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Henoch R.,Skidmore
Structures Congress 2017: Buildings and Special Structures - Selected Papers from the Structures Congress 2017 | Year: 2017

Post-tensioned (PT) flat-plate gravity framing systems are highly efficient and reduce embodied carbon when compared to conventional reinforced concrete framing systems. Efficiency is especially apparent in multi-span applications with regular orthogonal support arrangements. Even though PT flat-plate gravity framing systems are less efficient in single-span or irregular support applications, they are is still useful in reducing slab thickness, improving construction efficiency, and reducing seismic mass. A novel approach to determining PT tendon arrangements has been applied to several buildings informed by topology optimization results. Topology optimization is an optimization method which determines optimal load paths in a finite element continuum. Thus, by orienting PT tendons along the optimal load paths suggested by topology optimization, it has been shown that 25% or more of PT quantities can be reduced while maintaining the same mild steel reinforcement. Many of the observed arrangements do not follow traditional uniform/banded arrangements. Also, the deflection performance is significantly more consistent since tendons are resisting load in a manner consistent with the load demands. This can help alleviate common issues with thin flat-plate gravity systems such as irregular floor flatness due to warping incited by PT systems and inconsistent deflection at the exterior wall. This new design method has been applied to three buildings and coordinated with construction teams for efficient application. This presentation will discuss the entire design procedure from initial concepts through complete construction documents as applied to three buildings. This presentation will be of interest to academics and practicing structural engineers. © ASCE.


Sarkisian M.P.,Skidmore
Life-Cycle of Engineering Systems: Emphasis on Sustainable Civil Infrastructure - 5th International Symposium on Life-Cycle Engineering, IALCCE 2016 | Year: 2017

Optimization theory has informed futuristic approaches to the design of tall buildings. These approaches help to inform optimal use and placement of materials and unique architectural solutions. These methods are appropriate for bridges and buildings and can be particularly beneficial for the design of tall buildings. Designs are usually optimized to achieve maximum stiffness where structural volume is minimized. Considerations for gravity, wind, and seismicity are all included with the optimal geometry derived from the elastic use of materials. For significant seismicity, new system elements have been developed to dissipate energy and increase ductility creating a balance of stiffness and softness. The goal of this method of approach to design is to create more sustainable structures with extended life-cycles, to lessen the impact of carbon on the environment, and to create more resilient structures. Specific design and construction examples of major international projects that consider these techniques will be presented. These projects include the 330m-tall Shenzhen Citic Tower, the 25-story 111 South Main office building, Salt Lake City, UT, the LAX Airport pedestrian bridges, Los Angeles, the 45-story Transbay Block 9 residential tower, and the 30-story 350 Mission Tower, San Francisco among others. © 2017 Taylor & Francis Group, London.


Bozorgnia Y.,University of California at Berkeley | Hachem M.M.,Skidmore | Campbell K.W.,EQECAT Inc.
Earthquake Spectra | Year: 2010

This paper presents the process and fundamental results of a comprehensive ground motion prediction equation (GMPE, or "attenuation" relationship) developed for inelastic response spectra. We used over 3,100 horizontal ground motions recorded in 64 earthquakes with moment magnitudes ranging from 4.3-7.9 and rupture distances ranging from 0.1-199 km. For each record, we computed inelastic spectra for ductility ranging from one (elastic response) to eight. Our GMPE correlates inelastic spectral ordinates to earthquake magnitude, site-to-source distance, fault mechanism, local soil properties, and basin effects. The developed GMPE is used in both deterministic and probabilistic hazard analyses to directly generate inelastic - spectra. This is in contrast to developing "attenuation" relationships for elastic response spectra, carrying out a hazard analysis, and subsequently adopting approximate rules to derive inelastic response from elastic spectra. © 2010, Earthquake Engineering Research Institute.


Mazurek A.,Skidmore
Structural and Multidisciplinary Optimization | Year: 2012

In this paper, similarities between three-force and three-point non-smooth optimization problems are highlighted. Starting from geometrical rules controlling discrete optimum solutions for three-point problems a reasonable hypothesis is created for similar geometrical rules to control discrete optimum structures for three-force problems. The hypothesis is confirmed through a numerical approach. A step-by-step method to graphically obtain a discrete optimum structure for any set of three balanced forces is provided. It is shown that discrete optimum structures with large number of elements converge to the known continuum optimum solutions in the literature. © Springer-Verlag 2011.


Yin Y.-J.,Skidmore | Li Y.,Michigan Technological University
Engineering Structures | Year: 2011

In some areas, e.g., mountainous areas in the western United States, both seismic and snow loads are significant. Limited research has been conducted to investigate the seismic risk of light-frame wood construction in those areas considering the combined loads, particularly the snow accumulation. An object-oriented framework of the risk assessment for light-frame wood construction subjected to combined seismic and snow hazards is proposed in this paper. A typical one-story light-frame wood residential building is selected to demonstrate the proposed framework. Economic losses of the building due to the combined hazards are evaluated using the proposed framework. It is found that in areas with significant snow accumulation, the snow load has significant effects on the seismic risk assessment for light-frame wood construction. © 2010 Elsevier Ltd.


A tubular building enclosure system with thermally-broken glass modules having evacuated air spaces assembled in rows and/or columns to form a structurally self-supporting, thermally insulating, and solar energy collecting facade.


Patent
Skidmore | Date: 2012-08-09

A tidal barrier is provided that may be selectively deployed in response to tidal changes. The tidal barrier includes a net having a tensile, membrane with an upper edge and a lower edge. The lower edge has a plurality of anchor points for affixing the lower edge to a seabed below a body of water. The tidal barrier further includes a bladder affixed to the upper edge and having a valve for selectively inflating and deflating the bladder. The bladder has a sufficient volume to cause the upper edge of the membrane to rise to a surface of the body of water when the volume is inflated with a gas. A pump is disposed in proximity to the tensile membrane and is in fluid communication with the valve of the bladder. The pump has a controller for selectively prompting the pump to inflate and deflate the bladder with the gas.


A tubular building enclosure system with thermally-broken modules having evacuated air spaces assembled in rows and/or columns to form a structurally self-supporting, thermally insulating, and solar energy collecting facade.


A tubular building enclosure system for unitized assembly in rows and columns to form a structurally self-supporting, thermally insulating, and solar energy collecting facade.


Tort C.,Skidmore | Hajjar J.F.,Northeastern University
Journal of Structural Engineering | Year: 2010

A computational study was conducted to investigate the nonlinear response of composite frames consisting of rectangular concrete-filled steel tube (RCFT) beam-columns and steel framing subjected to static and dynamic loads. Following mixed finite-element principles, a three-dimensional fiber-based beam finite-element model was developed, allowing slip deformation between steel tube and the concrete core. Comprehensive material constitutive relations were developed for the steel tube and the concrete core through examining the experimental results in the literature. The uniaxial stress-based steel and concrete constitutive relations include modeling of the effects of confinement, steel tube local buckling, cycling concrete into both tension and compression, cyclic softening, and other key cyclic phenomena observed for steel and concrete in RCFT members. The finite-element model was verified against a wide range of experimental tests under monotonic, quasistatic cyclic, and pseudodynamic loading conditions. The mixed finite-element model produced strong correlations with experimental results to simulate the nonlinear response of RCFT members with excellent computational efficiency. © 2010 ASCE.

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