Abstract
The paper reports a study into the strength and deformability of the node that connects precast slabs and monolithic flooring joists in a flat precast monolithic floor based on the work of dowel pins. Current regulations for the design of reinforced concrete structures do not take into consideration the calculation of nodes that connect precast-monolithic structures in flat floors using dowel pins. We have devised a procedure of experimental research that accounts for the specificity in the operation of a precast slab that forms a floor's part. It was established that a change in the type of supports changes parameters for the stressed-strained state of samples of a precast monolithic floor slab: relative deformations of concrete, deformations of samples, as well as strength.Testing the samples of a precast monolithic floor slab has demonstrated reliable operation of both the junction and the normal cross-section of the slab. It was determined that the node that connects precast multi-hollow slabs and a monolithic flooring joist using dowel pins has a 1.42-fold strength margin. The paper reports results from field testing a fragment of the frame of a building for the influence of vertical loads. It is shown that the development of deformations in the main bearing elements of a floor slab occurred almost in line with a linear dependence; they amounted to 18.55 mm (for the central precast slab of a floor slab's center) and 14.64 mm (for the bearing flooring joist). These deformations are more than 2 times less than the permissible value for vertical deformations (deflection) for these elements, which is equal to 40 mm.The results from field testing have led to a conclusion on that the precast and monolithic elements in the floor slab's disk operate as a solid structure. The tests did not detect any mutual displacements of the side ends of precast slabs relative to the load-bearing flooring joists. The procedure for calculating the strength of the connecting node has been improved. A change in the strength of samples of a flat precast monolithic floor slab is accounted for by the introduction of an appropriate coefficient for the operation conditions of transverse reinforcement, which is equal to 0.8.
Highlights
The period of up to 1990s was dominated by the trend implying the construction of residential, public, and industrial facilities using prefabricated structures
Acting standards on designing reinforced concrete structures do not contain provisions concerning the quantitative estimation of bearing capacity of the reinforced concrete dowel pin in a precast-concrete flooring slab
Each joint between the slabs hosts a reinforced concrete dowel with a width of 100 mm, which improves the spatial rigidity of the disc in a flooring slab and ensures that work of the precast slabs when calculating supporting cross-sections involves a monolithic flooring joist
Summary
The period of up to 1990s was dominated by the trend implying the construction of residential, public, and industrial facilities using prefabricated structures. A monolithic frame requires a large consumption of steel, considerable amount of expensive formwork and supporting devices Such a frame is dependent on a construction season (in summer, the need to apply specialized devices for concrete wetting; Engineering technological systems: Reference for Chief Designer at an industrial enterprise in winter, heating or the use of specialized cold-resistant admixtures). All this leads to higher construction costs. It is possible to combine benefits when applying the precast monolithic systems of structures with a flat flooring slab that largely employ individual industrially-prefabricated articles and monolithic structures. It is a relevant task to devise a structural solution for a flat precast monolithic flooring slab, to reveal patterns in the change of parameters of the stressed-strained state (strength, relative deformations, deformations of elements), as well as to construct methods for strength calculation
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