Refined Model for Inclined Load Capacity of Suction Caissons

2003 ◽  
Author(s):  
Charles P. Aubeny ◽  
Seungwoon Han ◽  
J. Don Murff
Keyword(s):  
Load Capacity ◽  
Full Range ◽  
Skin Resistance ◽  
Cohesive Soil ◽  
Offshore Structures ◽  
Resistance Coefficient ◽  
Soil Conditions ◽  
Aspect Ratios ◽  
Inclination Angles ◽  
Suction Caissons

Suction caissons used as mooring anchors for offshore structures can, depending on design concept, be subjected to pullout forces ranging from nearly vertical for tension leg platforms, to intermediate inclination angles for taut mooring systems, to nearly horizontal for catenary moored systems. Hence, the ability to understand and predict suction anchor pullout resistance for a full range of load orientations is becoming of increasing importance. A previous paper by the authors presents a plastic limit analysis for estimating the load capacity of suction anchors over a full range of load inclination ranging from horizontal to vertical. The model was capable of predicting load capacity for various load attachment (padeye) depths, caisson aspect ratios, and soil undrained strength profiles that vary linearly with depth. Loading conditions are assumed to be undrained; therefore, a purely cohesive soil is assumed. The original analysis assumed full adhesion on the boundaries of the caisson; i.e., a skin resistance coefficient α equal to unity. However, actual values of this coefficient are less than unity, with specific values varying according to soil conditions and the method of caisson installation. To overcome the limitation of the original model, this paper presents a modified formulation that allows a skin resistance less than unity. The modified formulation develops an interaction relationship between vertical and horizontal soil resistance on the sides of the caisson that is applicable for any skin resistance conditions ranging from no to full adhesion.

Uplift Capacity of Suction Caissons in Sand for General Conditions Of Drainage

2021 ◽  
Author(s):  
Ragini Gogoi ◽  
Charles P. Aubeny ◽  
Phillip Watson ◽  
Fraser Bransby
Keyword(s):  
Constitutive Model ◽  
Load Capacity ◽  
System Capacity ◽  
Soil Conditions ◽  
Uplift Capacity ◽  
Soil Response ◽  
Dense Sand ◽  
Centrifuge Tests ◽  
Numerical Predictions ◽  
Suction Caissons

Abstract Suction caissons have emerged as a viable solution for the foundations of offshore wind turbines, which are gaining momentum worldwide as an alternate energy source. When used in a multi-bucket jacket system, the system capacity is often governed by the uplift capacity of the windward bucket foundation. Seabed conditions at offshore windfarm sites often comprise dense sand where the soil response may be drained, partially drained or undrained depending on the loading regime, the foundation dimensions and the soil conditions. Given the large difference in uplift capacity of caissons for these different drainage conditions, predicting the behavior of a suction caisson under a range of drainage conditions becomes a paramount concern. Consequently, this paper presents the findings of a coupled finite element investigation of the monotonic uplift response of the windward caisson of a multi-bucket jacket system in a typical dense silica sand for a range of drainage conditions. The study adopts a Hypoplastic soil constitutive model capable of simulating the stress-strain-strength behavior of dense sand. This choice is justified by conducting a comparative study with other soil models — namely the Mohr Coulomb and bounding surface sand models — to determine the most efficient soil failure model to capture the complex undrained behavior of dense sand. The numerical predictions made in this study are verified by recreating the test conditions adopted in centrifuge tests previously conducted at the University of Western Australia, and demonstrating that the capacity from numerical analysis is consistent with the test results. The Hypoplastic soil constitutive model also provides an efficient method to produce accurate load capacity transition curves from an undrained to a drained soil state.

Performance of suction caissons in sand and clay

2002 ◽  
Vol 39 (3) ◽  
pp. 576-584 ◽  
Author(s):  
Magued Iskander ◽  
Sherif El-Gharbawy ◽  
Roy Olson
Keyword(s):  
Load Capacity ◽  
Strength Properties ◽  
Drilled Shafts ◽  
Soil Conditions ◽  
Driven Piles ◽  
Suction Caisson ◽  
Axial Tensile ◽  
Axial Load Capacity ◽  
Shearing Strength ◽  
Suction Caissons

The use of suction caissons (suction piles) in marine environments has been increasing in the last decade. A suction caisson is a steel pipe with an open bottom and a closed top that is inserted into the ground by pumping water out of it. Pumping creates a differential pressure across the caisson's top that pushes it into place, thus eliminating the need for pile driving. There are a number of uncertainties in the design of suction caissons. First, the state of stress and soil conditions adjacent to a suction caisson differs from those around typical driven piles or drilled shafts. Second, the axial load capacity of suction caissons depends on the rate of loading, hydraulic conductivity, drainage length, as well as the shearing strength properties of the foundation material. Finally, during pullout, volume change characteristics of the surrounding soils may change the theoretical suction pressures. A review of the existing knowledge relating to the design and construction of suction caissons is presented in this paper along with the results of a laboratory study on model caissons in sand and clay. Test results indicate that the use of suction pressure for installation of caissons is a viable alternative to conventional methods. Suction was also shown to resist some axial tensile loads.Key words: suction, pile, bucket, foundation, anchor, capacity.

scholarly journals Simulation of the Plug inside Open Steel Pipe Piles with Regards to Different Installation Methods

2016 ◽  
Author(s):  
Johannes Labenski ◽  
Christian Moormann ◽  
Johannes Aschrafi ◽  
Britta Bienen
Keyword(s):  
Field Tests ◽  
Cohesive Soil ◽  
Offshore Structures ◽  
Steel Pipe ◽  
Soil Conditions ◽  
Small Scale ◽  
Driven Piles ◽  
Pile Installation ◽  
Pile Diameter ◽  
Port Structures

Open steel pipe piles are used for various applications in costal engineering and port structures and they are becoming increasingly more important for offshore structures. A plug formed during the installation of open steel pipe piles has an influence on the installation process of the steel pipe pile as well as on the final bearing behaviour and the pile resistance. Forming of the plug depends on different influences, e.g. the pile diameter, the soil conditions and the installation method. To obtain a better understanding of the formation of the plug and its consequences several experimental small-scale tests, experimental field tests and numerical simulations have been performed. But so far this phenomenon is not completely investigated yet. At the beginning of this paper a structured overview about the characterization of the plug as well as soil mechanical processes during the pile installation in non-cohesive soil are provided. Then, the results of a centrifuge study are shown. The focus of this paper is the numerical simulation of the installation process of impact and vibratory driven piles in non-cohesive soil to investigate the effect of plugging with regard to different installation methods. Centrifuge experimental results are utilized to validate the numerical model, which can provide detailed insights into the physical processes occurring in the soil but are difficult to measure in experiments. The numerical analyses hence illustrate zones of densification/loosening, which highlight the differences resulting from the installation methods.

Hydrodynamic Loading on Macro-Roughened Cylinders of Various Aspect Ratios

1989 ◽  
Vol 111 (3) ◽  
pp. 214-222 ◽  
Author(s):  
A. Theophanatos ◽  
J. Wolfram
Keyword(s):  
Offshore Structures ◽  
Water Tank ◽  
Fluid Loading ◽  
Test Rig ◽  
Test Program ◽  
Number Range ◽  
Marine Fouling ◽  
Aspect Ratios ◽  
The Uk ◽  
Regular Arrays

This paper describes experiments which comprise part of the UK joint SERC/industry-sponsored program on fluid loading. The experiments have been undertaken in a novel test rig which accelerates a cylinder from rest to a constant velocity in a still water tank and cover the Reynolds number range 105 to 106. Results are presented for 30 cylinders ranging in diameter from 150 mm to 400 mm. The test program comprised: (a) cylinders with different distributions of marine growth (mussels and kelp) and artificial roughness at low surface cover; (b) fully sand/gravel-roughened cylinders with aspect ratios (L/D) from 3.75 to 10 and relative roughness (k/D) up to 0.025; (c) cylinders covered in regular arrays of pyramids at (k/D) up to 0.1. Based on the results, some tentative conclusions are drawn about the estimation of the effect of marine fouling on the fluid loading of offshore structures.

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

2006 ◽  
Author(s):  
Mostafa Zeinoddini ◽  
Mahmood Nabipour
Keyword(s):  
Aspect Ratio ◽  
Numerical Investigation ◽  
Production Systems ◽  
Friction Angle ◽  
Critical Issue ◽  
Order Effect ◽  
Offshore Structures ◽  
Pull Out ◽  
Soil Cohesion ◽  
Suction Caissons

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.

MIXED CONVECTION IN AN INCLINED AND LID-DRIVEN RECTANGULAR ENCLOSURE HEATED AND COOLED ON ADJACENT WALLS

2008 ◽  
Vol 32 (2) ◽  
pp. 213-226 ◽  
Author(s):  
Elif Büyük Öğüt
Keyword(s):  
Mixed Convection ◽  
Differential Quadrature Method ◽  
Side Wall ◽  
Temperature Fields ◽  
Convection Flow ◽  
Rectangular Enclosure ◽  
Aspect Ratios ◽  
Laminar Mixed Convection ◽  
Inclination Angles ◽  
Steady Laminar

Steady, laminar, mixed convection flow was considered in an inclined lid-driven rectangular enclosure heated from one side moving with a constant speed and cooled from the stationary adjacent side while the other sides are kept stationary and adiabatic. The governing equations were solved numerically for the stream function, vorticity, and temperature ratio using the differential quadrature method for various Reynolds, Grashof, and Richardson numbers as well as different aspect ratios and inclination angles for the enclosure. The results show that the motion of the side wall, the aspect ratio, and the inclination angle of the enclosure had significant effects on the flow and temperature fields.

Limit Equilibrium Solutions to Anti-overturning Bearing Capacity of Suction Caissons in Uniform and Linearly Increasing Strength Clays

2021 ◽  
Author(s):  
Yuqi Wu ◽  
Qing Yang ◽  
Dayong Li ◽  
Yu Zhang
Keyword(s):  
Bearing Capacity ◽  
Failure Mechanism ◽  
Wind Turbines ◽  
Limit Equilibrium ◽  
Soil Surface ◽  
Equilibrium Analysis ◽  
Offshore Wind ◽  
Offshore Wind Turbines ◽  
Aspect Ratios ◽  
Suction Caissons

Suction caissons supporting offshore wind turbines are exposed to great horizontal loading above the soil surface, which may lead to overturning failure of the caisson. This paper presents a modified three-dimensional failure mechanism to analyze the anti-overturning bearing capacity of suction caissons. The modified failure mechanism is composed of meniscus-conical wedge having meniscus shape at the soil surface and scooped shape. The analytical solution to the anti-overturning bearing capacity of suction caisson is deduced in terms of the limit equilibrium method, following by a parametric study of wedge depth ratio (c) to optimize the critical failure mechanism that satisfies both the force and moment equilibriums. Thus, the methodologies are relatively easy to implement in traditional spreadsheets and the analyses tend to perform very fast. Meanwhile, the effects of gap formation at the rear side of the caisson, loading eccentricity and adhesion factor at caisson-soil interface on anti-overturning bearing capacity are investigated. Comparing with finite element limit analysis results, experimental data and existing theoretical solutions, it is proved that the presented limit equilibrium analysis can satisfactorily predict the anti-overturning bearing capacity of suction caissons with low aspect ratios for offshore wind turbines in uniform and linearly increasing strength clays.

Structural Optimization of Laminated Composite Plates for Maximum Buckling Load Capacity Using Genetic Algorithm

2007 ◽  
Vol 348-349 ◽  
pp. 725-728 ◽  
Author(s):  
Omer Soykasap ◽  
Şükrü Karakaya
Keyword(s):  
Genetic Algorithm ◽  
Structural Optimization ◽  
Load Capacity ◽  
Laminated Composite ◽  
Global Solutions ◽  
Composite Plates ◽  
Buckling Load ◽  
Laminated Composite Plates ◽  
Static Loads ◽  
Aspect Ratios

In this study, the structural optimization of laminated composite plates for maximum buckling load capacity is performed by using genetic algorithm. The composite plate under consideration is a 64-ply laminate made of graphite/epoxy, is simply supported on four sides, and subject to in-plane compressive static loads. The critical buckling loads are determined for several load cases and different plate aspect ratios using 2-ply stacks of 02, ±45, 902. The problem has multiple global solutions, the results of which are compared with previously published results.

A Numerical Study on the Ultimate Strength of Damaged Tubular Bracing Members Under Axial Compression

2018 ◽  
Author(s):  
Ling Zhu ◽  
Jieling Kong ◽  
Qingyang Liu ◽  
Han Yang ◽  
Bin Wang
Keyword(s):  
Ultimate Strength ◽  
Axial Compression ◽  
Numerical Study ◽  
Load Capacity ◽  
Approximate Equation ◽  
Offshore Structures ◽  
Experimental Investigations ◽  
Pipe Length ◽  
Axial Load Capacity ◽  
Parametric Studies

The tubular bracing members of offshore structures may sustain collision damages from the supply ships, which lead to the deterioration of the load carrying capacity of tubular bracing members. This paper presents a numerical simulation of the ultimate strength of damaged tubular bracing members under axial compression with the nonlinear finite element code ABAQUS, based on previous experimental investigations. Parametric studies are conducted to investigate the load capacity of damaged tubular bracing members, by considering the effects of diameter (D), wall thickness (H), pipe length (L) and the damage positions on the ultimate strength of tubular members. It is found that lateral damage can cause great reduction of the axial load capacity of tubular members. In addition, an approximate equation to predict the ultimate strength of tubular members based on the given damage depth is proposed.

Inclined load capacity of suction caissons

2003 ◽  
Vol 27 (14) ◽  
pp. 1235-1254 ◽  
Author(s):  
C. P. Aubeny ◽  
S. W. Han ◽  
J. D. Murff
Keyword(s):  
Load Capacity ◽  
Inclined Load ◽  
Suction Caissons
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