This page has only limited features, please log in for full access.

Dr. Ivan Duvnjak
Department for Engineering Mechanics, University of Zagreb, Faculty of Civil Engineering, Zagreb, Croatia

Basic Info

Basic Info is private.

Research Keywords & Expertise

0 DAMAGE DETECTION
0 SHM
0 Theory of elasticity
0 Assessment of structures
0 Static and dynamic testings of structures

Honors and Awards

The user has no records in this section


Career Timeline

The user has no records in this section.


Short Biography

The user biography is not available.
Following
Followers
Co Authors
The list of users this user is following is empty.
Following: 0 users

Feed

Journal article
Published: 18 May 2021 in Applied Sciences
Reads 0
Downloads 0

The main principle of vibration-based damage detection in structures is to interpret the changes in dynamic properties of the structure as indicators of damage. In this study, the mode shape damage index (MSDI) method was used to identify discrete damages in plate-like structures. This damage index is based on the difference between modified modal displacements in the undamaged and damaged state of the structure. In order to assess the advantages and limitations of the proposed algorithm, we performed experimental modal analysis on a reinforced concrete (RC) plate under 10 different damage cases. The MSDI values were calculated through considering single and/or multiple damage locations, different levels of damage, and boundary conditions. The experimental results confirmed that the MSDI method can be used to detect the existence of damage, identify single and/or multiple damage locations, and estimate damage severity in the case of single discrete damage.

ACS Style

Ivan Duvnjak; Domagoj Damjanović; Marko Bartolac; Ana Skender. Mode Shape-Based Damage Detection Method (MSDI): Experimental Validation. Applied Sciences 2021, 11, 4589 .

AMA Style

Ivan Duvnjak, Domagoj Damjanović, Marko Bartolac, Ana Skender. Mode Shape-Based Damage Detection Method (MSDI): Experimental Validation. Applied Sciences. 2021; 11 (10):4589.

Chicago/Turabian Style

Ivan Duvnjak; Domagoj Damjanović; Marko Bartolac; Ana Skender. 2021. "Mode Shape-Based Damage Detection Method (MSDI): Experimental Validation." Applied Sciences 11, no. 10: 4589.

Technical paper
Published: 10 September 2020 in Structural Concrete
Reads 0
Downloads 0

Diagnostic load testing can be a suitable method for condition assessment of existing bridges. This paper presents the evaluation of a concrete railway bridge built in the 1940s based on diagnostic load testing. The test was the outcome of a visual inspection and preliminary theoretical analysis that found the bridge to be in unsatisfactory condition. Unlike the other possibilities that infrastructure management bodies have in such situations, for example, structure replacement, traffic reorganization, closure of the bridge, etc., diagnostic load testing is a low cost and quick method that indicates the bridge response to real traffic load. The paper describes the test plan and implementation covering the static and dynamic load tests. The experimental methods comprise superstructure displacements measurement, strain measurement on concrete and reinforcement and determination of bridge dynamic parameters. The obtained test results analysis enabled more accurate diagnosis of the actual bridge condition. The bridge demonstrated satisfactory load bearing capacity and response to real service load in terms of registered levels of displacement and strain and proper dynamic performance.

ACS Style

Ivan Duvnjak; Marko Bartolac; Domagoj Damjanović; Janko Košćak. Performance assessment of a concrete railway bridge by diagnostic load testing. Structural Concrete 2020, 21, 2363 -2376.

AMA Style

Ivan Duvnjak, Marko Bartolac, Domagoj Damjanović, Janko Košćak. Performance assessment of a concrete railway bridge by diagnostic load testing. Structural Concrete. 2020; 21 (6):2363-2376.

Chicago/Turabian Style

Ivan Duvnjak; Marko Bartolac; Domagoj Damjanović; Janko Košćak. 2020. "Performance assessment of a concrete railway bridge by diagnostic load testing." Structural Concrete 21, no. 6: 2363-2376.

Journal article
Published: 31 August 2020 in Applied Sciences
Reads 0
Downloads 0

Tie rods are structural elements that transfer axial tensile loads and are typically used on walls, vaults, arches, and buttresses in historical buildings. To verify their load-bearing capacity and identify possible structural damage risks, the forces transferred by tie rods and the corresponding stresses must be determined. However, this is often a challenging task due to the lack of project documentation for historical buildings. Uncertainties like complex boundary conditions or unknown material and geometrical properties make it hard to assess the tie rods’ load level. This paper presents a methodology for the determination of axial forces in tie rods that combines on-site experimental research and a numerical model-updating technique. Along with the common approach based on a determination of the natural frequency of tie rods, this paper presents an approach based on tie rods’ mode shapes. Special emphasis is placed on the boundary conditions coefficient, which is a crucial parameter in the analytical solution for axial forces determination based on the conducted on-site experiments. The method is applied in a historical building case study.

ACS Style

Ivan Duvnjak; Suzana Ereiz; Domagoj Damjanović; Marko Bartolac. Determination of Axial Force in Tie Rods of Historical Buildings Using the Model-Updating Technique. Applied Sciences 2020, 10, 6036 .

AMA Style

Ivan Duvnjak, Suzana Ereiz, Domagoj Damjanović, Marko Bartolac. Determination of Axial Force in Tie Rods of Historical Buildings Using the Model-Updating Technique. Applied Sciences. 2020; 10 (17):6036.

Chicago/Turabian Style

Ivan Duvnjak; Suzana Ereiz; Domagoj Damjanović; Marko Bartolac. 2020. "Determination of Axial Force in Tie Rods of Historical Buildings Using the Model-Updating Technique." Applied Sciences 10, no. 17: 6036.

Book
Published: 01 January 2020 in TEORIJA ELASTIČNOSTI I PLASTIČNOSTI S METODAMA RJEŠAVANJA ZADAĆA
Reads 0
Downloads 0
ACS Style

Mladenko Rak; Ivan Duvnjak; Domagoj Damjanović. TEORIJA ELASTIČNOSTI I PLASTIČNOSTI S METODAMA RJEŠAVANJA ZADAĆA. TEORIJA ELASTIČNOSTI I PLASTIČNOSTI S METODAMA RJEŠAVANJA ZADAĆA 2020, 1 .

AMA Style

Mladenko Rak, Ivan Duvnjak, Domagoj Damjanović. TEORIJA ELASTIČNOSTI I PLASTIČNOSTI S METODAMA RJEŠAVANJA ZADAĆA. TEORIJA ELASTIČNOSTI I PLASTIČNOSTI S METODAMA RJEŠAVANJA ZADAĆA. 2020; ():1.

Chicago/Turabian Style

Mladenko Rak; Ivan Duvnjak; Domagoj Damjanović. 2020. "TEORIJA ELASTIČNOSTI I PLASTIČNOSTI S METODAMA RJEŠAVANJA ZADAĆA." TEORIJA ELASTIČNOSTI I PLASTIČNOSTI S METODAMA RJEŠAVANJA ZADAĆA , no. : 1.

Original research article
Published: 18 September 2019 in Frontiers in Built Environment
Reads 0
Downloads 0

This study presents a complex experimental research of a damaged steel railway bridge. Before the reconstruction, the elastic behavior of the material was evaluated using the hole-drilling strain gauge method of determining residual stresses at the relevant cross-sections. During the reconstruction project (lifting of the structure), a short-term monitoring system was installed at the critical cross-sections for continuous recording of strain. The aim was to evaluate the quality of the reconstruction intervention and prevent further damages. Following a successful reconstruction, a diagnostic load testing was performed according to Croatian standards. The purpose of the load testing (static and dynamic) was to evaluate the ability of the bridge to carry the design loads and calibrate the finite element models. During static load testing vertical displacement was measured as well as strain. Dynamic load testing of the bridge was performed in order to determine the main dynamic parameters of the structure and to calculate the dynamic factor. In order to select the appropriate measurement parameters and methods used during this experimental research it was necessary to consider the bridge type, materials and reconstruction or strengthening interventions. Especially, since this bridge was an example of insufficient inspection and maintenance during service. A well-designed monitoring and diagnostic load testing needed to be performed in order to obtain useful results for the decision makers involved.

ACS Style

Ivan Duvnjak; Domagoj Damjanović; Marko Bartolac; Marina Frančić Smrkić; Ana Skender. Monitoring and Diagnostic Load Testing of a Damaged Railway Bridge. Frontiers in Built Environment 2019, 5, 1 .

AMA Style

Ivan Duvnjak, Domagoj Damjanović, Marko Bartolac, Marina Frančić Smrkić, Ana Skender. Monitoring and Diagnostic Load Testing of a Damaged Railway Bridge. Frontiers in Built Environment. 2019; 5 ():1.

Chicago/Turabian Style

Ivan Duvnjak; Domagoj Damjanović; Marko Bartolac; Marina Frančić Smrkić; Ana Skender. 2019. "Monitoring and Diagnostic Load Testing of a Damaged Railway Bridge." Frontiers in Built Environment 5, no. : 1.

Original research article
Published: 16 April 2019 in Frontiers in Built Environment
Reads 0
Downloads 0

Ultra-high-performance fiber-reinforced cement-based composite (UHPFRC) has been increasingly adopted for rehabilitation projects over the past two decades, proving itself as a reliable, cost-efficient and sustainable alternative against conventional methods. High compressive strength, low permeability and high ductility are some of the characteristics that render UHPFRC an excellent material for repairing existing aged infrastructure. UHPFRC is most commonly applied as a surface layer for strengthening and rehabilitating concrete structures such as bridge decks or building slabs. However, its implementation with steel structures has so far been limited. In this work, the UHPFRC strengthening of a steel bridge is investigated both in simulation as well as in the laboratory, by exploiting a real-world case study: the Buna Bridge. This Croatian riveted steel bridge, constructed in 1893, repaired in 1953, and decommissioned since 2010, was removed from its original location and transported to laboratory facilities for testing prior to and after rehabilitation via addition of UHPFRC slab. The testing campaign includes static and dynamic experiments featuring state-of-the-art monitoring systems such as embedded fiber optics, acoustic emission sensors and digital image correlation. The information obtained prior to rehabilitation serves for characterization of the actual condition of the structure and allows the design of the rehabilitation solution. The UHPFRC slab thickness was optimized to deliver optimal fatigue and ultimate capacity improvement at reasonable cost. Once the design was implemented, a second round of experiments was conducted in order to confirm the validity of the solution, with particular attention allocated to the interface between the steel substrate and the UHPFRC overlay, as the connection between both materials may result in a weak contact point. A detailed fatigue analysis, based on updated FEM models prior to and after strengthening, combined with the results of a reliability analysis prove the benefits of adoption of such a solution via the significant extension of the structural lifespan.

ACS Style

Henar Martín-Sanz; Konstantinos Tatsis; Domagoj Damjanovic; Irina Stipanovic; Aljosa Sajna; Ivan Duvnjak; Uros Bohinc; Eugen Brühwiler; Eleni Chatzi. Getting More Out of Existing Structures: Steel Bridge Strengthening via UHPFRC. Frontiers in Built Environment 2019, 5, 1 .

AMA Style

Henar Martín-Sanz, Konstantinos Tatsis, Domagoj Damjanovic, Irina Stipanovic, Aljosa Sajna, Ivan Duvnjak, Uros Bohinc, Eugen Brühwiler, Eleni Chatzi. Getting More Out of Existing Structures: Steel Bridge Strengthening via UHPFRC. Frontiers in Built Environment. 2019; 5 ():1.

Chicago/Turabian Style

Henar Martín-Sanz; Konstantinos Tatsis; Domagoj Damjanovic; Irina Stipanovic; Aljosa Sajna; Ivan Duvnjak; Uros Bohinc; Eugen Brühwiler; Eleni Chatzi. 2019. "Getting More Out of Existing Structures: Steel Bridge Strengthening via UHPFRC." Frontiers in Built Environment 5, no. : 1.

Conference paper
Published: 01 January 2019 in IABSE Symposium, Guimarães 2019: Towards a Resilient Built Environment Risk and Asset Management
Reads 0
Downloads 0

Damage assessment of structures includes estimation of location and severity of damage. Quite often it is done by using changes of dynamic properties, such as natural frequencies, mode shapes and damping ratios, determined on undamaged and damaged structures. The basic principle is to use dynamic properties of a structure as indicators of any change of its stiffness and/or mass. In this paper, two new methods for damage detection are presented and compared. The first method is based on comparison of normalised modal shape vectors determined before and after damage. The second method uses so-called 𝑙l-norm regularized finite element model updating. Some important properties of these methods are demonstrated using simulations on a Kirchhoff plate. The pros and cons of the two methods are discussed. Unique aspects of the methods are highlighted.

ACS Style

Ivan Duvnjak; Domagoj Damjanović; Natalia Sabourova; Niklas Grip; Ulf Ohlsson; Lennart Elfgren; Yongming Tu. Damage Detection in Structures – Examples. IABSE Symposium, Guimarães 2019: Towards a Resilient Built Environment Risk and Asset Management 2019, 471 -478.

AMA Style

Ivan Duvnjak, Domagoj Damjanović, Natalia Sabourova, Niklas Grip, Ulf Ohlsson, Lennart Elfgren, Yongming Tu. Damage Detection in Structures – Examples. IABSE Symposium, Guimarães 2019: Towards a Resilient Built Environment Risk and Asset Management. 2019; ():471-478.

Chicago/Turabian Style

Ivan Duvnjak; Domagoj Damjanović; Natalia Sabourova; Niklas Grip; Ulf Ohlsson; Lennart Elfgren; Yongming Tu. 2019. "Damage Detection in Structures – Examples." IABSE Symposium, Guimarães 2019: Towards a Resilient Built Environment Risk and Asset Management , no. : 471-478.

Conference paper
Published: 01 January 2019 in IABSE Symposium, Guimarães 2019: Towards a Resilient Built Environment Risk and Asset Management
Reads 0
Downloads 0

Structural damage is often a spatially sparse phenomenon, i.e. it occurs only in a small part of the structure. This property of damage has not been utilized in the field of structural damage identification until quite recently, when the sparsity-based regularization developed in compressed sensing problems found its application in this field.In this paper we consider classical sensitivity-based finite element model updating combined with a regularization technique appropriate for the expected type of sparse damage. Traditionally, (I), 𝑙2- norm regularization was used to solve the ill-posed inverse problems, such as damage identification. However, using already well established, (II), 𝑙l-norm regularization or our proposed, (III), 𝑙l-norm total variation regularization and, (IV), general dictionary-based regularization allows us to find damages with special spatial properties quite precisely using much fewer measurement locations than the number of possibly damaged elements of the structure. The validity of the proposed methods is demonstrated using simulations on a Kirchhoff plate model. The pros and cons of these methods are discussed.

ACS Style

Natalia Sabourova; Niklas Grip; Ulf Ohlsson; Lennart Elfgren; Yongming Tu; Ivan Duvnjak; Domagoj Damjanovic. Detection of Sparse Damages in Structures. IABSE Symposium, Guimarães 2019: Towards a Resilient Built Environment Risk and Asset Management 2019, 515 -522.

AMA Style

Natalia Sabourova, Niklas Grip, Ulf Ohlsson, Lennart Elfgren, Yongming Tu, Ivan Duvnjak, Domagoj Damjanovic. Detection of Sparse Damages in Structures. IABSE Symposium, Guimarães 2019: Towards a Resilient Built Environment Risk and Asset Management. 2019; ():515-522.

Chicago/Turabian Style

Natalia Sabourova; Niklas Grip; Ulf Ohlsson; Lennart Elfgren; Yongming Tu; Ivan Duvnjak; Domagoj Damjanovic. 2019. "Detection of Sparse Damages in Structures." IABSE Symposium, Guimarães 2019: Towards a Resilient Built Environment Risk and Asset Management , no. : 515-522.

Conference paper
Published: 27 July 2018 in MATEC Web of Conferences
Reads 0
Downloads 0

Overhead line system is a vital element of any electrified railway infrastructure. Its performance reflects to all vital parameters such as traction, reliability, availability and safety of railway infrastructure. Operator GPP Osijek runs a 27.5 km long tramway network which plays a key role in transit system of the city of Osijek, Croatia. In 2016 GPP Osijek applied to a tender for acquisition of new rolling stock with 85% EU investment. Mayor requirement prior to rolling stock acquisition was to document, analyse and upgrade current infrastructure (including track structure, electric substations and catenary) to an optimal level. Task of measurement and evaluation of tram track structure and catenary has been appointed to University of Zagreb Faculty of Civil Engineering. Overhead line analysis comprised from several measuring procedures, including supporting columns evaluation, catenary stagger, height, shocks and wear. Such extensive analysis included GPS positioning and on-site evaluation of 1214 supporting columns of overhead line, as well as overhead line measurements using an instrumented tram vehicle on 18 km of track. For conducting overhead catenary wire measurements, a tram pantograph has been fitted with equipment for measuring catenary height, accelerometers for shock measurement, camera, ruler and GPS for stagger measurement. Catenary wire wear was checked manually from catenary inspection vehicle. To conduct measurements, power had to be switched off on all electric substation along the route and tram vehicle had to be towed by a catenary inspection vehicle. All the data has been analysed and presented to end user in a user-friendly and intuitive GIS environment capable of further updates and detailed analyses. Evaluation of overhead line based on direct measurement results pointed out all the defects and weak spots on the system. It resulted in a series of recommendations for reconstruction and upgrade of the catenary system to fit the need of existing state and further development of tramway network.

ACS Style

Ivo Haladin; Stjepan Lakušić; Ivan Duvnjak. Evaluation of tramway overhead line system in city of Osijek. MATEC Web of Conferences 2018, 180, 1 .

AMA Style

Ivo Haladin, Stjepan Lakušić, Ivan Duvnjak. Evaluation of tramway overhead line system in city of Osijek. MATEC Web of Conferences. 2018; 180 ():1.

Chicago/Turabian Style

Ivo Haladin; Stjepan Lakušić; Ivan Duvnjak. 2018. "Evaluation of tramway overhead line system in city of Osijek." MATEC Web of Conferences 180, no. : 1.

Proceedings article
Published: 17 May 2018 in Road and Rail Infrastructure V
Reads 0
Downloads 0
ACS Style

Domagoj Damjanović; Ivan Duvnjak; Marko Bartolac; Janko Košćak. Operational modal analysis of two identical single span road bridges. Road and Rail Infrastructure V 2018, 1 .

AMA Style

Domagoj Damjanović, Ivan Duvnjak, Marko Bartolac, Janko Košćak. Operational modal analysis of two identical single span road bridges. Road and Rail Infrastructure V. 2018; ():1.

Chicago/Turabian Style

Domagoj Damjanović; Ivan Duvnjak; Marko Bartolac; Janko Košćak. 2018. "Operational modal analysis of two identical single span road bridges." Road and Rail Infrastructure V , no. : 1.

Conference paper
Published: 01 January 2018 in IABSE Symposium, Nantes 2018: Tomorrow’s Megastructures
Reads 0
Downloads 0
ACS Style

Ivan Duvnjak; Marko Bartolac; Jonny Nilimaa; Gabriel Sas; Thomas Blanksvärd; Björn Täljste; Lennart Elfgren. Lessons Learnt from Full-Scale Tests of Bridges in Croatia and Sweden. IABSE Symposium, Nantes 2018: Tomorrow’s Megastructures 2018, S24 -127.

AMA Style

Ivan Duvnjak, Marko Bartolac, Jonny Nilimaa, Gabriel Sas, Thomas Blanksvärd, Björn Täljste, Lennart Elfgren. Lessons Learnt from Full-Scale Tests of Bridges in Croatia and Sweden. IABSE Symposium, Nantes 2018: Tomorrow’s Megastructures. 2018; ():S24-127.

Chicago/Turabian Style

Ivan Duvnjak; Marko Bartolac; Jonny Nilimaa; Gabriel Sas; Thomas Blanksvärd; Björn Täljste; Lennart Elfgren. 2018. "Lessons Learnt from Full-Scale Tests of Bridges in Croatia and Sweden." IABSE Symposium, Nantes 2018: Tomorrow’s Megastructures , no. : S24-127.

Journal article
Published: 09 January 2014 in JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT
Reads 0
Downloads 0

In line with current ”green” transport initiatives, Croatia plans to build over the next investment period a high speed railway line which will connect central Croatia and its capital with coastal regions of the country. According to design documents, the track system will be built using ballastless concrete solutions. In the scope of the project “Concrete track system – ECOTRACK”, researchers from the University of Zagreb - Faculty of Civil Engineering analysed a new material, i.e. the rubberized hybrid fibre reinforced concrete (RHFRC), in order to find out whether its properties are adequate for the proposed concrete track system. The RHFRC contains by-products from mechanical recycling of waste tyres (rubber and steel fibres). The study of fibre and rubber interaction and their contribution to mechanical properties of the fibre reinforced concrete is presented, as extensive research on positive interaction between industrial and recycled steel fibres has not as yet been made. The results show that the RHFRC is an innovative, sustainable and cost-effective concrete, which is fully compliant with criteria prescribed in relevant standards.

ACS Style

Dubravka Bjegovic; Ana Baricevic; Stjepan Lakusic; Domagoj Damjanovic; Ivan Duvnjak. POSITIVE INTERACTION OF INDUSTRIAL AND RECYCLED STEEL FIBRES IN FIBRE REINFORCED CONCRETE. JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 2014, 19, S50 -S60.

AMA Style

Dubravka Bjegovic, Ana Baricevic, Stjepan Lakusic, Domagoj Damjanovic, Ivan Duvnjak. POSITIVE INTERACTION OF INDUSTRIAL AND RECYCLED STEEL FIBRES IN FIBRE REINFORCED CONCRETE. JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT. 2014; 19 (Supplement):S50-S60.

Chicago/Turabian Style

Dubravka Bjegovic; Ana Baricevic; Stjepan Lakusic; Domagoj Damjanovic; Ivan Duvnjak. 2014. "POSITIVE INTERACTION OF INDUSTRIAL AND RECYCLED STEEL FIBRES IN FIBRE REINFORCED CONCRETE." JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 19, no. Supplement: S50-S60.