| 1. |
- Kuai, Le, et al.
(author)
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A numerical and experimental investigation of non-linear deformation behaviours in light-frame timber walls
- 2022
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In: Engineering structures. - : Elsevier. - 0141-0296 .- 1873-7323. ; 252
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Journal article (peer-reviewed)abstract
- In recent decades, there is a trend in Scandinavian countries to build multi-storey residential houses using prefabricated timber modules. It is a highly efficient construction process with less environmental impact and less material waste. A significant building element in the timber modules is the light-frame timber wall, which has to be carefully analysed and optimized in this process. This paper presents a new parametric Finite Element (FE) model that can simulate both in-plane and out-of-plane deformations in the light-frame walls. A new and flexible (Eurocode based) approach to define the properties of the mechanical connections is introduced. A numerical model is presented through simulations of several walls that were verified with full-scale experiments. The results indicate that the numerical model could achieve fairly reasonable accuracy with the new approach. Furthermore, several parametric studies are presented and discussed from global and local points of view, to investigate the effects of certain parameters that are not considered in the design method according to Eurocode 5.
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| 2. |
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| 3. |
- Kuai, Le, et al.
(author)
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Modelling and experimental verification of light-frame timber modules loaded in shear
- 2021
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In: World Conference on Timber Engineering 2021, WCTE 2021. - : World Conference on Timber Engineering (WCTE).
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Conference paper (peer-reviewed)abstract
- Building with prefabricated light-frame modules is an innovative construction method whose market share is increasing in Sweden. It is often used to build low and mid-rise residential buildings where the modules are premanufactured in factories with high efficiency and accuracy. This building method has many advantages, though more research regarding wind stabilization of both individual and assembled modules is still needed. To study the racking stiffness and strength of such timber modules, a numerical model of their shear walls was created and verified based on experimental results from specially prefabricated test modules. A new test facility was built for this work, where several potentiometers and a digital image correlation system collected the data used to verify the simulation model. The results from the simulations agree well with the experimental findings, which indicate that the three-dimensional finite element model works with reasonable accuracy for this application. © WCTE 2021. All rights reserved.
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| 4. |
- Kuai, Le, et al.
(author)
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Nonlinear FE-analysis and testing of light-frame timber shear walls subjected to cyclic loading
- 2023
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In: Construction and Building Materials. - : Elsevier. - 0950-0618 .- 1879-0526. ; 362
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Journal article (peer-reviewed)abstract
- Light-frame timber shear walls have been used as load-bearing elements in buildings for several decades. To predict the performance of such structural elements under loading, numerous analytical and numerical models have been developed. However, little focus has been on the prediction of the plastic damage behaviour and unloading of the walls. In this paper, a parametric Finite Element (FE) model is further developed by introducing elasto-plastic connectors to simulate the mechanical behaviour of the sheathing-to-framing connections. To verify the accuracy of the elasto-plastic model, full-size walls were tested and compared with results from simulations. The numerical results, from a few loading cycles, indicate that the model achieves reasonable accuracy in predicting both the nonlinear elastic and plastic deformations. Both experimental and simulation results demonstrate the importance of opening locations relating to the external racking force. The results also indicate that for a double-layer wall, its racking strength can be achieved by summation of the separate contribution from each layer. Furthermore, the internal layer was observed to contribute significantly less than the external layer since its nail pattern was based on the sheathing pattern of the external layer. © 2022 The Authors
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| 5. |
- Kuai, Le, et al.
(author)
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Numerical and experimental investigations of cracked light-frame timber walls
- 2024
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In: Journal of Building Engineering. - : Elsevier. - 2352-7102. ; 96
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Journal article (other academic/artistic)abstract
- This study investigates the impact of sheathing panel cracks on the structural performance of light-frame, modular-based timber buildings, focusing on the racking stiffness and strength of the individual timber walls in the modules. Previous research has investigated such walls for decades and lead to practical design methods in the harmonized European design code, Eurocode 5. Such hand calculation methods are effective for simple geometries but for walls with openings or complex forms, a correct prediction of stiffness and strength is considerably harder to achieve and load levels where cracks initiate are almost impossible to predict. The paper presents both experimental and numerical studies to investigate how significant cracking in sheathing panels affects the load-carrying capacity of various light-frame timber walls. Finite element simulations using Abaqus are conducted to model the cracking of sheathing panels with the extended finite element method. Moreover, an orthotropic elasto-plastic connector model is introduced for the nail joints. The results indicate that significant cracking of the sheathing panels influences the stiffness and the load-carrying capacity of the wall elements and that the crack initiation and propagation is strongly affected by factors such as the location of openings, the shape of the sheathing panels and the type and position of sheathing-to-framing connections. The numerical results presented align satisfactory with the experimental data particularly regarding load levels at crack initiation and propagation. Furthermore, a parametric study investigates how cracks, orthotropic connector properties and vertical constraint of bottom rails influence the racking strength of different timber walls.
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| 6. |
- Kuai, Le, et al.
(author)
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Numerical and experimental investigations of prefabricated light-frame timber modules
- 2024
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In: Engineering structures. - : Elsevier. - 0141-0296 .- 1873-7323. ; 303
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Journal article (peer-reviewed)abstract
- Structures built with prefabricated timber modules have been recognised as an innovative construction method and have been implemented in several countries and regions. In recent years, there have been considerable research activities directed towards these types of structures. However, most of the studies have focused on modules made of steel and concrete in their load-bearing structures and only a few of them are exploring light-frame timber modules. This study focuses on the racking behaviour of light-frame timber modules through experimental and numerical investigations. Full-size tests were performed to examine the global and local structural behaviours of several test modules. A novel finite element model of the modules is also presented. It is a parameterised structural model with high flexibility concerning the generation of different module geometries, materials, fastener types and assembly methods etc. The numerical model was developed in the commercial finite element software ABAQUS, and the numerical results obtained were validated against results from experimental tests. The validation results indicate that the model is capable of achieving satisfactory accuracy in predicting both the global and local structural behaviour of light-frame timber modules. Furthermore, several parametric studies are conducted and discussed to examine how certain parameters affect the structural response of the modules.
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| 7. |
- Kuai, Le
(author)
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Parametric FE-modelling of non-linear racking behaviour of light-frame shear walls and modules used for multi-storey timber buildings
- 2024
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Doctoral thesis (other academic/artistic)abstract
- Wood is a sustainable material from nature that has a longstanding traditionas a building material. Compared to other construction materials, such as steeland concrete, the significance of using structural timber and engineered wood products has increased in recent years because they are regarded as a renewable source and require a low carbon footprint and less energy consumption during production. In Scandinavia, the European design standard EN 1995-1-1 (EC5) is extensively used to guide structural engineers in the design of timber structures, while addressing safety and service ability issues. However, this standard relieson multiple simplifications to achieve simple semi empirical hand calculations. In addition to these simplified expressions, engineers and researchers need reliable numerical models to study the racking behaviour of light-frame timber structures with arbitrary geometry under complex loading conditions. Such modelling tools must be computationally effective, easy to use and able to simulate the global structural behaviour as well as the local fastener force distributions and the crack growth in the sheathing panels.The main aim of this doctoral thesis is to develop a numerical model to analyse the complex structural behaviour of prefabricated light-frame timber modules. The model is developed in the commercial finite element software ABAQUS® with the assistance of the parametric Python scripting method. This thesis work also includes development of a graphical user interface in Python for user-friendly inputs, outputs, and visualisation of the numerical results. The simulation tool was used to study two different structural applications, firstly light-frame timber walls and then light-frame timber modules. For these applications, the modelling of the mechanical sheathing-to-framing joints is very important. In the first paper application, oriented and uncoupled elastic spring-based connectors were used to simulate the sheathing-to-framing joints. To define the material parameters for the connector, new Eurocode-based expressions were also presented. To simulate the permanent displacements in the sheathing-to-framing joints a coupled elasto-plastic spring-based connector model was proposed in papers II and III for both isotropic and orthotropic joint properties.To validate the accuracy of the numerical model, full-scale experimental tests were conducted for light-frame timber walls and modules. The validation indicates that by using effective 3D structural elements, the model achieves a satisfying balance between computational efficiency and reasonable accuracy. The numerical results presented for the applications agreed well with experimental results, regarding the global and local displacements and crack growth in the sheathing panels. The simulation results also increased the understanding of local joint behaviour in terms of fastener forces and their directions. The developed model was used to perform numerous parametric studies and thus investigate how different geometries, sheathing panels, connection types orboundary conditions affect the global and local structural behaviour of light-frame timber structures. These studies demonstrate how the parametric modelling can easily be used to analyse how different parameters have influence on these types of structures and significantly reduce the number of experimental tests necessaryto perform.The parametric model has also the potential to be further developed for the structural design of more complex modular-based multi-storey timber buildings. Furthermore, the proposed orthotropic elasto-plastic spring-based connector model can be further calibrated to simulate the performance of dowel-type connections in wood-based materials.
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| 8. |
- Mahapatra, Krushna, 1974-, et al.
(author)
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A behavioral change-based approach to energy efficiency in a manufacturing plant
- 2018
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In: Energy Efficiency. - : Springer. - 1570-646X .- 1570-6478. ; 11:5, s. 1103-1116
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Journal article (peer-reviewed)abstract
- In the realm of industrial energy efficiencystudies, very little research has been done to understandthe barriers and opportunities to influence behavior ofproduction workers and the corresponding energysavingpotentials. This paper analyzes a case study ofVolvo Construction Equipment AB in Braås, Sweden(VCE Braås), that has reduced its relative idle electricityuse by more than 10 percentage points during 2013–2016 by implementing a strategy of changing everydaybehavior of production workers. The results based oninterviews with actors involved in the energy efficiencyproject showed that a concrete goal, the employment ofa fulltime operational leader who earlier worked as aproduction worker at VCE Braås, and the involvementof both the leadership and employees in project managementwere key to the success of the project.
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| 9. |
- Mahapatra, Krushna, Professor, 1974-, et al.
(author)
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Behavioural change based energy efficiency at Volvo Construction Equipment, Braås, Sweden
- 2016
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In: Industrial Efficiency 2016. - : European Council for an Energy Efficient Economy (ECEEE). - 9789198048285 - 9789198048292 ; , s. 351-357
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Conference paper (peer-reviewed)abstract
- Industrial energy efficiency studies have mostly focused on innovative technological approaches and solutions and discussed hindrances to investments oriented measures. However, very little research has been done to understand the challenges of implementing interventions to change employee behavior and the corresponding energy savings potentials. Behaviour may be investment (e.g. decision to buy an expensive machine) or non-investment (e.g. turn of machines when not in operation) in nature, but in this paper behavioral change refers to the transformation in executing everyday non-investment tasks. Volvo Construction Equipment AB in Braås, Sweden (VCE Braås) has recently implemented a behavioral change strategy to improve energy efficiency of the production process. The approach was introduced following the global Volvo CE goal that all production plants of the company would reduce idle electricity use during off-production hours to 15 % (from 25 % to 40 % in different plants) during the period 2013-15. This paper analyzes the factors contributing to the energy efficiency achievements of VCE Braås through the application of behavioral change theories and focus group interviews with production leaders and group leaders. Results showed that a concrete goal, the commitment of the leadership including employment of a fulltime project leader who earlier worked as a production worker at VCE Braås, and the involvement of both the leadership and employees (production leaders, group leaders and floor workers) in project management were key to the success of the project.
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| 10. |
- Maharjan, Rajan, 1985-, et al.
(author)
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An experimental analysis of full scale light-frame timber modules
- 2024
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In: Engineering structures. - : Elsevier. - 0141-0296 .- 1873-7323. ; 304
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Journal article (peer-reviewed)abstract
- Prefabricated timber modules are being increasingly used in the load-bearing structure of entire residential buildings reaching heights up to six stories. The development is driven by the demand of high-quality housing that remains affordable while fulfilling tough environmental requirements imposed on modern construction. To enable further development of this type of buildings additional research is needed despite the considerable number of studies previously performed. This study provides an extensive experimental investigation by subjecting three modules to three different load cases. In each load case, the modules were initially loaded with dead-load placed atop of the module. Thereafter the modules were laterally loaded at the top using a servo hydraulic piston in displacement control. The main aim of the study was to assess the structural behavior of these modules under combined lateral and vertical loading, and also to generate experimental data suitable for verification of finite element models. Results from the test series reveal significant variation in racking stiffness and racking strength depending on the module’s design. Furthermore, in some cases more stiff and stronger mechanical inter-module connections are needed to enhance their global structural performance. Finally, the experimental results reveal that the modules are relatively ductile in their shear response when subjected to horizontal load.
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