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1

Behavior of RC columns strengthened with steel jacket under static axial load

Ghoneim Abd Rahman Mujahid Ahmed, Mohamed Mohamed Mahmoud Ahmed, Haridy Kader, Ahmed Hazem, Pyram Mohmmad, Khalf Abdu

Archives of Civil Engineering

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2023

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Vol. 69, nr 2

367--379

EN

The column is one of the most significant structural elements, which is designed to support mainly the compressive load. Strengthening of existing reinforced concrete columns is required to enhance ductility and increase load capacity to sustain the overload as sometimes there may be a change in use. Ten rectangular concrete columns were constructed and tested. H/b ratio was kept constant and equals 6 for all columns. The aim of this work is to study the behaviour and efficiency of RC columns strengthened with steel jackets subjected to axial load. An experimental study of the behaviour of ten strengthened concrete columns with slenderness ratio (H/b) equals 6 was carried out. Variables such as aspect ratio (t/b), the volume of steel batten plates, and spacing of steel batten plates at centres (S) were considered. The results showed that using this method of strengthening is very effective and an increase in the axial load capacity of the strengthened columns is obtained.

2

Experimental investigation of bond–slip behavior of between-anchored steel strips to concrete surface

Kopraman Yağmur, Özdemir Anil, Anil Özgür, Sakin Shaimaa, Armakan Furkan

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 4

art. no. e198, 2022

EN

Reinforced concrete and masonry structures may need strengthening or retrofitting for many different reasons. It is known that strengthening/retrofitting details developed with steel elements are used and widely preferred in these studies. Realistic knowledge of the bond–slip material model between the existing concrete surface and the steel strip in the strengthening/retrofitting details developed using steel strips is extremely important to determine the designed strengthened structural bearing capacity and load–displacement behavior. In the literature review, no study was found in which the bond–slip material model between concrete surfaces and steel strips was investigated extensively. For this reason, an experimental study was planned. In the experimental program, using a special axial tensile test setup designed by the authors, 72 test specimens were tested under the effect of monotonically increased axial tensile force. Axial load displacement, shear stress–shear displacement, and strain distribution values along the steel strip of the test specimens were obtained. It was interpreted how the results were affected by the experimental variables. An innovative bond–slip material model was proposed using the experimental results between the non-anchored and anchored steel strips and the concrete surface. It is thought that the bond–slip model between the developed steel strips and the concrete surface will be useful in the realistic calculation of the bearing capacity and general load–displacement behaviors of the strengthening/retrofitting details designed using steel strips. It can be used in finite element models. It can be used in finite element models. The increase in concrete compressive strength from 10 to 25 MPa increased the axial load maximum bearing capacity values of the steel strips by an average of 44%. The maximum bearing capacity values of the steel strips bonded with a 2 mm thickness epoxy layer were calculated by, on average of 86% higher than the test specimens bonded with 6 mm thickness epoxy. The maximum axial bearing forces of the test specimens in which the axial tensile force was applied concentrically were obtained on an average of 27% greater than the test specimens tested by applying eccentric loading. The maximum bearing capacity values of the test specimens with two anchors on the steel strips adhered to the concrete surface were obtained on an average of 42% higher than the non-anchored test specimens in which only epoxy was used. The maximum bearing capacity values of the test specimens with 400 mm steel strip adhesion length exhibited an average of 108% higher maximum bearing capacity values than the test specimens with 100 mm steel strip bond length.

3

Obróbka cieplna stali średniomanganowych dla motoryzacji

Grajcar Adam, Morawiec Mateusz, Skowronek Adam

Stal, Metale & Nowe Technologie

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2019

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nr 7-8

12--18

PL

Nowoczesne materiały konstrukcyjne wykorzystywane w branży automotive powinny łączyć wysoką wytrzymałość z dobrą formowalnością – są to własności do niedawna wykluczające się. Z drugiej strony koszty produkcji muszą być relatywnie niskie, gdyż aspekt ekonomiczny jest niezwykle ważny w obecnych czasach. Wymienione własności wytrzymałościowe można uzyskać dzięki rozdrobnieniu ziarna, jak również wygenerowaniu w stali austenitu szczątkowego, którego przemiana powoduje znaczne umocnienie materiału podczas odkształcenia. Koszty produkcji maleją wraz z ograniczeniem zawartości drogich dodatków stopowych. Cechy te wykazują stale średniomanganowe.

EN

Advanced structural materials used in the automotive industry should combine high strength and good formability – a pair of properties which until recently were mutually exclusive. On the other hand, production costs must be relatively low because the economic aspect is extremely important nowadays. The mentioned strength properties can be obtained due to grain refinement as well as the generation of retained austenite in steel, which is transformed during deformation causing the significant strain hardening of the material. Production costs decrease with the reduction of the content of expensive alloying elements. These features are the domain of medium manganese steels.

4

Chłodzenie blach taśmowych ze stali wielofazowych dla motoryzacji

Grajcar Adam

Stal, Metale & Nowe Technologie

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2019

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nr 5-6

95--99

PL

Nowoczesne wysoko wytrzymałe stale wielofazowe dla motoryzacji są produkowane w wąskich oknach technologicznych obróbki cieplnej lub cieplno-plastycznej. Typowe struktury dwufazowe lub wielofazowe wymagają kilkustopniowego chłodzenia z temperatury austenityzacji, niepełnej austenityzacji lub z temperatury końca walcowania na gorąco. Wymaga to dostosowania szybkości chłodzenia do kinetyki przemian fazowych austenitu przechłodzonego dla realizacji kolejnych przemian fazowych, tzn. ferrytycznej, bainitycznej czy martenzytycznej.

EN

Advanced high-strength multiphase steels for the automotive industry are produced in narrow technological windows of heat treatment or thermomechanical processing. Typical dual-phase or multiphase structures are subjected to a multi-step cooling from the austenitizing temperature, intercritical annealing temperature or finish rolling temperature. This requires to adjust the cooling rates to the kinetics of undercooled austenite phase transitions to realize successive phase transformations, i.e. ferritic, bainitic or martensitic. An isothermal holding step is very often needed within bainitic or martensitic transformations. Using universal laminar cooling lines is necessary.

5

Komputerowe wspomaganie systemu produkcyjnego walcowni taśm stalowych na gorąco

Kubiński W., Niekurzak M., Kubińska-Jabcoń E.

Hutnik, Wiadomości Hutnicze

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2013

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Vol. 80, nr 12

839--846

PL

W artykule przedstawiono model logistycznego systemu walcowni taśm stalowych walcowanych na gorąco, uwzględniający podsystemy przepływu i składowania materiałów. Elementami systemu walcowni są urządzenia produkcyjne, transportowe oraz magazyny międzyoperacyjne i wyrobów gotowych. Logistyczne podejście do procesu wymaga m.in. minimalizowania czasu przepływu materiałów przez system, minimalizowania zapasów do produkcji oraz ograniczenie zużycie energii i narzędzi produkcyjnych użytych do procesu wytwarzania. Zbudowany model może być podstawą do sformułowania logistycznego systemu walcowni taśm, gdyż uwzględnia zarówno aspekty technologiczne, jak i ekonomiczne funkcjonowania badanej walcowni. Do realizacji zadania wykorzystano symulator przepływu materiałów Dosimis-3.

EN

This paper presents a model of logistic system of steel strip mill hot-rolled, taking into account the sub-movement and storage of materials. System components are mill production equipment, transport and storage intermediate and finished products. Logistic approach to the process requires, among others time minimizing the flow of materials through the system, minimizing production and inventory to reduce energy consumption and production tools used in the manufacturing process. Built model can be the basis for the formulation of logistics strip mill system, it takes account of both the technological and economical operation of the test mill. To accomplish the task of material flow simulator was used Dosimis-3.

6

Repairing and strengthening of elliptical paraboloid reinforced concrete shells with openings

Meleka N. N., Safan M. A., Bashandy A. A., Abd-Elrazek A. S.

Archives of Civil Engineering

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2013

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Vol. 59, nr 3

401--420

EN

This investigation is carried out to evaluate the repair and strengthening the techniques of elliptical paraboloid reinforced concrete shells with openings. An experimental program of several different techniques in repair and strengthening is executed. The materials, which are considered for strengthening, are; Glass fiber reinforced polymers GFRP at different position of the shell bottom surface, steel strip and external tie. They loaded by four concentrated loads affected on the corners of the opening. The initial and failure loads as well as the crack propagation for the tested shells at different loading stages, defl ections and failure load for repaired and shells are recorded. A non-linear computer program based on finite element techniques is used to study the behavior of these types of shells. Geometric and materials nonlinearities are considered in the analysis. The efficiency and accuracy of computer program are verifi ed by comparing the program results with those obtained experimentally for the control shell with opening and strengthened shells.

7

Przeprowadzenie prób i badań laboratoryjnych pod kątem doboru obróbki cieplnej taśm i pasów stalowych walcowanych na zimno

Maciosowski A., Radwański K., Gazdowicz J., Cesarz S.

Prace Instytutu Metalurgii Żelaza

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2009

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T. 61, nr 3

54-56

PL

Celem pracy było określenie możliwości zastąpienia obróbki cieplnej taśm i pasów ze stali konstrukcyjnych i narzędziowych polegającej na hartowaniu i następnym odpuszczaniu w ołowiu, procesem hartowania izotermicznego i/lub wydłużonego chłodzenia w sprężonym azocie. W tym celu przeprowadzono w warunkach przemysłowych Przeróbki Plastycznej na Zimno - Baildon Sp. z o.o. próby hartowania i odpuszczania taśm i pasów wykorzystując dotychczas stosowaną technologię oraz próby wydłużonego ich chłodzenia sprężonym azotem. W warunkach laboratoryjnych wykonano obróbkę cieplną taśm polegającą na hartowaniu izotermicznym. Uzyskane wyniki badań taśm/pasów chłodzonych z temperatury austenityzowania azotem, wskazują, że możliwe jest uzyskiwanie porównywalnych właściwości mechanicznych i twardości taśm i pasów do właściwości mechanicznych i twardości taśm/pasów hartowanych i odpuszczanych w ołowiu.

EN

The purpose of the work was to define the possibilities to replace heat treatment of strips and belts from constructional and tool steel, which was quenched followed by tempering in lead bath, with isothermal hardening and/or elongated cooling in compressed nitrogen. In this purpose, the hardening and tempering tests using the currently applied technology as well as tests of elongated cooling with compressed nitrogen were carried out under the industrial conditions of Przeróbka Plastyczna na Zimno - Baildon Sp. z o.o. The heat treatment of strips, which was isothermal hardening, was performed under the laboratory conditions. The obtained results of testing strips/belts cooled from the nitrogen austenitising temperature show that it is possible to obtain mechanical properties and hardness of the strips and belts comparable to those of the strips/belts hardened and tempered in lead bath.