New Methods for Ponding Analysis of Open Web Steel Joist Roofs

November 11, 2020 @ 12:30 pm – 2:00 pm

Mark D. Denavit, PhD, PE
University of Tennessee, Knoxville


Session Description

Requirements for rain loads and ponding on open web steel joist roofs are spread across many documents, including the SJI Specifications, ASCE 7, the International Building Code, AISC Specification, and more. A key requirement from ASCE 7 is that bays of roofs that are susceptible to ponding shall be investigated by structural analysis to ensure that they possess adequate stiffness to preclude progressive deflection (i.e., instability) and adequate strength to resist the additional ponding load.  The direct analysis method for ponding, described in SJI Technical Digest 3, is a new method for performing such an investigation.


This SE University session will review requirements for rain loads and ponding on open web steel joist roofs, and show how the recently improved SJI Roof Bay Analysis Tool helps to meet those requirements. This tool uses the direct analysis method for ponding, allowing engineers to easily perform these necessary analyses while also identifying the most economical roof bay configuration. Several examples will be presented with comparisons to traditional methods of assessment defined within the AISC Specification.


Learning Objectives

  • Recall the main roof ponding requirements from design standards
  • Describe the limitations of the method of ponding analysis given in Appendix 2 of the AISC Specification
  • Investigate the stability of simple roof systems for ponding using the SJI Roof Bay Analysis Tool
  • Identify the main factors influencing the ponding stability of open web steel joist roofs


Handout and registration emails for this session will be sent to SE University companies on Friday, November 6th.