Experimental Research on Axial Compression of Reinforced Concrete Short Circular Columns Strengthened with Prestressed Semicircular Steel Plates

According to the statistics of relevant departments, the total area of various existing buildings in China is at least 10 billion m2, of which about one-third of the houses have reached the design life and the safety reserve is insufficient. It is not economical to demolish these houses and rebuild them, and the benefits of new buildings are far less than those of extending the service life of old buildings through reinforcement. Therefore, reinforcement technology is increasingly indispensable. Currently varying methods for the prestressed reinforcement of concrete columns are developed, but they are generally not practical. Strengthening concrete columns with prestressed semicircular steel plate is a new prestressed strengthening technology. In this article, the experimental study on the axial compression of a reinforced concrete circular section short column strengthened with prestressed semicircular steel plate is carried out by combining experimental and numerical simulation methods, and the calculation formula of the bearing capacity of the reinforced short column is established by finite element analysis.

EVALUATION OF THE EFFECT OF EXTERNAL PRESTRESSED STEEL STRANDS ON CABLE-STAYED BRIDGES BASED ON FINITE ELEMENT ANALYSIS AND STATIC TEST

This article relies on the reinforcement project of the Mulinghe cable-stayed bridge to explore the changes in the mechanical properties of the reinforced concrete cable-stayed bridge before and after reinforcement. The bridge has large cable spacing, large internal force of a single cable, and the main beam is mainly Reinforced Concrete. Therefore, structural calculation, disease analysis, and damage state simulation are carried out. Afterwards, the bridge's commonly used reinforcement methods were compared, and suitable reinforcement schemes were selected. After the reinforcement, the field test was carried out on the cable-stayed bridge, the main beam deflection, the strain of the main beam and the main tower, and the increase in the cable force of the cable- stayed were analyzed. The results show that external prestressed reinforcement is the best way, which can significantly reduce the vertical displacement of the main beam and the horizontal displacement of the main tower, and also improve the stress on the upper and lower edges of the main beam. After the external prestressed reinforcement, the ratio of the observed value to the observed value in the filed load test of the cable-stayed bridge's decreased significantly. It is up to 31% increase in bending capacity of main beams and up to 24% increase in stiffness. This article is instructive for the reinforcement of the early-built sparse-cable reinforced concrete cable-stayed bridge, while also expanding the scope of implementation of external prestressed reinforcement technology.

Shear resistance of prestressed concrete beams with the constant and variable height

One of the methods of increasing the efficiency of using prestressed reinforcement involves transferring a certain amount of longitudinal tensioned reinforcement from the tensile zone in the span to the upper compressed zone on the support, where it is not fully used to ensure the bending resistance. More effective may be a solution in which, due to the broken outline along the length of the element, the pre-stressed tendons are arranged at an angle to the longitudinal axis, creating vertical compression of the support zone and increasing the beam shear resistance. In this study presented information about stress-strain state of prestressed concrete straight and curved beams based on the experimental investigations.

Strengthening timber-concrete composite girders with prestressed reinforcement

Timber-concrete composite girders are a modern type of structure. They are formed by composite connection of a timber and concrete girder. They are designed in such a way that the concrete part of the girder is placed in the compression zone and the timber part of the girder in the tension zone. Various types of shear connectors are used for establishing this connection: from mechanical ones (bolts, nails, perforated plates, parts of steel sections, etc.) to chemical ones (various types of glue). The possibility of active strengthening of such girders with prestressed reinforcement is investigated in this paper. One possibility of applying external prestressing force is presented. Some strengthened-girder test results are presented and compared with results for similar girders but without strengthening.

Bearing capacity of steel-fiber-concrete slabs with biaxially prestressed reinforcement

The aim of the research is to obtain new experimental data of biaxially prestressed steel-fiber-concrete slabs under transverse loading and to develop a method for calculating their bearing capacity. Experimental-theoretical studies of biaxially prestressed steel-fiber-concrete slabs under the action of a uniformly distributed load were performed. Experimental studies were performed on plates measuring 40x800x800 mm with prestressed reinforcement Ø5Bp-II in two directions. Samples of the first series were reinforced with a mixture of steel fibers of STAFIB 50/1.0 and STAFIB 30/0.6 with anchors at the ends, the percentage of which was 0.5% by volume of each fiber. The samples of the second series contained 1.0% by volume of NOVOKON URW 50/1.0 corrugated fibers. A method for calculating steel-fiber-concrete (SFB) slabs based on the deformation method is proposed. This takes into account the real diagram "σ-ε" for uniaxial and biaxial compression of steel-fiber-concrete and increase the compressive strength of steel-fiber-concrete under conditions of biaxial compression. Stress losses in the reinforcement from creep and shrinkage deformations of steel-fiber-concrete are also taken into account. The results of calculation of experimental samples and their comparison with the results of experimental researches are given. They showed sufficient convergence. The difference was 1.1… 2.5%. It is established that the bearing capacity of biaxially prestressed slabs is 1.55… 1.61 times higher than unstressed slabs and 42.4… 55.5% higher than uniaxially stressed slabs.

Steel Reinforcement Corrosion - Its Impact on Features of Steel PSC Strand

Steel reinforcement made of refined maraging steel in the form of wires and strands has been for a long time used commonly for reinforcement of prestressed concrete structures. Defects on some of them and unfortunately even accidents of some cases of bridge objects, mainly recently published by media, related to corrosion of prestressed reinforcement awoke interest of both professional and wide non-professional public related to its durability. This issue also opens up a question of durability and liability of prestressed structures. In majority of existing prestressed structures the anticorrosion protection of reinforcement was traditionally secured mainly by alkalinity of the environment, i.e. concreting and/or grouting of prestressed elements in ducts. The abstract presents information related mainly to mechanical characteristics of corrosion-affected prestressed elements.

Prestressing Steel Ropes - Corrosion Impact on its Properties

Steel reinforcement made of refined maraging steel in the form of wires and tendons has been for a long time used commonly for reinforcement of prestressed concrete structures. Defects on some of them and unfortunately even accidents of some cases of bridge objects, mainly recently published by media, related to corrosion of prestressed reinforcement awoke interest of both professional and wide non-professional public related to its durability. This issue also opens up a question of durability and liability of prestressed structures. In majority of existing prestressed structures the anticorrosion protection of reinforcement was traditionally secured mainly by alkalinity of the environment, i.e. concreting and/or grouting of prestressed elements in ducts. The abstract presents information related mainly to mechanical characteristics of corrosion-affected prestressed elements.