Precast Concrete Engineering

Begin & End On Time! Information Exchange Not Painful PDH s Earned!

Why Design with Precast? Stand out amongst Owners & Contractors Become known for providing VALUE in that others do not

What Value? Increased Durability Reduced Disruption & Downtime Improved Safety More Reliable Time of Completion Less Dependence on Plant Labor

Precast Utility Structures Design and Installation

Outline Introduction Specifying Design Shipping, Handling and Installation Wrap-Up

Outline QUESTION How many of you have specified or been a part of the design or installation of precast concrete utility structures?

Introduction Utility Structures encompass a wide variety of precast concrete products Electrical Utilities Gas Utilities Water/Wastewater Emerging Technologies Telecommunications

Applications

Applications Sasol Steam Vaults

Applications

Applications Renewable Energy

Precast Concrete Utility Structures Stock Items Many precasters stock various size items that are made to industry standards. Non-Stock Items Custom utility structures can be made in unlimited sizes and shapes for a project.

Project Solutions

Types of Precast Utility Structures Square, Round or Rectangular Vaults Pole Bases Transformer pads Prestressed Lighting Poles Wind Turbine/Solar Panel Bases Precast Conduit Utility Trenches

Initial Questions Is the Utility wet or dry? Wet water infiltration minimized but allowable Consider including a sump in the floor Use of knockout panels are acceptable Dry water infiltration is not permitted Water tight access (casting or hatch) Use duct terminators, gasketed or other water tight connections What provisions must be made to accommodate the planned equipment?

Specifying Specifying

Specifying Clear, concise specification is key to project success. Items to include in any specification: Applicable industry reference standards What should be expected with product submittal packages Appropriate design loads Concrete and material properties Producer qualifications

Specifying (cont.) Reference Standards and Submittals Applicable ASTM standard specifications ASTM C857 Min. Structural Design Loads for Precast Concrete Underground Utility Structures (UUS) ASTM C858 Specification for Precast UUS ASTM C891 Practice for Installation of Precast UUS ASTM C990 Specification for Joints for Concrete Pipe, Manholes, and Precast Box Sections using Preformed Flexible Joint Sealants ASTM C1037 Practice for Inspection of Precast UUS

Specifying (cont.) Recommended Mix Design f c = 4000psi minimum at 28 days Materials to conform to applicable ASTM specs Maximum water-cementitious ratio of 0.45 Air-entrained, especially if subject to freezethaw Dry-Cast max absorption of 9% in accordance with ASTM C497, method A or 8.5% method B

Major Changes in our Industry Compressive Strength: Design up to 10,000 PSI The shear strength of aggregate Increased Density Resistance to Corrosion

Self Consolidating Concrete (SCC) Video

Specifying (cont.) Quality Control Producer Qualifications Producers should be expected to meet minimum QC standards to assure that products are made in accordance with drawings and specifications. Demonstrating quality standards through third party inspection is an option

Specifying (cont.) ASTM C858 - Standard Specification for Underground Precast Concrete Utility Structures C858 contains a comprehensive list of ASTM standards for constituent materials and product testing. Included in the standard are: Manufacturing Requirements Design Standards Permissible Variations Repair Guidance Rejection of products which do not meet the standard Product Marking

Accessories Special attention should be given when developing plans and specifications to the following features: Lifting Devices Knockouts vs. Terminators Pulling Irons Inserts Sleeves

Accessories Cable Rack Uni-strut Arm Brackets Ladders/steps Grounding Rod Sleeve or attachment to internal reinforcing Coatings Sump drains Hatches and castings

Lifting Devices

Lifting Best Practices Follow manufacturer recommendations. Do not move / lift or handle product until specified handling strength is achieved. Store in a manner that minimizes stress on structure. Specifications should address the development of a rigging/hoisting plan for products. Use a 4:1 Factor of Safety on inserts per OSHA Standards

Lifting Devices / Rigging How should a lifting device be specified? If structure is project specific allow manufacturer to select. If structure is a standard for repeat use, engineer or utility may select.

Pulling Irons Consider specifying pulling irons for electric/communication UUS Location Type Size Capacity Material

Entering and Exiting Utility Structures

Entering and Exiting (cont.) Access Hatches and Castings Labels and Lettering Lift Assist Gasketed Locking Accepts Vehicular and Airport Loadings Ladders Steps Safety Grate

Design

Design Environmental Factors (Corrosion) Video Inspection PS #3 Town of Livingston

10 Dia.- 22 deep Installed in 2007 Coal tar epoxy in & out 2 High FMs w/ 10 + drops Ductile Iron nonepoxy coated eaten through on one side Loss of wall thickness Exposed reinforcing steel

Hatch: 7.0 Lift Station walls: 2.0-3.0 Ductile Iron Pipe Walls: 1.0

Design -Why High Strength Concrete? Durability 3 Days

High Performance Concrete Acid Trials

Design -Why High Strength Concrete? Increased Corrosion Resistance 4 Months

Design - Coatings in Wastewater Chemical Resistance not that tough (ph of 3) -So why has there been variable success? Must be Adhered (proper surface prep) Must be Continuous (combat outgassing) At design thickness Must deal with joints

Calibrated for - Dielectric of Coating - Mil Thickness With variable voltage set - pass over substrate - makes a sound over problem spots - identified areas patched - test assures continuity and correct thickness

Design Admixtures in Concrete Conshield Anti-microbial Breaks the cycle in Phase II Interrupts the cell membrane of Thiobacillus Difficult to prove it is present, in correct dosage and activated Superplasticizers

Design Factors Compressive Strength 6500 PSI Reinforcement Wall Thickness 12

Design of Utility Structures Loads to Consider Surface surcharge Concentrated wheel loads Lateral loads Hydrostatic forces Point loads Live loads Dead loads Construction loads Pulling iron loads Other Factors to Consider Soil Bearing Capacity Connection Locations Penetrations Lifting and Handling Stresses

Design of Utility Structures (Cont.) Typical Design Loads per ASTM C857 A16 (AASHTO HS20) 16,000lbf/wheel Heavy Traffic A12 (AASHTO HS15) 12,000lbf/wheel Medium Traffic A8 (AASHTO H10) 8,000lbf/wheel Light Traffic A-0.3 300PSF Walkways (H20 Load) (A16 Load) Grade 2-0

Design of Utility Structures (Cont.)

Design (Cont.) Precast Concrete Utility Structures and the associated castings and hatches can even be designed for airport, railroad and port loadings.

Design of Utility Structures (Cont.) Concrete Thickness Sufficient to meet minimum reinforcement cover and withstand design loading conditions. Reinforcement Reinforcement design by structural calculations as required by code or as proven by testing.

Reinforcement Larger Diameter Reinforcement Shear Reinforcement - Stirrups Accurate Placement

Structural Calculations If Needed

Quality Assurance

Quality Assurance- Water Testing

Quality Assurance- Dry Stacking

Shipping

Precast VS. Cast In Place What are the Limitations of Heavy Precast vs. Cast In Place? Ship under 18 wide.

Just-In-Time Delivery On Time No Weather Delays Precast risers ready and waiting to ship Completion Date Assurance!

Shipping Things to Consider Transportation Restrictions Height Width Weight Permitting Requirements What design criteria controls product size? Where is the center of gravity of the piece? Is specialized equipment and/or rigging required to load or install?

Installation

Rapid Installation

Installation Safety Requirements Site Conditions Excavation Bedding Placement Joints Joint Sealants Backfilling

Safety Considerations Verify that lifting apparatus such as slings, lift bars, chains, and hooks have adequate capacity and proper safety factors (at least 5) Safety factor of at least 4 is required on all devices (inserts) Safety factor of at least 5 is recommended on all lifting apparatus (chains, sling, spreader beams) OSHA regulation 29 CFR, Part 1926.650-652 on excavation work should be followed at all times.

Site Conditions Survey of the site Site must be accessible to the equipment necessary for offloading and installation. Verify overhead and below grade obstacles are not a concern.

Excavation Prior to excavation, all buried utilities should be identified and located. Excavations should be made with approximately 18 inches of clearance to allow for adequate compaction of backfill material Excavation slopes to comply with all applicable construction safety requirements.

Bedding Engineered bedding material should be used as necessary to provide a uniform bearing surface. A minimum 4 inch thick sand or granular bed overlaying a firm and uniform base is recommended unless otherwise specified.

Placement Improper installation can lead to damage of the structure, reduced structure life and safety hazards. Reference ASTM C891 Standard Practice for Installation of Underground Precast Concrete Utility Structures Reference NPCA Best Practices Manual for Precast Concrete Utility Vaults

Placement (Cont.) Prior to placement the structure s orientation should be confirmed. Inlet penetrations aligned in the proper directions. After placement, ensure the structure is level.

Joints For the manufacture of utility vaults, it is recommended that only interlocking joints be used. Typical joints include lap joints or tongue and groove joints. In cases of frost heave, differential settlement and ground water exposure, mechanical fasteners or secondary pours may be necessary

Joint Sealants High quality, flexible joint sealants and/or wraps can be used to achieve a dependable seal. Some characteristics: Workability over a wide range of temperatures Adhesion to clean, dry surfaces Good Performance over time (no shrinkage) Sealants should conform to ASTM C990 and be applied per manufacturers recommendations.

Installation Proper Installation Proper application of joint sealants Joint Sealant

Installation Different applications depending on nature of tank

Installation Joint Installation Guidelines

Installation Recommended Practice

Backfilling Place backfill in uniform, mechanically compacted layers. Layers should be less than 24 thick. Backfill material should be free of large stones (greater than 3 in diameter) and other debris.

Wrap-Up Questions??? Specifying Design Shipping Handling Installation

QUESTIONS PRECAST CONCRETE UTILITY STRUCTURES

To Sum It Up Our Precast will make YOU Look Good!