Experimental Investigation on Dynamic Characteristics Changes of Fire Exposed Reinforced Concrete and Steel Members


Altunışık A. C. , Akbulut Y. E. , Başağa H. B. , Mostofi S., Mosallam A., Wafa L. F.

Fire Technology, 2021 (Journal Indexed in SCI Expanded) identifier identifier

  • Publication Type: Article / Article
  • Publication Date: 2021
  • Doi Number: 10.1007/s10694-021-01189-9
  • Title of Journal : Fire Technology
  • Keywords: Ambient vibration measurement, Column, Damage, Dynamic characteristics, Elevated temperature, Fire, Frame, Operational modal analysis, Reinforced concrete, Steel, PORTAL FRAMES, BEHAVIOR, TEMPERATURE, COLUMNS, RESISTANCE, SLABS, TESTS

Abstract

Damages to structures may occur due to construction defects during various stages such as design, construction, and operation phases, or due to natural disasters during their lifetime. The Operational Modal Analysis (OMA) method enables engineers to experimentally determine the changes in dynamic characteristics of the structures that resulted from these undesirable incidents. This method can also help to estimate the structural damages and determine the usage situations depending on stiffness changes. Fire is one of the most important effects that can cause changes in dynamic behavior of structures. Considering the damages caused by fire disasters in recent years, there is a crucial need to address the effects of high temperature on the relevant field of study. This study experimentally examined the effects of elevated temperature on changes in dynamic characteristics of reinforced concrete (RC) and steel structural members. In this regard, a total of 14 (10 columns and 4 frames) laboratory models are built. These models have been constructed with various cross-sectional dimensions considering furnace dimensions. The models have undergone high temperature tests based on ISO 834 standard fire curve. Ambient vibration measurements are conducted to identify and compare the experimental dynamic characteristics both before and after fire exposure. The results show that the damages caused by high temperature significantly affect the dynamic characteristics. Damping ratios generally show a tendency to increase and some minor alterations have been observed in the mode shapes. After the fire the natural frequencies of the models have decreased. It is also observed that increases in the cross-sectional area of RC elements are an effective parameter on these decreases. The use of steel bars affects the dynamic characteristics and temperature distribution within their sections. Besides, different types of steel profiles have an effect on deformations caused by high temperatures.