Walls, as components of the lateral-force-resisting system of a building, are defined as shear walls. This study aims to determine the behavior of shear wall panel cross-laminated-timber-based mangium wood (Acacia mangium Willd) (CLT-mangium) in earthquake-resistant prefabricated houses. The earthquake performance of CLT mangium frame shear walls panels has been studied using monotonic tests. The shear walls were constructed using CLT-mangium measuring 2400 mm × 1200 mm × 68 mm with various design patterns (straight sheathing, diagonal sheathing/45°, windowed shear wall with diagonal pattern and a door shear wall with a diagonal pattern). Shear wall testing was carried out using a racking test, and seismic force calculations were obtained using static equivalent earthquake analysis. CLT-mangium sheathing installed horizontally (straight sheathing) is relatively weak compared to the diagonal sheathing, but it is easier and more flexible to manufacture. The diagonal sheathing type is stronger and stiffer because it has triangulation properties, such as truss properties, but is more complicated to manufacture (less flexible). The type A design is suitable for low-intensity zones (2), and types B, D, E1 and E2 are suitable for moderate-intensity zones (3, 4), and type C is suitable for severe-intensity zones (5).
An efficient implementation of the capacity design requires high ductility combined with a low overstrength of the critical regions. Conventional timber connections do not generally offer such ideal combination, resulting in modest behaviour and relatively high overstrength factors. Inspired by the Buckling Restrained Brace a new hold-down has been developed where the timber wall directly acts as a casing. The new hold-down has been given an adaptive stiffness allowing the structure to be stiff in the wind, while becoming more flexible in the case of an earthquake. Furthermore, local crushing of the timber members is completely avoided, and the new hold-down could be replaced after an earthquake. Experimental investigations were performed on hold-down specimens. The results show ultimate displacement values vu,c of more than 30 mm in a cyclic test according to EN12512. Eleven Cross Laminated Timber shear walls, in which the new hold-down has been implemented, were tested following monotonic and static-cyclic tests procedures, with and without vertical load. A very high ductility has been achieved with almost no strength degradation, little pinching and limited overstrength.
It is fairly common for mid-rise wood buildings to include shaft walls made from other materials. However, wood shaft walls are a code-compliant option for both light-frame and mass timber projects—and they typically have the added benefits of lower cost and faster installation.
This paper provides an overview of design considerations, requirements, and options for light wood-frame and mass timber shaft walls under the 2018 and 2021 IBC, and considerations related to non-wood shaft walls in wood buildings.
Current environmental crisis calls for sustainable solutions in the building industry. One of the possible solutions is to incorporate timber-framed constructions into designs. Among other benefits, these structures are well established in many countries, originating in traditional building systems. This paper focuses on experimental timber-frame walls. Different wall assemblies vary in thermal insulation materials and their combinations. We investigated ten experimental wall structures that have been exposed to natural external boundary conditions since 2015. The emphasis was on their state in terms of visual deterioration, mass moisture content, and thermal conductivity coefficient. We detected several issues, including defects caused by inappropriate realization, causing local moisture increase. Material settlement in loose-fill thermal insulation was another issue. Concerning was a significant change in the thermal conductivity of wood fiber insulation, where the current value almost doubled in one case compared to the design value determined by the producer.
This paper presents structures of timber-framed walls designed for passive houses, using natural and waste resources as insulation materials, such as wool, wood fibers, ground paper, reeds (Phragmites communis), and Acrylonitrile Butadiene Styrene (ABS) wastes. The insulation systems of stud walls composed of wool–ABS composite boards and five types of fillers (wool, ABS, wood fibers, ground paper, and reeds) were investigated to reach U-value requirements for passive houses. The wall structures were designed at a thickness of 175 mm, including gypsum board for internal wall lining and oriented strand board (OSB) for the exterior one. The testing protocol of thermal insulation properties of wall structures simulated conditions for indoor and outdoor temperatures during the winter and summer seasons using HFM-Lambda laboratory equipment. In situ measurements of U-values were determined for the experimental wall structures during winter time, when the temperature differences between outside and inside exceeded 10 °C. The results recorded for the U-values between 0.20 W/m2K and 0.35 W/m2K indicate that the proposed structures are energy-efficient walls for passive houses placed in the temperate-continental areas. The vapour flow rate calculation does not indicate the presence of condensation in the 175 mm thick wall structures, which proves that the selected thermal insulation materials are not prone to degradation due to condensation. The research is aligned to the international trend in civil engineering, oriented to the design and construction of low-energy buildings on the one hand and the use of environmentally friendly or recycled materials on the other.
Seismic strengthening of existing RC buildings with external cross-laminated timber (CLT) walls hosting an integrated energetic and architectural renovation
In this study a timber-based integrated solution is presented to solve at once common issues affecting typical reinforced concrete (RC) existing buildings, such as seismic and energy performances, providing an eco-friendly alternative to steel external bracing systems. Cross-laminated timber (CLT) walls are provided perpendicularly to the external façades as strengthening elements while interposed CLT slabs are foreseen at each floor level to host new architectural units together with a new envelope. While the connections to the foundations and to the existing RC frames are provided respectively with steel brackets and axial-connectors distributed along the height of the building, a post-tensioned connection, between CLT panels (PT-CLT connection), is implemented in the system to guarantee resistance to horizontal actions acting parallel to existing façades with consequent structural independence and architectural freedom. On this regards a first look at the findings of an experimental campaign carried on the Technical University of Munich are presented. A numerical model is developed with finite element software characterizing each type of connector for linear and non-linear analyses. Modal analyses with response spectrum are performed to verify structural elements and connectors, while pushover analyses with target displacement checks are performed to assess the obtained seismic improvement. Finally, the preassembled architectural components that allow to renovate the envelope and the provided assembly procedure are revealed.
Additive manufacturing of fully recyclable walls, made of a composite of renewable secondary resources, offers the wood construction industry the possibility to manufacture structures within a circular economy. The newly developed composite material is extruded in a dry state before using water and heat to ensure proper bonding. Following a summary of the state of the art, concepts for material, manufacturing, application and recycling are presented. First preliminary experiments and an evaluation of the environmental impact show the potential of the innovative strategy. Considering the obtained results, current issues and future research demand are presented.
There is widespread enthusiasm toward utilizing mass timber panels (MTP), mainly cross-laminated timber (CLT), in construction, including for the basements of low-rise buildings. CLT is deemed a sustainable alternative to the widely used concrete foundation walls due to significant advantages such as less vulnerability to cracking due to uneven load distribution and presence of concentrated loads, higher thermal resistance, less construction time due to whole-wall prefabrication and installation, and less detrimental environmental effects. This study is part of an extensive research program aimed at developing the structural analysis and design concepts and methodology for constructing house foundation walls using MTPs, focusing on the usage of CLT. After comparison of CLT basements with their equivalent concrete ones from the sustainability point of view, and a brief discussion on geotechnical and hygrothermal considerations, the main theme of the article includes the structural analysis and design methodology, requirements, and the procedure to achieve a reliable and efficient design of a CLT basement. A simplified analysis procedure to design the laminate thicknesses and the number of layers in CLT foundation walls for different scenarios considering various variables such as soil type and backfill height is discussed, and results in the form of pre-engineered design tables are provided. The findings of this study demonstrate that, depending on the soil type and backfill height, 3–7-ply CLT panels would be needed for net wall heights of up to 3 m. Additionally, advanced finite element analyses are performed on sample architypes to validate the simplified analysis procedure used for design. It is shown that the proposed analysis procedure and the pre-engineered tables produce conservative and efficient results.
This paper advances the current knowledge on the use of prefabricated timber-based panels in building renovation by analyzing in detail the thermal performance achieved by two different renovation solutions developed in the framework of the ongoing e-SAFE H2020 project. In particular, these solutions apply to the external walls of a pilot building located in Catania (Italy) as a double-skin façade that increases also the seismic performance of the building. The dynamic energy simulations reveal that the proposed solutions allow reducing the energy need for space heating and space cooling by 66% and 25%, respectively. One further finding is that, although the proposed timber-based renovation solutions are not affected by mould growth and surface condensation risk, the impact of thermal bridges cannot be neglected after renovation. Indeed, despite the strong reduction in the magnitude of heat losses due to thermal bridges (from 667 W·K-1 down to 213.1 W·K-1), they still account for about 21% of total heat losses after the renovation. This suggests that more complex and expensive technological solutions should be introduced to further reduce heat losses in some thermal bridges, but a cost-benefit analysis should justify their adoption. Finally, overlooking these thermal bridges in dynamic energy simulations can lead to an average underestimation of the heating and cooling energy demand after the renovation, by about 16% and 5% respectively. In this regard, the paper proposes a simplified yet reliable approach to include heat transfer through thermal bridges in the post-processing stage of dynamic energy simulations under thermostatic control.
The overall objective of this study is to provide information to building design practitioners that will help to improve accuracy of hygrothermal models and enable them to better use these models to predict the durability and thermal performance of wood-based building envelopes. To achieve this, hygrothermal models using WUFI Pro software are validated with experimental data obtained from five wood-frame wall assemblies, with different insulation and vapour control strategies, exposed to the climatic conditions of Vancouver from October 2018 to May 2020. This exercise provides a set of model input parameters that the practitioner can use to assess similar structures exposed to similar environmental conditions. Sensitivity analysis is conducted on the model input parameters to establish which are the most important in obtaining a good fit to experimental measurements, and therefore accurate prediction of assembly performance. There is also discussion on limitations of the hygrothermal model.
+Frame+Shear+Walls+Tested+Monotonically){kind=link}
+walls+hosting+an+integrated+energetic+and+architectural+renovation){kind=link}
