This paper presents the results of an experimental study conducted to understand the stress-transfer mechanism of fiber reinforced concrete matrix (FRCM) composites externally bonded to a concrete substrate for strengthening applications. The FRCM composite was comprised of a polyparaphenylene benzobisoxazole (PBO) fiber net and polymer-modified cement-based mortar. Direct shear tests were conducted on specimens with composite strips bonded to concrete blocks. Parameters varied were composite bonded length and bonded width. Results were analyzed to understand the effective bonded length, which can be used to establish the load-carrying capacity of the interface to design the strengthening system. The normalized load carrying-capacity was plotted against the width of the composite strip to study the width effect. Finally, strain gage measurements along the bonded length were used to investigate the stress-transfer mechanism.

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.

Despite that steel fiber concrete (SFC) has been used in concrete structures during more than 50 years there is still a lack of practical recommendations. In Sweden, SFC has been used in concrete overlays on bridges during more than 25 years but the usage frequency is fairly low. The current Swedish guidelines for SFC overlays are based solely on empirically determined relationships between the amount of conventional reinforcement for crack control and amount of fibers. In a recent study at the Swedish Cement and Concrete Research Institute, the current recommendations have been critically reviewed. The experience shows that this empirical recommendation works fairly well for traditional concrete mixes and for the most frequently used fibers but there is a need of recommendations that promote the development of better concrete mixes and more efficient fibers. In order to reach this goal, guidelines which are much broader in their application field need to be developed. A novel approach taking the mechanical properties of the actual SFC into account has been proposed. This approach may also be used for concrete with synthetic fibers if their mechanical and long-term properties are proven to be sufficient.

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 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.