Use the correct class name to add stripes to the progress bar.
<div class="progress">
<div class="progress-bar @(20)"
role="progressbar"
style="width:70%">
</div>
</div>
<div class="progress">
<div class="progress-bar progress-bar-striped"
role="progressbar"
style="width:70%">
</div>
</div>