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Upper floors
Published in Derek Worthing, Nigel Dann, Roger Heath, of Houses, 2021
Derek Worthing, Nigel Dann, Roger Heath
Traditionally, joists were normally spaced at 16 inch (i.e. 400mm) centres. This is probably still the most economic arrangement of the timbers. Joists spaced more widely apart require deeper sections because they are carrying extra load and the floorboards also need to be deeper in section due to their increased span. Joists that are closer together use excessive amounts of timber, even allowing for their smaller cross-sectional area. However, building control was fairly lax until the development of Model Bye-laws in the first part of the 20th century and it is not unusual to find joists at centres of 500mm or even 600mm in older houses.
Introduction: Wood properties, species, and grades
Published in Abi Aghayere, Jason Vigil, Structural Wood Design ASD/LRFD, 2017
The options for floor framing involve using wood framing members, such as floor joists, beams, girders, interior columns, and interior and exterior stud walls, to support the floor loads. Floor joists can be sawn lumber or engineered wood such as an LVL or I-joist. Beams that transfer loads from other joists are sometimes called header beams. The floor joists are either supported by bearing on top of the beams or supported off the side faces of the beams with joist hangers, or they might bear directly on walls. The floor framing supports the floor sheathing, usually plywood or OSB, which in turn provides lateral support to the floor framing members and acts as the floor surface, distributing the floor loads. In addition, the floor sheathing acts as the horizontal diaphragm that transfers the lateral wind and seismic loads and sometimes lateral soil load to the vertical diaphragms or shear walls. Floor framing members are spaced in a way to coincide with the width of floor sheathing, which is typically a 4 ft. by 8 ft. sheet. Therefore, common spacings of floor framing are 12 in., 16 in., 19.2 in., and 24 in. Examples of floor framing layouts are shown in Figure 1.12.
Timber Shear
Published in Paul W. McMullin, Jonathan S. Price, Timber Design, 2017
For I-joists, the web may buckle under point loads or end reactions. Though this is really a column-buckling-type behavior, it applies to the design of bending members. In these cases, it is necessary to place blocking to stiffen the web of the joists, as shown in Figure 5.4. Note the gap at the top of the block to accommodate thermal and moisture movement.
Madras Terrace Construction: Seismic Upgrade of a Historic Composite Floor Slab System
Published in International Journal of Architectural Heritage, 2023
S. Krishnachandran, Arun Menon, Karunakar Reddy Kurri
The allowable displacement is determined as 40% of the ultimate displacement, which corresponds to half the thickness of the wall (NZSEE 2017) on which the diaphragm rests. In general, this diaphragm typology is common with URM buildings less than three stories constructed using one-brick thick (230 mm) walls. The diaphragm deformation is dominated by the relative sliding between the timber joist and masonry overlay due to the absence of proper force transfer from the timber joist to the masonry overlay. Hence, it is inappropriate to use a shear beam idealization for the diaphragm in the as-built configuration. A negligible deformation of the diaphragm was obtained from the LVDTs placed in the orthogonal direction and no evidence of diaphragm uplift was also observed. For the as-built configuration, since the diaphragm unit does not act together, and relative slip occurs, the displacement considered is the maximum translation occurring at any point in the diaphragm, which happens with timber joist in this case. The force–displacement curve is developed with respect to the maximum displacement occurring at any point in the diaphragm. The ductility of the system cannot be defined based on this information since it is the local failure of a timber joist and not a system failure. For all practical purposes, failure should be defined at the commencement of sliding and not at the exceedance of maximum allowable displacement.
Development of an Innovative Approach for the Renovation of Timber Floors with the Application of CLT Panels and Structural Glass Strips
Published in International Journal of Architectural Heritage, 2021
Žiga Unuk, Miroslav Premrov, Vesna Žegarac Leskovar
where is the coefficient of composite action for the CLT panel, the elastic modulus of the CLT panel, the cross-section area of the CLT panel (only longitudinal layers considered), the distance between the centroids of the CLT panel cross-section and the composite cross-section, the elastic modulus of the timber joist, the timber joist width, the timber joist height, the distance between the centroids of the timber joist cross-section and the composite cross-section, the crack factor for shear resistance, the effective bending stiffness, the design shear force.
Application of small-diameter round timber as structural members in light frame construction
Published in Journal of Asian Architecture and Building Engineering, 2022
Guofang Wu, Enchun Zhu, Haiqing Ren, Yong Zhong, Meng Gong
The horizontal diaphragm plays a key role in the transmission of the lateral load to the vertical shearwalls. To investigate the effect of using the developed wood-steel joists in the framing on the structural performance of the diaphragm, 3 full size 4.88 m × 3.66 m diaphragms were manufactured and tested, as shown in Figure 17. It should be noted that only the top chord of the wood-steel joist instead of the whole joist was adopted as the framing members of the diaphragm in the test specimen. This was because the steel web contributes little to the in-plane stiffness of the diaphragm.