일계 이차모멘트법을 이용한 FRP RC 휨부재의 구조안전성 평가

Abstract

ABSTRACT

Structural Safety Evaluation of FRP RC Flexural Members Using Aevanced First Order Second Moment Methods

Seo, Dea Won Dept. of Architectural Environmental Engineering The Graduate School Hanyang University

The corrosion of steel reinforcement is one of the major problems that shorten the lifetime serviceability of concrete structures. There are many existing methods to prevent, delay, or repair the deterioration of concrete structures due to corrosion of steel reinforcements. Examples include decreasing concrete porosity, coating steel bars with a protective epoxy, increasing reinforcement cover requirements, and taking cathodic protection measures. However, these methods are costly and their long-term effectiveness is uncertain. Lately, fiber reinforced plastic (FRP) materials such as glass fiber reinforced plastic (GFRP) bars, as a reinforcing material for concrete structures, have received a great deal of attention among many engineering societies worldwide. Many engineers consider FRP as one of the most innovative material that may overcome the inherited deficiency of reinforcing concrete structures by steel bars in harsh environments due to corrosion. Therefore, it is necessary to accesss a suitable design approach which avoid the occurrence of non-desired modes of failure. Several design codes and recommendations for concrete members reinforced with FRP reincorcements have been already been prepared in Japan (JSCE, 1997), Canada (CSA, 2000), United States (ACI 440.1R, 2003, 2006) mainly as modifications to the existing steel reinforced concrete codes of practice. Modification principles are directly influenced by the unconventional mechanical properties of FRP reinforcement and empirical equations based on the limited experimental work on FRP RC elements. Thus, the FRPP RC design guidelines do not clear that both the structural reliability levels and the resistance capacity margins between various failure modes. This study focused on the reliability analysis of flexural FRP RC members. To determine the actual structural reliability levels, it is necessary to have accurate predictive resistance capacity models, a good understanding of the variability of material and behavior of FRP RC members. With these concerns in minds, both steel and FRP RC members were tested and analyzed. Also, this study presents the development of resistance models for concrete members (beams and slabs) reinforced with FRP bars (FRP RC), for carrying out reliability analysis. Probability of failure, , and Reliability Index, , of FRP RC sections are calculated using the developed resistance model. A wide range of design variables 432 FRP RC beams and 126 FRP RC slabs are designed to cover a wide range of variables (concrete strengths, cross sectional dimensions, and FRP reinforcement ratios) and used to develop resistance models for FRP RC beams and slabs. A structural reliability analysis is conducted based on the established resistance models and load model (buildings) obtained from the literature. The reliability index, , is calculated using AFOSM for all FRP RC beams and slabs for five ratios of live load moment and dead load moment. A detailed parametric study is carried out to study the parameters which affect the reliability index, . These results may be used to enhance the current recommendations for resistance factors, .