混凝土外文翻譯----既有鋼筋混凝土拱肋極限承載力測試與分析（原文）

1、Test and Analysis for Ultimate Load-Carrying Capacity of Existing Reinforced Concrete Arch RibsJianren Zhang1; Chuanxi Li2; Feihong Xu3; and Xiaoming Yu4Abstract: The structural performance of reinforced concrete bridges

2、 gradually deteriorates due to material aging and concrete cracking. Reported here are the experimental investigations and the nonlinear finite-element analysis of two arch ribs removed from a decommis- sioned bridge and

3、 reinstalled in the laboratory. The old bridge had been in service for 28 years. The full-scale static tests for two arch ribs were performed. The load–displacement and load–strain relationships, the residual load-carryi

4、ng capacity, and the failure form are explored in detail. The structural analysis software Marc is invoked in the theoretical computations. Both geometrical and material nonlinearities are considered. Moreover, the mater

5、ial aging and the structural damage are introduced in the finite-element model. For comparison, the undamaged and geometrically perfect arch rib is analyzed at the same time. A comparison between the experimental and the

6、oretical results is made. It can be concluded that the initial cracks, the reinforcement corrosion, and the variation of the arch axial line shape are the crucial effects for the structural ultimate load-carrying capacit

7、y and failure mode.DOI: 10.1061/?ASCE?1084-0702?2007?12:1?4?CE Database subject headings: Bridges; Concrete, reinforced; Bearing capacity; Finite element method; Ultimate loads.IntroductionEvaluation of the residual stre

8、ngth and remaining life of concrete bridges have attracted much attention in recent years as the struc- tures continue to age. A large number of reinforced concrete ?RC? bridges were built in the past 50 years in China.

9、Unfortunately, many of them are greatly damaged due to the increasing traffic loads, environment, material aging, and inadequate maintenance. More and more old RC bridges need to be repaired, rehabilitated, or be put out

10、 of service and replaced. A crucial problem is the assessment of their residual load-carrying capacities. This is a challenge for the bridge engineers because of the complexity and randomness of concrete cracking, concre

11、te damage, and rein- forcement corrosion in these existing aged RC bridges. The researchers were, therefore, motivated to investigate whether it is rational to take advantage of the insight they gained from the nondestru

12、ctive static and dynamic tests integrating the- oretical analysis. Valuable investigations have been done byBakht and Jaeger ?1990?, Douglas et al. ?1990?, Law et al. ?1995a,b?, Enright and Frangopol ?2000?, Farhey et al

13、. ?2000?, Nowak et al. ?2000?, Maragakis et al. ?2001?, Brownjohn et al. ?2003?, and Fu and Lu ?2003?. However, it is very difficult to obtain the load curves and the vibrating modes by experiment in the field, especiall

14、y near the failure period. In some cases, the analytical rating factors would be misleading. The experimental study on the existing bridge members in the laboratory is a direct and effective way to evaluate the ultimate

15、load-carrying capacity. The structural response parameters could be easily obtained. On the other hand, the various parameters describing the aged RC bridge behaviors could not be easily quantified. Consequently, the exp

16、erimental results provide a ratio- nal reference for the theoretical analysis. In this work, two arch ribs were salvaged from a 28-year-old RC bridge and sent to the laboratory. The experimental procedure, including the

17、reinstalla- tions of two arch ribs in the laboratory, is explained. The static and dynamic tests were carried out. By invoking the structural finite-element analysis software Marc, the theoretical analysis is performed i

18、n which both the geometrical and material nonlineari- ties are considered. The theoretical results are in agreement with the static test results.Test BackgroundAs shown in Fig. 1, Beimen Bridge, a uniform cross-section c

19、at- enary arch bridge with three spans, was constructed in 1973. It is located in Changing County, Hunan Province, China. The main load-carrying members are the RC arch ribs with the span of 20 m. In 2002, the bridge was

20、 found to be in a dangerous state. The surface concrete of some arch ribs had flaked and the con- crete strength could not satisfy the bridge codes and regulations. In conclusion, it had no values to be rehabilitated and

21、 reinforced. Consequently the owner decided to dismantle this bridge. Before the bridge was demolished, in order to study the me- chanical property and the residual strength of its main structural1Prof., College of Bridg

22、e and Struct. Engrg., Changsha Univ. of Science and Technology, 45 Chiling Road, Tianxin Distr., 410076, Changsha, Hunan, China. E-mail: jianrenz@hotmail.com 2Prof., College of Bridge and Struct. Engrg., Changsha Univ. o

23、f Science and Technology, 45 Chiling Road, Tianxin Distr., 410076, Changsha, Hunan, China. 3Assoc. Prof., College of Bridge and Struct. Engrg., Changsha Univ. of Science and Technology, 45 Chiling Road, Tianxin Distr., 4

24、10076, Changsha, Hunan, China. 4Assoc. Prof., College of Bridge and Struct. Engrg., Changsha Univ. of Science and Technology, 45 Chiling Road, Tianxin Distr., 410076, Changsha, Hunan, China. Note. Discussion open until J

25、une 1, 2007. Separate discussions must be submitted for individual papers. To extend the closing date by one month, a written request must be filed with the ASCE Managing Editor. The manuscript for this paper was submitt

26、ed for review and possible publication on April 15, 2004; approved on September 23, 2005. This paper is part of the Journal of Bridge Engineering, Vol. 12, No. 1, January 1, 2007. ©ASCE, ISSN 1084-0702/2007/1-4–12/$

27、25.00.4 / JOURNAL OF BRIDGE ENGINEERING © ASCE / JANUARY/FEBRUARY 2007Downloaded 07 Nov 2010 to 113.240.233.8. Redistribution subject to ASCE license or copyright. Visithttp://www.ascelibrary.orgof the damage condit

28、ions. To this end, some measurement items are chosen as follows: 1. Material properties of concrete; 2. Crack condition ?location, width, and length?; 3. Reinforcement corrosion; 4. Load values produced by jacks; 5. Hori

29、zontal displacement at the spring line; 6. Vertical and lateral displacements; and 7. Distribution strains of the typical cross sections.Arrangement of Measuring PointsIn order to compare the test results between two dif

30、ferent dam- aged arches, the measuring points of the displacements and strains for the two arch ribs were arranged in the same way. Nine points for measuring the vertical displacements and seven points for measuring the

31、lateral displacements were respectively chosen for each arch. In addition, one point for measuring the horizontal displacement at each support was arranged. As a result, there were eighteen displacement measuring points

32、in each arch. The loading P ?the value of load at single loading point? was applied simultaneously at three different locations, say L/4, L/2, and 3L/4, respectively, by a specific jack-reaction system. The loading point

33、s and the displacement measuring points are shown in Fig. 6. Before testing, it was found that there were many distributed cracks in each arch rib. These cracks would greatly affect the local strains. Thirty-seven points

34、 for measuring the local strain values were arranged in each arch as shown in Fig. 7.Test ProcedurePresent Conditions DetectionAn accurate detection of damage is of importance for the evalu- ation of the bridge. Therefor

35、e, the objective of this step is to know the damage conditions, the material properties, and the sectional sizes. The covering layer thicknesses and diameters of the steel bars were measured by equipment. The covering la

36、yer average thick- ness was 3.0 cm at the bottom and 3.5 cm at the side. The cross- sectional sizes were measured by the steel ruler. The results can be found in Fig. 2. Through the naked eye, the surface cracks of both

37、the arches were visible. The initial cracks observed by dial magnifying glass were mainly distributed in the areas of the west spring, the L/4 and 3L/4 locations, and the east spring. Relatively, the number of cracks for

38、 both the arches near the L/8 location was more than in other places. The maximum length of the vertical cracks was 12 cm in the north arch and 7.25 cm in the south arch. The maximum width was 0.12 mm in the north arch a

39、nd 0.15 mm in the south arch. There was a crack along the axial line in the north arch. The length was 45 cm and the width was 0.41 mm. In addition, there were two cracks in the south arch. The maximum length was 51 cm,

40、and the maximum width was 0.48 mm. The crack distributions are illustrated in Fig. 8. Accurate evaluation for the constitutive relationship of concrete was a key step to obtaining the reliable finite-elementFig. 6. Measu

41、ring points of displacements and loading pointsFig. 7. Measuring points of strains6 / JOURNAL OF BRIDGE ENGINEERING © ASCE / JANUARY/FEBRUARY 2007Downloaded 07 Nov 2010 to 113.240.233.8. Redistribution subject to AS