AMIRKABIR
Year:2004 | Volume:15 | Issue:57-C|Papers Count:5

A modified Displacement Based Design (DBD) procedure has been proposed to account for 1 ductility demand distribution through the height of the building. In this method the design force distribution among the height of the structure is obtained based on various ductility distributions derived from modal characteristics of the structure and mathematical formulations. The method has been applied to the steel braced frames with concentric and eccentric bracing systems in low medium and high-rise buildings. The plastic mechanism for each system has also been modeled and the efficiencies and deficiencies of each have been discussed through various numerical examples. The effect of yields mechanisms and ductility demand patterns for various building types on the equivalent SDOF parameters have been investigated compared to the time history analysis results to find the sensitive parameters. Using the capacity design criteria, which leads to a known plastic mechanism, a simple procedure has also been obtained as an alternative approach for Push Over Analysis with much less computer time and effort.

Abrasion damage in concrete slabs on the ground and hydraulic structures, which are widely used in the world, is a serious problem and may stop their serviceability. Nowadays, strength is not considered the only important factor in concrete properties, because of financial and engineering points of view; the durability of concrete in different conditions is prominent. In this study several mixtures of concrete with ordinary and granite aggregates, silica fume, S.B.R polymer and different WIC ratios were tested to evaluate abrasion resistance of concrete subjected to wearing caused by heavy traffics. The selected test was ASTM C779-a, test method for abrasion resistance of horizontal concrete surfaces. Also an rxperimental model for evaluating the abrasion resistance of concrete was suggested. The results show that the incorporation of silica fume, S.B.R polymer and also granite aggregates in concrete improve its abrasion resistance. The suggested mathematical method can predict abrasion resistance of concrete by determining the abrasion depth.

In this study, a boundary element formulation is presented for dynamic analysis of dam- foundation rock systems. A computer program is prepared, and dynamic response of an idealized triangular dam supported by semi-infinite foundation rock domain is investigated as an example. the results are compared with literature and it is concluded that boundary element method can be accurately applied to dam-foundation interaction problem and properly simulate radiation damping effects.

This paper investigates the Alkali-Silica Reaction (ASR) in concrete containing high potentially active aggregates. The effects of cement type and admixtures of silica fume and super plasticizer in the concrete mixture on ASR were studied. Also, different test methods to evaluate the alkali-silica reaction in concrete were compared. The experimental work comprised of manufacturing and 104 testing specimens in different test methods including ASTM C295, CAN/CSA A23.2-14A, CAN/CSA A23.2-25A, and Laval Accelerated Test Method. Test results showed that using 15 percent silica fume by weight of cement in the concrete mixture decreased the expansion of concrete due to ASR significantly less than the allowable values given by different standards. For the values of silica fume more than 15%, the reducing rate of expansion was not significant. The admixture of super plasticizer in the concrete mixture reduced the negative effect of ASR. It was also seen that the admixtures of silica fume and super plasticizer were more effective in reducing ASR when cement Type 5, instead Type 2, was used. Test methods of CAN/CSAA23.2-14A and CAN/CSA A23.2-25A estimated similar values of expansion in different specimens. The results obtained by Laval Accelerated Test Method were different from other results.

Watershed hydrologic response is viewed as a function of rainfall characteristics, geomorphology and soil physical properties .In this research a Gamma type geomorpho-climatic instantaneous unit hydrograph method with special emphasis to path types is presented as a physically based technique for modeling of watershed runoff. The proposed approach is an out-growth of the research on geomorphological instantaneous unit hydrograph (GIUH), geomorpho-climatic instantaneous unit hydrograph (GcIUH) and also the effect of path type on distributed runoff generation (Jin's model).Emameh, a representative watershed in northern LR. Iran, is selected for actual evaluation of the proposed methodology. The ensuing results showed the applicability of the proposed method to simulation of flood hydrographs. However, due to not-synchronized rainfall and runoff records, there was a low prediction for time to peaks of some events. The hypothesis of constant velocity was considered and it was shown that velocity is not constant neither in time nor in space. It was clearly shown that in contrast to high sensitivity of GIUH to mean velocity changes, such sensitivity is remarkably alleviated. Green-Ampt infiltration theory is used for a more proper treatment of soil physical behavior, ie., more realistic separation of excess rainfall values. Therefore, the proposed method brings out a chance for a better determination of flood events. Suitability of the proposed method was evaluated for application to ungaged watersheds. The results are within a 25% variation of the observed values, and so to some extent promising. However, in order to improve the capability of the method to be applied to ungaged watershed, additional research for information utilization is required.