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1

INTRODUCTION

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1.1 General

In any structure or structural element before application in actual field there is some testing should have to perform so that to check its reliability and serviceability. So in characterization process we have to set its limitation either they are structural or geometrical. At some extent, in beginning of service life of any structure  main aim of SHM is also that to characterize the limiting values only. Latter it defines rest of life and current performance of structure.

1.2     SHM

 The Structural health monitoring can be defined as non-destructive in-situ structural evaluation method in which several types of sensors and actuators are attached or embedded in structure. Structural Health Monitoring (SHM) aims to give, at every moment during the life of a structure, a diagnosis of the “state” of the constituent materials, of the different parts, and of the full assembly of these parts constituting the structure as a whole. The state of the structure must remain in the domain specified in the design, although this can be altered by normal aging due to usage, by the action of the environment, and by accidental events.

And the rest part is prognosis in which the prediction of residual life of the structure is to be done. Due to time-dimension of monitoring, which makes it possible to consider the full history database of the structure, and with the help of Usage monitoring, it can be able to provide a prognosis (evolution of damage, residual life, etc.).

 In structural health monitoring damage is defined as changes to the material and/or mechanical properties of a structure, including changes to the boundary conditions, which adversely affect the structural performance. These sensors collect data which is analyzed and stored for future analysis and reference that can be used for safety, integrity, strength or performance.

1.2.1 Components of SHM

(i)  The structure on which the SHM system will be placed.

(ii)   Sensors and Actuators

(iii)   Acquisition system

(iv)   Communication of information

(v)   Intelligent processing and analyzing of data

(vi)   Storage of processed data

(vii) Diagnostics

(viii) Damage modeling and damage detection algorithms

(ix)   Retrieval of information  as required

      A layout of structural health monitoring is shown bellow on figure

                 Fig.1.1: Layout of structural health monitoring

                         TABLE 1.1: Categories of SHM

S.no S.no. Categories Description

1

Static Field Testing Behavior tests

Diagnostic test

Proof tests

2

Dynamic Field Testing Stress history tests

Ambient vibration tests

Dyn. load Allowance (DLA) tests       .

Pullback (anchored cables) tests

3

Continuous Monitoring Active monitoring

Passive monitoring

4 Periodic Monitoring Field testing tests to determine                    changes in structure

1.2.2 Advantages of SHM

(i)    Increased understanding of in‐situ structural behavior

(ii)    Early damage detection

(iii)   Assurances of structural strength and serviceability

(iv)   Decreased down time for inspection and repair

(v)   Development of rational maintenance / management strategies

(vi)   Increased effectiveness in allocation of scarce resources  

(vii) Enables and encourages use of new and innovative materials

1.2.3Levels of SHM

(i)  Level I: This basic level SHM system is capable of detecting damage in a     structure, but cannot provide any information on the nature, location or severity of the damage .it cannot assess the safety of the structure.

(ii)  Level II: Slightly more sophisticated than level 1 SHM system level II system can detect presence of damage and can also provide information about its location. So that can be detect and repair

(iii) Level III: In this level we can locate pin point location and of damage and  its severity  

(iv) Level IV:  It is the most sophisticated system of  SHM  and provide detailed information about presence, location and severity of damage and in some extent it can also provide information about the life of the structure.

1.3    Loading frame

 A high stiffness support structure against which the test forces can react. The load frame comprises a base beam, two columns, and a moving crosshead. It is a self-straining structure that means no other load is transfers to ground except its self-weight.

                                            

                                      Fig.1.2: loading frame                          

1.3.1     Types of loading frame

1.3.1.1 According to axis of loading

(i) Vertical loading frame          

                                             

                                   Fig.1.3: Vertical loading frame          

  

(ii)  Horizontal loading frame

                                         Fig.1.4 Horizontal loading frame

1.3.1.2 Other types

(i)   Straight Sided  four column Type

(ii)  Straight Sided box Type

(ii) Straight Sided Column/C-Frame Type,

(vi)  H-frame Type,

1.3.2 Significance of loading frame

(i) The test-loading frame can be utilized to test the behavior and load-carrying capacity of both full-size structures as well as separate structural member.

(ii) This equipment is best suited for producing static and repeated loadings.

1.4   Objectives of the study

(i) Characterization of loading frame

(ii) To monitor health of loading frame.

(iii) Vertical stiffness means stiffness of structural member in vertical loadings

(iv) Displacements under characteristics load etc

(v) And comparative study of the general manual results with experimental results.

1.5 Outline of project

(i) Is to study various aspects of structural health monitoring and part of instrumentation involved in it.

(ii) Experimental procedure setup and methodology used.

(iii) Description of experimental investigation.

(iv) Description of strain gauges and their types.

(v) Comparative study of experimental and theoretical results.

1.6   Scope of the work

To achieve the above objective, to the scope of this work for the project generally involves the following.

(i) To verify the loading frame geometrically by performing flatness test and parallelism tests.

(ii) To verify structural performance of  frame using strain gauges LVDT’s, data logger and load cell as instrumentation part and hydraulic jack spacers as mechanical part.

(iii) To apply the tests more times to verify reliability of our instrumentation system.

(iv) To make completive study of results of theoretical and experimental calculation and prediction about health of frame.

2

Literature review

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  Medland, et al. (1966) The study of author was concerned about an investigation of the behavior of structures composed of the high yield-stress steel to B.S. 968. Moreover, it concerns about the applicability of the plastic theory to the design of such type of framed structures.  In this investigation, he had conducted a number of bending tests on simply supported beams of having I-sections. In the new steel to check the applicability of the previous theories to the estimation of the strain-hardening characteristic of such beams. He had found that the rigid-plastic-strain-hardening (r.p.s.h.) and rigid-plastic-rigid (r.p.r.1 theories both gave good estimates of the strain-hardening characteristic of high tensile steel beams and that the basic rigid-plastic-rigid theory could be used as a suitable basis for a design method.

  Sinha, et al, (1988) The study was concerned about CAD (computer-aided design) of hydraulic press structure of capacity 918KN in which they used finite element model to analyze the press because only through FEM method we can reach  near  about  to model exact shape like its topology. They also considered  factors such as  fillet, edge cutting, provision of openings, change in position of stiffeners and eccentric loading. They explained us merits of FEM (finite element method) for modeling of such types of complicated structure. Based on this Investigation, certain significant guidelines related to its behavior and its design has obtained for the analysis& design in future for press frames that are.

(i) Clearance between members should maintain as minimum, as much as accuracy expected from the machine tool;

(ii) Proper alignment of different elements, especially for sliding members must ensure with greater accuracy.

  Saleh, et al. (1992) This study describes the systematic procedure for investigation  of the structural  performance and the design and analysis of the welded structure of a 150-tonne hydraulic press machine in other sense load frame or load carrying structure . This machine was designed without any measurement earlier. The author has discussed the theoretical and experimental model of the machine structure to make the accurate and optimal design analysis for further development in the present machine design at minimum time and at lower cost. The applicability of the existing Computer based Finite Element package, as a CAD (computer-aided design) tool, was also discovered. They use both conventional analytical formula and numerical technique, using Finite Element to model it theoretically. But the conventional model is based on the simple bending theory in which they use the total strain energy principle for 2D beams or frames. The LUSAS Finite Element software used for numerical modeling because modeling and solving the equation of FEM f such type of complex structure is too problematic or can say impossible and why they waste their labor while facilities are. By using FE(finite element) model they able to be consider such factors which are not possible to replicate by other method. The factors they considered are the boundary condition the mesh density and the type of the element being used. The experimental model consist of load cells strain gages and LVDT’s and A comparison had made between the experimental and theoretical results.

  Bisby, et al. (2004) Study was  Concerned about the introduction to structural health monitoring and its various aspects like its components, classification, levels, methods of computation etc. they also gives a brief description of  sensors and actuators and there types which generally used in monitoring  with some example of bridge structure.

  Farrar, et al. (2006) The study was concerned about an introductory part of SHM that is The process of applying a damage identification technique for aeronautical, civil and mechanical engineering infrastructure is called structural health monitoring (SHM). The damage defined as changes in the mechanical properties of material and geometric and structural properties of the systems. It including changes in the boundary conditions and system inter connectivity, which adversely affect the system’s performance. It also concerned about huge variety of highly accurate local Non-destructive testing mechanisms are available for such type monitoring and  also tells about motivation for SHM technology development, feature retrieval and information collection, Operational evaluation and difficulties occurred in SHM.

  Osman, et al. (2011) This study is concerned about to develop simple and accurate three-dimensional (3D) finite element model (FE) which able to be analyze the actual behavior of beam-column joints in steel frames in the application of lateral loadings. The software named ANSYS used to model the joint. They had chosen bolted extended-end-plate connection as an important type of beam–column joints. The extended-end-plate connection had chosen due to its complexity in the analysis and behavior due to more number of connection components and their inheritable means having similarity in non-linear behavior. They chose two experimental tests from the literature to verify their finite element model. After that, they compared the results of both the experimental and the proposed finite element model were. One of those tests monotonic loading was used, whereas in the second cyclic loading was used. They improved the finite element model to overcome the defects of the finite element model used. These defects are; the long time need for the analysis and the inability of the contact element type to follow the behavior of moment–rotation curve under cyclic loading. As a contact element, the surface-to-surface element was used in place of node-to-node element to improve the model. The FE results showed good correlation with the experimental results. This was an attempt to improve a new technique for modeling bolts. In addition, they also concluded that FE results and the experimental results are compared to examine the validity and the predictability of the proposed model. The FE results have good agreement with the experimental one at different stages of loading. The FE model can provide a variety of results at any location within the model. A viewing of the full fields of stresses and strains are possible in the FE model. This provides a great advantage in monitoring the components of the connection. In addition, they showed that modeling a beam-to-column connection loaded cyclically is expensive and time consuming in both building and solving the model. Therefore, there is a great need to model the connection more simply and at the same time with an acceptable accuracy. And gave a proposal for a new technique of modeling bolts is presented. The proposal is to model the bolts as a mixing of shell elements (for head and nut) and link elements (for shank). This technique for modeling of bolts, called shell bolt, was examined and compared to other methods for modeling of bolts and was found to be accurate., it Also needs less time of solution and less storage volume comparing with other techniques for modeling the bolts.

  Rinn, et al. (2012) Study was concerned about physics of stochastic processes we present a new approach for structural health monitoring. This new method allows for an in-situ analysis of the elastic properties of a mechanical structure it also reliable in in-situ analysis because this method compensates the external noises, which ware normally occurred in actual condition. In this study, an experimental set-up of undistorted and distorted beam structures exposed to a noisy excitation under turbulent wind conditions. The method of reforming stochastic equations from measured data has been extended to realistic noisy excitations like those given here. In our analysis, the part which is to be determined had separated from the stochastic dynamics of the system and they showed that the slope of the deterministic part, which is linked to mechanical features of the material, changes sensitively with increasing damage. The results are more significant than corresponding changes in Eigen frequencies, as commonly used for structural health monitoring. Commonly detection systems use fast Fourier transformation (FFT) to extract system features and to determine the condition of the system from changes in the Eigen frequencies. One demerit of this method is that the noisy excitation of the structure increases the peaks of the frequency spectrum and so makes it harder to detect and analyze the changes reliability of approach.

  Kisioglu, et al. (2013) In this study author designed a straight sided four-pillar type  hydraulic press and calculated the stress distribution  using both analytical and finite element methods under different loading conditions. Three different loading types, axial, eccentric and oblique, are considered in design process. Six different types of standard sections having the same cross-sectional area are used for the press columns. Three different models for the press head are designed to hold the hydraulic cylinder. Therefore, eighteen different design combinations for a hydraulic press are modeled under three different loading conditions. Their stress distributions ware calculated using a computer-aided finite element analysis (FEA) tool, analytical formulas, and the obtained results ware compared. Two different types of finite elements, shell and beam, had used for the modeling processes. Based on the obtained results, the best model for the hydraulic press considering the head and body types has defined. And recommended that the T type head and hollow circular or I-sectioned column is the best design consideration.

  Zahalka, et al. (2013)  The study discuss the dynamic behavior of the forging machines is necessary to explore due to the increasing of speeds on large forging hydraulic presses for open die forging. The study describes the modal analysis of two selected presses, which represent the most common designs of hydraulic presses for forging. The first press is with double-column frame CKV 50 with the force 50MN and the second one is with four-column frame CKV 170 with the force 170 MN. Further are described the simulations of oscillation,  which was excited by time-dependent work force. Results of analysis ware compared with measurement in the real experiments. w and concluded that we can get higher second moment of area with the same area of cross section by changing of shape only.

  Kumar, et al. (2014)  In above study author Discussed about Using the optimum resources possible in designing the hydraulic presses frame can effect reduction in the cost of the hydraulic presses. By optimizing the weight of material utilized for building the structure. An attempt had made in this direction to reduce the volume of material. So here we consider an industrial application project consisting of mass minimization of H-frame type hydraulic press. This press has to compensate the forces acting on the working plates and has to fulfill certain critical constraints. ANSYS has been used for this analysis the main aim is to reduce the cost of the Hydraulic presses without compromising on the quality of the output. With regarding to design specification, stress distribution, deflection, and cost, are aimed on optimized design. The methodology followed in this work is comparison of stresses induced in machine for different thickness used for construction of frame and column of the H-frame type hydraulic press. In this project it has been compared original design of H frame type hydraulic press with design that have been optimized by using software tool (ANSYS).

2.2   Critique:

Since lot of studies had performed on structural health monitoring of steel frame for both static and dynamic condition the type of testing methods from analog to digital.

Further work has been done on structural analysis and optimization of loading frame and hydraulic presses we plant to replicate that for our loading frame.

                                                          

                                                                                                                       

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