| Citation: | LIU Bin, LIU Yong-jian, ZHOU Xu-hong, LI Zhou, WANG Kang-ning. Design of mid-span fabricated RCFST composite truss bridge[J]. Journal of Traffic and Transportation Engineering, 2017, 17(4): 20-31.
|
Compared with concrete beam bridges, steel-concrete composite bridges have the characteristics of lightweight, high strength, energy saving, environmental protection, earthquake resistance, and excellent life cycle. As a type of steel-concrete composite bridge, steel-concrete composite truss bridge is based on the optimized structural form of the concrete box girder web and bottom plate. After the concrete box girder web and bottom plate are replaced by a truss system, the advantage of clear stress on the truss system increases the utilization rate of structural materials and greatly reduces the self weight of the structure. Therefore, this type of bridge is increasingly favored and concerned by engineers and scholars.
The aspect ratio is an important parameter in the overall design of bridges, which directly affects the stress state and steel consumption of the structure. From the perspective of stress, the edge to mid span ratio should be taken as 0.6~0.8. At this point, the bending moment at the edge to mid span and the bending moment at the mid span are relatively close, and the structural bending moment distribution is uniform. From the perspective of standard assembly, the side span and mid span should be taken as the same span. In this case, the bending moment in the mid span of the side span is greater than that in the mid span, resulting in a significantly higher steel consumption for the side span chord than for the mid span chord. From the perspective of bridge aesthetics, after equal span arrangement, the bridge line appears simple, clear, and rhythmic.
The height to span ratio is another important design parameter for bridge design, which is closely related to the steel consumption of composite truss bridges,Figure 5The relationship between the amount of steel used and the height to span ratio for a 4 × 70m standard span composite truss bridge (bridge width 12.75m).
 |
DownLoad:
CSV
The connection structure of rectangular steel-concrete composite truss bridge is mainly divided into two parts: the connection structure between the main truss segment units and the connection structure between the bridge deck assembly units and the main truss segment units.
The on-site splicing method between the main truss segment units directly determines the overall construction quality of the main truss. The final selection of the splicing joint between the main truss segment units in this design is a combination of built-in flanges and outer ring welding. This connection method first uses bolts and splicing plates to connect the built-in flanges, smoothly positioning the steel truss segment, and then welding the outer ring steel plate. Compared with previous external flanges, the joint connection of internal flange and outer ring welding is more reliable and aesthetically pleasing（Figure 13、14）.
The connection structure between the bridge deck assembly unit and the main truss segment unit is directly related to the combination effect of the bridge deck and the main truss. The connection structure needs to consider the following factors: the truss node is the key structure for structural force transmission. In order to ensure the reliable force transmission of the bridge deck and the upper chord node, shear studs at the transverse wet joint need to be densely arranged（Figure 15）In order to match the shear slots in the bridge deck assembly unit, the shear studs at the main truss corresponding to the shear slots also need to be arranged in groups.
 |
DownLoad:
CSV
Based on the above analysis, the design of tension rods should fully utilize the advantages of good tensile performance of steel, while the design of compression rods should fully utilize the mechanical performance advantages of high compressive bearing capacity of steel-concrete components, while taking into account the insufficient compressive stability of steel pipes.
|
|
 |
DownLoad:
CSV
In summary, based on the initial input seismic force, the seismic performance of rectangular steel-concrete composite truss bridges is significantly better than that of prestressed concrete variable cross-section continuous beam bridges.
Due to the large distance between the two main trusses of the rectangular steel-concrete composite truss bridge, the shear lag effect of the bridge deck is significant. Especially at the fulcrum, the shear force is large and the bridge deck is in tension. The shear lag effect reduces the effective tensile area of the bridge deck. When calculating the crack width of the bridge deck, the effective width of the bridge deck must be considered. In design, the effective width coefficient of the bridge deck is generally used to consider the shear lag effect. The effective width coefficient of the bridge deck is the ratio of the effective distribution width of the bridge deck to the actual width. Taking the 4 × 70m rectangular steel tube concrete composite truss bridge as an example (bridge width 12.75m), the effective width coefficient at the midpoint is calculated based on domestic and foreign standards and finite element analysis.
Table 4Listed the effective width coefficient of the pivot point calculated according to domestic and international standards.
 |
DownLoad:
CSV
The effective distribution width of the bridge deck is
|
|
In the formula:σxNormal stress in the cross-section of the wing edge;σx, maxThe maximum normal stress in the cross-section of the wing edge;beThe effective distribution width of the wing edge;brThe actual width of the wing edge;xCalculate the location of stress points for the bridge deck panel.
When using the finite element method to analyze the effective width of the bridge deck, the stress and element division size can be calculated based on the transverse division positions of the bridge deck elements, and then approximated using equation (2)
|
|
In the formula:σiFor bridge deck panelsiThe normal stress at the corresponding point of the horizontal block;biFor bridge deck panelsiHorizontal block length;σmaxThe maximum transverse normal stress of the bridge deck.
The stress calculation results of the finite element space model are shown inFigure 21According to equation (3), the effective width coefficient at the fulcrum is 0.899. Compared with the calculation results of domestic and foreign standards, finite element analysis is more targeted, and the calculation results are more accurate and safe. Therefore, the effective width coefficient at the fulcrum in this design is based on the finite element calculation results, and is ultimately taken as 0.899.
The mechanical performance analysis of the negative bending moment zone has always been a difficult point in the design of steel-concrete composite beams, because in the negative bending moment zone, the concrete bridge deck is under tension, and the concrete itself is prone to cracking. This design adopts partial combination connection technology in the negative bending moment zone - anti pull and non shear connection bolts[27-28]To optimize the mechanical properties of this area. Taking the 4 × 70 m rectangular steel tube concrete composite truss bridge as a calculation example, the mechanical properties of the negative bending moment zone are analyzed.
Comparing the maximum axial tension envelope results of bridge decks under short-term load effect combinations using new anti pull and non shear connection bolts and traditional connection bolts in the negative bending moment zone. causeFigure 22It can be seen that when using the new anti pull and non shear connection bolts, the maximum axial tension of the pier top bridge deck under the short-term load effect combination is 1301kN. When using traditional connection bolts, the maximum axial tension of the bridge deck is 5277N. It can be seen that using the new anti pull and non shear connection bolts in the negative bending moment zone reduces the axial tension of the bridge deck by 75.3%, effectively improving the crack resistance performance of the bridge deck.
Compared with prestressed concrete box girder bridges, rectangular steel tube concrete composite truss bridges use slightly more steel, but significantly less concrete. Therefore, the weight of the upper structure will be greatly reduced, effectively reducing the reinforcement ratio of the bridge piers and the amount of foundation engineering. In addition, the reduction of the weight of the upper structure is very beneficial for the seismic fortification of the lower structure.
In order to conduct an intuitive economic analysis, a comparison case is now made between Scheme 1 equal section rectangular steel tube concrete composite truss bridge and Scheme 2 variable section prestressed concrete box girder bridge: Scheme 1 has a span arrangement of 4 × 70m=280m, a bridge width of 12.75m, and a main beam cross-section of two main trusses; Scheme 2 has a span arrangement of (50+90+90+50) m=280m, The bridge width is 12.75m, and the cross-section of the main beam is a single box single room.
causeFigure 23~25It can be seen that the ratio of steel consumption, concrete consumption, and upper structure quality between Scheme 1 and Scheme 2 is 1.241, 0.485, and 0.575, respectively. This indicates that compared with the rectangular steel tube concrete composite truss bridge, although the steel consumption is slightly reduced, the concrete consumption and upper structure quality are significantly increased, and the lower structure engineering and foundation engineering also need to be correspondingly increased. The rectangular steel tube concrete composite truss bridge has a lightweight structure, high material utilization rate, low engineering cost, and obvious economic advantages.
Medium span and large-span prestressed concrete box girder bridges generally use cantilever construction method, with complex construction processes such as concrete formwork, steel bar binding, and prestressed tensioning（Figure 26、27）During the construction process, precise monitoring of the structural assembly line shape is required, and the construction period is long. Especially in the western mountainous areas, the collection of sand and stone materials on site during the construction of prestressed concrete box girder bridges can seriously damage the local ecological environment.
Compared with prestressed concrete box girder bridges, the rectangular steel tube concrete composite truss bridge has a rectangular steel tube truss as the upper main structure, which can be prefabricated in standardized sections in the factory. The quality of component manufacturing is controllable. After the standard prefabricated sections are delivered to the site, they can be assembled conveniently and quickly using cantilever, lifting, and pushing construction methods（Figure 28、29）At the same time, with only a small amount of on-site wet welding work, prefabricated bridge decks and steel main trusses can be assembled through shear studs, and the construction of the upper structure can be fully prefabricated, standardized, and assembled.
(1) A new type of prefabricated bridge structure, the rectangular steel-concrete composite truss bridge, has been proposed, which can provide reference for the design of prefabricated bridges for highways with spans over 50 meters in China.
| [1] |
DAUNER H G, ORIBASI A, WRY D. The lully viaduct, a composite bridge with steel tube truss[J]. Journal of Constructional Steel Research, 1998, 46 (1-3): 67-68. doi: 10.1016/S0143-974X(98)00025-X
|
| [2] |
MATO F M, CORNEJO M O, RUBIO L M. Viaduct over River Ulla: an outstanding composite (steel and concrete) high-speed railway viaduct[J]. Structural Engineering International, 2014, 24 (1): 131-136. doi: 10.2749/101686614X13830788506279
|
| [3] |
ZHANG Gui-zhong. Study on the technologies of CFST truss of Wanzhou Bridge[D]. Chengdu: Southwest Jiaotong University, 2004. (in Chinese).
|
| [4] |
WU Qing-xiong, HUANG Yu-fan, CHEN Bao-chun. Shaking tables testing study of lightweight bridge with CFST composite truss girder and lattice pier[J]. Engineering Mechanics, 2014, 31 (9): 89-96. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-GCLX201409014.htm
|
| [5] |
LIU Yong-jian, ZHOU Xu-hong, ZOU Yin-sheng, et al. Experimental research on local bearing strength of concrete filled rectangular steel tube under transverse load[J]. Journal of Building Structures, 2003, 24 (2): 42-48. (in Chinese). doi: 10.3321/j.issn:1000-6869.2003.02.008
|
| [6] |
LIU Yong-jian, ZHOU Xu-hong, LIU Jun-ping. Experiment on force performance of concrete-filled rectangular steel tube K-joints[J]. Journal of Architecture and Civil Engineering, 2007, 24 (2): 36-42. (in Chinese). doi: 10.3321/j.issn:1673-2049.2007.02.007
|
| [7] |
LIU Yong-jian, ZHOU Xu-hong, LIU Jun-ping. Behavior of concrete filled rectangular steel tube T-joints and Y-joints under compression[J]. Journal of Chang'an University: Natural Science Edition, 2008, 28 (5): 48-52. (in Chinese). doi: 10.3321/j.issn:1671-8879.2008.05.012
|
| [8] |
LIU Yong-jian, LIU Jun-ping, YANG Gen-jie, et al. Experimental research on mechanical behavior of RHS trusses with concrete-filled in chord[J]. Journal of Building Structures, 2009, 30 (6): 107-112. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-JZJB200906015.htm
|
| [9] |
LIU Yong-jian, ZHOU Xu-hong, LIU Jun-ping. Experimental research on rectangular steel tube X-joints with chord concrete-inside subjected to tension and bending[J]. Journal of Building Structures, 2009, 30 (1): 82-86. (in Chinese). doi: 10.3321/j.issn:1000-6869.2009.01.012
|
| [10] |
LlU Yong-jian, LlU Jun-ping, ZHANG Jun-guang. Experimental research on RHS and CHS truss with concrete filled chord. Journal of Building Structures, 2010, 31 (4): 86-93. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-JZJB201004012.htm
|
| [11] |
ZHOU Xu-hong, LIU Yong-jian, MO Tao, et al. Design of concrete filled trusses with rectangular steel tube[J]. Building Structure, 2004, 34 (1): 20-23. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-JCJG200401005.htm
|
| [12] |
LIU Yong-jian, XIONG Zhi-hua, LUO Ya-lin, et al. Doublecomposite rectangular truss bridge and its joint analysis[J]. Journal of Traffic and Transportation Engineering: English Edition, 2015, 2 (4): 249-257. doi: 10.1016/j.jtte.2015.05.005
|
| [13] |
CHEN Bao-chun, HUANG Wen-jin. Experimental research on ultimate load canying capacity of truss girders made with circular tubes[J]. Journal of Building Structures, 2007, 28 (3): 31-36. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-JZJB200703004.htm
|
| [14] |
HAN Lin-hai, XU Wu, HE Shan-hu, et al. Flexural behaviour of concrete filled steel tubular (CFST) chord to hollow tubular brace truss: experiments[J]. Journal of Constructional Steel Research, 2015, 109: 137-151. doi: 10.1016/j.jcsr.2015.03.002
|
| [15] |
XU Wu, HAN Lin-hai, TAO Zhong. Flexural behaviour of curved concrete filled steel tubular trusses[J]. Journal of Constructional Steel Research, 2014, 93: 119-134. doi: 10.1016/j.jcsr.2013.10.015
|
| [16] |
FENG Ran, CHEN Yu, GAO Sheng-wei, et al. Numerical investigation of concrete-filled multi-planar CHS inversetriangular tubular truss[J]. Thin-Walled Structures, 2015, 94: 23-37. doi: 10.1016/j.tws.2015.03.030
|
| [17] |
CHEN Yu, FENG Ran, GAO Sheng-wei. Experimental study of concrete-filled multiplanar circular hollow section tubular trusses[J]. Thin-Walled Structures, 2015, 94: 199-213. doi: 10.1016/j.tws.2015.04.013
|
| [18] |
FONG M, CHAN S L, UY B. Advanced design for trusses of steel and concrete-filled tubular sections[J]. Engineering Structures, 2011, 33 (12): 3162-3171.
|
| [19] |
MUJAGIC J R U, EASTERLING W S, MURRAY T M. Design and behavior of light composite steel-concrete trusses with drilled standoff screw shear connections[J]. Journal of Constructional Steel Research, 2010, 66 (12): 1483-1491.
|
| [20] |
GAO Yan-mei, ZHOU Zhi-xiang, LIU Dong, et al. Research on crack resistance of prefabricated steel truss-concrete composite beam[J]. China Journal of Highway and Transport, 2017, 30 (3): 175-182, 209. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-ZGGL201703019.htm
|
| [21] |
ZHANG Zhen-xue, NIE Jian-guo, TAO Mu-xuan, et al. Optimization of mechanical behavior of steel and concrete continuous composite truss girder bridge[J]. Bridge Construction, 2012, 42 (6): 57-62. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-QLJS201206012.htm
|
| [22] |
LIU Yong-jian, ZHANG Ning, ZHANG Jun-guang. Mechanical behavior of concrete-filled square steel tube stiffened with PBL[J]. Journal of Architecture and Civil Engineering, 2012, 29 (4): 13-17. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-XBJG201204004.htm
|
| [23] |
LIU Yong-jian, LI Hui, ZHANG Ning, et al. Interface bond-slip performance of rectangular concrete-filled steel tube stiffened by PBL[J]. Journal of Architecture and Civil Engineering, 2015, 32 (5): 1-7. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-XBJG201505002.htm
|
| [24] |
ZHANG Ning, LIU Yong-jian, LI Hui, et al. Local buckling characteristics of stiffened rectangular plate on elastic foundation subjected to non-uniform loads[J]. Journal of Traffic and Transportation Engineering, 2017, 17 (1): 36-44. (in Chinese). http://transport.chd.edu.cn/article/id/201701005
|
| [25] |
CHENG Gao, LIU Yong-jian, TIAN Zhi-juan, et al. Tensile behavior of PBL stiffened concrete-filled rectangular steel tubular unequal T-connections[J]. Journal of Chang'an University: Natural Science Edition, 2015, 35 (3): 83-90. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-XAGL201503014.htm
|
| [26] |
CHENG Gao, LIU Yong-jian, QIU Jie-lin, et al. Analysis of stress concentration factor on concrete-filled rectangular steel tube T-joints stiffened with PBL[J]. Journal of Architecture and Civil Engineering, 2014, 31 (4): 74-79. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-XBJG201404013.htm
|
| [27] |
NIE Jian-guo, LI Yi-xin, TAO Mu-xuan, et al. Experimental research on uplift performance of a new type of uplift restricted-slip free connector[J]. China Journal of Highway and Transport, 2014, 27 (4): 38-45. (in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-ZGGL201404007.htm
|
| [28] |
NIE Jian-guo, LI Yi-xin, TAO Mu-xuan, et al. Uplift-restricted and slip-permitted T-shape connectors[J]. Journal of Bridge Engineering, 2015, 20 (4): 1-13.
|
Figures(29) / Tables(4)
Copyright《Journal of Traffic and Transportation Engineering》编辑部陕ICP备05001904号-1
Address ：Editorial Department of Journal of Traffic and Transportation Engineering, Chang 'an University, Middle Section of South Second Ring Road, Xi 'an, Shaanxi（710064） Tel：029-82334388 Email：jygc@chd.edu.cn
All visit:Today's visit:
Supported by:
Beijing Renhe Information Technology Co. Ltd
|
DownLoad:
CSV
|
DownLoad:
CSV
|
DownLoad:
CSV
|
DownLoad:
CSV
DownLoad:
DownLoad:
