TEMPORARY STRUCTURES DURING CONSTRUCTION

1
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• TEMPORARY STRUCTURES DURING CONSTRUCTION
• __________________________________________________
  ____________
•  
• Ronald Welch, Ph.D., P.E.
• University of Texas at Tyler
• John Brain, P.E.
• Patent Construction Systems, A Harsco Company
•  
•  _____________________________________
•  
• ASCE Construction Institute Conference
• Los Angeles, CA January 19, 2007

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• WHAT ARE TEMPORARY STRUCTURES ?
•  

"Temporary structures are those structures that
are erected and used to aid in the construction
of a permanent project . . . providing access,
support and protection."   They are "either
dismantled and removed when the permanent works
become self-supporting or completed, or . .
.Incorporated into the finished
work."     McGraw-Hill Encyclopedia of Science
Technology, 1997
3
Temporary Structures during Construction
Committee Charge

• Seek experts in areas not covered in current
  committee membership.
• Collect current resources, codes, standards, and
  best practices to determine what is available.
  List the available codes and standards.
• Develop resources through committee expertise in
  areas not fully populated with information.
• Begin dialogue with CI membership on issues
  concerning temporary structures design and
  construction and the necessary qualifications for
  engineers performing said work.
• Illicit input on current best practices and
  recommend improvements
• Prepare guidelines of best practices for design
  and construction of temporary structures.
• Inform and educate engineer practitioners through
  seminars and workshops.
• Promote research by developing a list of topic
  areas not fully developed and understood.

4
Temporary Structures during Construction
Committee Charge

• Seek experts in areas not covered in current
  committee membership.
• Collect current resources, codes, standards, and
  best practices to determine what is available.
  List the available codes and standards.
• Develop resources through committee expertise in
  areas not fully populated with information.
• Begin dialogue with CI membership on issues
  concerning temporary structures design and
  construction and the necessary qualifications for
  engineers performing said work.
• Illicit input on current best practices and
  recommend improvements.
• Prepare guidelines of best practices for design
  and construction of temporary structures.
• Inform and educate engineer practitioners through
  seminars and workshops.
• Promote research by developing a list of topic
  areas not fully developed and understood.

5
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Current Temporary Structures Sub-Topics

• Loads Created by Construction Equipment
• Construction Dewatering
• Construction Ramps / Platforms / Vehicular Runway
  
• Cofferdams
• Earth Retaining Structures
• Diaphragm / Slurry Walls
• Underground / Tunneling Supports
• Underpinning Foundations
• Bridges
• Scaffolding
• Falsework / Shoring
• Concrete Formwork
• Bracing / Guying for Stability
• Temporary structures in Repair / Restoration
• Utilities Underground / Overhead
• Temporary buildings
• Structures for the entertainment industry

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Why?

• MORE FAILURES OCCUR DURING CONSTRUCTION
• THAN DURING THE LIFETIMES OF STRUCTURES
•  
• and
•  
• MOST CONSTRUCTION FAILURES INVOLVE
• TEMPORARY STRUCTURES

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• EACH YEAR
• Close to 1,000 construction workers lose their
  lives
• in the U.S.
•  
• Direct and indirect cost of construction injuries
  is
• more than 17 billion
•  
• No one appears to have published the total of
  property losses in construction failures

8
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• THERE APPEARS TO BE A MISMATCH OF THE
• PRACTICES OF ONE GROUP,
• the designers-of-record who by necessity distance
• themselves from the construction of the project,
  
• AND THE OBJECTIVES AND CAPABILITIES OF THE
• OTHER GROUP,
• the constructors who by contract must perform
• under the constraints of agreed time and money.

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• FAILURES OF
• unbraced excavations
• scaffolding
• falsework
• formwork
• excavation supports
• temporary erection shoring
• bracing and guying
• (in approximately this order)
• ARE THE MOST FREQUENT OCCURRENCES OF
• CONSTRUCTION FAILURES

10
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• A TACIT ATTITUDE SEEMS TO PREVAIL IN THE
• DESIGN-CONSTRUCTION INDUSTRY
• "these things" are temporary only, hence
  generally less important, therefore greater risks
  are acceptable than in permanent structures

But a dollar, or a life, lost at a construction
site is no less valuable or less tragic than
its loss elsewhere !
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• MANY ASPECTS OF TEMPORARY STRUCTURES
• WORK ARE DIFFERENT FROM THOSE OF
• PERMANENT STRUCTURES

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• Intended function of the structure
• Nature of the loads
• Predictability of occurrence of the loads
• Certainty in the magnitudes of the loads
• Possibility of simultaneous occurrence of loads
• Strength and deformation characteristics of the
  material
• Reliability of the rated strength of the material
  (or member)
• Possible secondary stresses, redundancy and
  instability
• Condition of the member and its material (new,
  used, damaged, deformed)
• Acceptable behavior of the structure (such as
  tolerable deflections, vibrations)
• Acceptable probability of total failure
• Consequences of failure
• Construction tolerances
• Workmanship in the construction
• Inspection Standards
• Protection of the structure against damage,
  deterioration and extremities of weather
• Intended lifespan of the structure with the
  increasing probability of occurrence of maximum
  loads, abnormal loads, damage and deterioration
  with time

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• BAD DESIGN PHILOSOPHIES AND PRACTICES
•  
• These things are temporary only, so go for
• Higher allowable stresses
• Lower safety factors
•  

14
.
Current Temporary Structures Sub-Topics

• Loads Created by Construction Equipment
• Construction Dewatering
• Construction Ramps / Platforms / Vehicular Runway
  
• Cofferdams
• Earth Retaining Structures
• Diaphragm / Slurry Walls
• Underground / Tunneling Supports
• Underpinning Foundations
• Bridges
• Scaffolding
• Falsework / Shoring
• Concrete Formwork
• Bracing / Guying for Stability
• Temporary structures in Repair / Restoration
• Utilities Underground / Overhead
• Temporary buildings
• Structures for the entertainment industry

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Construction Institute - Temporary Structures
CommitteeFalsework and Shoring
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What is Shoring?

• Shoring (or Falsework), is a temporary
  structure used to support vertical loads during
  the process of construction. The loads supported
  can be from freshly placed concrete, existing
  structures, or from construction equipment.

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Engineering Requirementsfor Shoring Design
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Question?How does one go from

• To

This
This
Engineering
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Requirements for Cast-In-Place Concrete OSHA
Construction Standard Subpart Q 1926.703

• General requirements for formwork
• (1) Formwork shall be designed, fabricated,
  erected, supported,
• braced and maintained so that it will be
  capable of supporting
• without failure all vertical and lateral
  loads that may be
• reasonably be anticipated to be applied to
  the formwork.
• Formwork which is designed, fabricated,
  erected, supported,
• braced and maintained in conformance with
  the Appendix to this
• this section will be deemed to meet the
  requirements of this
• paragraph.
• (2) Drawings or plans, including all revisions,
  for the jack layout,
• formwork (including shoring equipment),
  working decks, and
• scaffolds, shall be available at the jobsite

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What A Engineer or Designer Requires To Provide
Proper Technical Support

• Are you dedicating enough time for proper
  engineering design and review?
• Do they have the most current contract documents
  (i.e. Drawings, Specifications, Photographs)?
• Type of equipment to be used
• Area to begin design
• Contractors preferences or ideas
• Any unusual site conditions or project
  requirements
• Equipment availability (i.e. sizes NOT to use)
• Are drawings and calculations required for
  submittal?
• Is a Professional Engineering Seal Required?
• Once drawings are completed, a timely review by
  field personnel and project management with
  positive or negative feedback returned to
  Engineering in a realistic and timely manner so
  revisions can be done.

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Engineerings Role

• Engineering plays a critical role in the
  overall success on most projects where shoring is
  being used. Shoring Engineers and Designers can
  provide contractors with the knowledge and
  experience that allows them to be competitive and
  have a safe working environment. Shoring
  Engineers and Designers are highly specialized in
  the skills required to form and shore complex
  shapes formed from cast-in-place concrete,
  supporting high concentrated loads and keeping
  your workforce safe. These design professionals
  can also provide you with many alternative ways
  to solve these complex situations, which are now
  common on todays projects.

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How Engineering Supports You!!

• Layout and field assembly drawings
• Calculations
• Product usage, capacities and capabilities
• Proper product applications
• Design of standard and special product components
• Field inspections and job walks
• Safety

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Standards Used In The Design And Erection Of
Shoring Systems

• American Concrete Institute Committee 347
• Scaffolding, Shoring Forming Institute
• Occupational Safety and Health Administration
• Local and State Building Codes
• AASHTO
• Local State Department of Transportation
• Military Specifications
• Department of Energy Specifications

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Standards Used In The Design And Erection Of
Shoring Systems

• In House Engineering Department Specifications
  and Design Guides

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• Without the proper communication, even the
  smallest project can potentially turn into
• I wish I never Quoted This Project

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Various Shoring Systems
Post Shores
Frame Shoring
Post/Ledger System
Adjustable Beam Systems
Table Systems Truss Column Mounted
Drop Head/Post Systems
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Post Shores

• One of the most common shoring systems/methods of
  shoring
• Simplest to use, little training required
• Lightweight
• Post have various ranges in shoring height
• Load capacity will vary with height
• Can be used in tight and unusual shapes

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Single Post Shore Safety RuleAs Recommended by
the Scaffolding, Shoring and Forming Institute,
Inc.
Item C. Plumb All Post Shores As The Erection
Proceeds. Check plumb of post shores JUST PRIOR
TO POUR Item G. For Stability, Single Post
Shores Shall Have Adequate Bracing provided in
the longitudinal, transverse and diagonal
directions. Bracing shall be installed as the
shores are being erected.
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Single Post Shore Safety RulePer OSHA
Construction Standard
Subpart Q 1926.703 Whenever single post shores
are used one on top of the other (tiered), the
employer shall comply with the following specific
requirements in addition to the general
requirements for formwork (i) The design of the
shoring shall be prepared by a qualified designer
and the erected shoring shall be inspected by an
engineer qualified in structural design.
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Post Shores Not Plumb
No Adequate Bracing
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Proper Usage of Single Post Shores
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Shoring Frames

• One of the most common shoring systems/methods of
  shoring.
• Simple to use, little training required.
• Most field personnel are knowledgeable in
  assembly and safe usage of systems
• Load capacities range from 10,000 lbs per leg to
  50,000 lbs per leg
• Systems are variable in frame heights and brace
  sizes
• Multitude of accessories to meet your
  requirements
• Have an integral screw leg to allow fine
  adjustment
• Most Shoring suppliers have a substantial
  inventory on hand

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Shoring Frames
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Steel Frame Shoring Safety RuleAs Recommended by
the Scaffolding, Shoring and Forming Institute,
Inc.
Item O. Avoid Eccentric Loads On U-Heads, Top
Plates and Similar Members By Centering Stringers
On Those Members.
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Simple Tower Layout Drafting Standard
This is the reason why stringers are most often
incorrectly erected
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Notice how stringer runs diagonally from one
leg to the other
Stringer is CENTERED on middle leg
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Post/Ledger Systems

• One of the newer shoring systems to be introduced
  to the US construction market
• Most of these systems have been developed by
  European Shoring suppliers (Metric)
• These systems require a more technical erection
  crew
• These systems are lightweight, most of the
  components are made from aluminum.
• High leg capacities. In certain configurations a
  single leg can carry 24,000 lbs
• Can be broken down into single posts for re-shore
  operations
• Systems can be assembled into tables or tall
  towers and flown into the required location on a
  project
• Fast erection/assembly times
• Uses less parts than standard frame systems
• System is best used for heavy slabs such as
  Turbine Pedestal Tops, Linear Accelerator or any
  other type of heavy reinforced concrete
  structures

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Post/Ledger Systems
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Adjustable Beam System

• One of the older systems on the market
• Simple to use
• Units come in various span combinations. Span
  sizes vary from 4 up to 30
• Great for tight locations or areas where
  obstructions limited the use of standard shoring
  towers.
• Can be used in tight and unusual shapes
• Available in both steel and aluminum

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Adjustable Beam Systems
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Table Systems

• These systems are best used on high rise type
  structures where there is a substantial amount of
  reuse
• Table units are designed for your projects
  requirements
• These systems components are either constructed
  from aluminum or steel
• These systems use modular parts that simply bolt
  together
• Little re-shoring of slabs is required due to
  limiting leg locations
• As for Column Mounted Tables, no re-shoring will
  be required, due to tables being supported by
  jacks at the structures column or shearwalls
• These systems all require the use of tower or
  track type cranes to move
• Contractors must keep crane location and
  capacities in mind when deciding on using one
  these types of systems
• Assembly area is typically required since these
  systems are job built. In some cases shoring
  suppliers may assemble tables for the contractor

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Table Systems
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How many systems are being used on this project?
46
Truss System
Column Hung System
Post/Ledger System
47
Bad Practice
Care must be taken during ALL stages of assembly
on any type of Shoring Systems. If care is NOT
taken, there is a potential for failure of that
system.
48
This jack has been installed properly
Since this jack is not plumb, damage or failure
of the jack may occur
49
Drophead/Post Systems

• This is the newest system to be introduced to the
  US construction market
• System uses a simple post shore that supports a
  ledger which can in turn support a prefabricated
  panel or LVL wood joist
• The benefit to this system is that the post stays
  in place while the decking material is stripped
  out around it
• These systems use a drop head which drops down
  to allow the joist/panel and ledgers to be
  removed and cycled onto the next pour, leaving
  the post in place for re-shoring
• Post are available in various heights
• Panels and LVL joist are available in several
  standard sizes
• For a typical 12 thick concrete slab, the
  typical area on a post will be 48 sq. ft.
  (Depending on shoring height)

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National Shoring Suppliers

• Patent Construction Systems
• Doka, USA
• Peri
• EFCO
• Aluma Systems
• Waco Scaffolding
• Symons Corporation
• Titian
• Hi-Lite, LTD.
• Meva

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References and Design Publications

• Formwork For Construction by Mary K. Hurd SP-4,
  ACI 347. 6th Edition, The American Concrete
  institute, P.O. Box 9094, Farmington Hills,
  Michigan, 48333-9094. The Bible for any
  formwork or shoring Engineer or designer
• Handbook of Temporary Structures in Construction
  by Robert T. Ratay, 2nd Edition, 1996, The
  McGraw-Hill Companies, ISBN 0-07-051261-2 . This
  is a good book that a designer/contractor on the
  proper design and usage of temporary structures
  in construction. Covers items such as
  underpinning, earth retention, shoring,
  scaffolds, formwork, piles, and many other
  topics.
• AASHTO Guide Design Specification for Bridge
  Temporary Works
• AASHTO Construction Handbook for Bridge Temporary
  Works
• ASCE 37-02 Design Loads on Structures During
  Construction
• Masonry Wall Bracing Standards

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Columbia Building Washington D.C.
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Post Shores Shown Correctly
Loads on structure are indicated on for Engineer
of Record to review
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Dulles ATCT
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All erection information (spacing's, type or
equipment, etc.) given
Erection Sequence
Specific Notes Indicated on Drawing
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All Required Details Given
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Sections Details for ALL Conditions
Areas indicated that are other responsibilities
for design
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Tampa Airport Monorail
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Connection Detail
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Built per detail shown on drawings
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• TEMPORARY STRUCTURE DESIGNER'S DONT'S
•  
• Don't design for a contractor you don't know
• Don't design unless you understand the
  construction process
• in which the temporary structure will be used 
• Don't reduce design loads
• Don't increase allowables
• Don't reduce safety factors
• . . . . . unless you have adequately
  considered all factors, and
• . . . . . unless inspection is part of your
  services
• Don't allow used materials without continuous
  quality control
• Don't allow material substitutions without your
  approval

70
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• ROLES AND RESPONSIBILITIES OF PROJECT
• DESIGN ENGINEER
• (STRUCTURAL ENGINEER OF RECORD)
•  
• Evaluate effects of temporary structures on the
• permanent structure
•  
• Normally not involved in the design of temporary
• structures means-and-methods
•  
• Usually does not review temporary structures shop
• drawings

71
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• THE BEST WAYS TO MITIGATE CONSTRUCTION
• FAILURES ARE, OBVIOUSLY
• competent designs
• good construction practices
• utmost care
• strict inspection
• unwavering enforcement of high standards
• clear definition of responsibilities

72
.
Current Temporary Structures Sub-Topics

• Loads Created by Construction Equipment
• Construction Dewatering
• Construction Ramps / Platforms / Vehicular Runway
  
• Cofferdams
• Earth Retaining Structures
• Diaphragm / Slurry Walls
• Underground / Tunneling Supports
• Underpinning Foundations
• Bridges
• Scaffolding
• Falsework / Shoring
• Concrete Formwork
• Bracing / Guying for Stability
• Temporary structures in Repair / Restoration
• Utilities Underground / Overhead
• Temporary buildings
• Structures for the entertainment industry

73
Questions?

• POCs
• Ron Welch, Committee Chair Ronald_Welch_at_uttyler.ed
  u, 903-566-7002
• John Brain, Committee Secretary,
  jbrain_at_pcshd.com, [phone]