Question about Bridge Estimation project? Thanks!?

Question

We got this project in class, and he never said anything besides to put the final estimation in lbs and tons. Other than that I don't have any ideas of how to do this. I was wondering if someone could give me some tips or ideas about how to do this or any other help you could supply.

You are to perform a weight estimation of the first floor entrance bridge on the Engineering Sciences Building (located on campus).

You will prepare a report with the drawings, figures, and references needed to complete a written report. The report will contain all of the assumptions that were used to arrive at the final weight estimation.

Thanks to anyone who helps. I just don't know where to begin.

Answer 1

I suppose you mean "constructing a bridge that will link two buildings," and not the 'steel bridges' that we pass by over water areas?

I have to say that this bridge is to be constructed between existing structures.

First, you have to identify where the bridge connects the two buildings and the location.The two openings of the existing building should be studied well as to its aesthetic value and structural soundness. Are the existing buildings in concrete or steel structures? How old are they?

By the way, you seem to be interested only in the estimated weight of the bridge structure. You have to have an idea of the section of a bridge, such as the girders or beams or joists and the flooring material.

You have to consider what level will the bridge be? If the bridge linking the two buildings will be in the 2nd, 3rd, 4th or upper floors,there are considerations to be done. Consider the span or distance of the link. If steel beams are considered, there are available weight tables for steel beams. Apply basic math formulas such as volume, know the density of the construction materials, the additional weights such as electrical materials,etc.

Question: Why be interested In the bridge weight? In engineering, this is called the Dead Load. However, in computing all the materials needed to construct a bridge that will not fail, the Live Load, Wind Load, Impact Load, Moving Load, etc. should also be considered. If not, how can you recommend a steel beam of dimensions x & y if all the possible loads are not considered? Since your Bridge Design Project is not a typical one, the estimated weight of the bridge shall be based on what materials you put in. You may find section weights of standard bridges in governmental projects.But these are road bridges and not a bridge that will link two buildings.  

Answer 2

Field engrs in the Corps/Eng have guidelines for this. They use it to grade bridges during combat moves of armor.

For your purposes, measure or estimate the sections of beams and slabs. If closely spaced and reinf. concrete, take the beams to be comprised of the beam proper and a portion of the slab both sides. With the span, you can estimate the section properties and go from there. Use the beam formulas for simply supported.

Allowable stress? Compute using a range of allowable stress, because you don't know the duty this bridge will encounter during the lifetime. An intelligent discussion surrounding this issue will gain you points.