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Journal articles on the topic 'Tubes][Structural collapse'

Author: Grafiati

Published: 4 June 2021

Last updated: 1 February 2022

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1

Mai, S. P., and N. A. Fleck. "Reticulated tubes: effective elastic properties and actuation response." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 465, no. 2103 (2008): 685–708. http://dx.doi.org/10.1098/rspa.2008.0328.

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The structural performance is explored for a reticulated circular tube made from a periodic lattice: triangulated; hexagonal; Kagome; and square lattices. The finite-element (FE) method is used to determine the macroscopic bending, torsional and axial rigidities of each tube. Additional insight is obtained by examining the structural mechanics of the pin-jointed version of each topology. For all pin-jointed lattices considered, no states of self-stress exist. However, collapse mechanisms do exist for all reticulated tubes, and for the Kagome and hexagonal lattices some of these mechanisms produce macroscopic generalized strain. These strain-producing collapse modes are additional to those observed in the planar version of these lattices. Consequently, the structural rigidities of tubes with walls made from the rigid-jointed Kagome lattice or hexagonal lattice are less than those predicted from the in-plane effective properties of these two lattices. The morphing capacity of reticulated tubes is also explored by replacing a single bar with an actuator in the FE simulations. The actuation stiffness of the structure is defined by the stiffness of the reticulated tube in resisting extension by the actuated bar. The actuation stiffness is explored as a function of the type of lattice, number of unit cells around the circumference, orientation of the actuated bar and of the bar stockiness. In all cases, the macroscopic shape change of the tube can be idealized as a combination of a local rotation, axial extension, axial twist and shear displacement of the cross-section.

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2

Alkhatib, Sami E., Faris Tarlochan, and Arameh Eyvazian. "Collapse behavior of thin-walled corrugated tapered tubes." Engineering Structures 150 (November 2017): 674–92. http://dx.doi.org/10.1016/j.engstruct.2017.07.081.

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3

Elchalakani, Mohamed, Raphael Grzebieta, and Xiao-Ling Zhao. "Plastic Collapse Analysis of Slender Circular Tubes Subjected to Large Deformation Pure Bending." Advances in Structural Engineering 5, no. 4 (2002): 241–57. http://dx.doi.org/10.1260/136943302320974617.

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This paper presents a plastic mechanism analysis for thin-walled circular hollow section (CHS) tubes deforming in a multi-lobe or diamond collapse mode under large deformation pure bending. The fold formation process was such that the shell curvature flattened on the compression side transforming into a definite number of flat triangles attached to each other. The collapse proceeded progressively by folding about the base and sides of these triangular planes and over traveling hinge lines. The collapse mechanism was similar to the diamond crush mode. An existing kinematic model for an axially compressed thin-walled circular tube was modified to predict the collapse curve of a thin-walled tube under bending. Inextensional deformation and rigid plastic material behaviour were assumed in the derivation of the deformation energy. Ovalisation was observed during the test and its deformation energy was determined and found significant. An expression for the plastic collapse moment was obtained by equating the total energy absorbed in bending, rolling and ovalisation to the external work carried out during a given cycle of deformation. Comparisons of the predicted post-buckling moments and slopes of the collapse curves with those obtained from experiments carried out by the authors on cold-formed circular hollow sections show very good agreement.

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4

Veillette, J. R., and J. F. Carney. "Collapse of braced tubes under impact loads." International Journal of Impact Engineering 7, no. 2 (1988): 125–38. http://dx.doi.org/10.1016/0734-743x(88)90021-8.

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5

Subramaniyan, S. Kanna, Shahruddin Mahzan, Mohd Imran Ghazali, Ahmad Mujahid Ahmad Zaidi, and Prasath Kesavan Prabagaran. "Energy Absorption Characteristics of Polyurethane Composite Foam-Filled Tubes Subjected to Quasi-Static Axial Loading." Applied Mechanics and Materials 315 (April 2013): 872–78. http://dx.doi.org/10.4028/www.scientific.net/amm.315.872.

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Foam-filled enclosures are very common in structural crashworthiness to increase energy absorption. However, very less research has been targeted on potential use of natural/recycled material reinforced foam-filled tubes. Therefore, an experimental investigation was performed to quantify energy absorption capacity of polyurethane (PU) composite foam-filled circular steel tubes under quasi-static axial loading. The thickness of the tubes was varied from 1.9, 2.9 and 3.6 mm. The tubes were filled with PU composite foam. The PU composite foam was processed with addition of kenaf plant fiber and recycled rubber particles that were refined at 80 mesh particulates into PU system. The density of PU resin was varied from 100, 200 and 300 kgm-3. The PU composite foam-filled tubes were crushed axially at constant speed in a universal testing machine and their energy absorption was characterized from the resulting load-deflection data. Results indicate that PU composite foam-filled tubes exhibited better energy absorption capacity than those PU foam-filled tubes and its respective empty tubes. Interaction effect between the tube and the foam and incorporation of filler into PU system led to an increase in mean crushing load compared to that of the unfilled PU foam or tube itself. Relatively, progressively collapse modes were observed for all tested tubes. Findings suggested that composite foam-filled tubes could be used as crashworthy member.

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6

Kim, Dae Yun, You Na Lee, Joon Han Kim, Yonghee Kim, and Young Soo Yoon. "Applicability of Swaging as an Alternative for the Fabrication of Accident-Tolerant Fuel Cladding." Energies 13, no. 12 (2020): 3182. http://dx.doi.org/10.3390/en13123182.

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We suggest an alternative to conventional coating methods for accident-tolerant fuel (ATF) cladding. A Zircaloy-4 tube was inserted into metal tubes of different materials and the inserted tubes were subjected to physical force at room temperature. The manufactured tube exhibited a pseudo-single tube (PST) structure and had higher thermal stability than a Zircaloy-4 tube. Optical microscopy and scanning electron microscopy images showed that the PST had a uniform and well-bonded interface structure, i.e., no gaps or voids were found at the interface between the inner and outer tubes. Energy-dispersive X-ray spectroscopy analysis confirmed that the metal components did not interdiffuse at the interface of the PST, even after being kept at 600 and 900 °C for 1 h and rapidly cooled to room temperature. Unlike pure Zircaloy-4 tubes, Zircaloy-4/stainless use steel (SUS) 316 PST did not show significant structural collapse, even after being stored at 1200 °C for 1 h. Based on these results, if a PST was fabricated using a Zircaloy-4 tube thinner than the Zircaloy-4 tube used in this study and an outer tube of micron-scale thickness, swaging may be a feasible alternative to Zircaloy-4-based ATF cladding.

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7

YASUI, Yoshiaki, Shigeru WADA, and Tsuneo IMAI. "521 Impact Collapse Characteristic of Thin-walled Structural Tubes with Various Reinforced Ribs." Proceedings of Autumn Conference of Tohoku Branch 2005.41 (2005): 217–18. http://dx.doi.org/10.1299/jsmetohoku.2005.41.217.

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8

Tang, D. S., L. C. Chen, L. J. Wang, et al. "Behavior of carbon nanotubes under high pressure and high temperature." Journal of Materials Research 15, no. 2 (2000): 560–63. http://dx.doi.org/10.1557/jmr.2000.0083.

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The structural changes of carbon nanotubes induced by high pressure and high temperature were investigated by means of x-ray diffraction, Raman scattering, scanning electron microscopy, and transmission electron microscopy. It is shown that, with increasing pressure and temperature, the lattice constant d002 of tubes shortens, and then tubes collapse into tapelike ones; at the same time the C–C bonds at high curvature break, which lead the tapelike tubes to break into graphite sheets as diamond crystallization centers. Compared with graphite, the diamond particles from carbon nanotubes have many defects as the trace of tubes.

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9

Park, M. S., and B. C. Lee. "Prediction of Mode Parameters and Moment-Rotation Curves for Crushed Thin-Walled Trapezoidal Tubes in Bending." Journal of Applied Mechanics 63, no. 2 (1996): 453–59. http://dx.doi.org/10.1115/1.2788889.

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In the context of kinematic models, a general procedure for the bending crush analysis of thin-walled members is proposed and applied to the trapezoidal and rectangular tubes in bending. The main emphasis of this study is given to the determination of collapse mode parameters and the prediction of post-collapse behaviors of the structural member. The mode shapes are determined by minimizing plastic energy rate of the members. Moment-rotation curves are obtained by differentiating the absorbed plastic energy with respect to the rotation angle. For small rotation angles the solution is modified by considering elastic buckling and plastic collapse moments. Through several examples a full range of post-collapse response of the thin-walled members is shown to be effectively calculated by the proposed method without making any recourse to experimental data.

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10

Gupta, N. K., and S. K. Sinha. "Transverse collapse of thin-walled square tubes in opposed loadings." Thin-Walled Structures 10, no. 3 (1990): 247–62. http://dx.doi.org/10.1016/0263-8231(90)90067-9.

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11

Qiao, Chuan, Yuli Chen, Shengtao Wang, Kuijian Yang, and Xinming Qiu. "Theoretical analysis on the collapse of dumbbell-shaped tubes." International Journal of Mechanical Sciences 123 (April 2017): 20–33. http://dx.doi.org/10.1016/j.ijmecsci.2017.01.031.

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12

Francisco, Alexandre Santos, and Tiago Simões. "A Bayesian updating of crack distributions in steam generator tubes." VETOR - Revista de Ciências Exatas e Engenharias 30, no. 2 (2021): 33–44. http://dx.doi.org/10.14295/vetor.v30i2.13067.

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The structural failure of steam generator tubes is a common problem that can a ect the availability and safety of nuclear power plants. To minimize the probability of occurrence of failure, it is needed to implement maintenance strategies such as periodic nondestructive inspections of tubes. Thus, a tube is repaired or plugged whenever it has detected a crack which a threshold size is overtaken. In general, uncertainties and errors in crack sizes are associated with the nondestructive inspections. These uncertainties and errors should be appropriately characterized to estimate the actual crack distribution. This work proposes a Bayesian approach for updating crack distributions, which in turn allows computing the failure probability of steam generator tubes at current and future times. The failure criterion is based on plastic collapse phenomenon, and the failure probability is computed by using the Monte-Carlo simulation. The failure probability at current and future times is in good agreement with the ones presented in the literature.

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13

Boria, S., S. Pettinari, and F. Giannoni. "Theoretical analysis on the collapse mechanisms of thin-walled composite tubes." Composite Structures 103 (September 2013): 43–49. http://dx.doi.org/10.1016/j.compstruct.2013.03.020.

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14

CORRADI, LEONE, LELIO LUZZI, and FULVIO TRUDI. "PLASTICITY-INSTABILITY COUPLING EFFECTS ON THE COLLAPSE OF THICK TUBES." International Journal of Structural Stability and Dynamics 05, no. 01 (2005): 1–18. http://dx.doi.org/10.1142/s0219455405001428.

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The imperfection sensitivity of cylindrical shells under external pressure is studied, focusing attention on tubes of considerable thickness, such as those to be employed for very deep water pipe lines or in some innovative nuclear power plant proposals. In such tubes collapse is dominated by yielding, but the decreasing nature of the post-collapse evolution makes the effects of interaction with instability significant enough to demand consideration. On the other hand, available theories assessing the imperfection sensitivity of thin shells do not apply in this context and empirical design formulas used for the medium-thick tubes typical of present oil industry applications are extremely conservative. The interaction phenomenon becomes inherently different as thickness increases, and its correct description appears a must in view of a rational assessment of the load bearing capacity. This paper is intended as a first step in this direction.

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15

AI-Hassani, S. T. S., and B. Vartdal. "Investigation into the effect of circumferential through-wall slits on a cantilevered pipe subjected to a transverse end load." Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering 212, no. 3 (1998): 163–70. http://dx.doi.org/10.1243/0954408981529385.

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The main motive for carrying out the investigation is to explore the possibility of using slits to weaken the main legs of an offshore jacket structure as a means of creating a structural mechanism that facilitates safe and predictable toppling of offshore platforms. Cantilevered mild steel tubes containing through-wall circumferential slits are subjected to a transverse end load which causes the slit to open by hoop cracking. The effect of the slit geometry on the collapse characteristics of the tube is investigated experimentally and theoretically. A number of methods are used to predict the global load-deflection characteristics of the tube. These include a number of semiempirical methods based on the J integral and a numerical analysis utilizing the ABAQUS finite element code. The effective net section stress criterion is also used as a simple method of predicting the collapse load. This investigation has relevance to safety in chemical and nuclear plants.

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16

Paruka, Perowansa, Mohd Hafizil Mat Yasin, Rizalman Mamat, Md Abdul Maleque, and Md Kamal Md Shah. "Performance Properties of Hybrid Aluminium–Composite Columnar Tube under Axial Crush Force." Advanced Materials Research 1115 (July 2015): 288–91. http://dx.doi.org/10.4028/www.scientific.net/amr.1115.288.

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This paper presents an experimental work on the influence of number of layers in the overwrap hybrid composite columnars under repeated axial crush force. The columnar test specimens were fabricated by hand lay–up process using commercial available of 0/90° ply oriented epoxy-glass fiber mats. In determining the energy absorption capacity, three different columnar tubes were prepared using one-layer, two-layers and three-layers in order to determine the utilize of such fibers in structural automotive applications. Quasi-static crush test for these tubes was carried out using Instron machine with axial loading. Results showed that the axial crush force and the numbers of layers influenced the level of energy absorption before structures collapse. It is found that the initial peak crush force, mean crush force, crush force efficiency and energy absorption properties of the collapsed hybrid composite columnars were increased by adding of layers in the overwrap thickness.

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17

Alkhatib, Sami E., Faris Tarlochan, Ahmed Hashem, and Sadok Sassi. "Collapse behavior of thin-walled corrugated tapered tubes under oblique impact." Thin-Walled Structures 122 (January 2018): 510–28. http://dx.doi.org/10.1016/j.tws.2017.10.044.

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18

Bai, Jiantao, Guangwei Meng, Hong Wu, and Wenjie Zuo. "Bending collapse of dual rectangle thin-walled tubes for conceptual design." Thin-Walled Structures 135 (February 2019): 185–95. http://dx.doi.org/10.1016/j.tws.2018.11.014.

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19

YASUI, Yoshiaki, Takahiro FUKATSU, and Masaharu ISHIGAMI. "1502 Impact Collapse Characteristics of Rib Reinforcement Thin-walled Structural Tubes under Oblique Impact Loading." Proceedings of The Computational Mechanics Conference 2007.20 (2007): 225–26. http://dx.doi.org/10.1299/jsmecmd.2007.20.225.

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20

Silva, Welington V., Ramon Silva, Luciano M. Bezerra, Cleirton A. S. Freitas, and Jorge Bonilla. "Experimental Analysis of Space Trusses Using Spacers of Concrete with Steel Fiber and Sisal Fiber." Materials 13, no. 10 (2020): 2305. http://dx.doi.org/10.3390/ma13102305.

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Space trusses are structural systems, generally made of tubes, used worldwide because of their advantages in covering long-span roofs. In addition to having a low cost, the truss weight is relatively reduced. The load capacity of these structures depends also on the strength of their node connection. Connections made with the superposition of flattened tube ends trespassed by one bolt are, generally, known as typical nodes. They are inexpensive but present eccentricities that reduce significantly the strength of such space trusses. To increase the truss load capacity, this research presents the results of an experimental program to reduce the eccentricities of the typical nodes. This reduction is done with a new type of spacer made of encapsulated concrete with steel fiber or sisal fiber. The experimental tests showed that the trusses with typical nodes collapsed under reduced load by local failure due to high distortions at the nodes. The trusses with encapsulated concrete spacer showed good results, with an increase in collapse load of 36% and failure by buckling bars.

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21

Zhang, Xiong, Hui Zhang, and Kehua Leng. "Experimental and numerical investigation on bending collapse of embedded multi-cell tubes." Thin-Walled Structures 127 (June 2018): 728–40. http://dx.doi.org/10.1016/j.tws.2018.03.011.

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22

Rossi, A., Z. Fawaz, and K. Behdinan. "Numerical simulation of the axial collapse of thin-walled polygonal section tubes." Thin-Walled Structures 43, no. 10 (2005): 1646–61. http://dx.doi.org/10.1016/j.tws.2005.03.001.

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23

Mamalis, A. G., D. E. Manolakos, M. B. Ioannidis, and D. P. Papapostolou. "The static and dynamic axial collapse of CFRP square tubes: Finite element modelling." Composite Structures 74, no. 2 (2006): 213–25. http://dx.doi.org/10.1016/j.compstruct.2005.04.006.

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24

Mahmoud, Abdullah, Shahabeddin Torabian, Angelina Jay, et al. "Modeling the Flexural Collapse of Thin-Walled Spirally Welded Tapered Tubes." Journal of Structural Engineering 144, no. 2 (2018): 04017201. http://dx.doi.org/10.1061/(asce)st.1943-541x.0001950.

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25

Robinson, M. "The application of stress resultant theory for incremental collapse of thin tubes." International Journal of Mechanical Sciences 33, no. 10 (1991): 805–14. http://dx.doi.org/10.1016/0020-7403(91)90003-l.

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26

Choi, Ju Ho, In Young Yang, and Woo Chae Hwang. "A Study on the Collapse Characteristics of CFRP Circular Member According to Collision Energy Conditions." Key Engineering Materials 535-536 (January 2013): 361–64. http://dx.doi.org/10.4028/www.scientific.net/kem.535-536.361.

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Vehicle structure must be lightweight in order to improve fuel-efficiency and reducing exhaust fumes. The most important goals in designing automobile are safety and environment-friendliness. There are lots of studies on the crushing absorption energy of a structural members in automobile. The crashworthy behavior of circular composite material tubes subjected to axial compression under same conditions is reported in this paper. Energy absorption of CFRP circular member is affected by lamination conditions. Test was executed in order to compare the results to the energy absorption and collapse shape.

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27

Zhang, Jianxun, Yang Ye, Jianfeng Li, et al. "Dynamic collapse of circular metal foam core sandwich tubes in splitting and curling mode." Thin-Walled Structures 161 (April 2021): 107464. http://dx.doi.org/10.1016/j.tws.2021.107464.

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28

Seo, Ji Hye, Deok Hee Won, Woo Sun Park, and Seung Jun Kim. "Buckling Behavior of Circular Steel Tubes under Fire." Key Engineering Materials 763 (February 2018): 270–78. http://dx.doi.org/10.4028/www.scientific.net/kem.763.270.

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Recently, several lives were lost because of the collapse of structures under fire. Steel members are mainly used in the columns and beams of buildings for improving construction efficiency. The fire resistance of steel structure is very important because when it don’t have fire resistive covering, it rapidly changes with high temperature. In fire resistance design of steel, steel structure must have fire resistive covering. But many facilities as temporary facilities, parking lot don’t have it. The buckling behavior of steel structures under fire is also significant because it can cause local buckling failure through the reduction in structural material properties by temperature. In this study, the elastic buckling behavior of a circular steel tube under fire was investigated using finite element analysis. The parameters for this analysis used were, diameter–thickness ratio, fire exposure area, and fire scenarios. The elastic buckling strength of circular steel tube rapidly decreased when subjected to the fire curve. Local buckling occurred and this can lead to global failure. When fire resistance design of circular steel tube was performed, buckling behavior must be considered.

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29

Gupta, N. K., G. S. Sekhon, and P. K. Gupta. "A study of fold formation in axisymmetric axial collapse of round tubes." International Journal of Impact Engineering 27, no. 1 (2002): 87–117. http://dx.doi.org/10.1016/s0734-743x(01)00041-0.

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30

Mamalis, A. G., D. E. Manolakos, G. A. Demosthenous, and W. Johnson. "Axial plastic collapse of thin bi-material tubes as energy dissipating systems." International Journal of Impact Engineering 11, no. 2 (1991): 185–96. http://dx.doi.org/10.1016/0734-743x(91)90005-z.

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31

Guan, Zhi Zhong, Jia Qi Ge, Bo Tao Ma, Ling Zhang, Ming Zhu Wang, and Man Sheng Zhang. "Performance-Based Design and Table Test Study on Hybrid Structure Combined with outside Steel Grid and Inner Reinforced Concrete Tube." Applied Mechanics and Materials 578-579 (July 2014): 106–12. http://dx.doi.org/10.4028/www.scientific.net/amm.578-579.106.

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With the hybrid structure including outer steel grids and inner reinforced concrete core tubes (RCCT) as the background, the key problems involved in the performance-based structural design are analyzed and the table test is conducted. Anti-seismic and stability indicators are defined based on the structural characteristics; The research on seismic response is made through elastic-plastic time-history analysis and verified through the table test; The overall stability of the outer steel grids and the anti-collapse capability following the ineffectiveness of some key components are analyzed. Results show that the structure in which the outer steel grids are connected with internal steel frame and RCCT is practicable, and the said three systems can work together effectively; The time-history analysis shows that the structure is weak at the elevation of 5-15m but can still meet the expected anti-seismic target under rare earthquakes. The space steel structure features sound stability and high redundancy, which ensures the structure will not collapse even if several key components are damaged.

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32

Mamalis, A. G., G. L. Viegelahn, D. E. Manolakos, and W. Johnson. "Experimental investigation into the axial plastic collapse of steel thin-walled grooved tubes." International Journal of Impact Engineering 4, no. 2 (1986): 117–26. http://dx.doi.org/10.1016/0734-743x(86)90012-6.

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33

Gupta, N. K., and Nagesh. "Collapse mode transitions of thin tubes with wall thickness, end condition and shape eccentricity." International Journal of Mechanical Sciences 48, no. 2 (2006): 210–23. http://dx.doi.org/10.1016/j.ijmecsci.2005.09.002.

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34

Zhang, Jianxun, Haoyuan Guo, Jinlong Du, Hui Yuan, Yuqing Zhu, and Qinghua Qin. "Splitting and curling collapse of metal foam core square sandwich metal tubes: Experimental and theoretical investigations." Thin-Walled Structures 169 (December 2021): 108346. http://dx.doi.org/10.1016/j.tws.2021.108346.

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35

Effendi, Mahmud Kori. "PENGARUH MODEL DAN SIFAT MATERIAL PADA ANALISIS METODE ELEMEN HINGGA BALOK TABUNG BAJA BUNDAR DIIISI BETON." Jurnal Teknik Sipil dan Perencanaan 19, no. 2 (2017): 106–14. http://dx.doi.org/10.15294/jtsp.v19i2.8785.

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The composite material concrete filled steel tubes, CFST) begin widely recommended in modern structural projects. This material is made of steel tubes filled with concrete. This CFST structure has better ductility than the conventional structure. The three-dimensional finite element modelby means of MSC Marc Mentat software is done by using non-linear material properties for both the steel and concrete. The non-linear geometry is also considered. The results of the finite element analysis method are then compared with experimental results of circular steel tubes filled with concrete. The results of this analysis for both load-deflection and collapse conditions are quite agree with the experimental results. However, the buckling phenomena cannot be modeled in the analysis of the finite element method. The effect of finite element model, which is half span and a quarter of half span, is investigated. The results of this analysis are similar to the results of full-scale analysis. There is plastic hinge in the middle of the beam span. The influence of the material properties of linear and non-linear geometric properties are also investigated. The the plastic hinge did not occur in the middle of beam span.

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36

Drazetic, P., Y. Ravalard, F. Dacheux, and B. Marguet. "Applying non-direct similitude technique to the dynamic bending collapse of rectangular section tubes." International Journal of Impact Engineering 15, no. 6 (1994): 797–814. http://dx.doi.org/10.1016/0734-743x(94)90066-t.

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37

Balagansky, Igor, Igor Batraev, Vladimir Ulianitsky, Andrey Plastinin, Alehandr Shtertser, and Alexey Vinogradov. "Analysis of material flow fields under explosive collapse of two-layer metal/ceramic tubes." International Journal of Impact Engineering 156 (October 2021): 103929. http://dx.doi.org/10.1016/j.ijimpeng.2021.103929.

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38

Gupta, N. K., and Atul Khullar. "Lateral collapse of orthogonal and non-orthogonal cross-layered arrays of square and rectangular tubes." International Journal of Mechanical Sciences 36, no. 5 (1994): 449–67. http://dx.doi.org/10.1016/0020-7403(94)90048-5.

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39

Gupta, N. K., and Venkatesh. "A study of the influence of diameter and wall thickness of cylindrical tubes on their axial collapse." Thin-Walled Structures 44, no. 3 (2006): 290–300. http://dx.doi.org/10.1016/j.tws.2006.03.005.

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40

Hoe, Tan Teck, and Lewis C. Schmidt. "Ultimate Load Behaviour of a Barrel Vault Space Truss." International Journal of Space Structures 2, no. 1 (1987): 1–10. http://dx.doi.org/10.1177/026635118700200101.

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The ultimate load capacity of a single-layer barrel vault space truss is investigated both experimentally and theoretically. The vault has a novel bracing system in that the diagonal bracing members are out of the plane of the chords, forming a pyramid system with each base in the plane of the chords. The test model is constructed from steel tubes with all-welded joints. Under an unsymmetrical patch load the vault is seen to perform well, as it is able to develop the axial load capacity of the struts, without the need for them to act in flexure. A local mechanism operates in the region of the loads, but no overall collapse occurs.

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41

Karagiozova, D., and Norman Jones. "On the mechanics of the global bending collapse of circular tubes under dynamic axial load—Dynamic buckling transition." International Journal of Impact Engineering 35, no. 5 (2008): 397–424. http://dx.doi.org/10.1016/j.ijimpeng.2007.04.002.

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42

Chahardoli, S., and A. Alavi Nia. "Experimental and numerical investigations on collapse properties of capped-end frusta tubes with circular triggers under axial quasi-static loading." International Journal of Mechanical Sciences 134 (December 2017): 545–61. http://dx.doi.org/10.1016/j.ijmecsci.2017.10.037.

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43

Nazari, A. R., and F. Taheri. "A parametric study into the influence of strain hardening slope on the stability and collapse responses of steel tubes under compressive loading." Structures 33 (October 2021): 2152–65. http://dx.doi.org/10.1016/j.istruc.2021.05.029.

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44

Oh, Eunsung, and Everett M. Hansen. "Histopathology of Infection and Colonization of Susceptible and Resistant Port-Orford-Cedar by Phytophthora lateralis." Phytopathology® 97, no. 6 (2007): 684–93. http://dx.doi.org/10.1094/phyto-97-6-0684.

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Port-Orford-cedar (POC) root disease, caused by Phytophthora lateralis, continues to kill POC in landscape plantings and natural forests in western North America. POC trees resistant to P. lateralis have been identified and propagated. Cytological observations of P. lateralis in susceptible and resistant roots and stems were made with light and transmission electron microscopy to identify resistance mechanisms. No differences in infection pathway and initial colonization were observed between susceptible and resistant roots, although there were differences in the rate and extent of development. Germ tubes formed appressoria, and penetration hyphae grew either between or directly through epidermal cell walls; inter- and intracellular hyphae colonized the root cortex. In susceptible roots, hyphae penetrated into the vascular system within 48 h of inoculation. In contrast, hyphae in roots of resistant seedlings grew more slowly in cortical cells and were not observed to penetrate to the vascular tissues. In resistant roots, infection was marked by general thickening of cortical cell walls, wall appositions around penetrating hyphae, collapse of cortical cells, and accumulation of osmophillic granules around hyphae. In susceptible stems, hyphae grew inter- and intracellularly in all cells of the secondary phloem except fiber cells, but were concentrated in sieve and parenchyma cells in the functional phloem. The pattern of penetration and colonization of hyphae was similar in the resistant stems, except that hyphae were found in the fiber cells of the xylem. In resistant stems, there were fewer hyphae in the functional phloem, and cytological changes such as damaged nuclei and disintegrated cytoplasm were evident. Structural changes in resistant stems included collapsed cells, wall thickening, secretory bodies, apposition of electron dense materials, and crystals in cell walls.

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45

Wilcke, Martin, Andrei Walther, Klaus Szielasko, and Sargon Youssef. "The MFL technique – Basic application for PT cable break detection in concrete structures." MATEC Web of Conferences 199 (2018): 06013. http://dx.doi.org/10.1051/matecconf/201819906013.

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From the beginning of building techniques creating pre-stressed and accordingly post-tensioned concrete structures until the late 1980ies manufacturers and construction companies dealt with pre-stressing steel material vulnerable to stress corrosion cracking. Almost every load-bearing structure requires regular inspection on a mandatory basis. Due to knowledge of pre-stressed structural reinforcement susceptible to stress corrosion cracking being used during construction or visible damage alongside the tendon area arises the demand for detailed investigation of cracks within the post-tensioned steel elements. Even though the pre-stressed steel elements of a structure are not especially at risk for stress corrosion cracking by its manufacturing process, the natural deterioration of the building fabric and manifold eventual defects and failure during structure erection encourage the requirement for an inspection of their structural integrity at least within the most important load-bearing areas. Therefore needed investigations can be carried out by application of the non-destructive magnetic flux leakage measurement technique for single bar elements and stranded wire tendons even inside cladding tubes. This testing method is subject to successful research work for more than 30 years now and has proven its validated functionality with impressive results on a big number of investigated structures including bridge elements, truss beams and container components.Starting with the basic physical measurement principle of magnetic flux leakage for dipole-formation in the area of fractures of the magnetized pre-stressed steel elements this document presents the practical application possibilities and development history of the testing method.With the consecutively presented further development of the BetoFlux-System we can provide a piece of testing equipment which combines the advantages of a pure physical measurement principle with the economical requirements for an on-site-application to investigate pre-stressed reinforcing steel elements at an early stage prior to structural collapse hazards.

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46

Igland, Ragnar T., and Torgeir Moan. "Reliability Analysis of Pipelines During Laying, Considering Ultimate Strength Under Combined Loads." Journal of Offshore Mechanics and Arctic Engineering 122, no. 1 (1999): 40–46. http://dx.doi.org/10.1115/1.533722.

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Structural reliability methods are applied to establish a measure of safety for pipelines during laying, and especially to calibrate semi-probabilistic ultimate limit state criteria based on measures of uncertainty, method of reliability, and a given target level. Ultimate collapse of thick tubes under combined external pressure, tension, and bending loads are studied applying the finite element method. Nonlinear effects of large deformations, effects of initial ovality, residual stresses, strain-hardening, yield anisotropy, and loading paths were accounted for in the analysis. A set of interaction equations is proposed. Load effects in the pipelines during installation by the S-lay method are studied. The effects of uncertainties in yield stress, mass, stiffness of the stinger, response amplitude operator and peak period for the wave spectrum were accounted for in the analysis. The major factors affecting strain concentration due to concrete coating are taken into account. A combination of design point calculation and importance sampling procedure is used to calculate the probability of failure. The study includes calibration of partial safety factors for the design format selected. The most important random variable is the model uncertainty for bending capacity, while the uncertainty of the load effect has minor importance for the probability of failure. The system effect is taken into account considering the correlation along the pipeline. The probability of failure is referred both to the total laying period as well as a 3-h period demonstrating that the target level needs to be defined in view of the reference time period. [S0892-7219(00)01501-6]

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47

Bernhard, Wolfgang, Andreas Gebert, Gertrud Vieten, et al. "Pulmonary surfactant in birds: coping with surface tension in a tubular lung." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 281, no. 1 (2001): R327—R337. http://dx.doi.org/10.1152/ajpregu.2001.281.1.r327.

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As birds have tubular lungs that do not contain alveoli, avian surfactant predominantly functions to maintain airflow in tubes rather than to prevent alveolar collapse. Consequently, we have evaluated structural, biochemical, and functional parameters of avian surfactant as a model for airway surfactant in the mammalian lung. Surfactant was isolated from duck, chicken, and pig lung lavage fluid by differential centrifugation. Electron microscopy revealed a uniform surfactant layer within the air capillaries of the bird lungs, and there was no tubular myelin in purified avian surfactants. Phosphatidylcholine molecular species of the various surfactants were measured by HPLC. Compared with pig surfactant, both bird surfactants were enriched in dipalmitoylphosphatidylcholine, the principle surface tension-lowering agent in surfactant, and depleted in palmitoylmyristoylphosphatidylcholine, the other disaturated phosphatidylcholine of mammalian surfactant. Surfactant protein (SP)-A was determined by immunoblot analysis, and SP-B and SP-C were determined by gel-filtration HPLC. Neither SP-A nor SP-C was detectable in either bird surfactant, but both preparations of surfactant contained SP-B. Surface tension function was determined using both the pulsating bubble surfactometer (PBS) and capillary surfactometer (CS). Under dynamic cycling conditions, where pig surfactant readily reached minimal surface tension values below 5 mN/m, neither avian surfactant reached values below 15 mN/m within 10 pulsations. However, maximal surface tension of avian surfactant was lower than that of porcine surfactant, and all surfactants were equally efficient in the CS. We conclude that a surfactant composed primarily of dipalmitoylphosphatidylcholine and SP-B is adequate to maintain patency of the air capillaries of the bird lung.

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Zhou, Junxian, Chuang Dong, Bingzhi Chen, and Xu Niu. "Design and Numerical Simulation of Pyramidal Prefolded Patterned Thin-Walled Tubes." Advances in Materials Science and Engineering 2021 (January 18, 2021): 1–16. http://dx.doi.org/10.1155/2021/6614381.

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An improved pyramidal prefolded pattern was designed and applied to thin-walled tubes. This delicately designed pattern modularizes the tube to control the folding process and act as an inducer to trigger deformation modes with outstanding crushing performance. Dynamic crushing tests were conducted numerically; the simulation results reveal that the patterned square tube developed a deformation mode with shorter wavelength, better load consistencies, and higher energy-absorption efficiency (up to 29%) than that of the traditional counterpart. Moreover, geometric analysis was performed and structural improvements were conducted by applying the optimal geometric parameters onto an octagonal profile. The designed patterned octagonal tube collapsed into a highly efficient deformation mode known as diamond mode. Furthermore, the comparative results show that patterned octagonal tubes demonstrated an energy absorption up to 90.1% higher than that of a conventional square column while improving the geometric compliance. These findings enrich research on patterned tubes and provide new explorations for the development of high-performance energy-absorbing structures.

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Chen, Xingxing, Wei Xie, Yunfeng Xiao, Yiguang Chen, and Xianjie Li. "Progressive Collapse Analysis of SRC Frame-RC Core Tube Hybrid Structure." Applied Sciences 8, no. 11 (2018): 2316. http://dx.doi.org/10.3390/app8112316.

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Steel reinforced concrete (SRC) frame-reinforced concrete (RC) core tube hybrid structures are widely used in high-rise buildings. Focusing on the progressive collapse behavior of this structural system, this paper presents an experiment and analysis on a 1/5 scaled, 10-story SRC frame-RC core tube structural model. The finite element (FE) model developed for the purpose of progressive collapse analysis was validated by comparing the test results and simulation results. The alternate load path method (APM) was applied in conducting nonlinear static and dynamic analyses, in which key components including columns and shear walls were removed. The stress state of the beams adjacent to the removed component, the structural behavior including inter-story drift ratio and shear distribution between frame and tube were investigated. The demand capacity ratio (DCR) was applied to evaluate the progressive collapse resistance under loss of key components scenarios. The results indicate that the frame and the tube cooperate in a certain way to resist progressive collapse. The core tube plays a role as the first line of defense against progressive collapse, and the frame plays a role as the second line of defense against progressive collapse. It is also found that the shear distribution is related to the location of the component removed, especially the corner column and shear walls.

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50

Heslop-Harrison, Y., and J. S. Heslop-Harrison. "The pollen tube activated abscission zone in the stigma of pearl millet: structural and physiological aspects." Canadian Journal of Botany 75, no. 7 (1997): 1200–1207. http://dx.doi.org/10.1139/b97-833.

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Abscission of the stigmas of pearl millet (Pennisetum typhoides (Burman) Stapf et Hubbard) after pollination results from the activation of a specialized zone of tissue near the base. This abscission zone comprises a well-defined stretch of the basal column made up of thin-walled cells lacking a cuticularized epidermis. The penetration of the first few pollen tubes following a compatible pollination results in loss of turgor throughout the tissue, followed by loss of adhesion between the cells and ultimately disruption of the whole zone. Pectolytic enzymes are released concomitantly, but the cellulosic skeletons of the cells persist. Numerous calcium oxalate druses, identified cytochemically and by energy-dispersive X-ray analysis, are present in the cells of the abscission zone; these undergo dissolution after activation of the zone, while simultaneously the druse population in the stigma stump and the upper ovary wall increases. The barrier formed by the degenerating abscission zone tissues excludes pollen tubes arriving after the initial activation and prevents the penetration of pathogens such as ergot and so has a prophylactic role. We suggest that the collapsed abscission zone forms not only a physical barrier but also a chemical one. Dissolution products of the numerous calcium oxalate druses during the breakdown of the tissue are likely to raise the calcium ion concentrations beyond the optimum for pollen-tube growth, thereby preventing further penetration. Inhibited tubes swell at the tips and may show growth disorientation before arrest, responses similar to those seen in pearl millet tubes in culture when exposed to higher than normal calcium ion concentration. Key words: Pennisetum typhoides, stigma abscission, millet (pearl), calcium oxalate druses, pollen-tube inhibition, abscission.

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