M. Zeinoddini

K.N.Toosi University of Technology | KNTU · Faculty of Civil Engineering

The experimental modeling of vortex-induced vibration (VIV) poses a significant challenge when dealing with marine growth due to its diversity in species, size, and texture. Soft marine growth, in particular, presents a more complex behavior compared to hard marine growth, and its influence on the VIV phenomenon has received less attention. Therefo...

Vortex-Induced Vibration (VIV) enhancement through the employment of Two Degrees of Freedom (2DOF) oscillators is an effective approach for bladeless energy harvesting improvement. The effectiveness of this measure in an aquatic environment is questionable since the oscillators are soon inhabited by marine fouling. The fouling affects the vibration...

This study presents experimental and analytical fatigue frameworks for the dynamic fatigue life prediction of nonlinear mechanical systems under hyperchaotic oscillations. Fatigue in aluminium notched beams under hyperchaotic/chaotic vibrations is studied using a time-based analytical model. The fatigue lives obtained by the analytical model provid...

Almost all previous experimental studies on the fire performance of steel circular hollow section (CHS) joints were conducted in the absence of external load in the chord [9-15, 17-19, 21-22, 24, 26-28]. This paper is focused on the chord compression effects on the fire performance of CHS T-joints under out-of-plane bending (OPB). Seven identical s...

Most previous studies on marine hydrokinetic energy harvesters focussed on clean cylindrical oscillators. The current paper presents the results of the first investigation on the vortex-induced vibrations (VIV) hydrokinetic energy conversion from cylindrical oscillators covered with soft marine fouling. The one-degree-of-freedom system oscillates i...

This paper proposes an extended finite element method (XFEM) modelling approach coupled with cyclic damage mechanics criteria to simulate the fatigue crack growth (FCG), progressive delamination, and bridging in metal-fibre reinforced polymer (FRP) composites. The FCG in the metal is described using linear elastic fracture mechanics. The cycle-by-c...

The unbounded linearly increasing responses in galloping instability make sharp-edge oscillators a beneficial solution for bladeless energy harvesting. While the performance of single square oscillators has been the subject of several studies in the past, there is still little knowledge about their hydrokinetic energy performance in tandem configur...

Marine fouling quickly covers the submerged surfaces of the man-made structures and affects the flow regime around them. Many important studies have already been conducted on the Vortex-Induced Vibration (VIV) of bluff bodies, but the two-Degree-of-Freedom (2-DoF) VIV of marine-fouled cylinders has received no previous attention. The current towing...

The behaviour of steel circular hollow section (CHS) T-joints under combined fire load and out-of-plane bending (OPB) is investigated. A review of the literature indicates that the subject has not been previously considered by researchers. The authors carried out the first laboratory experimental study on OPB behaviour of simple steel tubular T-joi...

The current paper presents a novel model which generates artificial corrosion morphologies for metallic tubulars. It computes pseudo-random 3D morphologies from the corrosion statistics, such as its mean depth, standard deviation, and correlation length. The non-repeating profiles are statistically comparable with each other and with the observatio...

The current paper deals with numerical simulation of out-of-plane bending (OPB) of steel tubular T-joints in a standard fire. The data from fire tests, already carried out by the authors on OPB of small-scale steel tubular T-joints, are used to validate the numerical model. An extensive parametric study is conducted on the fire response of full-sca...

Repair welds are frequently used to fix defects in the manufacturing process, remedy in-service degradations, and for the life extension of ageing steel components and pressure vessels. Nevertheless, repair welds may exert detrimental impacts on the integrity of these structures in the long term. The primary focus of the current study is on the vee...

Despite the valuable previous studies on energy harvesting from flutter instability, no decisive ranking still exists between fluttering generators and harvesters based on other Flow-Induced Vibration (FIV) instabilities. In the current empirical study, the hydroelastic response and the energy performance of a self-sustained NACA 0015 hydrofoil are...

Steel tubular structures are popular in ocean and offshore structures, buildings, bridges, space frames, mining equipment, recreation structures and transportation vehicles. A tubular joint has a critical role in maintaining the integrity of a steel tubular structure under operational and extreme loading conditions. This paper reports the first exp...

Previous experiments on the fouling/current and fouling/wave interactions were mostly limited to two dimensional (2D) net panels or isolated twines. The current paper deals with the wave-induced forces/moments in three dimensional (3D) physical models of a gravity net-cage. The colonial hydroid Ectopleura larynx, a common fouling organism in the aq...

Purpose In this paper, a closed-form analytical solution for the prediction of moment-rotation and the rotational stiffness-rotation curves of I-shaped beam to cylindrical column connections, commonly used on offshore platforms, at room and elevated temperatures, are presented. Design/methodology/approach An analytical solution for the prediction...

Marine fouling is a major concern in marine aquaculture industry. It changes the flow field around the cage, reduces water exchange across the nets and affects the current/wave-induced forces acting on the structure. The current/wave forces induced to marine-fouled planar net panels were studied by previous researchers. The current paper reports th...

The current paper reports the results of a series of small-scale physical model tests conducted to study the marine fouling effects on the wave attenuation/build-up around/inside a 3D floating gravity net cage. The artificial fouling modelled was representative of hydroids, an important fouling organism in the marine aquaculture industry. Regular w...

This paper presents the results of an experimental study in which for the first time the progressive inelastic deformation of high strength steel pressurized pipes with plain and gouged dents was analyzed. The effect of some key loading and geometrical parameters such as initial pre-strain (εmon), dent depth ratio (δ/D) and the presence of the goug...

The current paper reports the results of in-water experiments to study the effect of end conditions on cross flow induced vibration (FIV) of a pair of circular cylinders in a tandem arrangement. The upstream cylinder remains fixed but the downstream cylinder is elastically mounted. The single degree of freedom vibrating system has a low mass-dampin...

This paper reports the results of laboratory in-water experiments in which artificially marine-fouled circular cylinders were freely vibrating in the wake of a similar fixed upstream cylinder. Cross-flow vibrations at gaps of 3–7 diameters were examined. The marine fouling was simulated by CNC machining of uniformly distributed single-sized pyramid...

Dynamic fatigue crack growth (FCG) under chaotic excitations has not yet received due attentions. The current paper presents an analytical model for predicting the FCG in a metallic notched beam subject to external chaotic excitations. The proposed stand-alone analytical model only requires the physical properties of the cracked beam; initial crack...

Marine fouling changes the flow regime around sub-sea structures, such as Vortex-Induced Vibration Aquatic Clean Energy (VIVACE) converters. The present experimental study investigates the effects of marine fouling on mechanical power harvesting performance from the Vortex-Induced Vibration (VIV) of single circular cylinders. The towing tank VIV te...

The global demand for renewable energy sources has arisen significant research interests in marine hydrokinetic energy harvesting from flow induced vibrations. The current study deals with the hydrokinetic energy harvesting potentials of diamond and square oscillators at various inline configurations. Both the sharp edge sections and the wake induc...

The horizontal kinetic energy of the fluid flow, from on-land wind to ocean tidal stream, is one of the most promising sources of the energy. In the field of renewable energies, power extraction from Flow Induced Vibration (FIV) of bluff bodies is a fast growing research area which has seen a great advancement over the last decade. In this study, t...

The relative incompetency of rectangular galloping excavators against conventional circular VIV harvesters is already known. In this experimental study, the hydroelastic energy performances of new right-angle isosceles triangular cylinder against circular, square and diamond cross-sections are investigated. The triangular cylinder displays VIV or g...

Metallic tubes experiences a progressive accumulation of ovalisation, or ratchet, under cyclic inelastic bending. During their life time, the tubes may also suffer from different types of mechanically and/or chemically originated defects. The current paper discusses a closed-form solution for the response analysis of defective circular steel tubes...

This in-water experimental study deals with the effects of the after-body on the FIV response of round and sharp edge cylinders. Different circular, square, diamond, and right-angle isosceles triangular cross-sections are investigated. The triangular cylinder is examined in four different symmetrical and unsymmetrical configurations with respect to...

The current paper addresses the possibility of chaotic dynamics in the VIV response of cylinders covered by marine biofouling. The fouling was simulated by machining uniformly distributed pyramidal protrusions on the surface of the test cylinder. The Reynolds number varied from 5.8×103 to 6.6×104. The zero-one tests, Hilbert Transforms and Poincaré...

Endurance Wave Analysis (EWA) is a novel, simple, economical but yet reliable method for the integrity assessment of offshore platforms against extreme irregular waves. The current paper presents a framework for the probabilistic assessment of offshore platforms based on EWA. The stochastic nature and the uncertainties in the ocean waves were taken...

The current study is aimed at getting a further insight into the changes the fouling brings to the Vortex Induced Vibration (VIV) of circular cylinders. Instead of regular patterns considered in previous studies, using the Poisson Cluster Process, an aggregated spatial distribution was considered for the artificial marine fouling. This is believed...

The response of an oscillating circular cylinder at the wake of an upstream fixed circular cylinder was classified by different researchers as galloping, wake induced galloping or wake induced vibration. Furthermore it is already known that a sharp edge square cylinder would undergo galloping if it is subjected to uniform flow. In this study the in...

Metallic tubes experiences a progressive accumulation of ovalisation, or ratchet, under cyclic inelastic bending. The current paper deals with the ratcheting behaviour of defective small-scale API X80 carbon steel tubes subjected to cyclic bending. The subject appears not to have received due previous attentions but is important in the design and m...

The results of in-water vortex-induced vibration (VIV) experiments on circular cylinders artificially covered with barnacles are reported. The paper focusses on the effects of the partial coverage and the shape of the fouling elements. An artificial barnacle typical of marine fouling was synthesised using 3-D printing. Coverage ratios of 80, 50 and...

Endurance Wave Analysis (EWA) is a new dynamic pushover approach in which an offshore structure is examined against some gradually intensifying sea states. The approach was already used for the dynamic nonlinear deterministic analysis of offshore structures. In this paper, a direct probabilistic framework for generating fragility curves of offshore...

The current paper deals with the cyclic plastic response and strain ratcheting of circular steel tubes under repeated inelastic pure bending. A closed-form solution is proposed for the problem. The cyclic softening/hardening behaviour of the material is modelled using a combined bilinear kinematic/nonlinear isotropic hardening rule. The relative ha...

Underwater surface of man-made structures is quickly covered by unwanted aquatic organisms. They change the flow regime around the structure. Despite the important contributions of previous studies on the vortex induced vibration (VIV) of bluff bodies, the flow induced vibration of non-stationary cylinders covered by marine fouling appears not to h...

High strength steel pipes have found increasing applications in deep high pressure offshore oil/gas lines. Damages in the form of dent are among common causes of pipeline failure. Indentation, plastic buckling and residual strength of dented normal grade steel pipes under bending, axial and combined loading have previously been addressed by a numbe...

This paper reports results from an investigation into the suction caissons failure mechanisms under vertical pull-out loads. An insight to the failure mechanisms of suction caissons paves the path for developing analytical solutions to their pull-out capacity. The numerical models of suction caissons have first been calibrated by and verified again...

Estimation of fatigue life is of great importance in offshore platforms. The fatigue life is considered to be acceptable and within normal design criteria if the calculated fatigue life is longer than the total design service lifetime multiplied by the Fatigue Safety Factor (FSF). Actual fatigue life of an existing platform typically deviates from...

چکيده در حال حاضر، عمر مفید بهره‌برداری بسیاری از سازه¬های فراساحل به پایان رسیده و یا رو به اتمام است. از طرفی، بسیاری از صاحبان سکو و کارفرمایان به جای طراحی و ساخت سازه¬های جدید، علاقه‌مند به استفاده و بهره¬برداری بیشتر از سازه¬های موجود می¬باشند. بر همین اساس، ارزیابی صحیح و دقیق استحکام سازه¬ای سکوهای موجود از اهمیت به¬سزایی برخوردار است. آئین...

(A limited number of free online access is available via the following Email: http://www.tandfonline.com/eprint/UraxApJicRYMJSTyTCjX/full) Abstract Actual fatigue life of an existing offshore platform typically deviates from that intended by its designer because aging platforms commonly experience some degradations, mechanical damages, repairs and...

Behaviour of upright suction caissons with regard to their applications, installation, load-bearing, etc., has already been investigated by a number of researchers. Some researchers have also addressed the behaviour of tapered piles under different loading conditions. However, there has not been any previous experimental experience regarding the pe...

This paper presents numerical results of structural post- fire bahaviour of I-shaped beam-to-chord joints in offshore platforms topside. Considering the high risk of fire events in offshore oil/gas platforms, this study focuses on the structural behaviour of these connections at post- fire condition. A highly detailed three-dimensional (3-D) finite...

Beam-to-column connections are of great significance as they noticeably influence the mechanical behavior of structures at ambient and elevated temperatures. Observations from full-scale fire tests confirm that connections play an important role on the resistance time of structural components in fire. Because of the high cost of elevated temperatur...

Lake Urmia in the north-west of Iran is very large, very shallow and several times more saline than ocean water. The salinity of this terminal lake is of great ecological consequence for the existence and growth of Artemia Urmiana, a unique zooplankton endemic to the lake. It is a main food source for large bird populations. During the past decades...

Behaviour of jacket type offshore structures under ordinary ground excitations has already been addressed by a number of researchers. However, their performance under near-source ground excitations has not been particularly addressed in the literature. Records from recent earthquakes, such as the Kobe Japan (1995) and Chi-Chi Taiwan (1999), have re...

In seismic areas, a majority of such old buildings have only been designed for gravity loads or according to outdated seismic codes. Before1970's, smooth rebars were also extensively used in RC structures. As some of these buildings are still functioning, they need to be reassessed against seismic demands. Load bearing behaviour of concrete structu...

On many occasions, the effects of wind-induced waves and currents on flow and salinity fields in water bodies are evaluated separately. Some coupling mechanisms of the two phenomena, however, can have a significant impact on the flow and salinity conditions, in particular in sensitive aquatic ecosystems. This article attempts to quantify the wave c...

This study focuses on non-linear seismic response of concrete gravity quay-wall structures subjected to near-fault ground motions, a subject which seems not to have received much attention in the literature. A two-dimensional coupled fluid-structure-soil finite element modelling is employed to obtain the quay-wall response. The seawater medium is r...

The existing knowledge on the structural integrity assessment of offshore platforms may benefit from case studies on the life extension evaluations of aging structures. This paper presents a case study for the structural integrity assessment of an existing 8 legged aging drilling platform located in the Persian Gulf. The platform is now 42 years ol...

In recent years, application and evaluation of the efficiency of different data assimilation methods has been a subject of interest in both wave hindcasting and forecasting systems. The main goal of the current study is to assess the efficiency of an ensemble Kalman filter (EnKF) data assimilation scheme in improving the wave simulation results in...

This book is devoted to an engineering case study on an important, yet problematic, sea dike which crosses the Lake Urmia in Iran. This dike-type causeway appears to be an interesting case for studying the dike’s long-term behavior and their hydrodynamic/geological effects. The Lake Urmia dike is around 14 km long and begun being constructed in 197...

Incremental Wave Analysis (IWA) is a novel and robust methodology for performance base assessment of offshore jacket type platforms against wave loading. This approach can b employed to obtain a more realistic estimate for the ultimate capacity of offshore platforms, in comparison to the commonly used push-over analysis. On the other hand, ocean an...

In practice, steel tubulars lack a mathematically perfect cylindrical shape, due to nonuniformities introduced during the manufacturing process, construction methods, damages incurred in the transport. The imperfections might exist in the cross section and along the tubular member. Imperfections can greatly affect the behavior of tubular members. T...

Vortex induced vibration, especially at relatively high Reynolds number, will become a complex 3D phenomena. By changing the uniform shape of the cylinder and moving toward tapered cylinders, the situation will become even more complicated and the cylinder responses look unpredictable. Most previous experimental studies on tapered circular cylinder...

Subjects related to strength and durability of structures such as oil and gas transmission pipelines areof great importance. Considering the special characteristics of these structures including their construction and harsh working environment, they are especially prone to different types of damages. Repair welding is a viable optiontomitigatesuch...

Previous researchers have tried to predict the response of different types of structures under elevated temperatures. The results are important in preventing the collapse of buildings in fire. Post-fire status of the structures is also of interest for ensuring the safety of rescue workers during the fire and in the post-fire situations. Determining...

Submarine pipelines are usually laid unburied. Free spanning may be caused in the line by seabed unevenness, topology changes, scouring, or sand waves. In seismically active areas, the free spannings are prone to severe ground excitations. This article deals with the seismic performance of the submarine pipeline free spanning, and the water/pipelin...

The aim of this paper is to introduce a novel approach, called Endurance Wave Analysis (EWA), for non-linear dynamic analysis and assessment of offshore structures subjected to irregular wave forces. This is, in fact, an extension of the Endurance Time Analysis (ETA) already presented by previous researchers for the seismic assessment of onshore st...

This paper introduces a novel methodology for design and assessment of offshore structures exposed to irregular sea waves. For this, Constrained NewWave (CNW) is integrated with the Endurance Time Analysis (ETA) methodology, which is basically developed for the performance based analysis of onshore structures to earthquake loads. In this approach,...

The prediction of wind driven ocean waves is of primary importance for the safety of shipping and off-shore operations, as well as for scientific studies of, e.g., sediment transport and ocean-atmosphere interaction. Traditionally, wave models do not explicitly use the wave observations to estimate the present sea state: the only input to the model...

In this paper results from simulating the vortex shedding phenomena behind a fixed tapered circular cylinder, at relatively high Reynolds numbers, are reported. Ansys-CFX computational fluid dynamics model, based on solving three-dimensional (3D) incompressible transient Navier Stokes equations, is employed for this purpose. The geometries applied...

Steel tubular members are widely used as primary and secondary structural framing members in offshore oil and gas platforms. A platform is inherently liable to collisions from ships which can create severe structural damages in the rig. The effect of this damage has been studied by a number of researchers through investigating the impact behaviour...

Steel tubular members are widely used as primary and secondary structural framing members in offshore oil and gas platforms. A platform is inherently liable to collisions from ships which can create severe structural damages in the rig. The effect of this damage has been studied by a number of researchers through investigating the impact behaviour...

This paper reports results of a numerical investigation into the suction caissons penetration in sand. A 3D finite element model is used for this purpose. The water saturated soil domain is modelled as a two-phase medium, consisting of soil skeleton and pore-water phases. Nonlinear behavior of the solid phase is described by means of a bounding-sur...