Determining Movement in Expansion Joint

[CWEngineer]

I am interested in detemining how much two slabs are going to seperate in an Expansion Joint throughout the life of the project so that I can provide a waterstop that can handle the required stretch.

I had a few questions:
1. Would this be a Thermal Expansion problem, where I could use a thermal expansion or contraction of 5.5x10-6 in/in/deg F?
2. Do I need to obtain the tempererature for a specifc site, or can I use a conservative value for design?

Appreciate your guidance

 

[civilperson]

If the slabs are placed in a heated and cooled building, then shrinkage can by lessened by placing alternate strips of the slab in pours scheduled 5-7 days apart. Thus, the shrinkage of the first placement will not contribute to the overall shrinkage of the slab since the shrinkage in the horizontal dimension will be filled by subsequent placements. The temperature swing in a air-conditioned building is moderate, (<50 degree F), so 5/16" of potential movement for each 100 feet of horizontal dimension will be a conservative estimate for maximum movement.

 

[CWEngineer]

These slabs will be in a Channel in Flagstaff, where there is extreme weather conditions.

 

[civilperson]

The CAP, Central Arizona Project, had a good detail for expansion joints added as a change order, (for many million of dollars more the original bid). The silicon caulking was placed on foam backer rod with the movement of each joint designed for 3/8" with joints on forty or fifty foot intervals. I think I remember the movement was less than 35% of the joint width, so the joints were 1" wide or more.

 

[CWEngineer]

I am looking for guidance or a reference to help me calculate how much two slabs (46 and 39 ft long)will seperate at the joints. I am also interested in seeing what the difference would be if the construction is in the summer or in the winter.

Appreciate your help.

 

[tngolfer]

gman1, I believe the thermal coefficient of concrete and steel is closer to 0.0000065.

One thing to note, the wider the the expansion joint, the better the filler will behave. Take for example a 0.5" joint that you calculate will want to move 0.5". That is a 100% increase/decrease. If you can make that joint 1.0", the concrete will still want to move 0.5" but the increase/decrease is now only 50%.

I also agree with civilperson's first post. This is a common practice as the contractor can use the previously poured slabs as their forms. The slabs may be poured 1, 3, 5, 2, 4; 1, 3, 2, 5, 4; etc.

 

[jheidt2543]

There is a book titled "Construction Sealants and Adhesives" that is a very good reference for joint design and sealing. Here is a link to a book site that has both new and used copies of the book:

http://www.bookfinder.com/search/?a...tle=construction%20sealants%20and%20adhesives

You can pick one of the new listings and look at the Table of Contents to see the topics covered.

Good luck!