# Adam J. SadowskiImperial College London | Imperial · Department of Civil and Environmental Engineering

Adam J. Sadowski

MEng, MSc, MEd, MSc, PhD

## About

86

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Introduction

## Publications

Publications (86)

This paper explores the use of solid continuum finite elements and shell finite elements in the modelling of the nonlinear plastic buckling behaviour of cylindrical metal tubes and shells under global bending. The assumptions of shell analysis become increasingly uncertain as the ratio of the radius of curvature to the thickness becomes smaller, bu...

Many thin-walled cylindrical shells are used in structural applications in which the dominant loading condition is global bending. Key examples include chimneys, wind turbine support towers, pipelines, horizontal tanks, tubular piles and silos. The buckling behaviour of these structures in bending is complex due to the coupling between cross-sectio...

Modern design procedures for steel structures increasingly employ more realistic representations of the stress-strain behaviour of steel rather than a simple ideal elastic-plastic. In particular, for buckling failure modes in the plastic range, stresses in excess of the yield stress are always involved, together with a finite post-yield stiffness....

The new Reference Resistance Design (RRD) method, recently developed by Rotter [1], for the manual dimensioning of metal shell structures effectively permits an analyst working with only a calculator or spreadsheet to take full advantage of the realism and accuracy of an advanced nonlinear finite element (FE) calculation. The method achieves this b...

In the structural engineering limit state design philosophy of the Eurocodes, a target reliability is achieved by using partial safety factors on both the loading and the resistance that are, in principle, to be calibrated based on test data. The partial factor that is currently used for the buckling limit state of metal shells has been adopted fro...

This article describes a dataset used to calibrate a finite element model of a thick circular hollow section (CHS) with varying d/t (diameter to thickness) ratio under cyclic loading which may be used as a computational model validation benchmark by researchers working on similar problems in structural and mechanical engineering. The test data cons...

Shells of revolution under axisymmetric conditions exhibit a circumferentially uniform pre‐buckling stress state and are important fundamental systems which often serve as reference systems for those under more complex conditions. Given this status, work is continuing on a careful and complete characterization of their buckling response with the ai...

The ultimate limit state of buckling is an important consideration for the design of wind turbine support towers (WTSTs) which is increasingly being done with the aid of advanced nonlinear finite element analysis according to EN 1993‐1‐6. As these towers are relatively slender thin‐walled metal shell structures, their response and buckling resistan...

AQUINAS is a specialised MATLAB finite element (FE) toolbox for the nonlinear analysis of axisymmetric thin-walled shell systems, conceived by the Authors to recover a research functionality once widely available but now largely lost in the age of supposedly ‘general’ 3D FE software. AQUINAS exploits the powerful built-in sparse linear algebra rout...

An assessment of the elastic-plastic buckling limit state for multi-strake wind turbine support towers poses a particular challenge for the modern finite element analyst, who must competently navigate numerous modelling choices related to the tug-of-war between meshing and computational cost, the use of solvers that are robust to highly nonlinear b...

An assessment of the elastic-plastic buckling limit state for multi-strake wind turbine support towers poses a particular challenge for the modern finite element analyst, who must competently navigate numerous modelling choices related to the tug-of-war between meshing and computational cost, the use of solvers that are robust to highly nonlinear b...

A novel international initiative is underway to establish a purely computational database of synthetic buckling resistances on the basis of which the safety margin of metal wind turbine support towers can be calibrated within the Eurocode framework. This initiative has recently demonstrated that existing databases of laboratory-scale destructive bu...

Computational problems in structural engineering are growing ever larger and solutions must increasingly be based on correspondingly large datasets obtained from detailed parametric sweeps. However, the acquisition of computational datasets of useful size is also becoming increasingly unfeasible without extensive use of automation. In computational...

Corrugated walls are widely employed in the construction of metal silos. Despite the long history of testing to establish bulk material parameters for silo design, there does not appear to be an established test procedure to directly determine the effective friction coefficient for a corrugated wall other than an adaptation of a classical direct sh...

This paper reports on a series of shaking table tests on a full-scale flat-bottom steel silo filled with soft wheat, characterized by aspect ratio of around 0.9. The specimen was a 3.64-m diameter and 5.50-m high corrugated-wall cylindrical silo. Multiple sensors were used to monitor the static and dynamic response of the filled silo system, includ...

This paper presents a theory for the prediction of pressures in circular silos under concentric mixed flow, assuming an internal flow channel of conical profile with straight but inclined sides. The theory is based on a generalised application of the classical method of ‘slice equilibrium’ together with additional assumptions based on a treatment o...

Contrary to the large dataset of test results exploring the monotonic bending response of steel tubes, the corresponding dataset of cyclic bending tests remains very small. Seven compact and semi-compact S355J2H cold-formed circular hollow sections with diameter to thickness (D/t) ratios between 20 to 60, representative of piles used in piers and w...

Previous research has revealed shortcomings in the current Eurocode 3 (EC3) provisions for the design of semi-compact (Class 3) cross-sections. These shortcomings arise primarily from the lack of utilisation of partial plastification in bending, leading to a step in the design resistance function at the boundary between Class 2 and 3 cross-sections...

The resistance of cylindrical shells and tubes under uniform bending has received significant research attention in recent times, with a number of major projects aiming to characterise their strength through both experimental and numerical studies. However, the investigated cross-section slenderness ranges have mostly addressed low radius to thickn...

This paper presents a comprehensive computational investigation into the elastic nonlinear buckling response of near-perfect and highly imperfect uniform thickness thin cylindrical shells of varying length under combined uniform compression and bending. In particular, the elastic ovalisation phenomenon in cylindrical shell of sufficient length unde...

Subsea pipelines and PIP systems experience large bending moments during installation and operation. However, unlike single-walled pipelines, the behaviour of PIPs under bending has been only marginally addressed. In the current study, the bending response of PIP systems with diameter-to-thickness ratio (D/t) of 15-40 is investigated. Linear bifurc...

The global growth in wind energy suggests that wind farms will increasingly be deployed in
seismically active regions, with large arrays of similarly designed structures potentially at risk of simultaneous
failure under a major earthquake. The distance between the wind farm and the epicentre of the earthquake
affects the frequency content of the se...

Cable-supported structures such as bridges and stadia are critical for the surrounding community and the consequences arising from a major fire event can be substantial. Previous computational studies into the thermal response of cables often employed simplistic heat transfer models that assumed lump capacitance or cross-sectional homogeneity witho...

Metal wind turbine support towers are very tall and slender shell structures designed to exhibit a stepwise varying distribution of optimised wall thicknesses, with strakes in the upper regions of the tower usually being much thinner than those in the lower regions. Each strake is an individual shell and potentially a critical location for failure,...

Efforts are ongoing to characterise a comprehensive resistance function for cylindrical shells under uniform bending, a ubiquitous structural system that finds application in load-bearing circular hollow sections, tubes, piles, pipelines, wind turbine support towers, chimneys and silos. A recent computational study by Rotter et al. (2014) demonstra...

Four-point bending tests have been a staple in many structural engineering experiments as a reliable way of assessing the bending resistance of circular hollow sections, tubes and cylindrical shells, and they continue to be widely performed. However, relatively little attention appears to have been paid to quantify the effects of different boundary...

Thin-walled shells of revolution under circumferentially uniform pre-buckling stress
states are important fundamental systems, often serving as reference ‘base cases’ to
which the behaviour of more complex unsymmetrical systems can be related. However,
the same simplicity that often permits closed-form algebraic expressions for the critical
bucklin...

Silos are special structures used to store different kind of products that exhibit a complex behaviour because of the existence of specific phenomena such as the "silo effect". EN 1991-4 is a European standard, which is the reference code, employed worldwide to calculate the actions on silo walls produced by the stored material. Bin-hopper geometri...

Multi-strake cylindrical and conical shells of revolution are complex but commonplace industrial structures which are composed of multiple segments of varying wall thickness. They find application as tanks, silos, circular hollow sections, aerospace structures and wind turbine support towers, amongst others. The modelling of such structures with cl...

This is a Matlab .fig file of Figure 1 in IPVP3707 ("Influence of ovalisation on the plastic collapse of thick cylindrical tubes under uniform bending" - 10.1016/j.ijpvp.2018.05.004). The 3D plot may be rotated for a more detailed exploration of the data.

An accurate assessment of the bending resistance of thick cylindrical metal tubes is necessary for the safe and efficient design of pipelines, piles, pressure vessels, circular hollow sections and other common tubular structures. Bending tests continue to be widely performed as part of many engineering research programmes, but despite their ubiquit...

A number of recent publications have explored the crucial relationship between the length of a thin cylindrical shell and the influence of pre-buckling cross-sectional ovalisation on its nonlinear elastic buckling capacity under bending. However, the research thus far appears to have focused almost exclusively on uniform bending, with ovalisation u...

A recent computational study identified four distinct domains of stability behaviour at different lengths in thin elastic cylindrical shells under global bending. Cylinders of sufficient length suffer from fully-developed cross-sectional ovalisation and fail by local buckling at a moment very close to the Brazier prediction. Progressively shorter c...

1. SUMMARY This paper describes a project that seeks a better understanding of the influence of non-uniform support conditions during construction on the out-of-roundness distortions in both ground-supported and discretely supported thin-walled cylindrical silos and tanks. Distortions introduced when the shell is partially built become locked in, m...

The behaviour of cylindrical shells and circular hollow sections under uniform bending has long received significant research attention. This is mainly due to the phenomenon of Brazier cross‐sectional ovalisation which is known to lead to an almost 50% reduction in the buckling moment relative to the classical analytical prediction. However, very l...

Local buckling in circular tubes differs from that in cross‐sections formed from flat plate elements (I, H, RHS etc.) because the latter retain their original shape up to the point of local buckling and plates are not very sensitive to minor geometric imperfections. By contrast, the curved form of the circular tube or cylindrical shell is very sens...

New design methodologies are being developed that permit the full plastic condition and strain hardening properties of steel members and structures to be exploited. However, it has long been recognised that even the full plastic moment of a cross-section cannot be attained assuming only an ideal elastic-plastic material law, since infinite curvatur...

The length-dependent domains of behaviour of thin elastic cylindrical shells under uniform bending have recently received significant research attention. Ovalisation is known to affect very long cylinders which undergo significant cross-sectional flattening before failing by local buckling. This effect is restrained by the end boundary condition in...

Design formulas for thin‐walled cylinders in bending show remarkable differences in various codes, including versions of the Eurocodes. Thin‐walled, high grade steel cylinders are used in piles, e.g. in combined walls for quay wall construction or in large mono‐piles for mooring structures or offshore foundations. These piles experience a dominant...

The length-dependent behaviour domains of thin elastic cylindrical shells under uniform bending have recently received significant research attention. Ovalization is known to affect very long cylinders that undergo significant cross-sectional flattening before failing by local buckling. This effect is restrained by the end boundary conditions in sh...

Cylindrical metal shells with elliptical cross-sections are gaining increasing popularity as hollow sections due to their unique aesthetic appearance and different geometric properties about their two principal axes, with one axis exhibiting properties that are significantly more favourable than the other under flexure. However, in comparison with...

ABAQUS user subroutine GN_Riks_killer.f for the automated termination of geometrically nonlinear ‘Riks’ GNAs, GNIAs or GMNIAs.

ABAQUS user subroutine MN_Riks_killer.f for the automated termination of materially nonlinear ‘Riks’ MNAs based on the Convergence Indicator Plot (CIP) of Doerich and Rotter (2011).

New design methodologies are being developed to allow stocky steel members to attain and exceed the full plastic condition. For theoretical validation, such methods require a characterisation of the uniaxial stress-strain behaviour of structural steel beyond an idealised elastic-plastic representation. However, the strain hardening properties of ca...

An analytical model describing the nonlinear interaction between global and local buckling modes in long thin-walled rectangular hollow section struts under pure compression founded on variational principles is presented. A system of nonlinear differential and integral equations subject to boundary conditions is formulated and solved using numerica...

An analytical model describing the interactive buckling of a thin-walled box-section strut under axial compression, where global buckling is critical, is formulated based on variational principles. A system of nonlinear differential and integral equations subject to boundary conditions are derived and solved using numerical continuation. The result...

Classical shell finite elements usually employ low-order polynomial shape functions to interpolate between nodal displacement and rotational degrees of freedom. Consequently, carefully-designed fine meshes are often required to accurately capture regions of high local curvature, such as at the 'boundary layer' of bending that occurs in cylindrical...

The full plastic resistance under a combination of bending and axial force of tubes of all possible wall thicknesses, from thin cylinders to circular solid sections, does not ever seem to have been thoroughly studied, despite the fact that this is a relatively simple analysis. The first part of this paper presents a formal analysis of the state of...

The global growth in wind energy suggests that wind farms will increasingly be deployed in seismically active regions, with large arrays of similarly designed structures potentially at risk of simultaneous failure under a major earthquake. Wind turbine support towers are often constructed as thin‐walled metal shell structures, well known for their...

This paper presents the findings of a computational study into the effect of different support conditions and geometric imperfections on the nonlinear elastic stability of tubular members of varying length under global bending. Using the finite element analysis software ABAQUS, the tubular member was modelled as an isotropic thin-walled cylindrical...

Interactive buckling behaviour of thin-walled box-section columns under pure compression is investigated. The post-buckling behaviour of three example columns with typical slendernesses was analysed using the commercial finite element package ABAQUS. The results show that when the local buckling load is close to the global buckling load, unstable i...

Interactive buckling behaviour of thin-walled box-section columns under pure compression is investigated. The post-buckling behaviour of three example columns with typical slendernesses was analysed using the commercial finite element package ABAQUS. The results show that when the local buckling load is close to the global buckling load, unstable i...

This paper presents the findings of a computational study into the effect of different support conditions and geometric imperfections on the nonlinear elastic stability of tubular members of varying length under global bending. Using the finite element analysis software ABAQUS, the tubular member was modelled as an isotropic thin-walled cylindrical...

Geometric imperfections have long been known to play an important role in
determining the buckling resistance of metal cylindrical shells and tubes. Though the
effect is more important in thin shells rather than thicker tubular members, it may still
have a significant impact on the strength of tubulars where buckling occurs in the
plastic range.
Sp...

Thick tubular carbon steel members are commonly used in combination with sheet piles in large retaining walls where they provide the necessary bending stiffness. A current international research project aims to provide safe and efficient design rules for such ‘Combitubes’. These tubes are usually manufactured by continuous spiral welding from a car...

The behaviour of large tubular members under bending and axial load is complex due to the interaction of several nonlinear phenomena, including plasticity, buckling, ovalisation and the influence of geometric imperfections. Such members are currently either designed as a thin tube according to EN 1993-1-1 [1] or as a thick shell according to EN 199...

Combined constructions of steel tubes and sheet metal are used as retaining walls where high differences in ground levels have to be secured [1]. Such 'Combiwalls' consist of vertically positioned steel tubes (usually spiral welded) with diameter to thickness ratios in the range d/t = 70 - 100 (d = 800 – 1200 mm) that provide the necessary bending...

Spiral welding or bonding is a particularly efficient and cost-effective method of constructing continuous tubes. However the understanding of the mechanics of such structures is not yet well developed. This is in no small part due to the difficulties involved in their computational analysis.
Cylindrical shells are traditionally modelled using rect...

Many problems in structural mechanics involve complex principal stress fields that are not orthogonal to the geometric axis of the structure. Such problems are often analysed with finite elements, but the quality of a finite element solution may be sensitive to the orientation of the mesh with respect to the principal axes of stress. This paper pre...

Eccentric discharge in slender metal silos is known to be one of the most critical load conditions, responsible for many silo buckling disasters in the past. The high failure rate may be significantly attributed to difficulties in devising a suitable wall pressure representation for this condition. Where the flow of stored solids is eccentric and h...

The unsymmetrical discharge of a granular solid from a thin-walled cylindrical metal silo is well known to be a potential prelude to catastrophic buckling failure. The mechanics of this structure have only been very slowly unraveled in recent years with the help of powerful nonlinear finite element analyses. The associated buckling collapse is now...