Longitudinal bending strength of corrugated steel pipe

1980 ◽  
Vol 7 (3) ◽  
pp. 547-551
Author(s):  
C. D. Smith

Corrugated steel pipe (CSP) is used in large numbers for drainage structures, particularly in highway engineering. The corrugations increase the wall stiffness of the pipe by a factor of about 100, so relatively light-gauge material can be used to resist the earth loading on the buried pipe. These same corrugations, however, result in a decrease in longitudinal bending strength. This can be an important consideration in situations where the culvert may be undermined at the outlet, or is deliberately cantilevered beyond its imbedment. Strength tests were carried out on three sizes of standard 16 gauge (0.001676 m) rivetted CSP. From this it was determined that the safe cantilever length for a flowing full culvert is about 2 m for pipes of 0.61 m diameter and larger.

2021 ◽  
Author(s):  
Julissa Rojas-Sandoval ◽  
Pedro Acevedo-Rodríguez ◽  
A. I. Popay

Abstract S. oleraceus is a common seed crop contaminant and has been carried either deliberately or accidentally by humans to almost every corner of the earth, where it invades mainly open and disturbed areas. It grows in a wide variety of environments on a wide range of substrates - roadsides, cultivated land, gardens, construction sites, sand dunes, logged or burned areas, on walls, mountain slopes, and near water. Once introduced to a new area the plants spread quickly because they grow and flower quickly and produce copious wind- and bird-dispersed seeds that germinate quickly in large numbers. They invade many cropped areas, especially among vegetable and winter crops. They are almost perfect 'designer weeds'. Additionally, this species has small light seeds which are easily dispersed by wind and water.


Author(s):  
Richard A. Posner

You wouldn’t see the asteroid, even though it was several miles in diameter, because it would be hurtling toward you at 15 to 25 miles a second. At that speed, the column of air between the asteroid and the earth’s surface would be compressed with such force that the column’s temperature would soar to several times that of the sun, incinerating everything in its path. When the asteroid struck, it would penetrate deep into the ground and explode, creating an enormous crater and ejecting burning rocks and dense clouds of soot into the atmosphere, wrapping the globe in a mantle of fiery debris that would raise surface temperatures by as much as 100 degrees Fahrenheit and shut down photosynthesis for years. The shock waves from the collision would have precipitated earthquakes and volcanic eruptions, gargantuan tidal waves, and huge forest fires. A quarter of the earth’s human population might be dead within 24 hours of the strike, and the rest soon after. But there might no longer be an earth for an asteroid to strike. In a high-energy particle accelerator, physicists bent on re-creating conditions at the birth of the universe collide the nuclei of heavy atoms, containing large numbers of protons and neutrons, at speeds near that of light, shattering these particles into their constituent quarks. Because some of these quarks, called strange quarks, are hyperdense, here is what might happen: A shower of strange quarks clumps, forming a tiny bit of strange matter that has a negative electric charge. Because of its charge, the strange matter attracts the nuclei in the vicinity (nuclei have a positive charge), fusing with them to form a larger mass of strange matter that expands exponentially. Within a fraction of a second the earth is compressed to a hyperdense sphere 100 meters in diameter, explodes in the manner of a supernova, and vanishes. By then, however, the earth might have been made uninhabitable for human beings and most other creatures by abrupt climate changes.


2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Qiang Ma ◽  
Zhun Ku ◽  
Henglin Xiao

To obtain the optimal load-reduction scheme and calculation method of earth pressure on the crown of the pipe, the load-reduction efficiency of rigid pipe and flexible pipe with different thicknesses and layers of expanded polystyrene (EPS) is investigated by model tests, and the law of load reduction is obtained by analyzing the earth pressure and the displacements of the filling around the pipe. The test results show that the earth pressure is obviously reduced with EPS laying on the crown of pipe, and the load-reduction efficiency is increased to be constant with increasing of EPS thickness. In the case that the summation thickness of EPS is constant, the load-reduction efficiency of EPS with two layers spread on the pipe is higher than that of one layer only. Compared with the rigid pipe, the load-reducing effect of flexible pipe is more significant. Based on the data obtained from the model tests, the nonlinear earth pressure calculation formula obtained from regression analysis is adopted, and the results from it are compared with the existing formula consequences of the earth pressure on the buried pipe. The results show that the earth pressure calculated by nonlinear earth pressure theory is on the brink of that tested in the field. The research results can provide references for selection of load-reduction measures and calculation of earth pressure on the crown of the pipe.


Geophysics ◽  
1952 ◽  
Vol 17 (3) ◽  
pp. 505-530 ◽  
Author(s):  
R. Woodward Moore

Of the several geophysical methods used in exploration for oil and useful ore bodies, the earth‐resistivity and seismic‐refraction tests have been found to be the most adaptable to the shallow tests generally required in highway construction work. Of these, the earth‐resistivity test is the faster and has a wider range of application to highway problems than does the seismic test. Use of both methods of tests in subsurface explorations for engineering structures is expanding. The paper cites a growing need for a more thorough subsurface investigation of all engineering structure sites and gives examples of field data obtained by the Bureau of Public Roads when making preliminary geophysical surveys of proposed highway locations or structure sites. The economic aspects and the advantages and limitations of the two methods of test are discussed with particular reference to their application to highway engineering problems.


2013 ◽  
Vol 376 ◽  
pp. 366-370
Author(s):  
Hui Gao ◽  
Da Wei Zhang ◽  
Bin Liu ◽  
Long Chen Duan

One of the important objectives of lunar exploration is to obtain the lunar soil samples. However, the sampling process is very different from that on the Earth due to special characteristics of the lunar soil and surface environment. In order to ensure that the lunar exploration and sampling are successful, large numbers of ground experiments and computer simulations must be taken. In this paper, the surface lunar soil excavation simulation is investigated by three-dimensional discrete element method (DEM). It is implemented based on the open source LIGGGHTS, which takes the lunar soil as spherical particles. The interaction between the excavation tool and lunar soil is demonstrated. The excavation force and torque have also been calculated in real time. Moreover, the comparison of the excavation in different environments between the Earth and Moon corresponding to their different gravity accelerations was done. This paper shows that three-dimensional discrete element method can be used for the surface lunar soil excavation simulation and can provide important reference results for actual operations.


2009 ◽  
Vol 409 ◽  
pp. 185-192
Author(s):  
Lucia Hegedűsová ◽  
Alexandra Kovalčíková ◽  
Monika Kašiarová ◽  
Ján Dusza

The paper deals with the determination of the characteristic strength and the Weibull modulus m of Si3N4 and SiC ceramic materials using conventional four-point bending and unconventional contact tests between opposite rollers and opposite spheres. Ceramographic and fractographic methods were used for the characterization of strength degrading defects represented by processing flaws and by cracks of different types arising during the loading. The processing flaws influenced the Weibull parameters mainly in the bending mode, and the strength and its scatter in contact modes was influenced by lateral, median and contact end cracks, originated during the contact test using rollers, and by cone cracks originated during the contact test using spheres.


2003 ◽  
Vol 17 (3) ◽  
pp. 267-272 ◽  
Author(s):  
Petrus Pereira Gomes ◽  
Rubens Guimarães Filho ◽  
Renato Mazzonetto

The aim of this study was to evaluate, in vitro, the bending strength of internal fixation with absorbable and metallic screws in mandibular ramus sagittal split osteotomy in sheep hemimandibles. The screws were inserted as lag screws, with an inverted "L" configuration, and the set was submitted to bending strength tests. The load and displacement of the peak and final load averages were, respectively, 18.45 kgf, 8.19 mm and 14.38 kgf for Group I, and 16.67 kgf, 6.73 mm and 13.98 kgf for Group II. The results were submitted to statistical analysis by Student’s t test and by the Pearson correlation analysis. The groups showed no statistically significant differences, indicating the feasibility of both for osteosynthesis in mandibular ramus sagittal split osteotomies.


The realization that the behaviour of the Earth has changed radically during geological time has come about largely in the last decade. This development, which constitutes one of the major advances in geological thinking, results from the study of Precambrian phenomena in many parts of the world and in particular from the work of a small number of geochronologists. In the last ten years as large numbers of unfossiliferous Precambrian rocks have been dated, it has become clear that the nature of geological processes has varied throughout geological time and that one of the cardinal doctrines of geology - the concept that the present is the key to the past — could not be applied to the study of the early history of the Earth.


2017 ◽  
Author(s):  
Mark P Witton ◽  
Elizabeth Martin-Silverstone ◽  
Darren Naish

Pterosaur embryos and ‘hatchling’ specimens show a surprising level of skeletal development including well-ossified skeletons and large wings. This has prompted interpretations of pterosaurs as being flight-capable from the earliest ontogenetic stages, contrasting them against the majority of other flying animals, living or extinct. Though popular, this hypothesis is not universally accepted. Some authors propose that pterosaurs only became flight capable once they reached 50% of maximum size, explaining a slowing of growth rate in later ontogeny as metabolic resources were diverted into an energy-demanding form of locomotion. We investigated these hypotheses through glide performance and wing bone strength analysis on hatchling-grade specimens of two pterosaurs, Pterodaustro guinazui and Sinopterus dongi. We found that hatchling pterosaurs were excellent gliders, but with a wing ecomorphology more comparable to powered fliers than obligate gliders. Bone strength analysis shows that hatchling pterosaur wing bones are structurally identical to those of larger pterosaurs and – because of their very low body masses – their bending strength relative to body weight is very high, comparable to or exceeding the greatest values estimated for larger, more mature pterosaurs. Hatchling pterosaurs are thus as mechanically adapted to powered flight stresses as other pterosaurs, if not moreso. Together with our glide tests, this result supports interpretations of hatchling pterosaurs as flight-capable. Size differences between pterosaur hatchlings and larger members of their species dictate differences in wing ecomorphology and flight capabilities at different life stages, which might have bearing on pterosaur ontogenetic niching.


Zootaxa ◽  
2008 ◽  
Vol 1965 (1) ◽  
pp. 61-68 ◽  
Author(s):  
JOSÉ ANTONIO GONZÁLEZ-OREJA

One of the most crucial questions of twenty-first century systematic biology deals with the determination of the real number of living species currently sharing the Earth with us (Cracraft 2002); answers vary widely, but commonly range between 3 and 100 million (see, for example, Stork 1997 or May 2002 and references therein). However, in terms of completeness and correctness, our current inventory of living species is certainly unsatisfactory (Dubois 2003), as the total number of species described so far is known to correspond to only a very small fraction of the Earth´s biodiversity. Indeed, large numbers of species remain to be discovered, primarily insects, small invertebrates and, above all, microorganisms (Chevalier et al. 1997). On the other hand, this gap of knowledge regarding the magnitude of the Earth´s biodiversity limits our capacity to properly manage the world´s biotic resources and conserve biological diversity in this so-called Century of Extinctions (Dubois 2003): the current biodiversity crisis is wiping out a significant fraction of living species at an alarming rate and, sadly, an unknown number of species is being forever lost before being discovered, described, and named. Likewise, conservation priorities are clearly constrained by our limited knowledge of the total biodiversity (Dubois 2003, Scotland et al. 2003).


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