Bottom Fiber Research Articles

Compare the Results Between Model Laboratory-test for Rigid Pavement and EverStressFE Software Analysis

EverStressFE is a 3D finite element modeling software that can be used to analyze the multilayer model pavement (up to four layers possible), which requires elastic modulus and Poisson's ratio of each layer as an input value. The purpose of this paper is to develop a comparison between EversStress-FE-based analysis and laboratory test results and determine the accuracy of the software. In this study, displacement and microstrain behaviors are compared. The vertical strain governing at both the top and bottom fiber of the concrete layer from the laboratory test are 38 and 44, respectively, compared to the EverStressFE result (gz<5.65) (in microstrain). Displacement at the center is 3.4 mm and 0.3 mm according to laboratory test and EverStressFE, respectively. The outcome shows that results of EverStressFE are approximately 10 times smaller than the laboratory test result in terms of displacement and microstrain, meaning that the software is not accurate to validate the laboratory test.

Plastic hinge relocation in concrete structures using the double-slotted-beam system

Several plastic hinge relocation techniques were proposed in the past few decades to avoid the congestion of the transverse steel at the joint, avoid strain penetration into the joint, and maintain the strong-column weak-beam behavior. The challenging aspect of these designs is the level of accuracy in predicting the center of rotation of the beam element, which is a necessary component in the seismic design of reinforced concrete frames. In this research, a newly developed concrete beam-column connection called the double slotted beam (DSB) was developed and used to relocate the plastic hinges in concrete frames, with a high level of accuracy in controlling the location of the center of rotation. Two vertical slots made at the top and bottom fibers of the beam member were introduced in the DSB system to control the location of the center of rotation. The plastic hinge was relocated by moving the vertical slots away from the face of the column. Experimental evaluation of large-scale DSB connections with and without relocated vertical slots showed the excellent performance of the system in achieving high drift capacities, non-tearing action, minimal concrete damage, and reduced bond deterioration in the joint.

Hybrid Microfluidic Platform for Multifactorial Analysis Based on Electrical Impedance, Refractometry, Optical Absorption and Fluorescence.

This paper describes the development of a novel microfluidic platform for multifactorial analysis integrating four label-free detection methods: electrical impedance, refractometry, optical absorption and fluorescence. We present the rationale for the design and the details of the microfabrication of this multifactorial hybrid microfluidic chip. The structure of the platform consists of a three-dimensionally patterned polydimethylsiloxane top part attached to a bottom SU-8 epoxy-based negative photoresist part, where microelectrodes and optical fibers are incorporated to enable impedance and optical analysis. As a proof of concept, the chip functions have been tested and explored, enabling a diversity of applications: (i) impedance-based identification of the size of micro beads, as well as counting and distinguishing of erythrocytes by their volume or membrane properties; (ii) simultaneous determination of the refractive index and optical absorption properties of solutions; and (iii) fluorescence-based bead counting.

Nonsway Model for Lateral Torsional Buckling of Wooden Beams under Wind Uplift

AbstractSimply supported wooden beams nailed to deck boards subjected to wind uplift forces are subjected to compressive stresses at their bottom fibers. Because the restraining action provided by decking is at the top fibers, it is unclear to what extent such restraints are effective in controlling lateral torsional buckling as a possible mode of failure under wind uplift. Present design standards do not have provisions for such cases. Thus, the present study aims to quantify the effect of restraints provided by the deck boards on the lateral torsional buckling capacity of twin-beam-deck systems under wind uplift. Toward this goal, a series of analytical and numerical models were formulated. All models capture the continuous rigid lateral restraint and partial twisting restraint provided by the deck boards. The effects of load type and load position were investigated. The bending stiffness of deck boards was observed to have a significant influence on the lateral torsional buckling capacity of twin-beam-...

Support Conditions and Failure Load Of Beams above Openings

Experimental investigation of failure load is performed for straight and cambered beams above openings. Four cases of beam supports were investigated. These cases are hinge-roller, hinge-hinge, restraint–hinge, and restraint–restraint. Degree of restraining is normal restraining resulted from masonry walls and beams above these walls. Bending strains are measured at top and bottom fibers at mid-span. In compression zone, strains for cambered beams are larger than those for straight beams. The enhancement ratios ranges from 1.05 at beginning of load application to 1.02 at ultimate load. In tension zone, strains for cambered beams are smaller than those for straight beams. The enhancement ratio approximately equal to 0.99 at ultimate load. Failure loads for cambered beams are greater than those for straight beams. Maximum enhancement in failure load due to camber is 9.11% for a beam with a high degree of restraints. (good end restraining) and minimum enhancement is 0.52 % for hinge – roller beam (poor end restraining). Bending moment are predicted from bending strains and these are less than theoretical bending capacity of the section. The difference between experimental and theoretical moments is 0.89 kN.m for hinge-roller beams and 0.97 for restraint-hinge beams.

Effect of Steel Fibres Distribution on Impact Resistance Performance of Steel Fibre Reinforced Concrete (SFRC)

This paper investigate the effect of the mesh distribution on the impact performance of steel fibre reinforced concrete (SFRC) for the concrete slab of 300mm × 300mm size reinforced with varied thickness and fraction volume subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.236 kg drop at 0.57 m height has been used in this research work. The objective of this research is to study the effect of the mesh distribution on the impact resistance SFRC for various slab thickness and fraction volume. Random fibre distribution is the more effective than the top and bottom fibre distribution in terms of absorption of impact energy, crack resistance, the ability to control crack formation and propagation against impact energy.

Prediction of Flexural Strength of Concretes Containing Silica Fume and Styrene-Butadiene Rubber (SBR) with an Empirical Model

In the flexural test, the theoretical maximum tensile stress at the bottom fiber of a test beam is known as the modulus of rupture or flexural strength. This work deals with the effects of Silica Fume and Styrene-Butadiene Latex (SBR) on flexural strength of concrete. An extensive experimentation was carried out to determine the effects of silica fume and SBR on flexural strength of concrete. Two water-binder ratios and several percentages of silica fume and SBR were considered. Abrams’ Law, which was originally formulated for conventional concrete containing cement as the only cementations material, is used for prediction of flexural strength of these concretes. The aim of this work is to construct an empirical model to predict the flexural strength of silica fume-SBR concretes using concrete ingredients and time of curing in water. Also, the obtained results for flexural strength tests have been compared with predicted results.

Analysis of Bending Behavior of Laminated Composite Beam

This paper discusses about the impact of fiber volume fraction on the bending behavior of a laminated composite beam. A two layered composite beam with upper layer made of glass fiber epoxy resin and reinforced with Kevlar at the bottom side of the beam is modeled and structural analysis is carried out. The analysis shows that the tensile strength increases with increase in fiber volume fraction. The compression strength decreases with increase in fiber volume fraction in the upper fiber where as increases in the bottom fiber and the obtained results are correlating with the experimental and analytical studies.

Optimization of the mechanical performance of UD flax/epoxy composites by selection of fibres along the stem

In this study, we measure and compare the mass distribution, morphology and tensile properties of elementary flax fibres (Eden variety) along the stem. A significant improvement is found in the tensile properties of elementary fibres from the base to the middle of the stem, with the Young’s modulus and breaking stress being increased by 19.3% and 56.6%, respectively. UD thermoset composites were manufactured with fibres from the bottom, middle and top of the stem. The efficiency of the reinforcement is lowest with bottom fibres, which appear to be poorly individualized and have many cortical residues on their surface. Several scenarios are proposed to select the most suitable fibres according to the desired mechanical properties of the composite.

Analytical Approach to Predict Pre–Camber Deflection of the Pre-stressed Glulam Beams

A new approach to reinforce glulam timber beams using compressed wood (CW) has been developed by the Author. The compressed wood blocks are inserted into pre-cut holes on the top of glulam beams to produce pre-camber and to generate initial tensile and compressive stresses on the top and on the bottom extreme fiber of the glulam beam, respectively. A simple analytical approach has been developed to predict pre-camber deflections of the beams reinforced with three CW blocks. Assuming that moisture-dependent expansion of the CW block creates an interactive linear pressure between the glulam beam and the CW block, this would generate a pair of eccentric force away from the neutral axis of the beam. It is shown that the pre-camber deflection predicted at midspan of the short beams with various reinforcing arrangements give good agreement with the measured pre-camber from previous experimental results.

Detection of bubble and dew point using optical thin-film interference

Bubble and dew point data are essential for many practical applications, and particularly the safe pipeline transport of post-capture CO2 which contain impurities. These mixtures show highly composition-specific phase properties, necessitating much more experimental data and motivating more rapid and inexpensive measurement methods. Here we demonstrate a responsive small-scale pressure–volume–temperature (PVT) cell system enabled by thin-film interference, and its application to an industrially-relevant post-capture CO2 mixture stream. The small (5mL) volume is one-to-two orders of magnitude faster to equilibrate than conventional PVT cells with viewing windows. Inside the cell, top and bottom optical fiber sensors detect bubble and dew points, respectively. At vapor–liquid transition points, the reflection spectrum from the optical fiber tips report clear interference patterns caused by a thin film on the sensor. In addition to sharply delineating the phase change condition, the sensor also reports the real time thickness of the film (accuracy on the order of 1μm). The method is validated with the well characterized pure CO2 test case (average error of 2.8bar as compared to NIST data), and applied to an industrially-relevant CO2 stream, characteristic of post-capture oxyfuel combustion – an important source for downstream CO2 utilization and storage.

Adjustable prestressing for construction stages of incrementally launched bridges

Incrementally launched bridges, which are generally built with the static scheme of a continuous beam on supports, change their scheme several times during launching. In these different configurations, internal forces vary and bending moments of opposite signs occur in the same sections for different positions of deck during advancement. In these bridges, two different kinds of prestressing are necessary: a temporary one during launching and a definitive one in service life. In this study, the possibility of implementing automatic adjustable prestressing for the launching stages is investigated; the launch prestressing is partially supplied by a system which can change the tension value in the prestressing tendons according to the change in the loads acting on the structure. This adjustable prestressing can be either semi-automatic or totally automatic (auto-adjustable), following the concept of “organic prestressing.” The conditions of activation and deactivation of automatic prestressing through a control system of stresses and deformations are given, giving indications to designers on the additional tendons to be applied in the advanced part of the deck and on the control sections which system implementation needs. A numerical example is given to clarify the concept of adjustable prestressing, details being provided in the case study examined on the evaluation of stresses, on the choice of control sections and on the prestressing tendons, through the aid of diagrams of activation and deactivation of the adjustable prestressing. The results of the study highlight the fact that adjustable prestressing is useful for the advanced part of the deck, in the launching stages of bridges with several spans with similar lengths, especially for the bottom fibres, when sections are placed in the midspan, or for upper fibres when they pass over piers, in the case of limited nose lengths.

Vertical vibrations of composite bridge/track structure/high-speed train systems. Part 3: Deterministic and random vibrations of exemplary system

Abstract Based on the one-dimensional quasi-exact physical and mathematical modelling of a composite (steel-concrete) bridge/track structure/high-speed train system (BTT), developed in Part 2, advanced computer algorithms for the BTT numerical modelling and simulation as well as a computer programme to simulate vertical vibrations of BTT systems are developed. The exemplary bridge under numerical quasi-static and dynamic analysis, designed according to Polish standards, has a 15.00 m span length and belongs to the SCB series-of-types developed in Part 1. The bridge is loaded by a German ICE-3 high-speed train moving at the resonant and maximum operating speeds. A continuously welded ballasted track structure adapted to high operating velocities is applied. The output quantities include: time-histories of the vertical deflection of the main beams at the midspan, time-histories of the longitudinal normal stress in the bottom fibres of the main beams at the midspan, time-histories of the vertical acceleration of the bridge deck at the midspan, time-histories of the vertical accelerations of the suspension pivots in car-bodies, time-histories of the dynamic pressures of the wheel sets of moving rail-vehicles. The design quantities, understood as the extreme values of the output quantities, are used to verify the design conditions. The basic random factor, i.e. vertical track irregularities of the track, is taken into consideration. Basic statistics of the design quantities treated as random variables are calculated and taken into account in the design conditions.

SU‐E‐T‐289: Scintillating Fiber Based In‐Vivo Dose Monitoring System to the Rectum in Proton Therapy of Prostate Cancer: A Geant4 Monte Carlo Simulation

Purpose:To construct a dose monitoring system based on an endorectal balloon coupled to thin scintillating fibers to study the dose delivered to the rectum during prostate cancer proton therapyMethods:The Geant4 Monte Carlo toolkit version 9.6p02 was used to simulate prostate cancer proton therapy treatments of an endorectal balloon (for immobilization of a 2.9 cm diameter prostate gland) and a set of 34 scintillating fibers symmetrically placed around the balloon and perpendicular to the proton beam direction (for dosimetry measurements)Results:A linear response of the fibers to the dose delivered was observed within &lt;2%, a property that makes them good candidates for real time dosimetry. Results obtained show that the closest fiber recorded about 1/3 of the dose to the target with a 1/r2 decrease in the dose distribution as one goes toward the frontal and distal top fibers. Very low dose was recorded by the bottom fibers (about 45 times comparatively), which is a clear indication that the overall volume of the rectal wall that is exposed to a higher dose is relatively minimized. Further analysis indicated a simple scaling relationship between the dose to the prostate and the dose to the top fibers (a linear fit gave a slope of −0.07±0.07 MeV per treatment Gy)Conclusion:Thin (1 mm × 1 mm × 100 cm) long scintillating fibers were found to be ideal for real time in‐vivo dose measurement to the rectum for prostate cancer proton therapy. The linear response of the fibers to the dose delivered makes them good candidates of dosimeters. With thorough calibration and the ability to define a good correlation between the dose to the target and the dose to the fibers, such dosimeters can be used for real time dose verification to the target

Numerical Modelling of the Initial Stress and Upward Deflection of Glulam Beams Pre-Stresseed by Compressed Wood

A new approach to reinforce glulam timber beams has been developed by using compressed wood (CW) which is made of a lower grade wood through densification processes. In the reinforcing practice, compressed wood blocks are inserted into pre-cut holes on the top of glulam beams to produce pre-camber and to generate initial tensile and compressive stresses on the top and the bottom extreme fibre of the glulam beam. In order to optimize the size, the number and the location of CW blocks, 3-D finite element models have been developed. 3D non-linear finite element models have been developed to simulate the pre-camber of Glulam beams locally reinforced by compressed wood blocks. The models developed have also produced the initial tensile and compressive stresses at the top and bottom extreme fibres with building-up moisture-dependent swelling on the CW blocks. With the pre-camber and the initial stress state that cancel out proportions of working deflection and stresses.

Finite Element Modeling of Laminated Composite Plates with Locally Delaminated Interface Subjected to Impact Loading

This paper investigates the effects of localized interface progressive delamination on the behavior of two-layer laminated composite plates when subjected to low velocity impact loading for various fiber orientations. By means of finite element approach, the laminae stiffnesses are constructed independently from their interface, where a well-defined virtually zero-thickness interface element is discreetly adopted for delamination simulation. The present model has the advantage of simulating a localized interfacial condition at arbitrary locations, for various degeneration areas and intensities, under the influence of numerous boundary conditions since the interfacial description is expressed discretely. In comparison, the model shows good agreement with existing results from the literature when modeled in a perfectly bonded state. It is found that as the local delamination area increases, so does the magnitude of the maximum displacement history. Also, as top and bottom fiber orientations deviation increases, both central deflection and energy absorption increase although the relative maximum displacement correspondingly decreases when in contrast to the laminates perfectly bonded state.

Flexural behaviour of CFST members strengthened using CFRP composites

Concrete filled steel tubular members (CFST) become a popular choice for modern building construction due to their numerous structural benefits and at the same time aging of those structures and member deterioration are often reported. Therefore, actions like implement of new materials and strengthening techniques become essential to combat this problem. The application of carbon fibre reinforced polymer (CFRP) with concrete structures has been widely reported whereas researches related to strengthening of steel structures using fibre reinforced polymer (FRP) have been limited. The main objective of this study is to experimentally investigate the suitability of CFRP to strengthening of CFST members under flexure. There were three wrapping schemes such as Full wrapping at the bottom (fibre bonded throughout entire length of beam), U-wrapping (fibre bonded at the bottom throughout entire length and extended upto neutral axis) and Partial wrapping (fibre bonded in between loading points at the bottom) introduced. Beams strengthened by U-wrapping exhibited more enhancements in moment carrying capacity and stiffness compared to the beams strengthened by other wrapping schemes. The beams of partial wrapping exhibited delamination of fibre and were failed even before attaining the ultimate load of control beam. The test results showed that the presence of CFRP in the outer limits was significantly enhanced the moment carrying capacity and stiffness of the beam. Also, a non linear finite element model was developed using the software ANSYS 12.0 to validate the analytical results such as load-deformation and the corresponding failure modes.

Influence of forming conditions on fiber tilt

Fiber tilt describes the projection of fiber length in the thickness direction of paper. The projection is described by the tilt angle of fibers with respect to the plane of the sheet. A simple model for fiber tilt is based on jet-to-wire velocity differential in combination with cross-flows on the wire. The tilt angle of a fiber is found to vary as the sine of its in-plane orientation angle. The phase of variation is a large multiple of the fiber-misalignment angle associated with the cross flow. The multiple can decrease from 40 to 8 as the cross-flow angle increases from 1° to 10°, showing a high degree of nonlinearity. Application of the model was demonstrated by characterizing previously published tape-peels conducted at 45° intervals on both sides of a lightweight-coated base sheet. Degree of fiber pullout, a surrogate for fiber tilt, was indicated by measuring the mean gray value of images of the tape surface against a dark background. On tape peels from each side of the sheet, gray value versus angle was well described by a sine wave, but the phase of the wave was different on each side. By comparing the phases of the sine waves with those of the model, top and bottom fiber misalignment angles were calculated. The model is most sensitive to variations in misalignment angles less than 2.5°.

Integral Abutment Bridge behavior under uncertain thermal and time-dependent load

Prediction of prestressed concrete girder integral abutment bridge (IAB) load effect requires understanding of the inherent uncertainties as it relates to thermal loading, time-dependent effects, bridge material properties and soil properties. In addition, complex inelastic and hysteretic behavior must be considered over an extended, 75-year bridge life. The present study establishes IAB displacement and internal force statistics based on available material property and soil property statistical models and Monte Carlo simulations. Numerical models within the simulation were developed to evaluate the 75-year bridge displacements and internal forces based on 2D numerical models that were calibrated against four field monitored IABs. The considered input uncertainties include both resistance and load variables. Material variables are: (1) concrete elastic modulus; (2) backfill stiffness; and (3) lateral pile soil stiffness. Thermal, time dependent, and soil loading variables are: (1) superstructure temperature fluctuation; (2) superstructure concrete thermal expansion coefficient; (3) superstructure temperature gradient; (4) concrete creep and shrinkage; (5) bridge construction timeline; and (6) backfill pressure on backwall and abutment. IAB displacement and internal force statistics were established for: (1) bridge axial force; (2) bridge bending moment; (3) pile lateral force; (4) pile moment; (5) pile head/abutment displacement; (6) compressive stress at the top fiber at the mid-span of the exterior span; and (7) tensile stress at the bottom fiber at the mid-span of the exterior span. These established IAB displacement and internal force statistics provide a basis for future reliability-based design criteria development.

Dynamic Response of Composite Beams with Partial Shear Interaction Using a Higher-Order Beam Theory

Dynamic response of composite beams with partial interaction is presented using a one-dimensional finite-element model based on a higher-order beam theory. The proposed model takes into account the effect of partial shear interaction between the adjacent layers, as well as the transverse shear deformation of the beam. A third order variation of the axial displacement of the fibers over the beam depth is taken to have a parabolic variation of shear stress, which vanishes at both the top and bottom fibers of the transverse composite surface, as clearly derived on the free and tangentially unloaded surface of the continua. In the proposed finite-element model, there is no need to incorporate any shear correction factor, and the model is free from the shear locking problem. The proposed numerical model is validated by comparing the results with those available in the literature. Many new results are presented, because there are no published results on vibration and buckling of composite beams based on higher-order beam theory.