فهرست مطالب

Asian journal of civil engineering - Volume:14 Issue:4, 2013
  • Volume:14 Issue:4, 2013
  • تاریخ انتشار: 1391/12/14
  • تعداد عناوین: 10
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  • H. Dehghani, M.J. Fadaee Page 503
    This paper presents a statistical analysis for evaluating the four most common torsional analytical models of concrete beams strengthened with fiber reinforced polymer. For this aim, data are collected from experimental works and the results predicted by four analytical models are compared with the experimental results. The most appropriate analytical model is selected and is used for determining resistance factors conducting reliability analysis. The second purpose is to study load and resistance factor design calibration for the selected model. Two possible target reliability levels have been chosen from the literature and, an iterative procedure is used for resistance factors calculation.
    Keywords: Torsional strengthening, Statistical analysis, Load, resistance factor design, Composite materials, Calibration, FRP
  • K. Behfarnia, A. Keivan, A. Keivan Page 517
    In the present study, compressive strength of normal concrete together with gas permeability of concrete containing various percentages of TiO2 and ZnO nanoparticles were investigated and the results were compared with each other and with that of the normal concrete. More types of tests were carried out on the specimens including X-ray diffraction (XRD) and Scanning electron microscopy (SEM). The results indicated that TiO2 nanoparticles decreased the compressive strength after 28 days of curing; however, the permeability of concrete was lowered. Moreover, it seems that by adding TiO2 nanoparticles up to 4wt% of the cement the mechanical and physical properties of concrete may improve. The ZnO nanoparticles strongly retard the setting time and increasing the amount of ZnO nanoparticles in the mixture, thoroughly stops the hydration process within the concrete and prohibits the formation of mortar. As concluded from XRD diagrams, it seems that an amorphous layer of Zn(OH)2 is the main reason that prohibits C3S phase to participate in hydration process. Besides, with increase in percentage of the ZnO nanoparticles in concrete mixture, the lower compressive strength was obtained.
    Keywords: Concrete, nano particles, XRD, SEM
  • R. Madandoust, J. Sobhani, P. Ashoori Page 533
    An experimental investigation was carried out to evaluate the mechanical and durability properties of concrete mixtures containing natural zeolite (NZ) and metakaolin (MK) in binary blended system up to 20% replacements. Concrete mixtures were evaluated for compressive strength, penetration of water under pressure and water absorption in 30 minutes and 24 hours at various ages up to 90 days. Water to binder ratio and total cementitious materials content were kept constant for all mixtures as 0.4 and 400 kg/m3 respectively. The results showed that despite the observed decrease of compressive strength of proposed composites, they gained enough strength at the later ages similar to that of normal concrete. Moreover, the results confirmed the beneficial effects of zeolite and metakaolin on the durability indexes of concrete which lead a green and environmentfriendly concrete.
    Keywords: Concrete, durability, metakaolin, natural zeolite, water absorption, permeability
  • T. Mahdi, A. Mahdi Page 545
    In this paper, analytical techniques are used to determine the fragility of freestanding rigid equipment under seismic excitations and to further improve their seismic mitigation measures. These measures can be carried out using some types of restraints that reduce the displacements and accelerations considerably. The results show that fragility curves for restrained blocks are sensitive mainly to the dynamic coefficient of friction and to the ratio of the vertical component of the cable forces to the weight of the block and they have direct relation to the maximum magnitudes of the pseudo-velocity spectrum curves.
    Keywords: Non, structural components, fragility, sliding, SIMQKE, artificial records
  • M.A. Barkhordari, N. Dayhim, A. Nicknam, M. Razi, S. Mehdizad Page 557
    The use of Near-surface Mounted (NSM) FRP bars is an efficient strengthening technique to enhance the flexural strength of RC structures. This article is intended to analytically investigate the effectiveness of Glass Fiber Reinforced Polymer (GFRP) bars in combination with GFRP wraps on the flexural capacity of reinforced concrete (RC) columns with Fiber Element Modeling approach. The accuracy and reliability of the proposed fiber-based modeling method is demonstrated by numerical models on seven half-scale experimental RC reference columns under axial and cyclic lateral loads. These reference specimens are comprised of seven half-scale RC columns including two unstrengthened and five strengthened specimens with two GFRP bar reinforcement ratios under three axial load levels. Additionally, eight RC strengthened columns are analytically simulated with four complementary GFRP bar reinforcement ratios under two axial load levels. As the numerical results represent good correlation between the fiber-based modeling approach and the experimental results of the reference RC columns, it is concluded that the numerical simulations explicitly predict a considerable improvement in the flexural strength of the RC columns retrofitted with Glass Fiber Reinforced Polymer bars.
    Keywords: GFRP bar, near, surface mounted (NSM), GFRP wrap, flexural strengthening, fiber element model (FEM)
  • M. Mahmoudi, M. Zaree Page 577
    In performance based design, the hazard levels and relevant acceptable damages are clearly specified. Structural and non-structural performances are controlled by limiting stiffness, strength and members ductility characteristics. Using displacement amplification factors (Cd) and force reduction factors (R) related to hazard levels, this paper present a method for determination of the stiffness and strength demands needed for BFs (Braced Frames) design. It means that two force reduction factors and two displacement amplification factors are introduced for moderate and major earthquake levels (Immediate Occupancy and Life Safety performances) for determination of stiffness and strength demands. These factors depend on ductility factor, force reduction factor due to ductility and overstrength factor. The procedure for determination of R and Cd factors and value of these factors for Io and LS performance level will be presented in this paper. The results indicate that force reduction factors and displacement amplification factors may be easily used in performance based design methodology.
    Keywords: Displacement amplification factor, force reduction factor, overstrength factor, performance based design, reduction factor due to ductility
  • A. Kaveh, B. Hashemi Soudmand, R. Sheikholeslami Page 587
    Composite laminates have many applications as advanced engineering materials, primarily as components in civil engineering structures, aircrafts, power plants, ships, cars, rail vehicles, robots, sports equipment, etc. Due to widespread use of these materials in various fields in this paper the minimum thickness design of laminated composite plates under inplain loading is explored using a hybrid charged system search algorithm (CSS) and particle swarm optimization (PSO) where ply numbers and fiber orientations are considered as design variables. This optimization method is obtained by adding searching abilities of the PSO algorithm to those of the CSS approach. Static failure criteria are utilized to determine whether the load bearing capacity is exceeded for a configuration generated during the optimization process. In order to check the feasibility of solutions during an optimization procedure, both the Tsai–Wu and the maximum stress safety factors are employed. Numerical results are obtained and presented to evaluate the performance of the proposed algorithm for different loading cases. Compared to other approaches, the algorithm has proven to be quite reliable in performing these designs.
    Keywords: Optimal design, laminated composite structures, hybrid algorithm, charged system search, particle swarm optimization
  • C. Antony Jeyasehar, G. Saravanan, M. Salahuddin, S.Thirugnanasambandam Page 605
    In view of the serious impact of carbon dioxide on the environment and the continued anticipated growth of industrialization and urbanization, there is a need to redirect the building industry away from its overwhelming reliance on Portland cement by developing alternative binder systems like geopolymer binders. It is proposed that an alkaline liquid could be used to react with the silicon (Si) and the aluminum (Al) in a source material of geological origin or in by-product materials such as fly ash to produce cementitious binders. Experiments have been conducted at Annamalai University, India on the behaviour of fly ash based geopolymer concrete and structural elements such as beams. The mechanical properties of geopolymer concrete such as compressive strength, split tensile strength and flexural strength have been found out and compared with that of ordinary cement concrete. Five beams of size 125 x 250 x 3200 mm were cast and tested. Out of this five beams,one beam is control beam with normal cement concrete and the remaining four are geopolymer concrete beams with Alkali –Activator Solution / Fly ash ratio 0.40, 0.45, 0.50, 0.55 and comparable compressive strength. The alkaline Alkali –Activator Solution used in this study is a combination of sodium hydroxide and sodium silicate. The load-deflection and momentcurvature behaviours obtained from the experimental results are compared with analytical solutions.
    Keywords: Fly ash, geopolymer, precast, steam curing
  • S. Greeshma, L. Annilet Sheeja, K.P. Jaya Page 617
    An analytical study has been made of the interaction between laterally loaded flanged shear wall and floor slabs in building with cross- shear wall. Particular attention has been paid to study the influence of Height of Shear Wall (H) and Effective width of the slab (We) on the performance of wall – slab joint in a multi-storey building with shear wall. To carry out the analytical investigations, the structure was modelled in a Finite Element software ANSYS (Version 10 [1]). The specimens were sorted into two groups (Type 1 and Type 2) based on the ratio of height of shear wall and the effective width of the slab (H/We). The joints are detailed as per the provisions given for beam – column joint in IS 13920 [2]. The models were subjected to displacement-controlled lateral cyclic loading applied at the slab end. The performance of the connections in terms of the Von Mises stress, load-displacement hysteretic behaviour, ultimate load and energy dissipation were compared. Type 2 model performed better when compared to Type 1 model in terms of strength and energy dissipation.
    Keywords: Effective width, wall–slab joint, cyclic load, detailing
  • P. Jayajothi, R. Kumutha, K. Vijai Page 631
    This paper presents the nonlinear Finite Element Analysis (FEA) that has been carried out to simulate the behaviour of failure modes of Reinforced Concrete (RC) beams strengthened in flexure and shear by Fibre Reinforced Polymer (FRP) laminates. Four beams were modelled in FEM software using ANSYS. In those four beams, two beams were control beams without FRP and other two beams were Carbon Fibre Reinforced Polymer (CFRP) strengthened beams. A quarter of the full beam was used for modelling by taking advantage of the symmetry of the beam, loading and boundary conditions. From the analyses the load deflection relationships until failure, and crack patterns were obtained and compared with the experimental results available in the Literatures. The load deflection plots obtained from numerical studies show good agreement with the experimental plots reported by Balamuralikrishnan & Antony Jeyasehar, and Amer M. Ibrahim & Mohammed Sh. Mahmood. There was a difference in behaviour between the RC beams strengthened with and without CFRP layers. The crack patterns obtained in FEA in the beams were also presented. The use of computer software to model these elements is much faster, and extremely cost-effective. Therefore, modelling of experimental beams can be adoptable in ANSYS. Validation of experimental results can also be done using ANSYS.
    Keywords: Fibre Reinforced Polymer, finite element Analysis, ANSYS, CFRP, modelling