Detection of Fracture in Steel Members of Building Structures by Microstrain Measurement

Jun Iyama

doi:10.1007/s13296-020-00408-3

Abstract

This paper discusses a possibility of detecting structural damage caused by an earthquake, by measuring the time history of the strain of beams and columns before and/or after the earthquake. An index called “local stiffness” is defined as the ratio of section force amplitude to representative displacement amplitude, and this ratio can be physically interpreted as stiffness. By calculating section force amplitude at a section or node from the measured strain amplitude under a microtremor or small aftershocks and comparing it with the results of a static pushover analysis, it becomes possible to detect any structural damage, such as fractures. This methodology was applied and the microstrain data of a steel moment frame were measured in a large-scale shaking table test; beam-end fractures were observed after some excitation tests. After the beam-end fracture formed, the measured local stiffness dropped significantly below the analysis value, indicating the possibility of employing this value to detect fractures using the analysis value as a threshold value.

Highlights

Structural health monitoring (SHM) is a research field that has received considerable attention
SHM has been applied especially for bridge structures, and many projects that monitor the dynamic behavior of large bridges, such as Akashi Kaikyō Bridge (Sumitro et al 2001), and Tamar Bridge (Cross et al 2013), have been carried out
Strain measurement is widely performed for bridge structures, but it has been rarely applied for actual building structures

Summary

Introduction

Structural health monitoring (SHM) is a research field that has received considerable attention. In recent years, some commercial monitoring systems for building structures have been marketed and increasingly applied to high-rise buildings and large-scale structures. Compared to bridge structures, the application of SHM for building structures is still limited. One possible reason may be the limited monitoring information obtained considering the high cost of such measurement. In such monitoring systems, the floor response acceleration of a building is measured, and the displacement or other indexes are calculated. It is possible to detect some change in the Strain may be used as an alternative index that reflects the structural properties and performance better. Strain measurement is widely performed for bridge structures, but it has been rarely applied for actual building structures.

Objectives

Methods

Findings

Conclusion