How do I define temperature loads on a composite beam?

The load case temperature is very important in composite construction. A distinction is made here between the load cases top heating (by concreting) and bottom heating. Since a temperature change must be defined, the load is defined as Delta T. Often, a composite beam is modeled by an eccentric member coupled to a surface. For this, the difference of the temperature between these two elements (surface and member) must be divided. The load on the member is defined as the member load with the temperature difference times the height of the member divided by the total height of the composite cross-section ($\ triangle T \ times \ frac {h_s} {h_g}$). If the upper fibers of the member are colder than the lower ones, the value must be defined as negative.