Fyi _____ From: Jerry Holder To: Nancy Cline Sent: Sun Aug 23 19:25:30 2009 Subject: FW: Vitruvian Park Bridges Nancy, here is the response I received from our bridge guys. Might not be what you wanted to hear, but they are our thoughts. Let me know if you want to discuss. Jerry _____ From: Daniel Chapman Sent: Friday, August 21, 2009 2:31 PM To: Jerry Holder Cc: Mark Baker Subject: FW: Vitruvian Park Bridges Jerry: I reviewed the bridge plans with Mark. While they do reference AASHTO and TxDOT Specifications, none of the details in the plans reference TxDOT construction items. We would not be comfortable performing construction observation on these plans. While we can’t say with this cursory review that anything is wrong, we can say this set of plans appears to have been prepared by someone without vehicle bridge engineering experience. Many of the details are not consistent with current bridge design practices. For example, steel on steel bearings and using solid steel bars for hanger rods. We also noted that the plans are void of any hydraulic data outside of showing the water surface elevation on the bridge elevation drawing. There may be a separate drainage report but it is typical to include this information in a set of bridge plans. We strongly recommend the City have a independent design review performed on the vehicle bridges. Please call if you want to discuss further. Dan From: Mark Baker Sent: Wednesday, August 19, 2009 3:42 PM To: Daniel Chapman Subject: Vitruvian Park Bridges Dan, As requested, I have completed a very brief review of the Vitruvian Park bridge plans. My observations and comments are as follows: Bridge Descriptions · The plans show three proposed bridges in Vitruvian Park: Ponte Avenue Bridge, Bella Lane Bridge, and Southern Pedestrian Bridge, all crossing Farmer Branch Creek. The Ponte Avenue and Bella Lane bridges are two lane vehicular bridges with large sidewalk areas on both sides. · Ponte Ave and Bella Lane bridges are both to be 139.5’ single span arch bridges, 70’ wide. The vehicular and pedestrian traffic is carried on a cast-in-place (CIP), transversely post tensioned, deck varying in thickness from 13” to 19”. Vehicular traffic is separated from pedestrians by a pair of 30” square CIP barriers, which also act as longitudinal beams and connections for the 2.5” diameter hanger rods on 10.16’ centers. These rods hang from a pair of arches that will be 40” wide x 28” deep box sections, fabricated from steel plate. · The pedestrian bridge is to be a 150’ single span, truss bridge. The pair of steel trusses uses a combination of wide flange and tube sections and is roughly 19’ deep. The 9” thick by approximately 16’ wide concrete deck carries pedestrian traffic. Potential Problems and Recommendations · HNTB should recommend a peer review of these designs. · Although both AASHTO and TxDOT specifications have been specified, the designs and plan preparation do not follow conventional TxDOT methods. TxDOT construction specifications and bid items are not used. · The arch designs may be fracture critical. The arches are not connected or laterally braced. The arches appear to have no barriers to protect from vehicular impact (there is an inclined concrete thrust block which could serve to launch a vehicle up onto the arch). Failure of either arch could result in the collapse of the bridge. · Hangers are solid rods and may be fracture critical as well. No description of hanger replacement was noted. · The bearing connections are not typical (no neoprene pads). Steel on steel bearings typically do not perform well. · The foundations for the arch and abutment walls use 24” and 30” diameter drilled shafts that are inclined 30 degrees to resist lateral thrusts. This may pose constructability issues and may increase cost compared to vertically constructed shafts. Foundations (top of shafts) are located above flow line (scour potential). Mark D. Baker, PE Senior Structural Engineer HNTB Corporation 5910 West Plano Pkwy, Suite 200 Plano, TX 75093 Tel: 972.661.5626 Direct: 972.628.3091 Fax: 972.661.5614 www.hntb.com This e-mail and any files transmitted with it are confidential and are intended solely for the use of the individual or entity to whom they are addressed. If you are NOT the intended recipient or the person responsible for delivering the e-mail to the intended recipient, be advised that you have received this e-mail in error and that any use, dissemination, forwarding, printing or copying this e-mail is strictly prohibited.