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.

1. Fabricating the testing specimen
<ol>
	<li>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&#39;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 dimensions, concrete strength, insulation density and type, and connector.</li>
	<li>Indicate the target compressive strength of the concrete representative of the design situation of interest. If trying to model full-scale testing results, ensure that the concrete strength is the same as that of the full-scale specimen or the intended design at the time of testing. If targeting a certain scenario, like the minimum strength for the lifting of the panel, perform the test at that strength.</li>
	<li>Fabricate the concrete formwork using either a vertical or horizontal layout of the concrete layers. Ensure that the testing matches the construction style so that the installation of the connectors matches the in-field situation. 
	NOTE: Most in-service ICSWPs are fabricated with a horizontal layout of each layer.</li>
	<li>Perforate the foam insulation (for pin-style ties) or orient the insulation pieces (for seam-installed ties) and place the connectors at the locations indicated in the standard drawings provided by the manufacturer. Place the connectors using the orientation that the testing facility desires to gather the properties (e.g., a 0&#176; or 90&#176;-or other-angle to the strong axis and the applied load). 
	NOTE: The installation of the connectors should be as indicated by the manufacturer/supplier unless installation is a testing variable of interest.</li>
	<li>Place the first steel reinforcement layer in the forms to prevent the specimen from brittle failure if the concrete pieces crack during handling or testing. 
	NOTE: As the specimens rarely crack due to applied loads, mild reinforcement is not thought to be necessary unless it is expected to participate in the bond of the connector to the concrete. Figure 5 shows the organization of steps 1.5-1.14 through the process.</li>
	<li>If all the layers of concrete cannot be placed in a timely manner prior to the initial set of the concrete, cast the layers a minimum of 3 h apart or according to the connector manufacturer&#39;s recommendations. 
	NOTE: Steps 1.7-1.14 indicate consecutive concrete placement.</li>
	<li>Pour the fresh concrete into the forms and vibrate adequately to prevent the formation of large air voids in the concrete or the poor compaction of particles.</li>
	<li>Place the first insulation layer containing the connectors or push them into the foam, as appropriate. Place the insulation layer so that it makes contact with the fresh concrete. To ensure the concrete is consolidated around the connectors, vibrate the connector with an internal concrete vibrator at 12,000 vibrations/min, unless otherwise recommended by the connector&#39;s manufacturer. 
	NOTE: Vibrating for 2-5 s is enough to ensure consolidation around the connectors.</li>
	<li>Place a 1 ton capacity (or stronger depending on the specimen&#39;s final weight) lifting anchor in the middle layer of the concrete for ease of handling.</li>
	<li>Place the second steel reinforcement layer in the forms in the center of the center wythe.</li>
	<li>Pour the second layer of fresh concrete into the forms and adequately consolidate the concrete as described above.</li>
	<li>Place the second insulation layer containing the connectors or install them into the foam, as described in step 1.4. Carefully ensure that the concrete is consolidated around the connectors.</li>
	<li>Place the third steel reinforcement layer in the forms at the center of the third concrete layer.</li>
	<li>Pour the third and final layer of fresh concrete into the forms and vibrate adequately.</li>
	<li>Make concrete cylinders for each concrete used in the construction of the specimens for the purpose of compression strength documentation. 
	NOTE: This step may be completed at any time during the construction of the specimens but is recommended when halfway through the placement of a given batch. The cylinder preparation and field curing should follow ASTM C3121.</li>
	<li>Cure the specimens in a temperature-controlled environment until the concrete has reached the desired strength. Take the specimens out of the forms once the concrete has hardened adequately for the lifting hardware.</li>
</ol>
2. Testing the double-shear specimen
NOTE: Figure 6 shows a representative layout of the test specimen ready to be tested (ratchet strap not pictured).
<ol>
	<li>Take the specimen to the laboratory for sampling when the concrete used to fabricate the specimens has reached the desired strength. 
	NOTE: Compressive strength testing should follow ASTM C3922. The room temperature should remain relatively constant during the physical act of testing, with the temperature suggested to be 25 &#176;C &#177; 5 &#176;C, and during the testing and storing of the specimens. The testing temperature range is not intended to be rigorously controlled as the properties of the materials involved should not vary significantly with typical room temperatures.</li>
	<li>Place two 3 mm x 100 mm x 600 mm polytetrafluoroethylene (PTFE) pad strips at the bottom of the outer concrete wythes to minimize friction during testing.</li>
	<li>Set the specimen under the loading frame with the middle concrete layer centered under the loading apparatus. Use a hydraulic ram or a large universal testing machine to apply loading at the top of the middle wythe, taking care to spread the load out with a bearing plate that is sufficiently large to prevent a bearing failure for the expected loads.</li>
	<li>Attach the steel angle to the middle wythe with a concrete or masonry screw. Create a separation of at least 5 mm between the steel angle and the concrete surface using steel or plastic washers to prevent the angle from otherwise interacting with the specimen (Figure 6).</li>
	<li>Attach the displacement sensors to the two exterior wythes, on opposite sides of the specimen (four in total), to measure the movement of the steel angle relative to their fixed position on the exterior wythe. 
	NOTE: The recommended displacement sensors are linear variable differential transducers or potentiometers. Sensors should always be stored in a dry case that is free of dust, moisture, and magnetic effects to prevent the loss of calibration. Analog dial gauges are not recommended.</li>
	<li>Place a 50 mm wide nylon strap loosely around the upper part of the specimen to ensure that an unexpected brittle connector break will not cause any damage to the surroundings, including harming the technician and the sensors. Ensure that the strap is loose enough to not interfere with the specimen displacement, as shown in Figure 7. 
	NOTE: The strap will prevent the wythes from complete separation and facilitate the removal of the specimen after failure even if the wythes are no longer separated. However, this step (step 2.6) is optional.</li>
	<li>Place the load cell centered on top of the middle wythe, sandwiched in between two 20 mm x 150 mm x 150 mm steel plates. Ensure that the steel plates do not overhang the center wythe so as not to interfere with the insulation during the deformation of the specimen.</li>
	<li>Plug the load and displacement sensors into the data acquisition system (DAQ).</li>
	<li>Start the data collection using a sampling rate of at least 10 Hz to ensure the load and displacement are recorded properly.</li>
	<li>Load the specimen in the center wythe until the maximum realistic displacement has been reached and the strength has dropped substantially; after 50% of the load has been lost, stopping the test is recommended, although this is arbitrary. If additional information along the descending branch is desired, use any desired deformation. Apply loading in a monotonic, quasi-static fashion that is fast enough that the connector and concrete creep does not interfere with the test results but not so fast that it can no longer be considered static, unless a high load rate is the testing variable of interest. 
	NOTE: This would indicate that the test should take in the order of 5 min to perhaps several hours. Adequate results have been found using a hydraulic hand pump with a test duration in the order of 5-10 min.</li>
	<li>Stop the data acquisition and retract the load application apparatus to the original position.</li>
	<li>Remove all the sensors and store them in a safe place, as indicated above.</li>
	<li>Move the tested specimen to a clean area and separate the three concrete layers to identify the type of failure: concrete breakout, connector shear failure, or other. Record the failure mode, the quality of the insulation bond, and any other pertinent visual information. Remember to take photographs.</li>
</ol>
3. Analyzing the data and reporting the results
NOTE: This section describes the data analysis to assess several engineering properties that have been used in the literature. Other engineering properties may be of interest, and the data&#39;s usefulness is not limited to the properties below.
<ol>
	<li>Transfer the data files resulting from testing from the DAQ to the computer/folder where the data analysis is performed.</li>
	<li>Plot the average of the four displacement sensors on the abscissa with the connector load on the ordinate (defined as the measured load divided by the number of connectors). 
	NOTE: The user of the experimental method must review the data for any faulty sensors or unreliable measurements prior to averaging and reporting them.</li>
	<li>Find the maximum load and its corresponding displacement using the appropriate function of the data analysis software and store these values as Fu and &#948;u,&#160;respectively.</li>
	<li>Divide the maximum load by 2 to obtain the half-maximum force, F0.5Fu, and find its corresponding displacement &#948;0.5.</li>
	<li>Find the elastic stiffness (K0.5Fu) of the connector by dividing the half-maximum force, F0.5Fu, by the displacement at the half-maximum force, &#948;0.5. If the F0.5Fu&#160;is not in the generally elastic portion of the test, select a lower load that is obviously in the region and report the number. If a lower value is used, be sure to document the fraction of Fu and the corresponding magnitude of force. 
	NOTE: Currently, the end of the K0.5Fu&#160;line is used by some designers as an upper limit for service forces in the connector.</li>
	<li>Report the average results of five samples for each connector brand, type, or concrete strength sampled. 
	NOTE: The reported results are valid only for the specific combination of concrete wythe, insulation wythe, concrete strength, and connector selected.</li>
</ol>

<ol>
	<li>Collins, T. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Precast+concrete+sandwich+panels+for+tilt-up+construction.">Precast concrete sandwich panels for tilt-up construction.</a> Journal of the American Concrete Institute. 50 (2), 149-164 (1954).</li><li>Luebke, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Out-of-plane behavior of concrete insulated wall panels with 2-inch, 8-inch, and 10-inch insulation. , (2021).</li><li>Einea, A., Salmon, D. C., Tadros, M. K., Culp, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+structurally+and+thermally+efficient+precast+sandwich+panel+system.">A new structurally and thermally efficient precast sandwich panel system.</a> PCI journal. 39 (4), 90-101 (1994).</li><li>Frankl, B., Lucier, G., Rizkalla, S., Blaszak, G., Harmon, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structural+behavior+of+insulated+prestressed+concrete+sandwich+panels+reinforced+with+FRP+grid.">Structural behavior of insulated prestressed concrete sandwich panels reinforced with FRP grid.</a> Proceedings of the Fourth International Conference on FRP Composites in Civil Engineering (CICE2008). 2224, (2008).</li><li>Naito, C., Hoemann, J., Beacraft, M., Bewick, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Performance+and+characterization+of+shear+ties+for+use+in+insulated+precast+concrete+sandwich+wall+panels.">Performance and characterization of shear ties for use in insulated precast concrete sandwich wall panels.</a> Journal of Structural Engineering. 138 (1), 52-61 (2012).</li><li>Tomlinson, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Behaviour of partially composite precast concrete sandwich panels under flexural and axial loads. , (2015).</li><li>. AC320 - Fiber-reinforced Polymer Composite or Unreinforced Polymer Connectors Anchored in Concrete Available from: <a target="_blank" href="https://shop.iccsafe.org/es-acceptance-criteria/ac320-fiber-reinforced-polymer-composite-or-unreinforced-polymer-connectors-anchored-in-concrete-approved-oct-2015-editorially-revised-sept-2017-pdf-download.html">https://shop.iccsafe.org/es-acceptance-criteria/ac320-fiber-reinforced-polymer-composite-or-unreinforced-polymer-connectors-anchored-in-concrete-approved-oct-2015-editorially-revised-sept-2017-pdf-download.html</a> (2015)</li><li>. Developing a General Methodology for Evaluating Composite Action in Insulated Wall Panels. Report to PCI. Precast/Prestressed Concrete Institute Available from: <a target="_blank" href="https://digitalcommons.usu.edu/cee_facpub/3531">https://digitalcommons.usu.edu/cee_facpub/3531</a> (2017)</li><li>Gombeda, M. J., Naito, C. J., Quiel, S. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+and+performance+of+a+ductile+shear+tie+for+precast+concrete+insulated+wall+panels.">Development and performance of a ductile shear tie for precast concrete insulated wall panels.</a> Journal of Building Engineering. 28, 101084 (2020).</li><li>Kinnane, O., West, R., Grimes, M., Grimes, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Shear+capacity+of+insulated+precast+concrete+fa&#231;ade+panels.">Shear capacity of insulated precast concrete fa&#231;ade panels.</a> CERI 2014 - Civil Engineering Research in Ireland. , (2014).</li><li>Jiang, H., Guo, Z., Liu, J., Liu, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+shear+behavior+of+precast+concrete+sandwich+panels+with+W-shaped+SGFRP+shear+connectors.">The shear behavior of precast concrete sandwich panels with W-shaped SGFRP shear connectors.</a> KSCE Journal of Civil Engineering. 22 (10), 3961-3971 (2018).</li><li>ASTM International. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Standard+test+methods+for+strength+of+anchors+in+concrete+elements.">Standard test methods for strength of anchors in concrete elements.</a> ASTM. , (2022).</li><li>Syndergaard, P., Tawadrous, R., Al-Rubaye, S., Maguire, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparing+testing+methods+of+partially+composite+sandwich+wall+panel+glass+fiber-reinforced+polymer+connectors.">Comparing testing methods of partially composite sandwich wall panel glass fiber-reinforced polymer connectors.</a> Journal of Composites for Construction. 26 (1), (2022).</li><li>Woltman, G., Tomlinson, D., Fam, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Investigation+of+various+GFRP+shear+connectors+for+insulated+precast+concrete+sandwich+wall+panels.">Investigation of various GFRP shear connectors for insulated precast concrete sandwich wall panels.</a> Journal of Composites for Construction. 17 (5), 711-721 (2013).</li><li>Olsen, J., Maguire, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pushoff+shear+testing+of+composite+sandwich+panel+connectors.">Pushoff shear testing of composite sandwich panel connectors.</a> 2016 PCI Convention and National Bridge Conference. , (2016).</li><li>Gombeda, M. J., Naito, C. J., Quiel, S. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flexural+performance+of+precast+concrete+insulated+wall+panels+with+various+configurations+of+ductile+shear+ties.">Flexural performance of precast concrete insulated wall panels with various configurations of ductile shear ties.</a> Journal of Building Engineering. 33, 101574 (2021).</li><li>Bai, F., Davidson, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Composite+beam+theory+for+pretensioned+concrete+structures+with+solutions+to+transfer+length+and+immediate+prestress+losses.">Composite beam theory for pretensioned concrete structures with solutions to transfer length and immediate prestress losses.</a> Engineering Structures. 126, 739-758 (2016).</li><li>Cox, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lumped+GFRP+star+connector+system+for+partial+composite+action+in+insulated+precast+concrete+sandwich+panels.">Lumped GFRP star connector system for partial composite action in insulated precast concrete sandwich panels.</a> Composite Structures. 229, 111465 (2019).</li><li>Pozo, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> On thermal bowing of concrete sandwich wall panels with flexible shear connectors. , (2018).</li><li>ASTM International. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Standard+practice+for+making+and+curing+concrete+test+specimens+in+the+field.">Standard practice for making and curing concrete test specimens in the field.</a> ASTM International. , (2019).</li><li>ASTM International. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Standard+test+method+for+compressive+strength+of+cylindrical+concrete+specimens.">Standard test method for compressive strength of cylindrical concrete specimens.</a> ASTM International. , (2018).</li><li>Pozo-Lora, F., Maguire, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermal+bowing+of+concrete+sandwich+panels+with+flexible+shear+connectors.">Thermal bowing of concrete sandwich panels with flexible shear connectors.</a> Journal of Building Engineering. 29, 101124 (2020).</li><li>Al-Rubaye, S., Sorensen, T., Thomas, R. J., Maguire, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Generalized+beam-spring+model+for+predicting+elastic+behavior+of+partially+composite+concrete+sandwich+wall+panels.">Generalized beam-spring model for predicting elastic behavior of partially composite concrete sandwich wall panels.</a> Engineering Structures. 198, 109533 (2019).</li><li>Losch, E. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=State+of+the+art+of+precast/prestressed+concrete+sandwich+wall+panels.">State of the art of precast/prestressed concrete sandwich wall panels.</a> PCI Journal. 56 (2), 131-176 (2011).</li><li>Al-Rubaye, S., Sorensen, T., Maguire, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Iterative+and+simplified+sandwich+beam+theory+for+partially+composite+concrete+sandwich+wall+panels.">Iterative and simplified sandwich beam theory for partially composite concrete sandwich wall panels.</a> Journal of Structural Engineering. 147 (10), 4021143 (2021).</li><li>Holmberg, A., Plem, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Behaviour+of+Load-bearing+Sandwich-type+Structures.">Behaviour of Load-bearing Sandwich-type Structures.</a> The National Swedish Institute for Building Research. , (1965).</li><li>Naito, C. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Precast/prestressed+concrete+experiments+performance+on+non-load+bearing+sandwich+wall+panels.">Precast/prestressed concrete experiments performance on non-load bearing sandwich wall panels.</a> Air Force Research Laboratory. Materials and Manufacturing Directorate. , (2011).</li><li>Al-Rubaye, S., Sorensen, T., Olsen, J., Maguire, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluating+elastic+behavior+for+partially+composite+precast+concrete+sandwich+wall+panels.">Evaluating elastic behavior for partially composite precast concrete sandwich wall panels.</a> PCI Journal. 63 (5), 71-88 (2018).</li><li>ASTM International. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Standard+practice+for+conducting+ruggedness+tests.">Standard practice for conducting ruggedness tests.</a> ASTM International. , 1169-1121 (2021).</li></ol>

The authors have nothing to disclose.

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 ...

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 the concrete wythes to reduce the overall building costs while increasing the thermal and structural performance2. While it is known that structural efficiency largely depends on the structural connection between the concrete layers and that multiple proprietary shear connectors are available on the market, no standardized testing protocol exists in the literature to examine the mechanical properties of those connectors. The available connectors vary widely in their geometry, materials, and manufacturing, so it is difficult to obtain a unified analytical approach to determine their mechanical properties. For this reason, many researchers have used their own customized setups in the lab that try to mimic the fundamental behavior of the connectors at the service and strength limit states3,4,5,6,7,8,9,10. However, only two of them are part of a testing evaluation scheme5,8, despite them not being useful for all ranges of connectors due to their wide variation in shape, stiffness, and material composition.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/64292/64292fig01.jpg" /> 
Figure 1: Typical composition of a sandwich wall panel specimen. <a href="https://www.jove.com/files/ftp_upload/64292/64292fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
A common method for testing these connectors is what is often termed single shear with either one row or two rows of connectors, as described previously3,11,12, which is often based on ASTM E488, a concrete anchor testing standard13. ASTM E488 does not require, but strongly implies through drawings of the suggested test setups, that a single anchor protruding from a fixed base of concrete will be tested. Once the specimens are tested, a set of load versus displacement curves is plotted, and the average values of the ultimate elastic load (Fu) and the elastic stiffness (K0.5Fu) are obtained from such curves. One of the main advantages of using this approach is that it produces low-variability results and does not necessitate large lab spaces or many sensors14. A different approach consists of loading a wythe connector in double shear to determine the mechanical properties for use in the design of those panels6,7,14,15,16. The resulting data are processed in the same fashion, and the average values of the ultimate elastic load (Fu) and the elastic stiffness (K0.5Fu) are obtained from testing. Although this testing approach involves using more material and needs more sensors, it is anecdotally easier to apply the loading and boundary conditions in a laboratory.
The two styles of testing do not seem dramatically different but produce different results largely based on their ability to mimic the connector behavior in a full-scale panel. The single-shear, single-row test setup produces a pinching action, as displayed in Figure 2B,C, and an additional overturning moment, as described previously14,17, which would not be present in a full-scale panel. The double shear does a better job of mimicking this full-scale behavior-it models the pure shear translation of the outer wythes relative to the central wythe. As a result, the double-shear values employed in analytical methods have been shown to produce results that are closer to those obtained in large-scale testing of representative insulated wall panels14. Figure 3 shows the schematic test setup for the single- and double-shear testing of a connector.
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/64292/64292fig02.jpg" /> 
Figure 2: Examples of different connector testing configurations employed in the literature. Single connector specimens have been shown to cause loading that does not represent the parallel translation of wythes seen in full-scale panels. (A)&#160;Double shear with two connectors; (B) Double shear with one connector; (C) Single shear with one connector. <a href="https://www.jove.com/files/ftp_upload/64292/64292fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
A common denominator of all these studies&#39; conclusions is that both the testing methodologies are appropriate for determining the mechanical properties of flexible connectors, but the double-shear testing scheme results resemble more closely the behavior of the connector in a real panel under flexure. In other words, when the user employs such testing results in an analytical model, they closely match the results of large-scale tests where the connectors are used. It is important to mention that the results of such testing are appropriate for models that rely on the mechanical properties as input design parameters directly, such as empirically derived methods, closed-form solutions of the sandwich beam theory, and finite element models with 2-D and 3-D springs7,18,19,20.
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/64292/64292fig03.jpg" /> 
Figure 3: Schematic view of the testing protocols in the literature. A ram is used to translate the wythes of the specimens relative to each other.&#160;(A) Single-shear and (B) double-shear testing protocols. <a href="https://www.jove.com/files/ftp_upload/64292/64292fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
In this work, an experimental protocol for obtaining the values of the backbone curve and the mechanical properties of insulated wall panel wythe connectors, namely Fu and K0.5Fu, is presented. The method is based on testing connectors using a double-shear test approach with some modifications to eliminate sources of variability and produce more reliable results. All the samples are constructed in a temperature-controlled environment, where they are tested when the concrete reaches the target compressive strength. The main advantage of this testing protocol is that it can be easily followed, can be replicated by different technicians, and closely describes the real behavior of the wythe connector in a real, insulated concrete wall panel under flexure or flexure and axial force combined, as has been shown in the literature.
The application of the suggested wythe connector testing protocol for determining the mechanical properties and material behavior will enhance the accuracy of testing results for the insulated concrete wall panel industry and decrease the barriers for entrepreneurs interested in creating innovative new connectors. The future large increase in insulated panel construction in both the tilt-up and precast concrete industries will require better use of materials and more unified methods to obtain engineering properties of the panels.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Battery-powered Drill</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Concrete Screws</td>
			<td></td>
			<td></td>
			<td>50 mm long commercial concrete scews.</td>
		</tr>
		<tr>
			<td>Data Logger</td>
			<td></td>
			<td></td>
			<td>Capable of sampling at a frequency of at least 10 Hz.</td>
		</tr>
		<tr>
			<td>Double Shear Test Specimen</td>
			<td></td>
			<td></td>
			<td>Fabricated according to the dimmensions in the testing protocol.</td>
		</tr>
		<tr>
			<td>Four Linear Variable Displacement Transformer</td>
			<td></td>
			<td></td>
			<td>With at least 25 mm range for Fiber-reinforced Polymer (FRP) connectors and 50 mm for ductile steel connectors.</td>
		</tr>
		<tr>
			<td>Hydraulic Actuator</td>
			<td></td>
			<td></td>
			<td>With at least 50-Ton capacity.</td>
		</tr>
		<tr>
			<td>Lifting anchors rated at 1 Ton</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Load Cell</td>
			<td></td>
			<td></td>
			<td>With at least 50-Ton capacity.</td>
		</tr>
		<tr>
			<td>Load Frame</td>
			<td></td>
			<td></td>
			<td>Capable of resisting the forces generated by the testing specimen.</td>
		</tr>
		<tr>
			<td>Polytetrafluoroethylene (PTFE) Pads</td>
			<td></td>
			<td></td>
			<td>3 mm x 100 mm x 600 mm&#160;</td>
		</tr>
		<tr>
			<td>Ratchet Strap</td>
			<td></td>
			<td></td>
			<td>At least 50 mm wide.</td>
		</tr>
		<tr>
			<td>Steel angle</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Steel Plate</td>
			<td></td>
			<td></td>
			<td>Two 20 mm x 150 mm x 150 mm steel plates.</td>
		</tr>
		<tr>
			<td>Steel Washers</td>
			<td></td>
			<td></td>
			<td>Capable of producing a separation of at least 5 mm between the steel angle and the specimen.</td>
		</tr>
	</tbody>
</table>

determination of the mechanical properties of flexible connectors for use in insulated concrete wall panels

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.

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...

Watch this Scientific Journal Video about Determination of the Mechanical Properties of Flexible Connectors for Use in Insulated Concrete Wall Panels at JoVE.com

Determination of the Mechanical Properties of Flexible Connectors for Use in Insulated Concrete Wall Panels

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.

This document contains recommendations for performing a non-standard, double-shear test suitable for both continuous and discrete insulated concrete ...

determination-mechanical-properties-flexible-connectors-for-use

Research

Education

JoVE Core

JoVE Journal

Civil Engineering

Engineering

Unit 1

Masonry

SCIENTISTS IN ACTION

1.5K 조회수.  Pontificia Universidad Catolica Madre y Maestra. 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.

비디오: Determination of the Mechanical Properties of Flexible Connectors for Use in Insulated Concrete Wall Panels

Concurrent Quantitative Conductivity and Mechanical Properties Measurements of Organic Photovoltaic Materials using AFM

Organic photovoltaic (OPV) materials are inherently inhomogeneous at the nanometer scale. Nanoscale inhomogeneity of OPV materials affects performance of photovoltaic devices. Thus, understanding of spatial variations in composition as well as electrical properties of OPV materials is of paramount importance for moving PV technology forward.1,2 In this paper, we describe a protocol for quantitative measurements of electrical and mechanical properties of OPV materials with sub-100 nm resolution. Currently, materials properties measurements performed using commercially available AFM-based techniques (PeakForce, conductive AFM) generally provide only qualitative information. The values for resistance as well as Young's modulus measured using our method on the prototypical ITO/PEDOT:PSS/P3HT:PC61BM system correspond well with literature data. The P3HT:PC61BM blend separates onto PC61BM-rich and P3HT-rich domains. Mechanical properties of PC61BM-rich and P3HT-rich domains are different, which allows for domain attribution on the surface of the film. Importantly, combining mechanical and electrical data allows for correlation of the domain structure on the surface of the film with electrical properties variation measured through the thickness of the film.

Organic photovoltaic (OPV) materials are inherently inhomogeneous at the nanometer scale. Nanoscale inhomogeneity of OPV materials affects performance of photovoltaic devices. In this paper, we describe a protocol for quantitative measurements of electrical and mechanical properties of OPV materials with sub-100 nm resolution.

동시 수량 전도성과 AFM을 사용하여 유기 태양 광 재료의 기계적 성질 측정

Organic photovoltaic  (OPV) materials are inherently inhomogeneous at the nanometer scale. Nanoscale  inhomogeneity of OPV materials affects performance ...

연구

공학

A Cost-effective and Reliable Method to Predict Mechanical Stress in Single-use and Standard Pumps

Pumps are mainly used when transferring sterile culture broths in biopharmaceutical and biotechnological production processes. However, during the pumping process shear forces occur which can lead to qualitative and/or quantitative product loss. To calculate the mechanical stress with limited experimental expense, an oil-water emulsion system was used, whose suitability was demonstrated for drop size detections in bioreactors1. As drop breakup of the oil-water emulsion system is a function of mechanical stress, drop sizes need to be counted over the experimental time of shear stress investigations. In previous studies, the inline endoscopy has been shown to be an accurate and reliable measurement technique for drop size detections in liquid/liquid dispersions. The aim of this protocol is to show the suitability of the inline endoscopy technique for drop size measurements in pumping processes. In order to express the drop size, the Sauter mean diameter d32 was used as the representative diameter of drops in the oil-water emulsion. The results showed low variation in the Sauter mean diameters, which were quantified by standard deviations of below 15%, indicating the reliability of the measurement technique.

Shear stress investigations on an oil-water emulsion system result in drop breakup over the experimental time. To count drop sizes in pumping processes, the suitability of inline endoscopy was successfully demonstrated in this protocol.

Pumps are mainly used when transferring sterile culture broths in biopharmaceutical and biotechnological production processes. However, during the pumping ...

Design and Use of a Full Flow Sampling System (FFS) for the Quantification of Methane Emissions

The use of natural gas continues to grow with increased discovery and production of unconventional shale resources. At the same time, the natural gas industry faces continued scrutiny for methane emissions from across the supply chain, due to methane&#39;s relatively high global warming potential (25-84x that of carbon dioxide, according to the Energy Information Administration). Currently, a variety of techniques of varied uncertainties exists to measure or estimate methane emissions from components or facilities. Currently, only one commercial system is available for quantification of component level emissions and recent reports have highlighted its weaknesses.
In order to improve accuracy and increase measurement flexibility, we have designed, developed, and implemented a novel full flow sampling system (FFS) for quantification of methane emissions and greenhouse gases based on transportation emissions measurement principles. The FFS is a modular system that consists of an explosive-proof blower(s), mass airflow sensor(s) (MAF), thermocouple, sample probe, constant volume sampling pump, laser based greenhouse gas sensor, data acquisition device, and analysis software. Dependent upon the blower and hose configuration employed, the current FFS is able to achieve a flow rate ranging from 40 to 1,500 standard cubic feet per minute (SCFM). Utilization of laser-based sensors mitigates interference from higher hydrocarbons (C2+). Co-measurement of water vapor allows for humidity correction. The system is portable, with multiple configurations for a variety of applications ranging from being carried by a person to being mounted in a hand drawn cart, on-road vehicle bed, or from the bed of utility terrain vehicles (UTVs). The FFS is able to quantify methane emission rates with a relative uncertainty of &#177; 4.4%. The FFS has proven, real world operation for the quantification of methane emissions occurring in conventional and remote facilities.

Design and Use of a Full Flow Sampling System FFS for the Quantification of Methane Emissions

We have designed, developed, and implemented a novel full flow sampling system (FFS) for quantification of methane emissions and greenhouse gases from across the natural gas supply chain.

메탄 배출량의 정량화를위한​​ 설계 및 전체 흐름 샘플링 시스템 (FFS)의 사용

The use of natural gas continues to grow with increased discovery and production of unconventional shale resources. At the same time, the natural gas ...

A Novel Biaxial Testing Apparatus for the Determination of Forming Limit under Hot Stamping Conditions

The hot stamping and cold die quenching process is increasingly used to form complex shaped structural components of sheet metals. Conventional experimental approaches, such as out-of-plane and in-plane tests, are not applicable to the determination of forming limits when heating and rapid cooling processes are introduced prior to forming for tests conducted under hot stamping conditions. A novel in-plane biaxial testing system was designed and used for the determination of forming limits of sheet metals at various strain paths, temperatures, and strain rates after heating and cooling processes in a resistance heating uniaxial testing machine. The core part of the biaxial testing system is a biaxial apparatus, which transfers a uniaxial force provided by the uniaxial testing machine to a biaxial force. One type of cruciform specimen was designed and verified for the formability test of aluminum alloy 6082 using the proposed biaxial testing system. The digital image correlation (DIC) system with a high-speed camera was used for taking strain measurements of a specimen during a deformation. The aim of proposing this biaxial testing system is to enable the forming limits of an alloy to be determined at various temperatures and strain rates under hot stamping conditions.

This protocol proposes a novel biaxial testing system used on a resistance heating uniaxial tensile test machine in order to determine the forming limit diagram (FLD) of sheet metals under hot stamping conditions.

The hot stamping and cold die quenching process is increasingly used to form complex shaped structural components of sheet metals. Conventional ...

Scalable Solution-processed Fabrication Strategy for High-performance, Flexible, Transparent Electrodes with Embedded Metal Mesh

Here, the authors report the embedded metal-mesh transparent electrode (EMTE), a new transparent electrode (TE) with a metal mesh completely embedded in a polymer film. This paper also presents a low-cost, vacuum-free fabrication method for this novel TE; the approach combines lithography, electroplating, and imprint transfer (LEIT) processing. The embedded nature of the EMTEs offers many advantages, such as high surface smoothness, which is essential for organic electronic device production; superior mechanical stability during bending; favorable resistance to chemicals and moisture; and strong adhesion with plastic film. LEIT fabrication features an electroplating process for vacuum-free metal deposition and is favorable for industrial mass production. Furthermore, LEIT allows for the fabrication of metal mesh with a high aspect ratio (i.e., thickness to linewidth), significantly enhancing its electrical conductance without adversely losing optical transmittance. We demonstrate several prototypes of flexible EMTEs, with sheet resistances lower than 1 &#937;/sq and transmittances greater than 90%, resulting in very high figures of merit (FoM) &#8211; up to 1.5 x 104 &#8211; which are amongst the best values in the published literature.

This protocol describes a solution-based fabrication strategy for high-performance, flexible, transparent electrodes with fully-embedded, thick metal mesh. Flexible transparent electrodes fabricated by this process demonstrate among the highest reported performances, including ultra-low sheet resistance, high optical transmittance, mechanical stability under bending, strong substrate adhesion, surface smoothness, and environmental stability.

Here, the authors report the embedded metal-mesh transparent electrode (EMTE), a new transparent electrode (TE) with a metal mesh completely embedded in a ...

Magnet Assisted Composite Manufacturing: A Flexible New Technique for Achieving High Consolidation Pressure in Vacuum Bag/Lay-Up Processes

This work demonstrates a protocol to improve the quality of composite laminates fabricated by wet lay-up vacuum bag processes using the recently developed magnet assisted composite manufacturing (MACM) technique. In this technique, permanent magnets are utilized to apply a sufficiently high consolidation pressure during the curing stage. To enhance the intensity of the magnetic field, and thus, to increase the magnetic compaction pressure, the magnets are placed on a magnetic top plate. First, the entire procedure of preparing the composite lay-up on a magnetic bottom steel plate using the conventional wet lay-up vacuum bag process is described. Second, placement of a set of Neodymium-Iron-Boron permanent magnets, arranged in alternating polarity, on the vacuum bag is illustrated. Next, the experimental procedures to measure the magnetic compaction pressure and volume fractions of the composite constituents are presented. Finally, methods used to characterize microstructure and mechanical properties of composite laminates are discussed in detail. The results prove the effectiveness of the MACM method in improving the quality of wet lay-up vacuum bag laminates. This method does not require large capital investment for tooling or equipment and can also be used to consolidate geometrically complex composite parts by placing the magnets on a matching top mold positioned on the vacuum bag.

A new technique for applying consolidation pressure on the vacuum bag lay-up to fabricate composite laminates is described. The goal of this protocol is to develop a simple, cost-effective technique to improve the quality of laminates fabricated by the wet lay-up vacuum bag method.

자석 복합 제조 지원: 유연한 새로운 기술 진공 가방/Lay 업 프로세스에 높은 통합 압력을 달성 하기 위한

This work demonstrates a protocol to improve the quality of composite laminates fabricated by wet lay-up vacuum bag processes using the recently developed ...

Using Flexible Gold-Titanium Reaction Cells to Simulate Pressure-Dependent Microbial Activity in the Context of Subsurface Biomining

Laboratory studies investigating subsurface microbial processes, such as metal leaching in deep ore deposits (biomining), share common and challenging obstacles, including the special environmental conditions that need to be replicated, e.g., high pressure and in some cases acidic solutions. The former requires an experimental setup suitable for pressurization up to 100 bar, while the latter demands a fluid container with high chemical resistance against corrosion and unwanted chemical reactions with the container wall. To meet these conditions for an application in the field of in situ biomining, a special flexible gold-titanium reaction cell inside a rocking high-pressure reactor was used in this study. The described system allowed simulation of in situ biomining through sulfur-driven microbial iron reduction in an anoxic, pressure-controlled, highly chemically inert experimental environment. The flexible gold-titanium reaction cell can accommodate up to 100 mL of sample solution, which can be sampled at any given time point while the system maintains the desired pressure. Experiments can be performed on timescales ranging from hours to months. Assembling the high-pressure reactor system is fairly time consuming. Nevertheless, when complex and challenging (microbiological) processes occurring in the earth&#39;s deep subsurface in chemically aggressive fluids have to be investigated in the laboratory, the advantages of this system outweigh the disadvantages. The results found that even at high pressure the microbial consortium is active, but at significantly lower metabolic rates.

This protocol describes microbial experiments under elevated pressures to study in situ biomining processes. The experimental approach employs a rocking high-pressure reactor equipped with a gold-titanium reaction cell containing a microbial culture in an acidic, iron-rich medium.

유연한 금-티타늄 반응 세포를 사용하여 지하 생물 광의 맥락에서 압력 의존미생물 활성 시뮬레이션

Laboratory studies investigating subsurface microbial processes, such as metal leaching in deep ore deposits (biomining), share common and challenging ...

Macro-Rheology Characterization of Gill Raker Mucus in the Silver Carp, Hypophthalmichthys molitrix

The silver carp, Hypophthalmichthys molitrix, is an invasive planktivorous filter feeder fish that infested the natural waterways of the upper Mississippi River basin due to its highly efficient filter feeding mechanism. The characteristic organs called gill rakers (GRs), found in many such filter feeders, facilitate the efficient filtration of food particles such as phytoplankton that are of a few microns in size.
The motivation to investigate the rheology of the GR mucus stems from our desire to understand its role in aiding the filter feeding process in the silver carp. The mucus-rich fluid, in a &#8216;thick and sticky&#8217; state may facilitate the adhesion of food particulates. The permeation and transport through the GR membrane are&#160;facilitated by the action of external shear forces that induce varying shear strain rates. Therefore, mucus rheology can provide a vital clue to the tremendous outcompeting nature of the silver carp within the pool of filter feeding fish. Based on this it was posited that GR mucus may provide an adhesive function to food particles and act as a transport vehicle to assist in the filter feeding process.
The main objective of the protocol is to determine the yield stress of the mucus, attributed to the minimum shear stress required to initiate flow at which irreversible plastic deformation is first observed across a structured viscoelastic material. Accordingly, rheological properties of the GR mucus, i.e., viscosity, storage, and loss moduli, were investigated for its non-Newtonian, shear-thinning nature using a rotational rheometer. &#160;
A protocol presented here is employed to analyze the rheological properties of mucus extracted from the gill rakers of a silver carp, fished at Hart Creek location of the Missouri River. The protocol aims to develop an effective strategy for rheological testing and material characterization of mucus assumed to be a structured viscoelastic material.

Macro-Rheology Characterization of Gill Raker Mucus in the Silver Carp, Hypophthalmichthys molitrix

This protocol presents a method to perform rheology characterization of mucus that resides on gill rakers (GRs) of the silver carp. Viscoelastic characteristics of GR-mucus, obtained by measuring viscosity, storage and loss moduli, are evaluated for the apparent yield stress to understand the filter feeding mechanism in GRs.

실버 잉어, 하이포팔미치티스 몰리트리스의 길 레이크머 점액의 매크로-리로지 특성화

The silver carp, Hypophthalmichthys molitrix, is an invasive planktivorous filter feeder fish that infested the natural waterways of the upper Mississippi ...

Determining the Mechanical Strength of Ultra-Fine-Grained Metals

The mechanical strengthening of metals is the long-standing challenge and popular topic of materials science in industries and academia. The size dependence of the strength of the nanometals has been attracting a lot of interest. However, characterizing the strength of materials at the lower nanometer scale has been a big challenge because the traditional techniques become no longer effective and reliable, such as nano-indentation, micropillar compression, tensile, etc. The current protocol employs radial diamond-anvil cell (rDAC) X-ray diffraction (XRD) techniques to track differential stress changes and determine the strength of ultrafine metals. It is found that ultrafine nickel particles have more significant yield strength than coarser particles, and the size strengthening of nickel continues down to 3 nm. This vital finding immensely depends on effective and reliable characterizing techniques. The rDAC XRD method is expected to play a significant role in studying and exploring nanomaterial mechanics.

The protocol presented here describes the high-pressure radial diamond-anvil-cell experiments and analyzing the related data, which are essential for obtaining the mechanical strength of the nanomaterials with a significant breakthrough to the traditional approach.

The mechanical strengthening of metals is the long-standing challenge and popular topic of materials science in industries and academia. The size ...

Ion-Exchange Membranes for the Fabrication of Reverse Electrodialysis Device

Reverse electrodialysis (RED) is an effective way to generate power by mixing two different salt concentrations in water using cation-exchange membranes (CEM) and anion-exchange membranes (AEM). The RED stack is composed of an alternating arrangement of the cation-exchange membrane and anion-exchange membrane. The RED device acts as a potential candidate for fulfilling the universal demand for future energy crises. Here, in this article, we demonstrate a procedure to fabricate a reverse electrodialysis device using laboratory-scale CEM and AEM for power production. The active area of the ion-exchange membrane is 49 cm2. In this article, we provide a step-by-step procedure for synthesizing the membrane, followed by the stack&#39;s assembly and power measurement. The measurement conditions and net power output calculation have also been explained. Furthermore, we describe the fundamental parameters that are taken into consideration for obtaining a reliable outcome. We also provide a theoretical parameter that affects the overall cell performance relating to the membrane and the feed solution. In short, this experiment describes how to assemble and measure RED cells on the same platform. It also contains the working principle and calculation used for estimating the net power output of the RED stack using CEM and AEM membranes.

We demonstrate the fabrication of a reverse electrodialysis device using a cation-exchange membrane (CEM) and anion-exchange membrane (AEM) for power generation.

역전기분해 장치 제조를 위한 이온 교환 멤브레인

Reverse electrodialysis (RED) is an effective way to generate power by mixing two different salt concentrations in water using cation-exchange membranes ...