Tue 30 Oct, 20:46
The actions (loads) on structure are divided into two types: permanent actions and variable (or imposed) actions. Permanent actions are those which are normally constant during the structure's life. Variable actions, on the other hand, are transient and not constant in magnitude, as for example those due to wind or to human occupants. Recommendations for the loadings on structures aregiven in the European Standards some of which are EN 1991-1-1 General actions, EN 1991-1-3 Snow loads, EN 1991-1-4 Wind actions, EN 1991-1-7 Accidental actions from impact and explosions, and EN 1991-2 Traffic loads on bridges.
Tue 30 Oct, 18:55
Concrete structures, properly designed and constructed, are long lasting and should require little maintenance. The durability of the concrete is influenced by:
the exposure conditions;
the cement type;
the concrete quality;
the cover to the reinforcement;
the width of any cracks.
Fri 26 Oct, 17:52
The purpose of desigh is to achieve acceptable probabilities that a structure will not become unfit for its intended use - that is, that it will not reach a limit state. Thus, any way in which a structure may cause to be fit for use will constitute a limit state and the design aim is to avoid any such condition being reached during the expected life of the structure.
The two principal types of limit state are the ultimate limit state and the serviceability limit state.