@inproceedings{HirschmuellerKovrygaUnterbergeretal.2022, author = {Hirschm{\"u}ller, Sebastian and Kovryga, Andriy and Unterberger, Seraphin and Larbig, Harald and Marais, Brendan and Brischke, Christian and van de Kuilen, Jan-Willem and Krey, Adrian}, title = {Laminated veneer lumber made from cement-impregnated veneers}, series = {The 10th European Conference on Wood Modification}, booktitle = {The 10th European Conference on Wood Modification}, editor = {Gerardin, Philippe and Militz, Holger}, pages = {5}, year = {2022}, abstract = {Typically, to improve the fire resistance of wood, chemical substances, including phosphorus, borate, phenols, nitrogen and halogen based compounds, are impregnated into the wooden material. However, due to problems related to the toxic properties of these fire-retardant compounds, new fire-retardancy methods based on a mineralization process have been developed. Cementitious mineralization of wood is a novel and alternative approach for a non-toxic flame retardant, with viable application in laminated veneer lumber. This paper briefly describes the effects of different solid impregnation materials on the thermal properties and fire retardance of beech veneers (Fagus sylvatica L.). Beech veneers were impregnated with a suspension of (i) microfine binder and glycol, (ii) microfine binder mixed with calcium oxalate monohydrate and glycol, and (iii) aluminium hydroxide and glycol, in a vacuum/high pressure process. Single-flame source tests of with different solids impregnated veneers revealed a considerable improvement in flame retardancy of cementitious mineralized beech veneers compared to untreated control specimens.}, language = {en} } @article{MaderebnerGerhaherFlachetal.2017, author = {Maderebner, R. and Gerhaher, U. and Flach, M. and Hirschm{\"u}ller, Sebastian}, title = {Load carrying capacity of screwed CLT wall-ceiling joints with and without elastic supports}, series = {BAUINGENIEUR}, volume = {92}, journal = {BAUINGENIEUR}, pages = {495 -- 502}, year = {2017}, abstract = {Due to the application of elastic interlayers for acoustic decoupling, wood screws to connect timber elements are stressed beneath axial and shear loads additionally by a bending moment. The equations to calculate the load carrying capacity of wood-wood-connections according to the Eurocode 5, lose their validity in case of application of interlayers with low shear resistance. Furthermore, the increasing flexibilities of the joints should be considered for a realistic static modelling. Aim of the present work is to analyze the mechanical load bearing characteristics of wall-ceiling-connections of cross laminated timber with and without elastic interlayers. On the basis of experiments as well as analytical approaches, the load-deformation-behavior is discussed and contrasted to the current standards.}, language = {en} } @inproceedings{HirschmuellerMaraisBrischkeetal.2020, author = {Hirschm{\"u}ller, Sebastian and Marais, Brendan and Brischke, Christian and Krey, Adrian and B{\"o}sing, Janine}, title = {Wood protection with cement - Part 1: Coating matters and durability of cement coated wood}, series = {Proceedings IRG Annual Meeting. IRG/WP 20-60483. 51th IRG Annual Meeting}, booktitle = {Proceedings IRG Annual Meeting. IRG/WP 20-60483. 51th IRG Annual Meeting}, editor = {The International Research Group on Wood Protection,}, publisher = {The International Research Group on Wood Protection 2020}, address = {Stockholm}, pages = {1 -- 25}, year = {2020}, abstract = {The use of wood in geotechnical applications has seen renewed interest. However, concerns related to the durability and service life of wood in ground contact applications remain. Wood has the potential to substitute commonly used steel and concrete in the geotechnical engineering sector, but solutions to extending the service life and maintenance intervals require long-lasting wood protection systems capable of inhibiting fungal and bacterial decay. Cement, one of the constituents of concrete was identified as a potential coating material for wood used in soil stabilisation works. Spruce and beech wood rest rolls from commercial veneer peeling has been identified as a potential source for cement-coated geotechnical wood products. Norway spruce and European beech wood was subsequently used in this study. In this study, a series of tests related to dimensional stability and fungal durability were undertaken to investigate the adhesion of a cement coating to wood and to assess the effect of a cement coating on the resistance to fungal decay. Swelling and shrinkage tests of uncoated specimens were undertaken to investigate dimensional stability. Laboratory fungal durability tests assessed changes in wood durability of specimens coated with a novel, flexural cement coating. Wood impregnated with Polyethyleneglycol-dimethacrylate (PEGDMA) prior to cement coating was investigated to improve wood dimensional stability and reduce cracking of the cement coating under changing wood moisture conditions. Cement coating thickness and delamination tests then assessed the durability of the novel cement coating itself. Results from fungal durability tests showed that a continuous, flexural, and crack-free cement coating was imperative to a wood durability improvement. Double cement-coated spruce wood showed improved resistance to decay by basidiomycetes (Coniphora puteana and Trametes versicolor). Results from swelling and shrinkage tests showed that an improvement in dimensional stability would assist in achieving a durable cement coating and impregnation with Polyethyleneglycol-dimethacrylate (PEGDMA) is one manner to improve dimensional stability and therefore cement adhesion to the wood substrate.}, language = {en} } @phdthesis{Hirschmueller2019, author = {Hirschm{\"u}ller, Sebastian}, title = {Beech circular hollow laminated veneer lumber sections for temporary soil nailing applications}, school = {Technische Hochschule Rosenheim}, year = {2019}, abstract = {Beech Laminated Veneer Lumber (LVL) circular hollow sections for use as temporary geotechnical soil nailing systems are developed within this thesis. Due to their permanent subsoil cement embedment, combined with high water saturation and permanent loading, the timber sections will lose strength and stiffness over time. Taking into account a duration of load factor for permanent loading of two years, it is recommended to reduce the short term tensile and bending strength of beech circular hollow sections to be used as geotechnical soil nails by 80\%. In addition to the determination of material properties on small, clear specimens and full-sized cross-sections, an appropriate surface gluing quality between the veneers is fundamental to this subsoil application of the permanently cement-embedded, engineered timber product. The circular cross-section geometry and the permanently high-alkaline environment of the structural member is not covered by presently standardised testing and conditioning methods for examining LVL surface bond line quality. Standardised test methods had to be modified to determine bonding parameters for the circular, hollow LVL sections. As cement grout ensures the bond between the wooden nails and soil for the mobilisation of a soil reinforcement effect, a reliable connection between cement and wood is required. However, soluble wood constituents may inhibit cement hydration in the contact surface between the timber nails and cement. Pull-off tests on clear LVL specimens with different cement and wood surface modifications as well as the results of large-scale push-out tests are therefore presented. But to permanently ensure the contact between the wood and cement, a high degree of saturation above wood fibre saturation is necessary to keep the hollow sections in a swollen state without moisture-dependent wood shrinking. As no publications of wood moisture development in subsoil were available, long-term tests were performed, measuring the moisture content of subsoil-stored LVL in dependence on the soil moisture content, the suction and the precipitation during a time span of one year. Besides a negative cement influence on the material strength, a positive effect of cement coating on subsoil fungal destruction was realised, resulting in a significantly increased lifetime of cement-coated wood compared to uncoated wood. For temporary soil nailing applications, fungal wood deterioration was found to be of minor importance. But the reduced material strength due to a severe alkaline attack of wood demands a re-consideration of current soil nailing design methods, usually based on a mechanical limit equilibrium analysis of a rigid body motion where just tensile forces of the reinforcement elements are considered, and accompanying forces like bending moments and shear forces are neglected. Distributed fibre optic strain measurements of a steel-reinforced soil nail wall during a time span of six weeks reveal considerable nail curvatures, which are negligible in the case of ductile soil nails with low diameters, but are a significant factor for beech circular hollow laminated veneer lumber sections of larger diameters and brittle material behaviour.}, language = {en} } @article{HirschmuellerPravidaMarteetal.2019, author = {Hirschm{\"u}ller, Sebastian and Pravida, Johann and Marte, Roman and Flach, Michael}, title = {Long-term material properties of circular hollow laminated veneer lumber sections under water saturation and cement alkaline attack}, series = {Wood Material Science and Engineering}, volume = {14}, journal = {Wood Material Science and Engineering}, number = {3}, pages = {142 -- 156}, year = {2019}, abstract = {Innovative beech laminated veneer lumber (LVL) circular hollow sections for the use as temporary geotechnical soil nailing systems are currently being developed. Due to the permanent subsoil cement embedment, combined with high water saturation and permanent loading, the timber sections will lose strength and stiffness over time to a degree currently unknown. This paper presents the tensile and bending material properties of flat and curved beech LVL under various periods of immersion in a water-cement grout solution aiming at inducing both water saturation and long-term alkaline attack of the timber. In total, 824 and 279 samples were tested in tension and bending, respectively. Results show that samples manufactured from 3 mm thick veneers result in tensile strength and stiffness 17\% and 24\% higher, respectively, than samples manufactured from 2 mm thick veneers. A reduction in the initial bending and tensile strength of up to 70\% was found after 90 days of water saturation and cement contact. Taking into account a duration of load factor for permanent loading of two years, it is recommended to reduce the short-term tensile and bending strength of beech circular hollow sections to be used as geotechnical anchors by 80\%.}, language = {en} } @inproceedings{MonsbergerLienhartMarteetal.2018, author = {Monsberger, Christoph and Lienhart, Werner and Marte, Roman and Hirschm{\"u}ller, Sebastian}, title = {Monitoring of soil nailed slope stabilizations using distributed fiber optic sensing}, series = {Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2018}, volume = {10598}, booktitle = {Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2018}, editor = {Sohn, Hoon}, doi = {10.1117/12.2296674}, year = {2018}, abstract = {Soil nailing systems are a common way to stabilize slopes and construction pits. Their design is usually based on the mechanical equilibrium of a rigid body motion and therefore, only tensile stresses are considered and accompanying forces like bending (shear stresses) in the soil nails are neglected. Continuous strain measurements along nails could verify this assumption, but may not be performed using conventional sensing technologies. This paper reports about monitoring of a soil nailed slope stabilization using distributed fiber optic sensing. Soil nails in different anchoring horizons were instrumented and autonomously monitored over several weeks, in which the construction pit was excavated continuously. After the excavation, the final load bearing capacity of one selected nail was determined within a classical geotechnical load test. In addition to the field measurements, the bending behavior of the instrumented nail system was analyzed under laboratory conditions. The presented studies demonstrate the high potential of distributed fiber optic sensing systems and their capability to extend traditional measurement methods in foundation engineering applications.}, language = {en} } @article{HirschmuellerPravidaMarteetal.2018, author = {Hirschm{\"u}ller, Sebastian and Pravida, Johann and Marte, Roman and Flach, Michael}, title = {Adhesive properties of laminated veneer lumber poles for use in temporary soil nailing: development and evaluation of a test method for curved structures in a high-alkaline environment}, series = {Wood Science and Technology}, volume = {52}, journal = {Wood Science and Technology}, number = {4}, editor = {Springer,}, pages = {1061 -- 1092}, year = {2018}, abstract = {Innovative circular, hollow, laminated veneer lumber (LVL) beech sections for use as temporary geotechnical soil reinforcement members are currently being developed. Appropriate surface gluing quality between the veneers is fundamental to this subsoil application of the permanently cement-embedded, engineered timber product. The circular cross-section geometry and the permanently high-alkaline environment of the structural member is not covered by presently standardized testing and conditioning methods for examining LVL surface bond line quality. The sample conditioning and tensile shear test method compliant with EN 302-1 (Adhesives for load-bearing timber structures—test methods—part 1: determination of longitudinal tensile shear strength, European Committee for Standardization, Brussels, 2013) was modified to determine bonding parameters for circular, hollow LVL sections. Bond line curvature, groove cutting depth and sample geometry were found to greatly influence stress distribution, percentage of wood failure and tensile shear strength. Short-term alkaline treatment of test samples did not significantly influence the bonding performance, wood failure percentage, tensile shear strength and fracture patterns. To improve tensile shear strength, adhesives with different material rigidities were used and compared. An orthotropic, elastic numerical analysis revealed a greater influence of adherent elasticity than adhesive elasticity on the stress distribution within the bond line. With regard to determining the bond line integrity of curved veneer poles, a sample geometry compliant with EN 302-1 (2013) was developed and numerically evaluated.}, language = {en} } @inproceedings{HirschmuellerMartePravida2016, author = {Hirschm{\"u}ller, Sebastian and Marte, Roman and Pravida, Johann}, title = {Laminated veneer lumber poles for temporary soil nailing - investigation of material properties}, series = {Proceedings of the World Conference on Timber Engineering. World Conference on Timber Engineering. Vienna, 22.-25.08. Vienna}, booktitle = {Proceedings of the World Conference on Timber Engineering. World Conference on Timber Engineering. Vienna, 22.-25.08. Vienna}, editor = {Eberhardsteiner, Josef and Winter, Wolfgang and Fadai, A. and P{\"o}ll, Martha}, year = {2016}, abstract = {Within a current research project at Rosenheim University of Applied Sciences and Graz University of Technology the possibilities of using beech wood laminated veneer lumber poles as soil anchors for temporary soil nailing systems are investigated. Therefore tensile and bending properties of laminated veneers with high moisture and permanent cement contact concerning the influence of veneer bending rectangular to the fibre are determined. For investigation of material properties under different climate conditions tensile tests on small and faultless single beech wood veneers as well as tensile tests on 6 layered 3 mm samples and 9 layered 2 mm samples were carried out. Therefore all samples were stored in extreme climate conditions like high moisture content and permanent cement contact. Six layered samples with 3mm thick veneers show a slightly higher strength and stiffness under dry conditions as well as at a moisture content of the samples above fibre saturation. A strength reduction factor concerning temporary geotechnical applications is suggested which considers the influence of long term loading, veneer bending, water saturation and cement destruction on tensile properties of laminated veneer lumber poles.}, language = {en} } @article{HirschmuellerMartePravidaetal.2018, author = {Hirschm{\"u}ller, Sebastian and Marte, Roman and Pravida, Johann and Flach, Michael}, title = {Inhibited wood degradation of cement-coated beech Laminated Veneer Lumber (LVL) for temporary in-ground applications.}, series = {European Journal of Wood and Wood Products}, volume = {76}, journal = {European Journal of Wood and Wood Products}, number = {5}, editor = {Springer,}, pages = {1483 -- 1494}, year = {2018}, abstract = {This paper investigates the long-term tensile properties of laminated veneer lumber (LVL) beech sections coated with cement and exposed to fungal decay. A set of LVL coupon (dog-bone) samples was stored in compost, tested in tension after 6 and 12 months and compared to reference samples stored at 20 °C and 65\% relative humidity. Results showed that after 26 weeks of compost exposure, a fungus of the Ascomycota genus was identified in cement-coated samples using a molecular biology polymerase chain reaction (PCR) technique, which analyses the internal transcribed spacer (ITS) region of the ribosomal DNA. However, no visual deterioration was noticed. Still in cement-covered samples and after 12 months of exposure, a common white rot fungus was determined by DNA chip technology, but no fungal wood decay was visible in areas where the applied coating had a thickness of at least 5 mm. Decay in uncoated LVL samples was significant with the samples having an average residual strength equal to 7\%. This compares to the tensile strength of coated samples, which only decreased by 65\% relative to the reference samples. Strength and stiffness of coated samples did not differ significantly between 6 and 12 months of exposure. Preliminary investigations tend to show that the strength reduction in cement-coated samples is due to an alkaline degradation of the wood. The observed influence of the coating thickness on the visual fungal decay can probably be ascribed to the protection mechanism due to a physical fungal barrier with a high pH.}, language = {en} } @inproceedings{HirschmuellerPravidaMarteetal.2016, author = {Hirschm{\"u}ller, Sebastian and Pravida, Johann and Marte, Roman and Flach, Michael}, title = {Laminated veneer lumber poles for use in temporary soil nailing. Investigation of adhesive properties.}, series = {Holzbau Forschung und Praxis. 6. Doktorandenkolloqium 2016}, booktitle = {Holzbau Forschung und Praxis. 6. Doktorandenkolloqium 2016}, editor = {Universit{\"a}t Stuttgart,}, year = {2016}, abstract = {Within a current research-project the possibility of using laminated veneer lumber beech wood poles as temporary soil anchors in foundation engineering is investigated. Within this project adhesive properties of laminated veneer lumber beech wood poles are determined. For use in temporary ground applications the influence of veneer bending, veneer thickness and intensive cement contact is concerned. As standard version two different adhesive systemsmelamine formaldehyde resin (MUF) and a 1-component polyurethane adhesive (PUR) were investigated and compared. Melamine formaldehyde resin glued samples with 3 mm thick veneers and 1.0N/mm² press force show a higher tensile shear strength but also a higher adhesive failure percentage than polyurethane glued samples. In case of melamine formaldehyde resins the closed time has a great influence on bond line quality. A long closed time reveals a low penetration of adhesive in the cells and a low embedding on the wood surface. For curved structures best results were achieved with a bonding pressure of 1.0 N/mm². A significant difference in strength between the concerned MUF and PUR adhesive system was not recognized.}, language = {en} }