a.r. telvari

This paper deals with construction site layout planning (CLSP) problem in the context of a multi-objective optimization model. According to the operational plans in Iran, in execution of the construction projects, special places are considered to accommodate the respective facilities in the jobsite. As an important part of project execution, the site layout planning has always been of concern for clients, contractors and consultants which is majorly intended to layout the facilities by properly arranging the them such as offices, warehouses, residences etc. such that materials, information and staff could be transferred optimally. Noteworthy, an appropriate layout improves level of safety and efficiency, reduces transport costs, prevents formation of bottlenecks and obstructions ahead of materials and equipment transfer particularly in mega projects. The site layout could be arranged with respect to the decision maker’s opinions based on different criteria. The model’s target functions include maximizing the safety level of construction facilities along with minimizing the corresponding costs and finally, minimizing the respective risks in potential areas. The constraints involve unique layout of each facility as well as the allowable distance between various facilities. Given the fact that the CSLP is classified as an NP-hard problem, it would be difficult to derive viable results using mathematical models whose solution process is time-taking as well. In this respect, to solve the numerical examples in a realistic representation scheme, NSGAII and MOGWO metaheuristic algorithms are applied. In order to compare efficiency of the proposed algorithms with the results derived from mathematical model solution, a number of standard measures have been used. The results indicate that the Pareto frontier produced by the proposed algorithms in numerical examples, is significantly in agreement with the optimal Pareto frontier in the case of small sizes approving great efficiency of the algorithms. Moreover, it was observed that in medium and large sizes, performance of the MOGWO surpasses that of NSGAII, making it appropriate for real-size cases. Lastly, results of this study could be considered as a management tool to make optimal strategic decisions aiming to develop the CSLP studies.

The present research aimed to compare different methods of statistical analysis and to select the best method for achievement to the model among components of synthetic unit hydrograph by using of the physical characteristics of catchments, in northern catchments of Iran, with the area of 177000 km2 in Giulan, Mazandaran and Golestan Provinces. For execution of the research, 9 physical characteristics of catchment and 8 characteristics of unit hydrograph components for 44 storms in the north parts of Iran have been chosen. Regression test by using bivariate approach and various forms such as linear, logarithmic, inverse, quadratic, cubic, exponential, power and combined forms has been used after execution of factorial analysis. The obtained models were evaluated by relative errors, RMSE and efficiency coefficient. Results showed that the bivariate models have more accuracy in estimation of the amounts especially in the case of temporal variables (base time, time to peak, time to depletion). Regression of several variables has high accuracy in estimation of discharge and recursion regression of several variables has the highest accuracy.

The Clark method is one of the most applicable techniques for development of instantaneous unit hydrograph whose efficacy depends upon the accuracy in estimating storage coefficient. The present study was conducted in Kasilian watershed in Mazandaran Province to determine the efficiency of developed hydrograph using Clark's method and to compare the Muskingum storage coefficients obtained through graphical, Clark, Linsley, Mitchell, Johnstone-Cross and Eaton methods. To this aim, the time-area histogram of the study watershed was initially developed. The 3h-unit hydrograph was then derived using the data collected in Sangedeh climatological and Valikbon hydrometric stations. The efficiency of Clark’s instantaneous unit hydrograph developed based on 6 methods for calculation of Muskingum storage coefficient was ultimately compared with the observed average 3h-unit hydrograph of the study area. The results of the study revealed that the Clark’s instantaneous unit hydrograph obtained from graphical method for estimation of storage coefficient with estimation error of less than 33.33% and efficiency coefficient of 83% could suitably simulate different components of the observed average unit hydrograph for the study watershed.

Application of empirical models is a must owing to complexity of process, different features, spatial and temporal variation of soil erosion and non-existence or lack of pertaining data. In this study, the efficiency of rainfall and runoff variables of 11 storms during winter 2006 and spring 2007 in explanation of storm-wise sediment yield in Chehelgazi watershed of Gheshlagh Dam basin in Kurdistan province was evaluated with the help of bivariate and multivariate regression models by using different transformed data. The models’ efficacy was then assessed by using coefficient of determination, error of estimation and verification. The results showed that bivariate regression models, using different transformed data with determination coefficient of beyond 66%, and respective error of estimation and verification of below 40 and 30%, had a better efficiency in estimation of storm-wise sediment yield than multivariate regression models. The results also verified that the rainfall variables could explain storm-wise sediment yield variations better than runoff relating factors with overall contribution of some 80%.