فهرست مطالب

Asian journal of civil engineering - Volume:17 Issue:2, 2015
  • Volume:17 Issue:2, 2015
  • تاریخ انتشار: 1394/06/13
  • تعداد عناوین: 9
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  • E. Alizade*, F. Jandaghi Alaee, S. Zabihi Pages 147-158
    In developing countries, usage of steel fiber-reinforced cementitious composites is widely expanding in structures, due to their high mechanical performance and flexibility. In this paper, the behavior of steel fiber-reinforced concrete exposed to corrosive environments has been investigated. Three test programs were conducted: one dealt with the effect of corrosion on steel fiber-reinforced mortar specimens, next considered the effects of using pre-corroded fiber in mortar specimens, and the other dealt with the effect of corrosion on the behavior and the failure modes of a single fiber pull-out test. Different exposure periods, types of solutions and the temperature of environment were taken into account.
    Keywords: Concrete durability, corrosion, steel fiber, reinforced concretes, flexural tests, pull, out test, hooked fiber
  • R. Kishore*, N. Zia Nasiry, A. Muslim Rujhan Pages 159-167
    This paper presents the result of an experimental study investigating the effect of external wrapping using Carbon fiber Reinforced Plastics (CFRP) laminates on load carrying capacity of reinforced concrete beams. The main variables considered in this work were the internal reinforcement ratio and position of the strengthening. The result of this work generally indicates that beams strengthened by CFRP laminates are structurally efficient and were upgraded to more load carrying capacity. The deficient beams showed more softening due to crack propagation, whereas the beams, when strengthened by the laminates lost partial ductility. The maximum two point loads in which the beam deficient in flexure failed was recorded as 120 kN, and this load for the beam deficient in flexure and strengthened by CFRP laminates got enhanced to 168 kN. The corresponding loads for beam deficient in shear was 115 kN, whereas this load for the beam deficient in shear and strengthened by CFRP laminates increased to 167 kN. It is encouraging to note that about 40% increase in load carrying capacity for the beams deficient in flexure and strengthened by CFRP laminates, and about 45% increase in load carrying capacity for the beams deficient in shear and strengthened by CFRP laminates is attained.
    Keywords: RC beam, FRP laminates, flexural strength, compressive strength, ductility, strengthening
  • A. Jahanmohammadi, M. Soltani* Pages 169-192
    Accurate evaluation of RC members under shear is achieved by consideration of both size-dependency and participating local mechanisms. Following the fundamental concept of the smeared crack approach, local-average stress field concept is presented considering the localized and size-dependent characteristics. Adopting a proposed slip-strain model, application of local strain/stress information in combination with the average response is available. Accordingly, effective size-dependent parameters are included in the evaluation process; and the average and discrete responses are computationally updated regardless of the size-dependency limitations. The abilities of the proposed concept are discussed for size-dependent parameters and validated for shear-critical members.
    Keywords: Smeared crack, local, average stress field, slip, strain relation, size effect, nonlinear finite element, shear, critical RC members
  • M. Mirrashid, M. Givehchi, M. Miri, R. Madandoust* Pages 213-223
    In this paper, the ability of Adaptive Neuro-Fuzzy Inference System (ANFIS) for the seismic moment prediction of the next earthquake has been investigated. To do so, two seismic indicators were used as inputs which were computed from the data related to the earthquakes recorded during last 63 years in a region which is located in southern Iran with 1° N latitude and 4° E longitude. The first indicator is the logarithm of the mean annual rate of exceedance for each record which is determined based on definition of Gutenberg-Richter law and the second indicator is time duration from the specified time origin. The output indicator is the logarithm of cumulative amount of seismic moment between the origin event and the future earthquake of each event. The test results with correlation factor 98% showed that ANFIS can be a useful tool for earthquake prediction.
    Keywords: Earthquake, moment magnitude, Gutenberg, Richter law, neuro, fuzzy system, ANFIS, magnitude prediction
  • A. Moshref, M. Tehranizadeh*, M. Khanmohammadi Pages 235-247
    The objective of this study is to evaluate the effects of earthquake damage on future seismic performance of reinforced concrete columns. Strength and stiffness modification factors are proposed to modify force-deformation behaviors of damaged columns. Permanent displacement is considered to determine the damage severity. A method is developed to calculate the collapse fragility function of damaged RC columns using permanent displacement. Comparing the fragility function of intact and damaged columns the strength modification factor is calculated for different amount of residual displacement. The stiffness modification factor is also estimated using the change of the fundamental period of a RC column after exciting by ground motions. Having the modified the force-deformation behaviors of damaged columns, the performance of the damaged structure can be evaluated using pushover analysis.
    Keywords: Modification factors, aftershocks, residual displacement, fragility functions
  • P. Manikandan*, S. Sukumar Pages 249-257
    In this paper, a study on experimental and numerical investigation of the flexural strength and behaviour of cold-formed steel built-up closed section with intermediate web stiffener is presented. Totally, nine built up beams with various cross section geometries are experimented under simply supported end condition with two point loading. The section geometries are chosen such that all types of buckling modes are met with. A finite element model is developed using ANSYS and verified with experimental results and found to be in good agreement. The material and geometric nonlinearities are included in the finite element model. The results indicate that flange width and depth of intermediate stiffener is significantly affecting the strength and buckling behaviour of the member. The experimental and finite element analysis results are compared with the strength predicted from the North American Iron and Steel Institute Specification for the cold-formed steel structure and suitable recommendations are made based on the results. The accuracy of the proposed design equation is established by comparison with an experimental results reported by other researchers.
    Keywords: Cold, formed steel, built, up box section, intermediate stiffener, flexural strength, design rules
  • A. Kaveh*, Sh. Hasana Pages 259-270
    In this paper, optimal design of tapered latticed columns under static loads is performed utilizing four algorithms comprised of Colliding Bodies Optimization, Enhanced Colliding Bodies Optimization, Particles Swarm Optimization and Democratic Particles Swarm Optimization. In this optimization the cost function is based on of the material used in nonprismatic latticed columns. For introducing the objective function, the eigenvalue equation for the column buckling in the plane, relationships for determining the basic stiffness matrix, and geometric stiffness matrix are utilized. In this study, some parameters are known as: applying buckling load and prevailing relation as mentioned before; and the remaining parameters are unknown consisting of desirable profile (from AISC manual) for chords and lacings, and the entire geometric shape of the tapered column. Finally, an example is optimized and the corresponding convergence curves are compared for four algorithms.
    Keywords: Colliding bodies optimization (CBO), enhanced colliding bodies optimization
  • R. Rajesh Kumar*, K. Shalini, J. Guru Jawahar, P. Jagadeesh, P. Rama Mohan Rao Pages 271-276
    The demand of natural aggregates is rapidly becoming high day by day in the construction industry. Various attempts are being made to find substitutes for natural aggregates. In India, about 70% of electricity is produced by combustion of good quality coal. In the process of coal washing, large quantities of impure coal are being rejected and causing disposal problems. These rejected impure coals are called as Coal Washery Rejects (CWR). To maintain the environmental sustainability, an attempt has been made in the present study to use new material CWR as partial replacement of coarse aggregate in concrete. This investigation studied the compressive strength of concrete containing CWR at different replacement levels (0% - 50%). The compressive strength values were compared to M 25 grade of conventional concrete (CC). From the results, it is observed that the increase in CWR replacement level decreased the compressive strength. This decrease was marginal at 20% and 30% replacement levels, but beyond 30%, the decrease was very much significant. Hence, it is revealed that 30% CWR replacement can be considered as optimum level in the construction industry.
    Keywords: Coarse aggregate, coal washery rejects, compressive strength, conventional concrete