Year

1990

Degree Name

Doctor of Philosophy

Department

Department of Civil and MIning Engineering

Abstract

Research on the punching shear strength, Vu, of slab-column connections of reinforced and prestressed concrete flat plates with spandrel beams has received considerable attention by the engineering profession in recent years. In the case of slabcolumn-spandrel connections of flat plates at the edge- and corner- positions there is still no reliable procedure for the determination of Vu. Thus the main objective of the present study is to develop an analytical method for the prediction of Vu for these types of connections. Needless to say, the development of a sound analytical method requires the test results from large-scale models with proper boundary conditions.

Tests up to failure were carried out on five cast-in-situ flat plate models, four with spandrel beams of different depths and steel ratios, and one without any spandrel. Representing two adjacent panels at the comer of a real structure these half- scale models were tested under simulated uniformly distributed loads. For ease of construction, instead of concrete columns, each flat plate model was supported on six prefabricated steel columns (with equivalent stiffnesses). The three reaction components at each of the hinged column supports were measured by means of specially designed load cells. Strain gauges were also attached to the reinforcing bars of the slab. The strains and other electrical signals were logged using a Hewlett Packard 3054A data acquisition control system via a Hewlett Packard 9826 computer.

In conjunction with the experimental work a theoretical study was carried out. This led to the development of a prediction procedure for the punching shear strength, Vu, of reinforced concrete flat plates with spandrel beams. Details of the theoretical work are presented herein. Applicable to the analysis of failures at the corner and edge-column positions, the proposed procedure takes in to consideration the following parameters:

(1) the overall geometry of the connection,

(2) the concrete strength,

(3) the size and location of flexural reinforcement of the slab,

(4) the slab restraint on the spandrel, and

(5) the enhanced strength of the slab-column connection due to membrane effects.

Based on the model test results from the present study and those obtained by other authors, a comparative study is carried out. The proposed analytical procedure is found to be superior to the alternative approach recommended in the new Australian Standard for Concrete Structures (AS 3600-1988). While the proposed procedure is more accurate and consistent in its prediction, the Australian Standard approach suffers, at times, the serious drawback of considerably overestimating the value ofVu, especially for failure at the comer-column positions.

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