فهرست مطالب

Iranica Journal of Energy & Environment
Volume:4 Issue: 3, Summer 2013

  • Special Issue on Geo-hazards and Civil Engineering
  • تاریخ انتشار: 1392/05/21
  • تعداد عناوین: 20
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  • Yee Hooi Min, Choong Kok Keong Page 11
    Form-finding of tensioned fabric surface bordered by Möbius strip is investigated. Möbius strip is a surface with only one side and only one boundary component. Möbius strip has the mathematical property of being non-orientable. The form of Möbius strip has been adopted in the creation of sculpture, exploration of idea for bridges and buildings. In this study, the possibility of adopting the form of Möbius strip as surface shape for tensioned fabric structure has been studied. The combination of shape and internal forces for the purpose of stiffness and strength is an important feature of tensioned fabric surface. For this purpose, form-finding needs to be carried out. In this study, nonlinear analysis method is used for form finding analysis. The influence of non-orientable characteristic of Möbius strip on the modeling process using finite element procedures was investigated. Pattern of pre-stress in the resulting tensioned fabric surface is also studied. Form-finding has been found to converge for Möbius strip R/W 1.37 with initial assumed shape specified to follow the topology without opening which has been observed in experiment.
    Keywords: Form, finding Tensioned fabric structure Möbius strip Non, orientable Nonlinear analysis method
  • F. Nateghia., N. Parsaeifard Page 12
    Progressive collapse is a kind of failure in which the collapse of one or several load bearing elements is ended in partial or total collapse of structures. If earthquakes induce progressive collapse, seismic and gravity loads cause initial failure propagating to other parts of structures. Therefore, seismic progressive collapse can occur in structures regardless the number of stories. In this paper the behavior of a one story steel building is studied to investigate the effect of initial damaged column position on the seismic progressive collapse. In this regard the critical position of damaged column has been identified first and then, the effect of damaged column is studied. Accordingly, nonlinear dynamic analysis has been used to obtain the fragility curves of the structure and investigate its failure probability. A damage index has also been used to validate the results. Based on the results obtained in this research, the initial failure of a middle column can increase the failure probability of structures during earthquakes. Besides, among the evaluated design parameters, the failure probability is changed significantly in the columns in accordance with their axial loads.
    Keywords: Failure probability Fragility curve Nonlinear dynamic Progressive collapse
  • H.R. Tavakoli, M. Talebzadeh Amiri, G. Abdollahzade, A. Janalizade Page 13
    The risk of earthquake ground motion parameters in seismic design of structures and Vulnerability and risk assessment of these structures against earthquake damage are important. The damages caused by the earthquake engineering and seismology of the social and economic consequences are assessed. This paper determined seismic hazard analysis in Babol via deterministic and probabilistic methods. Deterministic and probabilistic methods seem to be practical tools for mutual control of results and to overcome the weakness of approach alone. In the deterministic approach, the strong-motion parameters are estimated for the maximum credible earthquake, assumed to occur at the closest possible distance from the site of interest, without considering the likelihood of its occurrence during a specified exposure period. On the other hand, the probabilistic approach integrates the effects of all earthquakes expected to occur at different locations during a specified life period, with the associated uncertainties and randomness taken into account. The calculated bedrock horizontal and vertical peak ground acceleration (PGA) for different years return period of the study area are presented.
    Keywords: Active fault, Seismic hazard assessment, Return period, Babol
  • M. Naghipour, G. Abdollahzadeh, M. Shokri Page 14
    In order to achieve the post buckling strength of BRB member, AISC seismic design provisions require that gusset plate axial capacity exceed ultimate compressive load of the BRB. The AISC code also requires that the gusset plate instability be considered because recent full scale tests demonstrated that out of plane buckling of a gusset plate occurs prior to BRB ultimate load. In this paper an analytical investigation is used to investigate inelastic compressive behavior and strength of gusset plates in BRBFs by finite element software considering plates of different dimensions. In order to verify analytical results one full scale tests was carried out on a simplified gusset plate connection. Also to increase gusset plate buckling strength and improve its energy absorption behavior, effects of adding free edge stiffeners at different sizes have been investigated and the results are presented. Finally, a design method accompanied by some design charts for rectangular type gusset plates subject to compression is proposed based on an inelastic plate buckling equation.
    Keywords: Buckling restrained brace Gusset plate Analytical investigation Plate buckling Gusset plate design
  • M. Hoseinzadeh, G.D. Najafpour, M.A. Beygi Page 15
    This paper focuses on addition of fillers in epoxy resin and aggregate for polymer concrete (PC) preparation. For the preparation of PC, two kinds of fillers, i.e. rice husk ash and broom stem ash were used. According to experimental results, addition of fillers had a positive impact on the physical and mechanical properties of the PC. In the PC sample with rice husk ash, with the filler/aggregate ratio of 0.075 and 18.4% polymer, maximum compressive strength of 86.41 Mpa was obtained; while the compressive strength of the polymer concrete without filler was 71.2 Mpa. The PC sample with broom stem ash, with the filler/aggregate ratio of 0.12 and 23% polymer showed the maximum flexural strength.
    Keywords: Aggregate Flexural strength Compressive strength Filler Polymer concrete Epoxy resin
  • Babak Mansouri Page 16
    The feasibility to develop a rapid urban seismic damage detection procedure utilizing satellite radar imagery is investigated. In direct observation of city-wide building loss, remote sensing damage detection techniques have shown merits in rapid damage detection in urban areas. Remote sensing technology has the capability of extracting buildings in urban scenes. Comparing “before” and “after” images and benefiting from image processing techniques, it is possible to detect the extent of high hit zones. In detecting post earthquake damages to buildings and in order to reduce detection errors and for minimizing the false alarms, it seems logical to apply the change detection algorithms only to the patches that correspond exactly to building footprints. For this purpose, urban database revealing the 3D reconstruction of the city is developed using parcels records. The parcels are extracted from aerial photos (stereography processing) then complemented and updated using VHR (very high resolution) optical satellite image (i.e. Quickbird imagery). The change detection algorithm and the calibration modeling are applied to “before” and “after” EnviSat SAR images considering only the building layer. The methodology is applied to the city of Bam and the associated building damages of its 2003 earthquake were emphasized. Results were compared with an independent direct visual damage interpretation using a VHR optical image.
    Keywords: Earthquake damage Remote sensing Satellite image VHR optical image Building damage
  • Bassam A. Tayeh, B.H. Abu Bakar, M.A. Megat Johari, S.M. Tayeh Page 17
    The deterioration of reinforced concrete structures is a major social problem. To minimize this problem and ensure effective structural management, the number and extent of repair interventions must be kept at the lowest probable level. Good bond is one of the main requirements for successful repair. The main aim of this study was to investigate the compressive stress-strain behaviour of the composite specimens consist of ordinary concrete (OC) substrate as old concrete and reactive powder concrete (RPC) as a retrofitting material, by using different types of OC substrate surface preparation methods. The results showed that the composite OC/RPC specimens were able to behave closely to individual OC, in the case of using OC substrate with surface prepared by sand blasted.
    Keywords: Reactive powder concrete Bond strength Repair material Substrate Compressive stress, strain
  • Lawend K. Askar, Bassam A. Tayeh, B.H. Abu Bakar Page 18
    Ultra-High Performance Fiber Concrete (UHPFC) is a new class of concrete. Because of its distinguished mechanical properties, UHPFC is considered as an ideal alternative material for use in developing new structural solutions. This paper discusses on influence of different curing conditions on mechanical properties of UHPFC. An experimental program was performed to study the mechanical properties of UHPFC which were cured under six different curing conditions. Test results indicated that steam and boil curing methods showed a promising performance particularly at early age of curing compared to other type of curing.
    Keywords: UHPFC Curing Compressive strength Flexure strength Steam curing
  • Mehdi Golestaneh, Ghasem Najafpour, Ghazaleh Amini, Morteza Beygi Page 19
    Polymer concrete (PC) with suitable mechanical and chemical properties was prepared. The properties of PCs are dependent upon the type of resins and filler materials. This research paper presents an assessment of the chemical resistance of polymer concretes in various chemical compositions. Epoxy resin was used to fabricate PC samples. The sample blocks were exposed to hostile environment in strong acidic and alkali conditions. The loss of compressive strength of the samples exposed to corrosive environment was insignificant. The strength of corrosive environment had significant effect on the chemical resistance of the fabricated PC samples. A desired blend of the optimized chemical composition of epoxy was used and tested in all corrosive environments. These samples were successfully passed all the designed testing conditions.
    Keywords: Chemical resistance Polymer concrete Filler Epoxy resin Corrosive environment
  • Gaddafi Ismaili, Badorul Hisham Abu Bakar, Alik Duju, Khairul Khuzaimah Abdul Rahim, Iskanda Openg Page 20
    Nowadays, the hardwood category which refers to heavy hardwood species no longer sustains to the market demand. The harvesting of this wood category takes longer period of time. Thus, several studies in timber engineering have been carried out to investigate the fast-growing indigenous species as the alternative to heavy hardwood categories. For this purpose, fast-growing indigenous species of Engkabang jantong were selected and also the test samples were prepared in small clear specimens. The British Standard, BS373.1957 method of testing small clear specimens of timber was adopted to evaluate the strength properties of the species. The strength properties determinations were referred to hardness, cleavage and shear parallel to grain. The results were represented into two different grain directions namely tangential and radial at two different conditions, i.e. green and air-dry condition. It was found that, hardness strength at tangential was higher than radial for both condition green and air-dry with 4.71and 8.86%, respectively. At cleavage strength, it was reported that tangential possessed higher strength values than the radial for both conditions green and air-dry with 23.06 and 27.22%, respectively. Shear strength at tangential was higher than radial for both conditions green and air-dry with 11.70 and 8.58%, respectively.
    Keywords: Hardness Cleavage Shear parallel to grain Radial Tangential Green Air, dry
  • Woo Yian Peen, Chua Yie Sue, Choong Kok Keong Page 171
    The Cholla cactus skeleton has been the inspiration source for this study, in our effort to search for light and more structural effective structures. This woody skeleton of Cholla with oval shaped perforations arranged in spiral pattern is found strong enough to support the cactus self weight. This research has been carried out to investigate the effects of percentage of perforations and perforations arrangements on structural behaviour of cylindrical hollow section. A total of eleven models consisting of one cylindrical hollow section without perforation as the control model and ten simplified perforated cylindrical hollow sections have been constructed using a finite element method software. The perforated models have been assigned with 10 to 50 percent of perforations area by fixing the number of perforations to twenty and altering the perforation size to achieve the percentage variable. Computational analyses have been carried out for three loading conditions: compressive, flexural and torsional. Findings have shown that the increment in percentage of perforations produces higher stresses to the cylindrical hollow section. This has effects on the structural capacity of the cylindrical hollow section. Array arrangement of the perforations shows better structural performance in compression and flexural loading conditions while spiral arrangement exhibits better structural performance under torsional loading condition.
    Keywords: Light, weight structure Biomimicry Sustainability Perforated hollow section Cholla skeleton
  • Javad Vaseghi Amiri, Mojtaba Naeej, Mohammad Reza Naeej Page 178
    Buckling-restrained braced frames (BRBFs) are used as primary lateral load resisting systems for buildings in high seismic areas. The main characteristics of buckling-restrained braces (BRBs) are enhanced energy dissipation potential, excellent ductility and nearly symmetrical hysteretic response in tension and compression. This paper presents an analytical study aimed to assess the feasibility of using BRBs as a retrofit scheme for existing steel frames. For that purpose, the seismic response of four two-dimensional frame models representative of typical steel frames was analyzed prior to and after including BRBs as a retrofit strategy. Comprehensive nonlinear static and time-history analysis were carried out for analyzing the frames. A set of seven code-compliant natural earthquake records was selected and employed to perform nonlinear time-history analysis. Frames were analyzed and designed based on 2800 Iranian Seismic Code. The evaluation was based on comparing seismic displacement demands such as target roof displacements, maximum displacements and inter-storey drifts. The results showed that the effectiveness of braced frames can vary significantly with ground motions, frame rises and retrofitting systems. It perceived that the seismic response of frames coincides well with the given design objectives.
    Keywords: Buckling, restrained brace Steel frames Retrofitting system Nonlinear static analysis Nonlinear dynamic analysis
  • Morteza Naghipour, Saleh Mohammad Ebrahimzadeh Sepasgozar Page 186

    Today Steel moment resistance connections are the most common type of connections that are widely used in steel structures and certainly play a significant role in retrofitting, reliability and economic benefits. It is used also for improvement of the quality and useful life cycle of buildings. Considering the motions importance and after the Northridge earthquake, the invention of RBS connection was a turning point in resistant steel moment connections. This research observes the seismic behavior of the RBS connection with reduced section of flange and a new AW- RBS with reduced section of web in a double section beams that are applicable in Iran. These observations are performed using ABQUS finite elements software. Many models are implemented under cycle loads and ductility. Energy absorption and plastic behavior in the reduced section were observed. Among the studied connections, AW- RBS with the least resistance and stiffness decrement had bearded 8% off the rotation of the story. These models have acceptable behavior in cyclic loads.

    Keywords: RBS connections, Accordion effect, Double beam, Plastic hinge, Hysteresis behavior
  • L. Kalani Sarokolayi, B. Navayi Neya, J. Vaseghi Amiri, H. R. Tavakoli Page 199
    In this work, rotational components of ground motion acceleration were defined according to improved method from the corresponding available translational components based on transversely isotropic elastic wave propagation in the soil. With such improvement, it becomes possible to consider frequency dependent wave velocities on rotational components of ground motion. For this purpose, three translational components of El Centro earthquake (24 January 1951) were adopted to generate their relative rotational components based on SV and SH wave incidence by Fast Fourier transform with 4096 discrete frequencies. The translational and computed rotational motions were then applied to the concrete elevatedwater storage tanks with different structural characteristics and water elevations. The finite element method is used for the nonlinear analysis of water storage tanks considering the fluid-structure interaction using Lagrangian- Lagrangian approach and the concrete material nonlinearities have been taken into account through William- Warnke model. The nonlinear response of these structures considering the six components of ground motion showed that the rotational components of ground motion can increase or decrease the maximum displacement and reaction force of the structure. These variations are depending on the frequency of structure and predominant frequencies of translational and rotational components of ground motion.
    Keywords: Elevated water storage tank Six correlated components Fluid, structure interaction Lagrangian approach
  • Gholamreza Abdollahzadeh, Seyed Mostafa Shabanian Page 208
    Behavioral study of connections using moment - rotation curve for analyzing different types of connections and also the concept of strength, ductility and rigidity of steel connections are important. One of the most common connections in bending frames of steel structures is beam to column connections with flange plates. A correct perception about structural behavior of beam to column connections and also appropriate knowledge of their force transmission and their behavior in modeling and analysis of the steel structures are essential. In present study, beam to column steel connection with flange plate under monotonic loading, both analytical and experimental would be investigated. The obtained results showed that moment - rotation curves of experimental sample and finite element (F.E.) model are reasonably close to each other. As a result, F.E. method could be an appropriate tool to investigate the behavior of these connections which would significantly decrease number of trial and error approaches.
    Keywords: Beam to column connection Moment, rotation curve Finite element meth
  • Farzad Jodeiri, A.R. Khalim Page 212
    Bracing elements and their connections have played a key role in the steel bracing frame energy dissipation through yielding and buckling. Whereas it is normally expected that gusset plates yield and buckle after that of bracing elements. Moreover, bracing elements buckling go with the plastic hinge formation in gusset plates. However, the geometry requirement to provide plastic hinge formation leads to larger and consequently thicker gusset plate. This article presents a research concerning steel bracing connection detail. In this proposed steel bracing connection, Hinge Plate manages the formation of the plastic hinge in the bracing connections. To verify the proposed idea a monotonic compression test was conducted on a bracing element; that was detailed with Hinge Plate. As a primary observational goal of the test, buckling mode of bracing element was depicted to be well managed by Hinge Plate. In addition, it was observed that the hierarchy of yielding in bracing element and then in Hinge Plate coincided with expected energy dissipation requirement in bracing frame.
    Keywords: Bracing connection Gusset plate Plastic hinge In, plane buckling
  • Fatimah Denan, Musniramustar, Adzhar Bin Hassan, Norbaya Omar Page 219
    Shear buckling occurred in the instability modes of steel beams when it slender. This paper develops a three-dimensional finite element model using LUSAS 14.3 to study on the effect ofthe triangularsteel beamweb profile (T WP) inshearbuckling behaviourof differentthicknesscompared RI to that of thenormalflatbeam (FW). All specimens are cantilever beam which are fixedat one ends. The flange is constant with variable web thickness. Eigenvalue buckling analysis was used in analysing the buckling load of the flat plate model and triangular web profile (TRIWP). Results showed that the web thickness gave a significant impact on the shear buckling of the TRIWP. In addition, the corrugation thickness of web was also effective in increasing the shear buckling capacity of the profile.
    Keywords: Triangular web profile Finite element analysis LUSAS Shear buckling Eigenvalue
  • Morteza Naghipour, Marzieh Nemati, Hossein Mohammadi, Doostdar, Reza Fooladvand Page 223
    Reinforcement and strengthening of reinforced concrete beams by unbounded external reinforcement is one of the methods of fortification used after loading and prior to failure of the beams. This method is used in different forms to strengthen members of reinforced concrete structures. To investigate the effect of fortification on cracked reinforced concrete beams, numbers of reinforced concrete beams were selected for testing. Strengthening was examined by attaching external reinforcing bars on both sides of the beams, at the level of internal flexural tensile reinforcement and by means of deflectors. The investigation was carried out through experimental data analysis and modeling using ANSYS finite element structural software. The results showed that the method of fortification used has increased the flexural capacity of the beams. It was also concluded that this method is suitable for strengthening of beams under their dead loads.
    Keywords: Strengthening External reinforcing bars Pre, loaded Reinforced concrete beams Nonlinear
  • Gholamreza Abdollahzadeh, Seyed Mostafa Shabanian Page 238
    Study destructive earthquakes which have occurred in recent year's shows that beam to column connection are the main component of force transmission and also play a vital role in stability of structure; such failure of these connections could lead to the destruction of structures. In current study, the behavior of beam to column steel connection with flange plate was studied by using component method. The correctness of results was examined by comparing the moment-rotation curve of beam to column connection with flange plate under monotonic loading which was obtained by component method and experimental method. Studying the result shows that moment-rotation curve which was obtained by component and by experiments method are reasonably close to each other. Therefore, it could be concluded that this component method is an appropriate tool for studying the behavior of this connections.
    Keywords: Beam to column connection Moment, rotation Component method Flange plate
  • Fatemeh Javidan, Mohammad Safarnejad, Sharif Shahbeyk Page 243
    Hollow concrete blocks are one of the widely used building elements of masonry structures in which they are normally loaded under combined action of shear and compression. Accordingly and due to their structural importance, the present study intends to numerically search for an optimum shape of such blocks. The optimality index is selected to be the ratio of block’s failure strength to its weight, a non dimensional parameter, which needs to be maximized. The nonlinear analysis has been done using a homemade code written based on the recently developed Lattice Discrete Particle Model (LDPM) for the meso-scale simulation of concrete. This numerical approach accounts for the different aspects of concrete’s complex behavior such as tensile fracturing, cohesive and frictional shearing and also its nonlinear compressive response. The model parameters were calibrated against previously reported experimental data. Various two-core configurations for the hollow blocks are examined, compared and discussed.
    Keywords: Hollow concrete block Strength Failure mechanism Lattice particle discrete method