JAX91
Structural
- Jul 26, 2007
- 45
My company does a lot of foundation designs for horizontal vessels, and I am looking for some insight on anchor rod design for these vessels. The vessels typically sit on two saddles, one on each end. One of the saddles is slotted to allow for thermal growth of the vessel. We normally put a slide plate under the sliding saddle, and use grout under the fixed saddle. We design the foundations for a thermal growth load equivalent to the coefficient of static friction between the slide plate and the saddle times the weight on the saddle. In the past, I have also designed the anchor rods for this same load; however, I am now thinking this may be overly conservative. The way the system is designed, the compressive force in the vessel increases as it heats up. It continues to increase until it overcomes the static friction at the sliding plate end, and then the vessel slides, releasing the load. Ultimately, the anchors on the sliding end never see a load from thermal growth because of the slotted hole. Because the load is released on the sliding end, the friction on the fixed end is never overcome. If this friction force is not exceeded, the vessel cannot slide to engage the anchors. Does that mean the thermal expansion never places load into any of the anchors? Essentially, if the vessel was set on the same grout/slide plate configuration with no anchors and no other transient loads, I would anticipate the same exact result. The fixed end would never move, and the sliding end would only move longitudinally with the thermal growth of the vessel. Does this sound correct?