No abstract

Regarding the failures due to corrosion, concern about corrosion damage has been intensified and some tests have been carried out in order to study the effect of corrosion on capability of bending and shear capacity of reinforced concrete beams. For as much as these studies is experimental commonly and using from its results subject to spend time and financial costs, this study is set to analyze behavior of corrosion found reinforced beams, using ABAQUS computer software. For this purpose, the sound reinforced concrete beams is modeled, first and simulating accuracy is confirmed by existing experiment results. Then corrosion found beams with different degrees are modeled by ABAQUS software and their results were compared with experimental results and finally, P-∆ charts are produced and provided for software models. In the way of simulations, effects of corrosion site, amount and intensity of corrosion, concrete compressive strength and bar yielding stress on behavior of reinforced concrete beams under corrosion is examined. In this investigation, the effect of different locations and different corrosion degrees is considered regarding changes which take place in cross section of steel, mechanical characteristics concrete and steel and integrity between steel and concrete.

In seismic design and evaluation of irregular buildings most codes recommend nonlinear time history analysis (NLTHA), which is very time-consuming, mainly since the time step size of the digitized accelerograms is usually very small. Therefore, if the NLTHA analysis can be performed by large time steps without losing much precision, it can be very helpful. This paper introduces a method for simplification of accelerograms based on the modification of their Fourier analyses. In the proposed method the Fourier Spectrum of the accelerogram is calculated first, and then, by using a computer program, developed by the authors, the corresponding Inverse Fourier Transform is calculated using a relatively large time step, depending on the structure's periods, which is usually 5 to 10 times of the original accelerogram's time step) to create the simplified accelerogram. Obviously, time history analysis by using this simplified accelerogram is much less time-consuming. Numerical results show that the maximum response values obtained by using the simplified accelerograms have only 5 to 10 percent error, depending on the type of the structure and the features of the used records.

Designing structures to resist progressive collapse during an earthquake is a key challenge for structural engineers working in seismic zones. This paper introduces a more appropriate brace configuration based on an upper-bound estimation of the probability of seismic progressive collapse in moment-resisting, eccentrically braced frames designed to the third edition of the Iranian seismic code. The code currently only has provisions for the capacity of moment frames, with no detail given for bracing elements. A numerical modelling study of low- to mid-rise residential and office buildings was undertaken. The results show that for five-storey buildings the optimum number of braced bays is 10–20% of the building's perimeter bays, whereas for eight-storey buildings the optimum proportion is 20–30%. Results also show that regular bracing in internal bays is more appropriate for resistance against progressive collapse.

In evaluation of structures, performing nonlinear response of model over a time analysis or incremental dynamic analysis needs more time. Hence, it can be beneficial if the event history report is carried out with long time steps without loss of accuracy. This study includes a method to simplify of accelerograms meant on the change of their Fourier reports. So, the Fourier Spectrum of the accelerogram is initially determined. Next applying a PC code generation, the similar Inverse Fourier Convert is computed utilizing a comparatively large time stage, depending on the structure's times; that is ordinarily five to ten times bigger than primary accelerogram's duration stage to generate the visible accelerogram. This application from the simplified accelerogram apparently takes much less time. Results indicates that the analysis time can be reduced up to 80 % by using the proposed method. While the maximum response shows an error of merely five to ten percent, about the sort of structure and the characteristics of the records used.