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The aim of this paper is to present the application of the FDEM in analysis of 2D and 3D RC structures. In presented numerical model, the reinforcing bar finite elements are implemented within the concrete finite elements and simulate the behavior of the reinforcing bar within the uncracked concrete assuming the linear elastic behavior of the reinforcing bar in the concrete finite element and a perfect bond between the concrete and the reinforcing bar. Fracture and fragmentation as well as material nonlinearity are described with contact elements for concrete and contact element for reinforcing bars which are implemented within the finite element mesh. The model, implicates few numerical algorithms which are based on approximation of the experimental curves for material behavior of the concrete and steel which are important for description of main non-linear effects in reinforced concrete structures. In presented model non-linear material model for steel is based on experimental stress-strain curve, while the cyclic behavior of the steel during the cyclic load is modelled with improved Kato’s model.

Building construction using stone or clay bricks that are held together by mortar is one of the oldest building techniques that is still in use today. Among the oldest construction are masonry stone huts in a form of a circle found nearby lake Hullen in Israel that come from a period between 9.000 and 8.000 BC [1]. The first masonry structures were amazing piles of natural stone. As humans became more skilled and began using tools, masonry structures began to be more symmetrical. Later humans learned to make bricks moulding them from mud or clay leaving them to dry in the air and later baking them in ovens. Bricks were strong, uniform and easy to make. In addition to improving the techniques of making blocks various cultures began to use architectural features such as pillars to obtain the height or beams, arches and domes for bridging over the spans of distance. Masonry has a long worldwide tradition of use in construction due to its simplicity. The durability of masonry structures is evident in the number of structures that are still in use after hundreds or even several thousands of years. A few examples of structures that have become symbols of certain cultures are the Egyptian pyramids that have their origin from a period between 2800.-2000. BC, the Parthenon in Greece from the fifth century BC, The Great Wall of China whose construction began in fifth century before Christ and the Colosseum in Rome from first century. In spite of the simplicity that is manifested during the construction of masonry structures, understanding and describing mechanical behaviour of those structures, especially in conditions of seismic loading, represents a true challenge due to the nature of masonry structure which due to the presence of joints among blocks that can but don’t have to be filled in with mortar shows a complex and particular nonlinear behavior. Various methods and numerical models are used for analysis of dry-stone masonry structures, based upon the degree of complexity, volume of input data and accuracy of required solution. There are two basic approaches in numerical modelling of masonry structures: idealization using continuum, and discontinuum. The most commonly used numerical tool in continuum approach is finite element method [1], where different modelling strategies at micro, meso and macro scale have been developed to model masonry structure with desired accuracy. Although the great number of numerical models based on finite element method, the need for modelling the discontinuities and mutual mechanical interaction, finite displacement and rotation including complete detachment of the structure, which is especially expressed in the masonry structures under dynamic loading conditions, led to the development of numerous discontinuum models represented through the framework of discrete element method. The main idea behind the application of the discrete element method to masonry refers to the idealisation of the structure as a discontinuum, where the blocks are represented by rigid discrete elements, while the joints are modelled as contact surfaces between different blocks. In recent times, a number of numerical models combine the advantages of discrete and finite element methods. One of the methods which combine the advantages of continuum and discontinuum approach is a combined finite- discrete element method (FDEM) pioneered by Munjiza [3, 4]. FDEM was developed mainly for the simulation of fracturing problems considering deformable blocks that may split and separate during the analysis. Within the framework of this method, the blocks are discretised by triangular (2D) or tetrahedral (3D) finite elements. The material model in the finite elements is linear elastic, while the material nonlinearity, fracture and fragmentation of discrete elements are considered through displacement-based contact elements implemented within a finite element mesh. The interaction between discrete elements is considered through the contact interaction algorithm for normal forces, which is based on potential contact forces. The method uses an explicit numerical integration of the motion equation. The purpose of this paper is to present the application of combined finite-discrete element method in analysis of dry stone masonry structures [5-7], masonry structures with mortar joints [9] and confined masonry structures [9]. For the purpose of validation of the method in analysis of dry stone masonry structures, experimental analysis [10] were conducted and compared with numerical results.

CILJ: Cilj ovog rada je prikazati broj zadržanih pobačaja s obzirom na dob pacijentica, učestalost u prethodnim trunoćama te metodu indukcije pobačaja u Klinici za ženske bolesti i porode, Kliničkog bolničkog centra Split. METODE: Istraživanje je provedeno u KBC-u Split, u Klinici za ženske bolesti i porode. Istraživanje je provedeno u razdoblju od siječnja do veljače 2019. godine. U istraživanju je korištena medicinska dokumentacija ispitanica s medicinskom dijagnozom zadržanog pobačaja (lat. Abortus retentus) koje su bile hospitalizirane u razdoblju od 2014. do 2018. godine. Promatrani parametri su bili broj zadržanih pobačaja, demografske karakteristike ispitanica, dob. Od klinički promatranih parametara promatralo se liječenje zadržanih pobačaja indukcijom prepidila i/ili karboprostom. REZULTATI: Pacijentice s dijagnozom zadržanog pobačaja su u rasponu 17- 47 godina starosti. Ukupan broj zadržanih pobačaja u razdoblju od 2014.-2018.g imalo je 130 pacijentica. U prethodnim trudoćama 36 pacijentica (27,69%) imalo je jedan ili više pobačaja. Tijekom indukcije poroda, liječnici su u večini slučajeva koristili prepidil gel i/ili ampule karboprosta. Od 130 pacijentica, kod 101 pacijentice (77,59%) indukcija poroda je započeta prepidil gelom, dok je kod 31 pacijentice (27,69%) indukcija poroda započeta ampulama karboprosta. Kombinaciju prepidil gela i ampula karboprosta u indukciji poroda imalo je 26 pacijentica (20%). ZAKLJUČAK: Provedeno istraživanje je pokazalo da se najviše zadržanih pobačaja događa između 10-og i 20-og tjedna trudnoće. Tijekom liječenja zadržanog pobačaja samo u dva slučaja je bilo komplikacija. U oba slučaja radilo se o prekomjernom krvarenju, jedan se dogodio tijekom kiretaže, dok se drugi dogodio nakon kiretaže maternice. Uzrok prekomjernog krvarenja nije bio poznat. AIM: The aim of this study is to present the number of abortions with regard to the age of patients, the frequency of previous pregnancies, and the method of inducing abortions at the Clinic for Women's Diseases and Births, Clinical Hospital Center Split. METHODS: The study was conducted at KBC Split, at the Clinic for Female Diseases and Births. The survey was conducted between January and February 2019. The study used the medical records of respondents with a medical diagnosis of delayed abortion (Lat. Abortus retentus) who were hospitalized between 2014 and 2018. The observed parameters were the number of abortions withheld, the demographic characteristics of the respondents, age. Treatment of delayed abortions by prepidyl induction and / or carboprost was observed from the clinically observed parameters. RESULTS: Patients diagnosed with delayed abortion ranged in age from 17 to 47 years. The total number of abortions withheld in the period 2014-2018 was 130 patients. In previous pregnancies, 36 patients (27.69%) had one or more miscarriages. During the induction of childbirth, doctors used prepidyl gel and / or carboprost ampoules in most cases. Of the 130 patients, in 101 patients (77.59%), the induction of labor was initiated by prepidyl gel, while in 31 patients (27.69%), the induction of labor was initiated by carboprost ampoules. 26 patients (20%) had a combination of prepidyl gel and carboprost ampoules in childbirth induction. CONCLUSION: The conducted research showed that most abortions occur between the 10th and the 20th week of pregnancy. There were complications in the treatment of delayed abortion in only two cases. In both cases, it was excessive bleeding, one occurred during the curettage, while the other occurred after the uterine curettage. The cause of the excessive bleeding was unknown.

A commonly used method for increasing the resistance of historical structures, made of stone blocks with dry joints, is strengthening with the metal connectors. The numerical modelling of these structures is demanded due to a discontinuous nature and composition of the materials with significantly different properties. This paper presents a finite-discrete element numerical model for analysis and prediction of the collapse of dry stone masonry structures strengthened with steel clamps and bolts. The model includes fracture and fragmentation of the blocks as well as a cyclic behaviour, yielding, stiffness degradation, failure and the influence of pulling out of the clamps and the bolts from the stone block. The developed model can capture damage mechanisms of the structure both at the joint and the block level, coupled with the deformation and extracting of the connectors from the holes. The capabilities of the presented approach are demonstrated in the seismic analysis of the strengthened dry-stone structure .The developed model can be used for the estimation of the seismic resistance of historical dry stone masonry structures reinforced with steel clamps and steel bolts, which is very important for the structures classified as cultural heritage.

This paper presents the results of numerical investigations of the behavior of the model of Protiron, an ancient dry-stone masonry structure located in Split, Croatia, under seismic excitation, in comparison with experimental tests. The numerical analysis was performed by 3D finite-discrete element model, which was enhanced with the additional elements, clamps and dowels, which connect the stone blocks and may deform, yield and pull out from the stone during the seismic excitation. The most significant results of the measured displacement versus time have been numerically reproduced by presented numerical model.

U ovom radu prikazan je novi numerički model za analizu grednih konstrukcija. Model koristi dvočvorne konačne elemente sa translacijskim stupnjevima slobode u svakom čvoru i pri tome uzima u obzir materijalnu nelinearnost, velike pomake, velike rotacije i velike deformacije. Prikazani numerički model implementiran je u numerički paket ‘Yfdem’ koji se bazira na kombiniranoj metodi konačnih i diskretnih elemenata. Prednosti novog numeričkog modela prikazane su na jednostavnom primjeru usporedbom rezultata s poznatim eksperimentalnim rješenjima iz literature.

This paper presents a new numerical model for the analysis of beam-type structures based on the combined finite-discrete element method (FDEM). The model uses straight two-node rotation free finite elements, and takes into account linear-elastic material behaviour, finite displacements, finite rotations and small strains. The presented numerical model is implemented into the open source FDEM package “Yfdem”. Performance of the new numerical model was demonstrated on simple benchmark tests where very good agreement of obtained numerical results with reference solutions was shown. Performed numerical analysis indicates that the presented numerical model is applicable in static, dynamic and stability analyses of beam type structures.

Historical structures in seismic active area of south Europe are often made of stone blocks with dry joints. Strengthening of these structures with metal connectors, i.e. clamps and bolts, is traditional approach in increasing their seismic resistance. Some structures were originally built with reinforcements, while others were reinforced later during reconstruction. Behaviour of these structures under the earthquakes and their ultimate capacity load can be analyzed by precise numerical models. This paper presents one such model based on finite-discrete element method which used 3D discrete elements with internal finite element mesh for modelling of stone blocks and line reinforcing elements that connect the blocks, allowing for better structural behaviour and higher load capacity to earthquake action. Presented model is an extension of previously developed 2D model for strengthened dry-stone structures [1] and 3D model for structures without strengthening [2]. The performance of the model was demonstrated on several examples which showed an efficiency of the connecting elements in increasing the seismic energy dissipation and protection of the structure from collapse.

Preservation and estimation of the resistance of historical dry-stone masonry structures, especially those that are classified as world cultural heritage represent great challenge to researchers nowadays. These structures are often reinforced with different types of metal connectors, such as clamps and bolts, embedded into the holes and filled with lead. In order to investigate mechanical behaviour and carrying capacity of such structures subjected to various dynamic effects of which the dominant is earthquake, it is necessary to develop the software which, among other algorithms, include numerical modelling of clamps and bolts. In this paper, a new numerical model of clamps and bolts suitable for implementation in computer programs based on discrete or finite-discrete element method 1-2 is presented. The model is based on force-displacement curves, experimentally obtained by testing of the specimens composed of two stone blocks connected with clamp or bolt 3. Increasing of the structural load accompanied with the tangential and shear separation of the blocks led to the reduction of the normal and shear stress in connecting elements, which were reflected in the experimentally obtained curves and implemented in material models of connectors.

Reinforced concrete buildings in a seismically active area can be designed as DCM (medium ductility) or DCH (high ductility) class according to the regulations of Eurocode 8. In this paper, two RC buildings, one with a wall structural system and the other with a frame system, previously designed for DCM and DCH ductility, were analysed by using incremental dynamic analysis in order to study differences in the behaviour of structures between these ductility classes, especially the failure mechanism and ultimate collapse acceleration. Despite the fact that a higher behaviour factor of DCH structures influences lower seismic resistance, in comparison to DCM structures, a strict application of the design and detailing rules of Eurocode 8 in analysed examples caused that the seismic resistance of both frames does not significantly differ. The conclusions were derived for two buildings and do not necessarily apply to other RC structures. Further analysis could make a valuable contribution to the analysis of the behaviour of such buildings and decide between two ductility classes in everyday building design.

Different types of impact loads jeopardize structures, starting from simple vehicle impact up to explosions caused by technological processes in industrial plants or terrorist attacks. Therefore, the analysis and design of RC structures resistant to impact loads has become an important aspect of the civil engineering industry. Numerical methods based on discrete crack approach, which naturally takes into account the discontinuities occurred by the failure and fragmentation process in concrete, are suitable for analysis of impact resistant RC structures. This paper presents the application of one such model, developed within the framework of finite-discrete element method in simulation of the response of RC structures under the impact load. The highly non-linear effects are realized in concrete and reinforcement joint elements through the coupling of concrete crack opening-closing mechanism with plastic deformation, slip and breaking of reinforcing steel bars. The accuracy and efficiency of the model was demonstrated on RC beam subjected to impact loads by comparison of numerical results with experimental impact tests, including displacement time history and crack pattern.

Comprehensive analysis of seismic resistance of historical ancient monuments is an important aspect in rehabilitation of such structures. Most of them are made of stone blocks with dry joints and sometimes strengthened with metal connectors. Due to discontinuous nature and composition of the materials with significantly different properties, computational analyses of those structures are based on advanced numerical models with discrete or finite discrete element approach, and also knowledge of numerous material and structural parameters. A comprehensive approach to the analysis of such structures should integrate model updating, calibration and validation, as well as experimental investigations which may include testing of the material properties, complex non-linear static and dynamic tests and hopefully, shaking table testing of the structural model. This paper presents integration of the mentioned numerical and experimental investigations in analysis of the seismic resistance of Protiron monument, placed in the Diocletian Palace in Split, Croatia. The applied numerical model based on finite- discrete element method includes sliding of the blocks, fracture and fragmentation, cyclic behaviour, yielding and pulling out of the clamps and the bolts from the stone blocks [1]. Force-displacement relationship for clamps and bolts, obtained by static tests on several specimens, are used to calibrate the model of the metal connectors. Finally, shaking table testing of Protiron model was performed [2] in order to validate applied numerical model in dynamic regime and to provide an insight into the seismic resistance with detailed behaviour of the monument model.

Monitoring of the behavior of the structure before and after the failure, including the transition from continuum to discontinuum, is very important in the modeling of the load capacity and collapse of reinforced concrete structures subjected to extreme loads. Numerical model presented in this paper was developed with the aim of modelling and monitoring the behavior of reinforced concrete spatial structures exposed to static and dynamic loads. The model is based on combined finite-discrete element method (FDEM) which has become an excellent tool to address a wide range of problems involving fracturing and fragmentation of solids. In presented numerical model, four-node tetrahedron finite elements of concrete and two-node finite elements of reinforcing bar are used to model the behavior of the material up to the cracking of concrete. Fracture and fragmentation as well as material nonlinearity are described with contact elements for concrete and contact element for reinforcing bars which are implemented within the finite element mesh. The continuity between the reinforcing bar finite elements and concrete tetrahedron finite elements in the pre-failure stage is ensured through the penalty method. The model, implicates few numerical algorithms which are based on approximation of the experimental curves for material behaviour of the concrete and steel and are important for description of main non- linear effects in reinforced concrete structures. Verification and validation of the presented model are shown in several examples.

One of the oldest techniques for improving resistance of dry stone masonry structures is strengthening by clamps and bolts which are inserted into the previously made holes that are subsequently backfilled with lead. Despite the complexity and high cost price of this procedure, stone masonry structures classified as cultural heritage, especially those built in seismic active area, are often reconstructed in this way. In order to evaluate the resistance of these structures, several experimental investigations of the behaviour of strengthened stone masonry structures were performed at the Dynamic testing laboratory of the Institute of Earthquake Engineering and Engineering Seismology (IZIIS) in Skopje, Macedonia. The first experiments refers to static analysis of the group of stone blocks connected with steel clamp and bolts in the way similarly as a technique applied during the building of Old Bridge in Mostar, Bosnia and Hercegovina. Six models of arched structure of the bridge were constructed in scale 1:3 and subjected to shearing and bending in two perpendicular directions. The second experiment was testing of the model (scale 1:4), of the Protiron structure in the Diocletian's Palace in Split, Croatia, under the seismic excitation on the 5×5 meters seismic shaking table. The model was firstly subjected to representative earthquake in linear range, and after that, in non-linear range by increasing of the acceleration gradually until the failure. The tests provided a clear insight into the behaviour of the system under monotonic and dynamic loading, the mechanism of damage and failure, especially in the efficiency of the connecting elements between the stone units, which had a special role in protection of the structure from collapse.

One of the main aims of the design of earthquake resistant structures is to ensure that the design seismic action do not cause collapse of the structure. Eurocode 8 includes prescriptions in order to guarantee ductile behaviour and adequate bearing capacity of the structure. According to Eurocode 8, concrete buildings in high seismic area are classified in two ductility classes, DCM (medium ductility) and DCH (high ductility), to predefine the behaviour of the structures, leading to different responses. However, the behaviour of the structure cannot be fully predetermined due to many factors that play a key role in such a problem. Specifically, the diversity of the nature of the earthquake can produce significant differences in structural behaviour with respect to the same ductility class. On top of that, each of the ductility classes implies completely different perspective regarding the design of the building. Thus, one needs to make a judicious choice between the two classes balancing between the desired response of the structure, costs and complexity of design and construction. Powerful numerical models stand as significant tools to obtain more insight into the peculiarity of each structure. The model of this kind should be able to produce highly nonlinear effects which are dominant in the behaviour of RC structures under the seismic loading until collapse. In this paper influence of ductility classes to seismic response of RC structure was performed by finite- discrete numerical model for RC structures. The model considers discrete representation of the cracks, the interaction between the reinforcement and concrete considered by steel strain-slip relation with the influence of adjacent cracks to the slip of reinforcing bar, local slip of reinforcing bar due to a high plastic deformation under reversed cyclic loading and the influence of the curvature of reinforcing bar to yield stress reduction of the steel. The structure is assumed to behave as a linear elastic continuum until the initiation of the cracks and discontinuities, which are allowed to propagate through the joint elements of concrete, leading to the deformation in the reinforcing bar joint elements. Analysis of the influence of ductility classes to seismic response was studied on a five-storey RC building with uncoupled wall system. The building was previously designed according to EC8 for importance factor II, type 1 response spectrum, damping 5%, ground type B, design ground acceleration ag=0.3g and ductility classes DCM and DCH. The behaviour factors equal to q=3, 0 for DCM and q=4, 4 for DCH are adopted. Incremental dynamic analysis of the left boundary wall was performed using previously described finite-discrete numerical model. Seismic loading is represented by a time function of horizontal ground acceleration recorded on the soil class B during real earthquakes. The set of seven ground motion records are chosen from the European Strong-Motion Database. Average acceleration response spectrum of applied earthquakes corresponds to elastic response spectrum for peak ground acceleration of 0.3g and soil class B according to EC-8. Analysis of the average dynamic response of the wall for a series of seven records of real earthquakes shows that the behaviour of the wall designed for DCM class is linear up to the ground acceleration a=0, 30g. Significant non- linearity starts for a=0, 48g, while the collapse of the wall happens for a=0, 70g. Wall designed according to DCH is in linear elastic region up to the a=0, 40g, followed by the occurrence of nonlinear behaviour. Average collapse acceleration a=0, 84g was observed for DCH class. The most destructive earthquake for both ductility classes is Bar, with ultimate collapse accelerations a=0, 40g and a=0, 50g for DCM and DCH classes respectively. The least destructive earthquakes, considered through the aspect of collapse accelerations, are Petrovac and Selsund, which produced the collapse of the wall for a=0, 90g (DCM) and a=1, 0g (DCH). It can be observed that the wall reinforced according to the high ductility class (DCH) possess average seismic resistance 20% higher with respect to medium ductility class (DCM). It is interesting to emphasize that the longitudinal flexural reinforcement in the boundary elements is same for both ductility classes in order to satisfy condition of the minimum percentage of reinforcement. The differences pertain to confining reinforcement in boundary elements and web shear reinforcement cause higher seismic resistance of the high ductility wall. The average responses for both ductility classes still remain linear before they reached design ground acceleration.

The behaviour of the earthquake excitated reinforced concrete (RC) structures up to the collapse, previously designed according to the prescriptions of Eurocode 8 cannot be fully predetermined because of the diversity of the nature of the earthquake. Thus, one needs to make a judicious choice between the two ductility classes balancing between the desired response of the structure, dimension of structural elements, costs and complexity of the design and construction. Powerful numerical models stand as significant tools to obtain more insight into the peculiarity of each structure. This paper presents a numerical model for dynamic analysis and prediction of the collapse of RC structures under the seismic loading based on finite discrete element method. The model includes several numerical algorithms which are essential for realistic description of highly non-linear effects of these structures: cyclic crack opening-closing mechanism based on discrete cracks, interaction between the reinforcement and concrete taken by steel strain-slip relation, the influence of adjacent cracks to the slip of reinforcing bar, local slip of reinforcing bar because of a high plastic deformation under reversed cyclic loading, the influence of the curvature of reinforcing bar to yield stress reduction of the steel and cyclic behaviour of concrete and steel. Performance of the model was demonstrated through incremental dynamic analysis of RC wall, previously designed according to the Eurocode 8 for medium and high ductility classes. The presented results demonstrated the ability of the model for simulation of the crack patterns and collapse of these structures.

U ovom radu provedena je numerička analiza utjecaja iznosa energije loma na predložak pukotina u betonskim blokovima prilikom slobodnog pada na apsolutno krutu podlogu. Numeričke analize su provedene numeričkim programom Y-2D koji je baziran na kombiniranoj metodi konačno-diskretnih elemenata (FDEM). Model pukotine implementiran u ovoj metodi namijenjen je za simulaciju nastanka i širenja pukotine u vlaku i posmiku i bazira se na aproksimaciji eksperimentalnih krivulja naprezanje-širina pukotine betona. Na temelju rezultata dobivenih iz provedenih analiza može se zaključiti da energija loma ima značajan utjecaj na predložak pukotina te predstavlja vrlo važan podatak kojeg je potrebno uzeti u obzir prilikom analize pukotina u kontaktnoj interakciji. Također se pokazalo da uzorci s većom energijom loma imaju veću duktilnost koja se očituje u sposobnosti apsorpcije kinetičke energije u unutrašnju potencijalnu energiju prilikom kontakta bloka s podlogom.

Izvješće o energetskom pregledu stambene zgrade u svrhu izrade energetskog certifikata

In this paper 2D and 3D numerical modelling of reinforcing concrete structures is presented. This model is based on the finite-discrete element method. This approach considers the structure as a deformable continuum until the opening of the cracks. The transition from the continuum to the discontinuum is a result of the fracture and fragmentation which are realized by contact elements implemented within the finite element mesh. The interaction between discrete elements is considered through the contact interaction algorithm based on the principle of potential contact forces which are computed using penalty function method. The non-linear behaviour of the concrete in tension and shear takes into account strain-hardening, strain-softening and cyclic behaviour during dynamic loading. The model of reinforcement is based on an approximation of the experimental curves for the bar strain in the crack. The presented numerical model includes interaction effects between reinforcement and concrete as well as cyclic behaviour of concrete and steel during dynamic loading.

Izvješće o energetskom pregledu stambene zgrade u svrhu izrade energetskog certifikata

This paper presents numerical model for confined masonry structures under seismic load based on combination of the finite discrete element models for reinforced concrete confining elements and masonry infill. Material non-linearity including fracture and fragmentation of discrete elements is considered through contact elements which are implemented within a finite element mesh. The model includes non-linear cyclic behaviour of concrete, reinforcement and masonry during the seismic event, interaction between the reinforcement and concrete, cracking of the reinforced concrete confining elements and masonry units as well as failure and softening in tension and shear for mortar joints. The application of the developed numerical model is shown on the example of confined masonry wall exposed to seismic excitation.

This paper presents numerical model based on the finite discrete element method for the analysis and prediction of the collapse of masonry structures with mortar joints and dry stone masonry structures. The model consists of a numerical model in a finite element, contact interaction algorithm which simulates the interaction between stone blocks in dry joint and numerical model in an interface element which simulate the behavior of the mortar joints and unit-mortar interface. The verification of the model was performed on examples by comparing it with the results obtained with the known numerical and experimental results from literature.

Izvješće o energetskom pregledu stambene zgrade u svrhu izrade energetskog certifikata

Sudar je fizikalna pojava koja se očituje u kontaktnoj interakciji dvaju tijela uslijed različitih brzina. Fizikalna veličina kojom se najčešće opisuje gubitak energije prilikom sudara dvaju tijela je koeficijent restitucije i njega je moguće eksperimentalno odrediti u ovisnosti o obliku kontaktnih površina, veličini sudarnih tijela, vrsti materijala itd. Gubitak energije koji se događa uslijed sudara dvaju tijela, u kombiniranoj metodi konačno-diskretnih elemenata (FEM/DEM) opisuje se modelom prigušenja koji je definiran koeficijentom prigušenja. Da bi se u FEM/DEM metodi mogao simulirati gubitak sudar dvaju diskretnih elemenata potrebno je ispravno procijeniti veličinu koeficijenta prigušenja. U ovom radu analizirana je veza koeficijenta prigušenja u FEM/DEM metodi i koeficijenta restitucije za slučaj sudara dvaju tijela različitih materijala, oblika i veličina.

Elaborat o energetskom pregledu stambene zgrade u svrhu izrade energetskog certifikata

Izvješće o energetskom pregledu stambene zgrade i pratećeg pslovnog prostora u svrhu izrade energetskog certifikata.

Izvješće o energetskom pregledu stambene zgrade u svrhu izrade energetskog certifikata

Prikazan je pregled metoda namijenjenih za modeliranje povijesnih zidanih konstrukcija, počevši od jednostavnih klasičnih pa sve do suvremenih prikladnih za primjenu u računalnim programima. Predočena su glavna obilježja zidanih konstrukcija te glavne značajke metoda za njihovu analizu kao što su dinamičke analitičke metode, metode graničnih stanja, konačnih elemenata te diskretnih elemenata. Dan je osvrt na primjenu pojedine metode obzirom na zahtijevanu razinu točnosti, količinu ulaznih podataka te vrijeme trajanja proračuna.

U radu je prikazan numerički model za dinamičku analizu zidanih i armirano-betonskih konstrukcija zasnovan na kombiniranoj metodi konačno-diskretnih elemenata (FEM/DEM). Model opisuje ponašanje takvih konstrukcija izloženih dinamičkom opterećenju, pojavu i razvoj pukotina, gubitke energije uslijed nelinearnih efekata, inercijalne efekte uslijed gibanja, kontaktno međudjelovanje i postizanje stanja mirovanja kao posljedicu gubitka energije u sustavu. Provedena je provjera točnosti modela te primjena u analizi konstrukcija izloženih različitim dinamičkim opterećenjima.

In this paper a numerical model for analysis of reinforced concrete structures based on finite-discrete element method (FEM/DEM) is used for analysis of reinforced beam-column joints. The model takes into account the discontinuous nature of the reinforced concrete at the failure stages. It is based on approximation of the experimental curves for behaviour of the concrete and steel in crack. Cracking of the structure is enabled by discrete model of cracks where the cyclic behaviour of concrete and steel was implemented. The interaction between reinforcement and concrete is defined by the average spacing between the cracks. This was taken into consideration by the steel strain-slip relation, the influence of adjacent cracks to the slip of the reinforcing bar and the influence of the curvature of the reinforcing bar to yield stress reduction of steel. The application of the developed numerical model is presented in the analysis of reinforced concrete beam-column joints subjected to static and cyclic load. The development of cracks is analyzed for mid and end RC beam-column joint under static and cyclic load.

U ovom radu prikazana je primjena kombinirane metode konačno-diskretnih elemenata u simulaciji dinamičkog odgovora starih kamenih suho zidanih konstrukcija. Kombinirana metoda konačno-diskretnih elemenata prikladna je za dinamičku analizu konstrukcija modeliranih s velikim brojem diskretnih elemenata. Svaki diskretni element modeliran je mrežom konačnih elemenata što omogućuje njegovu deformabilnost, dok se materijalna nelinearnost, pojava pukotina i fragmentacija odvija u kontaktnim elementima koji su implementirani između konačnih elemenata. Ovom metodom moguće je također obuhvatiti pojave vezane za ponašanje suho zidanih konstrukcija uslijed dinamičkog djelovanja od linearne elastične faze pa do potpunog sloma. Primjena metode prikazana je na primjeru inkrementalne dinamičke analize konstrukcije Protirona u Splitu na izvornoj konstrukciji bez metalnih klamfi i trnova. Konstrukcija je izložena horizontalnom ubrzanju podloge realnog potresa. Akcelelogram je najprije skaliran na vršno ubrzanje od 0.22g koje je karakteristično za Split, a potom je vršno ubrzanje postupno povećavano sve do potpunog sloma konstrukcije.

In this paper an incremental dynamic analysis of reinforced concrete walls under seismic load based on a combined finite-discrete element method (FEM/DEM) is presented. Fragmentation that may occur during and after seismic loading cannot be modelled by the continuum methods. Predicting of the behaviour of reinforced concrete structures under seismic load imposes the need to develop numerical model which will be able to include effects of the behaviour of reinforced concrete structures due to dynamic action in linear elastic stage, crack initiation and propagation, energy dissipation mechanisms due to non linear effects, inertial effects due to motion, contact impact and finally to attain state of the rest that is a consequence of energy dissipation mechanisms in the system. It is possible to include all previously mentioned effects with the FEM/DEM method. The performance of the FEM/DEM method is presented through incremental dynamic analysis of reinforced concrete wall.