## 4 Test Setup, Instrumentation, and Crack Formation
### The Effects of Investigated Parameters on the Behavior of Anchors
#### 5.3.1 The Effect of Mortar Strength  
The strength of the masonry mortar is expected to affect the behavior of anchors in tension, independent of whether the anchors are installed in brick or mortar locations. Indeed, as shown in Section 5.2, the mortar strength affects the failure mode and, by way of consequence, both the anchor resistance and the corresponding displacements. The effect of mortar strength is evaluated based on the average compressive strength of the weak and the strong mortar (3.2 MPa and 20.4 MPa, respectively). Figure 9 shows the load-displacement curves for two sets of tests performed on anchors installed in an uncracked mortar joint (L\({}_{\text{3T}}\) location). The only difference between the two sets was the compressive strength of the mortar. The data show that (a) on average,  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Test Name/Location** & \begin{tabular}{c} **Mortar** \\ **(MPa)** \\ \end{tabular}  & \begin{tabular}{c} **Crack Width** \\ **(mm)** \\ \end{tabular}  & \begin{tabular}{c} **F\({}_{\text{En}}\)** \\ **(km)** \\ \end{tabular}  & \begin{tabular}{c} **Mean Value** \\ **(kN)** \\ \end{tabular}  & \begin{tabular}{c} **CoV** \\ **per Series** \\ \end{tabular}  & \begin{tabular}{c} **d\({}_{\text{En}}\)** \\ **(\%)** \\ \end{tabular}  & \begin{tabular}{c} **Mean Value** \\ **(mm)** \\ \end{tabular}  & \begin{tabular}{c} **CoV** \\ **per Series** \\ \end{tabular}  & \begin{tabular}{c} **d\({}_{\text{En}}\)** \\ **(\%)** \\ \end{tabular}  & \begin{tabular}{c} **Mean Value** \\ **(\%)** \\ \end{tabular}  & \begin{tabular}{c} **Mean Value** \\ **(\%)** \\ \end{tabular}  & \ \begin{tabular}{c} **CoV** \\ **(\%)** \\ \end{tabular}  & \begin{tabular}{c} **Failure** \\ **Mode** \\ \end{tabular}  \\ \hline SS1-Test-2 PM-0.0-20.4(1/6) & & & 26.70 & & 2.22 & & & BS/BP \\ SS2-Test-PM-0.0-20.4(2/6) & & 55.80 & & 0.90 & & & BC \\ SS2-Test-PM-0.0-20.4(3/6) & 17.78 & Uncracked & 46.85 & 33.84 & 42.78 & 0.60 & 1.19 & 77.72 & BC/BS \\ SS3-Test-PM-0.0-20.4(4/6) & & & 21.95 & & 2.49 & & & BS/BP \\ SS3-Test-PM-0.0-20.4(5/6) & & & 19.67 & & 0.55 & & & BP \\ SS4-Test-PM-0.0-20.4(6/6) & & & 32.06 & & 0.37 & & & BC \\ \hline SS1b-Test-PM-0.0-20.4(1/3) & & & 39.79 & & & 0.81 & & & APB \\ SS1-Test-PM-0.0-20.4(2/3) & 26.31 & Uncracked & 44.49 & 41.08 & 7.25 & 0.62 & 0.64 & 26.02 & APM \\ SS1-Test-PM-0.0-20.4(3/3) & & & 38.97 & & & 0.48 & & & APB \\ \hline SS4b-Test-PM-0.5-0.20-20.4(1/3) & & & 16.06 & & & 4.88 & & & AP \\ SS4b-Test-PM-0.5-0.20-20.4(2/3) & 26.31 & 0.50 & 17.30 & 18.86 & 20.32 & 0.46 & 2.46 & 90.89 & APM \\ SS4b-Test-PM-0.5-0.20-20.4(7/3) & & & 23.23 & & & 2.05 & & & APB \\ \hline SS6b-Test-PM-0.5-0.20-20.4(1/3) & & & 18.11 & & & 0.34 & & & BP \\ SS3b-Test-PM-0.5-0.20-4(2/3) & 26.31 & 0.50 & 16.85 & 17.98 & 5.96 & 7.41 & 2.76 & 145.95 & BP \\ SS3b-Test-PM-0.5-0.20-4(3/4) & & & 18.98 & & & 0.53 & & & BP \\ \hline SW1-Test-PM-0.0-20.4(1/4) & & & 19.65 & & & 1.4 & & & BS/BP \\ SW1-Test-PM-0.0-20.4(1/4) & 3.42 & Uncracked & 23.37 & 23.28 & 22.01 & 0.19 & 0.53 & 110.49 & BS \\ SW2-Test-PM-PM-0.20.4(3/4) & & & 19.61 & & & 0.24 & & & BS/BP \\ SW3-Test-PM-0.0-20.4(4/4) & & & 30.50 & & & 0.28 & & & BS \\ \hline SW1b-Test-PM-0.0-20.4(1/3) & & & 21.52 & & & 0.25 & & & APB \\ SW1b-Test-PM-0.0-20.4(2/3) & 4.53 & Uncracked &  
the tension resistance of anchors installed in mortar joints of average compressive strength = 20.4 MPa was approximately twice as high as the tension resistance of those installed in mortar with low compressive strength (=3.2 MPa). Furthermore, (b) this higher resistance was activated for significantly smaller displacement. It is noted though that (c) despite the variability of mortar strength from wall to wall and, expectedly, also from joint to joint, the scatter of the obtained tension resistances is limited. However, (d) this is not the case for the displacement corresponding to the ultimate tension resistance; this property presents quite a large scatter, which is more pronounced for low-quality mortar.