Define Installation of Pot Bearings?
In a sliding POT bearing, positive fixing to the main structure may not be required if the bearing is always subjected to adequate vertical loading which is the case in most of the concrete bridges. In such a case, any horizontal movement will always occur on the plane of least resistance which is of course the sliding surface of bearing. However, it is prudent to provide some fixing to guard against displacement during installation, impact, vibrations and accidental loading. Malfunctioning in a bridge bearing, in majority of cases, can be traced to faulty installation and much of damage usually occurs during installation, handling or storage.
Careless handling on site and ingress of dirt can easily lead to abnormally high frictional resistance. The sliding POT bearings are, therefore, normally delivered at site with the top and bottom parts bolted together. The bearings should not be dismantled at site. The bearings should be transported and unloaded carefully and stored under cover in clean, dry conditions. The seating provided under the bearing should be perfectly levelled. It is common to use a mortar bedding composed of sand-cement mortar with or without epoxy resin. A cube crushing strength of 35 N/mm2 is usually recommended for the bedding mortar. While installing the bearing, the transit bolts must be in position and these should be removed after the mortar has set and before the bearing is called upon to slide or rotate.