Guideline for the assessment of existing structures

The use of design codes for the assessment of existing structures is at present common engineering practice in Germany. But since safety measures of design codes were developed to maintain a reliability level for a wide range of bridge types and configurations under the maximum expected live load over a certain period (in Germany this is 50 years), in most cases they are over-conservative for existing bridges. With this background it is considered to be essential to have a guideline which leads the practicing engineer through the process of structural assessment. Doing so on one hand it is supposed to describe and specify strategies and procedures for achieving an optimum balance between cost and safety or cost and serviceability and on the other hand regularise limits if necessary. Within the SAMCO (Structural Assessment, Monitoring and Control) network such described code of practice is going to be developed. The different levels of complexity of assessment procedures are considered. This will be undertaken for each of the three main parts of assessment: data acquisition, structural analysis and verification of safety / serviceability. In addition a paragraph will concentrate on special cases of assessment. This paper is supposed to introduce especially practicing engineers to a guideline for structural assessment based on ISO 13822 [1].

• Introduction

• Objectives

• Structural Assessment Methodology

• Non-Formal Assessment (Level 0)

• Measurement Based Assessment (Level 1):

• Assessment Based on Document Review and Visual Inspection (Level 2)

• Assessment Based on Supplementary Investigations (Level 3)

• Modified Partial Safety Factors (Level 4)

• Probabilistic Assessment Routines (Level 5)

• Special Cases of Assessment

• Conclusions

• References