Retrofit of RC hollow piers with CFRP sheets

Hollow bridge piers, particularly those built before the seventies, often have insufficient shear capacity due to inadequate transverse reinforcement details. Therefore, special attention must be given to this very important aspect when reinforced concrete (RC) piers with hollow sections are analysed and retrofitted. This paper covers the experimental analysis of retrofit solutions using CFRP sheets along the piers’ entire height to prevent shear failure. Experimental cyclic tests were carried out to evaluate the shear retrofit strategy efficiency on a set of RC piers with square hollow sections. This work also covers the study of design procedures for CFRP shear retrofitting and the evaluation of the associated ductility capacity improvement. The various transverse reinforcement detailing scenarios were assessed to determine their shear-failure prevention efficiency. The corresponding cyclic response behavior was also evaluated. The most relevant experimental information is presented in the paper, such as the evolution of the outer damage pattern. Finally, shear retrofit solutions, with a 40% increase over the maximum flexural force, show that this strategy is adequate to allow satisfactory ductility behavior.     

Crack propagation prediction of CFRP retrofitted steel plates with different degrees of damage using BEM

Although carbon fibre reinforced polymer (CFRP) materials have proven effective in strengthening steel structures especially when used to improve fatigue behaviour, further study is required to investigate their effectiveness when applied at different stages of crack propagation in steel elements. This paper presents a numerical study on CFRP retrofitted steel plates with different degrees of damage using the boundary element method (BEM). The numerical results compared well with the experimental data, which demonstrated that the BEM is reliable for crack propagation analysis of CFRP laminate retrofitted steel plates. Finally, a parametric analysis was conducted to investigate the influence of bond length, bond width, CFRP stiffness and adhesive shear modulus on stress intensity factor (SIF) values.     

Comparison of surface roughness quality obtained by high speed CNC trimming and high speed robotic trimming for CFRP laminate

This paper proposes an experimental approach for evaluating the surface roughness of the CFRP parts produced by high speed CNC trimming and high speed robotic trimming under various cutting conditions. A comparison is made between the surface roughnesses obtained by the two processes. The results obtained show that, the measured profiles obtained from high speed robotic trimming are dominated by a large trajectory deviation, as compared to machine tool trimming results. After the trajectory deviation effect is discounted, the results show that for the +45° ply orientation, the surface quality obtained through high speed robotic trimming is similar to what is obtained with the CNC machine. Furthermore, a significant relationship was observed between the surface quality and the ply orientation, whatever the machining process and the cutting conditions employed. The −45° ply orientation represents the worst case in terms of surface roughness, whatever the machining process. It is 4 times higher compared with that of +45° ply orientations,The results also show that the effect of cutting conditions on surface quality is significant for both machining processes tested.     

碳纤维导电玻璃钢阳极管的设计与制作

介绍了碳纤维导电玻璃钢阳极管在湿式静电除尘领域中的应用状况及性能要求。根据导电玻璃钢制品的特点,分析了阳极管的设计及成型工艺。     

Probabilistic modeling of hybrid transition structures

Within lightweight structures, often Fiber Reinforced Plastics (FRP) are used in combination with metallic materials. Most of these hybrid structures are manufactured by established methods like riveting, bolting or adhesive bonding. In order to avoid disadvantages like drilled FRP or large bond areas, the development of hybrid transition structures compatible to loads and material properties is required. To fulfill the requirements for enhanced lightweight design, novel, integral joint concepts are currently designed, dimensioned and produced by using textile, welding and casting techniques.Three concepts are under investigation which consist of different materials (titanium and Ti-alloys, glass fibers), manufacturing methods (casting, welding, textile techniques) and geometries.Various phase boundaries, materials and influences of the manufacturing processes have to be investigated that influence the structural behavior and its failure. Based on the results of Finite Element Models on the meso scale, further modeling is performed to include effects like material uncertainties and/or process influences.In this paper, a probabilistic computation procedure based on local survival probabilities and distribution functions is proposed and investigated. This approach allows to model the complex global failure behavior for each component or its interfaces as well as the whole hybrid transition zone. It also shows the interactions and consequences of certain component changes within the hybrid transition zone. First computations are carried out and compared with experiments.     

高强钢/碳纤维增强复合材料热冲压-连接一体化工艺可行性及试样弯曲性能研究

提出一种高强钢/碳纤维增强复合材料(CFRP)的多材料零件连接成形一体化加工工艺,利用热冲压工艺对高强钢和CFRP预浸料进行连接并成形高强钢/CFRP多材料零件。研究热冲压过程中不同的淬火温度下多材料复合板的制备工艺,并对试样中钢板进行微观观测,最后对复合件进行弯曲试验。微观检测结果表明,该工艺下钢板组织为全马氏体组织。三点弯曲试验结果表明,未铺设CFRP试样、铺设2层CFRP试样和铺设4层CFRP试样的弯曲角度分别为130°、110°和104°。对弯曲试验的力位移曲线进行积分,计算试样的能量吸收量,得到如下结论：未铺设CFRP试样、铺设2层CFRP试样和铺设4层CFRP试样的能量吸收量分别为9410 J、9692 J和10 050 J;铺设2层CFRP的试样和铺设4层CFRP的试样相比于未铺设CFRP的试样,能量吸收量分别增加2.9%和6.8%。     

预应力碳纤维板加固组合箱梁应用研究

目前,纤维材料已广泛应用于工程结构加固中.采用预应力碳纤维板加固受弯构件,可以充分发挥碳纤维板材料的强度,提高结构的正常使用性能和极限承载能力.在自主研发的一套预应力碳纤维板平板锚具的基础上,采用预应力碳纤维板成功应用于某一大桥组合箱梁加固中.结果表明,和加固前相比,整体刚度提升了20％左右;从挠度数据来看,和粘钢加固方法效果没有明显差异;但从应变数据来看,采用预应力碳纤维进行加固有效降低了应变幅值.     

碳纤维布加固箍筋锈蚀RC梁抗剪性能试验研究

为研究碳纤维布加固3种不同锈蚀率下钢筋混凝土梁斜截面受力性能,设计并制作了6根具有相同混凝土强度等级、相同配筋率以及相同尺寸的混凝土梁,并将这6根梁分为试验组和对照组,用碳纤维布对试验组的3根梁进行加固,对照组的3根梁不做加固处理,并对实验结果进行了分析比较,得出了一些有意义的结论。     

基于热稳定及等弯曲刚度的碳纤维层合板铺层设计与优化

针对碳纤维复合材料反射镜特殊应用,从热稳定性以及弯曲刚度均匀性两方面,对层合板进行铺层设计与优化。最终优化的16层铺层设计[22.5 90-45-22.5 67.5-67.5 0 45]s弯曲刚度均匀性最好,同时具有优异的热稳定性。该铺层设计为高精度、高热稳定性碳纤维层合面板研制提供参考,特别适合于变形镜的铺层设计应用。     

基于FBG传感器的碳纤维复合材料内部热应变监测

将光纤布拉格光栅(Fiber Bragg Grating,简称"FBG")传感器分别埋入单向板和平纹机织层压复合材料中,采用Sm125型光纤光栅解调仪测试两种复合材料在20~100℃温度范围内的内部热应变,分析单向板和平纹机织层压复合材料在仅受温度作用下内部热应变变化特征。结果表明,FBG传感器可以准确测量复合材料内部热应变变化;单向板和平纹机织层压复合材料的内部热应变均随温度升高而增大;织物结构影响复合材料内部热应变,且同一温度点,平纹机织层压复合材料内部热应变较单向板大。