Measurement of in situ dynamic properties in relation to geologic conditions

1979 ◽  
pp. 201-214 ◽  
Author(s):  
T. L. DOBECKI
Keyword(s):  
Dynamic Properties

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

Energies ◽  
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.

Managing Flow Induced Vibration in Subsea Jumpers

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.

scholarly journals All-GFRP footbridge under human-induced excitation

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.

In Situ and Laboratory Measured Dynamic Properties of a Marine Clay

2017 ◽  
Author(s):  
Albert R. Kottke ◽  
Andrew Keene ◽  
Yaning Wang ◽  
Boonam Shin ◽  
Kenneth H. Stokoe ◽  
...  
Keyword(s):  
Dynamic Properties ◽  
Marine Clay

AN INVESTIGATION OF EIGENVALUES OF SHEET METAL UNDERGOING BENDING STRESSES

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.

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

2012 ◽  
Vol 39 (6) ◽  
pp. 631-642 ◽  
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.

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

2017 ◽  
Vol 73 (3) ◽  
pp. 137-148 ◽  
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.

Three-dimensional dynamic response analyses of Cogswell Dam

1995 ◽  
Vol 32 (3) ◽  
pp. 452-464 ◽  
Author(s):  
Ross W. Boulanger ◽  
Jonathan D. Bray ◽  
Scott M. Merry ◽  
Lelio H. Mejia
Keyword(s):  
Dynamic Response ◽  
Dynamic Properties ◽  
Three Dimensional ◽  
Strong Motion ◽  
Topographic Effects ◽  
Embankment Dams ◽  
Rockfill Materials ◽  
Wide Range ◽  
Sierra Madre

The recorded strong motions at Cogswell Dam during the 1987 Whittier Narrows and 1991 Sierra Madre earthquakes provide a valuable opportunity to evaluate the applicability of established engineering procedures for evaluating the dynamic response of dams with highly three-dimensional geometries. In addition, these records provide an opportunity to back-calculate the dynamic properties of rockfill materials, which cannot be easily measured in the laboratory or in situ. Peak transverse crest accelerations of 0.15 g and 0.42 g were recorded during the Whittier Narrows and Sierra Madre earthquakes, respectively. Combined with analyses of the trailing portions of these strong motion records, the field data cover a wide range of induced shear strains. Two-dimensional and three-dimensional dynamic response analyses were performed using established engineering procedures, and their results are compared with the recorded responses. Dam–canyon interaction and topographic effects appear to have influenced the seismic response of the dam significantly. Estimates of the in situ dynamic rockfill properties, including the modulus degradation relationship, are presented. Key words : rockfill, dynamic properties, embankment dams, earthquake response.

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