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# Deflection calculation f

• To: seaoc(--nospam--at)seaoc.org
• Subject: Deflection calculation f
• From: Roger Turk <73527.1356(--nospam--at)compuserve.com>
• Date: Fri, 10 Apr 1998 13:29:32 -0400

```Try your calculator and use P*l^3/48EI for concentrated LL + I deflection
and 2[5*w*l^4/384EI] for your uniform load (DL) deflection.  [The "2"
accounts for long term (creep) deflection due to DL].  See any basic
statics, strength of materials or elementary structural analysis book for
positioning two or more loads for maximum moment.  For maximum deflection due
to 2 or more wheel loads, you have only two possibilities:  One wheel load at
mid span with the other at the specified distance away, or the center of the
span centered between wheel loads.  (Interstate alternate wheel loads would
have to be considered.)

Isn't this quicker than looking for a computer program?

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

. > Problem: Calculate the live load deflection for a timber bridge deck for
. > simple and continuous spans ranging from 8 feet to 34 feet for HS-15,
. > HS-20 and HS-25 loading. The specific timber bridge deck to be used is the
. > longitudinal glulam deck system as described by wood industry brochures.
. >
. > For simple spans up to 28 feet, positioning a single wheel (point) load
. > at the midspan gives the maximum moment and others have told me that this
. > is also gives the maximum live load deflection. For longer spans, the
. > deflection would be based on 2 wheel loads as AASHTO specifications
. > require.
. >
. > I have looked for software on the web, but have not found a reasonably
. > priced package that will perform the math. One engineer has suggested
. > that a software program named "PC Bridge" can do the work. Is anyone
. > familar with this program? If so, do you know who to contact about it?
. >
. > Thanks for your help.
. >
. > Bruce Pooley
. > Timber Design
. > 3448 South Newland Court
. > Lakewood, CO 80227

```