فهرست مطالب

Asian journal of civil engineering - Volume:18 Issue:7, 2017
  • Volume:18 Issue:7, 2017
  • تاریخ انتشار: 1396/06/01
  • تعداد عناوین: 11
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  • N. Alioua *, T. Messafer (Ms) Kachi, F. Mohri Page 1009
    The present paper deals with the behavior of reinforced concrete beams in presence of plasticity and cyclic loadings. The model takes into account the nonlinear material behaviors of the constituents steel and concrete. A numerical model based on the finite element method is investigated for the study of the reinforced concrete beams under cyclic loads undergoing large deformation in the plastic range. In the study, nonlinear material behavior laws are introduced in presence of plasticity and cyclic behavior in the concrete in compression and in the reinforcement steel bars under tension stresses. The concrete steel interactions as well as the crack damage are also considered in the model. An incremental iterative method in adopted in the solution of the equilibrium equations. The model is validated and compared to some benchmark solutions available in literature. The agreement is good in the case of beams under monotonic loads or cyclic loads with high cycles.
    Keywords: Reinforced concrete, cyclic behavior, non, linear, flat structures, plasticity
  • S. Bahrami *, F. Shirmohammadi, M. M. Saadatpour Page 1025
    In this paper, the spectral element method will be developed for thin plates subjected to the moving loads and axial forces. In this method, Fast Fourier Transform (FFT) and Inverse Fast Fourier Transform (IFFT) are utilized to obtain displacements in time domain and natural frequencies. The exact shape functions and dynamic stiffness matrix in frequency domain are extracted. The natural frequencies of the thin plate, computed by spectral element method are compared with frequencies, computed by other numerical methods.
    Keywords: Thin rectangular plate, moving load, dynamic of continues plates
  • D. S. Yerudkar, G. R. Vesmawala* Page 1041
    This research mainly concentrates on ultimate strength and buckling behaviour of CFS laterally un-braced longitudinally stiffened Channel (C) and Zed (Z) sections under flexure. A total ten various stiffener combinations for C and Z sections has been studied by modifying the shape of a simple end stiffened section by the provision of intermediate stiffeners along web, flange or both along web and flange. The influence of different types of stiffeners with respect to various aspect radio’s (H/T, B/T, C/T and H/B) have been studied using Finite Element Method (FEM), Direct Strength Method (DSM) and Indian Standard Method (IS) and recommendations have been proposed on provisions of different types stiffeners and design standards. In summary, in view of the increase in buckling strength of open C and Z flexural members, provision of V shape intermediate stiffeners along the web and flange has been proposed.
    Keywords: Stiffened sections, buckling analysis, finite element method
  • H. Kothari, P. Patel, D. Joshi * Page 1059
    Nowadays, there is an increasing trend towards construction of buildings using precast concrete. In precast concrete construction, all the components of structures are produced in controlled environment and they are being transported to the site. At site, such individual components are connected appropriately. In precast construction, ductility is essential for providing protection against the effects of unexpectedly large lateral forces. Dry connections in a precast structure usually introduce discontinuities in strength and stiffness which is expected to attract deformations and damage under lateral load during an earthquake. Therefore, it is important to study the behaviour of precast connection under lateral loading, since slender structures are mostly sensitive to lateral forces. In this paper, experimental study of behaviour of precast portal frame with different connection detailing under lateral load is reported. Experiments are conducted on three test specimens including one monolithic portal frame and two portal frames having precast connections with cleat angle and with reinforced concrete (RC) corbel, that are subjected to lateral load. Performance of test specimens are evaluated in terms of load carrying capacity, deflection profile of columns and measurement of strain at critical locations on concrete surface as well as steel reinforcement bars and failure pattern. From the results, it is observed that behaviour of precast portal frame having beam column connection with cleat angle is almost similar as that of monolithic portal frame.
    Keywords: Precast portal frame, lateral load, RC corbel, cleat angle, dry connection
  • M. Zameeruddin *, K. K. Sangle Page 1077
    In this study, an energy-based damage index (𝐷𝐼𝐸) was introduced and expressed as a simple formula on the basis of the nonlinear response obtained from nonlinear static procedures. The 𝐷𝐼𝐸 is advantageous because pushover analysis has to be performed only once for the lateral loads obtained from the equivalent static method given in the IS 1893 to represent the degree of damage to the structure under consideration. The 𝐷𝐼𝐸 was employed to assess the damage sustained by example RC frames representing different structures. To extend 𝐷𝐼𝐸 to different performance levels defined in the FEMA 356, the damage values were associated with the drift-based damage index. The results indicated that the 𝐷𝐼𝐸 concurred with drift-based damage criterion, and it is a valuable tool for practical applications.
    Keywords: Performance based seismic engineering, damage index, damage function, FEMA performance levels, pushover analyses
  • D. Najjar *, A. Kaadan, M. N. Alyagshi Eilouch, A. Al Helwani Page 1095
    Seismic isolation is used to minimize damage and prevent collapse in earthquakes. This research aims to study Multi Criteria Optimization of rubber bearing. A numerical model is proposed using FE simulation implemented in ABAQUS 6.11. Effect of parameters like number of rubber layers, thickness of steel shim, and shear modulus of rubber, on operational characteristics is investigated. Operational characteristics are effective horizontal stiffness, vertical stiffness, and equivalent viscous damping. Results show that number of rubber layers and thickness of steel shim have large effects on vertical stiffness. Furthermore, horizontal stiffness and equivalent viscous damping are highly dependent on shear modulus.
    Keywords: Seismic base isolation, effective horizontal stiffness, equivalent viscous damping ratio, multi criteria decision making, weighted sum method (WSM)
  • Y. M. Ghugal *, V. D. Sabale, S. S. More Page 1113
    The paper presents the results of an experimental investigation on the properties of structural concrete using steel fiber (SF) and metakaolin (MK). Crimped steel fibers of aspect ratio 85 and metakaolin were used. The effects of these fiber and metakaolin on workability, density, and on various strengths of M60 grade concrete are studied. Fiber content varies from 2.5% to 10 % by weight of cement and metakaolin content varies from 5% to 20% by weight of cement. The various strengths considered for investigation are compressive strength, flexural strength, split tensile strength, and shear strength. Cubes of 150mm for compressive strength, cylinders of size 150mm diameter x 300mm length for split tensile strength, beams of 100 x100 x 500 mm for flexural strength, push-off specimens of size 150 x 150 x 450 mm for shear strength were cast. All the specimens were water cured and tested after 28 days. Workability of wet mix is found to be reduced with increased fiber content. Ductility of steel fiber reinforced metakaolin concrete (FRMC) is found to increase as observed from the study of load–deflection behavior. A significant improvement in the various strengths is observed due to inclusion of fibers and metakaolin in the concrete.
    Keywords: Crimped steel fiber, metakaolin, M60 grade concrete, shear strength of concrete
  • M. Jalili Sadr Abad *, M. Mahmoudi, E. H. Dowell Page 1125
    In this research, a new numerical method is presented to evaluate the linear and especially the nonlinear dynamic response of single degree of freedom systems. This technique is based on the simultaneous usage of energy and force equilibrium equations which is called the Modified Energy Method. At first, a simple linear system is selected to illustrate the method in detail with harmonic and earthquake loading. Furthermore, several different nonlinear examples are studied such as: a-Coulomb Friction (nonlinear damping) b-Duffing Oscillator (material nonlinearity) and c-Large-angle Simple Pendulum (geometric nonlinearity). The results of the proposed method are compared with other methods, and it was found that this method is more accurate compared with the 4th order Runge-Kutta method for nonlinear analyses.
    Keywords: Dynamic analysis, SDOF systems, material nonlinearity, nonlinear damping, geometric nonlinearity, modified energy method (MEM)
  • S. M. Abdollahi *, M. Ranjbar Page 1147
    Reinforced concrete flat slab is a common structural system, which is widely used in the construction of various buildings. On the other hand, utilization of flat slabs directly resting on columns, in the case of punching shear failure, reveals their vulnerability, especially in seismic areas. Application of flat slab reinforced concrete system was primarily done due to necessity of passing the mechanical and electrical installations, in which presence of openings in vicinity of the column is inevitable. Strengthening the flat slabs with an opening in the slab-column connections has great importance. In the present study, some of the factors affecting punching shear strength of flat slabs with an opening were studied using a numerical method. To validate the numerical model, the obtained results were compared with those of experimental sample. Then, the impact of concrete compressive strength, tensile reinforcement percentage, presence and number of reinforcements in the compressive area, and presence of additional bar around the opening was investigated. It was observed that increasing the level of reinforcement connection, improved the condition of punching shear capacity and stiffness of slabs. Furthermore, by increasing concrete compressive strength, load bearing and ultimate connection deflection increased, as well.
    Keywords: Flat slab, punching shear strength, finite element method, opening
  • M. Surana, Y. Singh *, D. H. Lang Page 1167
    Non-linear static and dynamic analyses are performed on a set of reinforced-concrete frame buildings to derive static and dynamic capacity curves. The static capacity curve is ‘transformed’ using the displacement modification method for comparison with the dynamic capacity curve. It is observed that the static procedure predicts the collapse capacity in close agreement with the dynamic procedure, after adjusting for the effect of spectral shape. The obtained static and dynamic capacity curve parameters along with associated uncertainties are used to obtain the collapse fragility curves. Collapse probabilities obtained both from static and dynamic procedures, are observed to be in close agreement.
    Keywords: Collapse probability, static, dynamic capacity, seismic design, physical fragility, RC frame buildings
  • H. Dabiri *, A. Kheyroddin Page 1183
    Corrosion of reinforcement bars, large base shear due to earthquake load and tensile defect of concrete are the most important failure factors in an RC column. This paper investigates using elastomeric materials in a RC pier to diminish or even eliminate above-mentioned factors. For this purpose, totally seven numerical piers under Kobe earthquake load and constant axial load were modeled in nonlinear finite element software. Elastomeric material was used in plastic hinge zone of RC pier in different heights and thicknesses. Base shear and ductility of piers were evaluated. Results generally showed that, using elastomeric material in a RC pier reduced ductility but it will decreased base shear force in size of 10.61 percent. The other advantage of using elastomeric material is to eliminate concrete tensile defect in tension surface of pier section and reinforcement bars corrosion due to concrete cover ruin in corrosive environment.
    Keywords: Finite element, RC column, elastomeric materials, ductility, base shear force