Laboratory Testing: Retrofitted RC beam

Case study: SOFO System

Retrofitted RC beam monitoring
Crack monitoring
Shotcrete evaluation
Calibration of models
SOFO sensor verification

Project Description

Summary: Research on structural behavior of retrofitted RC beam with simulation of different types of degradation such as exfoliation or discontinuity (crack).

Clients: Kisarazu NCT, Keisoku RC, Toden Kogyo

Place: Chiba and Tokyo (Japan)

Period: 2004 - 2004

Installation: Kisarazu NCT, Keisoku RC, Toden Kogyo

Structure's short description: The needs related to concrete structure maintenance calls for (i) precise and economical monitoring system and (ii) safe and durable repair and retrofit engineering construction method. In oreder to evaluate both, laboratory test were performed on RC beams. Three specimens of RC beams were designed to have reinforcement tensile fracture at ultimate loading state. High-early-strength Portland cement was used. Beam A is the full rigidity health RC beam. The exfoliation was simulated on beam B, while, the discontiunity was simulated on beam C. Two SOFO sensors per specimen were used to monitor deformation during the tests. The schemas of specimens, loads and positions of SOFO sensors are presented in Figure 2.

Aim of monitoring: In this research, SOFO technology was utilized to monitor the deformational properties of full rigidity health RC beams and shotcrete-retrofitted RC beams. First, the reliability and stability of the optical fiber sensory system was verified by a separate verification test. After the sensors were verified, the test were performed in order to evaluate suitablity and performance of newly developed shotcrete Filcon S, desined for retrofitting RC structures.

Number of sensor: 6

Main Results: Example of test results concerning the crack analysis are presented in Figures 3, 4 and 5. All the beams were succesfully monitored and analysed and the following conclusions were carried out: 1. A practical equation was proposed for high accuracy precise displacement measurement by utilizing SOFO technology. 2. The thermal expansion properties of attachment material should be considered in a highly fluctuated temperature environment. 3. The reliability of structural deformational properties of newly developed shocrete Filcon S has been confirmed experimentally. There is no retrofitted material separation occurrence observed up to the entirely structural failure. 4. The most influence factor to structural durability, maximum crack of retrofitted structure was observed to be smaller than full rigidity health structure. 5. As structural degradation factor, crack width propagation of concrete structures can be monitored in high accuracy by utilizing SOFO FOS.

Figure 2. Specimen description and SOFO sensors configuration

Figure 3: Load, SOFO measurements and total crack width relationship

Figure 5: Load and maximum crack width relationship

Bibliography:

Global Concrete Structure Monitoring by utilizing Fiber Optic Sensor , S. Kurokawa, K. Shimano, S. Sumitro, M. Suzuki, IABMAS'04, Second International Conference on Bridge Maintenance, Safety and Management, October 19-22, 2004, Kyoto, Japan, 2004