Please give the details of "bridge bearing and stability" ppt for seminar. Its very urgent.

bridge bearing and stability ppt

Abstract

The designers of bridges must assure themselves that bridge bearings can transmit the high horizontal loads of current designs. The proportion of horizontal to vertical load is increasing due to the current trend toward continuous, joint‐free, redundant structures. From the 10‐20% level of some years ago, horizontal forces are now found at and above the corresponding vertical loads. These horizontal forces require that bearing stability be investigated. Two levels of stability criteria, for normal conditions and for extraordinary temporary conditions, are presented. An overturning factor of safety of 3.0 for rectangular surfaces (5.0 for circular surfaces) is proposed under normal (i.e., dead, wind, and live) loads, while a factor of 1.5 for rectangular surfaces (2.0 for circular surfaces) is proposed under extraordinary (i.e. seismic or construction) temporary loads. Examples of pot, disc, and spherical bearing stability checks are presented.

A bridge bearing is a component of a bridge which typically provides a resting surface between bridge piers and the bridge deck. The purpose of a bearing is to allow controlled movement and thereby reduce the stresses involved. Movement could be thermal expansion or contraction, or movement from other sources such as seismic activity. There are several different types of bridge bearings which are used depending on a number of different factors including the bridge span. The oldest form of bridge bearing is simply two plates resting on top of each other. A common form of modern bridge bearing is the elastomeric bridge bearing. Another type of bridge bearing is the mechanical bridge bearing. There are several types of mechanical bridge bearing, such as the pinned bearing, which in turn includes specific types such as the rocker bearing, and the roller bearing. Another type of mechanical bearing is the fixed bearing, which allows rotation, but not other forms of movement.