{"id":8304,"date":"2021-05-20T19:06:45","date_gmt":"2021-05-20T19:06:45","guid":{"rendered":"https:\/\/www.imegcorp.com\/?p=8304"},"modified":"2021-05-20T20:34:06","modified_gmt":"2021-05-20T20:34:06","slug":"early-collaboration-is-critical-for-a-monumental-stair","status":"publish","type":"post","link":"https:\/\/imegcorp.com\/insights\/blog\/early-collaboration-is-critical-for-a-monumental-stair\/","title":{"rendered":"Code compliance and early collaboration are critical for a monumental stair"},"content":{"rendered":"
By John Paul Goedken\u00a0and Danielle DeBoer<\/span>\u00a0<\/span><\/p>\n Monumental stairs are often THE feature of a lobby. They are typically several times more expensive than a\u00a0traditional\u00a0stair, but what they add to the overall feel of a project can be\u00a0priceless.\u00a0The American Institute of Steel Construction (AISC) issued updated guidelines for the design of monumental stairs in 2016.\u00a0Due to\u00a0code adoptions throughout the country, the\u00a0impact\u00a0of these guidelines\u00a0is\u00a0just beginning to be understood throughout the design and construction industry.\u00a0\u00a0<\/span>\u00a0<\/span><\/p>\n Structural\u00a0engineers typically design monumental stairs\u00a0for\u00a0vibration first, and then the strength of the stair is checked.\u00a0These stairs are not connected into a larger floor system, and\u00a0therefore\u00a0do not have the weight or damping\u00a0(vibration reduction)\u00a0of typical floor beams.\u00a0Because of these factors, vibration plays a crucial part in their design.<\/span>\u00a0<\/span><\/p>\n The updated\u00a0AISC\u00a0Steel Design Guide 11 provides current state-of-the-profession guidelines for vibration in many situations:\u00a0natural frequency of floor systems\u00a0(or the amount of time\u00a0it takes to go through a\u00a0complete\u00a0range of motion), design for walking excitation in floors and stairs, rhythmic excitation, design for sensitive equipment, and guidance for finite element models.\u00a0For monumental stairs, there are\u00a0three\u00a0checks prescribed by AISC:<\/span>\u00a0<\/span><\/p>\n The first two checks\u00a0are basic functions of the stair geometry (rise, run, plan layout, support), the weight of the stair, and the stiffness of the stair.\u00a0These need to be worked out by the architect and structural engineer early in the conceptualizing of the stair.\u00a0If these\u00a0general items\u00a0can\u2019t\u00a0be agreed upon and\u00a0result in a stair that\u00a0does not meet\u00a0the first two\u00a0criteria,\u00a0there is no point moving on\u00a0to the more intricate design of acceleration.\u00a0<\/span>\u00a0<\/span><\/p>\n The third check,\u00a0for vertical acceleration limits,\u00a0is defined from the point of view of a single person standing on the stair and \u201cfeeling\u201d the vibration.\u00a0The\u00a0sensitivity\u00a0a person has toward\u00a0vibration\u00a0varies widely\u00a0due to many factors:\u00a0lighting in the space, noise, activity,\u00a0or\u00a0simply\u00a0the mood\u00a0of the\u00a0person.\u00a0It can vary from person\u00a0to\u00a0person,\u00a0and from\u00a0day\u00a0to\u00a0day.\u00a0AISC has tried to codify this as best as possible.\u00a0There are\u00a0three different\u00a0sources of vibration\/acceleration\u00a0that are evaluated from this\u00a0standing\u00a0individual\u2019s point of view:<\/span>\u00a0<\/span><\/p>\n AISC has different parameters for each of these criteria.\u00a0They all need to be evaluated for the stair.<\/span>\u00a0<\/span><\/p>\n Besides the code-given factors for the criteria, the damping of the stair also comes into play.\u00a0This\u00a0value\u00a0is often\u00a0fairly minimal\u00a0for any\u00a0stair, as there are no floor-to-floor partitions limiting the movement of the stair.\u00a0One\u00a0factor that\u00a0can\u00a0play a\u00a0large\u00a0part in the damping of the stair\u00a0are\u00a0the railings.\u00a0Are they\u00a0glass, metal mesh, or minimalist tubes?\u00a0\u00a0Are they connected into each tread, or only at 4\u00a0feet\u00a0on center?\u00a0\u00a0Each\u00a0configuration\u00a0can affect the\u00a0overall\u00a0damping considerably.\u00a0Since the \u201cdesign\u201d of the railing is typically coming from the architect, the structural engineer is simply reacting to what\u00a0he or she is\u00a0given.\u00a0<\/span>\u00a0<\/span><\/p>\n Often,\u00a0most of the stair\u00a0is already designed\u00a0by the architect for aesthetics,\u00a0so\u00a0the\u00a0structural engineer\u2019s job is simply to size the stringer.\u00a0Larger stringers give more stiffness and will help with all three\u00a0AISC\u00a0checks. However,\u00a0larger stringer sizes may not be desirable based on aesthetics\u00a0and\u00a0can make an otherwise elegant stair look clunky.\u00a0<\/span>\u00a0<\/span><\/p>\n The best approach is to have the\u00a0architect and structural engineer\u00a0work as a team and\u00a0discuss\u00a0early on\u00a0what are the important\u00a0design\u00a0features of the stair.\u00a0Often, something simple\u00a0\u2014\u00a0like an added support brace\u00a0or a slight change in the railing design\u00a0\u2014\u00a0will\u00a0allow the stair design to still meet the architect\u2019s vision while also meeting\u00a0the AISC vibration criteria.<\/span>\u00a0<\/span><\/p>\n","protected":false},"excerpt":{"rendered":" The American Institute of Steel Construction\u2019s (AISC) updated guidelines for the design of monumental stairs is just beginning to be understood throughout the design and construction industry. The best approach is to have the architect and structural engineer work as a team and discuss early on what are the important design features of the stair.<\/p>\n","protected":false},"author":5,"featured_media":8305,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":"","_links_to":"","_links_to_target":""},"categories":[241,256],"tags":[],"class_list":["post-8304","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-acoustics","category-structural"],"acf":[],"yoast_head":"\n\n
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