Volume 8, Issue 8 (September 2011)

    Deflection Lag, Load Lag, and Time Lag of Buried Flexible Pipe

    (Received 20 November 2009; accepted 16 June 2011)

    Published Online: 2011


      Format Pages Price  
    PDF 5 $25   ADD TO CART


    The Iowa formula was published by Professor M. G. Spangler of Iowa State Univ. in 1941 to predict the deflection of buried flexible pipe. In the equation, he used the term “deflection lag” to describe the increase in flexible pipe defection after the maximum load was reached over the pipe. Unfortunately, the term is currently improperly used in ASTM, AWWA, and ASCE manuals and standards to reflect the increase in deflection starting the day the backfill is completed over the pipe, rather than when the maximum load occurs. The maximum load on a pipe is generally not attained until after 3–12 months after construction. The history of the deflection lag term and the use of the term “load lag” by Professor Spangler are explored. For the increase in pipe deflection following construction completion, the use of the term “time lag” should be used. A table of time lag values for use in estimating deflection is presented. The table is based on empirical data from field measurements.

    Author Information:

    Howard, Amster
    Civil Engineering Consultant,

    Stock #: JAI102888

    ISSN: 1546-962X

    DOI: 10.1520/JAI102888

    ASTM International is a member of CrossRef.

    Title Deflection Lag, Load Lag, and Time Lag of Buried Flexible Pipe
    Symposium Plastic Pipe and Fittings: Yesterday, Today, and Tomorrow, 2009-11-09
    Committee F17