Structural Optimization 12, — Download citation. Received : 16 August Revised : 24 October Issue Date : December Anyone you share the following link with will be able to read this content:.
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Skip to main content. Search SpringerLink Search. Abstract Michell derived his well-known optimality criteria for trusses in the context of unequal permissible stresses in tension and compression. Rozvany Authors G. Rozvany View author publications. Rights and permissions Reprints and Permissions. There are three main criteria which must be satisfied if a structure is to be successful and a large number of other minor criteria that the modern designer will also take into account ; they are those of strength, stiffness and stability.
The homely example of a four-legged table may make clear the three aspects of performance that are being examined. The legs of the table must not break when a normal weight is placed on top, and the table top itself must not deflect unduly, Both these criteria will usually be satisfied easily by the demands imposed by criterion may be manifest locally, or overall. If the legs of the table are slender, they may buckle when the overall load on the table is increased a dinner party. Finally, the stability Alternatively, if the legs are not at the four corners, but situated so that the top overhangs them, then placing a heavy weight near an edge may result in the whole table overturning.
A familiar example for pin-jointed trusses arises in the resolution of forces at nodes; the inclinations of the bars are assumed to remain fixed with respect to a set of reference axes. In Theory of Structures By Ramamrutham PDF the equation of virtual work is altered profoundly when the body being studies suffers slight deformations. Not only will external forces acting On the body be involved; account must somehow be taken of the internal forces in equilibrium with those external forces.
The image shows the piles, pile cap and tie beam layout. BS clause 3. Bending theory method states that the pile cap can be considered to behave as a short deep beam, transferring the load from column to piles by bending action, just like the pad footing. This method seems most appropriate for a two-pile cap. Truss analogy method states that the pile-cap may be imagined to act as a space frame, the inclined lines of force linking the underside of the column to the tops of the piles being assumed to form compression members and the pile heads being linked together by reinforcement acting as horizontal tension members.
This assumption appears particularly appropriate for analysing the more 'three-dimensional' pile caps, such as those required for three or more piles. NOTE: Unlike other foundation base like pad, strip, and raft, the pile cap does not require safe bearing capacity of the soil as input variable in the design of pile cap.
This is because the pile cap is supported on the piles, rather than the soil. Also the length of the piles is not required as input variable in the design of pile cap. This is to Orion 18 software users, Orion 18 software only sizes the pile cap, i. It does not calculate bending moment, shear force, and punching shear in the pile cap. The image shows the Main reinforcement arrangement for Pile caps for two, three and four piles. Note that the pile cap with two piles has only one main reinforcement, and minimum reinforcement is provided in the other direction as specified in code of practice.
For the pile cap with three piles, one main reinforcement connects two piles together, while the other main reinforcement runs along only one pile. Pile cap main reinforcements are inform of U bars, running along both direction. While side bars inform of links are used to control cracking in the pile caps. The side bars are evenly spaced along the depth of the pile cap. This image shows the idealized truss system of a pile cap with four piles. The Column Load N, is transmitted from the top of the pile cap at the center of column.
The Column load N is resisted through truss action i.
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