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Subassemblage tests and finite element analyses of sandwiched buckling-restrained braces
(2010-08-01)
Chou, Chung-Che
;
Chen, Sheng-Yang
;
土木工程學系
;
Department of Civil Engineering
This study presents the experimental and finite element analysis results of a proposed steel buckling-restrained brace (BRB). The proposed BRB has two components: (1) a steel core plate that carries all axial forces during tension and compression, and (2) two identical restraining members that sandwich the core plate with fully tensioned high-strength A490 bolts to prevent core buckling. Instead of using unbonded material, a small air gap is provided between the core plate and the restraining members to allow for lateral expansion of the core plate under compression. Since two restraining members can be disassembled easily by removing the bolts, a damaged steel core can be replaced after a large earthquake. Thus, manufacturing new restraining members is not required. Four BRB subassemblages were tested to investigate the inelastic deformation capabilities and verify the stability predictions for the braces. Test results indicate that three BRBs with sufficient flexural rigidity of the restraining member develop (1) stable hysteretic responses up to core axial strains of 2.1%-2.6%, (2) maximum compressive loads of 1724-1951 kN (1.4-1.6 times the actual yield load), and (3) a cumulative plastic ductility that is much higher than that specified in AISC seismic provisions (2005). One BRB, intentionally designed with inadequate flexural rigidity of the restraining member, experienced global buckling as predicted. Nonlinear finite element analysis was conducted for each BRB for a correlation study. The objective of the analysis was to conduct a parametric study for different BRBs to further verify the effects of restraining member size, number of bolts, core plate length and cross-sectional area on buckling load evaluation. The design procedure for the sandwiched BRB was provided based on test and finite element analysis results. (C) 2010 Elsevier Ltd. All rights reserved.
Numerical solution of active earth pressures on rigid retaining walls built near rock faces
(2010-11-01)
Fan, Chia-Cheng
;
Fang, Yung-Show
;
土木工程學系
;
Department of Civil Engineering
For retaining walls built in mountainous regions, narrow backfill spaces are often encountered. The space to fully develop the active wedge is restricted for walls with a limited backfill space. This paper presents a numerical study on the behaviour of active earth pressures behind a rigid retaining wall with limited backfill space of various geometries. The active earth pressure for a wall built with limited backfill space is considerably less than that of the Coulomb solution, and the location of the resultant of active earth pressures is noticeably higher than one-third of the wall height. The coefficient of active earth pressures is as low as 0.5-0.6 times the Coulomb solution and the h/H value reaches up to 0.4-0.37 if aspect ratio of the fill space is in the range from 0.1 to 0.2. A clear trend between the ratio of the coefficient of active earth pressures at constrained fill conditions over the Coulomb K(a) value and the aspect ratio of the fill-space geometry is obtained. (C) 2010 Elsevier Ltd. All rights reserved.
Biomechanical comparison of three stand-alone lumbar cages - a three-dimensional finite element analysis
(2013-10-02)
Chen, Shih-Hao
;
Chiang, Ming-Chieh
;
Lin, Jin-Fu
;
Lin, Shang-Chih
;
Hung, Ching-Hua
Background: For anterior lumbar interbody fusion (ALIF), stand-alone cages can be supplemented with vertebral plate, locking screws, or threaded cylinder to avoid the use of posterior fixation. Intuitively, the plate, screw, and cylinder aim to be embedded into the vertebral bodies to effectively immobilize the cage itself. The kinematic and mechanical effects of these integrated components on the lumbar construct have not been extensively studied. A nonlinearly lumbar finite-element model was developed and validated to investigate the biomechanical differences between three stand-alone (Latero, SynFix, and Stabilis) and SynCage-Open plus transpedicular fixation. All four cages were instrumented at the L3-4 level. Methods: The lumbar models were subjected to the follower load along the lumbar column and the moment at the lumbar top to produce flexion (FL), extension (EX), left/right lateral bending (LLB, RLB), and left/right axial rotation (LAR, RAR). A 10 Nm moment was applied to obtain the six physiological motions in all models. The comparison indices included disc range of motion (ROM), facet contact force, and stresses of the annulus and implants. Results: At the surgical level, the SynCage-open model supplemented with transpedicular fixation decreased ROM (>76%) greatly; while the SynFix model decreased ROM 56-72%, the Latero model decreased ROM 36-91%, in all motions as compared with the INT model. However, the Stabilis model decreased ROM slightly in extension (11%), lateral bending (21%), and axial rotation (34%). At the adjacent levels, there were no obvious differences in ROM and annulus stress among all instrumented models. Conclusions: ALIF instrumentation with the Latero or SynFix cage provides an acceptable stability for clinical use without the requirement of additional posterior fixation. However, the Stabilis cage is not favored in extension and lateral bending because of insufficient stabilization.
The development of a non-surgical direct drive hearing device with a wireless actuator coupled to the tympanic membrane
(2013-12-01)
Song, Yu-Lin
;
Jian, Jhong-Ting
;
Chen, Wei-Zen
;
Shih, Chih-Hua
;
Chou, Yuan-Fang
A non-surgical, direct driving hearing device with an actuator placed on the tympanic membrane was designed, fabricated and tested. The actuator consisted of two photodiodes, an aluminum ring, two neodymium iron permanent magnets, two opposing wound coils, a latex membrane and a Provil Novo (TM) membrane. The transducer coupled to the ear drum-utilizing photodiodes and permanent magnets on the motive components could eliminate the need for electrical connections to the moving components. An optic probe was designed to allow sound and light signals to enter the ear canal. By using opto-electromagnetic coupling, the developed hearing device could transmit information over a distance without using cables. The wireless actuator was achieved by two configurations: in one, two light emitting diodes were used for carrying the input signals, and in the other, the corresponding photodiodes were used for receiving the light signals and generating the currents in the actuator. The wireless actuator was designed to use light to carry energy and transmit the signals; thus, the occlusion effect created by traditional ear molds could be avoided. Finally, the wireless actuator was fabricated and tested with a laser Doppler vibrometer. The actuator showed displacements of vibration between 30-0.2 nm and from 400 Hz to 7 kHz with reduced vibration at higher frequencies. The gain of the actuator with 120 mu A on the umbo displacement was approximately 3-13 dB from 400 to1500 Hz and decreased to 6 dB between 1500 Hz to 3 kHz and down to -1 to -6 dB above 3 kHz. Distortions of the umbo vibration amplitude were approximately -1 to -10 dB across frequencies. The results suggest that light can transmit the sound signal remotely and that adequate amplification can be achieved by this actuator. The reduced amplitude above 3 kHz was a consequence of the mass effect of the actuator, which should be miniaturized in the future. Crown Copyright (c) 2013 Published by Elsevier Ltd. All rights reserved.
Internal flange stiffened moment connections with low-damage capability under seismic loading
(2013-08-01)
Chou, Chung-Che
;
Lo, Sheng-Wei
;
Liou, Gin-Show
;
土木工程學系
;
Department of Civil Engineering
This study presents the seismic performance of steel moment connections using internal flange stiffeners (IFSs) welded at the face of the wide-flange column and inner side of the beam flange. The objective is to develop a steel moment connection that can achieve good seismic performance with low-damage capability during a large earthquake loading and minimize the repair cost. Four large-scale moment connections were tested to validate the cyclic performance. One connection which represented a welded-unreinforced flange-bolted web connection failed before finishing cyclic tests at a drift of 4%. Three IFS moment connections showed excellent performance and low damage after experiencing the AISC seismic load twice up to the target drift of 4%, without strength reduction. The specimens were also modeled using the computer program ABAQUS to further verify the effectiveness of the IFS in transferring beam moment to the column and to investigate potential sources of connection failure. (C) 2013 Elsevier Ltd. All rights reserved.
Magnetoelectricity in coated fibrous composites of piezoelectric and piezomagnetic phases
(2013-01-01)
Kuo, Hsin-Yi
;
Peng, Cheng-You
;
土木工程學系
;
Department of Civil Engineering
This paper studies the effective magnetoelectric (ME) behavior of coated fibrous composites made of piezoelectric and piezomagnetic phases. We employ a micromechancial model, the two-level recursive scheme together with the Mori-Tanaka method, to evaluate the ME effect of the composites. The magnitudes and trends of the solutions are in good agreement with the calculations by the finite element analysis. Based on this model, we find the optimal volume fractions of the inclusion, the ratio of the radii between the core and shell for maximum ME coupling. Further, we correlate the ME effect with the material parameters of the constituent phases and propose useful engineering guide to the development of new ME coated fibrous composites. (C) 2012 Elsevier Ltd. All rights reserved.
Biomechanical comparison of unilateral and bilateral pedicle screws fixation for transforaminal lumbar interbody fusion after decompressive surgery - a finite element analysis
(2012-05-16)
Chen, Shih-Hao
;
Lin, Shang-Chih
;
Tsai, Wen-Chi
;
Wang, Chih-Wei
;
Chao, Shih-Heng
Background: Little is known about the biomechanical effectiveness of transforaminal lumbar interbody fusion (TLIF) cages in different positioning and various posterior implants used after decompressive surgery. The use of the various implants will induce the kinematic and mechanical changes in range of motion (ROM) and stresses at the surgical and adjacent segments. Unilateral pedicle screw with or without supplementary facet screw fixation in the minimally invasive TLIF procedure has not been ascertained to provide adequate stability without the need to expose on the contralateral side. This study used finite element (FE) models to investigate biomechanical differences in ROM and stress on the neighboring structures after TLIF cages insertion in conjunction with posterior fixation. Methods: A validated finite-element (FE) model of L1-S1 was established to implant three types of cages (TLIF with a single moon-shaped cage in the anterior or middle portion of vertebral bodies, and TLIF with a left diagonally placed ogival-shaped cage) from the left L4-5 level after unilateral decompressive surgery. Further, the effects of unilateral versus bilateral pedicle screw fixation (UPSF vs. BPSF) in each TLIF cage model was compared to analyze parameters, including stresses and ROM on the neighboring annulus, cage-vertebral interface and pedicle screws. Results: All the TLIF cages positioned with BPSF showed similar ROM (<5%) at surgical and adjacent levels, except TLIF with an anterior cage in flexion (61% lower) and TLIF with a left diagonal cage in left lateral bending (33% lower) at surgical level. On the other hand, the TLIF cage models with left UPSF showed varying changes of ROM and annulus stress in extension, right lateral bending and right axial rotation at surgical level. In particular, the TLIF model with a diagonal cage, UPSF, and contralateral facet screw fixation stabilize segmental motion of the surgical level mostly in extension and contralaterally axial rotation. Prominent stress shielded to the contralateral annulus, cage-vertebral interface, and pedicle screw at surgical level. A supplementary facet screw fixation shared stresses around the neighboring tissues and revealed similar ROM and stress patterns to those models with BPSF. Conclusions: TLIF surgery is not favored for asymmetrical positioning of a diagonal cage and UPSF used in contralateral axial rotation or lateral bending. Supplementation of a contralateral facet screw is recommended for the TLIF construct.
Finite element analysis on neck-spinning process of tube at elevated temperature
(2011-10-01)
Huang, Chi-Chen
;
Hung, Jung-Chung
;
Hung, Chinghua
;
Lin, Chia-Rung
;
機械工程學系
Tube spinning process is a metal forming process used in the manufacture of axisymmetric products and has been widely used in various applications. Finite element analysis has been successfully applied to the tube spinning processes, but no temperature effects have been considered on neck-spinning. For this reason, the aim of this research is to investigate numerically the neck-spinning process of a tube at elevated temperature. The commercial software Abaqus/Explicit was adopted in the simulation. For the construction of the material model, special uniaxial tensile tests were conducted at elevated temperature and various strain rates, since the material is sensitive to strain rates at high temperature. Comparisons between experimental and simulation results on thickness distribution and the outer contour of the spun tube are discussed. During the final stage, the average deviations between the simulation and experiment were 10.65% in thickness and 3.03% in outer contour. Good agreement was found between experimental and simulation results. The influence of the coefficient of friction, roller translation speeds, and the tip radius of the rollers were also investigated through numerical simulation.
Optimization of magnetoelectricity in multiferroic fibrous composites
(2012-07-01)
Kuo, Hsin-Yi
;
Wang, Yong-Liang
;
土木工程學系
;
Department of Civil Engineering
"We propose a method to optimize the effective magnetoelectric voltage coefficient of fibrous composites made of piezoelectric and piezomagnetic phases. The optimization of magnetoelectricity is with respect to the crystallographic orientations and the volume fraction for the two materials. We show that the effective in-plane (alpha(E.11)*) and out-of-plane (alpha(E.33)*) coupling constants can be enhanced many-fold at the optimal orientation compared to those at normal orientation. For example, we show that the constants are 101 and 5 times larger for the optimal orientation of CoFe2O4 fibers in a BaTiO3 matrix of the optimized volume fraction compared to the normal orientation, while they are 43 and 5 times larger for BaTiO3 fibers in a CoFe2O4 matrix. The predictions are in good agreement with the finite element analysis. (C) 2012 Elsevier Ltd. All rights reserved."
Compressive behavior of dual-gusset-plate connections for buckling-restrained braced frames
(2012-09-01)
Chou, Chung-Che
;
Liou, Gin-Show
;
Yu, Jiun-Chi
;
土木工程學系
;
Department of Civil Engineering
This work conducts compression tests and finite element analyses for steel dual-gusset-plate connections used for buckling-restrained braced frames (BRBFs). Compared to a single-gusset-plate connection, dual gusset plates sandwiching a BRB core reduce gusset plate size, eliminate the need for splice plates, and enhance connection stability under compression. The experimental program investigated ultimate compression load by testing ten large dual-gusset-plate connections. Out-of-plane deformation of the gusset plate in the test resembled that of a buckled gusset plate with low bending rigidity provided by the BRB end. The general-purpose nonlinear finite element analysis program ABAQUS was applied for correlation analysis. A parametric study of the dual-gusset-plate connection was performed to study the effects of plate size, presence of centerline stiffeners, and beam and column boundaries on ultimate compression load. The ultimate compression load of the dual-gusset-plate connection could not be predicted based on the AISC-LRFD approach due to beam flange out-of-plane deformation. The ultimate compression load of the dual-gusset-plate connection was reasonably predicted using a column strip length from the Whitmore section to the workpoint of the beam and column centerlines and a buckling coefficient of K = 2. (C) 2012 Elsevier Ltd. All rights reserved.

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