Flexural behavior of reinforced concrete (RC) beams retrofitted with hybrid fiber reinforced polymers (FRPs) under sustaining loads

This paper reports experimental studies of reinforced concrete (RC) beams retrofitted with new hybrid fiber reinforced polymer (FRP) system consisting carbon FRP (CFRP) and glass FRP (GFRP). The objective of this study is to examine effect of hybrid FRPs on structural behavior of retrofitted RC beams and to investigate if different sequences of CFRP and GFRP sheets of the hybrid FRPs have influences on improvement of strengthening RC beams. Toward that goal, 14 RC beams are fabricated and retrofitted with hybrid FRPs having different combinations of CFRP and GFRP sheets. The beams are loaded with different magnitudes prior to retrofitting in order to investigate the effect of initial loading on the flexural behavior of the retrofitted beam. The main test variables are sequences of attaching hybrid FRP layers and magnitudes of preloads. Under loaded condition, beams are retrofitted with two or three layers of hybrid FRPs, then the load increases until the beams reach failure. Test results conclude that strengthening effects of hybrid FRPs on ductility and stiffness of RC beams depend on orders of FRP layers.     

Effect of damaged concrete cover on the behavior of corroded concrete beams repaired with CFRP sheets

Fiber reinforced polymer matrix composites are being increasingly considered for use in civil infrastructure. These materials have found the maximum current use as materials for rapid and cost-effective rehabilitation (retrofit, repair and strengthening) of deteriorating and under-strength structural concrete components. This paper presents the experimental results of damaged/repaired reinforced concrete (RC) beams. The experimental program consisted of RC rectangular beam specimens exposed to accelerated corrosion. The corrosion rate was varied from 5% to 15% which represents loss in cross-sectional area of the steel reinforcement in the tension side. Half of the damaged beams were repaired by bonding Carbon Fiber Reinforced Polymer (CFRP) sheets to the tension side to restore the strength loss due to corrosion. The other half of the beams was first cleaned by removing spalled concrete cover and rusted bars were thoroughly cleaned. A new layer of concrete was cast to replace the removed spalled concrete cover. Then the CFRP sheets were attached to the new concrete layer. Corroded beams showed lower stiffness and strength than control (uncorroded) beams. Strength of damaged beams due to corrosion was restored to the undamaged state when repaired with CFRP sheets for all repaired beams, but the stiffness was almost unchanged. However, the repaired beams with replaced concrete cover layer resisted higher loads on average of 13% compared to damaged beams repaired without replacing the concrete cover layer.     

超声波辅助作用下糠醛强化萃取的研究

为了改善糠醛溶剂在润滑油抽出油在萃取过程中的溶解能力及选择性,选用超声波,在实验室做单段抽提实验。重点考察了超声波作用下超声波频率、强度、作用时间以及超声波作用方式对精制油收率及性质的影响。实验结果表明,操作温度为60℃时,通过超声波的辅助作用,能够使糠醛抽提的精制油收率提高2%~3%,精制油的基本性质没有很大变化并且质量提高。     

川西伟晶岩型锂辉石矿选择性磨矿—强化浮选试验研究

川西伟晶岩型锂辉石矿中锂辉石普遍结晶较大、易于解离且在碎磨过程中容易细化,而入选锂辉石矿样的粒度对浮选结果具有很大的影响,采用选择性磨矿—强化浮选的工艺来加强对锂辉石的回收。试验确立了最佳的磨矿条件:钢球球径配比制度为35 mm∶30 mm∶25 mm∶15 mm=2∶5∶3∶7,钢球充填率为30%,磨矿时间为8 min,磨矿浓度为65%。在这一最佳的磨矿条件下可以生产最大量的有利于锂辉石浮选分离的中粒级-74+38μm产品。磨浮选工艺闭路试验可获得Li2O品位5.81%、回收率79.52%的锂精矿。     

激光强化送料辊——台湾产GA6200木工四面刨床送料辊激光强化处理的研究与应用

激光作为一种精密可控的高能量密度的热源,可对金属表面进行多种强化处理。其中激光相变硬化最为成熟,在工业生产中己得到广泛地应用。经激光强化的含硼灰铸铁送料辊的硬度比高频淬火高约１６％,达到ＨＲＣ６０,耐磨性提高４倍,己在生产中得到应用。     

Effect of shear deformation on interfacial stresses in plated beams subjected to arbitrary loading

Bonding a fibre reinforced polymer (FRP) composite or metallic plate to the soffit of a reinforced concrete (RC), timber or metallic beam can significantly increase its strength and other aspects of structural performance. These hybrid beams are often found to fail due to premature debonding of the plate from the original beam in a brittle manner. This has led to the development of many analytical solutions over the last two decades to quantify the interfacial shear and normal stresses between the adherends. The adherends are subjected to axial, bending and shear deformations. However, most analytical solutions have neglected the influence of shear deformation of the adherends. For the few solutions which consider this effect in an approximate manner, their applicability is limited to one or two specific load cases. This paper presents a general analytical solution for the interfacial stresses in plated beams under an arbitrary loading with the shear deformation of the adherends duly considered. The shear stress distribution is assumed to be parabolic through the depth of the adherends in predicting the interfacial shear stress and Timoshenko's beam theory is adopted in predicting interfacial normal stress to account for the shear deformation. The solution is applicable to a beam of arbitrary prismatic cross-section bonded symmetrically or asymmetrically with a thin or thick plate, both having linear elastic material properties. The effect of shear deformation is illustrated through an example beam. The influence of material and geometric parameters of the adherends and adhesive on the interfacial stress concentrations at the plate end is discussed.     

染整专业《染色》课程教学的思考与实践

在中专染色课的教学工作中,应合理安排课程内容,突出应用性,加强实践性。学生提高动手能力,激发学生的学习兴趣,培养学生热爱专业的思想。     

制取二硫化钼粉的实践

用强浮选－加温酸浸的工艺,不产低品位尾矿,硝酸先行浸出,在工业制得高质的二硫化钼粉,效益显著。     

Failure hazard and strengthening of roof in steel industrial building after explosion of electric furnace

An explosion of electric furnace caused a local damage of the roof in steel industrial building. This building has a saw-tooth roof covering, constructed from prestressed plates with 12.62 m of span. The explosion caused a local damage of plates prestressed ribs, which are the roof main structural elements. The technical condition of the plates has been assessed as an emergency state due to the loss of the plates’ strength and the hazard of their fall down. The damage repair has been presented herein.