The idea is great. Actually,
this is exactly how I modeled it in 3D.
In reality, however, it will result
in the longitudinal seismic being transmitted to only one bearing out
Well, wait... Obviously, it won't be symmetrical, but it may just work...
Good one. Thanks.
As far as "surrendering" goes -
on a principle, I am against that, as long as I feel being right or proven
otherwise. However, I would readily agree with the opposing side, if any
good argument would be given, not like "my 3D model is better than
Besides, surrendering (man, what
a terrible word!) would result in me redesigning, like, 30% of the project
----- Original Message -----
Sent: Wednesday, October 06, 2004 10:36
Subject: Re: rotation at bearings
There should be a way to get out
of this battle. I agree with you; but sometimes you just have to
What happens if, in order to
retain your desired longitudinal stability, you slot the end of only one of
the beams? What about adding an end beam between your two pinned end
beams with a vertical "pinned" connection at mid point? Either idea
should eliminate the theoretical problem envisioned by the reviewer.
Just a couple of possible
solutions to solve what I also consider a non existing problem.
H. Daryl Richardson
"S. Gordin" wrote:
engineers.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office"
hate long posts.However, please hear
more than a month now I am going back and forth with an independent reviewer
on the design of two pedestrian bridges. I managed to prove my points
on all issues, but... On the remaining one issue I seem to have
exhausted all means of persuasion within reason and logic. So, I would
appreciate a good advice.
80'x8' steel half-truss pedestrian bridge with four bearings: two with two
dia.1-3/8" holes each on one end of the bridge, and two with 1-3/8"x3"
slotted holes on the other. A total of 8 anchors 1" diameter,
to the reviewer, the 3D analysis of the bridge shows that the application of
the transverse (wind or seismic) lateral force on the bridge produces the
longitudinal reactions in the pinned bearings on one end of the bridge.
responded that such forces will never develop, mainly, because there is no
such thing as an ideal hinge (unless it is so purposely
the ø1? anchor bolts of the subject bridges are located in ø1-3/8? baseplate
holes (3/8? gap).According to my own
3D analysis , the maximum movement of the bridge at the supports due to the
horizontal-plane rotation under the transverse force of a 100 MPH wind is
0.18? << 3/8?. This means that actual ?pins? and lengthwise reactions
(due to transverse forces) in those bearings will never
reviewer still insists on putting slotted holes in all four bearings and to
account for longitudinal seismic through actual dynamic impact on the
abutment backwall and anchors.Alternatively, the reviewer suggested
designing the bridge abutments and anchor bolts for the couple of
longitudinal forces resulting from the application of the transverse (wind
or seismic) force?
compare: the actual (transverse) wind reactions are about 9.3 kips per
longitudinal forces resulting from the same force are about 33 kips (acting
question is ? am I correct here? If so, how can I convey the message to the
Steve Gordin, PhD
Registered Structural Engineer
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