natgillin/translations-raw huggingface dataset:
The Latin hypercube method is applied so as to determine the level of risk on individual projects based on two basic indicators: internal rate of return and the net present value.
Primijenjena je metoda latin hypercube pri određivanju rizičnosti projekta s obzirom na dva osnovna pokazatelja interne stope rentabilnosti (ISR) i neto sadašnje vrijednosti (NSV).
It is stressed that the accuracy of input data is of crucial significance for making well-informed investment decisions.
Posebno je istaknut značaj točnosti ulaznih podataka u cilju donošenja racionalnih investicijskih odluka.
risk analysis, critical variables, investment projects, Latin hypercube method, net present value, internal rate of return
interna stopa rentabilnost, analiza rizika, kritične varijable, investicijski projekti, metoda latin hypercube, neto sadašnja vrijednost
Kartelo, R.: Risk analysis in the economic evaluation of projects: example of Zagreb water supply system, GRAĐEVINAR, 58 (2006) 11
Kartelo, R.: Analiza rizika u ekonomskoj ocjeni projekta na primjeru vodoopskrbnog sustava Zagreb, GRAĐEVINAR, 58 (2006) 11
Risk analysis in the economic evaluation of projects: example of Zagreb water supply system, GRAĐEVINAR, 58 (11)
Analiza rizika u ekonomskoj ocjeni projekta na primjeru vodoopskrbnog sustava Zagreb, GRAĐEVINAR, 58 (11)
Dynamic analysis of structures resting on highly-elastic bearings
Preuzmi članak (EN verzija): n/a
Truss girder joint with a large diameter mechanical fastener
Rješenje čvora rešetke spajalom velikog promjera
A joint with a large diameter fastener for connecting large span truss girder nodes is presented in the paper.
U radu je prikazan priključak spajalom velikog promjera za čvorove rešetkastih nosača velikih raspona.
The joint strength and slip modulus were analysed by means of experimental testing and the finite element method.
Eksperimentalnim istraživanjima i metodom konačnih elemenata provedena je analiza otpornosti i modula popustljivosti priključka.
The experimental testing was conducted on four truss girders with the proposed joint.
Eksperimentalna ispitivanja provedena su na četiri rešetkasta nosača s predloženim priključkom.
The nonlinear truss girder model analysis, was conducted using the Abaqus/CAE software with the UMAT subroutine.
U programskom paketu Abaqus/CAE s UMAT podrutinom, prikazana je nelinearna analiza modela rešetke.
Key words: truss girder joint, non-linear analysis, large diameter fastener, glued-in rods, UMAT subroutine
Ključne riječi: čvor rešetke, nelinearna analiza, spajalo velikog promjera, ulijepljene šipke, UMAT podrutina
Rješenje čvora rešetke spajalom velikog promjera
Truss girder joint with a large diameter mechanical fastener
U radu je prikazan priključak spajalom velikog promjera za čvorove rešetkastih nosača velikih raspona.
A joint with a large diameter fastener for connecting large span truss girder nodes is presented in the paper.
Eksperimentalnim istraživanjima i metodom konačnih elemenata provedena je analiza otpornosti i modula popustljivosti priključka.
The joint strength and slip modulus were analysed by means of experimental testing and the finite element method.
Eksperimentalna ispitivanja provedena su na četiri rešetkasta nosača s predloženim priključkom.
The experimental testing was conducted on four truss girders with the proposed joint.
U programskom paketu Abaqus/CAE s UMAT podrutinom, prikazana je nelinearna analiza modela rešetke.
The nonlinear truss girder model analysis, was conducted using the Abaqus/CAE software with the UMAT subroutine.
Ključne riječi: čvor rešetke, nelinearna analiza, spajalo velikog promjera, ulijepljene šipke, UMAT podrutina
Key words: truss girder joint, non-linear analysis, large diameter fastener, glued-in rods, UMAT subroutine
Primljen / Received: 10.6.2013.
Prihvaćen / Accepted: 15.10.2013.
Dostupno online / Available online: 10.11.2013.
Tehničko Veleučilište u Zagrebu Graditeljski odjel krunoslav.pavkovic@tvz.hr
Krunoslav Pavković, PhD. CE
Miljenko Haiman, dipl.ing.građ.
Polytechnic of Zagreb Building department krunoslav.pavkovic@tvz.hr
Sveučilište u Zagrebu Arhitektonski fakultet miljenko.haiman@arhitekt.hr
In the design of large-span structures, the truss girder system, due to its small consumption of material and simplicity, is a logical and economically more cost-effective system, when compared to glulam girders.
Prilikom projektiranja konstrukcija velikih raspona, statički sustav rešetkastih nosača, svojim malim utroškom materijala i jednostavnošću, logičan je i ekonomski isplativiji u odnosu na punostijene lamelirane nosače.
However, timber truss girders are very rarely used in our conditions for crossing large spans, i.e. the alternative solution involving the use of glulam girders is almost always adopted.
Međutim, drveni rešetkasti nosači u našim uvjetima se vrlo rijetko koriste za svladavanje velikih raspona, tj. kao alternativa se gotovo uvijek koriste lamelirani nosači.
Main reasons for such situation include the problem of truss node solving, wood industry lobby, and the negative attitude of architects toward truss girders.
Glavni razlog za ovakvo stanje u praksi je problem rješavanja čvorova rešetke, lobi drvne industrije te negativan stav arhitekata prema rešetkastim nosačima.
The usual and most frequently used solution for connecting timber truss girders is the connection by steel node plates and mechanical fasteners, which requires a large truss girder element area to adequately transfer force to the node plates and to ensure sufficient ductility.
Uobičajeno je i najčešće rješenje za spajanje drvenih rešetkastih nosača čeličnim čvornim limovima i štapastim spajalima koji zahtijevaju veliku površinu elemenata rešetke kako bi se sila adekvatno prenijela unutar čvora uz dostatnu duktilnost.
This frequently results in a bigger size of truss elements so that an appropriate number of fasteners can be distributed along an appropriate area, which leads to a greater consumption in wood and steel, and the structure becomes economically inefficient.
Sve to često rezultira povećanjem elementa rešetke kako bi se potreban broj spajala mogao razmjestiti na dostatnoj površini, što povećava potrošnju drva i čelika koja prelazi granice ekonomske isplativosti.
Some other reasons why truss girders are avoided for crossing large spans include: reduced fire resistance at joints, and difficulties with the precamber, which is indispensable in structural systems which are exceeding 30,0 m in span.
Postoje i drugi razlozi zbog kojih se izbjegavaju rešetkasti nosači za svladavanje velikih raspona, a to su: smanjena vatrootpornost u području spojeva i otežano zadavanje nadvišenja, što je nužno kod raspona većih od 30,0 metara.
In response to the belief that it is easier to use more than 50% of additional laminated timber for a glulam girder, rather than to solve the truss girders joints and fire-resistance problems, various possibilities have been investigated to see whether the situation can be changed through introduction of new connection systems.
Zbog uvjerenja da je jednostavnije utrošiti i više od 50 % više lameliranog drva za punostijeni nosač nego rješavati problem čvorova rešetke i vatrootpornosti, nameće se pitanje može li se stanje promijeniti uvođenjem novih sustava spajanja.
The objective of this paper is to find an appropriate solution for joints of large span trusses in order to enable fast assembly, proper definition of precamber during assembly, and a greater fire resistance.
Cilj rada je pronaći rješenje priključka za rešetke velikog raspona koje će omogućavati brzu montažu, zadavanje nadvišenja u montaži te povećanu vatrootpornost.
In this respect, it should be noted that an another solution based on a large diameter mechanical fastener, currently at the research stage, has been developed by SP-Trätek, Boras, Sweden [1].
Naime, postoji jedno razvijeno rješenje za rešetke velikih raspona koje je još u fazi istraživanja, SP-Trätek, Borås, Švedska, a bazira se na spojnom sredstvu velikog promjera [1].
The authors of this concept also consider that presentday solutions are overly complicated and costly, and that a new solution applicable to large-span trusses should be developed.
Autori ovog koncepta bavili su se također mišlju da su dosadašnja rješenja komplicirana i preskupa te da je potrebno novo rješenje primjenjivo za rešetke velikih raspona.
Concept of the joint
Koncept priključka
The concept of the joint studied in this paper is presented in Figure 1.
Na slici 1. prikazan je koncept priključka koji je tema rada.
It has been conceived through the use of a large-diameter fastener.
Koncept je osmišljen primjenom spojnog sredstva velikog promjera.
The timber element into which the force is introduced (truss girder cord) is 210.0 mm in width, cf. Figure 1, but its width is defined based on the required truss girder cord resistance.
Glavni element priključka je čelična cijev velikog promjera koji se određuje prema potrebnoj otpornosti priključka, a ugrađuje se u rupu izbušenu u pojasu okomito na os elementa.
The truss girder cord is conceived in such a way that its width can easily be changed via the number of lamellas depending on the required resistance, while the height is defined based on the width of lamellas.
Vijci su elementi priključka koji povezuju cijev s elementom koji unosi silu u priključak, a promjer i broj vijaka ovisi o veličini sile koju priključak treba preuzeti.
Bolts are connection elements that link the fasteners with the element that introduces the force into the joint, and the diameter and number of bolts depends on the size of the force to be transfer by the joint.
Pojas rešetke koncipiran je tako da se njegova širina može jednostavno mijenjati brojem lamela ovisno o potrebnoj otpornosti, a visina se određuje širinom lamela.
The second half of the joint consists of an element that introduces the force into the joint.
Druga polovina priključka sastoji se od elementa koji unosi silu u spoj.
The introduction of the force into the joint can be solved via a timber element with a glued-in rod (as shown in Figure 1) [2], or directly by steel rod.
Unos sile u spoj može biti riješen pomoću drvenog elementa s ulijepljenom šipkom [2] (kako je prikazano na slici 1.) ili direktno iz čelične šipke.
The end of the rod (regardless of whether it is glued-in or independent) is inserted into the connection bush.
Šipka se na svome kraju, neovisno o tome je li ulijepljena ili samostalna, montira u čahuru za nastavljanje.
View of the truss joint
Prikaz priključka rešetke
Ductility, yield force and resistance of joint
Duktilnost, modul popustljivosti i otpornost spojeva
The ductility (D) is expressed as the ratio of slip at yield force (dy) and max. force (dmax) [3]:
Duktilnost (D) se izražava kao odnos između pomaka u točkama sile popuštanja (dy) i čvrstoće (dmax) [3]:
CEN (European Committee for Standardisation) defines the test protocol for determining mechanical properties of connections/joints in timber structures through the following standards:
Drvene konstrukcije prilikom potresnog opterećenja trebaju pružiti dostatnu razinu duktilnosti kako bi iz deformacija u plastičnom području proizašla potrebna disipacija energije statičkog sustava.
However, these standards do not provide specific guidelines for determining ductility of joints subjected to static load [4].
- za ispitivanje spojeva statičkom silom u normi EN 26891 - za ispitivanje spojeva ciklički promjenjivom silom u normi
the maximum load (d0,1) and 40 % of the maximum load (d0,4), according to the following expression:
popustljivosti može se odrediti iz nagiba pravca određenog sa 10 % i 40 % maksimalne sile te odgovarajućeg pomaka na 10 % maksimalne (d0,1) i 40 % maksimalne sile (d0,4), prema izrazu:
The initial joint slip modulus is determined from the inclination of line defined with the initial slip and slip at the load of 40% of the maximum load Fmax (d0,4).
Inicijalni modul popustljivosti spoja određuje se iz nagiba pravca određenog s početnim pomakom i pomakom pri sili od 40 % maksimalne sile Fmax (d0,4).
The difference between these two slip modulus is determined by unrecoverable deformations caused by beading of a fastener.
Razlika između ova dva modula određena je nepovratnim deformacijama uzrokovanim dosjedanjem spojnog sredstva.
As in this case we are dealing with the fastener characterized by a large diameter, the relevant failure mode occurs after compressive strength exceeds embedment strength of the timber element.
Budući da se u promatranom priključku radi o spajalu velikog promjera, mjerodavan mod otkazivanja je uslijed dosezanja tlačne čvrstoće po omotaču rupe drvenog elementa pri čemu spajalo ostaje nedeformirano.
where: fh,a,d - design embedment strength, for the load under the
gdje su: fh,a,d - računska otpornost na tlak po omotaču rupe za silu pod
angle a with respect to grain, t - is the thickness of the timber element for which the
kutom a u odnosu na vlakanca, t - debljina drvenog elementa za koji se određuje računska
design resistance is determined, d - is the diameter of the fastener.
otpornost, d - promjer spajala.
The typical fastener embedment strength resistance is determined via experimental testing in accordance with EN 383 [6].
Karakteristična otpornost po omotaču rupe spajala određuje se eksperimentalnim ispitivanjima prema normi EN 383 [6].
According to this standard, the characteristic embedment strength is obtained by driving the fastener of a specified diameter into a timber element in which the hole of an appropriate diameter is previously made.
Prema spomenutoj normi, karakteristična čvrstoća na tlak po omotaču rupe dobiva se utiskivanjem spajala određenog promjera u drveni element u kojem je prethodno napravljena rupa odgovarajućeg promjera.
The fastener is inserted at a specified angle with respect to the grain, and the characteristic embedment force is obtained from the load (Fmax,5) which corresponds to a 5,0 mm slip value.
Utiskivanje spajala provodi se pod određenim kutom u odnosu na vlakanca, a karakteristična čvrstoća po omotaču rupe dobiva se iz sile (Fmax,5) koja odgovara pomaku od 5,0 mm.
2. Preparations for experimental study
2. Priprema istraživanja
Geometry and truss girder materials used in experimental study
Geometrija i korišteni materijali rešetkastih nosača za eksperimentalna ispitivanja
Truss girder elements were made of lamellas 42.0 mm in thickness, and each element consisted of five lamellas which, after planing, resulted in elements with the cross section measuring 21.0 x 20.0 [cm].
Elementi za rešetkaste nosače proizvedeni su od lamela debljine 42,0 mm. Svaki element sastojao se od pet lamela, a nakon blanjanja imao je poprečni presjek 21,0×20,0 [cm].
The melamine glue "Casco adhesives MUF system 1247/2526", manufactured in Casco Adhesives AB, Stockholm, Sweden, was used to glue the lamellas.
Za lijepljenje lamela upotrijebljeno je melaminsko ljepilo "Casco adhesives MUF system 1247/2526", proizvedeno u Casco adhesives AB, Stockholm, Švedska.
According to mechanical properties of the timber
Proizvedeni lamelirani
used in lamellas production, the produced laminated elements can be classified as GL24h according to the EC5 standard.
elementi prema mehaničkim karakteristikama primijenjenog drva za lamele mogu se svrstati u klasu GL24h prema EC5 normi.
To gain insight into the entire concept of this joint, glued-in rods, with the gluing-in depth of 35.0 cm, were installed in to vertical compression web elements of the truss girder.
Kako bi se dobio uvid u cijeli koncept priključka, izvedene su ulijepljene šipke dubine uljepljivanja 35,0 cm u vertikalnim elementima ispune rešetke.
A hole with the diameter exceeding by 2.0 mm the nominal diameter of the threaded rod was drilled in the centre of the timber element, as shown in paper [7].
U sredini drvenog elementa izbušena je rupa 2,0 mm većega promjera od nazivnog promjera navojne šipke, kako je prikazano u radu [7].
The glue is marketed under the commercial name "Epocon 88".
Ljepilo se vodi pod komercijalnim nazivom "Epocon '88".
The quality of the materials used for steel elements was selected based on stresses obtained by preliminary finite element models (FEM).
Kvaliteta primijenjenih materijala za čelične elemente odabrana je prema naprezanjima dobivenim preliminarnim numeričkim modelima.
The steel quality 42CrMo4 fu=1600 N/mm2 according to EN-10027-1 was selected for the fabrication of washers, connection pipe, and fasteners.
Za izradu podložnih profiliranih pločica, čahura za nastavljanje i cijevi odabrana je kvaliteta čelika oznake 42CrMo4 fu=1600 N/mm2 prema EN-100271.
The steel quality S235JRCu according to EN 10027-1 was used for connection elements that are less exposed to stresses (rings).
Za elemente spoja koji su manje izloženi naprezanjima (prsteni), upotrijebljen je čelik S235JRCu prema normi EN 10027-1.
Allen bolts DIN 912, steel quality 12.9, were used for bolts in connections, while two bolts type M20, quality 12.9, were used for introducing force into the connection from steel diagonals.
Za vijke u spojevima korišteni su inbus vijci prema DIN-u 912 kvalitete 12.9.,
One bolt type M12, quality 12.9, was used to ensure structural connection between the vertical and the truss girder cord.
a za unos sile u spoj iz čeličnih dijagonala korištena su dva vijka M20 kvalitete 12.9., te za konstrukcijsko povezivanje vertikale na pojas rešetke jedan vijak M12 kvalitete 12.9.
Steel rods 22.0 mm in diameter were used for tensile diagonals instead of timber elements with glued-in rods, as shown in Figure 1.
Za vlačne dijagonale upotrijebljene su čelične šipke promjera 22,0 mm umjesto drvenih elemenata s ulijepljenim šipkama, kako je prikazano na slici 1.
The reason why timber diagonals were replaced with steel ones lies in greater simplicity of measurement, easier control of stress in steel diagonals, and smaller manufacturing price of rods for experimental testing.
Razlog zamjene drvenih dijagonala čeličnima jest jednostavnije mjerenje i kontrola naprezanja u čeličnim dijagonalama te manja proizvodna cijena rešetki za eksperimentalna ispitivanja.
Tensile diagonals were made of steel quality 42CrMo4 fu=1600 N/mm2.
Vlačne dijagonale izvedene su od kvalitete čelika 42CrMo4 fu=1600 N/mm2.
Experimental testing procedure
Postupak eksperimentalnih ispitivanja
During the testing, the top cored of the truss girder was laterally supported by a structure composed of steel pipes (Figure 2), to prevent loss of global stability of the girder.
Za vrijeme ispitivanja gornji je pojas rešetke bočno pridržavan konstrukcijom sastavljenom od čeličnih cijevi (slika 2.) kako ne bi došlo do gubitka ukupne stabilnosti nosača.
The testing procedure consisted of applying concentrated load in each third of the span, with a controlled constant load rate.
Proces ispitivanja sastojao se od nanošenja koncentriranog opterećenja u trećinama raspona s konstantnim prirastom.
The load was applied by two hydraulic jacks connected to one another, so that the pressure in both jacks was always the same.
Unos opterećenja provodio se uz pomoć dva hidraulična cilindra međusobno spojena, tako da je pritisak u oba cilindra bio uvijek isti.
Truss girders were tested with the relaxation at total load of 60,0 kN, after the force was brought down to 20,0 kN, load was continuously increased until truss girder failure.
Ispitivanje rešetkastih nosača provodilo se uz relaksaciju ukupne sile na 60,0 kN, uslijed čega je sila vraćena na 20,0 kN, a nakon toga kontinuirano povećavana sve do loma rešetki.
The applied load was measured via measuring devices placed between hydraulic cylinders and the top cord of the truss girder, as shown in Figure 2.
Unesena sila mjerena je uređajima koji su postavljeni između hidrauličnih cilindara i gornjeg pojasa rešetke, što je vidljivo na slici 2.
During the testing, stresses in the steel diagonals were measured via tensometers marked T1 to T4.
Za vrijeme ispitivanja mjerena su naprezanja u čeličnim dijagonalama pomoću tenzometara s oznakama od T1 do T4.
Measuring of truss girder deformation was conducted in the thirds of the span using measuring devices marked L500/03 and L500/04.
Mjerenje deformacija rešetke provodilo se u trećinama raspona mjernim uređajima s oznakama L500/03 i L500/04.
Local deformation was measured for joints situated at
Građevinar 10/2013
the bottom cord of the truss girder, i.e. the displacement of the bolts end which are entering into the diagonals was measured with respect to the point situated in the bolt axis 100 mm away from the centre of the fastener.
Spojevima koji se nalaze na donjem pojasu rešetke praćena je lokalna deformacija, odnosno pomak vrha vijaka koji ulaze u dijagonalu u odnosu na točku koja se nalazi na osi vijka udaljena 100,0 mm od sredine cijevi.
The total of four measuring devices marked L100/02 to L100/05 were placed on two measured joints at the bottom cord of the truss girder, i.e. one measuring device per bolt by which the force from the tensile diagonal is introduced into the joint.
Ukupno četiri mjerna uređaja s oznakama od L100/02 do L100/05 postavljena su na dva promatrana spoja na donjem pojasu rešetke, odnosno jedan mjerni uređaj po vijku kojim se unosi sila u spoj iz vlačne dijagonale.
Deformation and displacement were monitored and records at one second intervals via personal computer.
Izmjerena naprezanja i pomaci praćeni su i zapisivani na osobnom računalu svake sekunde.
Experimental testing of trusses
Eksperimentalna ispitivanja rešetki
It should be noted that, during truss girder assembly in the laboratory, all bolts at joints were mounted using the controlled force of 4.5 kN, i.e. the fastening moment of 17.0 Nm. This bolt tightening resulted in a 12.0 mm precamber at the centre of the span.
Potrebno je spomenuti da su prilikom sastavljanja rešetke u laboratoriju, svi vijci u spojevima rešetke pritezani kontroliranom silom od 4,5 kN, odnosno momentom pritezanja 17,0 Nm. To pritezanje vijaka rezultiralo je nadvišenjem u sredini raspona od 12,0 mm.
During the testing, the moisture of truss girder elements varied from 11.8 to 13.7 percent.
Za vrijeme ispitivanja izmjerena je vlažnost elemenata rešetki u granicama od 11,8 % do 13,7 %.
The temperature in the room during the testing of the second truss girder was 30°C, and during other tests was 28°C.
Temperatura u prostoriji za vrijeme ispitivanja druge rešetke bila je 30°C, a za vrijeme ostalih ispitivanja 28°C.
Analysis by finite element method 2.3.1.
Analiza metodom konačnih elemenata 2.3.1.
Geometry and materials for numerical modelling
Geometrija i materijali numeričkog modela
of the truss
rešetke
The FEM geometry fully coincided with the truss girder geometry used in laboratory testing.
Geometrija numeričkog modela preuzeta je u cijelosti od rešetki za laboratorijska ispitivanja.
Volume finite elements C3D3, defined with six nodes [8], were used for modelling of timber elements.
Za modeliranje drvenih elemenata korišteni su volumni C3D6 konačni elementi određeni preko šest čvorova [8].
All steel elements of the connection, as well as tensile ties, were modelled with the volume finite elements C3D8 defined with eight nodes.
Svi čelični elementi spoja te vlačne zatege modelirane su s volumnim C3D8 konačnim elementima određenim preko osam čvorova.
The FEM of the truss girder was fully defined with 168,454 finite elements and, considering the great number of finite elements, only one half of the truss girder was modelled with boundary conditions which simulate symmetry , as shown in Figure 3.
Numerički model rešetke u cijelosti je određen sa 168.454 konačna elementa, a s obzirom na velik broj konačnih elemenata, modelirana je samo jedna polovina rešetke s rubnim uvjetima simetrije, kako je prikazano na slici 3.
A linear increase of prestressing load was modelled in each bolt in the time period varying from 0 t to 10 t.
Budući da se radi o nelinearnoj analizi s geometrijskom i materijalnom nelinearnosti, opterećenja su zadana u ovisnosti o vremenu.
After full prestressing
Sila prednapinjanja
Truss girder joint with a large diameter mechanical fastener
vijaka zadana je kao "bolt load", dok je prirast sile zadan u ovisnosti o vremenu.
The graphical presentation of time-related load amplitudes is given for both loading steps in Figure 3.
Modeliranje mehaničkih karakteristika čelika provedeno je elastoplastično, prema dijagramima prikazanim na slici 4.