Shen J.,State University |
Rou W.,Sharma & Associates Inc. |
Akbas B.,Gebze Technical University |
Seker O.,State University |
Uckan E.,Istanbul University
Journal of Constructional Steel Research
Abstract Inherent resistance to collapse has been observed in steel buildings with non-ductile concentrically braced frames (CBFs) during past major earthquakes. Understanding of the fundamental characteristics of near-collapse behavior of such buildings will help reveal seismic performance of non-ductile steel structures in existing buildings across the US, and lead to an efficient seismic retrofit of those in seismic zones. This paper presents a seismic evaluation of typical steel buildings using non-ductile CBFs as lateral load resisting structures with focus on their near-collapse behavior, based on the incremental dynamic analysis. The buildings with non-ductile CBFs were found to be fully operational up to 0.5% story drift ratio response with or without gravity frames participating in lateral-load-resisting system. However, the life safety and collapse prevention of the buildings were significantly improved by actually participating lateral-load-resisting systems including CBFs, steel gravity frames and concrete slabs. Furthermore, the post-damage response of the building was more significantly influenced by gravity frames as the damages progressed from its first brace fracture to near collapse, and the participation of the gravity frames had much more impact on the near collapse behavior of a taller building than that of a low-rise building. © 2015 Elsevier Ltd. Source
Agency: Department of Transportation | Branch: | Program: SBIR | Phase: Phase II | Award Amount: 605.17K | Year: 2004
During Phase I of the project, Sharma & Associates, Inc. developed a concept for a high speed freight truck intended for 70-ton, regular freight and bi-modal operation at speeds up to 150 mph. The truck uses a rigid frame and an independent, compliant, primary suspension for its basic architecture. Constant contact side-bearings and yaw dampers were also added to improve dynamic performance. Vehicle dynamics simulations performed as part of Phase I indicate that the concept truck can travel at 150mph prior to the onset of lateral instability (hunting). The concept trucks also performed well in the other Chapter XI test regimes indicating track worthiness at lower speeds. The primary objective of Phase II of the project is to develop the truck concept into a detailed, practical and track-worthy design that can be prototyped and built for successful over-the-road or Chapter XI testing. A secondary objective is to produce prototypes of its key componenets for additional testing/evaluation. As part of this process, we will conduct additional vehicle dynamics analysis to ensure that the truck performs well under a wide range of scenarios including worn conditions. The most practical methods to achieve the desired suspension characteristics will be determined and the necessary details specified. It is expected that the concepts developed will provide the required safety and track worthiness required for high speed operation.
Agency: Department of Transportation | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 149.71K | Year: 2015
Autorack cars transport one of the most valuable commodities – fully assembled Automobiles. Due to the longer and higher profile of an Autorack and the fact that heavy automobiles are loaded on to high deck levels, freight trucks with improved track-to-vehicle dynamics as well as higher speed capabilities are desired in anticipation of higher speed passenger service and shared corridors. Unique track-to-vehicle dynamics as well as space requirements create a unique challenge in designing improved freight truck designs for Autorack cars. The higher speed freight truck (HST) developed under FRA sponsorship holds promise for such application. SA will research current state-of-the-art truck designs and compare vehicle dynamics performance of the most prevelant design with those of the HST. SA will then develop a concept for the next generation freight truck for Autorack cars such that it meets desired dynamics as well as necessary clearance requirements..
Agency: Department of Transportation | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 0.00 | Year: 2000
Agency: Department of Transportation | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 95.87K | Year: 1999
Not Available Austral Engineering and Software, Inc. proposes to develop a methodology and computer tool that uses experimental data to create high-fidelity models for unsteady aerodynamic loading. This approach addresses the need for advanced models that accurately represent loading responses of air vehicles under varied flight conditions. This is particularly important for cost-effective development of uninhabited air vehicles (UAVs) due to their increased agility and autonomy requirements. The Phase I theoretical development consists of two major elements. First is the development of a new indicial response formulation that appropriately reflects the interrelationships between aerodynamic loading and flow mechanisms. In particular, effects of vortex breakdown, critical state crossings, and control surface deflections will be addressed. For critical state crossings, a novel model scheduling approach will be developed. Second, advanced system identification techniques will be used to populate the components of the mathematical formulation. In Phase I, this approach will be validated using the developed software and experimental data to model the body-axis rolling moment of a 65-degree delta wing studied by researchers at AFRL. Military, industrial, academic, and research organizations will be contacted to establish channels for validation during planning and development. Responsive organizations will be the basis for technology transfer and commercialization in Phases II and III.