Scientia Iranica
Volume:17 Issue: 3, 2010

This paper studies the behavior of a number of blasting (angular) and alluvium (rounded) modeled rock ll materials by conducting large-scale triaxial testing, as well as numerical modeling. The numerical modeling is based on an elasto-plastic theory and enables one to predict the stress-strainvolumetric behavior of materials during shearing. The material parameters were determined from the experimental and numerical modeling. Variations of the material parameters, with respect to the con ning pressure, Los Angeles abrasion, Point Load index, and particle breakage were investigated. Also, for design applications, curves fitted to the data are presented.

In order to evaluate the seismic behavior of confined masonry buildings, based on Iranian seismic code design, a single storey full-scale unreinforced confined brick masonry building has been constructed on the shaking table facility at the Earthquake Engineering Research Center (EERC) of Sharif University of Technology. The 4 by 4 meter model consists of four brick masonry walls confined with reinforced mortar tie-columns and steel bond beams, with a traditional jack-arch roof system. Three of the wall panels contained openings of di erent sizes and geometries. The model was subjected to the scaled earthquake records of Bam, Tabas and El Centro, as well as a harmonic acceleration with gradually increasing amplitude. The test results indicated that, for moderate strength earthquakes, the provisions provided by the Iranian seismic code is appropriate for life safety. Results also verified that proper workmanship of ties plays an important role in the integrity and stability of the unreinforced masonry buildings. Settlement of the masonry walls and subsequent reduction in frictional resistance between wall and roof horizontal steel bond beams were effective on the out-of-plane failure of the walls. Based on experimental observations, some suggestions are made to improve the current seismic code of Iran.

Within the framework of plasticity-based constitutive laws, a plastic-damage model is developed in a complete form for analysis of damaged structures under large tensile strains which is suitable for concrete subjected to cyclic loadings. This is based on the plastic-damage model proposed by Lee and Fenves, which utilizes two separate damage variables for tension and compression and also a scalar degradation simulating damage on sti ness. Implementation of the model is coded for threedimensional space in a special purpose nite element program to analyze the behavior of concrete subjected to large tensile cracking, which is inevitable in plain concrete structures. In order to include large crack opening/closing displacements in the model, the excessive increase in plastic strain causing unrealistic results in cyclic behaviors is prevented when the tensile plastic-damage variable controlling the evolution of tensile damage is larger than a critical value. To expedite the convergence rate for the overall equilibrium iterations, the consistent algorithmic tangent sti ness tensor is also derived, in detail, for large cracking states. The paper is completed with some numerical examples demonstrating the capability of the extended model in reproducing the behavior of cyclically loaded plain concrete subjected to large tensile strains.

In this paper, passenger behavior when travelling to business districts using their own cars, and when confronting various parking fares, is discussed. The nal goal is to determine the parking fare threshold (the price at which passengers would refrain from using their own cars) in the central business district of Tehran. Also, e ective variables that a ect passenger reaction at di erent levels of parking fare are evaluated. A logit model was made to predict passenger behavior using data gathered in di erent parking lots, located in the surveyed area. Data have been collected by a stated and revealed preferences method. Characteristics related to passengers and their trips, as well as their reaction to a rise in parking fares, were collected by a questionnaire. Analysis of the model showed that a 400 Tomans/hr increase in the hourly parking fare would eliminate the use of personal cars by the passengers (99% decreases in personal car use). It is concluded that travel time and passenger monthly income are the most in uential parameters a ecting personal car usage.

Using stochastic point source and nite fault modeling, the stochastic stress drop is estimated for 52 large shallow earthquakes listed in the ''Paci c Earthquake Engineering Research Center (PEER) Next Generation Attenuation of Ground Motions (NGA)'' database. The Pseudo Spectral Acceleration (PSA) of 541 accelerograms, recorded at National Earthquake Hazards Reduction Program (NEHRP) C-class sites from 52 earthquakes are simulated and compared with the PSA listed in the PEER NGA database. The magnitude of the analyzed earthquakes ranged from M4:4 to M7:6. The stress drop is calibrated by trial and error and based on the analysis of residuals where the residual is de ned as the log of the observed PSA minus the log of the predicted PSA by stochastic methods. The symmetric distribution of residuals around the zero line is considered as an indicator of good agreement between the simulated and observed PSAs. The calculated stress drops based on stochastic point source and nite fault modeling are di erent from the static stress drops that are currently listed in the PEER NGA database. It seems that there is no clear relation between stress drop and earthquake magnitude, but there is a good linear relation between estimated stress drops based on stochastic point source and nite fault modeling. The sensitivity of the estimated stress drop values on the Kappa factor and geometric speeding factor (b value) is also investigated.

This paper presents the application of the SWMM model to estimate the runoff due to rainfall over urban areas in Kuwait. The SWMM provides a powerful tool, in terms of its graphical capabilities and fast convergence to optimal design parameters for large urban areas. More importantly, simulation of the dynamic wave resulting from the urban runoff-transport phenomenon leads to a more accurate design for the storm drainage system, which, in Kuwait, has traditionally been based on the Rational Method. The results of this study con rm the quantitative viability of harvesting the otherwise lost runoff towards providing an additional water resource in Kuwait. A preliminary analysis of storm water quality also conforms its qualitative viability. A carefully designed, comparative questionnaire was used to solicit public opinion from various layers of society. The findings clearly indicate a strong public support in favor of using harvested storm water versus recycled waste water. Given the semi-arid nature of Kuwait, multiplicity of fresh water resources is vital. This study presents harvested storm water as a strong vital option. The strategic decision, vis-a-vis the optimal combination of fresh water resources, should be based on thorough technical and nancial analyses. Resorting to the SWMM in designing storm drainage systems instead of the Rational Method will certainly minimize the ill effects of ooding, as recently experienced in Kuwait.