Showing papers on "Caisson published in 2006"

A comparison of field and laboratory tests of caisson foundations in sand and clay

Abstract: Laboratory tests applying vertical and moment loads to suction caissons founded in sand and clay have been conducted to simulate an equivalent series of field tests. The caissons used in the laboratory were 0·15 m, 0·2 m and 0·3 m in diameter, whereas those for the field tests were 1·5 m and 3·0 m in diameter. The loads applied to the caissons in the laboratory tests were scaled from those in the field tests, and the models were loaded in a near-identical manner to the field trials. The test results are presented in non-dimensional form for comparison. The non-dimensional laboratory data from moment loading tests were similar to the field data in most cases. However, the non-dimensional data from vertically loaded caisson tests in the laboratory and in the field show more significant differences, and possible reasons for these are discussed.

Model testing of foundations for offshore wind turbines

Abstract: Suction caissons are a new foundation option for offshore wind turbines. This thesis is focussed on the behaviour of suction caisson foundations in sand and in clay during installation, and under subsequent vertical and combined moment-lateral loadings. The research is based on extensive experimental work carried out using model scaled caissons. The analysis of the results allowed the determination of parameters for hyperplasticity models. Model caissons were vertically loaded in loose and dense sands to study in service states and plastic behaviour. Bearing capacity increased with the length of the caisson skirt. The bearing capacity formulation showed that the angle of friction mobilised was close to the critical state value for loose sands and close to those of peak values due to dilation for dense sands. The vertical load increased, though at a lower rate than during initial penetration, after large plastic displacements occurred. A hardening law formulation including this observed behaviour is suggested. In sand the installation of caissons by suction showed a drastic reduction in the net vertical load required to penetrate the caisson into the ground compared with that required to install caissons by pushing. This occurred due to the hydraulic gradients created by the suction. The theoretical formulations of the yield surface and flow rule were calibrated from the results of moment loading tests under low constant vertical loads. The fact that caissons exhibit moment capacity under tension loads was considered in the yield surface formulation. Results from symmetric and non symmetric cyclic moment loading tests showed that Masing’s rules were obeyed. Fully drained conditions, partially drained and undrained conditions were studied. Caisson rotation velocities scaled in the laboratory to represent those in the field induced undrained response for relevant periods of wave loading, a wide range of seabed permeabilities and prototype caisson dimensions. Under undrained conditions and low constant vertical loads the moment capacity of suction caissons was very small. Under partially drained conditions the moment capacity decreased with the increase of excess pore pressure. In clay, vertical cyclic loading around a mean vertical load of zero showed that in the short term the negative excess pore pressures generated during suction installation reduced vertical displacements. The yield surface and the flow rule were determined from moment swipe and constant vertical load tests. The moment capacity was found to depend on the ratio between the preload Vo and the ultimate bearing capacity Vu. Gapping response was observed during cyclic moment loading tests, but starting at smaller normalised rotations than in the field. The hysteresis loop shape obtained during gapping cannot be reproduced by means of the Masing’s rules.

Real-Time Seismic Monitoring of the New Cape Girardeau Bridge and Preliminary Analyses of Recorded Data: An Overview

Abstract: This paper introduces the state-of-the-art seismic monitoring system implemented for the 1,206-m-long (3,956 ft) cable-stayed Bill Emerson Memorial Bridge in Cape Girardeau (Missouri), a new Mississippi River crossing, approximately 80 km from the epicentral region of the 1811 and 1812 New Madrid earthquakes. The real-time seismic monitoring system for the bridge includes a broadband network consisting of superstructure and free-field arrays and comprises a total of 84 channels of accelerometers deployed on the superstructure (towers and deck), pier foundations (caisson tops and bents), and in the vicinity of the bridge (e.g., free-field, both surface and downhole). The paper also introduces the high-quality response data obtained from the broadband network that otherwise would not have been possible with older instruments. Such data is aimed to be used by the owner, researchers, and engineers to (1) assess the performance of the bridge, (2) check design parameters, including the comparison of dy...

Large-Scale Experiments on Pore Pressure Generation underneath a Caisson Breakwater

Abstract: Results of large-scale model experiments in a wave flume are discussed. These experiments are concerned with the study of the generation of transient or instantaneous and residual pore pressure in a seabed beneath a caisson breakwater subjected to both pulsating and breaking wave loads. The simulated seabed and drainage conditions correspond to those encountered in a loose sand bed with thin clay or silt layers. Even under such unfavorable conditions total liquefaction due to residual pore pressures could not occur during the experiments. It is shown that the residual pore pressure is essentially generated by the caisson motions due to breaking wave loads and that they are closely related to residual soil deformations, which may lead to the failure of the breakwater.

Transient vertical loading of model suction caissons in a pressure chamber

Abstract: Vertical monotonic and cyclic loading tests on model suction caissons have been carried out to explore conditions relevant to the design of multiple-footing foundations for offshore wind turbines. The tests were conducted in a pressurised chamber, which simulates up to 20 m of water depth, to investigate the effect of cavitation on the ultimate tensile response of the caisson. Cyclic loading tests were also conducted at elevated pressures. Data from cyclic tests are presented to compare the response of caissons subjected to varying ambient pressures and rates of loading. The ambient pressure had little effect on the cyclic response. Faster rates of loading generated larger pressures beneath the lid of the caisson and increased the load-displacement stiffness. The ultimate tensile capacity was significantly affected by the ambient pressure and rate of loading. Implications for the design of offshore caisson foundations are discussed.

Large deformation analysis of suction caisson installation in clay

Abstract: Large deformation finite element (LDFE) analyses were performed to study the installation of caissons by suction and jacking in normally consolidated clay. The penetration of the caisson wall was m...

Modal Testing of Tamar Suspension Bridge

Abstract: The original bridge opened in 1961, was designed by Mott Hay and Anderson as a conventional suspension bridge with symmetrical geometry, having a main span of 335m and side spans of 114m, and with anchorage and approach spans the overall length is 642m. Unusually for a suspension bridge of this era, the towers were constructed from reinforced concrete, and have a height of 73m with the deck suspended at half this height. The towers sit on caisson foundations founded on rock. Main suspension cables are 350mm in diameter and each consists of 31 locked coil wire ropes, and carries vertical locked coil hangers at 9.1m intervals. The stiffening truss is 5.5 metres deep and composed of welded hollow boxes.

Method for providing a dry environment for underwater repair of the reactor bottom head using a segmented caisson

Abstract: Welding repairs are performed in an underwater environment adjacent the bottom head of the nuclear reactor vessel. To provide a dry welding environment, segments of a lower caisson are passed through the core plate holes and assembled along the interior surface of the bottom head. The assembled segments are held down by brackets and sealed to one another and to the bottom head by a water curable polymer. An upper caisson is passed through the core plate hole to sealingly engage the lower caisson. The caissons are pumped dry and welding equipment is passed through the caissons to effect weld repairs about the stub tube or along the bottom head cladding.

Collision protecting guard for a pier construction at the sea

Abstract: A collision prevention system for protecting a marine structure is provided to prevent collision of a ship according to water level by restricting the ship from being directly bumped into the marine structure and moving the ship far from the marine structure A collision prevention system for protecting a marine structure includes a post(10) spaced from a pier; plural cylindrical lift guide units(20) fixed around the post and provided with lift guide holes(21); a lift container(30) having plural lift rollers(31) lifted up and down and combined with the lift guide hole, and a revolution guide hole(32) moved up and down in the lift guide unit through the lift roller; a float installed in the lift container, filled with air or water to lift the lift container up and down on the sea according to the water level; a cylindrical revolution container having a cylindrical main wall(51), flanges(52,53) formed in upper and lower ends of the main wall and plural revolution rollers(54) formed in the inner periphery of the main wall in the circumferential direction and combined with the revolution guide hole by sliding and revolving around the lift container; and a cylindrical buffer roller(60) rotated by a rotation guide shaft(61) and installed between the upper and lower flanges of the revolution container The post comprises a cylindrical steel caisson(11), a cap(12) sealing an upper opening part of the caisson and a filler(13) cured in the caisson, and fixed to the seabed with plural anchors, wherein the anchor is inserted to the caisson, and fixed by charging the filler

Pile foundation construction method using temporary cofferdam caisson of improved for weakness ground

Abstract: A pile foundation construction method using a temporary caisson in an improved soft ground is provided to install a submergible structure safely by increasing bearing force of the soft ground, and to cut down construction cost by reducing the construction period. A sand compact pile is constructed in a hole formed in a soft ground(a) by a ground improvement machine, and an improved ground(6) is constructed by a mixture solid pile. The ground is improved around a temporary caisson(10) to install a support bar(13) attached to the temporary caisson. The soft ground is excavated by an excavator, and installed by tare. The support bar attached to the temporary caisson is installed stably in the improved ground by driving a blade edge(10a) of the temporary caisson in an excavation removal ground layer. A worktable is installed in an upper part of the temporary caisson, and a pile foundation(16) is constructed in a support layer(d) by a pile driving apparatus. The sand compact pile is constructed by excavating a bore, supplying sand, putting sand in the bore by a hollow rod, turning and lifting the hollow rod with a rotating unit, feeding sand from a sand injector to the hollow rod and compacting sand from the hollow rod.

Engine mounting structure for jet engine of aircraft, has rigid structure, whose back structure projects caisson toward back, and carries back wing attachment to retrieve exerting forces along vertical direction of mounting structure

Abstract: The mounting structure (4) has a rigid structure with a front longitudinal central caisson (22), and an anchoring unit for anchoring the structure (4) on a wing. The unit has a connection hinge (54) fixed to the caisson, and a back wing attachment located relative to lateral attachments. The structure has a back structure (21) with a transversal width reduced relative to that of the caisson, and projects the caisson towards the back. The back structure carries the back wing attachment to strictly retrieve exerting forces along a vertical direction of the mounting structure.

Prototype bucket foundation for wind turbines: natural frequency estimation

Abstract: The first full scale prototype bucket foundation for wind turbines has been installed in October 2002 at Aalborg University offshore test facility in Frederikshavn, Denmark. The suction caisson and the wind turbine have been equipped with an online monitoring system, consisting of 15 accelerometers and a real-time data-acquisition system. The report concerns the in service performance of the wind turbine, with focus on estimation of the natural frequencies of the structure/foundation. The natural frequencies are initially estimated by means of experimental Output-only Modal analysis. The experimental estimates are then compared with numerical simulations of the suction caisson foundation and the wind turbine. The numerical model consists of a finite element section for the wind turbine tower and nacelle. The soil-structure interaction of the soil-foundation section is modelled by lumped-parameter models capable of simulating dynamic frequency dependent behaviour of the structure-foundation system. (au)

Method for binding concrete caisson for open-shield method

Abstract: PROBLEM TO BE SOLVED: To provide a method for binding concrete caissons for an open-shield method, which can reduce the number of the caissons to be removed, which can simplify a structure, which imparts a specified tension so that a column of the concrete caissons can be fixed, and which enables the concrete caisson to be surely anchored in a prescribed position. SOLUTION: In this method for binding the concrete caissons 4 for use in the open-shield method, a binding bolt 14 is screwed into an insert 12 which is pre-embedded in the joint end of the concrete caisson 4; a leading end of the bolt 14 is protruded forward from the joint end; a protruding end of the bolt 14 is inserted into the next concrete caisson 4 which is laid ahead of the above concrete caisson 4; a nut 16 is attached to the protruding end of the bolt 14 so as to be temporarily fastened; a prestressing steel bar 21 is inserted into the front concrete caisson 4; a back end of the prestressing steel bar 21 is connected to the protruding end of the binding bolt 14, so that a tensioning jack 22 can make the tension applied to the bolt 14 via the prestressing steel bar 21; and in this state, the nut 16 pre-attached to the leading end of the bolt 14 is finally fastened so that the concrete caissons 4 in front and rear positions can be bound together. COPYRIGHT: (C)2008,JPO&INPIT

Work caisson for temporary cofferdam

Abstract: PROBLEM TO BE SOLVED: To provide a work caisson for temporary cofferdam capable of dispensing with underwater work for long hours in great depth under the water such as placing underwater concrete. SOLUTION: This work caisson 1 for temporary cofferdam is constituted in such a way that a caisson body 6 mounted on a wall face 4 of a structure and opening a mounting side and an upper side is formed, a water cut-off mechanism 11 is provided on mounting faces of a bottom part 7 and both side parts 9 on the mounting side of the caisson body 6, the water cut-off mechanism 11 is composed of a water cut-off main body 13, an external part seal 14 provided in an outer side part of the water cut-off main body 13, an intermediate part seal 15 provided in an intermediate part, and an internal part seal 16 provided in an inner side part, the external part seal 14 is an extending and contracting protruding body 17 having a hollow part 17a in its inside, the intermediate part seal 15 is composed of a water cut-off board 26 rotating centered on a one end part side and a pressurizing tube 27 provided between the water cut-off board 26 and the water cut-off main body 13, and the internal part seal 16 is a packing 30. COPYRIGHT: (C)2008,JPO&INPIT

Energy absorption beam, especially for a motor vehicle bumper beam and motor vehicle with such a beam

Abstract: The beam (1) has a caisson (2) connected to a chassis (3) of a motor vehicle and carrying a front vertical soleplate (4) maintaining a space with the caisson. The soleplate has a succession of alternate vertical projection and hollow parts (5, 6) with different stiffnesses. The stiffness at the summit of the projection part (5) is greater than that of the hollow part (6). The summit of each projection part (5) is connected to the caisson by a spacer (7). An independent claim is also included for a motor vehicle comprising an energy absorbing beam.

Construction method using caisson

Abstract: A caisson construction method is provided to shorten a period of construction for an underwater structure by reducing the cost and time required for settlement of a caisson, to improve bearing strength of a caisson by preventing the formation of a hollow caused by tidal subsidence, to prevent the partial disposition of a caisson and to prevent the permeation of water into a caisson by waterproofing with lubricates A caisson construction method comprises the steps of: making a tubular foundation reach a soil layer(1) on the water and settling down by dead weight; draining off water in the settled foundation using a pump; removing soils using equipment such as a clamshell and waterproofing the lower part of the foundation using a watertight mat or other watertight devices; installing a form on the upper part of the buried foundation to place an upper case having the same shape as the foundation; installing empty pipes(20) around the installed form at regular intervals, welding both ends of the pipe, installing an injection tube(22) connected with the inside of the welded pipe on the upper part of the form and fixing the pipe; forming an upper case(40) by placing and curing concrete in the form; removing the form; subsiding the upper case using dead weight or driving, injecting lubricants(30) into the inside of the pipe through the injection tube to settle the upper case and the foundation easily when the pipe is settled into the soil layer, and jetting out through a through-hole(21) formed on the outside of the pipe; subsiding the upper case and the foundation and removing the inside soils; and installing another upper case on the upper part of the settled upper case and subsiding repeatedly

Numerical Investigation on the Pull-Out Behaviour of Suction Caissons in Clay

Abstract: Since their inception suction caisson foundations have presented themselves as proven means of anchoring floating production systems and fixed offshore structures. The pull-out capacity of suction caissons remains a critical issue in their applications, and in order to produce effective designs, reliable methods of predicting the capacity are required. In this paper results from a numerical investigation on the behaviour of the suction caissons in clays against pull-out loading have been presented. Soil nonlinearities, soil/caisson interactions and the effects from the suction on the behaviour have been taken into account. A linear relationship has been observed between the soil cohesion values and the pull-out capacity. Under drained conditions, beyond specific limits of soil cohesion values, the increase in the cohesion value have found to demonstrate no further influence on the pull-out capacity. The soil internal friction angle has been noticed to have an exponential increasing effect on the pull-out capacity. With constant values of the caisson diameter, an increase in the aspect ratio noticed to have a second order effect of the friction originated part and a linear influence on the cohesion originated part of the resistance. With constant values of the caisson length, an increase in the aspect ratio values has found to result in an exponential decrease of the pull-out capacity. Based on the obtained numerical results simple formulations and approximations have been proposed in order to estimate the effects of the studied parameters on the pull-out capacities.Copyright © 2006 by ASME

Design, Construction, and Installation of a Floating Caisson Used as a Bridge Pier

Abstract: A suspension bridge over a river is generally supported on a structure mounted on large concrete piers placed on the river bottom near the two banks. Because of its massive size the piers are built by pouring concrete at site in a floating position. During this construction period, the floating caissons are moored in place to withstand any environmental currents and waves, which may be prevalent at the site. Since the draft of the caisson changes during construction, the mooring system must be capable of holding the caisson at all these drafts. Once the construction sequence reaches the required height, the caisson is ballasted down to rest on the river bottom and subsequently during further ballasting penetrates the soil to its desired depth. The design and construction of the piers in place and their mooring system provides several technical challenges. This paper describes these challenges experienced in the design of a caisson system for a new bridge at Tacoma Narrows, close to Seattle. This design process included towing the caissons at a shallow draft from the dock to the site, design and installation of the mooring system, construction of the caissons in place, and final touchdown and penetration to soil. The current at the Narrows was extremely high, which gave particular challenges in the construction sequence. Some of the critical areas of the associated design and their solution techniques are highlighted. It should be noted that the dimensions of the bridge caissons and their mooring system are of similar order of magnitude as typical offshore structures exposed to severe environment.

Structure of caisson

Abstract: PROBLEM TO BE SOLVED: To safely settle a caisson by automatically controlling an excavated quantity directly below the wall surface of the caisson without depending on a worker's intuition. SOLUTION: A rotary blade with a spiral cutting edge reciprocated along a bottom face of the wall surface 2 of the caisson is installed in a position directly under the wall surface 2. A horizontal rotary blade 4 comprising blades provided in a horizontal direction at the lower end of a vertical rotating shaft is installed at each corner part of a polygon. A settlement quantity control part 5 is composed of a detecting rope 51, a drum for delivering the rope by a fixed quantity per hour, and a measuring instrument 53 for measuring the tension degree of the rope. When the detecting rope 51 of a certain control part gets tense, the rotating drive of the rotary blade in the related range is stopped. When the detecting rope 51 slacks, the rotating drive of the rotary blade in the related range is continued. COPYRIGHT: (C)2006,JPO&NCIPI

Automatic water gate

Abstract: The invention relates to an automatic water gate provided in the form of a panel (P) that can pivot about a horizontal rod fixed to pillars installed on a weir having an active caisson (5) placed principally above the pivot rod in the upper portion of the panel (P) and having a water intake channel (9) provided in the upper portion of the panel (P) above the active caisson (5), said caisson (5) having drain holes (7) on the side of the reach downstream and being in communication with the water intake channel (9) whereas means forming a counterweight (14) are provided in the lower portion of the panel below the horizontal pivot rod whereby holding the gate in an inclined closed position so that in the event of an overflow upstream, the filling of the active caisson (5) causes the gate to tilt and be held it in a horizontal position against the force exerted by the means forming a counterweight (14), these means automatically returning the gate to a closed position when the overflowing ceases and the active caisson (5) empties. The invention is for use in a weir of a dam, pond or the like.