Performance of large size reinforced concrete beams containing a lap splice subjected to fatigue loads
Date
1990-06-01
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Degree Level
Masters
Abstract
Extensive research has been conducted into the areas of
low cycle high stress loading (seismic loading) and static
loading of reinforced concrete beams containing lap splices.
The knowledge acquired from this research has led to
recommendations for changes in how seismic and static
loading of lap splices are handled.
For splices subjected to high cycle low stress load
patterns (fatigue loading) current design of lap splices is
very similar to that used for statically loaded splices,
even though little research information is available on
performance of lap splices under high cycle fatigue,
particularly for larger size bars and members. With this in
mind a testing programme was initiated to determine the
effects of fatigue on the performance of lap splices
proportioned and confined with transverse reinforcing steel
according to the ACI Committee 408 recommendations for
tensile static loading. In the test programme described in
this report, only short lap lengths with heavy transverse
confinement were investigated.
Specimens used in this study were 7 m long with a 330
mm x 508 mm cross-section. Equal loading is applied at two
points symmetrically placed two meters apart on the simply
supported beam. Reinforcement consists of 2 - No. 30 Grade
400 tension reinforcement with either 2 - No. 30 or 3 - No.
25 Grade 400 compression reinforcement. Both tension bars
contain 900 mm lap splices confined with 7 - No. 10 Grade
300 stirrups. The splices are located at mid-span in the
constant moment, zero-shear region. Shear reinforcement
consists of No. 10 Grade 300 stirrups placed at 150 mm on
centre.
Eight specimens were constructed and subjected to
either cyclic loads or monotonically increasing loads
(static loads) until failure. Cyclic loads were applied to
seven specimens with a monotonically increasing load applied
to the eighth. Different load ranges were used in the
fatigue testing, but stress reversal was not applied. Six
of seven cyclically loaded specimens failed when one or both
of the main tension bars ruptured, while the seventh
specimen failed when the compression zone crushed after the
cyclic test was terminated at 3 million cycles and a
monotonically increasing load was applied. The one beam
subjected to a static load until failure exhibited a bond
failure in the splice region.
The tests showed that heavily confined splices
proportioned according to the guidelines set out in ACI
Committee 408 recommendations for static loading are
adequate for cyclic fatigue loading, and the splice does not
appear to influence the fatigue life of the specimen.
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Degree
Master of Science (M.Sc.)
Department
Civil Engineering
Program
Civil Engineering