Document Information

Document Type: FAQ

Product(s): LEAP Conbox/CIP RC/PT Girder

Version(s): All

Original Author: Bentley Leap Bridge Technical Support Group – VM

QUESTION : Where in Conbox, the moments for an “exterior strip” on a concrete slab bridge are obtained?  Are they listed in the output as “exterior strip width moments”?

ANSWER:

Conbox design is based on Article 4.6.2.1.2  which says
“ For slab bridges and concrete slabs spanning more than 15ft and which span primarily in the direction parallel to traffic, the provisions of article 4.6.2.3 shall apply “
Exterior strip width moment is not calculated everything is combined into one single equivalent strip width and final moment is shown in the output.
“Conbox does not design exterior strip separately because LRFD does not say so. However, if the user wants to compute reinforcement required for an exterior strip, there could be a work-around. The user could come up with an equivalent loading. However, CBX design is always for the whole width; so the work-around run for the "Exterior Strip" should be used accordingly. In other words, the reinf calculated will be for the whole width, user can use it only for the "exterior strip" and use the regular design reinforcement from the normal run for the rest of the reinf. and will have to define a custom live load per his needs.”