Bridge Deck Behaviour, 2nd Edition, E C Hambly

[steveyeung]

I have a question about the temperature difference load:

In Fig.11.5 of the mentioned book, all the three spans are subject to temperature load. In Fig. 11.5 (c) there is a pair of restrained moments at the ends because there are no adjacent members to balance them. My question is that if the temperature load is applied to the middle span (ONLY), the other two are not subject to this loading. Can anybody tell me whether the restrained and relaxing moments in fig.11.5 (c) & (d) should be moved to the interior supports and there is not bending moment on the 1st and last spans in Fig. 11.5(c).

Thanks

 

[steveyeung]

Correction:

I have a question about the temperature difference load:

In Fig.11.5 of the mentioned book, all the three spans are subject to temperature load. In Fig. 11.5 (c) there is a pair of restrained moments at the ends because there are no adjacent members/internal forces (induced by the temperature load) to balance them. My question is that if the temperature load is applied to the middle span ONLY (For example, the first and the last spans are sheltered from the sunlight); the other two are not subject to this loading. Can anybody tell me whether the restrained and relaxing moments in fig.11.5 (c) & (d) should be moved to the interior supports and there is not bending moment on the 1st and last spans in Fig. 11.5(c).

Thanks

 

[VoyageofDiscovery]

Hi steveyeung,

First, this case is not something typical in bridge design as the temperature of the bridge is mainly affected by the ambient temperature which will affect the entire bridge throughout its cross-section. If sunlight is your issue then I believe the resulting effect to consider is thermal gradient. This illustration in the Hambly book is for axial thermal effects as shown in Fig 11.2b.

Now to answer your question of moments, the moment diagram will not be limited to the internal span as it will carry over through your continuous span system.

HTH

VOD