Impulse Response Techniques for Floating Bridges and Breakwaters Subject to Short-Crested Seas

1984 ◽  
Vol 21 (03) ◽  
pp. 270-276
Author(s):  
Bruce L. Hutchison
Keyword(s):  
Bending Moments ◽  
Stochastic Excitation ◽  
Linear Superposition ◽  
Wave Fields ◽  
Directional Spectrum ◽  
Directional Wave ◽  
Floating Bridges ◽  
Six Degree Of Freedom ◽  
Proper Interpretation

A frequency domain technique is presented which permits the determination of the complete covariance matrix for the six degree-of-freedom motions, and the nodal shears and bending moments, for floating bridges and breakwaters. The structures are modeled as a series of interacting modules subject to stochastic excitation from directional short-crested seas. The two principal methods of analyzing such problems— linear superposition of responses to long-crested components of the directional spectrum, and beam sea responses modified by a scalar coherency function—are carefully examined. It is shown that, under proper interpretation, the two methods are logically consistent. The paper concludes by examining two types of coherency processes in directional wave fields.

Determination of collapse moment of different angled pipe bends with initial geometric imperfection subjected to in-plane bending moments

2021 ◽  
pp. 095440622199640
Author(s):  
Manish Kumar ◽  
Pronab Roy ◽  
Kallol Khan
Keyword(s):  
Finite Element ◽  
Cross Section ◽  
Circular Cross Section ◽  
Initial Imperfection ◽  
Bend Angle ◽  
Bending Moments ◽  
Element Analysis ◽  
Geometric Imperfection ◽  
Initial Geometric Imperfection

From the recent literature, it is revealed that pipe bend geometry deviates from the circular cross-section due to pipe bending process for any bend angle, and this deviation in the cross-section is defined as the initial geometric imperfection. This paper focuses on the determination of collapse moment of different angled pipe bends incorporated with initial geometric imperfection subjected to in-plane closing and opening bending moments. The three-dimensional finite element analysis is accounted for geometric as well as material nonlinearities. Python scripting is implemented for modeling the pipe bends with initial geometry imperfection. The twice-elastic-slope method is adopted to determine the collapse moments. From the results, it is observed that initial imperfection has significant impact on the collapse moment of pipe bends. It can be concluded that the effect of initial imperfection decreases with the decrease in bend angle from 150∘ to 45∘. Based on the finite element results, a simple collapse moment equation is proposed to predict the collapse moment for more accurate cross-section of the different angled pipe bends.

Error analyses of a Multi-Input-Multi-Output cantilever beam test

2021 ◽  
pp. 107754632110337
Author(s):  
Arup Maji ◽  
Fernando Moreu ◽  
James Woodall ◽  
Maimuna Hossain
Keyword(s):  
Transfer Function ◽  
Frequency Domain ◽  
Cantilever Beam ◽  
Transfer Functions ◽  
Linear Superposition ◽  
Transfer Function Matrix ◽  
Error Analyses ◽  
Pseudo Inverse ◽  
Function Matrix

Multi-Input-Multi-Output vibration testing typically requires the determination of inputs to achieve desired response at multiple locations. First, the responses due to each input are quantified in terms of complex transfer functions in the frequency domain. In this study, two Inputs and five Responses were used leading to a 5 × 2 transfer function matrix. Inputs corresponding to the desired Responses are then computed by inversion of the rectangular matrix using Pseudo-Inverse techniques that involve least-squared solutions. It is important to understand and quantify the various sources of errors in this process toward improved implementation of Multi-Input-Multi-Output testing. In this article, tests on a cantilever beam with two actuators (input controlled smart shakers) were used as Inputs while acceleration Responses were measured at five locations including the two input locations. Variation among tests was quantified including its impact on transfer functions across the relevant frequency domain. Accuracy of linear superposition of the influence of two actuators was quantified to investigate the influence of relative phase information. Finally, the accuracy of the Multi-Input-Multi-Output inversion process was investigated while varying the number of Responses from 2 (square transfer function matrix) to 5 (full-rectangular transfer function matrix). Results were examined in the context of the resonances and anti-resonances of the system as well as the ability of the actuators to provide actuation energy across the domain. Improved understanding of the sources of uncertainty from this study can be used for more complex Multi-Input-Multi-Output experiments.

Kinematic and Workspace Modelling of a 6-PUS Parallel Mechanism

2018 ◽  
Author(s):  
Jérôme Landuré ◽  
Clément Gosselin
Keyword(s):  
Kinematic Analysis ◽  
Parallel Mechanism ◽  
Inverse Kinematic ◽  
Degree Of Freedom ◽  
Accurate Description ◽  
Transmission Ratio ◽  
Inverse Kinematic Problem ◽  
Jacobian Matrices ◽  
Six Degree Of Freedom

This article presents the kinematic analysis of a six-degree-of-freedom six-legged parallel mechanism of the 6-PUS architecture. The inverse kinematic problem is recalled and the Jacobian matrices are derived. Then, an algorithm for the geometric determination of the workspace is presented, which yields a very fast and accurate description of the workspace of the mechanism. Singular boundaries and a transmission ratio index are then introduced and studied for a set of architectural parameters. The proposed analysis yields conceptual architectures whose properties can be adjusted to fit given applications.

Design Charts for Symmetrical Ring Girders

1957 ◽  
Vol 24 (1) ◽  
pp. 144-147
Author(s):  
G. P. Fisher
Keyword(s):  
Energy Analysis ◽  
Bending Moment ◽  
Bending Moments ◽  
Bending Energy ◽  
Normal Loading ◽  
Critical Design ◽  
Design Charts ◽  
Ring Location

Abstract Charts, based on classical bending-energy analysis, are presented for the determination of critical design moments in symmetrical ring girders varying in shape from circular through round to sharp-cornered rings. The girders are subjected to uniform normal loading in the plane of the ring. Location and magnitude of all critical bending moments are given, from which the maximum bending moment is easily selected.

Determination of the Workspace of 6-DOF Parallel Manipulators

1989 ◽  
Author(s):  
C. Gosselin
Keyword(s):  
Parallel Manipulator ◽  
Graphical Representation ◽  
Three Dimensional ◽  
Parallel Manipulators ◽  
Degree Of Freedom ◽  
Geometrical Properties ◽  
Cartesian Space ◽  
Six Degree Of Freedom

Abstract This paper presents an algorithm for the determination of the workspace of parallel manipulators. The method described here, which is based on geometrical properties of the workspace, leads to a simple graphical representation of the regions of the three-dimensional Cartesian space that are attainable by the manipulator with a given orientation of the platform. Moreover, the volume of the workspace can be easily computed by performing an integration on its boundary, which is obtained from the algorithm. Examples are included to illustrate the application of the method to a six-degree-of-freedom fully-parallel manipulator.

scholarly journals Problematic aspects of registering ecological land-use in the Real Estate Cadastre

2019 ◽  
Vol 86 ◽  
pp. 00007
Author(s):  
Piotr Benduch ◽  
Agnieszka Pęska-Siwik ◽  
Paweł Hanus
Keyword(s):  
Land Use ◽  
Real Estate ◽  
Surface Area ◽  
Statistical Data ◽  
Land Uses ◽  
Legal Regulations ◽  
The Real Estate ◽  
Proper Interpretation ◽  
Informational System

Land-use as a part of the earth’s surface used in an unitary manner, constitutes as one of the objects of Real Estate Cadastre in Poland. This register gathers data concerning actual grounds status, buildings and premises. Cadastre is carried out in an informational system on the basis of Geodetic and Cartographic Law and its implementing act. The contents of mentioned legal regulations are very general in terms of capturing and revealing data on ecological land-use. The rules are also related to environmental protection law. It often makes its proper interpretation difficult. In this article, the study aimed to systematize information about recording ecological land-uses in Polish Real Estate Cadastre has been performed. Practical and legal solutions concerning determination of the ecological land-uses coverage have been presented. The authors evaluate an order of individual activities leading to ecological land-use disclosure in cadastral database. The consequences and constraints in enforcing the ownership to land property or its parts where ecological land-use was allocated are analyzed as well. The statistical data in the scope of number and surface area of ecological land-uses in individual provinces have also been demonstrated.

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