Research Projects of the Croatian Science Foundation (HRZZ)

 

Project Title: Roman Water Systems of City of Salona and Diocletian's Palace and Their Impact on Urban Sustainability (RWSCSDP)
Project Title in Croatian: Antički vodni sustavi grada Salone i Dioklecijanove palače i njihov utjecaj na održivost urbane sredine
Principal Investigator: prof. Jure Margeta, Ph. D.
Starting Date: September 1, 2014
Ending Date: August 31, 2018
Web Pages: HR:   http://gradst.unist.hr/tabid/5145/Default.aspx
ENG: http://gradst.unist.hr/tabid/5148/Default.aspx
Project Summary: The aim of the project is to study two Roman Water Systems which are using the same water source - the Jadro spring. The first one is the Water System of Salona, capital of the Roman province Dalmatia, from the 1st century, and the second one is of Diocletian's Palace in Split from the 4th century. The study will consist of analysis and reconstruction of two, by their purpose, different Water System, one of typical urban character and the other very specific, of the Emperor Palace. Unlike the Water System of the Palace, which is partly preserved (aqueduct is in function) and therefore more studied, the Water System of Salona is mostly unknown. They will be studied separately using the same methodology.

All parts of the Water Supply system will be studied: water intake on the Jadro spring, route and elements of the aqueduct (channel, bridges and tunnels), water distribution tanks, lead pipe network and water appliances, together with water quantity and quality issues. The study of sewage will consider wastewater and storm water drainage, as well as protection from external surface water and groundwater. Besides those, methods, materials and techniques used by Roman engineers to establish an efficient urban Water System, indispensable for the life and health of the citizens, will be analyzed and compared with modern system. The study will be based on collecting all data regarding explored elements of the Water System and on new archaeological excavations financed by this project. The existing topographic and architectonic surveys will be summarized and supplemented by new ones which will enable reconstruction of the whole system and elements. The project team is multidisciplinary and gathers civil engineers, architects and archaeologist. Apart from new knowledge about planning, building and maintaining Roman Water Systems, this project will give the necessary data to protect elements of the system from devastation, to make a proper presentation and even to put some elements in use.

 

Project Title: Influence of creep strain on the load capacity of steel and aluminium columns exposed to fire
Project Title in Croatian: Utjecaj deformacija od puzanja na nosivost čeličnih i aluminijskih stupova pri djelovanju požara
Principal Investigator: Assistant Professor Neno Torić, Ph. D.
Starting Date: October 1, 2015
Ending Date: September 30, 2018
Web Pages: HR:   http://gradst.unist.hr/tabid/5151/Default.aspx
ENG: http://gradst.unist.hr/tabid/5152/Default.aspx
Project Summary: The purpose of the project is to develop new creep models applicable to new types of steel and aluminium alloys and to conduct the analysis of the influence of creep strain on the behaviour of steel and aluminium columns. The modern European structural codes (Eurocode) treat existence of creep strain implicitly, using a modified material behaviour model, which has proven inadequate according to very recent research for all of possible heating scenarios. The first part of the project is the development of a reliable creep model for steel and aluminium that will exist both in an analytical form and in the form of a rheological model. A creep model validated on the basis of coupon tests conducted on the modern steel and aluminium alloys currently used in construction would be used as a tool for analyzing the load-bearing capacity of the columns selected for testing within the proposed project.

Furthermore, the behaviour of steel and aluminium columns under the influence of high temperature creep is currently an open research area in the scientific community, since very few fire tests have been conducted on steel columns which could induce substantial creep development and the corresponding failure modes. Consequently, the second part of the project is to conduct successful testing of steel and aluminium columns. This part would also give a reliable answer to the question of the significance of the influence of creep strain on the load-bearing capacity, as well as elucidating the issue of particular combinations of loading and heating scenarios in which creep strain leads to significant consequences. The final results and conclusions covering the project’s deliverables would also be utilized to define a new set of rules for the design and analysis of steel and aluminium structures which have a high risk of being exposed to the effects of creep strain when exposed to fire.

 

Project Title: Development of numerical models for reinforced-concrete and stone masonry structures under seismic loading based on discrete cracks
Project Title in Croatian: Razvoj numeričkih modela armirano-betonskih i kamenih zidanih konstrukcija izloženih potresnom opterećenju zasnovanih na diskretnim pukotinama
Principal Investigator: prof. Željana Nikolić, Ph. D.
Starting Date: September 1, 2015
Ending Date: August 31, 2019
Web Pages:

HR: http://gradst.unist.hr/istrazivanje/projekti/projekti-hrzz/razvoj-numerickih-modela-armirano-betonskih-i-kamenih-zidanih-konstrukcija

EN: http://gradst.unist.hr/eng/research/projects/hrzz-projects/development-of-numerical-models-for-reinforced-concrete-and-stone-masonry-structures

Project Summary: Crack opening is one of the dominant causes of nonlinearity in brittle and quasi-brittle structures which leads to localized failure and stands out as a serious challenge in numerical modelling. The process of crack initiation starts at a micro-scale, and with progressive growth, micro-cracks coalesce into macro-cracks representing discontinuities in the material. Therefore, a realistic modelling of crack initiation and propagation is one of the key factors that affect the reliability of the model for analysing the structures, especially those subjected to earthquakes. Sophisticated numerical models based on time dependent and incremental dynamic analysis can play an important role in simulating the behaviour of such structures before and after collapse. This project aims to develop two nonlinear numerical models for incremental dynamic analysis of structures based on the model of discrete cracks. The first one will be a novel 3D model for reinforced concrete and stone masonry structures strengthened with clamps and bolts based on the combined finite discrete element method where the cracks are modelled through the contact elements implemented between finite elements. The model enables crack initiation and propagation, dynamic interaction of separate elements and monitoring of structural behaviour before and after the collapse. The second model will be based on the finite element method with embedded discontinuity and embedded reinforcement, which allows for crack initiation and propagation independent of finite element mesh and will be applied to reinforced concrete structures. The novel numerical models for reinforced concrete structures will be validated by available experimental research, while our own experiments are planned to be performed at shaking table for the validation of stone masonry structure model. Thereafter, the comparative analysis of the behaviour of real structures with both models will be conducted.

 

Project Title: Groundwater flow modelling in karst aquifers
Project Title in Croatian: Modeliranje tečenja u krškim vodonosnicima
Principal Investigator: Associate professor Hrvoje Gotovac, Ph. D.
Starting Date: October 1, 2014
Ending Date: September 30, 2017
Web Pages: HR:   http://www.hrzz.hr/default.aspx?id=78&pid=8103&rok=2013-11
Project Summary: Karst aquifers are very important groundwater resources around the world as well as in coastal part of Croatia. They consist of extremely complex structure defining by triple phases: slow porous medium, mostly laminar fractures and usually fast turbulent conduits/karst channels. Usually, karst aquifers have been analyzed by lumped hydrological models which ignore high heterogeneity of karst and consider only input (precipitation) and output (spring discharge) due to lack of extensive other input data and knowledge regarding the karst system. Last two decades full hydraulic (distributive) models have been developed exclusively by conventional finite elements considering karst heterogeneity structure that improves our understanding of complex processes in karst. Therefore, in this project we will develop novel “unique” flow model based on multi-resolution approach originally designed by Gotovac et al. (2007-2013) for 1-D and 2-D groundwater flow and transport simulations. Proposed approach is based on Fup basis functions with compact support and meshless collocation procedure enabling multi-scale representation of heterogeneity and other flow variables, closely related to the karst flow physical interpretation. Moreover, extending existing procedure to 3-D and constructing separate multi-scale solution for all three karst phases, proposed approach will enable the following impacts in comparison to conventional methods: desired spatial and temporal accuracy and high computational efficiency, modular model structure, incorporation of different heterogeneity scales related to existing measurements, enabling of transport and tracer test analysis and better understanding of karst aquifers due to solving of different engineering problems such as water usage and protection or contaminant pollution. Flow model will be verified by laboratory experiments and numerical synthetic benchmarks as well as real examples such as Jadro catchment and Ombla underground accumulation.

 

Project Title: Seismic base isolation of a building by using natural materials - shake table testing and numerical modeling
Project Title in Croatian: Seizmička izolacija osnove građevine s uporabom prirodnih materijala - testiranje s potresnom platformom i numeričko modeliranje
Principal Investigator: prof. Jure Radnić, Ph. D.
Starting Date: March 1, 2017
Ending Date: February 28, 2021
Web Pages: HR:   http://gradst.unist.hr/tabid/5145/Default.aspx
ENG: http://gradst.unist.hr/tabid/5358/Default.aspx
Project Summary: The primary objective of the project is creation and experimental verification of an innovative concept for reducing seismic forces acting on low and middle high buildings by using aseismic layer made of natural materials below foundation. Two solutions of such layer are planned. The intention is to make an efficient, rational and easy-to-implement concept, with its wide practical application. First, the effectiveness of the planned aseismic layers would be experimentally tested on the model of a rigid building, by varying several their technical - technological parameters, in order to transfer seismic acceleration (force) on the building as less as possible. The first aseismic layer is predicted as consisted only of natural stone pebbles, and the other of the natural stone pebbles in combination with a thin layer of a "sliding" material.

Afterwards, the behaviour of real buildings with the above mentioned non-seismic layers would be experimentally tested under different earthquakes. Simplified reduced models of buildings that simulate their dynamic characteristics well would be used. Four one-degree models with different stiffness would be tested to simulate the behaviour of buildings with different stiffness. The same building models would be tested for the case without the aseismic layer, in order to verify the effectiveness of the predicted seismic isolation.

If the results of the study would confirm expectations, the proposed concept of seismic isolation would have the following advantages compared to conventional seismic isolation using discrete, technically complex and expensive systems: rationality, simplicity, sustainability, market expansion, eligibility for poorer countries, etc. One of the objectives of the project is the development of numerical models for reliable seismic analysis of planar structures with the planned seismic isolation, as well as the proposal of simple engineering expressions for the calculation of the shear strength capacity and deformability of the aseismic layer.

It is believed that the successful implementation of the proposed project would provide a valuable contribution to the development of science and practice in the concerned area.

 

Project Title: Experimental and numerical investigations of mechanisms in unsaturated geomaterials
Project Title in Croatian: Eksperimentalna i numerička istraživanja mehanizama u nesaturiranim geomaterijalima
Principal Investigator: assoc. prof. Nataša Štambuk Cvitanović, Ph. D.
Starting Date: March 1, 2018
Ending Date: February 28, 2023
Web Pages: HR:   http://gradst.unist.hr/tabid/5415/Default.aspx
ENG: http://gradst.unist.hr/tabid/5416/Default.aspx
Project Summary: Weathering as rock degradation under the direct influence of environmental conditions and human activity in the engineering period of time, is a key process that affects geomorphologic, ecologic and societal processes and events. Soft rocks, such as marl, are very common in the Mediterranean and particularly susceptible to weathering. This is manifested through the decomposition of the binder from clayey rock structure and breaking of the rock structure due to physical and chemical processes. Under such influence, weathering degrades soft rocks to fine-grained material, which is related to environmental sustainability (erosion, climate change issues, slopes, rock falls and other geohazards), stability, bearing capacity and durability issues (temporal change of strength and deformability).

According to recent scientific findings, a significant contributor to the development of weathering is the process of differential suction and induced differential swelling, which occurs in unsaturated conditions. Differential suction comes as a result of capillary effects in voids of the material and it is closely related to slaking of the material. The consequences of differential swelling are development of tensile and shear stresses that cause weathering. Therefore, the aim of this project is to investigate and simulate the mechanisms of weathering from the aspect of suction, and to link the acquired new findings with the significant previous research carried out at the Faculty.

The shear strength and deformability in unsaturated conditions for the given degree of suction, and the characteristic SDSWCC curves (Stress Dependent Soil Water Characteristic Curve) will be determined by sophisticated testing equipment on still unexamined soft rock material from the Croatian coastal area. At the same time all “accompanying” tests, including physical, mechanical, mineralogical and petrological, will be carried out and new and existing databases will be linked. Full experimental programme will be carried out on approximately 30 specimens.

The obtained results will be incorporated into the existing numerical model (Plaxis) and into additionally developed new numerical model based on a discrete approach, which will include the fracture mechanism in geomaterials in unsaturated flow conditions. This will significantly improve the knowledge of weathering mechanisms in geomaterials and enable sustainable project solutions.

A newly formed research group with the necessary resources provides additional value of the project.