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Re: Box Culvert Design

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As per my experience on box culverts on few Highway projects and references consulted during the process, it is to be done in following ways.
 
1. Earth Pressure at rest Ko should be considered in place of normal active earth pressure Ka for Bridge Abutments.
 
2. The Members should be considered as slab.
 
3. The effective width of slab for individual live loads should be estimated by Grillage analogy / effective width method.
 
4. The analysis may be carried out using simple moment distribution method or by using any analysis program with spring constants at base slab as per Bowel's Book on foundation.
 
Hope the above provide some help.
 
Anand Pandey
Bridge / structural enginner
 
-----Original Message-----
From: À̼º¸é <hydroyi(--nospam--at)kopec.co.kr>
To: seaint(--nospam--at)seaint.org <seaint(--nospam--at)seaint.org>
Date: Friday, January 24, 2003 8:30 AM
Subject: Box Culvert Design

I am working on the design of box culvert passing under the railway and vehicle road. The box culvert is used for the channel irrigating the cooling water for power plant. In analysis of the box culvert, the culvert is simplified into frame structure with 1 foot strip in breadth of member. Of course, the structural analysis of the frame was done by SAP 2000 software. The roof, base slab, and walls of the frame undergoes both the axial and flexural loads based on the result of the structural analysis.
 
In the reinforcement of the culvert, the ACI 318 code has many different minimum steel ratios for the specific structural members. For example, the minimum reinforcement for the flexural member is about 0.0035. For the slab, that is 0.0018. For the wall, the minimum reinforcement is 0.0015 in the vertical bars.  And that in the horizontal bars of the wall is 0.0025.
 
Actually, the roof, walls, and base slab fo the culvert can be reinforced following the above three ways. I think that it is important to decide how the members behave under the design loading condition. If the members of the culvert under the design loads behave like beams, the minimum reinforcement for the member should comply the beam requirements of the ACI 318.
 
Please help me make a choice the one among three cases on the basis of the member behavior. According to the AASHTO, they recommends that the minimum steel raito for the elements of the culvert is 0.0025.
 
I am really looking forward to your reply.
 
Thanks in advance.