A Slipway Structure for River Ship Repair

1 Paper N 0 : III.05 A Slipway Structure for River Ship Repair Zorislav Sorić, Radovan Vugrinec Predrag Kvasnička, Tomislav Kišiček Josip Galić, Leo Matešić Abstract: A slipway structure for ship repair discussed in this paper has been designed and constructed on the River Sava near the town of Sisak in Croatia. The structure consists of reinforced concrete bored piles and girders. In the river, girders are supported by a trapezoidal concrete block of 16x2 m placed in the river bed. From this block up, girders of 2x2 m in cross-section are inclined from the river to a certain bank height after which they are horizontal. For the predicted loads foundation soil was too weak, and for this reason each girder rests on 9 piles from 3 to 12 m in length and 1.0 m in diameter. The joint between the girder and piles is rigid, and thus they make a frame element. There are 11 girders, whose inclined and horizontal parts have a length of 41 m and 26 m respectively. The whole structure covers an area of 82x86 m. Ships are to be supported by trolleys travelling on an inclined rail system. The structure extends underwater for a sufficient distance to enable the ships to float on and off. The movement of trolleys together with a ship is controlled by hauling winches that are situated at the upper end of the slipway. Keywords: slipway, ship repair, foundation, piles, concrete girders, reinforcement 1. Introduction There are over 300 river ships in the Croatian merchant fleet of inland waterway navigation. The average age of these ships is more than 25 years. By law, they are supervised by the Croatian Register of Shipping (the Register). According to the Rules for Technical Supervision of Inland Waterway Navigation Ships laid down by the Register, a river ship must be pulled up on shore once every five years. In addition to compulsory ship pull-ups for inspection and checks, ships are also pulled up for repair of damage, suffered in service,

248 Sorić, Vugrinec, Kvasnička, Kišiček, Galić, Matešić which cannot be repaid in the water. It should be noted that the slipway discussed in this paper is the first to be designed and constructed in Croatia. At present, only a small number of ships in the Croatian merchant fleet of inland navigation supervised by the Register are regularly repaired in the Slovenske Lodenice Shipyard in Komarno (Slovakia). Of all the other ships in the fleet, since 1990, only a few of them were pulled up onto dry land in Croatia, either on improvised slipways or by using the changes in the water level. For the reasons mentioned above, there is a need for the construction of two or three slipway structures on the Croatian inland waterways that will be economically justifiable. There are three suitable locations for their construction: 1) two on the River Sava in the area of the towns of Sisak and Slavonski Brod, and 2) one on the River Drava or on the Danube in the area of the city of Osijek and the town of Vukovar respectively. A study showed that the slipway structure on the River Sava at Sisak can attract at least 50 vessels. This number of ships can justify the construction of the slipway and provide employment for 70 workers. The Sisak slipway was constructed as a 13 0 inclined slipways with the horizontal top part (Figure 1). It can hold inland navigation ships of up to 400 tonnes deadweight and 80 metres in length. On this structure ships will be pulled up from the river and lowered into the water sideways using double trolleys on rails, the one for a sloping part of the structure and the other for a horizontal part. The trolleys are pulled up and down by means of special motor driven devices, hauling winches, and ropes. The inclined part of the slipway structure is expended at its top by the horizontal part of the structure extending towards inland. The horizontal part is also provided with supports and pulling system for sideways ship pulling. The slipway can accommodate three ships on the inclined part and two on the horizontal part at the same time. The structure design enables the pulling of ships from the river even at a low river level and holds ships high and dry even when the river level is high. The shipyard site has a shape of a right-angled triangle with the hypotenuse on the river bank. The part of the bank occupied by the shipyard is about 320 m long. The highest water level recorded at the Galdovo measuring station (located near the slipway structure) was 99.7 m above see level and the low water was at the level of 90.5 m with 95% of probability. An analysis of water levels measured over the period of last 10 years showed an average at 89.8 m. The maximum water level was at 99.0 m while the level of the river bottom at the site of the slipway structure is at 88.0 m and that in the waterway is at 85.5 m a.s.l. The elevation of the yard is approximately 100.0 m. 2. Foundation of the structure Geotechnical investigation showed that the foundation soil consisted of four horizontal layers: clay, silty sand, gravel and silty clay. The depths of the layers and their descriptions are given in Table 1:

A Slipway Structure for River Ship Repair 249 Table 1 Data on foundation soil Layer from [m] to [m] Type of material Description 1 0.0 2.5 Clay high plasticity, firm consistency 2 2.5 9.5 silty sand loose 3 9.5 12.5 Gravel dense, poorly graded 4 12.5 >15 silty clay high plasticity, firm consistency For the predicted loads the foundation soil was too weak and for this reason each girder rests on a set of nine piles. An analysis of foundation indicated that bored piles perform better when supported by the third layer (i.e. gravel) than when supported in deeper fourth layer (i.e. silty clay). Joints between the girders and piles are rigid, and thus they make a frame element. Figure 1 shows concreting of piles. Figure 1 Concreting of piles

250 Sorić, Vugrinec, Kvasnička, Kišiček, Galić, Matešić 3. Description of the slipway structure The slipway structure has shape of a rectangle having the length of 72 m and the width of 70 m. It consists of a horizontal part of 30 m in length at the elevation of 99.3 m and a sloping part inclined at 13 0 of about 53 m width. The lowest height of the latter part is 87.0 m above see level. Basic structural parts of the slipway are eleven reinforced concrete girders spaced 9.0 and 5.0 metres apart. The rails for trolleys/bogies are installed on the girders. The crosssection and the plan view of the slipway, together with pulled up ships are shown in Figure 2. Figure 2 The cross-section and the plan view of the slipway structure

A Slipway Structure for River Ship Repair 251 The foundation strips, that are underwater, have a width of 1.0 m. They are located at the elevations of 85.0 m and 86.25 m. The strips are constructed of reinforced concrete of concrete strength of 30 MPa, a concrete cover of 7 cm, and reinforcing steel of yield strength of 400 MPa. The other parts of the slipway structures consist of eleven girders supported by bored concrete piles. Piles have 100 cm in diameter and are made of reinforced concrete of 30 MPa concrete strength and reinforcing steel of 400 MPa yield strength. Eight piles are spaced 7.7 metres apart and the ninth is 6.2 metres apart. They are bored down to the depths from 4.85 to 10.85 m. The total number of piles installed is 99. The inclined part of the structure under construction is shown in Figure 3. Figure 3 Inclined part of the slipway structure under construction The horizontal girders are shown in Figure 4. The reinforced concrete girders of the slipway structure have a T-shape cross-section. The width of the girders at the bottom is 170 cm and at the top 210 cm so that rails for the trolleys can be installed. Figure 4 One horizontal girder completed and the other under construction

252 Sorić, Vugrinec, Kvasnička, Kišiček, Galić, Matešić The shapes of the girder cross-sections are shown in Figures 5 and 6. Figure 5 Detail A from Figure 2 and cross-sections of girders The reinforced concrete girders were constructed of concrete having compressive strength of 30 MPa and of steel reinforcement with yield strength of 500 MPa. At expansion joints, elastomer bearings of 100x250x52 mm and 625 kn bearing capacity were placed. These

A Slipway Structure for River Ship Repair 253 elastomer bearings allow horizontal movements of the structure caused by different reasons such as temperature effects, loading forces, settlement etc. Between the girders, transverse beams of 40 by 40 cm cross-section, perpendicular to the girders, were constructed. These transverse reinforced concrete beams with compression strength of 30 MPa and with steel reinforcement having yield strength of 400 MPa are placed in five lines (see Fig. 2). Figure 6 Cross-section 2-2 with reinforcement of girders shown in Figure 5 A working platform is at the height of 98.8 m above see level. The foundations for hauling winches are installed 4.20 m from the end of the horizontal part of the structure. There are ten winch foundations of 3.0x3.4x2.0 m. In the space between them and the slipway girders, concrete channels of 26 cm in depth and 120 cm in width were placed for hauling winch ropes to be used for ship pulling up from the water. After compaction of the subgrade to the modulus of 50 MPa, reinforced concrete slabs between all girders were constructed. A 2.4 by 5.0 by 2.0 m foundation block was constructed for a drive-motor for all ten hauling winches. The constructed slipway structure with trolleys is shown in Figure 7. Figure 7 The constructed slipway structure with trolleys

254 Sorić, Vugrinec, Kvasnička, Kišiček, Galić, Matešić 4. Conclusions The slipway structure designed for repair of inland water navigation ships was an interesting challenge both for designers and for constructors. Such a structure was needed for a long time, and this is the first slipway to be built in Croatia. It is planned to construct two additional similar structures on Croatian rivers in the near future. The entire slipway structure together with foundations, piles, girders and slabs contains 3606 m 3 of concrete and 2508 tonnes of steel reinforcement. References Miljković, B. (2002), Geotechnical report, E-048-02, Geokon-Zagreb d.o.o. Vugrinec, R., Miljković, B. & Matešić, L. (2002) Main and working design, E-062-02, Geokon-Zagreb d.o.o. Authors Professor, Ph. D. Sc., Dipl. Ing. C.E., Zorislav Sorić: Faculty of Civil Engineering, University of Zagreb, Kaciceva 26, Croatia. E-mail, soric@grad.hr Dipl. Ing. C.E., Radovan Vugrinec "Geokon-Zagreb", Starotrnjanska 16a, Zagreb, Croatia. E-mail, r.vuginec@geokonzg.com Professor, Ph. D. Sc., Dipl. Ing. C.E., Predrag Kvasnička: University of Zagreb, Faculty of Mining, Geology and Petroleum Engineering, Zagreb, Croatia E-mail, pkvasnic@rgn.hr Assistant, M. Sc., Dipl. Ing. C.E., Tomislav Kišiček: Faculty of Civil Engineering, University of Zagreb, Kaciceva 26, Croatia. E-mail, kisha@grad.hr Assistant, Dipl. Ing. C.E., Josip Galić: Faculty of Civil Engineering, University of Zagreb, Kaciceva 26, Croatia. E- mail, jgalic@grad.hr Assistant Professor Ph. D. Sc., Dipl. Ing. C.E., Leo Matešić: "Geokon-Zagreb", Starotrnjanska 16a, Zagreb & University of Rijeka, Faculty of Civil Engineering, Rijeka, Croatia. E-mail, l.matesic@geokonzg.com