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

[摘要] Flat-slab buildings designed and detailed for gravity loads only typically do not havethe ability to resist moderate earthquakes without experiencing severe damage. Thedamage potential of such seismically deficient buildings therefore needs to beassessed and strategies developed to improve their seismic resistance. Punchingfailure at slab-column connections in non-ductile flat-slab buildings duringearthquakes can trigger progressive collapse of floor slabs. Based on the test resultsof a large number of interior and exterior connections, a methodology is developedto predict shear and unbalanced moment-transfer capacities of connections undercombined gravity and lateral loads. Furthermore, a frame analysis procedure isdeveloped based on the equivalent frame concept which targets both the moment-transfercapacity as well as stiffness of the interior and exterior slab-columnconnections. The approach employs a parametric hysteretic model and is based onthe effective slab-width concept. The proposed procedure for evaluating the seismiccapacity of flat-slab connections and frames is verified by comparing the calculatedand measured responses of two-bay flat-slab subassemblies tested under earthquake-typeloading. Seismic reliability against punching failure of slab-column connectionsin flat-slab buildings designed for gravity loads was investigated using the proposedequivalent frame approach. The reliability analysis indicated that the flat-slabbuildings constructed prior to the 1960's could experience significant damage during moderate intensity earthquakes. By limiting the gravity load on floor slabs and bycontrolling the lateral drift, the potential for punching failure in flat-slab buildingscan be minimized. The seismic resistance of older flat-slab buildings can beimproved by retrofitting interior connections to protect against progressive collapseand by utilizing infill walls to control lateral drift. An economical connection retrofitscheme is proposed and verified experimentally. The equivalent strut concept is usedto model masonry infills whose effectiveness in controlling the lateral drift isdemonstrated through theoretical analysis of typical flat-slab frames.

[发布机构] Rice University

[效力级别] engineering