Gradual decay of natural frequency of reinforced concrete (RC) buildings is computationally investigated in view of the long-term moisture loss and associated shrinkage of concrete. The thermo-hygral analysis for RC lifetime over several decades is applied with monitoring data of existing multi-story buildings and nuclear power plants in service. The reduced natural frequency is numerically reproduced with delayed cracking near junction planes between structural members of different dimensions in multi-story buildings and dispersed cracks close to the surfaces of RC thick walls of nuclear power plants. In order to quantitatively clarify the impact of drying shrinkage, both sealed and open boundary conditions for moisture migration are assumed at simulation. It is also confirmed logically that the rate of decay for the natural frequency of the middle story RC building is faster because of the small thickness of walls, slabs and columns compared to structural members of nuclear power plants.

Aryl-functionalized 2,4,6-tris(2-thienyl)-1,3,5-triazine derivatives were applied as thin films via thermal vacuum deposition to investigate properties and potential of the thin films for use as active layers in organic field-effect transistors. All derivatives deposited on quartz substrates produced amorphous films. Ultraviolet–visible absorption spectra of the films resemble those of the molecules in solution, and fluorescence spectra depend largely on the aryl groups. When used in organic field-effect transistors, only the N,N-dibutylamino derivative could display the appropriate device characteristics under p-type operation, but it showed low mobility of charge carriers. The origin of the low mobility is discussed in terms of the electronic structure and film structure of the derivatives in the devices.

Rebar corrosion, which causes section loss of rebar, is one of the serious deterioration factors for RC structures. Section loss affects not only stiffness or load capacity but also interlock condition between lugs on deformed rebar and surrounding concrete. Interlock is a dominant factor of bond between rebar and concrete and interlock effects on structural behavior of RC member can be significant. This research focused on the influence of interlock loss on the structural behavior and bond performance of RC member from experimental and analytical investigations. The static loading test for the six beams and FE analysis were conducted for the investigation on the effects of residual interlock, with or without confinement effects from stirrups. In order to evaluate interlock effects precisely, a rebar shape including lugs was reproduced by fine hexahedron elements in the FE analysis. The authors also conducted FE analytical case studies for investigating the effects of non-uniform lug loss or partially interlocking condition due to section loss of rebar. Through these investigations, it was seen that interlock could work and keep sound bond as long as contact between a lug and concrete was maintained even when the rebar lug was flattened due to section loss. Furthermore, under the situation with non-uniform distribution of section loss, pull-out behavior of rebar was prevented by interlocking of parts in a member even when other regions completely lost their interlock due to serious section loss.

No abstract

No abstract