（節(jié)選）橋梁工程外文翻譯--斜交角度對(duì)連續(xù)組合梁橋的影響（原文）

1、Influence of Skew Angle on Continuous Composite Girder BridgeGholamreza Nouri, Ph.D.1; and Zahed Ahmadi, M.Sc.2Abstract: The design of skewed bridges is becoming more customary in the engineering community. In this paper

2、, the effect of the skew angle on continuous composite girder bridges is presented using three-dimensional finite-element analysis. Seventy-two models of two-span bridges with various span ratios (N ¼ 1, 1.55, and 1

3、.82), skew angles (0–60°), and various arrangements of intermediate transverse dia- phragms are analyzed. All models were subjected to AASHTO HS20-44 loading. Results for skewed bridges are compared with the referen

4、ce nonskewed bridge, as well as to the AASHTO standard specifications and AASHTO LRFD specifications. The results show that as the skew angle increases, the support moment in interior and exterior girders rapidly decreas

5、es. It decreases about 10% when the skew angle is less than 20° and reaches 33% for a 45° skew angle. The shear force increases in the pier support at the exterior girders and decreases at the interior ones wit

6、h increasing skew angle. For exterior girders, the ratio of shear force increases up to 1.3 for a skew angle of 45°. The AASHTO standard specifications overestimate the maximum bending moment by 20% for a skew angle

7、 of 30° and N ¼ 1 and by 50% for a skew angle of 45°. The overestimation of shear force is about 10% for a skew angle of 45°. The AASHTO LRFD specifications overestimate the longitudinal bending momen

8、t and shear force. This overestimation increases with an increase of the skew angle and reaches 12% for a skew angle of 20° and 45% for a skew angle of 45°. The results show that transverse diaphragms perpendic

9、ular to the longitudinal girders of the bridges are the best arrangement for load distribution. Comparing the results of the simplified relationships of the skewed decks with the finite-element analysis shows that the re

10、sults of the proposed equations are conservative for continuous-skewed bridges. It is noted that the results pertain to those bridges with specific configurations and the results may change if the presumed conditions var

11、y, although the tendency should be similar. DOI: 10.1061/(ASCE)BE.1943-5592.0000273. © 2012 American Society of Civil Engineers.CE Database subject headings: Continuous bridges; Composite bridges; Girder bridges; Sk

12、ew bridges.Author keywords: Skew angle; Continuous bridge; Distribution factor; Composite bridge.IntroductionSkewed bridges are especially common in developed areas where alignment issues rather than economic issues may

13、control the design of the bridge. Skewed bridges are also quite common in mountainous regions where topographical features may dictate that the bridge superstructure cannot be perpendicular to the abutments and piers. In

14、 nonskewed bridges, the load path is straight toward the sup- port in the direction of the span. In skewed bridges, this is not the case. For a solid slab-skew bridge, the load tends to take a shortcut to the obtuse corn

15、ers of the bridge. In bridge decks supported by longitudinal girders, this effect also occurs, although it is less pro- nounced. This change in direction of the load path in highly skewed bridges brings about the followi

16、ng special characteristics: signifi- cant torsional moments in the deck slab, decrease in longitudinal moment, increase in transverse moment, concentration of reaction forces and negative moments at the obtuse corners, s

17、mall reactions, and a possibility of uplift reaction forces at the acute corners. These special characteristics of skew bridges make their analysis and design more intricate than for nonskewed bridges.In the past, skewed

18、 bridges were analyzed, designed, and con- structed in the same way as straight bridges regardless of the mag- nitude of the skew angle. Many design factors were treated in the same way for skewed and straight bridges. O

19、ne example of this is the live-load distribution factor (LLDF), which in the design codes make the design straightforward and provide a simple and quick way of evaluating a bridge. The LLDF is a function of parameters su

20、ch as the bridge geometry, relative stiffness of the components, and nature of the loads. The AASHTO (2003) standard specifica- tions provide distribution factors for the interior girders of simply supported bridges as a

21、 function of girder spacing only. This code does not consider the effect of the skew angle and bridge continuity. The Ontario Highway Bridge Design Code (OMTC 1992) accounts for longitudinal and transverse rigidities of

22、bridges in addition to the girder spacing. However, the method is limited to simply sup- ported and small-skew-angle bridges. The current AASHTO LRFD Bridge Design Specifications (AASHTO 2010) recognizes that the LLDF is

23、 a function of girder spacing, span length, slab thickness, and beam stiffness. The LLDFs are specified differently for exterior and interior girders, for shear and moment, and for one-lane-loaded and two- or-more-lane-l

24、oaded cases. The AASHTO LRFD specifications in- troduce the reduction factor for the LLDF as a function of the skew angle. The skew angle is undoubtedly an important parameter for skewed bridge behaviors such as the load

25、 distribution factor and the load effect on bearings (Zokaie et al. 1991). Khaleel and Itani (1990) presented a method for determining the bending moment in continuous normal and skewed slab-and-girder bridges owing to l

26、ive loads. They concluded that the AASHTO standard1Assistant Professor, Civil Engineering Group, Payame Noor Univ., Tehran, Iran (corresponding author). E-mail: gholamrezanouri@gmail.com2Graduate, Structural Engineering,

27、 Univ. of Mohaghegh, Ardabili, Iran. Note. This manuscript was submitted on September 3, 2010; approved on May 24, 2011; published online on May 26, 2011. Discussion period open until December 1, 2012; separate discussio

28、ns must be submitted for individual papers. This paper is part of the Journal of Bridge Engineering, Vol. 17, No. 4, July 1, 2012. ©ASCE, ISSN 1084-0702/2012/4-617–623/ $25.00.JOURNAL OF BRIDGE ENGINEERING © AS

29、CE / JULY/AUGUST 2012 / 617J. Bridge Eng. 2012.17:617-623.Downloaded from ascelibrary.org by Changsha University of Science and Technology on 03/13/14. Copyright ASCE. For personal use only; all rights reserved.of N 

30、8; 1:55 and skew angles of 30°, the model was extended to be the same as the Ebeido and Kennedy (1996a, b) model. Compari- son of the moment distribution factor for the interior girder showed a difference of less th

31、an 2.5%. The FEA results for the two-lane bridges considered in terms of the maximum longitudinal bending moment and the shear force in the exterior and interior girders at the pier support are reported sub- sequently. T

32、he maximum FEA bending moment is presented in the form of the ratio Mα∕M0, where Mα is the maximum FEA moment in the bridge for a given skew angle of α (between 0 and 60°), and M0 is the FEA moment for a nonskewed b

33、ridge (skew angle of 0°). Similarly, the ratio Vα∕V0 is calculated for shear force.Maximum Longitudinal Bending Moment Ratio at Pier SupportThe ratio of Mα∕M0 for the maximum longitudinal moment at interior girders

34、is shown in Fig. 2(a) for each of the three span ratios (1, 1.55, and 1.82) versus skew angles. It is observed that the maxi- mum longitudinal moment in the interior girders at the pier supportdecreases with the increase

35、 of skew angle. This decrease is about 10% when skew angles are less than 20°; with an increase in skew angle up to 45°, the support moment decreases about 33%. As illus- trated in Fig. 2(b), the decrease of th

36、e bending moment for exterior girders appears to be insignificant when the skew angle is less than 20°. However, with an increase in the skew angle to 30°. the ratio decreases to about 0.86, and it further decr

37、eases to about 0.71 as the skew angle increases to 45°.Maximum Shear Forces Ratio at Pier SupportFig. 3(a) demonstrates the effect of skew angle on the shear force at the pier support for interior girders. The shear

38、 force decreased at the pier support in interior girders with an increase in the angle of skew. This ratio was about 0.87 for skew angles less than 30°, and it de- creased to about 0.78 for bridges with skew angles

39、of 45°. The shear force ratio Vα∕V0 for exterior girders at the pier sup- port is shown in Fig. 3(b), in which it can be observed that the shear force at the pier support for each of the three span ratios (1, 1.55,

40、and 1.82) increased significantly with an increase in the skew angleFig. 1. Cross section of the finite-element model and two arrangements of transverse diaphragms0.60.70.80.911.10 15 30 45Mα / Mo Skew angle (degree)N=1

41、N=1.55 N=1.820.60.70.80.911.10 15 30 45Mα / Mo Skew angle (degree) (a) (b)N=1 N=1.55 N=1.82Fig. 2. FEA maximum longitudinal bending moment ratio Mα∕M0 at the pier support of two-lane bridges for (a) internal girders and

42、(b) external girdersJOURNAL OF BRIDGE ENGINEERING © ASCE / JULY/AUGUST 2012 / 619J. Bridge Eng. 2012.17:617-623.Downloaded from ascelibrary.org by Changsha University of Science and Technology on 03/13/14. Copyright