RILEM TC: reinforcement of timber elements in existing structures

The paper reports on the activities of the RILEM technical committee “Reinforcement of Timber Elements in Existing Structures”. The main objective of the committee is to coordinate the efforts to improve the reinforcement practice of timber structural elements. Recent developments related to structural reinforcements can be grouped into three categories: (i) addition of new structural systems to support the existing structure; (ii) configuration of a composite system; and (iii) incorporation of elements to increase strength and stiffness. The paper specifically deals with research carried out at the Bern University of Applied Sciences Switzerland (BFH), the University of Minho Portugal (UniMinho), and the University of Trento Italy (UNITN). Research at BFH was devoted to improve the structural performance of rounded dovetail joints by means of different reinforcement methods: i) self-tapping screws, ii) adhesive layer, and iii) a combination of selftapping screws and adhesive layer. Research at UNITN targeted the use of “dry” connections for timber-to-timber composites, specifically reversible reinforcement techniques aimed at increasing the load-bearing capacity and the bending stiffness of existing timber floors. At UniMinho, double span continuous glulam slabs were strengthened with fibre-reinforced-polymers. All three examples demonstrate the improved structural performance of timber elements after reinforcing them.The research on RDJ was funded by BFH and supported by the staff at the BFH " tech-park" Huesser Holzbau AG and ArundaR. The research at UNITN was carried out by the Timber Research Group (in particular by M. Piazza, R. Tomasi, I. Giongo) within the framework of the RELUIS Project 2011-2013, which is financed by the Italian Emergency Management Agency (Dipartimento della Protezione Civile) and supported by Rothoblaas srl

MOE DISTRIBUTION IN VISUALLY GRADED PONDEROSA PINE LUMBER HARVESTED FROM RESTORATION PROGRAMS IN SOUTHERN OREGON AND NORTHERN CALIFORNIA

Every year, restoration programs in Southern Oregon and Northern California produce large amounts of low-value Ponderosa pine (PP) lumber, which has limited market in the US. Engineered wood products, such as CLT and glulam, are expected to provide a value-added market to offset the high costs of restoration programs. However, restoration program lumber has larger amounts of juvenile wood and visual grades are reported to show lower mechanical properties compared to commercially harvested material, on which the National Design Specification (NDS) design values are based. This research addresses a knowledge gap on the impact of juvenile wood and visual, strength-affecting characteristics on the mechanical performance of PP lumber generated in the region of interest. The purpose of this study was to assess this impact based on measured moduli of elasticity (MOE) of samples of visually graded and ungraded restoration program PP lumber. The results were compared to previous studies and published values for commercially harvested PP as reflected in the NDS Western Woods (WW) species group. The results show that characteristic MOE values of visual grades No. 1 and 2. of PP from restoration programs were lower than respective design values for NDS WW group. However, the mean MOE values of all groups considered individually as well as pooled together were higher than NDS WW grade No. 3. MOE distributions for all groups, except for the visual grade No. 1, were remarkably similar showing negligible differences at 5th percentile, which may indicate negligible differences in correlated strength design values, not measured in this study. The average MOE of PP harvested in Southern Oregon and Northern California were higher than those reported for Columbia PP harvested in North Idaho

Assessment, reinforcement and monitoring of timber structures: FPS Cost Action FP1101

Interest in extending the life of existing and historic timber structures has increased steadily in the last decade, owing to a shift in emphasis forward sustainability and low carbon emission of the construction industry. This increased interest and the growing number of researchers and institutions active in this field are the motivation for the setting of COST ACTION FP1101 on assessment, reinforcement and monitoring of timber structures, now nearing completion of its second year of activity. The paper explains what a COST Action is and presents the aims and objectives of this European Research network initiative. It discussed the state of the art in these three fields of research activities as outlined by the work developed jointly by the network. It discusses avenues for further international collaboration beyond Europe by using some of the implementation instruments available within the COST framework. The paper concludes with a discussion on the current research gaps identified through the network workshop, and a view as to how the major outcomes of the network activities can be further disseminated and find institutional outputs through collaboration with RILEM and European Standardisation Technical Committees.Cost Action FP110

Leveraging Structural Health Monitoring Data Through Avatars to Extend the Service Life of Mass Timber Buildings

Mass timber construction systems, incorporating engineered wood products as structural elements, are gaining acceptance as a sustainable alternative to multi-story concrete or steel-frame structures. The relative novelty of these systems brings uncertainties on whether these buildings perform long-term as expected. Consequently, several structural health monitoring (SHM) projects have recently emerged to document their behavior. A wide and systematic use of this data by the mass timber industry is currently hindered by limitations of SHM programs. These limitations include scalability, difficulty of data integration, diverse strategies for data collection, scarcity of relevant data, complexity of data analysis, and limited usability of predictive tools. This perspective paper envisions the use of avatars as a Web-based layer on top of sensing devices to support SHM data and protocol interoperability, analysis, and reasoning capability and to improve life cycle management of mass timber buildings. The proposed approach supports robustness, high level and large-scale interoperability and data processing by leveraging the Web protocol stack, overcoming many limitations of conventional centralized SHM systems. The design of avatars is applied in an exemplary scenario of hygrothermal data reconstruction, and use of this data to compare different mold growth prediction models. The proposed approach demonstrates the ability of avatars to efficiently filter and enrich data from heterogeneous sensors, thus overcoming problems due to data gaps or insufficient spatial distribution of sensors. In addition, the designed avatars can provide prediction or reasoning capability about the building, thus acting as a digital twin solution to support building lifecycle management

Teacher perceptions of training and pedagogical value of cross-reality and sensor data from smart buildings

This paper discusses elementary, and secondary (K-12) teachers’ perceptions of cross-reality (XR) tools for data visualization and use of sensor data from the built environment in classroom curricula. Our objective was to explore the use of sensor-informed XR in the built environment and civil engineering (BECE) field to support K-12 science, technology, engineering, and mathematics (STEM) experiential learning and foster BECE-related career awareness. We conducted surveys and informal questionnaires with 33 primary and secondary teachers attending an annual two-day university-based teacher professional development workshop as part of a statewide STEM afterschool program serving students in rural communities. We assessed teachers’ familiarity with, knowledge about, and appraisal of using cross-reality platforms and sensor data in classrooms and after school curricula. Findings show that, while all teachers reported relatively high interest in learning about sensor applications and innovative interactive techniques, middle school teachers in particular were most likely to see value in using these applications for teaching and learning. Implications for teacher professional development are discussed

Monitored Indoor Environmental Quality of a Mass Timber Office Building: A Case Study

A broad range of building performance monitoring, sampling, and evaluation was conducted periodically after construction and spanning more than a year, for an occupied office building constructed using mass timber elements such as cross-laminated timber (CLT) floor and roof panels, as well as glue-laminated timber (GLT) beams and columns. This case study contributes research on monitoring indoor environmental quality in buildings, describing one of the few studies of an occupied mass timber building, and analyzing data in three areas that impact occupant experience: indoor air quality, bacterial community composition, and floor vibration. As a whole, the building was found to perform well. Volatile organic compounds (VOCs), including formaldehyde, were analyzed using multiple methods. Formaldehyde was found to be present in the building, though levels were below most recommended exposure limits. The source of formaldehyde was not able to be identified in this study. The richness of the bacterial community was affected by the height of sampling with respect to the floor, and richness and composition was aected by the location within the building. Floor vibration was observed to be below recognized human comfort thresholds

Application of imaging techniques for detection of defects, damage and decay in timber structures on site

The manuscript presents the application of NDT imaging techniques as complementary tools to be used during visual inspection. NDT imaging can be used to map inhomogeneity and to identify the areas at the highest risk for damage in timber structures. The paper highlights the potential of imaging techniques accepted and practiced for the assessment of timber structures. Multi-sensor approaches are presented and recommended for multi-scale, multi-resolution correlated information, which allow the non-destructive, reliable and fast assessment of damage and risk level in the existing timber structures

Computation and Learning Partnerships: Lessons from Wood Architecture, Engineering, and Construction Integration

Examining an interdisciplinary university course for architecture, wood science, and engineering students, this paper studies how the students’ ability to master digital workflows influenced their success in learning collaborative design skills. It highlights potential challenges and opportunities posed by the introduction of new digital tools to support emerging integrated building design in both education and professional practice. The particular course focuses on the wood industry, which is rapidly changing from a very traditional to a highly innovative sector and increasingly embracing the latest technological developments in computational design, simulation, and digital fabrication. This study explores the influence of parametric design on collaboration dynamics and workflow within an interdisciplinary group of students embodying the roles of manufacturer, engineer, and architect. Student-generated data of the first three years of the class is analyzed thematically to find correlations with productive collaborations. Focusing on a stage of an evolving teaching and learning process, this analysis allows identifications of common themes and patterns, suggesting implications for practice and future research. The course highlights the need to integrate data interoperability, collaboration skill-building, and material awareness in contemporary digitally enabled architecture, engineering, and construction education. The lessons learned in this course can be of value to academic programs and professional firms involved in incorporating digital design and interdisciplinary collaboration