JOURNAL OF FACULTY OF ENGINEERING (UNIVERSITY OF TABRIZ)
Year:2009 | Volume:38 | Issue:3 (CIVIL ENGINEERING)|Papers Count:9

Vertical component of earthquake effects on bridges constructed near field of fault, and bridge decks that are flexible cannot be neglected. Especially, prestressed cantilever bridges, with regard to construction and completion phase and interaction of time dependent behavior of materials, such as concrete creep, which causes redistribution of internal forces and variable shift of stress and displacements of the bridge deck over time, leads the bridge deck to be sensitive to the effects of the vertical component of the ground acceleration. To study seismic behavior of prestressed cantilever box-girder bridges, a case study was carried out on a three-span continuous prestressed box-girder bridge. A three dimensional finite-element model is used for modeling and analysis of the balanced cantilever construction of the segmental bridges, including the effects of the load history and material time-dependent behavior with the use of nonlinear static staged construction analysis and under the action of the vertical component seismic excitation by means of nonlinear time-history analysis. Finally vulnerability of the decks of the prestressed cantilever box-girder bridges was investigated and some suggestions have been made to improve the seismic behavior of the bridge decks. 

Public parking as one of the important parts of a modern urban transportation system plays an important role in decreasing the load of heavy traffic. Optimum site selection for public parking spaces not only increases the parking efficiency, but also decreases marginal car parking and therefore, results in increase of streets’ width and traffic fluency. In the most cities, public parking site selection is done by traditional methods or just by visiting of the site. In this traditional method, considering all of the effective parameters in site selection is difficult and site selection is done by just considering some limited factors like land price. In this study, we introduce an optimum method for parking site selection using GIS and considering almost all of the effective parameters simultaneously. Effective factors are considered from two main points of view including parking efficiency and the problem of providing required land for parking especially in cities central regions. Then, conceptual model of parking site selection is presented. Suitable place for parking is also selected for one of the high traffic regions of shiraz. Different methods for information and layer integration are used and finally these methods are compared and the most suitable one is proposed.

SPS (standard positioning services) users of GPS can determine the position with C/A code observations in real-time. In order to improve the real-time positioning accuracy and standard navigation requirements some methods has been developed to increase the accuracy level of GPS observations in real-time. This concept contains DGPS correction generation methods. In this paper we discuss some DGPS methods and simulate some of them by using the GPS observations of five permanent GPS stations in Alborz network. According to the results Potential of errors decreases from 61m down to 1.5m. Applying the network-derived parameters result in better accuracy level. In code observation domain, LIMdh method and LCMxyh method show the most efficiency and the best accuracy improvement (up to 47%), while in carrier phase observation domain bilinear surface fitting results the best accuracy improvement (up to 40%).

Most if not all of the dams are located near or on the faults, and severe ground shaking from near-fault may cause significant damage to dams. Such damage usually is associated with changes in structural stiffness. Consequently, the actual performance of the dam can be predicted only by non-linear analysis. Moreover standard earthquake analyses of civil engineering structures use uniform ground motions even though considerable variations in both amplitude and phase can occur along the foundation interface for long-span bridges and large dams. The main purpose of this study is the identification of vibration properties, effect of interactions on these properties, and finally detection of nonlinearity in the dam-foundation rock-reservoir system by applying system identification methods on seismic response data from Pacoima Dam. For the identification of dam properties from seismic response data during 1994 Northridge earthquake, ARX models are applied using the time-invariant and time-variant or recursive approach to identify the dynamic characteristics of the dam-foundation rock-reservoir. The system modal damping, natural frequencies and frequency response functions are identified. The identified resonant frequencies and corresponding damping ratios have been compared with the results obtained from forced vibration measurements and analytical methods. All of the results are fairly in good agreement. It has also been shown that assumption of uniform input is not realistic and could lead to erroneous results. In addition time-varying modal parameters have been estimated. The method is useful for obtaining vibration properties of dam-foundation rock-reservoir system. These properties are essential in safety evaluation of existing dam structures. 

Rail cant parameter, applied in order to attain suitable movement of wheel on rail, directly influences in dynamic interaction of track-vehicle. In this paper, the effect of geometrical parameters on the behavior of dynamic interaction of wheel-rail is being investigated through a parametric study. A complex dynamic analyses using ADAMS/RAIL are being applied for one section of actual executed line and the records of geometrical parameters have been registered for this purpose. The necessary measurements have been recorded by KRAB measuring machine, safety levels and serviceability have been controlled based on these data. The results of the analysis show that non-conformity of the rail seat slope relative to its desired value, strictly influences on the coefficient of derailment (about 18 percent), horizontal dynamic forces (about 17 percent), and results in severe rail wear (about 18 percent). However, vertical dynamic forces and safety index are not of any concern form the derailment point of view, since it is within the acceptable range of the standards. The comparison of analyses' results in various operational speeds shows a remarkable impact on the vertical dynamic forces (up to 13 percent) and derailment index (up to 8 percent).

Turnbuckles have many applications in special structures including elevated water tanks. A proper seismic performance of elevated water tanks depend on its supporting structure behavior. And supporting structure comprises of bracing elements and turnbuckles. In this study, behavior of common types of turnbuckles is investigated. A number of them were tested under tensile loading to obtain the force-displacement curves. The results showed that the form of their connecting elements can play a major role in their behavior as components of bracing systems. This result reinforced by the observations made by the authors on a few of damaged elevated water tanks after March 2006, Silakhor (Iran) Earthquake. In conclusion, the turnbuckles with hook shaped connecting elements behaved unsatisfactory both under standard testing as well as during a real earthquake.

Water reservoir systems have important role to control the surface water and provide various demands, such as irrigation, domestic, industrial and hydroelectric power generation. Therefore, it is necessary to study the behavior of these systems to provide demand satisfactorily. Assessment the reservoir system behavior during the drought periods is very important. Water release, always is less then the demand during the drought period. This study, assess the performance of within-year and over-year reservoir systems under different values of vulnerability index. Sustainability index was used to obtain the optimal performance of reservoir systems. Reservoir system was simulated using modified SPA method. Assessment of reservoir performance under different values of vulnerability index in sites showed that the sustainability for within-year system is generally maximum at 25% vulnerability and for over-year system is maximum at 35%-40% vulnerability.

In this paper, the turbulent flow structure between two ripples is investigated numerically and experimentally. In this study, a 3D ultrasonic Micro-ADV is used to measure the flow field velocity components in 128 separate points over a structured grid around the ripples. The velocity components are then used to draw the streamlines and determination of separation region. In addition the flow field is also modeled numericaly by the finite volume method and using four turbulent models: Standard k-e, RNG k-e, Standard k-w and SST k-w. The results show that the turbulent models Standard k-e and RNG k-e are more compatible with experimental results.