Specify number of concurrent request in a given tps

Hello every one, does anyone know how to setup a scenario that specify number of concurrent request in a given tps and duration? sample

250 concurrent request in 0.56tps for 10 hours

i tried to understand and use any of the following injection but it seems it doesn’t fit my requirements or Im just missing something?
http://gatling.io/docs/2.1.1/general/simulation_setup.html

currently im using
scn.inject(constantUsersPerSec(0.56).during(10 hours)