REPAIR AND REHABILITATION

This post deals with the latest techniques in repair and rehabilitation of structures. The various causes of structural failure and the principles of rehabilitation of structures are discussed. 

A large stock of existing structures and infrastructure are deteriorated with use and time and might have passed their design life and require retrofitting and rehabilitation. The cost of retrofitting various infrastructures is estimated in the lakhs of rupees. To Overcome the ill effects caused by these deteriorated buildings Repair and Rehabilitation works are carried out from time to time. Many of the existing structures were designed to codes that have since been modified and upgraded. Change in use or higher loads and performance demands require modifications and strengthening of structural elements.

WHY DO SOME STRUCTURES FALL DOWN?

Site selection and site development errors: 

Failures often result from unwise land use or site selection decisions. Certain sites are more vulnerable to failure. The most obvious examples are sites located in regions of significant seismic activity, in coastal regions, or in flood plains. Other sites pose problems related to specific soil conditions such as expansive soils or permafrost in cold regions.

Design errors:

These failures include errors in concept; lack of structural redundancy; failure to consider a load or combination of loads; deficient connection details; calculation errors; misuse of computer software; detailing problems including selection of incompatible materials, failure to consider maintenance requirements and durability; inadequate or inconsistent specifications for materials or expected quality of work and unclear communication of design intent.

Construction errors:

Such errors may involve excavation and equipment accidents; improper sequencing; inadequate temporary support; excessive construction loads; premature removal of shoring or formwork; and non-conformance to design intent.

Material deficiencies:

While it is true that most problems with materials are the result of human errors involving a lack of understanding about materials, there are failures that can be attributed to unforeseeable inconsistencies in materials.

Operational errors:

Failures can occur after occupancy of a facility as the result of owner/operator errors. These may include alterations made to the structure, change in use, negligent overloading and inadequate maintenance.

PRINCIPLES OF REHABILITATION?

Elimination:

Remove the materials that cause damage to buildings. This is no easy matter, because everything from the floor to the roofing may contain various undesirable materials in the form of additives and admixtures.

Separation:

Some things just can't be eliminated, but can still be protected. Use sealants or foil backed drywall to separate structures from damage causing sources.

Ventilation:

Controlled, filtered ventilation may be the only way to insure that the air we bring indoors is ideal. High humidity air or extremely low humidity air can cause significant damage to concrete, plaster and brick walls.

GENERAL AREAS OF REPAIR/REHABILITATION WORK?

• Repair, removal, replacement and maintenance of mechanical supports, sanitary treatment plant and pipelines.
• Repair and modifications to diffuser ports, aeration systems, and discharge pipelines.
• Installation and maintenance of dewatering structures.
• Pile restoration and wood pile concrete encapsulation.
• Anode installation for cathodic protection.
• Repair and replacement of trash-rack and debris screen.