Effect of Strength Anisotropy on Failure Envelope of Offshore Shallow Foundations under Combined Loading

2015 ◽  
Vol 73 ◽  
pp. 521-526 ◽  
Author(s):  
Ke Wu ◽  
Qinglai Fan ◽  
Jing Zheng
Keyword(s):  
Shallow Foundations ◽  
Combined Loading ◽  
Strength Anisotropy ◽  
Failure Envelope

Numerical Study of the Combined Loading Envelope of a Skirted Spudcan Foundation

2014 ◽  
Author(s):  
Ning Cheng ◽  
Mark J. Cassidy ◽  
Yinghui Tian
Keyword(s):  
Clay Soil ◽  
Numerical Study ◽  
Failure Mechanisms ◽  
Small Strain ◽  
Offshore Structures ◽  
Combined Loading ◽  
Finite Element Analyses ◽  
Failure Envelope ◽  
Foundation Type ◽  
Jack Up

Foundations for offshore structures, such as mobile jack-up units, are subjected to large horizontal (H) and moment (M) loads in addition to changing vertical (V) loads. The use of a combined vertical, horizontal and moment (V-H-M) loading envelope to define foundation capacities has become increasingly applied in recent years. However, there is no study on the skirted spudcan, a new alternative foundation type to the conventional spudcan footing for jack-ups. In this study, the combined V-H-M yield envelope of a skirted spudcan foundation in clay soil is investigated with small strain finite element analyses using 3D modeling. The footing’s uniaxial bearing capacities and failure mechanisms are described. The failure envelope for the combined V-H-M loadings is presented. A comparison of the bearing capacities between the spudcan and skirted spudcan of various dimensions is also presented.

Capacity of shallow foundations on saturated cohesionless soils under combined loading

2009 ◽  
Vol 46 (6) ◽  
pp. 639-649 ◽  
Author(s):  
M. Tolga Yilmaz ◽  
B. Sadik Bakir
Keyword(s):  
Stress Path ◽  
Reduction Factor ◽  
Shallow Foundations ◽  
Combined Loading ◽  
Saturated Soils ◽  
Soil Behavior ◽  
Seismic Capacity ◽  
Moment Capacity ◽  
Overturning Moment ◽  
The Impact

Under seismically induced loading, shallow foundations commonly fail by overturning on saturated soils. While the excess pore pressures may have fully dissipated following construction, undrained conditions are typically presumed in the assessment of seismic capacity in conventional applications due to the high rates of loading induced during an earthquake. Undrained strength, however, can be critically dependent on the history of loading and significantly heterogeneous and anisotropic around a foundation. The finite element method is utilized in this study for a proper assessment of the impact of these factors on the overturning moment capacity of surficial foundations on saturated soils, with specific emphasis on failure under seismic loading. Uplift capability has been incorporated into the models and analyses have been conducted for different drainage conditions. Based on the analyses results and comparisons with analytical formulae, it is concluded that the assumption of homogeneous soil strength as well as the disregard of stress path followed can lead to significant overestimation of the overturning moment capacity. The proposed improved approach comprises calculation of the overturning moment capacity based on drained soil behavior and subsequent application of an undrained behavior reduction factor (URF) compatible with the representative pore-pressure parameter A.

scholarly journals Failure Envelopes of Composite Bucket Foundation for Offshore Wind Turbines under Combined Loading with considering Different Scour Depths

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Yuanxu Jing ◽  
Yuan Wang ◽  
Jingqi Huang ◽  
Wei Wang ◽  
Lunbo Luo
Keyword(s):  
Wind Turbines ◽  
Bending Moment ◽  
Offshore Wind ◽  
Combined Loading ◽  
Failure Envelope ◽  
Bucket Foundation ◽  
Offshore Wind Turbines ◽  
Failure Envelopes ◽  
The Stability ◽  
The Right

The composite bucket foundation of offshore wind turbines is subjected to a variety of loads in the marine environment, such as horizontal load H, vertical load V , bending moment M, and torque T. In addition, due to the characteristics of its connection section, the water flow around the foundation will produce scour pits of various degrees, reducing the depth of the bucket foundation, which has a nonnegligible impact on the overall stability of the bucket foundation. In this paper, the failure envelope characteristics of different combinations of loads on bucket foundations, including V -H-T, V -M-T, conventional V -H-M, and noncoplanar V -H-M, are numerically investigated with considering different scour depths. The numerical results indicate that the V -H-T, V -M-T, conventional V -H-M, and noncongruent V -H-M failure envelopes gradually shrink inwards with increasing scour depth, and the stability of the composite bucket foundation decreases; the conventional V -H-M failure envelope shows an asymmetry of convexity to the right, and the noncongruent V -H-M failure envelope shows an asymmetry of outward convexity to the left and right. The corresponding mathematical expressions for the failure envelope are obtained through the normalized fitting process, which can be used to evaluate the stability of the bucket foundation based on the relative relationship between the failure envelope and the actual load conditions, which can provide practical guidance for engineering design.

Undrained capacity of circular shallow foundations on two-layer clays under combined VHMT loading

2022 ◽  
Author(s):  
Pengpeng He ◽  
Tim Newson
Keyword(s):  
Bearing Capacity ◽  
Effective Area ◽  
Undrained Shear Strength ◽  
Chemical Processes ◽  
Shallow Foundations ◽  
Interface Condition ◽  
Failure Envelope ◽  
Limit States ◽  
Element Analysis ◽  
Clay Deposits

Wind turbines are typically designed based on fatigue and serviceability limit states, but still require an accurate assessment of bearing capacity. Overconsolidated clay deposits in Canada often have a thin layer of crust with a relatively high undrained shear strength developed from weathering, desiccation, and geo-chemical processes. However, existing design methods only assess the bearing capacity using effective area and inclination factor without consideration of surficial crusts. This paper studies the undrained VHMT (vertical, horizontal, moment and torsional) failure envelope of circular foundations founded on a surficial crust underlain by a uniform soil with a zero-tension interface condition using finite element analysis. An analytical expression for the VHMT failure envelope is derived.

A New Method to Investigate the Failure Envelopes of Offshore Foundations

2016 ◽  
Author(s):  
Yinghui Tian ◽  
Tianyuan Zheng ◽  
Tao Zhou ◽  
Mark J. Cassidy
Keyword(s):  
Test Method ◽  
New Method ◽  
Combined Loading ◽  
Resistance Force ◽  
Flow Conditions ◽  
Load Path ◽  
Failure Envelope ◽  
Load Paths ◽  
Failure Envelopes ◽  
Probe Test

This paper presents an alternative numerical method in addition to the traditional ‘probe test’ to investigate the combined loading failure envelopes of foundations in soil. In the ‘probe test’ method, the foundation is displaced with a specified displacement path and eventually the soil resistance force reaches a stabilised point sitting on the failure envelope in the load space. While the displacement paths are arbitrarily or empirically set, the positions of the stabilised loads on the failure envelope can not be predetermined or planned. This paper’s new method, however, can specify the load paths, which directly shoot onto the failure envelope. This allows the investigation of the failure envelope can be better achieved with planned load paths. In addition, this new method is advantageous in checking the plastic flow conditions (i.e. normality of the failure envelope) as the load path directions are predetermined.

scholarly journals Validating a Failure Surface Developed for ABS Fused Filament Fabrication Parts through Complex Loading Experiments

2019 ◽  
Vol 3 (2) ◽  
pp. 49 ◽  
Author(s):  
Gerardo A. Mazzei Capote ◽  
Alec Redmann ◽  
Tim A. Osswald
Keyword(s):  
Stress State ◽  
Complex Loading ◽  
Acrylonitrile Butadiene Styrene ◽  
Failure Surface ◽  
Tensile Tests ◽  
Combined Loading ◽  
Uniaxial Tensile ◽  
Failure Envelope ◽  
Fused Filament Fabrication ◽  
The Moment

Fused Filament Fabrication (FFF) is arguably the most widely available additive manufacturing technology at the moment. Offering the possibility of producing complex geometries in a compressed product development cycle and in a plethora of materials, it has gradually started to become attractive to multiple industrial segments, slowly being implemented in diverse applications. However, the high anisotropy of parts developed through this technique renders failure prediction difficult. The proper performance of the part, or even the safety of the final user, cannot be guaranteed under demanding mechanical requirements. This problem can be tackled through the development of a failure envelope that allows engineers to predict failure by using the knowledge of the stress state of the part. Previous research by the authors developed a failure envelope for acrylonitrile butadiene styrene (ABS) based, Fused Filament Fabrication (FFF) parts by use of a criterion that incorporates stress interactions. This work validates the first quadrant of the envelope by performing uniaxial tensile tests with coupons produced with a variety of raster angles, creating a combined loading stress state in the localized coordinate system. Results show the safe zone encompassed by the failure envelope proved adequate.

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