The effect of the residual stresses and strains is one of the most important parameter in the structure integrity assessment. A finite element model is constructed in order to simulate the multi passes mismatched submerged arc welding SAW which used in the welded tensile test specimen. Sequentially coupled thermal mechanical analysis is done by using ABAQUS software for calculating the residual stresses and distortion due to welding. In this work, three main issues were studied in order to reduce the time consuming during welding simulation which is the major problem in the computational welding mechanics (CWM). The first issue is dimensionality of the problem. Both two-and three-dimensional models are constructed for the same analysis type, shell element for two dimension simulation shows good performance comparing with brick element. The conventional method to calculate residual stress is by using implicit scheme that because of the welding and cooling time is relatively high. In this work, the author shows that it could use the explicit scheme with the mass scaling technique, and time consuming during the analysis will be reduced very efficiently. By using this new technique, it will be possible to simulate relatively large three dimensional structures.

Preliminary communicationThe linear buckling phenomenon is obviously very important for stability of compressed supports. The determination of buckling resistance is an important characteristic of the design of steel structure. Besides, the presence of stiffeners in structural plate elements has a vital role in order to increase critical buckling load capacity. However, these stiffeners cause a redistribution in buckling behaviour in terms of local and global buckling. In this paper the transverse and longitudinal stiffeners were employed on a real beam-column structure to maximize the critical buckling loads. The objective is to find the optimum geometry of stiffeners. Based on the finite element method, a numerical model is made using the Abaqus program in order to observe the critical buckling capacity. The results showed that the local critical buckling has been significantly affected by stiffener's position in the case of transverse stiffeners, but little effect is observed on the critical local and global buckling in the case of longitudinal stiffeners. Keywords: beam-column; finite element method; local and global buckling; transverse and longitudinal stiffener Numerička analiza lokalnog i globalnog izvijanja ojačane gredePrethodno pripćenje Fenomen linearnog izvijanja je očito vrlo bitan za stabilnosti tlačenih nosača. Kritična sila izvijanja predstavlja važnu karakteristiku za projektiranje čeličnih konstrukcija. Osim toga, postojanje ukrućenja na konstrukcijskim elementima ploče ima vitalnu ulogu u cilju povećanja kritične sile izvijanja. Međutim, ova ukrućenja izazvaju preraspodjelu načina izvijanja u smislu lokalnog i globalnog izvijanja. U ovom radu uvedena su poprečna i uzdužna ukrućenja stvarne gredne konstrukcije sa zadatkom da maksimalno povećaju kritične sile izvijanja. Funkcija cilja je pronaći optimalnu geometrijsku karakteristiku ukrućenja. Na osnovu metode konačnih elemenata, numerički model je napravljen uporabom Abakus programa za utvrđivanje kritične sile izvijanja. Rezultati su pokazali da poprečna ukrućenja i njhov položaj imaju znatan utjecaj na lokalno izvijanje, dok uzdužna ukrućenja imaju mali utjecaj na lokalno i globalno izvijanje.Ključne riječi: greda-stup; lokalno i globalno izvijanje; metoda konačnih elemenata; poprečno i uzdužno ukrućenje