Timber structures have experienced its revival as a viable structural solution lately, especially thanks to its relatively modern engineered version, i.e. the cross-laminated timber (CLT). Nevertheless, timber constructions are still lightweight and, therefore, inherently prone to experiencing vibration issue phenomena. This challenge motivated research trends within this field lately, in particular, to characterize the dynamical characteristics of hybrid structural solutions. This study presents preliminary findings from the dynamic analysis of a hybrid timber-concrete building case study. The research employs operational modal analysis (OMA) using output-only techniques for ambient vibration recordings and Hilbert Huang transforms (HHT) for forced vibration tests performed during construction stages. Finally, the results of a preliminary finite element model (FEM) updating procedure have been discussed. The current findings evidenced that greater research efforts should be demanded in the next years to better understand the vibration coupling phenomena in these hybrid structural typologies.

: 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.

Self-tapping screws, thanks to the speed and ease of installation have become more and more popular in the last 25 years.Slip modulus and strength increase when the screw axis is inclined with respect to the normal to the sliding plane, however, in this configuration screw is subjected to axial and shear force, together with bending moment.Moreover, interlayers having poor mechanical properties are often inserted between main connected members to ensure human comfort in the buildings or because it is required by the structural system.The complex interaction between axial and transversal behaviour of inclined screws may not be fully considered by some of the simplified models in literature and codes, in this paper the behaviour of steel-to-timber connection is experimentally assessed and a finite element model of non-linear beam on foundation is validated.Experimental results are compared with the results of finite element analysis and the with Eurocode 5 model results.

Engineered wood products (EWPs) are being increasingly used as construction materials. EWPs are currently being made using synthetic adhesives or metal fasteners, which lead to poor recyclability and reusability. Therefore, this review paper focused on emerging adhesive- and metal-free assembling techniques including wood dowels, rotary-dowel welding, wooden nails, and dovetail joining as alternative ways of making prefabricated EWPs. This will contribute towards green construction and optimising the building process to minimise its negative impact on the environment and its inhabitants, while maximising the positive aspects of the finished structure. The respective advantages and shortcomings will be compared with those of equivalent EWPs. In general, the dowel-laminated timber (DLT) provides sufficient load-bearing capacity and even better ductility than EWPs of equivalent size, but its relatively low stiffness under a bending load limits its application as a structural element. Optimised manufacturing parameters such as dowel species, dowel spacing, dowel diameter, dowel insertion angle, dowel shape, etc. could be studied to improve the stiffness. The improved mechanical properties and tight fitting due to set-recovery of densified wood support its use as sustainable alternatives to hardwood dowels in DLT to overcome problems such as the loosening of connections over time and dimensional instability. The rotary welding technology could also enhance the strength and long-term performance of dowel-type joints, but its poor water resistance needs further investigation. The main obstacles to implementing DLT products in the market are missing technical information and design guidelines based on national codes.

Thanks to the axial resisting contribution, inclined screw connections offer a mechanical advantage over connections with purely transversely loaded fasteners. However, the strong coupling between the axial and the transversal behaviour of the screw makes it challenging to predict the actual connection behaviour. Moreover, the presence of polyurethane interlayers for soundproofing or OSB interlayers of light-frame buildings between main members may increase the bending moment component interacting with the axial force in the screw, thus reducing the connection failure load. This paper experimentally assesses the behaviour of steel-to-timber connections, and a parametric finite element model of Winkler non-linear beam is presented and validated. Finally, a simplified analytical model for capacity prediction is presented. The results of the approach currently provided by the Eurocode 5, of an additive model and the proposed analytical model, are then compared with the results of 500 finite element analysis.

Nowadays, some innovative spatial structural typologies among others rely on timber-concrete hybrid solutions for designing modern buildings. However, the dynamic identification analysis may be more elaborate, and sometimes troublesome, due to the coupling effects of the different dynamic nature of cross-laminated timber and reinforced concrete members. In the current manuscript, the authors explore some preliminary results of the dynamic analysis of a hybrid timber concrete building case study. The operational modal analysis (OMA) based on output-only techniques has been employed, referring specifically to enhanced frequency-domain decomposition (EFDD) and the stochastic subspace identification (SSI) methods. The authors compared several ambient vibration OMA results with forced shaker-induced vibration responses highlighting the absence of nonlinearities during in-service operational conditions in two different moments.

Almost 200 nations, including the European Union, have signed the Paris Agreement that aims to limit the temperature rise to 1.5 °C above pre-industrial levels by reducing greenhouse gas (GHG) emissions. To meet this target, a significant decrease in GHG emissions by 2030 and net zero by 2050 is necessary. To determine the role of wood products in achieving a 55% reduction in GHG emissions by 2030 compared with 1990 levels, we investigated Slovenia’s potential, which has close to 60% forested areas. Therefore, the country could use wood-based products to achieve the agreed-upon climate goals. Nevertheless, uncertainties remain regarding the extent to which increased tree harvesting, local manufacturing, and the utilization of wood products can aid in substituting fossil-derived materials and reducing GHG emissions. A new model was constructed to increase the understanding of the wood products’ (throughout the forest-based industrial ecosystem, incl. construction) potential contribution to reaching the stated emissions targets. Using this linear programming (LP) mathematical optimisation model and carbon footprint calculations based on life cycle assessment methods, a wood flow distribution, the financial investment needed to process these quantities, and the GHG emissions produced and/or saved were calculated. The findings stipulated that Slovenia has the potential to achieve 55 % less GHG emissions by 2030 by expanding logging to at least 3 million m3 and converting the timber to a larger amount of long service-life wooden items made (and utilised) within the country. Such products accumulate carbon for a long time and decrease the need for materials that cause higher GHG emissions. Concomitantly, a better appreciation of the substitution effects in official carbon accounting would be needed. Moreover, to materialize the potential decrease in emissions would require Slovenia’s construction sector to replace fossil- and mineral-based materials with lignocellulosic products, and to increase the capacity to utilize lower-quality wood in high added value applications, which would require significant investment. This paper offers a comprehensive analysis of diverse optimisation outcomes obtained from the investigation into climate action through the use of wood products in Slovenia.

More than one hundred ninety nations, including the European Union, have signed the Paris Agreement to limit the temperature increase to 1.5 °C above pre-industrial levels. Meeting these conditions requires a steep decline in greenhouse gas (GHG) emissions by the year 2030 and zero GHG emissions by 2050. In this study, we investigated the role that wood products can play within Slovenia to reach the 2030 goal of a 55 % reduction in GHG, as compared to 1990 levels. Slovenia, with over 58 % forest cover, is well-positioned to utilize wood products to meet these climate goals. However, questions exist on how increased tree harvesting and local production, and the use of wood products contribute to replacing fossil-based materials and to lower lowering GHG emissions. To better understand the importance of wood products to GHG emission reduction, this study aimed to present a model showing how the forest-based value chain (including construction) could help reach the Paris Agreement goals. We investigated the associated environmental impacts and their related economic costs. The results indicated that Slovenia could reach the 55 % GHG emission reduction goal within 2030 through increasing tree harvesting and using these resources to increase the number of durable wood products produced within Slovenia that store carbon for long periods and substitute for other high GHG emitting materials. However, realizing these potential reductions would rely on the building industry within Slovenia to replace fossil- and mineral-based materials with wood products.

Southern regions of Europe are characterized by presenting a large number of existing buildings with reinforced concrete (RC) structures with masonry infills.From a structural point of view, they are characterized by one-way RC frames, with poor structural details and masonry infills, contributing to the high seismic vulnerability of these constructions.Current retrofitting technologies, such as reinforced concrete jacketing of columns, concrete shear walls or FRP wrapping, could be effective but require the occupants' relocation, available perimetral space and legislative constraints.The use of CLT panels, as an innovative retrofitting technique, seems to be a reasonable alternative for existing buildings given their easy and fast assembly, high performance and reversibility.This paper presents a numerical analysis to evaluate the seismic behavior of masonry-infilled RC portal frames strengthened by an external CLT panel.The 20 cm thick masonry wall was represented by two nonlinear diagonal elements with a multi-linear plastic constitutive law, including a Pivot hysteresis type in the axial direction.On the other hand, the 100 mm thick CLT panel was modeled through an orthotropic elastic shell-element.The study comprises four different connections between the RC frame and CLT panels.These connections are modeled through nonlinear Pivot links in both uplift and lateral directions.Their cyclic response, including degradation parameters, effective stiffness and force-deformation envelope curve, was calibrated based on previous experimental results.Numerical results confirm that CLT panels can be an efficient strengthening solution to increase the initial stiffness, as well as energy dissipation, while decreasing the impact of strength degradation on the response of masonry-infilled RC frames against in-plane quasi-static cyclic loading.

AbstractClimate change and other environmental problems from the production of raw materials, construction, and end of life of buildings are serious concerns that need to be solved urgently. Life cycle assessment (LCA) and the EU-recommended Environmental Footprint (EF) are well-known and accepted tools to measure a comprehensive set of environmental impacts throughout a product’s life cycle. But to assess how good (or bad) a wooden building performs environmentally is still a challenge. In the EU Environmental Footprint [11] pilot phase from 2013 to 2018, an average benchmark for the different product groups was found to be very useful. Based upon the recommendations for a benchmark of all kinds of European dwellings, we developed a scenario of a typical European wooden building. The EU Environmental Footprint method covers 16 recommended impact categories and can be normalized and weighted into one single point for easy and quick comparisons. The results are presented as the average impact per one square meter (m2) of floor area over 1 year. The developed benchmark for wooden buildings is a suitable comparison point for new wooden building designs. The benchmark can be used by architects and designers early in the planning stages when changes can still be made to improve the environmental performance of wooden buildings or the communication and interpretation of LCA results for customers and other stakeholders.

Structural design is a complex process of several stages that is used for the design and development structural plans. The stages of this of this process (planning, design and detailing) have to be performed sequentially, each stage using the output of the previous one as its input. As these stages are complex, even separately, efficient solution methods can be useful to aid the decision-making processes of civil engineers. Early decisions in the design process (such as topology and material combination choices) affect the future steps and overall performance (such as energy demand or costs). These effects are not known in advance and can only be estimated. Providing multiple possible design suggestions by quick heuristic algorithms can help with quantifying the effects of these early decisions. In this presentation, we will introduce heuristic optimization methods for the design stage of the above process. These methods use preliminary designs as their input and aim to improve their quality through several local transformation steps. Different constraints are considered during this process, and the solution is optimized by taking multiple different cost objectives into account. As each local transformation step shifts from a feasible solution into another one, multiple possible solutions are visited in the solution space. The best ones are saved and presented by the system as possible suggestions. To measure the quality of these resulting suggestions, we also develop a mathematical model that is able to calculate the costwise optimal solution. The quality of our suggestions will also be compared to this solution.

Wind-induced dynamic excitation is becoming a governing design action determin-ing size and shape of modern Tall Timber Buildings (TTBs). The wind actions generate dynamic loading, causing discomfo ...

Use of timber as a construction material has entered a period of renaissance since the development of high-performance engineered wood products, enabling larger and taller buildings to be built. In addition, due to substantial contribution of the building sector to global energy use, greenhouse gas emissions and waste production, sustainable solutions are needed, for which timber has shown a great potential as a sustainable, resilient and renewable building alternative, not only for single family homes but also for mid-rise and high-rise buildings. Both recent technological developments in timber engineering and exponentially increased use of engineered wood products and wood composites reflect in deficiency of current timber codes and standards. This paper presents an overview of some of the current challenges and emerging trends in the field of seismic design of timber buildings. Currently existing building codes and the development of new generation of European building codes are presented. Ongoing studies on a variety topics within seismic timber engineering are presented, including tall timber and hybrid buildings, composites with timber and seismic retrofitting with timber. Crucial challenges, key research needs and opportunities are addressed and critically discussed.

Monolithic full cross-sections represent independent of the respectively used material – concrete, steel or wood – resource inefficient, technically-economically insufficient solutions. This is especially true for elements subjected to bending. Intelligent construction elements such as ribbed plates or box-beams enable equal mechanical performance at substantially reduced material consumption. This is essential in view of the increasing importance of the sustainability of building products and construction methods.

: This paper explores the possibility of using flexible adhesives to dissipate energy in CLT buildings during earthquakes. In the first series of tests, a rod glued in a CLT panel with flexible adhesive was investigated. The connection was tested in pull-pull configuration using cyclic, tension-only loading. Different rod diameters and different thicknesses of the glue layer were tested. The tests have shown that the adhesive can resist large deformations and exhibits fairly large energy dissipation capacity. Based on the test results the numerical analyses were performed to test the behaviour of the connection when applied in CLT buildings. Existing constitutive models available in OpenSees software were used to simulate the specific hysteretic behaviour of the connection. The results have shown that the CLT wall anchored with “flexible” glued-in rods would have a significant energy dissipation capacity if a sufficient number of them were used as the hold-down devices. Such system could be used to dissipate energy in seismic areas.

: Cross laminated timber (CLT, X-lam) started its mass production in the beginning of the 21 st century. Over time it has become one of the most used products in the timber construction industry with its worldwide use constantly growing. The quantity of yearly cut timber especially in Europe is slowly reaching its maximum and its price is rising. Hence conventional CLT is becoming more expensive and less competitive on the market on the one hand and more straining on the forest on the other hand. CLT technology has still lots of potential for improvement that would allow for more effective and economic use under different boundary conditions. This paper presents a new type of cross-laminated timber plates called the “Xlam ribbed plates” (XR-lam). The main objective of the newly proposed plates is to optimise the structural performance of regular CLT in terms of material use by incorporating ribs into the main panel structure as well as simplifying their production. Analyses show that such plates could use up to 50% less timber for the same performance as well as speed up the construction of the buildings’ outer envelope. Hence, such elements could present a more competitive and forest friendly alternative to conventional CLT.

This paper presents the development of two new types of hybrid cross-laminated timber plates (HCLTP) with an aim to improve structural performance of existing cross-laminated timber plates (Xlam or CLT). The first type are Xlam plates with glued timber ribs and the second type are Xlam plates with a concrete topping. A numerical optimisation was performed to study optimal plate setups in terms of ultimate limit state and serviceability limit state requirements. The numerical outcomes served as input for defining the specimens for experimental tests on subassemblies and full-scale specimens. The new elements in general show improved structural performance with less material used. Experimental and numerical investigations serve as essential information for further extensive parametric studies of hybrid cross-laminated timer plates and development of design models and principles for implementation in the building codes.

This paper investigates the seismic analysis of multistory cross-laminated timber (XLAM) buildings. The influence of different parameters such as wall geometry, vertical load level, friction, and, most importantly, connection stiffness, strength, and ductility is assessed. Linear and nonlinear finite-element (FE) analyses are carried out on a hypothetical 4-story case study building. The actual load-carrying capacity of the case study building is calculated with the nonlinear static pushover method and assessed using displacement-based design. The XLAM building behavior factors are then derived for different cases using a simplified method. Values in the range 2-3 have been obtained depending on whether monolithic or segmental walls (namely made of approximately 2-m-wide panels screwed to the adjacent ones) are used. Further nonlinear dynamic analyses carried out on a part of the case study building show that friction may have a beneficial effect on the seismic resistance of XLAM buildings. However, it is advised that its influence is conservatively neglected until further investigations are performed. Lastly, the importance of considering the overstrength concept in design of XLAM buildings is presented via a wall case study. Obtained results provide an important insight for both academics and practicing engineers in the FE modeling and design of XLAM buildings using different code-based approaches. This data is also crucial for the preparation of new seismic design codes on XLAM timber buildings. (C) 2015 American Society of Civil Engineers.