Research

Research line 1/4:

Fabrication of new structural systems using laser cutting


We focus on the common problems in the fabrication of steel tubular joints and try to improve both the fabrication process and structural characteristics of such joints. In a recently concluded EU-RFCS research project we achieved this by Laser Cutting Technology (LCT). LASTEICON aimed to eliminate the use of excessive amount of stiffener plates and welding in steel joints, using LCT. 

In the project, 36 two-way steel joints have been tested under monotonic gravity, opposite bending and shear loading to quantify their structural performance in terms of stiffness, resistance, and ductility. The performance of LASTEICON joints is also experimentally compared with the structural performance of equivalent directly welded conventional joints. The project aimed to enhance the economy and sustainability of the fabrication as well as the aesthetic of any type of steel joints. Some of our articles about this research can be read here: 

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Our latest article on the subject: Couchaux M., Vyhlas V., Kanyilmaz A., Hjiaj M., Passing-through I-beam-to-CHS column joints made by laser cutting technology: Experimental tests and design model, Journal of Constructional Steel Research, Volume 176, 2021, 106298, ISSN 0143-974X, https://doi.org/10.1016/j.jcsr.2020.106298.

Das R., Kanyilmaz A., Couchaux M., Hoffmeister B., Degee H., Characterization of moment resisting I-beam to circular hollow section column connections resorting to passing-through plates, Engineering Structures, Volume 210, 2020, 110356, ISSN 0141-0296, https://doi.org/10.1016/j.engstruct.2020.110356.

Kanyilmaz, A., The problematic nature of steel hollow section joint fabrication, and a remedy using laser cutting technology: A review of research, applications, opportunities, Engineering Structures, Volume 183, 2019, Pages 1027-1048, ISSN 0141-0296, https://doi.org/10.1016/j.engstruct.2018.12.080.

Kanyilmaz, A., Castiglioni C.A., Fabrication of laser cut I-beam-to-CHS-column steel joints with minimized welding, Journal of Constructional Steel Research, Volume 146, 2018, Pages 16-32, ISSN 0143-974X, https://doi.org/10.1016/j.jcsr.2018.02.039

 

Research line 2/4:

Structural design using machine learning, bio-inspired topology optimization and additive manufacturing


Additive Manufacturing and bio-inspired structural design

Nature’s structures are also often tubular. Their joints (e.g. the knees of a human body, the nodes of trees and plants) are intrinsically optimized to maximize stiffness, resistance, and robustness. The 3D metal printing technology can enable a custom optimization of steel tubular joints, saving material waste and decreasing fabrication costs, since it is free from the constraints of traditional manufacturing. The challenge is to merge multiple players (architects, manufacturers, producers) to take advantage of MAM to reduce costs, increase customization and cut waste as well as the carbon footprint of the sector. We currently study new tubular joint shapes using solid isotropic material with the penalization method (SIMP) to maximize structural performance and minimize fabrication complexity. Such joints can be 3D-printed.

One article about this research-line can be read here:

Kanyilmaz, A., Berto, F., Paoletti I., Caringal, R.J., Mora, S., Nature-inspired optimization of tubular joints for metal 3D printing, Struct Multidisc Optim (2020). https://doi.org/10.1007/s00158-020-02729-7, Springer Nature

 

Conceptual design using machine learning

Nowadays we are studying the application of adaptative search techniques such as Genetic Algorithms (GA) in the development of interactive design assistants for conceptual structural design. More on this will be published soon.

 


Research line 3/4:

Mitigation of dynamic actions (seismic, fatigue) on structures


Fatigue strength of cold-formed structural steel details

Cold-formed steel is increasingly adopted in logistics warehouses, where heavy goods are handled automatically on a 7/24 basis. Fatigue related problems are causing large economic damages in this type of structures, due to their “dynamic” and “consistent” loading conditions. Despite this fact, in European standards, fatigue design concepts for cold formed steel is completely missing. Answering to an industrial need, FASTCOLD project aims to develop fatigue design rules for cold formed steel structural details, and classify such details according to their fatigue strength (as for hot-rolled steel in EN1993-1-9). Some studied details are of general applications, in view of Eurocode implementation.

Advanced structural solutions for automated steel rack supported warehouses

Automated Rack Supported Warehouses (ARSW) represents the future of storage technology, providing substantial savings in terms of cost, space and energy with respect to traditional warehouses. Currently, designers refer to building codes, without controlling their applicability to the specific typologies of such structures. This creates safety and efficiency problems being ARSWs’ structural characteristics considerably different from those of steel structures for normal buildings. Objective of the research is to analyse actual design practices, to investigate logistics’ imposed loading strategies, unconventional loading conditions, constructional phases and seismic design and to propose new approaches aiming at increasing ARSW safety, reliability and economy.

Earthquake design of concentrically braced frames under low-to-moderate seismicity

Within MEAKADO research project, we proposed an adjusted design approach for the low-to-moderate seismicity design of Concentrically Braced Frame (CBF) structures. With the new approach, we aim to satisfy both economy and safety criteria, based on the exploitation of the three features of CBFs, which had not been deeply examined before: “frame action provided by gusset plates”, “contribution of compression diagonal and its post-buckling strength and stiffness”, and “energy dissipation capacity of non-ductile bracing joint connections”.

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We investigated these aspects by means of incremental dynamic analysis of case studies, based on the numerical models calibrated on full-scale experimental tests published elsewhere by us.

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Based on the results of full-scale experiments, we quantified the ductility provided by the bolt hole ovalization and the slippage of preloaded bolts of standard bracing joints of concentrically braced frames that are not fulfilling the current over-strength design criteria.

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We studied the stiffness and post-buckling contribution of compression bracings in Concentrically braced frames (CBFs). Full scale experimental findings have been reported, which were obtained within EU-RFCS MEAKADO project and performance of CBFs with and without compression diagonal has been quantified.

We quantified the effective contribution of the frame action, provided by gusset plate connections, to the global performance of CBF frames.

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The following articles explain more on this research line:

Kanyilmaz, A., Degée, H. & Castiglioni, C.A. An adjusted design approach for concentrically braced frames in low-to-moderate seismicity areas. Bull Earthquake Eng 16, 4159–4189 (2018). https://doi.org/10.1007/s10518-018-0402-0

Kanyilmaz, A. Secondary frame action in concentrically braced frames designed for moderate seismicity: a full scale experimental study. Bull Earthquake Eng 15, 2101–2127 (2017). https://doi.org/10.1007/s10518-016-0054-x

Kanyilmaz, A., Role of compression diagonals in concentrically braced frames in moderate seismicity: A full scale experimental study, Journal of Constructional Steel Research, Volume 133, 2017, Pages 1-18, ISSN 0143-974X, https://doi.org/10.1016/j.jcsr.2017.01.023.

Kanyilmaz, A. Moderate ductility of the bracing joints with preloaded bolts. Bull Earthquake Eng 16, 503–527 (2018), https://doi.org/10.1007/s10518-017-0208-5

 

Experimental assessment of the seismic behavior of unbraced steel storage pallet racks

Within SEISRACKS2 research project, we focused on the seismic design of static steel pallet racks used for storage of various types of goods and located in areas of retail warehouse stores and other facilities, possibly accessible to the public.

We performed experimental tests on the full scale pallet-racking systems. The tests were performed in the down-aisle (longitudinal) direction of fully-loaded unbraced racking structures. Global capacity curves of the tested specimens have been provided, behavior factor (q) values of test specimens have been evaluated and vulnerability of unbraced racks to soft-storey mechanism has been demonstrated highlighting its cause.

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This article explains more on this research:

Alper Kanyilmaz, Carlo Andrea Castiglioni, Giovanni Brambilla, Gian Paolo Chiarelli, Experimental assessment of the seismic behavior of unbraced steel storage pallet racks, Thin-Walled Structures, Volume 108, November 2016, Pages 391-405, ISSN 0263-8231

 

Assessment of the seismic behaviour of braced steel storage racking systems by means of full scale push over tests

We performed experimental tests on the full scale pallet racking systems. The tests were performed in the down-aisle (longitudinal) direction of fully-loaded racking structures with spine bracings. Global capacity curves of the tested specimens have been provided, behavior factor (q) values of test specimens have been evaluated and vulnerability vulnerability of the racks to bracing connection failure is demonstrated, highlighting its causes.

This article explains more on this research:

Alper Kanyilmaz, Giovanni Brambilla, Gian Paolo Chiarelli, Carlo Andrea Castiglioni, Assessment of the seismic behaviour of braced steel storage racking systems by means of full scale push over tests, Thin-Walled Structures, Volume 107, October 2016, Pages 138-155, ISSN 0263-8231

 

Earthquake mitigation for industrial systems

Objective of the research is the development of enhanced seismic protection systems and related design rules for process plants, process units and storage units, through innovative antiseismic techniques: seismic isolation systems and energy dissipation systems. The systems shall be suitable for both the retrofit of existing industrial structures and the design of new ones. Particular attention was given to the self-centring capacities of the systems as it will constitute an innovative and efficient ability that will rise up the protection against the earthquake, avoid interruptions of production after the seismic event and make easier repairs of the structure.

In our team we study the feasibility of seismic isolation solutions on industrial steel silo systems. A retrofitting solution has been proposed by means of the curved surface single sliding pendulum devices. Incremental dynamic analysis has been implemented to evaluate the performance of the structure before and after retrofitting.

An article on this research can be read here:

Kanyilmaz, A., Castiglioni, C.A., Reducing the seismic vulnerability of existing elevated silos by means of base isolation devices (2017) Engineering Structures, 143, pp. 477-497.

 


Research line 4/4:

Earthquake-resistant structures using repairable connections with increased lifetime and sustainability


 

We have been performing experimental research to evaluate the performance of steel-concrete composite steel frames with fuse components under seismic actions.

This research line aims at developing innovative types of seismic resistant composite steel frames with dissipative fuses. In case of strong seismic events, damage will concentrate only in these fuses, without observing any significant damage in the structural elements such as steel beams, columns and reinforced concrete slab of the structure. After the seismic event, the repair work will be limited only to replacing the fuses.

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Currently, with our team in Politecnico di Milano, we are coordinating the research project DISSIPABLE “Fully Dissipative and Easily Repairable Devices for Resilient Buildings with Composite Steel-Concrete Structures”, funded by EU-RFCS with contract n. RFCS-PDP 800699, 2018-2021. Here we are performing large scale demonstration of the steel-concrete composite structures with anti-seismic reparable systems that were previously designed. In the project, systematic post-earthquake repair and reassembly procedures are being developed and will be provided as “instructions for use”. Ability of repaired systems to resist strong earthquakes are being examined. Economic and environmental benefits and improved resiliency properties of the proposed systems will also be quantified.

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Some articles can be read here:

Carlo A. Castiglioni, Alper Kanyilmaz, Luis Calado, Experimental analysis of seismic resistant composite steel frames with dissipative devices, Journal of Constructional Steel Research, Volume 76, 2012, Pages 1-12, ISSN 0143-974X

Alper Kanyilmaz, Milot Muhaxheri, Carlo Andrea Castiglioni, Influence of repairable bolted dissipative beam splices (structural fuses) on reducing the seismic vulnerability of steel-concrete composite frames, Soil Dynamics and Earthquake Engineering, Volume 119, 2019, Pages 281-298, ISSN 0267-7261, https://doi.org/10.1016/j.soildyn.2019.01.007.