15-Deliberate and possibly act on a resolution supporting an application to the Texas Department of Transportation to acquire the historic Goodman rainbow truss bridge from Angelina County

Home Browse Search

Historic Bridge Load Rating Report District: Lufkin County: Nacogdoches Bridge Number: 11-1740-A.A05-10-002 Roadway: CR 789 Feature Crossed: Angelina River 53562 r4 Analysis Notes. HS laad ratings were calculated at inventory and operatuig leveLs. The load factor method was used to rate the truss members, huss member connections, floorbeams, and steel suingers. The allowable load method was used to rate the timber deck. Load Ratings were based on dimensions, member cross sections, and connections details deternuned from field measurements. See Tcuss Member Listing Worksheet for a sketc6 of the truss, a Iisting of truss members and connection data, and calcularions of truss dead load and distribution factor for live load. Truss member loads were analyzed using RISA-313 Version 5.5. Since the truss is staticalIy determinate and deflections are not cansidered in the analysis or nting, unit properties were used for every member in the analysis. Analysis results were used in a modified version of a spreadsheet developed by TxDOT to calculate truss member ratings. Stee} floorbeams were rated using a modified version of the T7cDOT Load Rating Spreadsheet. The modified version uses routines for the HS nting of steel stringers with tive load calculations modified to madel floorbeam parameters. Sbeel stringers were rated using the TxDOT Load Rating Spreadsheet with an added calculation for pedestrian loadi.ng. Stringer spacing and deck tluckness were adjusted to correct for the difference in unit weights and distribution factors between concrete and timber decics. T'he timber deck was rated using the Texas Briclge Load Rating Program. The following additional assumptions were made based on engineering judgment: • Truss upper chord lateral stability is not a factor. • Foundation capaciries are not relevant to the analysis since original and proposed foundations are unlmown. • Original and proposed stringers are assumed to be 57 x 15.3 steel beams. Field measurements indicate origiaa] stringer spacing = 2'-7". An As-Built Vehicular Load Rating was done assuming no deterioration of structural members. The rating results do not meet the ininimum operaring load capacity of HS 15 required for continued use by vetucular traffic at this site. Current Condition Vehicular and Pedestrian Load Ratings were done based on estimated section losses of 5% for steel truss members and fioorbeams. Steel shiugers and tunber deck for the proposed (current) rehabilitated bridge are assumed to be new material or salvaged materiai with no deterioration. Rating Summary: As-Bailt Member Vehicular Load Rating Inventorv Oneratine Truss HS 14_3 HS 23.9 Floorbeam HS 8.4 HS 14.1 Truss Stringers HS 3.9 HS 6.5 Deck HS 14.5 HS 21.7 Overall Ratings HS 3.9 HS 6.5 Existing Bridge Ratings (Piling Contro() Current Condition Vehicutar Load Raling Inventorv Oaeratine HS 13.6 EiS 22.7 HS 7.9 HS 13.2 H5 4.8 HS 8.1 HS 14.5 HS 21.7 HS 4.8 RS 8.1 HS 9.1 HS 12.8 Current Condition Pedestrian Load Rating Inventon Ooeratine P 60 P 100 P 96 P 160 P 145 P 241 N/A N/A P 60 P 100 Comments: The original truss on this bridge remains in fair condition but does not meet the minirnum HS 15 operating load capacity required for cantinued vehicular use at this site. The bridge does meet the minimum P SS operating load capacity required for use as a pedestrian bridge. Refer to the Historic Bridge Condition Srrrvey Report for a list of work iterns thai should be considered if long-term preservation or rehabilitation of the original huss is needed. jt (7