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Philosophy of design
Published in Chanakya Arya, Design of Structural Elements, 2022
In permissible stress design, sometimes referred to as modular ratio or elastic design, the stresses in the structure at working loads are not allowed to exceed a certain proportion of the yield stress of the construction material, i.e., the stress levels are limited to the elastic range. By assuming that the stress–strain relationship over this range is linear, it is possible to calculate the actual stresses in the materials concerned. Such an approach formed the basis of the design methods used in early versions of the codes of practice for a number of the major construction materials such as concrete, steel and timber, respectively, CP 114, BS 449 and BS 5268. Whereas CP 114 was withdrawn in 1972 with publication of CP 110, the forerunner of BS 8110 and Eurocode 2, BS 449, was withdrawn more than a decade later in 1985 with publication of BS 5950, the forerunner of Eurocode 3. The code of practice for timber design, BS 5268, was only withdrawn in 2010 with the publication of Eurocode 5.
Design Strength of Glubam
Published in Yan Xiao, Engineered Bamboo Structures, 2022
The concept of allowable (also referred to as permissible) stress design (ASD) is that the working stress under the service load (so-called unfactored) determined using elastic structural analysis shall not exceed the permissible stress. The permissible stress is set by a code; that is, reduced strength value equal to the average failure strength of a materialdivided by a safety factor, typically ranging from 1.5 to 2.0. The concept of ASD is a traditional design method, but not necessarily obsolete and is still being used in practice. The main reason why the ASD method is still viable might be because with wood structures, the material is essentially elasto-brittle and is expected to work within the elastic range. Considering the similarity between glubam and glulam and timbers, and the fact that ASD is still utilized in the United States and elsewhere, it is of value to establish the allowable stresses for glubam.
Basic and Shortcut Tools for Structural Analysis
Published in Fiona Cobb, Structural Engineer’s Pocket Book, 2020
Allowable or permissible stress design — Where the ultimate strengths of the materials are divided by a factor of safety to provide design stresses for comparison with unfactored loads. Normally the design stresses stay within the elastic range. This method is not strictly applicable to plastic (e.g. steel) or semi-plastic (e.g. concrete or masonry) materials and there is one factor of safety to apply to all conditions of materials, loading and workmanship. This method has also been found to be unsafe in some conditions when considering the stability of structures in relation to overturning.
Philosophies of bamboo structural design and key parameters for developing the philosophies
Published in Cogent Engineering, 2022
Leule M. Hailemariam, Ermias A. Amede, Ezra K. Hailemariam, Denamo A. Nuramo
The design procedures and guidance provided within the code of practice are specific to individual materials. For example, as per (Arya, 2009) concrete, steelwork, and masonry is based on limit state design philosophy considering the British code of standards, and Arya also states that timber materials are based on a permissible stress design approach. But the author also did not explain the reason for using the permissible stress design philosophy for the design of timber structures (Arya, 2009).