Highly Damage Tolerant Slab-Column Frame Systems
Structural systems that combine reinforced concrete (RC) slab-column frames with moment resisting frames or shear walls find wide applications in zones of moderate and high seismicity. Due to combination of lateral displacements imposed during earthquakes with gravity loads, slab-column connections are prone to exhibit punching shear failures.
Traditionally, the required shear strength of slabcolumn connections is achieved by the use of drop panels or shear stud rails. The work outlined in this proposal is to develop a highly damage tolerant and smart slab-column frame system through the use of high-performance fiber reinforced cement composites (HPFRCCs) and wireless sensing technology. The development of new materials (HPFRCC) and smart structure technologies (computationally rich wireless sensors) have previously occurred in isolated research communities - this proposal is a first of its kind to explore their combination so that an intelligent HPFRCC structure capable of sustaining large drift demands and self-performance monitoring can be derived.
The revolutionary features of the NEES infrastructure offer exciting paths of exploration that will lead to a more profound investigation of intelligent HPFRCC slab-column systems. In order to develop the proposed frame system, a series of HPFRCC flat slab specimens will be first tested monotonically at the University of Michigan to optimize the HPFRCC material for this application. A total of six large-scale slab-column sub-assemblages will then be tested under simulated earthquake loading. Four of these sub-assemblages will be bi-directionally loaded using the NEES-MAST facility at the University of Minnesota. The MAST facility is ideally suited to this application as it can be used to load slab-column assemblages in a realistic manner to fully assess the shear capacity of HPFRCC connections. The results of these tests will be used to develop models to predict the seismic behavior of building systems employing these advanced materials and design provisions for the proposed slab-column connections.
To further enhance building safety, new technology in wireless sensors will be incorporated into the project to develop instruments that can self-detect and report structural damage due to seismic events. The high resolution cameras available at the NEES-MAST facility will enable the close correlation of the wireless measurements with the accumulated damage, aiding in the development of a damage index appropriate for this type of connection. An algorithm for the developed damage index will be embedded into smart wireless sensors to track the performance of the structural system, including selfidentification of damage. Construction operations design studies, through the use of discrete event simulation, will also be conducted to ensure the constructability of the proposed system. Intellectual Merit: The outcome of the proposed work will be a highly damage tolerant and smart slabcolumn frame system for use in seismic-resistant construction.
This innovative system integrates the latest developments in fiber cement-based materials and wireless sensing technology to deliver next-generation slab-column frames capable of 1) resisting extreme dynamic loads with outstanding damage tolerance, and 2) self-identifying structural damage. Hysteretic, damage, and design models, calibrated with results from large-scale multi-axial sub-assemblage tests, will be developed for the safe and optimum use of the proposed system. The experiments and associated models may ultimately lead to significant changes in the design and construction of slab column frames in areas of moderate and high seismicity. Additionally, smart wireless sensors, with the capability of self-detecting structural damage, will be developed. Broader Impacts: Society will benefit from the immediate self-identification of damage of structures, as building officials will be able to have access to the accumulated damage in a building immediately after a seismic event and will be able to make better informed decisions on the remaining life safety of the building. The use of the NEESgrid capabilities will allow an array of access to this research, from construction and design professionals to high school students. To encourage female and minority students to pursue graduate school careers in engineering, special activities are planned with the University of Michigan's Minorities in Engineering Program Office and the Women in Science and Engineering program such as including summer research activities for interested female or minority undergraduate students. The high-technology features of the NEES grid is a superb example of the power of interdisciplinary research and would motivate students to consider careers in Structural Engineering.
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