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 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 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 ; <EOS>