See the BGS Support Information document, linked in the same manner as the BGS User Guide, for instructions on how to report bugs and wishes about program functionality or get technical support. Technical support is available to all TxDOT BGS users and any consultant BGS users designing bridges for TxDOT.IMPORTANT NOTE: This 2/20/2020 release of BGS, Version 9.1.6 is a technical release intended to address Windows 10 compatibility and the false positives for malware by malware scanning software issues. The false positive for malware issue has persisted since shortly after the 02/12/2016 posting of BGS 9.1.6, as malware detection software began becoming increasingly more sensitive. The repackaging of the installer includes revised names and content for some documentation. The functionality of the compiled elements of the BGS software have not changed, hence the compile program version remains 9.1.6.
This TxDOT-customized version of PGSuper is versatile, user friendly, Windows-based software for the design, analysis, and load rating of multi-span precast-prestressed concrete bridge beams/girders in accordance with the AASHTO LRFD Bridge Design Specifications (thru the 9th Edition, 2020) and by TxDOT design policies and guidelines. Properties of TxDOT standard I-girders (TxGirders), U beams, slab beams, decked slab beams, box beams, and X-beams and TxDOT specific design criteria are included in templates and libraries published by TxDOT on a server accessible via the Internet. Thus, the software is capable of periodically updating the installed templates and libraries with the most current versions published by TxDOT. Though these templates and libraries are subject to change, the user may save PGSuper project data with its associated templates, libraries and settings in a .pgs file which can subsequently be opened by PGSuper preserving the templates, libraries, settings and design data of the bridges as originally designed.
See the PSTRS14 Support Information Document, linked in the same manner as the PSTRS14 v6.1.1 User Guide, for instructions on how to report bugs and wishes about program functionality or get technical support. Technical support is available to all TxDOT PSTRS14 users and any consultant PSTRS14 users designing bridges for TxDOT.
Bridge designers and constructors are always concerned with preserving their bridges for as long as possible. To combat the amplification of stresses and to offset the potential of harmonic amplification of the bridge deck, the designers installed shear keys in the new design of the eastern bridge span. Shear keys are blocks of concrete supported by large diameter bolts that are made from ASTM A354 Grade BD material in diameters from two to four inches and have been hot-dip galvanized.
The shear keys dampen the seismic energy transmitted to the bridge deck and help prevent damage during an earthquake. They are not intended to support the bridge deck itself but merely play a role in the suppression of forces during a seismic event. Each bolt within the shear key is heat-treated to meet the minimum specification of mechanical properties, and hot-dip galvanized to provide corrosion protection. These bolts were used throughout the Bay Bridge design, not just in the new shear key installation. These anchor rods, A354BD, are specified to have an ultimate tensile strength (Fu) of a minimum of 140,000 psi for bolts with diameters above 2.5 inches and a hardness range of a minimum of 31 HRC and a maximum of 39 HRC.
Figures 2a and 2b show the placement of the anchor rods used for the shear keys when the bolts were first put into place in the Pier E2 location. The anchor rods were installed into the shear keys in November 2008, and grouting of the rods began in January 2013. However, these anchor rods were not tensioned until March 2013 because they could not be installed until the superstructure of the bridge was put in place. Because of this, the very bottoms of the anchor rods were purposely damaged to hold the nuts until they could be properly tensioned. The top of the steel pipe sleeve assemblies holding the shear key rods were exposed to the environment during the period before the superstructure of the bridge was installed. This left little clearance between the top of the rods and the bottom of the bridge.
Once the superstructure of the bridge was erected in 2013, and the load transfer was completed, the anchor rods were pre-tensioned to 70% of their minimum specified ultimate tensile strength (Fu). After the first two weeks of tension, 32 of the 96 anchor rods had fractured, all occurring at or near the threaded engagements towards the bottom of the rods. Once the pre-tension level was reduced to 40% Fu, failure of the rods ceased. This resulted in the decision to abandon all 96 of the rods. An alternative anchoring system was successfully designed and installed.
This investigation, which began shortly after the tensioning of the shear key rods, included performing metallurgical testing and failure analysis on the rods. It was conducted by three investigators: Salim Brahimi, President of IBECA Technologies and Chairman of the ASTM F16 Committee on Fasteners; Rosme Aguilar, Branch Chief of Cal Trans Structural Metals Testing Branch; and Conrad Christensen, Principal and Founder of Christensen Materials Engineering. The design of the bridge created a very low clearance between the rods and the superstructure of the bridge. For testing to continue, the rods had to be removed in small sections by pulling them up as far as possible and sawing them off. This process was very extensive, so only a few rods ultimately were removed for the study.
After the results of the initial analysis on the A354BD rods had shown signs of hydrogen embrittlement, the various parties responsible for the bridge design were concerned about the potential of hydrogen embrittlement in other A354BD rods throughout the rest of the bridge. Therefore, another study was initiated to test rods throughout the bridge. A variety of rods of different sizes, tension levels, and locations were selected for detailed laboratory testing to determine chemical composition, hardness, and susceptibility to hydrogen embrittlement. All mechanical property tests showed that material properties were generally uniform and within specification requirements. Another Charpy impact toughness test was conducted which showed toughness levels of the majority of the rods within the normal ranges for the material. Only the tests on the samples of the 2008 rods showed lower toughness values.
Following the Townsend Test, the Raymond test was conducted on two types of small specimens cut from full-size rods. This test is a slow, rising step-load laboratory bend that allows for an examination to determine the susceptibility to hydrogen embrittlement. The results were consistent with the Townsend Test and again proved the failure was a result of hydrogen embrittlement based on their exposed environment, not internal hydrogen. The main results of the study were as follows: the 2008 rods failed by hydrogen embrittlement at the same load (0.70 Fu) that resulted in failure on the bridge. The outcome provided independent confirmation of the result obtained with full diameter rods.
In conclusion, there was no indication that the galvanizing process contributed in any way to the failure of the rods from 2008. The low hydrogen embrittlement threshold of the failed rods was likely due to fabrication methods and thermal treatment of the rods. The results of this study indicate the Bay Bridge rods installed in 2008 failed because of environmentally induced hydrogen embrittlement caused by tensioning above their threshold while simultaneously immersed in water. This created the perfect environment to introduce hydrogen into the steel. There was no evidence that hydrogen was present in the steel before installation or tensioning, nor that internal hydrogen contributed to the A354BD rod failures. The Townsend Tests performed on the A354BD rods confirmed that, without the presence of water, the rods would not have failed. All of the remaining rods on the bridge were tested and proved to have hydrogen embrittlement thresholds higher than their pre-tensioned stress levels and were concluded as safe. The remaining rods were designed to have supplemental corrosion protection measures that include dehumidification, paint systems, or grout. All of these measures will prevent corrosion and the possibility of hydrogen embrittlement as long as the galvanized coating remains intact.
High performance fiber reinforced concrete is developing quickly to a modern structural material with a high potential. As for instance testified by the recent symposium on HPFRC in Kassel, Germany (April 2008) the number of structural applications increases. At this moment studies are carried out with the aim to come to an international recommendation for the design of structures with HPFRC. Research projects are being carried out in order to supply missing information in relevant areas. Some examples of recent research at TU Delft are given. For the preparation of an internationally acceptable design recommendation for HPFRC a number of principles should be respected. The code should as much as possible be in harmony with the code for conventional fiber concrete. Moreover it should be consistent with existing design recommendations for structural concrete. Second thoughts on the introduction of such a new code are given.
High performance fiber reinforced concrete is still a material for which no internationally accepted design recommendations exist. Partially this is due to insufficient information with regard to the properties of the material. An example of this is the durability of high performance concrete. Designing thin-walled structural elements applying reinforced or prestressed HPFRC allows slender and large span structures. If in such structures large covers would be necessary, the advantage of using HPFRC would significantly be reduced. Research results on the durability of HPFRC are, however, very encouraging, see e.g. Schmidt  and Scheydt . In comparison with existing codes for structural concrete new design aspects have to be added. Light, large span, elegant and material saving structures in HPFRC are for instance only possible if reliable rules for control of fatigue loading are available. Other aspects of significance in design are crack width control and the possible use of steel fibers as shear reinforcement. However, it is not only important to have design rules for such phenomena, but as well to have design rules which are as much as possible compatible with existing codes for structural concrete. This would be most advantageous for the development of hybrid structures based on combinations of traditional reinforcement, prestressing steel and fibers. This is expected to become a large field of application. Moreover it would simplify the work of the structural engineer if he could consist of a set of design relations valid both for FRC and HPFRC which could be combined with the existing rules for reinforced and prestressed structures. Therefore it should be investigated if existing international code rules, like e.g. the Eurocode on Concrete Structures, could be extended to include the application of fibers. 153554b96e