Ports | NIRAS Fraenkel
combining placing the filling and revetted slope with piles projecting through the revetment. These have to be installed before the fill and rocks, but are then vulnerable to damage and displacement as the revetment is built around them. Expensive plant for piling and revetment work often have to be on site at the same time when they cannot be used as efficiently as if they were working on their own. This had significant cost effects on all traditional construction options examined. At this point the consulting engineers held informal discussions with a number of experienced marine civil engineering contractors and it became clear from these that substantial cost savings could be made if the operations of revetment construction and piling could be completely separated. It was decided to prepare a
preliminary design with such a separation which would require a clear spanning deck running from a front line of piles to a support at the revetment crest, a distance over 21m. The only realistic way this could be achieved would be to use steel girders as the main structural components, acting compositely with concrete deck elements, a form of construction often used in bridges, but rarely if ever in marine structures. A scheme based on this concept was put out to tender and a construction contract was awarded which was within the client’s budget. The consultants now developed a fully detailed design of the quay. This design utilised steel box girders supporting precast prestressed concrete bridge beams with in-situ concrete infill and topping, the whole system acting compositely for live loading on the deck. The piles which support the front of the deck are socketed 10m into granite rock with a grouted annulus between pile and rock 75mm thick. These are steel tubular piles 1420mm in diameter and of 19mm wall thickness. Rocker bearings are provided between the piles and the steel box girders. A continuous bank seat abutment is located at the rear of the deck at the crest of the revetment slope where the ends of the box girders are supported on sliding guided elastomeric bridge bearings with metal components in stainless steel.
CASE STUDY
The design of the new quay at Peterhead represents an advancement in harbour engineering which has application for future developments in many other ports. The design utilises principles which have been commonly used in bridge engineering, but which have hitherto not been applied to harbour structures. The quay deck system is in itself structurally efficient and the separation of revetment works from pile installation has considerable construction benefits. Each part of the structure works efficiently in itself and the parts come together to provide a particularly elegant design solution. The project was constructed on time and on budget which speaks for itself when compared with many projects elsewhere. Perhaps because of the simplicity and appropriateness of the design there was an unusual degree of cooperation between employer, contractor and engineer throughout the period of the works.
Had it not been for the development of a new concept in quay construction by the engineering consultants, the facility would not have been built and the port would have lost business and suffered reduced employment opportunities for some time to come. As it has turned out the new quay has been a great commercial success and has greatly benefited the port and local community.
The bearing arrangement caters for any settlement at the bank seat and consequent rotation of the box girders at the rockers. There is a deep downstand beam along the front of the quay deck on which cone fenders are mounted and the downstand beam is designed for local impact forces of 500t from vessels striking the quay face between fenders. In this way a quasi-solid quay face is obtained. All fender and impact forces are transmitted across the deck acting as a continuous plate structure to the guided bearings and on to a friction slab on filling behind the abutment. The quay deck is designed generally for 3t per sq.m uniformly distributed loading, normal UK highway bridge loading and for a variety of crane loads specified by the client. For these conditions it was found that the optimum spacing of the steel box girders was around 10.5m. The quay deck
184 GLOBAL OPPORTUNITY 2014 | ISSUE 01
at the western end is designated a heavy lift area where extremely high local loads may be generated in decommissioning of North Sea oil and gas installations. Here the deck is designed to carry 5t per sq.m uniform loading and in addition, the forces from a crane lifting a module weighting 500t at a radius of 20m. This can produce local loading over piles of around 1100t and in the heavy lift area the box girder spacing is reduced to 7m. The marine works involving
dredging and construction of the breakwater extension were undertaken first in the spring and summer of 2009. In this way protection was provided for the reclamation works over the following winter. During this period suitable material from dredging and imported filling was placed in the reclamation area which was brought up generally to above water level allowing plant to operate on the reclamation without restrictions. The separate operations of revetment construction and pile installation were then carried out over the winter of 2009/2010 and on completion of piling and the bank seat abutment the quay deck and adjacent dolphin were constructed. The works were substantially completed on budget on the contractual completion date of 30 September 2010. The requirement to use open forms of quay construction in enclosed harbours is not uncommon as reflection of residual wave activity from solid quay faces can affect conditions at other berths within the harbour and result in operational downtime at those berths. Peterhead harbour is particularly vulnerable to this sort of disruption with its wide entrance and with a number of existing solid quay structures, but it is by no means unique in this respect. While the form of construction adopted was particularly appropriate at Peterhead, there will be other ports elsewhere which require new quays to be built in similar situations and where the benefits of this novel form of construction could offer significant cost savings to the promoters.
GO
FURTHER INFORMATION
www.nirasfraenkel.com
global-opportunity.co.uk
PORTS
|
NIRAS FRAENKEL
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140 |
Page 141 |
Page 142 |
Page 143 |
Page 144 |
Page 145 |
Page 146 |
Page 147 |
Page 148 |
Page 149 |
Page 150 |
Page 151 |
Page 152 |
Page 153 |
Page 154 |
Page 155 |
Page 156 |
Page 157 |
Page 158 |
Page 159 |
Page 160 |
Page 161 |
Page 162 |
Page 163 |
Page 164 |
Page 165 |
Page 166 |
Page 167 |
Page 168 |
Page 169 |
Page 170 |
Page 171 |
Page 172 |
Page 173 |
Page 174 |
Page 175 |
Page 176 |
Page 177 |
Page 178 |
Page 179 |
Page 180 |
Page 181 |
Page 182 |
Page 183 |
Page 184 |
Page 185 |
Page 186 |
Page 187 |
Page 188 |
Page 189 |
Page 190 |
Page 191 |
Page 192 |
Page 193 |
Page 194 |
Page 195 |
Page 196 |
Page 197 |
Page 198 |
Page 199 |
Page 200