Wooden Roof Research Articles

FLEXURAL STRENGTHENING OF DIMENSIONAL WOOD JOISTS WITH STEEL REINFORCEMENT

ABSTRACT Traditional approaches to the strengthening of dimensional wood roof joist systems are often intrusive and require a substantial amount of additional labour to remove ceilings or roof sections. In an effort to design a less intrusive system for reinforcing over-stressed dimensional wood joists, a roof joist strengthening system was designed consisting of a tension steel plate installed along the bottom of the existing joists with bolted side plate connections. An experimental program was conducted at the University of Manitoba to assess the viability of the reinforcement design. A total of 15 joists were tested to failure under four-point bending conditions, consisting of 5 unreinforced control joists, 5 joists with steel reinforcement, and another 5 reinforced joists with an artificial defect introduced at mid-span along the tension side. The purpose of introducing an artificial defect at mid-span was to simulate the failure modes observed at R.W. Bobby Bend School in Stonewall, Manitoba, where certain roof joists contained knots, splits or cracks along the bottom of the joist within the mid-span region. Service loads based on the applied snow and dead loads applied to these joists were calculated using the National Building Code of Canada [1] and were approximated in the experiment as 8.5 kN. The results indicated that the steel reinforcement produced a 46.8% increase in average load-carrying capacity compared to control joists, and a 33.1% increase in capacity for reinforced joists with artificial defects. The average deflection at service loads was 19.5% lesser than the deflection of the control joists, and the apparent stiffness was determined to increase by 50.0%. The results from this research support the conclusion that the steel reinforcement system for dimensional wood joists is a viable alternative to traditional systems that effectively increases the load-carrying capacity, stiffness, and ductility of the structure.

FLEXURAL STRENGTHENING OF DIMENSIONAL WOOD JOISTS WITH STEEL REINFORCEMENT

ABSTRACT Traditional approaches to the strengthening of dimensional wood roof joist systems are often intrusive and require a substantial amount of additional labour to remove ceilings or roof sections. In an effort to design a less intrusive system for reinforcing over-stressed dimensional wood joists, a roof joist strengthening system was designed consisting of a tension steel plate installed along the bottom of the existing joists with bolted side plate connections. An experimental program was conducted at the University of Manitoba to assess the viability of the reinforcement design. A total of 15 joists were tested to failure under four-point bending conditions, consisting of 5 unreinforced control joists, 5 joists with steel reinforcement, and another 5 reinforced joists with an artificial defect introduced at mid-span along the tension side. The purpose of introducing an artificial defect at mid-span was to simulate the failure modes observed at R.W. Bobby Bend School in Stonewall, Manitoba, where certain roof joists contained knots, splits or cracks along the bottom of the joist within the mid-span region. Service loads based on the applied snow and dead loads applied to these joists were calculated using the National Building Code of Canada [1] and were approximated in the experiment as 8.5 kN. The results indicated that the steel reinforcement produced a 46.8% increase in average load-carrying capacity compared to control joists, and a 33.1% increase in capacity for reinforced joists with artificial defects. The average deflection at service loads was 19.5% lesser than the deflection of the control joists, and the apparent stiffness was determined to increase by 50.0%. The results from this research support the conclusion that the steel reinforcement system for dimensional wood joists is a viable alternative to traditional systems that effectively increases the load-carrying capacity, stiffness, and ductility of the structure.

Moisture Risk Analysis for Three Construction Variants of a Wooden Inverted Flat Roof

The paper presents an analysis of the hygrothermal performance of an inverted flat roof with a CLT (cross-laminated timber) structure in a building that meets the requirements of Passive House Standard (PHS) with regards to the potential risk of moisture. The calculations were made in the WUFI®Plus and WUFI®Bio software. The following variants were taken into account: three structure configurations, three different external climates and different scenarios of microclimate control and air change rate. The results of the calculations show that, especially in cooler climates, there is an actual moisture risk in the structure despite the excellent thermal insulation. The structure of the inverted flat roof, due to the use of a tight membrane on the outer side, allows for the partition to discharge the excess moisture only to the inside of the building. Ensuring the comfort of users may require periodic humidification of internal air, which translates directly into an increase in moisture content of the structure. The performed analysis clearly showed that there are no universal solutions. It is important to point out that for the proper performance of inverted wooden roofs, it is crucial to analyse moisture, not only thermal and energy parameters.

Structural bracing of wooden roofs under the extreme winds

An essential element of every building is a roof that protects it against the influence of weather conditions - rainfall, wind, and temperature changes. The shape of the roof, the type of roof covering, and the slope of the roof have the greatest impact on the type and material solutions. The roof structures are made of wooden, steel, or reinforced concrete. Especially in single-family residential buildings, wooden roof structures are most often used. Wood is perceived by many as the oldest and best building material, valued for its low weight, good strength, elasticity, and high thermal and insulation values. Traditional roof has been used over the centuries. The more common roof in wood framing roof is gable and hip roof which is consist of rafter, ridge, hip, collar tie and joist. The common slop for hip roof is 3/12 to 12/12. By increasing the slop, the length of the hip element in roof increases and needs to brace closely. The aim of the study is to analyse the location of roof braces in hip roof structures, due to the ultimate and serviceability limit states, under dead, live and wind loads based on finite element method model. Two wind speeds of 22 m/s and 40 m/s is taken into consideration. Elements with the different spans, cross-sections and slope of the roof are analysed.

The Wooden Roof Framing Elements, Furniture and Furnishing of the Etruscan Domus of the Dolia of Vetulonia (Southern Tuscany, Italy)

The Etruscan Domus of the Dolia remained hidden until 2009, when archaeological excavations began in the Etruscan–Roman district of Vetulonia (Southern Tuscany). Based on the classification of the archaeological materials recovered, the destruction of the Domus and the Etruscan city of Vetulonia was traced back to the 1st century BC. The highly various and precious materials recovered inside the Domus revealed the richness of the building and its inhabitants. With this study, we present the anthracological analyses from the Domus of the Dolia. Wood charcoals were recovered from different house rooms, which had different functions based on the archaeological evidence. The tree species employed for the construction of the roof of the building were deciduous and semi-deciduous oak wood (Quercus sect. robur, Quercus sect. cerris) and silver fir wood (Abies cf. alba). Evergreen oak wood (Quercus sect. suber), boxwood (Buxus sempervirens), beech wood (Fagus cf. sylvatica), maple wood (Acer sp.) and cherry wood (Prunus cf. avium) were adopted for the furniture and furnishings of the house. Moreover, wood charcoal fragments of fruit trees belonging to the family of Rosaceae were identified, documenting a possible garden inside the court of the house. The study shows the use of the local tree species primarily. The silver fir wood and beech wood were likely sourced from the nearby (roughly 60 km) Mount Amiata.

Estimation of Magnitude and Heat Release Rate of Fires Occurring in Historic Buildings-Taking Churches as an Example

Historical buildings often fail to meet today’s building and fire protection regulations due to their structure and space restrictions. For this reason, if such buildings encounter fire, serious damage will be resulted. The fire of the Notre-Dame Cathedral in Paris (Notre-Dame de Paris) in April 2019 highlights the seriousness of this problem. In this study, the historical building of “Tamsui Church” was selected as an example. The Fire Dynamics Simulator (FDS) was adopted to analyze the scale of damage and possible hazards when the wooden seats in the church are on fire, and improvement measures were proposed to ensure that such buildings can be used under safer conditions. It was found that the existing seat arrangement will cause the spreading of fire, and the maximum heat release rate is 2609.88 kW. The wooden roof frame above the fire source will also start to burn at 402.88 s (6.6 min) after the fire, which will lead to a full-scale fire. To maintain the safety of the historical building, it is necessary to add active firefighting equipment (smoke detector and water mist system).

Traces of Transport at the Vienna Hofburg Roof Constructions

Abstract The Vienna Hofburg is a large complex of buildings of unique historic importance with historical wooden constructions from the 13th to the 20th century. Within its wooden roof constructions, rafting wedges were found, which proves that the timber used did not originate in the surroundings of Vienna but had to be transported to the city. An ascertainment of these residual traces in eleven wings of the Hofburg building was made; five different types (within two main groups) of rafting wedges and withies (softened twigs that can be used like short ropes to tie trunks together) were defined: (1) simple flat wedges, driven into the fresh wood; (2) round or squared wedges, with or without withies driven into bored wholes. It was not possible to trace back the origin of the construction timber by means of that typology. However, the combination of dendroprovenancing and historic records found in archives led to first results.

Risk assessment of low-rise educational buildings with wooden roof structures against severe wind loadings

ABSTRACT This paper investigates the prominent failure modes of educational facilities by using field observations. Specifically, damage to the roof covering, roof structure and exterior windows were quantified. An archetype of these structures is modeled in a Monte Carlo Simulation wherein the probabilistic resistance capacities of the building envelope components are compared to their corresponding probabilistic wind loads. The probability of exceedance is then evaluated at three levels of damage state per 3-s gust wind speeds. For the vulnerability curve, the results were fitted into a cumulative probability density function with a mean of 4.7314 and a standard deviation of 0.4061. The results of the model are then evaluated through a case study of Typhoon Nina 2016. The model generally underpredicts the mean damage ratio per municipality by about 13.17% for wind speeds of 40.225 m/s and by about 3–6% for wind speeds between 49 m/s to 71 m/s. The reported damage by the respective government authorities was aggregated on a municipality level and compared to the performance of the model. A statistical analysis between the reported and mean predicted damage was also done by using the Spearman rank correlation coefficient. The results yielded a positive correlation of 0.856.

전통적 일본 종교건축물(社寺)의 양식적 상관성 분석

Purpose: This study focuses on the Buddhist temple architecture and the unique Japanese shrine architecture among Japanese religious structures, and by grasping the tangible and stylistic correlations and interrelationships of each of the traditional structural elements. Also, this study intends to provide basic data to examine the modern application of traditional building in the future. Method: This study conducted a basic study on the temple architecture influenced by Buddhist culture and architecture from China and Korea, and identifying the typology, characteristics, and mutual impact of each type of architecture. Based on existing research and literature, it was intended to derive traditional characteristics and types of Japanese architecture, especially by examining the types and characteristics of morphological components, and to comprehensively consider the characteristics and interrelationships of traditional Japanese religious architecture. Result: Through this study, the correlation between the shrine architecture and the temple architecture was examined through the relationship between the stylistic features of traditional Japanese religious buildings and the traditional form components. It shows that religious structures such as traditional shrines and temples have become the roots of modern Japanese architecture, and structural elements such as wooden structures and roofs still have a great influence.

Variation of rooftop thermal environment with roof typology: a field experiment in Kitakyushu, Japan.

While urban open spaces have been shrinking with the rapid urbanization, rooftop space use is an alternative solution to such problems. Rooftop thermal environment is a critical consideration under global warming and local warming. Although there have been studies on rooftop thermal environment, variation of rooftop thermal environment with roof typology has not been fully revealed to support rooftop space design. To fill this gap, a field experiment was conducted over green roof (GR), wooden roof (WR), and shaded roof (SR) in a temperate city of Kitakyushu, Japan. Environmental parameters such as solar radiation, air temperature, and relative humidity at different heights of these three roofs were recorded, to understand rooftop thermal environment and daily heat stress variation with rooftop types and the height above roof surface. The results indicate that WR had the highest diurnal near-surface temperature and the worst heat stress, where the near-surface heat stress could even reach the danger level. GR exhibited the lowest diurnal near-surface temperature and heat stress, where the heat stress was only under caution and almost safe condition. SR exhibited the lowest diurnal 1-m temperature and SR had the weakest heat stress, indicating the significance of installing shading devices for rooftop thermal environment improvement and heat stress alleviation. GR exhibited excellent performance in reducing air temperature and heat stress at the pedestrian level, where its worst heat stress was only in caution condition. Compared with that at 1-m height, moreover, 1-cm temperature and heat stress of WR and SR were generally higher, indicating that people may undergo worse heat stress when kneeling or sitting compared with upright activities. Moreover, GR suppressed near-surface heat stress due to its excellent cooling performance.

EVALUATION STUDY ON WOODEN PILLAR MOSQUES BUILT IN ANATOLIA IN THE 13TH CENTURY

In this article, mosques that are carried on wooden poles, which have a very important place among Anatolian Seljuk and Principalities (Beyliks) Period mosques and covered with flat wooden roofs, are discussed. With the continuation of the wooden pillar mosque tradition in Central Asia, very important examples of this building type, which were brought to Anatolia by the Turks in the Anatolian Seljuk State Period, were revealed in the 13th century. In this study, Beyşehir Eşrefoğlu Mosque, Afyon Ulu Mosque, Ankara Arslanhane (Ahi Şerafettin Mosque) and Sivrihisar Ulu Mosque, which are the most magnificent examples of this building type, were investigated. After the archive and literature researches about these buildings were done, a catalog study of the buildings was made. Within the scope of this study, the formal features of the buildings such as plan, facade, construction technique, plan type, number of entrances, the presence of the last congregation and the presence of a gathered floor, the environmental relation, the spatial characteristics such as the carrier element and the architectural elements were examined. The aim of the article is to make a general inference on the wooden pillar mosques built in Anatolia in the 13th century in line with the data obtained from the studies and to determine the common aspects of wooden pillar mosques built in four different parts of Anatolia. In the light of the information obtained as a result of the catalog studies and archive scans, it has been observed that the structures have similar characteristics especially in terms of the materials and construction techniques used, but some of their features differ and take shape in line with the construction traditions of the places where they are located. Konya Sahipata Mosque, which was built in the 13th century, was excluded from the scope of the study, as its general characteristics were completely changed after the fire.

EVALUATION STUDY ON WOODEN PILLAR MOSQUES BUILT IN ANATOLIA IN THE 13TH CENTURY

In this article, mosques that are carried on wooden poles, which have a very important place among Anatolian Seljuk and Principalities (Beyliks) Period mosques and covered with flat wooden roofs, are discussed. With the continuation of the wooden pillar mosque tradition in Central Asia, very important examples of this building type, which were brought to Anatolia by the Turks in the Anatolian Seljuk State Period, were revealed in the 13th century. In this study, Beyşehir Eşrefoğlu Mosque, Afyon Ulu Mosque, Ankara Arslanhane (Ahi Şerafettin Mosque) and Sivrihisar Ulu Mosque, which are the most magnificent examples of this building type, were investigated. After the archive and literature researches about these buildings were done, a catalog study of the buildings was made. Within the scope of this study, the formal features of the buildings such as plan, facade, construction technique, plan type, number of entrances, the presence of the last congregation and the presence of a gathered floor, the environmental relation, the spatial characteristics such as the carrier element and the architectural elements were examined. The aim of the article is to make a general inference on the wooden pillar mosques built in Anatolia in the 13th century in line with the data obtained from the studies and to determine the common aspects of wooden pillar mosques built in four different parts of Anatolia. In the light of the information obtained as a result of the catalog studies and archive scans, it has been observed that the structures have similar characteristics especially in terms of the materials and construction techniques used, but some of their features differ and take shape in line with the construction traditions of the places where they are located. Konya Sahipata Mosque, which was built in the 13th century, was excluded from the scope of the study, as its general characteristics were completely changed after the fire.

Dynamic Authenticity: Understanding and Conserving Mosuo Dwellings in China in Transitions

Mosuo dwellings are distinctive vernacular architecture forms that are shaped by the unique matriarchal society of Mosuo in Southwest China. They have undergone dramatic transformations during the 21st century as a result of modernization and tourism. There is a lack of theoretical and empirical studies regarding the impact on the authenticity. This paper aims to fill this gap and develops a theoretical framework—cultural architectural assets—to understand and interpret the transitions of Mosuo dwellings and their authenticity in transitions. Adopting an anthropological methodology approach, this article examines the changes and continuities of Mosuo dwellings during the last thirty years. Fieldwork was conducted in nine Mosuo villages in Yongning Township through a range of qualitative methods, including participatory observations, photographic survey and photo elicitation interviews. The investigation results revealed cultural-architectural elements that are continued in the transitions include the courtyard form, the sacred chamber and the grandmother’s house; cultural-architectural elements that are changing include the flower house and grass house; cultural-architectural elements that are disappearing include the back room (Dupan) and the upper hearth in the grandmother’s house as well as the wooden shingle roof. As a result, the study constructs a conservation approach for sustainable development in three dimensions: living culture, building culture and values and beliefs. This analytical framework can be adapted to be applied to different contexts as a sustainable approach for the conservation and development of vernacular architecture in transitions.

Environmental protection problems in the areas of former mines with emphasis on sinkholes: selected examples

The paper concerns an analysis of causes of sinkholes in the area of the former mines located in the Upper Silesia (Poland). The conducted statistical analysis allowed to determine the share of some types of shallow excavations in the formation of sinkholes. Analyses covered the period from 1966 to 2003 and records of more than 300 sinkholes. The research team determined—on the basis of the considerations—that the factor that poses the greatest threat and contributes to the formation of sinkholes during the operation of the mine is shallow goafs. Other such factors are dog headings that have not been decommissioned yet. It can be assumed that they will also generate a significant number of collapses in mines that are no longer in operation. The transition into the state of cave-in of old and shallow dog headings is often caused by loss of load-bearing capacity of a wooden roof support which biodegrades. Collapses linked to these excavations may be predicted with the use of tools such as the method presented in the paper.

Wooden Truss Analysis, Preservation Strategies, and Digital Documentation through Parametric 3D Modeling and HBIM Workflow

The main focus of this paper is the most recent phase of a large research project that has studied several wooden roof structures in the area of Bologna, belonging to a set of important historical buildings, all dating back to the 16th and 18th centuries. In particular, the behavior of the wooden trusses that support pitched roofs is analyzed, according to a methodological approach, based on generative algorithms that can help researchers and technicians to improve the comprehension of wooden structures’ behavior during their entire lifespan. While all the previous case studies concerned churches, this latest step extends the survey to the roofing system of the Municipal Theater of Bologna, which has a span of approximately 25 m. The core of the process concerns the automatic transformation of the point cloud into 3D models using parametric modeling tools, such as Grasshopper generative algorithms. Following this workflow, it is possible to speed up the creation of different truss models by changing only a few input parameters. This updating of the research protocol automatically creates a Building Information Modeling (BIM) model and a calculation model for the wooden trusses to perform a structural stress analysis by linking Grasshopper tools with Dynamo-Revit features. The procedure that has been developed from previous studies is still evolving and aims to speed up the modeling procedure and introduce new tools and methods for interpreting the functioning of these structural elements when surveyed through terrestrial laser scanning (TLS) devices.

Wind Design Procedures for Wood Roof Trusses of Low-Rise Structures

Abstract Wind design procedures for wood roof trusses of low-rise structures are evaluated in this paper using wind tunnel test data and two-dimensional finite-element frame models. The adequacy of...

Das Odeion im Artemision von Ephesos

Das Odeion im Artemision von Ephesos

Wind Resistance and Fragility Functions for Wood-Framed Wall Sheathing Panels in Low-Rise Residential Construction

AbstractThe wind uplift resistance of wood roof sheathing panels has been the subject of many engineering studies due to the high probability that roofs are subjected to large uplift loads during i...

Surveying and Dating the Wooden Roof Structure of St Francis of Assisi Church in Valletta, Malta

ABSTRACT St Francis of Assisi Church is an historic religious building in the centre of Valletta, Malta’s capital. Through analysis of the roof structure we have determined the timber species used in its construction, their state of conservation and the date of different building phases and maintenance work. The study provides an historical and cultural framework for the entire building. Apart from identifying the type of timber and typically English way of construction, dendrochronological dating has revealed two precise phases of intensive restoration, dating to 1681 and 1876, respectively. For both periods, the timber’s provenance points to the Eastern Alps, based on dendrochronological master chronologies of European larch (Larix decidua). Furthermore, a single Norway spruce (Picea abies) board from the vault was dated to 1684. This church is a typical example of Maltese culture, intermingled with other cultures that have resulted in a very particular architectural-work.

Uşak-Banaz-Yeşilyurt (Holuz) Köyü Camii ve Kalemişi Bezemeleri

The inner Aegean region is an area where mosques with depictions can be seen frequently. Yesilyurt (Holuz) village mosque in the Banaz district of Usak province is an important village mosque because it has rubble stone masonry, a wooden roof covering where the lath-and-plaster (bagdadi) dome is used, a writing program, rich painting works (kalemisi), and the name of the master who completed the painting works. The motif repertoire of the painting works consists of miniature trees placed in vases, symbolic religious lodge (tekke) tools, urban depictions, floral decorations placed on curved branches and various motifs that are under the plaster. The structure, which is owned by the village legal entity, is registered with the decision of the Izmir Cultural and Natural Heritage Protection Board No.1 dated 1988 and numbered 463. Although it is not known by whom and when the mosque was built since it does not have an inscription, when its decoration characteristics are evaluated, it can be dated to the end of the 19th century. In the study, the architectural characteristics and painting work decorations of the building have been examined in detail, and its place and importance within its period have been determined. The work, which provides important clues about its period, is significantly ruined and about to collapse. It should be repaired as soon as possible following its original form and passed onto future generations.