钢筋混凝土梁侧粘钢板网抗剪加固的试验研究

通过对六根钢筋混凝土梁的斜截面抗剪试验,研究了采用梁侧粘贴钢板网对梁进行抗剪加固的效果,并与未加固的钢筋混凝土梁作对比,对试验结果进行分析,得出这种加固方法的设计计算公式。     

碳纤维片材加固技术在某工程框架梁抗剪加固中的应用

粘贴碳纤维片材加固技术是一项新的应用外粘高性能复合材料加固结构的技术．碳纤维片材重量轻、高强度、高弹性、高耐久性，易于施工，现已开始应用于各类混凝土结构的加固处理．本文根据工程实际情况，简要介绍了碳纤维片材加固技术在混凝土框架梁抗剪加固工程中的应用．     

碳纤维布加固钢筋砼吊车梁抗弯疲劳性能试验

为研究碳纤维布(CFRP)对加固后钢筋混凝土梁的抗弯疲劳性能的影响,进行了3根CFRP加固梁及1根对比梁的抗弯疲劳试验.研究了碳纤维布加固方式、构件使用荷载等参数对碳纤维布加固损伤钢筋混凝土吊车梁的抗弯疲劳性能影响.试验研究表明:采用碳纤维布加固后,构件裂缝的宽度减小50.2%~66%,发展速度也得到控制,钢筋应力减小24.1%~28.2%,构件的刚度提高14.9%~16.1%.依据试验结果,从现有规范中关于构件刚度计算方法出发,进行了CFRP加固钢筋混凝土吊车梁的疲劳刚度计算分析,该计算方法可用于吊车梁加固工程设计.最后给出了CFRP加固梁的疲劳设计的合理化建议.     

二次受力下碳纤维布加固梁抗弯性能试验研究

进行了4根不同二次受力条件下碳纤维布加固的钢筋混凝土梁和1根对比混凝土梁的抗弯性能试验研究。试验及分析结果表明,用粘贴碳纤维布的方法来提高梁的承载力十分有效,且预加载的存在使加固梁的极限荷载降低;碳纤维布能有效约束裂缝的开展,但裂缝的数量增加和分布区域变大,且预加载的大小会影响加固梁裂缝的开展和分布;碳纤维布加固可以增强梁的刚度,但延性有所降低。     

碳纤维布加固混凝土结构技术及应用

介绍国内外对碳纤维材料加固技术的主要试验研究成果,结合工程实例讲述了碳纤维加固施工技术,并提出了一些补充建议,供设计及工程技术人员参考。     

CFRP板加固PPC梁抗剪性能试验研究

通过4片部分预应力混凝土(PPC)梁试件采用CFRP板抗剪加固的试验,研究不同预应力水平对CFRP板加固PPC梁抗剪性能的影响.结果表明:采用CFRP板对PPC梁进行抗剪加固,能有效抑制斜裂缝的发展,提高加固梁的斜截面抗剪承载力,并在试验研究的基础上进行了非线性有限元分析,与试验结果吻合良好.     

梁板结构承载力不足的原因分析及碳纤维加固

粘贴碳纤维加固技术是指采用高性能粘结剂将碳纤维布粘贴在建筑结构构件表面,以提高结构构件的(抗弯、抗剪)承载能力,由此达到对建筑物进行加固、补强的目的。本文对梁板结构的承载力不足的原因进行了系统总结,并对碳纤维材料在梁板结构加固工程中的应用进行了介绍。     

干湿交替与荷载作用下CFRP加固混凝土梁的耐久性

对8根持载与恶劣环境作用后的碳纤维增强聚合物(CFRP)加固混凝土梁进行了试验研究.梁的尺寸为1700 mm×120 mm ×200 mm.首先采用4点分加栽方式对梁进行预裂,卸载后粘贴CFRP片材,然后放入腐蚀环境.影响因素考虑了干湿交替与持载水平(持载水平分别为30%和60%混凝土梁极限荷载).分析了干湿交替单一因素和荷载与干湿交替双重因素对CFRP加固梁的长期性能.试验结果表明:荷载与干湿交替双重因素对CFRP加固梁的承载力和破坏形态影响较大,这主要是由于CFRP与混凝土界面的劣化引起;对CFRP加固梁的刚度几乎没有影响.     

碳纤维布加固钢筋混凝土柱的研究

碳纤维布加固混凝土结构是一种新型加固方法。本文在试验研究的基础上,将抗拉强度很高的碳纤维布用环氧树脂预浸成为复合增强材料;用环氧树脂粘结剂沿受拉方向粘贴在要补强的柱子上,形成一个新的复合体,使补强碳纤维布与原有钢筋混凝土共同受力,增大结构的抗剪、抗弯强度和提高柱的延性。     

GFRP加固混凝土梁受弯性能试验研究

对15根玻璃纤维布加固的钢筋混凝土梁进行了试验研究。试验结果表明,玻璃纤维布加固的钢筋混凝土梁抗弯承载力显著提高,加固效果明显,但要有足够的粘贴长度以避免发生剥离破坏。     

Shear strengthening of pre-damaged reinforced concrete beams with carbon fiber reinforced polymer sheet strips

This paper presents the results of an experimental investigation on the response of pre-damaged reinforced concrete (RC) beam strengthened in shear using applied-epoxy unidirectional carbon fiber reinforced polymer (CFRP) sheet. The reasearch included four test rectangular simply supported RC beams in shear capacity. One is the control beam, two RC beams are damaged to a predetermined degree from ultimate shear capacity of the control beam, and the last beam is left without pre-damaged and then strengthened with using externally bonded carbon fiber reinforced polymer to upgrade their shear capacity. We focused on the damage degree to beams during strengthening, therefore, only the beams with side- bonded CFRPs strips and horizontal anchored strips were used. The results show the feasibility of using CFRPs to restore or increase the load-carrying capacity in the shear of damaged RC beams. The failure mode of all the CFRP-strengthened beams is debonding of CFRP vertical strips. Two prediction available models in ACI-440 and fib European code were compared with the experimental results.     

Shear capacity of reinforced concrete columns strengthened with CFRP sheet

INTRODUCTION There is increased need in recent years for strengthening or rehabilitation of existing reinforced concrete structures adversely affected by overloading, construction material deterioration, seismic loads, structural deformation, etc. An effective method for increasing the shear capacity of reinforced concrete columns is the use of externally bonded carbon fiber reinforced plastic (CFRP) systems (ACI, 2002). FRP systems were first applied to reinforced concrete col-umns i…     

Flexural rigidity evolvement laws of reinforced concrete beams strengthened with carbon fiber laminates

Extensive research has shown that externally bonded carbon fiber reinforced polymer (CFRP) laminates are particularly suitable for improving the fatigue behavior of reinforced concrete (RC) beams. This paper presents the research on flexural rigidity evolvement laws by testing 14 simple-supported RC beams strengthened with carbon fiber laminates (CFL) under cyclic load, and 2 under monotone load as a reference. The cyclic load tests revealed the peak load applied onto the surface of a supported RC beam strengthened with CFL is linear to the logarithm of its fatigue life, and the flexural rigidity evolvement undergoes three distinct phases: a rapid decrease from the start to about 5% of the fatigue life; an even development from 5% to about 99% of the fatigue life; and a succedent rapid decrease to failure. When the ratio of fatigue cycles to the fatigue life is within 0.05 to 0.99, the flexural rigidity varies linearly with the ratio. The peak load does not affect the flexural rigidity evolvement if it is not high enough to make the main reinforcements yield. The dependences of the flexural rigidity of specimens formed in the same group upon their fatigue cycles normalized by fatigue life are almost coincident. This implies the flexural rigidity may be a material parameter independent of the stress level. These relationships of flexural rigidity to fatigue cycles, and fatigue life may be able to provide some hints for fatigue design and fatigue life evaluation of RC member strengthened with CFL; nevertheless the findings still need verifying by more experiments.     

碳纤维布加固法在建筑工程中的应用

钢筋混凝土结构中,由于钢筋的锈蚀而使钢筋混凝土结构的耐久性大大降低.针对沿海建筑加固工程的设计、施工过程,对锈蚀钢筋混凝土构件的受弯破坏形态,提出了碳纤维布加固锈蚀钢筋混凝土结构的实用设计与施工方法.     

Numerical Determination of Shear Strength of Steel Reinforced Concrete Column Strengthened by CFRP Sheets

The earthquake-resistant property of reinforced concrete members depends on the interaction between reinforcing bars and surrounding concrete through bond to a large degree,In this paper a general system aimed at dealing with the failure analysis of reinforced concrete columns strengthened with carbon-fiber-reinforced plastic(CFRP) sheets including bond-slip of the anchored reinforcing bars at the foot of the columns is presented.It is based on the yield design theory with a mixed modeling of the structue,according to which the concrete material is treated as a classical two-dimensional continuum ,whereas the longitudinal reinfocing bars are regarded as one-dimensional rods including bond-slip at the foot of the columns,In shear reinforced zones both the shear CFRP sheets and transvers reinforcing bars are incorporated in the analysis throuth a homogenization procedure and they are only in tesion ,The approach is then implemented numerically by means of the finite-element formulation,The numerical procedure produces accurate estimates for the loading-carrying capactiy of the shear members taken as an illustrative application by correlation with the experimental results,so the proposed approach is valid.     

GFRP布与钢筋混凝土梁界面之间应力行为

为了解玻璃纤维(GFRP)布与钢筋混凝土梁界面之间的粘结性能,进行了7根GFRP布加固的钢筋混凝土梁与2根对比梁的试验研究.试验的变化参数为GFRP布层数、粘结长度及配筋率.试验结果表明,GFRP布加固的钢筋混凝土梁极限荷载显著提高,但是发生剥离破坏的试验梁极限荷载有所降低,粘结长度是影响加固梁剥离破坏的主要因素.根据试验结果提出了GFRP布与钢筋混凝土梁界面粘结剪应力的试验分析方法并分析了界面间粘结剪应力的分布.同时,提出了GFRP布加固的钢筋混凝土梁剥离正应力与粘结剪应力的理论分析方法.最后,给出了GFRP布加固钢筋混凝土梁剥离荷载的计算方法.为验证理论分析方法的正确性,计算了试验梁界面间的粘结剪应力、剥离正应力及剥离荷载.计算结果表明,所提出的理论分析方法与试验值吻合较好.     

Strengthening an in-service reinforcement concrete bridge with prestressed CFRP bars

Carbon fiber reinforced polymer(CFRP)bars were prestressed for the structural strengthening of 8 T-shaped rein-forced concrete (RC)beams of a 21-year-old bridge in China.The ultimate bearing capacity of the existing bridge after retrofit was discussed on the basis of concrete structures theory.The flexural strengths of RC beams strengthened with CFRP bars were controlled by the failure of concrete in compression and a prestressing method was applied in the retrofit.The field construction processes of strengthening with CFRP bars-including grouting cracks,cutting groove,grouting epoxy and embedding CFRP bars,surface treating,banding with the U-type CFRP sheets,releasing external prestressed steel tendons-were introduced in detail.In order to evaluate the effectiveness of this strengthening method,field tests using vehicles as live load were applied before and after the retrofit.The test results of deflection and concrete strain of the T-shaped beams with and without strengthening show that the capacity of the repaired bridge,including the bending strength and stiffness,is enhanced.The measurements of crack width also indicate that this strengthening method can enhance the durability of bridges.Therefore,the proposed strengthening technology is feasible and effective.