Seismic assessment of RC core-wall building capable of three plastic hinges with outrigger

Abstract

In a core-wall structure with buckling restrained braces (BRB) outrigger, locations of the plastic hinges are influenced by the outrigger action. Therefore, the designer should consider the issue and use suitable details in the plastic hinge area. The essential questions that arise here are the plastic hinge location and the design moment demand used for design of this kind of structure. In this paper, responses of the core-wall buildings with BRB outrigger designed by using the traditional response spectrum analysis procedure are assessed by implementing the nonlinear time history analysis. The result demonstrates that the plasticity can extend over anywhere within the core-walls specially, at the base and above or below the outrigger levels. Formation of three plastic hinges in the core-wall is recognized suitable for the system. To control the plasticity extension in the core-wall, it is recommended that a new modal combination method be applied to calculate the moment strength of the three plastic hinges over the height. A capacity design concept is used to design other regions of the core-wall where the plasticity does not extend to. The proposed procedure improves behavior of the system by restricting the plasticity extension to the predefined plastic hinge regions. levels in the first case. Therefore, placement of the outrigger at 0.5H is not recommended according to the displacement demand. CAPACITY DESIGN APPROACHThe philosophy of capacity design in structural seismic engineering ensures that during an earthquake, the structure responds in a favorable ductile manner. This is achieved by pre-selecting an appropriate plastic mechanism and then providing special detailing to the plastic hinge regions. Providing enough ductility in these regions leads to energy dissipation under severe earthquakes (Park and Paulay, 1975;Paulay and Priestley, 1992). Capacity design approach can keep the large portion of the core-walls elastic and facilitate the detailing of the reinforcement there. The ease of detailing and reduction in Figure 11. Average of the (a) curvature ductility, (b) moment, (c) shear, (d) inter-story drift ratio and (e) lateral displacement envelop, in 40-story core-wall.

Distribution of strong earthquake input energy in tall buildings equipped with damped outriggers

“…The modelling of the core wall requires the definition of plastic regions, usually located at the base zone. However, related studies have pointed out the formation of plastic hinges in other places, such as at the middle height or at the regions adjacent to outriggers . However, by modelling some portions of the structure with elastic elements, the energy dissipation associated with yielding and cracking might not be captured.…”

Forward directivity near-fault and far-fault ground motion effects on the responses of tall reinforced concrete walls with buckling-restrained brace outriggers

“…Approximately, this happens all over the RC core-wall height subjected to both sets of FF and NF records; therefore, the mean moment demand envelopes of both sets of records are similar. It is worthy to mention that some FF data in this paper has been taken from Beiraghi and Siahpolo [53]. Figure 8 shows the mean shear demand envelope along the height of the buildings subjected to the NF and FF records.…”

Effect of damped outriggers arrangement on the seismic response of high-rise steel structures

“…To increase the damping of the outrigger system, other passive energy dissipators, such as Buckling-Restrained Brace (BRB), are also implemented [18][19][20][21]. This element limits the maximum force that the outrigger can develop [18].…”

“…This element limits the maximum force that the outrigger can develop [18]. It was observed that the location of the plastic hinges in the core wall was in uenced by the BRB outriggers [20]. Moreover, a response modi cation factor of 5 is recommended for the Reinforced Concrete (RC) core-wall with BRB [21].…”