Srinivas Sriramula

University of Aberdeen | ABDN · School of Engineering

This paper presents a stochastic approach to study the natural frequencies of thin-walled laminated composite beams with spatially varying matrix cracking damage in a multi-scale framework. A novel concept of stochastic representative volume element (SRVE) is introduced for this purpose. An efficient radial basis function (RBF) based uncertainty qu...

Redundant safety systems are commonly used in the process industry to respond to hazardous events. In redundant systems composed of identical units, Common Cause Failures (CCFs) can significantly influence system performance with regards to reliability and safety. However, their impact has been overlooked due to the inherent complexity of modelling...

The current design of offshore wind turbines follows mainly the IEC 61400-3 standard. The list of Design Load Cases (DLCs) implied for this standard is comprehensive and the resulting number of time domain simulations is computationally prohibitive. The aim of this paper is to systematically analyse a subset of ultimate limit state load cases propo...

The extensive use of FRP composite materials in a wide range of industries, and their inherent variability, has prompted many researchers to assess their performance from a probabilistic perspective. This paper attempts to quantify the uncertainty in FRP composites and to summarise the different stochastic modelling approaches suggested in the lite...

This paper presents a stochastic performance modelling approach that can be used to optimise design and operational reliability of complex chemical engineering processes. The framework can be applied to processes comprising multiple units, including the cases where closed form process performance functions are unavailable or difficult to derive fro...

The need for more robust design of dynamic cables used for power export in floating wind turbine (FWT) systems is accentuated by the frequent occurrence of power cable failures. Such failures contribute considerably to the cost of global offshore wind farm losses. Fatigue is often times a critical consideration in the structural safety of these cab...

Numerous services are available today to develop an optimised asset management solution to enhance asset operations by improving the system availability, decreasing down-time and operation and maintenance costs. Three cases of engineering problems are explored in this paper, with data-driven machine learning solutions proposed for these problems. T...

Previous studies have investigated the behaviour of prestressed stayed steel columns with a view to developing design guidelines. As most of the modern standards move towards calibrated safety factors, there is a need to explore the design expectations of these structures from a probabilistic perspective. This has not been studied in the literature...

Pipeline lateral Out-of-Straightness (OoS) can act as buckle trigger in unburied (exposed) subsea pipelines. Determining the Critical Buckling Force (CBF) of the pipeline is a computationally challenging task due to the inherent uncertainties in contributing parameters which requires utilising reliability-based approaches. This implies the need for...

This paper presents the development and assessment of a smoothing technique for the random properties of the matrix phase of a fibre reinforced composite as part of a multi-scale reliability framework. Many sectors in the industry are using fibre reinforced composite materials, utilising their high stiffness-to-mass density ratio. Still, many uncer...

This study presents the results of a small-scale experimental campaign on prestressed stayed steel columns, subsequent numerical model validation and design guideline development. The majority of previous experimental studies have focused on large-scale systems, which are expensive and can be difficult to perform due to the required specialised exp...

The information and communication technology-driven smart cities make the lives of city dwellers safe and convenient. Recently, sustainable reinforced concrete (RC) structures that last longer have become a matter of considerable interest. RC structures are subjected to various damage such as corrosion, debonding, and concrete degradation. The corr...

Due to the pipelay vessel motions during installation of a subsea pipeline, as-laid direction of the pipeline changes along a nominally straight section of the route. In a High Pressure High Temperature (HPHT) pipeline, presence of rogue lateral Out of Straightness (OoS) can adversely influence the reliability of buckle initiation at engineered buc...

The accidents of subsea pipelines due to third-party interference often result in catastrophic impacts, therefore, risk assessment has progressively become substantial to ensure the safety and reliability of the systems. However, the current risk analysis approaches are unable to minimize the uncertainties in the analysis due to the high demands of...

Safety and reliability of the assets in the Oil and Gas sector is considered critical to maximize availability and minimize downtime in production and operations. The industry, due to ageing assets, are re-visiting the maintenance planning of critical equipment through Reliability-Centered Maintenance (RCM). The RCM process comprises of the hierarc...

Turbulent wind and stochastic waves-the main sources of environmental loading on floating wind turbine (FWT) structural components, significantly contribute to uncertainty in the characterisation of design load values. Given there is an infinite number of possible realizations of these environmental states, a minimal number of wind and wave seeds t...

Accurate structural reliability assessment of floating wind turbine (FWT) systems is a desideratum for achieving consistent optimal reliability levels and cost-effective design. Such reliability assessment should consider relevant system uncertainties—a nontrivial task. Formulation of the reliability problem requires structural demand in form of lo...

The offshore wind industry experienced a boost during the last decade in terms of size of wind farms and rated capacity of the wind turbines: towers are getting taller and blades are getting longer, constantly facing new and complex challenges. Because of the relative immaturity of the wind industry, and the fact that the offshore design standards...

Purpose The purpose of this study is to enable performing reliability-based design optimisation (RBDO) for a composite component while accounting for several multi-scale uncertainties using a large representative volume element (LRVE). This is achieved using an efficient finite element analysis (FEA)-based multi-scale reliability framework and sequ...

The ever-increasing complexity of intelligent electronic devices (IED) for the protection of electrical equipment leads to significant research challenges in evaluating their safety integrity level (SIL). The development of new technologies, components, operation, and maintenance requirements are factors that increase uncertainties and risks associ...

Nowadays, different industries such as nuclear, automotive, process, chemical, and oil & gas industry, must meet specific requirements in order to keep and reduce safety risks to as low as reasonably practicable (ALARP) level. As a result, the number of electrical/electronic/programmable electronic safety-related systems (E/E/PES) to control, preve...

The current blast wall design guidelines do not capture the random nature of underlying parameters. The main issues are the appropriate treatment of various uncertainties in the explosion loadings and the complex blast wall behaviour considering dynamic and nonlinearity effects. To capture these effects a new methodology needs to be developed based...

Failure threats in subsea pipelines are hard to inspect, but parameters influencing them are easier to observe. Hence, nowadays, Bayesian network models became more relevant, as the model can be updated with the sparse observations while considering the underlying uncertainty. This holds for failure threat assessment of subsea pipelines, specifical...

Achieving substantial reductions in Levelized Cost of Energy (LCOE) of floating wind turbines (FWTs) requires robust reliability assessment that accounts for inherent design uncertainties. A key aspect of such reliability assessment is the definition of limit states. In this regard, load effects need to be evaluated accurately. This paper presents...

In this paper, a Finite Element-based surrogate model is developed to efficiently estimate stiffness properties of unidirectional composite laminas, while accounting for geometric and material property uncertainties at micro, meso and laminate scale, all within a probabilistic framework. In the multi-scale build-up nature of composites, uncertainti...

EasyPBC is an ABAQUS CAE plugin developed to estimate the homogenised effective elastic properties of user created periodic representative volume element (RVE), all within ABAQUS without the need to use third-party software. The plugin automatically applies the concepts of the periodic RVE homogenisation method in the software’s user interface by c...

Composites provide improved stiffness/weight properties compared with conventional materials such as alloys. However, their heterogeneous nature and manufacturing process introduce many uncertainties. As a result, the use of composite materials is still limited to advanced products in aerospace, transportation and wind energy (Yancey, 2016). Thus,...

This paper focusses on developing an initial model for dynamic reliability analysis to predict the aging pipeline performance due to corrosion. The corrosion failure mechanism and the associated data requirements are identified by combining outputs from the literature and project experiences. Bayesian networks (BN) are developed to manage and overc...

The existence of uncertainties in material properties, environmental loads and soil properties as well as the presence of nonlinearities introduced by the control systems have a remarkable influence on the dynamic response of offshore wind turbine (OWT) support structures. The reliability computations of these structures need to consider implicit e...

This article presents a non-probabilistic fuzzy based multi-scale uncertainty propagation framework for studying the dynamic and stability characteristics of composite laminates with spatially varying system properties. Most of the studies concerning the uncertainty quantification of composites rely on probabilistic analyses, where the prerequisite...

Slender columns exhibit instability under compression, which causes buckling. Prestressed stayed system can be used to improve the load carrying capacity of these columns. In this study, three-dimensional prestressed stayed column was investigated through the use of commercially available finite element software-ABAQUS. Although many numerical stud...

In this study a numerical-based surrogate model is proposed to estimate the effective elastic properties of unidirectional composite lamina, while accounting for geometric and material property uncertainties at both micro and meso scales. In the multi-scale build-up nature of composites many uncertainties occur, mainly in material properties and ge...

This study investigates the effect of micro-scale geometric and material property uncertainties on the elastic properties and reliability of fibre reinforced composite materials. Composite materials are often designed using conservative design factors to account for a limited understanding of how multi-scale uncertainties effect reliability. Struct...

This paper presents the effect of noise on Radial basis function (RBF) based stochastic natural frequency analysis of thin-walled laminated composite beams. The RBF based method is built up on the basis of information acquired regarding the behaviour of the response quantity throughout the entire design space utilizing few algorithmically chosen de...

This study evaluates the effect and sensitivity of micro-scale geometric and material property uncertainties on the numerically determined effective elastic properties of unidirectional fibre reinforced matrix composite materials. Due to the multi-scale build-up nature of composites many uncertainties occur, mainly material properties and geometric...

This study evaluates the effect and sensitivity of micro-scale geometric and material property uncertainties on the numerically determined effective elastic properties of unidirectional fibre reinforced matrix composite materials. Due to the multi-scale build-up nature of composites many uncertainties occur, mainly material properties and geometric...

This article presents a probabilistic framework to characterize the dynamic and stability parameters of composite laminates with spatially varying micro and macro-mechanical system properties. A novel approach of stochastic representative volume element (SRVE) is developed in the context of two dimensional plate-like structures for accounting the c...

Fibre reinforced composite materials are being widely used in many industries for their improved stiffness-weight ratio compared with other materials. However, the full benefits are often not realised in practice as conservative design factors are often used to account for the current limited understanding of how complex multi-scale uncertainties e...

Unique features of the Arctic region, such as sub-zero temperatures and glacial activities, pose serious risk to ships. The potential for ship accidents requires tailored guidelines for ship-ice interactions which justify the need for a suitable performance and risk assessment model for ships navigating in the Arctic waters. Research on the develop...

This chapter presents an exhaustive comparative investigation on the performance of neural network based models for the stochastic natural frequency analysis of composite plates. Both individual and combined variations of input parameters are considered to account for the effect of low and high dimensional input parameter spaces in the surrogate ba...

Common Cause Failures (CCFs) can compromise reliability performance of safety related systems and hence configurations with identical redundant units receive special attention in many industries, including in automotive, aviation and process applications. This paper introduces a new reliability model for redundant safety related systems using Marko...

The process industry has always been faced with the challenging task of determining the overall unavailability of safeguarding systems such as the safety instrumented systems (SISs). This paper proposes an unavailability model for a redundant SIS using Markov chains. The proposed model incorporates process demands in conjunction with dangerous dete...

Performing optimum design, reliable assessment or suitable verification for stainless steel profiled barrier blast wall structures requires dealing with various challenges, stemming from the associated uncertainties in material properties, fabrication, installation, and more importantly variations in the blast load characteristics. In the analysis,...

Ship collision accidents are rare events but pose huge threat to human lives, assets, and the environment. Many researchers have sought for effective models that compute ship stochastic response during collisions by considering the variability of ship collision scenario parameters. However, the existing models were limited by the capability of the...

This works presents an efficient framework for the reliability analysis of offshore wind turbine support structures based on a computational interface between an aero-hydro-servo-elastic simulator FAST and a finite element analysis software Abaqus®. This framework is used to evaluate the safety levels achieved by following the largely used IEC 6140...

Ship collision analysis outcomes are generally used in computational models to derive damage distributions. However, damage is usually assessed after the collision energy has been fully absorbed by structural members rather than at the onset of outer hull fracture. Furthermore, the deformation behaviour of ship structural members under load depends...

The objective of this paper is to assess the impact of soil axial resistance on initiation of the buckles on sleepers. It also covers the effects of history of pressure and temperature increase on effective axial force as well as the incorporation of external pressure in the Finite Element (FE) models. This is carried out for 6″, 8″, 10″ and 12″ pi...

This paper presents the probabilistic characterisation of basic variables of ship structures and their application in characterising ship hull response during collisions. 83 dog-bone samples from mild steel are tested until fracture by axial displacement and basic strength variable data are collected from their resulting stress-strain relations. Th...

This paper presents the quantification of uncertain natural frequency for laminated composite plates by using a novel surrogate model. A group method of data handling in conjunction to polynomial neural network (PNN) is employed as surrogate for numerical model and is trained by using Latin hypercube sampling. Subsequently the effect of noise on a...

Ship collision events are often analyzed by following the approach of internal mechanics and external dynamics. The uncertainties in collision scenario parameters, which are used in the calculation of external dynamics, are usually quantified during ship collision analysis. However, uncertainties in the material and geometric properties are often o...

Stainless steel profiled walls have been used increasingly in the oil and gas industry to protect people and personnel against hydrocarbon explosions. Understanding the reliability of these blast walls greatly assists in improving the safety of offshore plant facilities. However, the presence of various uncertainties combined with a complex loading...

Biodiesel production, like other engineering projects, involves critical decisions which have to be made under uncertainties stemming from a range of sources such as the inherent variation in operating conditions and market forces featuring inflation, depreciation factors, variations in equipment/production costs, etc. Although the effect of such u...

As chemical engineers seek to improve plant safety, reliability, and financial performance, a wide range of uncertaintyladen decisions need to be made. It is widely agreed that probabilistic approaches provide a rational framework to quantify such uncertainties and can result in improved decision making and performance when compared with determinis...

Probabilistic tools are being used to understand the inherent uncertainty of FRP composites. Over the years different approaches have developed, focusing on behaviour and associated uncertainties at a micro-/meso-/macro-scale, each with specific advantages/limitations depending on the type, and scope, of the analysis being undertaken. Consideration...

In probabilistic composite mechanics, uncertainty modelling may be introduced at a constituent (micro-scale), ply (meso-scale) or component (macro-scale) level. Each of these approaches has particular advantages/limitations and appropriate fusing and benchmarking is desirable in order to improve confidence in probabilistic performance estimates of...

The physical uncertainty associated with fiber-reinforced polymer composites has to be quantified and dealt with for their widespread use to be reliable. Developing probabilistic models based on experimental studies form an important part of this task. In the present paper, such models are developed for glass fiber-reinforced polymer (GFRP) composi...

In this paper, spatial variability of geometric and material properties of GFRP composites is studied for the first time based on an extensive experimental study. Random field characteristics are developed considering pultruded structural composite plates. In addition to improving existing stochastic mechanics approaches, such experimental studies...

The design formulations of pavements and bridges are significantly influenced by the uncertainties associated with the prevailing vehicle weight characteristics. Accurate modelling of load spectra and the estimation of possible vehicle growth and composition are the main components in the safety assessment of transportation structures. The vehicle...

The design formulations of pavements and bridges are significantly influenced by the uncertainties associated with the prevailing vehicle weight characteristics. Accurate modelling of load spectra and the estimation of possible vehicle growth and composition are the main components in the safety assessment of transportation structures. The vehicle...

Safety assessment and rational design of bridge structures requires the uncertainty associated with vehicle loads to be modeled as accurately as possible. This modeling is rendered difficult by the presence of vehicle axle weights that involve different combinations of unimodal and multimodal probability distributions with different dependence stru...

Spatial variability of FRP composites is relatively unexplored compared to the traditional random variable based stochastic analysis. The available literature points to subjective assumptions regarding these models rather than a rational experimentally based approach. As part of an ongoing research project, the present study presents bi-variate sta...