In this paper, static loading tests on columns using hybrid fiber reinforced cementitious composites (HFRCC) under varying axial load were carried out. HFRCC columns were provided with higher deformation capacity and fewer damage such as residual crack width and crushing of cover concrete comparing to a column using normal concrete. Evaluation method of shear and deformation capacities of HFRCC columns was investigated based on test data including previous experiments. The shear and deformation capacities can be predicted by addition of the tensile strength of HFRCC, σT, to lateral reinforcement, pwσwy, in the design formula in AIJ's Guidelines. Moreover, the condition to prevent brittle failure after flexural yielding was studied.
This paper reports test results of mixing method applying forced-mixing type mixer for the purpose of reducing mixing time of ultra high strength fiber reinforced concrete. From some test results, it was investigated that the mixing time with that type mixer could be reduced less than 50% comparing with that of ordinary type mixer by setting up the mixing speed and product of circumferential speed of two type of shafts appropriately. Also it was investigated that the qualities of the mixing concrete applying that type mixer in short time were satisfied with required qualities.
This paper reports the RC piles with the damage reducing system which have the cylindrical joint between the pile cap and pile head(the RC Pile with Hinge Isolated Structure System as follows). The main steel bars absorbing the seismic energy are un-bonded in order to mitigate damage of concrete at hinge region of the joint and pile head, and supplementary main steel bars which are not anchored into pile cap are arranged to resist bending moment and shear. The cross section area of the joint is half size of pile to reduce bending moment of pile head. The static loading tests are carried out to examine structure performance of the RC in high axial stress. The results showed that the piles proposed in this paper had excellent structural performance.
The present paper proposed the evaluation procedure of seismic risks, which consists of PhaseI:seismic hazard analysis, PhaseII: ground motion at site, PhaseIII:capacity spectrum method, PhaseIV:seismic vulnerability and fragility analysis and PhaseV:seismic event risk analysis. Among these phases, capacity spectrum method and event-flag matrix method are featured in our proposed procedure. Simulations of event risk assessment for two types of reinforced concrete railway viaducts designed by old and present specifications were conducted. Then, major risk indices such as NEL, PML, AEL, and event risk curves are figured out and carefully discussed. It is concluded that these calculated results reflect the directions of railway viaducts as well as differences of seismic performance due to differences of design specifications.
The authors developed a new seismic strengthening method for existing RC columns. In this new method, the shear reinforcing bar, for example re-bar, welled mesh, carbon fiber grid, is mounted around the column, and special polymer cement mortar is sprayed by dry spray system over the shear reinforcing bar. Seismic strengthening effect of existing RC columns with the new method was estimated based on the results of reversed cyclic loading test for the strengthened RC columns. It was cleared that the new method was very applicable for seismic strengthening of existing RC columns from the points of both ductility capacity and shear carrying capacity. Furthermore, the equations for the ultimate shear strength of the columns strengthened by the new method were proposed.