Materials

Research

16 pages, 5793 KiB

Open AccessArticle

Experimental Study on Secondary Anchorage Bond Performance of Residual Stress after Corrosion Fracture at Ends of Prestressed Steel Strands

by Rihua Yang, Yiming Yang, Xuhui Zhang and Xinzhong Wang

Materials 2023, 16(23), 7441; https://doi.org/10.3390/ma16237441 - 29 Nov 2023

Viewed by 950

Abstract

In order to explore the secondary bond anchorage performance between prestressed tendons and concrete after the fracture of steel strands in post-tensioned, prestressed concrete (PPC) beams, a total of seven post-tensioned, prestressed concrete specimens with a size of 3 × 7ϕ15.2 mm were [...] Read more.

In order to explore the secondary bond anchorage performance between prestressed tendons and concrete after the fracture of steel strands in post-tensioned, prestressed concrete (PPC) beams, a total of seven post-tensioned, prestressed concrete specimens with a size of 3 × 7ϕ15.2 mm were constructed firstly, and the steel strands at the anchorage end were subjected to corrosion fracture. Then, the pull-out test of the specimens was conducted to explore the secondary anchorage bond mechanism of the residual stress of prestressed tendons experiencing local fracture. Moreover, the influences of factors such as the embedded length, release-tensioning speed, concrete strength, and stirrup configuration on anchorage bond performance were analyzed. Finally, the test results were further verified via finite element analysis. The results show that the failure of pull-out specimens under different parameters can be divided into two types: bond anchorage failure induced by the entire pull-out of steel strands and material failure triggered by the rupture of steel strands. The bond anchorage failure mechanism between steel strands and the concrete was revealed by combining the failure characteristics and pull-out load–slippage relation curves. The bond strength between prestressed steel strands and concrete can be enhanced by increasing the embedded length of steel strands, elevating the concrete strength grade, and enlarging the diameter of stirrups so that the specimens are turned from bond anchorage failure into material failure. Full article

(This article belongs to the Special Issue Repair and Strengthening of Existing Reinforced Concrete Structures)

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16 pages, 7322 KiB

Open AccessArticle

Salt Spray Resistance of Roller-Compacted Concrete with Surface Coatings

by Huigui Zhang, Wuman Zhang and Yanfei Meng

Materials 2023, 16(22), 7134; https://doi.org/10.3390/ma16227134 - 12 Nov 2023

Cited by 1 | Viewed by 997

Abstract

In order to evaluate the feasibility of surface coatings in improving the performance of RCC under salt spray conditions, sodium silicate (SS), isooctyl triethoxy silane (IOTS), and polyurea (PUA) were used as surface coatings to prepare four types of roller-compacted concrete (RCC): reference [...] Read more.

In order to evaluate the feasibility of surface coatings in improving the performance of RCC under salt spray conditions, sodium silicate (SS), isooctyl triethoxy silane (IOTS), and polyurea (PUA) were used as surface coatings to prepare four types of roller-compacted concrete (RCC): reference RCC, RCC-SS, RCC-IOTS, and RCC-PUA. A 5% sodium sulfate solution was used to simulate a corrosive marine environment with high temperatures, high humidity, and high concentrations of salt spray. This study focuses on investigating various properties, including water absorption, abrasion loss, compressive strength, dynamic elastic modulus, and impact resistance. Compared to the reference RCC, the 24 h water absorption of RCC-SS, RCC-IOTS, and RCC-PUA without salt spray exposure decreased by 22.8%, 77.2%, and 89.8%, respectively. After 300 cycles of salt spray, the abrasion loss of RCC-SS, RCC-IOTS, and RCC-PUA reduced by 0.3%, 4.4%, and 34.3%, respectively. Additionally, their compressive strengths increased by 3.8%, 0.89%, and 0.22%, and the total absorbed energy at fracture increased by 64.8%, 53.2%, and 50.1%, respectively. The results of the study may provide a reference for the selection of coating materials under conditions similar to those in this study. Full article

(This article belongs to the Special Issue Repair and Strengthening of Existing Reinforced Concrete Structures)

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16 pages, 4855 KiB

Open AccessArticle

Improved Shear Strength Equation for Reinforced Concrete Columns Retrofitted with Hybrid Concrete Jackets

by Kyong Min Ro, Min Sook Kim and Young Hak Lee

Materials 2023, 16(10), 3734; https://doi.org/10.3390/ma16103734 - 15 May 2023

Viewed by 2763

Abstract

The adequacy of retrofitting with concrete jacketing is influenced by the bonding between the old section and jacketing section. In this study, five specimens were fabricated, and cyclic loading tests were performed to investigate the integration behavior of the hybrid concrete jacketing method [...] Read more.

The adequacy of retrofitting with concrete jacketing is influenced by the bonding between the old section and jacketing section. In this study, five specimens were fabricated, and cyclic loading tests were performed to investigate the integration behavior of the hybrid concrete jacketing method under combined loads. The experimental results showed that the strength of the proposed retrofitting method increased approximately three times compared to the old column, and bonding capacity was also improved. This paper proposed a shear strength equation that considers the slip between the jacketed section and the old section. Moreover, a factor was proposed for considering the reduction in the shear capacity of the stirrup resulting from the slippage between the mortar and stirrup utilized on the jacketing section. The accuracy and validity of the proposed equations were examined through a comparison with the ACI 318-19 design criteria and test results. Full article

(This article belongs to the Special Issue Repair and Strengthening of Existing Reinforced Concrete Structures)

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28 pages, 11915 KiB

Open AccessArticle

Experimental and Numerical Study of the Ultimate Flexural Capacity of a Full-Size Damaged Prestressed Concrete Box Girder Strengthened with Bonded Steel Plates

by Yong Li, Zijie Yu and Yongqian Liu

Materials 2023, 16(6), 2476; https://doi.org/10.3390/ma16062476 - 20 Mar 2023

Cited by 4 | Viewed by 1396

Abstract

Using steel plates attached with epoxy resin adhesive to strengthen prestressed reinforced concrete bridges has become a common method to increase bearing capacity in engineering because of the simple technology, low cost and good strengthening effects. The strengthening method of steel plates has [...] Read more.

Using steel plates attached with epoxy resin adhesive to strengthen prestressed reinforced concrete bridges has become a common method to increase bearing capacity in engineering because of the simple technology, low cost and good strengthening effects. The strengthening method of steel plates has been gradually applied to repair damaged bridges in practical engineering. After a cross-line box girder bridge was struck by a vehicle, the steel bars and concrete of a damaged girder were repaired and strengthened by steel plates, and then the ultimate bending bearing capacity was studied through a destructive test. The results of the destructive test were compared with those of an undamaged girder to verify the effect of the repair and strengthening of the damaged girder. The results showed that the actual flexural bearing capacity of the repaired girder strengthened by steel plates was 1.63 times the theoretical bearing capacity, 36.7% more than that of the damaged girder and 95.3% of that of an undamaged girder. The flexural cracking moment of the repaired girder strengthened by steel plates reached 66.3% of that of the undamaged girder. The maximum crack width decreased by 24.6%, and the maximum deflection increased by 2.7%, compared with the undamaged girder when the repaired girder strengthened by steel plates finally failed. Moreover, this method of attaching steel plates can increase the ductility of bridges and reduce the degree of cracking. Additionally, the actual safety factor of the repaired girder was greater than three, and it had a large safety reserve. Full article

(This article belongs to the Special Issue Repair and Strengthening of Existing Reinforced Concrete Structures)

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30 pages, 14142 KiB

Open AccessArticle

Investigation of the Failure Modes of Textile-Reinforced Concrete and Fiber/Textile-Reinforced Concrete under Uniaxial Tensile Tests

by Giorgio Mattarollo, Norbert Randl and Margherita Pauletta

Materials 2023, 16(5), 1999; https://doi.org/10.3390/ma16051999 - 28 Feb 2023

Cited by 6 | Viewed by 1966

Abstract

Recently, innovations in textile-reinforced concrete (TRC), such as the use of basalt textile fabrics, the use of high-performance concrete (HPC) matrices, and the admixture of short fibers in a cementitious matrix, have led to a new material called fiber/textile-reinforced concrete (F/TRC), which represents [...] Read more.

Recently, innovations in textile-reinforced concrete (TRC), such as the use of basalt textile fabrics, the use of high-performance concrete (HPC) matrices, and the admixture of short fibers in a cementitious matrix, have led to a new material called fiber/textile-reinforced concrete (F/TRC), which represents a promising solution for TRC. Although these materials are used in retrofit applications, experimental investigations about the performance of basalt and carbon TRC and F/TRC with HPC matrices number, to the best of the authors’ knowledge, only a few. Therefore, an experimental investigation was conducted on 24 specimens tested under the uniaxial tensile, in which the main variables studied were the use of HPC matrices, different materials of textile fabric (basalt and carbon), the presence or absence of short steel fibers, and the overlap length of the textile fabric. From the test results, it can be seen that the mode of failure of the specimens is mainly governed by the type of textile fabric. Carbon-retrofitted specimens showed higher post-elastic displacement compared with those retrofitted with basalt textile fabrics. Short steel fibers mainly affected the load level of first cracking and ultimate tensile strength. Full article

(This article belongs to the Special Issue Repair and Strengthening of Existing Reinforced Concrete Structures)

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17 pages, 4715 KiB

Open AccessArticle

Evaluating the Impact of Concrete Design on the Effectiveness of the Electrochemical Chloride Extraction Process

by Zofia Szweda

Materials 2023, 16(2), 666; https://doi.org/10.3390/ma16020666 - 10 Jan 2023

Cited by 7 | Viewed by 1615

Abstract

This paper presents a simple comparative method for evaluating the impact of concrete design on the effectiveness of repair with the electrochemical chloride extraction (ECE) process of reinforced concrete structures. This comparison covered two concretes with different types of used cement. Penetration of [...] Read more.

This paper presents a simple comparative method for evaluating the impact of concrete design on the effectiveness of repair with the electrochemical chloride extraction (ECE) process of reinforced concrete structures. This comparison covered two concretes with different types of used cement. Penetration of chloride ions to induce corrosion processes was accelerated with the electric field. However, the corrosion process itself occurred naturally. When the corrosion process was found to pose a risk to the reinforcement, the profile of chloride ion concentration was determined at the depth of concrete cover. Corrosion current intensity during migration and extraction processes of chloride ions was measured with the LPR method. Then, this serious condition for the structure was repaired with electrochemical chloride extraction. Rates of chloride extraction were determined from the derived concentration profiles. It should be noted that the critical concentration C_crit = 0.4% at the rebar surface was reached after 21 days of the migration process. Moreover, after the same time of extraction, the concentration was reduced by 95% at the rebar surface, which could suggest that extraction rate was slower than chloride ion migration to concrete within the electric field. Using the migration coefficient for predicting the extraction time, as well as ignoring the variability of the extraction coefficient and the initial concentration over time, may result in too short or unnecessarily long extraction times. Full article

(This article belongs to the Special Issue Repair and Strengthening of Existing Reinforced Concrete Structures)

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11 pages, 2883 KiB

Open AccessArticle

Concrete-Filled Prefabricated Cementitious Composite Tube (CFPCCT) under Axial Compression: Effect of Tube Wall Thickness

by Bi Kai, A. B. M. A. Kaish and Norhaiza Nordin

Materials 2022, 15(22), 8119; https://doi.org/10.3390/ma15228119 - 16 Nov 2022

Cited by 4 | Viewed by 1591

Abstract

Research on different prefabricated cementitious composites for constructing composite concrete columns is comparatively more limited than that of concrete filled steel tube columns. The main objective of this study was to observe the axial compressive behavior of concrete-filled prefabricated cementitious composite tube (CFPCCT) [...] Read more.

Research on different prefabricated cementitious composites for constructing composite concrete columns is comparatively more limited than that of concrete filled steel tube columns. The main objective of this study was to observe the axial compressive behavior of concrete-filled prefabricated cementitious composite tube (CFPCCT) specimens. In the CFPCCT composite column, the spiral steel bar is arranged as a hoop reinforcement in the cementitious tube before its prefabrication. Following this, the concrete is poured into the prefabricated cementitious composite tube. The tube is able to provide lateral confinement and can carry the axial load, which is attributed to the strength of CFPCCT composite column. The effect of tube wall thickness on the behavior of CFPCCT is studied in this research. A total of eight short-scale CFPCCT composite columns, with three different tube wall thicknesses (25 mm, 30 mm and 35 mm), are tested under axial compressive load. The cementitious composite tube-confined specimens showed a 24.7% increment in load-carrying capacity compared to unconfined specimens. Increasing the wall-thickness had a positive impact on the strength and ductility properties of the composite column. However, poor failure behavior was observed for thicker tube wall. Therefore, concrete-filled cementitious composite tube columns can be considered as an alternative and effective way to construct prefabricated concrete columns. Full article

(This article belongs to the Special Issue Repair and Strengthening of Existing Reinforced Concrete Structures)

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26 pages, 7597 KiB

Open AccessArticle

Impact of Polypropylene Fibers on the Mechanical and Durability Characteristics of Rubber Tire Fine Aggregate Concrete

by Arash Karimi Pour, Zahra Mohajeri and Ehsan Noroozinejad Farsangi

Materials 2022, 15(22), 8043; https://doi.org/10.3390/ma15228043 - 14 Nov 2022

Cited by 6 | Viewed by 1574

Abstract

In this research, the consequence of using rubber tire aggregates (RTA) on the durability and mechanical characteristics of polypropylene fibers (PF) reinforced concrete is evaluated. Fifteen concrete mixtures were produced and tested in the laboratory. RTA was utilized instead of fine natural aggregates [...] Read more.

In this research, the consequence of using rubber tire aggregates (RTA) on the durability and mechanical characteristics of polypropylene fibers (PF) reinforced concrete is evaluated. Fifteen concrete mixtures were produced and tested in the laboratory. RTA was utilized instead of fine natural aggregates (FNA) to the concrete at concentrations of 0%, 5%, 10%, 15%, and 20% by a volumetric fraction; also, the contents of PF in the concrete mixtures were 0%, 1%, and 2% by weight fraction. Finally, the following parameters were tested for all the mixtures: compressive and tensile resistances, fracture, changes in drying shrinkage, bulk electrical resistivity, elastic moduli, and resonance occurrences. The control sample was the one without RTA and PF. According to the results, by adding RTA to the mixtures, the shrinkage deformation amplified, but the PF addition caused a decrease in the shrinkage deformation. Furthermore, adding 0%, 5%, 10%, and 15% RTA, with 2% PF leads to an upsurge in the flexural resistance by 34%, 24%, 16%, and 6%, respectively, relative to the control sample without PF and RTA. Moreover, the fracture energy of mixtures increased by utilizing PF and RTA simultaneously. Full article

(This article belongs to the Special Issue Repair and Strengthening of Existing Reinforced Concrete Structures)

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18 pages, 5046 KiB

Open AccessArticle

Numerical Analysis on Transverse Splicing Structure for the Widening of a Long Multi-Span Highway Concrete Continuous Box Girder Bridge

by Wenqing Wu, Hui Zhang, Zheng Liu and Yunpeng Wang

Materials 2022, 15(19), 6805; https://doi.org/10.3390/ma15196805 - 30 Sep 2022

Cited by 3 | Viewed by 1795

Abstract

For the bridge widening of long multi-span highway concrete continuous box girder with a conventional splicing structure, due to the large longitudinal difference deformation by concrete shrinkage and creep between the existing and new ones, the widened structure will have an overlarge bending [...] Read more.

For the bridge widening of long multi-span highway concrete continuous box girder with a conventional splicing structure, due to the large longitudinal difference deformation by concrete shrinkage and creep between the existing and new ones, the widened structure will have an overlarge bending deformation after widening, especially an obvious transverse deformation at the end of girder, which will lead to structural damage to the newly widened structure. To effectively absorb the difference deformation mentioned above, this study proposes a novel transverse splicing structure based on the folding effect of a corrugated steel plate (CSP) (hereinafter referred to as “the CSP splicing structure”). Then, a finite element structural analysis was performed on the mechanical properties of the widened structure with the CSP splicing structure, and compared to those of a widened structure adopting the conventional concrete splicing mode, to clarify the transverse load transferring mechanism of the structure. Finally, by conducting a sensitivity analysis on CSP thickness, corrugation length, splicing stitch width, and other structural parameters, a sound parameter combination scheme was put forward. According to the research results, to ensure effective utilization of the CSP folding effect, the corrugation pattern direction of CSP should be set as horizontal, and the wave angle as the degree of 90°. In addition, it mitigated the transverse tensile stress to effectively avoid concrete cracking feasibility on the top flange of the box girder at the end of the girder. This study offers a feasible way of avoiding the structural damage produced by an excess transverse deformation at the end of the girder after bridge widening of a long multi-span concrete continuous box girder. Full article

(This article belongs to the Special Issue Repair and Strengthening of Existing Reinforced Concrete Structures)

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21 pages, 5810 KiB

Open AccessArticle

Concrete with a High Content of End-of-Life Tire Materials for Flexural Strengthening of Reinforced Concrete Structures

by Thomaida Polydorou, Nicholas Kyriakides, Andreas Lampropoulos, Kyriacos Neocleous, Renos Votsis, Ourania Tsioulou, Kypros Pilakoutas and Diofantos G. Hadjimitsis

Materials 2022, 15(17), 6150; https://doi.org/10.3390/ma15176150 - 5 Sep 2022

Cited by 3 | Viewed by 2340

Abstract

This research investigates the performance of Steel Fiber Reinforced Rubberized Concrete (SFRRC) that incorporates high volumes of End-of-life tire materials, (i.e., both rubber particles and recycled tire steel fibers) in strengthening existing reinforced concrete (RC) beams. The mechanical and durability properties were determined [...] Read more.

This research investigates the performance of Steel Fiber Reinforced Rubberized Concrete (SFRRC) that incorporates high volumes of End-of-life tire materials, (i.e., both rubber particles and recycled tire steel fibers) in strengthening existing reinforced concrete (RC) beams. The mechanical and durability properties were determined for an environmentally friendly SFRRC mixture that incorporates a large volume (60% by volume aggregate replacement) of rubber particles and is solely reinforced by recycled tire steel fibers. The material was assessed experimentally under flexural, compressive and impact loading, and thus results led to the development of a numerical model using the Finite Element Method. Furthermore, a numerical study on full-scale structural members was conducted, focusing on conventional RC beams strengthened with SFRRC layers. This research presents the first study where SFRRC is examined for structural strengthening of existing RC beams, aiming to enable the use of such novel materials in structural applications. The results were compared to respective results of beams strengthened with conventional RC layers. The study reveals that incorporation of End-of-life tire materials in concrete not only serves the purpose of recycling End-of-life tire products, but can also contribute to unique properties such as energy dissipation not attained by conventional concrete and therefore leading to superior performance as flexural strengthening material. It was found that by incorporating 60% by volume rubber particles in combination with recycled steel fibers, it increased the damping ratio of concrete by 75.4%. Furthermore, SFRRC was proven effective in enhancing the energy dissipation of existing structural members. Full article

(This article belongs to the Special Issue Repair and Strengthening of Existing Reinforced Concrete Structures)

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21 pages, 11656 KiB

Open AccessEditor’s ChoiceArticle

Bond Modification of Carbon Rovings through Profiling

by Paul Penzel, Maximilian May, Lars Hahn, Silke Scheerer, Harald Michler, Marko Butler, Martin Waldmann, Manfred Curbach, Chokri Cherif and Viktor Mechtcherine

Materials 2022, 15(16), 5581; https://doi.org/10.3390/ma15165581 - 14 Aug 2022

Cited by 11 | Viewed by 2261

Abstract

The load-bearing behavior and the performance of composites depends largely on the bond between the individual components. In reinforced concrete construction, the bond mechanisms are very well researched. In the case of carbon and textile reinforced concrete, however, there is still a need [...] Read more.

The load-bearing behavior and the performance of composites depends largely on the bond between the individual components. In reinforced concrete construction, the bond mechanisms are very well researched. In the case of carbon and textile reinforced concrete, however, there is still a need for research, especially since there is a greater number of influencing parameters. Depending on the type of fiber, yarn processing, impregnation, geometry, or concrete, the proportion of adhesive, frictional, and shear bond in the total bond resistance varies. In defined profiling of yarns, we see the possibility to increase the share of the shear bond (form fit) compared to yarns with a relatively smooth surface and, through this, to reliably control the bond resistance. In order to investigate the influence of profiling on the bond and tensile behavior, yarns with various profile characteristics as well as different impregnation and consolidation parameters are studied. A newly developed profiling technique is used for creating a defined tetrahedral profile. In the article, we present this approach and the first results from tensile and bond tests as well as micrographic analysis with profiled yarns. The study shows that bond properties of profiled yarns are superior to conventional yarns without profile, and a defined bond modification through variation of the profile geometry as well as the impregnation and consolidation parameters is possible. Full article

(This article belongs to the Special Issue Repair and Strengthening of Existing Reinforced Concrete Structures)

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22 pages, 7665 KiB

Open AccessArticle

Tensile Experiments and Numerical Analysis of Textile-Reinforced Lightweight Engineered Cementitious Composites

by Mingzhao Chen, Xudong Deng, Rongxin Guo, Chaoshu Fu and Jiuchang Zhang

Materials 2022, 15(16), 5494; https://doi.org/10.3390/ma15165494 - 10 Aug 2022

Cited by 3 | Viewed by 1856

Abstract

Despite many cases of textile-reinforced engineered cementitious composites (TR-ECCs) for repairing and strengthening concrete structures in the literature, research on lightweight engineered cementitious composites (LECC) combined with large rupture strain (LRS) textile and the effect of textile arrangement on tensile properties is still [...] Read more.

Despite many cases of textile-reinforced engineered cementitious composites (TR-ECCs) for repairing and strengthening concrete structures in the literature, research on lightweight engineered cementitious composites (LECC) combined with large rupture strain (LRS) textile and the effect of textile arrangement on tensile properties is still lacking. Therefore, this paper develops textile-reinforced lightweight engineered cementitious composites (TR-LECCs) with high strain characteristics through reinforcement ratio, arrangement form, and textile type. The study revealed that, by combining an LRS polypropylene (PP) textile and LECC, TR-LECCs with an ultimate strain of more than 8.0% (3–4 times that of traditional TR-ECCs) could be developed, and the PP textile’s utilization rate seemed insensitive to the enhancement rate. The basalt fiber-reinforced polymer (BFRP) textile without epoxy resin coating had no noticeable reinforcement effect because of bond slip; in contrast, the BFRP grid with epoxy resin coating had an apparent improvement in bond performance with the matrix and a better reinforcement effect. The finite element method (FEM) verified that a concentrated arrangement increased the stress concentration in the TR-LECC, as well as the stress value. In contrast, a multilayer arrangement enabled uniform distribution of the stress value and revealed that the weft yarn could help the warp yarn to bear additional tensile loads. Full article

(This article belongs to the Special Issue Repair and Strengthening of Existing Reinforced Concrete Structures)

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20 pages, 2354 KiB

Open AccessArticle

Influence of Cross-Section Shape and FRP Reinforcement Layout on Shear Capacity of Strengthened RC Beams

by Muhammad Ahmed, Piero Colajanni and Salvatore Pagnotta

Materials 2022, 15(13), 4545; https://doi.org/10.3390/ma15134545 - 28 Jun 2022

Cited by 3 | Viewed by 1855

Abstract

The evaluation of the shear capacity of an FRP-strengthened reinforced-concrete beam is challenging due to the complex interaction between different contributions provided by the concrete, steel stirrup and FRP reinforcement. The shape of the beam and the FRP inclination can have paramount importance [...] Read more.

The evaluation of the shear capacity of an FRP-strengthened reinforced-concrete beam is challenging due to the complex interaction between different contributions provided by the concrete, steel stirrup and FRP reinforcement. The shape of the beam and the FRP inclination can have paramount importance that is not often recognized by the models that are suggested by codes. The interaction among different resisting mechanisms has a significant effect on the shear capacity of beams, since it can cause a reduction in the efficiency of some resisting mechanisms. A comparative study of the performance in the shear resistance assessment provided by three models with six different effectiveness factors (R) is performed, considering different cross-section shapes, FRP wrapping schemes, inclination and anchorage systems. The results revealed that the cross-section shape, the FRP inclination and the efficiency of the FRP anchorages have a significant effect on the shear strength of beams. The analysis results show that the three models are able to provide an accurate average estimation of shear strength (but with a coefficient of variation up to 0.35) when FRP reinforcement orthogonal to the beam axis is considered, while a significant underestimation (up to 19%) affected the results for inclined FRP reinforcement. Moreover, all the models underestimated the resistance of beams with a T section. Full article

(This article belongs to the Special Issue Repair and Strengthening of Existing Reinforced Concrete Structures)

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23 pages, 5360 KiB

Open AccessArticle

Seismic Assessment and Retrofitting of Existing Road Bridges: State of the Art Review

by Dominik Skokandić, Anđelko Vlašić, Marija Kušter Marić, Mladen Srbić and Ana Mandić Ivanković

Materials 2022, 15(7), 2523; https://doi.org/10.3390/ma15072523 - 30 Mar 2022

Cited by 13 | Viewed by 4576

Abstract

The load-carrying capacity assessment of existing road bridges, is a growing challenge for civil engineers worldwide due to the age and condition of these critical parts of the infrastructure network. The critical loading event for road bridges is the live load; however, in [...] Read more.

The load-carrying capacity assessment of existing road bridges, is a growing challenge for civil engineers worldwide due to the age and condition of these critical parts of the infrastructure network. The critical loading event for road bridges is the live load; however, in earthquake-prone areas bridges generally require an additional seismic evaluation and often retrofitting in order to meet more stringent design codes. This paper provides a review of state-of-the-art methods for the seismic assessment and retrofitting of existing road bridges which are not covered by current design codes (Eurocode). The implementation of these methods is presented through two case studies in Croatia. The first case study is an example of how seismic assessment and retrofitting proposals should be conducted during a regular inspection. On the other hand, the second case study bridge is an example of an urgent assessment and temporary retrofit after a catastrophic earthquake. Both bridges were built in the 1960s and are located on state highways; the first one is a reinforced concrete bridge constructed monolithically on V-shaped piers, while the second is an older composite girder bridge located in Sisak-Moslavina County. The bridge was severely damaged during recent earthquakes in the county, requiring urgent assessment and subsequent strengthening of the substructure to prevent its collapse. Full article

(This article belongs to the Special Issue Repair and Strengthening of Existing Reinforced Concrete Structures)

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17 pages, 5011 KiB

Open AccessArticle

Prediction of Bonding Strength of Externally Bonded SRP Composites Using Artificial Neural Networks

by Sofija Kekez and Rafał Krzywoń

Materials 2022, 15(4), 1314; https://doi.org/10.3390/ma15041314 - 10 Feb 2022

Cited by 5 | Viewed by 1457

Abstract

External bonding of fiber reinforced composites is currently the most popular method of strengthening building structures. Debonding performance is critical to the effectiveness of such strengthening. Many models of bond prediction can be found in the literature. Most of them were developed based [...] Read more.

External bonding of fiber reinforced composites is currently the most popular method of strengthening building structures. Debonding performance is critical to the effectiveness of such strengthening. Many models of bond prediction can be found in the literature. Most of them were developed based on laboratory research, therefore, their accuracy with less popular strengthening systems is limited. This manuscript presents the possibility of using a model based on neural networks to analyze and predict the debonding strength of steel-reinforced polymer (SRP) and steel-reinforced grout (SRG) composites to concrete. The model is built on the basis of laboratory testing of 328 samples obtained from the literature. The results are compared with a dozen of the most popular analytical methods for predicting the load capacity. The prediction accuracy in the neural network model is by far the best. The total correlation coefficient reaches a value of 0.913 while, for the best analytical method (Swiss standard SIA 166 model), it is 0.756. The sensitivity analysis confirmed the importance of the modulus of elasticity and the concrete strength for debonding. It is also interesting that the width of the element proved to be very important, which is probably related to the low variability of this parameter in the laboratory tests. Full article

(This article belongs to the Special Issue Repair and Strengthening of Existing Reinforced Concrete Structures)

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13 pages, 6579 KiB

Open AccessArticle

Experimental and Numerical Investigation on the Size Effect of Ultrahigh-Performance Fibre-Reinforced Concrete (UHFRC)

by Andreas Lampropoulos, Demetris Nicolaides, Spyridon Paschalis and Ourania Tsioulou

Materials 2021, 14(19), 5714; https://doi.org/10.3390/ma14195714 - 30 Sep 2021

Cited by 8 | Viewed by 2225

Abstract

In the last few years, there has been increasing interest in the use of Ultrahigh-Performance Fibre-Reinforced Concrete (UHPFRC) layers or jackets, which have been proved to be quite effective in strengthening applications. However, to facilitate the extensive use of UHPFRC in strengthening applications, [...] Read more.

In the last few years, there has been increasing interest in the use of Ultrahigh-Performance Fibre-Reinforced Concrete (UHPFRC) layers or jackets, which have been proved to be quite effective in strengthening applications. However, to facilitate the extensive use of UHPFRC in strengthening applications, reliable numerical models need to be developed. In the case of UHPFRC, it is common practice to perform either direct tensile or flexural tests to determine the UHPFRC tensile stress–strain models. However, the geometry of the specimens used for the material characterization is, in most cases, significantly different to the geometry of the layers used in strengthening applications which are normally of quite small thickness. Therefore, and since the material properties of UHPFRC are highly dependent on the dimensions of the examined specimens, the so called “size effect” needs to be considered for the development of an improved modelling approach. In this study, direct tensile tests have been used and a constitutive model for the tensile behaviour of UHPFRC is proposed, taking into consideration the size of the finite elements. The efficiency and reliability of the proposed approach has been validated using experimental data on prisms with different geometries, tested in flexure and in direct tension. Full article

(This article belongs to the Special Issue Repair and Strengthening of Existing Reinforced Concrete Structures)

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