Expansion Joints Issues and Concepts - PowerPoint Presentation Example

Some structures would not support ground movements such as earthquakes leading to destruction of buildings and bridges. This led to the idea of expansion joints that would later solve the problem (Rosignoli, 2002). Functions of expansion joints The main function of expansion joints is to safely absorb the high temperatures of various construction materials as a result of the constant expansion and contraction. As explained earlier the contraction and expansion is due to the changing weather conditions (Brown, 2001).

The expansion joints therefore make structures to remain intact thereby they become safe for public use. There are many types of expansion joints and each is designed to solve a specific problem though the purpose or function still comes back to absorbing stress to avoid damage. Types of Expansion joints used in bridges in Australia Bridge expansion joints are joints that are designed to allow traffic to cross the bridge structure while at the same time permitting the movement of the bridge deck due to thermal effects, wind, traffic loading, seismic effects among others.

The joints should provide a watertight connection for the lifetime of the bridge as the lack of it could reduce the durability of the main bridge structure that may result in the need for major remedial works. These kinds of joints are rather unique because of their relatively delicate construction and severe loading conditions and therefore need to be replaced several times during the life time of the bridge (Gottermoeller, 2004). Bridge expansion joints can be broadly classified into two types: open joints and closed joints.

The open joints are not water proof. Water and debris are allowed to fall through the joints. The water erodes the soil under the structure, strains the bent cap and columns, is detrimental to adjacent steel girders, diaphragms, bearings and is a nuisance to any traffic under the structure. The closed joints on the other hand are water proof and have become an alternative to open joints due to the many advantages that they provide (Blockley, 2010). There are three most common types of open joints used in Australia.

The butt joints provide an open space between adjacent edges of the deck. They are used where the movements are of a rotational nature or where the thermal movements are small. The edges are usually protected with metallic armor which is subject to corrosion (Lima, 2006). The open space frequently fills with debris making the joint less effective. Period maintenance is mandatory to clear up the joint and the debris. The second type is the plate joint which accommodate greater movements than the butt joints, usually between one and three inches.

A sealant is placed in the joint that prevents some water from passing through. It also prevents the accumulation of debris that can make the joint ineffective. The third type of joint is the tooth joint or the finger joint (Gottermoeller, 2004). They are usually used on long bridges to accommodate large movements. They are usually placed in the span near the point of contra flexure. Drains are placed to prevent drainage across the joint if feasible. In some areas they are provided with a drainage system to collect the water passing through.

These joints are used where water and debris passing through cannot damage anything below the bridge. The performance of these joints