Year:2006 | Volume:39 | Issue:5 (93)|Papers Count:12

This paper presents the results of an experimental study on the behavior of reinforced concrete columns, confined by CFRP wraps, under eccentric loading. Experimental specimens consist of 6 RC square columns. The dimensions of the sections of columns were 200 by 200 mm and the length of all columns was 700 mm. six specimens were wrapped using unidirectional Carbon Fibers. Experimental results show that the positive effect of confinement due to CFRP Wraps on the column strength decreases with increasing the load eccentricity

By development of ship dimensions and the necessity of berthing of high tonnage ships, there was a need for an appropriate structure with optimum energy absorption behavior. Since the conventional berthing facilities (such as quays, sheet piles, etc.) could not experience large displacements, absorbing a large amount of energy by them is satisfied by applying high forces. Besides, due to the high drought of big ships, providing the proper depth for berthing of these ships will cost a lot. All above discussions have led the designers to use an appropriate structure in deep water that in addition to absorbing energy through experiencing large displacement, the repairing cost of that be independent to the other facilities. The most appropriate structure fulfilling this purpose is the monopile. Because of high forces exerted on monopile, the large displacement will occur in the surrounding soil which makes the soil behavior nonlinear. In addition, presence of water around the structure and also dynamic behavior of ship impact phenomenon makes the analysis complicated. In this paper in order to satisfy the above mentioned parameters, and to consider the water-structure-soil interaction, Ansys7.0 is used and based on the obtained results, the design curves have been extracted in such a way that the dimension of monopile could be obtained via them by having soil characteristics, water depth, ship tonnage and its velocity as input.

The concrete pavements have more advantages in performance and maintenance cost, due to high durability and bearing capacity when compared with asphalt pavements. Hence, making decision on type of pavement for different projects will be important mainly in road tunnels where frequent closure for necessary maintenance become vital, which normally leads to extra costs on commuters who use the road.In this paper, different pavement types in tunnels have been analyzed in term of economical aspects, based on logical and scientific processes.The analysis for flexible and three different rigid pavements taking different sub-grade and traffic conditions in tunnels are made.  Construction, maintenance, rehabilitation, user and environmental costs are considered in the latter and the results are presented using Net Present Cost (NPC) method.The aforementioned results showed that, the Whole Life Cost (WLC) for concrete pavements in tunnels with same conditions is lower than asphalt pavements.  The difference increases with increasing traffic volume or diverted road lengths for rehabilitation works due to tunnel closure. Also it can be said that whenever, the discount rate for capital is low, the use of pavements which have lower maintenance cost and shorter rehabilitation periods is economically justified

In this paper the effects of surface topographies on earthquake ground motion is considered using direct boundary element method in time domain. The presented method is effective for modeling of surface irregularities with arbitrary shape under complex incident wave form. A real topography with particular importance in Iran, Gisha Hill, which represents a complex surface irregularity, is considered as study case and its behavior is studied under several incidences. An area of about 1400 by 1200 meters is modeled with quadrilateral serendipity boundary elements and the problem is solved for synthetic earthquake time history with various azimuths and angles of incidences. The results show that the areas nearby the top of the hill experience more excitations in some cases while more amplifications occur in the edges in other cases. The amplification pattern shows to be completely dependent on wave type, azimuth and angle of incidence..

Aircraft crash is an external, potentially man-induced event, load condition to be considered in the evaluation of the design of the concrete containment of a nuclear power plant according to safety requirements of International Atomic Energy Agency (IAEA). This loading can cause local/global structural damage and/or functional failure of safety systems or components. Using Riera (also proposed by IAEA) load/time history for this type of loading, an attempt is made in this paper to study the global behavior of a German design nuclear power plant concrete containment. A nonlinear dynamic finite element program (NDARCS) using eight-nodded reinforced concrete shell elements is utilized for this purpose. The results are compared with those of other investigators who used 3-D elements. Very few codes offer design criteria for this type of loading. These criteria are also evaluated in the paper. The effects of reducing shell thickness and altering the concrete failure criteria on the behavior of containment are also assessed.

In this research, an effort is made to determine three dimensional bearing capacity of rectangular foundations by Discrete Element Method. The soil mass is modeled as several discrete blocks connected with Winkler springs. The equations employed in this method completely satisfy the equilibrium conditions of forces and moments, with the assumed Elasto-Plastic behavior for the springs. Similar to the conventional bearing capacity theories, the failure of footing occurs by a wedge of soil below the footing pushing its way downward into the soil. The geometry of the failure surface is not fixed and can be altered due to all factors affecting the problem. The geometry of the failure surface under the foundation is determined by six independent angles. By trial and error the optimum shape of failure surface beneath the foundation can be found. This optimum failure surface corresponds the minimum collapsing load.The paper includes several examples to explain the capability of the method. The results are compared with other methods currently in use for determining the ultimate bearing capacity of rectangular shallow foundations. Also, several graphs and tables are presented expressing the coefficients of bearing capacity and shape factors for various values of internal friction for underneath soil and foundation aspect ratio.

Detailed gravity field modeling requires ground, sea, airborne and satellite gravity observations. Sea gravity observations have been always suffering from the low accuracy and noises.  On the other hand satellite altimetry provides accurately sea level variations. In this paper possibility of gravity field modeling at sea areas, especially at islands, using satellite altimetry is studied. A method for this purpose is devised which algorithmically can be explained as follows: (1) Obtain Mean Sea Level (MSL) from satellite altimetry. (2) Obtain Sea Surface Topography (SST) from oceanographic sea current and studies. (3) Compute the geoid by removing SST from MSL. (4) Apply inverse ellipsoidal Bruns formula and compute the gravity potential at the reference ellipsoid. (5) Remove gravitational effect of ellipsoidal harmonic expansion to degree and order 360 and the centrifugal acceleration. (6) Remove terrain effect using Newton integral over the terrain masses at the radius of 55 km around the computational points. (7) Upward continue the harmonic gravitational potential derived in step 6 using ellipsoidal Abel-Poisson integral. (8) Restore the effects removed in steps 5 - 6 at the computational point. This procedure is applied for gravity field modeling at Geshm Island and its surrounding area. The details of the method and results of the case study are presented in this paper.

In this paper the issue of leveling and centering of total stations have been considered and has been proved that if the goal is to obtain the coordinates and/or geometry of an object it is not necessary to level and occupy a station, but instead the formulas introduced based on the orthogonal frame imbedded in the total station can be used to obtain the coordinates and/or geometry of the object without leveling and centering. In this way the time, which is needed, for the observations would be drastically reduced and as such it would be possible to use the total stations in the industrial environments in which only very short observation time is permitted. The details of the idea along with the proof of the formulas that are prevailing the geometry of an unleveled total station are given in the paper.

Total Station (TS) observations {horizontal angle, vertical angle, slop angle} are made in Local Astronomy (LA) coordinate system, while GPS observation {geodetic longitude, geodetic latitude, ellipsoidal height} are made in a Geodetic (G) coordinate system named WGS84. Connecting parameters between these two coordinate systems are components of deflections of vertical   {ξ , η} Possibility of making TS and GPS observations at the same points motivated us to make a feasibility study of using these two observations at the same points for computation of the deflections of vertical. Knowing the deflection of vertical and GPS coordinates; astronomical longitude and latitude can be computed. In this study first the required mathematical models for computing astronomical longitude and latitude via combination of TS and GPS observations are derived and next tested at a Laplace station of 1st order triangulation network of Iran. The mathematical model is built in a way that the number of observations (equations) be more than unknowns so that the least squares adjustment can be performed. The derived astronomical coordinates are compared with those observed at the Laplace station. The result of the comparison indicates that 5.6" accuracy can be achieved in the computation of astronomical coordinates using the derived procedure. The results of the test computations assures that the combination of TS and GPS observation can be regarded as an alternative method for obtaining astronomical coordinates at the GPS era. Besides knowing the transformation parameters between LA and G coordinates systems, the GPS coordinates can be generated by TS. The latter possibility can be regarded as an answer to long time open problem of using GPS at the urban areas with high risk of multi path and frequent blockage of the GPS signals due to obstacles in the urban areas.

This paper describes a new approach in medical photogrammetry for the 3D reconstruction of the surface of bedsores. The implemented method utilizes four convergent digital cameras for acquiring four synchronized images of the bedsores. The exterior and interior orientations of the cameras as well as the cameras systematic errors are determined by a pre-calibration approach using accurately measured target points. As the bedsore texture is not appropriate for stereo matching, ambiguity will occur during the detection of the homologous points and hence image matching becomes complicated and very much exposed to gross error occurrences. Disambiguation is achieved by the enforcement of four focal epipolar geometry by which homologous points are detected based on the geometry of the cameras. The solutions of the space/resection intersection based on four camera geometry are discussed, the hardware components are described and the preliminary tests and results are presented.

During the last decade airborne laser scanning (LIDAR) has become a mature technology which is now widely accepted for 3D data collection. Nevertheless, these systems have the disadvantage of not representing the desirable bare terrain, but the visible surface including vegetation and buildings. To generate high quality bare terrain using LIDAR data, the most important and difficult step is filtering, by which non-terrain 3D objects such as buildings and trees are eliminated while keeping terrain points for quality digital terrain modeling. The main goal of this paper is to investigate and compare the potential of procedures for clustering of LIDAR data for 3D object extraction. The study aims at a comparison of K-means clustering, SOM and fuzzy C-means clustering applied on range laser images. For evaluating the potential of each technique, the confusion matrix concept is employed and the accuracy evaluation is carried out both qualitatively and quantitatively.

Presentation of spatially distributed phenomena in local, regional or global scale is a need for development of multi map projection. This issue has not been addressed by researchers properly. As such, the selection of a proper map projection in the currently available software is a neglected task.  The developed expert systems suffer from functionalities of dealing with such a huge data especially in a continuous environment.This paper introduces the concept of multi-map projection, identifies the parameters affecting map projections, and finally models them. The findings are then used to develop intelligent map projection selection software such that it provides the most suitable presentation of the spatial data in a continuous dynamic environment.  For transforming the projection system during visualization in different regions an expert system is required. The selection of the most appropriate map projection is mostly governed by location, size, shape, and map-usage. The knowledge part of the developed algorithm considers latitude as location, zoom as size, and country applied projection as shape, to choose one predefined projection. In order to optimize the software ability, a zonation map presenting the magnitudes of distortions and also various datum's are included.