2021 Vol. 36, No. 6

Processing and Manufacturing
Practice and Considerations on Steel Structure Manufacturing of Hong Kong-Zhuhai-Macao Bridge
Wenbo Gao, Jinwen Zhang, Quanke Su, Jizhu Liu
2021, 36(6): 1-23. doi: 10.13206/j.gjgSE20111601
The 55-km-long Hong Kong-Zhuhai-Macao Bridge (HZMB) is the world's longest sea-crossing bridge, connecting Hong Kong with Zhuhai and Macao at the mouth of the Pearl River Estuary in China. Due to the construction constraints such as high temperature, high humidity, high salt and windy offshore environment, dense sea routes,low obstruction rate of the water flow,life cycle cost,durability, and so on,the steel structure bridge, as the preferable bridge type, is the most reasonable choice for HZMB. The total length of the steel structure bridge of HZMB is about 22.9 km and the steel consumption is 425 000 t, and it is the largest scale and the longest designed service life at home and abroad, therefore, the manufacturing of the steel structure of this bridge is full of challenges.
To meet this challenge, at the beginning of the project, the HZMB management team conducted an in-depth investigation of the steel structure manufacturing industry at home and abroad, focusing on the gaps in computer-aided design, automatic manufacturing, detection technology, and construction management between domestic and foreign, and seeking for improvement methods. At that time, the steel structure manufacturing and processing level of China could not complete the manufacturing of 425 000 t of steel structures with high quality and efficiency within 48 months. To this end, the management team carried out the transformation and upgrading of the manufacturing model and the innovative planning of the management model, including the automation and intellectualization of steel plate element manufacturing, industrialization of assembly and painting workshop, full coverage of detection, flattening and internationalization of management, and manufacturing informatization management, etc. The construction and operation of the comprehensive innovation system for the steel structure manufacturing of the HZMB was successfully realized, the steel structure manufacturing of HZMB was completed with high quality and rich technical achievements, which mainly include:the automatic and intelligent production line for plate element, the factory assembly and mechanized coating of in large segments, the PAUT technical standard for the U-rib weld and the group welding information management system, the large-segment offshore installation and control technology, the accessible, detectable and maintainable design, and management innovation, etc.
At the end of the article, some thoughts and suggestions on the development of China's steel structure bridge industry were put forward based on the practical experience of the HZMB. Through the planning and practice of the steel structure manufacturing of the HZMB, it can be seen that:1)The requirement of standardization, factorization, and large-scale segment promotes the technological innovations in each construction stage of HZMB. The application of mechanization, automation, and information technologies has improved the overall construction and management level. 2)The extensive offshore assembly constructions promote the development, application of large offshore equipment, and innovative hoisting methods. 3)Standardization of technology and management enables the effective implementation of the concept of full process control. 4)In accordance with the concept of equal emphasis on construction and maintenance, the development of accessible, detectable and maintainable design can promote the lowest life-cycle cost of steel structure bridges. The construction of the HZMB has promoted the progress of China's steel structure industry and provided rich and valuable experience for the development of the industry. The 55-km-long Hong Kong-Zhuhai-Macao Bridge (HZMB) is the world's longest sea-crossing bridge, connecting Hong Kong with Zhuhai and Macao at the mouth of the Pearl River Estuary in China, comprising 22.9-km-long steel bridges. HZMB is the leading steel bridge in China, with top-level manufacturing and installation technology. This paper outlines the steel bridge construction experiences of HZMB to provide comparisons for the construction of other long sea-crossing steel bridges at home or abroad. The main considerations of construction background, constraints, manufacturing market survey, procure strategies, scheme selection, structural and aesthetic design of HZMB are presented, and the following points related to new strategies in the steel bridge preliminary and construction stage of HZMB are elaborated:(1) biding strategy, (2) automatic manufacturing technology, (3) large segment offshore installation, (4) eco-friendly paint (content limitation of volatile organic compounds). The successful implementation of those strategies shows that the steel bridge construction of HZMB promotes improvement in the overall construction and management level of the Chinese bridge industry.
The Allowable Deviation of Assembly Dimension in Steel Bridge Manufacturing Specification
Junping Li
2021, 36(6): 24-28. doi: 10.13206/j.gjgS21012201
Bridges will bear frequent dynamic loads after being put into operation, which is different from the general building structure. For steel bridge, compared with reinforced concrete bridge, it also has some special performance requirements, such as higher standard requirements for the geometric accuracy and welding quality of steel bridge bar or steel beam (steel tower) section. The reasonable allowable deviation requirement of steel beam assembly size is particularly important to ensure the dimensional accuracy, convenient production and quality of finished products. However, in the current industry norms, local norms or manufacturing rules of the project, the allowable deviation of assembly size given is often not scientific and reasonable, and it is difficult to meet or match the allowable deviation of the final basic size of the finished product.
Based on the analysis of steel bridge manufacture assembly size with the current situation of allowable deviation in the specification, it expounded the steel bridge assembly dimensions determine the allowable deviation of basis and related examples:1)the height of the steel truss girder lord bar assembly tolerance requirements, Standard of Railway Steel Bridge Manufacture(Q/CR 9211-2015) is more rational and comprehensive; 2)the allowable deviation requirements of bridge steel tower segment assembly. In general manufacturing and acceptance specifications, it is unreasonable to adopt the allowable deviation of steel tower segment assembly consistent with the allowable deviation of the basic size of the finished product; 3)the allowable deviation of steel box girder segment assembly size is not distinguishable between the allowable deviation of the final basic size of the girder segment and the allowable deviation of the assembly size in the current industry standard, local standard or the manufacturing acceptance rule of steel box girder project. It is unreasonable to require that the allowable deviation between the two is basically the same. Then, the paper introduced the making steel component assembly dimension deviation should be allowed the problems:1)assembly of allowable deviation for the part of the steel girder structure analysis, such as:steel tower, steel box girder segment, due to the manufacturing process, influencing factors, should not put the finished product basic size deviation and assembly size allowed allowable deviation as a consistent or near; 2)How to determine the assembly allowable deviation of complex steel beam members should be determined according to the allowable deviation of the basic size of the finished product combined with its structural characteristics and manufacturing technology; 3)to develop the basic size of the steel girder components allowed deviation should be scientific and reasonable, such as:large steel box girder width tolerance requirements were too strict was meaningless, should be combined with the specific structural characteristics of the steel girder components, the importance of the point of the degree of development.
Finally it drew the conclusion:the basic dimension tolerance to determine the scientific and reasonable steel components was of great significance, the assembly tolerance was closely related to the manufacturing process, should be determined by the factory according to the basic allowable deviation of steel components, combining with the characteristics of structure, welding shrinkage factors such as given on process, specification, just set forth some basic requirements for the assembly process.
Effects on Aerodynamics of Long-Span Bridges with Different Vertical Clearance Under Bridges Decks
Bingzhi Pei, Bolin Sun, Menzhe Zhang, Shengzhi Liu, Zhiwen Zhu
2021, 36(6): 29-35. doi: 10.13206/j.gjgS20052502
In order to investigate aerodynamics of long-span bridges with different vertical clearance under bridges stiffening girder, the Reynolds-Averaged Navier-Stokes Equations and SST k-ω turbulent model were employed to solve the flow field around bridge girder of the Great Belt East Bridge main span with different vertical clearance in natural wind. The aerodynamic coefficients under various vertical clearance is presented and compared to wind tunnel test, and its flow mechanism relating to those changes is analyzed.
The results find that the variation of vertical clearance presents mix effects on pressure distribution on girder surface, on lift and drag acting on girder, and on vortex shedding St number. When the vertical clearance decreases, the lift and drag coefficients will increase. Compared to the results from vertical clearance of 5B, the vertical clearance of 0.4B produces an increase of 87.8% for lift coefficient and an increase of 13.3% for drag coefficient, and the vortex shedding St number also indicates slightly increase. The monitored pressure distribution on girder surface indicates that when the vertical clearance is small, the peak pressure at the positive zone ahead of leading edge of the girder increases, and the peak negative pressure at the windward corner of the deck and bottom also increase, with significant increase observed at the deck corner. It is concluded that when the vertical clearance under the bridge is very small, the water surface will generate significant aerodynamic interference to the bridge girder, hence the increase wind loads acting on the bridge girder due to significantly small vertical clearance should be considered as to insure bridge safety against wind.
Design and Research of Main Weld of Track Beam of Suspension Monorail
Ning Zhang, Lijun Li
2021, 36(6): 36-43. doi: 10.13206/j.gjgS20071001
The track beam of suspension monorail is a combination of beam and rail structured by a thin-walled box with an opening at lower location and deck layout lower than the load-bearing structure. The main weld of flange and web on track beam is critical weld with force transferred by structure. The main weld has a complex load-carrying status which is difficult to design and check by conventional design method. Therefore, on the basis of the existing international design of track beam of suspension monorail and with reference to the Zhong Tang New Resource Sky Train Test Line Project participated by our company, the method combining finite element and theoretical calculation was used to analyze and calculated the load-carrying status of the main weld of track beam of suspension monorail. The transferring force rule of main weld seam of top/bottom flange of the track beam, main weld seam in region 1 and main weld seam along the beam length direction were studied. By the transferring force calculation of weld seam, track beam the main weld seam design of was carried out, in accordance with the Code for Design on Steel Structure of Railway Bridge (TB 10091-2017), and the weld seam strength and fatigue have been checkup. By this design method, the main weld of track beam of suspension monorail could be analyzed quantitatively, so as to avoid the main weld from being designed with overlarge size or exceed the actual need to reduce investment cost. The relevant conclusions were as follows:
1) A stress analysis for the main weld (connecting web and top/bottom flange) of the track beam of suspension monorail was comlished. The top/bottom flange and web were connected by main welds and stiffeners. The bottom flange, as the vehicle travelling surface, was subjected to the local load effect given by the wheel, thus its weld seam bore the most stress.
2) The main weld seam connecting the top/bottom flange and web were subjected to the shear effect, with the basically same shear force magnitude and the opposite shear force direction on the same section, with the calculation results concurring with the simply supported beam main weld seam capability of shear force; main weld seam of the bottom flange in the middle of the two stiffeners showed a definitely better capability of bearing vertical stress compared to the main weld seam of the top flange; bottom flange weld seam at stiffeners presented a slightly better capability of bearing vertical stress compared with top flange weld seam at stiffeners, with both of which better than the bottom flange weld in the middle of the two stiffeners in terms of bearing vertical stress; Mx moment of force of bottom flange weld seam in the middle of two stiffeners was significantly larger than any other positions.
3) The vertical force in the stiffener was much larger than any other positions; the closer the longitudinal Fx to the stiffener, the quickly the Fx at stiffeners reduced under the effect of the stiffener; Mx distributed as a "V" shape, in which the least moment of force at stiffener, and it gradually increased to both sides. My distributed as a "M" shape.
4) The transferring force rule of Fx gradually growed from the middle of the span to the support position, Fx in Q 1 position close to hanging suspension frame position reduced because the hanging suspension frame bore the shear force exerted by the track beam. Fx in the middle of each stiffener gradually growed from the middle of the span to the support position. The vertical force Fz was mainly caused by vehicle wheel, with the basically same magnitude at each location. From the middle of the span to support location, Mx reduced at first and then increased, My increased gradually.
Comparison of Chinese and US Code
Design of Members for Shear
Lijun Wang
2021, 36(6): 44-53. doi: 10.13206/j.gjgS20081801
The design method of members for shear in Specification for Structural Steel Buildings (AISC 360-16) is introduced and compared with that in Standard for Design of Steel Structures (GB 50017-2017).
The strength calculation of shear members is listed in Chapter G of AISC 360-16, in which the design shear strength takes ϕvVn, and the shear resistance coefficient ϕv=0. 9.
1)For I-shape and channel sections, post-buckling strength after shear buckling can improve the shear capacity of the web, which is induced by the internal force redistribution and tension field in the web. For the web without stiffeners or with the spacing between stiffeners a>3h, post-buckling strength is only provided by internal force redistribution. However, for the web with the spacing between stiffeners a ≤ 3h, both of them are contributors.
2) When shear strength without considering tension field of webs, h/tw ≤ 1. 10 √kvE/Fy:shear strength is supported by shear yielding of the web, namely Cv1=1. 0; h/tw > 1. 10 √kvE/Fy:shear strength originates from both buckling of the web and its post-buckling strength, namely Cv1 < 1. 0.
3)If there is no stiffener,the shear buckling coefficient of the web kv=5. 34, the cut-off point between heightto-thickness ratios under shear yielding and shear buckling is h/tw=1. 10 √kvE/Fy=74√235/Fy, so 74εk is the critical height-to-thickness ratios between yielding and buckling.
4)When the web has stiffeners and a/h ≤ 3, tension field works and shear strength of the web should be calculated.
For the calculation of buckling bearing capacity of members under shear, GB 50017-2017 provides the formulas to calculate the shear buckling stress of the web in Article 6. 3. 3 without considering post-buckling strength, and presents the formulas considering post-buckling strength of the web in Chapter 6. 4.
1) When shear buckling stress of the web without considering post-buckling strength, GB 50017-2017 (6. 3. 3-8-12) presents the relationship between critical shear stress τcr of web regardless of post-buckling strength and regularized width-to-thickness ratio λn,s. If η=1. 11 is adopted for simply supported beams, h0/tw=76εk, consistent with the value 74εk in AISC 360-16. GB 50017-2017 takes h0/tw=80εk as the cut-off point between yielding and buckling, and points out in Article 6. 3. 1 that buckling stability of the web should be computed when h0/tw > 80εk.
2)When the shear buckling of the web is considered post-buckling strength, for the beam under shear, GB 50017-2017 takes into account the effect of tension field after buckling.
Analyses reveal that:AISC 360-16 presents the strength calculation of shear members considering the postbuckling strength of web plates, and GB 50017-2017 provides the formulas for the shear strength with and without post-buckling strength of the web respectively.
2021, 36(6): 54-54.