o DL/LL has considerable influence on choice of structure, beam types, and span length.
As spans increase so do bending effects caused by Dead and Live Loads, causing more material to be used, further increasing the DL/LL, further increasing the bending forces. (double downward spiral 1.5 Basic Functional Requirements The principal functional requirements of a building structure are: o Stability and equilibrium Concerned with the balancing of forces to ensure buildings components will not move. Every building has some amount of movement due to loads (deformed or loaded condition), stable structures return to equilibrium (unloaded condition) with a minimum amount of effort. o Strength and stiffness Requires knowledge of material properties, member cross sections, and ability of materials to resist breaking. o Continuity and redundancy Continuity: direct, uninterrupted paths for loads through the building structure. Redundancy: providing multiple paths for loads, so one system back up another. Helpful in extreme load conditions (wind, snow, earthquake) o Economy o Functionality o Aesthetics 1.6 Architectural Issues Historic Overview o Until 19 th century construction was mostly stone construction. High compressive resistance, low tensile o Neolithic Buildings used drystone techniques: corbelling and coursed masonry walling. o Egypt and Greece have earliest examples of voussoir arches and vaults o Romans place semicircle arch atop piers or columns, which increased spans, which decreased number of columns needed to support the roof. o Gothic construction was made possible by advancements in concrete foundation, which allowed for taller construction. o Structural cast iron and larger, stronger sheets of glass became available by the end of 18 th century o Steel and reinforced concrete allowed for the first skyscrapers to be built o Today we use post and pretensioned concrete, engineered wood products, tensile fabric, and pneumatic structures and other developments Criteria for the selection of structural systems o Nature and Magnitude of loads Weight of material and self-weight of structural elements and loads o Building use/function
Different material and design for different applications Ex. Sports facility needs tall, long, wide open spans. (lightweight materials) o Site Conditions Topography and soil conditions determine foundation which influences entire design Low bearing soil may need series of piers loaded by columns, rather than a conventional spread footing used in high bearing soils Climactic conditions like wind, snowfall, and temperature variance all affect design o Building systems integration All building systems have a rational basis that govern arrangement, which can be optimized in design for certain types of structures o Fire Resistance Building codes require building components to meet minimum fire resistance standards Materials are tested on how long they can last in a fire before losing structural integrity Wood is naturally combustible but maintains much of its strength for an extended period of time Steel can be weakened to the point of breaking without fireproof coverings Concrete is naturally fire resistant, but can be significantly weakened by a fire Construction Variables Local availability of labor and materials effect the design of building structures Architectural form and space CHAPTER 2: Statics 2.1: Characteristics of a Force
You've reached the end of your free preview.
Want to read all 9 pages?