Analysis of CFRP strap-strengthened reinforced concrete beams using the modified compression field theory (MCFT)

External, prestressed carbon fiber reinforced polymer (CFRP) straps can be used to enhance the shear strength of existing reinforced concrete beams. In order to effectively design a strengthening system, a rational predictive theory is required. The current work investigates the ability of the modified compression field theory (MCFT) to predict the behavior of rectangular strap strengthened beams where the discrete CFRP strap forces are approximated as a uniform vertical stress. An unstrengthened control beam and two strengthened beams were tested to verify the predictions. The experimental results suggest that the MCFT could predict the general response of a strengthened beam with a uniform strap spacing < 0.9d. However, whereas the strengthened beams failed in shear, the MCFT predicted flexural failures. It is proposed that a different compression softening model or the inclusion of a crack width limit is required to reflect the onset of shear failures in the strengthened beams.

Effects of solution exposure on the combined axial-shear behaviour of unidirectional CFRP rods

In fibre reinforced polymer (FRP) prestressed concrete applications, an FRP tendon must sustain high axial tensile stresses and, if cracks occur, additional dowel forces. The tendon may also be exposed to solutions and so the combined axial-shear stress performance after long-term environmental exposure is important. Experiments were conducted to investigate the combined axial-shear stress failure envelope for unidirectional carbon FRP tendons which had been exposed to either water, salt water or concrete pore solution at 60 °C for approximately 18 months. The underlying load resisting mechanisms were found to depend on the loading configuration, restraint effects and the initial stress state. When saturated, CFRP tendons are likely to exhibit a reduced shear stiffness. However, the ultimate limit state appeared to be fibre-dominated and was therefore less susceptible to reductions due to solution uptake effects. © 2012 Elsevier Ltd. All rights reserved.

Three-dimensional distribution of Al in high-k metal gate: Impact on transistor voltage threshold

The three-dimensional spatial distribution of Al in the high-k metal gates of metal-oxide-semiconductor field-effect-transistors is measured by atom probe tomography. Chemical distribution is correlated with the transistor voltage threshold (VTH) shift generated by the introduction of a metallic Al layer in the metal gate. After a 1050 °C annealing, it is shown that a 2-Å thick Al layer completely diffuses into oxide layers, while a positive VTH shift is measured. On the contrary, for thicker Al layers, Al precipitation in the metal gate stack is observed and the VTH shift becomes negative. © 2012 American Institute of Physics.

应变异质结构(InGaAs/Al)GaAs材料的分子束外延生长.性质及其相关器件的研究

Submitted by zhangdi (zhangdi@red.semi.ac.cn) on 2009-04-13T11:45:31Z

GaAs基应变自组织In(Al)As量子点材料生长、性质及器件应用

Submitted by zhangdi (zhangdi@red.semi.ac.cn) on 2009-04-13T11:45:31Z

GaAs基In(Ga, Al)As复合量子点材料的生长及量子点超辐射发光管的研制

Submitted by zhangdi (zhangdi@red.semi.ac.cn) on 2009-04-13T11:45:31Z

内嵌Al 氧化物限制条的AlGaInAs 边发射激光器

Submitted by zhangdi (zhangdi@red.semi.ac.cn) on 2009-04-13T11:45:31Z

(In,Al)GaN 材料的MOCVD 生长及其物性研究

Submitted by zhangdi (zhangdi@red.semi.ac.cn) on 2009-04-13T11:45:31Z

高Al组分AlGaN薄膜的MOCVD生长和特性研究

Submitted by zhangdi (zhangdi@red.semi.ac.cn) on 2009-04-13T11:45:31Z