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1

A new model for predicting the axial compression capacity of reinforced concrete cylinders strengthened with CFRP

Guo Guang, Zhou Li, Wang Bangkang

Archives of Civil Engineering

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2024

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Vol. 70, nr 1

389--404

EN

Numerous scholars have identified the shortcomings of imprecise terminology and substantial computational inaccuracies in the current models for predicting the axial compression capacity of CFRPstrengthened reinforced concrete (RC) cylinders. To improve the prediction accuracy of the axial compressive capacity model for CFRP-strengthened RC cylinders, the present axial compressive capacity model for CFRP-strengthened RC cylinders was scrutinized and evaluated. Drawing on Mander’s constraint theory and the concrete triaxial strength model, a novel axial compressive capacity model for CFRP-strengthened RC cylinders was proposed. This study collected 116 experimental data on the axial compression of CFRP-strengthened RC cylinders and analyzed the accuracy of various models using the data. The findings indicate that the model proposed in this study outperforms other models in predicting axial compression capacity and demonstrates high prediction accuracy. Furthermore, an analysis is conducted on the variation law of the model’s predicted value with respect to the design parameters. The proposed model in this study identifies concrete strength, stirrup spacing, and elastic modulus of CFRP as the primary factors that influence the axial compression capacity of CFRP-strengthened RC cylinders.

2

Effects of stirrup spacing on shear performance of hybrid composite beams produced by pultruded GFRP profile infilled with reinforced concrete

Özkılıç Yasin Onuralp, Gemi Lokman, Madenci Emrah, Aksoylu Ceyhun

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 1

art. no. e36, 2023

EN

Pultruded Glass Fiber-Reinforced Polymer (pultruded GFRP) composite produced by the pultrusion method has become popular in civil engineering applications due to its lightness, corrosion resistance and high strength. However, the use of the pultruded profile combining with reinforced concrete is still limited due to a lack of knowledge. Therefore, the behavior of the pultruded GFRP profile infilled with reinforced concrete beams (hybrid beams) is investigated. This study focused on the effects of stirrup spacing for the hybrid beams. Pursuant to this goal, a total of eight different beams were tested under four-point loading. One reference beam without the pultruded profile and seven hybrid beams having different stirrup spacings were considered. Moreover, the hybrid beams with and without stirrups were wrapped by unidirectional GFRP composite to investigate the effects of stirrup spacing on shear capacity of the beams strengthened by GFRP composite. The experimental findings revealed that tightening stirrups increased the load and energy dissipation capacities of the hybrid beams; however, it could not prevent brittle failure. On the other hand, wrapping hybrid beams with GFRP composite increased the load and energy dissipation capacities and also prevented brittle failure regardless of the presence of the stirrups. Therefore, it is strongly recommended that the unidirectional pultruded profiles should be strengthened with 90° GFRP wrapping to have ductile behavior.

3

Bond behavior of corroded reinforcements in concrete: an experimental study and hysteresis model

Zhang Yi‑Bo, Zheng Shan-Suo, Dong Li-Guo, Zheng Yue

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 2

ar. no. e95, 2023

EN

In order to study the effect of both longitudinal reinforcement and stirrups corrosion on the bond performances at steel-concrete interface under reversed cyclic loading, in this paper, the eccentric pull-out tests under reversed cyclic loading were carried out on reinforced concrete (RC) specimens with five corrosion degrees, three concrete cover thicknesses, and three stirrup spacings. The influence of the corrosion rate of longitudinal reinforcement, corrosion rate of stirrups, cover thickness, and stirrup spacing on bond performance indicators was examined, including the initial bond stiffness, peak bond stress, slip at peak bond stress, bond strength at unloading, unloading stiffness, frictional bond resistance, and cumulative energy dissipation. Moreover, the effects of coupling corrosion on cover cracking morphology and bond degradation mechanism were also analyzed. Results indicated that after severe corrosion of longitudinal reinforcement and stirrups, the cover appears cracking or local spalling, and the bond performances are signifcantly reduced. It was also showed that thickening cover or densifying stirrups could improve the interface bond performance and energy dissipation capacity. Each hysteresis parameter degrades apparently under the controlling slip corresponding to the peak bond stress. Subsequently, based on the analysis results and previous studies, empirical local bond stress-slip hysteresis models for corroded longitudinal reinforcement and corroded stirrup under reversed cyclic loading were proposed. Good consistency was observed for the hysteresis model with existing experimental data.

4

Ocena trwałości konstrukcji żelbetowej zagrożonej korozją

Gwoździewicz Piotr

Mosty

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2022

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nr 2

24--29

PL

Artykuł zawiera zestawienie podstawowych sformułowań opisujących postęp zjawisk korozyjnych w elementach betonowych ze zbrojeniem oraz ilustrację ich zastosowań w postaci przykładu analizy porównawczej konstrukcji, w której skonfrontowano wyniki teoretycznych oszacowań rozwoju procesów korozji z wynikami badań konstrukcji.

EN

The article contains a summary of the basic phrases describing the progress of corrosion phenomena in reinforced concrete elements and an illustration of their applications in the form of an example of the comparative analysis of structures, in which the results of theoretical estimates of the development of corrosion processes are compared with the results of structural research.

5

A review on autogenous self‑healing behavior of ultra‑high performance fiber reinforced concrete (UHPFRC)

Yao Chao, Shen Aiqin, Guo Yinchuan, Lyu Zhenghua, He Ziming, Wu Hansong

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 3

art. no. e145

EN

Ultra-high performance fiber reinforced concrete (UHPFRC) is well known for its superior workability, strength, ductility as well as durability, but its intrinsic self-healing ability is rarely valued and developed. This review focuses on the inherent potential or superiority, characterization, and mechanism of autogenous healing UHPFRC, aiming to obtain fundamental data for its mixture innovation, design, and application. High potentialities of autogenous self-healing UHPFRC depend on its excellent component requirements (fiber; abundant binding particles), mix design (high cementitious materials content, low water-binder ratio, moderate fiber content), rehydration capacity, and shrinkage or loading-initiated cracking features. Meantime, the generation of cracks makes the internal substances include active ingredients exposed to the external environment such as air, water, and temperature, which induces physical, chemical, and mechanical interaction between them at cracks. Intrinsic partial or entire sealing of the multiple cracks in UHPFRC has been proven to improve the safety and durability of UHPFRC infrastructures. A higher healing rate exists in cracks with a width of 75-175 μm, which is connected with crack healing kinetics, and the width of total healing cracks can reach up to 162 μm, which is mainly filled with calcium carbonate. Continuous accumulation of healing products at cracks can effectively improve the mechanical properties and suppress the decay of transport performance and steel fiber corrosion. Furthermore, mild fiber corrosion contributes to the partial restoration of flexural strength during the self-healing process.

6

Predicting changes of the state of a bridge reinforced with concrete superstructures in view of operational changes

Ovchynnykov Pavlo, Dubinchyk Olha, Tiutkin Oleksii, Kildieiev Vitalii, Sedin Volodymyr, Bikus Kateryna

Civil and Environmental Engineering Reports

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2019

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Vol. 29, no. 3

134--152

EN

To solve the problem of predicting the service life of superstructures, this work proposes the basis and methodological developments of creep theory with increasing loads as well as regression analysis of the results of laboratory experiments. The main limitation in terms of reinforcement is corrosion in the concrete cracks, which was determined during laboratory experiments. Based on the results, the approximate analytical dependences concerning reinforcement corrosion depth change over time at a constant value of crack width were selected. The paper substantiates the validity of the analytical dependences as a result of regression analysis; it proposes formulae for determining the corrosion rate of rebars in reinforced concrete superstructures. The obtained analytical dependences allowed for the developing of a process for predicting changes to the state of the superstructure in light of operational changes.

7

Experimental study on the shear strength of reinforced concrete beams cast with Lava lightweight aggregates

Nawaz W., Abdalla J. A., Hawileh R. A., Alajmani H. S., Abuzayed I. H., Ataya H., Mohamed H. A.

Archives of Civil and Mechanical Engineering

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2019

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Vol. 19, no. 4

981--996

EN

This paper investigates experimentally the shear strength behavior of reinforced concrete (RC) beams cast with Lava lightweight aggregates as a replacement of normal coarse aggregates. A total of 24 shear deficient RC beams were fabricated and cast with normal (NWC) and lightweight (LWC) concrete and tested under three-point bending after 28 and 56 days. The variables of the experimental program include type of aggregate, concrete compressive strength, and beam size. The experimental results include load–deflection response curves along with failure mode for each beam specimen. The experimental result showed that all beams failed in a similar fashion, due to diagonal tension shear crack. However, a larger number of cracks with less spacing occurred in the LWC beams as compared to NWC specimens. Based on the experimental results, it can be also concluded that LWC specimens tested after 56 days achieved comparable shear strength results to that of NWC beams. In addition, the strength reduction factor (l) for LWC specimens was in the range of 0.69–0.98. The concrete shear strength (Vc) was also predicted using different shear design provisions and the results has shown that Eurocode 2 provisions yielded the lowest C. O.V. of 2.3 and 10.2% for NWC and LWC specimens, respectively.

8

Analysis of FRP bars used as reinforcement in concrete structures

Brózda K., Selejdak J.

Production Engineering Archives

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2016

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Vol. 12, No. 3

2--4

EN

In the design and construction of building and engineering structures, it is of utmost importance to provide their reliability and safety. The use of FRP (Fiber Reinforced Polymers) bars as reinforcement of structural concrete elements could help reducing the typical defects of reinforced concrete and increase its strength parameters. In the paper the selected FRP bar characteristic properties are presented and advantages derived therefrom are specified. Furthermore, the most commonly used in construction types of FRP bars, depending on the raw material used during the production process are listed. In addition, the possibility of recycling of elements reinforced with FRP bars is presented and compared with traditional reinforced concrete (reinforced with steel bars). The production method of FRP bars (pultrusion) is shown. Moreover, the advantages and disadvantages of using this method are discussed.

9

Organic substances as corrosion inhibitors for steel in concrete – an overview

Osial M., Wiliński D.

Journal of Building Chemistry

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2016

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Vol. 1, iss. 1

43-53

EN

Organic inhibitors have attracted considerable attention due to their promising application as admixtures in concrete protecting against corrosion of rebars. Over the last decade the use of those inhibitors significantly raised. The inhibition efficiency depends on their physical and chemical properties. This paper gives short overview of the protection of steel in concrete against the ingress of chlorides, oxygen and carbon dioxide in concrete, as species causing the corrosion of rebars. This work involves only organic inhibitors.

10

Application of fibres from recycled PET bottles for concrete reinforcement

Wiliński D., Łukowski P., Rokicki G.

Journal of Building Chemistry

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2016

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Vol. 1, iss. 1

1-9

EN

Waste PET can be reused as partial or complete substitute of an aggregate in a concrete composition or as a concrete reinforcement. However, the main drawback of such applications is the hydrolysis of ester linkages of poly(ethylene terephthalate) in highly alkaline environment of the cement matrix. To prevent alkaline hydrolysis, the PET fibres were coated with commercially available ethylene/vinyl acetate copolymer (EVA). Effectiveness of the use of copolymer EVA as a protection layer against strong alkali solutions has been demonstrated and discussed. Chemical changes in PET fibres after alkaline treatment have been referred to mechanical properties of the fibres. Mechanical properties, like compressive and flexural strength of the composites as well as the long-term durability performance of recycled PET fibres in alkaline environment were also investigated. The preliminary results indicated that the introduction of the PET fibres does not deteriorate the mechanical strength of the concrete composite.

11

Effect of strength and stiffness deterioration on seismic behaviour of R/C asymmetric buildings

Das P. K., Dutta S.C.

International Journal of Applied Mechanics and Engineering

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2002

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Vol. 7, no 2

527-564

EN

Past earthquakes (e.g., 1985 Mexico earthquake) have demonstrated the severe seismic vulnerability of asymmetric buildings due to coupled lateral-torsional vibration in elastic as well as in inelastic range, even under a purely translational ground shaking. Extensive research effort on inelastic behaviour of asymmetric buildings has generally used an elasto-plastic or bilinear hysteresis behaviour for the structural load-resisting elements, ignoring the strength and stiffness deteriorating characteristics of RC structural elements under cyclic loading. Hence, these studies could not recognize the possibility of progressively increasing torsional damage of load resisting elements near one edge, due to continuous shifting of centre of resistance caused by such degradations during inelastic excursions. The present study on asymmetric one storey building systems aims to assess these possible detrimental effects. The system responses are studied using a) elasto-plastic, b) stiffness degrading, c) strength deteriorating, and d) stiffness degrading as well as strength deteriorating hysteresis models for the load-resisting elements. These responses are expressed in terms of the maximum displacement demand and hysteretic energy demand in load-resisting elements. Variations of these two response quantities are studied for feasible ranges of influencing parameters due to each of the four hysteresis behaviours. The results are compared to understand the effects of stiffness degradation and strength deterioration. The remedial measures are also outlined to control the excessive response found to be generated due to such degradation effects. The study may prove useful to arrive at more justified torsional code provisions.