Steffen Franke | Bern University of Applied Sciences (original) (raw)

Papers by Steffen Franke

Journal of sustainable architecture and civil engineering, Feb 19, 2024

15th World Congress on Computational Mechanics (WCCM-XV) and 8th Asian Pacific Congress on Computational Mechanics (APCOM-VIII), 2022

The load-bearing behaviour of bonded-in steel threaded rods (BiR) in hardwood was investigated wi... more The load-bearing behaviour of bonded-in steel threaded rods (BiR) in hardwood was investigated with special focus on the prevention of the splitting behaviour using a recess (not bonded zone) in the bondline. The main objective was to analyse the influence of the not-bonded length and the rod edge distance on the distribution of longitudinal shear and transverse tensile stresses in joints with bonded-in rods in beech glulam. Several BiR joint configurations were tested experimentally and a wide range of joint configurations with various combinations of recess and bonded lengths and edge distances were numerically investigated. According to the experimental and numerical analyses, a recess length of 2d (two times rod diameter) produced a significant positive effect on the stress distribution reducing the risk of splitting of beech glulam in the studied joint configurations.

Wood is a hygroscopic material and can absorb or release moisture from the surrounding climate. T... more Wood is a hygroscopic material and can absorb or release moisture from the surrounding climate. The wood moisture content (MC) influences the material strengths and stiffnesses as well as the long-term load-bearing behaviour. For this reason, the continuous monitoring of wood moisture content is a suitable early warning system to increase the quality of wood structures in a pioneering way and to detect changes in time. The paper presents several suitable measuring methods for the MC and explains their advantages, accuracies, and applications. The explanations are supported by case studies.

Wood is a hygroscopic material. The moisture content of wood changes due to ambient climate varia... more Wood is a hygroscopic material. The moisture content of wood changes due to ambient climate variations. The moisture content changes first on the surface and a moisture gradient develops over the cross section and results in moisture induced stresses (MIS). MIS occur in addition to normal stresses for the load-bearing resistance and can affect mechanical reinforcements. The paper shows results from experimental test series on the load, moisture, and deformation investigation of structural glulam members reinforced with internal mechanical fasteners. Stepwise climate scenarios were applied and considered climates experienced by the structural timber member before or after reinforcement. For the estimation of the swelling and shrinkage behaviour, effective hygro-expansion coefficients have been determined. The coefficients are significantly lower than previously assumed in the standards. This enables engineers to estimate more realistic wood deformations and the impact on reinforcements which is not neglectable and reduces damage in a wide range of applications. The research results promote the use of wood by ensuring quality, performance, and aesthetics in timber constructions.

With the worldwide construction sector being responsible for one third of carbon dioxide emission... more With the worldwide construction sector being responsible for one third of carbon dioxide emissions, as well as forty percent of the world's energy use and waste production, a shift to sustainable and renewable construction techniques is crucial. Engineered timber, a champion of sustainable construction materials, has evolved to a stage that enables the construction of not only family housing but also taller buildings so far commonly built from concrete or steel. Designing taller timber buildings made is more demanding than their concrete and steel counterparts. Whereas different design aspects (architectural, structural, fire safety, acoustics, etc.) of concrete buildings can work almost independently, the design of taller timber buildings should be performed with intensive collaboration among the design teams. It is therefore crucial to address taller multi-storey timber buildings from a collaborative and interdisciplinary perspective, considering static, dynamic, fire, acoustic, human health, and other aspects in parallel and not in isolation. Only through interdisciplinary analysis and interaction can a set of holistic design guidelines be developed that will enable the safe construction of taller timber buildings, as well as respect human wellbeing demands. In this paper, the COST Action CA20139 will be presented and the main aims will be discussed.

World Conference on Timber Engineering (WCTE 2023)

The quality assurance of timber bridges is currently ensured mainly manually by regular visual in... more The quality assurance of timber bridges is currently ensured mainly manually by regular visual inspections over the entire life cycle. To reduce this (cost) effort, the possibility of continuously recording the condition of bridges through monitoring is being investigated. This would also increase the confidence in the long-term load-bearing capacity of timber bridges among planners and public. In addition to the permanent recording of the wood moisture content, conclusions can also be drawn about the condition and even possible damage by recording the natural frequencies which depends on the stiffness. For this purpose, a stand-alone vibration measurement and evaluation system was developed, which is easy to handle and suitable for long-term monitoring due to its energy efficiency. Beside a first application on a low-traffic timber bridge for several months, the system was validated with investigations on various types of artificial damages on the natural frequency of timber components.

Wood Material Science & Engineering

Franke, Steffen; Schiere, Marcus Jacob; Franke, Bettina (2018). Pressverklebung aus der Sicht der Forschung In: S-Win-Tagung 2018, Von der Forschung zur Praxis. Biel/Bienne, Switzerland. 16.05.2018., 2018

The increasing number of large timber structures and particularly of public buildings requires th... more The increasing number of large timber structures and particularly of public buildings requires the assessment and monitoring of timber structures for safe, reliable timber constructions. Within the assessment, one obvious sign are cracks, which occur due to the natural behaviour of wood but also due to physical and/or mechanical excessive stresses. The paper present, categorize and discuss the causes of cracks, explains test standards for the quality control of glulam members and shows possibilities for the assessment

The combination of modern architecture with the renewable raw material wood leads to impressive a... more The combination of modern architecture with the renewable raw material wood leads to impressive and demanding timber structures with high requirements for planning, production, logistics, commissioning and use. The demands placed on modern wooden structures are constantly increasing in terms of design, appearance, slender cross sections and large spans. Meanwhile, quality assurance during the construction and operational phase is crucial. The realistic estimation of the risks for the timber structure during the construction and operation phase as well as the distribution of wood moisture content in the timber load bearing elements, the risk of cracking and the shape stability of the cross sections are important.

Construction and Building Materials, 2015

Abstract Highly loaded and large span timber beams are often used for halls, public buildings or ... more Abstract Highly loaded and large span timber beams are often used for halls, public buildings or bridges. Reinforcement of beams may be required to extend the life of the structure, due to deterioration or damage to the material/product or change of use. The paper summarises methods to repair or enhance the structural performance of timber beams. The main materials/products cross sections and geometries used for timber beam are presented. Furthermore, their general failure modes are described and typical retrofitting and reinforcement techniques are given. The techniques include wood to wood replacements, use of mechanical fasteners and additional strengthening materials/products.

Schiere, Marcus Jacob; Franke, Bettina; Franke, Steffen (2018). Antworten zur Tragfähigkeit infolge dynamischer Klimawechsel In: S-Win-Tagung 2018, Von der Forschung zur Praxis. Biel/Bienne, Switzerland. 16.05.2018., 2018

Journal of sustainable architecture and civil engineering, Feb 19, 2024

15th World Congress on Computational Mechanics (WCCM-XV) and 8th Asian Pacific Congress on Computational Mechanics (APCOM-VIII), 2022

The load-bearing behaviour of bonded-in steel threaded rods (BiR) in hardwood was investigated wi... more The load-bearing behaviour of bonded-in steel threaded rods (BiR) in hardwood was investigated with special focus on the prevention of the splitting behaviour using a recess (not bonded zone) in the bondline. The main objective was to analyse the influence of the not-bonded length and the rod edge distance on the distribution of longitudinal shear and transverse tensile stresses in joints with bonded-in rods in beech glulam. Several BiR joint configurations were tested experimentally and a wide range of joint configurations with various combinations of recess and bonded lengths and edge distances were numerically investigated. According to the experimental and numerical analyses, a recess length of 2d (two times rod diameter) produced a significant positive effect on the stress distribution reducing the risk of splitting of beech glulam in the studied joint configurations.

Wood is a hygroscopic material and can absorb or release moisture from the surrounding climate. T... more Wood is a hygroscopic material and can absorb or release moisture from the surrounding climate. The wood moisture content (MC) influences the material strengths and stiffnesses as well as the long-term load-bearing behaviour. For this reason, the continuous monitoring of wood moisture content is a suitable early warning system to increase the quality of wood structures in a pioneering way and to detect changes in time. The paper presents several suitable measuring methods for the MC and explains their advantages, accuracies, and applications. The explanations are supported by case studies.

Wood is a hygroscopic material. The moisture content of wood changes due to ambient climate varia... more Wood is a hygroscopic material. The moisture content of wood changes due to ambient climate variations. The moisture content changes first on the surface and a moisture gradient develops over the cross section and results in moisture induced stresses (MIS). MIS occur in addition to normal stresses for the load-bearing resistance and can affect mechanical reinforcements. The paper shows results from experimental test series on the load, moisture, and deformation investigation of structural glulam members reinforced with internal mechanical fasteners. Stepwise climate scenarios were applied and considered climates experienced by the structural timber member before or after reinforcement. For the estimation of the swelling and shrinkage behaviour, effective hygro-expansion coefficients have been determined. The coefficients are significantly lower than previously assumed in the standards. This enables engineers to estimate more realistic wood deformations and the impact on reinforcements which is not neglectable and reduces damage in a wide range of applications. The research results promote the use of wood by ensuring quality, performance, and aesthetics in timber constructions.

With the worldwide construction sector being responsible for one third of carbon dioxide emission... more With the worldwide construction sector being responsible for one third of carbon dioxide emissions, as well as forty percent of the world's energy use and waste production, a shift to sustainable and renewable construction techniques is crucial. Engineered timber, a champion of sustainable construction materials, has evolved to a stage that enables the construction of not only family housing but also taller buildings so far commonly built from concrete or steel. Designing taller timber buildings made is more demanding than their concrete and steel counterparts. Whereas different design aspects (architectural, structural, fire safety, acoustics, etc.) of concrete buildings can work almost independently, the design of taller timber buildings should be performed with intensive collaboration among the design teams. It is therefore crucial to address taller multi-storey timber buildings from a collaborative and interdisciplinary perspective, considering static, dynamic, fire, acoustic, human health, and other aspects in parallel and not in isolation. Only through interdisciplinary analysis and interaction can a set of holistic design guidelines be developed that will enable the safe construction of taller timber buildings, as well as respect human wellbeing demands. In this paper, the COST Action CA20139 will be presented and the main aims will be discussed.

World Conference on Timber Engineering (WCTE 2023)

The quality assurance of timber bridges is currently ensured mainly manually by regular visual in... more The quality assurance of timber bridges is currently ensured mainly manually by regular visual inspections over the entire life cycle. To reduce this (cost) effort, the possibility of continuously recording the condition of bridges through monitoring is being investigated. This would also increase the confidence in the long-term load-bearing capacity of timber bridges among planners and public. In addition to the permanent recording of the wood moisture content, conclusions can also be drawn about the condition and even possible damage by recording the natural frequencies which depends on the stiffness. For this purpose, a stand-alone vibration measurement and evaluation system was developed, which is easy to handle and suitable for long-term monitoring due to its energy efficiency. Beside a first application on a low-traffic timber bridge for several months, the system was validated with investigations on various types of artificial damages on the natural frequency of timber components.

Wood Material Science & Engineering

Franke, Steffen; Schiere, Marcus Jacob; Franke, Bettina (2018). Pressverklebung aus der Sicht der Forschung In: S-Win-Tagung 2018, Von der Forschung zur Praxis. Biel/Bienne, Switzerland. 16.05.2018., 2018

The increasing number of large timber structures and particularly of public buildings requires th... more The increasing number of large timber structures and particularly of public buildings requires the assessment and monitoring of timber structures for safe, reliable timber constructions. Within the assessment, one obvious sign are cracks, which occur due to the natural behaviour of wood but also due to physical and/or mechanical excessive stresses. The paper present, categorize and discuss the causes of cracks, explains test standards for the quality control of glulam members and shows possibilities for the assessment

The combination of modern architecture with the renewable raw material wood leads to impressive a... more The combination of modern architecture with the renewable raw material wood leads to impressive and demanding timber structures with high requirements for planning, production, logistics, commissioning and use. The demands placed on modern wooden structures are constantly increasing in terms of design, appearance, slender cross sections and large spans. Meanwhile, quality assurance during the construction and operational phase is crucial. The realistic estimation of the risks for the timber structure during the construction and operation phase as well as the distribution of wood moisture content in the timber load bearing elements, the risk of cracking and the shape stability of the cross sections are important.

Construction and Building Materials, 2015

Abstract Highly loaded and large span timber beams are often used for halls, public buildings or ... more Abstract Highly loaded and large span timber beams are often used for halls, public buildings or bridges. Reinforcement of beams may be required to extend the life of the structure, due to deterioration or damage to the material/product or change of use. The paper summarises methods to repair or enhance the structural performance of timber beams. The main materials/products cross sections and geometries used for timber beam are presented. Furthermore, their general failure modes are described and typical retrofitting and reinforcement techniques are given. The techniques include wood to wood replacements, use of mechanical fasteners and additional strengthening materials/products.

Schiere, Marcus Jacob; Franke, Bettina; Franke, Steffen (2018). Antworten zur Tragfähigkeit infolge dynamischer Klimawechsel In: S-Win-Tagung 2018, Von der Forschung zur Praxis. Biel/Bienne, Switzerland. 16.05.2018., 2018