Academic literature on the topic 'Steel-timber structures'

ABSTRACT THE PERFORMANCE OF MEDIUM AND LONG SPAN TIMBER ROOF STRUCTURES: A COMPARATIVE STUDY BETWEEN STRUCTURAL TIMBER AND STEEL ERTASTAN, Evren M.S, in Building Science, Department of Architecture Supervisor: Assoc. Prof. Dr. Erc&uuml<br>ment ERMAN December 2005, 174 pages This thesis analyzes the performance of structural timber and steel in medium and long span roof structures. A technical background about roof structures including structural elements and roof structure types, span definitions, and classification of roof structures are discussed. Roof structures are detailed with traditional and the contemporary forms. The thesis comprises the comparison between structural timber and steel by using structural, constructional and material properties. Structural forms and the performance of timber and steel are discussed. The research also includes the roof structures built with structural timber in Turkey, application, marketing and examples in Turkey are indicated. In the conclusion part the performance criteria of timber and steel are summarized, the researcher has prepared a table to compare the performance of timber and steel. Keywords: Timber, Steel, Roof, Structure, Span

Thesis: M. Eng., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, May, 2020<br>Cataloged from the official PDF of thesis.<br>Includes bibliographical references (pages 41-43).<br>Topology optimization in structural design is still a relatively new tool. Most existing research on truss and frame structures focuses on single material applications, and the developments of ground structure-based topology optimization in multi-material structures are limited. This research presents a truss topology optimization algorithm that designs with a mix of glue-laminated timber (GLT) and steel elements. The motivation behind allowing the choice of both these materials is to utilize the strengths of each material in both tension and compression. In addition, this work seeks to include environmental consideration, by incorporating in the algorithm that timber has a smaller embodied carbon coefficient (ECC) compared to steel. This work uses the ground structure approach to truss topology optimization and designs are generated and compared using (i) a minimum compliance and (ii) a stress-constrained algorithm.<br>The algorithms are constructed such that both the area and a choice of material is made for each element in the ground structure. Both frameworks use fmincon in MATLAB as the gradient-based optimizer. The Solid Isotropic Material with Penalization (SIMP) interpolation is used to relate elastic modulus and embodied carbon for two materials with respect to normalized density variables. To demonstrate the versatility of this design methodology, designs obtained from different objectives and different constraints are presented and compared. We find that, for minimum compliance objectives, the weight-constrained problem produced all-steel truss solutions, while global warming potential (GWP)-constrained problem produced all-timber truss solutions. These results align with our expectations based on material stiffness properties.<br>For the stress-constrained problem with minimum GWP objectives, the solutions obtained from two modeling assumptions were compared: (i) with real material stress constraints and (ii) with modified stress constraints, where timber was considered as a compression-only material and steel as a tension-only material. Surprisingly, we find that the solutions obtained with the real stress limits are more polluting than the modified stress limit solutions. While the modified stress solutions placed steel in tension and timber in compression for the most environmentally friendly design, the real stress solutions generally favored steel over timber. This is believed to be caused by the nonlinearities introduced through the SIMP interpolation.<br>by Ho Yin Ernest Ching.<br>M. Eng.<br>M.Eng. Massachusetts Institute of Technology, Department of Civil and Environmental Engineering

<p>Joints are critical parts of timber structures, transmitting static and dynamic forces between structural members. The ultimate behavior of a loaded building depends strongly on the structural configuration and the capacity of the joints. The collapse of a whole building or less extensive accidents that may occur is usually starting as a local failure inside or in the vicinity of a joint. Such serious failures have recently occurred in our Nordic countries. Especially the collapse of two large glued laminated timber structures clearly indicates the need of an improved joint design. The trend toward larger and more complex structures even further increases the importance of a safer design of the joints.</p><p>An aim of this partly experimental and partly numerically based thesis has been to investigate if steel-to-timber dowel joints are affected by moisture-induced stresses. The experimental results showed that the load-bearing capacity of the joints is reduced by such a moisture influence. Most of the decrease in load-bearing capacity observed was found in joints initially exposed to restrained shrinkage deformations caused by the presence of dowel fasteners in the joint area. The load-bearing capacity was, however, also found to decrease in joints exposed to an initial decrease in moisture without any fasteners present in the specimens during storage before loading. An explanation of this unexpected behavior is that moisture gradients cause tensile stresses. It is shown by numerical simulations that the moisture-induced stresses are so large that they may have a considerable influence on the joint behavior.</p><p>Use of contact-free measurement methods, used in some of the experimental tests, was in many ways found to be superior to traditional measurement techniques, but was also found to be a valuable complement to the numerical analysis performed. From numerical results obtained in combination with results from contact-free measurements several observations of considerable interest were made. For dowel-type joints loaded in tension parallel to the grain a strongly non-uniform strain distribution was found in the joint area. It was further observed that the shear and tensile strains were concentrated close to the fasteners in the joint area. These concentrations will influence the failure mode of the joint. A general observation was that the larger sized joints failed in a brittle manner.</p><p>Keywords: constraint stresses, contact-free measurement, dowel-type joints, humidity variations, moisture-induced deformations, timber structures</p>

Joints are critical parts of timber structures, transmitting static and dynamic forces between structural members. The ultimate behavior of e.g. a building depends strongly on the structural configuration and the capacity of its joints. The complete collapse of a building or other less extensive accidents that may occur usually start as a local failure inside or in the vicinity of a joint. Such serious failures have recently occurred in the Nordic countries. Especially the collapses of two large glued-laminated timber (glulam) structures clearly indicate the need of an improved joint design. The trend toward larger and more complex structures even further increases the importance of a safer design of the joints. One aim of this partly experimentally and partly numerically based work has been to investigate if the short term capacity of steel-timber dowel joints loaded parallel to the grain is affected by an initial drying exposure. The experimental results showed that the load-bearing capacity of the joints is indeed reduced by such moisture changes. Moisture induced stresses was mentioned to be the explanation. The key point is that the climates chosen in the present work (20°C / 65% RH and 20°C / 20% RH) are equivalent to service class 1 according to EC5 (Eurocode 5 2004). Thus, EC5 predicts no decrease in load-bearing capacity, in relation to the standard climate used during testing. A decrease in load-bearing capacity in the range of 5-20%, which was found in the present work, is of course not negligible and, therefore, there could be a need to introduce the effect of drying in design codes. Because similar results were also observed for a double-tapered glulam beam, further work should consider timber structures in general. Two numerical methods in order to predict the capacity of multiple steel-timber dowel joints loaded parallel to the grain were tested in the thesis. For the first method, where fracture mechanics (LEFM) concepts were implemented, a good correlation with the experimental results was seen. Also for the second method, where the capacity for a single dowel-type joint as given in EC5 was used as a failure criterion, a good correlation to traditional EC5 calculations of multiple dowel-type joints was seen. One advantage of using numerical methods in design is that the capacity of the joint can be calculated also for cases when the dowels are placed in more complex patterns. From both a structural and an architectural point of view this can be very important. In addition, such numerical methods are effective tools for the structural engineer when considering complicated loading situations in joints, i.e. eccentric loading giving moments in the joint.

In the light of today’s effort to achieve sustainable future of the planet, timber as building material makes a comeback on the construction market. Since the requirements on the buildings and the internal comfort increase, there is a need for finding new solutions and products; one of them is cross-laminated timber (CLT), which has the potential to be used for high-rise buildings due to its mechanical properties. The aim of this work was to study the vibration performance of CLT floors as it is often the governing factor in design of CLT structures unlike for other common building materials. The orthotropic mechanical properties of CLT were determined by the shear analogy method and verified with a finite element (FE) model of a simply supported beam compared to hand calculations of shear forces, bending moments and deflections. The properties based on Timoshenko’s approach were evaluated as less precise regarding the deflection. The non-composite structural behaviour of a steel-CLT hybrid floor structure was predicted for FE dynamic analysis based on a comparison between modelling exercise and hand calculations. Two different methods, the Concrete Society (SC) and Steel Construction Institution (SCI) methods, both seemed to be applicable for determination of the response factor first since the mechanical properties are not used as input in the calculations. These two methods differ in certain aspects, and based on FE analysis of simply supported slab even the resulting response factor for the CLT differs significantly. Moreover, the hand calculation results were similar to those of the FE analysis for the CS method, but in less agreement for the SCI method. Nevertheless, it is not recommended to reject the latter method based on this study and further studies should be performed on real structures with response factor known from on-site measurements. A part of the first floor of Canary Wharf College was modelled and analysed, and previous measurements of the frequency and response factors enabled a validation of some assumptions. The SCI approach showed to be inadequate for this type of structure and therefore only the CS method was applied further. Analysis of the floor structures supported by walls demonstrated similar results from both the measurements and the dynamic analysis. However, if the floor slab was supported by beams, the response factor was significantly overestimated although on the conservative side. This difference suggests that the modelling of such conditions are not satisfactory. The CS method appears to assess correctly the magnitude of the response factor for CLT floors supported by walls but overestimates it in case of beam supports. The first finding shall be confirmed through analysis of other structures and a more extensive research should focus on the latter one to determine more exact behaviour of the model under different conditions.

The demand for complex structures and the urge to perform more detailed structural analyses in an early stage of the project design phase has increased the use of parametric design in the construction sector, especially among architects and structural engineers. Also, an increasing demand for sustainable structures is creating pressure on engineers and architects to design optimized structures that consume as little resources as possible. Keeping these demands in mind, this thesis tries to uncover the benefits of parametric design and optimization by applying these processes to industrial roof truss structures.The primary objective of the thesis is to investigate the feasibility and reliability of parametric design and optimization processes in real-life designs. For this purpose, a parametric algorithm has been developed in the visual programming software Grasshopper 3D. The workflow performs structural analysis and design verification on a parametric FE-model using the FEA software for parametric engineering, Karamba 3D in combination with Python where standards for design verification were scripted. These procedures were developed to be applied on both steel and timber truss structures. The workflow then performs a constrained cross-sectional and geometrical optimization of the truss structures. For the optimization process, the plug-in Galapagos have been used which uses evolutionary and simulated annealing techniques.After analyses of different cases and on comparison of the results from the model response verification, the resulting models showed that the workflow and analysis procedure was capable of obtaining a solution that is more effective and as reliable as the traditional structural analysis procedures and thus can be used for real case. When used during preliminary design, the parametric design procedure displayed great potential in saving time, thus saving resources and cost which paves a promising path for implementations in this sector.

Les structures hybrides acier-bois sont de plus en plus utilisées dans le secteur de la construction. Elles offrent plusieurs avantages pratiques en tant que solutions durables avec des capacités de charge et des résistances au feu élevées. Cependant, en raison de la conductivité thermique de l'acier et de la diminution de ses performances mécaniques à haute température, les structures en acier doivent être protégées contre le feu. Le bois, bien que combustible, a un effet isolant et peut être utilisé comme protection passive de l'acier en vue de maintenir sa résistance mécanique aussi longtemps que possible. Les travaux menés dans le cadre de la thèse visent à analyser le comportement thermique d'éléments hybrides acier-bois en combinant essais d’exposition au feu et modélisation numérique. Les essais sont réalisés dans un four construit au laboratoire permettant de monter à une température de 1200 °C. Ils permettent d’obtenir l'évolution de la température sur les surfaces des profilés en acier et dans le bois. Ainsi, des thermocouples sont installés sur la surface des profilés en acier et à différentes profondeurs dans les éléments en bois. Les essais au feu ont été réalisés sur différentes associations acier-bois en utilisant des sections en acier (T et I) et différentes essences de bois. Les résultats montrent que le bois offre une protection significative à la section en acier, principalement au profilé IPE entièrement encapsulé. Le bois se comporte comme un matériau isolant qui réduit de manière significative l'augmentation de température de l'acier. Cette solution contribue au développement de la protection passive des structures en acier en utilisant des matériaux biosourcés. Les résultats expérimentaux sont comparés à ceux obtenus par des simulations thermiques à l'aide du logiciel Abaqus. La comparaison montre que le modèle numérique peut être utilisé pour évaluer l'augmentation de température dans l'élément en acier protégé par du bois dans des conditions de haute température<br>Steel-timber hybrid structures are becoming more and more common in the construction industry. They offer high practical advantages as sustainable solutions with high load-bearing capacities and fire resistance. However, due to steel thermal conductivity and the decrease of mechanical performance with high temperatures, steel structures need to be protected in case of fire. Wood is occasionally used as passive protection of steel to maintain its mechanical strength as long as possible with the aim to prevent structural collapse under fire. This thesis aims to analyse the thermal behaviour of hybrid steel-timber elements through experimental tests and numerical modelling. Experiments in the furnace are performed to obtain the evolution of temperature on the steel profile surfaces and inside the timber element. Thus, thermocouples are installed on the steel profile surface and different depths of timber elements. The fire tests were performed on various steel-timber combinations using T and I steel cross-sections with various wood species. A high-temperature furnace up to 1200 °C built in the laboratory was used. The results show that wood provides significant protection to the steel cross-section mainly the fully encapsulated IPE profile. Wood behaves as an insulating material that significantly reduces the temperature rise in steel. This solution contributes to the development of passive protection of steel structures using bio-based materials. The experimental results are compared to those obtained through thermal simulations using Abaqus software. The comparison shows that the numerical model can be used to evaluate the temperature increase in the steel element protected by timber in high-temperature conditions

The theme of the master´s theses is to design a wooden structure of city theater with internal steel construction. The concept of wooden structure is developed in two versions according to standard ČSN EN. The theses solve the static effect of the construction and design of individual parts and materials. Theater has dimensions 49.0 x 25.6 m, max. height of 12.5 meters. The construstion is devise to withstand a weight and applicability. The supporting structure of the roof is solved using by 13 arched plate girders. The second variant is designed as arched truss girders. The gable wall is glassed-in, glass envelopes support by wooden structure with columns and side runners. The work also includes solutions for joins and construction details. The structure was solved in the program RSTAB Dlubal 8. The assessment of the components was done using additional module TIMBER Pro. First Variant of plate girder was checking by manual report. The work includes drawings.

This thesis describes the influence of thermal mass on the space conditioning energy consumption and indoor comfort conditions of multi-storey buildings with concrete, steel and timber structural systems. The buildings studied were medium sized educational and commercial buildings. When calculating a building’s life-cycle energy consumption, the construction materials have a direct effect on not only the building’s embodied energy but also on the space conditioning energy. The latter depends, amongst other things, on the thermal characteristics of the building’s materials; thermal mass can also be an influence on comfort conditions in the building. A modelling comparison has been undertaken between three very similar medium-sized buildings, each designed using structural systems made primarily of timber, concrete and steel. The post-tensioned timber version of the building is a modelled representation of a real three-storey educational building that has been constructed recently in Nelson, New Zealand. The concrete- and steel-structured versions have been designed on paper to conform to the required structural codes and meet, as closely as possible, the same performance, internal space layout and external façade features as the real timber-structured building. Each of these three structurally-different buildings has been modelled with two different thermal envelopes (code-compliant and New Zealand best-practice) using a heating, ventilating and air conditioning (HVAC) system with heating only (educational scheme) and heating and cooling (commercial scheme). The commercial system (with cooling) was applied only to the buildings with the best-practice thermal envelope. The analysis of each of these nine different construction and usage categories includes the modelling of operational energy use with an emphasis on HVAC energy consumption, and the assessment of indoor comfort conditions using predicted mean vote (PMV). From an operational energy use perspective, the modelling comparison between the different cases has shown that, within each category (code-compliant, low-energy and low-energy-commercial), the principal structural material has only a small effect on overall performance. The most significant differences are in the building with the best-practice thermal envelope with the commercial HVAC system, were the concrete building has slightly lower HVAC energy consumption, being 3 and 4% lower than in the steel and timber buildings respectively The assessment of indoor comfort conditions during occupied periods through using PMV for each of the three categories shows that the timber structure consistently exhibited longer periods in the over-warm comfort zone, but this was much less pronounced in south-facing spaces. To examine the reasons for the less acceptable PMV in the timber-structure versions, an analysis of indoor timber and concrete surface temperatures was carried out in both buildings. It was found that, particularly in north-facing spaces, there were large diurnal swings in the temperatures of timber surfaces exposed to solar radiation. These swings were much less in the case of concrete surfaces so the environment was perceived to be more comfortable under such conditions because of the reduced influence of higher mean radiant temperatures. To moderate this potential downside of solar-exposed internal timber surfaces, better results are achieved if, when timber is used for thermal mass, the timber is not exposed to direct solar radiation, for example locating it in the ceilings or on the south side of the building. Two other approaches to combating the potential overheating problem in the timber-structured buildings were analysed in an illustrative mode; addition of external louvres to reduce direct solar gains at critical times of day and year; and use of phase change material (PCM) linings to act as light-mass energy buffers. Although external louvres increase comfort conditions significantly by reducing the periods of an overly warm environment, they produce an increase in heating energy consumption through reducing beneficial solar gains. The use of PCM linings shows little benefit to overall indoor comfort conditions for the building of this case-study.