Research Of Design Theory For Prestressed RPC Girder Based On Bearing Capacity

Reactive powder concrete (RPC) is one of new composite materials. Comparing with common concrete, RPC possesses apparent merits such as ultra-high strength, high toughness, and high durability and so on. RPC has become the new research hot point in the field of engineering material. Presently, the research of RPC generally gives more attention to material itself and appointed structures. But at research is few to RPC structure's design theory and not still systematic. RPC possesses unique mechanical properties, but the present its structural design mainly profits from the common concrete or the steel textile fiber concrete design theory. Although above theories provide certain reference, uses for reference directly lacks the basis and the theory support, and the safety of structure is also difficult to be evaluated. Comparing to the applications of RPC, the lag of its design theory and design method's has limited the application and extension in engineering. Therefore, in this paper, the systematic and in-depth study on pre-stressed RPC Girder's bearing capacity are done, and the practical design theory and method of pre-stressed RPC Girder based on the control of bearing capacity is presented. The research works and principal results are as follows:(1) The experiments for cube and prism of RPC on axial center compression test and axial center pulling force test as well as the bending property experiment are made, and the mechanical performance indexes and related statistic parameters including cubes crush strength, prismoidal strength, and peak strain value are acquired. At the same time, the uniaxial full stress- strain curves of pull and compression are determined. Based on the analysis of experiment data, the Young's module and elastic working interval are defined newly.(2) Based on mechanical parameters of RPC specimens, the full-range mechanical analysis of basic bending structural members are carried out with general finite element software MARC and self-compiling program FX-RPCT, and the numerical calculation results are very close to the experimental results of RPC beams. The models and parameters of MARC used for analyzing the RPC beams are determined and make the MARC be general analysis program for RPC beam's stress computation. At the same time, the FX-RPCT can be used in design and experimental datum simulated.(3) The full-range analyses of prestressed RPC girder with different forms of reinforcement are carried out with FX-RPCT, and the influence of prestressed reinforcement and non-prestressed reinforcement amount used on bearing capacity both cracking and ultimate is given. The main factor of controlling the cracking bearing capacity of RPC girder is the amount of prestressed reinforcement. The ratio of strength reinforcement is defined, and the ultimate bearing capacity of RPC girder depends on the ratio of strength reinforcement. The reliable and economic design of RPC girder can be obtained under the control of bearing capability by considering the reasonable reinforcement combination.(4) A series of design indexes and evaluation indexes are given for prestressed RPC girder, and the suitable working mode and failure mode are acquired by studying. The calculation formula and method corresponding to the bearing capacity of both cracking and ultimate on prestressed RPC girder are given, and the semi-probabilistic limit design theory for prestressed RPC girder is presented. The design theory for prestressed RPC girders is verified by damage experiments of low-height RPC girders which will be applied in practical engineering.(5) Considering the discreteness of material strength and geometric parameters as well as calculation errors, the reliability analysis of cracking bearing capacity and ultimate bearing capacity is finished for prestressed RPC girders. Based on the reliability theory, the failure probability of cracking bearing capacity and ultimate bearing capacity is computed with self-compiling programs using the method of Monte Carlo. According above calculated results, the economic and reasonable partial coefficients are analyzed and given. For RPC bending girder, the suggestion value of tension partial coefficient is 0.75 and the compression partial coefficient is 1.35.