\usepackage[explicit]{titlesec}
\usepackage{pgfplots}
\pgfplotsset{compat=newest}

\providecommand{\DUdocumentsubtitle}[1]{%
  %\begin{nthcolumn}{1}
  \color{black}
  \em
  \TitleFont\selectfont
  \Large
  #1
  %\end{nthcolumn}
}

\makeatletter

\def\@maketitle{%
  \vspace*{1cm}
  \begin{nthcolumn*}{0}%
  \textcolor{altColor}{%
    \huge \@title
  }
  \end{nthcolumn*}
}
\makeatother

\newcommand\SecTitle[1]{%
\begin{tikzpicture}

  \node (A) at (0,0)
      {\Large{\textsf{[ #1 ]}}};

  \draw [line width=0.2mm]
    (-7,0) -- (A.west);

  \draw [line width=0.2mm]
    (A.east) -- (7,0);
\end{tikzpicture}}

% Titre de niveau 1
\titleformat{\section}
  {\centering}
  {\thesection}
  {}
  {\SecTitle{#1}}

% Titre de niveau 2
\titleformat{\subsection}
  {\large}
  {\thesubsection}
  {}
  {\textcolor{altColor}{\Large \bf {#1}}}

% Titre de niveau 3
\titleformat{\subsubsection}
  {\bfseries\normalsize}
  {\thesubsubsection}
  {2em}
  {}
  {}