Project 1: Bridge building
Initial design:
Research:
Part 1: Truss Bridge:
There are 4 main characteristics for all bridges which are form, span, material, and travel surface in relation to the structure. There are many forms that a bridge can take and a truss bridge is one of them, actually there are about 30 variety kinds of truss bridges including the Warren, Pratt, and Howe designs among others.
Truss bridges should have one of 3 span types including simple, continuous, or cantilever. However, most of bridges were made from metal especially from steel and iron, while other bridges can build of wood (covered bridges). Every truss bridge have travel surface that called deck, pony, or through truss. A deck truss have a small different from a pony truss which it is allows traffic to travel on top of the structure while a pony truss allows traffic to travel between two superstructures that do not connect at the top. Finally, through truss and pony trusses are similar, but they are different in the superstructures connect overhead.
Part 2: Beam Reaction:
Beam reaction means there are equilibrium of parallel force systems.
Beam types:
Beams can be categories into several types depending on the size of beams for example straight and curved beams. Moreover, according to their geometry and the manner in which they are supported beams can be classified. However, geometrical classification includes such features as the shape of cross section, whether the beam is straight or curved or whether the beam is tapered or has a constant cross section.
Types of beams based on the manner in which they are supported:
Õ Cantilever.
Õ Simply supported.
Õ Overhanging.
Õ Continuous.
Õ Fixed ended.
Õ Cantilever; simply supported.
Beams used in building and bridges:
- Girders: Usually the most important beams, which are frequently at wide spacing.
- Joists: Usually less important beams, which are closely spaced, frequently with truss-type webs.
- Stringers: Longitudinal Bridge beams spanning between floor beams.
- Purlins: Roof beams spanning between trusses.
- Girts: Horizontal wall beams serving principally to resist bending due to wind on the side of an industrial building.
- Lintels: Members supporting a wall over window or door opening.
Theory of beams reaction:
There are two mine equations that are used to calculate the moment and the reaction forces on any beams which are:
- Sigma of forces equal to zero ; Where Force= mass * gravity
- Sigma of moments equal to zero ; Where Moments=force*distance
Sketches:
There are many types of truss bridge, 2 designs have chosen for sketching by AutoCAD software in this section.
Figure 1, Sketch 1 by AutoCAD.
Figure 2, Warren truss sketch by AutoCAD.
Manual calculation or use of Maxwell’s diagram for bridge:
In this section, two designs have calculated by Maxwell’s diagram method (hand sketches & AutoCAD sketches) with defaults numbers. There are calculation for each member with their magnitude and direction.
Figure 3, Maxwell’s diagram sketch by AutoCAD.
Figure 4, Reaction force calculations.
Figure 5, Maxell’s diagram.
Figure 6, Warren truss Maxwell’s diagram.
Figure 7, Warren Maxwell’s diagram by AutoCAD.
Member load calculations.
Initial designs on software:
Moodle software was used to design several bridges, and this section will show 5 designs of them.
Figure 8, design 1.
Figure 9, design 2.
Figure 10, design 3.
Figure 11, design 4.
Figure 12, design 5.
Number of sticks:
In this project, there are maximum numbers for sticks that can use to build bridge which are 150 sticks at most. Actually, some members needs more than one stick depending on the value of the compression and tension load on that members. However, this addition make a support to member and increase the value of sustaining of bridge.
Size of sticks:
Maximum length that can used to build bridge is 60 cm. In fact, there are several sizes of sticks and each one can hold specific values of load. The size of sticks must take into account in bridge publishing becuase there are many sizes of sticks were tested by tensile test (Compression & Tension) and each size has a specific sustaining value. However, we can investige that there is a inverse propotional between the size and the loading applied, so each member needs specific size depending on the hold value of load.
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