Graphene and its derivatives have been studied as nanomaterials in many different fields owing to their various interesting properties. Many researchers have investigated the mechanical properties of different graphene cementitious composites, and the current study investigates the effect on the mechanical properties of cement mortar of adding graphene with and without the use of an ultrasonic homogeniser. To examine this effect, all other testing conditions and requirements such as mix design content, mixing procedure, curing time, specimen size and sonication parameters were maintained at the same levels across tests. Cement mortar specimens containing different percentages of graphene (0, 0.003, 0.006, 0.009, 0.012 and 0.03% by weight of cement) were experimentally tested after 7 and 28 days to determine the effect of graphene dosage on their quasi-static strengths. The results showed an obvious enhancement in both compressive and flexural strengths after adding each graphene dosage to the mix without sonication; the compressive strength was increased by 12% with a 0.006% dose of graphene and the flexural strength was increased by 27% at a 0.009% dose of graphene. On using the sonicator at the specified parameters, the compressive strength increased by 33% for the 0.006% dose of graphene, offering an increment of 20% in strength due to the sonication effect; however, there was no noticeable effect on the flexural strength.

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The primary aim of this study is to evaluate the overall ductility factor of ordinary moment steel frames with viscoelastic bracing system. Similar frames without viscoelastic bracing assessed and compared as well. Linear history analysis of two types with different number of stories and spans lengths is carried out using different earthquake records to determine the elements sizes for the pushover analysis. Pushover analysis has been performed after defining the elements sizes and assigning material nonlinearity to discrete hinge where plastic rotation occurs to beams and columns according to FEMA 356. Such analysis allows evaluating the ductility factor of each building of concern by using the yield and ultimate displacements obtained from the pushover curve. The results showed that the overall ductility factor decreases with increasing the number of stories for all buildings or when the bay length increased. Adding viscoelastic dampers increased the ductility factors for all buildings significantly.

Abstract. In this study a number of seismic behavior factors (overall ductility, response modification, and overstrength) of ordinary moment steel frames with viscoelastic bracing system were evaluated. These factors are not provided for ordinary moment steel frames with viscoelastic bracing system in building seismic codes such as the International Building Code (IBC) or Euro Code (EN). Moreover, similar frames without viscoelastic bracing were assessed and compared as well. A linear history analysis both two types with a different number of stories and span lengths was carried out using different earthquake records, which were selected to include variability in ground motion characteristics. Pushover analysis was then performed after defining the sizes of the elements and assigning material nonlinearity to the discrete hinge where plastic rotation occurs to beams and columns according to FEMA 356. Such analysis allows evaluating the overall ductility and the overstrength of each building of concern by using the yield and ultimate displacements and base shear forces obtained from the pushover curve. The results showed that overall ductility, overstrength, and response modification decreased with an increase of the number of stories for all buildings or when the bay length increased. Adding viscoelastic dampers increased the seismic behavior factors for all buildings significantly.