**Executive Summary Report:**

**FHWA Bay Bridge Pile Connection Plate Welding Investigation**

**By John W. Fisher PhD, PE**

Following is a brief summary of my findings on the partial penetration
welds that connect the vertical pile head shear plates to the pile
sleeves in the steel foundation boxes which were alleged to be
improperly made.

Examination of the Contractors QC and Caltrans QA requirements
demonstrated that the job conformed to the AWS specifications and
exceeded those used in most states. The welds were machine made with
E71T-1 flux core electrodes which was found to produce welds with
excellent notch toughness and strength. QC and QA throughout the welding
of each connection resulted in a portion of each weld pass being
visually examined. The root pass and the cap passes were all magnetic
particle inspected.

Although early in 2003, problems developed with the highly restrained
joints in the shear plate to pile and pile sleeve connections as a
result of hydrogen cracking and brittle fracture when the crack extended
into the pile or pile sleeve base metal, those problems were corrected.
The welding equipment was replaced, run-out tabs were used at the access
holes at the ends of the connection plates to start and stop each pass
of the PJP welds, and increased preheat was provided at the bottom end
of the connection to offset heat loss. After welding, the run-off tabs
were removed and the access hole areas profiled and ground smooth to
insure removal of unacceptable discontinuities. The access hole base
metal was also ultrasonically tested to insure that no unacceptable
discontinuities remained. These procedures have prevented subsequent
fractures.

Our site visit to Pier E4W provided a first hand look at connections in
a variety of conditions. This ranged from a joint with only the root
pass and the welding machine and heating pads in place; several
connections with the run-off tabs removed after welding and the access
holes shaped by torch, to a connection with the access hole region
ground smooth. None of the connections were indicated to have had the
QC/QA completed. The physical appearance of all weld passes was normal
and characteristic of vertical up welding.

The limit states of the pile, pile sleeves, connection plates and the
partial penetration joint welds were evaluated. That demonstrated that
the partial joint penetration welds had a shear capacity that exceeded
the yield force that the pile and connection plates could deliver to the
welds by a substantial margin. Furthermore, weld qualification tests
indicated that the weld metal had high values of notch toughness and
would be very resistant to fracture from assumed large cracks.

The results of the field inspections and the destructive examination by
Mayes Testing Engineers of the full depth weld samples removed from Pier
W4E at Pile 2B, Pile 3G and Pile 5D demonstrated that the welds showed
excellent workmanship and no evidence of major and unacceptable
discontinuities.

It was concluded that:

1.) The weld quality provided in the steel footing boxes for the
connection of the steel piles to the pile sleeves was found to be very
good. The QC/QA provided by this project equals or exceeds that required
by most states.

2.) The partial joint penetration welds (PJP) used to connect the
vertical pile head shear plates to the piles and the pile sleeves are
very conservative in their design. Their design limit state exceeds the
shear yield capacity of the connection plate and the maximum yield
capacity of the pile by over 100%.

3.) Weld qualification test data demonstrate that the E71T-1 weld metal
provided high levels of fracture toughness. Normal fabrication defects
and even a 1/4in. deep crack in the weld metal at the access holes
region would not result in crack instability if subjected to yield level
loads during an earthquake.

4.) The pile cap design provides a very high level of redundancy with
many alternate load paths. There should be no concern with the capacity
and performance of the steel pile pier caps and their welded
connections. Even if a fracture occurred in one of the shear plate
welds, the other weld could still transfer the load to the shear plate.

5.) Traffic loads will produce negligible cyclic stresses in the
concrete encased, concrete filled steel pier caps. There is no
possibility of fatigue crack extension from cyclic loads in service. The
cycle frequency from earthquakes is infrequent and will not enlarge any
defect in low cycle fatigue, since millions of cycles are required for
cracks to form and propagate.