Considering the changes in design codes, many structures built in recent decades do not meet the requirements of the new codes. Therefore, in order to maintain the performance of these structures, it is necessary to retrofitting them. FRP materials are one of the suitab More
Considering the changes in design codes, many structures built in recent decades do not meet the requirements of the new codes. Therefore, in order to maintain the performance of these structures, it is necessary to retrofitting them. FRP materials are one of the suitable materials for strengthening structures against vibration loads such as earthquakes. However, due to the high cost of FRP and the difficulty of execution in the strengthening of existing structures, it is very important to provide new efficient methods for the use of these materials. For this reason, in the present study, the use of FRP strips for stregthening of beam to column joints was investigated and its effect on joint behavior was studied. For this purpose, ten models were introduced, modeled and analyzed with ABAQUS software. The results showed that the use of horizontal and diagonal strips on the beams increased the joint strength up to 37%. The final displacement of the beam also increased up to 102%. The present study showed that the use of FRP stripes is an effective technique for improving RC joints
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Concrete- Filled Double Skin Steel Tubular (CFDST) columns are members of the Concrete- Filled Steel Tubular columns (CFST) family. In CFDST the steel skin and the existing concrete affect each other behavior so that the concrete prevents buckli More
Concrete- Filled Double Skin Steel Tubular (CFDST) columns are members of the Concrete- Filled Steel Tubular columns (CFST) family. In CFDST the steel skin and the existing concrete affect each other behavior so that the concrete prevents buckling of the inner and outer steel skins and the both steel skins under load result in the development of the confinement force and subsequently increase the ductility of the concrete and prevent the concrete from brittle damage. To ensure the accuracy of the finite element modeling, the experimental results were compared with the finite element and the accuracy of the modeling was verified. In this research, the section geometry, under monotonic and cyclic loading was investigated. The out-come results show that the CFDST columns have a good ductility, higher energy absorption capacity during an earthquake event and improved behavior under cyclic loading in comparison with CFST columns
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Abstract
An experimental investigation of the behavior of retrofitted FRP wrapped exterior beam-column joints under seismic conditions is presented. Also, the experimental study on exterior beam-column joint of a multistory reinforced concrete building under the seismi More
Abstract
An experimental investigation of the behavior of retrofitted FRP wrapped exterior beam-column joints under seismic conditions is presented. Also, the experimental study on exterior beam-column joint of a multistory reinforced concrete building under the seismic has been analyzed using ANSYS software. Two specimens were cast and tested to failure during the present investigation. One is control specimen test up to 70% of the ultimate load (without FRP), and another specimen test up to 70% of the ultimate load (with one layer of FRP).The results show that an increase about 18% has been obtained by retrofitting with FRP sheets in load carrying capacity. Also an increase about 54% has been obtained by retrofitting with FRP sheets in cumulative ductility.
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Nowadays, it is recommended to use non-stiffened steel plate shear wall. One of the innovations that can be applied to the steel plate shear wall is the use of corrugated sheets instead of flat sheets. Therefore, corrugated sheets are utilized to delay the occuranc More
Nowadays, it is recommended to use non-stiffened steel plate shear wall. One of the innovations that can be applied to the steel plate shear wall is the use of corrugated sheets instead of flat sheets. Therefore, corrugated sheets are utilized to delay the occurance of buckling. In this study, regarding to the importance of the subject, to ensure the accuracy of the modeling, a laboratory sample of Choi and Park was selected for verification and after ensuring the accuracy of the results, 8 samples of corrugated sheet steel plate shear wall were modelled by ABAQUS software. In these samples, parameters such as thickness of the steel sheet, the length-to-width ratio of the sheet (a/­b) and change in the geometric characteristics of the perimeterial elements are investigated. Numerical results presented that the stability of the hysteresis curve cycles in the specimen with a plate thickness of 8 mm was not constant, as observed in the final loading steps, loss of resistance and local buckling in the loading cycles. Numerically, it can be said that the sample with a sheet thickness of 8 mm has the highest bearing capacity compared to the samples with a sheet thickness of 4 and 6 mm. The effect of boundary elements on the performance of the specimens was negligible. Finally, it was revealed that with increasing the length of the sheet relative to its height, the amount of plasticity has significantly increased.
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Extensive studies carried out following the Northridge earthquake showed that several factors contributed to this failure. The high stress concentration in the welds and the attachment vulnerability to high ductility requirements were identified as tw More
Extensive studies carried out following the Northridge earthquake showed that several factors contributed to this failure. The high stress concentration in the welds and the attachment vulnerability to high ductility requirements were identified as two main causes of this rupture. A logical way to solve this problem is to reduce the need for a weld in the welded areas and to lower the concentration level of stress. Several corrective methods have been proposed for the construction after the Northridge earthquake as well as the retrofitting of existing reinforced steel structures. One of these methods is the configuration of the shotgun. In this research, after verifying the modeling results using Abacus software, 9 models of modeling of the beam with the dropped wing to the cross column were modeled in three groups. The results of this study are as follows: Reducing the length of the graft has the greatest effect of shear force on non-elastic performance. The shorter graft shear submission mechanism is better than the flexural bending mechanism of the long joints, and the main reason is that in shear joints, the shear forces are constant throughout the bond, so non-elastic strains will be uniformly distributed throughout the graft. Also in the specimen with a 0.6b interval, which has the weakest function, the initial failure (third cycle) of the resistance drop has begun. So that the amount of energy absorption is lower than other samples. The non-cross-sectional sample with energy absorption of 9272 kN / m is 0.75b and 0.6b, respectively, with 11.5% and 66.6% respectively, with energy absorption and greater depreciation than other samples. In the specimen with a bone geometry in the elementary cycles (third cycle), the resistance drop has begun. So that the amount of energy absorption is lower than other samples. The sample with a circular cross section with an energy absorption of 8875 kN / m is 18.6% and 1. 54%, respectively, with a geometric bone and oval geometry, with energy absorption and greater depreciation than other specimens.
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The growth of population and technology along with the costs of maintenance and repair of structures after the occurrence of natural disasters such as storms, floods and earthquakes have caused people to look for safer shelter than in the past. Dampers are used to impro More
The growth of population and technology along with the costs of maintenance and repair of structures after the occurrence of natural disasters such as storms, floods and earthquakes have caused people to look for safer shelter than in the past. Dampers are used to improve the cyclic behavior of structures against wind and earthquake loads. In this research, the experimental and numerical research results published in open access journals that considered the effect of the type and form of the damper on the performance of the structures, including the reduction of displacement and the reduction of foundation shear, are given. By applying cyclic load to the structure, usually the dampers have reduced the base shear and reduced the displacement of the structure. In the laboratory samples where only the damper itself has been tested, more attention has been paid to the performance of the damper. As a result of applying the earthquake record to the structure, the dampers have caused a decrease in a number of records and an increase in the base shear and displacement of the structure in some records, and at the same time, they have not shown a uniform performance for the base shear and displacement.
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