International Concrete Abstracts Portal

The most advanced method of investigating the performance of a structure is to continuously track the strain, deflection, and acceleration by analysing data collected from a series of wireless sensors installed on the structural member. Before analysing the data, it is important to assure the reliability of the data by verifying that all sensors are working properly. For an instance, in the reinforced concrete structure sensors are attached to the reinforcement bars and might be destroyed while pouring the concrete. Besides, sensors might malfunction due to excessive variation of temperature, load, or any other causes. Data-driven and structural models-based are two damage detection techniques in civil structures. In this study, the data driven method, a direct approach to damage assessment, was followed; this approach does not require structural modeling, such as finite element analysis. In this method, the existence of damage and its location are interpreted by pattern matching of the data series at different time ranges. The objective of this study was to develop new techniques to detect defective sensors based on the pattern matching method that included the Auto Regression Xeogeneous model. As a case study, Portage Creek Bridge was selected, located in British Colombia, Canada. Data sets of strain and temperature gages were downloaded from a database connected to the instrumented pier of the bridge and filtered and normalized continuously. The condition of a set of sensors installed in the pier was determined, using a method developed based on the concept of the sequential and binary search techniques. Using sensitivity analyses of the developed models, defective sensors were detected by pattern matching of simulated and measured or real data.

This paper presents an initial experimental result concerning the behavior of near-surface mounted (NSM) carbon fiber reinforced polymer (CFRP) strips embedded in a concrete substrate at elevated temperatures. Thermal stresses varying from 25°C [77°F] to 200°C [392°F] are applied for three hours. The experimental program is comprised of 48 CFRP-concrete specimens bonded with an ordinary or high-temperature epoxy adhesive and their comparative performance is of interest in the present investigation. Emphasis is placed on the residual capacity of the conditioned NSM CFRP-concrete interface and corresponding failure mode. Test results show that the interfacial strength of the specimens bonded with the ordinary epoxy is maintained until 75°C [167°F] is reached, while the strength noticeably decreases with an increasing temperature above this limit. The specimens with the high-temperature epoxy preserve interfacial capacity up to 200°C [392°F] despite a trend of strength-decrease being observed. The failure of the test specimens is brittle irrespective of adhesive type. Interfacial damage is localized along the bond-line with the presence of hairline cracks that further develop when interfacial failure is imminent.

Recently, several infrastructure failures have highlighted the importance of structural inspection and increase awareness of the need for efficient structural health monitoring and damage detection techniques. The Development of non-contact monitoring technique that is efficient and requires little preparation to implement would greatly benefit the civil engineering and construction community. Close range photogrammetry is a non-contact measurement technique that can be used to monitor a specimen’s deformation as it undergoes loading. This research investigates utilising an image matching algorithm to measure the deflection profile of concrete beams. The present paper illustrates the efficiency of the image matching algorithm (digital image correlation) in measuring the full deflection profile along a concrete beam. Five reinforced concrete beams, 2400 mm (94.48 in.) long, 250 mm (10 in.) deep and 150 mm (6 in.) wide were tested under 4-point bending. Three different surface treatment configurations for the test specimen’s side faces as well as two types of longitudinal flexural reinforcement, steel and CFRP, were used. Two LVDTs were used to measure the deflection to validate the proposed digital image correlation algorithm. It was concluded that the image matching algorithm can be used efficiently to measure deflection profile of a flexural member. Despite all existing health monitoring techniques, image matching has the potential to reconstruct the deflection profile along the whole member length to evaluate its current structural behaviour.

This paper presents the performance of constructed bridge decks in a cold region with the aid of an extensive database acquired in North Dakota. A total of 1,328 decks are sampled from a 15 year inspection period. These data are statistically characterized and probabilistically analyzed. The importance of timely technical action for enhancing the condition rating of the decks is discussed. The stochastic response of the existing decks is effectively represented by Gaussian probability distributions, regardless of inspection years. The performance of the decks tends to converge to a certain state with time. The state-transition of the in-situ decks is identified through the global health index proposed. A new nondestructive testing method is developed to diagnose the physical damage of concrete based on near-field microwave.

Fiber-Optic Sensors (FOSs) are being introduced in structural health monitoring of bridges and other structures as an alternative to conventional sensors such as electrical strain gauges and vibrating wires. Advantages of FOS, from a materials point of view, include resilience and durability. This study examines the viability of using Osmos FOSs to monitor corrosion-damage in scaled-down reinforced concrete columns. The test variables include the corrosion level, different rebar diameters and concrete covers. Five circular RC columns were cast. The columns were 300mm (12 inch) in diameter by 900 mm (36 inch) long. Each column was reinforced longitudinally with 6 rebars (15M or 20 M or 25 M) and 10M stirrups were provided at 200mm (8 inch) o/c. The concrete cover was 30mm or 45mm or 60mm (1.25 inch or 1.75 inch or 2.15 inch). Accelerated corrosion technique was used to corrode the longitudinal rebars in the columns up to 10% mass loss. The columns were instrumented with Osmos FOSs that were externally mounted around the column’s circumference to monitor the lateral deformation due to corrosion. In addition, corrosion crack widths on the column face were monitored during corrosion exposure. The test results showed that Farady’s law prediction works well for low corrosion levels (up to 5% mass loss) but not for high corrosion levels (10% mass loss) and that it becomes un-conservative as the rebar diameter increases. Corrosion expansion measured based on the Osmos FOS readings and the summation of crack widths across the circumference of the column showed very good correlation. It was found that the corrosion expansion increases as the rebar size increases at any corrosion level and that the corrosion expansion increases as the concrete cover increases at high corrosion level. Therefore, based on the findings of this study, Osmos FOSs can be used in the assessment and monitoring corrosion of steel reinforcement in reinforced concrete columns.