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• Sample of a mezzanine column investigation

  
  Investigation of Existing Columns for New Mezzanine Loads
  
  TABLE OF CONTENTS
  
  
  I. Introduction
  
  II. Background
  
  III. Mezzanine Information
  
  IV. Existing Column Checks & Results
  
  V. Proposed Column Modifications & Solutions
  
  VI. Conclusions and notes
  
  VII. Appendix
  
  I. Introduction
  
  A preliminary engineering investigation has been undertaken to address the
  proposed building changes only as they affect existing
  building columns due to the addition of a 50' x 165' x 12' high mezzanine to an existing
  metal building.
  
  The objective of this engineering investigation was basically twofold in nature:
  
  1) to determine the extent of the structural impact and effects on certain metal building
  rigid frame sidewall built-up columns, interior pipe columns, along with specific
  endwall columns along line 1.
  
  2) to suggest structural modifications, changes, alterations or similar improvements to
  the existing columns so that it can properly support the added mezzanine loads and
  forces.
  
  II. Background
  
  The building in question is a pre-engineered metal building manufactured by an MBMA certified producer. It is
  a gabled structure measuring 200' wide by 250' long having a low eave height of 25' and a
  roof slope of 1/4:12.
  
  The primary frames are modular, gabled rigid frames with spans of 4 @ 50' and are spaced
  at 50' on center with intermediate sidewall wind columns @ 25' spacings. The interior
  frame columns are 10'' diameter pinned top and bottom pipe columns. Endwall line 1 is a
  post & beam type consisting of 12'' deep built-up and wideflange column members.
  
  
  III. Mezzanine Information
  
  Mezzanine size: 60' wide X 165' long X 12' high.
  Mezzanine Loads: Total Dead Load = 50 psf
  Total Live Load = 50 psf
  Total Load = 100 psf
  
  See attached sketches showing the proposed layout of support steel which denote 6
  different existing column types affected by the new mezzanine loads.
  
  These columns are summarized as follows:
  
  Designation Type Depth Materials Fy(ksi)
  
  A - sidewall SBU 12" @base Flange: 6" x 1/4" 50
  Web: 3/16"
  
  B - interior pipe 10 3/4" dia. X .365" thick. 42
  
  
  E - sidewall TBU 21''@base Flange: 10''x 1/2" 50
  Web: 3/16"
  
  F - Endwall WF W12X14 wideflange 36
  
  G - Endwall SBU 12''@base Flange: 5" x 1/4" 50
  Web: 3/16"
  
  H - Endwall SBU 12''@base Flange: 8" x 1/4" 50
  Web: 3/16"
  
  
  All above columns to be field verified.
  TBU - Tapered Built Up column
  SBU - Straight Built Up column
  
  
  
  IV. Existing Column Checks & Results
  
  Column types noted as follows will NOT receive mezzanine loads:
  
  A, B & E
  
  Mezzanine beams and forces at these locations to be supported by the following independent
  columns:
  
  4"x4"x3/16" Tube columns; Fy = 46 ksi
  9" x 5" x 3/4" baseplate, K = 1.0 , pinned top and bottom
  2 - 3/4" dia. anchor bolts. Length = 11'-0 maximum
  
  The maximum mezzanine floor area assumed to be supported by these columns is 325 square feet.
  The following is a summary of the results of the analysis of endwall columns along line 1
  including the new mezzanine forces:
  
  Designation Max .Combined Stress Ratio Percent Overstressed
  
  Column F 1.03 3.0
  @ corner
  
  Column H1 0.647 ---
  8 feet from sidewall
  
  Column H2 0.985 ---
  34 feet from sidewall
  
  Column G 2.578 157.8
  
  
  
  The results indicate that the new mezzanine loading causes a significant overstress only
  in column type G.
  
  
  The following section will propose a reinforcement solution for the overstressed column G.
  
  
  V. Proposed Column Modification Solutions
  
  
  There are three main options which appear appropriate for the new forces and conditions:
  
  Option1: Build up and reinforce the column member by coverplating
  to improve its section properties including moments of inertia, rx , ry, section modulus,
  etc., along with the compression flange area to accommodate the significantly increased
  axial loads.
  
  Option 2: Replace the existing column with a new column.
  
  Option 3: Support the new mezzanine loads with independent, separate columns as is the
  case in the other area of the mezzanine.
  
  Option 1: Column G Coverplating
  
  In order to meet required combined allowable stresses the existing column will need the
  following field-installed materials:
  
  two --- 2 x 1/2 inch 50 ksi plates field welded to the girt side inner flange of the column.
  
  one --- 4 x 1/2 inch 50 ksi plates field welded to the inside flange of the column.
  
  
  Option 3: Replace the existing Column
  
  This option represents a significant contrast to Option 1 and is not considered in this
  investigation.
  
  Option 3: Add new Support Column
  
  This option represents a significant contrast to Option 1 and is not considered in this
  investigation.
  
  
  VI. Conclusions and notes
  
  
  Only one endwall column (G) was found to be overstressed and requiring
  reinforcement through coverplating. Assumptions and design consideration for this
  investigation is as follows:
  
  --- The mezzanine system is independently laterally braced. Columns investigated do not
  carry lateral mezzanine loads or forces.
  
  --- Columns must be properly braced at the mezzanine level by the mezzanine system.
  
  --- All built up columns supporting mezzanine beams must have their web-flange welds
  reinforced on the opposite side of all conrac welds 6''above and below the mezzanine
  beams.
  
  --- Minimum of 4 rows of two 3/4 '' diameter bolts for mezzanine framing into the 3/16"
  built up column webs for bearing.
  
  --- All columns materials dimensions to be field verified.

  
  
  

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