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Roofings
Published in Michael McEvoy, External Components, 2014
The roof pitch is the angle of slope to the horizontal. For the form of pitch shown in fig. 8.2 (symmetrical, sloping from a central ridge), the pitch used to be expressed as the fraction rise/span because this relationship of the rise to span was more expressive of the setting out techniques of traditional pitched roof construction (when using site-cut timber or metal structural sections). For example, a roof finish laid at an angle of 3313. degrees would have a rise/span = 13. However, since not all roofs have symmetrical slopes and since prefabricated roof trusses are more usual today, most manufacturers of pitched roof finishes indicate the suitability of their product according to the angle of slope.
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
Published in International Journal of Architectural Heritage, 2023
Michele Mirra, Andrea Gerardini, Sergio Ghirardelli, Geert Ravenshorst, Jan-Willem van de Kuilen
In order to meet the requirement of seismic improvement, retrofitting interventions were applied to the structural element responsible for most vulnerabilities, i.e. the wooden roof, seizing also the opportunity to combine both strengthening and architectural conservation. Taking into consideration the improvement of seismic shear transfer and redistribution of the existing roof, the main retrofitting intervention consisted of transforming it in a diaphragm. To this end, an overlay of 30-mm-thick C24 structural plywood panels fastened to the existing sheathing with 4 × 60 mm Anker nails at 80 mm spacing, was realized (Figure 5). The plywood panels overlay was designed considering each roof pitch as a shear wall. Since the panels have a standard width of bi = 1200 mm, 15 nails were present on each panel’s short side, following the adopted spacing s = 80 mm. The long side of the roof above the barrel vault featured 16 rows of panels (see Figure 5), thus the total strength was derived as the design shear strength Fv,Rd of a single nail, multiplied by the number of nails in the panel’s width (equal to bi/s) and by the number n of rows of panels. For this case, Fv,Rd = 1.15 kN, bi/s = 15, and n = 16, thus the total strength of a roof pitch is 1.15∙15∙16 = 276 kN. During a seismic event with the design PGA of 0.08 g, this value would enable the roof to effectively transfer the shear loads of 200 kN induced by the seismic weights of the gables.
Modelling vulnerability of Australian housing to severe wind events: past and present
Published in Australian Journal of Structural Engineering, 2020
Daniel J. Smith, Mark Edwards, Korah Parackal, John Ginger, David Henderson, Hyeuk Ryu, Martin Wehner
In 2006, Geoscience Australia facilitated a workshop at the Cyclone Testing Station (TimberEd 2006) to develop a series of heuristic vulnerability curves to broadly cover a range of both residential and light industrial building types in Australia. The study was based on expert opinion from the Australian wind engineering community (Wehner et al. 2010a) and produced a set of curves representing the vulnerability of a population of buildings. As part of the development process, the study ranked important features for modelling building performance in severe wind events. The rankings for residential buildings were the following (in descending rank order): age; roof material; roof shape; openings (% glass); applicable building standard; roof pitch; structural complexity; openings (doors); design wind speed; wall cladding; and building height. Six curves were developed (Figure 5) for several structural systems including brick veneer cladding, double brick wall construction with tiled roofs, timber wall framing and concrete blockwork wall construction with metal clad roofs. Each curve is modelled using an s-shaped two-parameter Weibull function, which relates loss ratio to the 0.2-s gust wind speed at 10 m height as follows:
Predicting the energy production by solar photovoltaic systems in cold-climate regions
Published in International Journal of Sustainable Energy, 2018
Hadia Awad, Mustafa Gül, K. M. Emtiaz Salim, Haitao Yu
For simplicity and given that the monitored PV systems are installed at a wide range of azimuth angles, these angles are systematically divided into eight bins. Each bin is 45° wide and divided evenly around the directions of true north (0°), northeast (45°), east (90°), etc., as demonstrated in Table 3. Additionally, a wide range of tilt angles is investigated in this study, including 2:12 (9°), 3:12 (14°), 4:12 (18°), 5:12 (23°), 6:12 (27°), 7:12 (30°), 8:12 (34°), 9:12 (37°), 10:12 (40°), and 21:12 (60°). Table 3 shows the distribution of tilt and azimuth angles deployed in this study. In keeping with conventional practice in North America for roof pitch, 74% of the monitored houses are constructed at a slope ratio of 6:12, 7:12, or 8:12, and 32% of these slopes are south-oriented. For the purpose of testing, the developed forecast model, rare tilts, and orientations are hidden during the training of the model and are instead reserved for later testing. The purpose of this is to validate the hypothesis that the proposed model is capable of predicting the PV performance of varying layouts and locations.