tsman UDC 624.073.7 In the concretin E of floors of hydraulic structures 2-3 m thick, as well as of deep beams, the supportin E structures used are flat reinforced-concrete decks, decks made from I or angle beams, and metal trusses with concrete enveloped lower chords, which are incorporated into the effect section of the floor. As principal reinforcement of the supporting structures, use is made of the principal reinforcement of the floor, designed for the action of the operation loads.Such prefabricated-cast-in-p~ace floors are structurally designed in just the same manner as cast-in-place elements, in which the reinforcement area is determined for each design section accordinE to its full heiEht under the action of the internal design forces obtained from static analysis of the structure subjected to all the transmitted loads, including the dead weight of the floor. It is necessary to ensure the load-carrying capacity of the supporting deck under the action of the construction loads (i.e., the dead weight of the deck, the freshly placed concrete, and the erection loads). This is achieved by determining, from the same design relations, the required effective height of the deck for the 8iven reinforcement area.
Comparatively recently, the analysis of dock-type lock chambers was performed for the action of external loads (including earth pressure from the backfill in the state of limiting equilibrium or repose) without taking into account the compatibility of the deformations of the structure and the surrounding soil.The lock walls were considered as cantilever beams whose relations were applied to the bottom slab together with its dead loads as in a beam on an elastic foundation of any type.In works by V. I. Vutsel', V. M. Gogolitsyna and S. A. Frid, G. K. Klein, B. N. Leont'ev, A. V. Mikhailov, A. B. Moshkov, I. K. Samarin, and others, substantial improvements of the above scheme have been introduced, in which the compatibility of the deformations of the structure and the surrounding soil is considered, and a separate analysis of the bottom slab and wall, which constitute a single structure, is rejected.In the limiting and beyond-limiting stress state, the soil behaves as a granular medium whose pressure on a barrier opposing the formation of the natural slope is determined by the action of the forces of gravity and internal friction.Under these conditions, dock structures are statically indeterminate.However, in the prelimiting stress state of the soil, which is produced in the absence of displacements, or for displacements of the barrier toward the backfill resulting in its compaction without formation of through-flow zones, the granular medium performs elastically.In this case, when the condition of compatibility of the deformations of the retaining structure and the soil is met, static indeterminacy arises which can be solved by static analysis of the structure in an elastic medium.A characteristic of the behavior of dock structures for locks is their joint operation with the surrounding soil as a result of cyclic rises of the water level in the chambers and seasonal variation of the ambient temperature, for which beside the basic loads, additional soil reactions occurring in the zones of additional compaction act on the wall.In analyses of dock structures these additional soil reactions must be taken into account when determining the internal forces.The complexity of the solution lies in the fact that movement of portions of the wall away from the backfill is not attended by substantial variation of the earth pressure (it may decrease from the values during the state of repose to the values during the state of limiting equilibrium), by development of a soil compaction reaction in addition to the basic (acting on the unmoved wall).Yet, in the region of contact between the bottom slab and the foundation soil, any absolute increase in the reaction pressure (equal to the weight of the suspended structure) is impossible, but there is a redistribution in the intensity of this pressure along the bottom slab as a result of variations in the shape of its elastic curve.In order to determine the internal design forces when selecting the reinforcement, a continuous reinforced-concrete dock structure should be analyzed as a si...
Several theories have been proposed for determining the lateral pressure of earth backfill Their practical application often gives rise to difficulties, bound up with the nece~ity to reconcile discrepancies between them. Recent observations have shown that many formerly accepted assumpuons regarding soils are invalid. Therefore, persistent endeavors to solve this complicated problem should be continued.Lateral earth pressure differs from hydrostatic by virtue of frictional and cohesive forces existing in the soil These forces reduce the lateral pressure if the wall, as the result of uneven settlement, deflects away from the backfill, and increase it if the wall leans back onto the backfill "reclination." The lateral pressure on a stationary wall corresponds to the angle of static internal friction; on the other hand, where the wall deflects or reclines, the respective limiting values of the lateral pressure depend on the limiting values of the frictional and cohesive forces in the soil.The limiting-equilibrium theory currently utilized in practice, which is based on Coulomb's propositions (notwithstanding that more rigorous-but also more complicated-theories are available), permits determination of the lower and upper limits of lateral earth pressure, irrespective of soil deformations, structure displacements, and the state of the backfill under normal operating conditions. However,.lateral earth pressure on a structure's rear face may assume some intermediate value which will depend on its displacement but will lie between two extreme limits-the so-called active and passive earth pressures. The basic principles of Coulomb's theory for granular materials remain generally true a n d -f r o m the practical viewpoint-give acceptable results for extreme values of lateral earth pressure on vertic~ and steeply-inclined rear faces of structures.
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