U radu je prikazana analiza nosivosti zidanog polukružnog luka za opterećenjevertikalnom koncentriranom silom u četvrtini raspona. Proračun zidanih lučnihkonstrukcija svodi se na problem geometrije, ...dok je provjera čvrstoće od sporednogznačenja. Ukoliko je moguće pronaći potpornu liniju koja se nalazi unutar geometrijeluka u ravnoteži s vanjskim opterećenjem, tada je luk stabilan. Principom virtualnograda određena je granična vrijednost sile pri kojoj dolazi do gubitka stabilnosti.Rezultati su zatim uspoređeni s rezultatima dobivenim eksperimentalno na drvenommodelu luka, gdje je opterećenje postepeno povećavano sve do rušenja luka.
This paper presents the structural analysis of a masonry semicircular arch loadedwith a point force at quarter span. The analysis of masonry arch structures is basedon the arch geometry instead on its strength. The arch is stable if a thrust line inequilibrium with the external load can be found within the arch geometry. Using theprinciple of virtual work the limit force at which the arch collapses is determined.The results were finally compared with experimentally obtained results on a timberarch model, where the load was gradually increased until the arch collapsed.
Pedestrian bridges are an important component of an active transportation system. As part of digital and green transformation, active travel is recognized as an essential strategy for reducing ...vehicle fuel consumption and exhaust emissions, but also for improving public health. Pedestrian bridges and other active travel infrastructure must be designed to be accessible to all users. Bridges that do not meet the conditions for comfortable use can force detours that discourage walking and bicycling. Adapting bridges that are not universally accessible requires challenging and expensive construction work. When accessibility issues are considered in the planning and design of new bridges, cost-effective, and often cost-neutral solutions, can be found. Some countries ensure the accessible design of pedestrian bridges through national regulations, but it is important to educate and raise awareness among all bridge designers about the importance of accessible design to achieve sustainable structures. Therefore, this paper provides an overview, comparison and commentary on the most comprehensive current standards, guidelines and manuals for pedestrian bridges that contain information on accessible design. Special attention is given to the design of stairs and ramps as critical elements of bridge accessibility.
•We present an embedded-crack layered-beam finite element for analysis of reinforced-concrete beams.•Slippage between the reinforcement and the surrounding concrete is included.•A transversal crack ...in the beam element opens when the tensile strength in a layer has been reached.•Crack formation and development may be predicted without initial imperfections.
In this work crack formation and development is addressed and implemented in a planar layered reinforced-concrete beam element. The crack initiation and growth is described using the strength criterion in conjunction with exact kinematics of the interlayer connection. In this way a novel embedded-discontinuity beam finite element is derived in which the tensile stresses in concrete at the crack position reaching the tensile strength will trigger a crack to open. Since the element is multi-layered, in this way the crack is allowed to propagate through the depth of the beam. The cracked layer(s) will involve discontinuity in the cross-sectional rotation equal to the crack-profile angle, as well as a discontinuity in the position vector of the layer’s reference line. A bond–slip relationship is superimposed onto this model in a kinematically consistent manner with reinforcement being treated as an additional layer of zero thickness with its own material parameters and a constitutive law implemented in the multi-layered beam element.
Emphasis in this work is placed on the definition and finite-element implementation of kinematics of such a layered beam set-up with embedded cracking, rather than on constitutional details of the concrete, steel and interface between them. Several numerical examples are presented, in which the ability of the proposed procedure to predict crack occurrence and development is investigated.
Operacionalna modalna analiza nathodnika Malonji Štimac Grandić, Ivana; Franković, Tomislav; Šćulac, Paulo ...
Zbornik radova (Građevinski fakultet Sveučilišta u Rijeci),
02/2019, Volume:
20, Issue:
1
Journal Article, Paper
Peer reviewed
Open access
U radu su prikazani rezultati terenskog dinamičkog ispitivanja pješačkog nathodnika Malonji korištenjem operacionalne modalne analize za određivanje modalnih parametara konstrukcije. Izmjereni ...modalni parametri uspoređeni su s modalnim parametrima izračunatim na numeričkom modelu nathodnika. Pokazano je da ovom vrstom dinamičkog ispitivanja i obrade podataka moguće dobiti dobro poklapanje između izmjerenih i izračunatih vlastitih frekvencija dok bi za točnije određivanje vlastitih oblika na temelju izmjerenih ubrzanja trebalo uvesti poboljšanja geometrijskog modela u ModalVIEWu boljim rasporedom ili povećanjem broja mjerenih stupnjeva slobode te korištenjem akcelerometara veće osjetljivosti.
This paper presents the results of an on-site dynamic testing of the pedestrian overpass Malonji using operational modal analysis for obtaining structural modal parameters. The measured modal parameters were compared to the modal parameters calculated on the numerical model of the overpass. It is shown that this type of dynamic testing and data processing can provide a very good match between measured and calculated frequencies. A more accurate determination of modal shapes derived from measured acceleration requires: (i) improvement in the ModalVIEW geometry model, (ii) using a greater number or different positions of accelerometers, (iii) accelerometers with better measuring accuracy.
This paper describes the design procedure for reinforced concrete rectangular cross-sections according to the standard FprEN 1992-1-1 (second generation of Eurocode 2). Design was carried out in two ...ways: using design tables for reinforced concrete rectangular sections and using a direct analytical procedure. The stress-strain diagram in the form of a parabola-rectangle was used for concrete, while for the reinforcing steel a bilinear stress-strain diagram with a horizontal post-elastic branch without strain limit was applied. For this reason, when designing the reinforced concrete cross-section, it is necessary to limit the strain in the compression zone of the concrete. Tables for the design of reinforced concrete rectangular sections were obtained using a new procedure in which the mechanical reinforcement ratio is varied. A direct analytical procedure was used for comparison, which can be used for the design of reinforced concrete rectangular sections without the need to use tables. The limit values of the coefficient of the height of the compression zone for pure bending were calculated according to the standard FprEN 1992-1-1.
A preliminary condition assessment using non-destructive testing methods for determining material quality, has been carried out on three adjacent wooden hangars near Šibenik with the aim of ...exploring the possibilities of their repurposing. Through visual inspection and detailed geometric measurements, it has been verified that their unique structure embodies the original Zollinger lamella vault system in which the joint typology is decisive for both, the overarching structural analysis and the execution of the structure. In this paper, the results of conducted investigation, including the developed detailed geometric model are presented, and guidelines for future comprehensive research focusing on the influence of joint stiffness on global structural features are discussed, as well.
In the current European Code EN 1992-1-1 a truss model with variable inclination angle of concrete compressive struts with a quite wide range of inclination angle, from 21,8° to 45°, is intended for ...use for shear design of reinforced concrete beams. However, some researches and recommendations indicate special attention when choosing the lower bound of inclination angle of the concrete compressive struts, due to the reduced compressive strength of cracked concrete. This work reviews theoretical background and shear design methods of reinforced concrete beams. Relation of the shear resistance to crushing of the compressive struts as a function of their inclination angle has been investigated through a parametric study, where three different approaches have been used in order to limit stresses in the compressive struts. Based on the comparison of results from the analysis a recommendation for shear resistance calculation of reinforced concrete beams in dependence on concrete strength in compressive struts of the truss model is given.
U aktualnoj europskoj normi EN 1992-1-1 za dimenzioniranje armiranobetonskih greda na poprečne sile predviđa se uporaba rešetkastog modela sa slobodnim odabirom nagiba betonskih tlačnih ispunskih ...štapova u širokim granicama, to jest od 21,8° do 45° prema osi grede. Međutim, postoje istraživanja i prijedlozi koji upućuju na oprez kod odabira donje granice nagiba ispunskih tlačnih štapova s obzirom na umanjenje tlačne čvrstoće raspucanog betona u hrptu armiranobetonskih elemenata izloženih poprečnim silama. U radu je dan pregled teorijskih postavki i metoda proračuna armiranobetonskih elemenata na poprečne sile. Provedena je parametarska analiza nosivosti na poprečne sile pri drobljenju tlačnih štapova kao funkcije njihovog nagiba. Pri tom su korištena su tri različita pristupa za ograničenje naprezanja u tlačnim štapovima. Na temelju provedene analize i usporedbe rezultata u radu je dan prijedlog za određivanje nosivosti armiranobetonskih greda na poprečne sile po kriteriju čvrstoće betona ispunskih tlačnih štapova rešetkastog modela.
U radu je opisan postupak dimenzioniranja armiranobetonskih pravokutnih presjeka prema normi FprEN 1992-1-1 (druga generacija Eurokoda 2). Dimenzioniranje je provedeno na dva načina: tablicama za ...dimenzioniranje armiranobetonskih pravokutnih presjeka i direktnim analitičkim postupkom. Korišten je proračunski dijagram naprezanje-deformacija betona u obliku parabole i pravca, dok je za čelik za armiranje korišten bilinearni proračunski dijagram naprezanje-deformacija s horizontalnom gornjom granom bez ograničenja deformacije. Zbog toga je kod dimenzioniranja armiranobetonskog presjeka potrebno ograničiti deformaciju u tlačnoj zoni betona. Tablice za dimenzioniranje armiranobetonskih pravokutnih presjeka dobivene su novim postupkom kod kojeg se varira mehanički koeficijent armiranja vlačnom armaturom. Za usporedbu primijenjen je direktni analitički postupak kojim se mogu dimenzionirati armiranobetonski pravokutni presjeci bez upotrebe tablica. Izračunane su limitirajuće vrijednosti koeficijenta visine tlačnog područja za čisto savijanje prema normi FprEN 1992-1-1.
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