Behaviors of a Very Large Floating Structure Supported With Dolphins Under Earthquake Loading

2003 ◽  
Author(s):  
Yoshiyasu Watanabe
Keyword(s):  
Elastic Plate ◽  
Time History ◽  
Type Structure ◽  
Earthquake Loading ◽  
Rigid Plate ◽  
Floating Structure ◽  
Floating Structures ◽  
Reaction Forces ◽  
Time History Response ◽  
Very Large Floating Structures

In recent years, tremendous research efforts have been directed toward developing very large floating structures (VLFSs) for the purposes of airports, terminals etc. on the sea to utilize ocean space. There is a VLFS which has a pontoon type structure supported with many dolphins and it is important to investigate sufficiently the behaviors of such VLFSs under earthquake loading, because large reaction forces will be exerted on the dolphins and fenders that connect the dolphins and the floating structure. This paper reports the results of the time history response analyses of a VLFS supported with dolphins with varying the period and velocity of the applied sinusoidal waves as an earthquake loading when gaps between fenders and dolphins are equal to zero. In the analyses, the floating structure supported with dolphins is modeled as a horizontally elastic plate and a rigid plate both supported with springs and dashpots through gap elements.

Behaviors of a Very Large Floating Structure Supported With Dolphins Under Earthquake Loading: The Second Report — In Cases of Actual Earthquake Wave and Existence of Gaps Between Fenders and Dolphins

2006 ◽  
Author(s):  
Yoshiyasu Watanabe
Keyword(s):  
Time History ◽  
Preceding Paper ◽  
Type Structure ◽  
Earthquake Loading ◽  
Rigid Plate ◽  
Floating Structure ◽  
Floating Structures ◽  
Reaction Forces ◽  
Time History Response ◽  
Very Large Floating Structures

In recent years, tremendous research efforts have been directed toward developing very large floating structures (VLFSs) for the purposes of airports, terminals etc. on the sea to utilize ocean space. There is a VLFS which has a pontoon type structure supported with many dolphins and it is important to investigate sufficiently the behaviors of such VLFS under earthquake loading, because large reaction forces will be exerted on the dolphins and fenders that connect the dolphins and the floating structure. The preceding paper reported the behaviors of the floating structure, fenders and dolphins obtained from the time history response analyses of the structure with varying the period and velocity of the sinusoidal earthquake wave, when the horizontal rigidity of the floating structure was elastic and rigid and when the gaps between the fenders and dolphins were assumed to be zero. This paper reports, succeeding to the preceding paper, the results of the time history response analyses of a VLFS supported with 49 dolphins with varying the period and velocity of the applied actual earthquake wave in both cases where gaps between the fenders and dolphins are equal to zero and non-zero. In the analyses, the floating structure supported with dolphins is modeled as both a horizontally elastic and rigid plate supported with linear springs and dashpots through gap elements.

Two-Dimensional Hydroelastic Analysis of Very Large Floating Structures

1992 ◽  
Vol 29 (01) ◽  
pp. 13-24
Author(s):  
Xiling Che ◽  
Dayun Wang ◽  
Minglun Wang ◽  
Yingfan Xu
Keyword(s):  
Deformable Body ◽  
Vertical Direction ◽  
Offshore Structures ◽  
Integrated System ◽  
Flexible Beam ◽  
Two Dimensional ◽  
Floating Structure ◽  
Floating Structures ◽  
Strip Theory ◽  
Very Large Floating Structures

We have reached a stage at which we are capable of building very large floating structures to meet the steadily increasing needs of ocean resource utilization or to fulfill some special industrial or civil purpose. When such a structure is large enough, its behavior in waves may be substantially different from that of ordinary offshore structures due to low resonant frequencies of the deformable body, and its analysis may require different techniques. In this paper, a two-dimensional hydroelastic theory is applied to a very large floating structure that may be multimodule and extend in the longitudinal direction. A revised strip theory is employed to analyze the hydrodynamic coefficients, but some modifications are introduced to allow for multibody cross sections. The structure is considered to be a flexible beam responding to waves in the vertical direction. Numerical examples are presented with reference to an integrated system of semisubmersibles. A simple model for engineering estimation is also presented.

A Numerically Efficient Method for Analysis of Very Large Articulated Floating Structures

1998 ◽  
Vol 42 (03) ◽  
pp. 174-186
Author(s):  
C. J. Garrison
Keyword(s):  
Hydrodynamic Interaction ◽  
Near Field ◽  
Three Dimensional ◽  
Computational Effort ◽  
Floating Structure ◽  
Complete Structure ◽  
Field Interaction ◽  
Floating Structures ◽  
Computing Effort ◽  
The Individual

A method is presented for evaluation of the motion of long structures composed of interconnected barges, or modules, of arbitrary shape. Such structures are being proposed in the construction of offshore airports or other large offshore floating structures. It is known that the evaluation of the motion of jointed or otherwise interconnected modules which make up a long floating structure may be evaluated by three dimensional radiation/diffraction analysis. However, the computing effort increases rapidly as the complexity of the geometric shape of the individual modules and the total number of modules increases. This paper describes an approximate method which drastically reduces the computational effort without major effects on accuracy. The method relies on accounting for hydrodynamic interaction effects between only adjacent modules within the structure rather than between all of the modules since the near-field interaction is by far the more important. This approximation reduces the computational effort to that of solving the two-module problem regardless of the total number of modules in the complete structure.

A statistical study on artificially generated earthquake records

1976 ◽  
Vol 3 (1) ◽  
pp. 11-19
Author(s):  
W. K. Tso ◽  
B. P. Guru
Keyword(s):  
Statistical Study ◽  
Spectral Response ◽  
Flexible Structures ◽  
Time History ◽  
Maximum Response ◽  
Response Analysis ◽  
Seismic Region ◽  
Natural Period ◽  
Earthquake Records ◽  
Time History Response

A statistical study has been done to investigate (i) the variation of spectral responses of structures due to artificially generated earthquake records with identical statistical properties, (ii) the effect of duration of strong shaking phase of artificial earthquakes on the response of structures, and (iii) the number of earthquake records needed for time-history response analysis of a structure in a seismic region. The results indicate that the flexible structures are more sensitive to the inherent statistical variations among statistically identical earthquake records. Consequently several records must be used for time-history response analysis. A sample of eight or more records appear to provide a good estimate of mean maximum response. The duration of strong shaking can significantly affect the maximum response. Based on the results, it is suggested that for the purpose of estimating peak response, the strong shaking duration of the input earthquake motion should be at least four times the natural period of the structure. The maximum responses due to statistically identical ground motion records are observed to fit approximately the type 1 extreme value distribution. Thus, it is rationally possible to choose a design value based on the mean, standard deviation of the spectral response values and tolerable probability of exceedance.

Dynamic Simulation of Piping System Around Safety Valve for Closed Discharge System

2011 ◽  
Author(s):  
Yoshiaki Sakamoto ◽  
Hisao Izuchi ◽  
Naoko Suzuki
Keyword(s):  
Dynamic Simulation ◽  
Safety Valve ◽  
Flow Direction ◽  
Reaction Force ◽  
Time History ◽  
Piping System ◽  
Discharge System ◽  
Fluid Transient ◽  
Short Period ◽  
Reaction Forces

Reaction force of safety valves acting to the piping system is one of key factors for the piping system design around the safety valves. In case of open discharge system, it is well known that a large reaction force acts to the piping corresponding to the fluid momentum force at the atmospheric discharge. On the other hand, reaction forces for closed discharge system may be relatively small since the forces acting to the adjacent two points with flow direction change such as elbows and tees are balanced within very short period. However, large reaction forces may act as a result of unsteady flow just after the initial activation of the safety valve. API RP520 mentioned that a complex time history analysis of the piping system around the safety valves may be required to obtain the transient forces. This paper explains a method of a comprehensive dynamic simulation of piping system around safety valves taking interaction among the valve disc motion, the fluid transient for compressible flow and the piping structural dynamics into account. The simulation results have good agreement with the experimental data. The effectiveness of this method is confirmed throughout an application to actual piping system around safety valves.

Settlement Analysis of Soft Ground Replacement under Earthquake

2012 ◽  
Vol 166-169 ◽  
pp. 2379-2382 ◽  
Author(s):  
Zhong Liu ◽  
Shu Hong An ◽  
Rong Hong Yuan ◽  
Fei Li
Keyword(s):  
Time History ◽  
Vertical Displacement ◽  
Response Analysis ◽  
Soft Ground ◽  
Positive Contribution ◽  
Foundation Soil ◽  
Time History Response ◽  
Dynamic Time ◽  
Settlement Analysis ◽  
Different Thickness

The dynamic time-history response analysis method was employed to analyze the dynamic response of soft ground replacement with sand-gravel cushion. The deformation distribution of soft ground replacement with different thickness sand-gravel cushion was investigated under seismic wave. The results reveal that the bearing and asti-deformation capacity can be improved effectively for replacement sand-gravel cushion under earthquake loads by increasing the thick of cushion. The vertical displacement of foundation soil decreases gradually with the increase of the thick of cushion. The practice shows that replacement sand-gravel cushion provides a positive contribution to the aseismic effect of foundation soils mass. The present research can provide some references to similar projects.

Sign in / Sign up

Export Citation Format

Share Document