Essay: Behavior of structures

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  • Behavior of structures
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Collapse load of steel frame works allowing for the effect of strain hardening, M.R. Horne and I.C. Medland , (1966).

Concerned with an investigation into the behavior of structures composed of the new high yield-stress steel to B.S. 968 and the applicability of the plastic theory to the design of such structures. As part of this investigation, he had conducted a number of bending tests on simply supported beams of more realistic I-sections in the new steel to check the applicability of the Authors’ 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 r.p.r. theory could be used as a suitable basis for a design method.

Experimental investigation on the behavior of frame with and without bracing under horizontal loading, Wakabayashi and Tsuji, (1966)

This study is concerned about behavior of steel frames under horizontal loading condition. Experiments are conducted on various types of portal frames on single storied and double storied frames by using load cells wire type strain gages and dial gages. They find the behavior of frames (both with and without bracing) under monotonous and repeated loading condition. and concluded that in simple portal frame of without bracing softening type of load displacement curve was found. also done the comparative study between frames with and with without bracing with the help of load displacement curve under respective loading.

Computer aided design of hydraulic press by S.P. Sinha and P.D.Murarka (1988)

The study was concerned about computer aided design of hydraulic press in which they used finite element model to analyze the press structure and it has been used in making a comparative study of the behavior of the structure. The factors considered are fillet, edge cutting, provision of openings, change in position of stiffeners and eccentric loading. On the basis of this investigation, certain significant guidelines have been obtained for the design of press frames that are..

(i) Clearance between sliding members to be kept to a minimum, according accuracy expected of the machine tool;

(ii) Proper alignment of different elements, particularly sliding ones should be ensured.

Design study of heavy duty hydraulic machine using FEM technique, Dr. Mohamad M. Saleh ( 1992)

This thesis describes the systematic procedure for investigating the performance and the design analysis of the welded structure of a 150-tonne hydraulic press machine. This machine was designed without any measurement or variable hydraulic system. The investigation discusses the theoretical and experimental model of the machine to establish the accurately optimal design analysis and further development of the present machine at minimum time and lower cost. The applicability of the existing PC based FE package, as a computer aided design tool, was also investigated. The theoretical model takes into account both conventional analytical formula and numerical technique, using Finite Element Analysis. The conventional model is based on the simple bending theory using the total strain energy principle for 2D beams. The LUSAS Finite Element software system is used as a tool to establish the theoretically predicted numerical model. This model has been discussed with different factors. The factors 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 L.V.D.T. and A comparison has been made between the experimental and theoretically predicted results.

An Introduction to structural health monitoring, L.A. Bisby 2004

Concerned about the introduction to structural health monitoring and its various aspects like its components, classification, levels, methods of computation etc.

also gives a brief description of sensors and actuators and there types with some example of bridge structure.

 An Introduction to structural health monitoring, Charles R. Farrar and Keith Worden (2006)

The study is concerned about an introductory part about SHM that The process of implementing a damage identification strategy for aerospace, civil and mechanical engineering infrastructure is referred to as structural health monitoring (SHM). damage is defined as changes to the material and/or geometric properties of these systems, including changes to the boundary conditions and system connectivity, which adversely affect the system’s performance. it also concerned about wide variety of highly effective local Non-destructive evaluation tools are available for such monitoring and also tells about motivation for SHM technology development, feature extraction and information condensation, Operational evaluation and Challenges for SHM.

 Finite element analysis of beam-column joints in steel frames under cyclic loading, Mohammad Osman et al (2011)

This study is concerned to develop simple and accurate three-dimensional (3D) finite

element model (FE) capable of predicting the actual behavior of beam-to-column joints in steel frames subjected to lateral loads. The software package ANSYS is used to model the joint. The bolted extended-end-plate connection was chosen as an important type of beam–column joints. The extended-end-plate connection is chosen for its complexity in the analysis and behavior due to the number of connection components and their inheritable non-linear behavior. Two experimental tests in the literature were chosen to verify the finite element model. The results of both the experimental and the proposed finite element were compared. One of these tests was monotonically loaded, whereas the second was cyclically loaded. The finite element model is improved to enhance 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 is used instead of node-to-node element to enhance the model. The FE results show good correlation with the experimental one. An attempt to improve a new technique for modeling bolts is conducted. And 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.and shown that modeling a beam-to-column connection loaded cyclically is expensive and time consuming in both building and solving the model. So, 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. Also, it needs less time of solution and less storage volume comparing with other techniques for modeling the bolts.

 Stochastic method for in situ damage analysis, Philip Rinn et al (2012)

study is 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 features of a mechanical structure even for realistic excitations with correlated noise as it appears in real world situations. In particular an experimental set-up of undamaged and damaged beam structures was exposed to a noisy excitation under turbulent wind conditions. The method of reconstructing stochastic equations from measured data has been extended to realistic noisy excitations like those given here. In our analysis the deterministic part is separated from the stochastic dynamics of the system and we show 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 drawback of this approach is that noisy excitation of the structure broadens the peaks of the frequency spectrum and thus makes it harder to detect changes reliably

 Hydraulic press design under different loading conditions using finite element analysis, Mehmet Aydin and Yasin Kisioglu (2013)

this study, a suitable hydraulic press having four-column is designed and the stress distribution is calculated 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 are calculated using a computer-aided finite element analysis (FEA) tool and analytical formulas and the obtained results are compared. Two different types of finite elements, shell and beam, are used for the modeling processes. Based on the obtained results, the best model for the hydraulic press considering the head and body types is defined. and recommended that T type head and hollow circular or I-sectioned column is the best design consideration.

 Modal analysis of hydraulic press frames for open die forging,

Martin Zahalka (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 are compared with measurement in the real operation. w and concluded that we can get higher second moment of area with the same area of cross section by changing of shape only.

 Analysis and structural optimization of 5 ton H-frame hydraulic press, Santosh kumar S.Malipatil et al (2014)

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 has been 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 focused 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 work has been done on SHM of steel frame for both static 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.

3

SETUP Required

——————————————————————

Instrumentations setup

Because there are so many difficulties in analogue signals about collection and retrieval of result data. So we are performing such the experiment which gives us results in digital form. Which needs an electronic data acquisition system which also enable to store the data which can be retrieved when required that’s why we have to involve some electronics Instruments and circuits which are as follows

 Multi-channel Digital Automatic Data Loggers for Strain measurement.

 Strain Gauges

 Load Cells & Digital Load Indicators

 Displacement Transducers

Multi-channel Data Loggers

It’s a major part of data acquisition system as name define its work itself it logs the data in it in its own units or we can also define them. In some cases it also works as an actuator which means it gives excitation or input to the sensors but which haven’t such excitation system in that cases we have to involve external excitation system or external controlled supply like some battery or other one. In our case we are using a sixteen channel data logger names DT-85 no. of channels define that how many sensors we can attach and read the values. So in our case we can read 16 sensors at one time instant. There is also such type of arrangement is available by which we can expand the no of channels with the help of channel expansion module up to 10 channels. It is also preferred as an actuator for some small range of excitation from 300 mille volt to 3 volt. In this case it receives the signals in certain fix time interval vary from 1 second to 30 seconds. We can also set it in a triggering system by which we can control the frequency of data collection with the help of a small button. Its having some memory in which it can store data up to a certain limit we can retrieve in the system in excel sheet or we can also retrieve it in some other storage device with the help of USB port. Data loggers are available in different frequency range small frequency data loggers are static loading cases.

Data logger

For experiment dynamic loading high frequency data loggers are required. Our data logger is of small frequency range so we using it for our case.

Strain Gauges

Again name suggesting instruments or can say transducer used for strain measurements is called strain Gauges over a free surface of any structure. They follow different principals according to their types. That means there are different types of strain gauge are available according there range least count type of measurement and scope which are as follows.

Mechanical strain gauges

Acoustical strain gauges

Optical strain gauges

Pneumatic strain gauges

Electrical strain gauge

Mechanical strain gauges

These are involves with mechanical arrangements in its working principal consist of two jaws clamped with the surface or structural on which strain is desired by means of spring or some clamping arrangements at certain specific distance which is called gauge length. So when specimen or component was loaded it get elongated so the jaw clamped with component is also get displaced from its original position. And this displacement is amplified and by some mechanical arrangement and visualized on the proving ring or some dial meter. Due to its working principal in some extent it was also called extensometer. These are also having so many types are as follows.

• Berry’s strain gauge

• Huggenbeger extensometer

• Johnsson extensometer

Berry’s strain gauge

Acoustical Strain Gauge

Its working principal is based on the propagation or traveling of wave. Which mean when bonded wire is stressed or elongated its natural frequency get altered or differs from its original values so we have to amplify this change in terms strain developed. These types of gauges are highly accurate in nature.

Optical strain gauges

As the name suggests it is based on the principal of optics. In this type of gauge the pivot jaw containing a mirror and the other jaw o edge is clamped with surface of component on which strain is desired. So when the component is stressed or elongated the pivoted edge which is carrying mirror got tilt and that ‘s why mirror will also got tilt and the reflection of the illuminated scale is visible on this mirror which can be read with the help of telescope. There are two types of optical strain gauge s are known named as follows.

• Marten’s optical strain gauge

• Tuckerman optical strain gauge

Marten’s optical strain gauge

Pneumatic strain gauges

The working principal of these type of gauges are based on relative study of discharge of air between two orifice in which one is fixed and other is variable. Sensitivity of these type gauges are 100000 times of other types. And can be used for both static and dynamic condition.

Pneumatic strain gauges

Electrical strain gauge

It also having three types but hear we are using resistance so we will explain about resistance type only. Others name are as follows.

• Inductance type

• Capacitance type

• Resistance type

These strain gauges works on the principal that they amplify the mechanical deformation or change of structural component in electrical output. It may be of any type in impedance or resistance. It consists of a conductor circuit in its structure attached with component. So when conductor is starched or compressed it results change in resistance of conductor because cross sectional area of conductor got change either increased or decreased. Change in resistance per unit strain is known as gauge factor which indicates about the sensitivity of strain gauge. There different types of strain gauges are available are as follows.

• Un-bonded wire strain gauge

• Bonded wire strain gauge

• Foil strain gauge

• Weldable strain gauge

Un-bonded wire strain gauge

This type of strain gauge gives electrical signal output of relative displacement of one body to another body. It consists of a stationary frame and a movable platform and pins made of insulated material are in those pins loops of wire are wounded which are in pretension. So when component is elongated or contracted the relative movement between frame and platform will occurs and tension in loops get alters after that this is connected with for arm wheat stone bridge for the accuracy purpose. These type of strain gauges are also used for the measurement of force pressure acceleration etc.

Un-bonded wire strain gauge

Bonded wire strain gauge

it consists of wire bonded around a core which is sandwiched between two insulating layers. Sometimes core is flattened this then this is called Flat-grid strain gauge type is also sub divided into three another types.

• Wrap-around wire strain gauge

• Flat-grid strain gauge

Bonded wire strain gauge

Weldable strain gauge

They are mainly invented due to ease in installation working principal is same as that of other resistance based strain gauges. There installation is easy. And they can work in any environment. It consists of strain sensitive material and stain component is highly insulated by compacted ceramic. Stain gauge is spot weld on structural component and when structure is stressed the stress get transmitted through weld into strain tube. These types of strain gauges also have dynamic application.

Weldable strain gauge

Foil strain gauge

This type of strain gauge consisting of a membrane of larger width as compare to its thickness and it is made up of strain sensitive material and principal is same means when structural component is strained foil also experiences strain and its resistance get changed. A suitable cementing material should also be required for bonding of strain gauge with structural component.

The strain gauge which we are using is of foil type having following specification

Resistance – 120 ohm and 350 ohm lead attached

We have also used wheat stone bridge system for better accuracy purpose.

Wheat stone bridge

It’s an arrangement of resistances used for achieving greater accuracy in measurement. It consists of two resistances connected in series an again they connected parallel with another two resistance of same resistance value.

Load Cells & Digital Load Indicators

As the name suggests it is an electromechanical device or equipment used to read the value of load is called load cell gives the value of load in digital format. It can be say that it’s a transducer as it converts mechanical forces into the form of electrical energy or signals .Its basic principal of working is based on the strain gauges. The internal structure or sensing system of load cell consists of a Wheatstone full bridge system of strain gauges. So when load is applied then the strain in strain gauges will increases linearly because of another principal hook’s law and because of that resistance will also increasing linearly with the deformation. There are so many different types of load cells are available according to different criteria’s as follows.

• According to construction material

• Aluminum load cell

• Tool steel load cell

• Stainless steel load cell

• According to external structure and working

• Canister type

• Single ended beam type

• Double ended beam type

• Cantilever beam type

• S-beam type

• Platform type

Hear we used a canister type of load cell having capacity of 50 ton or 500 KN shown bellow.

Displacement Transducers (LVDT)

Displacement transducer name LVDT expands and form linear variable differential transducer.

We also require some more instruments which are not have any electronic phase

Name as

• Loading frame

• Hydraulic Jack

• Tool kit etc.

Loading frame

We have given its brief introduction earlier. And our loading frame having following specifications.

Firstly sectional properties of beam-

• Depth of the section h = 600 mm

• Width of the flange bf = 210 mm

• Thickness of the flange tf = 20.8 mm

• Thickness of the web tw = 12 mm

• Radius at root r1 =20 mm

• Depth of web d = h- 2(tf + r1) = 518.4 mm

• Section Modulus Ze= 3060.4 x 103 mm3

• Plastic Modulus Zp = 3510.63 x 103 mm3

• . Weight per Meter W = 1202.71 N/m

• Capacity of frame=500 KN

Specifications of stiffeners

• ISLC 75 section

Loading frame

Hydraulic Jack

It’s a setup in which we can apply large mechanical loads with help of a suitable hydraulic arrangement. Consists of a pressure gauge with analog dial, piston, cylinder, oil filling and exit arrangement and a lever by which we can apply pumping force and it also have a release valve to remove or to release pressure.

The hydraulic jack we used having maximum capacity to apply load of 50 ton or 500 KN its least count is 2 KN and it also have locking arrangement for lever pump.

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