Markku Heinisuo - Academia.edu (original) (raw)

Papers by Markku Heinisuo

3D component method for welded tubular T joints

Tubular Structures XVI, 2017

The paper deals with the recursive definitions of criti cal points when designing steel skeletons... more The paper deals with the recursive definitions of criti cal points when designing steel skeletons. The points are dependent on the previous points and other design data. The design data used are the initial data in the database and when considering connections the profile data. Twelve definitions are given in the paper. These are proved to be sufficient for the applications, whi ch are: outlines of the steel skeletons, connections and analysing models of the steel skeleton s. The system developed is especiall y suitable for the definition of connections. The code to generate the geometrical and analyzing models of connections remains valid althought the amount of connections is increasing.

Buckling Length in Mixed-Integer Linear Frame Optimization

In structural optimization of trusses and frames, the member profiles have to be selected from ma... more In structural optimization of trusses and frames, the member profiles have to be selected from material supplier’s selection. This means that the optimization problem becomes discrete. The discrete frame optimization problem can be formulated as mixed-integer linear program (MILP) and thus solved for global optimality using well-known deterministic methods such as branch-and-cut. Within the formulation it is possible to include member buckling constraints. When using design standards as basis for member buckling resistance evaluation, the critical forces or buckling lengths of the members are required. Buckling length can be determined using many methods, both numerical and analytical. Regardless of the method, buckling length of a single member is dependent on surrounding members’ stiffness which makes it practically impossible to include the correct buckling lengths in MILP formulation directly. In general, the question of buckling length in frame optimization has rarely been disc...

Parametric study on axially loaded square hollow section T-joints at elevated temperature

Fire Safety Journal, 2021

Abstract The paper presents the numerical study of tubular square T-joints under fire conditions.... more Abstract The paper presents the numerical study of tubular square T-joints under fire conditions. The sequentially coupled thermal-displacement numerical model was proposed to examine the performance of square hollow section (SHS) joints. The developed finite element (FE) model was validated against available experimental test results and applied to study the influence of dimensionless parameters on the strength of SHS tubular T-joints at elevated temperatures. These parameters include brace-to-chord width ratio β, chord-width-to-thickness ratio γ, chord-to-brace thickness ratio τ and loading ratio nF. The obtained results show that the critical temperature of T-joints is mostly influenced by the loading ratio nF and β parameter. Different methods to obtain the joint resistance are presented. The strength of the joint obtained based on EN 1993-1-8 was compared with FE analysis, which showed that the decrease in the joint resistance in brace axial compression follows the curve of Young's modulus reduction factors. Finally, the strength of the joint was calculated based on the component method, with a temperature increase specified for each individual component. This method gave higher results in joint strength, when the non-uniform temperature distribution within the joint was taken into account.

Summary. The paper demonstrates the use of metamodels in a cost optimization of single story indu... more Summary. The paper demonstrates the use of metamodels in a cost optimization of single story industrial or commercial steel building including one span symmetric tubular steel roof trusses. A cost optimal solution for truss and wall combination is presented by varying the unit cost of the wall. One span truss metamodel is used. The main conclusions are: Optimize larger compositions, not only one product; cost optimal span/height ratio for one span Warren-type truss is 10; for low cost walls, say 50 - 70 e/m 2 , the optimal span/height ratio is 12; for more expensive walls the span/height ratio should be more than 12; careful building of metamodels enables their use in many kinds of optimization problems to quickly get results for preliminary design; the metamodels are essential tools in optimization still a long time, although software and hardware are getting more and more ecient.

Rakenteiden Mekaniikka, 2021

An analytic method is presented for the analysis of flexural restraint of members by sandwich pan... more An analytic method is presented for the analysis of flexural restraint of members by sandwich panels. Using the method, which is based on the solutions of the fourth order differential equations, the restraint effect of sandwich panels can be approximated in practical cases. The reliability of the method is shown based on tests and finite element analyses. New results are shown using the analytic method for buckling cases and for P-δ analysis in the elastic range. The exact finite element method (FEM) formulation is given for more complicated cases.

Fire Research, Aug 9, 2018

The temperature calculation of hollow steel sections at elevated temperatures is a well-documente... more The temperature calculation of hollow steel sections at elevated temperatures is a well-documented and standard procedure. Through this standard procedure, the temperature can be calculated by assuming a uniform gas temperature all around the section, which is called a symmetric fire in this paper. Embedding in surrounding structures or connecting to another steel member results in non-symmetric heat distribution in the member. This non-symmetricity of the surrounding temperature may cause surface-to-surface heat radiation inside the member, thus affecting the steel section temperature distribution. This effect is considered in this paper by adopting analytical and finite element method analysis.

New Steel‐Timber Composite Beam, Nordic System

ce/papers, 2019

The design of new steel‐timber composite beam, called Nordic system, is proposed. The beam consis... more The design of new steel‐timber composite beam, called Nordic system, is proposed. The beam consists of CLT (Cross Laminated Timber) slabs that are installed on the bottom flanges of an asymmetric welded steel box. The composite action is achieved through connection the slabs to the steel beam by steel plates which are screwed to the timber and bolted to the top flange of the beam. The composite action reduces the stresses of the steel beam compared to the pure steel beam without composite action. This means that there exists a large potential to search lightweight, dry slim floor, low emission and cost optimal solutions using this composite beam due to large variations for available steel grades of the welded beam, as has been shown previously for pure welded steel beams.

Rakenteiden Mekaniikka, 2018

In steel frame design, the definition of buckling lengths of members is a basic task. Computers c... more In steel frame design, the definition of buckling lengths of members is a basic task. Computers can be used to calculate the eigenmodes and corresponding eigenvalues for the frames and using these the buckling lengths of the members can be defined using Euler's equation. However, it is not always easy to say, which eigenmode should be used for the definition of the buckling length of a specific member. Conservatively, the lowest positive eigenvalue can be used for all members. In this paper, methods to define the buckling length of a specific member is presented. For this assessment, two ideas are considered. The first one uses geometric stiffness matrix locally and the other one uses strain energy measures to identify members taking part in a buckling mode. The behaviour of the methods is shown in several numerical examples. Both methods can be implemented into automated frame design, removing one big gap in the integrated design. This is essential when optimization of frames i...

Rakenteiden Mekaniikka, 2017

In the frame analysis, the local model of the joint must follow the behavior of the joint. When c... more In the frame analysis, the local model of the joint must follow the behavior of the joint. When completing the elastic global analysis, the initial rotational stiffness of joints should be known to obtain reliable moment distributions in frames. This paper consists of two parts. The first one evaluates the existing calculation approach for the initial rotational stiffness of welded rectangular hollow section T joints. The validation with the experimental data shows that the current approach significantly underestimates the initial rotational stiffness. An improvement for determining the initial stiffness of T joints is proposed. The second part deals with the influence of the axial force in the main member on the rotational stiffness of the joint. The conducted numerical study shows the extreme reduction of the initial stiffness, when the main member is loaded by axial loads. To consider this effect in the frame analysis, the paper proposes a chord stress function for the initial ro...

Journal of Constructional Steel Research, 2019

The resistance of a steel joint is one of the most crucial elements of a structure under fire con... more The resistance of a steel joint is one of the most crucial elements of a structure under fire conditions. The aim of the study was to investigate the temperature distribution within the square hollow section (SHS) joints with different geometric parameters under fire conditions. The commercial finite element (FE) software, Abaqus/Standard CAE, was used to simulate the behaviour of the SHS joints. Extensive numerical research was conducted on different joint types (T-, Y-, and K-joints) to examine the influence of the joint configuration on the temperature distribution within the joint. To provide reliable observations, a model was validated against the experimental results. The FE simulation results were compared to the predictions of Eurocode equations. The FE simulation results showed that the simulated temperatures are different from the temperatures determined using the Eurocode method. The β parameter was found to have hardly any influence on the temperature distribution within the joint area, whereas different joint configurations strongly influence the distribution.

Rakenteiden Mekaniikka, 2018

Major developments in hardware and software enable researchers and engineers to apply non-linear ... more Major developments in hardware and software enable researchers and engineers to apply non-linear finite-element analyses to study the behavior of tubular structures. However, to provide reasonable results, constructed finite element models should be verified and validated with experimental data. This article develops a finite element model for high strength steel rectangular hollow section T joints. The joints are considered under in-plane bending moment and axial brace loading. The paper determines the most suitable finite elements and the number of layers in the thickness direction for the numerical assessment of initial stiffness and modeling the whole action-deformation behavior of joints. Finally, the proposed FE model is validated with the series of experimental tests. The validation shows that the developed model properly captures the local behavior of tubular joints and can efficiently serve as a reliable tool in routine numerical analyses.

Engineering Structures, 2018

Based on recent studies, high strength steels (HSS) can be efficiently used in civil engineering,... more Based on recent studies, high strength steels (HSS) can be efficiently used in civil engineering, reducing the consumption of material and CO2 emissions. The present Eurocode contains the reduction coefficients (0.8 and 0.9 depending on the steel grade) for high strength steel joints. These reduction factors lead to the excessive consumption of material, making the usage of HSS for construction not as economically viable as they might be. In addition, the present Eurocode contains no method to determine the stiffness of hollow section joints. The scope of this paper is to present experimental results dealing with the welded in-plane moment-loaded HSS joints. Twenty tests on square hollow-section T joints were performed to observe their moment-rotation relationship, studying the following parameters: 1) bending resistance, 2) rotational stiffness, 3) ductility. The results show that the reduction factors are needed only for butt-welded joints, as well as for joints with small fillet welds and made of steel grades higher than S500. The required ductility was achieved by all the samples, even when using welds smaller than full-strength fillet welds. In addition, it was shown experimentally that fillet welds considerably increase the resistance and stiffness of joints.

Journal of Constructional Steel Research, 2017

In the frame analysis, the local analysis model of the joint must follow the behavior of the join... more In the frame analysis, the local analysis model of the joint must follow the behavior of the joint. When completing the elastic global analysis, the initial rotational stiffness of the joints should be known to obtain the reliable moment distribution between the members of the frame. This paper evaluates the existing calculation approach for the initial rotational stiffness of welded rectangular hollow section T joints. Validation with the experiments shows that the current calculation approach significantly underestimates their initial rotational stiffness. Based on the existing experimental data, the paper proposes the improvement for determining the initial stiffness. The second part of the article investigates the effect of the axial force in the main member on the initial rotational stiffness of the joint. The conducted numerical study on square hollow section T joints shows that the reduction of their initial stiffness can reach 50%, when the main member experiences the normal stresses close to yielding. Using the curve fitting approach, the paper proposes and validates a corresponding chord stress function, similar to the existing ones for the moment resistance.

ce/papers, 2017

The component method is a design approach for the characterization of the mechanical properties o... more The component method is a design approach for the characterization of the mechanical properties of structural joints and it is referred to in Eurocode 3 Part 1-8. Eurocode design rules for open sections are already based on the component method. The design rules for joints between tubular hollow sections are still based on simple theoretical mechanical models validated against experimental test results. However, there are research activities in progress to extend the application of the component method also to hollow section joints in the next revision of Eurocode. The fire design of steel joints is carried out in accordance with Eurocode 3 Part 2. Eurocode gives only a guidance on how the temperature of the joint components can be assessed based on the local values of thermal resistance of the joint's fire protection. The method is not sufficient for the component method and Tampere University of Technology is currently carrying out experimental fire research to better understand the temperature distributions in the vicinity of the joint. The aim of the research is to develop experimental methods to determine steel temperatures at the actual joint component, spring, locations and to transfer this information into the joint design approach based on the component method. This paper introduces an experimental research demonstrating the actual temperature distributions within the joint area and highlights the differences between the failure modes and the design criteria at normal temperature design and fire design of a joint.

The effect of steel grade on weight and cost of Warren-type welded tubular trusses

Proceedings of the Institution of Civil Engineers - Structures and Buildings, 2017

The effect of steel grade on the weight and cost of Warren-type welded tubular roof trusses was i... more The effect of steel grade on the weight and cost of Warren-type welded tubular roof trusses was investigated. For an unbiased comparison, best truss designs were obtained through optimisation. The steel strength investigated ranged from S355 to S960. Costs were calculated based on the features of the trusses. The starting point was the exact geometry of the truss, from which a finite-element model was derived. This approach allowed the resistance and other requirements of design standards of both members and joints to be included as constraints in the optimisation problem. The design variables were the truss height, the locations of joints, the gap width at the joints and the member sections, from a catalogue of cold-formed square tubes. Eurocode 3 requirements were applied. The results of the comparison imply a significant saving in weight when using high-strength steel (HSS), by as much as 50% for S960. The cost reduction was smaller, but still about 20%, for a hybrid solution of ...

End-Plate Connections in Bi-Axial Bending - Measurements

Key Engineering Materials, 2016

In this paper we consider the measurements of bolted end-plate connections of tubular beams with ... more In this paper we consider the measurements of bolted end-plate connections of tubular beams with cold-formed hollow rectangular aluminium sections. The motivation for these measurements originates from the fact that the aluminium standard (EN 1999-1-1) [1] does not cover the design of this very frequently used type of connection, where the bolts are located outside the edge-lines of the cross-section, i.e. corner bolts. Many tests and studies regarding this area have been conducted, but this paper brings value to the case where bi-axial bending is applied. The measurements have been carried out and the detailed results shall be shown. In this paper, we will focus on the six measurements where the tubular beams were bent uniaxially and biaxially to these limit points. The tests were stopped when the ultimate limit state was reached. In this case the connection never actually broke, but effectively the joint had lost its load bearing capacity. Some residual capacity still remained, bu...

Construction Information Technology 2000 Taking the Construction Industry into the 21st Century Isbn 9979 9174 3 1 Reykjavik Iceland June 28 30 2000, 2000

The paper includes summaries of three national development projects, which all deal with product ... more The paper includes summaries of three national development projects, which all deal with product modelling and data exchange of structural steelwork. Two of the projects belong to Finnsteel technology program, one belongs to Vera technology program and both these programs are organised by Technology Development Centre of Finland (TEKES). In all the three projects product data models applying ISO 10303-11 (EXPRESS) and product data exchange based on ISO 10303-21 have been used to define the models and to carry out the data exchange between organisations and between disciplines. The views to structural steelwork have been different in all the projects. The experience obtained in the projects is a good starting point to the new century with its challenges. The most essential results of the three projects are presented and summarised in the paper.

The goal of this study is to present background both for car fires and sprinklers design, focus b... more The goal of this study is to present background both for car fires and sprinklers design, focus being in sprinklers, because Eurocode method has not been yet accepted in all European countries, including Finland. The car-fires were not yet included in Eurocodes, although their calculation data has been widely accepted and validated with numerous tests completed in many fire laboratories in Europe and overseas. The effect of sprinklers to the design value of the fire load [MJ/m 2 ] is taken into account in EN 1991-1-2 Annex E using factors considering different active firefighting measures. Two factors deals with sprinklers and take into account: automatic water extinguishing system (0.61) and independent water supplies (0 => 1.0, 1 => 0.87, 2 => 0.7). In this report the Eurocode method is studied for car fires numerically by modeling the fires with the program FDS Version 5.5.3 of NIST. Firstly, the computer model is validated against tests completed in UK 2006-2009. Tests included car fires without and with sprinklers. Secondly, the case studies of three medium size car fires are modeled without and with sprinklers recommended to car-parks. In the case studies the environment is modeled aiming to extreme conditions in car-parks when considering the structural design in fire. This means that the design space is without walls to ensure enough available oxygen and the height of the space is small, 3 m. Temperatures near the ceiling are reported in all cases. Temperatures are calculated reducing the cars' heat release rates per area [kW/m 2 ] without sprinklers corresponding to reductions of the design fire loads with factors 0.61 x 1.0 = 0.61, 0.61 x 0.87 = 0.53 and 0.61 x 0.7 = 0.43. These temperatures are compared to the results which are calculated by modeling the sprinklers with car fires. Details of the numerical models are reported. The Eurocode reduction does not take into account the fact that adjacent cars do not ignite, as is the case using the developed model and observed in the tests in the literature. The Eurocode reduction of fire load with sprinklers gives the same maximum temperatures as the simulation with sprinklers at the first peak of the heat release rate (HRR). The Eurocode method is reliable for design within this range, if the maximum temperatures in the beginning of the fire are those needed in fire design of structures. If it is used to simulate the temperatures after the first peak of HRR, then the temperatures are very conservative, based on the results.

Steel Construction, 2015

The Nordic Steel Construction Conference (NSCC) is a conference with proud traditions. The confer... more The Nordic Steel Construction Conference (NSCC) is a conference with proud traditions. The conference was held for the first time in Stockholm in 1970 and since then with about three years apart it has circulated between the Nordic countries. The last conference was held in Oslo in 2012 and gathered scientists, representatives of steel producers, steel wholesalers, contractors, consultants, architects, etc. Finland is responsible for the event in 2015. The last time the conference was organized in Finland was in 2001. The organizer was the Finnish Constructional Steelwork Association (FCSA) together with Helsinki University of Technology (HUT). Now the baton once again has come to Finland. Also this time FCSA will be responsible for the administrative part of the event. This time Tampere University of Technology (TUT) takes the responsibility for the scientific process. The scientific process will be led by Professor Markku Heinisuo, TUT, as chairman of the Scientific Committee and with Associate Professor Jari Mäkinen as vice chairman. The Scientific Committee is composed of leading steel professors and researchers from the Nordic countries and the rest of Europe. For this year's conference we received 123 abstracts from all over the world, which have been reduced to 94 presentations after the reviewing process. The contributions will cover most of the important issues for modern steel construction; building structures, bridges, high strength and stainless steel, connection, fire and sustainable engineering and composite structures. The editors are thankful for the opportunity to publish a selection of the NSCC presentations in the journal "Steel Construction-Design and Research". The editors are also grateful to the members of the scientific committee who carried out the reviews of the submitted manuscripts.

3D component method for welded tubular T joints

Tubular Structures XVI, 2017

The paper deals with the recursive definitions of criti cal points when designing steel skeletons... more The paper deals with the recursive definitions of criti cal points when designing steel skeletons. The points are dependent on the previous points and other design data. The design data used are the initial data in the database and when considering connections the profile data. Twelve definitions are given in the paper. These are proved to be sufficient for the applications, whi ch are: outlines of the steel skeletons, connections and analysing models of the steel skeleton s. The system developed is especiall y suitable for the definition of connections. The code to generate the geometrical and analyzing models of connections remains valid althought the amount of connections is increasing.

Buckling Length in Mixed-Integer Linear Frame Optimization

In structural optimization of trusses and frames, the member profiles have to be selected from ma... more In structural optimization of trusses and frames, the member profiles have to be selected from material supplier’s selection. This means that the optimization problem becomes discrete. The discrete frame optimization problem can be formulated as mixed-integer linear program (MILP) and thus solved for global optimality using well-known deterministic methods such as branch-and-cut. Within the formulation it is possible to include member buckling constraints. When using design standards as basis for member buckling resistance evaluation, the critical forces or buckling lengths of the members are required. Buckling length can be determined using many methods, both numerical and analytical. Regardless of the method, buckling length of a single member is dependent on surrounding members’ stiffness which makes it practically impossible to include the correct buckling lengths in MILP formulation directly. In general, the question of buckling length in frame optimization has rarely been disc...

Parametric study on axially loaded square hollow section T-joints at elevated temperature

Fire Safety Journal, 2021

Abstract The paper presents the numerical study of tubular square T-joints under fire conditions.... more Abstract The paper presents the numerical study of tubular square T-joints under fire conditions. The sequentially coupled thermal-displacement numerical model was proposed to examine the performance of square hollow section (SHS) joints. The developed finite element (FE) model was validated against available experimental test results and applied to study the influence of dimensionless parameters on the strength of SHS tubular T-joints at elevated temperatures. These parameters include brace-to-chord width ratio β, chord-width-to-thickness ratio γ, chord-to-brace thickness ratio τ and loading ratio nF. The obtained results show that the critical temperature of T-joints is mostly influenced by the loading ratio nF and β parameter. Different methods to obtain the joint resistance are presented. The strength of the joint obtained based on EN 1993-1-8 was compared with FE analysis, which showed that the decrease in the joint resistance in brace axial compression follows the curve of Young's modulus reduction factors. Finally, the strength of the joint was calculated based on the component method, with a temperature increase specified for each individual component. This method gave higher results in joint strength, when the non-uniform temperature distribution within the joint was taken into account.

Summary. The paper demonstrates the use of metamodels in a cost optimization of single story indu... more Summary. The paper demonstrates the use of metamodels in a cost optimization of single story industrial or commercial steel building including one span symmetric tubular steel roof trusses. A cost optimal solution for truss and wall combination is presented by varying the unit cost of the wall. One span truss metamodel is used. The main conclusions are: Optimize larger compositions, not only one product; cost optimal span/height ratio for one span Warren-type truss is 10; for low cost walls, say 50 - 70 e/m 2 , the optimal span/height ratio is 12; for more expensive walls the span/height ratio should be more than 12; careful building of metamodels enables their use in many kinds of optimization problems to quickly get results for preliminary design; the metamodels are essential tools in optimization still a long time, although software and hardware are getting more and more ecient.

Rakenteiden Mekaniikka, 2021

An analytic method is presented for the analysis of flexural restraint of members by sandwich pan... more An analytic method is presented for the analysis of flexural restraint of members by sandwich panels. Using the method, which is based on the solutions of the fourth order differential equations, the restraint effect of sandwich panels can be approximated in practical cases. The reliability of the method is shown based on tests and finite element analyses. New results are shown using the analytic method for buckling cases and for P-δ analysis in the elastic range. The exact finite element method (FEM) formulation is given for more complicated cases.

Fire Research, Aug 9, 2018

The temperature calculation of hollow steel sections at elevated temperatures is a well-documente... more The temperature calculation of hollow steel sections at elevated temperatures is a well-documented and standard procedure. Through this standard procedure, the temperature can be calculated by assuming a uniform gas temperature all around the section, which is called a symmetric fire in this paper. Embedding in surrounding structures or connecting to another steel member results in non-symmetric heat distribution in the member. This non-symmetricity of the surrounding temperature may cause surface-to-surface heat radiation inside the member, thus affecting the steel section temperature distribution. This effect is considered in this paper by adopting analytical and finite element method analysis.

New Steel‐Timber Composite Beam, Nordic System

ce/papers, 2019

The design of new steel‐timber composite beam, called Nordic system, is proposed. The beam consis... more The design of new steel‐timber composite beam, called Nordic system, is proposed. The beam consists of CLT (Cross Laminated Timber) slabs that are installed on the bottom flanges of an asymmetric welded steel box. The composite action is achieved through connection the slabs to the steel beam by steel plates which are screwed to the timber and bolted to the top flange of the beam. The composite action reduces the stresses of the steel beam compared to the pure steel beam without composite action. This means that there exists a large potential to search lightweight, dry slim floor, low emission and cost optimal solutions using this composite beam due to large variations for available steel grades of the welded beam, as has been shown previously for pure welded steel beams.

Rakenteiden Mekaniikka, 2018

In steel frame design, the definition of buckling lengths of members is a basic task. Computers c... more In steel frame design, the definition of buckling lengths of members is a basic task. Computers can be used to calculate the eigenmodes and corresponding eigenvalues for the frames and using these the buckling lengths of the members can be defined using Euler's equation. However, it is not always easy to say, which eigenmode should be used for the definition of the buckling length of a specific member. Conservatively, the lowest positive eigenvalue can be used for all members. In this paper, methods to define the buckling length of a specific member is presented. For this assessment, two ideas are considered. The first one uses geometric stiffness matrix locally and the other one uses strain energy measures to identify members taking part in a buckling mode. The behaviour of the methods is shown in several numerical examples. Both methods can be implemented into automated frame design, removing one big gap in the integrated design. This is essential when optimization of frames i...

Rakenteiden Mekaniikka, 2017

In the frame analysis, the local model of the joint must follow the behavior of the joint. When c... more In the frame analysis, the local model of the joint must follow the behavior of the joint. When completing the elastic global analysis, the initial rotational stiffness of joints should be known to obtain reliable moment distributions in frames. This paper consists of two parts. The first one evaluates the existing calculation approach for the initial rotational stiffness of welded rectangular hollow section T joints. The validation with the experimental data shows that the current approach significantly underestimates the initial rotational stiffness. An improvement for determining the initial stiffness of T joints is proposed. The second part deals with the influence of the axial force in the main member on the rotational stiffness of the joint. The conducted numerical study shows the extreme reduction of the initial stiffness, when the main member is loaded by axial loads. To consider this effect in the frame analysis, the paper proposes a chord stress function for the initial ro...

Journal of Constructional Steel Research, 2019

The resistance of a steel joint is one of the most crucial elements of a structure under fire con... more The resistance of a steel joint is one of the most crucial elements of a structure under fire conditions. The aim of the study was to investigate the temperature distribution within the square hollow section (SHS) joints with different geometric parameters under fire conditions. The commercial finite element (FE) software, Abaqus/Standard CAE, was used to simulate the behaviour of the SHS joints. Extensive numerical research was conducted on different joint types (T-, Y-, and K-joints) to examine the influence of the joint configuration on the temperature distribution within the joint. To provide reliable observations, a model was validated against the experimental results. The FE simulation results were compared to the predictions of Eurocode equations. The FE simulation results showed that the simulated temperatures are different from the temperatures determined using the Eurocode method. The β parameter was found to have hardly any influence on the temperature distribution within the joint area, whereas different joint configurations strongly influence the distribution.

Rakenteiden Mekaniikka, 2018

Major developments in hardware and software enable researchers and engineers to apply non-linear ... more Major developments in hardware and software enable researchers and engineers to apply non-linear finite-element analyses to study the behavior of tubular structures. However, to provide reasonable results, constructed finite element models should be verified and validated with experimental data. This article develops a finite element model for high strength steel rectangular hollow section T joints. The joints are considered under in-plane bending moment and axial brace loading. The paper determines the most suitable finite elements and the number of layers in the thickness direction for the numerical assessment of initial stiffness and modeling the whole action-deformation behavior of joints. Finally, the proposed FE model is validated with the series of experimental tests. The validation shows that the developed model properly captures the local behavior of tubular joints and can efficiently serve as a reliable tool in routine numerical analyses.

Engineering Structures, 2018

Based on recent studies, high strength steels (HSS) can be efficiently used in civil engineering,... more Based on recent studies, high strength steels (HSS) can be efficiently used in civil engineering, reducing the consumption of material and CO2 emissions. The present Eurocode contains the reduction coefficients (0.8 and 0.9 depending on the steel grade) for high strength steel joints. These reduction factors lead to the excessive consumption of material, making the usage of HSS for construction not as economically viable as they might be. In addition, the present Eurocode contains no method to determine the stiffness of hollow section joints. The scope of this paper is to present experimental results dealing with the welded in-plane moment-loaded HSS joints. Twenty tests on square hollow-section T joints were performed to observe their moment-rotation relationship, studying the following parameters: 1) bending resistance, 2) rotational stiffness, 3) ductility. The results show that the reduction factors are needed only for butt-welded joints, as well as for joints with small fillet welds and made of steel grades higher than S500. The required ductility was achieved by all the samples, even when using welds smaller than full-strength fillet welds. In addition, it was shown experimentally that fillet welds considerably increase the resistance and stiffness of joints.

Journal of Constructional Steel Research, 2017

In the frame analysis, the local analysis model of the joint must follow the behavior of the join... more In the frame analysis, the local analysis model of the joint must follow the behavior of the joint. When completing the elastic global analysis, the initial rotational stiffness of the joints should be known to obtain the reliable moment distribution between the members of the frame. This paper evaluates the existing calculation approach for the initial rotational stiffness of welded rectangular hollow section T joints. Validation with the experiments shows that the current calculation approach significantly underestimates their initial rotational stiffness. Based on the existing experimental data, the paper proposes the improvement for determining the initial stiffness. The second part of the article investigates the effect of the axial force in the main member on the initial rotational stiffness of the joint. The conducted numerical study on square hollow section T joints shows that the reduction of their initial stiffness can reach 50%, when the main member experiences the normal stresses close to yielding. Using the curve fitting approach, the paper proposes and validates a corresponding chord stress function, similar to the existing ones for the moment resistance.

ce/papers, 2017

The component method is a design approach for the characterization of the mechanical properties o... more The component method is a design approach for the characterization of the mechanical properties of structural joints and it is referred to in Eurocode 3 Part 1-8. Eurocode design rules for open sections are already based on the component method. The design rules for joints between tubular hollow sections are still based on simple theoretical mechanical models validated against experimental test results. However, there are research activities in progress to extend the application of the component method also to hollow section joints in the next revision of Eurocode. The fire design of steel joints is carried out in accordance with Eurocode 3 Part 2. Eurocode gives only a guidance on how the temperature of the joint components can be assessed based on the local values of thermal resistance of the joint's fire protection. The method is not sufficient for the component method and Tampere University of Technology is currently carrying out experimental fire research to better understand the temperature distributions in the vicinity of the joint. The aim of the research is to develop experimental methods to determine steel temperatures at the actual joint component, spring, locations and to transfer this information into the joint design approach based on the component method. This paper introduces an experimental research demonstrating the actual temperature distributions within the joint area and highlights the differences between the failure modes and the design criteria at normal temperature design and fire design of a joint.

The effect of steel grade on weight and cost of Warren-type welded tubular trusses

Proceedings of the Institution of Civil Engineers - Structures and Buildings, 2017

The effect of steel grade on the weight and cost of Warren-type welded tubular roof trusses was i... more The effect of steel grade on the weight and cost of Warren-type welded tubular roof trusses was investigated. For an unbiased comparison, best truss designs were obtained through optimisation. The steel strength investigated ranged from S355 to S960. Costs were calculated based on the features of the trusses. The starting point was the exact geometry of the truss, from which a finite-element model was derived. This approach allowed the resistance and other requirements of design standards of both members and joints to be included as constraints in the optimisation problem. The design variables were the truss height, the locations of joints, the gap width at the joints and the member sections, from a catalogue of cold-formed square tubes. Eurocode 3 requirements were applied. The results of the comparison imply a significant saving in weight when using high-strength steel (HSS), by as much as 50% for S960. The cost reduction was smaller, but still about 20%, for a hybrid solution of ...

End-Plate Connections in Bi-Axial Bending - Measurements

Key Engineering Materials, 2016

In this paper we consider the measurements of bolted end-plate connections of tubular beams with ... more In this paper we consider the measurements of bolted end-plate connections of tubular beams with cold-formed hollow rectangular aluminium sections. The motivation for these measurements originates from the fact that the aluminium standard (EN 1999-1-1) [1] does not cover the design of this very frequently used type of connection, where the bolts are located outside the edge-lines of the cross-section, i.e. corner bolts. Many tests and studies regarding this area have been conducted, but this paper brings value to the case where bi-axial bending is applied. The measurements have been carried out and the detailed results shall be shown. In this paper, we will focus on the six measurements where the tubular beams were bent uniaxially and biaxially to these limit points. The tests were stopped when the ultimate limit state was reached. In this case the connection never actually broke, but effectively the joint had lost its load bearing capacity. Some residual capacity still remained, bu...

Construction Information Technology 2000 Taking the Construction Industry into the 21st Century Isbn 9979 9174 3 1 Reykjavik Iceland June 28 30 2000, 2000

The paper includes summaries of three national development projects, which all deal with product ... more The paper includes summaries of three national development projects, which all deal with product modelling and data exchange of structural steelwork. Two of the projects belong to Finnsteel technology program, one belongs to Vera technology program and both these programs are organised by Technology Development Centre of Finland (TEKES). In all the three projects product data models applying ISO 10303-11 (EXPRESS) and product data exchange based on ISO 10303-21 have been used to define the models and to carry out the data exchange between organisations and between disciplines. The views to structural steelwork have been different in all the projects. The experience obtained in the projects is a good starting point to the new century with its challenges. The most essential results of the three projects are presented and summarised in the paper.

The goal of this study is to present background both for car fires and sprinklers design, focus b... more The goal of this study is to present background both for car fires and sprinklers design, focus being in sprinklers, because Eurocode method has not been yet accepted in all European countries, including Finland. The car-fires were not yet included in Eurocodes, although their calculation data has been widely accepted and validated with numerous tests completed in many fire laboratories in Europe and overseas. The effect of sprinklers to the design value of the fire load [MJ/m 2 ] is taken into account in EN 1991-1-2 Annex E using factors considering different active firefighting measures. Two factors deals with sprinklers and take into account: automatic water extinguishing system (0.61) and independent water supplies (0 => 1.0, 1 => 0.87, 2 => 0.7). In this report the Eurocode method is studied for car fires numerically by modeling the fires with the program FDS Version 5.5.3 of NIST. Firstly, the computer model is validated against tests completed in UK 2006-2009. Tests included car fires without and with sprinklers. Secondly, the case studies of three medium size car fires are modeled without and with sprinklers recommended to car-parks. In the case studies the environment is modeled aiming to extreme conditions in car-parks when considering the structural design in fire. This means that the design space is without walls to ensure enough available oxygen and the height of the space is small, 3 m. Temperatures near the ceiling are reported in all cases. Temperatures are calculated reducing the cars' heat release rates per area [kW/m 2 ] without sprinklers corresponding to reductions of the design fire loads with factors 0.61 x 1.0 = 0.61, 0.61 x 0.87 = 0.53 and 0.61 x 0.7 = 0.43. These temperatures are compared to the results which are calculated by modeling the sprinklers with car fires. Details of the numerical models are reported. The Eurocode reduction does not take into account the fact that adjacent cars do not ignite, as is the case using the developed model and observed in the tests in the literature. The Eurocode reduction of fire load with sprinklers gives the same maximum temperatures as the simulation with sprinklers at the first peak of the heat release rate (HRR). The Eurocode method is reliable for design within this range, if the maximum temperatures in the beginning of the fire are those needed in fire design of structures. If it is used to simulate the temperatures after the first peak of HRR, then the temperatures are very conservative, based on the results.

Steel Construction, 2015

The Nordic Steel Construction Conference (NSCC) is a conference with proud traditions. The confer... more The Nordic Steel Construction Conference (NSCC) is a conference with proud traditions. The conference was held for the first time in Stockholm in 1970 and since then with about three years apart it has circulated between the Nordic countries. The last conference was held in Oslo in 2012 and gathered scientists, representatives of steel producers, steel wholesalers, contractors, consultants, architects, etc. Finland is responsible for the event in 2015. The last time the conference was organized in Finland was in 2001. The organizer was the Finnish Constructional Steelwork Association (FCSA) together with Helsinki University of Technology (HUT). Now the baton once again has come to Finland. Also this time FCSA will be responsible for the administrative part of the event. This time Tampere University of Technology (TUT) takes the responsibility for the scientific process. The scientific process will be led by Professor Markku Heinisuo, TUT, as chairman of the Scientific Committee and with Associate Professor Jari Mäkinen as vice chairman. The Scientific Committee is composed of leading steel professors and researchers from the Nordic countries and the rest of Europe. For this year's conference we received 123 abstracts from all over the world, which have been reduced to 94 presentations after the reviewing process. The contributions will cover most of the important issues for modern steel construction; building structures, bridges, high strength and stainless steel, connection, fire and sustainable engineering and composite structures. The editors are thankful for the opportunity to publish a selection of the NSCC presentations in the journal "Steel Construction-Design and Research". The editors are also grateful to the members of the scientific committee who carried out the reviews of the submitted manuscripts.