1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Force Resolving Structural Engineering Problem

  1. Nov 9, 2005 #1
    Can someone please help me start this question, I missed some vital notes in class and don't know how to do it. I just need to know the method so I can go on to do it myself Thanks :)

    Last edited: Nov 9, 2005
  2. jcsd
  3. Nov 9, 2005 #2


    User Avatar

    Staff: Mentor

    Apply the Method of Joints, i.e. in static equilibrium, the sum of the forces in the x and y directions is zero.

    Reference - http://mac6.ma.psu.edu/em11/p09a.html [Broken] - look at section on Method of Joints.

    http://physics.uwstout.edu/StatStr/Strength/StatII/stat22.htm [Broken]

    Some examples

    http://web.pdx.edu/~cpch/c415ep7.htm [Broken]

    Please don't miss class!
    Last edited by a moderator: Apr 21, 2017 at 9:36 PM
  4. Nov 14, 2005 #3
    Thanks for the help but i'm still a little stuck. I can work out the magnitudes fine but i'm a bit confused as to where the negatives should be and what they actually represent. This is my working so far (the joints are labelled A-K from left to right):

    Fab = Force along member AB

    Consider Joint A:

    Sum of Verticals at A=25+Fab*sin60=0

    Since this is negative it is a compressive force.

    Sum of Horizontals at A=Fab*cos60+Fac=0

    Since this is positive it is a tensile force.

    Consider Joint B (This is where I get confused:

    Sum of Verticals at B=Fab*sin60+Fbc*sin60+Fbd*sin0=0

    Since this is negative it is a compressive force.

    Sum of Horizontals at B= Fab*cos60-Fbc*cos60+Fbd*cos0=0

    Have I got all of the negatives right because I really have no idea how they are determined and also, is it even possible for Fbd to have a force of 0N on this bridge given that there is a force of 50N on the center of the bridge?

    Thanks for any help.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Force Resolving Structural Engineering Problem
  1. Resolving Forces (Replies: 1)

  2. Resolving force (Replies: 7)

  3. Resolving Forces (Replies: 11)