Overview of Tacoma Narrows Bridge Floating Caisson Design

2004 ◽  
Author(s):  
M. Sri Krishna ◽  
Partha Chakrabarti ◽  
Subrata K. Chakrabarti ◽  
Adinarayana Mukkamala ◽  
Nagaraj Anavekar
Keyword(s):  
Design Procedure ◽  
Suspension Bridge ◽  
Offshore Structures ◽  
Mooring Lines ◽  
Critical Areas ◽  
Dynamic Forces ◽  
Order Of Magnitude ◽  
Associated Design ◽  
Tacoma Narrows Bridge ◽  
Full Height

Tacoma Narrows Constructors is building a new suspension bridge in Tacoma, close to Seattle, Washington State, USA next to an existing bridge at the location. The new bridge is being built just south of the existing bridge. This new bridge will be built on towers mounted on two caissons. The caissons are towed to the site from the harbor with the cutting edge, first full lift, and the second and third exterior lifts. The piers are constructed on site up to their full height as floating caissons at varying drafts. During the construction, the floating caissons on both ends of the new bridge are moored in place with 32 catenary mooring lines. The current flow due to ebb and flood tide in the narrows is very high. This high current and the consequent vortex-induced dynamic forces provided a technical challenge in the design of the caisson and its mooring system whose dimensions are of similar order of magnitude as typical offshore structures exposed to severe environment. This paper provides an overview of this challenge, and describes the steps taken in overcoming these difficulties. The design procedure adopted of the moored caisson system and the piers in the overall scheme of the Tacoma Narrows Bridge are summarized. This overview stresses the practical side of towing, mooring and in place construction of the caissons. Some of the critical areas of associated design challenges and their solution techniques are highlighted.

Design, Analysis and Verification of Moored Floating Caisson System

2004 ◽  
Author(s):  
Partha Chakrabarti ◽  
Subrata K. Chakrabarti ◽  
Adinarayana Mukkamala ◽  
Nagaraj Anavekar ◽  
Shen Qiang ◽  
...  
Keyword(s):  
Bottom Topography ◽  
Suspension Bridge ◽  
Design Tool ◽  
Mooring System ◽  
Mooring Lines ◽  
Hydrodynamic Analysis ◽  
Analysis And Design ◽  
Dynamic Forces ◽  
Tacoma Narrows Bridge ◽  
Line Loads

Tacoma Narrows Constructors (TNC) is building a new suspension bridge in Tacoma, close to Seattle, Washington State, USA. The new bridge will be built just south of the existing bridge mounted on two caissons, referred to as East Caisson (Tacoma side) and West Caisson (Gig Harbor side). Each pier is about 80’ wide and 130’ long in plan. The mooring system for each caisson consists of two sets of mooring lines: lower and upper. Each set consists of 16 mooring lines. The lower 16 lines consist of anchors that form a radius of about 300 feet. The fairlead locations for these lower 16 lines are kept constant throughout the construction process. These 16 lines are hooked-up after the caisson is towed from the harbor and positioned at the site. For the upper 16 lines (except three lines on East Pier), the anchor locations form a radius of 600’. The fairlead locations for these upper 16 lines vary based on the draft. Due to the proximity of the proposed caissons to the existing piers and the varying bottom topography, considerable turbulence and vortex shedding is expected which will cause current induced dynamic forces on the caissons. This paper describes the design and analysis of this multi-line mooring system for Tacoma Narrows Bridge caissons, based on the construction sequence in the floating condition. The analysis involved optimizing the anchor locations and the line pretensions, determining the dynamic motions of the caissons, maximum line loads, and corresponding safety factors. The paper includes the hydrodynamic analysis for added mass, and damping, the methodology used for the nonlinear moored caisson analysis (MOTSIM), and the validation of the design tool with other similar models (e.g., StruCAD*3D). The results of the analysis and design are discussed.

Design Analysis of Moored Floating Caisson System

2004 ◽  
Vol 127 (2) ◽  
pp. 75-82 ◽  
Author(s):  
Partha Chakrabarti ◽  
Subrata K. Chakrabarti ◽  
Adinarayana Mukkamala ◽  
Nagaraj Anavekar ◽  
Shen Qiang ◽  
...  
Keyword(s):  
Bottom Topography ◽  
Suspension Bridge ◽  
Design Tool ◽  
Mooring System ◽  
Mooring Lines ◽  
Hydrodynamic Analysis ◽  
Construction Sequence ◽  
Close Proximity ◽  
Dynamic Forces ◽  
Line Loads

Tacoma Narrows Constructors (TNC) are building a new suspension bridge in Tacoma, close to Seattle, Washington State, USA. The new bridge is being built just south of the existing bridge mounted on two caissons. The caissons are constructed on location after the shallow draft caissons are towed to site. During the construction sequence, the mooring system for each caisson consists of two sets of 16 mooring lines. The lower 16 lines are hooked-up after the shallow draft caisson is towed from the harbor and positioned at the site. The fairlead locations for these lines are kept constant throughout the construction process. The fairlead locations for the upper 16 lines (except three lines on the East Caisson) vary based on the caisson draft. The caissons are subject to a high current from the ebb and flood tide flow in the Narrows. The new caissons are in close proximity to the existing piers and the bottom topography at the site is varying. Therefore, considerable turbulence and vortex shedding is expected in the prevailing current, which will cause current-induced dynamic forces on the caissons. This paper describes the design and analysis of this multiline mooring system for Tacoma Narrows Bridge caissons, based on the construction sequence in the floating condition. The analysis involved optimizing the anchor locations and the line pretensions, determining the dynamic motions of the caissons, the maximum line loads, and the corresponding safety factors. The paper also describes the hydrodynamic analysis for added mass, and damping, the methodology used for the nonlinear moored caisson analysis (MOTSIM), and the validation of the design tool with other similar models (e.g., STRUCAD*3D). The results of the analysis and the design of the system are discussed.

Investigation Into the Sensitivity of the Dynamic Hook Load During Subsea Deployment of a Suction Can

2007 ◽  
Author(s):  
J. Ireland ◽  
G. Macfarlane ◽  
Y. Drobyshevski
Keyword(s):  
Nonlinear Damping ◽  
Added Mass ◽  
Offshore Structures ◽  
Hydrodynamic Properties ◽  
Deep Basin ◽  
Mooring Lines ◽  
Number Range ◽  
North West ◽  
Order Of Magnitude ◽  
Decay Tests

Suction cans are commonly used as foundations of fixed offshore structures, subsea equipment, and anchors of mooring lines. During the offshore installation phase, when a suction can is submerged, it attracts large heave added mass, which may be an order of magnitude higher than the mass of the can in air. Due to motions of an installation vessel the dynamic hook load may significantly exceed the submerged weight of the can. The dynamic hook load must be accurately predicted, as it governs selection of the vessel, lifting gear and rigging, and defines the allowable installation sea state. The objective of this paper is to examine the sensitivity of the dynamic hook load to hydrodynamic properties of the suction can, in particular its heave added mass and damping. This research is motivated by the lack of data on such properties, which are usually estimated by simplified methods with some engineering judgement and assumptions. A single degree of freedom system is considered and the frequency domain spectral analysis is used, which employs the stochastic linearization of the nonlinear damping component. The added mass and damping of a 6-meter diameter suction can of dimensions typical for Australian North West Shelf developments have been determined by testing a 1:10 model in the 4.1 m deep basin of the Australian Maritime College. Free decay tests were conducted at several frequencies and the added mass, linear and nonlinear damping components determined. The effect of open hatches on the hydrodynamic properties was examined by fitting the model with hatches of various diameters, with up to 4.8% of the relative area open. Results of the tests demonstrate that the added mass and damping are higher, when compared with estimates based on empirical data for non-oscillatory flow. Within the Keulegan-Carpenter number range of 0.1–1.0, open hatches impact significantly on the added mass and produce additional damping, which is found to be linear with the heave velocity. Results of the tests and their interpretation are discussed. Sensitivity analysis shows that if the model test results are used in the dynamic lift analysis for an installation vessel and sea states considered, the predicted hook load is generally less than its values obtained by using simplified estimates. In particular, the increase in linear damping due to open hatches is responsible for up to 20% reduction in the dynamic hook load, with 2.4% of the relative top area open.

scholarly journals Effect of Roughness of Mussels on Cylinder Forces from a Realistic Shape Modelling

2021 ◽  
Vol 9 (6) ◽  
pp. 598
Author(s):  
Antoine Marty ◽  
Franck Schoefs ◽  
Thomas Soulard ◽  
Christian Berhault ◽  
Jean-Valery Facq ◽  
...  
Keyword(s):  
Marine Species ◽  
Offshore Structures ◽  
Offshore Wind ◽  
Mooring Lines ◽  
Shape Modelling ◽  
Offshore Wind Turbines ◽  
Specific Effects ◽  
Hydrodynamic Loading ◽  
Floating Offshore Wind Turbines ◽  
Realistic Shape

After a few weeks, underwater components of offshore structures are colonized by marine species and after few years this marine growth can be significant. It has been shown that it affects the hydrodynamic loading of cylinder components such as legs and braces for jackets, risers and mooring lines for floating units. Over a decade, the development of Floating Offshore Wind Turbines highlighted specific effects due to the smaller size of their components. The effect of the roughness of hard marine growth on cylinders with smaller diameter increased and the shape should be representative of a real pattern. This paper first describes the two realistic shapes of a mature colonization by mussels and then presents the tests of these roughnesses in a hydrodynamic tank where three conditions are analyzed: current, wave and current with wave. Results are compared to the literature with a similar roughness and other shapes. The results highlight the fact that, for these realistic roughnesses, the behavior of the rough cylinders is mainly governed by the flow and not by their motions.

Very Large Floating Structures

2007 ◽  
Author(s):  
H. Suzuki ◽  
H. R. Riggs ◽  
M. Fujikubo ◽  
T. A. Shugar ◽  
H. Seto ◽  
...  
Keyword(s):  
Design Procedure ◽  
Offshore Structures ◽  
Floating Structure ◽  
Floating Structures ◽  
Design Procedures ◽  
Novel Technology ◽  
Hydroelastic Analysis ◽  
Behavior Design ◽  
Hydroelastic Response ◽  
Near Future

Very Large Floating Structure (VLFS) is a unique concept of ocean structures primary because of their unprecedented length, displacement cost and associated hydroelastic response. International Ship and Offshore Structures Congress (ISSC) had paid attention to the emerging novel technology and launched Special Task Committee to investigate the state of the art in the technology. This paper summarizes the activities of the committee. A brief overview of VLFS is given first for readers new to the subject. History, application and uniqueness with regard to engineering implication are presented. The Mobile Offshore Base (MOB) and Mega-Float, which are typical VLFS projects that have been investigated in detail and are aimed to be realized in the near future, are introduced. Uniqueness of VLFS, such as differences in behavior of VLFS from conventional ships and offshore structures, are described. The engineering challenges associated with behavior, design procedure, environment, and the structural analysis of VLFS are introduced. A comparative study of hydroelastic analysis tools that were independently developed for MOB and Mega-Float is made in terms of accuracy of global behavior. The effect of structural modeling on the accuracy of stress analysis is also discussed. VLFS entails innovative design methods and procedure. Development of design criteria and design procedures are described and application of reliability-based approaches are documented and discussed.

Design of One-Piece Jet-Engine Compressor End Seals

1968 ◽  
Vol 90 (4) ◽  
pp. 709-721
Author(s):  
L. W. Winn ◽  
R. L. Thorkildsen ◽  
D. F. Wilcock
Keyword(s):  
Design Procedure ◽  
Labyrinth Seals ◽  
Jet Engine ◽  
Supersonic Transport ◽  
Face Type ◽  
High Pressure Compressor ◽  
Order Of Magnitude ◽  
Engine Compressor ◽  
Gas Bearing

Performance of advanced air-breathing propulsion systems can be significantly improved through the utilization of effective sealing devices. One of the areas in which immediate benefits are realizable from improvements in sealing efficiency is the high-pressure compressor end area. This paper describes the design of a face-type flexible seal and a face-type rigid seal for a compressor end seal based upon the cruise conditions expected in one version of the supersonic transport (SST) jet engine. The seals, non-contacting during operation, operate on air films achieved through the employment of hybrid gas-bearing geometries on the seal faces. The design procedure discussed consists primarily of the selection of the most applicable seal-face geometries force and moment balance, determination of seal tracking capability, establishment of leakage characteristics, thermal gradients, and stress and deflection calculations. The design results indicate that satisfactory seal performance can be obtained with either of the two configurations. Leakage reductions of an order of magnitude compared to that encountered with labyrinth seals commonly used in existing jet-engine systems can be achieved.

Influence of Nonlinear Mooring Stiffness on Hydrodynamic Performance of Floating Bodies

2009 ◽  
Author(s):  
Huilong Ren ◽  
Jian Zhang ◽  
Guoqing Feng ◽  
Hui Li ◽  
Chenfeng Li
Keyword(s):  
Equilibrium Position ◽  
Equations Of Motion ◽  
Offshore Structures ◽  
Hydrodynamic Performance ◽  
Coupled Analysis ◽  
Mooring System ◽  
Main Function ◽  
Ocean Engineering ◽  
Mooring Lines ◽  
Floating Structures

Coupled dynamic analysis between floating marine structures and flexible members such as mooring lines and risers, is a challenging work in the ocean engineering field. Coupled analysis on mooring-buoy interactions has been paid more and more concern for recent years. For floating offshore structures at sea, the motions driven by environmental loads are inevitable. The movement of mooring lines occurs due to the excitation on the top by floating structures. Meanwhile the lines restrict the buoy’s motion by forces acting on the fareleads. Positioning is the main function of mooring system, its orientation effects can’t be ignored for floating structures such as semi-submersible, FPS, and TLP, especially when the buoy’s equilibrium position shifting to another place. Similar as hydrostatic restoring forces, mooring force related with the buoy’s displacement can be transformed into mooring stiffness and can be added in the differential equations of motion, which is calculated at its equilibrium point. For linear hydrodynamic analysis in frequency domain, any physical quantity should be linear or be linearized, however mooring stiffness is nonlinear in essence, so the tangent or differential stiffness is used. Steel chains are widely used in catenary mooring system. An explicit formulation of catenary mooring stiffness is derived in this article, which consists of coupled relations between horizontal and vertical mooring forces. The effects of changing stiffness due to the shift of equilibrium position on the buoy’s hydrodynamic performance are investigated.

Sensitivity of Mooring Line Pretension in the Design Cycle for Floating Caissons

2004 ◽  
Author(s):  
Adinarayana Mukkamala ◽  
Partha Chakrabarti ◽  
Subrata K. Chakrabarti
Keyword(s):  
Reinforced Concrete ◽  
System Design ◽  
Mooring Line ◽  
Mooring System ◽  
Mooring Lines ◽  
Design Cycle ◽  
Overall Performance ◽  
The Difference ◽  
Tacoma Narrows Bridge ◽  
System Layout

The new parallel Tacoma Narrows Bridge being constructed by Tacoma Narrows Constructors will be mounted on two towers and these towers in turn will be supported by reinforced concrete caissons referred to as East Caisson (Tacoma side) and West Caisson (Gig Harbor side). Each Caisson is towed to the location and several stages of construction will take place at the actual site. During construction, the floating caissons will be moored in place to hold it against the flood and ebb currents in the Narrows. During the mooring system design, a desired pretension is established for the lines at each draft. However, due to practical limitations in the field some variations to this design pretension value may be expected. It is important to study the effect of this variation on the overall performance of the mooring system. In this paper, the sensitivity of the mooring line pretension on the overall performance of the mooring system for the above caisson is presented. During this study, all the variables that affect the mooring system design such as mooring system layout, mooring line makeup, anchor positions, fairlead departure angles, and fairlead locations are kept constant. The only variable changed is the pretension of the mooring lines. Two approaches for defining the variations in the pretension have been studied in this paper. In the first approach, the pretension is changed in a systematic way (predicted approach). In the second method the pretension is changed randomly. The latter is considered more likely to occur in the field for this type of complex mooring system. Both sets of results are presented for some selected drafts attained by the caisson during its construction. The difference in the results from the two methods is discussed.

Water Deluge System Design for Fire Fighting

2016 ◽  
Author(s):  
Jin Lee ◽  
Sang Hwan Kim ◽  
Jung Kwan Seo ◽  
Jeom Kee Paik
Keyword(s):  
Fluid Dynamic ◽  
Design Procedure ◽  
Offshore Structures ◽  
Offshore Platforms ◽  
Probabilistic Sampling ◽  
Spray System ◽  
Safety Design ◽  
Fire Scenarios ◽  
Fire And Explosion ◽  
The Cost

The ships and offshore structures are exposed to inherently the risk of fire and explosion. These fire and explosion, accident caused by grave consequences not only to the ships and offshore platforms on the sea but the environment all mankind. The aim of this paper is to focus on an optimization of water deluge and mist spray system locations subjected to jet on the ships and offshore platforms. A trustworthy set of fire scenarios is identified and classified using probabilistic sampling methods calling for Latin Hyper Sampling. These events of fire are numerically calculated for selected scenarios by the computational Fluid Dynamic (CFD) code using a KFX. The Water Deluge Location Index (WLI) is then calculated by using the frequency and consequence of fire scenarios. And then, WLI are utilized to prioritize the optimal locations of water deluge and mist spray systems. The recommended methodology believes that can increase to certainties in the design procedure of unreliability and can regard the cost-effectiveness of safety design.

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