Guide for Evaluation of Concrete Structures before Rehabilitation

Description

This report outlines procedures for the evaluation of concrete structures before rehabilitation; however, it may also be useful for evaluation of structures even if rehabilitation is not contemplated. These procedures are intended to be used as a guide to assist the architect/engineer responsible for the evaluation. The evaluation work is generally performed for one or more of the following purposes:(a) To assess deterioration due to exposure conditions;(b) To evaluate structural damage or distress resulting from unusual loadings, improper design, poor construction, overloads, fire, flood, foundation settlement, abrasion, fatigue effects, chemical attack, weathering, or inadequate maintenance;(c) To determine the feasibility of changing the use of astructure;(d) To assess the capacity of a structure to accommodatelarger loads;(e) To enlarge a structure or change the appearance of the structure;(f) To determine the feasibility of modifying an existingstructure to conform to current codes and standards; and(g) To verify the structural adequacy and integrity of astructure or selected elements within a structure.

The objective and extent of the rehabilitation effort shouldbe clearly defined, thereby providing focus for the evaluation.The owner should be consulted and provided with relativecosts for various levels of interference during the evaluationprocess so that an informed decision can be made as to howto proceed with the rehabilitation work. The cost associatedwith items, such as interference with normal operations or acomplete shutdown of a structure, can easily exceed those ofthe actual rehabilitation work. Although rehabilitation canoften be planned and executed with minimal interferencewith normal operations, it is usually more cost effective tocease normal operations during rehabilitation work.

There is no absolute measurement of structural safety in anexisting structure, particularly in structures that havedeteriorated due to prolonged exposure to the environment,or that have been damaged by a physical event. Guidance forthe strength evaluation, however, is provided in ACI 318,Chapter 20, Strength Evaluation of Existing Structures.Engineering judgment and close consultation with the ownerregarding the intended use of the structure are required inthe evaluation of structures. Many repair failures have beenobserved in rehabilitation projects due to erroneous reha-bilitation procedure and or improper judgment.