Longitudinal Bending Strength Research Articles

Reliability analysis of the impact of thickness measurement accuracy on the longitudinal strength assessment of CAP

The reliability analysis of the longitudinal bending strength of ships is conducted using the total probability method, taking into account and analyzing the accuracy error in thickness measurement of transverse section members on existing servicing ships. A mathematical model for calculating failure probability CAP ratings is established. By calculating the CAP rating of an aged LPG carrier, it is observed that when the deterministic method reaches the target rating, the failure probability in rating calculation by the reliability analysis method is high. This indicates a significant influence of thickness measurement accuracy on CAP rating accuracy.

Probabilistic Modelling of Bending Strength of Timber Beams with the Help of Weak Zones Model

The variability of longitudinal bending strength of timber beams due to the presence of knots and other defects is analyzed. The weak zones model of timber beam bending strength used in the analysis consists of short weak zones (knots or group of them) and strong sections of clear wood. The load bearing capacity of timber beams is defined as an extreme (minimum) value problem or as a first downcrossing problem. Assuming a marked Poisson random field with zero correlation between all random variables, cumulative probability distribution functions of the load carrying capacity of timber beams were determined by analytical methods for typical load cases: pure bending, midspan point load and one-third point load. These results, as well as the marked Poisson random field as a model of longitudinal variability of the bending strength of timber beams, can be applied in the reliability analysis of timber structures. Furthermore, the analytical formulae for the cumulative distribution functions of load carrying capacity of timber beams can provide a good reference for numerical analysis conducted with Monte Carlo simulation to determined statistics for specific timber members.

Mammoth ivory was the most suitable osseous raw material for the production of Late Pleistocene big game projectile points

Late Pleistocene societies throughout the northern hemisphere used mammoth and mastodon ivory not only for art and adornment, but also for tools, in particular projectile points. A comparative analysis of the mechanical properties of tusk dentine from woolly mammoth (Mammuthus primigenius) and African elephant (Loxodonta africana) reveals similar longitudinal stiffness values that are comparable to those of cervid antler compacta. The longitudinal bending strength and work of fracture of proboscidean ivory are very high owing to its substantial collagen content and specific microstructure. In permafrost, these properties can be fully retained for thousands of years. Owing to the unique combination of stiffness, toughness and size, ivory was obviously the most suitable osseous raw material for massive projectile points used in big game hunting.

종굽힘강도시험방법을 이용한 폴리에틸렌 보트 선체의 구조 설계

레저 보트 선체의 구조설계규격과 재료는 ISO 12215-5에 규정되어 있으며 선체 전장이 2.5m이상 24m미만이면서 선체재료가 강, 알루미늄, FRP등에 대해서만 적용할 수 있다. 따라서 선체 전장이 2.5m이하이거나 선체 재료가 ISO 12215-5의 규정 재료이외인 레저 보트인 경우 ISO 12215-5의 구조설계규격을 적용시킬 수 없고 ISO 12215-5의 부속서에 규정된 낙하시험만으로 구조 신뢰성을 확보할 수 있다. 그러나 선체낙하시험은 제작된 선체에 대하여 적용하는 것은 가능하나 선체를 구조설계단계에서 적용하는 것은 상당한 설계 및 시험 비용등을 초래하므로 현장 적용성이 떨어진다. 따라서 본 연구에서는 이러한 문제점을 극복하기 위하여 일본 소형 선박 검사 사무 규정 세칙에서 제안하고 있는 선체의 종굽힘강도시험규격을 폴리에틸렌 보트 선체의 구조 설계에 응용하여 ISO 12215-5의 비선급표준재료로 제작된 폴리에틸렌 보트의 종굽힘강도시험규격의 허용 설계 변위 기준을 제안하였다. 【ISO 12215-5 standard describes allowable stress design specifications of monohull small boat with a length of hull between 2.5 m and 24 m constructed from fiber reinforced plastics, aluminium or steel alloys, glued wood or other suitable boat building material. If small boat hull is under 2.5m in overall length or nonstandard material is used as boat building material, structural reliability of small boat hull is assured by drop test specification, but not by structural design specification in accordance with ISO 12215-5. Drop test specification of boat hull can be applied to manufactured product. But it is difficult and complicated to apply drop test specification to structural design of boat hull. In this study, we present structural design method of polyethylene boat hull on the basis of longitudinal bending strength test specification.】

Overall buckling of lightweight stiffened panels using an adapted orthotropic plate method

The ultimate longitudinal bending strength of thin plated steel structures such as box girder bridges and ship hulls can be determined using an incremental–iterative procedure known as the Smith progressive collapse method. The Smith method first calculates the response of stiffened panel sub-structures in the girder and then integrates over the cross section of interest to calculate a moment–curvature response curve. A suitable technique to determine the strength behaviour of stiffened panels within the Smith method is therefore of critical importance. A fundamental assumption of the established progressive collapse method is that the buckling and collapse behaviour of the compressed panels within the girder occurs between adjacent transverse frames. However, interframe buckling may not always be the dominant collapse mode, especially for lightweight stiffened panels such as are found in naval ships and aluminium high speed craft. In these cases overall failure modes, where the buckling mode extends over several frame spaces, may dominate the buckling and collapse response. To account for this possibility, an adaptation to large deflection orthotropic plate theory is presented. The adapted orthotropic method is able to calculate panel stress–strain response curves accounting for both interframe and overall collapse. The method is validated with equivalent nonlinear finite element analyses for a range of regular stiffened panel geometries. It is shown how the adapted orthotropic method is implemented into an extended progressive collapse method, which enhances the capability for determining the ultimate strength of a lightweight stiffened box girder.

複合荷重下における船体梁の縦曲げ最終強度に関する研究

FEM analysis using fine-mesh shell models has been increasingly applied to the ultimate longitudinal strength analysis of ship's hull girder. However, the cost and elapsed time necessary for FEM analyses including FE modelling are still large for the design stage. Therefore, it is a common procedure to apply the Smith's method and to evaluate approximately the maximum longitudinal bending strength of a specified cross section. In this case, the effect of shear and warping stresses, which is significant in very large container ships, is not considered. The objective of this study is to propose a method of the analysis of ultimate hull girder strength under combined bending and torsion. The hull girder is modelled by a series of thin-walled beam elements and the average stress-average strain relationship of plate and stiffened panel segments under axial loads considering the effect of shear stress is implemented in the beam elements. The shift of instantaneous neutral axis and shear center can be automatically considered by introducing axial degree of freedom as well as the bending ones in the beam elements, and keeping the zero axial load condition. The proposed simplified method is applied to the test model explained in the 1st report. First, bending and torsional moment is applied to the beam model for a whole model within the elastic range. Then, the ultimate bending strength of cross sections is calculated applying the Smith's method to a beam element considering the warping and shear stresses. On the other hand, nonlinear explicit finite element analyses are adopted for analysis of the test model by using LS-DYNA. The effectiveness of present simplified analysis method of ultimate hull girder strength under combined loads is discussed comparing with the results of experiments and LS-DYNA analyses.

Bending strength of thin 3-ply poplar plywood in relation to core veneer joints

Effect of core veneer joints on the longitudinal bending strength of thin 3-ply poplar plywood used for fruit boxes.

紡績型炭素繊維強化熱可塑性複合材料の曲げ特性に及ぼす成形条件の影響 繊維軸方向曲げ特性と含浸挙動

Thermoplastic composites have several advantages over thermoset composites in productivity and properties. However, thermoplastic composites have not been used so widely. Several impregnation techniques have been specially developed for thermoplastic composites to solve the difficulty in impregnation of their matrix resins.In this paper, we propose a new impregnating system using a commingled yarn of spun yarn, in order to facilitate the impregnation process. This yarn consists of carbon fibers and Nylon 6 fibers. We fabricated unidirectional composites using spun yarn. We performed a longitudinal bending tests and examined the influence of processing conditions on the bending properties. It was observed that the resin-rich regions between fiber bundles in composites were formed due to the original twist structure of fiber bundle. Impregnating behavior of resin was affected by processing conditions and progressed with two steps, that is, the resin firstly impregnated inside of fiber bundles and next impregnated between fiber bundles. Longitudinal bending strength was saturated at a rather lower pressure and in a shorter period of compression.

Impregnation Behavior and Longitudinal Bending properties of Thermoplastic Composites Made from Commingled Twisted Spun Yarn

Unidirectional composites were fabricated from twisted spun yarn commingled of carbon fiber and Nylon 6 fiber by compression molding. Longitudinal bending strength was saturated with a rather lower pressure and shorter period of compression. A clear fiber bundles- boundaries pattern is observed. Two steps of impregnation is also presumed.

Design of supporting devices for large diameter thin pipes

When an analysis is made in accordance with ASME Code Class 1 for piping by the stress indices method (NB 3650), the stresses induced locally in the piping by the supports are not taken into account. For piping whose thickness is small in relation to its diameter, which is subject to sudden temperature changes and to seismic shocks and which also operates at high temperature, it is undesirable to ignore these effects. This is particularly the case with piping carrying liquid sodium since the classic solutions do not provide a satisfactory answer to the thermomechanical problems and cannot resolve many uncertainties in the analysis. The design finally selected must meet the double requirement of permitting free radial expansion of the piping whilst enabling it to withstand considerable loads with minimal deformation. The design must also be justifiable by easily verified hypotheses. The design adopted consists of a rigid collar connected to the piping by blades which are flexible radially in relation to the pipe and rigid tangentially. These blades are attached to very short ring lugs welded on to the piping. In this way, the outside forces acting on the piping are reduced almost exclusively to circumferential forces which, combined with the circumferential shearing flux due to the adjacent sections, constitute a distribution of forces which is particularly favourable for limiting the circumferential bending moments in the pipe. The resulting deformation of the circular section is thus sufficiently small not to affect the longitudinal bending strength, and particularly the buckling strength. The most significant stresses prove to be those due to the moment on the lug; these are well known and are limited due to the small height of the lug. The thermal stresses due to the presence of the lug were calculated by the finite element method. The thermal and mechanical disturbance created by the lug has the effect of multiplying by about a factor of 2 the maximum total stresses occurring during thermal transients in the straight part; they thus remain limited and less than those developed in other straight discontinuities affecting the piping; for instance, the changes in thickness between straight parts and bends. To back up these calculations, a series of tests was performed to check that the technological requirements of manufacture did not question the load distribution hypotheses taken into account in the calculations.

Longitudinal bending strength of corrugated steel pipe

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.

The Strength of Rails with Particular Reference to Rail Joints

This three-part paper describes recent work on rails carried out by the Research Department of British Railways. Part I details the rail sections considered, theoretical considerations of longitudinal bending strength and an analysis of failures in service. Part II describes a site investigation which was made into the dynamic stresses experienced by rail joints under traffic. Stresses in both flat bottom (F.B.) and bull head (B.H.) rail joints have been measured with both normal and abnormal conditions of sleeper packing. Electrical resistance strain gauges were used at the calculated positions of maximum stress in each fishbolt hole, and at other positions in the joint. The work initially covered the effects of steam locomotives and steam hauled stock, but was later extended to a second site so that electric locomotives and multiple unit electric stock could be similarly covered. The investigation brought out the marked influence of speed, wheel diameter and axle load on the magnitude of the stresses induced; and in view of the prospective increase in speeds, and the employment of diesel electric and electric locomotives with heavy axle loads on smaller wheels than as is usual currently, importance attaches to these results and their implications on the life expectancy of rail steel under fatigue loading. Part III describes fatigue tests which have been made on B.H. and F.B. rails, both plain and when drilled with fishbolt holes. The susceptibility to cracks starting at bolt holes, due to shear stresses in the web, is compared for the two rail sections, and some consideration is given to various methods of increasing the resistance to cracking of this type. It is shown that ordinary atmospheric corrosion greatly reduces the fatigue strength of rails, and any proposed method of reducing bolt hole failures must therefore take this into account.

RECENT RESEARCH IN REINFORCED CONCRETE, AND ITS APPLICATION TO DESIGN. STRUCTURAL PAPER NO 26. (INCLUDES PHOTOGRAPHS).

Synopsis The Paper presents a general plastic theory for the solution of statically indeterminate reinforced-concrete frameworks, and also for calculating the ultimate strength in bending of reinforced-concrete and pre-stressed-concrete beams, of both bonded and non-bonded types. The Author has attempted to avoid the use of complex mathematical methods by assuming that all bending strains have linear distribution. The neutral axis of members subject to bending is located by the ultimate strains at the extremities of the section for non-sustained load, and safe limiting values are determined by tests. The shape of the compression-stress distribution and the position of its centre of gravity are denoted by symbols for which safe limiting values are obtained experimentally. A plastic theory for the ultimate longitudinal bending strength of cylindrical shells is also presented. The Author indicates the distribution of longitudinal stress which causes maximum transverse bending stress so that, again, simplification is achieved by the use of safe limiting values which may be based on experimental evidence. Tests to destruction on pre-stressed beams and two cylindrical shells, and the methods employed for measuring strains by dial and electrical gauges, are described and also the procedure for determining, from the tests, safe limiting values of the factors which govern ultimate strength. The experimental work is not yet complete, but some of the results so far obtained are given. Final results will be given in an Addendum to the Paper. A new method of testing is described, in which a machine referred to as a bending-simulation machine, is used to obtain the fundamental stress-strain data required for calculations within the plastic range.