Vikas Arora

Most of finite element model updating techniques do not employ damping matrices and hence, cannot be used for accurate prediction of complex frequency response functions (FRFs). In this paper, damped finite element model updating procedure is proposed and tested with the objective that the damped finite element updated model is able to predict the...

Most of the model updating techniques do not employ damping matrices and hence cannot be used for the accurate prediction of complex frequency response functions (FRFs) and complex mode shapes. In this paper, the response function method (RFM) is extended to deal with the complexity of FRF and modal data using complex updating parameters. In the pr...

Model updating techniques are used to update the finite element model of a structure, so that updated model predicts the dynamics of a structure more accurately. The application of such an updated model in dynamic design demands that it also predicts the effects of structural modifications with a reasonable accuracy. Most of the model updating tech...

Most of the structural health monitoring (SHM) methods is either based on vibration-based and contact acoustic emission (AE) techniques. Both vibration-based and acoustic emission techniques require attaching transducers to structure. In many applications, such as those involving hot structural materials for thermal protection purposes or in rotati...

In this paper, a new scaffold anchor system is presented. The developed scaffold system overcomes the problems associated with the existing scaffold anchors. The existing scaffold anchors damage the surrounding insulation layers subsequently decreases the stability of scaffold anchors. The developed scaffold system has a new type of the facade anch...

Axial piston pumps (APP) are energy efficient while operating, but they are prone to catastrophic failures by virtue of their construction and tight tolerances. Reliability can be improved either by (i) increasing the robustness of each component used in the APPs or (ii) predicting their health status by using different techniques, so that failures...

A stiffened structure is integral to complex structures such as ships. An advantage of the stiffened plate is that it has a greater load-carrying capacity. Therefore, structural health monitoring of stiffened structures is essential in a ship structure. The stiffened structure is modeled as a coupled system with a plate and stiffener forming the su...

Welded structures are integral to complex bodies such as ships and offshore rigs. Welded joints are frequently used in connecting various plates and substructures, making their assessment pivotal. The numerical model used here consists of plates coupled using springs and dashpots. The coupling models the welded joint and exemplifies the uncertainti...

Axial piston pumps (APP) are energy efficient while operating, but they are prone to catastrophic failures by virtue of their construction and tight tolerances. Reliability can be improved either by (i) increasing the robustness of each component used in the APPs or (ii) predicting their health status by using different techniques, so that failures...

Complex engineering systems are generally manufactured using joints. This paper proposes a methodology for accurately identifying the stiffness and damping properties of welded stiffened plates. The results of the substructure based finite element models are compared with the actual experimental data. Discrepancies have been observed between the fi...

Most of the rainflow counting methods are developed for uniaxial stress states. In this paper, a new method for rainflow counting of multiaxial stress states has been proposed. The proposed method is a two-step procedure based on a modified three-point ASTM uniaxial rainflow counting algorithm where normal stress ranges are identified along with st...

The levels of non-proportionality in fatigue stress-time series are difficult to determine. Approaches from literature are not easy to interpret and predicts different levels for variable and constant amplitude stresses. In this paper, an extension to the PCA-based method is proposed in which variable amplitude stresses are transformed into equival...

Offshore structures are exposed to cyclic loading and thereby at risk of fatigue failure, especially at the welded joints between trusses in offshore jacket foundations. In this paper, an optimization framework for welded joints considering fatigue damages is presented. The framework can be used to optimize the orientation and location of welds con...

This paper evaluates three critical plane criteria, namely the Findley, Matake and modified Wöhler curve method and compares them to the IIW’s implementation of the Gough-Pollard criteria. Assessment is conducted on a large set of fatigue data of thin-walled tube-tube laser beam welded specimens made of magnesium and aluminum alloys that were teste...

Non-proportional multiaxial stresses in welded structures cause higher fatigue damage than proportional stresses. In this paper, a new approach based on principal component analysis for quantifying the level of non-proportionality in stress signals is developed. The quantifier is developed for large-scale structures (civil and offshore structures),...

Stiffened structures form an integral part of the ship structure. The fatigue life and the load-carrying capacity of the ship structure are dependent on the stiffened panels. Stiffened structures are formed by welding beam stiffeners on bare plates. The current study proposes a methodology to accommodate the welding uncertainties in the theoretical...

The stochastic behaviour of materials and loading is of great importance for buckling and analysis of prestressed beam and frame structures. In this paper, the stochastic stiffness and stress stiffness matrices are developed for stochastic analysis and buckling analysis. The bending rigidity and the buckling load are modelled as stochastic fields....

Several methods for finite element modelling and analysis of tubular welded joints are described in various design codes. These codes provide specific recommendations for modelling of the welded joints, using simple weld geometries. In this paper, experimental strain range results from two full-scale semi-automatically welded K-nodes tests are comp...

Fatigue assessment of welded joints is vital for accurately designing and predicting lifetime of many engineering structures. Assessing weld fatigue is challenging due to the high variability in weld quality and geometry because of the volatile nature of the joining method and further challenges arise when assessing multiaxial fatigue. In this pape...

Dynamically loaded structures are generally in risk of fatigue damage. The fatigue lives of such structures can be improved using traditional methods like producing a better weld or using post-weld treatment. Another method is to improve the overall design of the structure by using the finite element method in combination with shape optimization. I...

Model updating is a crucial tool for dynamically loaded structures as natural frequencies and damping can have a vital impact on normal operation and fatigue life. Finite element models always deviate from experimentally obtained results due to variations in mass and stiffness and the lack of a damping matrix. Thus, it is vital for many large struc...

Stiffened structures are often utilized as structural members for numerous applications in various fields of engineering like Civil, Automobiles, Naval, Aerospace, etc. Thus analyzing stiffed structure for their structural integrity become pivotal. Simplest instance of a stiffened structure could be a plate with a beam acting as a reinforcement. Th...

Several methods for modelling and finite element analysis of tubular welded joints are described in various design codes. These codes provide specific recommendations for modelling of the welded joints, using simple weld geometries. In this paper, experimental hot-spot strain range results from a full-scale automatically welded K-node test are comp...

Typically, a ship structure is composed of stiffened plate structure which is a combination of beams and plates. The natural frequency of the beams and plates are subject to variability due to manufacturing process. This induces change in the modal parameters of the system. The present work would focus on identification of modal parameters of beams...

Damping still remains one of the least well-understood aspects of general vibration analysis. In this paper, a new experimental damping identification method, which can be able to identify both viscous and structural damping in the dynamic system, is proposed. The proposed method is a direct method and gives explicit structural and viscous damping...

Though Blind Source Separation (BSS) techniques have typically been applied within Operational Modal Analysis (OMA) framework, there joint diagonalization property can also be utilized within traditional input-output Experimental Modal Analysis (EMA) for the purpose of modal parameter estimation. This paper explores this possibility and suggests an...

The paper focuses on the updating of the finite element models of the newly developed façade scaffold anchor in the light of the experimental results. The experiments (force-displacement curves) have been carried out on the anchor. The façade scaffold anchor overcomes the problems arising in the process of joining them to the façades through the th...

Damping still remains one of the least well-understood aspects of general vibration analysis. The effects of damping are clear, but the characterization of damping is a puzzle waiting to be solved. A major reason for this is that, in contrast with inertia and stiffness forces, it is not clear which state variables are relevant to determine the damp...

Most of the identification methods are based only on the viscous damping model and uses modal data. In this paper, a new FRF-based direct structural damping identification method is proposed. The proposed method is a direct method and identifies structural damping matrix explicitly. As the new method is a FRF-based method, it overcomes the problem...

An accurate finite element (FE) model of a structure is essential for predicting reliably its dynamic characteristics. Such a model is used to predict the effects of structural modifications for dynamic design of the structure. These modifications may be imposed by design alterations for operating reasons. Most of the model updating techniques negl...

Most of the finite element model updating methods use resonance frequencies and modeshapes for updating mass and stiffness matrices. These model updating methods are not very accurate as modeshapes cannot be estimated accurately. Whereas, antiresonance frequencies can be estimated accurately from measured frequency response functions (FRFs). In thi...

All structures exhibit some form of damping, but despite a large literature on the damping, it still remains one of the least well-understood aspects of general vibration analysis. The synthesis of damping in structural systems and machines is extremely important if a model is to be used in predicting vibration levels, transient responses, transmis...

Most of the finite element model updating method uses resonance frequencies and mode shapes. The mode shapes are not very accurate as suggested by many researchers. Whereas, antiresonance frequencies can be identified accurately from measured frequency response functions (FRFs). In this paper, a new model updating method is proposed, which uses res...

An accurate finite element model of a structure is essential for predicting reliably its dynamic characteristics. Such a model can be used to predict the effects of structural modifications for dynamic design of the structure. These structural modifications may be imposed by design alterations for operating reasons. Most of the model updating techn...

All structures exhibit some form of damping, but despite a large literature on the damping, it still remains one of the least well-understood aspects of general vibration analysis. The synthesis of damping in structural systems and machines is extremely important if a model is to be used in predicting vibration levels, transient responses, transmis...

Most of the finite element model updating methods uses resonance frequencies and mode shapes. The mode shapes are not very accurate as suggested by many researchers. Whereas, antiresonance frequencies can be indentified accurately from measured frequency response functions (FRFs). In this paper, a new model updating procedure is proposed, which use...

The effects of vibrations present major hazards and operating limitations ranging from discomfort (including noise), malfunctioning, reduced performance, early breakdown and structural failure which, in the worst case can be catastrophic. Hence, accurate mathematical models are required to describe the vibration characteristics of structures, which...

Air-foil bearings (AFBs) are self acting hydrodynamic bearings made from sheet metal foils comprised of at least two layers. The innermost “top foil” layer traps a gas pressure film that supports a load while the layer or layers underneath provide an elastic foundation. AFBs are currently used in many commercial applications, both terrestrial and i...

Model updating techniques are used to correct the finite element model of a structure using experimental data such that the updated model more correctly describes the dynamic properties of the structure. One of the applications of such an updated model is to predict the effects of making modifications to the structure. These modifications may be im...

Air-foil bearings (AFBs) are self acting hydrodynamic bearings made from sheet metal foils comprised of at least two layers. The innermost “top foil” layer traps a gas pressure film that supports a load while the layer or layers underneath provide an elastic foundation. Air-foil bearings are currently used in many commercial applications, both terr...

Most of the model updating techniques do not employ damping matrices and hence cannot be used for accurate prediction of complex frequency response functions (FRFs) and complex mode shapes. In this paper, response function method (RFM) is extended to deal with the complexity of FRF by updating damping matrices along with mass and stiffness matrices...

Most of finite element (FE) model updating techniques do not employ damping matrices and hence, cannot be used for accurate prediction of complex frequency response functions (FRFs) and complex mode shapes. In this paper, a detailed comparison of two approaches of obtaining damped FE model updating methods are evaluated with the objective that the...

Model updating techniques are used to update the finite element model of a structure so that updated model predicts the dynamics of a structure more accurately. The application of such an updated model in dynamic design demands that it also predicts the effects of structural modifications with a reasonable accuracy. Most of the model updating techn...

Most of the first level model updating techniques do not employ damping matrices and can't be used for accurate prediction of complex Frequency Response Functions (FRFs) and complex mode shapes. This paper presents an FRF-based finite element model updating procedure in which FE model is update in such a way that the updated model reflects the visc...