Re-centering Capability of Inverted-Y Dual Eccentrically Braced Frame

Amir Gomaa,Ashraf Osman 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.4

Repair process of structures after a strong earthquake is often governed by the level of permanent deformation experienced by these structures during the shaking event. These phenomena drastically aff ect the repair cost in addition to the prolonged time needed to accomplish this complex process. In this research the feasibility of utilizing the Re-centering capability of a dual system consisting of steel special moment resisting frame ‘SMRF’ and Inverted-Y geometric confi guration eccentric braced frame ‘EBF’ to create an easy-repairable structure after a severe earthquake was examined. In this structural system a removable vertical shear link (i.e. using bolted connection) which is part of the EBF will act as a fuse to dissipate the earthquake input energy while the SMRF will act as a Re-centering system that will force the structure to return to its original position after removing the shear links by intentionally keeping it in the region of elastic behavior. The proposed system’s seismic performance was evaluated through performing series of pushover analyses under diff erent loading patterns, and time history analyses under the action of seven earthquakes. Furthermore, the design provisions provided in the American Code “ Seismic Provisions for Structural Steel Buildings ” ANSI/AISC 341-10 were verifi ed against the required response and extra recommendations for designing and detailing such structural system were introduced in order to achieve the required behavior. The performed study showed that during severe earthquakes the majority of the inelastic actions were localized within the shear links only while the SMRF behaved almost elastically with few exceptions. In addition, the study provided design and detailing recommendations to create an easy repairable structure after severe earthquakes.

Synthesis and Biological Evaluation of New Thiazolopyrimidines

Makarem Said,Khaled Abouzid,Ashraf Mouneer,Ali Ahmedy,Abdel Moneim Osman 대한약학회 2004 Archives of Pharmacal Research Vol.27 No.5

In this study, a series of 4-amino-5-cyano-3-substituted-2,3-dihydrothiazol-2-thiones (1a-c), as well as their triazolo and triazinopyrimidine derivatives such as 8-substituted-3-benzyl-5-methylthiazolo[ 5,4-e][1,2,4] triazolo[1,5-c]pyrimidin-2-thiones (4-6, 10) and 3-benzyl-5-methyl thiazolo[ 5,4-e]pyrimidino[3,4-b][1,2,4]triazin-2-thiones (7a-b) were prepared as potential antimicrobial and antitumor agents. Some of the tested compounds showed promising antimicrobial activity and non of them showed any appreciable antitumor activity.

Strengthening Steel CHS X-Joints Subject to Compression by Outer Ring stiffeners

Peter Gerges Melek,Sameh Gaawan,Ashraf Osman 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.4

This study investigates the behavior of strengthened CHS X-joints by adding symmetrically two distant outer ring stiff eners to the chord on each side of the brace outside the brace-chord welding zone. Compared to previously utilized strengthening techniques, this new technique has the advantage of being external, thus can be used for strengthening of already erected joints. Also, it avoids welding to previously aff ected zones resulting from welding brace to chord; and utilizing minimum radius to ring stiff ener keeping the aesthetic appearance of the structure unchanged. In this research, a parametric study is carried out to evaluate the impact of diff erent geometric parameters for the stiff eners such as their diameters, thicknesses and spacing on the effi ciency of such strengthening technique. The results provided guidelines for proper detailing of these stiff eners to signifi cantly increase the joints strength up to double the strength of the original unstiff ened joint.

The use of SMA wire dampers to enhance the seismic performance of two historical Islamic minarets

El-Attar, Adel,Saleh, Ahmed,El-Habbal, Islam,Zaghw, Abdel Hamid,Osman, Ashraf Techno-Press 2008 Smart Structures and Systems, An International Jou Vol.4 No.2

This paper represents the final results of a research program sponsored by the European Commission through project WIND-CHIME ($\underline{W}$ide Range Non-$\underline{IN}$trusive $\underline{D}$evices toward $\underline{C}$onservation of $\underline{HI}$storical Monuments in the $\underline{ME}$diterranean Area), in which the possibility of using advanced seismic protection technologies to preserve historical monuments in the Mediterranean area is investigated. In the current research, the dynamic characteristics of two outstanding Mamluk-Style minarets, which similar minarets were reported to experience extensive damage during Dahshur 1992 earthquake, are investigated. The first minaret is the Qusun minaret (1337 A.D, 736 Hijri Date (H.D)) located in El-Suyuti cemetery on the southern side of the Salah El-Din citadel. The minaret is currently separated from the surrounding building and is directly resting on the ground (no vaults underneath). The total height of the minaret is 40.28 meters with a base rectangular shaft of about 5.42 ${\times}$ 5.20 m. The second minaret is the southern minaret of Al-Sultaniya (1340 A.D, 739 H.D). It is located about 30.0 meters from Qusun minaret, and it is now standing alone but it seems that it used to be attached to a huge unidentified structure. The style of the minaret and its size attribute it to the first half of the fourteenth century. The minaret total height is 36.69 meters and has a 4.48 ${\times}$ 4.48 m rectangular base. Field investigations were conducted to obtain: (a) geometrical description of the minarets, (b) material properties of the minarets' stones, and (c) soil conditions at the minarets' location. Ambient vibration tests were performed to determine the modal parameters of the minarets such as natural frequencies and mode shapes. A $1/16^{th}$ scale model of Qusun minaret was constructed at Cairo University Concrete Research Laboratory and tested under free vibration with and without SMA wire dampers. The contribution of SMA wire dampers to the structural damping coefficient was evaluated under different vertical loads and vibration amplitudes. Experimental results were used along with the field investigation data to develop a realistic 3-D finite element model that can be used for seismic risk evaluation of the minarets. Examining the updated finite element models under different seismic excitations indicated the vulnerability of such structures to earthquakes with medium to high a/v ratio. The use of SMA wire dampers was found feasible for reducing the seismic risk for this type of structures.

The use of SMA wire dampers to enhance the seismic performance of two historical Islamic minarets

Adel El-Attar,Ahmed Saleh,Islam El-Habbal,Abdel Hamid Zaghw,Ashraf Osman 국제구조공학회 2008 Smart Structures and Systems, An International Jou Vol.4 No.2

This paper represents the final results of a research program sponsored by the European Commission through project WIND-CHIME (Wide Range Non-INtrusive Devices toward Conservation of HIstorical Monuments in the MEditerranean Area), in which the possibility of using advanced seismic protection technologies to preserve historical monuments in the Mediterranean area is investigated. In the current research, the dynamic characteristics of two outstanding Mamluk-Style minarets, which similar minarets were reported to experience extensive damage during Dahshur 1992 earthquake, are investigated. The first minaret is the Qusun minaret (1337 A.D, 736 Hijri Date (H.D)) located in El-Suyuti cemetery on the southern side of the Salah El-Din citadel. The minaret is currently separated from the surrounding building and is directly resting on the ground (no vaults underneath). The total height of the minaret is 40.28 meters with a base rectangular shaft of about 5.42 × 5.20 m. The second minaret is the southern minaret of Al-Sultaniya (1340 A.D, 739 H.D). It is located about 30.0 meters from Qusun minaret, and it is now standing alone but it seems that it used to be attached to a huge unidentified structure. The style of the minaret and its size attribute it to the first half of the fourteenth century. The minaret total height is 36.69 meters and has a 4.48 × 4.48 m rectangular base. Field investigations were conducted to obtain: (a) geometrical description of the minarets, (b) material properties of the minarets’ stones, and (c) soil conditions at the minarets’ location. Ambient vibration tests were performed to determine the modal parameters of the minarets such as natural frequencies and mode shapes. A 1/16th scale model of Qusun minaret was constructed at Cairo University Concrete Research Laboratory and tested under free vibration with and without SMA wire dampers. The contribution of SMA wire dampers to the structural damping coefficient was evaluated under different vertical loads and vibration amplitudes. Experimental results were used along with the field investigation data to develop a realistic 3-D finite element model that can be used for seismic risk evaluation of the minarets. Examining the updated finite element models under different seismic excitations indicated the vulnerability of such structures to earthquakes with medium to high a/v ratio. The use of SMA wire dampers was found feasible for reducing the seismic risk for this type of structures.