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Showing 1-5 of 684 Abstracts search results

Document: 

SP-356_01

Date: 

October 1, 2022

Author(s):

Ali F. Al-Khafaji, John J. Myers, and Hayder H. Alghazali

Publication:

Symposium Papers

Volume:

356

Abstract:

This paper presents an investigation of the bond performance of corrosion-free sand-coated glass fiber reinforced polymer bars (GFRP) implanted in two types of fly ash-based eco-friendly concrete. Steel reinforcement is prone to corrosion and is expensive to fix, therefore finding an effective alternative has become a must. One of these alternatives is GFRP bar. On the other hand, conventional concrete (CC) is not issueless, as it significantly affects the environment through its high-intensity CO2 emissions. Thus, other alternatives have been looked into to mitigate the CO2 problems. One of these alternatives is partially substituting Portland cement with another CO2 emission-free material such as fly ash. In this study, two levels (50% and 70%) of high-volume fly ash concrete (HVFAC) were used to investigate their bond performance with GFRP bars. Cylindrical specimens were tested under the effect of pullout load. Furthermore, the bars were investigated chemically and microstructurally to see if the fly ash had some influence on the GFRP bar. For concrete, performance rank analysis was carried out to identify the best concrete mixture in terms of slump, unit weight, cost, and bond strength. In addition, to verify the experimental work, two-dimensional finite element models were built using translator elements to present the bond action between the concrete and its reinforcement. The results of the investigation showed that the bond strength of GFRP bars was less than that of mild steel owing to GFRP bar deformation. In addition, CC resulted in a higher bond strength than HVFAC. The bar analyses did not yield any obvious signs of microstructural deterioration or chemical attack.


Document: 

SP-356_13

Date: 

October 1, 2022

Author(s):

Mohamed Ahmed, Slimane Metiche, and Radhouane Masmoudi

Publication:

Symposium Papers

Volume:

356

Abstract:

The development of rehabilitation strategies for reinforced concrete bridges is a significant concern for civil engineers. Bridges exposed to harsh environmental conditions and subjected to daily fatigue loading are vulnerable to corrosion and accelerated deterioration of their components. Previous studies and field applications have shown that bonding carbon fiber-reinforced polymer (CFRP) to the bridge element surface is an attractive solution for bridge strengthening. This paper aims at reviewing and evaluating the use of externally bonded CFRP for bridge rehabilitation. The article is structured in two main parts. The first part is an experimental and field survey on using CFRP as external reinforcement for concrete bridges. The second part focuses on evaluating the performance of the Original Champlain Bridge (OCB) edge girder strengthened with externally bonded CFRP under live load tests, which were performed by the developers of the bridge. The results of truckload tests on the edge girder of the OCB show that the rehabilitation technique using externally bonded CFRP sheets on the edge girder of the bridge was able to keep the shear strains constant and extend their service life for up to 10 years until deconstruction of the bridge.


Document: 

SP-356_03

Date: 

October 1, 2022

Author(s):

Mohammod Minhajur Rahman, Xudong Zhao, Tommaso D’Antino, Zahra Ameli, Francesco Focacci, and Christian Carloni

Publication:

Symposium Papers

Volume:

356

Abstract:

Fiber-reinforced polymer (FRP) bars are an alternative solution to traditional steel bars for internal reinforcement of reinforced concrete (RC) structures. The potential reduction of damage in RC structures due to the absence of corrosion and the low weight-to-strength ratio of the FRP bars when compared to steel bars make FRP bars a cost-effective solution when durability is a concern. While a recent ASTM standard (ASTM D7913) has been issued to test the bond of FRP bars, limited work is available in the literature that deals with the determination of the interfacial properties between the FRP bars and concrete and the bond mechanism.

In this paper, experimental results are presented that aim at identifying a suitable setup to study the bond behavior and determining the effect of different bonded lengths on the stress transfer mechanism. Pull-out tests present some advantages to studying the bond mechanism without the complication of flexural stresses. Once the mechanism of the bond is studied at the small scale, and the interfacial cohesive material law is obtained, it is possible to simulate the behavior of full-scale members. The majority of the pull-out tests are performed with a short bonded length, which does not allow to fully establish the stress transfer between the bar and the surrounding concrete. In this paper, bars are embedded in concrete cylinders and pull-out tests are performed in displacement control with four bonded lengths. The first bonded length is equal to 5 times the bar diameter in order to consider the case of ASTM D7913. The other three bonded lengths are equal to 10, 20, and 40 times the diameter of the bar, respectively. Loaded-end displacement is obtained from the measurements of three linear variable displacement transformers (LVDTs). For some specimens, the free-end displacement was measured by two additional LVDTs. The load responses in terms of applied load versus machine stroke, loaded-end slip, and free-end slip are plotted and compared for the different bonded lengths. The results show that the average shear stress calculated according to ASTM D7913 is not constant for the different bonded lengths. In addition, the slip at the free end is activated at a different percentage of the peak load as the bonded length increases, which indicates that the bond phenomenon requires a certain bonded length to be fully established. The experimental peak stress versus bonded length and the stress level in the bar as a function of the embedded (bonded) length, according to ACI 440.1R-15, are compared. The results indicate that for the bar type studied in this paper, the provisions of ACI 440.1R do not match the results of the pull-out tests.


Document: 

SP-356_11

Date: 

October 1, 2022

Author(s):

Ahmed G. Bediwy and Ehab F. El-Salakawy

Publication:

Symposium Papers

Volume:

356

Abstract:

Deep beams are common elements in concrete structures such as bridges, water tanks, and parking garages, which are usually exposed to harsh environments. To mitigate corrosion-induced damage in these structures, steel reinforcement is replaced by fiber-reinforced polymers (FRPs). Several attempts have been made during the last decade to introduce empirical models to estimate the shear strength of FRP-reinforced concrete (RC) deep beams. In this study, the applicability of these models to predict the capacity of simply supported deep beams with and without web reinforcement was assessed. Test results of 54 FRP-RC, 24 steel-fiber-reinforced concrete (FRC), and 7 FRP-FRC deep beams were used to evaluate the available models. In addition, a proposed model to predict the shear strength of FRPFRC deep beams was introduced. The model was calibrated against experiments conducted previously by the authors on FRP-FRC deep beams under gravity load. The model could predict the ultimate capacity with a mean experimental-to-predicted value of 1.04 and a standard deviation of 0.14.


Document: 

SP-355_13

Date: 

July 1, 2022

Author(s):

Francesca Tittarelli, Alessandra Mobili, Paolo Chiariotti, Gloria Cosoli, Nicola Giulietti, Alberto Belli, Giuseppe Pandarese, Tiziano Bellezze, Gian Marco Revel

Publication:

Symposium Papers

Volume:

355

Abstract:

To guarantee concrete infrastructure functionality over time inspection and maintenance interventions are required. These inspections are typically scheduled on a periodic basis but may not be sufficient to prevent the onset of deterioration. When these problems occur, extraordinary maintenance operations shall be carried out, causing inconvenience to users and additional costs. The continuous monitoring of the infrastructures allows the transition from programmatic maintenance to predictive maintenance strategies, with a consequent increase in the safety of the structures as well as a reduction in management costs. This work aims to provide a brief overview of continuous monitoring systems for concrete structures developed by Università Politecnica delle Marche, focusing in particular on methods based on free corrosion potential measurement and electrical impedance spectroscopy in the so-called “self-sensing” concrete. The “self-sensing” characteristic of concretes can be improved through conductive additions such as fillers and fibers. The study conducted within the H2020 EU project EnDurCrete has demonstrated how expensive and sometimes toxic commercial conductive carbon-based additions, can be replaced by low-cost, non-toxic industrial by-products, enabling to perform relatively cheap and sustainable continuous monitoring of structures.

DOI:

10.14359/51736019


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