The authors wish to express their gratitude to Sika SAU for their support and, particularly for their supply of the material for the anchors and for the reinforcements. Betazul is especially acknowledged for their help with the customized drill bit and with the preparation of the video.

1. Anchor Installation Method
NOTE: This method includes the hole drilling, cleaning, and smoothing of the hole edge, as well as impregnation and insertion of the anchor.
<ol>
	<li>Drill the hole to the required embedment length and with the specified diameter.
	<ol>
		<li>Use an appropriate drilling tool (that is to say, electrical hammer or diamond core). For concrete structures, the criteria for selection of drilling tools are the same as in adhesive anchors, and can be found in previously published work10,11. For an electrical hammer, drill with a maximum speed of 800 rpm.
		<ol>
			<li>Provide a hole clearance (i.e., the difference between the diameter of the drill and that of the connector) of no less than 4 mm. Furthermore, it is recommended that this difference be 8-10 mm. This eases the smoothing of the hole and allows bending of the anchor inside the drill. 
			&#8203;NOTE: It should be noted that commercial fiber ropes have nominal diameters (when impregnated) ranging from 10 to 12 mm. The anchors displayed in the filmed protocol were made from fiber ropes with a nominal diameter of 12 mm.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Control the embedment length and smooth the hole. Length control is extremely important, as anchor performance is extremely length-sensitive. Embedment lengths ranging from 75 to 150 mm are recommended.
	<ol>
		<li>To perform length control, insert a rigid bar into the drilling hole, and compare the total length of the bar and the length that remains out of the hole when inserted with a measuring tape.</li>
		<li>Use a blow-out hand pump, once the drilling is complete, to perform a first dust removal. Follow the instructions of the manufacturer of the pump. Blow out no less than two times for the first dust removal.</li>
		<li>Smooth the hole with a rotary, non-percussive tool. See Figure 2 for details of the customized drill bit. A drill bit such as that proposed can be easily adapted to most electrical hammers. Refrigerate the substrate continuously with water while working. Smoothing is complete when no sharp edges appear, and the upper part of the drill bit touches the concrete surface.</li>
	</ol>
	</li>
	<li>Clean the hole with a combination of blowing and brushing cycles, as it is crucial to achieve the highest bond strength. The cleaning process is similar for FRP spikes and for adhesive anchors. It is recommended that at least two cleaning cycles be performed. Please refer to existing guidelines10 for additional recommendations on the cleaning process, and always follow the recommendations of the manufacturer if other cleaning tools are used.
	<ol>
		<li>Always blow before and after brushing. Consequently, each cycle of mechanical brushing involves two blowings and one brushing.</li>
		<li>Blow from the inside towards the opening of the hole in order to remove the loose particles inside the drilled hole. There are two ways of blowing. If the anchor is installed on dry concrete, blowing can be done with a blow-out hand pump. If it is installed on wet concrete, blowing must be done with pressurized air (maximum pressure of 10 bar). 
		&#8203;NOTE: The protocol has been developed for dry supports, though it could be adapted to wet conditions. It is worth noting that the smoothing technique involves moisturizing the substrate. Therefore, the resulting grade of humidity will depend on the environmental conditions and on the time elapsed between the smoothing of the hole and the insertion of the connector. The condition of dry support is defined for a relative humidity of below 5%, which normally corresponds to normal drying conditions of several days. In the case of existing concrete structures, the holes can be considered dry when 24 h have elapsed between the smoothing of the hole edge and the insertion of the anchor. A humid condition refers to near 100% relative humidity, which typically corresponds to maritime structures.</li>
		<li>Use a wire brush to radially brush the hole. The diameter of the brush must be equal or up to 20 mm greater than the diameter of the drill. Select the diameter of the brush to be as close as possible to that of the hole, to allow equal friction around the hole section.</li>
		<li>Install the anchors immediately after cleaning. If this is not possible (if the anchor is not inserted within 1 h from cleaning), perform an additional cleaning cycle before inserting the anchors. This last cleaning cycle is especially critical for horizontal anchors and holes made on the top surface of the substrate.</li>
	</ol>
	</li>
	<li>Prepare and install the anchors. This involves three different processes.
	<ol>
		<li>Cut the fiber bundle or rope to the required length. The length of the anchor must be equal to the embedment length (or dowel length) plus the length of the anchor fan.</li>
		<li>Impregnate the anchor dowel with low-viscosity epoxy primer with a soft brush. Always respect the pot-life of the resin, according to the manufacturer. Approximately 150 g of resin per anchor are needed. Impregnation requires partially fanning out the fiber bundle to maximize the penetration of the resin.
		<ol>
			<li>Always impregnate towards the end of the connector to avoid bending the fibers. Hold the bending region to prevent slippage of some fibers from the bundle and to prevent the free end from being fanned out at this step.</li>
		</ol>
		</li>
		<li>Fasten the impregnated end with a cable tie immediately after impregnation. Then, insert the anchor dowel. Assist the insertion with a wire that pushes the cable tie, to guarantee that the fibers actually reach the required embedment length.</li>
	</ol>
	</li>
	<li>Connect the reinforcement to the anchor to ensure a proper transfer mechanism to the connector. This protocol has been developed and is further explained for end anchorage of multiple-plied externally bonded FRP reinforcements. See Figure 3 for a graphic explanation of the process.
	<ol>
		<li>Apply the first ply of the reinforcement before the insertion of the anchor (but always after preparation and cleaning of the hole), as shown in Figure 3. Alternatively, use a first ply shorter than the ones adhered onto the anchor fan, to allow insertion of the anchor before applying the first ply of the reinforcement.</li>
		<li>Provide end anchorage when end-plate debonding (or delamination) is expected to occur. For the wet application of the external reinforcement, always prepare the surface of the substrate according to current standards or guidelines12,13. 
		&#8203;NOTE: Anchor fans should be fully bonded to the reinforcement, as this bond will accumulate the stress-transfer mechanism. In the case of FRP reinforcements made from multiple layers and with end-anchorage, anchor fan installation between two plies is recommended. This eliminates the need for piercing the laminate with the anchor, and avoid damaging the reinforcement. To date, no minimum fan length has been determined in the literature. The authors recommend that fan lengths of no less than 50 mm be used.</li>
		<li>Apply epoxy resin to both the external FRP reinforcement and the anchor fan. The resin can be applied with either a roller or a brush. Use the same resin to bond the external FRP reinforcement to the substrate and the anchor fan to the external reinforcement. Always consider the pot life of the resin, according to the manufacturer.
		<ol>
			<li>Prevent the emergence of air voids between the plies of the reinforcement by using a bubble roller that allows air relief after the impregnation of each layer (including the anchor fan). 
			NOTE: For the development of the protocol, a resin with a pot life of 90 min at 20 &#176;C was employed.</li>
		</ol>
		</li>
	</ol>
	</li>
</ol>
2. Design with Spike Anchors
NOTE: The design method is explained here for fan anchors, but similar procedures could be followed for different anchorage devices. This method consists of the evaluation of anchor capacity, bond strength, and contribution of the anchors to the overall strength of the reinforced member.
<ol>
	<li>Evaluate the anchor&#39;s capacity. This primarily depends on whether the anchor is subjected to tensile or shear forces. In the most common cases with dowel angles less than 180&#176; (shear applications), the dowel angle will limit the efficacy of the connector due to stress concentration in the bend region. Control the bend strength by following the installation method presented above.
	<ol>
		<li>Express the anchor capacity as a fraction of its tensile strength. The design capacity for the anchor will be the minimum of the following: the concrete cone strength, bond strength (calculated as in any post-installed anchor in concrete10), bend strength, and tensile strength, with a safety factor. This results in a design capacity of the anchors (). In Villanueva Llaurad&#243; et al.14, expressions for all the expectable failure modes of spike anchors are discussed.</li>
		<li>Estimate the concrete cone strength with an expression such as the one in Kim and Smith15 in order to prevent the concrete cone failure. The concrete cone strength is only critical for extremely shallow anchors, and, in general, it can be disregarded for anchors with embedment lengths greater than 75 mm.</li>
		<li>Calculate the bond strength of the anchor dowel. This can be performed with the general expressions for post-installed anchors from codes and design guidelines. According to those expressions, the bond strength depends on the following: the tensile strength of the concrete, the diameter of the drilled hole, and the embedment length15,16. Adopt a value for the average shear strength in the concrete-to-resin interface ranging from 8 to 15 MPa when epoxy resin is used.</li>
		<li>Estimate the reduction of strength due to bending. This mainly depends on the inner bending radius, in accordance with the expression provided by JSCE8, which has been widely adopted for internal FRP rebars. However, complementary testing on isolated anchors is recommended in order to evaluate the real as-built strength of the connectors in a given geometrical configuration. This testing should be performed with shear tests and with anchors installed following the procedure proposed in this paper.</li>
		<li>Calculate the tensile strength of the anchor with the fraction of fibers in the cross section of the connectors and the tensile strength of the fiber. For fiber ropes, manufacturers generally specify the tensile strength of the impregnated connector, which could be adopted for design with a sufficient reduction factor (from 1.25 to 1.5). For fiber bundles of hand-made anchors, flat coupon tests should be conducted as in ASTM standards17.</li>
	</ol>
	</li>
	<li>Calculate the bond strength of unanchored reinforcements with any expression from international codes or from analytical models such as those provided in the references18,19. Alternatively, single or double shear tests on bonded, unanchored specimens can be conducted. The design value of bond strength (Pdb,d) must be used in further calculations.</li>
	<li>Estimate the overall strength as the result of the bond strength of the reinforcement plus anchor capacity, for reinforcements with one anchor. This hypothesis can be accepted, according to the existing data, when the anchor fan completely covers the width of the FRP, which is coherent with the findings by authors comparing the performance of bonded and unbonded anchored specimens20,21. Calculate the design strength for anchored FRP with one spike anchor with the following equation: 
	&#160; &#160;Pd = Pdb,d + Panc,d&#160; &#160;(1)</li>
	<li>For multiple anchors, determine the anchor efficiency and contribution as a function of the arrangement of the anchors (number of plies and rows, anchor spacing). Please test the desired arrangement in order to assess the reduction of efficiency due to multiple anchors, and express the design strength of the anchored joint (Pd) as follows: 
	&#160; Pd = Pdb,d + y&#39; &#8226; n &#8226; Panc,d&#160; &#160;(2) 
	Obtain the coefficient y&#39; from tests with each specific arrangement of the project, given the number of spike anchors, as in the references20,23. As an alternative to testing, consider the efficiency y&#39; as suggested in the approaches reported from such tests in those same publications20,23.</li>
</ol>

<ol>
	<li>Grelle, S., Sneed, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+evaluation+of+anchorage+systems+for+fiber-reinforced+polymer+(FRP)+laminates+bonded+to+reinforced+concrete+elements.">An evaluation of anchorage systems for fiber-reinforced polymer (FRP) laminates bonded to reinforced concrete elements.</a> Struct Cong. , 1157-1168 (2011).</li><li>Kalfat, R., Al-Mahaidi, R., Smith, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anchorage+devices+used+to+improve+the+performance+of+reinforced+concrete+beams+retrofitted+with+FRP+composites:+State-of-the-art+review.">Anchorage devices used to improve the performance of reinforced concrete beams retrofitted with FRP composites: State-of-the-art review.</a> J Compos Constr. , 14-33 (2013).</li><li>Orton, S. L., Jirsa, J. O., Bayrak, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Design+considerations+of+carbon+fibre+anchors.">Design considerations of carbon fibre anchors.</a> J Compos Constr. 12 (6), 608-616 (2008).</li><li>Ozbakkaloglu, T., Saatcioglu, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tensile+behavior+of+FRP+anchors+in+concrete.">Tensile behavior of FRP anchors in concrete.</a> J Compos Constr. 13 (2), 82-92 (2009).</li><li>Zhang, H. W., Smith, S. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+FRP+anchor+fan+configuration+and+dowel+angle+on+anchoring+FRP+plates.">Influence of FRP anchor fan configuration and dowel angle on anchoring FRP plates.</a> Compos Part B: Eng. 43 (8), 3516-3527 (2012).</li><li>Koutas, L., Triantafillou, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+anchors+in+shear+strengthening+of+reinforced+concrete+T-beams+with+FRP.">Use of anchors in shear strengthening of reinforced concrete T-beams with FRP.</a> J Compos Constr. 17 (1), 101-107 (2012).</li><li>Villanueva-Llaurad&#243;, P., Fern&#225;ndez-G&#243;mez, J., Gonz&#225;lez-Ramos, F. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+geometrical+and+installation+parameters+on+performance+of+CFRP+anchors.">Influence of geometrical and installation parameters on performance of CFRP anchors.</a> Compos Struct. 176, 105-116 (2017).</li><li>Machida, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recommendation+for+design+and+construction+of+concrete+structures+using+continuous+fiber+reinforcing+materials.">Recommendation for design and construction of concrete structures using continuous fiber reinforcing materials.</a> Japan Society of Civil Engineers (JSCE). , (1997).</li><li>Lee, C., Ko, M., Lee, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bend+strength+of+complete+closed-type+carbon+fiber+reinforced+polymer+stirrups+with+rectangular+section.">Bend strength of complete closed-type carbon fiber reinforced polymer stirrups with rectangular section.</a> J Compos Constr. 18 (1), 04013022 (2013).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Qualification of post-installed adhesive anchors in concrete and commentary. , 4-11 (2011).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Metal anchors for use in concrete. Part 5: Bonded Anchors. , (2013).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures. , (2008).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Design Guidance for Strengthening Concrete Structures Using Fibre Reinforced Composite Materials. , (2012).</li><li>Villanueva-Llaurad&#243;, P., Ibell, T., Fern&#225;ndez-G&#243;mez, J., Gonz&#225;lez-Ramos, F. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pull-out+and+shear-strength+models+for+FRP+spike+anchors.">Pull-out and shear-strength models for FRP spike anchors.</a> Compos B Eng. 116, 239-252 (2017).</li><li>Kim, S., Smith, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pullout+strength+models+for+FRP+anchors+in+uncracked+concrete.">Pullout strength models for FRP anchors in uncracked concrete.</a> J Compos Constr. 14 (4), 406-414 (2010).</li><li>Cook, R. A., Konz, R. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Factors+influencing+bond+strength+of+adhesive+anchors.">Factors influencing bond strength of adhesive anchors.</a> ACI Struct J. 98 (1), 76-86 (2001).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Standard test method for Tensile Properties of Polymer Matrix Composite Materials. , (2014).</li><li>Chen, J., Teng, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anchorage+strength+models+for+FRP+and+steel+plates+bonded+to+concrete.">Anchorage strength models for FRP and steel plates bonded to concrete.</a> J Struct Eng. 127 (7), 784-791 (2001).</li><li>Lu, X. Z., Teng, J. G., Ye, L. P., Jiang, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bond-slip+models+for+FRP+and+steel+plates+bonded+to+concrete.">Bond-slip models for FRP and steel plates bonded to concrete.</a> Eng Struct. 27 (6), 920-927 (2005).</li><li>Brena, S. F., McGuirk, G. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Advances+on+the+behavior+characterization+of+FRPanchored+carbon+fiber-reinforced+polymer+(CFRP)+sheets+used+to+strengthen+concrete+elements.">Advances on the behavior characterization of FRPanchored carbon fiber-reinforced polymer (CFRP) sheets used to strengthen concrete elements.</a> Int J Concr Struct Mater. 7 (1), 3-16 (2013).</li><li>Eshwar, N., Nanni, A., Ibell, T. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Performance+of+two+anchor+systems+of+externally+bonded+fiber-reinforced+polymer+laminates.">Performance of two anchor systems of externally bonded fiber-reinforced polymer laminates.</a> ACI Mater J. 105 (1), 72-80 (2008).</li><li>Zhang, H. W., Smith, S. T., Kim, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optimisation+of+carbon+and+glass+FRP+anchor+design.">Optimisation of carbon and glass FRP anchor design.</a> Constr Build Mater. 32, 1-12 (2012).</li><li>Zhang, H. W., Smith, S. 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The authors have nothing to disclose.

A step-by-step protocol for installation and design of FRP spike anchors is presented. To the best of the authors&#39; knowledge, no detailed protocols on spike anchors have been developed regarding the effect of installation parameters and process on anchor capacity.
The proposed smoothing drill bit is beneficial in the performance of spike anchors, by means of reducing the stress concentration, and has proven its efficacy in reducing the scatter of the tests performed on isolated anchors. Th...

FRP anchors offer a promising way to enhance the performance of externally bonded FRPs applied to existing structures, given that they can delay or even prevent debonding failure1,2. However, a major concern for designers entails the premature failure of the anchors in shear due to stress concentration in the bending region. Installation quality and preparation of the clearance holes are crucial to limit this stress concentration that provokes such premature failure.
This paper deals with an installation method that aims to reduce the impact of the stress concentration and to provide a proper quality control of the preparation of the drill hole and the installation of the anchors. The method involves four parts: drilling and cleaning the holes, smoothing the hole edges with a customized drill bit to avoid irregularities in the stress-distribution within the bending region, installation of the anchor itself, including the impregnation of the anchor dowel and its insertion, and adhesion of the anchor to the reinforcement.
From previously published research3,4,5,6,7, it can be concluded that spike anchors with a bending region (that is to say, with a certain angle between the free end and the embedded region), suffer stress concentration that is prone to provoke premature failure. This cannot always be avoided due to the geometry of the original members. In many cases, 90&#176; dowel angles are broadly employed, although it is generally agreed that 135&#176; dowel angles allow a reduction in stress concentration and lead to better performance of spike anchors. The main reasons for the use of 90&#176; dowel angles are that they are simpler to execute and control in any direction and that they reduce the possibility to meet internal reinforcements.
Figure 1 shows a typical spike anchor with the most common dowel angles. Spike anchors installed with 90&#176; dowel angles can, nevertheless, display a relatively good performance if proper control of the stress concentration is provided. Limiting stress concentration generally involves designing the anchors with a large inner bending radius, as the inner bending radius has been found to play a major role in fiber kinking8,9. In this sense, authors such as Orton et al.3 suggest that a bending radius of four times the anchor diameter should be used. This recommendation results in impractical bending radii, even for small anchor diameters, as increasing the bending radius involves diminishing the actual embedment length for a given hole depth.
The authors believe that the recommendation of large bending radius is related to the difficulty of controlling the real inner bending radius, from a geometrical point of view, when smoothing is done by hand. A customized drill bit has been consequently designed that allows an easy quality control of the installation and ensures that the bending radius is considered in the design.
Two different processes are considered in the paper. The first one is related to the installation procedure for the connectors (anchors, especially before fanning out the free end), whereas the second includes the proposed method for design with spike anchors and the verification needs.

<table border="0" cellpadding="0" cellspacing="0" style="width:957px;" width="957">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Concrete</td>
			<td style="width:96px;"></td>
			<td style="width:119px;"></td>
			<td style="width:527px;">The concrete for support has a dosage made by the authors, and a strength class no lower than C40</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:216px;">SikaWrap anchor C</td>
			<td style="width:96px;">SIKA</td>
			<td style="width:119px;"></td>
			<td style="width:527px;">This material has been used for the FRP spike anchors. SikaWrap Anchor C is a unidirectional, carbon fiber rope, sheathed in an elastic gauze. The gauze can be cut onsite to create a fan end that anchors CFRP fabrics and plates used in the structural strengthening of masonry and concrete.&#160;</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:216px;">Sikadur 330</td>
			<td style="width:96px;">SIKA</td>
			<td style="width:119px;"></td>
			<td style="width:527px;">Impregnating resin, apt for manual saturation methods. The product was used for impregnating the anchor dowel before insertion</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Sikadur 30</td>
			<td style="width:96px;">SIKA</td>
			<td style="width:119px;"></td>
			<td style="width:527px;">Thixotropic, two part epoxy resin applied by spatula and therefore suitable for virtually any application, including overhead</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Drill bit</td>
			<td style="width:96px;">Betazul</td>
			<td style="width:119px;"></td>
			<td style="width:527px;">Drill bit employed to smooth the holes that was designed by the authors and developed by Betazul SA</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Hammer drill</td>
			<td style="width:96px;">Hilti</td>
			<td style="width:119px;"></td>
			<td style="width:527px;">Tool for the execution of anchor holes on masonry and concrete, for different drilling ranges</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Wire brush</td>
			<td style="width:96px;">Hilti</td>
			<td style="width:119px;">Hit series</td>
			<td style="width:527px;">For the proper brushing of drilled holes of varying diameters and embedment depths</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Blow-out pump</td>
			<td style="width:96px;">Hilti</td>
			<td style="width:119px;">Hit series</td>
			<td>Manual blow-out pump&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">SikaWrap-230 C</td>
			<td style="width:96px;">SIKA</td>
			<td style="width:119px;"></td>
			<td style="width:527px;">Unidirectional woven carbon fiber fabric for dry application process</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Aluminium Bubble Roller</td>
			<td style="width:96px;">Fibre glast</td>
			<td style="width:119px;"></td>
			<td style="width:527px;">For laminations where increased pressure is necessary to release air bubbles. They are straight across the width of the head and provide excellent air relief for nearly all applications.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Brush</td>
			<td style="width:96px;"></td>
			<td style="width:119px;"></td>
			<td>For impregnation of FRP bundle and sheet</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">600 kN testing machine</td>
			<td style="width:96px;">Proeti</td>
			<td style="width:119px;">DI-CP/S</td>
			<td style="width:527px;">This is used for the shear test of anchors, in order to evaluate the efficacy of the proposed insertion method</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:216px;">Cable ties</td>
			<td style="width:96px;"></td>
			<td style="width:119px;"></td>
			<td style="width:527px;">Cable ties are needed to fasten the end of the anchor dowel in order to prevent fanning out of the fibers during insertion</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Measuring tape</td>
			<td style="width:96px;"></td>
			<td style="width:119px;"></td>
			<td style="width:527px;">The measuring tape is necessary to control the embedment length as well as the diameter of the drill bit and hole clearance</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Steel wire</td>
			<td style="width:96px;"></td>
			<td style="width:119px;"></td>
			<td>Required to assist insertion</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Rigid (steel) bar</td>
			<td style="width:96px;"></td>
			<td style="width:119px;"></td>
			<td style="width:527px;">A rigid bar of any material (in this case, it was made with a steel bar) is needed to control the embedment length</td>
		</tr>
	</tbody>
</table>

installation method to enhance quality control for fiber reinforced polymer spike anchors

Fiber reinforced polymer (FRP) anchors are a promising way to enhance the performance of externally-bonded FRPs applied to existing structures, as they can delay or even prevent debonding failure. However, a major concern faced by designers is the premature failure of the anchors due to stress concentration. Poor installation quality and preparation of the clearance holes can result in stress concentration that provokes this premature failure. This paper deals with an installation method that aims to reduce the impact of the stress concentration and to provide a proper quality control of the preparation of the drill hole. The method involves three parts: the drilling and cleaning of the holes, the smoothing of the hole edges with a customized drill bit, and the installation of the anchor itself, including the impregnation of the anchor dowel and its insertion. Anchor fans (the free length of the spikes) are then bonded to the external FRP reinforcement. For the end anchorage, and in the case of reinforcements with multiple plies, it is recommended that the anchor fan be inserted between two plies to assist the stress-transfer mechanism. 
The proposed procedure is complemented with a design approach for spike anchors, based on an extensive database. It is proposed that the design follow a number of steps, namely: selection of the anchor diameter and subsequent tensile strength of the connector (that is to say, the anchor before fanning out the free end), evaluation of the reduction in the tensile strength due to bending, provision of enough embedment to prevent slippage failure, and consideration of the number and spacing of anchors for a given reinforcement. In this sense, it should be noted that further research is needed in order to obtain a general expression for the contribution of spike anchors to overall bond strength of FRP reinforcements.

Tests were conducted on isolated connectors to evaluate the effectiveness of the smoothing method. In addition, two methods of impregnation and insertion of the connectors were compared. The wet method involved impregnating the anchors immediately before insertion, as in the presented protocol. The hardened (or pre-impregnated) method consisted of impregnation of the embedded region of anchors in advance, at least 24 h before insertion.
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Installation Method to Enhance Quality Control for Fiber Reinforced Polymer Spike Anchors

This manuscript presents a method for controlling the quality of installation for spike anchors designed to delay delamination of externally bonded fiber reinforced polymers. The protocol includes the preparation of the drill hole and the insertion process. The most influential parameters on the efficiency of the anchors are discussed.

Fiber reinforced polymer (FRP) anchors are a promising way to enhance the performance of externally-bonded FRPs applied to existing structures, as they ...

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7.0K Views.  Technical University of Madrid. This manuscript presents a method for controlling the quality of installation for spike anchors designed to delay delamination of externally bonded fiber reinforced polymers. The protocol includes the preparation of the drill hole and the insertion process. The most influential parameters on the efficiency of the anchors are discussed.

Video: Installation Method to Enhance Quality Control for Fiber Reinforced Polymer Spike Anchors

Fabricating Metamaterials Using the Fiber Drawing Method

Metamaterials are man-made composite materials, fabricated by assembling components much smaller than the wavelength at which they operate 1. They owe their electromagnetic properties to the structure of their constituents, instead of the atoms that compose them. For example, sub-wavelength metal wires can be arranged to possess an effective electric permittivity that is either positive or negative at a given frequency, in contrast to the metals themselves 2. This unprecedented control over the behaviour of light can potentially lead to a number of novel devices, such as invisibility cloaks 3, negative refractive index materials 4, and lenses that resolve objects below the diffraction limit 5. However, metamaterials operating at optical, mid-infrared and terahertz frequencies are conventionally made using nano- and micro-fabrication techniques that are expensive and produce samples that are at most a few centimetres in size 6-7. Here we present a fabrication method to produce hundreds of meters of metal wire metamaterials in fiber form, which exhibit a terahertz plasmonic response 8. We combine the stack-and-draw technique used to produce microstructured polymer optical fiber 9 with the Taylor-wire process 10, using indium wires inside polymethylmethacrylate (PMMA) tubes. PMMA is chosen because it is an easy to handle, drawable dielectric with suitable optical properties in the terahertz region; indium because it has a melting temperature of 156.6 &deg;C which is appropriate for codrawing with PMMA. We include an indium wire of 1 mm diameter and 99.99% purity in a PMMA tube with 1 mm inner diameter (ID) and 12 mm outside diameter (OD) which is sealed at one end. The tube is evacuated and drawn down to an outer diameter of 1.2 mm. The resulting fiber is then cut into smaller pieces, and stacked into a larger PMMA tube. This stack is sealed at one end and fed into a furnace while being rapidly drawn, reducing the diameter of the structure by a factor of 10, and increasing the length by a factor of 100. Such fibers possess features on the micro- and nano- scale, are inherently flexible, mass-producible, and can be woven to exhibit electromagnetic properties that are not found in nature. They represent a promising platform for a number of novel devices from terahertz to optical frequencies, such as invisible fibers, woven negative refractive index cloths, and super-resolving lenses.

Metamaterials at terahertz frequencies offer unique opportunities, but are challenging to fabricate in bulk. We adapt the fabrication procedure for microstructured polymer optical fibers to inexpensively fabricate metamaterials potentially on an industrial scale. We produce polymethylmethacrylate fibers containing ~10 &mu;m diameter indium wires separated by ~100 &mu;m, which exhibit a terahertz plasmonic response.

Metamaterials are man-made composite materials, fabricated by assembling components much smaller than the wavelength at which they operate 1. They owe ...

Integrating a Triplet-triplet Annihilation Up-conversion System to Enhance Dye-sensitized Solar Cell Response to Sub-bandgap Light

The poor response of dye-sensitized solar cells (DSCs) to red and infrared light is a significant impediment to the realization of higher photocurrents and hence higher efficiencies. Photon up-conversion by way of triplet-triplet annihilation (TTA-UC) is an attractive technique for using these otherwise wasted low energy photons to produce photocurrent, while not interfering with the photoanodic performance in a deleterious manner. Further to this, TTA-UC has a number of features, distinct from other reported photon up-conversion technologies, which renders it particularly suitable for coupling with DSC technology. In this work, a proven high performance TTA-UC system, comprising a palladium porphyrin sensitizer and rubrene emitter, is combined with a high performance DSC (utilizing the organic dye D149) in an integrated device. The device shows an enhanced response to sub-bandgap light over the absorption range of the TTA-UC sub-unit resulting in the highest figure of merit for up-conversion assisted DSC performance to date.

An integrated device, incorporating a dye-sensitized solar cell and triplet-triplet annihilation up-conversion unit was produced, affording enhanced light harvesting, from a wider section of the solar spectrum. Under modest irradiation levels a significantly enhanced response to low energy photons was demonstrated, yielding a record figure of merit for dye-sensitized solar cells.

The poor response of dye-sensitized solar cells (DSCs) to red and infrared light is a significant impediment to the realization of higher photocurrents ...

Preparation and Friction Force Microscopy Measurements of Immiscible, Opposing Polymer Brushes

Solvated polymer brushes are well known to lubricate high-pressure contacts, because they can sustain a positive normal load while maintaining low friction at the interface. Nevertheless, these systems can be sensitive to wear due to interdigitation of the opposing brushes. In a recent publication, we have shown via molecular dynamics simulations and atomic force microscopy experiments, that using an immiscible polymer brush system terminating the substrate and the slider surfaces, respectively, can eliminate such interdigitation. As a consequence, wear in the contacts is reduced. Moreover, the friction force is two orders of magnitude lower compared to traditional miscible polymer brush systems. This newly proposed system therefore holds great potential for application in industry. Here, the methodology to construct an immiscible polymer brush system of two different brushes each solvated by their own preferred solvent is presented. The procedure how to graft poly(N-isopropylacrylamide) (PNIPAM) from a flat surface and poly(methyl methacrylate) (PMMA) from an atomic force microscopy (AFM) colloidal probe is described. PNIPAM is solvated in water and PMMA in acetophenone. Via friction force AFM measurements, it is shown that the friction for this system is indeed reduced by two orders of magnitude compared to the miscible system of PMMA on PMMA solvated in acetophenone.

The methodology to perform friction force microscopy experiments for contacting brushes is presented: Two polymer brushes that are grafted from (a) substrates and (b) colloidal probes are slid to show that, by using two contacting immiscible brush systems, friction in sliding contacts is reduced compared to miscible brush systems.

Solvated polymer brushes are well known to lubricate high-pressure contacts, because they can sustain a positive normal load while maintaining low ...

A Testing Platform for Durability Studies of Polymers and Fiber-reinforced Polymer Composites under Concurrent Hygrothermo-mechanical Stimuli

The durability of polymers and fiber-reinforced polymer composites under service condition is a critical aspect to be addressed for their robust designs and condition-based maintenance. These materials are adopted in a wide range of engineering applications, from aircraft and ship structures, to bridges, wind turbine blades, biomaterials and biomedical implants. Polymers are viscoelastic materials, and their response may be highly nonlinear and thus make it challenging to predict and monitor their in-service performance. The laboratory-scale testing platform presented herein assists the investigation of the influence of concurrent mechanical loadings and environmental conditions on these materials. The platform was designed to be low-cost and user-friendly. Its chemically resistant materials make the platform adaptable to studies of chemical degradation due to in-service exposure to fluids. An example of experiment was conducted at RT on closed-cell polyurethane foam samples loaded with a weight corresponding to ~50% of their ultimate static and dry load. Results show that the testing apparatus is appropriate for these studies. Results also highlight the larger vulnerability of the polymer under concurrent loading, based on the higher mid-point displacements and lower residual failure loads. Recommendations are made for additional improvements to the testing apparatus.

The durability of polymers and fiber-reinforced polymer composites in service is a critical aspect for their designs and condition-based maintenance. We present a novel low-cost laboratory testing platform for the investigation of the influence of concurrent mechanical and environmental loadings, and may help design more efficient yet safer composite structures.

The durability of polymers and fiber-reinforced polymer composites under service condition is a critical aspect to be addressed for their robust designs ...

Morphology Control for Fully Printable Organic&#8211;Inorganic Bulk-heterojunction Solar Cells Based on a Ti-alkoxide and Semiconducting Polymer

The photoactive layer of a typical organic thin-film bulk-heterojunction (BHJ) solar cell commonly uses fullerene derivatives as the electron-accepting material. However, fullerene derivatives are air-sensitive; therefore, air-stable material is needed as an alternative. In the present study, we propose and describe the properties of Ti-alkoxide as an alternative electron-accepting material to fullerene derivatives to create highly air-stable BHJ solar cells. It is well-known that controlling the morphology in the photoactive layer, which is constructed with fullerene derivatives as the electron acceptor, is important for obtaining a high overall efficiency through the solvent method. The conventional solvent method is useful for high-solubility materials, such as fullerene derivatives. However, for Ti-alkoxides, the conventional solvent method is insufficient, because they only dissolve in specific solvents. Here, we demonstrate a new approach to morphology control that uses the molecular bulkiness of Ti-alkoxides without the conventional solvent method. That is, this method is one approach to obtain highly efficient, air-stable, organic-inorganic bulk-heterojunction solar cells.

Morphology Control for Fully Printable Organic&amp;#8211;Inorganic Bulk-heterojunction Solar Cells Based on a Ti-alkoxide and Semiconducting Polymer

A method for fully printable, fullerene-free, highly air-stable, bulk-heterojunction solar cells based on Ti alkoxides as the electron acceptor and the electron-donating polymer fabrication is described here. Moreover, a method for controlling the morphology of the photoactive layer through the molecular bulkiness of the Ti-alkoxide units is reported.

The photoactive layer of a typical organic thin-film bulk-heterojunction (BHJ) solar cell commonly uses fullerene derivatives as the electron-accepting ...

Fabrication of Polymer Microspheres for Optical Resonator and Laser Applications

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, interface precipitation, and mini-emulsion. In all methods, well-defined, micrometer-sized spheres are obtained from a self-assembling process in solution. The vapor diffusion method can result in spheres with the highest sphericity and surface smoothness, yet the types of the polymers able to form these spheres are limited. On the other hand, in the mini-emulsion method, microspheres can be made from various types of polymers, even from highly crystalline polymers with coplanar, &#960;-conjugated backbones. The photoluminescent (PL) properties from single isolated microspheres are unusual: the PL is confined inside the spheres, propagates at the circumference of the spheres via the total internal reflection at the polymer/air interface, and self-interferes to show sharp and periodic resonant PL lines. These resonating modes are so-called "whispering gallery modes" (WGMs). This work demonstrates how to measure WGM PL from single isolated spheres using the micro-photoluminescence (&#181;-PL) technique. In this technique, a focused laser beam irradiates a single microsphere, and the luminescence is detected by a spectrometer. A micromanipulation technique is then used to connect the microspheres one by one and to demonstrate the intersphere PL propagation and color conversion from coupled microspheres upon excitation at the perimeter of one sphere and detection of PL from the other microsphere. These techniques, &#181;-PL and micromanipulation, are useful for experiments on micro-optic application using polymer materials.

Protocols for the synthesis of microspheres from polymers, the manipulation of microspheres, and micro-photoluminescence measurements are presented.

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, ...

Experimental Protocol to Determine the Chloride Threshold Value for Corrosion in Samples Taken from Reinforced Concrete Structures

The aging of reinforced concrete infrastructure in developed countries imposes an urgent need for methods to reliably assess the condition of these structures. Corrosion of the embedded reinforcing steel is the most frequent cause for degradation. While it is well known that the ability of a structure to withstand corrosion depends strongly on factors such as the materials used or the age, it is common practice to rely on threshold values stipulated in standards or textbooks. These threshold values for corrosion initiation (Ccrit) are independent of the actual properties of a certain structure, which clearly limits the accuracy of condition assessments and service life predictions. The practice of using tabulated values can be traced to the lack of reliable methods to determine Ccrit on-site and in the laboratory.
Here, an experimental protocol to determine Ccrit for individual engineering structures or structural members is presented. A number of reinforced concrete samples are taken from structures and laboratory corrosion testing is performed. The main advantage of this method is that it ensures real conditions concerning parameters that are well known to greatly influence Ccrit, such as the steel-concrete interface, which cannot be representatively mimicked in laboratory-produced samples. At the same time, the accelerated corrosion test in the laboratory permits the reliable determination of Ccrit prior to corrosion initiation on the tested structure; this is a major advantage over all common condition assessment methods that only permit estimating the conditions for corrosion after initiation, i.e., when the structure is already damaged.
The protocol yields the statistical distribution of Ccrit for the tested structure. This serves as a basis for probabilistic prediction models for the remaining time to corrosion, which is needed for maintenance planning. This method can potentially be used in material testing of civil infrastructures, similar to established methods used for mechanical testing.

We propose a method to measure a parameter that is highly relevant for corrosion assessments or predictions of reinforced concrete structures, with the main advantage of permitting testing of samples from engineering structures. This ensures real conditions at the steel-concrete interface, which are crucial to avoid artifacts of laboratory-made samples.

The aging of reinforced concrete infrastructure in developed countries imposes an urgent need for methods to reliably assess the condition of these ...

Preparation of Aligned Steel Fiber Reinforced Cementitious Composite and Its Flexural Behavior

The aim of this work is to present an approach, inspired by the way in which a compass needle maintains a consistent orientation under the action of the Earth&#39;s magnetic field, for manufacturing a cementitious composite reinforced with aligned steel fibers. Aligned steel fiber reinforced cementitious composites (ASFRC) were prepared by applying a uniform electromagnetic field to fresh mortar containing short steel fibers, whereby the short steel fibers were driven to rotate in alignment with the magnetic field. The degree of alignment of steel fibers in hardened ASFRC was assessed both by counting steel fibers in fractured cross-sections and by X-ray computed tomography analysis. The results from the two methods show that the steel fibers in ASFRC were highly aligned while the steel fibers in non-magnetically treated composites were randomly distributed. The aligned steel fibers had a much higher reinforcing efficiency, and the composites, therefore, exhibited significantly enhanced flexural strength and toughness. The ASFRC is thus superior to SFRC in that it can withstand greater tensile stress and more effectively resist cracking.

This protocol describes an approach for manufacturing aligned steel fiber reinforced cementitious composite by applying a uniform electromagnetic field. Aligned steel fiber reinforced cementitious composite exhibits superior mechanical properties to ordinary fiber reinforced concrete.

The aim of this work is to present an approach, inspired by the way in which a compass needle maintains a consistent orientation under the action of the ...

Microfluidic Channel-Based Soft Electrodes for Capacitive Pressure Sensing

Microfluidic Channel-Based Soft Electrodes and Their Application in Capacitive Pressure Sensing

Flexible and stretchable electrodes are essential components in soft artificial sensory systems. Despite recent advances in flexible electronics, most electrodes are either restricted by the patterning resolution or the capability of inkjet printing with high-viscosity super-elastic materials. In this paper, we present a simple strategy to fabricate microchannel-based stretchable composite electrodes, which can be achieved by scraping elastic conductive polymer composites (ECPCs) into lithographically embossed microfluidic channels. The ECPCs were prepared by a volatile solvent evaporation method, which achieves a uniform dispersion of carbon nanotubes (CNTs) in a polydimethylsiloxane (PDMS) matrix. Compared to conventional fabrication methods, the proposed technique can facilitate the rapid fabrication of well-defined stretchable electrodes with high-viscosity slurry. Since the electrodes in this work were made up of all-elastomeric materials, strong interlinks can be formed between the ECPCs-based electrodes and the PDMS-based substrate at the interfaces of the microchannel walls, which allows the electrodes to exhibit mechanical robustness under high tensile strains. In addition, the mechanical-electric response of the electrodes was also systematically studied. Finally, a soft pressure sensor was developed by combining a dielectric silicone foam and an interdigitated electrodes (IDE) layer, and this demonstrated great potential for pressure sensors in soft robotic tactile sensing applications.

Author Spotlight: Microfluidic Channel-Based Soft Electrodes and Their Application in Capacitive Pressure Sensing  

Flexible electrodes have a wide range of applications in soft robotics and wearable electronics. The present protocol demonstrates a new strategy to fabricate highly stretchable electrodes with high resolution via lithographically defined microfluidic channels, which paves the way for future high-performance soft pressure sensors.

Flexible and stretchable electrodes are essential components in soft artificial sensory systems. Despite recent advances in flexible electronics, most ...

Fabrication and Mechanical Property Assessment of Fiber Composite Laminates

Measuring the Mechanical Properties of Glass Fiber Reinforcement Polymer Composite Laminates Obtained by Different Fabrication Processes

The traditional wet hand lay-up process (WL) has been widely applied in the manufacturing of fiber composite laminates. However, due insufficiency in the forming pressure, the mass fraction of fiber is reduced and lots of air bubbles are trapped inside, resulting in low-quality laminates (low stiffness and strength). The wet hand lay-up/vacuum bag (WLVB) process for the fabrication of composite laminates is based on the traditional wet hand lay-up process, using a vacuum bag to remove air bubbles and provide pressure, and then carrying out the heating and curing process. 
Compared with the traditional hand lay-up process, laminates manufactured by the WLVB process show superior mechanical properties, including better strength and stiffness, higher fiber volume fraction, and lower void volume fraction, which are all benefits for composite laminates. This process is completely manual, and it is greatly influenced by the skills of the preparation personnel. Therefore, the products are prone to defects such as voids and uneven thickness, leading to unstable qualities and mechanical properties of the laminate. Hence, it is necessary to finely describe the WLVB process, finely control steps, and quantify material ratios, in order to ensure the mechanical properties of laminates. 
This paper describes the meticulous process of the WLVB process for preparing woven plain patterned glass fiber reinforcement composite laminates (GFRPs). The fiber volume content of laminates was calculated using the formula method, and the calculated results showed that the fiber volume content of WL laminates was 42.04%, while that of WLVB laminates was 57.82%, increasing by 15.78%. The mechanical properties of the laminates were characterized using tensile and impact tests. The experimental results revealed that with the WLVB process, the strength and modulus of the laminates were enhanced by 17.4% and 16.35%, respectively, and the specific absorbed energy was increased by 19.48%.

Author Spotlight: Enhancing Fiber Composite Laminate Quality with the Wet Hand Lay-Up/Vacuum Bag Process 

This paper describes a fabrication process for fiber-reinforced polymer matrix composite laminates obtained using the wet hand lay-up/vacuum bag method.

The traditional wet hand lay-up process (WL) has been widely applied in the manufacturing of fiber composite laminates. However, due insufficiency in the ...