Scientia Iranica
Volume:23 Issue: 3, 2016

A simple equation to estimate beam maximum ductility (µθb) of regular steel structures under ordinary (i.e., without near fault effect) earthquakes is proposed. This equation is a function of period, number of span and global ductility. The proposed procedure enables the rapid assessment of beam plastic rotation of existing buildings and direct deformation-controlled seismic design of new ones. To prepare rational databank, a considerable number of steel MRF with different geometric configuration were analyzed using nonlinear static and dynamic procedure (NSP and NDP). The NSP is used to evaluate the plastic hinge sequencing, force and deformation demands over the height of frames. However, the NDP is applied to prepare databank of demands. The proposed relation is based on nonlinear regression of the results of thousands of NDP. The result of study shows that the µθb is significantly higher than interstory and global ductility. Furthermore, the higher modes effect is completely sensible on increase of rotation ductility in upper stories of high-rise buildings. Finally, the ability of calculating µθb with acceptable precision is the advantage of proposed relation. The result of the proposed relation then could be compared with acceptance criteria of FEMA356 and therefore the performance level would be indicated.

The available three-dimensional (3D) solutions reported for the analysis of functionally graded piezoelectric (FGP) laminates are based on this simplifying assumption that the FGP layer is consists of a number of homogeneous sub-layers. The accuracy of these formulations not only is dependent on the number of sub-layers but also leads to inaccurate results in the prediction of higher natural frequencies of the FGP laminates. In the present paper, a 3D Peano series solution is developed for the cylindrical bending vibration of the FGP laminates. This novel formulation satisfies exactly the equations of motion, the charge equation, and the boundary and interface conditions of the continuously nonhomogeneous piezoelectric layers. The obtained solution is exact because no priori assumption for the displacement components and the electric potential along the thickness direction of FGP layers is introduced. The influences of the different functionally gradient material properties and different electric boundary conditions on the natural frequencies and mode shapes of the FGP laminate have been also studied through examples. The present solution and its obtained numerical results can be employed to assess the accuracy of different FGP laminated beam/plate theories.It can be also used for FGP vibration behavior comprehension purposes.

The success or failure of a project depends on the adoption of a suitable Project Delivery System (PDS). This paper presents an integrated Fuzzy AHP Multi- Criteria Group Decision Making (FMCGDM) approach for the project delivery system selection. The proposed approach can select the best PDS option based on the opinions of a heterogeneous group of experts. The relative weights of decision criteria as well as their scores are evaluated using Analytic Hierarchy Process (AHP) technique. The criteria weights and scores assigned by di erent decision makers are aggregated and converted to a fuzzy number. The relative weight of decision makers is determined using a new fuzzy logic based method. Finally, the score of each PDS option is determined as a fuzzy number by the use of Zadeh''s extension principle and performing interval arithmetic at discrete -cuts. To evaluate the performance of the proposed method, it is implemented on a real dam and hydropower plant project.

Compared to other industrial endeavors the construction industry has the highest percentage rate of injuries and illnesses severely causing construction delays. The Critical Path Method (CPM) scheduling technique was known to control and to monitor construction activities to meet the project deadlines effectively but not to control and to monitor the project in terms of forecasted injuries and illnesses. The researcher proposed to develop a solution by deriving the Safety Factor to manage delays. The Safety Factor originated from the statistics of injuries and illnesses through classification of the annual percentage rate of the construction activities. Five Color Coding Categories were formulated, guiding the users towards early detection of risks level in the CPM diagram, enabling immediate action and lessening the adverse impact to the entire construction process. The research focused on getting back to the normal time schedule as-planned when disruptive injuries and illnesses occurred by using a safety factor. In which, more dynamic CPM techniques were included in the formulation of the Safety Factor, therefore, increasing construction safety and decreasing construction risks.

The Energy Dissipating Restraint (EDR) is a friction device which can be used to dissipate the energy introduced to a structure by a seismic event. In this paper, the performance of the structures which are outfitted with the EDR is investigated in several intensity levels by using a novel seismic analysis method, namely the Endurance Time (ET) method. By reasonably estimating the response of structures over the entire range of the desired intensity levels through each time-history analysis, this method can effectively reduce the computational cost, offering an appropriate procedure for performance-based design of structures. The EDR performance in the seismic control of steel frames is evaluated at low to high intensity levels through three case studies with various story numbers. Additionally, a comparison is made between the ET results and those of conventional time-history analysis, in which a good concordance between the two methods is observed.

Increasing competition in the global market to gain customer satisfaction and maximize pro tability has been a challenge in the last decade for many construction corporations. In recent years, Supply Chain Management (SCM) has been introduced as one of the most e ective approaches in the construction industry literature; further, the rst step in SCM implementation is supplier evaluation and thus nding and resolving its weaknesses. In this regard, this research identi ed the criteria for evaluation of two types of suppliers in the construction industry ( rst, material and equipment suppliers named suppliers, and second, service suppliers named subcontractors) and their fuzzy membership functions, distinctly, through literature review, questionnaire survey, and statistical analysis of expert judgment. Since most of them are linguistic parameters, fuzzy approach through Mamdani''s inference mechanism has been utilized to develop a new methodology of fuzzy expert system. Thus, the developed expert system would evaluate and select the subcontractors and suppliers, distinctly, through three main criteria which are Quality, Cost, andWork relations history-timely delivery. The developed system was tested in three major companies and the results revealed signi cant performance improvement of these construction companies.

The non-parametric regression method of K-nearest neighbour (K-NN) has been used in a variety of eco-hydrological issues. In this study, some techniques are presented to improve the accuracy of the K-NN method in forecasting the accumulated 9-month inflow of Zayandeh-rud dam in Iran, from winter to the end of the following summer. The improving techniques considered at current study include: 1) selection of the best data pre-processing functions, 2) selecting the best number of neighbour, 3) selecting the best distance functions, 4) specifying the best weights of predictors at distance functions, and 5) Adding the ability of extrapolation to K-NN using a simple method. Final results show that the use of mentioned techniques can improve the accuracy of K-NN’s forecast meaningfully. The results of goodness-of-fit criteria for the optimized K-NN in comparison with a regular K-NN can present an increase of 31% at correlation coefficient (from 65% to 96%), a decrease from 31 to 8 at volume error, and finally a drop from 54 to 25 at root mean square error.

Classical methods such as limit equilibrium or limit analysis, dealing with the stability analysis of open cuts and trenches and calculation of critical excavation depth for them, do not fully satisfy the theoretical requirements for stability problems leading to di erent solutions depending on the adopted method. It is now appreciated that geomaterials exhibit considerable heterogeneity, caused by the lithological and inherent variation, which cannot be fully covered by simple methods. This paper highlights the uncertainty embedded in critical excavation depth calculation, arising from spatial variability of shear strength parameters, using Random Finite Di erence Method (RFDM) and Random Limit Equilibrium Method (RLEM). In the present study, the lognormally distributed undrained shear strength is considered spatially correlated throughout the domain. Surface cohesion value and the shear strength density were introduced as the deterministic parameters along with the coecient of variation of undrained shear strength and its scale of uctuation as stochastic parameters; these parameters were studied to see their e ect on uncertainty in critical excavation depth estimation. The results clearly demonstrated the uncertainty in critical excavation depth arising from the inherent variability of shear strength parameters using the RFDM results; however, RLEM did not prove to reflect such uncertainty eciently due to local averaging in prescribed failure surfaces.

This paper deals with numerical modeling of water flow which is generated by the break of a dam. The problem is solved by applying Eulerian equations with mapping technique over a horizontal bottom considering unsteady, incompressible flow with free surface. The proposed model has been used to simulate a two-dimensional problem of the collapse of a water column inside a rectangular tank. A new mapping was developed to transform the governing equations from the physical domain to a computational domain. It is shown that the model predictions of the changes of wave profile and the free surface elevation of water. Also, the results compare with experimental data.

Land subsidence phenomenon due to human activities and natural factors has been observed in the plains of Fars province which impose heavy damage to agricultural lands, rural buildings and historical monuments. In this paper, after identifying and determining rate of damage in Fars province, Marvdasht plain and its damaged villages have been chosen as the case study. The land subsidence map of Marvdasht and villages were presented by the data obtained from state of ground water, soil and soil parameters. Also, the effect of faults, tectonic situation, dried qanat, occurred earthquakes in this area and the observed fissured are taken into account. Generally, uncontrolled withdrawals from deep drilling wells caused subsidence and extended damage in other areas. Earthquakes intensified the damage to rural buildings and contributed to opening gaps. The altered subsidence achieved in different parts of Marvdasht plain and the damage in rural areas along with the predictions made could represent the progressive damage of this phenomenon in the future. Finally, with respect to the climate, geology, land status, characteristic of soil layers and regional potential, appropriate solutions for the land subsidence prevention and consequently reduction of the related damages were presented.

In this study, mechanical and physical properties of cement mortars containing marble dust and glass fiber in various combinations were investigated, in addition to analyzing the corrosion behavior of reinforcing steels embedded in these mortars. To this end, cement mortars containing glass fiber (0 kg/m3, 0.25 kg/m3, 0.50 kg/m3 and 0.75 kg/m3) were prepared. Besides, with the purpose of determining effect of marble dust addition on the corrosion resistance of the glass fiber reinforced mortars, marble dust were added to all series by substituting with filler sand at proportions of 0%, 10%, 30% and 50% by volume. Corrosion studies were carried in two stages. Firstly, corrosion potential of reinforcing steels in the mortars was measured every day for a period of 150 days based on the ASTM C-876 standard. Secondly, cathodic polarization values of the steels were obtained by using the Tafel extrapolation techniqueand subsequently corrosion current densities were determined. Thanks to the study, it was observed that a decrease in the corrosion resistance of the mortars had taken place as a result of glass fiber addition. But, it was determined that with the addition of marble dust into the mortars, corrosion resistance of the specimens was significantly increased.

Sedimentation is a problematic issue concerningsewer system design. In order to reducesediment deposition in sewersystems, two new equationsarepresented with asmoothing function and Group Method of Data Handling (GMDH) to estimateminimum flowvelocity. For this purpose, dimensional analysis is used to determine the factors affecting sediment transport at limit of deposition. These factors are categorized in five different groups: transport, transport mode, flow resistance, sediment and motion. Six different models are presented for predicting the densimetric Froude number (Fr) using the smoothing function and GMDH. Themodels presented withthese two methods are compared with existing equations. The results indicate that the equations proposedusing thesmoothingfunction (MAPE= 5.05, RMSE= 0.24 & AIC= -43.04) and GMDH (MAPE= 5.39, RMSE= 0.3 & AIC= 72.78) are more accurate than existing models. Furthermore, sensitivity analysis is performed to examine the efficacy of each of the dimensionless parameters presented by the best model in estimating Fr.

In this paper, the effect of step geometry with five different tread values from 0.40 m to 0.60 m with an increment of 0.05 m and three different types of water namely potable, non-potable and recycled water on aeration efficiency of stepped cascade aeration was studied. Detailed experimental investigations were carried out for different hydraulic loading rates of 0.005 m2/s to 0.035 m2/s. All the experiments were conducted for nappe flow condition. Results revealed that overall aeration efficiency at standard conditions (E20) approaches maximum for t/h = 4, number of steps = 12, hydraulic loading rate = 0.02 to 0.025 m2/s for potable and non-potable water. In the case of recycled water maximum efficiency was achieved for t/h = 3.67. Results also revealed that stepped cascade aeration was found to be a very suitable option for enhancing DO content in treatment of waste water before discharging it to water bodies to save aquatic life.