Loading Strip Research Articles

Debonding resistance of FRP-to-clay brick masonry joints

Debonding at the FRP-to-masonry interface has been identified as the preferred failure mechanism in fibre-reinforced polymer (FRP) retrofitted masonry as it allows for some redistribution of forces. The results of 14 FRP-to-masonry bond tests are presented, where the FRP was near surface mounted (NSM) to stack-bonded clay brick masonry. These tests were conducted to investigate the effect that variables such as cyclic loading and FRP strip dimensions have on the debonding resistance of a NSM FRP-to-masonry joint. These results were then incorporated into a large database of FRP retrofitted masonry pull test results by various researchers over the past 10years. The database includes results for both externally bonded (EB) and NSM retrofitting techniques. From this database, local bond–slip parameters such as the maximum interface shear stress, τmax, and the maximum slip, δmax, were investigated to determine correlations between these values and masonry material properties. Further, 15 existing concrete and masonry bond strength (maximum load at the FRP-to-substrate interface) models in the literature were assessed for their use with masonry by comparing these models against the results in the pull test database. Based on the comparative statistics of the test-to-predicted bond strength it is concluded that a new FRP-to-masonry bond model is required which gives more accurate predictions. Results include a discussion on the global load–slip response and FRP-to-masonry interface behaviour.

Multiresonance coplanar waveguide-fed monopole antennas with meander strips for GSM/GPS/PCS/DCS/WCDMA applications

A multiband multiresonance coplanar waveguide (CPW)-fed monopole antenna is proposed in this article. The antenna consists of various monopole strips of including a meander strip, a w-shape strip, and an m-shape strip for the multiresonance operation and miniaturization of antenna. The operation modes are associated with the length and shape of loading strips, in which the lower frequency bands vary along a long meander and the higher bands along an m-shape. Experimental results showed that the impedance bandwidths of the multiresonant antenna less than −10 dB return loss were 8.4, 2.5, 17.6, and 19.3 % with omni-directional radiation patterns at 860, 1570, 1860, and 2140 MHz, respectively, and those antenna gains were −2.13, −0.77, 1.25, and 2.45 dBi, respectively. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2438–2441, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26276

Evanescent Wave Amplification in Meta-Materials

Performance of amplifying evanescent wave is investigated on the basis of simulation. Three cases of waveguides loading SRR resonators, strip lines and composite meta-materials are analyzed individually. In certain frequencies, these three kinds of arrays all have the ability of evanescent wave amplification.

Ultrawideband Strip-Loaded Circular Slot Antenna With Improved Radiation Patterns

An ultrawideband strip-loaded circular slot antenna is proposed in this Communication, which presents a measured impedance bandwidth of 144.8% , much stable radiation patterns and small dimensions. The loading strip is used for redistributing the electric field within the slot to achieve stable radiation patterns across a wide frequency band, and it is optimized to influence on the impedance bandwidth as slightly as possible. For clarity, the simulated three-dimension (3-D) radiation patterns are given and compared with those of a conventional circular slot antenna without strip loading. The measured gain of the proposed antenna in the broadside direction is over 0 dBi from 2.4 to 11 GHz. The measured and simulated return losses and radiation patterns of the proposed antenna are given, and finally, parametric studies are performed for practical applications.

Quasi-static deformation of a poroelastic half-space with anisotropic permeability by two-dimensional surface loads

SUMMARY An analytical solution is obtained of the fully coupled diffusion–deformation system of equations governing the quasi-static plane strain deformation of a poroelastic half-space with anisotropic permeability and compressible constituents. The stresses and the pore pressure are taken as the basic state variables. Displacements are obtained by integrating the coupled constitutive relations. The problem of surface loads is discussed in detail. Explicit analytical solutions are derived for normal line loading, shear line loading and normal strip loading. The permeability anisotropy is found to have a significant effect on the quasi-static deformation of the half-space. However, in the drained and undrained limits, the anisotropy has no effect. The stresses in the drained and undrained states are independent of the poroelastic parameters. Numerical computation of the pore pressure indicates that ignoring permeability anisotropy may lead to an overestimation of the pore pressure at points vertically below the point of normal loading. Further, anisotropy in permeability may lead to a dilution in the theoretical prediction of the Mandel–Cryer Effect.

Evaluation of Tensile Strength of Cement-Treated Sand Based on Several Types of Laboratory Tests

There exist differences in the values of the tensile strength of cement-treated soils among results from direct tension, splitting tension, and bending tests. This paper presents numerical simulations that serve to explain such differences in the tensile strength properties obtained from the three types of tests. Finite element (FE)-analyses were performed to simulate the three tests as boundary value problems. A simple elasto-plastic model that simulates the behavior of cement-treated sands under a general three-dimensional stress state was used for these analyses. The analytical results showed that the direct tension tests yield reliable values of the actual tensile strength that will be mobilized under an ideal condition of uniaxial tension. On the other hand, in the splitting tension and bending tests, the tensile strength values are calculated from an external load by assuming a linear-elastic behavior in estimating the stress distribution. However, these values do not correspond to the actual tensile strength. The splitting tensile tests underestimate the tensile strength because the shear failure occurs below the loading strip and restrains further increase of the applied load. On the other hand, the bending tests overestimate the tensile strength because of the redistribution of stresses induced by the strain-softening behavior on the tensile side.

Lateral force and centroid location caused by horizontal and vertical surcharge strip loads on a cross‐anisotropic backfill

AbstractThis work presents analytical solutions for determining lateral force (force per unit length) and centroid location caused by horizontal and vertical surcharge surface loads acting on a cross‐anisotropic backfill. The surcharge loading types are point load, line load, uniform strip load, upward linear‐varying strip load, upward nonlinear‐varying strip load, downward linear‐varying strip load, and downward nonlinear‐varying strip load. The planes of cross‐anisotropy are assumed parallel to the backfill ground surface. The proposed solutions, derived by integrating the lateral stress solutions (Int. J. Numer. Anal. Meth. Geomech. 2005; 29:1341–1361), do not exist in literature. Clearly, the type and degree of material anisotropy, loading distance from the retaining wall, and loading types markedly impact the proposed solutions. Two examples are utilized to illustrate the type and degree of soil anisotropy, and the loading types on the lateral force and centroid location in the isotropic/cross‐anisotropic backfills generated by the horizontal and vertical uniform, upward linear‐varying and upward nonlinear‐varying strip loads. The parametric study results demonstrate that the lateral force and centroid location accounting for soil anisotropy, loading distance from the retaining wall, dimension of the loading strip, and loading directions and types differ significantly from those estimated using existing isotropic solutions. The derived solutions can be added to other lateral pressures, such as earth pressure or water pressure, required for stability and structural analysis of a retaining wall. Additionally, they can simulate realistically actual surcharge loading problems in geotechnical engineering when backfill materials are cross‐anisotropic. Copyright © 2007 John Wiley & Sons, Ltd.

The Paranapanema Lithospheric Block: Its Importance for Proterozoic (Rodinia, Gondwana) Supercontinent Theories.

This work considers the tectonics of the southeastern portion of the South American Platform based on new geological and geophysical grounds. For the last decade, only three (Amazonic, São Francisco and La Plata) of the many other cratonic blocks have been attributed/remarked to the South America portion for most of the usual Rodinia reconstitutions. The possibility of the existence of other blocks has rarely been mentioned. The postulation of the presence of a considerable Paleoproterozoic (pre-Brasiliano) fragment as part of Paraná Basin basement is highly probable. In order to infer the basement structure of Paraná Basin, previous to the sedimentation process, an isostatic modeling was applied to a large-scale gravity survey looking to correlate topographic and gravity anomalies caused by sub-surface loads. The Bouguer anomaly obtained from the gravity survey represents the crustal contribution of crystalline basement, in addition to the sedimentary and volcanic layers of the basin. Following the isostatic modeling and the basin load stripping, the residual anomaly allows observing similarities between the basement gravity signature and outcropping units. Besides, the stress pattern of the two earlier events obtained through the back stripping analysis presents a geographically coincident maximum, and a new E-SE high emerging for the second event, suggesting continuous change of the stress field as a precursor for South American plate rotation. The evident correlation between gravity highs and main attenuation suggests the presence of some pre-existing suture zones. The weakened lithosphere during Ordovician and Carboniferous provided the magma conduits to form in Early Cretaceous tectonic stress field pattern. The resultant mosaic of gravity blocks and the main faults site give support to the presence of this cratonic Proterozoic unit, here on referred to as the Paranapanema Block, which had been neglected in most of the models reported for the reconstruction of Gondwana (and Rodinia).

Identification of a Physical Model to Evaluate Rutting Performance of Asphalt Mixtures

Abstract The objective of this study is to identify a physical model that can provide reliable predictions about a mixture's ability to resist permanent deformation under realistic stress states. Key differences were identified between stress states under the existing Asphalt Pavement Analyzer (APA) loading device (hose) and stress states under radial truck tires, which may indicate potentially different rutting mechanisms. It was shown that the APA hose was not capturing the critical lateral stresses found to be detrimental to rutting and cracking of HMA pavements. A new loading device (rib) was designed and constructed for use in the APA that more closely represents stress states found under radial tires. Contact-stress measurements under the two loading devices — hose and rib — showed that the rib was able to reproduce the lateral stresses found under individual ribs on a radial-tire tread. Subsequent finite element modeling also showed that the rib appeared to generate similar shear stress patterns to those found under the modeled radial-tire load. A new method was developed to measure deformations on the surface of APA specimens, where a contour gauge was used to record and store the entire surface profile of the sample throughout the progress of the test. An area-change parameter, which reflects volume change, was introduced to calculate the volumetric changes in the specimen. The area-change parameter can be used to determine whether specimen rutting is primarily due to shear instability or consolidation. Two mixtures of known field performance — poor and good — were tested to evaluate the test's ability to predict performance with the new loading device and the new measurement and interpretation system. Results showed that the new system (loading strip and profile measurement method) appears to have greater potential of evaluating a mixture's potential for instability rutting than the original (hose and single rut-depth measurement) configuration.

Simple Performance Test for Fatigue Cracking and Validation with WesTrack Mixtures

Viscoelastic characterization of asphalt concrete in indirect tensile (IDT) testing and development of a simple performance test for fatigue cracking are described. A 50-mm gauge length was adopted to measure the horizontal and vertical deformations with surface-mounted linear variable differential transducers on an IDT specimen with a 100- or 150-mm diameter and 38-mm thickness. The effect of a concentrated load under loading strips on vertical displacement within the 50-mm gauge length was evaluated by the digital image correlation method, a noncontact, full-field displacement and strain measurement technique. The theory of viscoelasticity was used to develop analytical solutions for creep compliance and center strain from displacements measured on the specimen surface. These solutions were verified by three-dimensional finite element viscoelastic analysis. IDT creep and strength tests were performed on fine and coarse mixtures from WesTrack with various asphalt contents and air void contents, and various parameters determined from the analysis of these data were compared with the known fatigue performance of these mixtures from the WesTrack testing facility. The fracture energy obtained from viscoelastic analysis of the IDT strength test at 20°C correlated highly with the field performance of these mixtures at WesTrack.

The Effect of Hard Coating Properties on Substrate Stresses Under Tribological Loads

A study has been carried out using finite element methods to investigate the influence of hard coatings on substrate stresses under tribological and thermal loads. The study was performed under a uniform distribution of traction (normal and tangential pressure) and temperature. The stresses have been calculated in terms of the ratio of the modulus of elasticity between coating and substrate and the ratio of the coating thickness to the loading strip length at different coefficients of friction and temperatures. The heat transfer problem was solved with regard to a variety of coating properties and the output temperature applied as a thermal load in the structure problem. It is shown that altering the coating modulus of elasticity and coefficient of friction in the presence of a temperature change affects the maximum equivalent stress in the substrate and changes its location. The simulations carried out are discussed in terms of the potential benefits of plasma-based surface coatings and treatments in improving tool performance and the requirements for coating design specifications which will allow design engineers to build surface treatments into new tool designs.

Selection of diluents for copper extraction from oil products

A series of oil products taken from oil refining factories were used as diluents for copper extraction. The influence of diluents on extraction properties has been investigated. The extractants used are Lix984(Henkel) and M5640(Zeneca), and the adaptability of this diluents to these extractants is compared. The checked extraction properties include loading capacity, extraction and strip kinetics, copper/iron selectivity and phase disengagement. The results showed that DSR3 is a suitable diluent for M5640 and Lix984. Further research has been done to reduce the cost of this product by omitting several steps from its production process.

Lateral confinement in generalized strip-loaded optical waveguides

Mode structure in strip-loaded waveguides is studied using an eigenvalue method based on a two-dimensional Fourier analysis. Modified guides where the loading strip is displaced above the core by an additional layer of cladding are considered as a general case. Lateral confinement is found to depend largely on the extent to which the field decays over the strip, and generally worsens as vertical confinement (in the direction perpendicular to the layers of the guide) improves. Conditions that degrade lateral confinement include a large difference in refractive index between core and cladding, a core wide relative to operating wavelength, and large separation between strip and core. Lateral confinement does not vary monotonically with vertical confinement, moreover, but instead may be maximized over a specific range of the guide’s refractive indices.

Strip-loaded waveguide using an underlay

We describe how an ion-exchange waveguide was used as a strip-loading region for a planar polymer waveguide. The loading strip forms an underlay that is well preserved in the substrate. Some branching-channel waveguides were formed by this method, and wall losses were measured. The result shows that the wall losses decrease as a result of strip loading.

Strip-loaded diffused optical waveguides

A strip-loaded diffused optical waveguide consists of a one-dimensional diffused guide with a narrow loading strip of dielectric deposited on the surface. Two-dimensional modes can exist in the diffused material, confined in depth by the diffusion and in width by the loading strip. The propagation constants of these two-dimensional modes are calculated. The requirements for the index of refraction and width of the loading strip are discussed along with the rate of decay of electric-field amplitude away from the strip. A numerical example typical of Ti-diffused LiNbO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> is given.

Optical waveguide loaded with high refractive-index strip film

Mode propagation and field distribution in a strip-loaded waveguide are analyzed for the case where the refractive index of the loading film is higher than that of the waveguide. It is found that the propagation constant is remarkably changed by loading the film with the thickness around the cutoff. As a result, the effect of the optical energy confinement below the strip film is large compared with the previously proposed case where the low-index film is loaded, and the use of the high refractive-index film as the loading strip is very attractive for constructing a three-dimensional waveguide structure.

Strip-Loaded Film Waveguide

Low-loss strip-loaded guides, consisting of 7059 glass film on fused quartz substrate with sputtered SiO 2 as the loading strip, have been investigated. The number of modes supported by the strip-loaded structures were determined experimentally and compared with the values predicted by the application of an equivalent index analysis. Agreement between theory and experiment is good in the case of the smaller number of modes which result from small loading, with the 7059 film thickness far away from cutoff.

A New Roll-Film Dryer

Roll film has become an established feature of serial roentgenography (1–3). Developing, fixing, and washing have been relatively simple with the Fairchild-Smith motor-driven x-ray roll-film processing unit. Drying, however, because of the length of the film, up to 75 feet, has been difficult, requiring careful hanging and separation to prevent sticking (4). Standard hot-air dryers are ill suited for this purpose because of the long time required for the drying, and the necessity of draping and looping of the roll film, demanding constant attention to prevent scratching and falling. Recently, a new drying apparatus has been made available.2 Mechanism of Dryer Parts: The dryer is sturdily constructed of stainless steel and built to process films of varying widths up to 12 inches. Essentially, it is of simple design, consisting of four main parts: a 1/3-horse-power, 60-cycle, 115-volt motor; a spring-type 60-minute timer; three 15-ampere coil heater units; and two fans. The motor has a dual purpose: it provides, through a gear arrangement, transport of the film and furnishes the power for the twin fans. The blowers are arranged on either side, and a baffle forces jets of warmed air to circulate on both sides of the film. Hot air is generated by the three heating units located at the bottom of the dryer. The timer can be pre-set for the estimated drying period and automatically shuts the unit off. Operation: The operation is simple. The Fairchild-Smith processing x-ray roll film developing device is attached to the dryer (Fig. 1). The “leader edge” is detached from the reel and is drawn by hand into the drying chamber. The dryer is then turned “on.” The loading strip is allowed to dry, which usually takes half a minute. It is then attached to the “take-up” spool with a strip of adhesive (Fig. 2). The timer is set according to the length of film to be dried. For a full 75-foot roll at a speed of 22 inches per minute, the drying time is fifty minutes. In case of excessive humidity, the speed of film transport may be slowed. There are four speeds, with a maximum of 22 inches per minute. Adjustment to the desired rate of film transport may be had by pre-setting the lever drive at the clutch. Discussion The roll-film dryer herein described has had constant use during the past year. A total of 150 rolls of film of approximately 75 feet each have been processed. Film varying from 9 1/2 to 12 inches has been used without mechanical difficulties. Because of the compactness of the unit (25 × 25 × 20 inches), it occupies only a small corner of the dark room. Considerable time has been saved in the actual film drying period and, more important, the automatic feature obviates the need of attention. In no instance was there failure to secure a dry, finished, and unmarred product. Summary and Conclusion A new automatic roll-film dryer is here described.