The Experimental Observation of the Prestress Forces in the Structural Elements of a Tension Fabric Structure

2013 ◽  
Vol 486 ◽  
pp. 189-194 ◽  
Author(s):  
Petr Fajman ◽  
Michal Polak ◽  
Jiří Maca ◽  
Tomáš Plachy
Keyword(s):  
Experimental Observation ◽  
Measurement System ◽  
Geometrical Nonlinearity ◽  
Structural Elements ◽  
Frequency Method ◽  
Temperature Changes ◽  
Fabric Structure ◽  
Cable Forces ◽  
Non Destructive

The periodic experimental observation of the prestress forces in some selected structural elements of the tension fabric structure is mentioned in this paper. The described experiment was focused to the tension fabric roof which covers the tram stop K Barrandovu in Prague. So far the observation was performed three times and it was every time aimed on three types of basic structural elements support cables anchored to the ground, edge cables placed in a fabric pocket and fabric membranes. The used non-destructive experimental procedures are based on the geometrical nonlinearity and the frequency method, the applied measurement system was developed by authors. The dependence of cable forces on temperature changes can be found out from the obtained results.

Vibration-Based Crack Detection in L-Frames

2014 ◽  
Vol 658 ◽  
pp. 261-268
Author(s):  
Jean Louis Ntakpe ◽  
Gilbert Rainer Gillich ◽  
Florian Muntean ◽  
Zeno Iosif Praisach ◽  
Peter Lorenz
Keyword(s):  
Strain Energy ◽  
Crack Detection ◽  
Natural Frequencies ◽  
Vibration Modes ◽  
Structural Elements ◽  
Element Analysis ◽  
Accurate Localization ◽  
Mathematical Expressions ◽  
Measurement Results ◽  
Non Destructive

This paper presents a novel non-destructive method to locate and size damages in frame structures, performed by examining and interpreting changes in measured vibration response. The method bases on a relation, prior contrived by the authors, between the strain energy distribution in the structure for the transversal vibration modes and the modal changes (in terms of natural frequencies) due to damage. Using this relation a damage location indicator DLI was derived, which permits to locate cracks in spatial structures. In this paper an L-frame is considered for proving the applicability of this method. First the mathematical expressions for the modes shapes and their derivatives were determined and simulation result compared with that obtained by finite element analysis. Afterwards patterns characterizing damage locations were derived and compared with measurement results on the real structure; the DLI permitted accurate localization of any crack placed in the two structural elements.

Development of a neutron measurement system in unified non-destructive assay for the PRIDE facility

2013 ◽  
Vol 63 (11) ◽  
pp. 2080-2084 ◽  
Author(s):  
Hee Seo ◽  
Se-Hwan Park ◽  
Byung-Hee Won ◽  
Seong-Kyu Ahn ◽  
Hee-Sung Shin ◽  
...  
Keyword(s):  
Measurement System ◽  
Neutron Measurement ◽  
Non Destructive

Study of the residual imperfections using methods of probability theory

2021 ◽  
Vol 87 (9) ◽  
pp. 44-49
Author(s):  
D. A. Kuzmin
Keyword(s):  
Probability Theory ◽  
Generalized Equation ◽  
Structural Elements ◽  
Non Destructive Testing ◽  
Operational Control ◽  
Destructive Testing ◽  
Control Procedures ◽  
Non Destructive ◽  
A Current

Discontinuities in the products that occur during manufacture, mounting or upon operation can be missed during non-destructive testing which do not provide their complete detectability at a current level of the technology. Therefore, it is necessary to take into account that certain structural elements may have discontinuities of significant dimensions. We present the results of using the methods of probability theory in studying the residual imperfections that remains in the structure after non-destructive control and repair of the previously identified defects. We used the results of operational control of units carried out by ultrasonic and radiographic methods. We present a method for determining a multifactorial coefficient that takes into account the detectability of defects, the number of control procedures and the errors in the instrumentation and methodological support, as well as a generalized equation for the probability distribution of detecting discontinuities. The developed approach provides assessing of the level of damage to the studied objects, their classification proceeding from the quantitative data and determination of the values of postulated discontinuities for deterministic calculations. The results obtained can be used to improve the methods of monitoring NPP facilities.

scholarly journals Research on Temperature Compensation Method in Crankshaft Online Measurement System

2021 ◽  
Vol 11 (16) ◽  
pp. 7558
Author(s):  
Tingting Gu ◽  
Xiaoming Qian ◽  
Peihuang Lou
Keyword(s):  
Ambient Temperature ◽  
Measurement System ◽  
Temperature Compensation ◽  
Compensation Method ◽  
Displacement Sensor ◽  
Online Measurement ◽  
High Precision Measurement ◽  
Temperature Changes ◽  
Dragonfly Algorithm ◽  
Measuring Machine

The crankshaft online measurement system has realized the full inspection function with fast beats, at the same time it requires for high-precision measurement. Considering the effect of ambient temperature and temperature changes on measuring machine, the calibration part, the measured crankshaft and displacement sensor, a temperature compensation method is proposed. Firstly, relationship between calibration part and ambient temperature can be get through the zero calibration. Then use the material properties to obtain compensation values of the calibration part and the measured crankshaft part at different temperatures. Finally, the compensation parameters for displacement sensor can be obtained through the BP algorithm. The improved dragonfly algorithm (DA) is used to optimize the parameters of BP neural network algorithm. Experiments verify the effectiveness of IDA-BP for LVDT in temperature compensation. After temperature compensation, the error range of main journal radius is reduced from 0.0156 mm to 0.0028 mm, the residual error decreased from −0.0282 mm~+0.0018 mm to −0.0058 mm~−0.0008 mm. The influence of temperature changes on the measurement is reduced and measurement accuracy is improved through the temperature compensation method. The effectiveness of the method is proved.

scholarly journals Proposta de consolidação estrutural da Igreja de Nossa Senhora do Monte do Recôncavo

2014 ◽  
Vol 4 (3) ◽  
pp. 228-236
Author(s):  
M. Oliveira ◽  
R. Muñoz ◽  
A. Magalhães
Keyword(s):  
Eighteenth Century ◽  
Historic Buildings ◽  
Structural Elements ◽  
Roof Structure ◽  
Intervention Measures ◽  
Wood Beams ◽  
Non Destructive

RESUMOA Igreja de Nossa Senhora do Monte, construída na Bahia, Brasil, provavelmente no início do século XVIII, está localizada em São Francisco do Conde, no Recôncavo Baiano. Atualmente, o edifício encontra-se em estado geral de eversão, principalmente em relação à cobertura e ao desaprumo de paredes. Este trabalho tem como objetivo propor medidas de intervenção patrimonial para estabilização dos referidos elementos construtivos, considerando a manutenção da mesma lógica estrutural existente. Como resultados, serão apresentados: detalhe de reforço do sistema estático das tesouras de linha baixa da nave principal; sumário do projeto de substituição dos atuais barrotes de madeira por vigas metálicas; e detalhe do atirantamento da abóbada do fundo da capela-mor. Ressalta-se a importância deste trabalho de estabilização como metodologia a ser adotada em outras edificações históricas, uma vez que contempla intervenções não destrutivas, relevantes para sítios que contam com patrimônios de significativo valor histórico e cultural.Palavras chave: consolidação; patrimônio; estrutura; reforço.ABSTRACTThe Church of Nossa Senhora do Monte, built in Bahia, Brazil, probably in the eighteenth century, is located in São Francisco do Conde, in the Recôncavo. Currently the building is in a deplorable state of degradation, especially in terms of the roof and stability of the walls. This work proposes intervention measures to stabilize the said structural elements while taking into consideration and respecting the existing structural logic. The following results will be presented: detail of the reinforcement of the wood roof structure of the nave; summary of the project for the replacement of existing wood beams by metal ones; and finally the proposal to repair the vault after the presbytery. This paper emphasizes the importance of this stabilization work as a methodology to be adopted in other historic buildings, since it suggests non-destructive interventions, relevant to sites that have assets of significant historical and cultural value.Keywords: consolidation; heritage; structure; strengthening.

Experimental Evaluation of Tensile Forces in Short Steel Rods

2015 ◽  
Vol 732 ◽  
pp. 333-336 ◽  
Author(s):  
Michal Polak ◽  
Tomáš Plachy
Keyword(s):  
Tensile Force ◽  
String Model ◽  
Beam Model ◽  
Building Structures ◽  
Structural Elements ◽  
Frequency Method ◽  
Natural Modes ◽  
Tensile Forces ◽  
Torsion Springs ◽  
Fixed Beam

There are a lot of structures in building and civil engineering where the significant structural elements are loaded by large tensile forces (e.g. tension bars of building structures). In many practical cases it is important to know the actual value of tensile forces in tensile structural elements for assessment of their reliability. The four experimental techniques are used for determination of tensile forces in practice most often. The vibration frequency method, which is one of them, is very suitable for experiments done only one time or sometimes, especially in cases when the examined structural elements are already activated and the application of an experimental method is necessary in this situation. The experiment described in this paper was focused on the tensile force determination in steel rods, which were very short and relatively stiff. The evaluated tensile forces of the investigated short steel rods were affected by a significant error when only the simplest models (the string model, the simply supported beam and the fixed beam) and measured natural frequencies were applied. In order to precise the determined tensile forces, the theoretical beam model supported by simple supports with torsion springs (“the elastically fixed beam”) and the measured natural modes of the rods had to be necessarily taken into account.

scholarly journals Application of Terrestrial Laser Scanner with an Integrated Thermal Camera in Non-Destructive Evaluation of Concrete Surface of Hydrotechnical Objects

2017 ◽  
Vol 39 (4) ◽  
pp. 35-43 ◽  
Author(s):  
Maria Kowalska ◽  
Janina Zaczek-Peplinska
Keyword(s):  
Laser Scanner ◽  
Concrete Surface ◽  
Terrestrial Laser Scanner ◽  
Thermal Camera ◽  
Concrete Wall ◽  
Temperature Changes ◽  
Thermal Data ◽  
Technical Assessment ◽  
Non Destructive ◽  
Source Of Information

Abstract The authors present possible applications of thermal data as an additional source of information on an object’s behaviour during the technical assessment of the condition of a concrete surface. For the study one of the most recent propositions introduced by Zoller + Fröhlich company was used, which is an integration of a thermal camera with a terrestrial laser scanner. This solution enables an acquisition of geometric and spectral data on the surveyed object and also provides information on the surface’s temperature in the selected points. A section of the dam’s downstream concrete wall was selected as the subject of the study for which a number of scans were carried out and a number of thermal images were taken at different times of the day. The obtained thermal data was confronted with the acquired spectral information for the specified points. This made it possible to carry out broader analysis of the surface and an inspection of the revealed fissure. The thermal analysis of said fissure indicated that the temperature changes within it are slower, which may affect the way the concrete works and may require further elaboration by the appropriate experts. Through the integration of a thermal camera with a terrestrial laser scanner one can not only analyse changes of temperature in the discretely selected points but on the whole surface as well. Moreover, it is also possible to accurately determine the range and the area of the change affecting the surface. The authors note the limitations of the presented solution like, inter alia, the resolution of the thermal camera.

Analytic Methods of Main Cable Initial Curve Calculation in Variable Temperature Field

2010 ◽  
Vol 163-167 ◽  
pp. 307-312
Author(s):  
Xiang Ren
Keyword(s):  
Temperature Field ◽  
Variable Temperature ◽  
Suspension Bridge ◽  
Horizontal Component ◽  
Length Variation ◽  
Calculation Methods ◽  
Initial Curve ◽  
Temperature Changes ◽  
Main Cable ◽  
Cable Forces

In order to study temperature effect on initial curve of main cable, three different temperature models were built about temperature changes of main cable along span direction, and iteration calculation methods to find initial curve of main cable in variable temperature field was proposed based on the theory that the length of non-stress wire strand is persistence in unloaded cable station and construction completion station. The catenary equation in variable temperature field was deduced and the suspender length variation as well as horizontal component of cable forces were calculated based on the catenary equation. Taking some suspension bridge for an example, suspender length variation, horizontal component of the cable forces and node coordinate under three different temperature models were calculated by iteration calculation methods.

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