Beer Smith has a grain addition of fruit based on the US average brix (% sugar, ) of the fruit.
Bottom line, unless your wort is pushing 100% fruit very little impact
Raspberries have an average potential of 5 pppg so you are adding 3lbs* 5 pppg = 15 gravity points, so for the same volume in a 5 gallon batch your OG will go up 15/5 = .003, This will increase abv by about .4%abv