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In This Article

  • Summary
  • Abstract
  • Introduction
  • Protocol
  • Results
  • Discussion
  • Disclosures
  • Acknowledgements
  • Materials
  • References
  • Reprints and Permissions

Summary

We propose a testing protocol that can be combined with widely available analytical methods to assess the mechanical properties of shear connectors for use in the design of insulated concrete wall panels to predict full-scale insulated panel behavior.

Abstract

This document contains recommendations for performing a non-standard, double-shear test suitable for both continuous and discrete insulated concrete sandwich wall panels (ICSWPs). Such a standardized test does not exist, but several iterations of this and similar tests have been performed in the literature to varying degrees of success. Further, the tests in the literature are rarely-if ever-described in detail or discussed at length with respect to the testing, data analysis, or safety procedures. A test specimen configuration is recommended herein, and variations are discussed. Important mechanical properties are identified from the load versus displacement data, and their extraction is detailed. The use of test data for design, such as for determining the stiffness of the connectors, is briefly demonstrated to show how ICSWP deflection and cracking behavior may be calculated. The strength behavior of panels may be determined using the full load versus displacement curve or only the maximum connector strength. Shortcomings and unknowns are acknowledged, and significant future work is delineated.

Introduction

Insulated concrete sandwich wall panels (ICSWPs) comprise a layer of insulation placed in between two concrete layers, often called wythes, which synergically provide a thermally and structurally efficient component for building envelopes or load-bearing panels1 (Figure 1). To adapt to the rapidly changing construction industry and new building code regulations on thermal efficiency, precasters are fabricating ICSWPs with thinner concrete layers and thicker insulation layers with higher thermal resistance; additionally, designers are using more refined methods to account for the partially composite interaction of t....

Protocol

1. Fabricating the testing specimen

  1. Select the discrete or continuous shear connector to test and adhere to the dimensions of the specimen indicated in Figure 4. Modify the dimensions to the test edge distance clearances if needed by changing the edge distance for the connector.
    NOTE: Generally, adhering to the manufacturer's guidelines is important, though this test may be used to develop these guidelines. The concrete and insulation wythe dimensions will be dictated by the connector of interest. The mechanical properties from the test are only valid for this specific combination of wythe dimension....

Results

Figure 8 and Figure 9A show a typical load per connector versus the average displacement curve resulting from a double-shear test of a fiber-reinforced polymer (FRP) connector in the laboratory. As the figures depict, the load increases steadily up to the maximum point and then drops dramatically, which is typically observed in most testing involving polymers. However, as Figure 9B suggests, the curve flattens after the maximum load.......

Discussion

Many researchers have used some variation of this type of test for ICSWP, but this is the first instance of outlining all the individual steps. The literature does not address the critical steps in testing, including sensor types and specimen handling. This method describes a manner of testing that mimics more closely the behavior of the connectors when a panel is loaded in flexure as opposed to the single-shear test. There are several variables for this work that are yet to be studied. Specifically, information related .......

Disclosures

The authors have nothing to disclose.

Acknowledgements

The work described above was not directly financed by a single organization or over the course of a single grant, but the information was gathered over years of industry-sponsored research. To that end, the authors thank their sponsors from over the last decade and are grateful to work in a rapidly evolving industry.

....

Materials

NameCompanyCatalog NumberComments
Battery-powered Drill
Concrete Screws50 mm long commercial concrete scews.
Data LoggerCapable of sampling at a frequency of at least 10 Hz.
Double Shear Test SpecimenFabricated according to the dimmensions in the testing protocol.
Four Linear Variable Displacement TransformerWith at least 25 mm range for Fiber-reinforced Polymer (FRP) connectors and 50 mm for ductile steel connectors.
Hydraulic ActuatorWith at least 50-Ton capacity.
Lifting anchors rated at 1 Ton
Load CellWith at least 50-Ton capacity.
Load FrameCapable of resisting the forces generated by the testing specimen.
Polytetrafluoroethylene (PTFE) Pads3 mm x 100 mm x 600 mm 
Ratchet StrapAt least 50 mm wide.
Steel angle
Steel PlateTwo 20 mm x 150 mm x 150 mm steel plates.
Steel WashersCapable of producing a separation of at least 5 mm between the steel angle and the specimen.

References

  1. Collins, T. F. Precast concrete sandwich panels for tilt-up construction. Journal of the American Concrete Institute. 50 (2), 149-164 (1954).
  2. Luebke, J. . Out-of-plane behavior of concrete insulated wall panels with 2-inch, 8-inch, and 10-inch insulation....

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