Calibration of an Existing Creep Model for Analysis of Aluminium Members Exposed to Constant Temperature

The paper presents the development of a creep model applicable for the analysis of aluminium members exposed to a constant temperature. The model is intended as a base for defining a creep model in a transient heating regime. The behaviour of aluminium members exposed to the transient heating regime is a relatively unexplored topic in the scientific community. There is a need for defining an advanced creep model for aluminium, which should cover any heating regime to model the influence of creep on members exposed to fire. A comparison of results between the existing experimental data and the built-in creep models from commercial software ANSYS 16.2 for specific temperature and stress levels is provided. The experimental data used was extracted from previous tests carried out on coupons of aluminium alloy EN 6082 AW T6 and fitted in the aforementioned ANSYS models which serve as a base for defining the representative advanced creep model

Reliability of steel structures in case of fire

Na primjeru čelične krovne konstrukcije sportske dvorane „Spaladium“ u Splitu prikazan je novi način proračuna nosive konstrukcije na djelovanje požara u velikim zatvorenim prostorima sukladno Eurokodu. Modelom zona dobiveni su odnosi temperatura-vrijeme u zatvorenom prostoru i to za dvije požarne situacije: požar na borilištu i požar na tribinama. Na temelju krivulja temperatura-vrijeme u nosivim elementima čelične konstrukcije analizirana je pouzdanosti krovne konstrukcije.A new method for analyzing fire resistance of load bearing structures in big indoor spaces, based on Eurocode, is presented through case study of the steel roof structure of the Spaladium Sports Hall. The temperature-time relationships for indoor space are obtained by the zone model, and this for two fire situations: fire in the arena, and fire on the grandstand. The reliability of the roof structure is analyzed based on temperature-time curves in load-bearing elements of the steel structure

Numerical model for determining fire behaviour of structures

U radu je prikazan numerički model i razvijeni računalni program za predviđanje ponašanja konstrukcija uslijed djelovanja požara. Nelinearni numerički postupak provodi se u zadanim vremenskim inkrementima, pri čemu se u svakom inkrementu proračunava razdioba temperature, u ovisnosti o njoj korigiraju karakteristike materijala i krutost elementa te rješava statički problem. Na jednostavnom primjeru čeličnog grednog nosača prikazana je efikasnost i točnost razvijenog modela i računalnog programa.A numerical model and computer program for predicting behaviour of structures subjected to fire action are presented in the paper. The nonlinear numerical procedure is conducted in pre-defined time increments. At that, the distribution of temperature is calculated in each increment and, depending on this calculation, material properties and stiffness of the element are corrected, and the static problem is resolved. The efficiency and accuracy of the model and computer program are presented on an example of a simply supported beam

NUMERICAL ANALYSIS OF WELDED BEAM-COLUMN JOINTS IN ALUMINUM STRUCTURES

The objective of this study is to compare the performance for welded beam-column joints in aluminum structures using moment-rotation diagrams and to evaluate the influence of welding on joint rigidity. A nonlinear numerical calculation of welded beam–column joints is performed using the finite element method. Material and geometric nonlinearities were included in the model. The connection was analyzed for two cases: variants with and without welded stiffener plates. Two material models were used. The first was derived from the applicable standard for aluminum structures, while the other was based on the results of a previous material study and calibrated using a separate numerical calculation. From the results of the calculations, moment-rotation diagrams for different geometries and material properties of joints were constructed and compared. The obtained moment-rotation diagrams for the stiffened and unstiffened joints demonstrate that stiffening of the joints in aluminum structures improves the properties of the joint in terms of higher rigidity, resistance, and ductility, regardless of the existence of the heat affected zone

PERFORMANCE OF DIFFERENT CREEP MODELS IN THE ANALYSIS OF FIRE EXPOSED STEEL MEMBERS

In order to model the impact of the creep strains on the behaviour of steel in fire, several creep models have been implemented into Vulcan research code. The paper presents verifications of these creep models for fire-exposed steel against transient fire tests of simply supported steel beams with various loading arrangements, including bending combined with axial compression. In addition, a creep-free analysis of the fire tests has been performed using a newly developed creep-free methodology. Creep-free analysis is vital in explicit modelling of steel creep in fire, since most of the available material models of steel in fire were derived from transient coupon tests and inherently included creep associated with the particular heating rates used in the tests

STRUCTURAL ANALYSIS OF A STEEL COLUMN EXPOSED TO A LOCALIZED FIRE

This paper presents an investigation on the structural analysis of a steel column exposed to a localized fire. Because EN 1991-1-2 does not provide a simplified method to calculate heat transfer to vertical elements, a CFD (Computational Fluid Dynamics) model of a localized fire is developed, based on previously conducted experiments. Furthermore, a heat transfer analysis was performed based on the results of CFD modeling and for the ISO temperature–time curve. Finally, a nonlinear structural analysis of the steel column was conducted for the localized fire scenario, as well as for the ISO temperature–time curve. A comparison between the localized fire and ISO fire exposure points indicates that localized fires can cause earlier failure of a column, depending on the level of external load

Reduction of Postfire Properties of High-Strength Concrete

This paper presents an experimental study of behaviour of high-strength concrete at high temperature. Reduction of the mechanical properties of concrete was determined starting from the period when the concrete specimens were heated to the maximum temperature and cooled down to ambient temperature and the additional 96 hours after the initial cooling of the specimens. The study includes determination of compressive strength, dynamic and secant modulus of elasticity, and stress-strain curves of concrete specimens when exposed to temperature level up to 600°C. The study results were compared with those obtained from other studies, EN 1994-1-2 and EN 1992-1-2. Tests point to the fact that compressive strength of concrete continues to reduce rapidly 96 hours after cooling of the specimens to ambient temperature; therefore indicating that the mechanical properties of concrete have substantial reduction after being exposed to high temperature. The study of the dynamic and secant modulus of elasticity shows that both of the properties are reduced but remain constant during the period of 96 hours after cooling. The level of postfire reduction of compressive strength of the analyzed concrete is substantial and could significantly affect the postfire load bearing capacity of a structure

Projekt INFRA FGAG

U radu je prikazan sažetak ciljeva i učinaka projekta INFRA FGAG: “Implementacijom suvremene znanstveno-istraživačke infrastrukture na FGAG do pametne specijalizacije u zelenoj i energetski učinkovitoj gradnji” (KK.01.1.1.02.0027) kojeg je provelo Sveučilište u Splitu, Fakultet građevinarstva, arhitekture i geodezije a isti je vezan za sveobuhvatno jačanje postojeće i uvođenje nove znanstveno‐istraživačke infrastrukture te provođenje organizacijske reforme znanstveno‐istraživačke djelatnosti Fakulteta građevinarstva, arhitekture i geodezije

Degradation of mechanical properties of high-strength concrete after exposure to fire

Prikazani su rezultati eksperimentalnog određivanja preostalih mehaničkih svojstava betona velike čvrstoće nakon požara. Ispitivano je: tlačna i vlačna čvrstoća te tangentni i sekantni modul elastičnosti. Ispitivanja su se provodila zagrijavanjem betonskih uzoraka na ciljanu visoku temperaturu. Osim mehaničkih svojstava betona prikazana su i preostala svojstva nakon hlađenja uzoraka. Rezultati su uspoređivani s vrijednostima navedenih svojstava danih u EN1992-1-2 i EN1994-1-2.The results obtained by experimental determination of residual mechanical properties of high-strength concrete after fire exposure are presented. The following properties are analyzed: compressive strength and tensile strength, and the tangent and secant moduli of elasticity. The testing is conducted by heating concrete samples to a high target temperature. In addition to mechanical properties of concrete, other properties registered after sample cooling are also presented. The results are compared with corresponding properties given in EN1992-1-2 and EN1994-1-2

Projekt INFRA FGAG

U radu je prikazan sažetak ciljeva i učinaka projekta INFRA FGAG: “Implementacijom suvremene znanstveno-istraživačke infrastrukture na FGAG do pametne specijalizacije u zelenoj i energetski učinkovitoj gradnji” (KK.01.1.1.02.0027) kojeg je provelo Sveučilište u Splitu, Fakultet građevinarstva, arhitekture i geodezije a isti je vezan za sveobuhvatno jačanje postojeće i uvođenje nove znanstveno‐istraživačke infrastrukture te provođenje organizacijske reforme znanstveno‐istraživačke djelatnosti Fakulteta građevinarstva, arhitekture i geodezije