جمیل بهرامی

Chloride attack is one of the most destructive phenomena that has an adverse effect on concrete and steel materials in reinforced concrete structures. Corrosion of rebars and damage of concrete can significantly reduce the seismic capacity of these structures over time. Accordingly, it is necessary to model the deterioration of reinforced concrete sections before performing nonlinear analysis to evaluate their seismic behavior. In this regard, Instruction for Seismic Rehabilitation of Existing Buildings (code No. 360) recommends that in order to consider the corrosion effects of reinforced concrete sections, the moment-curvature relationships used in the definition of plastic joints are corrected by a fixed number called the knowledge factor. Due to the fact that the deterioration process of concrete structures under chemical attacks is time-dependent and also there are various uncertainties in modeling this phenomenon, it seems that considering the effects of corrosion with only one constant factor, is not enough and in this regard, more research needs to be done. In this regard, in the present paper, the seismic behavior of a reinforced concrete flexural frame with a lifetime of 50 years under chloride attack on the external aspects of the columns was studied. For this purpose, in the first step, chloride diffusion is modeled according to Fick's law and then the measure of damage in rebars and concrete was calculated using MATLAB software. In order to increase the modeling accuracy, a probabilistic framework based on Monte Carlo simulation was used to consider the uncertainties. In the next step, Moment-curvature curves of the sections were extracted using the results of deterioration modeling and were compared with those recommended by code No. 360. After that, the seismic behavior of the flexural frame was studied using static nonlinear analysis (Pushover) based on the moment-curvature results obtained from the present study and the recommendations of Code No. 360. A summary of the results obtained in this study can be expressed as follows: Corrosion due to chemical attacks can change the behavior of reinforced concrete members over time from deformation-control to force-control. For this reason, the type of failure mechanism of these structures changes from ductile to brittle. In correcting the moment-curvature diagrams of reinforced concrete flexural frame columns using the knowledge factor of Code No. 360, it is necessary to pay attention to the actual behavior of the member subject to corrosion. Using the method used in this research, it is possible to predict the actual behavior of concrete sections under the chloride attacks during the lifetime of the structure based on the modeling results of cross-sectional deterioration. For the studied moment frame, it was concluded that in the first half of the structure life, the use of a knowledge factor 0.75 to modify the curvature, is appropriate to correct the behavior of column sections subject to corrosion. But in the second half of the life of the structure, it is better to correct the moment-curvature relationship by applying the knowledge factor to the moment. In this study, the diameter of the rebars, ductility of steel, and the compressive strength of concrete were considered as indicators of damage due to chloride attacks. Based on statistical calculations, it was concluded that the determination of the reduction in diameter of rebars over time has a higher uncertainty than the other two parameters. Therefore, further research is needed to provide a suitable solution to more accurately estimate this parameter.

Flooding is one of the most dangerous and common natural disasters, which yearly causes many damages and causalities for communities and the environment. A comprehensive flooding assessment and management is essential to reduce the effects of flooding on people's lives and livelihoods. Due to an increase in flooding in recent years, locating and identifying flood-prone areas is very important to predict this environmental disaster as mis-identification of flood-prone areas in a watershed may have devastating effects. The main purpose of this study was to evaluate the performance of the Bayesian Logistic Regression (BLR) and the weight-of-evidence (WOE) models for preparing flooding susceptibility maps in the Talvar Watershed of Province of Kurdistan. The geographical location of 93 flood prone areas identified in the watershed was randomly divided into one group (70%) for calibration and another (30%) for validation. Both models consider ten effective factors in causing flooding, namely: slope, slope direction, curvature, digital elevation model, distance from stream, topographic wetness index (TWI), stream power index (SPI), rainfall amount, geology, and land use. According to the WOE model, about 35.8% of the area is placed in the medium to very high hazard class, and based on the Bayesian logistic regression model, about 45.08% of the area is placed in the medium to very high hazard class. The relative performance detection curve was used to validate the flooding potential maps. Even though both models offered sufficient accuracy, the higher accuracy was assigned to the BLR model (93.4%). Therefore, the BLR model has better performance than the WOE model in terms of the flooding risk potential.

In this study, changes in flood characteristics due to the failure of Vahdat Dam (Gheshlagh) in areas where the cross section of the river has changed, because of human activities, were investigated. For this purpose, the HEC-RAS model was used to simulate the failure of the dam and the resulting flood flow. Data on the dam structures and flow of the Gheshlagh River in Kurdistan Province, on which the Vahdat Dam is located, were obtained from the Kurdistan Regional Water Company. Using the ArcMap software, after converting the digital elevation model (DEM) to a three-dimensional model (TIN), the required parameters and lines related to the cross sections on the river were drawn. This data was transferred to the HEC-RAS model. Through field studies, cross sections were corrected and Manning coefficient was measured in different zones. After preparing images of bridges and embankments along the flow path, the height of the bridge and the embankments in the flow path were measured using station GPS. The Grize Bridge and the location of the studied embankments in this study located 23 and 33 km downstream of the Vahdat Dam, respectively, were selected to investigate the changes in flood characteristics due to local narrowing. Changes in water height and width in the study areas were investigated. At the site of the Grize Bridge, the peak of flooding due to dam failure and water depth was 4773.79 m3/s and 10 m, respectively. These values ​​at the embankments were 4330.04 m3/s and 10.8 m, respectively. Comparing these numbers with the data calculated in the previous sections of these contracted sites indicates a significant reduction in the flow capacity.

Local scour around bridge piers is the most common reason for bridge failures. many bridges have fractured because the lack of attention to the importance of hydraulic factors every year. Despite extensive researches on local scour, there is no precise method for predicting scouring because of the complexity of the scour mechanism, especially in bridges with complex piers. In this research the effect of pile cap's shape on the scour hole dimensions was investigated by using physical simulation. Laboratory data were extracted of three scaled down models of complex piers with different pile cape's shape. The experiments were conducted in clear water conditions with uniform sediment and constant discharge. The models were made with an appropriate scale from real piers of bridges. During experiments water depth was kept constant and it provided shallow water depth condition. The variation of scour hole's length, width and depth was recorded. A 3D illustration of the model for each experiment was drawn. The length, width and depth of the scour hole coordinates were measured in three directions. The results illustrated that the length and width of the scour hole, the same as depth, are also significantly dependent on the shape of the pile cap and its elevation. Results showed that The maximum length, width and depth of the scour hole were,11lpc, 8.5bpc and 9T respectively. These results can be used by engineers and researchers in order to attain at a pattern for predicting the dimensions of the scour hole in the complex bridge piers.

In recent years, low-impact development (LID) has been well established as a method to provide the best and most affordable solutions for managing and alleviating the negative impacts of urban floods. Application of this practical method is regarded as a major step toward sustainable development as it employs eco-friendly storage instruments, reduces the effects of urbanization on impervious surfaces, and helps water infiltration to recharge groundwater resuorces. Although low-impact development tools have proved effective in the management of surface water resources and conservation of water quality, finding proper locations for the deployment of the equipment and the optimal use of each tool are still questions of much controversy and no definitive solutions are provided yet as environmental conditions keep changing. The present study exploits bio-retention cells, rain barrels, green roofs, and vegetable swales as storage instruments under different rainfall scenarios with return periods from 2 to 100 years extracted from the statistical data of Sanadaj City to determine the flood volumes and hydrographs for each sub-basin before and after the low-impact development tools are employed. Moreover, SWMM 5.1 software developed by the American Environmental Protection Agency is used to develop hydraulic and hydrologic models of the basin and the changes are monitored with each development tool selected. The most outstanding results obtained from this study include the change observed in thet form of hydrograph, a reduction of 50% in time of concentration, and reductions of 35 to 50% in peak flow in the city of Sanadaj as a result of employing the low-impact development method. Classification of the equipment into infiltration and storage tools used for urban runoff control allows the best runoff control model to be developed such that the grounds are prepared not only for the return to the conditions before a certain development took place but even for flood management in challenging and riskful urban areas.