Timber Roof Research Articles

CROSS Safety Report: Collapse of folded plate timber roof at a school

This month's report discusses a critical safety issue concerning folded timber roofs, in various settings, including over school halls.

Typology, current state and non-destructive testing of timber roof trusses of historic churches in the West Vistula Delta, Poland

This paper presents the current state of conservation of historic roof churches located in the Żuławy of Gdańsk (Poland). It also describes the architecture of these temples, the region itself and old carpentry techniques for constructing roof trusses. Interdisciplinary tests were carried out in six churches. The geometry of the load bearing structures, the moisture content and the carpentry technique were specified. The field survey also included visual inspections and non-destructive testing of timber structural elements of the roof constructions. The ground penetrating radar and ultrasonic testing methods were used to assess the structure and extent of the damage to the timber elements. The interdisciplinary research presented in this article is important in the planning of historic buildings conservation works and it might be applied to other timber structures.

Enhancing Sustainable Construction: Optimization Tool for Glulam Roof Structures According to Eurocode 5

The construction industry has a notably negative impact on the environment; thus, the promotion of the use of timber structures is an alternative to mitigate its effects. This research develops an artificial intelligence-based decision approach in the calculation of timber structures focused on the enhancement of the sustainability of roof structures. Based on the optimization carried out through genetic algorithms and the framework established in Eurocode 5, a general set of equations has been proposed for a laminated timber roof structure. The tool, which determines the most suitable roof structure for each strength class of laminated timber, allows for the determination of the dimensions of beams and purlins and their respective separations in order to minimize wood consumption. The ultimate goal is to offer multiple solutions regarding strength classes and structural designs in order to foster sustainability-informed choices that promote efficient use of resources in construction.

Automatic completion of geometric models from point clouds for analyzing historic timber roof structures

Automatic completion of geometric models from point clouds for analyzing historic timber roof structures

Life cycle analysis of timber roof structures

Construction industry is rapidly prospering. With numbers as high as they are in the construction industry, it is imperative to find alternative building materials and reduce waste. Proper combination and selection of materials helps to reduce the environmental burden on the surroundings. It is therefore appropriate to use local, natural, renewable, recyclable and low-emission materials in their production, which also helps to promote biodiversity and to restore and replace green spaces. In the fight against climate change, the construction industry is trying to reduce the emissions of buildings by means of life cycle assessment. The study assessed the life cycle of 55 wooden timber roofs in terms of their environmental impact. Based on the assessment of the timber roof compositions, it can be concluded that the best rating was achieved by the composition with structural construction timber, cellulose insulation, vented gap and aggregate backfill. When using wood fibre and cellulose insulation, a 65% reduction in global warming emissions is achieved.

Design and modelling tools for timber-based seismic retrofitting: from research to practice

Reversible retrofitting techniques for protecting existing or historical buildings against seismic events have found increasing application in the recent years. In particular, the use of wood-based strengthening solutions for both timber and masonry structures has shown promising results in terms of reversibility, compatibility, lightness, sustainability, and effectiveness. With reference to existing timber floors, an excellent method to enhance their seismic response is the fastening of an overlay of plywood panels to the existing sheathing, an intervention that greatly improves in-plane strength, stiffness, and energy dissipation. In order to promote the use of this retrofitting method in practice, calculation tools supporting the design and modelling of timber diaphragms strengthened with plywood panels, have been developed. As a result of a fruitful synergy between academic research and professional engineering, this work presents relevant recent examples of application of the developed calculation tools in the seismic retrofitting of timber diaphragms in existing buildings. Three significant case-study buildings are examined: two masonry churches with monumental timber roofs, and an ancient sawmill with a mixed timber-masonry structure, all located in the province of Brescia (Italy). The developed tools allowed to conduct parametric analyses to calibrate the best retrofitting strategy, and to analyse the additional benefits of the plywood-based retrofitting interventions, especially in terms of hysteretic energy dissipation, affordability, and cost- and execution-effectiveness. This work can contribute to the promotion of timber-based techniques in the combined structural, seismic, and conservation upgrading of existing buildings belonging to the architectural heritage of seismic-prone countries.

Historic timber roof structure vulnerability assessment procedures – Critical analysis and comparison

Historic timber roof structures in Europe are examples of some of the continent's most intricate and ingenious structural solutions. They were built in close connection with their context and the heritage building to which they belonged. In addition, they were built according to the knowledge of the craftsmen.Considering the value of historical construction techniques, in recent years, many researchers have attempted to develop complex methods that could be used to accurately evaluate them and determine both their value and vulnerability to ultimately develop suitable intervention solutions. However, existing historic roof structure assessment methodologies mainly analyse their structural aspects and state of conservation. Considering this, in recent years, a new assessment procedure was developed based on desk and on-site surveys. It approaches historic timber roof structures in a multi-, inter-, and transdisciplinary manner, highlighting their complexity while bringing forward more information about their historical and cultural value.Therefore, to bring forward the originality of the procedure, a series of roof structures from Timisoara, Romania, were evaluated using the developed procedure and their value and vulnerability identified. The results were subsequently compared with those obtained using two other score-based procedures, which approach roof structures mainly based on their structural characteristics and state of conservation.The paper shows that despite the apparent differences between the considered procedures, from assessed features to the interpretation of the results, the outcomes are pretty similar and that each one of them can be used depending on the primary purpose of the assessment.

DRVENA KONSTRUKCIJA CENTRALNOG DELA KROVA CRKVE U NIKŠIĆU

The paper presents the solution of the timber roof structure of the central nave in the town of Nikšić in Montenegro. The central part of the roof is shaped like a regular pyramid over an octagonal base. The basic structural system consists of eight curved timber girders, which are supported in the corners of the octagon and are connected at one point at the top of the roof. Above these girders, in their plane, the secondary supporting structure was added, in order to form the pyramidal shape of the roof. Considering the curved shape of the girders of the basic structural system, the design of the structure foresees glued laminated timber for the basic elements of the roof structure. The solution includes a presentation of all elements of the roof construction, according to the hierarchy of load transfer, as well as a solution of steel connectors for the mutual connection of timber elements.

Transplantation and Adaptation: Research on Reinforced Concrete Structures in Modern Nanjing (1909–1949)

Modern Nanjing experienced a boom in the construction industry. As an advanced material and construction system, reinforced concrete structure was also imported during this period. This paper presents the brief historical background and structural adaptability of reinforced concrete buildings in modern Nanjing. Reinforced concrete was used in industrial buildings in the districts along the Yangtze River in the early 20th century, and in public buildings along Zhongshan Road after 1927. Western-style reinforced concrete buildings used both pure frame structure system and mixed structure with a reinforced concrete frame, brick masonry and timber roof trusses. The Chinese Renaissance buildings used roof structures with different shapes and materials on the main reinforced concrete structure. Based on the study of existing modern reinforced concrete buildings in Nanjing, this paper classifies and compares different types of structures, and indicates that the selection of structures was the adaptive result of comprehensive trade-offs between structural performance, space availability and economy. This research implies the transplantation and adaptation of reinforced concrete structures in modern Nanjing and lays a fundamental structural foundation for the conservation of this architectural heritage.

The STUDY OF RESISTANT EARTHHQUAKE BUILDING OF TIMBER ROOFS STRUCTURE AND ITS RETROFIT AND REDESIGN AFTER THE SEPTEMBER 28 2018 EARTHQUAKE

Palu’s Earthquake on 28 September 2018 had caused structural failure including buildings with wooden structures which were knew as an earthquake-resistant structures. This study will discuss existing building timber roofs structure were damaged after the earthquake, various and caused of the damaged. Existing and retrofitted timber rooss and alternatives design of the roofs structures will be compared. Retroffited timber roof, truss roof with 70x70x6 double angle and gable frame roof structure with WF 250x125 will be design with 15 m length span and 45° slope. Based on these data collected from initial assessment of that buildings, analysis was conducted. Detailed assessments were carried out, when analysis of the truss, frame and joint of roofs structures were needed. Results of the initial assessment of wooden structure, showed that damages occurred at the many joints of member joints and joint-connection between wall and truss as the poor connection system. Redesign showed were structural behavior of retrofitted timber roof, double angle truss roof and gable frame roof structure showed better strength, stiffness and ratio of member force to self-weight.

Faceting the post-disaster built heritage reconstruction process within the digital twin framework for Notre-Dame de Paris

April 15th, 2019: Notre-Dame Cathedral in Paris was burning, the spire collapsed on the nave, vaults crumbled and most of the timber roof was gone. In the post-disaster context, the authenticity and the monitoring of the archaeological remains are crucial for their potential reuse during reconstruction. This paper analyzes the collapsed transverse arch from the nave of Notre-Dame as a case study of reconstruction, using the digital twin framework. We propose four facets for the digital twin experiment—physical anastylosis, reverse engineering, spatio-temporal tracking of assets, and operational research—that are described in detail, while being assembled to support a hybrid reconstruction hypothesis. The digital twin can realize the parallel unfolding of physical-native and digital-native processes, while acquiring and storing heterogeneous information as semantically structured data. The results demonstrate that the proposed modeling method facilitates the formalization and validation of the reconstruction problem and increases solutions performances. As result, we present a digital twin framework application ranging from acquisition to data processing that informs a successful hybrid reconstruction hypothesis.

Vulnerability analysis on a dataset of long-span timber structures in Italy

Long-span structures such as school gyms and sports centres are often used by the Italian Department of Civil Protection as post-catastrophe shelters or headquarters. The Emilia 2012 earthquake drew the attention of the department to this type of structure due to the damage that many of these buildings suffered. In this work, a dataset of 101 timber structures was analysed based on a simplified methodology that detects the major vulnerabilities in long-span timber roofs in order to help plan further investigations and retrofit interventions. Using fast and straightforward approaches, the elements most vulnerable to seismic action were analysed quantitatively and qualitatively. Quantitative evaluation of the vulnerabilities was achieved by applying the Italian Building Code. The aspects not considered in the quantitative evaluation were assessed through qualitative parameters inspired by damage identification forms (e.g. the AeDES form). The analysed structures are located near the epicentres of the last strong earthquakes that struck Italian territory: Abruzzo in 2009, Emilia in 2012 and central Italy in 2016. Damage and retrofits, identified by interviewing owners, designers and builders, showed a good correlation between the real behaviour shown by the surveyed structures and the vulnerabilities detected using the simplified methodology.

Combining Architectural Conservation and Seismic Strengthening in the Wood-Based Retrofitting of a Monumental Timber Roof: The Case Study of St. Andrew’s Church in Ceto, Brescia, Italy

ABSTRACT This work presents the application of timber-based retrofitting techniques to a case-study stone masonry church featuring a wooden roof from 18th century. From the static point of view, the original roof structure presented a number of undersized structural elements, and its members were poorly or not connected among each other and to the masonry, making the church vulnerable to seismic loads as well. Thus, the roof was retrofitted with wood-based techniques, including an overlay of plywood panels, against seismic actions. These affordable, rapid, easily realizable interventions enabled both the conservation and seismic retrofitting of the roof, providing an adequate load-carrying capacity for static loads, and an effective diaphragm action against seismic loads. The conducted numerical analyses showed that the realized interventions greatly improve the seismic behaviour of the building. Besides, when the additional energy dissipation provided by the plywood panels overlay is taken into account in the numerical model, the church would even potentially be able to fully withstand the expected seismic action of the site.

Assessment and Rehabilitation Solutions for an Industrial Hall Affected by Extreme Actions

The original structure of the industrial hall consisted of longitudinal reinforced concrete frames with columns and beams and 133 timber roof trusses (33.5 m span each), which were supported on longitudinal beams. Owing to the extreme action of snow, many trusses in the timber roof crashed down and fell onto the auxiliary structure. This led to the occurrence of a 200 mm distance between two elements in the bottom flange connection area, a 150 mm displacement in the upper part of the reinforced concrete (RC) columns, and many transversal cracks. The main causes that led to the collapse of the timber roof trusses were the high level of stress applied on the structure by snow loads in December 2018, as compared with the provisions of the Romanian code, the fact that the structure was designed for a rigid transversal frame instead of a deformable structure, and the insufficient dimensions of the cleats used on the bottom flange. The rehabilitation solution chosen consisted in lifting the timber roof trusses, after their crashing down, to near their initial level. The degraded structure was strengthened by: (1) consolidating each timber roof truss using a steel tension rod at the bottom flange of the truss, with the timber truss anchored at both ends by being inclined and perforated; and (2) for the RC columns, the strengthening solution was based on carbon fiber reinforced polymer (CFRP) lamellas and wraps.

Historic timber roofs, a knowledge-based approach to strengthening: the case study of a Renaissance palace in Ferrara

Knowledge is essential to preserve timber roof structures for their historical and architectural value, since it allows to fully understand their cultural significance and actual structural behavior, thus planning specific strengthening interventions. This paper presents the case study of Palazzo Costabili in Ferrara, Italy, to propose a method to plan architectural strengthening intervention on historical timber roof structures based on a detailed knowledge of the structures’ features and state. The palace object of this study is characterized by historical timber structures, an expression of traditional local building techniques, which were partially damaged in the 2012 earthquake. Therefore, an in-depth and careful study of the structure was carried out to identify specific parts that needed to be reinforced. A strengthening of the roof structure was thus designed considering the performances of the timber components and their historical-cultural value. More specifically, the timber roof was first assessed to identify the main wood species, the constructive types, and their related vulnerabilities. At the same time, the parts that showed consistent signs of structural stress were later evaluated by specialists using visual and instrumental analysis. Finally, data collected were critically analyzed to better plan the strengthening intervention, considering both the stress state of the single components and their specific weaknesses, in full compliance with preservation criteria and needs.

Buckling Load of Lattice Timber Roof Structure considering Stiffness of Connection with Asymmetric Snow Load

Buckling Load of Lattice Timber Roof Structure considering Stiffness of Connection with Asymmetric Snow Load

Reinforcement methodologies of timber elements in historic timber roofs

This paper aims to present a comprehensive review of the reinforcement of historic timber roofs, focusing on their main characteristics, advantages, and disadvantages, which would help professionals select and define the design of reinforcement solutions. Cultural heritage issues are taken into consideration. Reinforcement can be done via different methods – traditional and modern – using simple or sophisticated techniques. An overview of the main materials and the techniques used for selected case studies are presented, illustrating how various reinforcement methods are implemented in practice.

Learning from tradition: a case study of the diagnosis, dendrochronological dating, and intervention on a 16th-century timber roof structure in the western Italian Alps

The paper presents a significant case study: the Church of San Giovanni Battista in Salbertrand dates back to the 16th century and constitutes one of the most interesting examples of religious architecture in the Susa Valley of the western Italian Alps. Its historic timber roof structure was once at risk of demolition, but in 2000 finally became the object of necessary preservation and reinforcement works. Here, the interdisciplinary studies carried out for the diagnosis and assessment of the state of conservation are presented, starting with the identification of the wood species used, the geometrical survey, the visual and NDT diagnosis of the timber elements, and the structural evaluation. A special section is dedicated to the dendrochronological analysis, with a comparison of different case studies regarding larch roof structures of other historic architectures located in the northwest of Italy. The tree-ring sequences obtained from the buildings presented have also been used to define a larch chronology of the Susa Valley in Piedmont. Following the first assessment phase, a second phase involved defining the restoration and reinforcement interventions. The reinterpretation of historic craftsmanship rules and traditions, which already contemplated the use of steel devices, attempted to offer alternative design solutions. This reinterpretation constituted the basis of the reinforcement interventions carried out in Salbertrand in the early 2000s. This paper highlights the importance of learning from historical treatises, showing how, even in modern reinforcement interventions, the application of traditional carpentry rules can achieve the aims of preservation and structural efficiency with overall cost-effectiveness and durability, resulting in a favorable balance between tradition and innovation.

Remarkable historic timber roofs. Knowledge and conservation practice Part 2 - Investigation, analysis, and interventions

Remarkable historic timber roofs. Knowledge and conservation practice Part 2 - Investigation, analysis, and interventions

The timber roof structure of Chapel XVI at Sacro Monte of Orta: an example of conservative strengthening work

The principles of conservation of existing structures (like evidence of regional construction techniques) pose a significant challenge in the general field of structural safety, increasingly claimed by the new technical codes. The restoration building site of Chapel XVI at Sacro Monte of Orta San Giulio (Italy) testifies to a respectful design approach to enhance the timber elements still recoverable without distorting the original static scheme. The preliminary knowledge phase allowed for correctly interpreting the historical construction phases (including analysis of archival documents and diagnostic investigations), the vulnerabilities of the roof structure, and the peculiarity of the stone roof covering as a construction technique to be preserved and improved. The recovery project has exploited the potential of the laser scanner and micro-invasive diagnostic techniques to move towards limited replacement choices of wood elements that could no longer be recovered. The recovery of the roof of the XVI Chapel, as a pilot building site of an international research project on the maintenance of historical sites (INTERREG ITA-CH “Main10ance”), is evidence of a fruitful multidisciplinary discussion aimed at improving the methodological approach to the strengthening work of historical structures.