Rafal Krzywon | Silesian University of Technology (original) (raw)

Papers by Rafal Krzywon

Millennium: Journal of International Studies, 2019

espanolIntroduccion: Los geopolimeros son los materiales inorganicos modernos obtenidos como resu... more espanolIntroduccion: Los geopolimeros son los materiales inorganicos modernos obtenidos como resultado de la reaccion quimica bajo condiciones fuertemente alcalinas. Las principales ventajas de estos materiales son: parametros de alta resistencia, resistencia al fuego, resistencia a las heladas y resistencia al entorno agresivo. Debido a la menor emision de CO2 durante el proceso de produccion, tambien se consideran materiales ecologicos en comparacion con los materiales ordinarios de cemento Portland. Objetivos: El objetivo de la investigacion fue definir el impacto de la adicion de vidrio triturado reciclado en las propiedades mecanicas del aglutinante geopolimerico a partir de desechos de la mina de tungsteno. Metodos: Los parametros de fuerza de las muestras geopolimericas se determinaron sobre la base de la prueba de flexion de tres puntos y la prueba de compresion. Resultados: Las muestras de geopolimeros que contienen 20%, 40% y 80% de vidrio triturado reciclado presentan una...

MATEC Web of Conferences, 2019

It has been more than two decades, since FRP strengthening method was first time used in Poland. ... more It has been more than two decades, since FRP strengthening method was first time used in Poland. Therefore there is a natural need to develop an efficient quality assessment technique to verify design assumptions of strengthening in existing structures after many years. One of the promising non-destructive method of quality assessment is infrared thermography (IRT). In this paper, an initial study on recognition of delamination mainly in CFRP laminates using IRT was conducted as well as the influence of long-term loads on defects in CFRP strengthened RC beams was presented.

MATERIAŁY BUDOWLANE, 2016

Journal of Civil Engineering, Environment and Architecture, 2016

Przyklejane do konstrukcji kompozyty zbrojone włóknem węglowym zdobywają coraz większą popularnoś... more Przyklejane do konstrukcji kompozyty zbrojone włóknem węglowym zdobywają coraz większą popularność w zastosowaniach budowlanych, jednakże, z uwagi na kruche właściwości ich użytkowanie jest obarczone znacznie większym ryzykiem niż w przypadku tradycyjnych stali. Diagnostyka wzmocnionych elementów tylko przez obserwację ich zarysowań czy ugięć może być niewystarczająca, potrzebne są dodatkowe systemy monitorujące. W referacie przedstawiono opracowaną przez autorów inteligentną tkaninę, w której wiązki włókien węglowych łączą rolę rozciąganego zbrojenia i miernika odkształceń. Zasada jej pracy jest inspirowana budową klasycznego tensometru elektrooporowego, którego włókna przewodzące prowadzone są wężykowo. Rolę przewodnika pełni wiązka włókien węglowych, która jest izolowana w matrycy z włókien szklanych lub akrylowych. Opisane w referacie wybrane wyniki badań laboratoryjnych są bardzo obiecujące zarówno w zakresie jakości pomiaru odkształceń, jak i efektywności wzmocnienia. Obecnie dopracowywane są: dokładność kontroli grubości wiązki włókien, która wpływa na całkowitą oporność, czy też wpływ wilgoci na zmiany oporności. Słowa kluczowe: inteligentna tkanina, monitoring konstrukcji, pomiar odkształceń, laminat CFRP INFLUENCE OF CARBON FIBRE STRAIN SENSOR ON BEARING CAPACITY OF RC BEAMS S u m m a r y Externally bonded high-strength fiber composites are increasingly popular in structural applications, however, because of their brittle properties, their use is less secure than the common steel. Diagnosis this type of structure only by observing of cracks or deformations may be insufficient, they require additional monitoring systems. Paper presents developed by the authors' intelligent fabric, wherein the carbon fiber tow links the role of tensile reinforcement and strain gauge. Its way of working is inspired by the construction of traditional strain gauge, where electric wires are arranged in zigzag pattern. Carbon fiber thread plays the role of electrical conductor and is insulated by threads of glass or acrylic fibers. Described in the paper selected results of laboratory trials are very promising in both the accuracy of strain measurement, and the effectiveness of strengthening. Among the issues for improvement is the control of the cross-section of the fibers tow, affecting the total resistance of the fabric and moisture sensitivity.

Acta Polytechnica, 2021

A correct choice of a bond model for prestressing tendons is crucial for the right modelling of a... more A correct choice of a bond model for prestressing tendons is crucial for the right modelling of a structural behaviour of a pretensioned concrete structure. The aim of this paper is the determination of an optimal bond model for 7-wire strands in a prestressed concrete beam produced in a precast concrete plant of Consolis Poland. ATENA 3D is used to develop finite element models of the beam that differ only in a bond stress-slip relationship of tendons. The bond stress-slip relationships for modelling are taken from the results of bond tests carried out by different researchers in previous years. Moreover, for comparison purposes, a simplified 2D model of the beam is created in Autodesk Robot. The strain distribution at the time of the strand release is found for each of the finite element models. The determined strain distributions are compared with the strain distribution in the beam established by an experimental test using a measuring system based on a digital image correlation....

MATERIAŁY BUDOWLANE, 2016

Journal of Civil Engineering, Environment and Architecture, 2017

Journal of Composites Science, 2020

Bonding of external reinforcement is currently the simplest, fastest, and most popular method of ... more Bonding of external reinforcement is currently the simplest, fastest, and most popular method of strengthening concrete and masonry structures. Glass and carbon organic fibers are the dominant materials used, but alternatives also include high-strength steel wires. The mechanical properties of such steel are comparable to those of carbon fiber. Due to their good compatibility with mortars, steel wires are particularly well suited to the revitalization of historic buildings. The manuscript provides an overview of research and experience in the use of steel-reinforced polymers (SRPs) and steel-reinforced composite mortars (SRCMs, also called steel-reinforced grout (SRG)) for structural strengthening. The examples described are for concrete beams, slabs and columns, walls, and masonry arches. The results of laboratory tests are discussed. The summary presents the advantages and disadvantages of composites based on ultra-high-strength steels compared with more popular carbon fiber compo...

Materials, 2022

External bonding of fiber reinforced composites is currently the most popular method of strengthe... 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 metho...

Materials, 2021

The foaming of geopolymers lowers their density, thus opening up new environmental benefits, incl... more The foaming of geopolymers lowers their density, thus opening up new environmental benefits, including acoustic and thermal insulation. At the same time, foaming disturbs the homogeneity of the material, which worsens the strength parameters, and particularly those related to tension, which can be improved by introducing reinforcement. This paper presents the results of research on foamed geopolymers reinforced with glass fiber meshes, a type of reinforcement that provides an adequate bond. The samples tested here were based on three types of coal fly ash, and were foamed with varying doses of hydrogen peroxide. Samples were cured at 40 °C and were tested after 28 days of maturing at ambient temperature. The strength parameters of the synthesized geopolymers were determined via laboratory testing, and were used to evaluate load-bearing capacity models of the tested samples reinforced with glass fiber mesh. The results showed the importance of the type of ash on the strength properti...

Architecture Civil Engineering Environment, 2015

S t r e s z c z e n i e Kompozyty SRP są zbrojone drutami ze stali o wysokiej wytrzymałości w for... more S t r e s z c z e n i e Kompozyty SRP są zbrojone drutami ze stali o wysokiej wytrzymałości w formie splotów, które łączy się poprzecznie tworząc rodzaj maty. Właściwości mechaniczne stali wykorzystywanej do produkcji drutów są podobne do innych wysokowęglowych stali wytwarzanych w procesie obróbki plastycznej na zimno (np. stali do sprężania): nie występuje w nich płynięcie półka plastyczna. Prawie liniowa zależność naprężenie – odkształcenie upodabnia kompozyty SRP do laminatów zbrojonych włóknem węglowym. Podobnie pod względem łatwości kształtowania i ciężaru własnego, bardziej odpowiadają one taśmom węglowym niż stalowym płaskownikom. Z uwagi na te podobieństwa zasady projektowania i stosowania wzmocnień na zginanie, bazują na dobrze znanych procedurach do projektowania tego typu wzmocnień przy użyciu taśm CFRP. W artykule przedstawiono wyniki testów porównawczych kilkunastu belek wzmocnionych taśmami typu SRP i CFRP. K e y w o r d s : FRP Strengthening; Steel Reinforced Polymer...

Journal of Civil Engineering, Environment and Architecture, 2017

Klejenie zewnętrznych nakładek kompozytowych zbrojonych włóknami wysokiej wytrzymałości powoli st... more Klejenie zewnętrznych nakładek kompozytowych zbrojonych włóknami wysokiej wytrzymałości powoli staje się najpopularniejszą metodą wzmacniania konstrukcji żelbetowych. Zdarza się, że tego typu wzmocnienia mogą być bezpośrednio poddane nasłonecznieniu i tym samym zagrożone nadmiernym nagrzaniem. Badania prowadzone przez autora artkułu pokazały, że nawet w umiarkowanej strefie geograficznej, w której znajduje się Polska, temperatura kleju pod cienkim laminatem może osiągnąć 65°C, czyli temperaturę o 20°C wyższą niż temperatura zeszklenia najpopularniejszych na rynku klejów opartych na żywicy epoksydowej. W artykule przedstawiono wyniki badań laboratoryjnych belek żelbetowych podgrzanych od strony wzmocnienia promieniowaniem podczerwonym. Program badań objął grupę trzynastu belek żelbetowych w skali rzeczywistej. Sześć z nich zostało wzmocnionych taśmą CFRP, kolejnych sześć z taśmą SRP. Belki podgrzewano za pomocą liniowych promienników podczerwieni do mierzonej w warstwie adhezyjnej temperatury od 20°C do 80°C. Po jej osiągnięciu belki obciążano do zniszczenia w teście czteropunktowego zginania. Zauważalny spadek nośności obserwowano już dla temperatury 50°C. Nie stosowano mechanicznego kotwienia, dlatego przyczyną uszkodzenia we wszystkich przypadkach była delaminacja, zazwyczaj w warstwie kleju. Belki wzmocnione taśmą CFRP niszczyły się gwałtownie, bez szczególnych symptomów dźwiękowych towarzszących delaminacji. Ich nośność w temperaturach powyżej 65°C była bliska nośności nie wzmocnionej belki referencyjnej. Nieco korzystniej zachowywały się belki wzmocnione taśmą SRP, głównie dzięki większej szerokości i tym samym niższym naprężeniem w warstwie kleju.

Applied Sciences, 2020

This manuscript assessed the applicability of the existing ultimate bond formulas originally deve... more This manuscript assessed the applicability of the existing ultimate bond formulas originally developed for externally bonded carbon fiber-based composites in the analysis of steel-reinforced polymers (SRPs). In the first part, the methods of predicting the bond capacity are reviewed, the differences are indicated, and the factors determining the bond are discussed; then, using the bond test results of over 400 samples available in the literature, the bond prediction methods are assessed by graphical comparison. The evaluation mainly concerned concrete elements and epoxy adhesives; however, to a lesser extent, a similar analysis was performed for the masonry substrate and grout matrices. The results showed the relatively good applicability of the majority of bond prediction models for the analysis of SRP composites. In most cases, the ultimate bond force was slightly underestimated, which was beneficial in the design of this type of strengthening. Larger discrepancies concerned weake...

MATEC Web of Conferences, 2019

Cellular concretes cannot be reinforced as easily as traditional ones. Generally porous materials... more Cellular concretes cannot be reinforced as easily as traditional ones. Generally porous materials do not ensure sufficient bond of reinforcement; additionally, due to limited amount of aggregate, interlock between aggregate particles and reinforcement ribs is not satisfactory. The idea of reinforcement presented in the paper incorporates bi-directional composite reinforcing grids placed in tensile zone of the cellular concrete slab where transverse fibres are ensuring anchorage for fibres located in the main direction of stresses. The concept is based on geotechnical applications where grids are commonly used as soil stabilization, but the grids adopted in this solution are much stronger thanks to introduction of high strength fibres as composite reinforcement.

The paper describes preliminary studies on the influence of humidity on the electrical resistance... more The paper describes preliminary studies on the influence of humidity on the electrical resistance of a textile sensor made of carbon fibers. The concept of the sensor refers to externally bonded fiber reinforcement commonly used to strengthen building structures. However, the zig-zag arrangement of carbon fiber tow allows measuring strains, as it is done in popular resistive strain gauges. The sensor tests proved its effectiveness in the measurement of strains, but also showed a high sensitivity to changes in the temperature and humidity which unfavorably affects the readings and their interpretation. The influence of these factors must be compensated. Due to the size of the sensor, there is not possible electrical compensation by the combining of several sensors into the half or full Wheatstone bridge circuit. Only mathematical compensation based on known humidity resistance functions is possible. The described research is the first step to develop such relations. The tests were ca...

MATEC Web of Conferences, 2019

There are situations when timber structure requires strengthening caused by environmental deterio... more There are situations when timber structure requires strengthening caused by environmental deterioration or changes in load conditions. Its mechanical performance can be increased by use of externally bonded high strength fibre reinforced composite (FRP). The place of application increases the sensitivity of this technique to environmental effects, including heating by the sun rays. Surface temperature can exceed 70 °C, while usually as safe is considered 45 °C. Paper describes the tests of timber beams strengthened with two types of composites: unidirectional CFRP sheet and CFRP strip. They were heated at various temperature ranges and tested in bending. Out of the nine tested beams, only one heated to 95 °C was not damaged by the delamination of the composite overlay, remaining beams have not been destroyed due to achieved deflection exceeding the press cylinder range or were failed due to rupture of carbon fibres. The influence of the temperature was better recognizable in differe...

Architecture, Civil Engineering, Environment, 2016

The paper describes the measurements of temperature growth in different types of the epoxy adhesi... more The paper describes the measurements of temperature growth in different types of the epoxy adhesive bonding external strengthening. A total of six types of models were tested: CFRP sheet and strip, two SRP tapes adhered to the concrete sample, CFRP strip and SRP tape on a timber sample. Changes in temperature were investigated during the summer in the southern Poland. The maximum measured temperatures for all models exceeded regarded as safe temperature limit of 45°C. The highest recorded adhesive temperature refers to a sample of CFRP strengthened timber and exceeded 70°C. For the structure such a high temperature may result in almost complete loss of adhesion and thus the efficiency of strengthening. Test results may be a warning against the use of FRP external strengthening exposed to direct sunlight without any protection.

MATERIAŁY BUDOWLANE, 2016

Monitoring of structures is one of the engineering challenges of the 21st century. At the same ti... more Monitoring of structures is one of the engineering challenges of the 21st century. At the same time, as a result of changes in the conditions of use, design errors, many building structures require strengthening. The article presents research on the development of the external strengthening carbon fiber textile with an option of self-sensing. The idea is based on the pattern of resistive strain gauge, where thread is provided in a zig-zag of parallel lines. Already the first laboratory tests showed the high efficiency of the system in the measurement of strains, but also revealed the sensitivity of measurement to environmental conditions. The article presents studies on the influence of temperature and humidity on the measurement. To separate those effects, resistance changes were tested on unloaded concrete and wooden samples. The models were placed in a climatic chamber and the daily cycle of temperature and humidity changes was simulated. The results of the research confirm preli...

IOP Conference Series: Materials Science and Engineering, 2019

For centuries timber has been the most popular construction material. However, over the last few ... more For centuries timber has been the most popular construction material. However, over the last few decades, it gave way to man-invented structural materials, it is still willingly used in civil engineering, commonly for roof constructions, ceilings but also small bridges, lookout towers. Sometimes, as a result of environmental deterioration or changes in load conditions, timber structure requires to be strengthened. Flexural or tensile performance could be simply increased by using external fiber reinforced plastic (FRP) composite sheets or strips. Such type of reinforcement almost does not change the geometry, but uncovered may be exposed to environmental influences including sunrise heating. Its temperature can exceed 70°C, while commonly as save is considered temperature below 45°C. Paper describes the bending tests of timber beams externally strengthened with three types of composites: unidirectional CFRP sheet, CFRP strip and SRP tape. Beams were heated in the various ranges of temperatures and tested in flexure. Among nine tested beams only one, heated to 95°C failed by delamination of composite overlay, the remaining beams reinforced with CFRP strips and SRP tapes could not be destroyed due to deflection outside the press cylinder range, while beams strengthened with CFRP sheets failed after rupture of carbon fibers. Experiment results show that independently of the type of reinforcement danger temperatures can be recognized over 90°C. Under that temperature behaviour of heated beams is only slightly worse than tested in room temperature and differences are visible in deflections. As a result of slippage in the adhesive layer weakened by temperature measured deformation growths. This trend applies to both CFRP strip and sheet strengthened specimens. It should be emphasized that the obtained results are much better than in the case of commonly tested reinforced concrete beams, which were subjected to delamination failure just a little above 65°C.

Millennium: Journal of International Studies, 2019

espanolIntroduccion: Los geopolimeros son los materiales inorganicos modernos obtenidos como resu... more espanolIntroduccion: Los geopolimeros son los materiales inorganicos modernos obtenidos como resultado de la reaccion quimica bajo condiciones fuertemente alcalinas. Las principales ventajas de estos materiales son: parametros de alta resistencia, resistencia al fuego, resistencia a las heladas y resistencia al entorno agresivo. Debido a la menor emision de CO2 durante el proceso de produccion, tambien se consideran materiales ecologicos en comparacion con los materiales ordinarios de cemento Portland. Objetivos: El objetivo de la investigacion fue definir el impacto de la adicion de vidrio triturado reciclado en las propiedades mecanicas del aglutinante geopolimerico a partir de desechos de la mina de tungsteno. Metodos: Los parametros de fuerza de las muestras geopolimericas se determinaron sobre la base de la prueba de flexion de tres puntos y la prueba de compresion. Resultados: Las muestras de geopolimeros que contienen 20%, 40% y 80% de vidrio triturado reciclado presentan una...

MATEC Web of Conferences, 2019

It has been more than two decades, since FRP strengthening method was first time used in Poland. ... more It has been more than two decades, since FRP strengthening method was first time used in Poland. Therefore there is a natural need to develop an efficient quality assessment technique to verify design assumptions of strengthening in existing structures after many years. One of the promising non-destructive method of quality assessment is infrared thermography (IRT). In this paper, an initial study on recognition of delamination mainly in CFRP laminates using IRT was conducted as well as the influence of long-term loads on defects in CFRP strengthened RC beams was presented.

MATERIAŁY BUDOWLANE, 2016

Journal of Civil Engineering, Environment and Architecture, 2016

Przyklejane do konstrukcji kompozyty zbrojone włóknem węglowym zdobywają coraz większą popularnoś... more Przyklejane do konstrukcji kompozyty zbrojone włóknem węglowym zdobywają coraz większą popularność w zastosowaniach budowlanych, jednakże, z uwagi na kruche właściwości ich użytkowanie jest obarczone znacznie większym ryzykiem niż w przypadku tradycyjnych stali. Diagnostyka wzmocnionych elementów tylko przez obserwację ich zarysowań czy ugięć może być niewystarczająca, potrzebne są dodatkowe systemy monitorujące. W referacie przedstawiono opracowaną przez autorów inteligentną tkaninę, w której wiązki włókien węglowych łączą rolę rozciąganego zbrojenia i miernika odkształceń. Zasada jej pracy jest inspirowana budową klasycznego tensometru elektrooporowego, którego włókna przewodzące prowadzone są wężykowo. Rolę przewodnika pełni wiązka włókien węglowych, która jest izolowana w matrycy z włókien szklanych lub akrylowych. Opisane w referacie wybrane wyniki badań laboratoryjnych są bardzo obiecujące zarówno w zakresie jakości pomiaru odkształceń, jak i efektywności wzmocnienia. Obecnie dopracowywane są: dokładność kontroli grubości wiązki włókien, która wpływa na całkowitą oporność, czy też wpływ wilgoci na zmiany oporności. Słowa kluczowe: inteligentna tkanina, monitoring konstrukcji, pomiar odkształceń, laminat CFRP INFLUENCE OF CARBON FIBRE STRAIN SENSOR ON BEARING CAPACITY OF RC BEAMS S u m m a r y Externally bonded high-strength fiber composites are increasingly popular in structural applications, however, because of their brittle properties, their use is less secure than the common steel. Diagnosis this type of structure only by observing of cracks or deformations may be insufficient, they require additional monitoring systems. Paper presents developed by the authors' intelligent fabric, wherein the carbon fiber tow links the role of tensile reinforcement and strain gauge. Its way of working is inspired by the construction of traditional strain gauge, where electric wires are arranged in zigzag pattern. Carbon fiber thread plays the role of electrical conductor and is insulated by threads of glass or acrylic fibers. Described in the paper selected results of laboratory trials are very promising in both the accuracy of strain measurement, and the effectiveness of strengthening. Among the issues for improvement is the control of the cross-section of the fibers tow, affecting the total resistance of the fabric and moisture sensitivity.

Acta Polytechnica, 2021

A correct choice of a bond model for prestressing tendons is crucial for the right modelling of a... more A correct choice of a bond model for prestressing tendons is crucial for the right modelling of a structural behaviour of a pretensioned concrete structure. The aim of this paper is the determination of an optimal bond model for 7-wire strands in a prestressed concrete beam produced in a precast concrete plant of Consolis Poland. ATENA 3D is used to develop finite element models of the beam that differ only in a bond stress-slip relationship of tendons. The bond stress-slip relationships for modelling are taken from the results of bond tests carried out by different researchers in previous years. Moreover, for comparison purposes, a simplified 2D model of the beam is created in Autodesk Robot. The strain distribution at the time of the strand release is found for each of the finite element models. The determined strain distributions are compared with the strain distribution in the beam established by an experimental test using a measuring system based on a digital image correlation....

MATERIAŁY BUDOWLANE, 2016

Journal of Civil Engineering, Environment and Architecture, 2017

Journal of Composites Science, 2020

Bonding of external reinforcement is currently the simplest, fastest, and most popular method of ... more Bonding of external reinforcement is currently the simplest, fastest, and most popular method of strengthening concrete and masonry structures. Glass and carbon organic fibers are the dominant materials used, but alternatives also include high-strength steel wires. The mechanical properties of such steel are comparable to those of carbon fiber. Due to their good compatibility with mortars, steel wires are particularly well suited to the revitalization of historic buildings. The manuscript provides an overview of research and experience in the use of steel-reinforced polymers (SRPs) and steel-reinforced composite mortars (SRCMs, also called steel-reinforced grout (SRG)) for structural strengthening. The examples described are for concrete beams, slabs and columns, walls, and masonry arches. The results of laboratory tests are discussed. The summary presents the advantages and disadvantages of composites based on ultra-high-strength steels compared with more popular carbon fiber compo...

Materials, 2022

External bonding of fiber reinforced composites is currently the most popular method of strengthe... 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 metho...

Materials, 2021

The foaming of geopolymers lowers their density, thus opening up new environmental benefits, incl... more The foaming of geopolymers lowers their density, thus opening up new environmental benefits, including acoustic and thermal insulation. At the same time, foaming disturbs the homogeneity of the material, which worsens the strength parameters, and particularly those related to tension, which can be improved by introducing reinforcement. This paper presents the results of research on foamed geopolymers reinforced with glass fiber meshes, a type of reinforcement that provides an adequate bond. The samples tested here were based on three types of coal fly ash, and were foamed with varying doses of hydrogen peroxide. Samples were cured at 40 °C and were tested after 28 days of maturing at ambient temperature. The strength parameters of the synthesized geopolymers were determined via laboratory testing, and were used to evaluate load-bearing capacity models of the tested samples reinforced with glass fiber mesh. The results showed the importance of the type of ash on the strength properti...

Architecture Civil Engineering Environment, 2015

S t r e s z c z e n i e Kompozyty SRP są zbrojone drutami ze stali o wysokiej wytrzymałości w for... more S t r e s z c z e n i e Kompozyty SRP są zbrojone drutami ze stali o wysokiej wytrzymałości w formie splotów, które łączy się poprzecznie tworząc rodzaj maty. Właściwości mechaniczne stali wykorzystywanej do produkcji drutów są podobne do innych wysokowęglowych stali wytwarzanych w procesie obróbki plastycznej na zimno (np. stali do sprężania): nie występuje w nich płynięcie półka plastyczna. Prawie liniowa zależność naprężenie – odkształcenie upodabnia kompozyty SRP do laminatów zbrojonych włóknem węglowym. Podobnie pod względem łatwości kształtowania i ciężaru własnego, bardziej odpowiadają one taśmom węglowym niż stalowym płaskownikom. Z uwagi na te podobieństwa zasady projektowania i stosowania wzmocnień na zginanie, bazują na dobrze znanych procedurach do projektowania tego typu wzmocnień przy użyciu taśm CFRP. W artykule przedstawiono wyniki testów porównawczych kilkunastu belek wzmocnionych taśmami typu SRP i CFRP. K e y w o r d s : FRP Strengthening; Steel Reinforced Polymer...

Journal of Civil Engineering, Environment and Architecture, 2017

Klejenie zewnętrznych nakładek kompozytowych zbrojonych włóknami wysokiej wytrzymałości powoli st... more Klejenie zewnętrznych nakładek kompozytowych zbrojonych włóknami wysokiej wytrzymałości powoli staje się najpopularniejszą metodą wzmacniania konstrukcji żelbetowych. Zdarza się, że tego typu wzmocnienia mogą być bezpośrednio poddane nasłonecznieniu i tym samym zagrożone nadmiernym nagrzaniem. Badania prowadzone przez autora artkułu pokazały, że nawet w umiarkowanej strefie geograficznej, w której znajduje się Polska, temperatura kleju pod cienkim laminatem może osiągnąć 65°C, czyli temperaturę o 20°C wyższą niż temperatura zeszklenia najpopularniejszych na rynku klejów opartych na żywicy epoksydowej. W artykule przedstawiono wyniki badań laboratoryjnych belek żelbetowych podgrzanych od strony wzmocnienia promieniowaniem podczerwonym. Program badań objął grupę trzynastu belek żelbetowych w skali rzeczywistej. Sześć z nich zostało wzmocnionych taśmą CFRP, kolejnych sześć z taśmą SRP. Belki podgrzewano za pomocą liniowych promienników podczerwieni do mierzonej w warstwie adhezyjnej temperatury od 20°C do 80°C. Po jej osiągnięciu belki obciążano do zniszczenia w teście czteropunktowego zginania. Zauważalny spadek nośności obserwowano już dla temperatury 50°C. Nie stosowano mechanicznego kotwienia, dlatego przyczyną uszkodzenia we wszystkich przypadkach była delaminacja, zazwyczaj w warstwie kleju. Belki wzmocnione taśmą CFRP niszczyły się gwałtownie, bez szczególnych symptomów dźwiękowych towarzszących delaminacji. Ich nośność w temperaturach powyżej 65°C była bliska nośności nie wzmocnionej belki referencyjnej. Nieco korzystniej zachowywały się belki wzmocnione taśmą SRP, głównie dzięki większej szerokości i tym samym niższym naprężeniem w warstwie kleju.

Applied Sciences, 2020

This manuscript assessed the applicability of the existing ultimate bond formulas originally deve... more This manuscript assessed the applicability of the existing ultimate bond formulas originally developed for externally bonded carbon fiber-based composites in the analysis of steel-reinforced polymers (SRPs). In the first part, the methods of predicting the bond capacity are reviewed, the differences are indicated, and the factors determining the bond are discussed; then, using the bond test results of over 400 samples available in the literature, the bond prediction methods are assessed by graphical comparison. The evaluation mainly concerned concrete elements and epoxy adhesives; however, to a lesser extent, a similar analysis was performed for the masonry substrate and grout matrices. The results showed the relatively good applicability of the majority of bond prediction models for the analysis of SRP composites. In most cases, the ultimate bond force was slightly underestimated, which was beneficial in the design of this type of strengthening. Larger discrepancies concerned weake...

MATEC Web of Conferences, 2019

Cellular concretes cannot be reinforced as easily as traditional ones. Generally porous materials... more Cellular concretes cannot be reinforced as easily as traditional ones. Generally porous materials do not ensure sufficient bond of reinforcement; additionally, due to limited amount of aggregate, interlock between aggregate particles and reinforcement ribs is not satisfactory. The idea of reinforcement presented in the paper incorporates bi-directional composite reinforcing grids placed in tensile zone of the cellular concrete slab where transverse fibres are ensuring anchorage for fibres located in the main direction of stresses. The concept is based on geotechnical applications where grids are commonly used as soil stabilization, but the grids adopted in this solution are much stronger thanks to introduction of high strength fibres as composite reinforcement.

The paper describes preliminary studies on the influence of humidity on the electrical resistance... more The paper describes preliminary studies on the influence of humidity on the electrical resistance of a textile sensor made of carbon fibers. The concept of the sensor refers to externally bonded fiber reinforcement commonly used to strengthen building structures. However, the zig-zag arrangement of carbon fiber tow allows measuring strains, as it is done in popular resistive strain gauges. The sensor tests proved its effectiveness in the measurement of strains, but also showed a high sensitivity to changes in the temperature and humidity which unfavorably affects the readings and their interpretation. The influence of these factors must be compensated. Due to the size of the sensor, there is not possible electrical compensation by the combining of several sensors into the half or full Wheatstone bridge circuit. Only mathematical compensation based on known humidity resistance functions is possible. The described research is the first step to develop such relations. The tests were ca...

MATEC Web of Conferences, 2019

There are situations when timber structure requires strengthening caused by environmental deterio... more There are situations when timber structure requires strengthening caused by environmental deterioration or changes in load conditions. Its mechanical performance can be increased by use of externally bonded high strength fibre reinforced composite (FRP). The place of application increases the sensitivity of this technique to environmental effects, including heating by the sun rays. Surface temperature can exceed 70 °C, while usually as safe is considered 45 °C. Paper describes the tests of timber beams strengthened with two types of composites: unidirectional CFRP sheet and CFRP strip. They were heated at various temperature ranges and tested in bending. Out of the nine tested beams, only one heated to 95 °C was not damaged by the delamination of the composite overlay, remaining beams have not been destroyed due to achieved deflection exceeding the press cylinder range or were failed due to rupture of carbon fibres. The influence of the temperature was better recognizable in differe...

Architecture, Civil Engineering, Environment, 2016

The paper describes the measurements of temperature growth in different types of the epoxy adhesi... more The paper describes the measurements of temperature growth in different types of the epoxy adhesive bonding external strengthening. A total of six types of models were tested: CFRP sheet and strip, two SRP tapes adhered to the concrete sample, CFRP strip and SRP tape on a timber sample. Changes in temperature were investigated during the summer in the southern Poland. The maximum measured temperatures for all models exceeded regarded as safe temperature limit of 45°C. The highest recorded adhesive temperature refers to a sample of CFRP strengthened timber and exceeded 70°C. For the structure such a high temperature may result in almost complete loss of adhesion and thus the efficiency of strengthening. Test results may be a warning against the use of FRP external strengthening exposed to direct sunlight without any protection.

MATERIAŁY BUDOWLANE, 2016

Monitoring of structures is one of the engineering challenges of the 21st century. At the same ti... more Monitoring of structures is one of the engineering challenges of the 21st century. At the same time, as a result of changes in the conditions of use, design errors, many building structures require strengthening. The article presents research on the development of the external strengthening carbon fiber textile with an option of self-sensing. The idea is based on the pattern of resistive strain gauge, where thread is provided in a zig-zag of parallel lines. Already the first laboratory tests showed the high efficiency of the system in the measurement of strains, but also revealed the sensitivity of measurement to environmental conditions. The article presents studies on the influence of temperature and humidity on the measurement. To separate those effects, resistance changes were tested on unloaded concrete and wooden samples. The models were placed in a climatic chamber and the daily cycle of temperature and humidity changes was simulated. The results of the research confirm preli...

IOP Conference Series: Materials Science and Engineering, 2019

For centuries timber has been the most popular construction material. However, over the last few ... more For centuries timber has been the most popular construction material. However, over the last few decades, it gave way to man-invented structural materials, it is still willingly used in civil engineering, commonly for roof constructions, ceilings but also small bridges, lookout towers. Sometimes, as a result of environmental deterioration or changes in load conditions, timber structure requires to be strengthened. Flexural or tensile performance could be simply increased by using external fiber reinforced plastic (FRP) composite sheets or strips. Such type of reinforcement almost does not change the geometry, but uncovered may be exposed to environmental influences including sunrise heating. Its temperature can exceed 70°C, while commonly as save is considered temperature below 45°C. Paper describes the bending tests of timber beams externally strengthened with three types of composites: unidirectional CFRP sheet, CFRP strip and SRP tape. Beams were heated in the various ranges of temperatures and tested in flexure. Among nine tested beams only one, heated to 95°C failed by delamination of composite overlay, the remaining beams reinforced with CFRP strips and SRP tapes could not be destroyed due to deflection outside the press cylinder range, while beams strengthened with CFRP sheets failed after rupture of carbon fibers. Experiment results show that independently of the type of reinforcement danger temperatures can be recognized over 90°C. Under that temperature behaviour of heated beams is only slightly worse than tested in room temperature and differences are visible in deflections. As a result of slippage in the adhesive layer weakened by temperature measured deformation growths. This trend applies to both CFRP strip and sheet strengthened specimens. It should be emphasized that the obtained results are much better than in the case of commonly tested reinforced concrete beams, which were subjected to delamination failure just a little above 65°C.