CE 5310 Lecture Notes - Lecture 12: Seismic Analysis, Ductility, Inflectional Phrase
Cyclic Performance of Deep Column Moment Frames with Weak
Panel Zones
*Sungyeob Shin1) and Michael D. Engelhardt2)
1), 2) Department of Civil Engineering, University of Texas at Austin, USA
1) syshin@utexas.edu
ABSTRACT
Deep columns are frequently used in steel special moment resisting frames in the
United States in order to control drift and reduce construction costs. This paper
presents an experimental study on welded unreinforced flange-welded web (WUF-W)
steel moment connections to a deep wide-flange column. Three large-scale interior
moment connection specimens with a full range of panel zone strength levels were
subjected to slowly applied cyclic loads up to failure. The objective was to investigate
the effect of panel zone strength on the seismic performance of WUF-W moment
connections with deep column sections. All specimens satisfied the qualifying drift
angle criteria for the seismic connection required in the current AISC Seismic
Provisions, at least 0.04 radian story drift angle prior to failure without significant
strength degradation. This paper summarizes the experimental program and key test
results.
1. INTRODUCTION
Steel moment resisting frames (MRFs) are used for seismic resistant building
construction in high seismic regions. A key design issue of steel MRFs is the balance of
yielding between the beams and column panel zones to achieve high levels of ductility
under strong earthquake motions.
One of the earliest studies on panel zone behavior was conducted by Krawinkler
(Krawinkler et al. 1971; Krawinkler 1978). The study showed that panel zone shear
yielding results in highly ductile behavior, with stable and repetitive hysteresis loops
under cyclic loading. El-Tawil et al. (1999) indicated that excessive shear deformation
of panel zone can increase the potential for brittle and/or ductile fracture despite its
contribution to the connection ductility. Tests by Jones et al. (2002) showed that the
specimens with weak panel zones achieved excellent performance, developing large
story drifts without strength degradation.
1) Graduate Research Assistant
2) Professor
Experimental studies on WUF-W moment connections were conducted by Ricles at
al. (2002) and Lee et al. (2005a, 2005b). The majority of column sections used in above
two studies were shallow wide-flange column sections (W14 sections).
Deep columns are frequently used in steel special moment resisting frames in the
United States in order to control drift and reduce construction costs. An experimental
study was conducted to collect additional data on the effect of panel zone strength on
the seismic performance of WUF-W moment connections with deep column sections.
This paper summarizes the experimental program and key test results
2. TEST SETUP AND SPECIMENS
Tests were conducted on three large-scale interior moment connection specimens.
Fig. 1 shows the test setup. Cyclic loads were slowly applied at the top of the column
and the lateral supports were provided at the connection area and beam ends as
shown. To simulate points of inflection under lateral load, the ends of the members
were pin connected. The bottom of the column was connected to a high capacity clevis
and the top of the column was rigidly attached to the loading crosshead, which can be
controlled to simulate a pin. Each beam end was supported by two actuators that are
intended to serve as a roller support. That is, the actuators were controlled to keep the
beam ends at a constant elevation, and allow free horizontal translation and rotation of
the beam ends.
West Beam East Beam
Loading Crosshead
: mm
2353
2769
4526 4526
Clevis
Two Actuators Two Actuators
: Lateral Brace
Units
Fig. 1 Test setup
Table 1. Test specimens
Specimen
Beam
Column
Doubler
Plate
Thickness
(mm)
Panel
Zone
Strength
Panel Zone
Requirement of the
AISC Seismic Provision
UT01
W30x108
W33x263
0
Weak
Violated
UT02
W30x108
W33x263
13
Balanced
Satisfied
UT03
W30x108
W33x263
2 at 13
Strong
Satisfied
Table 1 lists the key features of the three specimens. The specimens consisted of
W30x108 beams and W33x263 column, each of A992 steel. Note that the beams and
column for the Specimen UT03 were taken from different heats of steel as compared to
those of the other two specimens. The material properties from tension coupon testing
are not available at the time of writing. Specimens were designed with three different
levels of panel zone strength. Specimen UT01 with weak panel zone was intended to
promote severe inelastic deformation of the panel zone. Specimen UT03 with strong
panel zone was designed so that plastic hinges would occur in the beams. Specimen
UT02 with balanced panel zone was intended to share yielding between the beams and
the panel zone.
Connection details for the Specimen UT02 are shown in Fig. 2. The details were
identical for all three test specimens, with exception of the doubler plate thickness, as
summarized in Table 1. Complete-joint-penetration (CJP) groove welds of beam
flanges to column were made using the self-shielded flux core arc welding (FCAW-S)
process with a 2.4 mm diameter E70T-6 (Lincoln NR-305) electrode. The backing bar
was removed at the beam bottom flange groove welds and the root of CJP groove weld
was reinforced with fillet welds. The backing bar was left in place at the beam top
flange groove welds and reinforcing fillet welds were provided between the backing bar
and the column flange. The weld tabs were removed and ground smooth. A 1.8 mm
diameter E71T-8 (Lincoln NR-232) electrode was used for the CJP groove welds of
beam webs. Supplemental fillet welds were provided between the shear tab and the
beam web. The weld access holes were fabricated based on the research of Ricles et
al. (2002). All specimens were provided with 19 mm thick continuity plates.
3. TEST RESULTS
The test specimens were subjected to cyclic loads by applying increasing levels of
the total story drift angle. The pre-determined loading sequence, listed in Table 2,
followed the loading protocol specified in the 2010 AISC Seismic Provisions (AISC
2010). The cyclic loading was increased until severe failure was observed at each
specimen.
3.1 Overall specimen performance
The column tip load versus total story drift angle for all specimens is shown in Fig. 3.
A summary of test results is listed in Table 3, including: maximum total story drift angle;
Document Summary
Cyclic performance of deep column moment frames with weak. Department of civil engineering, university of texas at austin, usa syshin@utexas. edu. This paper presents an experimental study on welded unreinforced flange-welded web (wuf-w) steel moment connections to a deep wide-flange column. Three large-scale interior moment connection specimens with a full range of panel zone strength levels were subjected to slowly applied cyclic loads up to failure. The objective was to investigate the effect of panel zone strength on the seismic performance of wuf-w moment connections with deep column sections. All specimens satisfied the qualifying drift angle criteria for the seismic connection required in the current aisc seismic. Provisions, at least 0. 04 radian story drift angle prior to failure without significant strength degradation. This paper summarizes the experimental program and key test results: introduction. Steel moment resisting frames (mrfs) are used for seismic resistant building construction in high seismic regions.
