Iranica Journal of Energy and Environment (IJEE)

178 - 185

Authors: Javad Vaseghi Amiri, Mojtaba Naeej, Mohammad Reza Naeej

Buckling-restrained braced frames (BRBFs) are used as primary lateral load resisting systems forbuildings in high seismic areas. The main characteristics of buckling-restrained braces (BRBs) are enhancedenergy dissipation potential, excellent ductility and nearly symmetrical hysteretic response in tension andcompression. This paper presents an analytical study aimed to assess the feasibility of using BRBs as a retrofitscheme for existing steel frames. For that purpose, the seismic response of four two-dimensional frame modelsrepresentative 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 ofseven code-compliant natural earthquake records was selected and employed to perform nonlinear time-historyanalysis. Frames were analyzed and designed based on 2800 Iranian Seismic Code. The evaluation was basedon comparing seismic displacement demands such as target roof displacements, maximum displacements andinter-storey drifts. The results showed that the effectiveness of braced frames can vary significantly withground motions, frame rises and retrofitting systems. It perceived that the seismic response of frames coincideswell with the given design objectives.

199 - 207

Authors: L. Kalani Sarokolayi, B. Navayi Neya, J. Vaseghi Amiri, H. R. Tavakoli

Subjected to Six Correlated Ground Motion Components In this work, rotational components of ground motion acceleration were defined according toimproved method from the corresponding available translational components based on transversely isotropicelastic wave propagation in the soil. With such improvement, it becomes possible to consider frequencydependent wave velocities on rotational components of ground motion. For this purpose, three translationalcomponents of El Centro earthquake (24 January 1951) were adopted to generate their relative rotationalcomponents 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 elevated water storagetanks with different structural characteristics and water elevations. The finite element method is used for thenonlinear 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 motionshowed that the rotational components of ground motion can increase or decrease the maximum displacementand reaction force of the structure. These variations are depending on the frequency of structure andpredominant frequencies of translational and rotational components of ground motion.

212 - 218

Authors: Farzad Jodeiri, A.R. Khalim

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 ingusset 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.

223 - 237

Authors: Morteza Naghipour, Marzieh Nemati, Hossein Mohammadi-Doostdar, Reza Fooladvand

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.

243 - 250

Authors: Fatemeh Javidan, Mohammad Safarnejad, Sharif Shahbeyk

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.

258 - 264

Authors: F. Nateghi, N. Parsaeifard

Progressive collapse is a kind of failure in which the collapse of one or several load bearing elements are 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.

271 - 282

Authors: M. Naghipour, G. Abdollahzadeh, M. Shokri

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.

289 - 293

Authors: Babak Mansouri

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.

299 - 303

Authors: Lawend K. Askar,, Bassam A. Tayeh, B.H. Abu Bakar

Ultra-High Performance Fiber Concrete (UHPFC) is a new class of concrete. Because of itsdistinguished mechanical properties, UHPFC is considered as an ideal alternative material for use in developingnew structural solutions. This paper discusses on influence of different curing conditions on mechanicalproperties of UHPFC. An experimental program was performed to study the mechanical properties of UHPFCwhich 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.

311 - 315

Authors: Gaddafi Ismaili, Badorul Hisham Abu Bakar, Alik Duju, Khairul Khuzaimah Abdul Rahim, Iskanda Openg, Zurina Ismaili, Safarina Ismaili Nowadays, the hardwood cate

gory 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 4.71 and 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.