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Long-term tension-stiffening effects in beams and slabs were investigated by a comprehensive series of laboratory tests. Most tests used square prisms reinforced with a single, central bar loaded in pure tension but, in addition, a small number of slabs were tested to confirm the applicability of the tensile results to flexural situations. Three load levels and three concrete strengths were used and loads were sustained for periods of up to 4 months. Some specimens contained strain-gauged reinforcing bars to obtain very detailed data concerning reinforcement strain distributions. The results indicated that tension stiffening decayed much more rapidly than was previously thought, and that by 20 days, or sooner, after loading, it had reduced to its long-term value. The paper describes the test program in detail and discusses the important implications of the results on the current design rules for deflection control.

This paper proposes a modification to the ACI 318-02 equivalent frame method of analysis of reinforced concrete flat plate exterior panels. Two existing code methods were examined: ACI 318 and BS 8110. The derivation of the torsional stiffness of the edge strip as proposed by ACI 318 is examined and a more accurate estimate of this value is proposed, based on both theoretical analysis and experimental results. A series of 1/3-scale models of flat plate exterior panels have been tested. Unique experimental results were obtained by measuring strains in reinforcing bars at approximately 200 selected locations in the plate panel throughout the entire loading history. The measured strains were used to calculate curvature and, hence, bending moments; these were used along with moments in the columns to assess the accuracy of the equivalent frame methods. The proposed method leads to a more accurate prediction of the moments in the plate at the column front face, at the panel midspan, and in the edge column.

The application of a nonlinear finite element analysis package to the modeling of external beam-column connections is investigated. The behavior of the finite element model is compared with the results from 19 experimental tests. A parametric study was conducted to evaluate the effects of the main variables on both joint capacity and joint behavior. Details of the effects of column load on one of the connection details have been included. The study validates the suitability of both the software package and the applied modeling technique.

Laboratory tests on 17 reinforced concrete external beam-column connections are described-15 subjected to monotonic loading and two to simulated seismic loading. Parameters investigated were beam depth, beam tension steel percentage, reinforcement details for beam tension steel, and column load. Detailed measurements of strain distributions along both the beam and column bars were made using internally strain-gaged reinforcement, and results are presented to indicate influences exerted by the test parameters on reinforcement strain distributions. Bond stresses along the beam tension steel were evaluated and the means by which the reinforcement details effected load transfer by bond determined. Recommendations are made concerning the effectiveness and suitability of these details in practical connection design.