Study on Structure of Arched Longitudinal Beams of Deep Water Wharf

China Oeean Enginering, Vol.22, No.4, pp.705 -711◎2008 China Ocean Press, ISSN 0890-5487Study on Structure of Arched Longitudinal Beams of Deep-Water Wharf*ZHAI Qiu(翟秋)', LU Zi-ai (鲁子爱) and ZHANG Shu-hua (张淑华)College of Trafic and Oeean Enginering , Hohai University, Nanjing 210098, China(Received 17 March 2008; received revised formn 20 September 2008; accepted 31 October 2008)ABSTRACTHigh-pile and beam-slab quays have been widely used after several years development. They are mature enough tobe one of the most important structural types of wharves in China coastal areas. In order to accommodate large tonnagevesels, wharves should be constructed in deep water gradully. However, conventional high-pile and beam-slab struc-tures are hard to meet the requirements of large deep waler wharf. Accrding to arch' s stree characteristics, a new typeof wharf with catenary arched longitudinal beams is presented in this paper. The new wharf structure can make full use ofarch' S overhead crossing and reinforced concrete compression resistance, improve the interval between transverse bentsgreally, and decrease underwater construction quantity. Thus, the construction cost cab be reduced. Take the third phaseproject of the Yangshan Deep water Port for example, comparative analysis on catenary arched longitudinal beams andconventional longitudinal beams has been made. The result shows that with the same wharf length and width, the sameloads and same longitudinal beam moment, catenary arch structure can improve the interval between bents up to 28 m,decrease the number of piles and underwater construction quantity.Key words: wharf; structural lype; catenary arch; inermal force; cost1. IntroductionIn recent years, a trend of large tonnage vessels is increasing in port engineering. The interna-tional routes are now sailing the fifth and sixth generation container ships and over 300, 000 tons forbulk vessels and oil tankers(Leifer and Wilson, 2007). In China, at present, the number of berthswhich can handle vessels over 50,000 tons is about 260, but in fact, most of them can not meet therequirements of large-tonnage vessels, and construction of deep water wharves is in urgent need(Zhang, 2006). The deep-water wharf works under adverse conditions and is hard to be constructed,so design of deep water wharf is an important research topic in port engineering(Zhai and Lu, 2006).The high-pile and beam-slab quay is mainly applied to river port and sea port with kinds of com-plicated loads. It consists of slabs, longitudinal beams, transversal beams, pile caps, piles andberthing members. The superstructure of beam-slab quay is usually prefabricated; components such aslongitudinal beams and slabs are fabricated by prestressed reinforced concrete. The prestressing methodimproves the cracking and bending resistance capacity, increases the strength of structural members,and reduces the quantity of steel bar. The increase of interval between transverse bents leads to the fulluse of pile bearing capacity and reduces usage of materials, and the construction speed is accelerated.中国煤化工券This study was financially supported by the National Natural Sci.MYHC N M H GNo. 40776053)1 Corresponding author. E mail: zxq431 @ hhu. edu. cn706ZHA Qiu a al./ China Oean Enginering, 22(4), 2008, 705-711As a result of its structural rationality, high- pile and beam-slab quay was rapidly developed and matureenough to be one of the most important structural types of wharves in China coastal areas in the early1970s.In 1980s, with the continuously rapid development of wharf grade and progress of constructiontechnique, size of piles increased as well as bearing capacity . After the successful development of largediameter prestressed concrete tubular pile and steel pipe pile in China，single pile capacity hadreached more than 10000 kN, and it created conditions in construction of large wharf in deep water. Inorder to make full use of pile bearing capacity, interval between transversal bents should be improved.It is proved that design of larger span and fewer piles can reduce the cost of the project. However,stress of conventional longitudinal beams will be increased largely if the span is over certainn range(about 10~ 12 m). The usage of materials and project cost will correspondingly increase.In deep-water open sea, wharf piles have to be large enough to satisfy the stability requirementsdue to the complicated processes of hydrodynamics such as waves, curents and their interactions (Yanet al., 2000; Zheng et al., 2002, 2008; Zheng, 2007). Interval between transversal bents of 10 mcannot make full use of pile bearing capacity. Increasing the interval between transversal bents willlead to more fabrication cost of superstructure. Wharf with catenary arched longitudinal beams present-ed in this paper is expected to have some theoretical and practical significance in optimization design ofhigh-pile wharf.2. Catenary Arched Longitudinal Beam StructureIn consideration of the arch' s good overhead crossing and reinforced concrete compression resis-tance and in reference of spandrel-braced arch bridge, a new type of wharf with catenary arched longi-tudinal beams (Fig. 1) is put forward in this paper. The catenary arched longitudinal beans of prefab-ricated reinforced concrete consist of arch beams, top chords, web members, and tie-rod. The longitu-dinal beam is laid on the pile cap. The prefabricated crosswise horizontal braces which are laid on lon-gitudinal beam' s brackets are set among longitudinal beams. They fom beam gillages with longitudi-nal beams. The laminated slabs are laid on crosswise horizontal braces. Rectanglar transversal beamsare cast-in-situ and they are contour aranged with longitudinal beans. The longitudinal beams,transversal beams and laminated slabs are integrally jointed, and the longitudinal beams are also inte-gally jointed with piles, forming the superstructure of good integrity and nigidity. Tie-rod is set at thebottom of arch beam to bear arch' s thrust force.3. Superstructure of the Arched Longitudinal Beam Structure3.1 Selection of Rise -Span Ratio中国煤化工Rise-span ratio (Kim, 2003)depends on concreteMHCNMHGrust force, etc. .The increase of rise -span ratio will lead to more concrete btio will lead to the increase of mid- span moment and arch thrust force. In comprehensive considerationZHAI Qiu e al./China Oean Enginering .22(4), 2008, 705- 711707of the above factors, rise span ratio of catenary arched longitudinal beams may be best chosen from1/12 to 1/6.top chordcrosswise horizontal brace]web mambcarch beamdbrackethangor rodtie-rod_TTTTTtranaversal beamslabcrane beamFig. 1. Skelech map of wharf with catenary arched longiudinal beams.3.2 Selection of Arch AxisAccording to the load conditions in the third phase project of the Yangshan Deep-water Port, acomparison was made with the structural mechanic method. A catenary is used as rational arch axis oflongtudinal beams to derive the arch axis equation(Gu and Shi, 1996)y=_L(chKζ-1),(1)where, f is arch height; m is arch axis cofficient; K is a parameter related to m, K= ln(m +V m2-1); ζ is abciss paraneter, ζ =2x/L; chKζ is hyperbolice cosine, chKζ=(e%5+ e~ k5);L is height of arch.The ordinate of arch axis should be decided on arch axis cofficient m if rise-span ratio is con-fimned.4. Analysis on the ProjectThe Yangshan Deep-water Port(Li et al., 2006) is located on Shengsi Islands outside theHangzhou Bay and the Yangtze Estuary. It consists of several dozen islands such as the Big YangshanIslands and the Small Yangshan Islands. The northwest is 27. 5 km gwav fmm the Inchao Harbour ofShanghai, the south is 90 km away from the Beilun Harbc:YH中国煤化工the east is 104km away from the intemational shipping route. It is the rc N M H Gound Shanghai.The basin bottom of the Yangshan Deep water Port is stable and sediments are not easily to silt up,708ZHAI Qiu e al./China Oean Enginering, 22(4), 2008, 705- 711with a natural water depth over 15 m. It is suitable for building a large deep water wharf. The port hasdeep- water shorelines of about 13 km with excellent natural refuge conditions and 315 operating daysper year on the average.The third phase project of the Yangshan Deep water Port (Zhu, 2005) lies in the east of the har-bour district between the Huogaitang Island and the Xiaoyanjiao Island. There are seven deep waterberths for container ships of 70 ~ 150 thousand DWT. The desigon container ship is 150 thousand tonswith the mooring wind speed of 22.6 m/s, the design flow speed of 1.80 m/s, the maximum mooringforce of 2000 kN and impact force of 2574 kN. The design annual throughput is 5 million TEU. Thecoastal line is 2600 m, high water level is4.51 m, low water level is 0.53 m, the top of the pierheight is 8.10 m, and the design water depth in front of wharf is 18.0 m. There are 25 shore containercranes with track gauge of 35 m, lifting capacity of 65 tons and out-reach of 67 m.4.1 Load ConditionIn the third phase project of the Yangshan Deep water Port, the main design loads include struc-ture weight, cargo load (30 kPa) and container cranes loads.The basic parameters of container cranes loads are as follows: track gauge of 35 m, base length of14 m, 10 wheels per leg, spread of wheel 1 . 20 m, the minimum distance among centers when twocranes are working is 27 m. When the cranes work, the maximum sea-side wheel-load is 1070 kN perwheel, and the maximum land-side wheel-load is 940 kN per wheel.The top of the pier height is designed in the condition that superstructure cannot aford waveforce, thus, wave loads are not considered in the arched longitudinal beam structure except three typesof loads above.4.2 Sectional Structure of the Whar{In the original design, high-pile and beam-sab quay is used. The width of the wharf is 42.5 m;the interval between transversal bents is 12 m. Steel pipe piles with diameter of 1.5 m are used aspiles. Each transversal bent has 10 steel pipe piles and four pile cap joints; three steel pipe piles areset under pile cap of every crane beam, and two steel pipe piles are set under the pile caps of otherbeams. In the superstructure, transversal beams, crane beams, longitudinal beams and laminated slabsare precast with prestressed concrete. Longitudinal and transversal beams are contour arranged andtransversal beans next to pile caps are cast-in-situ.In the new type of wharf, the interval between bents is 28 m, calenary arch height is3.5 m,rise-span ratio is 1/8, and arch axis ceofficient m is 2. 566. The steel pipe piles with diameter 1.5 mare used as piles. Each transversal bent has 12 steel pipe piles and five pile cap joints; three steelpipe piles are set under pile cap of every crane beam, and two steel pipe piles are set under the pilecaps of other beams. In the superstructure, concrete trans:中国煤化宝，the catetaryarched longitudinal beam of reinforced concrete and lamina; transversalbeam section is5.0 mx 1.0m, top chord 1.5 mx0.8 m,YHCNMHGcrosswise hor-izontal brace 0.6 mx0.8 m, and web member 0.6 mx0.8 m. The interval of two arch beams isZHAI Qiu a al./ China Obean Enginering, 22(4), 2008, 705-7117098.75 m; the crosswise horizontal braces are set between arch beams, with the interval of3.5 m; theprefabricated slab is 4 m in length, 3.2 m in width, 0.4 m in thickness with the wearing carpet being0.05 m.I-bar is used as te-rod in the bottom of arch beam. Its elastic modulus E =2.1 x 10 N/mm? ,height h = 400 mm, flange widh b = 146 mn, web plate thickness tw = 14.5 mm, cross- section areaA= 10200 mm'. Since the tie-rod is too long, the hanger rods are set to decrease tie -rod deflection.Thus, the tie rod and the arch longitudinal beam form an integral structure. The hol-olled seamlesssteel tubes are used as hanger rods. The outer diameter of the pipe d= 146 mm, thickness t= 10mmn, and cross- section area A = 4273 mm2.4.3 Internal Force AnalysisTake a bent for example, when analyzing the intermal force, the section of transversal beams andtheir loads change very lttle, therefore, only analysis on longitudinal beam and its loads is done. Asto the load- combination, it considers the bearing capacity endurance state under limit condition.When loads are applied on catenary arched longitudinal beam, monent (M) variation of catenaryarched longitudinal beam (Fig. 2) is obtained with structural mechanical theory and finite elementmethod (Bijaya et al., 2007; Ju, 2003). It shows that the positive moment of longitudinal beam in-creases obviously from arch springing to mid-span, and the maximum moment 16500 kN.m is at mid-span. In the third phase project of the Yangshan Deep water Port under the original design loads, trackbeams are calculated according to simply supported beam in the construction period and elastically sup-ported continuous beam in the service period, and the maximum moment at mid-span is 20747 kN'm.It is concluded that when the interval between bents increases to 28 m, the maximum moment of archedlongitudinal beam is still smaller than that of the original design longitudinal beam. This new type ofwharf makes full use of arch compression resistance and overthead crossing.Table 1Comparison between the two structures on their main paranetersStnuctural type of wharfHigh-pile and banm-slabParametersstnucture (the third phaseArched longitudinalproject of the Yangshanbeam structureDeep-water Port)Type of longitudinal beamsInverted-T typeCatenary archInterval between transverse bents12 m28m.Number of piles in one tnansversal bent1517Maximum moment at mid-span20747 kN.m16500 kN.m中国煤化工~TYHCNMHG710ZHAI Qiu a al./China Ooun Enginering, 22(4), 2008, 705- 711景最点Fig. 2. Moment diagyam of catenary arched longitudinal beam ( kN.m) .5. ConclusionsThe underwater construction of open sea deep water wharf is dificult and definitely needs highcost. Without increasing the section size and steel bars of longitudinal beams , catenary arched longitu-dinal beam can grealy enlarge the interval between bents, which leads to the decrease of piles and un-derwater construction work. Constructional members are prefabricated and floated to working site so thatthe construction speed is accelerated and fabrication cost can be reduced. Actually, high-piled wharfproject costs great deal，however, wharf with catenary arched longitudinal beams needs fewer piles andthus reduces the manufacture cost largely .Wharf with catenary arched longitudinal beams has good stress states and lange interval betweentransverse bents ; the superstructure has large space stiffness and needs a small number of constructioncomponents; catenary arch is prefabricated with reinforced concrete and convenient to set mould andcast concrete. Large space under catenary arch and the good ventilation can improve the durability ofconstructional members. Generally speaking, wharf with catenary arched longitudinal beams is a newtype of good mechanical property and economic benefit. It will adapt to the request of large span newharbor constructions in the future.ReferencesBjaya, J., Kim, H. J, Kim, M. 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