نشریه سازه و فولاد
سال دهم شماره 20 (پاییز و زمستان 1395)

Construction of welded moment resisting connection is common. These connections have high potential for brittle failure of welds if quality of welding is not controlled. In this research new bolted bracket connection similar to Kaiser bolted bracket connection is introduced. Kaiser connection has invention patent so construction society can’t utilize them without authority. Proposed connection of this paper can be manufactured by both casting and welding methods and can eliminate patent problems. In this evaluation connection performance, pretention force of bolts, height of bracket, number of bolts and length of bracket have been evaluated. In modeling of connection in order to accuracy of results between different connected area and bolts faces contact elements were created. The standard cyclic history was selected for loading of specimens. The results shows that proposed connection can be accepted by connection code for using in special moment resisting frames from both ductility and strength aspects. Findings are extended as hysteresis curves, released energy of connection, rupture index indicators and slip of bolts.

In the Seismic design of Structures, in order to energy damping applied to Structure, when an earthquake occurs, various solutions have been proposed that dampers are also in this category. Due to the relatively simple design and also more economical than other methods of energy dissipations, dampers have been more attention of researchers, In this study, in order to performance improvement of rotational inertia damper, friction and viscous mechanisms added to this type of damper. The experimental sample of rotational friction damper was made in the Urmia university earthquake laboratory and studied in a simple frame. The 8-story structure under Kobe and Tabas will be analyzed to study the effects of made hybrid damper compared with the rotational inertia damper. These intended dampers can be used with different type of braces that embedded in the structure such as Chevron and diameter. At the first in the model studied the 8-story symmetrical structure are modeled in Sap2000. Subsequently the resulting section is modeled in Abaqus2016 to study the effects of different dampers. Experimental laboratory result, is significantly improved Rotational inertia friction damper compared to other friction damper and the loss of their sudden brakes. Also the dynamic responses of structure indicate the reduction of maximum roof displacement and also the base shear of structure. Analytical results indicate that Rotational inertia viscous damper act quickly compared with Rotational inertia friction damper and dissipate the energy applied to structure. But finally Rotational inertia friction damper will behavior better than similar viscous damper.

Researchers have been long investigating modern constructional approaches to improve the efficiency and reliability of the constructs and decrease time, costs, and effort. One such modern constructional approach is the use of prefabricated modular construction forms. Broad sustainable building (BSB) is a modern prefabricate modular steel form with special connections. In this paper, we investigate the effects of the thickness of the connection plates, the use of stiffener with different dimensions, and the use of a pyramid-shaped section on the load-displacement curve under cyclic loading. We use the finite-element software "ABAQUS" to model theconnections. For verification of the obtained results from the software has been checked by comparing them with experimental models. The obtained results indicate that 50% increment in the thickness of the connection plates causes an increment of approximately 7.56%, 1.51% and 19% in yielding force, the displacement at the beginning of the yielding, and maximum bearable force by the connection respectively. The obtained results also demonstrate that the connection has a good ductility such that most of the samples can bear a rotation of 0.70 radian without a decrease in the bearable load or a failure in the connection.

According to modern seismic codes, entering the behavior of the structure to nonlinear zone, is essential. Obviously if the nonlinear behavior of the structure enter the nonlinear zone, failure of some structural elements is inevitable. Experiments have been shown that repair of elements is necessary for moderate to high earthquakes. Hence, using a structural system that is easy to repair in seismic regions is beneficial. Logically For the structures that are focusing any nonlinear deformation in specific elements and in addition residual drift is inconsiderable, maintenance is easy. For this purpose in this research the behavior of the self-centering eccentrically braced frame (SC-EBF) with fuses distributed in height which has the characteristic of the maintainability structures, has been studied. In the SC-EBF columns are not attached to ground and have the ability to uplift. Furthermore, SC-EBF placed inside a gravity frame and fuses between rocking and gravity columns have been placed. In the following, post tensioned cables for bringing the frame to zero station along rocking columns was placed. For investigation the seismic behavior of this system, nonlinear quasi-static and dynamic analysis have been used and different amount of cables and fuses have been compared. Results indicate that this system shows the flag-shaped behavior and byincreasing fuses resistance, energy dissipation increases. Furthermore, by increasing post-tensioned cables, ultimate capacity of the frame, increases. Nonlinear dynamic analysis shows the drifts in all stories is the same and inconsiderable residual displacement exists after the earthquake.

One of the most damaging effect of near fault earthquakes is Forward directivity effect which can be witnessed in two Iran’s most catastrophic earthquakes, destroyed Tabas and Bam cities. The same effect is predictable for Tehran metropolis which is surrounded by numerous faults. Regarding the general trend in seismic design codes to accommodate seismic performance concepts in their design methodologies and the lack of regulations considering near field earthquake effects, this study attempts to envelop these topics. A six story steel frame building is designed according to the Iranian Seismic Cod, 2800, and is subjected to near field ground motions by dynamic analyses. The performance of steel frame is categorized to Immediate Occupancy, Life Safety, Collapse Prevention and Destruction level based on FEMA356 performance parameters. Distribution of underlying soil conditions in Tehran and location of seismic faults had great influence on seismic performance of the typical building considered.

One of the main components of industrial complexes is steel ground tanks which their performance during and after an earthquake event is of great importance. In recent years, innovative low-damage technologies have been proposed by researchers to mitigate nonlinear damage in structural elements and also to decrease time and cost of repairs needed for post-earthquake serviceability of structures. One of these technologies is rocking mechanism which, as a method for limiting seismic demands, could be employed for seismic behavior improvement of tanks. In this paper, a cylindrical steel ground tank with low aspect ratio (D/H less than 0.75), was analyzed under horizontal earthquake excitation. The seismic response of tank in two different configurations; a) anchored or fixed to the base and b) unanchored with free rocking motion over base were calculated and compared. Fluid-structure interaction was considered by using lumped mass analogy and the OpenSees software was employed for modeling and analysis. Furthermore, the bottom plate of tanks was considered rigid and restrained against sliding. The calculated responses include response of fluid-structure interaction system, roof displacement, base shear force and overturning moment. The results demonstrated that a) base shear forces and overturning moments in unanchored tank is reduced by 9% to 26%, b) displacement response of tank roof and fluid impulsive mass is increased in unanchored tank, and c) the increase in displacement response of fluid convective mass in unanchored tank is less than 3% of that in anchored tank.

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.