AASHTO Bridge Code 3.24

Distribution of Loads and Design of Concrete Slabs

‘For simple spans, the span length shall be the distance center to center of supports but need not exceed clear span plus thickness of slab’.

An engineer should ask their client a series of questions when designing a precast concrete slab which requires any type of opening.

  1. What loads are going to be applied to the structure?
  2. What is the weight of the fill or stone over the structure?
  3. What does the foundation below the structure consist of?
  4. Will there be vehicular traffic driving over or parked on the structure?

It Is All About the Load Path!
To achieve a quality design, it is crucial the design follow a load path from the point of origin to the final support or foundation. Delta Precast recommends and utilizes the AASHTO Bridge Code 3.24 as the design standard when designing precast slabs with any type of opening. Using the bridge code is a conservative approach and provides a measure of safety for any type of application scenarios.


What is a Load Path?
The load path is simply the direction in which each consecutive load will pass through connected members. The sequence commences at the highest point of the structure working all the way down to the footing system, ultimately transferring the total load of the structure to the foundation.

What is Shear Strength?
The shear strength is the load that an object is able to withstand in a direction parallel to the face of the material, as opposed to perpendicular to the surface.