1、毕业设计 外文文献及译文 - 1 - 英文原文 ： Rehabilitation of rectangular simply supported RC beams with shear deficiencies using CFRP composites Ahmed Khalifa a,* , Antonio Nanni b a Department of Structural Engineering, University of Alexandria, Alexandria 21544, Egypt bDepartment of Civil Engineering, University o
2、f Missouri at Rolla, Rolla, MO 65409, USA Received 28 April 1999； received in revised form 30 October 2001； accepted 10 January 2002 Abstract The present study examines the shear performance and modes of failure of rectangular simply supported reinforced concrete(RC) beams designed with shear defici
3、encies. These members were strengthened with externally bonded carbon fiber reinforced polymer (CFRP) sheets and evaluated in the laboratory. The experimental program consisted of twelve full-scale RC beams tested to fail in shear. The variables investigated within this program included steel stirru
4、ps, and the shear span-to-effective depth ratio, as well as amount and distribution of CFRP. The experimental results indicated that the contribution of externally bonded CFRP to the shear capacity was significant. The shear capacity was also shown to be dependent upon the variables investigated. Te
5、st results were used to validate a shear design approach, which showed conservative and acceptable predictions.C 2002 Elsevier Science Ltd. All rights reserved. Keywords: Rehabilitation； Shear； Carbon fiber reinforced polymer 1. Introduction Fiber reinforced polymer (FRP) composite systems, composed
6、 of fibers embedded in a polymeric matrix, can be used for shear strengthening of reinforced con-crete (RC) members 17. Many existing RC beams are deficient and in need of strengthening. The shear failure of an RC beam is clearly different from its flexural failure. In shear, the beam fails suddenly
7、 without sufficient warning and diagonal shear cracks are consid-erably wider than the flexural cracks 8. The objectives of this program were to: 毕业设计 外文文献及译文 - 2 - 1. Investigate performance and mode of failure of simply supported rectangular RC beams with shear deficien-cies after strengthening wi
8、th externally bonded CFRP sheets. 2. Address the factors that influence shear capacity of strengthened beams such as: steel stirrups, shear span-to-effective depth ratio (a/d ratio), and amount and distribution of CFRP. 3. Increase the experimental database on shear strength-ening with externally bo
9、nded FRP reinforcement. 4. Validate the design approach previously proposed by the authors 9. For these objectives, 12 full-scale, RC beams designed to fail in shear were strengthened with different CFRP schemes. These members were tested as simple beams using a four-point loading configuration with
10、 two different a/d ratios. 2. Experimental program 2.1. Test specimens and materials Twelve full-scale beam specimens with a total span of 3050 mm. and a rectangular cross-section of 150-mm-wide and 305-mm-deep were tested. The specimens were grouped into two main series designated SW and SO dependi
11、ng on the presence of steel stirrups in the shear span of interest. Series SW consisted of four specimens. The details and dimensions of the specimens designated series SW are illustrated in Fig. 1a. In this series, four 32-mm steel bars were used as longitudinal reinforcement with two at top and tw
12、o at bottom face of the cross-section to induce a shear failure. The specimens were reinforced with 10-mm steel stirrups throughout their entire span. The stirrups spacing in the shear span of interest, right half, was selected to allow failure in that span. Series SO consisted of eight beam specime
13、ns, which had the same cross-section dimension and longitudinal steel reinforcement as for series SW. No stirrups were provided in the test half span as illustrated in Fig. 1b. Each main series (i.e. series SW and SO) was subdivided into two subgroups according to shear span-to-effective depth ratio
14、. This was selected to be a/d = 3 and 4, resulting in the following four subgroups: SW3；SW4； SO3； and SO4. 毕业设计 外文文献及译文 - 3 - The mechanical properties of the materials used for manufacturing the test specimens are listed in Table 1.Fabrication of the specimens including surface preparation and CFRP
15、 installation is described elsewhere 10. Table 1 2.2. Strengthening schemes One specimen from each series (SW3-1, SW4-1, SO3-1 and SO4-1) was left without strengthening as a control specimen, whereas eight beam specimens were strengthened with externally bonded CFRP sheets following three different
16、schemes as illustrated in Fig. 2. In series SW3, specimen SW3-2 was strengthened with two CFRP plies having perpendicular fiber directions (90/0). The first ply was attached in the form of continuous U-wrap with the fiber direction oriented perpendicular to the longitudinal axis of the specimen (90)
17、. The second ply was bonded on the two sides of the specimen with the fiber direction parallel to the beam axis（ 0） .This ply i.e. 0ply was selected to investigate the impact of additional horizontal restraint on shear strength. In series SW4, specimen SW4-2 was strengthened with two CFRP plies havi
18、ng perpendicular fiber direction (90/0) as for specimen SW3-2. Four beam specimens were strengthened in series SO3. Specimen SO3-2 was strengthened with one-ply CFRP strips in the form of U-wrap with 90-fiber orientation. The strip width was 50 mm with center-to-center spacing of 125 mm. Specimen SO3-3 was strengthened in a manner similar to that of specimen SO3-2, but
