Wooden Roof Research Articles

Application of timber-based techniques for seismic retrofit and architectural restoration of a wooden roof in a stone masonry church

Recent seismic events in Italy highlighted several vulnerabilities in historical buildings belonging to the national architectural heritage. Among others, monumental constructions such as churches appeared to be prone to local (out-of-plane) collapses of masonry walls, often caused by the presence of poor-quality materials and inadequate connections among structural elements. Seismic retrofitting methods are thus necessary, but should also be reversible, not invasive, and aimed to the architectural conservation of the construction, preserving its historical value. In this framework, the potential of timber-based techniques as reversible and effective methods for seismic strengthening and restoration of buildings is promising. This work presents the case study of St. Andrew's Church in Ceto (Brescia, Italy), a stone-masonry monumental building featuring a timber roof from 18th century. Following several inspections commissioned by the curia of Brescia, the church was found in fair structural conditions, with the exception of the wooden roof, having structural elements poorly or not connected among each other and to the masonry. To reduce the evident seismic vulnerability of the church, the roof was retrofitted with plywood panels, allowing for an affordable, rapid, and easily realizable intervention. In this way, the original timber structure could be preserved, creating an adequate load-carrying capacity for static loads, as well as an effective diaphragm against seismic loads. The conducted calculations and numerical analyses showed that the realized intervention greatly improves the seismic behaviour of the building, demonstrating the benefits of wood-based retrofitting and supporting their use for the preservation of architectural heritage.

Wooden roof structures of the Moberg house

The preservation of cultural heritage sites is an important task. Historical monuments are a reflection and documentary evidence of the past, information about which must be preserved and passed on to future generations. One of the most vulnerable and fragile structures in a building is the roof. This work provides historical information and presents the results of a survey of the structures of the building of engineer Moberg in the urban-type settlement of Kalevala in the Republic of Karelia of the Russian Federation. The structural system of the roof and the joint work of its elements have been studied. The expediency of preserving the structural system, shape and geometric parameters of the roof, as well as replacing the existing structures before the reconstruction with new elements from modern sawn timber has been substantiated. The cultural heritage site “House of Engineer Moberg” is an architectural monument of regional significance of the early 20th century and the main historical building of the urban-type settlement of Kalevala, built under the influence of the ideas of Finnish national romanticism. According to archival sources, the house was built in 1906 and renovated in 1925-1926 with the participation of engineer Eduard Moberg and builder Tuomas Waller. Nowadays, the building houses the ethnocultural center kalevalatalo.

Semi-automatic 3D frame modelling of wooden trusses using indoor point clouds

Historical Building Information Modelling (HBIM) is a widely used methodology for the knowledge of the current state of historical buildings, centralizing digital data like geometry, which is the focus of this paper, and more specifically the geometry of the structure of wooden roofs. Their 3D modelling presents some difficulties due to the irregularities in the cross-section of the beams and the complex geometries of the structures, among other reasons. This paper presents a method for the semi-automatic estimation of the framed structure of these 3D structures composed of trusses and beams using as input an indoor point cloud. The methodology consists of the application of two consecutive planar analyses for the location of the beams in the 3D space. The proposed methodology is tested for three different real-world case studies. The framed structure of the three buildings is obtained, serving for the location of the beams in the 3D space and allowing accurate structural analysis. The semi-automatic methodology has shown to be a useful tool for its use in real-world case studies, allowing the performance of structural test, including the estimation of the axial forces diagrams, with the models generated.

Design of stick-framed wood roofs under tornado wind loads

Light-frame wood construction comprises nearly 90% of the housing industry in Canada and the United States. The roofs of these houses can be constructed either entirely on site or using prefabricated trusses. Assembling the roof structure on site, otherwise known as stick-framing, is a framing technique with current code guidelines that are based on past practice and limited consideration of wind loads. This makes these roof structures susceptible to failure in high-speed wind events, such as tornadoes. This research proposes improved stick-framing guidelines that would work for EF-2 tornadoes. Using non-linear finite element analysis, a stick-framed roof was designed following the guidelines in the National Building Code of Canada. Non-linear links were used to model all of the connections between the members in the roof structure, with frame elements used to represent the members. Increasing wind loads were applied to the structure and the first elements of the roof that failed were improved using an iterative performance-based design approach until the performance target of resistance to EF-2 tornadoes was achieved. The failure of the roof-to-wall-connections and the lack of members used in the framing were the two main issues highlighted and addressed. Damage survey photos were used to compare failures observed in the model with failures after real tornado events, which demonstrate many similar failure modes. The research recommends the requirements to ensure stick-framed roofs can withstand EF-2 tornadoes. Most notable is an improved gable end frame, which gives the structure more roof-to-wall connections, as well as a more structurally sound frame where the loads are the highest. Other additions include struts, hurricane ties at all roof-to-wall connection locations and increased number of nails in various connections throughout the repeating inner frames. Minimum member sizes and qualities for each type of member used in the roof structure are also recommended.

Wood Used in Brussels’ Old Buildings: Origin, Characterisation, and Use (12th–19th Centuries)

Abstract Since 1990 archaeologists, historians and dendrochronologists have worked on 128 sites in the Brussels-Capital Region. In addition to producing a typo-chronological inventory of wooden roof structures (12th–19th centuries), the studies have now extended to finishings and floor coverings, with an increasing focus being placed on the types of wood used. Although oak was the predominant material, especially before the 17th century, the resources used in Brussels and the surrounding villages were local. They came from three wooded areas, cleared or degraded to varying degrees: the Sonian Forest, state-owned forests, and hedgerows. Oak grows rapidly, with wide rings which make dendrochronological dating difficult, although this can be overcome by utilising more comparative data, employing carbon-14 dating, or knowing the historical context. The use of green wood has been confirmed, with unusual felling periods spread over two years. The sinuous profile of the fast-growing oaks was used to cut the knee braces in roofs over knee walls and porticoed wooden structures of monuments, urban housing, and vernacular architecture. Mediocre oak, or even wood from fruit trees, elm, or ash, was used for this kind of architecture. Moreover, from the 17th century onward, species other than oak began to appear in the roof frames of all buildings, especially after the centre of Brussels was bombarded in 1695. The typology of the reconstructed roof frames is the same as that prior to 1695, but a wider variety of woods were used to meet the high demand at the time of reconstruction. This diversity of species is more evident among floorboards, with poplar, elm, Scots pine, fir, and spruce being used. This may have been due to technical reasons, but, in the local context, it would also have been a question of using the precious oak of the Sonian Forest frugally.

Reliability of toe-nail connections in a gable roof houses under uplift wind loads

The latest devastating hurricanes have caused considerable damage to light frame wooden houses. The detachment of the roofs because of the high uplift wind loads is one of the typical damages. This detachment often occurs at the contact connections in between the roof trusses and the walls of the houses. For several decades, toe-nail connections, which are poor in uplift resistance, have been used in those contacts. The purpose of this paper is to develop an efficient numerical model for performing reliability assessment of wooden roofs under uplift wind loads taking into account the statistical variability in both the load–deflection curve of toe-nails and the uplift wind load. The model utilizes a three-dimensional semi-analytical solution previously developed to predict the behaviour and failure of wood roofs under spatially variable uplift loads. The random characteristics of the toe-nails were calculated based on experimental results found in the literature and were statistically simulated using a beta distribution. The randomness of the wind speed was evaluated using a normal distribution. A full-scale gable roof was considered as a case study to determine the probability of roof failure at different wind speeds, Monte Carlo simulations along with the semi-analytical model were used to obtain the fragility curve based on two different criteria. It was found that beyond a mean wind velocity of 32 m/s, the probability of roof failure increases rapidly.

Ancient wooden roofs in the area of Genoa: the structure with a curvilinear profile of the parish church of Cogoleto

A particular roof is that of S.M.Maggiore church in Cogoleto. The 19th century church, in fact, has an upper two-pitches roof and a lower roofbelow with a curvilinear profile. Both of them insist on the same perimeter, but they have no direct connection between them as far as it is visible. The study, therefore, focused on the understanding of this part of the building. The understanding of the building was obtained thanks to the use of both indirect sources (archive and bibliographic research) and direct sources: archaeological analyses (stratigraphic, mensiochronological, mineralogical-petrographic and wall textures), thermographic and ultrasonic analyzes. A particular effort had to be made in studying the details and reading the stratigraphic signs on the wood (this aspect is usually little developed). It was necessary to extend the analysis to the entire building for a better understanding. This study highlights a sequence of interventions in the church over the past two centuries; previous structures were usually preserved; new elements and stratifications were added. The two structures were chronologically different: the upper one is the most recent but was designed to preserve the older one below. Another interesting fact that emerged is the particular shape of the lower structure: a wooden roof with a curvilinear profile. This form of coverage is not particularly widespread in this part of the Ligurian territory. In any case, it is unusual for the historical period in which it was built (19th century). The research, therefore, focused on the reasons for this particular choice and the study of the dynamics of the 1877-78 construction site. It also allowed us to understand better the functioning of this specific structure, its technology, and its relationship with the remaining parts of the complex. The historic curved profile roofs highlighted differences in material and installation technique.

Technique at the service of a new liturgical model: the timber roof of the church of Saints Marcellino and Pietro in Cremona

At the turn of the 17th century, the Jesuit order settled in the city of Cremona, where, thanks to the support of Bishop Speciano and some notable families, it started the construction of the church of Saints Marcellino and Pietro (1606-1620), the Schools and the College. The church model of the aisleless rectangular hall – large enough to accommodate a large number of faithful – forced the fathers to resort to unusual solutions for the area of Cremona, which, over the centuries, also led to instability and structural problems. The careful archival and bibliographic research made it possible to investigate the wooden roof with wide-span “Palladian” trusses (about 15.20 m), directing the diagnostic analyzes, identifying the peculiarities of the technical solutions adopted, in a continuous comparison between indirect sources and in situ investigations. The construction events of the trusses and secondary framing were investigated over a long period of time, to include the succession of minute maintenance and repairs, also carried out in the last two centuries; the complexity and stratification of works carried out in phases and singular interventions, linked to the chronological succession of events, is the basis for the interpretation of the current state of the structure, therefore for a restoration intervention aimed at protecting the building palimpsest.

Ancient wooden roofs in the area of Genoa: an almost intact 17th century salt warehouse

The study on the wooden structure of the roof of the former Salt Warehouse in vico Malatti 13, in ancient Genoa port area, presented here, is part of a broader research plan including PRA (university research project) 2016 "The archeology of architecture in the restoration site" of DAD – Dipartimento Architettura e Design of Genoa (Italy) with Universidad del Pais Vasco - Facultad de Letras, Departamento de Geografia, Prehistoria y Arquelogia (Spain), PRA 2018 "Conservation and restoration: methods of analysis and strategies of monitoring" of DAD (Genoa-Italy) with CISAPSI - Coordinamento Intercomunale Studi e Analisi del Patrimonio Storico della Svizzera Italiana (Fado-Switzerland) and PRA 2019 "Conservation and restoration: methods of analysis and strategies for the maintenance of the material and restoration: strategies for a quality project" of DAD (Genoa-Italy). The roof under study has a special structure: the trestle structure. This building tehnique was very common in Genoese context between the 15th and 18th century. Nevertheless this technique had not yet been widely studied. Another very special feature, the roof remained almost intact since 17th century, when it was built. The difficulty of access and direct inspection of the roof structure, combined with the need for constant monitoring for its conservation, required a particular methodological effort, and an analysis procedure was identified making use of several sources and multiple tools. Beside the characterization and technological specificity of this roof, the methodological aspect is a very interesting one, as it could be adopted also in other similar contexts.

Review: Sculpture on a Grand Scale: Jack Christiansen’s Thin Shell Modernism

Review: <i>Sculpture on a Grand Scale: Jack Christiansen’s Thin Shell Modernism</i>

Experimental Characterization and Acoustic Correction of a Multipurpose Performance Hall: The Italian Theatre “Cavallino Bianco”

This study presents the retrofit acoustic dq1esign of the Italian theatre “Cavallino Bianco”. In its historical configuration, the hall had a curved roof with a pressed-plant fiber ceiling, which was demolished and replaced with a wooden roof without a false ceiling, leading to an increase in volume and a worsening of the reverberation time. This study proposed the realization of a wave ceiling and the application of sound-absorbing and reflecting panels on the walls, which have already been implemented. These modifications have affected the acoustic characterization of the theatre, as shown both through on-site measurements during the main construction phases and through numerical simulations. The reverberation time, clarity index, and speech transmission index (STI) are evaluated considering all the variations in the hall over different construction times, and the optimal solution is identified with regard to different specific uses. The final configuration with the new roof, by reducing the volume of the hall and using sound-absorbing materials, significantly reduces the reverberation time (e.g., at 2000 Hz, this reduction is from 2.33 to 1.47). In addition, the hall at full capacity with chairs and people shows evident improvement in terms of the clarity index, allowing the theatre to be used for a wide range of musical genres such as instrumental, symphonic, and opera performances. As regards the Combos 00 (concrete roof without vertical sound acoustic panels) and 01-a/b/c (wooden roof with draped curtains), the STI values are never lower than 0.42 and never higher than 0.70; therefore, the room never experiences poor or excellent conditions at any point. The Combos 01-a and 01-b, which have a non-performing C80, have a good STI index, confirming the difficulty of achieving a configuration that can be optimal a variety of uses. Combo 01 (wooden roof without vertical sound acoustic panels and no draped curtains), which has a good C80 value, presents a lower STI value, with an average performance. The STI values of Combo 02-a (characterized by wave false ceiling and vertical sound acoustic panels) are never lower than 0.52 and never higher than 0.60; therefore, neither poor nor excellent conditions are experienced in the room, but there is still a slight improvement over the combos 00 and 01.

Simulating a stone roof for the Maltese Neolithic temples: Analysing stress to understand specialisation

The Neolithic temples of Malta are large megalithic structures built between 3700 BC and 2400 BC. Around 30 temples have survived to present day, providing extensive evidence of Neolithic culture in the Maltese islands. However, while the temple walls are generally well preserved, there is a longstanding debate regarding the nature of the temples’ roofing, of which scarce indication remains. With material evidence existing both for wooden and stone roofs, new techniques are necessary to determine the overall plausibility of different roofing options. In this paper the possibility of a stone roof is tested using 3D simulation of stress within a temple model. By measuring the forces in play within the temple structure, and observing interesting architectural features in situ, the suggestion of a stone roof is reinforced. Temple walls appear to have been constructed with the direct aim of dispersing excessive weight, showing a complex understanding of architectural principles. Observations made by the study also have wider implications for the Maltese Neolithic, especially with regards to cultural transmission throughout the island and different generations.

Analysis of an empirical seismic fragility prediction model of wooden roof truss buildings

To explore the vulnerability of wood roof truss buildings (WRTBs) under earthquake action, the empirical damage typical characteristics of 12,343.4 × 104 m2 and 21,490 buildings of this type of building that suffered different degrees of loss in 22 typical destructive earthquakes in China from 1993 to 2013 were observed and analysed. Based on the analysis methods of the nonlinear vulnerability model, probability statistics, and prediction model, a novel fragility probability matrix, plane, surface, nonlinear regression curve, and function model of different intensity zones under the latest Chinese macrointensity standard (GB/T 17742–2020, CMS-20) assessment were established, and vulnerability curve models were employed based on the damage ratio (DR) and actual cumulative damage probability (ACDP) parameters. According to 1993–1999, 2000–2010, and after 2011, the time-varying fragility specimen data were classified and censusly analysed. The fragility prediction curve models of DR and ACDP were performed using the probabilistic demand modal analysis method. Combined with the matrix probability and confidence interval calculation model, a novel regional mean fragility index domain model for typical structural (WRTB) vulnerability assessment was developed.

The influence of the geometrical features on the seismic response of historical churches reinforced by different cross lam roof-solutions

Recent Italian earthquakes have shown the seismic vulnerability of many typical historical masonry churches characterized by one nave and wooden roofs. Under transverse earthquake, the nave transverse response of this kind of churches can be influenced by the geometrical and material features. To increase the seismic performance, strengthening interventions aimed to pursue the global box-behavior by the realization of dissipative roof-structure represent a valid strategy, especially to avoid out-of-plane mechanisms. In this way, the roof structure must be able to represent a tool for the damped rocking of the perimeter walls. Cross-laminated timber (CLT) panels with calibrated metal connections have been recently adopted in experimental tests as a valid solution to obtain a roof-diaphragm with ductile behavior, satisfying the conservative restoration criteria at the same time. In this paper, after a description of the numerical approach for the damped rocking mechanism for one nave configuration church, the effectiveness of different CLT based roof-diaphragms in the nave transverse response is investigated for four historical churches. The seismic responses are performed by comparative dynamic nonlinear analyses and the results are shown in terms of displacements and shear actions transferred to the façade. The influence of the geometrical features of the churches on the nave transversal response is deepened by sensitivity analyses with the aim to predict the displacements and shear variations under the same earthquake excitation.

EXPERIMENTAL STUDIES OF NODAL JOINTS OF WOODEN ELEMENTS IN TRUSSES AND GEODESIC DOMES

Introduction: In this paper, we consider LVL (laminated veneer lumber with unidirectional veneer) as an element of plane trusses and geodesic domes, acting as the bearing structure of roofs, and study destruction of LVL joints, which is necessary to improve designs of wooden roofs under consideration. Methods: Our studies were based on structural mechanics and wood science. In the course of the study, we used analytical, experimental, and statistical methods to process the results of tests. Results: Based on the experimental studies performed, we suggest a method to determine the design bearing capacity of treenails per edge joint (conventional shear) for joints of LVL elements with wood laminate (DSP-V, wood laminate where veneer fibers in the adjacent layers are mutually perpendicular) plates. Discussion: We obtained new values of the coefficient taking into account the compliance of connections for nodes and joints in LVL composite elements, which make it possible to quickly determine the required cross-sections of bearing rod elements in plane trusses.

Carbonized bamboo parenchyma cells loaded with functional carbon nanotubes for preparation composite phase change materials with superior thermal conductivity and photo-thermal conversion efficiency

Phase change materials (PCMs) are widely used in the field of energy storage management owing to their store and release thermal energy ability through latent heat. However, organic PCMs have the problems of easy leakage, low thermal conductivity and photo-thermal conversion performance, which greatly prevent their practical application. In order to solve these defects, a novel shape stable composite PCMs was prepared by adding polyethylene glycol (PEG) into porous carbonized bamboo parenchyma cells (CPC) containing carbon nanotubes (CNTs). The supporting materials containing CNTs not only had unique three-dimensional porous structure, but also had continuous heat transfer network structure. Compared with pure PEG, the thermal conductivity (TC) of PEG/CPC-CNTs with 0.494 W/m·K was increased by 128%. The prepared composite PCMs had melting and crystallization latent heat with 149.4 J/g and 144.1 J/g. In terms of shape stability, the PEG encapsulation rate by CPC reached 80% which was better than that of untreated PC. Thermo-gravimetric (TG) analysis and thermal cycling experiments showed that PEG/CPC-CNTs had superior physical and chemical stability. More importantly, the matrix material composed of CPC and CNTs made the composite PCMs with a photo-thermal conversion efficiency up to 87.2%. So, PEG/CPC-CNTs composite PCMs with a simple preparation method have great application potential in the field of bamboo or wood based buildings materials such as wood plastic composite, particleboard, floor or roof panels and so on.

What Elevation Makes 2.5D Prints Perceptually Natural?

Elevation plays a considerable role in naturalness perception of 2.5D prints. The necessary level of elevation to make 2.5D prints look perceptually natural may vary from application to application. Therefore, one needs to know the right elevation for specific applications to make the prints look perceptually natural. In this work, we investigated what elevation makes 2.5D prints of wood images perceptually natural. We worked with various wood content images such as wooden wicker, wall, roof, and floor. We found that the optimal elevation that makes 2.5D prints of wood images perceptually natural is content-dependent and in a range between 0.3 mm and 0.5 mm. Moreover, we found that the optimal elevation becomes 0.5 mm if we consider images of wood regardless of the wood content. In addition, there was a high correlation between majority of observers on naturalness perception of 2.5D prints of wood images.

Evaluation of residual and fumigant effects of Deltamethrin WG250 on different surfaces against Anophels stephensi for malaria control

Malaria is one of the public health problem in southern Iran. The main activity of vector control is indoor residual spraying using pyrethrpids. The aims of study was to evaluate the biological assays of deltamethrin WG250 at different surfaces of wall. The persistency of deltamethrin WG250 at 25 mg/m2 was studied on different local surfaces of rooms such as plaster and mud surfaces (sorbent) as well as wooden and thatch roofs (as non-sorbent). Contact bioassays were carried out using WHO standard cones and lab-bred sugar-fed, 48-72 h old females of Anopheles stephensi (Iranshahr strain). In contact bioassays carried out on sprayed surfaces for 150 days. Deltamethrin WG250 (25 mg/m2) caused 43.43-100.0% on sorbent surfaces and 61.11-100.0% on non-sorbent surfaces and persist about 3.5 months in the environmental condition of Saravan district. The fumigant bioassay of deltamethrin WG250 revealed 50-100% mortalities after one month.

Интеграция анкерных линий на кровлях зданий в проектные решения

Ensuring safety during work at height is the most important task in the context of the development of a modern construction complex. Falling from a height occupies one of the first places in terms of the number of victims among all the traumatic factors, based on the statistical data, and its share among other traumatic factors is 28 %. Works at height include construction works, in which there are risks associated with a possible fall of an employee from the height of more than 1.8 m. The employer is obliged to ensure the implementation of measures to reduce injuries at the construction site in accordance with the current legislation. Protective measures when working at height include personal and collective protective equipment, including the use of anchor lines on the building roofs. The article provides for a comparative analysis of five options for the installation of anchor lines suitable for wooden, concrete, metal, and green roofs. For the analysis, a flexible anchor line using a metal cable, a rigid anchor line on high supports, a rigid anchor line on low supports, a flexible anchor line with weights for use on the roofs with landscaping and a flexible anchor line with supports were selected. All the selected anchor line systems comply with the international safety requirements and can be used by one or more workers. The advantages of each system of the anchor lines are revealed, a wide variety of roofing materials are considered: metal seam, made of polyvinyl chloride, with oriented strand board and thermoplastic polyolefin reinforced membrane, which is a high-tech polymer roofing material. All the anchor lines have a variability in terms of the shape and can be used on the roofs of any configurations in the building design without additional efforts and search for the complex solutions on the part of the designer.

Structural Fire Risk for Heritage Buildings by the Performance-Based Engineering Format

ABSTRACT This paper discusses and presents an example of fire risk analysis for a case study of an existing heritage building: the Duomo of Modena Cathedral, located in Italy. The main issues related to the application of the fire risk analysis to heritage buildings are discussed in detail, and an ad-hoc procedure is proposed to manage them for the case study. In order to assess the performances of the building in probabilistic terms, the fire risk analysis is conducted by the event-tree method, the fire dynamics are analyzed by numerical thermo-fluid dynamics models, while the structural behavior is investigated by advanced nonlinear thermomechanical finite element models. Results are expressed in terms of risk curves related to a fixed return period, which quantify the occurrence probability of different damage levels induced by fire in the wooden roof of the case study building. This kind of result is fully compatible with probabilistic performance-based engineering frameworks commonly accepted for other hazards (i.e., earthquakes).