Tabela de bootstrap combina colunas
<thead>
<tr>
<th rowspan="2">State</th>
<th rowspan="2">Utilities Company</th>
<th colspan="3">Summer Period</th>
</tr>
<tr>
<th>data1</th>
<th>data2</th>
<th>data3</th>
</tr>
</thead>
JavierMendozain