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1

Innowacyjna metoda ciągłego pomiaru odkształceń ściany osłonowej aluminiowo-szklanej oraz opracowanie doświadczalno-numerycznej metody analizy stanu naprężeń w konstrukcji

Rusin Dawid, Juraszek Janusz

Przegląd Budowlany

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2024

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R. 95, nr 3

30--33

PL

W artykule przedstawiono nowatorską metodologię badań oraz monitoringu fasad aluminiowych z wykorzystaniem światłowodowych czujników odkształceń FBG (Fiber Bragg Grating) w budynkach wysokościowych HRB (High-Rise Building). Celem jest wyznaczenie rzeczywistego oddziaływania wiatru na te konstrukcje. Zaproponowane rozwiązania pozwalają na dokładniejsze i bardziej szczegółowe pomiary odkształceń i ugięć niż tradycyjne. Umożliwiają ich monitorowanie nieprzerwanie w długim czasie – dzięki temu możliwe będzie optymalizowanie konstrukcji fasady pod kątem bezpieczeństwa i wpływu na środowisko, a także sprawdzenia jej stanu technicznego. Metoda ta zostanie zastosowana do badań fasady elementowej MB-SE65 firmy Aluprof S.A. Wyniki badań i analiz umożliwią opracowanie nowych wytycznych projektowania fasad aluminiowych. Przedstawiona metodologia ma duży potencjał i może być wykorzystana do badań innych typów konstrukcji aluminiowych.

EN

The article presents a novel methodology for research and monitoring of aluminium facades using FBG (Fiber Bragg Grating) optical strain sensors in high-rise buildings (HRB). The aim is to determine the real impact of wind on these structures. The proposed solutions allow for more accurate and detailed measurements of deformations and deflections than traditional methods. They enable continuous monitoring over long periods of time. This will allow for the optimization of facade design in terms of safety and environmental impact, as well as to verify its technical condition. The method will be applied to the research of the MB-SE65 element facade by Aluprof S.A. The results of the research and analysis will allow for the development of new guidelines for the design of aluminium facades. The presented methodology has a high potential and can be used for research on other types of aluminium structures.

2

Progress in modelling and simulation of the machining process - part II: Mesh-free modelling and simulation

Grzesik Wit

Mechanik

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2024

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R. 97, nr 5-6

6--15

EN

In this paper some rules of mesh-free/meshless modelling and numerical simulations of fundamental physical phenomena associated with the machining process, including mechanisms of plastic deformation, chip formation and interfacial friction are overviewed. Some representative examples of the mesh-free modelling application to material removal processes at different scales, i.e.: machining processes, water jet-assisted processes, additive machining processes and simulation of micromachining processes using predominantly SPH (smoothed particle hydrodynamics) method are given.

PL

W artykule omówiono zasady bezsiatkowego modelowania i symulacji numerycznej podstawowych zjawisk fizycznych towarzyszących procesom obróbki, w tym mechanizmów odkształcania materiału, tworzenia wióra i tarcia. Podano przykłady zastosowania bezsiatkowego modelowania procesów obróbki ubytkowej, m.in.: obróbki skrawaniem, wysokociśnieniową strugą wody (WJM i AWJM) oraz obróbki i symulacji mikroobróbki z użyciem metody SPH (hydrodynamiki wygładzonych cząstek).

3

Progress in modelling and simulation of the machining process - part I: Multiscale modelling

Grzesik Wit

Mechanik

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2024

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R. 97, nr 3

30--37

EN

In this paper some rules of a multiscale modelling and numerical simulations of fundamental physical phenomena associated with the machining process, including mechanisms of plastic deformation, chip formation and interfacial friction are overviewed. Some representative examples of the modelling application to multiphase and composite materials, determination of constants in the material constitutive equations and simulation of nano- and micromachining processes using MD-FEM and SPH-FEM hybrid methods are given.

PL

W artykule omówiono zasady wieloskalowego modelowania i symulacji numerycznej podstawowych zjawisk fizycznych towarzyszących procesowi skrawania, w tym mechanizmów odkształcania materiału, tworzenia wióra i tarcia. Podano przykłady zastosowania modelowania materiałów wielofazowych i kompozytowych, wyznaczania stałych materiałowych w równaniu konstytutywnym oraz symulacji mikro- i nanoobróbki z użyciem hybrydowej metody MD-FEM i SPH-FEM.

4

Numerical simulation of the influencing factors of array jet shock cooling

Zhou Nianyong, Zhou Youxin, Zhao Yingjie, Bao Qingguo, Tang Guanghua, Lv Wenyu

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2024

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Vol. 72, nr 4

art. no. e150200

EN

Array jet impingement cooling is a significant technology of enhanced heat dissipation which is fit for high heat flux flow with large area. It is gradually applied to the cooling of electronic devices. However, The research on the nozzle array mode and the uniformity of the cooling surface still has deficiencies. Therefore, the influence of heat flux, inlet temperature, jet height, array mode, and diversion structure on jet impingement cooling performance and temperature distribution uniformity is analyzed through numerical calculation. The results show that the heat transfer coefficient of jet impingement cooling increases linearly with the increment of heat flux and inlet temperature. With the increment of the ratio of jet height to nozzle diameter (H/d), the heat transfer coefficient increases first and then decreases, that is, there is an optimal H/d, which makes the heat transfer performance of the array jet impact cooling best. The temperature uniformity of array jet impact cooling is greatly affected by array mode. The improvement effect of nozzle array mode on temperature uniformity is ranked as sequential >staggered >shield >elliptical array. The overall temperature uniformity and heat transfer coefficient are increased by 5.88% and 7.29% compared with the elliptical array. The heat transfer performance can be further improved by adding a flow channel to the in-line array layout, in which the heat transfer coefficient is increased by 6.53% and the overall temperature uniformity is increased by 1.45%.

5

A pre-protection method for a pipe-jacking channel over shield tunnels

Cui Yunliang, Yang Xukun, Wang Xinquan, Diao Hongguo, Li Xiao, Gao Yuanyuan

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2024

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Vol. 72, nr 2

art. no. e148443

EN

With the improvement of the planning level of underground space, the location of the planned under-crossing tunnel can be known in advance when constructing the upper-span tunnel. Therefore, pre-protection measures can be taken in advance during the construction of the upper-span tunnel. A new pre-protection method of a pipe-jacking channel was proposed to reduce the adverse effects of under-crossing shield tunnels. Numerical simulations of different pre-protection schemes were carried out using the finite element method to analyze its deformation control effect. The simulation results show that the deformation control effect of the gantry reinforcement scheme is the most significant. It is shown that the displacement of the pipe-jacking channel is more significantly suppressed with pre-protection measures than without preventive protection measures. The vertical displacement curve of the pipe-jacking channel exhibits a “W” shape after the construction of the double-lane shield underpass. By comparing the three different working conditions, it is found that the maximum vertical displacement and surface settlement of the pipe-jacking channel greatly reduced the gantry reinforcement pre-protection. Compared with Case 3, the effect of the pre-protection measures adopted in Case 2 was less obvious, which indicated that the form of the pre-protection had an important influence on controlling the deformation of the pipe-jacking channel.

6

Study on failure modes and calculation method of the cast steel joint with branches in treelike structure

Chen Feng, Sun Yun, Sun Shuxuan, Song Da, Liu Yangbing

Archives of Civil Engineering

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2024

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Vol. 70, nr 1

589--604

EN

The treelike structure links members and transfers loads via its solitary cast steel joint with branches. Therefore, the joint’s bearing capacity significantly affects the treelike structure’s stability, security, and economics. This paper utilized experimental verification and numerical modeling to examine the mechanical behavior of cast-steel joints with branches in the treelike structure under various loading conditions. Then, researchers investigated the failure process and mechanism of joints, and the three most common failure modes were outlined. Furthermore, the researchers proposed the bearing capacity calculation formula based on the common failure modes. The results show that the three common failure modes of the cast-steel joints with branches under different loading conditions are the failure in the joint core area under the axial load, the failure in the main pipe compression side under eccentric load, and the failure in the compression side of the single branch pipe root when the single branch pipe is under the uneven load. The suggested empirical calculation method can serve as a reference point for similar engineering practices design.

7

Safety assessment of the construction of double track tunnels underneah exsiting railway tunnels

Guo Fengfeng, Chen Yupeng, Zhang Yongjie, Feng Qi, Cui Da

Archives of Civil Engineering

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2024

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Vol. 70, nr 1

375--387

EN

The ground disturbance caused by the tunnel construction will inevitably have an impact on the upper part of the constructed tunnel structure, and the railroad tunnel requires a very high level of control over the structural settlement deformation. For the problem of double-hole tunnel under the built tunnel, this paper takes Chongqing Mingyue Mountain Tunnel under the built Shanghai-Rong Railway Paihua Cave tunnel and Zheng-Yu Railway tunnel as the engineering background, and starts from the mechanism of ground loss caused by tunnel excavation, firstly, the settlement at the height of the existing tunnel strata is obtained through theoretical analysis, and the new Mingyue Mountain Tunnel under the Shanghai-Rong Railway tunnel is determined to be a more dangerous section. Further simulate and calculate the dynamic excavation process of the new double-hole tunnel underpass, and study the settlement deformation law of the Mingyue Mountain Tunnel underpassing the Hurong Railway Tunnel. According to the requirements of railroad tunnel for settlement deformation control, the new tunnel is determined to be constructed by step method to ensure the safety of railroad tunnel. The shortcomings of the theoretical calculation are analyzed to illustrate the important role of numerical simulation in the evaluation of tunnel underpass projects.

8

Ground settlement and estimation of maximum settlement value in adjacent foundation pit excavation

Wu Yan

Archives of Civil Engineering

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2024

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Vol. 70, nr 1

605--619

EN

The excavation of adjacent pits following the initial foundation pit excavation can significantly influence ground settlement. Using a foundation pit excavation project in Changzhou as a prototype, this study employed the numerical simulation method in conjunction with the HSS model to analyze the settlement deformation characteristics of the original excavation and compare them with the recorded monitoring values. In this study, the analysis focused on the ground settlement between two pits by varying the spacing between them at different excavation depths. The findings revealed that the ground settlement does not exhibit a significant increase when the new pit is excavated at a shallow depth. However, it rapidly increases when the excavation depth of the new pit surpasses that of the existing pit. Furthermore, an increase in the distance between the two pits causes the maximum settlement position to shift towards the edge of the new pit. The maximum ground settlement is found to have a linear relationship with both the maximum horizontal displacement of the two pits and the spacing between them.

9

Analiza nośności na ścinanie betonowych próbek zespolonych z wrębami w płaszczyźnie zespolenia

Sadowski Grzegorz, Wiliński Piotr, Halicka Anna

Przegląd Budowlany

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2023

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R. 94, nr 5-6

87--92

PL

W pracy przedstawiono badania próbek zespolonych z powierzchnią prefabrykatu z wrębami oraz referencyjnych elementów monolitycznych. Na podstawie wyników badań laboratoryjnych wykonano modele numeryczne, które posłużyły do analizy sposobu zniszczenia złącza. Przeprowadzono analizę porównawczą efektywności złącza badanych elementów z modelami numerycznymi oraz wynikami badań dostępnymi w literaturze. Badania i analizy wykazały, że zniszczenie złącza nastąpiło przez ścięcie wrębów, poprzedzone zerwaniem adhezji w styku. Nośność złącza uzależniona jest od geometrii próbek oraz sposobu ich obciążenia.

EN

The paper presents tests of composite specimens with the indented surface element and reference monolithic elements. Based on the results of laboratory tests, numerical models were made, which were used for further analysis of the interface cracking. A comparative analysis of the effectiveness of the notches of the tested elements with numerical models and the results of research available in the literature was carried out. Testing and analysis showed that the failure of the joint occurred by notch shear, preceded by adhesion rupture at the interface. The bearing capacity of interface between the concrete depends on the specimens’ geometry and the way they are loaded.

10

Research on stability of rock mass and þ30 level surface construction works when re-exploiting the seam H10 at Mong Duong Coal Mine, Vietnam

Vu Tien T., Dao Doan V.

Journal of Sustainable Mining

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2023

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Vol. 22. iss. 2

100--109

EN

The re-exploitation of coal seams located near the ground is one of the solutions to increase output, reduce mining investment costs, and avoid wasting coal resources. The re-exploitation of coal seams will also cause instability of the surrounding rock mass and may affect surface construction works. Through the process of re-exploiting the longwall in seam H10 at Mong Duong Coal Mine, the authors have studied and evaluated the stability of the rock mass and þ30 level surface works (including fan station and gateroad). To achieve the results in this study, the numerical simulation model method and the analytical method were applied. The model analysis results have determined that the displacement and deformation areas of the rock mass around the mining area correspond to the length of the cut in the strike direction of the longwall H10. The analysis and calculation results from the model show that the longwall in seam H10 can be re-exploited when leaving a protective coal pillar about 50 m from the center of the þ30 fan station at the east side; this distance ensures the stability of the rock mass that located near the ground and the surface works at þ30.

11

Numerical simulation of hydrogen storage in the Konary deep saline aquifer trap

Luboń Katarzyna, Tarkowski Radosław

Gospodarka Surowcami Mineralnymi

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2023

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T. 39, z. 3

103--124

EN

Nowadays, hydrogen is considered a potential successor to the current fossil-fuel-based energy. Within a few years, it will be an essential energy carrier, and an economy based on hydrogen will require appropriate hydrogen storage systems. Due to their large capacity, underground geological structures (deep aquifers, depleted hydrocarbon fields, salt caverns) are being considered for hydrogen storage. Their use for this purpose requires an understanding of geological and reservoir conditions, including an analysis of the preparation and operation of underground hydrogen storage. The results of hydrogen injection and withdrawal modeling in relation to the deep Lower Jurassic, saline aquifer of the Konary geological structure (trap) are presented in this paper. A geological model of the considered structure was built, allowable pressures were estimated, the time period of the initial hydrogen filling of the underground storage was determined and thirty cycles of underground storage operations (gas injection and withdrawal) were simulated. The simulations made it possible to determine the essential parameters affecting underground hydrogen storage operation: maximum flow rate of injected hydrogen, total capacity, working gas and cushion gas capacity. The best option for hydrogen storage is a two-year period of initial filling, using the least amount of cushion gas. Extracted water will pose a problem in relation to its disposal. The obtained results are essential for the analysis of underground hydrogen storage operations and affect the economic aspects of UHS in deep aquifers.

PL

Ze względu na bardzo dużą pojemność podziemne struktury geologiczne (głębokie poziomy wodonośne, sczerpane złoża węglowodorów, kawerny solne) są rozważane do magazynowania wodoru. Ich wykorzystanie w tym celu wymaga rozpoznania uwarunkowań geologiczno-złożowych, w tym analizy przygotowania oraz pracy podziemnego magazynu wodoru. Przedstawiono wyniki modelowania zatłaczania i odbioru wodoru do głębokiego dolnojurajskiego poziomu solankowego struktury geologicznej Konary. Zbudowano model geologiczny rozważanej struktury, oszacowano dopuszczalne ciśnienia szczelinowania oraz ciśnienie kapilarne nadkładu, wyznaczono długości wstępnego okresu zatłaczania wodoru do podziemnego magazynu, przeprowadzono modelowanie przebiegu 30-letniej pracy podziemnego magazynu (zatłaczania i odbioru gazu). Przeprowadzone symulacje umożliwiły określenie istotnych parametrów wpływających na prace podziemnego magazynu wodoru: maksymalną wielkość przepływu zatłaczanego wodoru, pojemność całkowitą, pojemność roboczą i wielkość poduszki gazowej. Pozwoliły stwierdzić, że im dłuższy wstępny okres zatłaczania wodoru, tym większą musimy zastosować poduszkę gazową. Za najlepszą opcję dla magazynowania wodoru zaproponowano dwuletni okres wstępnego zatłaczania gazu do struktury; opcja z najmniejszą wielkością poduszki gazowej. Stwierdzono, że ilość wody, jaka jest eksploatowana w trakcie odzyskiwania wodoru, podczas cyklicznej eksploatacji magazynu, spada wraz ze zwiększeniem długości wstępnego okresu zatłaczania wodoru. Eksploatowana woda będzie stanowiła znaczący problem związany z jej unieszkodliwieniem. Otrzymane wyniki są istotne w analizie pracy podziemnego magazynu wodoru i wpływają na aspekty ekonomiczne UHS w głębokich solankowych poziomach wodonośnych.

12

Numerical simulation study on NO oxidation by OH radical clusters in flue gas

Wen Zhengcheng, Zhang Xiaofeng, Huang Ju, Yang Zhengyin

Environment Protection Engineering

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2023

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Vol. 49, nr 3

69--82

EN

Fenton reaction is an important method to remove NO from flue gas. •OH radicals generated in the Fenton reaction can effectively oxidize NO to NO2, which is absorbed and removed by alkali sorbent. To supply guidance for engineering research, numerical simulation of NO oxidation by •OH radical clusters in flue gas has been carried out using Fluent software. The average concentration of NO on the cross sections at various positions of a cylindrical pipe with a circular surface was calculated by simulation. Under various working conditions (temperature, •OH/NO molar ratio, NO concentration in flue gas, and jet velocity), NO oxidation efficiency by •OH radical was simulated and the key factors affecting NO oxidation were analyzed. The results show that temperature and •OH/NO molar ratio are the key factors affecting the oxidation of NO by •OH radicals. The injection velocity has also a significant effect on the oxidation efficiency while the moisture and oxygen content are minor factors influencing the process. The optimum oxidation efficiency of NO is obtained at 473–523 K, the molar ratio of •OH/NO ca. 1.4, the jet velocity 10 m/s, and the flue gas velocity of 3 m/s.

13

Impact of thermal backfill parameters on current-carrying capacity of power cables installed in the ground

Szultka Seweryn, Czapp Stanisław, Tomaszewski Adam

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2023

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Vol. 71, nr 3

art. no. e145565

EN

Proper design of power installations with the participation of power cables buried in homogeneous and thermally well-conductive ground does not constitute a major problem. The situation changes when the ground is non-homogeneous and thermally low-conductive. In such a situation, a thermal backfill near the cables is commonly used. The optimization of thermal backfill parameters to achieve the highest possible current-carrying capacity is insufficiently described in the standards. Therefore, numerical calculations based on computational fluid dynamics could prove helpful for designers of power cable lines. This paper studies the influence of dimensions and thermal resistivity of the thermal backfill and thermal resistivity of the native soil on the current-carrying capacity of power cables buried in the ground. Numerical calculations were performed with ANSYS Fluent. As a result of the research, proposals were made on how to determine the current-carrying capacity depending on the dimensions and thermal properties of the backfill. A proprietary mathematical function is presented which makes it possible to calculate the cable current-carrying capacity correction factor when the backfill is used. The research is expected to fill the gap in the current state of knowledge included in the provisions of standards.

14

Damage and stability analysis of sandstone-type uranium ore body under physical and chemical action of leaching solution

Liu Yulong, Huang Lei, He Guicheng, Hu Nan, Zhou Shuhui, Yu Qing, Ding Dexin

Archives of Mining Sciences

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2023

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Vol. 68, no. 3

409--423

EN

In this paper, the typical sand-conglomerate uranium ore in north China was taken as the research object. The uniaxial compression and tensile tests of sand-conglomerate specimens under natural status and acidic solution status were used to research the compressive strength, tensile strength, Young’s modulus, cohesion and internal friction angle. Focusing on this type of uranium deposit, during the underground design of the in-situ leaching mining method, the three-dimensional finite element method was used to conduct a numerical simulation of the liquid collecting tunnel with different structural parameters of 10 m×2 m, 3 m×2 m, 2 m×2 m, and comprehensively analyse the vertical displacement, principal stress and plastic deformation zone changes of the tunnelbefore and after leaching. Based on the results, influenced by an acidic aqueous solution, the grain of the conglomerate became soft and secondary pores appeared, resulting in the superimposed effect of physical damage and chemical damage. Macroscopically, an obvious decrease was witnessed in mechanical property. Based on the stability and economy factor of three scenarios before and after leaching, the scenario was recommended as the experimental testing scenario, specifically, two longitudinal collecting tunnel were arranged along the strike of the orebody, with the size of 3 m×2 m and the width of the middle pillar of 4 m. The results of the numerical simulation are significant in guiding the design of underground in-situ leaching technology and determining the structural parameters of the deposit.

15

Quantitative Prediction of Air Entrainment Defects in Casting Filling Process

Yin Yajun, Xie Yao, Song Yingchen, Shen Xu, Ji Xiaoyuan, Zhou Jianxin

Archives of Foundry Engineering

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2023

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Vol. 23, iss. 4

117--126

EN

Air entrainment defect is a common type of defect in the casting process, which will seriously affect the quality of the casting. Numerical simulation technology can predict the occurrence of casting defects according to the evolution law of liquid metal in the process of filling and solidification. The simulation of air entrainment process is a hot and difficult issue in the field of numerical simulation. The evolution law of air entrainment and the tracking of induced bubbles in the process of metal filling are still lacking. So is the quantitative prediction of trained gas. In this paper, based on the numerical simulation software of Inte CAST, this paper proposes an algorithm for air entrainment search and tracking, which is used to develop a quantitative prediction system for air entrainment. The feasibility of the system is verified through the simulation calculation of the typical test pieces of the air entrainment and the prediction of air entrainment defects of the casting in the process of filling is obtained through the simulation calculation of the actual casting, which can provide a certain guiding role for the optimization of the process in the production practice.

16

Uniaxial compression test and numerical simulation of rock-like specimen with T-Shaped cracks

Liangxiao Xiong, Chen Haijun, Xu Zhongyuan, Hu Deye

Archives of Civil Engineering

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2023

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Vol. 69, nr 2

227--244

EN

In this study, the uniaxial compression test and PFC2D numerical simulation were carried out on the artificial rock specimen with T-shaped prefabricated fractures. The effects of the lengths l1, l2 of the main fractures, the length l3 of the secondary fracture, and the angle β between the secondary fracture and the loading direction on the uniaxial compressive strength and crack evolution law of specimen were studied. The research results show that the change of l1, l2 and β has obvious effect on the compressive strength and crack growth of the specimen, but the change of l3 has little effect on the compressive strength of the specimen. When l3 = 40 mm and l1 ≠ l2, the angle β influences on the crack propagation and failure mode of the specimen.

17

Refined energy method for the elastic flexural-torsional buckling of steel H-section beam-columns. Part II: Comparison and verification for elements LTU and LTR

Giżejowski Marian, Barszcz Anna, Wiedro Paweł

Archives of Civil Engineering

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2023

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Vol. 69, nr 2

265--289

EN

In investigations constituting Part I of this paper, the effect of approximations in the flexural-torsional buckling analysis of beam-columns was studied. The starting point was the formulation of displacement field relationships built straightforward in the deflected configuration. It was shown that the second-order rotation matrix obtained with keeping the trigonometric functions of the mean twist rotation was sufficiently accurate for the flexural-torsional stability analysis. Furthermore, Part I was devoted to the formulation of a general energy equation for FTB being expressed in terms of prebuckling stress resultants and in-plane deflections through the factor k1. The energy equation developed there was presented in several variants dependent upon simplified assumptions one may adopt for the buckling analysis, i.e. the classical form of linear eigenproblem analysis (LEA), the form of quadratic eigenproblem analysis (QEA) and refined (non-classical) forms of nonlinear eigenproblem analysis (NEA), all of them used for solving the flexural-torsional buckling problems of elastic beam-columns. The accuracy of obtained analytical solutions based on different approximations in the elastic flexural-torsional stability analysis of thin-walled beam-columns is examined and discussed in reference to those of earlier studies. The comparison is made for closed form solutions obtained in a companion paper, with a scatter of results evaluated for k1 = 1 in the solutions of LEA and QEA, as well as for all the options corresponding to NEA. The most reliable analytical solution is recommended for further investigations. The solutions for selected asymmetric loading cases of the left support moment and the half-length uniformly distributed span load of a slender unrestrained beam-column are discussed in detail in Part II. Moreover, the paper constituting Part II investigates how the buckling criterion obtained for the beam-column laterally and torsionally unrestrained between the end sections might be applied for the member with discrete restraints. The recommended analytical solutions are verified with use of numerical finite element method results, considering beam-columns with a mid-section restraint. A variant of the analytical form of solutions recommended in these investigations may be used in practical application in the Eurocode’s General Method of modern design procedures for steelwork.

PL

W I części niniejszej pracy zastosowano różne rodzaje aproksymacji w analizie wyboczenia giętno-skrętnego elementów ściskanych i zginanych w płaszczyźnie większej bezwładności przekroju. Punktem wyjścia było sformułowanie zależności na pole przemieszczeń w konfiguracji odkształconej. Pokazano, że macierz rotacji, otrzymana przy zachowaniu funkcji trygonometrycznych średniego kąta skręcenia, jest wystarczająco dokładna do analizy stateczności giętno-skrętnej. Szczególną uwagę zwrócono w Części I na sformułowanie ogólnego równania energetycznego dla FTB, wyrażonego w funkcji sił przekrojowych na podstawowej ścieżce równowagi, przed utratą płaskiej postaci zginania II rzędu, a także wpływu efektu ugięć w płaszczyźnie większej bezwładności przekroju, wyrażonego za pomocą współczynnika k1. Otrzymane równanie energetyczne zostało przedstawione w kilku wariantach zależnych od założeń upraszczających, jakie można przyjąć do rozwiązywania problemów wyboczenia giętno-skrętnego, tj. w postaci klasycznej analizy liniowego problemu własnego (LEA), w postaci kwadratowego problemu własnego (QEA) oraz w postaci udoskonalonej (nieklasycznej) analizy nieliniowego problemu własnego (NEA). W części II, w pierwszej kolejności, została zbadana i dyskutowana dokładność otrzymanych rozwiązań analitycznych w odniesieniu do propozycji przedstawionych we wcześniejszych opracowaniach. Przeprowadzone są też porównania dla rozwiązań w postaci zamkniętej uzyskanych w Części I, z oceną rozrzutu wyników, po przyjęciu k1 = 1 w rozwiązaniach odpowiadających LEA i QEA, a także wszystkich opcji w rozwiązaniach odpowiadających NEA. Do dalszych badań rekomendowano najbardziej wiarygodne rozwiązanie analityczne. Szczegółowej weryfikacji poddano rozwiązania uzyskane dla wybranych asymetrycznych przypadków obciążenia: momentem na lewej podporze i równomiernie rozłożonym obciążeniem w połowie długości nieusztywnionego, smukłego elementu ściskanego i zginanego. Ponadto w Części II zbadano, w jaki sposób kryterium wyboczeniowe, uzyskane dla elementu ściskanego i zginanego bez usztywnień poprzecznych i przeciwskrętnych między przekrojami końcowymi, może być zastosowane dla elementu z dyskretnymi stężeniami poprzecznymi. Zalecane rozwiązania analityczne zweryfikowano z wykorzystaniem wyników numerycznych metody elementów skończonych dla elementów stężonych w przekroju środkowym. Wariant analitycznej postaci rozwiązania zalecanego w zaprezentowanych badaniach może być wykorzystany w praktyce w eurokodowej Metodzie Ogólnej (GM).

18

Experimental study on the dynamic tensile mechanical properties of marble under water and oil conditions

Li Chaoxin, Liu Dongyan, Zhu Yunhui

Archives of Civil Engineering

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2023

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Vol. 69, nr 3

317--330

EN

To investigate the dynamic tensile properties and energy dissipation characteristics of marble in three different conditions: dry, water-saturated, and oil-saturated, a Brazilian disk splitting test was conducted using a 50 mm diameter Hopkinson pressure bar (SHPB) device. The findings indicate that the peak strain and dynamic tensile strength of the three conditions increase with strain rate, exhibiting a clear strain rate effect. Additionally, lubricating effects of water and oil weaken internal shear sliding friction, thus promoting crack expansion. Furthermore, immersion of fluid in marble weakens the cementation of internal mineral particles, leading to lower tensile strength of marble saturated with water and oil compared to dry marble under dynamic impact. When analyzing the energy dissipation of marble, both the absorption energy and dissipation energy density increase with oil strain rate, indicating a positive correlation. Moreover, numerical results obtained from ANSYS/LS-DYNA correspond well with experimental data, thus verifying and interpreting the experimental outcomes.

19

Buckling resistance of metal columns with smoothly variable cross sections

Błażejewski Paweł, Klekiel Tomasz, Kołodziej Sebastian, Marcinowski Jakub, Sakharov Volodymyr

Archives of Civil Engineering

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2023

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Vol. 69, nr 3

613--628

EN

Metal columns of hollow and smoothly variable cross-sections, simply supported at their ends are considered in the paper. Columns of such shapes are recently frequently designed by architects in public utility buildings of various types. In this work authors present the comparatively simple method of buckling resistance assessment which can be used by designers of metal columns of such shapes. The formula on critical force required in the procedure was derived for columns of variable cross section by means of Mathematica™ system. The closed formulae were obtained for a rod with a certain, predefined geometry being the surface of revolution. Critical forces obtained by means of derived formulae were compared with results of numerical solutions. To assess the compression resistance of considered rods the general Ayrton-Perry approach was applied and bow imperfection with assumed amplitude was used in the analysis. Results of numerical simulations and experimental tests inserted in the paper confirm the correctness and the effectiveness of the proposed procedure of buckling resistance assessment of considered struts.

PL

Przedmiotem rozważań zaprezentowanych w artykule są słupy metalowe o przekroju pierścieniowym zmiennym wzdłuż ich osi wzdłużnej i swobodnie podpartych na końcach. Słupy tego kształtu są ostatnio często projektowane przez architektów w różnego typu obiektach użyteczności publicznej. Relatywnie prosty sposób oszacowania nośności wyboczeniowej słupów rozważanego kształtu został zaprezentowany przez autorów pracy. Wzór na siłę krytyczną niezbędną do oszacowania nośności wyboczeniowej został wyprowadzony z wykorzystaniem systemu Mathematica™. Zamknięte wzory na siły krytyczne zostały wyprowadzone dla pewnej klasy prętów o wstępnie zdefiniowanej geometrii stanowiącej powierzchnię obrotową. Siły krytyczne otrzymane z pomocą wyprowadzonych wzorów były porównane z wynikami symulacji numerycznych. Aby oszacować nośność wyboczeniową zastosowano ogólne podejście Ayrton-Perry’ego i wstępne wygięcie łukowe prętów o założonych różnych amplitudach. Wyniki symulacji numerycznych i badań eksperymentalnych zamieszczone w pracy potwierdziły poprawność i efektywność zaproponowanej metody szacowania nośności wyboczeniowej rozważanych prętów.

20

Theoretical and experimental analysis of guided wave propagation in plate-like structures with sinusoidal thickness variations

Zima Beata, Moll Jochen

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 1

art. no. e34, 2023

EN

Guided waves have attracted significant attention for non-destructive testing (NDT) and structural health monitoring (SHM) due to their ability to travel relatively long distances without significant energy loss combined with their sensitivity to even small defects. Therefore, they are commonly used in damage detection and localization applications. The main idea of incorporating guided waves in NDT and SHM is based on processing the received signals and appropriate interpretation of their characteristics. A great amount of research devoted to diagnostics of plate-like structures considers specimens with constant thickness, which significantly facilities the diagnostic process. In such a case the velocity is also assumed to be constant. However, the developed diagnostic methods should be applicable, especially for the structures exposed to an aggressive environment, excessive load, or unfavorable weather conditions, etc., when the probability of damage occurring is much higher. In such cases, the assumption about the uniform thickness alongside the propagation path cannot be applied in every case. Thus, the present study is focused on wave propagation in metallic plates with variable thickness. The results of theoretical, numerical and experimental investigations of antisymmetric Lamb mode propagation in aluminum plates with a sine-shaped surface are presented. In the first step, the influence of non-uniform thickness distribution on wave velocity has been described. Next, the inverse problem aimed at shape reconstruction based on time of flight (ToF) analysis and spatially varying wave velocity was solved and compared with the standard dispersion curve-fitting method.