In Situ and Laboratory Measured Dynamic Properties of a Marine Clay

Large negative skin friction loads were observed on a 160 ft (49 m) steel pipe test pile floating in marine clay. The test pile was driven, open-ended, on the centerline of a 30 ft (9 m) high granular approach fill on the Quebec Autoroute near Berthierville. Since the installation was made in 1966 the fill has settled 21 in. (53 cm), dragging the pile down with it. Negative skin friction acting along the upper surface of the pile was resisted by positive skin friction acting along the lower end as it penetrated the underlying clay. Under these conditions the pile compressed about [Formula: see text] (2 cm). Analysis of the axial strains indicated that a peak compressive load of 140 t developed at the inflection point between negative and positive skin friction 73 ft (22 m) below the top of the pile. Negative and positive skin friction acting on the upper surface of the pile exceeded the in situ shear strength and approached the drained strength of the soil where excess pore water pressures had dissipated. At the lower end where the positive excess pore pressures were high and relative movement between the pile and the soil was large, the positive skin friction approached the remoulded strength as measured with the field vane. Skin friction was increasing, however, as positive escess pore pressures dissipated.This paper shows that skin friction loads are related to the combination of (a) in situ horizontal effective stresses, (b) horizontal stresses due to embankment loads, and (c) horizontal stresses due to differential settlement of the fill.

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Evaluation of Stiffness and Dynamic Properties of a Mine Shaft Steelwork Structure through In Situ Tests and Numerical Simulations

Energies ◽

10.3390/en14030664 ◽

2021 ◽

Vol 14 (3) ◽

pp. 664

Author(s):

Jacek Jakubowski ◽

Przemysław Fiołek

Keyword(s):

Numerical Simulations ◽

Dynamic Properties ◽

Vertical Motion ◽

Load Test ◽

Mode Shapes ◽

Dynamic Amplification Factor ◽

In Situ Tests ◽

Mine Shaft ◽

Numerical Investigations

A mine shaft steelwork is a three-dimensional frame that directs the vertical motion of conveyances in mine shafts. Here, we conduct field and numerical investigations on the stiffness and dynamic properties of these structures. Based on the design documentation of the shaft, materials data, and site inspection, the steelwork’s finite element model, featuring material and geometric non-linearities, was developed in Abaqus. Static load tests of steelwork were carried out in an underground mine shaft. Numerical simulations reflecting the load test conditions showed strong agreement with the in situ measurements. The validated numerical model was used to assess the dynamic characteristics of the structure. Dynamic linear and non-linear analyses delivered the natural frequencies, mode shapes, and structural response to dynamic loads. The current practices and regulations regarding shaft steelwork design and maintenance do not account for the stiffness of guide-to-bunton connections and disregard dynamic factors. Our experimental and numerical investigations show that these connections provide considerable stiffness, which leads to the redistribution and reduction in bending moments and increased stiffness of the construction. The results also show a high dynamic amplification factor. The omission of these features implicates an incorrect assessment of the design loads and can lead to over- or under-sized structures and ultimately to shortened design working life or failure.

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Managing Flow Induced Vibration in Subsea Jumpers

10.1115/omae2021-61849 ◽

2021 ◽

Author(s):

Rakshith Naik ◽

Yetzirah Urthaler ◽

Scot McNeill ◽

Rafik Boubenider

Keyword(s):

Dynamic Properties ◽

Fatigue Analysis ◽

Management Program ◽

Measured Data ◽

Operating Conditions ◽

Valuable Insight ◽

Fe Model ◽

Flow Induced Vibration ◽

Vibration Measurements

Abstract Certain subsea jumper design features coupled with operating conditions can lead to Flow Induced Vibration (FIV) of subsea jumpers. Excessive FIV can result in accumulation of allowable fatigue damage prior to the end of jumper service life. For this reason, an extensive FIV management program was instated for a large development in the Gulf of Mexico (GOM) where FIV had been observed. The program consisted of in-situ measurement, modeling and analysis. Selected well and flowline jumpers were outfitted with subsea instrumentation for dedicated vibration testing. Finite Element (FE) models were developed for each jumper and refined to match the dynamic properties extracted from the measured data. Fatigue analysis was then carried out using the refined FE model and measured response data. If warranted by the analysis results, action was taken to mitigate the deleterious effects of FIV. Details on modeling and data analysis were published in [5]. Herein, we focus on the overall findings and lessons learned over the duration of the program. The following topics from the program are discussed in detail: 1. In-situ vibration measurement 2. Overall vibration trends with flow rate and lack of correlation of FIV to flow intensity (rho-v-squared); 3. Vibration and fatigue performance of flowline jumpers vs. well jumpers 4. Fatigue analysis conservatism Reliance on screening calculations or predictive FE analysis could lead to overly conservative operational limits or a high degree of fatigue life uncertainty in conditions vulnerable to FIV. It is proposed that in-situ vibration measurements followed by analysis of the measured data in alignment with operating conditions is the best practice to obtain a realistic understanding of subsea jumper integrity to ensure safe and reliable operation of the subsea system. The findings from the FIV management program provide valuable insight for the subsea industry, particularly in the areas of integrity management of in-service subsea jumpers; in-situ instrumentation and vibration measurements and limitations associated with predictive analysis of jumper FIV. If learnings, such as those discussed here, are fed back into design, analysis and monitoring guidelines for subsea equipment, the understanding and management of FIV could be dramatically enhanced compared to the current industry practice.

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All-GFRP footbridge under human-induced excitation

MATEC Web of Conferences ◽

10.1051/matecconf/201926210013 ◽

2019 ◽

Vol 262 ◽

pp. 10013

Author(s):

Beata Stankiewicz ◽

Piotr Górski ◽

Marcin Tatara

Keyword(s):

Dynamic Properties ◽

Complex Problem ◽

In Situ Tests ◽

Critical Range ◽

Reinforced Polymer ◽

Glass Fiber Reinforced ◽

Free Decay ◽

Technical Guide ◽

Pedestrian Excitation

The dynamic behavior of lively footbridge is a complex problem. Recently there were numerous publications and recommendations related to the dynamic nature of footbridge. The complicated procedure which was set in a number of instructions and standards says nothing about actions aimed at avoiding critical frequency range in structure. In the paper, results of dynamic in-situ tests of cable-stayed all-GFRP (Glass Fiber Reinforced Polymer) footbridge are presented. Fiberline Footbridge, located in Kolding city in Denmark, was constructed in 1997 using 12 different pultruded profiles all made of GFRP material. The dynamic characteristics as well as vertical response of the tested footbridge under human excitation are given and discussed. Firstly, in order to estimate the dynamic properties of the footbridge, a series of free-decay responses under human jumping were conducted. The fundamental frequency of the analyzed structure was within a critical range. A methodology for footbridge classification with regard to their dynamic sensitivity was worked out and the correlation between the structure's properties and its dynamic response under pedestrian excitation was formulated. It was found that the analyzed footbridge fulfilled vibration comfort criteria elaborated by technical guide Sétra, however, more restricted acceleration limits suggested by Eurocode were not met.

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Test fill on soft plastic marine clay at Onsøy, Norway

Canadian Geotechnical Journal ◽

10.1139/cgj-2012-0479 ◽

2014 ◽

Vol 51 (1) ◽

pp. 30-50 ◽

Cited By ~ 9

Author(s):

Toralv Berre

Keyword(s):

Soft Clay ◽

Marine Clay ◽

Coefficient Of Consolidation ◽

Geotechnical Parameters ◽

Second Stage ◽

Direct Simple Shear ◽

Rapid Construction ◽

Loading Case ◽

The Town

The test fill at Onsøy, close to the town of Fredrikstad in Norway, was built on a very soft marine clay with in situ vane strength as low as 11 kPa and a plasticity index varying from 34 to 50. The dimensions at the bottom of the long fill were 20 m × 60 m and the height 2.3 m. The fill, as placed, had a computed factor of safety against foundation failure of 1.35 based on in situ vane strength. The fill was allowed to sit for about 3 years (from 1972 to 1975) before it, in a second stage, was brought to failure by raising the height. The main purpose of the first stage was to study the stress–strain–time relationships for the soft clay and compare the values of geotechnical parameters determined by careful laboratory tests with those back-calculated from the observed field behaviour. The test fill foundation was heavily instrumented to measure clay deformations and pore pressures with time. Field observations showed that the Onsøy test fill turned out to be more of a drained loading case than an undrained case in spite of the fairly rapid construction of the fill. Actually, subsequent undrained triaxial and direct simple shear tests strongly indicate that the fill might have failed if less drainage had taken place, i.e., if the drainage paths had been longer and (or) if the coefficient of consolidation had been lower.

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AN INVESTIGATION OF EIGENVALUES OF SHEET METAL UNDERGOING BENDING STRESSES

Jurnal Teknologi ◽

10.11113/jt.v76.5621 ◽

2015 ◽

Vol 76 (8) ◽

Author(s):

Wan Sulaiman Wan Mohamad ◽

Ahmad Azlan Mat Isa ◽

Ahmad Syahmi Abu Talib

Keyword(s):

Natural Frequencies ◽

Dynamic Properties ◽

Modal Parameters ◽

Structural Members ◽

Sheet Metals ◽

Ansys Software ◽

Bending Stresses ◽

Different Shapes ◽

Bent Plates

Accurate prediction of dynamic properties of system is important to ensure the dynamic based design integrity of its member is not compromise. It will reduce or possibly eliminate the possibilities of further modifications in-situ of real system. On this account, this study investigates the modal parameters of the pre-stress sheet metals undergoing bending stresses which is commonly used in practice as structural members. In addressing this issue, three different shapes of sheet metals of similar thickness were studied i.e. straight plate, U-shaped and V-shaped plates. The natural frequencies of these configurations were determined experimentally using the Operational Modal Analysis (OMA). Numerical values were obtained using ANSYS software. Results of these shapes acquired experimentally and numerically were then compared and analyzed. Significant reduction in the eigenvalues of is observed on bent plates both experimentally and numerically as compared to flat plate.

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Identification of the dynamic properties of a reinforced concrete coupled shear wall residential high-rise building

Canadian Journal of Civil Engineering ◽

10.1139/l2012-047 ◽

2012 ◽

Vol 39 (6) ◽

pp. 631-642 ◽

Cited By ~ 2

Author(s):

Natthapong Areemit ◽

Michael Montgomery ◽

Constantin Christopoulos ◽

Agha Hasan

Keyword(s):

Reinforced Concrete ◽

State Of The Art ◽

Dynamic Properties ◽

Shear Wall ◽

Full Scale ◽

Design Parameters ◽

High Rise ◽

Coupled Shear Wall ◽

Current State

As high-rise buildings increase with height and slenderness, they become increasingly sensitive to dynamic vibrations, and therefore the natural frequency of vibration and damping ratio are very important design parameters, as they directly impact the design wind forces. Recent advances in sensing and computing technology have made it possible to monitor the dynamic behaviour of full-scale structures, which was not possible in the past. Full-scale validation of the dynamic properties is useful for high-rise designers to verify design assumptions, especially since recent measurements have shown that damping decreases as the height of the building increases, and in situ damping measurements have been lower than many currently assumed design values, potentially leading to unconservative designs. A 50-storey residential building in downtown Toronto, with a reinforced concrete coupled shear wall lateral load resisting system with outriggers was monitored using current state-of-the-art sensing technologies and techniques to determine, in situ, the dynamic properties under real wind loads. The in situ measurements were then compared with results obtained using current state-of-the-art computer modelling techniques.

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Lightpiers on Friction Piles in Deep Soft Marine Clay

Canadian Geotechnical Journal ◽

10.1139/t71-045 ◽

1971 ◽

Vol 8 (3) ◽

pp. 434-445

Author(s):

J. V. Danys

Keyword(s):

Soil Mechanics ◽

Present Knowledge ◽

Turn Of The Century ◽

Marine Clay ◽

Foundation Design ◽

Pile Testing ◽

Marine Clays ◽

Ice Forces ◽

Novel Design

The deposit of marine clays in Lake St. Peter, Quebec, is as much as 300 ft (91 m) deep. Construction of lightpiers was started shortly after the turn of the century but settlement, tilting, and even failures of the structures occurred and construction of the new piers was not continued. As the navigation season is being extended into winter, the need for lightpiers becomes greater. Apart from the sensitive and very compressible clays, the heavy ice forces made a design very difficult. Introducing novel design features and applying the present knowledge of soil mechanics, two piers were designed and built in 1966 on 157 friction piles each, and two more in 1969. An advance field test of piles in situ was impractical as the structures were in the middle of the lake. Extensive boring and laboratory testing program preceded construction, and the shear strength data of the clay was used for the pile foundation design. Field pile testing confirmed the design assumptions.

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An Experience with Heave of Cast In Situ Expanded Base Piles

Canadian Geotechnical Journal ◽

10.1139/t73-022 ◽

1973 ◽

Vol 10 (2) ◽

pp. 246-260 ◽

Cited By ~ 1

Author(s):

L. S. Brzezinski ◽

L. Shector ◽

H. L. Macphie ◽

H. J. Vander Noot

Keyword(s):

Special Interest ◽

Glacial Till ◽

Load Testing ◽

Marine Clay ◽

Factors Affecting ◽

Concrete Piles ◽

Sensitive Marine Clay ◽

The City

On a project just west of the City of Montreal pile heave was experienced during the installation of groups of cast in situ cased expanded base concrete piles, driven through about 30 ft (9 m) of sensitive marine clay to end bearing in a glacial till formation. The paper describes the observed heave occurrence and discusses factors affecting pile and soil heave. Of special interest is the behavior of the piles during retapping since a number had final refusal elevations which were both high and low with respect to initially installed elevations. Possible explanations for this behavior and considerations pertinent to installation procedure, site inspection, load testing, and specifications for this type of pile are discussed within the paper.

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`NMR Crystallization': in-situ NMR techniques for time-resolved monitoring of crystallization processes

Acta Crystallographica Section C Structural Chemistry ◽

10.1107/s2053229616019811 ◽

2017 ◽

Vol 73 (3) ◽

pp. 137-148 ◽

Cited By ~ 8

Author(s):

Kenneth D. M. Harris ◽

Colan E. Hughes ◽

P. Andrew Williams ◽

Gregory R. Edwards-Gau

Keyword(s):

Solid State ◽

Solid State Nmr ◽

Solid Phase ◽

Dynamic Properties ◽

Time Resolved ◽

Nmr Techniques ◽

Versatile Technique ◽

Crystallization From Solution ◽

In Situ Nmr

Solid-state NMR spectroscopy is a well-established and versatile technique for studying the structural and dynamic properties of solids, and there is considerable potential to exploit the power and versatility of solid-state NMR for in-situ studies of chemical processes. However, a number of technical challenges are associated with adapting this technique for in-situ studies, depending on the process of interest. Recently, an in-situ solid-state NMR strategy for monitoring the evolution of crystallization processes has been developed and has proven to be a promising approach for identifying the sequence of distinct solid forms present as a function of time during crystallization from solution, and for the discovery of new polymorphs. The latest development of this technique, called `CLASSIC' NMR, allows the simultaneous measurement of both liquid-state and solid-state NMR spectra as a function of time, thus yielding complementary information on the evolution of both the liquid phase and the solid phase during crystallization from solution. This article gives an overview of the range of NMR strategies that are currently available for in-situ studies of crystallization processes, with examples of applications that highlight the potential of these strategies to deepen our understanding of crystallization phenomena.

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