,1],center=true);

translate([4.5,0,1])

cube(size =[1,21,1],center=true);

translate([-4.5,0,1])

cube(size =[1,21,1],center=true);

union(){ translate ([4.5,9,-3])

cylinder(h=5, r=1, center=true, $fn=100);

translate ([-4.5,9,-3])

cylinder(h=5, r=1, center=true, $fn=100);

translate ([-5.5,9,-1.5]) rotate ([90,0,90]) cylinder (r=1, h=11,$fn=100);

}

union(){

translate ([4.5,-9,-3])

cylinder(h=5, r=1, center=true, $fn=100);

translate ([-4.5,-9,-3])

cylinder(h=5, r=1, center=true, $fn=100);

translate ([-5.5,-9,-1.5])

rotate ([90,0,90]) cylinder (r=1, h=11,$fn=100);

}

some ideas that the has came up with is to use:

Servo Motors

Hydraulic Systems [[1]] We plan on using Hydraulic get our draw bridge to go up

Bill of Materials

A picture of the Bill of Materials for project 2 truss bridge

The bill of materials for the project will include the prices of the wood for the base and the sides of the truss. The syringes and plastic tubing for the hydraulic system.

Tools glue. Bill of Materials

How We Made The New Bridge

After we reconstructed the first prototype gave us an idea of how we were gong to get the bridge to go up so instead of using the old prototype we create a new frame made out of white foam like material because it was easier to cut out of the cardboard, and instead of using a wooden block I decided to use a foam.

After doing this our next goal was to provide frames with support to hold it up. So we decided to make 4 stands (one for each side).

Our Next Steps

We want to install a syringe under the bridge in order to move the bridge up.

Similar to this design [[2]]

But we had to find a syringe that had enough presser to push the bridge upward.

So we found 60 ml syringe which can contain enough water to push the bridge upward picture.

We installed the bridge but we had to figure out what was going to hold the syringe in place so our group member, Melissa Chaput, suggested that we take piece of foam that could hold the syringe together.

Melissa pointed out that a rode will be needed to help move the bridge up and down and not get stuck in just one place like what would happen if glue was used. We decided to pierce a hole into the side of the stands to allow the rode to go through, and allow the bridge move up and down freely.

Holes that I injected to insert the rodes

Putting the materials together

So I insert the the rode into the hole into holes of the stands

Results