The aim of this study was to assess the potential of hardwoods harvested in Croatian forests for the production of glued laminated timber (glulam), mainly of those species for which there is no ...published performance assessment. Nine sets of glulam beams were produced: three sets using lamellas from European hornbeam, three sets from Turkey oak, and three sets from maple. Each set was characterized by a different hardwood species and surface preparation method. The surface preparation methods included planing, planing followed by sanding with fine grit, and planing followed by sanding with coarse grit. The experimental investigations included shear tests of the glue lines in dry conditions and bending tests of the glulam beams. The shear tests showed satisfactory performance of the glue lines for the Turkey oak and European hornbeam, but not for the maple. The results of the bending tests showed superior bending strength of the European hornbeam compared to the Turkey oak and maple. Planing followed by rough sanding of the lamellas was shown to have a significant influence on the bending strength and stiffness of the glulam from Turkey oak.
The paper presents an experimental and numerical analysis of EN AW 6082 T6 aluminium alloy columns exposed to high-temperature creep in transient conditions. Transient tests with columns subjected to ...a constant heating rate for a persistent external load in the form of the horizontal and transversal forces were carried out. A total of ten columns were examined with varying ratios of horizontal and transversal loads. The test results were compared to numerical results obtained from ANSYS 16.2. The coefficients for an ANSYS built-in Modified Time Hardening creep model were calibrated from the previously conducted tests on coupons and used as a base for the numerical analysis of the column. The study results reveal that creep reduces column load-bearing capacity, starting at temperatures above 150 °C. Furthermore, the level of reduction in the aluminium column capacity, which manifests itself as a runaway failure of the column between the creep and creep-free model, deviates with a difference exceeding 160% in vertical displacement upon failure, while the creep model correlates very well with the results obtained from the tested specimens in terms of failure time and the displacement ratio.
This paper presents the parametric study of a simple aluminium frame made of EN 6082 T6 aluminium alloy exposed to transient heating. The heating rates up to 5
∘
C/min were used in numerical ...calculations to simulate fire protection essential in modern structures. The main focus of the study was to determine the influence of creep strain on the reduction of the load-bearing capacity of the main columns in a typical structure. A significant impact of creep strain on the critical temperature and failure time is given with a total of 60 numerical simulations with the comparison between creep and the creep-free model. The results have shown that for the applied creep model, the failure of the column due to buckling was accelerated with the developed creep strain for 28% than without taking creep into account for the middle column. For faster heating rates and other specific columns, the given failure time gradually decreases but still with significant impact on the overall load-bearing capacity. Numerical calculations were carried out in ANSYS 16.2 software with the use of the Modified Time Hardening creep model whose parameters were obtained within the previous studies.
The paper presents a new validation study of a unified rheological model, in reproducing creep strains from a recent experimental study performed on grade S275JR coupons. The objective of this ...research is to further test the modelling capabilities of the proposed rheological model and its validity for application in general structural fire engineering analysis. The rheological model is composed of two serially connected Kelvin‐Voight elements, used to represent the material's sensitivity to strain‐rate‐governed changes of yield strength, temperature and heating rate. The paper presents the performance of the model in stationary‐creep conditions.
This paper presents a newly developed rheological model capable of modelling the behaviour of carbon steel at high temperature under stress- and strain-rate controlled tests. By combining two serial ...Kelvin elements with the appropriate spring-and-damper constitutive behaviour models it is possible to model creep strain development under stationary and transient heating conditions. Furthermore, the model is able to take into account the inherent increase of the yield strength if the strain rate is raised to moderately high levels usually expected in a fire-induced collapse of the structure. Constitutive behaviour models for each of the rheological elements are based on the test data from which the Eurocode 3 stress-strain law originated. The model was verified by using the test results of constant stress- and strain-rate tests from various sources. Overall comparison of results indicates the applicability of the proposed rheological model to structural fire engineering analysis for steel grades S275 and S355.
•A new type of rheological model is developed for fire analysis of carbon steel.•Its constitutive components are sensitive to strain- and heating-rate.•The model was verified by using various transient and stationary test studies.•The model is applicable for fire analysis of steel grades S275 and S355.
The paper presents an experimental study that investigates the influence of high-temperature creep on reduction of the buckling load capacity of aluminium grade EN6082AW T6 columns. The study was ...performed by performing constant-temperature capacity and creep tests on 17 column specimens of approximately 2.6 m length. A total of eight capacity tests and nine creep tests were carried out. Results obtained within the study have revealed a critical temperature interval of 160–260 °C within which high-temperature creep significantly influences the columns' buckling load capacity. The load level at which high-temperature creep influences the reduction of columns' buckling-load capacity, by exhibiting low short-term creep resistance, is above 90% of the column's axial load capacity. The study provides relevant thermo-mechanical criteria for the assessment of creep-induced buckling of the tested aluminium alloy, in the form of the load level intervals at prescribed temperatures, which induce column buckling within the 240 min interval that is generally considered as a relevant fire resistance period for building structures over 18 m in height.
•We test high-temperature behaviour of 17 EN6082AW T6 columns.•Critical temperature interval for the influence of creep is within 160–260°C.•Creep resistance of aluminium columns is rather low for load ratios above 90%.
This paper presents the results of an experimental investigation of glued laminated timber (glulam) beams made from European hornbeam (Carpinus betulus L.) under constant loading for three months. ...Glulam beams were experimentally tested as a part of the last phase of the research project conducted by Drvene konstrukcije Ltd. and the Faculty of Civil Engineering, Architecture and Geodesy, Split. Beams were loaded in four-point bending tests with the applied load levels of 20% and 30% of the maximum force obtained from previously performed short-term tests. The experiments were carried out under minor environmental changes at the specialized laboratory unit at the Faculty of Civil Engineering, Architecture, and Geodesy, Split. The objective of this study is to present the research results of bending creep tests for hardwood species not included in the European Assessment Document. The experimentally obtained deflection-time curves were fitted with the power law equation used for the prediction of creep behavior. The results indicate that the power law fits well with experimental data. A comparison with requirements from Eurocode 5 is given.
The paper presents test results for the mechanical and creep properties of European aluminium alloy EN 6082AW T6 at high temperatures. Mechanical properties of the aluminium alloy were determined by ...means of two types of test: constant stress-rate and stationary creep tests. Mechanical properties were determined up to a temperature of 350 °C, while the creep tests were conducted within the temperature interval 150-300 °C. The creep tests conducted identified the critical temperature interval for creep development, which represents an important factor when analysing creep behaviour of aluminium structures. This temperature interval was found to be within the range 200-300 °C. Test results for stress at 0.2% strain and modulus of elasticity at different temperatures showed good agreement with the codified values from Eurocode 9 and with other comparable studies.
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.
Summary
The paper presents a rheological model capable of reproducing the temperature‐, stress‐, and time‐dependent strain component, which occurs in steel and aluminium during exposure to high ...temperature. The model is capable of providing the creep strain output for the primary, secondary, and tertiary creep phases for both steel and aluminium. Constitutive parameters of the rheological model are calibrated using 2 recent coupon test studies based on the European steel grade S275JR and aluminium grade EN6082AW T6, both of which are currently used in the construction industry. The calibrated constitutive parameters are valid within the temperature range, within which creep is expected to occur (400‐600°C for steel and 200‐300°C for aluminium). The rheological model proposed in the paper can easily be used for application in finite element–based computer codes.
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