Smart Energy Dissipation: Damped Outriggers for Tall Buildings under Strong Earthquakes

The use of outriggers in tall buildings is a common practice to reduce response under dynamic loading. Viscous dampers have been implemented between the outrigger and the perimeter columns, to reduce vibrations produced by strong winds. However, its behaviour under strong earthquakes has been not yet properly investigated. Strong earthquakes introduces larger amount of energy into the building’s structure, compared to moderate earthquakes or strong winds. In tall buildings, such seismic energy is dissipated by several mechanisms including bending deformation of the core, friction between structural and non-structural components, and eventually, damage. This research focuses on the capability of tall buildings equipped with damped outriggers to undergo large deformations without damage. In other words, when ground motion increases due to strong earthquakes, the dampers can be assumed to be the main source of energy dissipation whilst the host structure displays an elastic behaviour. These investigations are based on the assessment of both the energy demands due to large-earthquake induced motion and the energy capacity of the system, i.e. the energy capacity of the main components, namely core, outriggers, perimeter columns and dampers. The objective of this research is to determine if the energy dissipated by hysteresis can be fully replaced by energy dissipated through the action of passive dampers. The results show that the use of a set of outriggers equipped with oil viscous dampers increases the damping ratio of tall buildings in about 6-10%, depending on the loading conditions. As the ground motion becomes stronger, viscous dampers effectively reduce the potential of damage in the structure if compared to conventional outriggers. However, the use of dampers cannot entirely prevent damage under critical excitations. Combining a damped outrigger at 0.5 of the total building’s height (h), with a conventional outrigger at 0.7 h is more effective in reducing hysteretic energy ratios and economically viable if compared to a single damped outrigger solution.A+BE | Architecture and the Built Environment No 12 (2018)OLD Structural Desig

Teaching Structures with Models: Experiences from Chile and the Netherlands

This paper states the importance of using scaled models for the teaching of structures in the curricula of Architecture and Structural Engineering studies. Based on 10 years’ experience working with models for different purposes, with a variety of materials and constructions methods, the authors will address the advantages and possible approaches for a methodology of working with models.Architectural Engineering +TechnologyArchitecture and The Built Environmen

Performance Driven Design and Design Information Exchange: Establishing a computational design methodology for parametric and performance-driven design of structures via topology optimization for rough structurally informed design models

This paper presents a performance driven computational design methodology through introducing a case on parametric structural design. The paper describes the process of design technology development and frames a design methodology through which engineering, -in this case structural- aspects of architectural design could become more understandable, traceable and implementable by designers for dynamic and valid performance measurements and estimations. The research further embeds and customizes the process of topology optimization for specific design problems, in this case applied to the design of truss structures, for testing how the discretized results of Finite Elements Analysis in topology optimization can become the inputs for designing optimal trussed beams or cantilevers alternatives. The procedures of design information exchange between generative, simulative and evaluative modules for approaching the above mentioned engineering and design deliverables are developed and discussed in this paper.Architectural Engineering +TechnologyArchitecture and The Built Environmen

Distribution of large-earthquake input energy in viscous damped outrigger structures

This article provides an analytical framework to assess the distribution of seismic energy in outrigger structures equipped with viscous dampers. The principle of damped outriggers for seismic control applications lies on the assumption that the total earthquake energy will be absorbed by the dampers, as the rest of the structure remains elastic during the seismic event. Nevertheless, under large or severe earthquake-induced motion, some plastic hinges or failures may be produced in the structure before the dampers are able to dissipate the total input energy. Therefore, hysteretic behaviour of the host structure need to be evaluated along the dampers’ performance in order to determine how the earthquake input energy is distributed by all the components. In order to effectively assess the inter-dependency between structural properties of tall buildings equipped with damped outriggers and ground motion characteristics of large earthquakes in the control performance, a parametric study -considering building predominant period, position of the outrigger, damping coefficient, and stiffness ratio core/perimeter columns- on the nonlinear behaviour of two building models –fixed and with viscous damper - is examined under two large-earthquake records. The results show that the use of passive control –viscous dampers- gradually reduce the potential of damage in the building structure as they reduce both the input and the hysteretic energy demands, and thus eventually extending the capabilities of the damped outrigger to large-earthquake induced motion control.Accepted Author ManuscriptOLD Structural Desig

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

The seismic design of optimal damped outrigger structures relies on the assumption that most of the input energy will be absorbed by the dampers, whilst the rest of the structure remains elastic. When subjected to strong earthquakes, nevertheless, the building structure may exhibit plastic hinges before the dampers begin to work. In order to determine to which extent the use of viscously damped outriggers would avoid damage, both the host structure's hysteretic behaviour and the dampers' performance need to be evaluated in parallel. This article provides a parametric study on the factors that influence the distribution of seismic energy in tall buildings equipped with damped outriggers: First, the influence of outrigger's location, damping coefficients, and rigidity ratios core-to-outrigger and core-to-column in the seismic performance of a 60-story building with conventional and with damped outriggers is studied. In parallel, nonlinear behaviour of the outrigger with and without viscous dampers is examined under small, moderate, strong, and severe long-period earthquakes to assess the hysteretic energy distribution through the core and outriggers. The results show that, as the ground motion becomes stronger, viscous dampers effectively reduce the potential of damage in the structure if compared to conventional outriggers. However, the use of dampers cannot entirely prevent damage under critical excitations.Accepted Author ManuscriptOLD Structural Desig