Finite-element (FE) simulations of the deformation behavior of a 5.4-m-long, 8-m-wide, and 0.27-m... more Finite-element (FE) simulations of the deformation behavior of a 5.4-m-long, 8-m-wide, and 0.27-m-thick stress-laminated timber bridge deck were conducted. The simulation results were compared with full-scale test results when using a load resembling an axle load placed near the edge and when cycling the load between a high and low value. Two separate approaches to nonlinear FE modeling were used. The first FE model simulates a frictional slip between the glulam beams with an elastic-plastic material model. The second FE model simulates a frictional slip by modeling each discrete contact surface between each beam in the deck. The results show good agreement between simulation and test results and reveal that the simulation model that models contact surfaces produces slightly better results at the expense of a greater modeling effort and increased computational time. Hysteresis in the load versus deformation curves is clearly visible and was due to significant slip between the glulam beams, which was successfully simulated.
The aim of this project was to evaluate the innovative strengthening method (called here Chalmers... more The aim of this project was to evaluate the innovative strengthening method (called here Chalmers/TENROC method) on the bridge over Nossan (Nossan at S. Harene church, bridge no. 15-376-1) with regard to practical production experience and sustainability, as well as, propose ideas for further development of the method. The scope of this project was to present: 1) planning, logistics and assembly of pre-stressed laminate on the bridge, 2) environmental impact and LCC analysis. 3) material usage and adaptation of laminates for pre-stressing work 4) safety conditions for conducting on-site woks before and during pre-stressing of the laminates on a concrete bridge.
Design knowledge reuse is the most common design method in structural engineering and dominates c... more Design knowledge reuse is the most common design method in structural engineering and dominates completely in the design of steel connections. This paper describes a case study and a prototype with the objective of gaining knowledge on how to create computer support for knowledge reuse in the design of steel connections. The case study identified the key characteristics of the design knowledge reuse process in the form of subprocesses. It also showed that the most commonly used documents in these processes are drawings and that these contain most of the information needed for reuse. The prototype was implemented using the Case-Based Design approach. Evaluation of this prototype confirmed the findings of the case study and suggested that information about the geometry and topology of the members connected was sufficient for indexing previous steel connections. The prototype significantly facilitated the process of finding the documentation of recalled previous connections and thus mo...
The limiting factors when it comes to design of timber structures are often stiffness properties ... more The limiting factors when it comes to design of timber structures are often stiffness properties of timber products. The stiffness requirements in serviceability limit state, both short-term and longterm deformation especially in horizontal members, is a factor that often makes it necessary to increase the dimensions of the member. Both the results from experimental studies and the results of analytical modelling are presented. The experimental study comprises results from short-term tests to failure of nine glulam beams strengthened with bonded steel plates or CFRP laminates and mechano-sorptive creep tests of strengthened glulam lamellas loaded in bending at 8 MPa. Positive effects on the strengthening when it comes to short-term and long-term behaviour were shown. The arrangement of the reinforcement in the cross-section makes it possible to control the behaviour of the beams in terms of strength, stiffness and ductility. The experimental results agreed very well with the propose...
This paper clarifies the extent to which models based on two- and three-dimensional material desc... more This paper clarifies the extent to which models based on two- and three-dimensional material descrip- tions can predict bow and spring deformation. Changes in longitudinal shrinkage and swelling and their varia- tions over cross-sections of studs cause these studs to develop distortion in terms of spring and/or bow. Radial variation from pith to bark (two-dimensional) of the longitudinal shrinkage in the cross-section is often as- sumed to be the only physical data needed to predict spring and bow in a stud. However, using measurements from 240 studs of Norway spruce (fast-grown and one slow-grown stand), it was found that there was no correlation between shrinkage gradients measured at one longitudinal position and three-dimensional bending distortion (spring and bow). As a result, two studs, one with large spring (and no bow or twist) and one with large bow (and no spring or twist), were cut longitudi- nally in sections 200 mm long. From these sections, sticks were cut and the lon...
The ideal open building system is a vision that the building industry should aim at. It means a s... more The ideal open building system is a vision that the building industry should aim at. It means a system that combines the industrial efficiency with the traditional flexibility. Such a system would mean individual designs, built up with different elements that could be bought from any producer around the world, connected to each other with connections from different producers. Even more challenging would be to have components that are flexible, compatible with each other and interchangeable at a later date. In order for manufacturers of different components to be able to sell their products to a large number of contractors; flexible, integrated connections are needed, that also are very easy to use during assembly and are cheap and effective to produce. To make this possible it is necessary to find a way to communicate connection features and requirements in an easy manner. The aim of this paper is to show two strategies, i.e. design-based strategy and function-based strategy, analyse them and to produce guidelines on further development of such strategies. The question is which strategy is best suited to be used when working with open building systems. The final output is the idea of the standardisation of information; the Part Request Form with which the performance of connections in term of specifications could be communicated so that it is understandable for everyone, from the system owner to the manufacturer of connections.
Glulam beams made of Norway spruce are stressed together with high strength steel bars creating a... more Glulam beams made of Norway spruce are stressed together with high strength steel bars creating a Stress laminated timber deck (SLTD). Deflections and stresses can be estimated with both finite element models based on orthotropic plate theory as well as with simplified hand calculation methods based simple beam theory. If SLTDs are loaded until failure in the ultimate limit state (ULS), phenomena which generally do not occur in serviceability limit state (SLS) must be taken into account. Slip will occur in the interlaminar surface between the stressed glulam laminations. Once slip has occurred, stress will redistribute between the laminations. A rectangular SLTD was tested for several load levels and pre-stress levels. Deflections were compared with a finite element orthotropic model. These results were also compared with several established design methods. After failure occurred in the ULS, the load was first removed and then applied again, in order to emphasize the reliability of ...
A general assumption reported in the literature is that the structural response of a stress-lamin... more A general assumption reported in the literature is that the structural response of a stress-laminated-timber (SLT) bridge deck is linear until failure. However, few studies of ultimate-load tests (ULTs) on timber bridges have been reported. A full-scale test of a SLT deck (span, 4.9 m; thickness, 270 mm) was performed to obtain the deformations at various prestress levels as well as at the ultimate-load capacity of such a structure. Prior to the ULT, nondestructive tests (NDT) were performed at three different prestress levels. The load was applied as an axle load positioned both centrically and eccentrically. The deflections were about 10% larger at a prestress level of 300 kPa compared with a prestress level of 600 and 900 kPa. For applied loads larger than 150–250 kN, the deflection of the deck was nonlinear at certain positions. This was most likely owing to large concentrated shear forces that resulted in interlaminar slip between the laminates. The limit for linearity seems to be dependent on the applied prestress. A prestress of 600 kPa and an eccentrically positioned load was used for the ULT. Failure occurred at a load level of 900 kN. The existing design codes and new procedures in development may be verified and calibrated against the results in this paper.
Stress-laminated timber (SLT) bridge decks are generally designed using either linear hand calcul... more Stress-laminated timber (SLT) bridge decks are generally designed using either linear hand calculation methods or linear finite-element models. Several studies have shown, however, that the behavior of SLT decks is nonlinear when loaded until failure. In this paper, several linear design methods are compared with one another and with an ultimate load test of a full-scale SLT deck subjected to an eccentric load. Some of the linear hand calculation methods show significant discrepancies in results, depending on the load position. There are also variations in the results from finite-element models, depending on the material properties assigned to the deck. All the design methods failed to predict the deflection of the tested deck when loaded to failure. A larger deflection was observed in the full-scale test than that predicted by the design methods. As a result, the linear design method could underestimate the bending stresses in the deck. Several hand calculation methods are also unable to calculate the transverse forces and moments necessary for design according to Eurocode 5.
Timber and wood-based engineered products are important as structural materials, especially in th... more Timber and wood-based engineered products are important as structural materials, especially in the drive towards sustainable technologies and construction. It is very important to improve the properties of these products, making them more competitive and reliable. This applies particularly to larger, more complicated structures where timber is becoming a realistic alternative to other construction materials. The orthotropic properties of timber are well known - strong and stable along the grain, weak and susceptible to movement across the grain. Combining wood with other materials, to achieve composite action, enables the strength of wood to be realized and its shortcomings to be strengthened or eliminated. COST Action FP1004, “Enhance mechanical properties of timber, engineered wood products and timber structures” provides a network for learning and development in a range of connected topics. This conference will present and record various methods for improving wood with other materials. It brings researchers and practitioners together to learn about various applications, and enables them to take part in discussions about future research and development. The purpose of the COST program is to strengthen Europe and other countries in scientific and technological research, for peaceful purposes, through the support of cooperation and interaction between European researchers. This conference adheres to these principles. It will be an extraordinary opportunity to hear presentations from highly specialist, invited speakers and to participate in debate, in the island of Cyprus, which is located at the crossroads of three continents Europe, Asia and Africa in the Northern-east part of the Mediterranean Sea.
Finite-element (FE) simulations of the deformation behavior of a 5.4-m-long, 8-m-wide, and 0.27-m... more Finite-element (FE) simulations of the deformation behavior of a 5.4-m-long, 8-m-wide, and 0.27-m-thick stress-laminated timber bridge deck were conducted. The simulation results were compared with full-scale test results when using a load resembling an axle load placed near the edge and when cycling the load between a high and low value. Two separate approaches to nonlinear FE modeling were used. The first FE model simulates a frictional slip between the glulam beams with an elastic-plastic material model. The second FE model simulates a frictional slip by modeling each discrete contact surface between each beam in the deck. The results show good agreement between simulation and test results and reveal that the simulation model that models contact surfaces produces slightly better results at the expense of a greater modeling effort and increased computational time. Hysteresis in the load versus deformation curves is clearly visible and was due to significant slip between the glulam beams, which was successfully simulated.
The aim of this project was to evaluate the innovative strengthening method (called here Chalmers... more The aim of this project was to evaluate the innovative strengthening method (called here Chalmers/TENROC method) on the bridge over Nossan (Nossan at S. Harene church, bridge no. 15-376-1) with regard to practical production experience and sustainability, as well as, propose ideas for further development of the method. The scope of this project was to present: 1) planning, logistics and assembly of pre-stressed laminate on the bridge, 2) environmental impact and LCC analysis. 3) material usage and adaptation of laminates for pre-stressing work 4) safety conditions for conducting on-site woks before and during pre-stressing of the laminates on a concrete bridge.
Design knowledge reuse is the most common design method in structural engineering and dominates c... more Design knowledge reuse is the most common design method in structural engineering and dominates completely in the design of steel connections. This paper describes a case study and a prototype with the objective of gaining knowledge on how to create computer support for knowledge reuse in the design of steel connections. The case study identified the key characteristics of the design knowledge reuse process in the form of subprocesses. It also showed that the most commonly used documents in these processes are drawings and that these contain most of the information needed for reuse. The prototype was implemented using the Case-Based Design approach. Evaluation of this prototype confirmed the findings of the case study and suggested that information about the geometry and topology of the members connected was sufficient for indexing previous steel connections. The prototype significantly facilitated the process of finding the documentation of recalled previous connections and thus mo...
The limiting factors when it comes to design of timber structures are often stiffness properties ... more The limiting factors when it comes to design of timber structures are often stiffness properties of timber products. The stiffness requirements in serviceability limit state, both short-term and longterm deformation especially in horizontal members, is a factor that often makes it necessary to increase the dimensions of the member. Both the results from experimental studies and the results of analytical modelling are presented. The experimental study comprises results from short-term tests to failure of nine glulam beams strengthened with bonded steel plates or CFRP laminates and mechano-sorptive creep tests of strengthened glulam lamellas loaded in bending at 8 MPa. Positive effects on the strengthening when it comes to short-term and long-term behaviour were shown. The arrangement of the reinforcement in the cross-section makes it possible to control the behaviour of the beams in terms of strength, stiffness and ductility. The experimental results agreed very well with the propose...
This paper clarifies the extent to which models based on two- and three-dimensional material desc... more This paper clarifies the extent to which models based on two- and three-dimensional material descrip- tions can predict bow and spring deformation. Changes in longitudinal shrinkage and swelling and their varia- tions over cross-sections of studs cause these studs to develop distortion in terms of spring and/or bow. Radial variation from pith to bark (two-dimensional) of the longitudinal shrinkage in the cross-section is often as- sumed to be the only physical data needed to predict spring and bow in a stud. However, using measurements from 240 studs of Norway spruce (fast-grown and one slow-grown stand), it was found that there was no correlation between shrinkage gradients measured at one longitudinal position and three-dimensional bending distortion (spring and bow). As a result, two studs, one with large spring (and no bow or twist) and one with large bow (and no spring or twist), were cut longitudi- nally in sections 200 mm long. From these sections, sticks were cut and the lon...
The ideal open building system is a vision that the building industry should aim at. It means a s... more The ideal open building system is a vision that the building industry should aim at. It means a system that combines the industrial efficiency with the traditional flexibility. Such a system would mean individual designs, built up with different elements that could be bought from any producer around the world, connected to each other with connections from different producers. Even more challenging would be to have components that are flexible, compatible with each other and interchangeable at a later date. In order for manufacturers of different components to be able to sell their products to a large number of contractors; flexible, integrated connections are needed, that also are very easy to use during assembly and are cheap and effective to produce. To make this possible it is necessary to find a way to communicate connection features and requirements in an easy manner. The aim of this paper is to show two strategies, i.e. design-based strategy and function-based strategy, analyse them and to produce guidelines on further development of such strategies. The question is which strategy is best suited to be used when working with open building systems. The final output is the idea of the standardisation of information; the Part Request Form with which the performance of connections in term of specifications could be communicated so that it is understandable for everyone, from the system owner to the manufacturer of connections.
Glulam beams made of Norway spruce are stressed together with high strength steel bars creating a... more Glulam beams made of Norway spruce are stressed together with high strength steel bars creating a Stress laminated timber deck (SLTD). Deflections and stresses can be estimated with both finite element models based on orthotropic plate theory as well as with simplified hand calculation methods based simple beam theory. If SLTDs are loaded until failure in the ultimate limit state (ULS), phenomena which generally do not occur in serviceability limit state (SLS) must be taken into account. Slip will occur in the interlaminar surface between the stressed glulam laminations. Once slip has occurred, stress will redistribute between the laminations. A rectangular SLTD was tested for several load levels and pre-stress levels. Deflections were compared with a finite element orthotropic model. These results were also compared with several established design methods. After failure occurred in the ULS, the load was first removed and then applied again, in order to emphasize the reliability of ...
A general assumption reported in the literature is that the structural response of a stress-lamin... more A general assumption reported in the literature is that the structural response of a stress-laminated-timber (SLT) bridge deck is linear until failure. However, few studies of ultimate-load tests (ULTs) on timber bridges have been reported. A full-scale test of a SLT deck (span, 4.9 m; thickness, 270 mm) was performed to obtain the deformations at various prestress levels as well as at the ultimate-load capacity of such a structure. Prior to the ULT, nondestructive tests (NDT) were performed at three different prestress levels. The load was applied as an axle load positioned both centrically and eccentrically. The deflections were about 10% larger at a prestress level of 300 kPa compared with a prestress level of 600 and 900 kPa. For applied loads larger than 150–250 kN, the deflection of the deck was nonlinear at certain positions. This was most likely owing to large concentrated shear forces that resulted in interlaminar slip between the laminates. The limit for linearity seems to be dependent on the applied prestress. A prestress of 600 kPa and an eccentrically positioned load was used for the ULT. Failure occurred at a load level of 900 kN. The existing design codes and new procedures in development may be verified and calibrated against the results in this paper.
Stress-laminated timber (SLT) bridge decks are generally designed using either linear hand calcul... more Stress-laminated timber (SLT) bridge decks are generally designed using either linear hand calculation methods or linear finite-element models. Several studies have shown, however, that the behavior of SLT decks is nonlinear when loaded until failure. In this paper, several linear design methods are compared with one another and with an ultimate load test of a full-scale SLT deck subjected to an eccentric load. Some of the linear hand calculation methods show significant discrepancies in results, depending on the load position. There are also variations in the results from finite-element models, depending on the material properties assigned to the deck. All the design methods failed to predict the deflection of the tested deck when loaded to failure. A larger deflection was observed in the full-scale test than that predicted by the design methods. As a result, the linear design method could underestimate the bending stresses in the deck. Several hand calculation methods are also unable to calculate the transverse forces and moments necessary for design according to Eurocode 5.
Timber and wood-based engineered products are important as structural materials, especially in th... more Timber and wood-based engineered products are important as structural materials, especially in the drive towards sustainable technologies and construction. It is very important to improve the properties of these products, making them more competitive and reliable. This applies particularly to larger, more complicated structures where timber is becoming a realistic alternative to other construction materials. The orthotropic properties of timber are well known - strong and stable along the grain, weak and susceptible to movement across the grain. Combining wood with other materials, to achieve composite action, enables the strength of wood to be realized and its shortcomings to be strengthened or eliminated. COST Action FP1004, “Enhance mechanical properties of timber, engineered wood products and timber structures” provides a network for learning and development in a range of connected topics. This conference will present and record various methods for improving wood with other materials. It brings researchers and practitioners together to learn about various applications, and enables them to take part in discussions about future research and development. The purpose of the COST program is to strengthen Europe and other countries in scientific and technological research, for peaceful purposes, through the support of cooperation and interaction between European researchers. This conference adheres to these principles. It will be an extraordinary opportunity to hear presentations from highly specialist, invited speakers and to participate in debate, in the island of Cyprus, which is located at the crossroads of three continents Europe, Asia and Africa in the Northern-east part of the Mediterranean Sea.
Timber and wood-based engineered products are important as structural materials, especially in th... more Timber and wood-based engineered products are important as structural materials, especially in the drive towards sustainable technologies and construction. It is very important to improve the properties of these products, making them more competitive and reliable. This applies particularly to larger, more complicated structures where timber is becoming a realistic alternative to other construction materials.
The orthotropic properties of timber are well known - strong and stable along the grain, weak and susceptible to movement across the grain. Combining wood with other materials, to achieve composite action, enables the strength of wood to be realized and its shortcomings to be strengthened or eliminated.
COST Action FP1004, “Enhance mechanical properties of timber, engineered wood products and timber structures” provides a network for learning and development in a range of connected topics. This conference will present and record various methods for improving wood with other materials. It brings researchers and practitioners together to learn about various applications, and enables them to take part in discussions about future research and development.
The purpose of the COST program is to strengthen Europe and other countries in scientific and technological research, for peaceful purposes, through the support of cooperation and interaction between European researchers. This conference adheres to these principles. It will be an extraordinary opportunity to hear presentations from highly specialist, invited speakers and to participate in debate, in the island of Cyprus, which is located at the crossroads of three continents Europe, Asia and Africa in the Northern-east part of the Mediterranean Sea.
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Papers by Robert Kliger
The orthotropic properties of timber are well known - strong and stable along the grain, weak and susceptible to movement across the grain. Combining wood with other materials, to achieve composite action, enables the strength of wood to be realized and its shortcomings to be strengthened or eliminated.
COST Action FP1004, “Enhance mechanical properties of timber, engineered wood products and timber structures” provides a network for learning and development in a range of connected topics. This conference will present and record various methods for improving wood with other materials. It brings researchers and practitioners together to learn about various applications, and enables them to take part in discussions about future research and development.
The purpose of the COST program is to strengthen Europe and other countries in scientific and technological research, for peaceful purposes, through the support of cooperation and interaction between European researchers. This conference adheres to these principles. It will be an extraordinary opportunity to hear presentations from highly specialist, invited speakers and to participate in debate, in the island of Cyprus, which is located at the crossroads of three continents Europe, Asia and Africa in the Northern-east part of the Mediterranean Sea.