<div class="panel-group" id="accordion11">
<div class="panel panel-default">
<div class="panel-heading">
<h4 class="panel-title">
<a data-toggle="collapse" data-parent="#accordion11" href="#collapse11">заголовок 1-й панели</a>
</h4>
</div>
<div id="collapse11" class="panel-collapse collapse">
<div class="panel-body">
контент 1-й панели
</div>
</div>
</div>
</div>
<div class="panel-group" id="accordion12">
<div class="panel panel-default">
<div class="panel-heading">
<h4 class="panel-title">
<a data-toggle="collapse" data-parent="#accordion12" href="#collapse12">заголовок 2-й панели</a>
</h4>
</div>
<div id="collapse12" class="panel-collapse collapse">
<div class="panel-body">
контент 2-й панели
</div>
</div>
</div>
</div>