moeR

This R package contains functions to generate stress-strain diagrams and estimate modulus of elasticity (MOE) from tree winching studies, e.g., Cannon et al 2015 and Cannon et al. 2024

The core functionality is to automatically

1. Combine tension data from load cell (kN) and angle measurements from a title gauage (degrees) to generate stress-strain diagrams, and
2. Estimate modulus of elasticity automatically from the linear portion of a stress-strain curve.

Fig. 1. Diagram of measurements used in calculation of critical turning moment in tree winching study. From Cannon et al. 2024

Install required packages

install.packages('remotes')
remotes::install_github('jbcannon/moeR')

Load required packages after installing

library(readR)
library(moeR)

Workflow

Load and view data data

# load from example data. (try tree_2, tree_3, tree_4)
tree = read_csv(system.file('extdata', 'tree_1.csv', package = 'moeR'))

# plot raw data
par(mfrow = 1:2, mar = c(4,4,1,1))
plot(F_kN ~ datetime, data = tree, type = 'l', ylab = 'Tension (kN)')
plot(tilt ~ datetime, data = tree, type = 'l', ylab = 'tilt (deg)')

Fig. 3. Diagram of typical data derived from tree winching experiment including (left) measurements from tension guage and (right) measurements from title guage. Data from Cannon et al. 2024

Calculate stress-strain and Modulus of Elasticity

#calculate turning moment, multiply tension (F) by height of strap attachment
tree$M_kNm = tree$F_kN* tree$strap_ht_m

#calculate stress-strain diagram
ss = stress_strain(moment_kNm = tree$M_kNm,
              tilt_deg = tree$tilt,
              ht_m = 1.3,
              diam_cm = 20.2,
              plot = TRUE)

# calculate modulus of elasticity
moe = getMOE(ss$stress, ss$strain)
print(moe)

Output

       moe intercept     rmse        r2
1 4436.657  36.25342 6.340209 0.9866051

Fig. 3. Diagram of typical stress-strain figure. Slope of red line indicates modulus of elasticity automatically estimated from linear portion of stress-strain curve. Data from Cannon et al. 2024

Write loop to repeat for several trees

tree1 = read_csv(system.file('extdata', 'tree_1.csv', package = 'moeR'))
tree2 = read_csv(system.file('extdata', 'tree_2.csv', package = 'moeR'))
tree3 = read_csv(system.file('extdata', 'tree_3.csv', package = 'moeR'))
tree4 = read_csv(system.file('extdata', 'tree_4.csv', package = 'moeR'))

treelist = c('tree1', 'tree2', 'tree3', 'tree4')
par(mfrow = c(2,2), oma=c(1,1,1,1))
for(t in treelist) {
  tree = get(t)  
  #calculate turning moment
  tree$M_kNm = tree$F_kN* tree$strap_ht_m
  #calculate stress-strain diagram
  ss = stress_strain(moment_kNm = tree$M_kNm,
                     tilt_deg = tree$tilt,
                     ht_m = 1.3,
                     diam_cm = tree$diam_cm[1],  #grab first tree diam measuremnt
                     plot=FALSE)
  # calculate modulus of elasticity
  moe = getMOE(ss$stress, ss$strain, plot=TRUE)
  cat('---', t, '---\n')
  print(moe)
  title(sub = t)
}

Output:

--- tree1 ---
       moe intercept     rmse        r2
1 4436.657  36.25342 6.340209 0.9866051
--- tree2 ---
       moe intercept     rmse        r2
1 48262.12  292.5438 136.0751 0.8988749
--- tree3 ---
       moe intercept     rmse        r2
1 31313.44 -193.1908 21.15497 0.9858685
--- tree4 ---
       moe intercept     rmse        r2
1 69353.22  128.3207 82.18812 0.9528323

Fig. 4. Stress-strain curves for four Pinus elliottii. Slope of red line indicates modulus of elasticity automatically estimated from linear portion of stress-strain curve. Data from Cannon et al. 2024