P. H. Arundas ¹, U. K. Dewangan ¹

Affiliations
1 Department of Civil Engineering, National Institute of Technology, Raipur, IN

Abstract

Objectives: In this paper non destructive tests are used to find the location of multiple cracks in the cantilever beam. Methods/ Analysis: The impact echo test along with Ultrasonic Pulse Velocity (UPV) test is used to find the crack locations. These tests are conducted on cantilever beam having two cracks at different positions. The frequency spectrum is recorded from the impact echo test. While the ultrasonic pulse time is recorded from ultrasonic pulse velocity test. A MATLAB based code is used to find out the dominant frequency of the sound signals corresponding to each impact echo test. The ultrasonic pulse velocities are calculated from the travel time and the distance between the transducers. Findings: It was found that the frequency values are increasing when the cracks move away from the fixed end of the cantilever beam since the frequency ratio increases when the distance of the crack increases from fixed end (based on Equation 3). Ultrasonic pulse velocity also increases since the distance between the transducers of the UPV equipment decreases when the location of crack changes. Applications/Improvements: From the values of frequency and ultrasonic pulse velocity, mathematical expressions of crack location are developed. The developed expressions are tested on the cantilever beam to find the crack locations in a laboratory model.

Keywords

Crack Location, Impact Echo Test, MATLAB, Multiple Cracks, Non Destructive Tests, Ultrasonic Pulse Velocity Test.

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P. H. Arundas ¹, U. K. Dewangan ¹

Affiliations
1 Department of Civil Engineering, National Institute of Technology, Raipur - 492010, Chhattisgarh, IN

Abstract

Objectives: This paper presents a health monitoring criteria development aspect based on the frequency response spectrum under axial compressive load on wooden samples. Methods/Statistical Analysis: The compression tests are performed on different wooden specimens as per IS:1708 (Part VIII and IX):1986. The impact echo test is conducted at certain load intervals under increased compressive load and the frequency spectrum was monitored. A MATLAB based code is used to calculate the dominant frequency values of the sound signals corresponding to each impact echo test. The graphs for frequency and compressive load are plotted for different samples. Findings: Interesting conclusions were obtained from the frequency plots under compressive load before failure and after failure. It was observed that loading decreases the frequency values. But at the point of initial major crack, frequency was increased due to length reduction. Applications/Improvements: A health monitoring criteria can be developed based on the frequency response trends by observing these increased value of frequency when tested on the wooden samples. The damaged and undamaged state were predicted successfully.

Keywords

Compressive Load, Frequency Response Spectrum, Health Monitoring, Impact Echo Test, MATLAB.

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K. K. Riyas Moideen ¹, U. K. Dewangan ¹

Affiliations
1 Department of Civil Engineering, National Institute of Technology, Raipur - 492010, Chhattisgarh, IN

Abstract

Background/Objectives: To examine the effect of material nonlinearity of mild steel on the total deflection of beams and frames. Method of Analysis: In the linear analysis, value of Young’s modulus is same in all over the analysis, hence the load-deflection plot is also linear, whereas in material nonlinear analysis of structures the elastic modulus is constant upto yield stress and it decreases thereafter. In the present study linear and material nonlinear analysis of beams and frames are carried out using ANSYS mechanical APDL software. The linear deflection of the structures is also computed using a finite element based MATLAB code. Material nonlinearity is incorporated using bilinear stress-strain curves with tangent modulus E/65. E is the elastic modulus of the material. It has been found that the tangent modulus of stress-stress curve of mild steel is more resemble to E/3, so this value is also considered separately for the nonlinear analysis. In this paper cantilever beam with an end load and a two storey building frame with horizontal load is considered with above tangent modulus. The loads are applied incrementally, deflection and stress at each load increment is computed. Findings: In linear analysis the full strength of the material is not utilized and it is assumed that material will fail after reaching the yield stress. In material nonlinear analysis the strain hardening property is considered by taking the tangent modulus after the yield stress. The linear analysis is giving linear variation of deflection and stress with respect to load, but for material nonlinear (bilinear) the deflection and stress will be same as that of linear upto yield point and after that the deflection is found more and stress value found less than that of linear values. Application/Improvements: For the economical usage of materials nonlinear analysis is preferred over the linear analysis, because it is giving the actual behavior of structures and we are utilizing the maximum capacity of the material.

Keywords

Bilinear Stress-strain Curve, Finite Element Method, Linear Analysis, Load-Deflection Behavior, Nonlinear Analysis.

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K. K. Riyas Moideen ¹, U. K. Dewangan ¹

Affiliations
1 Department of Civil Engineering, National Institute of Technology Raipur, Opp. Ayurvedic College, GE Road, Raipur - 492010, Chattisgarh, IN

Abstract

Background/Objectives: The proper analysis of beam is important for understanding the actual behavior and economical use of sections. The prime objective of this research paper is the comparative study of linear and geometric nonlinear load-deflection behavior of beams under vertical load. Methods/Statistical Analysis: In geometrically linear analysis, the equations of equilibrium are formulated before the deformation state and are not updated with the deformation, while in geometrical nonlinear analysis updated stiffness matrix is used at each load increment. In this study a three noded steel beam is formulated for linear and nonlinear analysis. The incremental central point load is applied to the beam. Linear and geometrically nonlinear deflection is computed for the beams. Three beams of the same length were taken for analysis, but having different thickness&support conditions. The linear and geometrical nonlinear load-deflection behavior is studied using STAAD PRO. The linear deflection is also computed by developing a finite element based code using MATLAB. Findings:The results obtained after the analysis of beams deformations are quite interesting. The percentage variation of linear and geometrical nonlinear deflection is very high for beam with lesser thickness. It was found that the support conditions also affect variation of deflection for the linear and nonlinear cases. The variation between linear and geometrical nonlinear deflection of beam is negligible when the ends are fixed. But for the same beam with simply supported end conditions the defections were found having variation up to 37 percentages. Geometrical nonlinearity is more when the load is very high and section is thin. At the initial stages of loading behavior of beam is linear only and it behaves nonlinear when we go for higher loads. Application/Improvements: Linear analysis is only an approximation, so for understanding the actual behavior of the structure and for the economical/optimized usage of sections it is suggested to go for nonlinear analysis.

Keywords

Finite Element Method, Geometrical Nonlinear Analysis, Linear Analysis, Load-Deflection Behavior, STAAD PRO, MATLAB.

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P. H. Arundas ¹, U. K. Dewangan ¹

Affiliations
1 Department of Civil Engineering, National Institute of Technology, Raipur - 492010, Chhattisgarh, IN

Abstract

Background/Objectives: This paper presents development of non destructive testing methods for calculating the compressive strength of concrete. Methods/Statistical Analysis: The compression tests along with impact echo tests and Ultrasonic Pulse Velocity (UPV) tests are carried out at different load which was the increased compressive loadat certain interval on concrete cubes of various mixes. The frequency spectrum and the ultrasonic pulse time are recorded. A MATLAB based code is used to calculate the maximum frequency of the sound signals corresponding to each impact echotest under a certain compressive load. The graphs for frequency and compressive load are plotted. The graph for ultrasonic pulse velocity on the various compressive load are also plotted for different samples of concrete. Findings: Important observations are found from the graphs of frequency and ultrasonic pulse velocity. The frequency and ultrasonic pulse velocity peak values were continuously found decreasing under the increase in the compressive load. After initial crack formation with the further increase in load the frequency was found increasing trend but with showing a small increased value. Whereas the ultrasonic pulse velocity was found reducing trend in nature. These plots give the clear indication of crack formation. Application/Improvements: These graphs are used for comparison of variation of frequency and ultrasonic pulse velocity to predict the undamaged and damaged state of concrete under compression. A mathematical expression is developed between compressive strength, frequency and ultrasonic pulse velocity.

Keywords

Compressive Load, Frequency Spectrum, Impact Echo Test, MATLAB, Non Destructive Testing, Ultrasonic Pulse Velocity

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K. K. Riyas Moideen ¹, U. K. Dewangan ¹

Affiliations
1 Department of Civil Engineering, National Institute of Technology Raipur, G.E Road, Raipur – 492001, Chhattisgarh, IN

Abstract

Background/Objectives: To study about different models used for nonlinear analysis of stainless steel and to find an optimized equation for the nonlinear strain hardening exponent for stainless steel material. Methods/Statistical Analysis: There are lots of models proposed for analyzing the nonlinear behavior of the stainless steel. The base of all the models are model suggested by¹. But there exist lots of uncertainties in Ramberg Osgood suggested equation for nonlinear strain hardening parameter, which is using proof stress at 0.01 and 0.2 strains. In 2014 ²also proposed an equation for computing the nonlinear strain hardening parameter, which is using proof stress at 0.05 and 0.2 strains. The percentage error is less when compared with the Ramberg-Osgood equation, but still it shows some errors. In this work a new equation for nonlinear strain hardening model is developed using nonlinear regression technique with an optimized algorithm based on the comparative study of the above two models. Findings: A new equation for computing the nonlinear strain hardening parameter for stainless steel was proposed. The presently proposed equation for nonlinear strain hardening parameter is calculated by using proof stress corresponding to 0.01, 0.05 and 0.2 strains, which is showing excellent matching with the computer optimized values of nonlinear strain hardening exponent. The percentage errors with respect to the computer optimized values are very less when compared other models percentage errors. The Ramberg-Osgood equation is giving total error of thirty-five percentages; ²model gives nearly nine percentages for ferritic stainless steel. Proposed model is showing an error percentage of two only. Application/Improvements: Proper nonlinear analysis of stainless steel is required for the economical use of sections and for getting more realistic assessment of the structural response of the material.

Keywords

Material Nonlinear Analysis, Nonlinear Strain Hardening Exponent N, Nonlinear Regression Analysis, Ramberg Osgood Model, Stainless Steel.

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