The SH 249/SH 99 interchange in Northwest Houston implements a unique girder type on two new direct connectors. The curved spliced concrete U-girder system has been used in other states such as Colorado, Florida, and Utah, but the bridges at 249/99 are the first of its type to be constructed in Texas. The continuous girders offer an alternative to curved steel girders, which comes with both advantages and challenges throughout the design, construction, and maintenance phases of the project. The presentation will include an overview of the project including aerials and schematic views of the interchange, as well as some of the design challenges that were encountered throughout the engineering and construction of the bridges. Unique details and structural analyses will be discussed, as well as in-depth design procedures followed for one of the 4 continuous girder unit designs. Design engineers from LJA Engineering, Modjeski & Masters, and Costello Inc. designed four continuous curved spliced concrete U-girder units within two new direct connectors at the interchange. The owner of the project is Harris County Toll Road Authority (HCTRA), the contractor was Williams Brothers Construction. Both direct connectors are currently open to traffic.
David Pretorius PE
Senior Structural Engineer