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10m foot bridge

  1. May 12, 2010 #1
    hey ppl,
    In a nutshell, need to come up with a 10mX2m foot bridge over a river made from steel and concrete

    also to include foundation design.

    borehole data are as follows.

    Depth. Description

    0.2M Topsoil
    2.60M Loose silty sand
    4.56M Boulder clay

    water was met 1M below ground level.

    any ideas??????

    trying to work to BS4 prt1 2005
    trying to take into account that a max of 10 people maybe on this at one time.

    Thanks guy's
  2. jcsd
  3. May 12, 2010 #2
    Looks like coursework?

    So what are your initial ideas?
  4. May 12, 2010 #3


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    Gold Member

    My apologies for this but I can't resist. Why do you need a bridge over a stream made of concrete and steel?
    I am aware that English my not be your native tongue, in English we need to get the adjectives next to the word they describe. Perhaps;
    " 2mX10m steel and concrete bridge over a river" is what you mean.

    Sorry for the distraction.
  5. May 12, 2010 #4
    does it have a requirement for functionality or minimum weight bearing or anything like that? if not it's jsut like drafting and u can draw any bridge u want... >_>
  6. May 12, 2010 #5
    "trying to take into account that a max of 10 people maybe on this at one time." Assume 100kg a person (to be safe, 225lbs) or more would give you a load estimate.

    Do you have any ideas where to start?
  7. May 12, 2010 #6

    Well for a starting point,
    using two steel I beams as the main support ontop of a concrete abutment at each end.

    Aiming for more functionality as apposed to aethstetic's.

    unsure where to start for the calculations to be honest.
    (trying to factor in hand rails and decking also but unsure on BS on the overall bulding of this)
  8. May 12, 2010 #7
    Well I would start with a X section of the stream valley.

    Your borehole data is useless without relation to the section.

    Then you can roughly locate the foundations on the section.

    Then you can get the effective span.

    Then I would get a rough idea of the foundation loads = foundation weight + dead + super dead + live. (times partial factors as set out in the BS)
    Assumptions about the size of the bridge would need to be made for this.

    This will give you foundation pressures so you can design the foundation areas to suit.
    You may have to take the founds lower to avoid undercutting by groundwater or the stream. Again this is why you need the section.

    This should get you started.
  9. May 22, 2010 #8

    Another way to start might be to list all the features you think are required. Then arrange them in order of importance.

    Certainly from an engineering point of view you need to determine the loading: people, snow, wind, seismic, and whatever else, handrail loads from people, vehicles. Most of that is usually dictated by a building code. I can be argued that "correctly" determining the load requirements is more challenging than the design of the bridge itself.

    In terms of a beam or bridge span remember that depth is a key, and note that handrails are usually 3 feet high, take advantage of that if you can.
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