How to keep navigation bar collapsed on all screen sizes?

I tried these two different solutions suggested here on SO :

• How to keep Bootstrap 3 navbar as collapsed for all screen sizes
• Change bootstrap navbar collapse breakpoint without using LESS

I've also tried many other different solutions suggesting more or less the same. None worked for me.

How can I keep Bootstrap 3 navigation bar collapsed on all screen sizes, both big and small?

This is the HTML :

<nav class="navbar navbar-default navbar-custom">
  <div class="container-fluid">
    <div class="navbar-header">
      <button type="button" class="navbar-toggle" data-toggle="collapse" data-target="#myNavbar">
        <span class="icon-bar"></span>
        <span class="icon-bar"></span>
        <span class="icon-bar"></span>
      </button>
        <a class="navbar-brand" href="index.html">
             <img class="img-responsive imglogoheader" src="images/logo1.png">
        </a>
    </div>
    <div class="collapse navbar-collapse" id="myNavbar">
      <ul class="nav navbar-nav">
        <li class=""><a href="index.html">Home</a></li>
        <li><a href="profile.html">Profile</a></li>
         <li><a href="settings.html">Settings</a></li>
      <ul style="display:none !important;" class="nav navbar-nav navbar-right"></ul>
    </div>
  </div>
</nav>