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Number of results: 8
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Abstract

The paper presents an analysis of the behaviour of bent reinforced concrete beams strengthened with CFRP laminates fixed with adhesive before and after unloading, and more importantly, an analysis of the work of reinforced concrete beams strengthened with pre-stressed CFRP laminates fixed with adhesive. The analyses were based on a moment-curvature model prepared by the author for reinforced concrete beams strengthened under load with pre-stressed CFRP laminates. The model was used to determine the effect of compression with CFRP laminates and their mechanical properties on the effectiveness of strengthening the reinforced concrete beams analysed in this study.

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Authors and Affiliations

J. Korentz
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Abstract

The paper presents the test description and results of thermal bowing of RC beams exposed to non-uniform heating at high temperature. Bending of a non-uniformly heated element is caused by free thermal elongation of the material it is made of. The higher the temperature gradient, the greater the bending. In the case when an element is exposed to load and high temperature simultaneously, apart from free bending also deformation of the RC element may occur, which is caused by the decrease of the concrete or reinforcing steel mechanical properties. In order to examine the contribution of the deflection caused by thermal bowing to the total deformation of the bent element with a heated tension zone, an experimental study of freely heated (unloaded) beams was performed. RC beams were heated: (1) on three sides of the cross-section or (2) only on the bottom side. Deflection of elements loaded by a substitute temperature gradient was calculated using the Maxwell-Mohr formula. The test results show that deflection of freely heated RC beams (caused by the thermal bowing phenomenon) can be 10 to 20% of the total deflection of loaded RC beams with a heated tension zone.

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Authors and Affiliations

R. Kowalski
M. Głowacki
J. Wróblewska
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Abstract

The composite materials as FRP (Fiber Reinforced Polymers), which are characterized by benefits resulting from the combination of high strength reinforcement (as carbon, glass, steel or aramid fibers) with synthetic matrix are increasingly used to reinforce existing structures. Reinforcing System as FRCM (Fibre Reinforced Cementitious Matrix), which includes, among others, Ruredil X Mesh Gold System, is much less commonly used. However, the uniform and practical methods for calculating composite reinforced structures are not determined. Especially when considering the real conditions of structure exploitation, which requires further research in this field. In the paper the initial loading level influence on the efficiency of reinforced concrete beams strengthen using system Ruredil X Mesh Gold was investigated.

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Authors and Affiliations

Z. Blikharskyy
K. Brózda
J. Selejdak
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Abstract

Due to the increase in traffic volume, load level, and service life of existing bridges, the bending bearing capacity of reinforced concrete beams (hereinafter referred to as RC beams) has decreased, leading to safety issues. In order to solve the problem of insufficient flexural bearing capacity of RC beams, this article adopts the method of ultra-high performance concrete (UHPC) flexural strengthening RC beams, establishes a finite element model of UHPC-RC reinforcement system, and conducts stress analysis with reinforcement thickness, reinforcement range, reinforcement form, and reinforcement height as parameters to determine the optimal scheme of the reinforcement system. Based on the calculation results, a theoretical formula for the maximum principal stress and maximum deflection of the reinforcement system is proposed. To verify the feasibility of the plan, a reinforcement design was carried out on an existing beam, and it was found that the bending bearing capacity of the RC beam increased by 21%; the high tensile strength of UHPC and the addition of steel fibers have a good limiting effect on cracks; The steel plate of the reinforcement system can be used as a template, reducing construction costs and having good economy.
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Authors and Affiliations

Jiawei Wang
1
ORCID: ORCID
Feifei Ying
1
ORCID: ORCID

  1. Anhui Polytechnic University, School of Architecture and Civil Engineering, Wuhu City, Beijing MiddleRoad, China
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Abstract

In recent years, bridge safety accidents caused by insufficient shear bearing capacity of bridges have attracted increasing attention. The main causes include internal factors such as insufficient bridge section and deterioration of steel bars, as well as external factors, for example, vehicle load surge and improper maintenance. To address this issue to some degree, this article adopts the method of strengthening RC beams with ultra-high performance concrete (UHPC) and conducts parameter analysis using finite element method, taking into consideration the influence of four parameters: reinforcement material, reinforcement thickness, reinforcement length, and reinforcement form on the shear strengthening characteristics of RC rectangular beams. After obtaining the optimal reinforcement plan through parameter analysis, the author applied the research results to an existing bridge with insufficient shear strength. It then turned out that the shear bearing capacity of the reinforced bridge’s inclined section increased by approximately 27.1%. Simple and fast in construction, this reinforcement method is one of the methods that is effective to increase cross-section reinforcement; besides, it features good economic characteristics and applicability.
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Authors and Affiliations

Jiawei Wang
1
ORCID: ORCID
Ziqian Wang
2
Feifei Ying
3
ORCID: ORCID
Haitao Yu
4
ORCID: ORCID

  1. Anhui Polytechnic University, School of Architecture and Civil Engineering, Wuhu City, BeijingMiddle Road, China
  2. Anhui Polytechnic University, School of Architecture[ and Civil Engineering, Wuhu City, Beijing MiddleRoad, China
  3. Anhui Polytechnic University, School of Architecture and Civil Engineering, Wuhu City, Beijing MiddleRoad, China
  4. Heilongjiang Longfeng Highway Engineering Test Co.,LTD, Harbin City, Hexing Road, China
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Abstract

The growth in high-rise building construction has increased the need for hybrid reinforced concrete and steel structural systems. Columns in buildings are the most important elements because of their seismic resistance. Reinforced concrete (RC) columns and steel columns were used herein to form hybrid structural systems combining their distinct advantages. Eleven 3D building models subjected to earthquake excitation with reinforced concrete beams and slabs of 12 floors in height and with different distributions of mixed columns were analyzed by the SAP2000 software in order to investigate the most suitable distributions of a combination of reinforced concrete and steel columns. Top displacements and accelerations, base normal forces, base shear forces, and base bending moments were computed to evaluate the selected hybrid structural systems. The findings are helpful in evaluating the efficiency of the examined hybrid high-rise buildings in resisting earthquakes.

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Authors and Affiliations

D.P.N. Kontoni
A.A. Farghaly
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Abstract

The widespread use of Fibre-Reinforced Polymers (FRP) reinforced concrete (RC) structural members is hindered by their low fire resistant characteristics, limiting their use to cases, where fire resistance is not a priority. Presented and discussed are experimental results pertaining to the flexural members subjected to heating and simultaneous loading. Solely non-metallic FRP bars: (i) Basalt FRP (BFRP), (ii) Hybrid FRP (HFRP) with carbon and basalt fibres and (ii) nano-Hybrid FRP (nHFRP) with modified epoxy resin, were used as internal reinforcement for beams. The destruction of the beams was caused in different ways, beams reinforced with BFRP bars were destroyed by reinforcement failure while those reinforced with hybrid FRP bars were destroyed by concrete crushing. The BFRP reinforced beams obtained a maximum temperature, measured directly on the bars, of 917 °C, compared to beams reinforced with hybrid FRP bars, where the temperature on the bars reached 400-550 °C at failure. Moreover, the highest registered ductility was obtained for BFRP reinforced beams as well, where the maximum deflections reached approximately 16 cm.

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Authors and Affiliations

Kostiantyn Protchenko
ORCID: ORCID
Marek Urbański
ORCID: ORCID
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Abstract

For non-metallic reinforcement to be successfully integrated into residential and commercial construction, extensive research is required to understand the structural performance of Fiber Reinforced Polymer (FRP) reinforced concrete (RC) elements in various conditions, including the effect of elevated temperatures on structural performance. To accomplish this, a full-scale investigation was performed on the structural performance of FRP-RC elements subjected to elevated temperatures. The study involved conducting fire tests on beams, where the midsection was heated from below (tension zone) and the sides while being simultaneously loaded with 50% of their ultimate loads. The beams were reinforced with Basalt FRP (BFRP) bars and a hybrid composite of Carbon and Basalt Fibers (HFRP) bars. The HFRP-RC beams showed better resistance to the combined effect of loading and elevated temperatures compared to BFRP-RC beams. This study provides insights into the behavior of FRP materials in RC structures subjected to high temperatures, and contributes to the advancement of knowledge in this field.
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Authors and Affiliations

Kostiantyn Protchenko
1
ORCID: ORCID

  1. Warsaw University of Technology, Faculty of Civil Engineering, Al. Armii Ludowej 16,00-637 Warsaw, Poland

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