Structural Condition Assessment of Existing Buildings: A Guideline

A structural condition assessment of an existing building can be undertaken for a number of purposes. They vary on the type of structure and the needs of the client or owner. All personnel involved in the assessment should possess the technical qualifications, including practical experience, education, and professional judgment required to perform the individual technical tasks assigned. Interpretation of observations, test and probe results, and conclusions must be performed by a licensed design professional qualified in the appropriate discipline. The scope of services for the structural condition assessment should be defined by the licensed design professional qualified in the appropriate discipline, and all conditions and services must be mutually agreed on by the client and design professional. Bridge structural systems are environmentally exposed and, therefore, subject to more severe weathering, have less redundancy, and typically cannot be abandoned as they deteriorate.

The process of assessing the structural condition of an existing building consists of assembling and systematically analyzing information and data regarding the building or portions thereof to determine structural adequacy. A general procedure for conducting a structural assessment and evaluation of existing buildings is described. Because of the potential cost of a comprehensive structural assessment for an existing building, a multilevel approach is generally recommended. The preliminary assessment provides the initial analytical data for estimating the structural adequacy of an existing building and establishing the need and priority for a more detailed analysis. The basic steps include available documents review, site investigation, preliminary analysis, and preliminary findings and recommendations. A detailed assessment may be performed on the building being analyzed as a result of the findings of the preliminary assessment, as directed by the Authority Having Jurisdiction, or by the client.

State-of-the-art practices and methods for assessing the condition of selected materials in buildings include visual investigation, nondestructive evaluation (NDE) tests, and destructive tests including both field and laboratory procedures. The practices and methods for assessing the condition of several building materials are included and described in general terms with reference to documents that provide additional information. The information obtained from using the described practices and methods may assist in the selection of additional tests to be used in the evaluation process. Other appropriate practices and tests should not be excluded from consideration. The chapter also includes assessment of the following commonly used construction materials: concrete, steel, masonry, and wood.

Evaluation is defined as the process of determining the structural adequacy of the building or component for its intended use. Evaluation by its nature implies the use of personal judgment by qualified design professionals. Because these design professionals must ultimately take professional responsibility for the evaluation, the evaluation process cannot be standardized. Due consideration and weight should be given to an element or unit being tested, evaluated, and so on with respect to the other elements or units in the overall system being evaluated. Interpretation of the evaluation results is based on the experience and judgmental opinions of design professionals who are responsible for the evaluation. Because these design professionals will be accepting the professional responsibility for the overall evaluation, interpretation criteria are not standardized herein.

The report content should be consistent with the agreed-on scope of services. A simple checklist may suffice for a Cursory Assessment and a letter report for a Preliminary Assessment. A full report is more appropriate for a Detailed Assessment. This section is a guide since the order and content of the report may vary with the scope of the engagement, methods and techniques employed by the design professional, and for specific investigations. It provides a description of the various parts of the Preliminary and Detailed Assessments as may be used. The section as written presents a form for a typical client/consultant relationship but does not preclude a different format. An “Executive Summary” at the beginning of the report is discretionary. If included, it should contain brief statements of the purpose, scope, conclusions, and recommendations.

The condition of a concrete structure is best determined through understanding its material properties and physical conditions by visual examination in conjunction with applicable computational methods and testing. Major material properties and physical conditions are discussed. Test methods that can be used to evaluate these properties and physical conditions are provided. A condition assessment of concrete may require determinations of strength and quality. Proper assessment and subsequent evaluation should be utilized to reveal the concrete's ability to sustain loads and endure the impacts of the environmental conditions to which it is being or will be subjected. Basic information for conducting an engineering analysis of existing structural concrete requires knowledge about how new structures are designed.