Miroslav Premrov

Reinforcing methods for composite timber frame–fiberboard wall panels

This paper presents different possibilities on how to reinforce timber frame wall panels, which are mainly used as load-carrying capacity elements in the construction of prefabricated timber structures. These walls can be treated as composite elements composed of a timber frame and fiber-plaster boards. As the boards are the weaker part of the system they need to be somehow reinforced in order to assure the resistance and ductility of the elements especially in multi-level buildings located in seismic or windy areas. The aim of this research is to determine the differences in resistance and ductility between elements, reinforced using two different methods. Whilst the first, using additional fiberboards, does not improve the resistance and especially the ductility in the contended sense, it is more convenient for finding a solution when inserting diagonal steel strips, which are fixed to the timber frame.

DEFORMATION MEASUREMENT OF A STRUCTURE WITH CALCULATION OF INTERMEDIATE LOAD PHASES

Abstract At the Centre for Geodesy of the University of Maribor, Slovenia, we engaged in the measurement and analysis of displacements for the last ten years. We wanted to find the connections between the displacements and the applied loads. Therefore, reliable and accurate results were needed. A reinforced-concrete plate was loaded to 42 kN in pre-calculated steps and the resulting deformations measured by three independent methods. The results were compared to analytical ones. The analyses and calculations of the most suitable method were implemented. An electronic tacheometer, photogrammetry and a pressure length transducer on the hydraulic cylinder were used.

Influence of openings on horizontal load-carrying capacity of timber-frame wall elements with fibre-plaster sheathing boards

The paper presents an experimental analysis of timber - framed wall panels with openings, coated with single fibre-plaster boards fastened to a timber frame. The present study is a continuation of the research work realized in the last years in reinforcing of the prefabricated timber-frame wall panels without any openings. The aim of the study presented here was to provide the information about the influence of the openings on the walls racking load-carrying capacity as well as on the horizontal stiffness of the timber-frame wall panels. The tests were carried out on three groups of full-scale wall panels with different areas of openings. The measured results were compared to the results of wall panels without openings. Subsequently, the strength/stiffness ratios, defined as the ratios of strength/stiffness of wall panels with openings to those of no-opening wall panels were calculated. Finally, the obtained results were compared to three analytical procedures from the literature, namely the equations proposed by Yasumura and Sugiyama, by the Method B from Eurocode 5 and by the equations presented in Supek, Dujic and Zarnic. The presented experimental study also emphasizes the conclusion that the timber-frame wall panels containing an opening may be accounted to contribute to the overall horizontal load-carrying capacity, especially when a considerable part of the structure is made of such panels.

Shape and discrete sizing optimization of timber trusses by considering of joint flexibility

The paper presents the shape and discrete sizing optimization of timber trusses with the consideration of joint flexibility. The optimization was performed by the Mixed-Integer Non-linear Programming (MINLP) approach. In the optimization model an economic objective function for minimizing the structures self-manufacturing costs was defined. The design conditions in accordance with Eurocode 5 were considered as optimization constraints. The internal forces and deflections were calculated by finite element analysis. The structural stiffness matrix was composed by considering fictiously decreased cross-sectional areas of all the flexibly connected elements. The cross-section dimensions and the number of fasteners were defined as discrete sizing variables, while the joint coordinates were considered as shape variables. The applicability of the proposed approach is demonstrated through some numerical examples, presented at the end of the paper.

Energy-Efficient Timber-Glass Houses

The introductory chapter sets a background frame and reveals the main reasons which encouraged the authors into researching the topic of energy efficiency of buildings. Section 1.2 is a brief overview of the authors’ activities in the fields of energy efficiency and timber-glass construction, while Sect. 1.3 shortly outlines the content of the book. 1.1 Why Dealing with the Topic of Timber-Glass Buildings? Climate changes of the last few decades do not only encourage researches into the origins of their onset, but they also mean a warning and an urgent call for a need to remove their causes and alleviate the consequences affecting the environment. Construction is, besides the fields of transport and industry, one of the main users of the prime energy from fossil sources, which makes this sector highly responsible for the implementation of climate-environmental policies. Activities linked to energy efficiency and the related use of renewable sources of energy are not infrequent in Slovenia, nevertheless, the fields of architecture and construction still offer numerous possibilities of reaching the goals set by directives on energy efficiency in buildings. Looking for alternative, eco-friendly solutions in residential and public building construction remains our most vital task, whose holistic problem solving requires knowledge integration. The present book represents merely a piece in the jigsaw of different kinds of knowledge that will need to undergo mutual integration and upgrading in order to be used in designing an optimal energy-efficient timber-glass building. The current work can be useful to designers and future experts in their planning of optimal energy-efficient timber-glass buildings. The study is based on using timber and glass which used to be rather neglected as construction materials in certain historical periods. Nevertheless, timber achieved recognition as one of the V. Zegarac Leskovar and M. Premrov, Energy-Efficient Timber-Glass Houses, Green Energy and Technology, DOI: 10.1007/978-1-4471-5511-9_1, Springer-Verlag London 2013 1 oldest building materials in different countries worldwide. With the appearance of cast and wrought iron in the eighteenth century along with the subsequent use of reinforced concrete and steel in the twentieth century, which all enabled mass production and construction of larger structural spans, timber lost its dominance as a building material McLeod [1]. Only in recent decades has timber been rediscovered, partly due to the contemporary manufacture of prefabricated timber elements and partly owing to high environmental potential of this renewable natural building material. Although glass has been used to enclose space for nearly two millennia, the roots of modern glass construction reach back to the nineteenth century green houses in England, witnessing one of the first instances of using glass as a loadbearing structural element in combination with the iron skeleton, Wurm [2]. Throughout the twentieth century, glass was no longer used as load-bearing element, but rather as an aesthetic element of the building skin with strongly emphasized potential of transparency enabling natural lighting and visual contact of the interior and exterior space. In contrast to the listed positive properties, glass used to be treated as the weakest point of the building envelope from the thermal point of view. Dynamic evolution of the glazing in the last 40 years resulted in insulating glass products with highly improved physical and strength properties, suitable for application in contemporary energy-efficient buildings, not only as material responsible for solar gains and daylighting, but also as a component of structural resisting elements. With suitable technological development and appropriate use, timber and glass are nowadays becoming essential construction materials as far as the energy efficiency is concerned. Their combined use is extremely complicated, from both the constructional point of view as well as from that of energy efficiency and sets multiple traps for designers. Moreover, a novelty value of modern glass is seen in its being treated as a load-bearing material replacing the elements (diagonal elements, sheathing boards) which normally provide horizontal stability of timber structures. A good knowledge of advantages and drawbacks of timber-glass structures is thus vitally important. 1.2 Authors’ Work in the Field of Energy Efficiency and Timber-Glass Construction Within a selection of most important issues, our activities in the frames of the University of Maribor, Faculty of Civil Engineering, focus primarily on research work and its application into practice, on educating students and the broader public (Fig. 1.1). Our scientific work in the field of energy efficiency of the buildings concentrates on researching design models of energy-efficient timber-glass buildings, which combines the knowledge of architecture, timber-glass construction and building physics. We strive to link the findings of our research work with practice 2

Numerical analysis of sheathing boards influence on racking resistance of timber-frame walls

This paper provides a numerical analysis of sheathing boards influence on racking resistance of timber-frame walls coated with single sheathing boards fastened to a timber frame. Worldwide, the walls are usually broadly used as main bearing capacity vertical elements in prefabricated residential timber buildings. Designers or producers usually face the important dilemma of using the best sheathing board with regard to the height and location of a building. The presented research thus aims at comparing the results obtained through calculations made on test samples covered with either fibre-plaster or wood-based sheathing boards. Therefore, the presented conclusions, supported by the measured results, propose some important indications in behaviour of the timber-framed wall elements under a horizontal load covered with different sheathing boards and present some useful recommendations in designing of tall timber-framed buildings located on heavy windy or seismic area.

Solving exterior problems of wave propagation based on an iterative variation of local DtN operators

This paper discusses the problem of wave reflection from the fictitious boundary, with particular regard to the higher harmonic modes. This problem occurs when solving the wave equation in exterior domains using an asymptotic local low-order Dirichlet-to-Neumann (DtN) map for computational procedures applied to a finite domain. We demonstrate that the amplitudes of the reflected fictitious harmonics depend on the wave number, the location of the fictitious boundary, as well as on the local DtN operator used in the computations. Moreover, we show that a constant value of the asymptotic local low-order operator cannot sufficiently eliminate the amplitudes of all reflected waves, and that the results are poor especially for higher harmonics. We propose therefore an iterative method, which varies the tangential dependence of the local operator in each computational step. We only discuss some logical and interesting choices for the operators although this method permits several possibilities on how to vary the operator. The method is simple to apply and the presented examples demonstrate that the accuracy is considerably improved by iterations.

Design Approach for the Optimal Model of an Energy-Efficient Timber Building with Enlarged Glazing Surface on the South Façade

Abstract This paper presents the reasonability of using an increased proportion of glazing surfaces in prefabricated timber-frame buildings with a special focus on energy efficiency by using an enlarged glazing area in the south façade. The research is based on a case study of a two-storey house built in a prefabricated timber-frame structural system taking the climate data for Ljubljana into consideration. Parametric analysis is performed on the variation of an increased proportion of the glazing surfaces impact in the south side of the building according to the total surface of the south façade (AGAW) as a basic variable. The analysis was carried out on different exterior wall elements having different thermal properties, while the rest of the parameters, such as the ground plan of the model as well as the active systems, roof and floor slab assemblies, climate condition, etc. remain constant. The basic theoretical contribution of the presented research is the transformation of a complex energy related problem to only one single independent variable (Uwall-value) which becomes the only variable parameter to determine the optimal glazing area size value (AGAWopt) for all contemporary prefabricated timber construction systems.

Design approach for the optimal model of an energy-efficient timber building with various glazing types and surfaces on the south façade

The paper presents the reasonability of using an increased proportion of glazing surfaces in prefabricated timber buildings with a special focus on energy efficiency by using an enlarged glazing area on the south facade of the object. The research is based on a case study of a two-storey house built in a prefabricated timber-frame structural system taking the climate data for Ljubljana into consideration. Parametric analysis is performed on a variation of an increased proportion of the glazed surfaces’ impact on the south side of the building according to the total surface of the south facade (AGAW) as a basic variable. The analysis was carried out on different exterior wall elements having different thermal properties, while the rest of the parameters, such as the ground plan of the model as well as the active systems, roof and floor slab assemblies, climate condition, etc. remain constant. The impact of different types of glazing with various Uglass-values is additionally studied. The basic practical contribution of the study is that the results presenting the determined function for the optimal south oriented glazing size (AGAWopt) offer us the opportunity of selecting the optimal way of energy-efficient renovation of existing timber-frame housing with a possible combination of improving the thermal properties of the external walls with the installation of an additional insulation layer (decreasing U-wall value) and of the optimal of glazing area size on the south-oriented facade, which is, in the case of a lower Uwall-value, noticeably lower.

Wave motion in infinite inhomogeneous waveguides

The analysis of wave motion in infinite homogeneous waveguides, having a complicated cross-section and/or an irregular inclusion, is a rather difficult task for the majority of available methods, especially when striving for accurate results. In contrast, this presented procedure performed in the frequency domain, is simple to apply. It yields correct results because the radiation conditions are considerably accurately satisfied, and it offers a clear parametric insight into wave motion. This procedure uses the FE modelling of an analysed section of the waveguide. It is based on the decomposition of wave motion, distinguishing propagating and non-propagating wavemodes by solving the eigenvalue problem. The presented examples demonstrate the effectiveness of this procedure, whilst a comparison between computed and analytical results demonstrates its accuracy.