Proprietary Edge Anchor Evaluation:

Bend Testing

Performed for Kansas City Structural Steel

William Collins, University of Kansas

Matthew Fadden, Wiss, Janney, Elstner Associates, Inc.

Eugene Boadi-Danquah, University of Kansas

Duncan MacLachlan, University of Kansas

January 5, 2019

Introduction

Kansas City Structural Steel has requested the testing of a proprietary edge condition detail (edge

anchor) for potential use supporting building facades. The cast channel/angle system serves as both

a pour-stop edge condition detail as well as a connection point for the attachment of cladding

systems. Kansas City Structural Steel is interested in the capacity of the system under both direct

tensile load and applied moment. Testing reported herein pertains only to applied moment.

Procedure

Specimens were fabricated and supplied by Kansas City Structural Steel with edge anchors,

accompanying bolts, and loading angles attached to a tie-down beam. The tie-down beam and

projected framing members simulated the proposed edge anchor in-service conditions. This

assembly is schematically represented in Figure 1. Details of the tie-down test frame, provided by

Kansas City Structural Steel, can be found in Appendix A. Six specimens were supplied by Kansas

City Structural Steel: four edge anchors attached directly to the tie-down beam designated A1

through A4, and two edge anchors connected to projected framing members composed of steel

angles designated as B1 and B2.

Figure 1. Schematic of Bend Test Setup

Force was eccentrically applied to the edge anchors through the use of a hydraulic jack with a

nominal maximum capacity of 100,000 lbf. During testing measurements of pressure were

manually recorded from a dial gauge at discrete intervals. Corresponding values of applied force

were determined by multiplying pressure times the area of the hydraulic cylinder. Displacements

of the test specimen, tie-down beam, and projected frame were recorded at various locations

through the use of an Optotrak non-contact displacement measurement system. The placement of

the loading jack and Optotrak measurement locations for specimen A3 is shown in Figure 2. In

this figure Optotrak markers are located on the loading angles above the jack (1), on the edge

anchor (2), and on the tie-down beam (3 and 4). Location of markers was similar for all test

specimens, with additional markers located on edge anchor channel edges on some tests.

Figure 2. Specimen A3 with Loading Jack and Optotrak Markers

Four specimens were tested in total: specimens A1 and A3 directly attached to the tie-down beam

and specimens B1 and B2 attached to the projected framing elements. It should also be noted that

the edge anchor clear span between the projected framing elements in specimens B1 and B2 were

not the same. The clear span for specimen B1 was approximately 11.5 in., while it was

approximately 17 in. for specimen B2. This difference is shown in Figure 3. In an attempt to

observe permanent deformation and identify yielding, specimens were loaded and unloaded at

least once during each test. Although various small drops in load were observed corresponding

with loud popping sounds, no catastrophic failure was observed for any test. Tests were terminated

when deemed to be dangerous due to excessive specimen rotation. Rotation of the specimens

during testing caused separation between the hydraulic jack and the loading surface, creating a

potentially dangerous condition. Therefore, all tests were stopped before the edge anchor was able

to reach maximum capacity.

Figure 3. Edge Anchor Clear Spacing between Framing Elements for a) B1 and b) B2

Results

The average maximum applied load for specimens directly attached to the tie-down beam (A1 and

A3) was 20,000 lbf. The maximum applied loads for the specimens attached to the projected

framing elements was 17,780 lbf. and 13,335 lbf. for B1 and B2, respectively. Results for each of

the four specimens can be seen in Table 1. Force-displacement curves for the specimens can be

seen in Figure 4 and Figure 5. These figures plot the applied force versus relative vertical

displacement between loading angles and edge anchor (Optotrak markers 1 and 2 in Figure 2). It

should be noted that this is not a perfect measure of relative displacement, as Optotrak marker 2

was located at the end of the edge anchor, while marker 1 was located near the point of load

application. Data markers in the plots indicate the discrete data points recorded during testing,

while lines connecting the data markers are presented for clarity.

Table 1. Maximum Applied Force Results

Specimen Number Maximum Applied Force (lbf)

A1 19,685

A3 20,320

B1 17,780

B2 13,335

a) b)

Figure 4. Force-Relative Displacement for Specimens A1 and A3

Figure 5. Force-Relative Displacement for Specimens B1 and B2

Specimens were unloaded during testing to observe permanent deformations and identify specimen

yielding. Initial load-unload cycles produced non-linear force-displacement records. This could be

indicative of bolt heads “settling in” against the interior channel face of the edge anchor. Removal

of initial load-unload cycles and resetting displacements to zero produced the force-displacement

curves presented in Figure 6 and Figure 7. The force-displacement record of Specimens A1 and

A3 indicate the edge anchors behaved similarly. Although the initial slopes differ slightly, the

curves converge as behavior becomes more non-linear. The slopes of both force-displacement

curves appear to be approaching zero, indicating that tests were nearing the ultimate capacity of

the edge anchors.

This similar behavior was not observed for Specimens B1 and B2, where the specimen stiffnesses

appear to be quite different. This behavior was expected however, as the clear span for B2 was

roughly 50 percent larger than that of B1.

Figure 6. Force-Relative Displacement for A1 and A3 with Initial Unloading Removed

Figure 7. Force-Relative Displacement for B1 and B2 with Initial Unloading Removed

In an attempt to capture any opening occurring on the edge anchor channel, Optotrak markers were

installed near the lips of the channel on specimens B1 and B2, as seen on Specimen B1, markers

3 and 4, in Figure 8.

Figure 8. Optotrak Marker Locations on Specimen B1

Evaluation of this data is not as intuitive as that of the previously-presented force-displacement

results. Vertical and horizontal displacement of markers 3 and 4 were adjusted relative to the

displacements of marker 2, and presented in Figure 9 and Figure 10. Although not perfect, this

does remove some effects of rigid body motion experienced by the tie-down beam and projected

framing elements. Horizontal displacements were initially set to zero for easier comparison, and a

schematic of the edge anchor with approximate Optotrak marker locations and direction of loading

is provided in each figure. Note that displacement results correspond with the orientation of the

edge anchor shown in the figure, not in the as-tested orientation.

On both B1 and B2 evidence of bolt prying is clear when examining the displacement of marker

3. After initial load causes relatively linear displacement of both channel lips, the bolt head pries

against the upper channel lip, causing rotation of the pour-stop lip (marker 3). This observed

rotation is more severe in specimen B1 than B2, possibly due to differences in stiffness between

specimens.

Figure 9. Edge Anchor Channel Opening for Specimen B1

Figure 10. Edge Anchor Channel Opening for Specimen B2

Conclusions

Bend tests were performed on four different edge anchor specimens. Two edge anchors were

attached directly to the tie-down beam (A1 and A3) and two were attached to projected framing

elements (B1 and B2). Edge anchors connected to framing elements had clear spans of

approximately 11.5 in. for B1 and 17 in. for B2. Force was not applied to failure, as testing was

terminated when conditions were deemed to be unsafe. Regardless, testing was conducted well

into the inelastic range. Behavior for specimens A1 and A3 were very similar with an average

maximum applied force of 20,000 lbf. Due to differing clear spans specimens B1 and B2 exhibited

different behavior, reaching a maximum applied forces of 17,780 lbf. and 13,335 lbf. for B1 and

B2, respectively. Further testing would be required to develop a more accurate description of

overall behavior, connection stiffness, and ultimate strength.

If there are any questions regarding this report, William Collins can be reached at

william.collins@ku.edu or (785) 864-0672.

Appendix A: Details of Tie-Down Beam Test Frame