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# LRFD Live L application on simple span bridge

• To: seaint(--nospam--at)seaint.org
• Subject: LRFD Live L application on simple span bridge
• From: ozturk_ozgur(--nospam--at)cm.jip-ts.co.jp
• Date: Thu, 16 Oct 2003 20:33:40 +0900

```Hi,

I would be glad if anyone can explain or show me a way that I can find
especially on simple span girders. I'm familiar with Japanese standars, in
which there is only one truck to be considered with the uniform live load.
As far as I know, according to LRFD, 2 trucks must be considered with the
uniform load and the min. distance between the rear axle of one and the
front axle of the other is 15m., and I should consider 90% of the effect of

Do I need to consider two trucks for positive moment region like it is in a
simple span bridge? Is it for only negatif moment regions? I'm trying to
calculate the live load effect on a 25m(approx. 80 ft) simple span bridge
with 3 lanes and I was asked to compare the live load effects with AASHTO
LRFD. I guess it would be enough to apply only one truck for max. positive
moment but I couldn't be sure. Also for lane loading, I will apply a
9.3KN/m per girder, however, if I try to apply the lane loading on a 3D
model, shall I use a 3m width on transverse direction? (9.3/3=3.1KN/m2?).
In Japan, there is "L" type of loading, in which P1 is taken as 9.8KN/m2
for bending moment (uniformly distributed in 5.5m in transverse, 10m in
longitudinal dir.) and half of that for rest of the width(4.9KN/m2 for 10m
longitudinal), and for rest of the span, similar loading system is applied
but 3.43KN/m2 is considered for P1(named P2). I would appreciate if anyone
can help me to understand or find an LRFD LL loading sample especially for
a simple span bridge.

Best Regards,

Ozgur

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