NONLINEAR ANALYSIS OF STRUCTURAL FRAME-WALL SYSTEM: INFILL WALL WITH CENTRIC DOOR OPENING

Izrazito seizmički aktivna područja Europe su njezin južni i jugoistočni dio, a vrlo uobičajen konstrukcijski sustav za niske i srednje visoke zgrade toga područja su okvir ispunjeni ziđem. U skladu s dosadašnjim spoznajama o potresnim djelovanjima, konstrukcijski sustav okvir-ziđe sastoji se od seizmički otpornih elemenata, okvira koji se izvodi od armiranog betona ili čelika, te ispune za koju se u Republici Hrvatskoj koriste blok opeka ili betonski blokovi. U ispunskom ziđu najčešće se nalaze otvori različitih veličina i smještaja. Ispuna mijenja odgovor konstrukcije na potres i njen se utjecaj mora na odgovarajući način uzeti u proračun. Do danas razvijeni proračunski postupci određivanja potresne otpornosti razvijeni za konstrukcijski sustav okvir-ziđe, ne smiju se rabiti nekritično i bez opreza. Razlog tome je najčešće nedovoljno razumijevanje njihova utjecaja. Najčešće se ispunsko ziđe modelira dijagonalnim tlačnim štapom. Pri proračunu debljina štapa je jednaka debljini zida, a širinu štapa je potrebno odrediti. Više autora nude različite postupke određivanja širine dijagonalnog tlačnog štapa. Do danas nije jasno utvrđeno koji je pristup najprikladniji .Različite vrste elemenata i morta te različite vrste, smještaje i veličine otvora moguće je preciznije obuhvatiti ukoliko se koriste simulacije neelastičnog ponašanja pomoću proračunskih mikromodela. Proračunski mikromodeli zbog svoje složenosti i trajnosti proračuna ograničeni su na manje probleme te ih je zbog pouzdanosti potrebno provjeriti eksperimentalnim ispitivanjima. U okviru rada istraženo je ponašanje konstrukcijskog sustava okvir-ziđe, u slučaju kada se u ispunskom ziđu nalazi otvor za vrata postavljen centrično, pri simulaciji potresa u i izvan vlastite ravnine.U tu svrhu potrebno je izraditi prostorni model primjenom metode konačnih elemenata u računalnom programu ATENA 3D kako bi se odredila otpornost sustava u svojoj i okomito na svoju ravninu. Usporedit će se rezultati dobiveni eksperimentalnim ispitivanjem s rezultatima dobivenim pojednostavljenim proračunskim postupcima.The southern and southeastern parts of Europe are considered to be regions with great seismic activity. Therefore, frames with masonry infill are for this region a very common construction system for low and medium high buildings Based on the knowledge of previous earthquakes, construction system frame-masonry is consisted of seismic resistant elements, reinforced with concrete or steel, as well as masonry infill which is in Croatia blocks of bricks or concrete blocks. Masonry infill mostly has openings of different sizes and positions, and it significantly changes the construction response to the earthquake, so its response must be considered. Many calculation procedures that have been developed so far to determine earthquake resistance for construction system frame-masonry, should not be used uncritically and unadvisedly. The main reason for that is the lack of knowledge of their actual impact. The most common way of modelling masonry infill is by replacing infills with one diagonal compressive strut. In the analysis the thickness of the strut is equal to the thickness of the wall, and it is necessary to determine the width of the strut. Many authors offer different procedures to determine the width of the diagonal strut, but they haven't still agreed which one is the best. It is possible to include different elements such as mortar as well as different types, positions and dimensions of openings more precisely if simulations of nonelastic behaviour with the help of numerical micromodels are used. Numerical micromodels, due to their complexity and time-consuming calculations, can have some problems, therefore it is necessary to check the reliability of such models using experimental tests. Within the scope of work, the behaviour of construction system frame-masonry was analysed, but only in the case when there is a centric door opening in infill, under earthquake simulation in plane and out of plane. For this purpose, it is necessary to develop a spatial model using finite element method in the computer programme Atena 3D software, to determine the resistance of system in its plane and perpendicular to its plane. The results of experimental tests will be compared with the results of analytical calculations