Civil Engineering April 2021 | Vol 29 No 3

38 April 2021 Civil Engineering series). Load-displacement behaviour is highly dependent on the achieved grout body diameter. Larger grout bodies often result in smaller displacements at similar load (Bayesteh & Sabermahani, 2018). Strand anchors are expected to have larger grout body diameters, but from the authors’ experience similar displacement can be expected from load testing using SDAs and strand anchors. This however requires further research. The authors believe that the use of SDA grouted anchors could either result in higher or lower displacements, de- pending on the actual circumstances and when assuming the same SDA and strand anchor ultimate bond capacity: 1. Higher displacement will result for strand grouted anchors if the shear parameters assumed in the design are higher than those of the materials found on site (or other ULS scenarios) and large loads exceeding those locked- off are attracted to the anchors. This is due the lower axial stiffness (AE) and elastic extension of strand anchors. 2. If the shear parameters assumed are similar, SDA grouted anchors will displace slightly more than an equiva- lent grouted strand anchor due to the increased displacement expected during shear capacity development (i.e. SLS). Further research is required to establish if this statement is valid. The designer and contractor are cau- tioned to consider the effect of increased capacity that could result during load testing due to grout placed over the free length during single stage grouting. As the fixed length displaces it tends to com- press the grout around the free length, increasing the bond capacity measured (Figure 5). This can be tested by installing a test SDA over only the free length AutoCAD ® World-Leading CAD Software WaterMate Water Reticulation Design SurfMate Survey & Digital Terrain Modelling AeroTURN Aircraft Movement & Space Analysis RebarMate Reinforced Concrete Detailing & Scheduling Autodesk Civil 3D ® Site Development & Transportation AutoTURN Vehicle Manoeuvre Simulation & Analysis DatumMate Datum Conversion of Drawings RoadMate Urban & Rural Road Design ParkCAD Automated Parking Area Layouts Architecture Engineering & Construction Collection PipeMate Sewer & Stormwater Design and Analysis Figure 5 Increased bond capacity due to grout over free length being compressed Assumed fixed length grout body under tension Increased bond capacity grout body under compression T