PEER welcomes engineers to come watch upcoming testing of the beam hoop reinforcement for full-scale 48” x 30” concrete SMRF beams in the Davis Hall Laboratory at UC Berkeley. Professors Marios Panagiotou and Jack Moehle are coordinating this project with graduate students Grigorios Antonellis and Tea Visnjic. The test is funded by the Pankow Foundation, Webcor Builders, ACI Foundation’s Concrete Research Council, and the CRSI Foundation.
The purpose of the testing is to determine if the transverse reinforcement requirements in plastic hinge zones of large size SMRF beams can achieve the seismic deformation capacity intended by current Building Code provisions.
TEST #1
Date: Friday, January 14, 2011
Time: testing began at 10:45 am
Location: Structures Laboratory, 2nd floor, Davis Hall, UC Berkeley
Specimen: Beam 1 was designed to satisfy all provisions for special moment frame beams according to the current Building Code provisions.
Report:Download a report describing the preliminary test results from Beam 1
- (PDF file – 2.1 MB)
TEST #2
Date: Thursday, February 3, 2011
Time: 1:00 pm; the test will run approx. 5 hours. (UPDATED 12:15 pm, February 3, 2011)
Location: Structures Laboratory, 2nd floor, Davis Hall, UC Berkeley
Specimen: Beam 2 – designed by some proposed Code changes that require closer spacing of hoop reinforcement
**NOTE: All testing dates are subject to change if necessary to meet test objectives. If the test is delayed or canceled, a notification will be posted on this website.**
Background
Recent developments in the construction of high-rise buildings in the seismically active West Coast have resulted in construction of reinforced concrete special moment frame beams larger than was typical in past practices. The current Building Code requirements for these beams were written around prevailing practices from many years ago and, when applied to these new buildings, can result in hoop spacing as large as 12 inches in the beam plastic hinge zone (see ACI 318-08, Section 21.5.3.2). Some engineers have questioned the performance capability of these beams and have recommended Building Code changes to reduce the maximum hoop spacing. An ongoing research project at the University of California, Berkeley is investigating the requirements through a laboratory test program.
Test Specimens
(see Figures 1 through 4 below)
Two test beams have been designed and constructed to test current Building Code provisions and some proposed Code changes. The beams cantilever from a common reaction block that is anchored to the laboratory floor (Figures 1 and 2). The beams will be cycled up and down to simulate the effects of deformation reversals that occur during a major earthquake.
Beam 1 is designed to satisfy all provisions for special moment frame beams according to the current Building Code provisions. The beam transverse reinforcement comprises three legs of No. 5 hoops closed at the top by crossties at spacing s = 11 inches, corresponding to a volumetric confinement reinforcement ratio (ρs = volume of vertical legs of hoops divided by volume of core) = 0.31%. In Beam 2, the hoop spacing s is reduced to 6 inches, corresponding to a volumetric reinforcement ratio ρs = 0.57%. Concrete is normal weight, using pea gravel (not crushed) as the maximum size aggregate, with target compressive strength of 5000 psi. All reinforcement is Grade 60.
Testing Plan
Tests on Beam 1 are planned for 12 January 2010 in the Structures Laboratory, 2nd floor, Davis Hall, UC Berkeley. Tests on Beam 2 are planned about a week later. All testing dates are subject to change if necessary to meet test objectives. According to the results of these two tests, a third beam is planned to be designed and tested at a later time.
Figure 1: Plan view of test specimen
Figure 2: Side view of test specimen
Figure 3: Side view of specimen - anchorage of beam longitudinal reinforcement
Figure 4A: Beam 1 section detail
Figure 4B: Beam 2 section detail