Introduction - Retrofitting Design of Building Structures - page 1

CHAPTER 1

Introduction

1.1 The Significance of Structural Retrofitting

Before the 1980s, the key issue for retrofitting of building structures was the assessment
and strengthening of old houses. After the middle of the 1990s, however, structural assess-
ment and strengthening for both old and new buildings is becoming more intensive due to
the rapid development of the construction industry in China. Especially in the real estate
market, privately owned houses have become a majority, and many disputes between house
developer and house buyer have resulted. To solve these problems technically it is neces-
sary to perform structural assessment and strengthening of building structures. In some
cases the result of inspection and assessment of building structures is becoming an increas-
ingly important basis for government ocials to mediate the disputes in the real estate
market.
Generally speaking, the following building structures need to be evaluated and retrofitted.
(1) The buildings whose serviceability or strength cannot meet the requirements of struc-
tural codes or regulations, due to misuse, irregular maintenance, aging of materials and
structures.
(2) The buildings that have quality or safety problems due to design flaws or deficiency
in construction quality. These problems are often met in new construction and existing
buildings.
(3) The buildings in which structural damages are caused by disasters such as earthquakes,
strong winds, fires, etc.
(4) Those historic buildings and memorial buildings that need to be rehabilitated and
protected.
(5) The buildings that will be reconstructed, or have additional stories built.
(6) The buildings whose structural members may be changed during renovation, which
may influence the performance of whole structural system.
(7) When the buildings are located close to the site of a deep pit foundation of a new
construction, this deep excavation may cause unequal settlement of the surrounding soil and
the surrounding buildings may consequently face potential damages or risks. The assess-
ment and retrofitting of this kind of building is also an important safety measure for the
construction of the deep foundation as well as the new structure.

1.2 The Retrofitting Procedure of Building Structures

The retrofitting procedure of a building structure is as follows.
(1) Inspection of mechanical properties of structural materials
Generally the material properties may be obtained from design documents and construc-
tion daily records, especially the checking and accepting record upon completion of the
project. If there is doubt concerning material strength, testing of materials is necessary.
(2) Assessment of structural vulnerability and safety
Vulnerability assessment is to evaluate serviceability of a building structure by inspecting
the appearance of members and structural system to provide a basis for maintenance and
rehabilitation of the building. The safety assessment evaluates the strength of members and
structural system by structural analysis and section checking according to related design
code to provide a basis for structural retrofitting of the building.