In conventional seismic design codes of building structures severe structural damage due to large earthquakes is accepted, provided that the structure does not collapse, and life safety of the residents is guaranteed. The extent of this... more
In conventional seismic design codes of building structures severe structural damage due to large earthquakes is accepted, provided that the structure does not collapse, and life safety of the residents is guaranteed. The extent of this allowed damage can be so high that after earthquake, demolition and reconstruction of the building becomes inevitable, particularly in near-fault areas. The idea followed in this study is to relocate the damage to some predetermined fuse elements, other than the main structural members, so that the building could be quickly and easily repaired, even after major earthquakes. For this purpose, dividing the building’s structure into two inner and outer parts with different dynamic characteristics, and creating dynamic interaction between them by using yielding plate or hysteretic dampers was investigated. At first, a 5-storey building model was developed and divided into two interactive parts using hysteretic dampers at roof level, and it was tried, by ...
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ABSTRACT: This paper gives a brief explanation of the earthquake in Bam, casualties, as well as a report on rescue and relief operations, emergency shelters, temporary housing, and the country's plan for the reconstruction of the... more
ABSTRACT: This paper gives a brief explanation of the earthquake in Bam, casualties, as well as a report on rescue and relief operations, emergency shelters, temporary housing, and the country's plan for the reconstruction of the city, which includes, debris removal, rebuild- ...
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Abstract: The seismic vulnerability of an existing two span reinforced concrete slab bridge with round columns as piers was studied for its retrofit design. First, the bridge design was checked by American Association of State Highway and... more
Abstract: The seismic vulnerability of an existing two span reinforced concrete slab bridge with round columns as piers was studied for its retrofit design. First, the bridge design was checked by American Association of State Highway and Transportation Officials (AASHTO ...
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Abstract: The seismic vulnerability of an existing two span reinforced concrete slab bridge with round columns as piers was studied for its retrofit design. First, the bridge design was checked by American Association of State Highway and... more
Abstract: The seismic vulnerability of an existing two span reinforced concrete slab bridge with round columns as piers was studied for its retrofit design. First, the bridge design was checked by American Association of State Highway and Transportation Officials (AASHTO ...
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In dynamic analysis of structures subjected to earthquake excitations, particularly in nonlinear cases, the efficiency of the response calculation technique is of paramount importance. In this study the efficiency (computation speed and... more
In dynamic analysis of structures subjected to earthquake excitations, particularly in nonlinear cases, the efficiency of the response calculation technique is of paramount importance. In this study the efficiency (computation speed and precision) of Newmark beta method and, as the two mostly used techniques for time history analysis of structures, have been compared considering different values of nonlinearity tolerance and time step size. For this purpose a set of three 10-, 15-, and 20-story steel buildings having moment frames with X-bracing as their lateral load bearing system, have been considered subjected to 3-components accelerograms of both far- and near-filed selected earthquakes. Displacement and acceleration time histories of the buildings’ roofs, particularly their maximum values have been compared. As the achievement, in analysis of buildings structures nonlinear dynamic behaviors against earthquakes, the accuracy of responses obtained from Newmark average acceleration method can be considerably higher than that obtainable from the HHT method, and this can be independent from the nonlinearity tolerance, and even the parameter of the HHT method.
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The aim of this study is to evaluate the effect of thread density and weave design on the bending properties of fine-grained concrete beams reinforced with single layer carbon/polypropylene woven fabric. In this study, at first, fabrics... more
The aim of this study is to evaluate the effect of thread density and weave design on the bending properties of fine-grained concrete beams reinforced with single layer carbon/polypropylene woven fabric. In this study, at first, fabrics were woven with two types of design (plain and twill) and four different thread densities. Then, they were compounded into fine-grained concrete as a beam. After 4 weeks, the bending properties of all the samples were tested using four-point bending test method. The bending properties of these composite samples were evaluated using different parameters including the load at the elastic zone (limit of proportionality [LOP]) as well as the highest-peak point (modulus of rupture), toughness values, and toughness indices at the specific deflections. New parameters namely: toughness value and toughness index at the highest-peak point were also suggested in this study. The results showed that the bending load of concrete beams reinforced with plain fabric at the elastic region (LOP point) is identical to that of simple concrete beam whereas concrete beams reinforced with twill fabric exhibited lower value. Also, increasing thread density increased the bending load at the composite failure point while the effect of weave design was not significant. It is also indicated that the toughness properties of concrete composite beams have been improved with a denser carbon/polypropylene fabric particularly at higher bending deflections whereas the weave design did not show any significant effect and only influenced on toughness properties at small deflection values. The obtained results of this work suggest that concrete composite beams reinforced with carbon/polypropylene woven fabrics on average are 6.5–40.75 times tougher than simple concrete beams.
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Using seesaw structural system in buildings is a way for creating earthquake-resilient buildings, namely buildings which can be easily and quickly repaired with little cost, even after major earthq...
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The seismic design of the structures is carried out by technical regulations and codes in free-field conditions (regardless of underground cavities). With the availability of tunnels and the complex interaction between the tunnel and the... more
The seismic design of the structures is carried out by technical regulations and codes in free-field conditions (regardless of underground cavities). With the availability of tunnels and the complex interaction between the tunnel and the aboveground structures, which may be contemplated wrongly, it could be dangerous for over ground buildings and structures. Consequently, the examination of the underground tunnels and their impact on the land surface and adjacent buildings seismic response seems to be significant. The present research focuses on formation of the plastic hinges in steel structures due to underground cavities and the soil–tunnel–structure interaction of underground structures. First, an existing model was verified by finite element method and the results were compared with a sample specimen. Thus, several effective parameters were considered and studied such as soil type, multi-story structures (4, 8 and 12 stories) and dynamic load type. Then the models were evaluated under real earthquake records. As a result, the seismic response of the structures and plastic conditions of plastic hinge conditions were obtained. The results indicate that the underground cavities have affected the formation of plastic hinges in the structure. They increased the input energy to the structure and had an impact on the total behavior of the structures. Also, the high-rise structures were much more vulnerable to underground tunnels. Therefore, the structures which are located above the underground cavities should be retrofitted and rehabilitated.
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Regarding the previous earthquake damages in offshore structures, as vital structures in the oil and gas industries, it is important that their seismic design will be performed with very high reliability. Accepting the Nonlinear Time... more
Regarding the previous earthquake damages in offshore structures, as vital structures in the oil and gas industries, it is important that their seismic design will be performed with very high reliability. Accepting the Nonlinear Time History Analyses (NLTHA) as the most reliable ...
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In this study a modified entropy-based measure is presented for evaluating the serviceability level of water distribution networks in which the hydraulic uncertainties (flow rates in pipes) as well as the uncertainties due to mechanical... more
In this study a modified entropy-based measure is presented for evaluating the serviceability level of water distribution networks in which the hydraulic uncertainties (flow rates in pipes) as well as the uncertainties due to mechanical parameters (failure probabilities of links) are considered simultaneously. In the proposed entropy calculation method, the connectivity order of the network demand nodes is incorporated in the entropy calculations by defining a factor based on the ratio of the nodal demand to the total flow rates of all links of the network. The failure probability of the network links has been incorporated by using a penalty function based on their failure probability in any specified hazard scenario. Then, this penalty function is inserted satisfactorily in the existing hydraulic entropy function (defined by previous researchers) of the network. In this way, the effect of mechanical behavior of links is also taken into account in the hydraulic entropy function of the network, while keeping its simplicity and applicability. By calculating the entropy values of some sample networks, it has been shown that the proposed entropy-based index is an efficient tool to find the optimum hydraulic layout for designing a new system, or to make decision on the best mitigation plan for an existing network subjected to different natural and man-made hazards.