scholarly journals Strengthening of Concrete Column by Using the Wrapper Layer of Fibre Reinforced Concrete

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5432
Author(s):  
Peter Koteš ◽  
Martin Vavruš ◽  
Jozef Jošt ◽  
Jozef Prokop
Keyword(s):  
Reinforced Concrete ◽  
Cross Section ◽  
Limit State ◽  
Fibre Reinforced Concrete ◽  
Limit States ◽  
Load Bearing Capacity ◽  
Concrete Core ◽  
Fibre Concrete ◽  
Special Cases ◽  
Ultimate Limit

Structures and bridges are being designed on the proposed and requested design lifetime of 50 to 100 years. In practice, one can see that the real lifetime of structures and bridges is shorter in many cases, in some special cases extremely shorter. The reasons for the lifetime shortening can be increased of the load cases (e.g., due to traffic on bridges, or due to other uses of a structure), using the material of lower quality, implementation of new standards and codes according to Eurocode replacing older ones. During the whole lifetime the structures must be maintained to fulfil the code requests. If the constructions are not able to fulfil the Ultimate Limit States (ULS) and the Serviceability Limit State (SLS), the structures or bridges have to be strengthened (whole or its elements). The purpose of the paper is the presentation of using a layer of the fibre concrete for a columns’ strengthening. Using the fibre reinforced concrete (FRC) of higher tensile strength makes it possible to increase the load-bearing capacity of the cross-section the column. The contact between the old concrete (core of column) and newly added layer (around column) is very important for using that method of strengthening. In the article, there is also a comparison of the surface modification methods.

Combined Reinforced Concrete Columns Strengthening with Steel Clipping and Concrete Surfacing

2021 ◽  
pp. 11-22
Author(s):  
Ю. Г. Москалькова ◽  
С. В. Данилов ◽  
В. А. Ржевуцкая
Keyword(s):  
Reinforced Concrete ◽  
Load Transfer ◽  
Limit State ◽  
Concrete Columns ◽  
Ultimate Limit State ◽  
Concrete Core ◽  
Reinforced Concrete Columns ◽  
Entire Height ◽  
Complex Structural ◽  
Ultimate Limit

Постановка задачи. Исследуется метод усиления железобетонных колонн устройством стальной обоймы с обетонированием, который позволяет восстанавливать эксплуатационные показатели колонн, имеющих значительные дефекты и повреждения. Предпосылкой настоящих исследований явилось предположение о том, что усиление стальной обоймой с обетонированием является эффективным способом повышения несущей способности железобетонных колонн, причем вариант приложения нагрузки - только на бетонное ядро или ко всему сечению - существенно на эффективность усиления не влияет. В связи с этим целью исследования является определение необходимости устройства стального оголовка и включения в работу ветвей стальной обоймы при условии обетонирования стержня колонны по всей высоте. Результаты и выводы. Рациональным признан способ передачи нагрузки только на бетонное ядро усиленных колонн, поскольку устройство оголовка стальной обоймы требует применения сложных конструктивно-технологических решений, но при этом дополнительно увеличивает несущую способность незначительно (согласно проведенным исследованиям менее чем на 10 %). Ввиду отсутствия необходимости устройства конструкций стального оголовка снижаются трудоемкость и сроки производства работ по усилению колонн. Statement of the problem. The method of strengthening reinforced concrete columns with a steel clipping and the concrete surfacing is investigated. This method allows one to repair the columns with significant defects and damage. The prerequisite for this study was the assumption of strengthening with a steel clipping and the concrete surfacing is an effective way to increase the ultimate limit state of reinforced concrete columns, furthermore, the option of applying the load (only to the concrete core or to the entire section) does not significantly affect the strengthening effectiveness. In this regard, the purpose of the investigation was to identify the need to include the steel jacketing in the work, on the condition the column is coated with concrete along with the entire height. Results and conclusions. The load transfer method only to the concrete core of the strengthened columns is recognized as rational since the device of the steel clipping head requires the use of complex structural and technological solutions, but at the same time additionally increases the ultimate limit state insignificantly (according to the studies by less than 10 %). Due to the absence of the need to establish structures of the steel jacketing head, the labor intensiveness and terms of work production on strengthening the columns are reduced.

scholarly journals Research on Intelligent Evaluation System of Load-bearing Capacity of Existing Reinforced Concrete Bridge

2020 ◽  
Vol 165 ◽  
pp. 04056
Author(s):  
An Zhao ◽  
Qiang Xu ◽  
Jianyong Song
Keyword(s):  
Reinforced Concrete ◽  
Bearing Capacity ◽  
Evaluation System ◽  
Limit State ◽  
Concrete Bridge ◽  
Parametric Modelling ◽  
Limit States ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Reinforced Concrete Bridge

The intelligent evaluation system of existing reinforced concrete bridge “BLP” is a special software for the load-bearing capacity rapid analysis and evaluation of the existing reinforced concrete bridge, which was developed by the Highway Research Institute of the Ministry of Transport. Based on the parametric modelling method, it can quickly and easily establish the finite element plane model of the bridge structure for the static analysis of ultimate bearing capacity limit states and serviceability limit state, under variety norms. And it can easily and quickly build variable-section beams and rebars, with the special module. According to the comprehensive modification method of the load-bearing capacity evaluation, it can automatically recommend checking sections, and automatically calculate partial modification coefficient of resistance effect, and conveniently judge the safety coefficient of the sections, and quickly get the results of bridge load-bearing capacity. In summary, this system can significantly improve the work efficiency and accuracy of load-bearing capacity for exiting reinforced concrete bridge. This paper introduces in detail the characteristics of the intelligent analysis technology, calculation principle and real bridge application examples of the system.

scholarly journals Designing Reinforced Concrete Beams Containing Supplementary Cementitious Materials

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1248 ◽  
Author(s):  
Alessandro P. Fantilli ◽  
Francesco Tondolo ◽  
Bernardino Chiaia ◽  
Guillaume Habert
Keyword(s):  
Reinforced Concrete ◽  
Environmental Impact ◽  
Cement Content ◽  
Limit State ◽  
Carbon Dioxide Emission ◽  
Cementitious Materials ◽  
Reinforced Concrete Beams ◽  
Supplementary Cementitious Materials ◽  
Limit States ◽  
Ultimate Limit

If supplementary cementitious materials (SCMs) are used as binders, the environmental impact produced by cement-based composites can be reduced. Following the substitution strategy to increase sustainability, several studies have been carried out with the aim of measuring the mechanical properties of different concrete systems, in which a portion of Portland cement was substituted with SCMs, such as fly ashes. On the other hand, studies on the structural behavior of reinforced concrete (RC) elements made with SCMs are very scarce. For this reason, in this paper, a new procedure is introduced with the aim of fulfil a new limit state of sustainability, in accordance with the serviceability and ultimate limit states required by building codes. Although the environmental impact of concrete decreases with the reduction of cement content, the proposed approach shows that the carbon dioxide emission of an RC beam is not a monotonic function of the substitution rate of cement with SCMs. On the contrary, there are favorable values of such substitution rates, which fall within a well-defined range.

End-Plate Connections in Bi-Axial Bending - Measurements

2016 ◽  
Vol 710 ◽  
pp. 275-280
Author(s):  
Jari Mäkinen ◽  
Keijo Fränti ◽  
Matti Korhonen ◽  
Joshua Fillion ◽  
Markku Heinisuo
Keyword(s):  
Bearing Capacity ◽  
Cross Section ◽  
Limit State ◽  
Ultimate Limit State ◽  
Load Bearing Capacity ◽  
End Plate ◽  
Residual Capacity ◽  
Plate Connections ◽  
Ultimate Limit ◽  
Is Strain

In this paper we consider the measurements of bolted end-plate connections of tubular beams with cold-formed hollow rectangular aluminium sections. The motivation for these measurements originates from the fact that the aluminium standard (EN 1999-1-1) [1] does not cover the design of this very frequently used type of connection, where the bolts are located outside the edge-lines of the cross-section, i.e. corner bolts. Many tests and studies regarding this area have been conducted, but this paper brings value to the case where bi-axial bending is applied. The measurements have been carried out and the detailed results shall be shown. In this paper, we will focus on the six measurements where the tubular beams were bent uniaxially and biaxially to these limit points. The tests were stopped when the ultimate limit state was reached. In this case the connection never actually broke, but effectively the joint had lost its load bearing capacity. Some residual capacity still remained, but the displacements were too great resulting in a totally different behavior of the connection. The behavior of this connection is highly non-linear, since aluminium (AW 5754) as a material is strain hardening and the mechanism in the connection changes as the displacements increase.

scholarly journals COURSE AND RESULTS OF TESTING A SUSPENDED COMPOSITE STRUCTURE/KABAMOSIOS BETONŠERDĖS KONSTRUKCIJOS BANDYMO EIGA IR REZULTATAI

2000 ◽  
Vol 6 (5) ◽  
pp. 315-321
Author(s):  
iaceslavas Šaraškinas ◽  
Audronis Kazimieras Kvedaras
Keyword(s):  
Cross Section ◽  
Limit State ◽  
Steel Shell ◽  
Flexural Stiffness ◽  
Limit States ◽  
Concrete Core ◽  
Roof Structure ◽  
Steel Members ◽  
Flexural Member ◽  
Supporting Zone

Testing a suspended roof structure has been performed. The span of construction is 10.65 m, the support height 2.60 m. Element supports are pins. Joint between elements in the middle of span is a pin, too. Structural elements were made from steel tubes with hollow concrete core. The thickness of the tube wall 1.60 mm, and a concrete core wall about 20 mm. The length of elements 5.35 m. The tested roof structure was loaded with 8 vertical loads. The strain distribution in 3 sections of the composite elements was analysed. In seven points of the structure, vertical deflections were measured. The horizontal reaction was measured too as it is shown in Fig 10. Additionally, horizontal deflections of columns were controlled by 3 indicatory tenzometers. The roof structure resistance was analysed and indicated loads of the ultimate and the serviceability limit states were reached. During the test, the serviceability limit state was reached under the load of 3,40 kN/m. The vertical deflection at the ¼ of span exceeded L/300, the ultimate value for member under asymmetrical loading. Failure occured under the load of 9,80 kN/m, when one of the composite roof elements collapsed close to its supporting zone at a distance of about 1 m from the support. The normal stress of this cross-section reached the value of steel tensile strength. An experimental ultimate load is by about 27% less than the theoretical one determined for flexural member. Investigation shows the developed equipment and applied methods being useful for testing suspended structures of final flexural stiffness made from straight concrete-filled steel tubular members. It has been finalised that overall behaviour of the tested structure is very close to that of straight suspension steel members of final flexural stiffness. It has been experimentally determined that the failure load łą 9.80 kN/m was achieved when total tension strength of the external steel shell was used up. The presented value is greater than the ultimate one calculated only for the flexural member. Because composite members of the suspended structure are not only flexural but also tensional ones, it is necessary, for prediction of their limit state, to take into account the interaction between both components of composite cross-section (external steel shell and hollow concrete core) under such loading conditions.

scholarly journals PROPERTIES OF FRESH POLYPROPYLENE FIBRE REINFORCED CONCRETE UNDER THE INFLUENCE OF POZZOLANS

2003 ◽  
Vol 9 (4) ◽  
pp. 271-279 ◽  
Author(s):  
Hau-yan Leung ◽  
Ramapillai V. Balendran
Keyword(s):  
Reinforced Concrete ◽  
Fly Ash ◽  
Silica Fume ◽  
Setting Time ◽  
Polypropylene Fibre ◽  
Partial Replacement ◽  
Fibre Reinforced Concrete ◽  
Polypropylene Fibres ◽  
Fibre Concrete ◽  
Time Substitution

This paper summarises experimental results of some fresh concrete tests. Polypropylene fibres were added to the concrete mix to produce fibre reinforced concrete. Pozzolanic materials, including pulverised fly ash and silica fume, were used as partial replacement of cement, and their effects on the fresh fibre concrete were reported. Test results showed that the polypropylene fibre reduced the concrete workability significantly by thixotropic effect and decreased the setting time. Substitution of pozzolans also greatly affected the properties. The presence of fly ash increased the workability and setting time but in the presence of silica fume a reverse trend was observed. Empirical equations were proposed.

Limit State of Torsion of Ship Hulls with Large Hatch Openings

2001 ◽  
Vol 45 (02) ◽  
pp. 95-102
Author(s):  
Yuren Hu ◽  
Bozhen Chen
Keyword(s):  
Cross Section ◽  
Structural Reliability ◽  
Limit State ◽  
Safety Margin ◽  
Plastic Shear ◽  
Torsional Moment ◽  
Limit States ◽  
Ship Hulls ◽  
Design Values ◽  
Bound Theorem

The limit state of torsion of ship hulls with large hatch openings is studied. A method to determine the distribution of the plastic shear flow on the hull cross section in the limit state by using the lower-bound theorem is presented together with the corresponding linear programming problem. The limit torsional moment of the hull cross section is obtained based on the distribution of the shear stress in the limit state. Three example limit states for typical containerships of different sizes with large hatch openings are calculated. The calculated limit torsional moments are compared with the design values of wave torque calculated by using the equations given by main classification societies in their rules. A rough estimate of the safety margin is obtained. The results show that for large containerships, it is necessary to pay attention to the safety with respect to torsion. The present method can serve as an effective tool in structural reliability analysis of ships with large hatch openings when the failure mode of torsion is taken into account.

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