Load-deflection Characteristics Research Articles

高配筋耐震壁の復元力特性に及ぼす開口の影響 : その1 水平加力実験

高配筋耐震壁の復元力特性に及ぼす開口の影響 : その1 水平加力実験

Nonlinear analysis of prestressed concrete box girder bridges under flexure

One-seventh scale direct models of single-cell and two-cell prestressed concrete box girder bridges, tested to destruction at McGill University, are analyzed by the nonlinear finite element technique. The nonlinear program NONLACS, utilized in the analysis, is described in detail together with the material models employed. The objective of the current study is to demonstrate the capabilities of the finite element program NONLACS in predicting the ultimate strength and complete response of prestressed concrete box girder bridges at all stages of loading up to the ultimate load. The load–deflection curves, concrete and steel stresses, and deflected shapes of the bridges at different load levels are compared with the corresponding experimental data. The results verify the applicability of the nonlinear finite element method as an economical and expedient alternative, in some cases, to expensive experimental work aimed at the investigation of the complete response of complex structures to applied loads. Key words: box girder bridges, concrete, concrete and steel strains, experimental data, finite element, load–deflection characteristics, nonlinear analysis, prestressing.

Large deflection analysis of cantilever beams of symmetrical cross-section subjected to a rotational distributed loading including the effect of material nonlinearity

AbstractCombined effects of geometrical and material non-linearities on a cantilever beam having symmetrical cross-section about its central axis with a rotational distributed loading are studied. It is assumed that the stress-strain relation in compression is identical to that in tension. Due to this, the neutral axis coincides with the central axis of the beam. The problem is formulated by means of an integral equation which is suitably converted to a system of nonlinear ordinary differential equations which are solved using a simple and accurate numerical method. Details of the load deflection characteristics for an I-beam and for a beam of rectangular cross-section are presented.

LOAD-DEFLECTION CHARACTERISTICS OF REINFORCED CONCRETE COLUMNS UNDER STATIC ALTERNATING CYCLIC LOADS

The objects of the study were columns of reinforced concrete viaducts used in large numbers for railway and urban transportation structures. The influences of variable factors such as longitudinal reinforcement ratio, hoop ratio, and axial load on behaviors of members such as limit states of crack occurrence, yielding and ultimate state of member, ductility, and load-deflection characteristics under static alternating cyclic loads were experimentally investigated.As a result, it was concluded that the load-deflection loop can be modelled as a maximum-point-directed type without slipping, that among various variable factors the influence of longitudinal reinforcement ratio is extremely great, and that plastic hinge length and longitudinal crack formation are determined by the combination of the quantities of longitudinal reinforcement and hoop reinforcement.

Experimental investigation into the axial plastic collapse of steel thin-walled grooved tubes

Experimental investigations were conducted into the quasi-static collapse and energy absorption characteristics of thin-walled steel tubes containing a number of geometrical discontinuities in the form of grooves of constant depth and axial length. The failure modes and load-deflection characteristics are discussed and compared with the corresponding theoretical values. An inextensional collapse mechanism is used to describe a non-symmetrical diamond mode shell folding which takes into account the concept of stationary circumferential and inclinded travelling hinges.

An integral-equation solution for the finite deflection of clamped skew sandwich plates

The large-deflection behaviour of skew sandwich plates is governed by a system of five coupled nonlinear partial differential equations which are highly complex in nature. In the reported study, this problem is analysed using an integral-equation approach. The integral equations of beams along the skew directions is used with appropriate boundary conditions to transform the governing nonlinear partial differential equations into a set of nonlinear algebraic equations. These equations are then solved using an iterative scheme suggested by Brown. The results obtained by this method are compared with available results of other investigators and the agreement is found to be good. Load-deflection characteristics have been presented for clamped skew sandwich plates.

Load-Deflection Analyses of Shock Mitigating Polyurethane–Silicone Foams

Three types of polyurethane-silicone foam are analysed in terms of their compression load-deflection, static load-deflection, recovery time and matrix transition temperature characteristics. The information produced is used to discuss their suitability as shock mitigating helmet liner materials. The rate of deflection during mechanical testing is shown to be highly significant at values <400% min-1 and the compression-deflection ‘plateau’ characteristics analysed in terms of a 10% load differential. Foam type 1085–47 is demonstrated to be of potential use in single impact shock absorption contexts and types 101–38 and 1085–41 of use where repeated impacts are anticipated and there is limited time available for recovery.

A Model Analysis of Tire Behavior Under Vertical Loading and Straight-Line Free Rolling

Abstract A structural analog, consisting of a flexible circular ring under tension with a nest of radially arranged linear springs and dampers, is developed as a pneumatic tire model. The model is concerned with the prediction of the tire's vertical load-deflection characteristics and its free rolling resistance. The mathematical formulation of the boundary of the model's region of contact with a smooth hard surface is based on approximations made using the theory of a tensioned string supported by an elastic foundation. Forces developed within the contact region are computed from geometrical considerations. The model's ring tension and radial foundation stiffnesses, as related to the tire's inflation pressure, are obtained experimentally by performing contact patch length measurements and static point-load tests on the specific tire modeled. Further, by prescribing a loss factor in the radial dampers, the model's free rolling resistance characteristics may be computed. Experimental verification conducted on a radial tire shows general agreement between the predicted and experimental vertical load-deflection characteristics for the normal working range of inflation pressure, deflection, and interacting surface curvature. The predicted rolling resistance characteristics are also found to be in good accord with experimental measurements.

On ship collisions: The plastic collapse of longitudinally framed shell plating subjected to oblique loading

Rigid plastic analysis is used for predicting the structural behaviour of longitudinally framed shell plating of struck vessels during a minor oblique collision. The shell plating is divided into T-beam units. Each unit is subjected to plastic straining under the action of an oblique concentrated load, up to its penetration and fracture. Load-deflection characteristics are established resulting in the prediction of the strength of the struck vessel at any stage of deformation and for obtaining information for the design of protective structures against collisions. Finally, the influence of the collision angle on the plastic deformation of the beam has been examined and a collision at right angles was found to be the most severe condition.

Orthodontic force characteristics of open coil springs

Applications of open coil springs in orthodontic tooth movement are many and varied. Current descriptions of force production by open coil springs are based upon force values produced in series of discrete compression tests. It was the purpose of this study to analyze and compare open-coil-spring force production from continuous load-deflection curves, thereby assisting the clinician in the selection of the ideal spring for a given application. Load-deflection curves were generated for open coil springs of various wire diameters and lumen sizes, as well as four wire alloys from three manufacturers. Testing was performed on an instron test machine using 0.016 inch round and 0.018 by 0.022 inch rectangular arch wires. With a constant lumen size, an increase in wire size produced an increase in force at a given activation. With a constant wire size, an increase in lumen size produced a decrease in force at a given activation. The effect of the arch wire size and shape was not significantly different for the coil springs with the smaller lumen sizes. For the larger lumen sizes, the springs used with the rectangular arch wire manifested a greater linear range than those used with the smaller arch wire. The difference between the load-deflection characteristics of the coil springs from different manufacturers was attributed to the difference in the pitch of the coils.

Low Velocity Transverse Impact Behavior of 8-ply, Graphite-Epoxy Laminates

This work discusses the behavior of 8-ply, quasi-isotropic, graphite epoxy laminates subjected to low velocity transverse impact loading. Large deflection theory of plates was used to predict the load-deflection characteristics during the impact event. The im pact model considered that the indentation, flexural and shear stiffnesses could be represented by 3-equivalent springs in series. The analysis of static and dynamic impact loading test-data concluded that the mem brane parameter, β, used in flexural stiffness relation was proportional to the square of the coefficient of restitution, e, of the impactor. Use of β = 0.443 e2 was made in load- deflection relations to consider the drop in plate stiffness due to delamination. The results of impact tests up to impact velocity 5.3 m/sec. were found in close agreement of the predictions.

Stacking Characteristics of Composite Cardboard Boxes

This paper presents a simplified model and method for finding the deflection char acteristics of stacked cardboard boxes, provided the load-deflection characteristic of the box is known. A computer program, based on this model, allows the stability of stacked boxes to be investigated and to indicate the limits to the height of the stack and box parameters required to prevent stack toppling.

Large deflection analysis of clamped skew sandwich plates by parametric differentiation

The differential equations governing the large deflection behavior of skew sandwich plates are highly complex in nature and do not lend themselves for easy solution. In the study reported herein, this problem is solved by a numerical technique known as “parametric differentiation”. The non-linear differential equations in terms of displacements are transformed into a set of linear differential equations with variable coefficients. These are solved to give the gradients of the displacements in the load direction. The subsequent solution of a set of initial value problems yield the displacements proper. The results obtained by this method are compared with available results of other investigators and the agreement is found to be good. Load deflection characteristics have been presented for clamped skew sandwich plates.

Model pile groups subject to lateral loading : Hughes, J M O; Fendall, H D W; Goldsmith, P R Proc 3rd Australia-New Zealand Conference on Geomechanics, Wellington, 12–16 May 1980, V1, P79–85. Publ Wellington: New Zealand Institution of Engineers, 1980

It is generally recognised today that the lateral load carrying capacity of a vertical pile is significant in resisting horizontal loads. Unfortunately the understanding of the mechanism of soil resistance to laterally load piles and particularly pile groups is far from complete. The ability of designers to predict the load-deflection characteristics of even a single pile has not been resolved to within acceptable measures of certainty. In this paper the authors attempt to indicate some of the uncertainties that exist in our fundamental understanding of pile-soil interaction. The results reported herein are concerned mainly with the interaction of two piles. The results indicate that the combined action of two piles can be substantially less than the contribution of two individual single piles. The authors believe that the state-of-the-art on laterally loaded piles and pile groups is well served by analytical techniques (Hughes, Goldsmith and Fendall, 1978). The problem facing designers today is not the lack of mathematical models but the uncertainties involved in choosing suitable soil parameters to use in the analysis, and a lack of understanding of the process of soil-structure interaction.

H -Pile Heave: A Field Test

A field test was conducted to investigate the possibility of reduction in pile capacity and the potential for excessive settlements resulting from the heave of H-piles. The piles were driven through relatively softer strata to be seated into an interbedded very dense/hard deposit. A group of 38 pi(es, arranged in an 8x5 cluster, were driven as part of this test. Six previously driven piles, located outside the cluster at distances of 17 ft to 37 ft (5.2 m to 11.3 m), and two previously driven piles located within the cluster were also monitored for heave. The maximum pile heave within the cluster was 1.04 in. (26.4 mm), while 75% of the piles experienced heave between 0.4 and 0.7 in. (10.2 mm and 17.8 mm). Incremental pile heave decreases exponentially with increasing distance from the driven piles. The radius of influence of pile heave was estimated to be approximately 50 ft (15.2 m). Pile load tests showed that pile heave up to 1.04 in. (26.4 mm) had no effect on pile load capacity or on pile load deflection characteristics. Pile tip heave was only slightly less than pile butt heave.

Elasto-plastic analysis as a basis for design of cylindrical pressure vessels with different end closures

The elasto-plastic investigations described in this paper have been carried out in order to study the performance of unfired cylindrical steel pressure vessels with hemispherical, torispherical, semi-ellipsoidal and toriconical end closures concave to pressure, using the finite element method. The various aspects covered by the study include spread of plastic zones, load-deflection characteristics, head-height growth characteristics, redistribution of effective stresses, effective plastic strain, limit analysis, excessive deformation and shakedown criteria of pressure vessel design. Based upon the results of this analysis, guidelines for the design of cylindrical pressure vessels are indicated in the form of various non-dimensional curves which will be useful for the better design of pressure vessels.

The characterization of arch wires for the initial alignment of irregular teeth

The standard measurements of the properties of orthodontic wire are of limited value to the orthodontist, and clinical impressions of wire behavior are unreliable. This article discusses the properties of clinical relevance to the selection of wires for the initial alignment of irregular teeth. These concepts are illustrated by measurements made on some commonly used orthodontic wires. It is evident that a compromise often has to be made between flexural rigidity and elastic recovery and that no single figure of merit can adequately characterize a wire in both respects. It is necessary for the clinician to understand the properties of importance and the nature of the compromise in order to be able to select the most appropriate wire for a particular application. An investigation into the load-deflection characteristics of a single span reveals that many arches are remarkably stiff and are not capable of applying light forces. The effects of incorporating loops in the wire in order to modify span characteristics are discussed with reference to the contributions of the different components.

A model of the periodontal vasculature in tooth support

Previous studies have suggested that the blood vessels in the periodontal space may be the most important of all the components of the periodontal ligament in providing support for the teeth. Since the relationship between intrusion of the teeth and applied load has been studied and the mathematical form of this relationship established to be f = ( αx + k) x, it was decided to determine whether the relationship could be accounted for by the mechanical characteristics of the blood vessels. The results reported here represent a preliminary study conducted on samples of man-made tubing in order to assess the load-deflection behaviour of a fluid-carrying, internally-pressurized cylinder subjected to transverse forces. The effects of the resulting occlusion of the tube on flow rates were also studied. The results of this work indicate that an equation of the form f = x( αx + k) will indeed adequately describe the load-deflection characteristics of a transversely loaded tube. The ratio α k , however, is several orders of magnitude less than that found for the periodontal ligament, suggesting that the vasculature does not predominate in tooth support. The effect of occlusion on flow, on the other hand, is quite similar to the observed effect of load on periodontal blood flow, suggesting that the periodontal vessels do, nonetheless, contribute measurably to the support of the teeth. The various observations concerning the periodontal vasculature and tooth support can be reconciled by means of a simple mathematical model, which is presented.

A ceramic spring for high-temperature valves

A ceramic seat preloading spring has been built for use in hightemperature coal gasification valves. The use of a ceramic material avoids many of the problems associated with coal conversion environments, which consist of hot, corrosive gases, mixed with abrasive solids of varying sizes. The design initially relied on conventional spring formulas, and was refined on the basis of testing. The resulting ceramic spring displays essentially linear load-deflection characteristics, and can be used at temperatures up to 900 °C without taking a permanent deflection. The spring will be tested further in an 8 in. valve designed specifically for use on coal gasification plants.

Orthodontic effects of loop design and heat treatment.

The effects of heat treatment on Blue Elgiloy wire and loops formed from this wire were determined. The optimum heat treatment temperature was established to be in a narrow range in the vicinity of 950 degrees F. This regimen increases the yield and ultimate strengths of this wire. Heat treatment also produced a modification of the load-deflection characteristics of the loop configuration tested. Overall, heat treatment of the wire is indicated by this study.