فهرست مطالب

Asian journal of civil engineering - Volume:16 Issue:2, 2014
  • Volume:16 Issue:2, 2014
  • تاریخ انتشار: 1393/09/10
  • تعداد عناوین: 9
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  • M. Rezaiee-Pajand*, F. Shahabian, M. Bambaeechee Pages 135-159
    An exact formulation for computing the critical buckling load of semi-rigid steel frames with tapered columns will be obtained. The presented methodology is based on the precise solution of the governing differential equations for elastic buckling of the uniform and non-uniform frames. These formulations also can be used for the tapered column with various support conditions. Moreover, the effect of tapered columns, with parabolic and quadratic functions for variation of the moment of inertia, flexibility of connections, and lateral support, such as bracing, on the equivalent buckling length factor of the frame will be studied parametrically as well as numerically. Comparing the findings with the available results indicates the accuracy, validity and capabilities of the proposed approach.
    Keywords: Stability analysis, tapered columns, semi, rigid connections, steel frames, equivalent buckling length factor, critical buckling load
  • S. M. Zahrai L. Sarkissian Pages 161-181
    The influence of the in-plane flexibility of composite floor systems on the seismic response of the structures may become significant, particularly when considerable floor slab cracking and yielding are expected. As in recent years the use of composite floor systems is increasing, in this study the lateral in-plane behavior of composite floor diaphragms in steel structures is investigated through numerical simulations. The structures considered in the study were two models of the prototype buildings, where the elastic and inelastic responses of the diaphragms under lateral load are analyzed using 3-D finite element models and FEM linear and nonlinear structural analysis. It was found that under the seismic load specified in the code, the criterion of diaphragm rigidity is too small, so the composite floor systems can be assumed as rigid body, however under lateral loads with higher amplitudes, by developing the cracks in the concrete slabs, nonlinear behavior and stiffness degradation of the diaphragms might occur. The results showed that for both single story structures the ultimate strength of the diaphragms was very high about 20 to 33 times of the seismic load specified in Iran''s seismic code, however the ultimate strength of the second model, where the joists direction was perpendicular to the lateral load direction, was considerable showing a reduction about 50~60% compared to the ultimate strength of the first model, where the joists direction was parallel to the lateral load direction. The comparisons between the numerical and previously obtained experimental results showed that FEM overestimates the diaphragm response in terms of stiffness and deformability; however conservatively estimates the diaphragms strength.
    Keywords: Composite floor system, numerical simulation, nonlinear analysis, diaphragm, seismic load, crack pattern, ultimate strength, in, plane stiffness
  • M. Amini, S. Shojaee, S. Rostami Pages 183-202
    Quartic B-spline time integration method has been recently proposed for solving linear problems in structural dynamics. This paper developed this method to nonlinear dynamic analysis of single-degree-of-freedom (SDOF) systems under exploding loads. Using quartic B-spline basis function, this method gained second order of acceleration at each time-step. Thus it benefits from high accuracy compared to the methods in the literature. In this research, in order to applying the iterative process in the procedure, firstly, a series of standard formulas were derived from previous formulation. Then the Newton-Raphson iterative method used to develop new formulation for solving nonlinear dynamic problems. Finally, for the new scheme, a simple step-by-step algorithm is implemented and presented to calculate dynamic response of SDOF systems. The validity and effectiveness of the proposed method is demonstrated with two examples. The results were compared with those from the famous numerical method. The comparison shows that the proposed method is a fast and simple procedure with trivial computational effort.
    Keywords: Quartic B, spline, time integration, nonlinear dynamic analysis, SDOF, blast load, explosion
  • A. Okakpu, G. Ozay Pages 203-218
    Nowadays, old existing buildings with less load carrying capacity are usually strengthened by the application of a suitable strengthening method. Such methods include the use of steel bracing, FRP jacketing or wrap, concrete jacketing, steel plating, shear wall and hybrid methods. However, there are the possibilities of selecting a strengthening method without comparing for the most efficient method, due to time constraint or little knowledge about strengthening methods. These will however, lead to ignoring the differences among the strengthening methods.In the present study, information about strengthening methods is highlighted as obtained from the survey. According to this information, decision selection program is set up, where different strengthening methods are encoded with their characteristics of solving problems. A case study is applied herewith to check the efficiency of the decision selection program. The recommended strengthening methods are ascertained to be relatively more economical, efficient and time saving.
    Keywords: Strengthening, global strategy, choice selection, local strategy
  • H. Saffari, A. A. Hedayat, N. Soltani Goharrizi Pages 219-233
    Due to the closed shape of box columns and difficult access to its inside for developing a reliable load path regarding rigid I-beam to box columns connections, in this study, some alternatives have been suggested to replace continuity plates. These alternatives are: two triangular plates, two rectangular plates and added stiff web. To evaluate the efficiency of these suggested alternatives, using ANSYS software, several beam-column connections in each alternative have been modeled. Based on the finite element results the behavior of I-beam connection to steel box column has been studied. Then the effects of suggested stiffeners on connection stiffness, strength and ductility have been investigated. The results showed that each of the suggested methods might be a good alternative for rigid connection with internal uniform continuity plates. However specimens of additional stiffened webs achieved highest connection strength and ductility.
    Keywords: Panel zone, moment resisting connections, box columns, continuity plates
  • L. Nouri, S. Yousfi, M. Saidani, H. Hadjab, M. Nouri Pages 235-248
    The artificial cement characterization requires the measurement of a large number of control parameters. In the present work, twenty four parameters that are monitored on a daily basis during three years of observation are investigated. Due to the large amount of data to be collected, a monthly overage is calculated. This allows the result fluctuations due to managing difficulties to be reduced.The purpose of this study is to show that it is possible, with an acceptable approximation rate, to make a variable reduction, which is to reduce the number of control parameters, as these measurements are identified every hour at the exit of the clinker crusher and daily at the expedition.The aim of the present investigations is to suggest a manufacturing supervision that can give improvements in the characteristics of the finished product and that can reduce, in an objective way, the number of tests. The consequences of such pertinent supervision are a great deal of saving time and lower cost.
    Keywords: Manufacturing supervision, artificial cement, control parameter correlation, factorial analysis methods, variable reduction, stochastic models, crusher, expedition
  • M. Shahrouzi, A. Kaveh, M. Saidani, H. Hadjab, M. Nouri Pages 249-268
    A new hybrid framework is proposed for optimization of orderable search spaces. It is based on fuzzy-membership of design variable alternatives to the optimal solution. The method has dynamic behavior since the membership values are assigned as any solution candidates arises during the search and they are summed based on their overlaps in the alternatives scope. A trail matrix is also utilized to indirectly share values of the fuzzy memberships further ranked regarding closeness of an individual to the optimal solution both in the objective function and in the design space scope. The method takes benefit of different random, vector-sum and probability-based walks to move new solutions toward the global optimum. Utilizing a generalized cooling procedure, the related thresholds are tuned to choose between different walk types in searching the design space and also a search refinement strategy is developed. Two variants of such a framework is then proposed and compared with each other in addition to some well-known procedures including genetic algorithm and particle swarm optimization. Test results with some treated problems, reveals the superior performance of the proposed algorithm and its special feature in adaptive tuning the diversity index during the search.
    Keywords: Meta, heuristic algorithms, information share, fuzzy logic, structural optimization
  • Shrithi S. Badami, P. Kamatchi, Nagesh R. Iyer Pages 269-290
    In the present study, 2D linear ground response analyses of typical alluvial strata located at Ahmedabad has been carried out for Mw 7.6 scenario earthquake and the comparison has been made with 1D equivalent linear ground response analyses results. The spectral amplifications from the present study are compared with field measured site amplifications reported for similar site. Using the surface ground motions from 2D and 1D ground response analyses, linear time history analyses are carried out for typical 15 and 6 storey reinforced concrete framed buildings and the base shears are compared with design base shear as per Indian Seismic code.
    Keywords: 2D ground response analyses, 1D ground response analyses, deeper alluvial basin, Bhuj earthquake, artificial ground motion, site, specific
  • M. Priya, S. Greeshma, K. N. Suganya Pages 291-300
    In flat plates, a brittle punching failure can rise in connections due to poor transfer capacity of shearing forces and unbalanced moments. Once, the punching shear failure occurs, the resistance of the structure is significantly reduced, which causes the separation of the column and slab which leads to collapse of the whole structure. In the present work, analytical investigations are carried out to study the performance of interior slab – column joints of reinforced concrete multi storey buildings. The connection between slab and column is an essential link in the load resisting mechanism of flat plate building. From the literature reviewed it is clear that paucity of information exists in the area of detailing of slab to column joint. Hence an attempt has been made to study the effect of detailing of slab – column joint under lateral loading. In order to study the performance of interior slab–column connection, a multistoried flat plate RC building has been analysed and one of the interior slab – column joints is designed. Seismic analysis is performed using the equivalent lateral force method given in IS 1893(Part 1):2002 [5]. Analytical modelling of the slab– column joint was carried out using finite element software package ANSYS [1]. The model is analysed under axial vertical load and varying lateral load at the top of the column. The critical stress resultants were observed at the slab – column joint.
    Keywords: Flat plate, punching, slab – column joint, seismic analysis