Журнал гражданской и экологической инженерии

In Japan, various kinds of failure modes in steel structures have been reported in severe past earthquake disasters. Also, the various type of repair method for damaged building structure is suggested, and it has been published as restoration manual and guideline. However, it is guessed that these repair methods have some difficulties related to construction technique and estimation of recovery of seismic resistant performance after repair. This study focuses on the seismic ultimate state of steel brace connection of original state and repaired state after damaged, and the effective restoration method is suggested herein. In our past researches, new repairing method for damaged steel bracing joint which has angle-section brace member has been suggested already, and its applicability and feasibility were investigated experimentally. Herein, H- shaped section brace members are focused which are adopted on middle-rise or high-rise steel building structures, and also, various kinds of failure modes of these bracing structure has been reported after past terrible seismic disasters in Japan. So, the effective restoration method is proposed here. First, to reproduce the seismic ultimate state, the vertical loading test on H-shaped bracing test specimen are performed as parameters with bolt layout, thickness of gusset plate, that is, out-of-plane rigidity of joint. Next, the damaged bracing joints are repaired. Finally, the loading test is done on repaired specimen again. From test results, the restoring force characteristics after repair can be recovered, and any type of failure modes are observed. So, 3D model of damaged bracing joint is constructed by using 3D scanner, and it helps to identify the failure mode and yield lines on gusset plate. Furthermore, the plastic limit analysis is performed by reference of 3D model, and it can predict the ultimate state of test results well.

The use of reactive polymers as modifiers for asphalt appears promising. Asphalt penetration grade 60/70 cannot be used in coating applications for its long drying time at ordinary temperature and for its brittleness at very cold temperature. This material is very cheap as compared to blown asphalt that usually used in industrial applications. This study aims to use reactive polymers in modification of soft asphalt to produce very specific asphaltic material for use in infrastructure applications especially coating instead of highly expensive materials. The new asphaltic material is low cost and has high quality performance at low temperature.

To achieve the aim of study, RRNP was used as additive to modify asphalt in percentages of 3, 5, 7 and 10% w/w. The prepared RRNP was then tested for their particles size using DLS and TEM, SEM, 1HNMR. RRNP was used to modify the thermo mechanical properties of asphalt via forming chemical bond, and the changing in mechanical and thermal properties of the mixes as well as the storage stability were studied. Also, the morphology (SEM), thermal characterization (TGA), Dynamic mechanical analysis (DMA), rheological tests, while, the prepared coatings were applied to carbon steel panel and tested for bending, Abarsion test and impact test were detected. Overall, the results show that the chosen modifiers are the best so far in the modification of soft asphalt to suit the industrial applications in different climate conditions.

The probability density function (PDF) for the stream wise velocity fluctuations was obtained for various cross sections in a patchy vegetated open channel. The pdf obtained for all the cross sections appeared to be qualitatively Gaussian, hence adequate to predict the extreme values arising from coherent structures of the patchy vegetated open channel for two experimental conditions. Relative to gravel bed, it is shown that the vegetation stem density produces asymmetric velocity fluctuations over the vegetated bed due to more distortion of large scale flow structures. At the boundary region however, the pdf is negatively skewed in experiment two relative to experiment one. This asymmetry is attributed to the enhanced lateral transport of momentum at the boundary region.

Recently, there are many discussions about repairability and recovery on damaged buildings. It is desirable to establish the design manuals for recovery considering continuous use of structures. In our previous researches, the damaged steel members of H-shaped and square tube section were reproduced by loading test. From the loading test results, the inelastic behavior and restoring force characteristics were clarified, and also the analytical model were proposed which can chase test results well. It means that we have already conducted the member based research on repairability. So, in this study, to investigate the inelastic behavior and restoring force characteristics of repaired steel frames, the loading test is performed on half size scaled - partial frame model as parameters with strength ratio of column-beam and panel-beam. It is assumed that the various type of failure mode is generated on original state and repaired state. During loading test on original state, local buckling is observed on H-shaped steel beam. Therefore, the damaged area is repaired by welding cover plates method which is recommended by Japanese restoration manual for damaged building structure by severe seismic disasters. And also, the loading tests on repaired state is performed, and it is confirmed that the strength is restored at the same or high level compared with original state. However, in case of beam failure mode on original state, different failure mode is observed on repaired state. Furthermore, a finite element analysis is performed, and the resistant mechanism during ultimate state is investigated analytically in detail.