Award Date

5-1-2014

Degree Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering

Department

Civil and Environmental Engineering

First Committee Member

Ying Tian

Second Committee Member

Samaan Ladkany

Third Committee Member

Moses Karakouzian

Fourth Committee Member

Aly Said

Fifth Committee Member

Zhiyong Wang

Number of Pages

205

Abstract

Catastrophic progressive collapse of a building can be triggered by a sudden loss of a load-bearing element in an abnormal loading event. There is a large inventory of reinforced concrete flat plate buildings designed in accordance with older codes. Without using shear and integrity reinforcement in slabs, these older flat plates are vulnerable to progressive collapse. The overall goal of this research is to numerically examine the resilience of older flat plate buildings against progressive collapse due to instantaneous removal of an exterior or interior column.

To achieve the research goal, a macro behavioral model of slab-column frame is created and applied to a prototype flat plate building designed following the ACI 318-71 code. The macro model employs both connector and shell elements. The shell elements are used to mainly simulate the flexural behavior of slab and the load redistribution over floor slabs. The connector elements are adopted to simulate bending moment, shear, and torsion transferred from slab to column, and to simulate connection punching shear failure. To ensure applicability of the proposed macro model, it is validated by 24 large-scale tests conducted on isolated slab-column connections under three different types of loading conditions.

Both dynamic and static analyses are conducted on the prototype building under service live loads. The nonlinear dynamic analyses indicate that, following the sudden removal of a column, punching failure will occur in the neighboring slab-column connections and the failure will immediately propagate over the slab floors, leading to a collapse of the building. The dynamic analyses also reveal that neglecting strain rate effects on materials would lead to considerably overestimated global and local deformation demands on slabs.

The nonlinear static analysis approach specified in the DoD progressive collapse design guideline is found inadequate in equivalently estimating the dynamic response of a flat plate system. The energy-based nonlinear static analysis procedure is therefore examined and proved to be an effective approach. To indirectly account for strain rate effects, parameters defining dynamic strengths of materials are suggested. To further examine the likelihood of progressive collapse, nonlinear dynamic and energy-based static analyses are applied to the prototype building under three gravity load levels and with varied properties of slabs.

Keywords

Building failures; Buildings, Reinforced concrete; Reinforced concrete; Structural failures

Disciplines

Civil Engineering

Language

English


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