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Cracking of the End Diaphragm of a Post-tensioned Beam Bridge 后张梁桥端隔膜开裂
IF 1
Nordic Concrete Research Pub Date : 2019-06-01 DOI: 10.2478/ncr-2019-0001
Mikko Kuusela, Olli Asp, Anssi Laaksonen
{"title":"Cracking of the End Diaphragm of a Post-tensioned Beam Bridge","authors":"Mikko Kuusela, Olli Asp, Anssi Laaksonen","doi":"10.2478/ncr-2019-0001","DOIUrl":"https://doi.org/10.2478/ncr-2019-0001","url":null,"abstract":"Abstract In concrete beam bridges, the end diaphragm at the end of the bridge is a common structural component that connects the main beams and transfers the beam loads to the bridge bearings. In integral bridges the end diaphragm also retains the soil of embankments due to the absence of abutments. Cracking of the front surface on the end diaphragm has been detected in post-tensioned beam bridges in Finland and Sweden. Presumably the post-tensioning of the bridge and the shaping and detailing of the connection of the end diaphragm and main beam have an effect on cracking tendency. The aim of this study is to examine the structural behaviour and the cracking potential of end diaphragms using linear analysis of the post-tensioned bridge and to find measures to prevent the cracking. The observations collected through field surveys are compared to results of linear FE analysis to clarify the cause of the cracking. The verification of model is performed by comparison of patterns of cracking observed in field surveys and the distribution of maximum tensile stresses in the FE model. With model variations, the effectiveness of measures for the prevention of cracking are observed.","PeriodicalId":42762,"journal":{"name":"Nordic Concrete Research","volume":"16 1","pages":"104 - 89"},"PeriodicalIF":1.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86298762","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
A Refined Model for Predicting Concrete-Related Failure Load of Tension Loaded Cast-in-Place Headed Anchors in Uncracked Concrete 未开裂混凝土中受拉现浇锚杆破坏荷载的改进预测模型
IF 1
Nordic Concrete Research Pub Date : 2019-06-01 DOI: 10.2478/ncr-2019-0091
R. Nilforoush
{"title":"A Refined Model for Predicting Concrete-Related Failure Load of Tension Loaded Cast-in-Place Headed Anchors in Uncracked Concrete","authors":"R. Nilforoush","doi":"10.2478/ncr-2019-0091","DOIUrl":"https://doi.org/10.2478/ncr-2019-0091","url":null,"abstract":"Abstract Current theoretical models for predicting the concrete cone breakout capacity of tension loaded headed anchors do not consider the influence of member thickness, size of anchor head, and orthogonal surface reinforcement. In the present study, the influence of the aforementioned parameters was studied both numerically and experimentally. Both the numerical and experimental results showed that the tensile resistance of headed anchors increases by increasing the member thickness or if orthogonal surface reinforcement is present. In addition, the anchorage capacity further increases with increase of the anchor head size. The current model for predicting the concrete cone failure load of tension loaded headed anchors were refined and extended by incorporating three modification factors to account for the influence of the member thickness, size of anchor head, and orthogonal surface reinforcement. The accuracy of the proposed model was verified based on the results of 124 tests on single headed anchors from literature.","PeriodicalId":42762,"journal":{"name":"Nordic Concrete Research","volume":"24 1","pages":"105 - 129"},"PeriodicalIF":1.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78094358","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 7
Plastic Shrinkage Cracking of Self-compacting Concrete: Influence of Capillary Pressure and Dormant Period 自密实混凝土塑性收缩开裂:毛细压力和休眠期的影响
IF 1
Nordic Concrete Research Pub Date : 2019-06-01 DOI: 10.2478/ncr-2019-0012
F. Sayahi, M. Emborg, H. Hedlund, A. Ćwirzeń
{"title":"Plastic Shrinkage Cracking of Self-compacting Concrete: Influence of Capillary Pressure and Dormant Period","authors":"F. Sayahi, M. Emborg, H. Hedlund, A. Ćwirzeń","doi":"10.2478/ncr-2019-0012","DOIUrl":"https://doi.org/10.2478/ncr-2019-0012","url":null,"abstract":"Abstract This research investigates the effect of capillary pressure and the length of the hydration dormant period on the plastic shrinkage cracking tendency of SCC by studying specimens produced with different w/c ratios, cement types and SP dosages. A relationship between the capillary pressure rate and the length of the hydration dormant period is defined, which can explain the cracking severity of the concrete when the volumetric deformation is unknown. The results show, that the cracking tendency of SCC was the lowest in case of w/c ratio between 0.45 and 0.55, finer and more rapid hardening cement, and lower dosage of SP. The dormant period was prolonged by increasing the w/c ratio, using coarser cement, and higher SP dosage. It was concluded that the cracking tendency of concrete is a function of the capillary pressure buildup rate and the length of the dormant period.","PeriodicalId":42762,"journal":{"name":"Nordic Concrete Research","volume":"69 1","pages":"67 - 88"},"PeriodicalIF":1.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83807299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 7
Failure of Lightweight Aggregate Concrete in Compression under Stress Gradients 应力梯度作用下轻骨料混凝土受压破坏
IF 1
Nordic Concrete Research Pub Date : 2019-06-01 DOI: 10.2478/ncr-2019-0011
J. Živković, J. Øverli
{"title":"Failure of Lightweight Aggregate Concrete in Compression under Stress Gradients","authors":"J. Živković, J. Øverli","doi":"10.2478/ncr-2019-0011","DOIUrl":"https://doi.org/10.2478/ncr-2019-0011","url":null,"abstract":"Abstract The objective of this experiment is to investigate the behaviour of lightweight aggregate concrete (LWAC) under compression and with stress gradients. Experimental program contained three sets of LWAC which were used for production of 21 prisms. Lightweight aggregate argillite slate, called Stalite, from North Carolina had been used. The sets differed in using dry (0.10% moisture content) or saturated (7.9% moisture content) aggregate. The third set included a small amount of polyvinyl alcohol fibres (PVA). The geometry of the prisms were 100 × 140 × 480 mm (width × length × height). Prismatic samples were loaded centrically and eccentrically in compression. From the achieved experimental results, it is visible that the lateral deformation of the most stressed fibre is counteracted by the less stressed fibres that confine compressive stress and increase strains. The obtained strain level was much higher than expected, especially for the third set of concrete samples with PVA fibres. Recorded strains in prisms test was in range from 3.08‰ to 6.82‰). In general, LWAC with Stalite showed ductile behaviour followed with very high strains. The third set of samples included a small amount of polyvinyl alcohol fibres (0.5% of volume fractions) was even more ductile and non-brittle.","PeriodicalId":42762,"journal":{"name":"Nordic Concrete Research","volume":"28 1","pages":"51 - 66"},"PeriodicalIF":1.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90618878","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 2
Clays as SCM – Reactivity of Uncalcined Kaolinite and Bentonite, and Impact on Phase Assemblage and Strength Development of PC Mortars 粘土作为SCM -未煅烧高岭土和膨润土的反应性及其对PC砂浆相组合和强度发展的影响
IF 1
Nordic Concrete Research Pub Date : 2019-06-01 DOI: 10.2478/ncr-2019-0006
M. Geiker, E. Gallucci
{"title":"Clays as SCM – Reactivity of Uncalcined Kaolinite and Bentonite, and Impact on Phase Assemblage and Strength Development of PC Mortars","authors":"M. Geiker, E. Gallucci","doi":"10.2478/ncr-2019-0006","DOIUrl":"https://doi.org/10.2478/ncr-2019-0006","url":null,"abstract":"Abstract The impact of substitution of cement paste with uncalcined clay (bentonite and kaolinite) in the range of 5% by volume of paste on the development of hydration and properties of mortar was investigated. Two issues were addressed, the expected filler effect of the dispersed sub-micron clay particles, and the possible chemical reactivity of the clay. The study indicated that Portland cement paste may be modified by addition of well dispersed clay and that the impact includes accelerated cement hydration as well as altered distribution of products. Compressive strength development was accelerated, but later age strength was reduced, especially for the bentonite mixes. In contrast, microscopic porosity measurements indicated no detrimental impact on the coarse capillary porosity. The investigation indicates that for durability related engineering properties, the application of uncalcined clay might be a potential means for reduction of the clinker factor in concrete in support of sustainability.","PeriodicalId":42762,"journal":{"name":"Nordic Concrete Research","volume":"174 1","pages":"13 - 30"},"PeriodicalIF":1.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78461970","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 2
Stability of Air Content in Fresh Concretes with PCE-Based Superplasticizers 掺pce基高效减水剂的新拌混凝土中空气含量的稳定性
IF 1
Nordic Concrete Research Pub Date : 2019-06-01 DOI: 10.2478/ncr-2019-0093
Fahim Al-Neshawy, Teemu Ojala, J. Punkki
{"title":"Stability of Air Content in Fresh Concretes with PCE-Based Superplasticizers","authors":"Fahim Al-Neshawy, Teemu Ojala, J. Punkki","doi":"10.2478/ncr-2019-0093","DOIUrl":"https://doi.org/10.2478/ncr-2019-0093","url":null,"abstract":"Abstract Air contents of concrete are necessary for concrete durability in freeze-thaw exposure. According to the Finnish concrete code, the target value for air content varies between 4% and 5.5% for XF - exposure classes. Lately in Finland, some cases showed an elevation of air contents up to 15% in fresh air-entrained concrete at construction site and in drilled concrete samples. The objectives of this study were to investigate the stability of air entrainment by measuring the air content elevation 30 minutes and 60 minutes after concrete mixing and investigating the concrete sensitivity to segregation. Composition of concretes used in this study include 7 different combination of PCE based superplasticizer and air-entraining agent admixtures, cement content of 425 kg/m3, two consistency classes S3 with water to cement ration of 0.33 and F5 with water to cement ration of 0.38. One cement type was used for all concrete mixes. The concretes were mixed for 2 minutes and 5 minutes mixing times. The results show that the elevation of the air content of fresh concrete depends on the consistency of the concrete and on the used combination of superplasticizer and air-entraining agents. The higher consistency classes concretes have more risk of air elevation with some combinations of PCE-based superplasticizers and air-entraining agents. The results also indicate that short mixing time would not be enough to achieve total effectivity of some air-entraining agents, especially for higher consistency classes concrete.","PeriodicalId":42762,"journal":{"name":"Nordic Concrete Research","volume":"94 1","pages":"145 - 158"},"PeriodicalIF":1.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89359073","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 11
Influence of Cracking on Effects of Restrained Deformations in a Post-tensioned Concrete Bridge 裂缝对后张混凝土桥梁约束变形效果的影响
IF 1
Nordic Concrete Research Pub Date : 2018-12-01 DOI: 10.2478/ncr-2018-0017
Kimmo Jalonen, J. Tulonen, Anssi Laaksonen
{"title":"Influence of Cracking on Effects of Restrained Deformations in a Post-tensioned Concrete Bridge","authors":"Kimmo Jalonen, J. Tulonen, Anssi Laaksonen","doi":"10.2478/ncr-2018-0017","DOIUrl":"https://doi.org/10.2478/ncr-2018-0017","url":null,"abstract":"Abstract Imposed and restrained deformations cause stresses in continuous concrete bridges, and in analyses of the superstructure these stresses are usually reduced to some degree due to creep and cracking of concrete. This study examines cracking and redistribution of stresses in a bridge superstructure under the loads and load combinations used in the original bridge design. The subject of this study is a three-span post-tensioned continuous concrete cantilever beam bridge. The bridge was analysed with non-linear calculation utilising the general force method and moment-curvature relationships. The analysis yielded the bending stiffness of the post-tensioned bridge superstructure as a function of bridge length under different loads. It was discovered that the secondary moment from prestressing force increased as the bending stiffness of the central span decreased due to cracking under external loads, which is not normally considered in design. The bending moment effects of linear temperature difference and support settlement decreased as expected as the superstructure bending stiffness decreased. The analysis provided new information on the effects of secondary moment from the prestressing force and on the difference between the cracked state and the linear elastic analysis of the concrete bridge superstructure.","PeriodicalId":42762,"journal":{"name":"Nordic Concrete Research","volume":"20 1","pages":"110 - 95"},"PeriodicalIF":1.0,"publicationDate":"2018-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78822250","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
Early Age Autogenous Shrinkage of Fibre Reinforced Concrete 纤维增强混凝土的早期自收缩
IF 1
Nordic Concrete Research Pub Date : 2018-12-01 DOI: 10.2478/ncr-2018-0015
F. Ullah, Fahim Al-Neshawy, J. Punkki
{"title":"Early Age Autogenous Shrinkage of Fibre Reinforced Concrete","authors":"F. Ullah, Fahim Al-Neshawy, J. Punkki","doi":"10.2478/ncr-2018-0015","DOIUrl":"https://doi.org/10.2478/ncr-2018-0015","url":null,"abstract":"Abstract Concrete is often sensitive to cracking during the hardening process, and these cracks could be the result of early-age shrinkage. One method to reduce shrinkage is to add different types of fibres to concrete. The aim of this study was to study the effects of different types of fibres on the early-age autogenous shrinkage of concrete. Three different types of fibre materials were used in the research. A “Schleibinger Bending-drain” test setup was used to record early-age autogenous shrinkage of fresh concrete immediately after mixing. The results show that, a fibre dosage of 0.38% by volume was found to be effective in reducing the effects of early-age autogenous shrinkage of concrete.","PeriodicalId":42762,"journal":{"name":"Nordic Concrete Research","volume":"51 1","pages":"59 - 72"},"PeriodicalIF":1.0,"publicationDate":"2018-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83292083","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 11
Rice Husk Resource for Energy and Cementitious Products with Low CO2 Contributions 能源和低二氧化碳贡献胶凝产品的稻壳资源
IF 1
Nordic Concrete Research Pub Date : 2018-12-01 DOI: 10.2478/ncr-2018-0014
O. During, Silu Bhochhibhoya, R. Maskey, Rajendra Joshi
{"title":"Rice Husk Resource for Energy and Cementitious Products with Low CO2 Contributions","authors":"O. During, Silu Bhochhibhoya, R. Maskey, Rajendra Joshi","doi":"10.2478/ncr-2018-0014","DOIUrl":"https://doi.org/10.2478/ncr-2018-0014","url":null,"abstract":"Abstract Rice Husk Ash (RHA) is a well-known supplementary cementitious materials (SCMs) that can be used for concrete with reduced CO2 contributions. In 2016, only Nepal produced 5.2 million tonnes rice that gave about 1.14 million tonnes rice husk. The rice husk can also be used directly in a cement kiln as a fuel. This study analysis the potential CO2 reductions from three scenarios and emphasis strengths, weaknesses, opportunities and treats in the production systems for initiate a decision process with possibilities to get an industry project financed from the green climate found. The highest CO2 benefits were from rice husk used in a cement kiln were half of the yearly rice husk production in Nepal could reduce the climate impact with 808000 tonnes CO2.","PeriodicalId":42762,"journal":{"name":"Nordic Concrete Research","volume":"19 12 1","pages":"45 - 58"},"PeriodicalIF":1.0,"publicationDate":"2018-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82897359","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
Prediction of Restraint Moments in Precast, Prestressed Structures Made Continuous 预制、预应力连续结构约束矩的预测
IF 1
Nordic Concrete Research Pub Date : 2018-12-01 DOI: 10.2478/ncr-2018-0016
Ulla Kytölä, Anssi Laaksonen
{"title":"Prediction of Restraint Moments in Precast, Prestressed Structures Made Continuous","authors":"Ulla Kytölä, Anssi Laaksonen","doi":"10.2478/ncr-2018-0016","DOIUrl":"https://doi.org/10.2478/ncr-2018-0016","url":null,"abstract":"Abstract This paper studies restraint moments developing in simple-span precast, prestressed beams made continuous. Methods of evaluating restraint moments produced by creep and differential shrinkage are presented. Shrinkage and creep properties of composite structures, beam and deck parts were tested and compared to values defined according to Eurocode models. Finally, the restraint moments were calculated with both material models for the two-span parking deck structure. The study confirmed the findings of previous studies: that the methods that are used overestimate the negative restraint moment produced by differential shrinkage.","PeriodicalId":42762,"journal":{"name":"Nordic Concrete Research","volume":"38 1","pages":"73 - 93"},"PeriodicalIF":1.0,"publicationDate":"2018-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76657187","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
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