Ricardo Laguardia Justen de Almeida, Guilherme Aris Parsekian, Marco Antonio Carnio
The present research investigated the flexural behavior of high‐strength fiber‐reinforced concrete (HSFRC) with six different types of fiber: hooked‐end and crimped steel fibers, chopped and pultruded glass fibers; monofilament and twisted polymeric fibers. An extensive experimental program with 108 specimens for 3‐point bending tests was carried out and the parameters analyzed were the fiber content (0.50%, 0.75% and 1.00% in volume), the fiber type and the compressive strength of the concrete (60 and 90 MPa). Statistical analyses were performed and showed that regardless of the fiber material, increasing the amount of fibers added to concrete increases residual strength and toughness. Limit of proportionality is not affected by the addition of fibers, while postcracking behavior, on the other hand, is controlled by the fibers. Increasing the compressive strength of the concrete matrix affect mainly the limit proportionality of all mixes and the postcracking behavior of the concrete reinforced with hooked‐end steel fibers. The classification of HSFRC and the conditions required for HSFRC for use in structural applications according to the fib Model Code 2010 were also discussed, and it was verified that such conditions are not consistent with the experimental results and should be revised for high‐strength fiber‐reinforced concrete.
{"title":"Investigation on the flexural behavior of high‐strength fiber‐reinforced concrete","authors":"Ricardo Laguardia Justen de Almeida, Guilherme Aris Parsekian, Marco Antonio Carnio","doi":"10.1002/suco.202301031","DOIUrl":"https://doi.org/10.1002/suco.202301031","url":null,"abstract":"The present research investigated the flexural behavior of high‐strength fiber‐reinforced concrete (HSFRC) with six different types of fiber: hooked‐end and crimped steel fibers, chopped and pultruded glass fibers; monofilament and twisted polymeric fibers. An extensive experimental program with 108 specimens for 3‐point bending tests was carried out and the parameters analyzed were the fiber content (0.50%, 0.75% and 1.00% in volume), the fiber type and the compressive strength of the concrete (60 and 90 MPa). Statistical analyses were performed and showed that regardless of the fiber material, increasing the amount of fibers added to concrete increases residual strength and toughness. Limit of proportionality is not affected by the addition of fibers, while postcracking behavior, on the other hand, is controlled by the fibers. Increasing the compressive strength of the concrete matrix affect mainly the limit proportionality of all mixes and the postcracking behavior of the concrete reinforced with hooked‐end steel fibers. The classification of HSFRC and the conditions required for HSFRC for use in structural applications according to the <jats:italic>fib</jats:italic> Model Code 2010 were also discussed, and it was verified that such conditions are not consistent with the experimental results and should be revised for high‐strength fiber‐reinforced concrete.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141930960","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To investigate the dynamic mechanical response and damage mechanisms of I‐shaped steel‐concrete composite beams under explosive loads, experimental research and numerical simulations were conducted on steel‐concrete composite structures. The accuracy of the numerical analysis model was validated by comparing the damage characteristics of the structures obtained from explosive tests on the steel‐concrete composite components. Based on this, numerical simulations were performed on steel‐concrete composite beams using the explicit dynamic analysis software ANSYS/LS‐DYNA, and a study on their damage mechanisms was conducted. This study resulted in the acquisition of dynamic mechanical response patterns, including time‐dependent stress, strain, displacement, acceleration, and so on. Different structural damage characteristics under various explosive conditions were summarized, and key parameters affecting the blast resistance of the structure were analyzed. The research findings indicated that, in contrast to the failure characteristics of I‐shaped reinforced concrete (RC) beams, the failure characteristics of I‐shaped steel‐concrete composite beams mainly include punching and shearing failure of the steel‐RC slab and local buckling of the steel beam. Under the same explosive conditions, steel‐concrete composite structures exhibit superior blast resistance, with certain changes in structural parameters significantly improving blast resistance. The research results can provide theoretical support and a scientific basis for the proactive design of blast protection in steel‐concrete beams.
{"title":"Dynamic response and blast resistance of I‐shaped steel‐concrete composite beam under explosive loading","authors":"Yuan Li, Qutong Lin, Jianyu Liu","doi":"10.1002/suco.202400385","DOIUrl":"https://doi.org/10.1002/suco.202400385","url":null,"abstract":"To investigate the dynamic mechanical response and damage mechanisms of I‐shaped steel‐concrete composite beams under explosive loads, experimental research and numerical simulations were conducted on steel‐concrete composite structures. The accuracy of the numerical analysis model was validated by comparing the damage characteristics of the structures obtained from explosive tests on the steel‐concrete composite components. Based on this, numerical simulations were performed on steel‐concrete composite beams using the explicit dynamic analysis software ANSYS/LS‐DYNA, and a study on their damage mechanisms was conducted. This study resulted in the acquisition of dynamic mechanical response patterns, including time‐dependent stress, strain, displacement, acceleration, and so on. Different structural damage characteristics under various explosive conditions were summarized, and key parameters affecting the blast resistance of the structure were analyzed. The research findings indicated that, in contrast to the failure characteristics of I‐shaped reinforced concrete (RC) beams, the failure characteristics of I‐shaped steel‐concrete composite beams mainly include punching and shearing failure of the steel‐RC slab and local buckling of the steel beam. Under the same explosive conditions, steel‐concrete composite structures exhibit superior blast resistance, with certain changes in structural parameters significantly improving blast resistance. The research results can provide theoretical support and a scientific basis for the proactive design of blast protection in steel‐concrete beams.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141931086","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In order to fully utilize the advantages of stud and perfobond leiste (PBL) connectors, a new composite shear connector was proposed in which the studs were welded to the H‐beam of the PBL shear connectors. In addition, to further improve the durability performance of the structure, steel‐fiber‐reinforced polymer composite bars (SFCBs) were used to replace steel rebars as penetrating rebars. In this study, the shear behaviors of SFCBs‐reinforced composite shear connectors were investigated by push‐out tests. The effects of the number of studs, the number of holes, and the type of penetrating rebars on the failure mode, load–slip curve, and shear behavior of the composite shear connectors were analyzed. The specimens' failure modes were mainly shearing the studs and crushing the concrete. Increasing the number of studs and holes has resulted in an increase of at least 7.47% in the shear resistance and 12.36% in the stiffness. SFCB had little effect on the shear resistance and reduced the stiffness but could improve ductility, with a maximum improvement of 11.49%. Additionally, a finite element model was established for parametric analysis. The results showed that the diameter of the SFCB and hole had a significant impact on the shear resistance. An equation for calculating the shear resistance based on the contributions of various components has been established that was applicable to composite shear connectors and has good accuracy and applicability.
{"title":"Shear behavior of stud and SFCBs‐reinforced PBL composite connectors in steel‐concrete structures","authors":"Fangwen Wu, Bitong Zhao, Zhuo Liu, Zirun Li, Lanqing He, Zhou Fan","doi":"10.1002/suco.202400267","DOIUrl":"https://doi.org/10.1002/suco.202400267","url":null,"abstract":"In order to fully utilize the advantages of stud and perfobond leiste (PBL) connectors, a new composite shear connector was proposed in which the studs were welded to the H‐beam of the PBL shear connectors. In addition, to further improve the durability performance of the structure, steel‐fiber‐reinforced polymer composite bars (SFCBs) were used to replace steel rebars as penetrating rebars. In this study, the shear behaviors of SFCBs‐reinforced composite shear connectors were investigated by push‐out tests. The effects of the number of studs, the number of holes, and the type of penetrating rebars on the failure mode, load–slip curve, and shear behavior of the composite shear connectors were analyzed. The specimens' failure modes were mainly shearing the studs and crushing the concrete. Increasing the number of studs and holes has resulted in an increase of at least 7.47% in the shear resistance and 12.36% in the stiffness. SFCB had little effect on the shear resistance and reduced the stiffness but could improve ductility, with a maximum improvement of 11.49%. Additionally, a finite element model was established for parametric analysis. The results showed that the diameter of the SFCB and hole had a significant impact on the shear resistance. An equation for calculating the shear resistance based on the contributions of various components has been established that was applicable to composite shear connectors and has good accuracy and applicability.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141930963","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To accurately and timely evaluate the long‐term performance of cables in cable‐stayed bridges, an automatic perception technology scheme by on‐line monitoring of cable vibrations is proposed for the fatigue damage evaluation of in‐service cables. In the fatigue‐stress amplitude of cables, the stress produced by tension changes caused by external actions like traffic, wind, and temperature is the main component. When cables vibrate significantly, the stress caused by changes in cable vibration‐induced additional stress should not be neglected. Besides axial stress, bending stress is also significant in cable fatigue damage analysis. To make cable fatigue life prediction closer to real engineering scenarios, this factor should be considered. First, based on the cable dynamic stiffness theory, a method is proposed for the automatic gathering of the actual full‐stress time history of a cable by on‐line vibration monitoring. Furthermore, based on Miner's linear fatigue damage accumulation theory, an automatic fatigue life assessment method is proposed and applied to the vibration monitoring data of cables on an operational bridge. The results indicate that the proposed technology realizes automatic on‐line monitoring of cable forces and fatigue assessment of cables. Through statistical analysis of cable fatigue stress amplitude, it was determined that in cable‐stayed bridges, compared to long cables, short cables are more sensitive to external variable loads, typically experiencing larger and more frequent tension changes, and are more prone to fatigue. Therefore, short cables should be given more attention when analyzing cable fatigue in cable‐stayed bridges.
{"title":"Automatic assessment of the fatigue life of cables of cable‐stayed bridges by on‐line monitoring","authors":"Bin Xu, Zirao Wu, Joan R. Casas, Danhui Dan","doi":"10.1002/suco.202400609","DOIUrl":"https://doi.org/10.1002/suco.202400609","url":null,"abstract":"To accurately and timely evaluate the long‐term performance of cables in cable‐stayed bridges, an automatic perception technology scheme by on‐line monitoring of cable vibrations is proposed for the fatigue damage evaluation of in‐service cables. In the fatigue‐stress amplitude of cables, the stress produced by tension changes caused by external actions like traffic, wind, and temperature is the main component. When cables vibrate significantly, the stress caused by changes in cable vibration‐induced additional stress should not be neglected. Besides axial stress, bending stress is also significant in cable fatigue damage analysis. To make cable fatigue life prediction closer to real engineering scenarios, this factor should be considered. First, based on the cable dynamic stiffness theory, a method is proposed for the automatic gathering of the actual full‐stress time history of a cable by on‐line vibration monitoring. Furthermore, based on Miner's linear fatigue damage accumulation theory, an automatic fatigue life assessment method is proposed and applied to the vibration monitoring data of cables on an operational bridge. The results indicate that the proposed technology realizes automatic on‐line monitoring of cable forces and fatigue assessment of cables. Through statistical analysis of cable fatigue stress amplitude, it was determined that in cable‐stayed bridges, compared to long cables, short cables are more sensitive to external variable loads, typically experiencing larger and more frequent tension changes, and are more prone to fatigue. Therefore, short cables should be given more attention when analyzing cable fatigue in cable‐stayed bridges.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141882552","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Morteza Naghipour, Mohammad Akbarzadeh, Seyed Mohammad Reza Hasani
This study proposes a novel reduced beam section concrete‐filled double steel tube (RBS CFDST) beam‐to‐column joint and investigates the effect of RBS length and the beam moment of inertia on the plastic hinge formation in such joints. Therefore, a set of nine RBS CFDST connections were fabricated and cast with self‐consolidating concrete in the laboratory. Then, parameters including failure pattern, buckling mode, plastic hinge location, joint maximum load‐bearing capacity, and column rotation were inspected. The findings reveal that when the RBS length is equal to that of the beam dimension, the entire plastic hinge length is formed within the RBS zone. As such, the plastic hinge occurs away from the column face and brittle failure is avoided, while the joint column rotation is significantly reduced. It was also concluded that the maximum load‐bearing capacity is the highest when the RBS length is at its lowest.
{"title":"Experimental study on a novel reduced beem section self consolidating concrete‐filled double steel tube","authors":"Morteza Naghipour, Mohammad Akbarzadeh, Seyed Mohammad Reza Hasani","doi":"10.1002/suco.202301030","DOIUrl":"https://doi.org/10.1002/suco.202301030","url":null,"abstract":"This study proposes a novel reduced beam section concrete‐filled double steel tube (RBS CFDST) beam‐to‐column joint and investigates the effect of RBS length and the beam moment of inertia on the plastic hinge formation in such joints. Therefore, a set of nine RBS CFDST connections were fabricated and cast with self‐consolidating concrete in the laboratory. Then, parameters including failure pattern, buckling mode, plastic hinge location, joint maximum load‐bearing capacity, and column rotation were inspected. The findings reveal that when the RBS length is equal to that of the beam dimension, the entire plastic hinge length is formed within the RBS zone. As such, the plastic hinge occurs away from the column face and brittle failure is avoided, while the joint column rotation is significantly reduced. It was also concluded that the maximum load‐bearing capacity is the highest when the RBS length is at its lowest.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141882496","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The most common and well‐known method for evaluating the sulfate resistance of cement blends is ASTM C1012 procedure. It takes at least 12–18 months to evaluate the results, considering this standard. The present research proposes two supplementary methods to accelerate the sulfate ions penetration into the mortar bars used in ASTM C1012. Both of these two supplementary methods were evaluated by studying mortar samples' expansion, mass change, visual condition, compressive strength, ultrasonic pulse velocity, and XRD. In the first method, a developed device provided an electrical conduction environment for mortar bars made of three cement blends. The results showed that this method produced between 8 and 16 times more expansion considering different studied cement blends. In the second method, mortar bars of seven cement blends were exposed to a devised prior condition under vacuum. Considering the results, this method produced between 2.5 and 9 times more expansion in relation to each cement blend and approach. Additionally, an excellent polynomial correlation was observed between the expansion of new accelerated methods and ASTM C1012 results. It can be concluded that using these accelerated methods as complementary to ASTM C1012 can help to evaluate the sulfate resistance of cement blends in a shorter time period.
{"title":"Accelerated external sulfate attack: Improved laboratory methods, considering physical and chemical processes","authors":"Arian Biook Aghazadeh, Sajjad Mirvalad","doi":"10.1002/suco.202400051","DOIUrl":"https://doi.org/10.1002/suco.202400051","url":null,"abstract":"The most common and well‐known method for evaluating the sulfate resistance of cement blends is ASTM C1012 procedure. It takes at least 12–18 months to evaluate the results, considering this standard. The present research proposes two supplementary methods to accelerate the sulfate ions penetration into the mortar bars used in ASTM C1012. Both of these two supplementary methods were evaluated by studying mortar samples' expansion, mass change, visual condition, compressive strength, ultrasonic pulse velocity, and XRD. In the first method, a developed device provided an electrical conduction environment for mortar bars made of three cement blends. The results showed that this method produced between 8 and 16 times more expansion considering different studied cement blends. In the second method, mortar bars of seven cement blends were exposed to a devised prior condition under vacuum. Considering the results, this method produced between 2.5 and 9 times more expansion in relation to each cement blend and approach. Additionally, an excellent polynomial correlation was observed between the expansion of new accelerated methods and ASTM C1012 results. It can be concluded that using these accelerated methods as complementary to ASTM C1012 can help to evaluate the sulfate resistance of cement blends in a shorter time period.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141882489","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Klajdi Toska, Flora Faleschini, Anne‐Lise Beaucour, Carlo Pellegrino, Albert Noumowe
The paper investigates the effect of high temperature exposure on the performance of concrete confined through textile/fabric‐reinforced composites. Small‐scale cylindrical specimens (150 × 300 mm) were confined using two types of carbon fibers (dry and epoxy‐resin coated). For the sake of comparison, two confining layers were applied to all specimens. After curing, cylinders were exposed to four ranges of increasing temperatures—being 20°C (ambient), 80°C, 100°C, and 250°C and, after cooling down, were tested under compressive cyclic loading. The experimental results show that thermal stress significantly influences the confinement effectiveness of textile‐reinforced composites. Exposure to high temperatures reduces the ultimate confined strength and significantly influences the overall axial stress–strain behavior.
{"title":"Effect of high temperature on FRCM‐confined concrete","authors":"Klajdi Toska, Flora Faleschini, Anne‐Lise Beaucour, Carlo Pellegrino, Albert Noumowe","doi":"10.1002/suco.202301022","DOIUrl":"https://doi.org/10.1002/suco.202301022","url":null,"abstract":"The paper investigates the effect of high temperature exposure on the performance of concrete confined through textile/fabric‐reinforced composites. Small‐scale cylindrical specimens (150 × 300 mm) were confined using two types of carbon fibers (dry and epoxy‐resin coated). For the sake of comparison, two confining layers were applied to all specimens. After curing, cylinders were exposed to four ranges of increasing temperatures—being 20°C (ambient), 80°C, 100°C, and 250°C and, after cooling down, were tested under compressive cyclic loading. The experimental results show that thermal stress significantly influences the confinement effectiveness of textile‐reinforced composites. Exposure to high temperatures reduces the ultimate confined strength and significantly influences the overall axial stress–strain behavior.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141882562","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Arash K. Pour, Amir Shirkhani, Ehsan Noroozinejad Farsangi
The present study aims to investigate how the use of high‐range water reducer (HRWR) and variations in water/cement (W/C) ratio affect the properties of self‐consolidating concrete (SCC) while taking into account different proportions of polypropylene fibers (PF) and natural zeolite (NZ). A total of 28 samples were cast and analyzed. PF fractions ranging from 0% to 1.5% by weight were added, along with a substitution of 10% NZ for cement (50 kg/m3). Four W/C ratios (0.30, 0.35, 0.40, and 0.45) were tested, in addition to seven HRWR contents ranging from 5 to 6.5 kg/m3. Various tests were conducted to assess slump, T500, V‐funnel, L‐box, modulus of elasticity, and compressive, tensile, and flexural strengths. Novel models were developed to predict the properties of hardened concrete based on W/C, HRWR, PF, and NZ content. Findings indicated that optimal performance of PF‐reinforced SCC with NZ was achieved when up to 0.75% PF was combined with an HRWR content equivalent to 1.25% of the cement fraction and NZ ratio. Furthermore, the proposed models offer accurate predictions of both fresh and hardened‐state properties of PF‐reinforced SCC with NZ based on W/C and HRWR ratios.
{"title":"Effect of high‐range water reducer and W/C ratio on the fresh and mechanical properties of fiber‐reinforced natural zeolite SCC","authors":"Arash K. Pour, Amir Shirkhani, Ehsan Noroozinejad Farsangi","doi":"10.1002/suco.202301071","DOIUrl":"https://doi.org/10.1002/suco.202301071","url":null,"abstract":"The present study aims to investigate how the use of high‐range water reducer (HRWR) and variations in water/cement (W/C) ratio affect the properties of self‐consolidating concrete (SCC) while taking into account different proportions of polypropylene fibers (PF) and natural zeolite (NZ). A total of 28 samples were cast and analyzed. PF fractions ranging from 0% to 1.5% by weight were added, along with a substitution of 10% NZ for cement (50 kg/m<jats:sup>3</jats:sup>). Four W/C ratios (0.30, 0.35, 0.40, and 0.45) were tested, in addition to seven HRWR contents ranging from 5 to 6.5 kg/m<jats:sup>3</jats:sup>. Various tests were conducted to assess slump, T<jats:sub>500</jats:sub>, V‐funnel, L‐box, modulus of elasticity, and compressive, tensile, and flexural strengths. Novel models were developed to predict the properties of hardened concrete based on W/C, HRWR, PF, and NZ content. Findings indicated that optimal performance of PF‐reinforced SCC with NZ was achieved when up to 0.75% PF was combined with an HRWR content equivalent to 1.25% of the cement fraction and NZ ratio. Furthermore, the proposed models offer accurate predictions of both fresh and hardened‐state properties of PF‐reinforced SCC with NZ based on W/C and HRWR ratios.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141882555","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Talip Cakmak, Ilker Ustabas, Zafer Kurt, Ali Gurbuz
Geopolymer mortars, which cause less CO2 emissions than concrete and its raw material cement, are an innovative, environmentally friendly and sustainable building material. Geopolymers are formed by activating silica and alumina materials with alkaline activators. In this study, a geopolymer mortar containing obsidian (OB), also known as volcanic glass, which is free, and silica fume (SF), which is the waste material of the silicon and ferrosilicon industry, was investigated. The behavior of OB‐based geopolymer mortars under different curing times ranging from 2 to 120 h and different thermal treatment temperatures such as 90, 150, and 200°C were examined. The effectiveness of OB and SF on the physical features, compressive strength (CS), and micro‐structural of the geopolymers were characterized. Results demonstrated that the peak CSs were acquired in 96 h at 90 and 150°C heat treatment temperatures, while the highest CSs were acquired in 72 h for specimens subjected to 200°C heat treatment. Reduces in CSs were detected when the curing time exceeded the ideal limit. OB‐based geopolymer was found to be stable with SF and there was a linear relationship between SF substitution ratio and CS. The density of the mortar pieces decreased with increasing thermal curing hours. Devolving on the thermal temperature and curing time, the microstructures became more compact and microvoids and cracks decreased. It was observed that SF substitution reduced the total pore size of the geopolymers and allowed the pore structure size to be reduced. The results obtained from the study are expected to encourage the utilize of industrial wastes and new binders in the manufacture of geopolymers.
土工聚合物砂浆比混凝土及其原材料水泥的二氧化碳排放量更少，是一种创新、环保和可持续的建筑材料。土工聚合物是用碱性活化剂活化二氧化硅和氧化铝材料而形成的。本研究调查了一种土工聚合物砂浆，其中含有游离的黑曜石（OB）（又称火山玻璃）和硅灰（SF）（硅和硅铁工业的废料）。研究了基于 OB 的土工聚合物砂浆在 2 至 120 小时不同固化时间和 90、150 和 200°C 不同热处理温度下的行为。研究了 OB 和 SF 对土工聚合物的物理特性、抗压强度（CS）和微观结构的影响。结果表明，在 90 和 150°C 热处理温度下，96 小时内获得的 CS 值达到峰值，而在 200°C 热处理温度下，72 小时内获得的 CS 值最高。当固化时间超过理想极限时，CSs 会降低。研究发现，OB 基土工聚合物与 SF 具有良好的稳定性，SF 替代率与 CS 之间呈线性关系。砂浆的密度随着热固化时间的增加而降低。随着热温度和固化时间的变化，微观结构变得更加致密，微空洞和裂缝减少。据观察，SF 替代降低了土工聚合物的总孔径，并使孔隙结构尺寸减小。这项研究的结果有望鼓励在制造土工聚合物时利用工业废料和新型粘合剂。
{"title":"The importance of early strength in structural applications: Obsidian‐based geopolymer mortars and silica fume substitution study","authors":"Talip Cakmak, Ilker Ustabas, Zafer Kurt, Ali Gurbuz","doi":"10.1002/suco.202400726","DOIUrl":"https://doi.org/10.1002/suco.202400726","url":null,"abstract":"Geopolymer mortars, which cause less CO<jats:sub>2</jats:sub> emissions than concrete and its raw material cement, are an innovative, environmentally friendly and sustainable building material. Geopolymers are formed by activating silica and alumina materials with alkaline activators. In this study, a geopolymer mortar containing obsidian (OB), also known as volcanic glass, which is free, and silica fume (SF), which is the waste material of the silicon and ferrosilicon industry, was investigated. The behavior of OB‐based geopolymer mortars under different curing times ranging from 2 to 120 h and different thermal treatment temperatures such as 90, 150, and 200°C were examined. The effectiveness of OB and SF on the physical features, compressive strength (CS), and micro‐structural of the geopolymers were characterized. Results demonstrated that the peak CSs were acquired in 96 h at 90 and 150°C heat treatment temperatures, while the highest CSs were acquired in 72 h for specimens subjected to 200°C heat treatment. Reduces in CSs were detected when the curing time exceeded the ideal limit. OB‐based geopolymer was found to be stable with SF and there was a linear relationship between SF substitution ratio and CS. The density of the mortar pieces decreased with increasing thermal curing hours. Devolving on the thermal temperature and curing time, the microstructures became more compact and microvoids and cracks decreased. It was observed that SF substitution reduced the total pore size of the geopolymers and allowed the pore structure size to be reduced. The results obtained from the study are expected to encourage the utilize of industrial wastes and new binders in the manufacture of geopolymers.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141882554","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xu Binlin, Tian Zhongchu, Shen Xiaoping, Bai Wenguang
During the cantilever casting process of reinforced concrete arch bridges with cantilever cast‐in‐situ method, it is difficult to select representative training samples for reliability analysis due to its complex structural system. Many random variables and large computational sample size, this paper proposes to solve the reliability indexes based on the combination of the improved sparrow search algorithm (LGSSA) and the support vector regression (SVR) method. Firstly, random variables are selected according to the actual situation of the bridge structure. Then representative training samples are designed to be substituted into the finite element model through the homogeneous method. The resultant data samples are used to fit the functional function by the support vector regression. Then combined with the penalized function method to transform the nonlinear optimization into the problem of solving the extreme value of the function. Based on the improved SSA to solve the extreme value of the final function. Finally the reliability index of the structure is obtained. With the background of reinforced concrete arch bridge of 200 m, the method is used to analyze the reliability of its buckling cable stress, arch stress, buckling tower deviation and structural system reliability during the cantilever casting process. The results show that the overall structural reliability of the arch ring during cantilever casting is 3.502–3.608. The indexes of buckling cable stress reliability are 3.806–6.784. The indexes of arch ring stress reliability are 4.379–7.562, and the indexes of buckling tower deflection reliability are 3.608–8.123.
{"title":"Reliability evaluation of reinforced concrete arch bridges during construction based on LGSSA‐SVR hybrid algorithm","authors":"Xu Binlin, Tian Zhongchu, Shen Xiaoping, Bai Wenguang","doi":"10.1002/suco.202400166","DOIUrl":"https://doi.org/10.1002/suco.202400166","url":null,"abstract":"During the cantilever casting process of reinforced concrete arch bridges with cantilever cast‐in‐situ method, it is difficult to select representative training samples for reliability analysis due to its complex structural system. Many random variables and large computational sample size, this paper proposes to solve the reliability indexes based on the combination of the improved sparrow search algorithm (LGSSA) and the support vector regression (SVR) method. Firstly, random variables are selected according to the actual situation of the bridge structure. Then representative training samples are designed to be substituted into the finite element model through the homogeneous method. The resultant data samples are used to fit the functional function by the support vector regression. Then combined with the penalized function method to transform the nonlinear optimization into the problem of solving the extreme value of the function. Based on the improved SSA to solve the extreme value of the final function. Finally the reliability index of the structure is obtained. With the background of reinforced concrete arch bridge of 200 m, the method is used to analyze the reliability of its buckling cable stress, arch stress, buckling tower deviation and structural system reliability during the cantilever casting process. The results show that the overall structural reliability of the arch ring during cantilever casting is 3.502–3.608. The indexes of buckling cable stress reliability are 3.806–6.784. The indexes of arch ring stress reliability are 4.379–7.562, and the indexes of buckling tower deflection reliability are 3.608–8.123.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141868665","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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