Information for Engineers
The HCB comes in several different forms depending on the Project needs. They are:
- Single-web box beam, usually 2 feet wide by the required depth. For standard highway loads, these beams can span up to 85 feet.
- Double-web box beam – a trapezoidal box beam for spans 80 feet and longer or heavy loads.
- Triple-web box beam for railroad loadings.
- HCB Pile Cap – 3 foot or 4 foot wide, designed to set on two or more columns or piles.
- All of these different shapes can be pre-filled either on-site prior to setting or at a precast facility near the jobsite.
- The HCB Prefabricated Bridge Module – Ideal for Accelerated Bridge Construction, these pieces are pre-filled and include a concrete deck. In addition, parapets, railings or other appurtenances can be added to greatly reduce the overall construction time.
- Design loads: As with any structure, the design loads including; self-weight, dead load, superimposed dead load and live load, must be determined. The responses from these loads can be analyzed using the appropriate load factors and load factor combinations as contained in conventional bridge specifications such as AASHTO or AREMA.
- Deflection criteria: Where required by code, the HCB must be checked for live load deflections. This serviceability limit state typically governs design.
- Live load distribution: Are there different distribution factors based on material? The live load distribution factors from AASHTO and AREMA bridge design specifications are applicable to the HCB. A more rigorous analysis is not required for a code compliant design.
- Multi-span continuity: HCB bridges can be made continuous for live loads by placing negative moment reinforcing steel in composite concrete deck in the same manner as a prestressed concrete beam. Typically a cast-in-place concrete diaphragm is cast between the beams at pier locations to transfer the compression forces from the continuous moments.
- Conventional linear elastic design assumptions hold true for the analysis of an HCB structure.
- Limit states design: The ultimate capacity of the HCB in bending can be calculated using strain compatibility and force equilibrium in the same manner as a reinforced concrete beam. The ultimate shear capacity combines the resal’s effect of an arch structures with the tension field action of the FRP laminate with the shear capacity of the concrete to provide exceptional shear resistance.
LOAD RATING: Load ratings can be performed for HCB structures using conventional design vehicles as well as permit vehicles. As the deflection limit state typically governs design, the HCB typically has considerable reserve capacity for strength.
INSPECTION: A zero to nine rating criteria has been developed for the HCB to be consistent with the United States NBIS standards for bridge health evaluations. Guidance for visual and NDE techniques for inspection of HCB bridges are contained in the HCB Inspection and Maintenance Manual.
HCB Preliminary Sections
The links below provide you with preliminary sections for Highway and Railroad Bridges.
HCB Design Manual
The HCB Design Manual explains the theory behind the limit states for design of the HCB and provides the tools necessary for Engineers to complete the design of an HCB structure.
HCB DESIGN MANUAL COMING SOON
HCB Inspection and Maintenance Manual
The HCB Inspection and Maintenance Manual provides engineers and owners of HCB structures with sufficient information regarding the techniques and methods for the inspection and maintenance of the HCB so that they can maintain safe operability of the HCB bridge over the duration of its service life.
HCB Sample Specifications
The Sample Specifications for the fabrication and installation of the HCB are a good starting point for developing specifications for each project. They include material properties, manufacturing requirements, etc. Contact us for the right sample specification for your project.
Need assistance with a design? Need drawings for inclusion in plan sets? Need assistance finalizing a specification? With these questions or anything else, please contact us.