ON THE EFFECTS OF CIRCULAR BOLT PATTERNS ON THE ...

The instrumented bolts were connected to the data acquisition system and the shunt of the Wetson-
Bridge was zeroed and calibrated while the bolts were in a relaxed state. The LVDTs and load cell were
connected to the data acquisition system and all the readings were set to zero. The bolts were then
tightened, using a calibrated torque-wrench to the proof load specified by the LRFD design manual [1]. A
cross-pattern tightening sequence was used. The bolts were pre-tensioned in two steps to prevent the
damage to the bolts and the instrumentation. The two pieces of the T-Stubs were pulled together in the
first step of bolt tightening, and the proof load was applied on the second step.
A monotonic load was applied on to the specimen at approximately5kips/min. The specimens were
loaded to failure. The observations were documented and the photographs were taken while the test was
in progress.
3.2.6 Test Results
As mentioned before, the main scope of this experimental study was to investigate the behavior of
the T-Stubs under various bolt pattern configuration. In addition, the data collected in this section was
used to validate the results of the numerical models in Chapter-4.
Table 3-2 shows the summary of the test results. The tensile yield forces presented in this table are
determined by using a bi-linear curve fit of the T-Stubs data. In addition, the flange separations versus
the applied force for three specimens are presented and compared in Figure 3-14. The first line
represents the initial stiffness of the T-Stubs and the second line represents the post-yield stiffness. The
intersection of the two lines is considered as the yielding tensile force; thus, the corresponding flange
separation is recorded as flange separation at yield (∆y). The ultimate tensile force (Pu) is the maximum
tensile force resisted by the specimen, and the maximum flange separation was reported as ∆u in this
table.
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