فهرست مطالب محمد قاسم وتر

The huge number of failures and collapsed structures in the 1994 Northridge earthquake is always referred to as a turning point in the design of moment-resisting connections because it influenced the design of this type of beam-to-column connections. The occurrence of brittle failures in the welding of the joints, which led to the rupture of the connection plate, beam or column flanges, was one of the major damages that occurred in this type of connection in the mentioned enormous ground motion. After the Northridge earthquake, the attitude of researchers about designing moment-resisting connections completely changed. Many researchers tried to propose novel methods and ideas to improve the performance of rigid beam-to-column connections. Some of these methods are focused on different areas of the connections such as preventing the creation of three-dimensional stresses at the location of beam-to-column connection, reducing the shear deformation of the panel zone of connections, and removing the double or continuing plates of them. Furthermore, the proper seismic performance of each method was assessed based on numerous experimental and analytical studies. One of the most applicable rigid connections that we can refer to in this case is the connection with Welded Flange Plates (WFP). This connection is designed in such a way that the plastic hinge occurs at the end of the connecting plates. This type of connection is often used with hollow box columns. In this connection, due to the creation of concentrated forces in the column, which are created in the alignment of the connection plates, the flange or the web of the column may be damaged. For this reason, connection plates are used inside the column (continuing plates), which are generally installed by going through multiple steps and making additional cuts in the column. On the other hand, the occurrence of significant shear forces in the panel zone of connection may cause damage to it and require the implementation of double plates. The implementation of these types of steel plates can also cause difficulties in implementing the whole connection. For this reason, finding a solution that makes the implementation of rigid connections with welded flange plates unnecessary from continuing plates or double plates can be an important solution to facilitate the implementation of such connections. Rigid connections such as connection with the side plate and connection with the diaphragm plate (external stiffener) are options that have provided modifications to remove the connection continuing and double plates. The side plates prevent three-dimensional stresses and assist in strengthening the panel zone of connection. On the other hand, by removing the connection plates and preventing the discontinuity of the column, the diaphragm plate makes the panel zone stiffer and improves its seismic performance. In this article, a novel idea for rigid connection is proposed, which is a combination of connection with side plate, connection with diaphragm plate and rigid connection with welded flange plates, prequalified in steel structures standard of Iran. The new method has been tried to use the advantages of three rigid connection methods (WFP, connection with side and diaphragm plate) in hollow square (box) columns. In other words, the main purpose of this study is to integrate the advantages of the three mentioned methods and help to improve the seismic performance of the rigid connection. To assess the seismic performance of this connection, its 3D model has been created in finite element software and then analyzed with a nonlinear method. To perform the analysis, the models are analyzed under dynamic loading and their results, including the distribution of plastic strains, the location of failures, and the moment-rotation and shear force-deformation diagrams of the connection panel zone are calculated and evaluated. To show the damage in the components of this steel connection, the Birth and Death method is used in the analysis.The results show that the proposed connection has significant advantages. In addition to removing the internal connection plates, this connection has significantly strengthened the panel zone of the connection, and by removing the direct connection of the beam to the column, it has reduced the deformation of the column flange and, as a result, eliminated the three-dimensional stresses at this location.

One of the ways to reduce damages caused by earthquakes is to concentrate the damage in predetermined members (fuses). By absorbing a major part of the earthquake force, these members minimize the damage to other members of the structure. In this article, the performance of the fuse element with simple replaceability in eccentrically braced frames is studied. The proposed fuse element consists of three steel sheets that connect the link beam to the out-of-link beam through a joint connection, in the form of tongue and pin. When the loads are repeatedly applied to the divergent frame, the fuse causes the concentration of force in the connecting beam with the occurrence of shearing action and thus dissipates the force of the earthquake. In this study, ETABS software was used for frame design and ABAQUS was used for finite element analysis. The results show that the damage was limited to the fuse section, and there was no damage to other components of the structure. Also, this system has shown similar hysteresis behavior in tension and pressure, and the coefficient of behavior of this system is higher than conventional diverging frames, which indicates better performance and malleability of this system. On the other hand, since the damage is concentrated on a relatively small element, and the connection of this member to the frame is through pins, after a large

Structural vibrations caused by earthquakes, wind or other factors can be controlled by various methods. The conceptual approach of structural control includes changes in member stiffness, structural mass and damping to deal with forces passively, semi-actively and actively. Until today, a number of these structural control methods have been successfully used and researchers are promoting methods to increase their applicability and scope by improving performance.In recent years, researches have significantly been focused on the development and expansion of structural control methods and equipment. Also, in the last three decades, many efforts have been made to transform the conceptual approaches of structural control into usable and practical technologies in structures. It has been clarified that the structural control is one of the important and key points in the design of new structures and a suitable solution for improving structures against wind and earthquake loads. However, until today, most of the existing programs and strategies have led to the use of passive mass dampers or isolation of vibrations from the base. Over the past years, various control equipment and algorithms have been proposed, each of which has its own advantages according to the required performance and the part used.Semi-active control systems are a separate and emerging example, similar to active control systems. In this control system, the required external energy is much less compared to the energy controlled by the structure. Basically, the semi-active control system does not introduce external energy into the structural system, so the output band of the structure's seismic response is guaranteed [1].The resistive force or energy dissipation is determined by the internal mechanism of the system members based on the feedback of external or internal sensors. Therefore, this system has combined the advantages of passive and active control systems. Studies have clearly shown that the use of semi-active control equipment and systems has been significantly better than passive control systems in reducing the seismic response of structures, and this system has the ability and potential of this has the ability to perform at the same level or even better than active control systems [2].In this study, the use of electromagnetic force in the friction damper has been considered and a controllable friction damper has been introduced. In this damper, electric current changes are used to change the force perpendicular to the sliding surfaces of the friction plates. In this method, by using powerful electric magnets that require little electrical energy and by controlling the intensity of the passing current, the function of the friction damper is controlled. For this purpose, taking into account the magnetic behavior of the material and using computer modeling, in addition to validating the analytical results, the behavior of this electromagnet was analyzed parametrically and the test results confirmed the proper behavior and controllability of this damper. To change the force perpendicular to the surface of the electromagnets, using electronic circuits, the current passing through them was changed from zero to 1.5 amps, and the maximum force produced by the damper reached about 1200 N. The electric power needed to create the maximum power capacity was measured to be 8.5 watts. Also, the response time of power generators to current changes was measured to be maximum 56 milliseconds to reach the maximum capacity and 68 milliseconds to reset the damper force. The results of this study showed that this type of power generator has the ability to be used in the direction of semi-active structural control. The analytical and experimental results of electromagnets showed that the maximum tension perpendicular to the surface that this type of power generator can create is around 10 kg/cm [22].

With attention to the importance of the three span continuous bridges and complexity of analyzing structures with multi degree of freedom, utilizing desirable numerical models to estimate the internal forces of this group of structures is highly effective. A new analyzing method is introduced in this study which can be used to the 3-span continuous bridges with constant section and heavy moment resistance in transverse direction. The defined pattern is based on employing sinusoidal shape function both the bridge’s deflection shape and its corresponding applied forces. This model is developed by assuming a simple beam on the elastic constraints and thereby its results can be earned by minimizing the created potential function of whole structure. Creating a desirable manual method in calculating the internal shear forces of columns in the three-span bridges is a good comparative idea over the complicated method proposed by Aashto needing 3-dimentinal modeling in related software. By considering 5 different state of an example sample and analyzing those, the obtained results of the suggested way proves its high precision and efficiency on controlling the calculations manually because of having the deference lesser than 10 percent related to the exact method.

One of the effective methods to improve dynamic response of steel structures is using adjunct elements among which metal yielding dampers are the most common. The working mechanism of these dampers in the lateral load-resisting structural system is related to the fact that development of inelastic strains in metallic dampers as the fuse elements results in dissipating the earthquake input energy imparted to the structure in a major seismic event. On the other hand, the aim of implementation of such damping devices is to substantially reduce the seismic demand in main structural systems, such as beams and columns, and hence, these members remains essentially elastic. One of the types of metallic yielding dampers is Added Damping and Stiffness (ADAS) metal damper that is a series of X-shaped steel sheets, which can be efficient in dissipating seismic energy but have shown apparent weakness due to the buckling resulted from development of axial forces in the dampers. The objective of the present paper is to investigate the characteristics of a Modified Added Damping and Stiffness (MADAS) damper to be used as a supplementary device to improve seismic performance of low- and mid-rise steel structures. In MADAS damper, X-shape plates are configured in a way that their displacement along vertical axis is quite free, and hence, no axial force is developed in such metallic dampers. In this paper, a numerical Finite Element (FE) model of MADAS damper was simulated in ABAQUS and used to compare the predicted numerical results to those of experimental results of the MADAS damper subjected to cyclic displacements. It should be noted that, the experimental cyclic tests have been conducted by previous researchers for MADAS dampers, and, have shown superior cyclic performance compared to conventional metallic dampers such as Triangular Added Damping and Stiffness (TADAS) dampers. In addition, three 4-, 5-, and 6-story buildings with steel moment-resisting frames have been studied, as the representative of the low- and mid-rise structures. For each building, two design alternatives, one for the case of conventional Steel Moment-Resisting Frame (MRF) and the other alternative is the one equipped with MADAS dampers, have been designed to be studied using numerical models. The structural members of the adopted buildings equipped with metallic MADAS dampers are designed according to ASCE/SEI 7-10 design code. The behavior of the numerical models has been investigated regarding seismic parameters including the Response Modification Factor, R, and Overstrength Factor, (Ω). The application of metallic dampers have shown to provide an increase of about (50%-80%) in the Response Modification Factor, R, and about (10%-20%) in the Overstrength Factor, (Ω). Pushover analyses for the numerical models have been conducted to obtain Base shear-Displacement curves. Based on the obtained pushover results, a maximum decrease of about 20% was noticed in the inter-story drifts of the numerical models in the Collapse Prevention (CP) performance level. In addition, to investigate the seismic performance of analysis cases, time-history analyses of the numerical models subjected to 1940 El-Centro, 1994 Northridge, and 1978 Tabas earthquakes have been conducted. The earthquake records have been scaled to Maximum Credible Earthquake (MCE) and Design Based Earthquake (DBE) intensity levels. Based on the obtained time-history results, a decrease of about (40%-50%) has been observed in the peak inter-story drift values due to the application of metallic MADAS dampers compared to that of moment-resisting steel frames. In addition, regarding the results of time-history analyses, the values of equivalent damping has been observed to be in the range of about (15%-20%) for the analysis cases. The obtained results indicate significant improvement in the seismic response of the structures equipped with MADAS dampers compared to the same buildings utilizing Steel Moment-Resisting Frames (MRFs) as their lateral-resistant structural system.

Nowadays, manufacturing of high strength concrete is not an arduous work due to progress of concrete technology. In executive projects, the construction of the concrete with a compressive strength of 60 to 70 MPa is efficient but expensive. Increasing the strength of concrete reduces its ductility and causes brittle behavior in concrete. Confinement of concrete with glass and carbon fiber can decrease the brittle behavior. In this study, the behavior of the concrete with a compressive strength of 60 MPa made with non-standard aggregates in most construction workshops enclosed with carbon fiber coatings was tested. The behavior of this type of concrete was studied using the analytical methods presented by the researchers in this field such as Atard and Ciyan. There is an appropriate adaptation between theoretical and experimental results. The obtained results indicated the high effect of carbon fiber coating on the rate of ductility and compressive strength of concrete. A high-strength, economic, and fully executive concrete with a compressive strength of over 100 MPa and perfect ductility was constructed by this method

Passive energy dampers are as an effective lateral load resistance systems comparison to other lateral load resistance systems. The metallic passive energy dampers are acceptable among other damper because of simplicity in putting up, availability of the equipment and materials. In other hand, these dampers had a good performance in laboratories and last earthquakes. However these dampers excel from other ones but it does not applicable for general buildings. Therefore, an innovative passive energy damper have introduced that the main featureof its performance is shear yielding of the proposed damper. It has a high simplicity in installation and good capability for repairing after strong earthquake. Numerical results showed that the proposed damper enhances the seismic parameters of the structures. The proposed damper increases ductility, capacity, stiffness, damping ratio. Also, in this article required equations for designing of the damper have been introduced.

Despite of the adequate performance of thin Steel Plate Shear Wall (SPSW) in last earthquakes and also during studies performed in the laboratories in all of the world, some problems and some defects such as lake of capability of commercial civil engineering software for modeling of the buckling and post buckling under lateral loading, lake of national Cod in this field of steel structures, have made an obstacle about its expanding in civil projects. Based on these mentioned problems, in this paper, a new and innovative model (method) is presented that the steel plate replaced with diagonal single brace member. This proposed method decrease analysis time due to decreased elements comparing with other presented methods. In other hand, the proposed method (model) provide a capability for static analysis and dynamic analysis of structures. Comparing the experimentally results with the proposed method shows a good convergence on stiffness and ultimate strength.

Signi cant di erences between speci cations of struc-tural damage occurrence for buildings subjected to near- eld and far- eld earthquakes have been observed inrecent years. According to recent experiences¡ therehas been extensive damage occurrence in structures sub- jected to near- eld earthquakes compared to far- eld ones. The adopted approach in existing design codes isthe consideration of coecients¡ to take into account the e ects of near- eld earthquakes in evaluating the design base shear of structures. The aim of the present paper is the development ofstructural design methods for more adequate simula- tion of near- eld earthquakes e ects in the structural design process in order to take into account an increase in the seismic demand of structural systems. In this method¡ the e ects of near- eld earthquakes are not lim- ited to only consideration of additional design base shear demands¡ but extra capacity¡ in addition to the ulti- mate strength of the structure is demanded also. In the present study¡ the proposed development of current Ira- nian seismic design provisions for estimating near-fault earthquake e ects in the structural design process ofbuildings is investigated. In this manner¡ some near- eld coecients are proposed for some of the near-faultareas of the country¡ based on the results of seismic haz- ard analysis. It should be noted that in this investi- gation¡ both deterministic and probabilistic approaches are followed in the seismic hazard assessment procedure and various attenuation relationships have been con- sidered with judgmental weighting factors and the ob- tained results have been combined in a logic tree. In addition¡ the proposed modi cations and corresponding results are compared with the current code-conforming seismic demands for two special cases; the Imam Reza holy shrine site and Ahwaz oil eld. The obtained re- sults lead to a signi cant increase in design base shear¡ especially for structures with low and medium natural periods in near-fault areas¡ when compared with corre- sponding structures located on far- eld sites.

O‌n‌e o‌f t‌h‌e m‌o‌s‌t i‌m‌p‌o‌r‌t‌a‌n‌t i‌s‌s‌u‌e‌s i‌n e‌a‌r‌t‌h‌q‌u‌a‌k‌e a‌n‌d s‌t‌r‌u‌c‌t‌u‌r‌a‌l e‌n‌g‌i‌n‌e‌e‌r‌i‌n‌g i‌s i‌n‌v‌e‌s‌t‌i‌g‌a‌t‌i‌o‌n o‌f s‌a‌f‌e‌t‌y m‌a‌r‌g‌i‌n‌s a‌g‌a‌i‌n‌s‌t t‌h‌e p‌o‌t‌e‌n‌t‌i‌a‌l f‌o‌r p‌r‌o‌g‌r‌e‌s‌s‌i‌v‌e c‌o‌l‌l‌a‌p‌s‌e. H‌e‌r‌e, t‌h‌e s‌p‌r‌e‌a‌d o‌f c‌o‌l‌l‌a‌p‌s‌e i‌s i‌n‌v‌e‌s‌t‌i‌g‌a‌t‌e‌d b‌y t‌r‌a‌c‌k‌i‌n‌g d‌o‌w‌n t‌h‌e l‌o‌c‌a‌t‌i‌o‌n a‌n‌d t‌y‌p‌e o‌f c‌o‌l‌l‌a‌p‌s‌e‌d b‌e‌a‌m a‌n‌d c‌o‌l‌u‌m‌n e‌l‌e‌m‌e‌n‌t‌s, f‌r‌o‌m t‌h‌e f‌i‌r‌s‌t e‌l‌e‌m‌e‌n‌t t‌o t‌h‌e e‌n‌t‌i‌r‌e s‌y‌m‌m‌e‌t‌r‌i‌c/a‌s‌y‌m‌m‌e‌t‌r‌i‌c b‌u‌i‌l‌d‌i‌n‌g, v‌i‌a c‌o‌m‌p‌a‌r‌i‌n‌g t‌h‌e r‌e‌s‌u‌l‌t‌s o‌b‌t‌a‌i‌n‌e‌d b‌y n‌o‌n‌l‌i‌n‌e‌a‌r t‌i‌m‌e h‌i‌s‌t‌o‌r‌y a‌n‌a‌l‌y‌s‌e‌s. D‌a‌m‌a‌g‌e c‌o‌n‌c‌e‌n‌t‌r‌a‌t‌e‌s l‌o‌c‌a‌l‌l‌y i‌n a‌s‌y‌m‌m‌e‌t‌r‌i‌c b‌u‌i‌l‌d‌i‌n‌g‌s, w‌h‌i‌c‌h i‌n‌t‌e‌n‌s‌i‌f‌i‌e‌s t‌h‌e p‌r‌o‌g‌r‌e‌s‌s‌i‌v‌e c‌o‌l‌l‌a‌p‌s‌e m‌e‌c‌h‌a‌n‌i‌s‌m. I‌n t‌h‌i‌s p‌a‌p‌e‌r, w‌e s‌t‌u‌d‌y 3 s‌t‌o‌r‌y r‌e‌i‌n‌f‌o‌r‌c‌e‌d c‌o‌n‌c‌r‌e‌t‌e o‌r‌d‌i‌n‌a‌r‌y m‌o‌m‌e‌n‌t r‌e‌s‌i‌s‌t‌i‌n‌g f‌r‌a‌m‌e b‌u‌i‌l‌d‌i‌n‌g‌s i‌n 3 d‌i‌m‌e‌n‌s‌i‌o‌n‌s, w‌i‌t‌h v‌a‌r‌i‌o‌u‌s l‌e‌v‌e‌l‌s o‌f 0\%, 5\%, 15\% a‌n‌d 25\%, o‌n‌e d‌i‌r‌e‌c‌t‌i‌o‌n‌a‌l m‌a‌s‌s e‌c‌c‌e‌n‌t‌r‌i‌c‌i‌t‌y i‌n t‌h‌e p‌r‌e‌s‌e‌n‌c‌e o‌f e‌a‌r‌t‌h‌q‌u‌a‌k‌e l‌o‌a‌d, w‌i‌t‌h r‌e‌s‌p‌e‌c‌t t‌o t‌h‌e b‌e‌h‌a‌v‌i‌o‌r o‌f s‌t‌o‌r‌y d‌r‌i‌f‌t‌s a‌n‌d t‌h‌e n‌u‌m‌b‌e‌r o‌f c‌o‌l‌l‌a‌p‌s‌e‌d h‌i‌n‌g‌e c‌r‌i‌t‌e‌r‌i‌a. R‌e‌s‌u‌l‌t‌s s‌h‌o‌w t‌h‌a‌t m‌a‌s‌s a‌s‌y‌m‌m‌e‌t‌r‌i‌c‌a‌l d‌i‌s‌t‌r‌i‌b‌u‌t‌i‌o‌n‌s r‌e‌s‌u‌l‌t i‌n f‌u‌r‌t‌h‌e‌r l‌o‌c‌a‌l d‌a‌m‌a‌g‌e, w‌h‌i‌c‌h, c‌o‌n‌s‌e‌q‌u‌e‌n‌t‌l‌y, l‌e‌a‌d‌s t‌o a l‌a‌r‌g‌e‌r p‌r‌o‌g‌r‌e‌s‌s‌i‌v‌e c‌o‌l‌l‌a‌p‌s‌e i‌n t‌h‌e t‌o‌r‌s‌i‌o‌n‌a‌l b‌u‌i‌l‌d‌i‌n‌g‌s. T‌h‌e‌r‌e‌f‌o‌r‌e, w‌h‌e‌n m‌a‌s‌s e‌c‌c‌e‌n‌t‌r‌i‌c‌i‌t‌y i‌n‌c‌r‌e‌a‌s‌e‌s, t‌h‌e p‌o‌t‌e‌n‌t‌i‌a‌l o‌f p‌r‌o‌g‌r‌e‌s‌s‌i‌v‌e c‌o‌l‌l‌a‌p‌s‌e i‌n‌c‌r‌e‌a‌s‌e‌s, i‌n b‌o‌t‌h s‌t‌i‌f‌f a‌n‌d f‌l‌e‌x‌i‌b‌l‌e e‌d‌g‌e‌s, t‌o‌o. B‌y i‌n‌c‌r‌e‌a‌s‌i‌n‌g m‌a‌s‌s e‌c‌c‌e‌n‌t‌r‌i‌c‌i‌t‌y, t‌h‌e p‌e‌r‌c‌e‌n‌t‌a‌g‌e o‌f i‌n‌c‌r‌e‌m‌e‌n‌t‌s i‌n t‌h‌e n‌u‌m‌b‌e‌r o‌f c‌o‌l‌l‌a‌p‌s‌e‌d h‌i‌n‌g‌e‌s i‌n t‌h‌e e‌n‌t‌i‌r‌e b‌u‌i‌l‌d‌i‌n‌g a‌r‌e s‌i‌m‌i‌l‌a‌r t‌o t‌h‌e p‌e‌r‌c‌e‌n‌t‌a‌g‌e o‌f i‌n‌c‌r‌e‌m‌e‌n‌t‌s i‌n t‌h‌e s‌t‌o‌r‌y d‌r‌i‌f‌t‌s o‌f t‌h‌e m‌a‌s‌s c‌e‌n‌t‌e‌r‌s. T‌h‌e‌s‌e p‌e‌r‌c‌e‌n‌t‌a‌g‌e‌s a‌r‌e l‌e‌s‌s t‌h‌a‌n t‌h‌o‌s‌e i‌n t‌h‌e s‌t‌o‌r‌y d‌r‌i‌f‌t‌s o‌f t‌h‌e s‌t‌i‌f‌f a‌n‌d f‌l‌e‌x‌i‌b‌l‌e e‌d‌g‌e‌s. T‌h‌e b‌e‌h‌a‌v‌i‌o‌r o‌f t‌h‌e s‌t‌o‌r‌y d‌r‌i‌f‌t‌s i‌n t‌h‌e s‌t‌i‌f‌f e‌d‌g‌e i‌s a‌l‌s‌o s‌i‌m‌i‌l‌a‌r t‌o t‌h‌a‌t o‌f t‌h‌e m‌a‌s‌s c‌e‌n‌t‌e‌r‌s. H‌o‌w‌e‌v‌e‌r, t‌h‌e v‌a‌l‌u‌e o‌f s‌t‌o‌r‌y d‌r‌i‌f‌t‌s i‌n t‌h‌e m‌a‌s‌s c‌e‌n‌t‌e‌r‌s i‌s l‌e‌s‌s t‌h‌a‌n t‌h‌a‌t i‌n t‌h‌e s‌t‌i‌f‌f a‌n‌d f‌l‌e‌x‌i‌b‌l‌e e‌d‌g‌e‌s. O‌u‌r r‌e‌s‌u‌l‌t‌s d‌e‌m‌o‌n‌s‌t‌r‌a‌t‌e t‌h‌a‌t, a‌s a‌n a‌l‌t‌e‌r‌n‌a‌t‌i‌v‌e t‌o a m‌u‌c‌h d‌i‌f‌f‌i‌c‌u‌l‌t-t‌o-c‌a‌l‌c‌u‌l‌a‌t‌e l‌o‌c‌a‌l r‌e‌s‌p‌o‌n‌s‌e p‌a‌r‌a‌m‌e‌t‌e‌r o‌f t‌h‌e ``n‌u‌m‌b‌e‌r o‌f c‌o‌l‌l‌a‌p‌s‌e‌d h‌i‌n‌g‌e‌s'', t‌h‌e ``s‌t‌o‌r‌y d‌r‌i‌f‌t'', a‌s a g‌l‌o‌b‌a‌l r‌e‌s‌p‌o‌n‌s‌e p‌a‌r‌a‌m‌e‌t‌e‌r, m‌e‌a‌s‌u‌r‌e‌s t‌h‌e p‌o‌t‌e‌n‌t‌i‌a‌l o‌f p‌r‌o‌g‌r‌e‌s‌s‌i‌v‌e c‌o‌l‌l‌a‌p‌s‌e m‌o‌r‌e e‌a‌s‌i‌l‌y a‌n‌d c‌o‌m‌f‌o‌r‌t‌a‌b‌l‌y.

This paper presents an experimental study about applicability of Buckling-restrained braces (BRBs) by polyethylene sheets. Buckling-restraining unit (encasing member), whose function is to prevent the brace from buckling, is almost tube that is filled by concrete or mortar and has many problems and difficulties as concreting, shuttering, curing, reinforcing, transporting and wasting of time. This research shows that polyethylene can be used as Buckling-restraining unit instead of steel tube and concrete or mortar. And also they can be used as a reducer of compressive forces at steel braces for strengthening the existing building. The advantages of this innovative and new method are save the time, light weighting, economic, easy and quick installation, decreasing the construction problems, no need to shuttering and curing.

Ease and low cost implementation Hmmhvr Mharbndhay cause large applications They are steel structures. In rder to investigate the benefits motive Increase in ductility over the past two decades. One of the ways to increase They use ductile ductile element is in Mharbndhay Hmmhvr. This article energy absorption and ductility as a ring of steel Ductile element analysis and review laboratory is located. Steel ring Two pages can be easily and welding steel in a variety Mharbndhay Hmmhvr be embedded. Steel ring load function length, radius, thickness And the yield tress, and this design makes it appropriate to provide capacity Mharbnd Will. The results of this study suggests a very good ductility and energy absorption Steel ring and the support of a new idea on how to use this article Is the ring of steel.

This paper is an experimental study on the behavior of vertical shear link in the normal (steel section with and without stiffener) and composite (steel section with concrete is located the area limited to web and flanges of the section) configurations. There have been four specimens selected for examining the effects of different details. The first specimen was an I section with no stiffener, while the second specimen composed of I section with stiffeners designed according to AISC 2005. Third and fourth specimens were composed of I section with reinforced concrete located at the area between its flanges and web..The tests carried out were of quasi-static kind and conducted on a full scale. The comments on composite links are at first, explained in details and construction method, loading and test are then expressed. The details rendered for composite vertical link have been in such a way that the results obtained show remarkable increase in its shear capacity and ductility.

Braced frames are popular a type of steel frames in Iran. In these structures different kind of braced are used to resist lateral loads and all connections are considered as fix-type connections. In practice great care is taken, but it is not possible to construct fully fix-type connections and they are partially fixed, however, to be on the safe-side this fixity is neglected.In this research, experimental behavior of the braced frame connection with scale of 0.5 under cyclic load has been investigated. This study has been performed under the same loading condition using three tests: 1- bare frame made of beam and columns; 2- frame with gusset plates; 3- x-braced frame (braced made of two U sections). Results show that connection in these type of frames, although neglected in calculations, have some fixity and with use of gusset plates this fixity becomes much more.

Braces are used as effective seismic elements in seismic regions. They are widely used in low to high-rise buildings. However under an earthquake loading, Conventional braces are directed to the buckling rapidly. Repeated buckling and yielding of the braces cause a stiffness and strength degradation which may reduce the overall frame stability. To solve the above problem, a number of studies have been introduced on the use of new Ductile brace using in Concentrically Braced Frames (DCBF), in which buckling has been restrained. This new brace is yielded in tension as well as in compression in which dissipate seismic energy in both direction of loading. This paper describes the main characteristics of the inelastic seismic response of the such Ductile Braces (DCB).In order to study the seismic behavior of the new developed DCBs with the new proposed cover and encasing material achieving a series of new effective and economical DCB, several large-scale braces have been tested. In this study, first the new four types of DCBs that have been developed at IIEES are introduced, designed and tested, then the hysteretic characteristics and energy dissipation of the DCBs under cyclic loading are investigated.

In this paper a new type of earthquake energy dissipation element has been introduced. The element is supposed to be used as a supplementary element in concentrically braced frames to improve the ductility of the whole system. Such elements usually yields before critically (instability) load of the braced systems. Using this approach, during a strong earthquake cause only this element yields and other frame elements (beams, columns, braces, connections) should be remain in the elastic range of behaviors. The current studies have theoretically and experimentally investigated the application of this special link element.The importance of such mechanism is the ability of this device in dissipation of the input earthquake energy by using torsional behaviors.This member could be used as a fuse element in seismic design and rehabilitation of the concentrically braced frames