The research team is very active in the application of the research results. The knowledge has been applied in the case of many specific projects. However, a single application is typically limited to only one or few structures. When a standard (in particular European standard) is improved, the benefit is multiplied many times. Therefore, we consider the continuous active participation of the research team members in the development of Eurocodes (in particular EC8 – Design of seismic resistant structures) and in the implementation of Eurocodes in Slovenia as one of the key results. Slovenia was the first country which adopted Eurocodes standards as a National code. The research team importantly contributed to this. Several related research projects were accomplished and a manual for earthquake resistant design of structures according to EC8 (241 pages) was published one year after adoption. The manual includes interpretation of the theoretical background of EC8, commentaries on important clauses, and examples of application. In the year 2017 the updated re-print was prepared. Based on this outstanding experience in comparison to many other European countries, several members of the research group were invited to further participate at the development of the new versions of Eurocodes. On the highest level, are the representatives of Slovenia in: - CEN/TC250/SC8 - Design of earthquake resistant structures (Peter Fajfar) and - CEN/TC 250/SC 11 – Structural Glass, which is the newest part of Eurocodes (Roko Žarnić) Several members are active in project teams, which are involved in development of the new versions of standards: CEN/TC250/SC8/PT1 (Matjaž Dolšek) CEN/TC250/SC8/PT3 (Tatjana Isaković) and in research working groups, in support of further developments of standards: CEN/TC250/SC8/WG2 (Roko Žarnić) CEN/TC250/SC8/WG4 (Peter Fajfar, Matjaž Dolšek) CEN/TC250/SC8/TG1 (Peter Fajfar) CEN/TC250/SC6/WG1 (Vlatko Bosiljkov) Tatjana Isaković is the Chairman of the SIST Technical Committee for structures. Based on their proposal in the reporting period (2015-18) the following important improvements have been incorporated into the new versions of Eurocodes: - EC8-1: Extended N2 method for inelastic analysis, which considers the contribution of the higher modes along the height of the building and the contribution of torsion (originally published in 2012, COBISS 5591649); - EC8-1: Simplified reliability-based verification format (COBISS.SI-ID 8273761); - EC8-1: Procedure to evaluate story response spectra (COBISS.SI-ID 7896673); - EC8-1: Completely renewed chapter has been prepared for seismic resistant design of precast structures and connections between precast elements. Contribution regarding the evaluation of the capacity of the cladding-to-structure connections has been particularly important. - EC8-3: Several modifications were included in the EC8-3 - Seismic Assessment of Existing Structures (COBISS 8336993); - Amendment of the masonry chapter of EC8 was prepared (COBISS 7984993).
F.31 Development of standards
COBISS.SI-ID: 4746081For many years, the research group has successfully collaborated with the NPP Krško, GEN group, Slovenian Nuclear Safety Administration and other stakeholders to addressing the problems associated with the seismic safety of nuclear installations and their equipment. It would not be possible to achieve a high quality of the review work without the knowledge generated in research in the field of earthquake engineering. Inter alia, we led international consortiums for two large studies of the re-evaluation of seismic hazard at the plant site. In recent years, the main work has been associated with independent reviews of projects within the NPP Krško modernization related to seismic safety. After the accident at the Fukushima nuclear power plant in Japan, safety of all EU nuclear plants was reviewed, on the basis of a comprehensive and transparent risk assessment (“stress tests”). As a part of this action, NEK prepared in August 2011 the Special Safety Review Interim Report. Our research team was engaged in the independent evaluation of the document Evaluation of Seismic and Flooding Margins. We have critically reviewed the NEK report and requested substantial modifications of the original report, especially related to the treatment of seismic risk. After an iteration procedure, the final report was prepared by NEK, which was approved by the evaluators (COBISS.SIID 5620577). We performed independent evaluations of several projects, conducted by a U.S. company, comprising the determination of floor spectra and structural displacements for all objects of the nuclear island at increased seismic loading (maximum ground acceleration of 0.6g, 0.7g and 0.8g). Floor spectra and displacements were calculated also for the Essential Service Water Intake Structure (ESWIS) and the new building for the new diesel generator. The methods of analysis used and the obtained results were summarized in the new version of the update safety analysis report (USAR). Within the review procedure, we developed, independently of the contractors, the mathematical model of the buildings of the nuclear island and of the diesel generator building and conducted several independent control analyses. A number of review reports have been prepared, of which only some are included in COBISS (ID 6465377, 6466401, 6465889, 6465633, 466657, 6466145, 6466913). The work done within this reporting period (2015-18) was concentrated on three general projects: - We performed an independent review of the seismic analysis for reconstruction of the NPP dam (e.g. COBISS 8337761). In addition to the basic seismic analysis, we have also examined the control seismic analysis of NPP dam by ACI standard. We have found a number of shortcomings and proposed several improvements in modelling and structural solutions. - We assessed the seismic resistance of the container for the dry storage of spent nuclear fuel elements (e.g. COBISS 8345697). Based on our analysis, we estimate that it is very likely to avoid instability of free-standing container at PGA = 0.78 g. - Faculty of Civil and Geodetic Engineering has been involved in the project Low and Medium Nuclear Waste Repository (NSRAO Vrbina) since 2008, when the first study on seismic design parameters was performed. In the last year the group participates in the independent expert opinion on the project for building permit (PGD) for NSRAO Vrbina (e.g. COBISS 8338273). We identified several shortcomings, among which there are also critical deficiencies. Among other things, we did not find a link between safety analysis that demonstrate nuclear safety on the basis of selected scenarios, and structural design to ensure mechanical resistance and stability. Several disadvantages related to modelling and analysis were identified and described. Consequently, the results of dimensioning are also questionable. The project is in the stage of improvement by the designer.
D.06 Final report on a foreign/international project
Precast buildings represent a considerable part of industrial and commercial infrastructure in Europe. While tenths of millions of square meters of precast buildings are built each year, the behaviour of the connections between different elements, which are essential for their seismic safety, was poorly understood. These connections were frequently designed by (inadequate) feeling. The structural details, designed for the non-seismic regions have been often uncritically adopted also in the earthquake prone areas. In several cases, this led to severe direct and indirect damage, e.g during the recent earthquakes in Northern Italy. Considering the lack of knowledge and design tools as well as ambiguous design procedures, the leading associations of the European precast producers gave an initiative to join the efforts for the improvements of the design practice. This initiative resulted in long-term coordinated action of associations, main companies and research organizations all over EU within several large EU Research Framework projects (ECOLEADER, PRECAST, SAFECAST, SAFECLADDING). Within these projects the design practice has been importantly improved, the overall knowledge about the seismic response of precast buildings was considerably enhanced, the new design procedures were developed, their seismic vulnerability has been evaluated by probabilistic studies. Our research group participated considerable share in these joint activities. The new design procedures have been developed for the connections between beams and columns (see also Research achievements 19.7) as well as for the connections between façade claddings and main structure. They were included into the joint guidelines published by JRC centre, which is one of the leading European institutions supporting the future development of Eurocode standards. The design procedure for dowel connections has been already included into the draft of the new Eurocode 8 standard. The joint efforts were not focused only to studies of existing design practice, but also toward its improvements. Several new structural solutions have been invented. One of the novel structural solution, which have been developed by our research group should be specially emphasized. To protect the façade cladding panels, which were the main source of damage in recent earthquakes, new types of seismic restrainers were invented. They consist of ropes, which are used to attach panels to main structure and to prevent their falling after the failure of their primary connections. The ropes are manufactured using modern highly capable synthetic materials. In this way more efficient, more reliable and cost effective solution than the traditional steel restrainers was obtained. One of the major challenges in the development of the new types of restrainers was related to the design of the ropes’ fastenings to panels and the main structure. Special epoxy based technology has been invented for this purpose. A patent application for this invention is foreseen.
F.09 Development of a new technological process or technology
COBISS.SI-ID: 7584097For many years, the members of the program have been actively involved in the protection and strengthening of cultural heritage buildings. The results of experimental and numerical investigations in the field of diagnostic and strengthening methods, in order to increase the resilience of cultural heritage buildings to the seismic loads, are transferred to building construction and restoration/conservation practice. The workshops carried out in the framework of large European projects are aimed to increase awareness of individuals and companies, in the EU and neighbouring countries, with the latest approaches to the protection of built heritage. The knowledge is transferred also to young generations, as part of regular and invited lectures in Slovenia and Worldwide. Here we are particularly intensively involved with the University of Newcastle in Australia, where we have been invited lecturers and researchers for many years. A new breakthrough in this area is the successful completion of the major EU project PERPETUATE (PERformance-based aPproach to Earthquake protection of cUlturAl heritage in European and Mediterranean countries) in 2013, which received excellent reviews. The main result of the project, in addition to numerous scientific publications in the Bulletin of earthquake engineering (COBISS.SI-IDs 6642785, 6643297, 6643041, 6649441, 6642529 , 6643809, 6794849), is intensive transfer of results into the academic sphere (COBISS.SI-IDs 8331105, 8330849, 8329569, 6648417) and building construction and restoration practices (COBISS.SI-IDs 6648929, 6019681, 6019937). The main results of the project are European Guidelines for evaluation and mitigation of seismic risk to cultural heritage assets. The use of seismic risk based safety verification that is based on displacement, rather than strength enabled new approach of defining performance levels correlated both to architectonic and artistic assets. The results of the project were implemented in the new proposal for the Eurocode 8-3. Architectural elements with artistic value are vulnerable already to earthquakes of smaller intensities. In the case they are damaged, they are repaired by restorers/conservators. That is why we included in the research a doctoral student, who is a restorer/conservator with many years of practical experience with strengthening and renovation of wall paintings (see Cobiss of the programme group). During her doctoral study in framework of Built environment she received basic knowledge about structural behaviour of cultural heritage elements. On the other hand, we have gained a new perspective to the architectural elements and new priorities for their protection and consolidation. Currently, she is researcher of the PG, working on her own postdoctoral project (Operation No. C3330-17-529030 -Researchers-2.0-UL-FGG-529030, “Advanced lime based injection grouts for strengthening of cultural heritage buildings.” With this project development of injection grouts for the structural and non-structural strengthening was extended and upgraded. The development of custom-made grouts is done for each building separately and is adapted to the original materials and other relevant building parameters. Both, non-structural and structural mixtures are parallel developed, in close cooperation with the company TKK Srpenica, which is the manufacturer of chemical admixtures for building sector and of injection grouts for the structural strengthening. Protection of cultural heritage is complex issue. In order to overcome large gaps of the knowledge of different groups of experts an interdisciplinary consortium of researchers (IMFM, UL FGG and FE, IJS) was assembled together under umbrella of research project »Sensor technologies for the assessment of interventions in cultural heritage assets« (ARRS J2-8194, leader prof. dr. Zvonko Jagličić). Within the framework of the project, new more powerful non-destructive methods for investigations by means of advanced senso
F.06 Development of a new product
COBISS.SI-ID: 6201953Using innovative materials and technologies the research team has developed several products and systems up to the high level of technological development or actual use. These achievements are presented in more detail in Section 23 of this report. As an example we have chosen highly innovative hybrid structural element composed of laminated timber frames infilled with laminated glass panels. Invented by a member of the research group R. Žarnić, it is now jointly developed with the University of Zagreb. Contemporary trends in sustainable construction are oriented to low carbon solutions where the laminated timber structures are the most appreciated. On the other hand, the laminated glass is the material that offers interesting architectural solutions and is one of the most used emerging materials for public and residential buildings. The developed multi-functional structural element does not contain any structural adhesives and is therefore ecologically unproblematic and completely degradable and reusable after the expiration of its life. The element can sustain vertical and earthquake load, being structurally ductile (it sustains the story drifts up to 2.5%) and having ability to dissipate energy due to the ductility of the frame’s joints (configured as the glued-in rod type of timber joints) and friction between the wooden frame and the glass infill without intermediate layer of adhesive or sealant. The hybrid element has great potential for various uses such as: prefabricated wooden houses, seismic strengthening of existing prefabricated buildings, construction of load-bearing adaptive facade structures, strengthening and bracing of the existing frame structures of all types (reinforced concrete, timber, steel) and temporary or permanent supporting structural elements in historic buildings during and after their renovation. In 2017, the Technology Readiness Level TRL 5 was achieved by development of the higher level prototype. It is envisaged that by the end of 2019, a prototype will be ready for production. In Slovenia and Croatia, several companies have declared interest in production of this hybrid structural element.
F.06 Development of a new product
COBISS.SI-ID: 6631265