Visualizations of Gaussian and Mean Curvatures by Using Mathematica

U radu je dan prikaz programa, pisanog u jeziku Mathematica, koji omogućuje bojanje plohe bojom koja je funkcija njene Gaussove ili srednje zakrivljenosti kao i crtanje grafova tih funkcija. Dano je deset primjera vizualizacija dobivenih pomoću tog programa. Članak je mali ulomak iz studentskog rada [7] koji je 2004. godine nagrađen Rektorovom nagradom.The paper gives an overview of the program written in the language Mathematica, which enables colouring of a surface with the colour that is the function of its Gaussian and mean curvatures, as well as drawing the graphs of those functions. Ten examples of visualizations obtained by the use of that program are presented. The article is a small extract from the students\u27 paper which was awarded Rector\u27s Prize in 2004

Evaluation of infill strut properties based on in-plane cyclic tests

U nelinearnoj analizi AB okvira sa zidanom ispunom jednostavni se zamjenjujući tlačni štap često primjenjuje za modeliranje ispune, posebice u slučaju opsežnih numeričkih proračuna. Stoga je pažljiv odabir odgovarajućih svojstava tlačnog štapa od iznimne važnosti za vjerodostojni prikaz odziva zgrade. U ovom je radu predložen i primijenjen postupak određivanja svojstava tlačnog štapa za prikaz zidane ispune temeljem interpretacije rezultata cikličkih, statičkih ispitivanja u ravnini na uzorcima jednoetažnih, jednorasponskih armiranobetonskih okvira s ispunom i bez nje.In the nonlinear analysis of masonry infilled RC frame structures, simple strut models are often adopted to represent the masonry infill, particularly in the case of extensive parametric numerical studies. Therefore, a careful definition of the corresponding strut properties is of exceptional significance for achieving a realistic building response. A method for evaluation of masonry infill strut properties is proposed and applied in this paper, based on the interpretation of results obtained by cyclic in-plane testing of single-storey, single-bay bare and infilled RC frame specimens

On the design of walls with openings

U radu se opisuje postupak proračuna zidova s otvorima koji je Veselin Simović uveo početkom sedamdesetih godina prošloga stoljeća. Rješenje je izvedeno u zatvorenom obliku prevođenjem sustava jednadžbi metode sila u linearnu diferencijsku jednadžbu s konstantnim koeficijentima. Spomenuti je postupak proračuna zidova s otvorima uspoređen s „modernijim“ postupkom proračuna metodom pomakâ, provedivim samo primjenom računala. Usporedbe rezultata pokazuju ograničenja primjenjivosti postupka, odnosno, vrste zidova za koje se rezultati mogu smatrati pouzdanima

Post-earthquake damage assessment of buildings – procedure for conducting building inspections

Procjene oštećenja i uporabljivosti građevina u Hrvatskoj, iskočile su u prvi plan nakon potresa u Zagrebu 22. ožujka 2020. S obzirom na manjkavosti pripremne faze, pri čemu nije provedena edukacija stručnjaka prije potresa, nego u hodu, procjene su sadržavale dozu subjektivnosti i interpretacije na temelju znanja, iskustva, ali i intuicije pojedinaca. U radu je detaljno prikazana metodologija koja može pomoći u brzim procjenama te kod detaljnih inženjerskih pregleda koji se moraju napraviti prije obnove. Prikazana metodologija se može iskoristiti u slučaju novoga razornog potresa koji se može dogoditi već sutra.Assessments of building damage and usability were of primary importance after the Zagreb earthquake of 22 March 2020. Due to deficiencies of preparatory phase, where education of experts was not carried out before the earthquake, but later on, the assessments contained certain subjectivity and interpretations, based on knowledge and experience, but also on intuition of individuals. Detailed methodology, which should improve rapid assessments and detailed engineering inspections to be performed before reconstruction, is highlighted in the paper. This methodology may be utilized if another devastating earthquake occurs, which could happen already tomorrow

Nrf2-interacting nutrients and COVID-19 : time for research to develop adaptation strategies

There are large between- and within-country variations in COVID-19 death rates. Some very low death rate settings such as Eastern Asia, Central Europe, the Balkans and Africa have a common feature of eating large quantities of fermented foods whose intake is associated with the activation of the Nrf2 (Nuclear factor (erythroid-derived 2)-like 2) anti-oxidant transcription factor. There are many Nrf2-interacting nutrients (berberine, curcumin, epigallocatechin gallate, genistein, quercetin, resveratrol, sulforaphane) that all act similarly to reduce insulin resistance, endothelial damage, lung injury and cytokine storm. They also act on the same mechanisms (mTOR: Mammalian target of rapamycin, PPAR gamma:Peroxisome proliferator-activated receptor, NF kappa B: Nuclear factor kappa B, ERK: Extracellular signal-regulated kinases and eIF2 alpha:Elongation initiation factor 2 alpha). They may as a result be important in mitigating the severity of COVID-19, acting through the endoplasmic reticulum stress or ACE-Angiotensin-II-AT(1)R axis (AT(1)R) pathway. Many Nrf2-interacting nutrients are also interacting with TRPA1 and/or TRPV1. Interestingly, geographical areas with very low COVID-19 mortality are those with the lowest prevalence of obesity (Sub-Saharan Africa and Asia). It is tempting to propose that Nrf2-interacting foods and nutrients can re-balance insulin resistance and have a significant effect on COVID-19 severity. It is therefore possible that the intake of these foods may restore an optimal natural balance for the Nrf2 pathway and may be of interest in the mitigation of COVID-19 severity

Prediction of inter-storey drifts for regular RC structures with masonry infills based on bare frame modelling

The traditional construction of masonry infills adjacent to RC structural elements is still widely adopted in European countries, including seismically active regions. Given the repeated field observations from damaging earthquakes, pointing to unacceptably high levels of masonry infill damage, the present study is motivated by the need to improve further the European seismic design approach for new RC structures with masonry infills, in order to exclude the poor seismic behaviour probably caused by deficiencies in the verification procedure. Since the in-plane damage to non-structural panels is commonly controlled through the limitation of inter-storey drifts, the possibility to introduce more effective verification criteria, accounting for structural properties, infill layouts and masonry properties is explored. Therefore, starting from the assumption that analyses and verifications in the design of buildings are commonly accomplished neglecting the presence of infills, results of extensive nonlinear numerical analyses for different building configurations are examined. As a result, a simplified procedure for the prediction of expected inter-storey drifts for infilled structures, based on the corresponding demands of bare configurations, in function of a simple parameter accounting for structural properties and the presence of infills, is introduced. Possible implications of the proposed approach aimed at the improvement of the current design provisions are discussed

Mechanical characterization and force-displacement hysteretic curves from in-plane cyclic tests on strong masonry infills

This article contains information related to a recent study “Performance-based interpretation of in-plane cyclic tests on RC frames with strong masonry infills” (Morandi et al., 2017 [1]). Motivated by the necessity to improve the knowledge of the in-plane seismic response of rigid strong masonry infills, a wide experimental campaign based on in-plane cyclic tests on full-scale RC infilled frame specimens, supplemented with a complete characterization of the materials, has been conducted at the laboratory of the Department of Civil Engineering and Architecture of the University of Pavia. The masonry is constituted by vertically perforated 35 cm thick clay units with tongue and groove and dry head-joints and general-purpose mortar bed-joints. The paper reports the results of the mechanical characterization and of the force-displacement hysteretic curves from the in-plane cyclic tests

From the history of development of iterative procedures

U članku su opisani doprinosi koje su članovi Zavoda za tehničku mehaniku zagrebačkoga Građevinskog fakulteta dali razvoju iteracijskih postupaka za rješavanje sustava jednadžbi inženjerske metode pomaka u štapnoj statici: Čališevljev postupak dvostruke iteracije za okvirne sisteme s translacijski pomičnim čvorovima, Kanijev postupak jednostruke iteracije, Wernerov postupak ubrzavanja drugog dijela Crossova postupka i njegove inačice te Kuševićeva usporedna analiza postupaka.The authors describe contributions made by members of the Department of Technical Mechanics of the Faculty of Civil Engineering in Zagreb to the development of iterative methods for solving systems of equations of displacement method in rod structure statics: Čališev’s double iteration procedure for sway frames, Kani\u27s single iteration procedure, Werner\u27s procedure for acceleration of the second part of Cross method and its variants, and comparative analysis of procedures by Kušević

From the history of development of iterative procedures

U članku su opisani doprinosi koje su članovi Zavoda za tehničku mehaniku zagrebačkoga Građevinskog fakulteta dali razvoju iteracijskih postupaka za rješavanje sustava jednadžbi inženjerske metode pomaka u štapnoj statici: Čališevljev postupak dvostruke iteracije za okvirne sisteme s translacijski pomičnim čvorovima, Kanijev postupak jednostruke iteracije, Wernerov postupak ubrzavanja drugog dijela Crossova postupka i njegove inačice te Kuševićeva usporedna analiza postupaka.The authors describe contributions made by members of the Department of Technical Mechanics of the Faculty of Civil Engineering in Zagreb to the development of iterative methods for solving systems of equations of displacement method in rod structure statics: Čališev’s double iteration procedure for sway frames, Kani\u27s single iteration procedure, Werner\u27s procedure for acceleration of the second part of Cross method and its variants, and comparative analysis of procedures by Kušević