GFRP 보강근 경량콘크리트 슬래브의 거동 특성에 관한 연구

Abstract

Abstract Recently, with the development of industrial society, reinforced concrete structures get higher and larger and high strengthening of reinforced concrete materials and lightweight of structures can be said to be essential for this trend. Also, due to abnormal climate change caused by recent global warming, cold wave and heavy snow etc. are frequent in winter in Korea and existing bridge structures etc. are expected to be under the environment increasingly exposed to the risk of corrosion.

Therefore, this study targeted concrete structures expected to require lightweight and noncorrosion (bridge slab, water treatment related slab structure, slab structure of marine leisure facilities and industrial facilities etc.) in the future and attempted to examine the behavior characteristics of lightweight concrete slab using GFRP(Glass Fiber Reinforced Polymer) bar as flexural reinforcing bar.

This study conducted fracture energy measurement of concrete, bond strength measurement between reinforced bar and concrete, slab flexural experiment, comparison of the result of numerical analysis and the result of the flexural experiment, the numerical experiment of slab considering various parameters and conclusions were drawn as follows.

1)Concrete fracture energy was measured through beam specimens produced with normal and lightweight concrete and as a result, fracture energy of lightweight concrete decreased by 17% compared to normal concrete.

2) When based on the maximum bond stress of specimens using normal concrete and reinforcing bar, the stress of specimens that used normal concrete and GFRP bar turned out to decrease by 34% and that of specimens that used light weight concrete and GFRP bar by 54%, respectively.

3) Compared to slab made ​​of reinforced concrete, the weight of proposed slab was light, 72% but failure load was decreased by 42%.

4) There were some problems such as incorrect simulation etc. of normal direction stiffness coefficient when using the finite element, elastic behavior problem of GFRP bar in the non-linear numerical analysis using midas FEA but the result of the numerical analysis and the result of flexural experiment showed similar results. Also, the result of numerical analysis using the gap element between GFRP bar and lightweight concrete boundary surface to consider adhesion reduction characteristics of light weight concrete showed that use of the gap element is a way to get closer to the experimental results. 5) Of the parameters used in the numerical analysis, tensile strength and compressive strength of concrete, the elastic modulus of GFRP bar was investigated to affect the result of the numerical analysis but normal direction stiffness coefficient, a constant by experimental data, shear slip and GFRP flexural reinforcing bar ratio were investigated to have a minimal impact.

6) In various numerical experiments for GFRP bar lightweight concrete slab, deflections calculated for working load 124.8kN of first class bridge showed less value than deflection limit standard value of road bridge design criteria. Also, strain rates that occurred in GFRP bar for the same working load appeared as the value less than the strain rate for creep fracture so it is determined that long-term behavior will be satisfactory.

In the subsequent research, the experiment that can induce punching shear failure by producing slab that increased the thickness of slab specimens to the thickness of slab actually used and increased the width of slab by twice more than the present should be conducted and then the behavior characteristics of slab are needed to be invested in more detail. Also, more research is thought to be necessary on selection etc. of GFRP flexural reinforcing bar ratio recommended through the numerical analysis for changes in the boundary conditions, changes in the thickness of slab, changes in span length etc.