ENGINEERING CONSULTANCY

Advanced analysis.
Practical engineering
decisions.

We are a dynamic group of chartered engineering consultants with multi-disciplinary background and several years of experience between us, providing structural design and asset-integrity assessment services for Energy and Civil infrastructure.

Discuss your project Explore project cases ↓
MECHANICS / SIMULATION / STRUCTURES↓
01

Energy Infrastructure analysis and design

Onshore and subsea pipelines, Pressure vessels, Special components design

02

Built environment - Structural Engineering

Concrete, Steel and Composite structural design of commercial and industrial buildings

03

Asset Integrity

Fitness-for-Service assessments, Asset Integrity Management

04

R&D

Advanced Computational Mechanics applications

01 / THE CONSULTANCY

Engineering depth.
Real-world perspective.

Engineering consultancy with in-depth experience in the structural analysis and design of:

  • Energy infrastructure
  • Industrial and commercial buildings
  • Asset-integrity assessment of energy and civil infrastructure
  • Assessment and seismic retrofit of existing buildings

Our toolset includes Advanced Engineering Mechanics, Finite Element Analysis (FEA) and Computational Fluid Dynamics (CFD).

We are familiar with major international design codes, including Eurocodes, ASME, API, BS, DNV and NORSOK.

02 / OUR EXPERTISE

Specialist knowledge.
Connected disciplines.

From understanding behaviour
to designing the way forward.

01MECHANICS

Advanced Engineering
Mechanics

Understanding how materials and systems respond to load. Mechanics-based analysis of stress, deformation, stability and failure.

Structural behaviour / Failure mechanisms
02SIMULATION

Numerical Modelling

Finite Element Analysis (FEA) and Computational Fluid Dynamics (CFD) for structural response and fluid flow. Coupled analyses address flow-induced vibration, fluid–structure interaction and fatigue.

Numerical modelling / Performance analysis
03ASSET INTEGRITY

Fitness-for-Service
Assessment

Fitness-for-Service (FFS) assessment for petrochemical equipment, informed by experience in API 579 Levels 1, 2 and 3 and ASME VIII. Nonlinear analysis, fatigue and fracture mechanics support decisions on operating limits, repair and remaining life.

Petrochemical / Defect assessment
04DESIGN

Civil & Structural
Engineering

Structural analysis and design for buildings and engineering structures. Turning project requirements into clear, technically grounded solutions.

Structural analysis / Engineering design
05STRUCTURES

Concrete, Steel & Composite Structures

Design and assessment of concrete, steel and steel–concrete composite structures, with attention to load paths, stability, reinforcement detailing, connections and composite action.

Concrete / Steelwork / Steel–concrete systems
06EXISTING STRUCTURES

Seismic Assessment
& Retrofit

Assessment and seismic retrofit of existing structures. Understanding vulnerabilities and developing strengthening solutions suited to the building and its constraints.

Seismic performance / Strengthening

03 / OUR APPROACH

Understand.
Analyse.
Resolve.

A clear line from the engineering question to an informed decision.

01

Define the problem

Establish the objectives, operating conditions and constraints. Identify the information needed to understand the structure or asset.

02

Model what matters

Select the appropriate level of analysis. Examine critical behaviour, check assumptions and interpret results in their physical context.

03

Make the outcome useful

Translate the findings into practical design, assessment or retrofit recommendations, with a clear explanation of the engineering basis.

04 / OUR PROJECTS

Engineering in practice.

Example projects
Models, results and built structures.

Energy InfrastructureStructural Engineering

OUR ENGINEERING DISCIPLINES

Energy Infrastructure

Pipeline mechanics, piping components and asset integrity.

Stress contours and deformation of the steel casing pipe joint
ADVANCED NONLINEAR ANALYSIS01

Steel casing pipe joint

Northwest Pipe Company · University of Thessaly

Assessment of a steel casing pipe joint under multiple loading conditions, using an advanced three-dimensional finite element model.

View analysis & project images
Method
Advanced three-dimensional FEA with nonlinear materials, large deformation and frictional contact.
Assessment output
Definition of structural capacity using stress- and strain-based criteria.
Three-dimensional finite element model and loading arrangements
Three-dimensional finite element model and loading arrangements
Material true stress–strain relationship
Material true stress–strain relationship
Normalised force–displacement response
Normalised force–displacement response
Stress contours under combined loading
Stress contours under combined loading
Finite element animation of the steel casing pipe joint. No audio.
Numerical results for reinforced and unreinforced tees under bending
PIPELINE MECHANICS02

Geohazard-resistant pipe bends & tees

Northwest Pipe Company · University of Thessaly

Assessment of miter bends and tees for Geohazard Resistant Steel Pipe (GRSP) subjected to extreme ground displacement.

View analysis & project images
Method
Advanced three-dimensional FEA with nonlinear materials, large deformation and frictional contact.
Load cases
Internal pressure combined with opening/closing bending in 90-degree miter bends, and in-plane bending of unreinforced and reinforced tees.
Assessment output
Structural capacity evaluated using stress- and strain-based criteria, including critical strain versus stress triaxiality.
Material engineering stress–strain relationship
Material engineering stress–strain relationship
Critical strain versus stress triaxiality
Critical strain versus stress triaxiality
Numerical results for 90-degree miter bends
Numerical results for 90-degree miter bends
Numerical results for tees under bending
Numerical results for tees under bending
Related ASCE publication ↗
Finite element mesh of the Bottom Steam Distribution Manifold
INDUSTRIAL ASSET ASSESSMENT03

Bottom Steam Distribution Manifold

Location undisclosed

Undisclosed client · University of Thessaly

Structural capacity assessment of a Bottom Steam Distribution Manifold (BSDM) to EN 1993-1-6 provisions.

View analysis & project images
Scope
Structural capacity assessment of the manifold.
Assessment output
Structural capacity evaluated for different operating phases, and capacity improvement modifications were proposed.
Finite element mesh of the manifold
Finite element mesh of the manifold
Alternative view of the finite element mesh
Alternative view of the finite element mesh
Shell stress result
Shell stress result
Deformation-mode output
Deformation-mode output

OUR ENGINEERING DISCIPLINES

Structural Engineering

Concrete, steel and composite structures, building design and seismic retrofit.

Bocamar Beach Bar, completed building at night
COMPOSITE STRUCTURES04

Commercial Building

Rhodes, Greece

MOSQ + Associates

Structural design and detailing of a steel–concrete composite structure for Bocamar Beach Bar.

View analysis & project images
Scope
Structural design and detailing.
Project evidence
Structural model, construction-stage photograph and completed-building photographs.
Structural analysis model
Structural analysis model
Steelwork during construction
Steelwork during construction
Completed bar interior
Completed bar interior
Completed building exterior
Completed building exterior
Completed suspended steel canopy in Almyros, Greece
STRUCTURAL DESIGN05

Commercial Building

Almyros, Greece

Structural design and detailing of a suspended steel canopy roof supported by composite columns.

View analysis & project images
Scope
Structural design of the canopy and its supporting system.
Project evidence
Three-dimensional structural model, design-detail drawing and photographs of the installed steelwork.
Three-dimensional canopy structural model
Three-dimensional canopy structural model
Canopy and column design detail
Canopy and column design detail
Wide view of the installed suspended steel canopy
Installed suspended canopy — wide view
Oblique view of the installed suspended steel canopy and supporting columns
Installed suspended canopy — oblique view

Clients & collaborators

Northwest Pipe Company
MOSQ + Associates
Lindos Royal Resort
ΕΥ ΖΗΝ — TED, Τεχνική Εταιρεία Δωδεκανήσου
University of Thessaly
Northumbria University

05 / RESEARCH & DEVELOPMENT

Research that informs
engineering practice.

Research experience across energy infrastructure, advanced computational mechanics and structural engineering, through University and Industry collaborations.

Research & collaborations

Worley R&D — Various projects (undisclosed)

From 2022

RESEARCH BEHIND THE PRACTICE

Selected publications

Collaborative research with University and Industry partners connects structural behaviour, advanced numerical modelling and energy infrastructure.

  1. Design considerations for hydrogen pipelines ↗
    Citation detailsVarelis, G.E., Briffett, A., Latif, H., Papatheocharis, Th., Bernardi, L.Journal of Pressure Vessel Technology, ASME, 147(5): 051504, Paper No: PVT-25-1033, October 2025.
  2. A-State-Of-The-Art review on modular building connections ↗
    Citation detailsRajanayagam H., Poologanathan K., Gatheeshgar P., Varelis G.E., Sherlock P., Nagaratnam B., Hackney P.Structures, 34, September 2021.
  3. High-strength Steel Tubular Welded Joints under Extreme Loading Conditions ↗
    Citation detailsVarelis, G.E., Papatheocharis, Th., Perdikaris, P.C., Karamanos, S.A.Marine Structures, 71 102701, January 2020.
  4. Finite Element Analysis of Cyclically-Loaded Steel Pipes During Deep Water Reeling Installation ↗
    Citation detailsChatzopoulou G., S.A. Karamanos, Varelis G.E.Journal of Ocean Engineering, 124, 113–124, Elsevier, August 2016.
  5. Monotonic, Low-Cycle Fatigue and Ultra-Low Cycle Fatigue Behaviours of the X52, X60 and X65 Piping Steels Grades ↗
    Citation detailsJ.C.R. Pereira, A.M.P. de Jesus, A.A. Fernandes, G.E. VarelisJournal of Pressure Vessel Technology, ASME, December 2015.
  6. Finite Element Analysis of UOE Manufacturing Process and its Effect on Mechanical Behavior of Offshore Pipes ↗
    Citation detailsChatzopoulou G., S.A. Karamanos, Varelis G.E.International Journal of Solids and Structures, December 2015.
  7. Low-cycle Fatigue of Pressurized Steel Elbows under In-plane Bending ↗
    Citation detailsVarelis, G. E., Karamanos, S. A.Journal of Pressure Vessel Technology, ASME, Vol. 137(1), Article Number: PVT-13-1116, September 2014.
  8. Buckling of High-strength Steel Cylinders under Cyclic Bending in the Inelastic Range ↗
    Citation detailsVarelis, G. E., Karamanos, S. A.Journal of Pressure Vessel Technology, ASME, Vol. 136, No. 2, Article Number: PVT-13-1104, January 2014.
  9. Pipe Elbow Response Under Strong Cyclic Loading ↗
    Citation detailsVarelis, G. E., Karamanos, S. A., and Gresnigt, A. M.Journal of Pressure Vessel Technology, ASME, Vol. 135, No. 1, Article Number: PVT-12-1005, December 2012.

06 / WHO WE ARE

Who we are

Engineering.
Innovation.
Impact.

We are engineering consultants with several years of experience between us in advanced mechanics, computational simulation and structural engineering.

Our collective experience covers civil and structural practice, advanced analysis, research, and technical leadership on energy, industrial and building projects.

We connect the behaviour of materials and structures with the decisions a project needs: how to design, what to strengthen and how to assess an existing asset.

NEW STRUCTURESEXISTING BUILDINGSINDUSTRIAL ASSETS
Dr George E. Varelis, founder of 4struct

CHIEF ENGINEER · FOUNDER

Dr George E. Varelis

PhD · CEng MIMechE

Google Scholar profile ↗

Civil engineer and computational mechanics specialist with professional experience since 2007. George combines structural design and seismic research with advanced nonlinear analysis, fatigue, fracture mechanics and industrial Fitness-for-Service assessments.

Academic foundation
PhD in Structural Mechanics (2013), MSc in Structural Mechanics (2010) and Diploma in Civil Engineering (2007), University of Thessaly.
Professional standing
Chartered Engineer and Member of the Institution of Mechanical Engineers, UK (CEng MIMechE), since 2015. Chartered Civil Engineer, Technical Chamber of Greece, since 2007.
Technical leadership
Chief Advanced Analysis Engineer and Technology & Innovation Lead at Worley, London (2023–2026); earlier specialist and principal roles at INTECSEA and PDL Solutions.
Specialist expertise
Nonlinear FEA; fatigue and fracture mechanics; coupled CFD/FEA vibration assessment; steel and seismic structural behaviour, ASME and API 579 Fitness-For-Service assessments

07 / GET IN TOUCH

Contact us

Start with the structure or asset, the decision you need to make and your timescale.

Email
[info@4struct.com]
Telephone
[+30 6976634257]
Office
[Archangelos, Rhodes, Greece]

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