Bridge demolition Methods
Bridge demolition is increasingly becoming an important issue, as more bridges reach their end of service life and require rehabilitation or replacement. Furthermore, as the capacity of bridges and highways are reached, partial or total removal of bridges becomes necessary to allow for widening of the highway underneath the bridge or for widening the bridge itself to increase the capacity of the transportation system.
Bridge demolition, like all demolition projects, requires careful planning and the use of proven and uniform methods and procedures. The type of bridge to be demolished and circumstances surrounding it determine the type of demolition process to be utilized.
There are two kinds of demolition:
• Explosive Demolition: it is conducted by very specialized engineering firms
• Conventional (non-explosive) Demolition: It is taking apart a structure and lowering its components to grade so there is no potential energy that can be released.
The vast majority of highway bridge demolition is a conventional, utilizing excavators and cranes. There have been a limited number of publications found in the literature on bridge demolition. The general sequence in a highway bridge demolition typically starts with the removal of the concrete deck. Concrete can either be hammered to the ground or panelized and moved away from the bridge. Sometimes shielding is placed under the bridge so that concrete debris does not fall into a waterway, traffic, or property below. After concrete is removed, the girders are removed from the structure with a crane or excavator (equipped with grapple or shear attachment) and lowered to grade. It is not mandatory to remove the concrete first. However, the concrete weighs much more relative to the steel on a typical highway bridge .
WHY IS ENGINEERING NEEDED?
For the demolition process there is much structural analysis that goes into the removal sequence. The structure must be checked for strength and stability at every planned component removal, as the structural system, loads, and the load path will change. The removal of lateral bracing diaphragms between girders becomes very important for the demolition operation. It is more convenient for the contractor to remove as many braces as possible prior to supporting a girder to be removed with a crane or excavator. Thus, the engineer needs to analyze and determine how many braces can be removed so the structure remains safe for the work crews.
Engineering is required because:
1) The work is performed by people, and their safety is of utmost importance: Every stage during the process needs to be analyzed in detail, and the important information clearly presented in the demolition plan drawings to be used in the field.
2) The structure being removed is usually located near other structures: Often to-be-demolished highway bridge structures are in close proximity to other structures. Sometimes, the structure being removed is in the direct vicinity of the travelling public. The demolition sequence and stability of the structure at every stage should be analyzed and the safety of the proximity structures and the people should be ensured.
See the image below of one of our more recent bridge demolition projects at Los Angeles International Airport (LAX). We at ECG expertly, proudly, and safely execute all of our bridge projects.
We pride ourselves in providing Demolition Services you can depend on. Contact us to get started on your next project, Call us: 562-438-7999.