LIFE Design: g The Future of Highway Substructures Oliver S. Delery, Jr., P.E. Oliver S. Delery, Jr., P.E. Hanson Pipe & Precast, LLC
Realities of the Current Design/Construction Industry The SAFETEA-LU Legislation expires on September 30, 2011. At the current time, there is a framework for a Senate Bill and a separate House Bill for Re-authorization on the table but neither includes an agreed upon funding mechanism over and above the current Highway Trust Fund capacity. Future Federal money will most probably have restrictions on how money is used on projects, calling for more durable and sustainable installations. There is no money available for any maintenance; cities and states will have to fully fund these costs. Highways and bridges designed for 50 years will have to last for Highways and bridges designed for 50 years will have to last for 75 years; designers must add a service life correction factor to all future designs. All culverts should be designed as bridges All culverts should be designed as bridges.
Life Design New design concept that should be adopted for all highway projects. p j Basic assumption is that only the actual roadway surface should be considered for replacement during the “extended” life of the roadway. All sub-roadway components, including base material, underground bridges (culverts) and backfill should be designed underground bridges (culverts) and backfill should be designed to require only minimal maintenance for the design life of the project (corrected for future maintenance funding shortfalls). Life cycle costing should be applied strictly to the roadway surface materials.
Components of Life Design Relating to Culverts Inherent Structural strength Stability of foundation and backfill material Stability of foundation and backfill material Hydraulic Capacity Maintenance Requirements Ability to resist non-traditional detrimental events Environmentally friendly products Design Liability D i Li bilit
Life Design – Inherent Structural Strength Ability to carry both dead and live loads independently of: – Improper Installation Improper Installation – Lack of Inspection – Insufficient maintenance – Unexpected loading conditions U t d l di diti Absent material inherent strength, maintenance of soil/liner (pipe) system design strength for the entire life of the project is (p p ) y g g p j mandatory.
Life Design – Culvert Structural Design and Analysis Initial assumption is that the design engineer has conducted the required soil tests for the particular project site. q p p j Each culvert must be designed structurally using the latest version of the AASHTO LRFD design procedure for the particular culvert material culvert material. Pre-cast Concrete Pipe “Bridges” can be designed for any loading conditions and virtually any existing and anticipated soil conditions. Flexible installations require the designer to use insitu soil properties to design a soil/pipe interaction system that will properties to design a soil/pipe interaction system that will survive all exterior forces for the design life of the project.
Life Design – Stability of Foundation and Backfill When using concrete pipe: – Initial compaction under the haunches to properly support the “structure” Initial compaction under the haunches to properly support the structure – Protection against loss of “fines” in the pipe zone When using flexible pipe: – Assumption that there will be no movement of soil surrounding the “pipe” for the entire design life expectancy of the roadway as the soil constitutes the structural component of the soil/pipe installation. – The passive resistance of the soil will not be diminished for the life of the project. – Inspection must be conducted at installation and again before acceptance p g p of the installation and, as required for all “bridges” re-inspection must be performed on an annual basis to insure that the deflection allowance is not exceeded.
Life Design – Post Installation Inspection (PII) All culvert installations should be inspected no sooner than 30 days following initial installation to insure that proper procedures were used to prevent mis-alignment, deflection or damage to the installed line. Flexible installations should be inspected through the use of p g either a mandrel or laser video inspection. Concrete structures should be inspected visually or through the use of video inspection. p A second or “Warranty” inspection should be conducted on each flexible pipeline no sooner than 30 days prior to final acceptance of the project in order to: of the project in order to: – Check for excessive deflections – Insure that no construction damage has occurred – Prevent the acceptance of a failed pipeline – Prevent the acceptance of a failed pipeline.
Warranty Test Precedent: UFGS 33-40-00
Life Design – Hydraulic Capacity Hydraulic capacity of the culvert must be maintained for the entire design life of the system to avoid: g y – Erosion of roadway base surrounding inlet structures – Flooding of roadway surfaces – Washout of entire “bridge” structure W h t f ti “b id ” t t
Washouts
Life Design – Hydraulic Capacity Pipe that will lose capacity due to “rippling” under loads must be designed for that loss of hydraulic capacity. Pipes can lose capacity due to deflection. It is therefore important to design using the hydraulic capacity of the anticipated maximum deflection. Vertical misalignments due to hydrostatic pressures must be avoided.
Life Design – Maintenance Requirements Materials should have minimal or no maintenance requirements for the life of the project. The initial design should avoid any p j g y possible future maintenance issues. All maintenance procedures are subject to 100% local or state funding; federal highway funds cover new construction only funding; federal highway funds cover new construction only. Required inspections to determine increased deflection and or pipe movements are also a local responsibility but are vital to the performance of the system. This cost must be considered in the initial evaluation.
Life Design – Resistance to Detrimental Events Construction Damage Environmental Attack – Soil – Effluent Historic Events that should be considered in the design Historic Events that should be considered in the design – Grass, forest and wild fires – Tanker accidents & spills Ability of the selected “Bridge” material to survive detrimental Ability of the selected “Bridge” material to survive detrimental events must be considered in each location.
Life Designs - Fires “Flammability of Plastic Drainage Pipe” Dr James Quintiere Dr. James Quintiere ‘It is concluded that HDPE pipe, once ignited will sustain burning, and its energy release rate can be relatively l t b l ti l high, thereby creating the potential for significant damage both to itself and surrounding areas’. ‘The PE and PP materials, unless indicated do not have any special indicated, do not have any special fire retardant treatment; and this is generally true for commercial HDPE drainage pipe drainage pipe.
San Diego, CA Wildfires
Stoneburg, TX
TxDOT Policy Memorandum Jan. 4, 2010 “ On April 9 2009 wildfires in the On April 9, 2009, wildfires in the Wichita Falls district resulted in damage to a multi-barrel HDPE pipe damage to a multi-barrel HDPE pipe installation. In order to minimize the chance of fire-related damage on chance of fire-related damage on future installations, we are modifying the criteria for use of thermoplastic the criteria for use of thermoplastic pipe on TxDOT projects”.
Life Design – Protecting the Environment Eliminate the use of highway drainage products that result in the creation or release of persistent, bioaccumulative toxins (PBTs) p , ( ) by using available drainage products that are chemically inert and environmentally friendly. In eliminating the persistent toxic pollution over the material's In eliminating the persistent toxic pollution over the material s lifecycle from production, through use, and ultimately disposal, we will ensure the health of our waterways and all biological creatures therein. t th i
Life Design – Design Liability The Design Engineer assumes total liability for the “bridge”.
HDPE Pipe Failure at Texas Fish Hatchery Offers Costly Lessons p y y Oct 4 06:27 PM US/Eastern JASPER, Texas, Oct. 4 /PRNewswire-USNewswire/ -- The Texas JASPER, Texas, Oct. 4 /PRNewswire USNewswire/ The Texas Parks and Wildlife Department recently learned a very costly lesson when it was forced to replace two miles of high-density p y polyethylene (HDPE) pipe with reinforced concrete pipe (RCP), y ( ) p p p p ( ), after portions of the plastic drainage system collapsed, and 11,000 feet of pipe was determined to have questionable structural integrity, at the new John D. Parker East Texas Fish Hatchery near Jasper.
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