（節(jié)選）外文翻譯--對節(jié)段式體外預應力混凝土連續(xù)梁在負彎矩區(qū)受剪性能的試驗研究（原文）

1、Experimental Study on Shear Behavior in Negative Moment Regions of Segmental Externally Prestressed Concrete Continuous BeamsGuoping Li1; Chunlei Zhang2; and Changyan Niu3Abstract: External prestressing technology has ac

2、hieved wide application in bridges. Although previous tests have made great progress in shear behavior of externally prestressed concrete beams, the research mainly focused on simply supported beams. To study the effects

3、 of joints and large negative moments on the shear behavior of segmental externally prestressed concrete continuous beams, a series of cantilever beam specimens were designed to simulate the negative moment regions in co

4、ntinuous beams. Then, the crack developing behavior, failure mode behavior, and mechanical behavior of specimens with different shear span to effective depth ratios, joint types, joint locations, and ratios of internal t

5、o external tendons were investigated in this experimental study. The test results show that failure cracks of segmental specimens are web shear cracks, whose locations and inclination angles are independent of joints. Ev

6、entually, both sides of the specimens move relatively along failure cracks and the specimens fail suddenly. The results also reveal that the deflections of segmental specimens after cracking develop very quickly, and the

7、 stress increments of prestressing tendons reach 20–24% of the tensile strength, which are larger than those of monolithic specimens. In addition, the shear strength provided by the concrete effects in regions near the i

8、nterior supports of continuous beams islower than that in regions near the supports of simply supported beams, and the contributions of the stirrup and prestressing tendon to the shear strength are 14–21 and 8–18%, respe

9、ctively, in which the contribution of stirrup is greater than that of simply supported beams. DOI: 10.1061/(ASCE) BE.1943-5592.0000351. © 2013 American Society of Civil Engineers.CE Database subject headings: Concre

10、te bridges; Prestressed concrete; Continuous beams; Joints; Shear failures; Cracking.Author keywords: External prestressing; Continuous beams; Joints; Shear failure; Cracking.IntroductionExternal prestressing technology

11、has been widely adopted in con- crete bridges for more than 30 years. Previous research has shown that there is no obvious difference in the structural behavior be- tween internally and externally prestressed structures

12、regarding service limit states; however, this is different from ultimate limit states: external tendons are anchored only at the two ends of the beam, resulting in their stress increments limited and the yielding point h

13、ardly reached. On the basis of the investigations of externally prestressed con- crete bridges in service, it is found that many applications of external prestressing technology have been made on segmental bridges (Virlo

14、geux 1993; Corven 1993; Eibl 1993; Muller 1993). A number of tests have been made on monolithic and segmental externally prestressed beams (Foure et al. 1993a, b; Rezende-Martins et al. 1993; Ramirez et al. 1993; Aparici

15、o et al. 2002; Li 2007; Saibabuet al. 2009), and the results show that joints have a significant in- fluence on the formation of cracks and failure modes of beams. Tan and Tjandra (2003) reported shear deficiency of exte

16、rnal tendons for strengthening the shear strength of beams, and Li (2007) developed tests on segmental externally prestressed con- crete beams and identified their differences with monolithic ones in shear behavior and s

17、hear strength based on the existence of joints. However, when summarizing the previous results, it can be seen that research on segmental externally prestressed beams primarily fo- cused on flexural strength (Foure et al

18、. 1993b; Rezende-Martins et al. 1993; Naaman and Jeong 1993; Dronnadulla 1993; Li and Zhang 2007; Tan and Tjandra 2007; Ng 2003; Harajli 1993), and limited experimental results are reported in the literature on shear str

19、ength. The experimental programs focused on shear behavior of simply supported beams and flexure-shear behavior of con- tinuous beams (Aparicio et al. 2002; Ramirez et al. 1993; Li 2007; Buyukozturk et al. 1990; Turmo et

20、 al. 2006). The moment and shear in negative moment regions near interior supports of continuous beams are relatively large compared with those near supports of simply supported beams. Most previous studies have not cons

21、idered the characteristics of shear behavior in these regions in externally prestressed continuous beams. Foure et al. (1993a) designed a series of tests comprising six T-shaped externally prestressed cantilever beams to

22、 simulate the negative moment regions of continuous beams and investigate the differences in shear strength between externally and internally prestressed beams. However, the effect of joints on the mechanical behavior wa

23、s not included in their tests. Therefore, it should be beneficial to study shear behavior in negative moment regions of segmental externally prestressed con- crete continuous beams and to investigate the whole process fr

24、om1Professor, Dept. of Bridge Engineering, Tongji Univ., Shanghai 200092, China. E-mail: lgptj@#edu.cn 2Ph.D. Candidate, Dept. of Bridge Engineering, Tongji Univ., Shanghai 200092, China (corresponding author). E-m

25、ail: 3zhang@#edu.cn 3Assistant Engineer, Shanghai Municipal Engineering Design Institute (Group) Co., Ltd., 3 Guokang Rd., Shanghai 200092, China. E-mail: Neiltj@gmail.com Note. This manuscript was submitted on Sep

26、tember 5, 2011; approved on November 30, 2011; published online on December 2, 2011. Discussion period open until September 1, 2013; separate discussions must be sub- mitted for individual papers. This paper is part of t

27、he Journal of Bridge Engineering, Vol. 18, No. 4, April 1, 2013. ©ASCE, ISSN 1084-0702/ 2013/4-328–338/$25.00.328 / JOURNAL OF BRIDGE ENGINEERING © ASCE / APRIL 2013J. Bridge Eng., 2013, 18(4): 328-338 Download

28、ed from ascelibrary.org by Sultan Qaboos University on 08/30/16. Copyright ASCE. For personal use only; all rights reserved.Stress-strain curves of conventional reinforcements and the steel strand used in the specimens w

29、ere obtained after tensile tests, and their mechanical properties are listed in Table 2.Fabrication of SpecimensThe procedure started with installing reinforcing cages and then placing prestressing tendon ducts and ancho

30、rages, followed by casting concrete. At the end of the casting procedure, the specimens were moved to the test bed in the laboratory. Some tendons were partially tensioned (for S-1, S-2, S-3, and S-4, the external tendon

31、s with a straight layout were tensioned to ～30% of design value), and some tendons were completely tensioned (for S-5 and S-6, the in- ternal tendons; for S-7, the external tendons with polyline layout) before the specim

32、ens were moved to the test bed. Before loading, the prestressing tendons were jacked to 0.67–0.76 fu each, one at a time. Because of the inevitable prestress losses, the magnitude of effective prestress fpe across all th

33、e specimens was later found to be in the range of 0.40–0.50 fu.Test Setup and InstrumentationLoad was applied in increments of 10 kN until failure occurred. The YDC240Q jack was used to tensile prestressing tendons, and

34、the ZB4-500 (OVM Machinery Co., Ltd) superpressure elec- tric oil pump was applied in tension and loading. The reaction frame and mechanical jacks were adopted to press on the top of the specimens at Support B during the

35、 loading procedure in case of detachment of the support. The test setup is shown in Fig. 4. In testing regions, strain gauges were placed on the middle part of each prestressing tendon, on stirrups intersecting with diag

36、onal cracks, on the top and bottom surfaces, and near the load point and Support A to determine corresponding stress changes. Straingauge rosettes measured principle stress levels of concrete on the surface of webs. Defl

37、ections and displacements were monitored from displacement transducers attached to the load point, sup- ports, joint, and midpoint between Support A and the joint. At each load increment, data from strain gauges and disp

38、lacement transducers were collected and recorded while cracks were ob- served and numbered according to their occurrence sequences. Displacement transducers, strain gauges pasted on stirrups, and prestressing tendons are

39、 illustrated in Fig. 5, in which the desig- nation of tendons can be explained as follows: the first letter I or E denotes the tendon type, i.e., internal or external tendons, re- spectively; the second letter P or S ind

40、icates the tendon shape, i.e., polyline or straight.Test ResultsThe behavior of specimens was evaluated in terms of cracking pattern, failure mode, load versus deflection, and load versus ex- ternal tendon stress respons

41、es. Test results showed that for all specimens, concrete compression strains in the compression zone increased with the increased load, and the maximum value occurred on the bottom surface of the specimens at Support A.

42、Stirrup stresses were small in the beginning and increased suddenly up to stirrup yielding once stirrups intersected with the diagonal cracks, and eventually, the stirrup strains exceeded those at other locations.Monolit

43、hic Specimens (M-1, M-2, M-3)Crack Propagation and Failure Modes Flexural cracks started on the top surface of the specimens near Support A. Web shear cracks (Crack 1) were found on the web 150 mm away from the diaphragm

44、, which extended from the bot- tom surface of the top flange to the diaphragm at angels of 40–50? with a horizontal line. With an increase in load, Crack 2 emerged on the upper web, a location at z from the face of suppo

45、rts, where z 5 d, and led to Support A at angles of 30–40? with the horizontal line. Crack 3 of M-1 and M-3 initiated at the right side of Crack 2 with a distance of about 150 mm and extended to Support A at angles of 25

46、 and 30? with the horizontal line, respectively. The bottom flange near Support A crushed, and the relatively large deformation appeared along with the failure of the specimen. The crack patterns and photos after failure

47、 of monolithic specimens are shown in Fig. 6. Cracks indicated by dashed lines developed to failure cracks.Fig. 3. Details of dry joint: (a) dimensions of shear key (mm); (b) photograph of dry jointTable 1. Summary of Sp

48、ecimen ParametersSpecimen Shear span: a (mm) Shear span ratio: a/d Ratio of external to internal tendonsPrestressing tendon Longitudinal conventional reinforcementsDistance between joint and Support A: b (mm) Joint type

49、(number) External InternalM-1 800.0 2.20 1/0 2 3 fs15:2 — 10 f 16 mm — — M-2 800.0 2.20 4/3 2 3 fs15:2a 1 3 fs15:2b 10 f 16 mm — — M-3 800.0 2.20 1/0 2 3 fs15:2 — 6 f 16 mm — — S-1 800.0 2.20 1/0 4 3 fs15:2 — 6 f 16 mm 4

50、00 Epoxy (1) S-2 1,050.0 2.92 1/0 4 3 fs15:2 — 6 f 16 mm 400 Epoxy (2) S-3 500.0 1.40 1/0 4 3 fs15:2 — 6 f 16 mm 400 Epoxy (1) S-4 800.0 2.20 1/0 4 3 fs15:2 — 6 f 16 mm 200 Epoxy (2) S-5 800.0 2.20 11/3 2 3 fs15:2 1 2 3

51、fs15:2a 1 3 fs15:2b 6 f 16 mm 400 Epoxy (1) S-6 800.0 2.20 11/3 2 3 fs15:2 1 2 3 fs15:2a 1 3 fs15:2b 6 f 16 mm 200 Epoxy (2) S-7 800.0 2.20 1/0 4 3 fs15:2 — 6 f 16 mm 200 Dry (2)Note: M 5 monolithic specimen; S 5 segment

52、al specimen. aStrand of fs15:2 in which three wires were cut off but not removed; the remaining effective section area reached 80 mm2. bStrand of fs15:2 in which one wire was cut off but not removed; the remaining effect

53、ive section area reached 120 mm2.330 / JOURNAL OF BRIDGE ENGINEERING © ASCE / APRIL 2013J. Bridge Eng., 2013, 18(4): 328-338 Downloaded from ascelibrary.org by Sultan Qaboos University on 08/30/16. Copyright ASCE. F