T-shaped Cross-section Research Articles

Hysteretic behavior of multi-cell T- Shaped concrete-filled steel tubular columns

Several multi-cell improvement methods for solving existing problems of conventional T-shaped concrete-filled steel tubular (T-CFST) columns and for determining steel׳s optimal distributions for increasing the strength and ductility of the columns are presented. An experimental study with eight multi-cell T-shaped concrete-filled steel tubular (MT-CFST) columns and one conventional T-CFST column under low frequency cyclic loading was conducted. Effects of the multi-cell layout and the concrete strength on the hysteretic behavior of the specimens were investigated. Experimental results showed that the lateral load-displacement hysteretic curves of the columns were generally saturated with a slight pinching effect. Owing to the asymmetry of the T-shaped cross section, the hysteretic behavior of the composite columns is asymmetrical in different loading directions. The improved MT-CFST columns showed better seismic behavior due to high load bearing capacity, ductility and energy dissipation capacity. Furthermore, the non-linear finite element analysis was performed to simulate the hysteretic behavior of the specimens and the numerical results agreed well with the test results. In conclusion, with an increasing axial load ratio, the ultimate lateral load in the pushing direction gradually decreases and is reached earlier, whereas the ultimate lateral load in the pulling direction increases slightly under low axial ratio and decreases under high axial load ratio.

Power evaluation of flutter-based electromagnetic energy harvesters using computational fluid dynamics simulations

H- and T-shaped cross sections are known to be susceptible to rotational single-degree-of-freedom aerodynamic instabilities. Here, such self-excited aerodynamic response of a T-shaped cantilever structure is used to extract energy, which is then converted into electric power through an electromagnetic transducer. The complex fluid–structure interaction between the cantilever harvester and wind flow is analyzed numerically and experimentally. To study the dynamic response of the cantilever and estimate the power output from the harvester, numerical simulations based on the vortex particle method are performed to determine the aerodynamic damping of the harvester section and to analyze the stability behavior of the section. The estimated aerodynamic damping parameter together with the mechanical and electrical damping parameters in the harvester are used to find the critical wind speed of flutter onset as well as the optimum load resistance. Wind tunnel experiments are conducted to validate the simulation results.

Experimental and numerical study on the effect of repairing reinforced concrete cracked beams strengthened with carbon fibre reinforced polymer laminates

This paper presents experimental and numerical investigations on the effect of repairing cracks in reinforced concrete (RC) beams prior to strengthening them with carbon fibre reinforced polymer (CFRP) laminates. The experimental campaign comprised flexural tests on three types of full-scale RC beams with T-shaped cross-section: (i) two reference un-strengthened beams, (ii) two CFRP-strengthened beams previously loaded and cracked, and (iii) two CFRP-strengthened beams, previously loaded, cracked and repaired with epoxy resin. The repair and strengthening techniques consisted of respectively injecting the cracks with epoxy resin and applying CFRP laminates according to the externally bonding reinforcement technique. In the numerical study, the structural response of all beams tested was simulated using the finite element software Atena, which features a smeared cracked model constitutive relationship for concrete. A parametric study was carried out in which the influence of material parameters, namely the fracture energy, on the beams structural response was assessed. Experimental results showed that repairing cracks by means of epoxy injection before strengthening them with CFRP laminates provided a considerable increase of stiffness, but only a slight increase of ultimate strength, as failure was triggered by the debonding of the strengthening system at the anchorage zones. In the numerical study a very good agreement with experimental data was obtained. For the repaired and strengthened beams, such agreement was obtained by increasing concrete’s fracture energy when compared to that of the reference beams.

Prestressed Concrete Beam Bridge Design and Main Parameters of Prestressed Steel Beam Calculations and Arrangement

Prestressed concrete beam bridge cross-section using T-shaped cross-section. Anti-shrinkage reinforcement requirements adopted under the dense arrangement of all the memorial steel welds are double-sided welding, using a special form of prestressed reinforcement arranged in assembly is completed, tension on the deck to prevent the beam edge cracking.

A New Solution to the Height of the Compressive Area of Reinforced Concrete Beams during Service Stage

The compressive height of reinforced concrete flexural members in service stage is generally obtained by equations based on the concept, moment-of-area of conversion area with respect to the neutral axis in tension zones equaling to that in compression zones. In this paper a specific calculation method of compressive height for singly or doubly reinforced rectangular and T-shaped cross sections is proposed.

Fabrication and Characterization of Micromachined Piezoelectric T-Beam Actuators

This paper presents a monolithically fabricated microelectromechanical piezoelectric cantilever beam with a T-shaped cross section capable of in-plane and out-of-plane displacements and sensing. High-aspect-ratio T-beams are achieved by direct micromachining of bulk lead zirconate titanate (PZT-4) via reactive ion etching of 65- μm-deep features. Electrodes deposited on the top and bottom web and flange regions of the T-shaped structure allow in-plane and out-of-plane motion actuation and sensing. The T-beam structures were tested for in-plane and out-of-plane tip displacements, out-of-plane blocking force, and impedance response. These results are explained using analytical models that predict static deflection, blocking force, and resonance frequency. Nine prototype micromachined T-beams are fabricated that achieve up to 129 μm of out-of-plane displacement, 11.6 μm of in-plane displacement, and 700 μN of out-of-plane blocking force.

UPT rectangular and flanged shear walls of high-strength CASIEL-TLM masonry: Experimental and numerical push-over analysis

The mechanical behaviour of unbonded post-tensioned (UPT) shear walls of high-strength CAlcium SIlicate ELement masonry with Thin-Layer Mortar (CASIEL-TLM masonry) was investigated experimentally and numerically. Eight walls were tested with the following key variables: unit type, prestress level and cross-sectional shape (rectangular or T-shaped with interlocking of web and flange). An extensive measurement scheme was adopted that allowed derivation of average curvatures and strains in the bottom region of the wall in addition to wall displacements. Since UPT masonry is characterised by the absence of local compatibility between masonry and the UPT tendons, a numerical model for quasi-static, monotonic push-over analysis was developed that provides an iterative solution for the global interaction between masonry and UPT tendons. A common masonry stress–strain diagram was adopted in the numerical model. A peculiarity of CASIEL-TLM masonry is the kicker course, which reduces the stiffness of the bottom region of the shear wall. This layer was modelled with no-tension, linear-elastic behaviour and a reduced stiffness. Nevertheless, the model underestimates the experimental deformations of the rectangular shear walls, while the strength is in reasonable agreement. The walls with T-shaped cross-section failed prematurely by shear of the web-flange interface, resulting in diagonal splitting cracks in the interlocking units. This paper deals with the experimental results of UPT CASIEL-TLM masonry shear walls with rectangular and T-shaped cross-section and with the numerical modelling of the overturning behaviour of UPT shear walls with rectangular cross-section.

The Flange Effect of Brick Masonry Wall Subjected to Seismic Effect

This paper researces the effect of flange width on anti-seismic performance of flanged brick masonry walls. Four T-shaped cross section unreinforced brick masonry walls with different flange width and one rectangular shaped cross section brick masonry wall are studied and analyzed by ABAQUS finite element method.Analyze and compare the force-displacement curves of flanged brick masonry wall under the composed of vertical and lateral load.The results indicate that the flange width has a significant effect on the shear bearing capacity and ductility. The shear bearing capacity and ductility factor of T-shaped cross section brick masonry walls with 1.6m flange width are respectively 20% and 50% higher than the no flange wall .The flange effect is obvious when the flange width is not more than 1.6m, the value of shear bearing capacity and ductility are higher when the flange width become longer.

Enhancing predicted shear strength for the assessment of existing concrete bridges

This paper presents a method of calculating the enhanced shear capacity of concrete T-beams that arises from the increased concrete contribution provided by the flange overhangs of reinforced concrete (RC) T-beams in positive bending or sagging. The method applies recognised provisions in the Australian Concrete Bridge Design Code AS5100-5:2004 to enhance the prediction of shear strength of concrete T-beams based on failure mechanisms reported in published experimental work. The method is applied to specimens reported in previous experimental studies that report shear failure in RC T-beams in positive bending or sagging. It is shown to yield conservative estimates of shear strength enhancement that arise in a T-beam giving consideration to the flange overhangs. A discussion is provided to outline the application of this method for calculating shear strength of concrete highway bridge decks where T-shaped cross-sections resist an applied shear. The paper discusses the variability that arises in the prediction of shear strength from applying the method. The variability observed in the application is consistent with that observed in shear strength tests used as a basis for code-based formulations. All international codes use a lower value of strength reduction for shear than pure flexure to cater for this. It is recommended that confidence in the method be increased by applying the method to more testing targeted at isolating the flange proportions on the shear strength of RC T-beams in sagging.

Enhancing Predicted Shear Strength for the Assessment of Existing Concrete Bridges

This paper presents a method of calculating the enhanced shear capacity of concrete T-beams that arises from the increased concrete contribution provided by the flange overhangs of reinforced concrete (RC) T-beams in positive bending or sagging. The method applies recognised provisions in the Australian Concrete Bridge Design Code AS5100–5:2004 to enhance the prediction of shear strength of concrete T-beams based on failure mechanisms reported in published experimental work. The method is applied to specimens reported in previous experimental studies that report shear failure in RC T-beams in positive bending or sagging. It is shown to yield conservative estimates of shear strength enhancement that arise in a T-beam giving consideration to the flange overhangs. A discussion is provided to outline the application of this method for calculating shear strength of concrete highway bridge decks where T-shaped cross-sections resist an applied shear. The paper discusses the variability that arises in the prediction of shear strength from applying the method. The variability observed in the application is consistent with that observed in shear strength tests used as a basis for code-based formulations. All international codes use a lower value of strength reduction for shear than pure flexure to cater for this. It is recommended that confidence in the method be increased by applying the method to more testing targeted at isolating the flange proportions on the shear strength of RC T-beams in sagging.

Piezoelectric T-Beam Actuators

This paper develops models, fabricates, experimentally tests, and optimizes a novel piezoelectric T-beam actuator. With a T-shaped cross-section, and bottom and top flanges and web electrodes, a cantilevered beam can bend in both in-plane and out-of-plane directions upon actuation. Analytical models predict the tip displacement and blocking force in both directions. Six mesoscale T-beam prototypes are monolithically fabricated by machining and microfabrication techniques and experimentally tested for in-plane and out-of-plane displacements and out-of-plane blocking force. The analytical models closely predict the T-beam displacement and blocking force performance. A nondimensional analytical model predicts that all T-beam designs for both in-plane and out-of-plane actuations, regardless of scale, have nondimensional displacement and blocking force equal to nondimensional voltage. Another form of nondimensional model optimizes the T-beam cross-section for maximum performance. Optimization study shows that a cross-section with width ratio, b*, and thickness ratio, t*, approaching zero produces maximum displacement, b*=t*=0.381 produces maximum blocking force, and b*≈0.25, t*≈0.33 produces maximum mechanical energy.

The Equivalence Method of Protective Structures

In this paper, according to the structure of warships, the equivalence method of the protective structure with reinforcing ribs is presented abided by the principal of equivalence in rigidity. The minimized model and the equivalence model of the protective structure with reinforcing ribs penetrated by projectiles are investigated in experiment and numerical simulations, and the results show that the equivalence method of the protective structure is reasonable. The reinforcing ribs are extensively used in protective structures, especially in ship structures. The reinforcing ribs are characterized in extensive distribution range and little weight of unit length, and have the main effect that the rigidity requirement of the structure is satisfied so that the structure has enough rigidity stability. However, the big and the small reinforcing ribs in actual structures originally have small size of the cross sectional area (CSA). According to a usual model research method, after an original structure is proportionally reduced according to the minimized proportion of one to four [1], the size of the CSA of the big and the small reinforcing ribs becomes smaller, and the shape of the cross sectional area is shown in Figure1. Under such circumstances, an experimental research on the dynamic response of the reinforcing ribs under the impact load has the characteristics of great difficulty and bad feasibility, and in addition, the reliability of reflecting target characteristic by a proportionally reduced model is very low[2]. In order to study the action of the reinforcing ribs more objectively, the T-shaped cross section of the reinforcing ribs is converted to a rectangular cross section according to the principle of rigidity equivalence, and then, the action can be researched actually. The study method is given as follows.

Synthesis of In2O3 Nanowire-Decorated Ga2O3 Nanobelt Heterostructures and Their Electrical and Field-Emission Properties

We report on the synthesis of In2O3 nanowire-decorated Ga2O3 nanobelt heterostructures via a simple catalyst-free method. A typical heterostructure, where an In2O3 nanowire forms a sort of a "dorsal fin" on the Ga2O3 nanobelt, exhibits the T-shaped cross-section. The structure, electrical porperties, and field-emission properties of this material are systematically investigated. The heterostructures possess a typical n-type semiconducting behavior with enhanced conductivity. Field-emission measurements show that they have a low turn-on field (approximately 1.31 V/microm) and a high field-enhancement factor (over 4000). The excellent field-emission characteristics are attributed to their special geometry and good electrical properties. The present In2O3-decorated Ga2O3 heterostructures are envisaged to be decent field-emitters useful in advanced electronic and optoelectronic nanodevices.

Performance Evaluation of Glass Fiber-Reinforced Polymer Shear Reinforcement for Concrete Beams

Using fiber-reinforced polymer (FRP) reinforcing bars as the main reinforcement for concrete structures in severe environments is becoming a widely accepted solution to overcome the problem of steel corrosion and the related deteriorations. Due to the relatively lower cost of glass FRP (GFRP) bars compared to the other commercially available FRP bars, the use of GFRP bars in reinforced concrete (RC) structures has been widely investigated in the last few years. This paper reports experimental data on the shear strength of concrete beams reinforced with GFRP stirrups. A total of four large-scale RC beams with a total length of 7000 mm (276 in.) and a T-shaped cross section were constructed and tested up to failure. The test variables were type and ratio of shear reinforcement (stirrups). The test beams comprised three beams reinforced with sand-coated GFRP stirrups of 9.5 mm (3/8 in.) diameter spaced at d/2, d/3, and d/4 (where d is the beam depth), and a reference beam reinforced with conventional steel stirrups of 9.5 mm (3/8 in.) diameter spaced at d/2. As designed, the beams failed in shear due to GFRP stirrup rupture or steel stirrups yielding. ACI 440.1R-06 and the updated version of CAN/CSA S6-06 are able to predict the shear strength of beams reinforced with GFRP stirrups with a reasonable accuracy. The analytical approach using Response 2000 (R2K), which is based on the modified compression field theory (MCFT), predicted well the shear capacity of the beams reinforced with GFRP stirrups, but overestimated their shear crack width.

Shear Performance of RC Bridge Girders Reinforced with Carbon FRP Stirrups

One of the main components in girder-type bridges is bridge girder. This paper presents experimental data on the behavior and shear strength of concrete bridge girders reinforced with carbon fiber-reinforced polymer (CFRP) stirrups. A total of four large-scale reinforced concrete beams with a total length of 7,000 mm and a T-shaped cross section were constructed and tested up to failure. The test variables were the type and ratio of shear reinforcement (stirrups). The test beams included three beams reinforced with sand-coated CFRP stirrups of 9.5-mm-diameter spaced at d/2, d/3, and d/4 (where d is the beam depth) and a control beam reinforced with conventional steel stirrups of 9.5-mm-diameter spaced at d/2. The geometry of the test prototypes were selected to simulate the New England Bulb Tee (NEBT) beams that are being used by the Ministry of Transportation of Québec, Canada. As designed, three beams failed in shear due to CFRP stirrup rupture or steel stirrup yielding. While, the forth one, reinforced with CFRP stirrups spaced at d/4, failed in flexure due to yielding of longitudinal reinforcement. The test results were compared to predictions provided by different codes and design guidelines. The current ACI 440.1R-06 design method provides conservative predictions; however, the CAN/CSA S6-06 and JSCE 1997 underestimate the contribution of the FRP stirrups due to low strain limits.

Behavior of Double Skin Composite Wall Subjected to In-Plane Cyclic Loading

Double skin composite walls are composed of two steel plate skins connected by tie bars, with the space between them filled with concrete. They were developed to reduce wall thickness, to enhance constructability, and to enable rapid construction by eliminating the use of formwork and reinforcing bars. In the present study, cyclic testing was performed to investigate the seismic behavior of isolated and coupled double skin composite walls with rectangular and T-shaped cross sections. The wall specimens failed mainly by tensile fracture of the welded joints at the wall base and coupling beams, or by local buckling of the steel plates. Because of their large depth, the ductility of the wall specimens was not as good as that of beams having less depth. In particular, the ductility of the walls was significantly affected by the strengthening methods used for the wall base. The load-carrying capacities of the isolated and coupled wall specimens were evaluated using plastic stress distributions in their cross sections, which provided satisfactory predictions.

Fire resistance of reinforced concrete columns with L-, T-, and +-shaped cross-sections

Four full-scale reinforced concrete (RC) columns with L-shaped cross-sections, four full-scale RC columns with T-shaped cross-sections, three full-scale RC columns with +-shaped cross-sections, and one full-scale RC column with a square cross-section were experimentally investigated for fire resistance following the ISO834 standard heating process. The effects of axial load ratio and fire exposure condition on failure mode, axial deformation and fire resistance of the columns were analyzed. The experimental results showed that: (a) when the axial load ratio is 0.55, the fire resistances of the columns with L-, T-, and +-shaped cross-sections subjected to fire on all sides were 60–73% that of the column with the square cross-section. (b) In the case of samples subjected to fire on all sides, the fire resistance of columns with differently-shaped cross-sections increased in the following order: L-shaped cross-section <T-shaped cross-section <+-shaped cross-section. A computer program RCSSCF was developed to calculate temperature, deformation, and fire resistance of the loaded columns with L-, T-, and +-shaped cross-sections. The results of the numerical simulation were compared with those of the full-scale fire resistance tests.

Effectiveness of the use of steel fibres on the torsional behaviour of flanged concrete beams

Abstract The behaviour under torsion of reinforced concrete beams with steel fibres as mass reinforcement is experimentally investigated. Short hooked-ended steel fibres with aspect ratio lf/df = 37.5 are used. Test results of 35 beams with rectangular, L-shaped and T-shaped cross-sections tested in pure torsion are presented and discussed. Various configurations of conventional and fibre steel reinforcement are examined. The experimental program includes (i) plain concrete beams (control specimens), (ii) specimens with longitudinal reinforcing bars and (iii) specimens with bars and stirrups. All cases are examined with 0%, 1% and 3% steel fibre volume fractions. The use of steel fibres as the only shear torsional reinforcement is also reported herein, in an attempt to examine the effectiveness of fibres as a potential replacement of stirrups. Test results indicated that fibrous concrete beams exhibited improved overall torsional performance with respect to the corresponding non-fibrous control beams. The addition of steel fibres was essential to the tested beams without or with inadequate conventional steel reinforcement. Fibres prevented the sudden brittle failure of both rectangular and non-rectangular beams and proved to be under some circumstances adequate to provide for enhanced torsional moment capacities, even in the case of full replacement of stirrups with steel fibres.

In the ear hearing aid utilizing annular acoustic seals

Disclosed is a hearing aid assembly (12) wherein the hearing aid is comprised of an acoustic receiver, an acoustic transmitter (32), and a body (13), and an annular channel (25), wherein the acoustic receiver is designed to fit into a external acoustic meatus of an ear (10), the acoustic transmitter (32) is designed to fit into a inner ear canal (14), and the generally cylindrical body (13) is disposed between the receiver and the transmitter (32), the annular channel (25) is disposed on the surface of the body (13) such that it circumscribes the body's (13) circumference. The annular channel (25) is adapted to receive an annular ring (16) which functions as an acoustic seal and which, in one preferred embodiment, has a T-shaped cross-section.

Experimental Behavior of Prestressed LVL-Concrete Composite Beams

The paper investigates the stiffness and strength of composite laminated veneer lumber (LVL) and concrete beams intended for use in long-span flooring systems. Quasi-static bending tests and impact tests were conducted on four, 6 m long specimens to observe the failure mechanisms and to estimate the static and dynamic properties of the systems. One specimen, with a plain LVL member, a strong shear connection, and a concrete slab, was used as a control. The other three specimens investigated the use of (i) a proprietary, lightweight nonstructural concrete panel as a slab; (ii) a straight prestressing tendon and a strong shear connection; and (iii) a draped prestressing tendon and a weaker shear connection. All four specimens had a T-shaped cross section, with the slab supported by either one or two LVL beams. The stiffness of control beam, which is mostly related to the stiffness of the shear connection, is shown to be almost three times that of a bare LVL beam, but the beam is only 74% stronger than the bare beam. The prestressing tendons are shown to have little effect on the stiffness and strength, but reduce the deflection due to permanent load, particularly when they are draped. The proprietary lightweight concrete panels are shown to provide little structural benefit.