AASHTO T4 2016 Agenda Items Proposed Revisions to LRFD BCS Section - PowerPoint PPT Presentation

AASHTO T‐4 2016 Agenda Items Proposed Revisions to LRFD BCS Section 11 Jeff Carlson, P.E. West Regional Director ‐ NSBA Denver, CO

Before We Start Need to emphasize that these proposed revisions are • for 2016, not 2015. Recognize that a new Bolt Specification is now available • and eventually needs to be incorporated. ASTM F3125 is a new structural bolt specification replacing six • existing ASTM specifications; A325, A325M, A490, A490M, F1852 and F2280.

Agenda Item Articles C11.5.6.4.1, 11.5.6.4.2, C11.5.6.4.2, & 11.10 • Issues: • The definition of “snug tightened” needs to be updated. • Lock pin and collar type fasteners are no longer used. • Twist ‐ off bolts and bolts installed using a DTI or captive DTI/nut do not rely upon the inelastic strength and ductility of the fastener; therefore the rotational capacity test does not apply. • Required steps in the rotational ‐ capacity test need to be reorganized for greater clarity. • A reduced rotation requirement from the snug condition is needed for bolts longer than 8 diameters in the rotational ‐ capacity test. Doubling the rotation for the longer bolts would require extensive inelastic deformation of the bolt threads, much larger than that required in shorter bolts.

Agenda Item Articles C11.5.6.4.1, 11.5.6.4.2, C11.5.6.4.2, & 11.10 (cont.) Description of Proposed Revisions: • • Article C11.5.6.4.1 – Revised the definition of “snug tightened” per Research Council on Structural Connections (2014). • Article 11.5.6.4.2 – Removed lock ‐ pin and collar type fasteners and added DTIs, captive DTI/nuts, and twist ‐ off bolts to the list of exceptions for rotational capacity testing. • Article C11.5.6.4.2 – Added paragraphs that explain the rationale for not including DTIs, captive DTI/nuts, and twist ‐ off bolts in the requirements for rotational capacity testing. • Reorganized Rotational Capacity Testing procedures in Article 11.5.6.4.2 by adding subsections for general testing requirements, requirements for “long” bolts, requirements for “short” bolts, and revised the additional rotation requirement for longer bolts.

Agenda Item Articles 11.3.2.6, C11.3.2.6, 11.5.6.4.7, and C11.5.6.4.7 Issue : • • Due to recent changes in DTI specifications regarding the relationship between size and number of protrusions, revisions are proposed to align AASHTO with current DTI manufacturing practices. Description of Proposed Revisions : • • Article 11.3.2.6 – Changed article heading to Direct Tension Indicators and made editorial revisions. • Article C11.3.2.6 – Revised language to clarify the definitions of DTIs, captive DTI/nuts, and self ‐ indicating DTIs. Also added commentary regarding different Owner policies on self ‐ indicating DTIs.

Agenda Item Articles 11.3.2.6, C11.3.2.6, 11.5.6.4.7, and C11.5.6.4.7 (cont.) Description of Proposed Revisions : • • Article 11.5.6.4.7 – Revised language regarding the proper method of initially installing a DTI. • Article 11.5.6.4.7a – Revised language pertaining to the verification testing of DTIs. Revised Table 11.5.6.4.7a ‐ 1 (Verification Tension), and added Table 11.5.6.4.7a ‐ 2 (Refusal Requirements). • Article C11.5.6.4.7a – Added language to better clarify the revisions in the corresponding article and the revisions/additions to the two Tables. Also provided commentary explaining why a thread test is required for DTI verification and not for any other bolt installation method. • Article 11.5.6.4.7b – Revised/streamlined language pertaining to the tightening/tensioning of fastener assemblies using DTIs.

Agenda Item Articles 11.3.1.1 and 11.10 Issue: • • The AASHTO Guide Specification for Highway Bridge Fabrication with HPS70W is now incorporated directly in the AASHTO/AWS D1.5M/D1.5 Bridge Welding Code and no longer needs to be referred to in the AASHTO LRFD BCS. Description of Proposed Revisions : • • Article 11.3.1.1 – Deleted the last paragraph in this section referring to AASHTO Guide Specification for Highway Bridge Fabrication with HPS70W . • Article 11.10 – Deleted reference to AASHTO Guide Specification for Highway Bridge Fabrication with HPS70W .

Agenda Item Articles 11.3.1.7 and C11.3.1.7 Issues: • • A1085 is more suitable for dynamically loaded structures; specifies a minimum CVN value of 25 ft ‐ lbs at 70°F (Zone 2) . • Tighter material tolerances in A1085 will result in more area available for design. • CFSTs were added to AASHTO LRFD BDS in 2015 and need to be added to the AASHTO LRFD BCS for completeness. Description of Proposed Revisions : • • Articles 11.3.1.7 and C11.3.1.7 – Added the recently adopted ASTM A1085 Standard Specification for Cold ‐ Formed Welded Carbon Steel Hollow Structural Sections (HSS) to the approved list of materials for structural tubing in the AASHTO BDS. Added provisions for steel tubing used with Concrete ‐ Filled Steel Tubes (CFSTs).

Agenda Item Articles 11.4.8.1.1 and C11.4.8.1.1 Issues: • • Larger hole sizes for bolts greater than or equal to 1 in. in diameter are needed to eliminate field reaming in order to fit large ‐ diameter hot forged bolts, which often have a longitudinal forging seam that interferes with holes 1/16 in. larger than the bolt diameter. • AISC is in the process of making a similar revision to their specification, and Europe is taking a similar approach. Description of Proposed Revisions : • • Article 11.4.8.1.1 – Added provisions to state that for bolts larger than or equal to 1 inch in diameter, the width of each standard hole shall be the nominal diameter plus 1/8 inch.

Agenda Item Articles 11.5.6.4.1 and C11.5.6.4.1 Issue: • • Twist ‐ off bolts rely on a controlled torque ‐ to ‐ tension relationship, and field relubrication with an arbitrary lubricant destroys that relationship. Description of Proposed Revisions : • • Article 11.5.6.4.1 – Added language stating that twist ‐ off bolts shall not be relubricated, and shall be discarded if the lubrication is compromised.

Agenda Item Articles 11.5.6.4.1 and C11.5.6.4.1 (cont.) Issues: • • Tolerances on the rotation of the turned element during bolt installation should be changed to correspond with the more liberal plus and minus nut rotation tolerances given in the 2014 RCSC Specification. • Bolt tension in the inelastic range is not very sensitive to rotation, however AASHTO and some DOTs have changed to plus tolerance only in order to be conservative. Description of Proposed Revisions: • • Article 11.5.6.4.1 – Revised language in the 1 st paragraph after Table 11.5.6.4.1 ‐ 2 regarding nut rotation tolerance to correspond with the tolerances given in the 2014 RCSC Specification.

Agenda Item Article 11.5.6.4.8 Issue: • • Lock ‐ Pin and Collar Fasteners are no longer used. Description of Proposed Revisions : • • Article 11.5.6.4.8 – Deleted this article related to Lock ‐ Pin and Collar Fasteners and renumbered subsequent Articles.

Agenda Item Articles 11.4.8.4, 11.5.5, 11.5.5.1, and 11.5.5.3 Issue: • • Ribbed Bolts are no longer used. Description of Proposed Revisions : • • Articles 11.4.8.4, 11.5.5, 11.5.5.1, and 11.5.5.3 ‐ Deleted all references to ribbed bolts.

Agenda Item Articles 11.3.2.5, 11.5.6.1, C11.3.2.5, 11.5.6.4.1, 11.5.6.4.3, 11.5.6.4.6, and C11.5.6.1 Issue: • • ASTM F1852 and F2280 specifications have existed for several years and need to be included in the construction specification. Description of Proposed Revisions : • • Articles 11.3.2.5, 11.5.6.1, C11.3.2.5, 11.5.6.4.1, 11.5.6.4.3, 11.5.6.4.6, and C11.5.6.1 ‐ Revised language to refer to the ASTM F1852 and F2280 specifications for twist ‐ off fasteners, which are the twist ‐ off equivalents of A325 and A490 bolts, respectively.

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