Show 'Site Actions' ribbon menu only for SP Group members in SharePoint 2010

Step 1:

Create a SharePoint group 'SiteAdmins' at Site Collection level with Design and Contribute access

Step 2:

Add\Upload below 2 JS files to SiteAssets of root site

1. jquery.SPServices-0.7.2.min.js
2. jquery-1.8.3.min.js

Step 3: 

Refer above 2 JS in Master file.

Edit default Master page, find ‘<asp:ScriptManager’ under Form tag and replace(or include the script references) to include JQuery and SPServices scripts

 <asp:ScriptManager id="ScriptManager" runat="server" EnablePageMethods="false" EnablePartialRendering="true" EnableScriptGlobalization="false" EnableScriptLocalization="true" >

  <Scripts>                             

                                <asp:ScriptReference Path="<%$SPUrl:~SiteCollection/SiteAssets/jquery-1.8.3.min.js%>"></asp:ScriptReference>                         

                                <asp:ScriptReference Path="<%$SPUrl:~SiteCollection/SiteAssets/jquery.SPServices-0.7.2.min.js%>"></asp:ScriptReference>                               

                </Scripts>             

</asp:ScriptManager>

Step 4:

Hide ‘Site Actions’ and top ribbon for all users by default.

<!--<div id="s4-ribbonrow" class="s4-pr s4-ribbonrowhidetitle">-->

<div id="s4-ribbonrow" style="display: none;">

Step 5:

Include below script block before between </Body> and </HTML> to check if current user is member of 'SiteAdmins' group and display if yes.

<script type="text/javascript">

$(document).ready(function() {$().SPServices({

      operation: "GetGroupCollectionFromUser",

      userLoginName: $().SPServices.SPGetCurrentUser(),

      async: false,

      completefunc: function(xData, Status) {

        if($(xData.responseXML).find("Group[Name='SiteAdmins']").length == 1) {

$('#s4-ribbonrow').show();

}

      }

   });  

   });

</script>

Step 6 (Optional): If you want to display 'Welcome <current user>',  add wssuc:Welcome control (copy & paste) to some other location other than ribbon. 

Thats all, the Ribbon will be hidden for all users except for 'SiteAdmins' members. They have access to 'Site Actions' menu.