A semi-trailer for transporting a load to be moved and having its own longitudinal axis; the semi-trailer comprising: - a front wheeled module comprising a right-hand front row and a left-hand front row of front bogies, each provided with its own hydraulic cylinder for actuating a respective hydraulic suspension; - a rear wheeled module comprising a right-hand rear row and a left-hand rear row of rear bogies, each provided with a respective hydraulic cylinder for actuating a corresponding hydraulic suspension; - a coupling unit (24,25,26) for coupling the front wheeled module to a tractor and comprising at least one hydraulic jack for transferring part of the load to be moved to the tractor; and - a hydraulic circuit for connecting and controlling said hydraulic cylinders; said hydraulic circuit comprising a first hydraulic distribution unit interposed between the hydraulic cylinders of the front and rear rows of bogies and configured in such a way that the sum of the instantaneous load-supporting pressures acting on the cylinders of the right-hand front row and the cylinders of said left-hand rear row is equal to the sum of the instantaneous pressures controlling the cylinders of the left-hand front row and the cylinders of the right-hand rear row, wherein said hydraulic circuit also comprises a second hydraulic distribution unit; said second hydraulic unit being configured to send to said hydraulic jack a pressure signal based on the sum of the instantaneous load-supporting pressures acting on the hydraulic cylinders of said right-hand front row and of said left-hand front row; wherein said second hydraulic unit comprises a first and a second double-acting hydraulic member having respective movable members firmly connected to each other; the movable member of said first hydraulic member separating two first variable-volume chambers from one another and the movable member of said second hydraulic member separating two second variable-volume chambers from one another; one of said first chambers being hydraulically connected to the hydraulic cylinders of said left-hand front row of front bogies, and the other to said hydraulic jack; one of said second chambers being hydraulically connected to the hydraulic cylinders of said right-hand front row, and the other to said hydraulic jack. - a front wheeled module comprising a right-hand front row and a left-hand front row of front bogies, each provided with its own hydraulic cylinder for actuating a respective hydraulic suspension; - a rear wheeled module comprising a right-hand rear row and a left-hand rear row of rear bogies, each provided with a respective hydraulic cylinder for actuating a corresponding hydraulic suspension; - a coupling unit (24,25,26) for coupling the front wheeled module to a tractor and comprising at least one hydraulic jack for transferring part of the load to be moved to the tractor; and - a hydraulic circuit for connecting and controlling said hydraulic cylinders; said hydraulic circuit comprising a first hydraulic distribution unit interposed between the hydraulic cylinders of the front and rear rows of bogies and configured in such a way that the sum of the instantaneous load-supporting pressures acting on the cylinders of the right-hand front row and the cylinders of said left-hand rear row is equal to the sum of the instantaneous pressures controlling the cylinders of the left-hand front row and the cylinders of the right-hand rear row, wherein said hydraulic circuit also comprises a second hydraulic distribution unit; said second hydraulic unit being configured to send to said hydraulic jack a pressure signal based on the sum of the instantaneous load-supporting pressures acting on the hydraulic cylinders of said right-hand front row and of said left-hand front row;