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1

Overstrength and ductility factors of XBF structures with pinned and fixed supports

Yahmi Djamal, Branci Taïeb, Bouchaïr Abdelhamid, Fournely Eric

Studia Geotechnica et Mechanica

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2023

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Vol. 45, nr 1

41--54

EN

In today's time, most seismic design codes are based on a linear elastic force-based approach that includes the nonlinear response (ductility and over strength) of the structure through a reduction factor (named behavior factor q in Eurocode 8 [EC8]). However, the use of a prescribed q-factor that is constant for a given structural system may fail in providing structures with the same risk level. This paper focuses on the estimation of actual values of q-factor for X-braced steel frames (XBFs) designed according to the European codes and comparing these values to those suggested in EC8. For this purpose, a nonlinear pushover analysis has been performed. The effects of specific parameters, such as the stories number, the brace slenderness ratio, the local response of structural members, and the support type, are evaluated. The results show that the most important parameter that affects the q-factor is the brace slenderness ratio, while the support type has less effect on this factor. Furthermore, a local strength criterion has been proposed to implicitly ensure that the suggested value of the q-factor is conservative.

2

Stale konstrukcyjne typu maraging wytapiane próżniowo – zależność ciągliwości od zawartości wtrąceń niemetalicznych

Pawlak Stanisław Jerzy

Stal, Metale & Nowe Technologie

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2022

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nr 3-4

30--36

PL

W pracy analizowano ilościową zależność pomiędzy ciągliwością a zawartością wtrąceń niemetalicznych w odkuwkach o dużym przekroju z wytapianej próżniowo stali wysokostopowej typu maraging X2NiCoMo18-9-5. Wykonano badania własności wytrzymałościowych odkuwek i czystości metalurgicznej stali pochodzących z 17 wytopów przemysłowych. Obróbkę cieplną prowadzono według dwóch technologii różniących się sposobem austenityzowania, przy czym warunki starzenia były takie same, co prowadziło do uzyskania zbliżonych wartości wytrzymałości stali. Natomiast własności plastyczne stali przy ustalonej technologii produkcji były znacznie zróżnicowane, a główną przyczyną tego była czystość metalurgiczna stali.

EN

In the paper, the quantitative relationship between the ductility and volume fraction of the non-metallic inclusions in the vacuum melted X2NiCoMo18-9-5 maraging steel has been analysed. The tensile properties and cleanliness of steels from 17 industrial melts in the form of forged bars were determined. Two variants of the heat treatment in the austenitic range were used, followed by the same ageing conditions, which lead to the similar strength values of the steels. In contrary to that, significant variability in the tensile ductility was observed, which was attributed to the cleanliness of the steels.

3

Stress–strain relationship of ductile materials and flexural behavior of ductile over-reinforced concrete beams

Duhaim Hussein M., Mashrei Mohammed A.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2022

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Vol. 31, No. 4

225--237

EN

This paper aimed to investigate the effect of using ductile materials in the compression zone on the flexural performance of over-reinforced concrete beams. In order to avoid brittle compression failure, partial replacement of concrete with ductile materials layer in the compression zone was used. Four over-reinforced concrete beams of size 120 × 180 × 1,300 mm were cast and tested under three-point loading conditions. The steel fibers reinforced concrete (SFRC), slurry infiltrated fiber concrete (SIFCON), and ultra-high performance fiber reinforced concrete (UHPFRC) were used as ductile materials. The flexural capacity of the beams, failure modes, crack patterns, load-deflection relationships, ductility index, and toughness were investigated. The results showed that using ductile materials in the compression zone is an effective technique to increase the ultimate load, ductility, and toughness by up to 52.46, 84.78 and 279.93%, respectively, compared to the reference beam. In addition, the failure mode changed from brittle to ductile failure. Noting that the use of SFRC layer enhanced the ductility of over-reinforced concrete beams more than using UHPFRC and SIFCON layers. Also, one of the main advantages of this technique is led to increase the tensile reinforcement ratio up to 8.548% without needing the compressive reinforcement. Thus, ductile composite beams with a high flexural capacity were generated using an economical amount of ductile materials.

4

Prediction of shear strength of CFRP-strengthened reinforced recycled aggregate concrete beams using various strengthening methods

Sahib Hiba A., Al-Asadi Ali K.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2022

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Vol. 31, No. 4

238--248

EN

Fibre reinforced polymer (FRP) strengthening is a possible option when the load carrying capacity of a structure needs to be increased for various reasons. On the other hand, the focus nowadays aims to save the environment by reducing the waste material. A suggestion was made to use waste concrete as an aggregate. If this new material was used more, it would be possible to use recycled concrete aggregate (RCA) and carbon fibre reinforced polymer (CFRP) to strengthen reinforced concrete (RC) structures and make them more environmentally friendly. An experimental investigation study on the shear behaviour of RC beams strengthened with CFRP strips was carried out. Tests were conducted on six reinforced concrete beams, with variations in the replacement ratio of RCA and strengthened by different configurations of CFRP under four-point loading. The results indicated that the load carrying capacity was increased, on average, by 18.09 and 35.04% for beams strengthened with CFRP with an inclined strip (IS) and continuous strip (CS) configurations respectively. The results also indicated that the increases in the stiffness were 21.08 and 37.31 for beams strengthened with CFRP in the IS and CS configurations, respectively. In addition the ductility of the beams increased after strengthening.

5

Influence of material thickness on the ductile fracture of steel plates for shipbuilding

Jakub Kowalski, Janusz Kozak

Polish Maritime Research

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2022

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nr 3

160--166

EN

In the shipbuilding industry, the risk of brittle fractures is relatively high because some units operate in arctic or subarctic zones and use high thickness (up to 100 mm) steel plates in their structures. This risk is limited by employing certified materials with a specific impact strength, determined using the Charpy method (for a given design temperature) and by exercising control over the welding processes (technology qualification, production supervision, and non-destructive tests). However, for offshore constructions, such requirements may prove insufficient. For this reason, regulations employed in constructing offshore structures require conducting crack tip opening displacement (CTOD) tests for steel and welded joints with thicknesses exceeding 40 mm for high tensile strength steel and 50 mm for other steel types. Since classification codes do not accept the results of CTOD tests conducted on specimens of sub-sized dimensions, the problem of theoretically modelling the steel construction destruction process is of key importance, as laboratory tests for notched elements of considerable thickness (100 mm and higher) are costly and problems stemming from high loads and a wide range of recorded parameters are not uncommon. The aim of this research is to find a relationship between material thickness and CTOD value, by establishing and verifying a numerical model that allows recalculating a result obtained on a sub-size specimen to a full- size specimen for a ductile fracture mode. This work presents results and conclusions from numerical modelling and compares them with laboratory test results of the elastic-plastic properties of high thickness steel, typically used in offshore applications.

6

Ductility, load capacity and bending stiffness of scandinavian pine beams from waste timber strengthened with jute fibres

Wdowiak-Postulak Agnieszka

Drewno : prace naukowe, doniesienia, komunikaty

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2022

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Vol. 65, nr 210

art. no. 1644-3985.417.01

EN

The paper presents experimental studies of bending heterogeneous pine beams reinforced with jute fabrics. Pinus Sylvestris L, a Scandinavian wood species, was used in this study, originating from discard, subjected to 5-year atmospheric influences and biological degradation. The use of recoil wood is an excellent choice, forced by the increasing shortage of high-quality assortments and the need for economical management of scarce raw material. The article presents experimental results regarding the effectiveness of pre-stressed jute reinforcements in the tension zone of pine wood. The effects of using jute fabrics in beams were analysed, and the results were compared to beams without reinforcement. Additionally, the aim of the research is to investigate the influence of jute fabrics on the ductility of wooden beams. Research has been conducted on these polymer composites reinforced with natural fibres due to environmental awareness, their many advantages and, above all, the fact that they are sustainable materials. The conducted tests revealed that the jute fibres had a positive impact when applied to wooden beams and the load-bearing capacity increased by 24% and stiffness 24% compared to unreinforced beams. Moreover, the tests confirmed enhanced strength (24%) of reinforced pine beams in relation to the reference beams. In contrast, the ductility increased from 6.6% for reference beams to 75.7% for reinforced pine wood. Reinforcements with jute fibres have considerable ductility, which indicates that jute fibres are an excellent material for reinforcing the structure.

7

Effect of the mix composition with superplasticizer admixture on mechanical properties of high-strength concrete based on reactive powders

Siwiński Jarosław, Szcześniak Anna, Nasiłowska Barbara, Mierczyk Zygmunt, Kubiak Katarzyna, Stolarski Adam

Archives of Civil Engineering

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2022

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Vol. 68, nr 4

77--95

EN

This paper outlines effect of the mix composition on mechanical properties of high-strength concrete based on aggregate size like in of Reactive Powder Concrete (RPC) but without fiber reinforcement. The main purpose which guided the authors choosing proportion of water and superplasticizer (SP) was to achieve a similar consistency in the test slump for various concrete mix. Test results for 3 groups of superplasticizers, designated as D - with chemical base - acrylic polymer, V - with chemical base - polycarboxylate ether, P - with chemical base - modified polycarboxylates, two cement groups, designated as Cem A - with fineness Blaine 3980 cm2/g, Cem B - with fineness Blaine 4430 cm2/g and 2 types of aggregate: basalt and granite were presented. After curing for 1, 7 and 28 days samples were tested for compressive strength and flexural tensile strength. The article also presents the study of the elemental composition and structure of the SP with the use of the SEM electron microscope. The amount of solid particles in the SP was also determined by the water vaporization. The assumption of the paper was to maintain the consistency of the mixture at the S2 level according to the Eurocode standard. The paper proposes a method based on SEM analysis in order to select a superplasticizer with the best ductility parameters, and the best results of the compressive and flexural tensile strength of concrete samples were obtained. The best results for compressive strength after 28 days are obtained for concrete series with the polycarboxylate ether superplasticizer and modified polycarboxylate ether superplasticizer in combination with the use of type A cement and it is greater than for the concrete series with type B cement by 11.7%.

PL

W artykule zamieszczono wpływ składu recepturowego betonu na jego właściwości mechaniczne. Badaniom poddano betony wysokowytrzymałościowe bazujące na proszkach reaktywnych, ale bez wykorzystania dodatkowego zbrojenia rozproszonego. Głównym założeniem autorów było uzyskanie klasy konsystencji S2 dla wszystkich receptur uwzględnionych w artykule. Betony zaprojektowano posługując się zmodyfikowaną procedurą de Larrarda opartą na modelu CPM (concrete packing model). W metodzie tej wprowadzono dodatkowe współczynniki uwzględniające ilość włókien zbrojenia rozproszonego, rodzaj i kształt formy próbek badawczych, czas, w którym wyznaczana jest wytrzymałość oraz współczynnik kruszywowy uwzględniający ilość frakcji poniżej 0,2 mm w mieszance betonowej. W badaniach uwzględniono dwa rodzaje kruszywa: granitowe i bazaltowe, dwa rodzaje betonu oznaczonych jako Cem A o powierzchni właściwej Blaina 3980 cm2/g i Cem B o powierzchni właściwej Blaina 4430 cm2/g oraz 3 rodzaje superplastyfikatorów oznaczonych jako D - z chemiczną bazą polimeru akrylowego, V - z chemiczną bazą eteru polikarboksylanowego i P - z chemiczną bazą zmodyfikowanego eteru polikarboksylanowego. Dla wszystkich wykonanych serii próbek badawczych wykonano test opadu stożka. Wyniki wytrzymałości betonów na ściskanie i rozciąganie przedstawiono dla serii próbek badawczych spełniających kryterium klasy konsystencji S2. Określono współczynnik ciągliwości wytrzymałościowej jako proporcję wytrzymałość betonu na rozciąganie przy zginaniu w stosunku do wytrzymałości betonu na ściskanie. Przedstawiono wyniki współczynnika ciągliwości dla średnich wytrzymałości wszystkich serii próbek badawczych po 1, 7 i 28 dniach. W artykule przedstawiono również badanie składu pierwiastkowego odparowanego superplastyfikatora z wykorzystaniem analizy SEM. Przedstawiono zdjęcia odparowanych i przygotowanych próbek superplastyfikatorów w celu określenia, który z SP ma największą ciągliwość, tzn. największe wymiary jednorodnych obszarów pomiędzy powstałymi pęknięciami. Wskazano na jakościową zgodność wyników opartych na współczynniku ciągliwości wytrzymałościowej i ciągliwości struktury superplastyfikatorów obserwowanej na podstawie analizy SEM. W wyniku przeprowadzonych badań i analiz stwierdzono, że zastosowanie superplastyfikatora typu P pozwala uzyskać największe wytrzymałości betonu na rozciąganie przy zginaniu oraz wytrzymałości betonu na ściskanie przy zachowaniu założonej klasy konsystencji S2. Podkreślić należy również, że metodyka projektowania betonów UHPC oraz RPC z założenia uwzględnia domieszkę superplastyfikatora.

8

Ductility and formability of Al-Mn ultrafine-grained plates processed by incremental equal channel angular pressing

Ciemiorek Marta, Goliński Jacek, Majchrowicz Kamil, Lewandowska Małgorzata

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 4

art. no. e169, 2022

EN

The article discusses the ductility and formability of ultrafine-grained 3003 aluminum alloy plates processed using incremental equal channel angular pressing. The influence of temperature and strain rate is evaluated by means of tensile tests and cupping tests under various conditions. It is reported that tensile elongation increases two-fold at elevated temperature, without excessive grain growth. With the right selection of processing conditions, the formability of the plate, expressed as cup height deformed in a cupping test, can be enhanced—as much as 62% compared with room temperature when the processing takes place at 150 °C. The improvement in ductility was attributed to a reduced apparent activation volume due to grain refinement, which translated into improved strain rate sensitivity.

9

Experimental and numerical investigation on specimen geometry effect on the ctod value for VL-E36 shipbuilding steel

Kowalski Jakub

Polish Maritime Research

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2021

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nr 3

110--116

EN

There are special cases in the marine industry, where additional material tests, such as the fracture toughness test, must be performed. Additional fracture toughness tests, such as CTOD (Crack Tip Opening Displacement), are typically performed on three-point bend specimens. The dimension that defines all the specimen dimensions is the thickness of the material to be tested. It is recommended by classification societies (e.g. DNVGL) to test specimens that are twice as high as the material thickness. The width determines the length and, therefore, the weight of the specimen which, for a 100 mm plate is over 140 kg. Current ASTM E1820, BS7448-1 and ISO 12135 testing standards also allow for proportions other than those recommended. This results in a much smaller test piece. Reducing the specimen size allows the testing machine to achieve lower forces than a specimen with a width to thickness ratio of two. This paper presents the effect of changing the specimen geometry on CTOD test results. Research was performed for specimens with a height to thickness ratio of one and two. Abaqus software was used for numerical calculations. The numerical results were, at selected points, verified experimentally.

10

Wpływ rezerwy nośności i ciągliwości konstrukcji na jej zachowanie pod obciążeniem sejsmicznym

Grzeszykowski Bartosz, Szmigiera Elżbieta

Inżynieria i Budownictwo

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2021

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R. 77, nr 4

174--181

PL

Na podstawie nieliniowej dynamicznej analizy ramy portalowej poddanej wymuszeniu sejsmicznemu przedstawiono zasady wyznaczania wymaganej ciągliwości poziomej konstrukcji. Obliczenia numeryczne wykonano za pomocą modelu lepko-sprężysto-idealnie plastycznego oscylatora o jednym stopniu swobody. Opisano metody projektowania konstrukcji stalowych i zespolonych stalowo-betonowych ze względu na oddziaływania sejsmiczne zgodnie z Eurokodem 8. Przedstawiono sposób wyznaczania sprężystego spektrum odpowiedzi konstrukcji oraz pokazano fizyczną interpretację współczynnika zachowania q, a także metody wyznaczania tego współczynnika.

EN

The method of determining the ductility demand of the portal frame subjected to the seismic forces was presented. Numerical calculations were performed using a viscoelastic ideally plastic SDOF oscillator. The Eurocode 8 provisions on designing steel and composite steel-concrete structures due to seismic actions and the method of determining the elastic response spectrum was described. The physical interpretation of the behavior factor q as well as the methods of determining this factor were presented.

11

Wpływ wielkości i kształtu kruszywa na wytrzymałość betonu na ściskanie i plastyczność

Darvishvand Hamid Reza, Haj Seiyed Taghia Seiyed Ali, Ebrahimi Masood

Cement Wapno Beton

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2021

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R. 26, nr 1

46--54

PL

Zagadnienie wielkości i kształtu kruszywa w betonie dla osiągnięcia maksymalnej wytrzymałości i plastyczności, jest jednym z ważniejszych zagadnień w budownictwie. Do zbadania tych właściwości wybrano dwa rodzaje kruszywa o czterech uziarnieniach. Pierwszym kruszywem był żwir o zaokrąglonych ziarnach zaś drugim grys o ziarnach ostrokrawędzistych. Maksymalne wymiary ziaren wynosiły dla obu kruszyw odpowiednio 9,5, 12,5, 19 i 25 mm. Dobrano zawartość cementu 250, 350, 450 i 550 kg/m3 oraz stosunek wody do cementu równy 0,4. W pierwszej kolejności wykonano badania wytrzymałości na ściskanie oraz odkształcalności próbek. Zgodnie z wynikami badań, wytrzymałość na ściskanie wzrastała wraz ze wzrostem zawartości cementu, co jest zgodne z oczekiwaniami. Beton z kruszywa o maksymalnej wielkości ziaren wynoszącej 12,5 mm ma największą wytrzymałość na ściskanie i plastyczność w porównaniu z innymi uziarnieniami i zostało wybrane jako optymalne, a betony z kruszywa ostrokrawędziste mają większą wytrzymałość na ściskanie i plastyczność w porównaniu z betonami z kruszyw o zaokrąglonych ziarnach.

EN

The issue of the size and shape of the aggregates in concrete is one of the most challenging subjects in the building industry, in order to reach maximum strength and ductility. To investigate this issue, two types of aggregate were selected. One was the river aggregate - gravel with rounded grains and the second was a crushed stone with sharp-edged grains, both with the maximum sizes of 9.5, 12.5, 19, and 25 mm respectively. The cement content was 250, 350, 450, and 550 kg/m3, and the water to cement ratio was equal to 0.4. At first, the compressive strength and stress-strain relationship were examined. According to the test results, the compressive strength increases with increasing cement content, as expected. The aggregate with the largest grain size of 12.5 mm gives the highest compressive strength and ductility compared to other grain sizes and it was selected as the optimal choice and finally, the sharp-edged aggregates have higher compressive strength and ductility in comparing to the rounded grain aggregates.

12

Structural performance of reinforced concrete interior beam-column joints with high-strength bars

Kim Sang-Woo, Chang Hyo-Jun

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 3

200--213

EN

This study evaluates the structural performance of reinforced concrete interior beam–column joints having high-strength screw-type steel bars mechanically connected with couplers. A total of six full-scale specimens were cast and subjected to repeated cyclic lateral loads. High-strength screw-type reinforcing bars, with a yield strength of 690 MPa, were used as longitudinal reinforcement of the specimens. The main test variables were designed with and without couplers and the longitudinal reinforcement ratio of the beam. The couplers were applied to the plastic hinge zones of columns and beams to maximize their impact. The experiment confirmed that the flexural cracks generated near the couplers slightly influenced the initial stiffness, the yielding point of the longitudinal reinforcement of the beams, and the displacement at peak load of the specimens. However, the load versus story drift relationship, the peak load, and the ductility capacity of the specimens were not significantly affected. In addition, the analytical results obtained using the current structural design codes and finite element analysis were similar to the experimental results.

13

Processing of commercially pure copper tubes by hydrostatic tube cyclic extrusion–compression (HTCEC) as a new SPD method

Eftekhari M., Faraji G., Bahrami M.

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 3

595--606

EN

In this study, severe plastic deformation (SPD) process of hydrostatic tube cyclic extrusion–compression (HTCEC) was performed through two passes on the commercially pure copper tubes with the purpose of fabricating relatively long ultrafine-grained (UFG) tubes. In HTCEC process, the presence of pressurized hydraulic fluid around the piece plays a key role in the reduction of the friction load and, consequently, in the reduction of required pressing load. In principle, this facilitates the production of long and large tubes. After processing by HTCEC, the mechanical characteristics and microstructure evolution were examined. Microstructure analysis revealed that after the first pass of HTCEC process, an ultrafine cell microstructure with an average size of ~ 993 nm was attained. After two passes of HTCEC, the average size of cells/subgrains was reduced to ~ 340 nm. This was while the average grain size of the annealed sample was 41 μm. Also, after two passes of HTCEC process, a remarkable increase in the yield strength from 154 to 336 MPa, and the ultimate strength from 223 to 414 MPa was observed. Furthermore, the mean value of microhardness increased from 74 to 149 HV, and a more uniform distribution of microhardness along the thickness was seen, compared to the first pass of HTCEC. Meanwhile, unlike most conventional SPD methods, the value of elongation to failure was slightly lessened from 59.5 to 41.6%. SEM fractography analysis denoted that mostly ductile fracture occurred in the HTCEC-processed samples. In general, two main advantages of HTCEC process can be the production of relatively long ultrafine-grained tubes and the significant increase in the strength and hardness besides a low loss of ductility.

14

Poprawa własności stali typu maraging w postaci kęsów kutych

Pawlak Stanisław Jerzy

Stal, Metale & Nowe Technologie

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2020

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nr 3-4

34--40

PL

W pracy opisano badania prowadzące do poprawy własności mechanicznych (ciągliwości) stali typu maraging X2NiCoMo18-9-5 w postaci kęsów kutych o dużym przekroju. Zmodyfikowano proces kucia poprzez zastosowanie większych odkształceń plastycznych w niższych wartościach temperatury w stosunku do tradycyjnej technologii. Opracowano też nową trój-etapową obróbkę cieplną odkuwek. Korzystne zmiany własności przypisano zmniejszonej wielkości ziarna austenitu oraz rozdrobnieniu wtrąceń niemetalicznych.

EN

The paper describes experiments leading to the improvement in the mechanical properties (ductility) of the X2NiCoMo18-9-5 maraging steel in the form of forged billets of a large cross-section. The forging process was modified in relation to the traditional technology by applying higher deformations at lower temperatures. A novel three-stage heat treatment was also developed. The improvement of the properties was attributed to the austenite grain refinements and finer size of non-metallic inclusions.

15

Seismic strengthening of nonductile bridge piers using low-cost glass fiber polymers

Rodsin K., Hussain Q., Joyklad P., Nawaz A., Fazliani H.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2020

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Vol. 68, nr 6

1457--1470

EN

Several recent earthquakes have indicated that the design and construction of bridges based on former seismic design provisions are susceptible to fatal collapse triggered by the failure of reinforced concrete columns. This paper incorporates an experimental investigation into the seismic response of nonductile bridge piers strengthened with low-cost glass fiber reinforced polymers (LC-GFRP). Three full-scale bridge piers were tested under lateral cyclic loading. A control bridge pier was tested in the as-built condition and the other two bridge piers were experimentally tested after strengthening them with LC-GFRP jacketing. The LC-GFRP strengthening was performed using two different configurations. The control bridge pier showed poor seismic response with the progress of significant cracks at very low drift levels. Test results indicated the efficiency of the tested strengthening configurations to improve the performance of the strengthened bridge piers including crack pattern, yield, and ultimate cyclic load capacities, ductility ratio, dissipated energy capacity, initial stiffness degradation, and fracture mode.

16

Ductility and internal forces redistribution in lightweight aggregate concrete beams

Waśniewski Tomasz, Kołodziejczyk Ewelina

Budownictwo i Architektura

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2020

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Vol. 19, no 4

95--108

EN

Lightweight Aggregate Concrete (LWAC) is typically defined as concrete having a density smaller than or equal to 2200kg/m3 and can be obtained by mixing natural or artificial lightweight aggregates. There is a general scepticism regarding the use of lightweight aggregate concrete (LWAC) for structural applications. This concern is attached to the more brittle material behaviour which leads to lower ductility. This article presents a numerical parametric analysis of the behaviour of the reinforced LWAC cross-sections under the immediate load taking into account the density of the LWAC concrete, concrete strength and tensile reinforcement ratio. Numerical analysis of the beams was conducted in OpenSees, an open–source nonlinear finite element method framework. One-dimensional elements, with three degrees of freedom at each end, were used. Bending stiffness in the integration points was calculated based on the sectional moment – curvature relationship. The analysis showed that there is a relationship between the ductility of the cross-sections made of lightweight concrete and its density class. It is associated with limited compressive strains and the brittle behavior of LWAC. The limited rotation capacity of the reinforced concrete sections made of LWAC also affects the ability of redistribution of internal forces in statically indeterminate beams

PL

Beton lekki kruszywowy (LWAC) jest zwykle definiowany jako beton o gęstości mniejszej lub równej 2200 kg / m3 i można go otrzymać na bazie naturalnych lub sztucznych kruszyw. Istnieje ogólny sceptycyzm co do użycia lekkiego betonu kruszywowego (LWAC) do zastosowań konstrukcyjnych. Obawa ta jest związana z bardziej kruchym zachowaniem się tego betonu, co może prowadzić do mniejszej ciągliwości. W artykule przedstawiono numeryczną analizę parametryczną zachowania się przekrojów wykonanych z betonu lekkiego z uwzględnieniem gęstości betonu, wytrzymałości na ściskanie i stopnia zbrojenia rozciąganego. Analiza numeryczna belek została przeprowadzona w systemie OpenSees, przy użyciu nieliniowej metody elementów skończonych. Do analizy użyto elementów jednowymiarowych z trzema stopniami swobody na każdym końcu. Sztywność giętna była wyznaczana na podstawie przekrojowych relacji moment zginający - krzywizna. Analiza wykazała, że istnieje zależność między ciągliwością przekrojów wykonanych z betonu lekkiego a jego gęstością. Jest to związane z ograniczeniami odkształceń ściskających i kruchym zachowaniem betonu lekkiego. Ograniczona zdolność do obrotu przekrojów krytycznych wykonanych z betonu lekkiego wpływa również na stopień redystrybucji sił wewnętrznych w belkach statycznie niewyznaczalnych.

17

Analysis of composite shear walls with a gap between reinforced concrete wall and steel frame

Bahrami Alireza, Yavari Mojtaba

Archives of Civil Engineering

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2020

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Vol. 66, nr 1

41--53

EN

In this research, nonlinear analysis of composite shear walls (CSWs) with a gap between reinforced concrete wall and steel frame is investigated under cyclic loading by the use of the finite element method (FEM) software ABAQUS. For the purpose of the verification, an experimental test is modelled and comparison of its obtained result with that of the experimental test demonstrates an inconsiderable difference between them; therefore, the reasonable accuracy of the modelling is revealed. Then, effects of different parameters on the behaviour of the CSWs are examined. Gap size between reinforced concrete wall and steel frame, reinforcement percentage, steel sections of beams and columns, and existence of reinforced concrete wall are considered as parameters. It is concluded that change of the parameters affects the ultimate strength, ductility, and energy dissipation of the system. A steel shear wall (SSW) is also modelled and compared with the CSWs. Buckling of the walls is presented as well.

18

Improving the workability of materials during the dieless drawing processes by multi-pass incremental deformation

Milenin Andrij, Furushima Tsuyosh, Du Peihua, Pidvysots’kyy Valeriy

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 3

323--336

EN

The paper explores the new method of improving the workability of materials in the dieless drawing processes. The proposed method is based on the implementation of a multi-pass incremental deformation. Moreover, in each pass, strain and strain rate sensitivity of flow stress should be positive and significant. An approach based on the finite element calculation of instability coefficient of plastic deformation and simultaneous modeling of material ductility were applied for prediction of the workability. Two dieless drawing processes have been investigated. The difference was related to the heating system-induction heating and laser heating. FE simulations and experimental tests for three materials, two magnesium alloys (MgCa0.8 and MgNi19) and pure copper were performed. It was shown that the most effective increase in workability by multi-pass deformation can be achieved using laser dieless drawing. This is possible due to the shorter heating area and, as a consequence, the larger strain rate, which leads to better stability of the deformation process.

19

Wpływ warunków austenityzowania na ciągliwość i odporność na pękanie konstrukcyjnej stali maraging X2NiCoMo18-9-5

Pawlak Stanisław Jerzy

Stal, Metale & Nowe Technologie

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2019

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nr 1-2

64--69

PL

W pracy badano wpływ różnych zabiegów cieplnych w zakresie wysokich wartości temperatury austenityzowania na własności wytrzymałościowe i odporność na pękanie stali X2NiCoMo18-9-5. Stal w stanie niestarzonym charakteryzuje się bardzo wysoką ciągliwością w próbie rozciągania, nawet gdy ma bardzo duże ziarno byłego austenitu po specjalnej obróbce cieplnej w zakresie austenitycznym.

EN

The effect of various heat treatment processes in the high austenitizing temperature range on the tensile properties and fracture toughness of the X2NiCoMo18-9-5 steel has been studied. Unaged steel is characterised by very high tensile ductility in the tensile test, even when it has former austenite grain of a large size. Brittleness can occur after such a heat treatment but only in aged steel of very high strength. A linear correlation between the ductility and strength of the studied steel was demonstrated, while fracture toughness was not clearly correlated with steel ductility.

20

Wpływ warunków austenityzowania na ciągliwość i odporność na pękanie konstrukcyjnej stali maraging X2NiCoMo18-9-5. Cz. 2

Pawlak Stanisław Jerzy

Stal, Metale & Nowe Technologie

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2019

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nr 3-4

38--39

PL

W artykule opublikowanym w wydaniu 1-2/2019 czasopisma ,,STAL Metale & Nowe Technologie” opisano badania wpływu różnych zabiegów cieplnych w zakresie wysokich wartości temperatury austenityzowania na własności wytrzymałościowe i odporność na pękanie stali X2NiCoMo18-9-5. Stal w stanie niestarzonym charakteryzuje się wysoką ciągliwością w próbie rozciągania, nawet gdy ma bardzo duże ziarno byłego austenitu po specjalnej obróbce cieplnej w zakresie austenitycznym. W niniejszym artykule przedstawiono wyniki badań odporności na pękanie stali w stanie starzonym.

EN

The effect of various heat treatment processes in the high austenitizing temperature range on the tensile properties and fracture toughness of the X2NiCoMo18-9-5 steel has been studied. Unaged steel is characterised by very high tensile ductility in the tensile test, even when it has former austenite grain of a large size. Brittleness can occur after such a heat treatment but only in aged steel of very high strength. A linear correlation between the ductility and strength of the studied steel was demonstrated, while fracture toughness was not clearly correlated with steel ductility.