Wyniki wyszukiwania - BazTech

1

Influence of the tie reinforcement on the development of a collapse caused by the failure of an edge column in RC flat slab system

Buda-Ożóg Lidia, Zięba Joanna, Sieńkowska Katarzyna, Nykiel Damian

Archives of Civil Engineering

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2023

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Vol. 69, nr 1

39--54

EN

RC flat slabs are one of the most popular and effective methods of shaping plates in buildings. Although failures of entire structures are relatively rare, they cannot be excluded from the occupancy cycle of the facility. The research analysis presented in this paper is an attempt to understand more precisely the phenomena that occur in the RC flat slab system and to assess the influence of the additional protection of the flat slabs against progressive collapse in the case of failure of one of the supports. The results were obtained from destructive experimental investigations of a flat reinforced concrete slab made in scale 1:3. The collapse in the analysed model was simulated by removing three edge columns and additional loading by means of hydraulic actuator. In place of the columns removed, differential tie reinforcement was applied. The results obtained confirm that the structure achieved a much higher ultimate load than the one resulting from the design calculations.

PL

Układy słupowo-płytowe są jedną z najbardziej popularnych i efektywnych metod kształtowania płyt w budynkach. Mimo że awarie całych konstrukcji zdarzają się stosunkowo rzadko, nie można ich wykluczyć z cyklu użytkowania obiektu. Przedstawione w niniejszej pracy analizy badawcze są próbą dokładniejszego zrozumienia zjawisk zachodzących w układzie płaskich płyt żelbetowych oraz oceny wpływu zastosowanego dodatkowego zbrojenia płyt przed postępującym zawaleniem w przypadku zniszczenia jednej z podpór. Wyniki uzyskano na podstawie niszczących badań doświadczalnych stropu żelbetowego wykonanego w skali 1:3. W analizowanym modelu symulowano zawalenie się stropu poprzez usunięcie trzech słupów krawędziowych i dodatkowe obciążenie siłownikiem hydraulicznym. W miejsce usuniętych słupów zastosowano zróżnicowane zbrojenie cięgnowe. Uzyskane wyniki potwierdzają, że konstrukcja osiągnęła znacznie większe obciążenie granicznie nośne niż to, które wynikało z obliczeń projektowych.

2

Serviceability of cut slope and embankment under seasonal climate variations

Apriyono Arwan, Yuliana, Kamchoom Viroon

Acta Geophysica

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2023

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Vol. 71, no. 2

983--995

EN

In the next 20 years, there will be an extensive investment in transport infrastructure. Although the cut and embankment slopes seem to have the same appearance, they have different responses to climate variations. Understanding their characteristics and performance is necessary to design a safer and more sustainable slope infrastructure. This paper provides a thorough examination of the seasonal performance of cut slopes and embankments. Furthermore, this study suggests an introduction to the impacts of climate change, amplifying seasonal shrinkage–swelling and progressive failure of slope construction under extreme drought and precipitation. Volumetric water content and pore water pressure fluctuations due to seasonal variation were analysed and compared from both the cut slope and the embankment. Moreover, stress path and slope deformation were also investigated in this study to understand the behaviour of the cut slope and the embankment. The results suggest that the cut slope retains more pore water pressure during the wet season due to its lower permeability than an embankment with respect to the construction history. However, pore water pressure and displacement in the cut slope tend to be increased due to the consolidation process after excavation, which requires more time to reach equilibrium. In addition, greater displacement in the cut slope can increase the possibility of delayed failure in the future.

3

Full‑scale experimental investigation on progressive failure characteristics of shield segmental lining connected through segmental joints containing ductile‑iron joint panels

Zhou Long, Zhu Hehua, Shen Yi, Guan Linxing, Yan Zhiguo, Sun Wei, Li Yaoliang

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 3

art. no. e120

EN

A full-scale experiment was conducted for a deep-buried drainage shield tunnel to be built in Shanghai, focusing on the evolution of mechanical properties and failure process of the segmental lining connected through segmental joints containing ductile-iron joint panels, during the changing process of the inner water pressure and lateral earth pressure. The test results indicate that the damage characteristics of the shield lining are the waterproof failure of the segmental and ring joints, and the concrete cracking failure in the lining. Being diferent from the shield lining without ductile-iron joint panels, the concrete cracks mainly exist around the hand holes of segmental joints. For these kinds of shield tunnel linings containing ductile-iron joint panels, local damage of concrete cracking is prone to occur around the hand holes of segmental joints because of the anchor bars of the joint panels distributed on both sides of the hand holes, and it has a signifcant efect on the lining deformation. In the design of shield linings, efective structural adjustment methods should be adopted to solve this local concrete failure problem.

4

A Hybrid Model of WTC Collapse

Cherepanov G. P., Esparragoza I. E.

International Journal of Applied Mechanics and Engineering

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2008

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Vol. 13, no 2

575-585

EN

A new theory of the WTC collapse is advanced that uses both fracture waves and progressive failure. According to the hybrid theory the WTC collapses ran in two phases: (i) in the first phase dynamic fracture waves disintegrated a considerable part of the towers producing the dust cloud and explosion sound well-documented and well-evidenced, and (ii) in the second phase the progressive failure front disintegrated the lower part of the towers that remained intact in the first phase. To illustrate many possible modes of progressive failure the slowest mode, the fastest mode, and three intermediate modes were first studied and then the hybrid mode was introduced. The hybrid theory allows one to get rid of evident defects of earlier theories and explain all basic facts and observations of the matter not understood before, in particular, why the time of all collapses was free fall time independent of the position of critical floor. An analysis and calculations given in the present paper do not depend on how fracture waves were produced.

5

Experimental and numerical investigation of plywood progressive failure in CT tests

Ivanov I. V., Sadowski T., Filipiak M., Kneć M.

Budownictwo i Architektura

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2008

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vol. 2, nr 1

79-94

EN

The plywood is considered as a layered cross-ply unidirectional fibre reinforced composite. The experimental Compact Tension (CT) tests carried out in different directions of plywood fibre orientation show that the characteristics of damages are fibre bundle rupture, matrix cracking along the fibres, and delamination at the ply interlayers of glue. The plywood CT specimens are modelled by continuum shell and cohesive finite elements with damage evolution in material models. The Finite Element (FE) model simulates the experimental behaviour of plywood samples very well and allows deep investigation of the different types of damage development and interaction. The FE model of plywood is useful for its lay-up optimization and for development of very efficient in large-scale simulations computational models of plywood.

6

Numeryczna i doświadczalna analiza procesu delaminacji struktury kompozytu

Morka A., Niezgoda T., Kiczko A., Gotowicki P.

Zeszyty Naukowe Politechniki Świętokrzyskiej. Nauki Techniczne

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2007

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Z. 4

91-92

PL

Materiały kompozytowe wzbudzają narastające zainteresowanie w zastosowaniu do absorpcji i rozpraszania energii kinetycznej. Uzyskanie stabilnego reżimu progresywnego niszczenia odpowiednio zaprojektowanego kompozytu pozwala na dyssypację stosunkowo dużej ilości energii kinetycznej w odniesieniu do jego masy. Trudność polega na znalezieniu optymalnej konfiguracji oraz uzyskaniu stabilnego procesu progresywnego niszczenia. W pracy przedstawiono próbę teoretycznego modelowania wewnętrznej struktury wielowarstwowego kompozytu z tkaniny szklanej w osnowie epoksydowej. Model ten powinien poprawnie opisywać proces dyssypacji energii kinetycznej w wyniku progresywnego niszczenia materiału kompozytowego. W rozważaniach wzięto pod uwagę trzy mechanizmy odpowiedzialne za absorpcję energii w procesie progresywnego niszczenia struktury kompozytu: delaminacja, zginanie warstw, tarcie (o podłoże, między warstwami kompozytu po delaminacji).

EN

Composite structures arouse growing interest in applying to kinetic energy absorption and dissipation. The stable progressive failure of the properly designed composite lead to dissipation of significant amount of the kinetic energy in relation to the composite mass. The problem rests on the optimum structure configuration and reaching the stable progressive failure stage. It is presented the theoretical model of the internal multilayer composite structure consisted of the glass fabric in epoxy resin matrix. The model should describe in proper way the kinetic energy dissipation process during progressive failure of a composite structure. Three energy absorbing mechanisms were considered: delamination, layers bending, and friction (with the base or/and between composite layers after delamination). The adequate description each of them is the necessary condition for the further study in seeking effective absorbing structures based on composite materials. Presented composite model leads to building primary absorbing elements with complicated shapes where the geometry could have a positive impact on an amount of absorbed energy.