Thanks for the reply Jon_Israel.
But here in this scenario, I think SLA event wont work as there is no time frame to reach to this status.
lets say there is a sla of priority 1 resolution and time frame is 2 hr. so within this two hour notification can be sent or escalation email can be sent and same after 2 hour, escalation can be done at specific interval.
but in this case there is no timeline.the only condition is to send repeated notifiction(i.e 8hrs interval) when ticket is in wip or some other specific status .