Showing papers by "Charles R. Farrar published in 1989"
TL;DR: Experimental modal analysis techniques have been shown to be applicable to both laboratory test specimens and in situ test structures made of reinforced concrete as mentioned in this paper, which can provide engineers with techniques for assessing the as-built condition of a structure without introducing damage into the structure.
Abstract: Summary
Experimental modal analysis techniques have been shown to be applicable to both laboratory test specimens and in situ test structures made of reinforced concrete. These techniques, in general, apply only to linear structures; however, many concrete structures are designed to remain in the linear, uncracked response region during dynamic excitation (nuclear power plant structures, for example). Data from the experimental analyses agreed well with finite-element modal analysis results, and the numerical models were further refined based on the experimental results. Because of the relatively low excitation levels required, these methods provide engineers with techniques for assessing the as-built condition of a structure without introducing damage into the structure. If a concrete structure is damaged, the experimental modal analysis methods could possibly be used to monitor its deterioration.
Further investigations are needed to evaluate the sensitivity to damage of the experimentally determined modal properties. Also, methods must be found to determine, without prior modal data, if an in-situ structure is in a damaged state. These topics are being pursued by other researchers in the experimental modal analysis field.6
In its current form, experimental modal analysis methods can provide both practicing and research engineers with a valuable tool for verifying dynamic properties of reinforced concrete structures.
2 citations
01 Jan 1989
TL;DR: In this article, a new configuration of a reinforced concrete shear wall structure was designed and tested to investigate the analytical-experimental differences observed during the previous model testing, and the test structures are shown in Fig. 1.
Abstract: The Seismic Category I Structures Program is being carried out at the Los Alamos National Laboratory under sponsorship of the US Nuclear Regulatory Commission (NRC), Office of Nuclear Regulatory Research. In the class of structure being investigated, the primary lateral load-resisting structural element is the reinforced concrete shear wall. Previous results from microconcrete models indicated that these structures responded to seismic excitations with initial frequencies that were reduced by factors of 2 or more over those calculated based on an uncracked cross-section strength-of-materials approach. Furthermore, though the structures themselves were shown to have sufficient reserve margins, the equipment and piping are designed to response spectra that are based on uncracked cross-sectional member properties, and these spectra may not be inappropriate for actual building responses. The current phase of the program is aimed at verification of these conclusions using conventional concrete structures to demonstrate that previous microconcrete results can be scaled to prototype structures. A new configuration of a shear wall structure was designed and tested to investigate the analytical-experimental differences observed during the previous model testing. Shear wall height-to-length aspect ratios were to vary from 1 to 0.25. Percentage steel ratios were to vary from 0.25% to 0.6% by area,more » in both horizontal and vertical directions. The test structures are shown in Fig. 1. TRG-1 and -2 were constructed with microconcrete. TRG-3, -4, -5, and -6 were constructed with conventional (19-mm aggregate) concrete. 11 refs., 4 figs.« less
1 citations