فصلنامه رویکردهای نوین در مهندسی عمران
سال سوم شماره 2 (تابستان 1398)

Although Earthquake prediction studies are being widely considered their findings are uncertain and criticized regarding problem complexity and scientific content. Therefore; based on the robust analysis, the detailed investigation can be of great value. The recent triggered events in Iran reveal that this country is under pressure and contemporary tectonic stress pattern of the region changes. This motivates researchers to explore its different aspects. In this research, statistical analysis is made on the records listed in International Institution of Earthquake Engineering and Seismology (IIEES) catalog and b-value of the Gutenberg-Richter Relationship was computed. The time-dependent values of being can act as a stress accumulation indicator in a region. Therefore, Iran was subdivided into 29 zones and b-value was explored in every zone between the years 2010 and 2017. The results are in a proper agreement with the seismic regime of the regions wherein earthquakes occurred recently. Furthermore, an interesting hazard map was resulted in, introducing the regions with accumulating stresses therefore, being susceptible for experiencing future events.

Nowadays, According to increasing development of RCC dams in the world, new offers are considered on the design and construction. Parts of these suggestions are including structural stresses, selection of construction methods and technical details of materials based on stresses. Stresses induced by earthquake are one of the major stresses in RCC dams in the seismic areas. In this research, Results of stress analyses and assessments of seismic safety of The Badavly RCC concrete dam with considering reservoir and dam are discussed. First, theoretical assumptions of dynamic analyses and loading methods are briefly presented. Second, highest levels of the spillway and dam selected and analyzed by ANSYS program. In continue dynamic answers evaluated.  It should be mentioned that, maximum tensile stress and minimum compressive stress values are comprised with allowable stress. Also, stresses separately up, under usual concrete and over RCC concrete are assessed. Dynamic analyses are performed on two MCE and DBE levels. Results of this study showed that compressive stress values are less than allowable stress. Also, tensile stresses are a little more than allowable stress in upper stream part of dam.

Conversion of rainfall to runoff according to the laws of gravity vivifies earth, replenishes groundwater, keeps rivers and lakes full of water, and varies the landscape by the action of erosion. Large uncertainties and high non-linearity of the Rainfall-Runoff (R-R) process make it complex task to have the process-based modeling, so it is preferred to create a black box relationship between driving and resultant variables. Therefore, several black box approaches including Artificial Intelligence (AI) models have been developed and used to simulate R-R process. In this paper, WANN and WSVM models are employed for Multi-Station (MS) modeling of R-R. However in any data driven modeling, some of the inputs may have no significant relationship with the output variables. Therefore, determination of dominant input variables, is one of the indispensable challenges in the model development procedure. For this purpose, to extract main features and inputs of the WANN, WSVM methods, two kinds of data pre-processing methods of Self-Organizing Map (SOM) based clustering and Mutual Information (MI) concepts are employed in this study. Therefore, spatio-temporal investigation, identification and using all sub-basins records as a cascade-based MS analysis can improve prediction of runoff in watersheds. For this purpose, two scenarios with distinct views were used for MS modeling of R-R to identify the suitable strategy for future hydro-environmental researches. The results indicated that the proposed AI-models coupled with the SOM and MI tools improved the performance of MS runoff prediction compared to the Markovian-based models up to 23%. Nevertheless, benefit of the seasonality of the process along with reduction of dimension of the inputs could help the AI-models to consume pure information of the recorded data.

Durability of cement based material due to its uses in the building industry, always has been recognized as one of the main components of sustainable development of infrastructure and urban buildings. One way to improve the durability of concrete, especially in corrosive environments is to use natural pozzolans. On the other hand, with increasing carbon dioxide gas production in cities, the effects of carbonation phenomenon on the durability properties of concrete have increased. In this research, the effect of carbonation phenomenon on the durability properties of mortars containing natural pozzolans is investigated. In sample making two natural pozzolans including Khash pumice and Jajroud trass as substitute for cement by 20% and three water/cement ratios of 0.485, 0.44 and 0.4 were used. In this study, compressive strength test was used as an indicator of mechanical properties as well as an indicator of hydration degree in specimens. In order to study of durability properties of mortars carbonation depth, water absorb capillary and electrical resistance of specimens were measured. According to results, use of natural pozzolans reduces the compressive strength of specimens and increase depth of carbonation in them. Also, electrical resistance increases in samples. The results of capillary absorb water test show that carbonation phenomenon decreases capillary absorption coefficient in some samples. Finally, it can be concluded that the trass samples showed better performance than the pumice at an early age, while the pumice improved with increasing age. It is expected that the pumice performance was better than the pumice with give over time

Plastic shrinkage occurs in fresh concrete usually within few hours after mixing the concrete and risk of its cracks endangered concrete structures especially in the elements with high surface to volume ratio such as slabs or highway pavement. An experimental investigation on capillary pore pressure, tensile strength and plastic shrinkage of concrete is presented here. The aim of research is to study the relationship between capillary pore pressure build up in concretes, early age tensile strength and plastic shrinkage strain. Capillary pore pressure apparatus was created for the first time in Iran for this research. Test was done in a climate chamber with the constant evaporation rate of 0.7 kg/m²/h .Eight types of concrete in two categories such as normal concrete and self-consolidating concrete were tested including mixture without any mineral admixtures and containing of pozzolanic materials such as silica fume and metakaolin. The results indicated that there is no strong relationship between capillary pore pressure and plastic shrinkage strain and it can be concluded that other parameters such as tensile strength development can play an important role in the plastic state of concrete. However, it should be mentioned that capillary pressure is the main cause and driving force of concrete shrinkage and the onset of capillary pressure is directly related to the onset of shrinkage. The results also showed that early age tensile strength can be effective factor in controlling cracks of concrete. No cracks appeared in the mixtures containing of silica fume and metakaolin in comparison with the reference mixture. However capillary pore pressure in these mixtures was higher than pressure in the reference mixture.