Barnhart Constructors, Inc. TX Registration #F‑669
Barnhart Constructors, Inc.
In addition to our bridge design capabilities, Barnhart Constructors is also a fully qualified bridge inspection firm.
We have managed over 30 Bridge Inspection projects as prime provider, and more as an authorized sub provider, in 113 Texas Counties, under the FHWA Bridge Inspection program.
In addition to the “TxDOT On-System Load Rating Spreadsheets”, and the “Texas Bridge Load Rating Programs” (Off-System), our staff uses design programs, spreadsheets, and hand analysis to rate bridges in accordance with the AASHTO “Manual for Condition Evaluation of Bridges”.
A rather unique inspection experience occurred in 2002 when Barnhart Constructors was contracted to inspect and load rate 7 bridges in Chad, Africa. We evaluated, selected and purchased equipment necessary to investigate and field inspect the seven bridges. We then determined load capacities and developed safe transport procedures for the 96,000 Kg loads.
The Third River is a canal with locks, designed for barge transportation, and to drain surrounding marshlands, enabling development of massive oilfields. There are few road crossings of the Third River. Bridge K44 is 44 km from the locks; approximately 40 km west of the nearest crossing, in Basra. Bridge K44 has 4 mild reinforced approach spans of 16.5m each, and 2 prestressed main spans of 33m each.
We found massive damage to span 2 from the south. The center two spans consist of prestressed beams; in very good condition, with minor damaged to deck and rails. The north 2, and south 2 spans are mild reinforced; the north 2 spans had recently been replaced, utilizing timber forms on temporary fill. Substantial honeycombs existed in soffit of a few of these beams, enabling visual verification of profometer reinforcing measurements. The south span had 4 original and 3 replacement beams; the replacement beams apparently installed following the first gulf war. Span 2 from south consisted of 7 original beams; beams 4, 5 and 6 had severe damage, with related large holes through the deck. Replacement plans for the beams had been started, we reviewed those plans and incorporated them into complete plans, specifications, and estimates for the bridge. The bridge has since been fully repaired.
The swing bridge consists of 7 spans; 3 simple prestressed concrete beam spans, 2 span continuous steel girder swing unit, and 2 simple prestressed concrete beam spans. We carefully measured each element of the steel girder unit. We field measured the sections of prestressed beams, and used a profometer to determine prestressing strands and mild shear reinforcement. We verified shear reinforcement in areas with spalls. We verified prestressing strands by inspecting a nearby (abandoned) beam fabrication yard. We inspected rejected (broken) beams of identical section and length, obtaining detailed verification of our bridge inventory findings. We also obtained steel samples for further testing, if needed.
The prestressed spans, having numerous beams at close spacing, are much stronger than the steel swing unit. Its two girder system, while capable of two lane HS-20 truck service, lacked the ability to carry planned permit loads of up to 100 tonnes. We designed steel shoring towers to provide temporary support to the spans for heavy transport. The steel supports may be removed if the planned canal is excavated; they provide support to the swing girders through elastomeric bearings.