SOURCE

<div id="warning">
	<ul class="list">
		<li class="item"></li>
		<li class="item"></li>
		<li class="item"></li>
	</ul>
</div>

#warning{
	position:absolute;
	top:0;
	right:0;
	bottom:0;
	left:0;
	margin:auto;
	width:200px;
	height:200px;
	background:#f3e15b;
	border-radius:100px;
	box-sizing:border-box;
	overflow:hidden;
}
#warning .item{
	position:absolute;
	width:200px;
	height:100px;
	right:50%;
	top:0;
	transform-origin:100% 100%;
	background:black;
}

#warning  .item:nth-child(1){
	transform: skew(30deg);
}
#warning  .item:nth-child(2){
	transform:rotate(120deg) skew(30deg);
}
#warning  .item:nth-child(3){
	transform:rotate(240deg) skew(30deg);
}