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1

Study of Stress Concentration on the Contour of Underground Mine Workings

Pysmennyi Serhii, Chukharev Serhii, Peremetchyk Andrii, Fedorenko Serhii, Matsui Anatolii

Inżynieria Mineralna

|

2023

|

no. 1

69--78

EN

Kryvyi Rih iron ore basin consists of complex structured ore deposits and is developed by the underground method at depths of over 1000 m. The underground method is used to mine reserves of rich iron ores with a useful component content of more than 59% applying bulk ore and rock caving systems. This leads to significant changes in the stress state of the rock massif. During underground operations, mine workings are strained and in some cases destructed. As a result, enterprises are constantly increasing operating costs for maintaining mine workings, which adversely impacts the cost of production. Industrial research results demonstrate that in most cases workings fail in their upper part which is vaulted in shape. Available methods for determining the state of rocks around mine workings do not fully take into account physical and mechanical properties of the rocks in which the working is located. The developed technique allows determining not only the destructive pressure impacting the workings, but also the angle at which the destructive force acts. This technique differs from the available ones in taking into account not only mining and geological characteristics of the deposit, but also most factors of physical and mechanical properties of rocks. This technique helps to choose a rational place for driving mine workings at the stage of design, thus avoiding significant additional cost for their maintenance.

PL

W kopalni Krzywy Róg występują złoża rudy o złożonej strukturze, wydobywane metodą podziemną z głębokości ponad 1000 m. Stosując systemy zawałowe eksploatuje się złoża bogatych rud żelaza o zawartości składników użytecznych powyżej 59%. Prowadzi to do znacznych zmian stanu naprężeń masywu skalnego. Podczas prac podziemnych wyrobiska kopalniane podlegają naprężęniom, a w niektórych przypadkach ulegają zniszczeniu. W efekcie przedsiębiorstwa stale podwyższają koszty eksploatacji wyrobisk górniczych, co niekorzystnie wpływa na koszty produkcji. Wyniki badań przemysłowych wskazują, że w większości przypadków wyrobiska zawodzą w swojej górnej części. Dostępne metody określania stanu skał wokół wyrobisk górniczych nie uwzględniają w pełni właściwości fizycznych i mechanicznych skał, w których znajduje się wyrobisko. Opracowana technika pozwala na określenie nie tylko ciśnienia destrukcyjnego działającego na wyrobiska, ale również kąta działania siły destrukcyjnej. Technika ta rożni się od dostępnych tym, że uwzględnia nie tylko cechy górniczo-geologiczne złoża, ale także większość czynników właściwości fizykomechanicznych skał. Technika ta pozwala już na etapie projektowania na dobór racjonalnych miejsc prowadzenia wyrobisk górniczych, unikając w ten sposób znacznych dodatkowych kosztów ich utrzymania.

2

Study of the behavior of the Al 2017-A aluminium plate corroded and with horizontal cracks treated by the technique of composite materials

Berrahou Mohamed, Benzineb Hayet

Advances in Materials Science

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2023

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Vol. 23, nr 2(76)

5--24

EN

This work presents a comprehensive study consisting of two aspects: a numerical analytical aspect and a laboratory experimental aspect. The numerical study was a three-dimensional finite element numerical analysis of performance of corroded and horizontally cracked aluminium plates, which were repaired by composite patching. The effect of the composite types on the variance of the damaged area of the adhesive (FM-73) and their efficiency on the stress intensity factor were studied. In the experimental study, corroded aluminium plates were prepared and repaired them using technology of the composite. The results showed that the panels that were repaired with composite (boron/epoxy) give values of stress intensity factor (KI) and damaged area ratio (DR) less than the other two studied composites (glass/epoxy and graphite/epoxy), and increase the ultimate strength of plates damage, and this leads to the conclusion that (Boron/epoxy) increases the performance and durability of (Al 2017-A) plates.

3

Compressive performance of AFRP reinforced laminated bamboo stub columns

Hong Chaokun, Li Haitao, Yang Dong, Li Hang, Zhang Huizhong, Lorenzo Rodolfo

Archives of Civil and Mechanical Engineering

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2022

|

Vol. 22, no. 1

art. no. e31, 2022

EN

Engineered bamboo construction can be affected by natural defects, insects, corrosion, etc., which will result in damaging the mechanical properties of structural components. However, traditional reinforcement methods such as setting steel supports and increasing the cross-sectional area of components may cost a lot and cause a negative influence on the appearance of building. Many engineering practices and research works show that applying FRP (Fiber Reinforced Polymer/Fiber) sheet is an economical and efficient method for reinforcing and retrofitting building structures. Therefore, the compressive performance of AFRP (Aramid Fiber Reinforced Polymer/Fiber) reinforced laminated bamboo lumber (LBL) stub columns was studied in this paper. Through six groups (three replicates for each group) of stub columns with six different cloth ratios, the influence of AFRP on the failure pattern and mechanical properties of bamboo columns was explored. The test results showed that AFRP could effectively restrain the lateral deformation and improve the mechanical behavior of LBL columns. With the increase in cloth ratio, the ultimate strength and elastic modulus increased linearly in general, while the Poisson’s ratio gradually decreased. The reduced modulus of reinforced columns in the elastoplastic stage increased up to 161.31% compared with normal columns. Although the ductility of LBL columns laterally wrapped by AFRP was greatly improved, the initial stiffness, yield point and turning points between elastoplastic stage and plastic stage basically remained unchanged in contrast to unreinforced columns. Based on the test results, an empirical equation considering the cloth ratio was proposed to calculate the ultimate strength of AFRP reinforced LBL columns, using ‘Lam and Teng’ model. In addition, a simplified equation was also proposed to calculate the compressive strength of reinforced LBL columns derived from Mises yield criterion. The results of this work can be a reference to promote the application of strengthening and retrofitting engineered bamboo structure with FRP.

4

Ultimate compressive strength assessment of uncleaned and cleaned corroded plates with locked crack

Woloszyk Krzysztof, Garbatov Yordan

Polish Maritime Research

|

2021

|

nr 3

117--127

EN

The work presented here investigates the structural response of cleaned corroded plates, subjected to compressive load in the presence of a locked crack, where the change of mechanical properties as a result of corrosion development and the cleaning process is also accounted for. A Finite Element model for assessing the compressive strength, considering geometric and material nonlinearities, is developed, and the analysed plates are compared with the available experimental data. An experimental design plan is generated using the Design of Experiments techniques, which quantifies the influence of the governing variables and their interactions with respect to the plate’s ultimate compressive strength. With a limited number of observations, the most significant effects are identified. The corrosion degradation is revealed to be the most crucial effect leading to an effective strength reduction. It was found that, in the case of a corroded plate with a locked crack subjected to a compressive load, the most severe case is when the crack is transversely oriented. The strength reduction is slightly lower than when the corrosion degradation and the presence of a crack are considered to be a simple summation of these two effects but acting separately. The outcome of the analysis is the development of several empirical formulations that allow a fast estimation of the ultimate strength of a corroded plate, subjected to compressive load in the presence of a locked crack, accounting for different cleaning.

5

Experimental and numerical investigations of ultimate strength of imperfect stiffened plates of different slenderness

Woloszyk Krzysztof, Garbatov Yordan, Kowalski Jakub, Samson Leszek

Polish Maritime Research

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2020

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nr 4

120--129

EN

The objective of this study is to analyse the behaviour of compressed stiffened plates of different slenderness using experimental and numerical methods. The presented results are part of a long-term project to investigate the ultimate strength of geometrically imperfect structures subjected to different degradation phenomena, including corrosion degradation and locked cracks. Several specimens were subjected to a uniaxial compressive force, and the most important quantities related to the structural behaviour were captured and analysed. A finite element model, accounting for material and geometrical nonlinearities and initial geometrical imperfections, was developed using the commercial software ANSYS. The residual welding-induced stresses were measured in the middle cross-section for two specimens. The initial imperfection was identified by employing a close-range photogrammetry approach. It was concluded that the numerical analyses, based on the finite element model, predict the ultimate strength of stiffened plates accurately, although some deviations were also observed. The detailed analysis with the indication of possible uncertainty is presented, and several conclusions are derived.

6

Analysis of ultimate compressive strength of cracked plates with the use of doe techniques

Woloszyk Krzysztof, Garbatov Yordan

Polish Maritime Research

|

2020

|

nr 3

109--120

EN

The objective of this work is to investigate the structural compressive response of plates with locked cracks accounting for all relevant factors and correlation between them. The nonlinear FE model considering both geometric and material nonlinearities is employed herein, and the FE model of the structural response of intact plates is validated with the available experimental data. In the common studies, based on One Factor at a Time analysis, some of the parameters and interactions between them are excluded. In the present study, the numerical investigations are conducted with the use of the Design of Experiments techniques, where all essential parameters and their interactions are adequately considered. With a total of 32 numerical analyses, the most influential factors and their interactions are identified. As a study outcome, empirical formulations, which allow for a fast estimation of the ultimate compressive strength of intact plates, plates with locked cracks, and repaired cracked plates, are derived. The developed formulations represent a fast and practical tool for estimating the ultimate compressive strength of intact, cracked, and repaired plates, which can be easily employed in the reliability analysis.results followed by their discussion.

7

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.

8

Structural reliability assessment of corroded tanker ship based on experimentally estimated ultimate strength

Woloszyk Krzysztof, Garbatov Yordan

Polish Maritime Research

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2019

|

nr 2

47--54

EN

This work deals with the reliability assessment of a tanker ship hull structure subjected to a vertical bending moment and corrosion degradation. The progressive collapse and ultimate load carrying capacity are estimated based on experimentally tested scaled box-shaped-specimens. The translation of the strength estimate of the scaled specimen to the real tanker ship hull structure is performed based on the dimensional theory developing a step-wise linear stressstrain relationship. The load-carrying capacity is considered as a stochastic variable, and the uncertainties resulted from the scaled-specimen to the real-structure strength translation, and the subjected load of the real ship are also accounted for. A sensitivity analysis concerning the stochastic variables, included in the ultimate limit state function is performed. The partial safety factors, in the case of a scaled specimen and real structure, are also identified, and conclusions are derived.

9

Progressive collapse test of ship structures in waves

Pei Z., Xu T., Wu W.

Polish Maritime Research

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2018

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S 3

91--98

EN

The external loads and structural ultimate strength are two important aspects for the safety of ship hull girder. It may collapse in case the structural capacity is less than the external forces in extreme seas. In the present research, progressive collapse test is performed to investigate the collapse mechanism of ship structure in waves. External load with time history and corresponding structural collapse behavior are measured and discussed to demonstrate the interaction of fluid and structures.

10

Maximum load carrying capacity estimation of the ship and offshore structures by progressive collapse approach

Ölmez H., Bayraktarkatal E.

Polish Maritime Research

|

2016

|

nr 3

28--38

EN

The aim of the paper is to represent step by step progressive collapse analysis for maximum load carrying capacity estimation of a hull girder by using variant of Smith Method, named HULT by authors, with different element separation including single plates, stiffeners, hard corners and stiffened panels. The structural elements that form the ships and offshore structures are exposed to large vertical bending moments and especially compression or tension forces in the longitudinal axis in case of hogging and sagging under bad sea conditions. In recent years, it becomes very important and valuable to practically, fast and nearly correct estimation of the maximum vertical bending moment just before breaks in two (collapse) under the worst conditions. The optimum (accuracy, time, practicality) estimation of these values depend on how accurate the stress-strain relation of the structural elements are established. In this first part of study, the ultimate strength behaviour of the stiffened panels in decks, bottoms and sides is estimated by developed semi-analytical method with updated orthotropic panel calculation approach under uniaxial (only longitudinal axis) compression loads. The second part of calculation is focused on the progressive collapse analysis of hull girders under longitudinal uniaxial compression with Smith Method but with different element discretization in contrast to the conventional beam-column elements. Also some benchmark studies of such methods on ultimate limit state assessment of stiffened panels and nine benchmark hull girders of ships are conducted, using some candidate methods such as IACS Common Structural Rules (CSR), FEA with Ansys v13 and HULT prepared by authors. The results from the tests, FEM analysis and different computational approaches are compared to determine performance of the method.

11

Analysis of stress and ultimate strength of modified single adhesive lap joints

Zielecki K., Witek L.

Logistyka

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2015

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nr 4

7015--7021, CD2

EN

This paper presents results of numerical stress analysis of single adhesive lap joints. In this work an original solution, where chamfers are located near the centerline of adherends was considered. In first part of work, the ultimate strength of joints made of both the aluminum alloy and also the steel were obtained. These results showed that the shape of chamfer has a large influence on destructive force of joint. Moreover the Young modulus of connected materials has an impact on ultimate strength of adhesive joints. In next part of the work, the numerical computations were performed for models with different materials and different shape of chamfers. In results of finite element analysis calculations, the stress distributions in the joints were obtained. Introduction of proposed chamfers is positive because the stresses were reduced and in consequence a larger ultimate strength is observed. Results of both numerical and experimental analysis were finally discussed. Moreover the influence of different end shape of specimens on stress state of joint was also considered.

PL

Niniejsza praca przedstawia wyniki numeryczno-eksperymentalnej analizy naprężeń oraz nośności granicznej zakładkowych połączeń klejowych. W pracy analizowano nietypowy przypadek połączenia, którego elementy składowe posiadały fazę (skos) zlokalizowaną od strony spoiny klejowej. W pracy rozpatrywano połączenia próbek wykonywanych ze stopu aluminium oraz ze stali. W pierwszej części pracy określono na drodze doświadczalnej wartości siły niszczącej dla połączeń z różnym kształtem fazy. Rezultaty badań doświadczalnych wykazały, że wprowadzenie skosu na krawędziach blach (zlokalizowanego od strony spoiny klejowej) znacząco zwiększa nośność połączeń, w szczególności dla łączonych materiałów o niskim module Younga. Przeprowadzona analiza numeryczna wskazała, że dla połączeń z fazą obserwowana jest znaczna redukcja naprężeń zredukowanych oraz tnących w linii środkowej połączenia, co bezpośrednio przekłada się na zwiększenie nośności granicznej.

12

Bezpośrednie i pośrednie wyznaczanie wytrzymałości obliczeniowej stali w konstrukcjach budowlanych

Gosowski B., Organek P., Redecki M.

Materiały Budowlane

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2014

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nr 3

56--59

PL

Przedstawiono metodykę statystycznego wyznaczania obliczeniowych parametrów stali konstrukcji budowlanych z uwzględnieniem rzeczywistej liczby prób. Pokazano, jak to należy zrobić w przypadku przeprowadzenia kilku lub kilkunastu badań niszczących, na podstawie których obliczeniowe parametry wytrzymałościowe wyznacza się bezpośrednio, a także – jak to zrobić w sposób pośredni, przez badania twardości stali sposobem Brinella. Dokonano porównania przedmiotowych parametrów stali otrzymanych bezpośrednio i pośrednio. Sposób pośredni jest polecany w przypadku stali stosowanej w konstrukcjach budowlanych, która występuje z reguły w stanie surowym lub normalizowanym. Artykuł zakończono zaleceniami i wnioskami praktycznymi.

EN

Methodology of determining statistical values for calculated parameters of constructional steel with regard to the actual number of test samples is presented. It was shown how it should be done in case carrying out a dozen or so numbers of destructive tests, according which calculated characteristics are determined directly and also how to do this in an indirect way, through research hardness of the samples in the Brinell scale. The comparison for the parameters obtained directly and indirectly was made. Indirect method is recommended for steel used in building structures, which is generally crude or normalized steel. The papers ends with recommendations and practical conclusions.

13

Determination of the ratinal plank thickness in sawing the zentral zone of pine logs

Ulasovec V.G.

Drewno : prace naukowe, doniesienia, komunikaty

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2004

|

vol. 47, nr 171

69-80

EN

The influence of the anatomic core of a tree with ring-type fractures in the annual ring around it as well as the minimal plank thickness deflection gradient of the core from the geometric centre in the cross-section of a log, cut from the central zone of pine logs in the Urals were investigated. It was established that the likely zone of arising of such fractures includes up to 5 annual rings.

PL

Badano wpływ rdzenia anatomicznego z pęknięciami okrężnymi (wzdłuż przyrostów rocznych) drzew na minimalną strzałkę ugięcia desek (bali) pozyskanych z centralnej części kłód sosnowych pochodzących z Uralu. Stwierdzono, że strefa kłody, w której występuje największe prawdopodobieństwo powstawania pęknięć rdzeniowych, obejmuje do 5 przyrostów rocznych. Więcej pęknięć powstaje w drewnie kłód odziomkowych i środkowych niż wierzchołkowych. Jest to spowodowane zmiennymi obciążeniami działającymi na pień drzewa w trakcie wzrostu. Zaproponowano optymalne grubości desek środkowych, zmniejszające wpływ pęknięć rdzeniowych na wytrzymałość desek.