نشریه مهندسی عمران دانشگاه علم و فرهنگ
پیاپی 1 (1393)

Over the past few decades, utilizing composite structures consisting of steel and reinforced concrete is widely developed because of its advantages. One of these structural systems is RCS moment frame, which consists of Reinforced Concrete columns and Steel beams. In this paper the performance of various types of RCS connections such as interior, exterior, corner and roof level (T) are investigated using FEM. All the studied models are beam through type and the joint details are consist of Face Bearing Plates, Band Plates, joint stirrups and using steel beam in incontinues direction. The performance of models is investigated in terms of lateral load-story drift response and the contribution of different joint shear mechanisms, such as inner and outer concrete panel and steel beam web, in joint shear strength. The results show that the performance of connections is highly related to concrete confinement of the joint region. Also the contribution of steel beam web in joint shear strength of exterior and corner connections is lower than interior connections. Moreover using steel beam in incontinues direction increases the joint strength.

In present study, dynamic analysis of thin circular plates under an orbiting load and mass by employing Boundary Characteristics Orthogonal Polynomials (BCOPs) would be explored. These polynomials would obviate the use of trigonometric or Bessel functions for the Rayleigh-Ritz method. BCOPs are widely utilized in plates with various geometries such as rectangular, circular, triangle and elliptic plates. The boundary conditions are applied to the first polynomial and the rests would be produced by the Gram-Schmidt process. In this regard, after verification of the accuracy and convergence rate of this method in evaluating the static response as well as the natural frequencies of the circular plates with simple and clamped boundary conditions, dynamic deflection of these plates excited by an orbiting load and mass. By introducing the vertical component of the orbiting load acceleration, the inertial effects of the moving load are investigated. The obtained results reveal the importance of the load inertia in dynamic response of the structure, especially near the resonant states.

A total of 8 hydrofrac stress measurements to about 1km depth were conducted in borehole PH-01during the geotechnical site investigation program of Uma-Oya multipurpose project in Sri Lanka in 2011. The in situ tests were carried out by Gamaneh kav wire line system, where the straddle packer tools is moved within the 76mm (HQ size) or 96mm (NQ size) diameter boreholes on a seven conductor borehole logging cable and a winch system. In this paper we present the results of a new development of equipment for determination of the hydraulic tensile strength of rock in laboratory conditions for the first time in Iran. In laboratory mini frac tests, the rock samples were subjected to axial stress and confining pressure. Internal pressurization was achieved by injection of water in to the 4mm diameter holes at a rate of approximately 1ml/s. Fracture initiation and dynamic fracture growth is characterized by a hydraulic short circuit between axial stress, confining pressure and injection pressure, which yields the breakdown pressure Pc. The fracturing pressure Pc then is plotted versus the confining pressure pm which in general leads to a linear relationship (Rummel, 1987). The pc-value for pm = 0 is the hydraulic tensile strength pco, the slope yields the Fracture coefficient (k).According to Rummel’s fracture mechanics approach the laboratory tensile strength values pco suggest in-situ tensile strength values Pco of approximately 2.55 MPa, compared to observed strength values of approximately6.16 MPa. The result is an expression of the size effect with an intrinsic crack size ao of the laboratory samples in the mm-range, while due to the larger rock surface exposed at the pressurization during the in-situ tests, the intrinsic crack-size Ao of the rock is more than 10 times larger.

Commoncold- rolled steel frames, constructed in a panel, have a behavior factor of 4 and their heights are limited to 20 m, according to IBC2009. The main objective of this paper is to investigate the behavioral coefficient of cold rolled steel frame, which are constructed with the balloon method (continuous studin height).Studs are fabricated by C-shapedcross sections and boxes of cold-rolled and lateral members are made by cold-rolled box sections. In order to seismic behavior evaluation, the bending moment–rotation diagrams associated with C-sections and box shapes are first determined by laboratory observations and Finite Element analysis of nonlinear buckling Method using ABAQUS. Then, the results have been compared to the nonlinear pushoveranalysis frames in SAP2000. Analytical frames have thesame span and the numbers of X braces are determined based on initial design criteria, in accordance with IBC and AISI. Nonlinear pushover analyses are conducted over one to five-story frames. The bending moment-rotation diagrams of cold-rolled sections have been obtained, and the results show the average behavioral factor of steel frames under analyses, by a substantial increase, reach to around 6, indicating an improvement in behavioral factor of the balloon system compared to the traditional panel.

Textile Reinforced Concrete (TRC) is anew generation of cement-based composites, which have good bending strength. Inthisstudy,concrete samplesintwo thicknessesof 15and25mm, with different numberofTextile layersand two different mesh sizes of5 mmand10mmare made in laboratory. Flexuralbehavior ofTRC specimens is studied using four-point bendingload test. The resultsshow thatincreasing the number ofTextile layers,in TRC specimen clearly improves its flexuralbehavior. Specimensreinforcedwith5mmmesh sizetextile have much better bendingbehaviorthan thespecimenswith10mmmesh sizetextile evenwith thesame fiber percent. Also Comparisonof sampleswithdifferentthicknessesshowed that10 mm increasingin specimen thickness, improve the flexuralcapacityof samples more than 100 percent. Comparing the specimens bendingtestsresultsshowedthatstrainhardening behaviorforspecimenswith 8layers of 5mmmesh sizetextileisachievable.

:Providing stiffness and lateral strength insurance along with energy absorption and inelastic behavior are of important specifications in structures design against seismic loading. These properties can be seen in eccentrically bracedframes (EBF) which do not buckle before reaching yield strength in thin walledmembers. Vertical stiffeners in the web of link beams have a great role in reaching this target. Since width to thickness ratio in stiffeners is too high, local buckling is possible in them. In this paper, the effect of width to thickness ratio (b/t) on loading capacity, rotating capacity and energy absorption in EBF have been investigated. The result of these researches shows that in EBF, b/t ratio should be between 5 to 10.

In this study, using of Boundary Characteristic Orthogonal Polynomials (BCOP) is investigated on dynamic analysis of a thin rectangular multi span plate excited by moving mass on arbitrary trajectory. Constitutive equation of motion for constant velocity of movin mass is derived. For solution the separation of variables method is used. longer edges of plate is freely supported and the spans are created by some middle simply supported conastraits.the mode shapes and inherent properties of vibration is obtained by BCOP method and time domain solution of equation is done by a transformation into state space and using a numerical iterative method. One of the accrued aims in this paper, is convergence investigation on BCOP results about some vibration characters such as frequency parameter.The required dynamic response spectra in terms of dimensionless parameter and for various magnitude of traveling mass and aspect ratio are presented. In these graphs also,the results of dynamic analysis for moving loads with neglecting the inertia effects are depicted.By this work the possibility of comparison between replies of plate under both moving load and mass excitation would be derivable,too

In this paper, the results of measuring dynamic characteristics of reinforced concrete chimney in Shazand Arak power plant, using the ambient vibration test, is presented. Frequencies, mode shapes and critical damping ratio are studied characteristics. Chimney structure is a reinforced concrete shell to form a hollow cylinder with variable diameter and a height of 200 meters. In this experiment, SSR-1 data acquisition system and SS-1 short period sensors have been used. The sensors at levels 100, 151 and 200 meters have been installed and for 5 minutes, the data have been recorded in two orthogonal directions. Consequently, the recorded data have been processed in the time and frequency domain and for each mode, the frequencies, mode shapes and critical damping ratios have been estimated. Finally, the modeling and modal analysis of the structure using finite element software and based on the existing information, has been performed. Comparison the modal analysis results of the mathematical models and empirical results have shown that the used elastic model and the linear analysis are accurately captured dynamic characteristics of the structure. Obviously, the results of this study can be used to estimate more precisely the empirical period of concrete chimneys and also can be used to design more secure of the similar structures