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Evaluation, Modeling, and Retrofit of Flat-Slab Buildings subjected to Seismic Loading

Flat-slab buildings designed and detailed for gravity loads only typically do not have
the ability to resist moderate earthquakes without experiencing severe damage. The
damage potential of such seismically deficient buildings therefore needs to be
assessed and strategies developed to improve their seismic resistance. Punching
failure at slab-column connections in non-ductile flat-slab buildings during
earthquakes can trigger progressive collapse of floor slabs. Based on the test results
of a large number of interior and exterior connections, a methodology is developed
to predict shear and unbalanced moment-transfer capacities of connections under
combined gravity and lateral loads. Furthermore, a frame analysis procedure is
developed based on the equivalent frame concept which targets both the moment-transfer
capacity as well as stiffness of the interior and exterior slab-column
connections. The approach employs a parametric hysteretic model and is based on
the effective slab-width concept. The proposed procedure for evaluating the seismic
capacity of flat-slab connections and frames is verified by comparing the calculated
and measured responses of two-bay flat-slab subassemblies tested under earthquake-type
loading. Seismic reliability against punching failure of slab-column connections
in flat-slab buildings designed for gravity loads was investigated using the proposed
equivalent frame approach. The reliability analysis indicated that the flat-slab
buildings constructed prior to the 1960's could experience significant damage during moderate intensity earthquakes. By limiting the gravity load on floor slabs and by
controlling the lateral drift, the potential for punching failure in flat-slab buildings
can be minimized. The seismic resistance of older flat-slab buildings can be
improved by retrofitting interior connections to protect against progressive collapse
and by utilizing infill walls to control lateral drift. An economical connection retrofit
scheme is proposed and verified experimentally. The equivalent strut concept is used
to model masonry infills whose effectiveness in controlling the lateral drift is
demonstrated through theoretical analysis of typical flat-slab frames.
Date January 1995
Source SetsRice University
Detected LanguageEnglish
TypeThesis, Text

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