Moment Restraint and Second- Order Analysis of a Cantilevered Precast Column Supported by an Isolated Footing

摘要

style="text-align: left;">This paper presents criteria for determining the base rotational spring restraint and the second-order analysis of a cantilevered precast concrete column supported by an isolated reinforced concrete footing  and its anchorages bearing on elastic soil or on piling. The column-base-footing system is analyzed, as well as the relative importance of its two interfaces: the column base plate to footing and     the footing to soil. This issue is of major importance in the analysis and design of framed structures and in the determination of their deflections, stability, and second-order effects. This paper extends the  procedure presented in Sections 3.8.2 through 3.8.4 of the PCI Design Handbook, Fifth Edition, and provides a practical tool for calculating the degree of fixity at the base of precast and monolithic columns on isolated footings bearing directly on soil or supported by piling. The steps for calculating the total overturning moment, overall stability, and stresses in the different materials and supporting  soil, in accordance with the AC! Building Code (AC! 318-99), are presented. The proposed model is limited to rigid footings and short-term behavior. Further research is ongoing to determine the effects  of secondary settlements in the soil, creep and shrinkage of the concrete, bond slippage in the anchor bolts, and other factors. >References style="text-align: left;">1. ACI Committee 318, a€?Building Code Requirements for Structural Concrete (ACI 3 18-99),a€? American Concrete Institute, Farmington Hills, MI. 1999. style="text-align: left;">2. AISC, Manual of Steel Construction: Load & Resistance Factor Design, Second Edition, V. II, Chapter 11, American Institute of Steel Construction, Chicago, IL, 1993, pp. 11-54 to 11-64. style="text-align: left;">3. Salmon, C. G., and Johnson, J. E., Steel Structures: Design and Behavior, Fourth Edition, Harper-Collins, New York, NY,  1996. style="text-align: left;">4. PCI Design Handbook: Precast and Prestressed Concrete, Fifth Edition, Precast/Prestressed Concrete Institute, Chicago, IL, 1999. style="text-align: left;">5. Thornton, W. A., a€?Design of Base Plates for Wide Flange Columns - A Concatenation of Methods,a€? Engineering Journal, American Institute of Steel Construction, V. 27, No. 4, Fourth Quarter,  1990, pp. 173-174. style="text-align: left;">6. Blodgett, 0. W., Design of Welded Structures, James F. Lincoln Arc Welding Foundation, Cleveland, OH, 1966.  style="text-align: left;">7. DeWolf, J. T., and Sarisley, E. F., a€?Column Base Plate with Axial Loads and Moments,a€? Journal of the Structural Division, American Society of Civil Engineers, V. 106, No.  ST1 1, November 1980, pp. 2176-2184. style="text-align: left;">8. Thambiratnam, D. P., and Paramasivam, P., target="_blank" title="a€?Base Plates Under Axial Loads and Moments,a€?" href="http://dx.doi.org/10.1061/(asce)0733-9445(1986)112:5(1166) ">a€?Base Plates Under Axial Loads and Moments,a€? Journal of Structural Engineering, American Society of Civil Engineers, V. 112 , No. 5,  May 1986, pp.  1166-1181. style="text-align: left;">9. Melchers, R. E., a€?Steel Base Plate-Footing-Soil Behavior,a€? Second International Workshop on Connections in Steel Structures: Behavior, Strength and Design, American Institute of Steel  Construction, Chicago, IL, 1992, pp. 132-139. style="text-align: left;">10. Bowles, J. E., Foundation Analysis and Design, Fourth Edition, McGraw-Hill Company, New York, NY, 1988. style="text-align: left;">11. Das, B. M., Principles of Foundation Engineering, Second Edition, PWS-Kent Publishing Company, Boston, MA, 1990. style="text-align: left;">12. Scott, R. F., Foundation Analysis, Prentice-Hall Inc., Englewood Cliffs, NJ, 1981. style="text-align: left;">13. Lin, G., target="_blank" tit