Composite bridge pier consisting of steel pipes with external ribs and concrete can reduce construction work by replacing a part of reinforcing bars with steel tube. Authors have arranged and evaluated inelastic behavior of 15 specimens subjecting to cyclic lateral loading, and then we defined limit deformation to hold bearing force, furthermore analyzed the causes affecting deformation capacity. The results showed that deformation capacity has high correlation to ratio of the volume of transverse confining rebars to the volume of confined concrete core and ratio of flexural shear strength. In this paper, we found that the concept of coefficient “κ” in consideration of these causes can evaluate deformation capacity with comparatively sufficient accuracy.
We studied fundamental properties, operation methods, and leachability of a cement solidification of municipal solid waste incineration fly ash (MSWI fly ash) contaminated with radiocesium. It was clarified that ordinary cement mix method can be adopted to the cement solidification of the MSWI fly ash. The leachability of the cement solidification MSWI fly ash decreases with increasing of the unconfined compressive strength; it is in a linear relation, so that we can predict the leachability from the compressive strength. From these results, we proposed a cement mix design method of the MSWI fly ash contaminated with the radiocesium.
This paper quantitatively evaluates the load-carrying and deformational mechanism of RC and SRC columns with solid and hollow cross sections, subjected to axial and cyclic horizontal forces, based on the damage of constitutive materials. The cyclic behavior of RC columns, with various dimensions and under various loading conditions, are fully investigated numerically by using a two-dimensional finite element analysis, with a help of an average normalized accumulated strain energy in core concrete that is newly proposed in this paper, in addition to the ordinary damage indices of concrete together with the index for reinforcement buckling. Moreover, the same target RC columns are also analysed by fiber theory-based frame analysis, with a use of average residual rate of elastic stiffness of concrete in cross section of the columns. Consequently, it is numerically clarified that the lateral load-displacement relationship and the axial force carrying performance of RC columns are governed by the failure of core concrete and the buckling of longitudinal reinforcement.
In this study, the degradation process of shear strength of RC members after flexural yielding subjected to cyclic loading was evaluated numerically. First, the validity of the 3-D RBSM with the proposed constitutive model subjected to cyclic loading was demonstrated by simulating the shear failure test of RC member after flexural yielding subjected to cyclic loading. Next, the degradation of shear strength was quantitatively evaluated by the proposed method, though the degradation is difficult to evaluate experimentally. As a result, it is confirmed that the degradation curves of shear strength obtained by the proposed method show similar tendency with the previous proposed formula obtained by statistical processing of the past experimental data. In addition, the effects of web reinforcement ratio, axial compressive force and main reinforcement ratio on the degradation behaviors of shear strength also were evaluated.
To ensure the required structural performance through the service life, a design method for concrete structures that takes into consideration the influence of material properties should be established. In this research, to clarify the time-dependent deformational behavior of RC beams with flexural cracks generated at early ages, continuous flexural loading of RC beams was conducted, and the effects of shrinkage property, loading age, and environmental condition were experimentally investigated. To understand the time-dependent behavior of RC beams, numerical simulation was performed, using a three-dimensional multi-scale coupled model where the microscopic characteristics of cementitious composites and nonlinear structural mechanics are integrated. This simulation system allows consideration of mechanistic and thermo-hygro induced deformations and the tension stiffening effect after cracking, as well as increases in the diffusivity of water caused by cracking are. The results of this study demonstrated that compressive deformation of concrete due to drying creep causes a significant increase in the tensile stress of reinforcement. Especially under high compressive stress/strength ratio, large creep deformation, which might be due to micro-cracks generated at the ITZ between the cement paste and aggregate, should be properly considered in numerical simulation. Furthermore, deterioration of the bond between compressive reinforcement and the surrounding concrete might be another reason for the large creep deformation. Based on the numerical simulation results (smeared crack model), a new calculation method for flexural crack width was proposed. Comparison of the calculated results and experimental results for total crack width in the equivalent moment zone suggested that concrete between flexural cracks generated at a very early age could deform with less bond deterioration following the deformation of tensile reinforcement. This might be due to the generation of micro-cracks at the ITZ between the cement paste and aggregate, which might prevent internal cracks around reinforcement, thus lessening deterioration of the bond.
We studied integrative evaluation method for the PC-Grout fluidity with using 14 varied test-samples, by focusing on the V-funnel flow time from tilting test (JSCE Method), and the flow value from the flow test, which are widely used to evaluate the fluidity of PC-Grout in Japan. These current evaluation techniques are unique to Japan. So for future, we searched correlation with Marsh Corn method prescribed at ISO and EN 445:1977. We searched the efficiency of quality control also, by using our newly introduced funnel equipment (automatic measuring device that used a scale together). Each fluidity evaluation test result showed the strong correlation. The V-funnel flow time and the flow value showed the indication of the yield values and the plastic viscosities, which indicate rheological characteristics. New funnel equipment (with automatic measuring device) showed the efficiency on quality control of the PC-GROUT.
For steel deck slabs subjected to fatigue loads, a strengthening method by both spraying a HPFRCC onto their undersurface from below and filling mortar into U-shaped ribs was developed. When applied to an existing bridge, this reinforcing method minimizes adverse effects on the traffic in comparison with conventional methods applied to top surfaces. The authors investigated the applicability of this method using mock-up bridge decks by both spraying a HPFRCC from the underside and filling mortar into U-shaped ribs. Fatigue tests under moving wheel loads were also conducted on specimens constructed similarly to actual bridges. As a result, soffit reinforcement by this method was found to mitigate the stress of deck slabs, and this effect was also confirmed by FEM analysis. Fatigue evaluation based on the test results also revealed a possibility that fatigue cracking be restrained during the service life of an actual bridge to which this method is to be applied.