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The ATLAS pixel detector will be upgraded with a new Insertable B-layer (IBL). The IBL will be inserted between the existing pixel detector and the reduced diameter vacuum pipe of the Large Hadron Collider. The extreme operating conditions at this location have required the development of new radiation hard pixel sensor technologies and a new front end chip.3D-silicon sensors will populate 25% of the IBL sensing area. They are a newgeneration of micro-machined sensors with electrodes etched inside the silicon bulk rather than on the wafer surface. 3D-silicon sensors were studied by performing simulations, laboratory measurements and beam tests on irradiated and not irradiated samples.This thesis describes the development of a fast algorithm of the signal response in 3D-silicon sensors using Geant4 simulations. The simulation of the signal response is compared to actual data from test-beam and radioactive source measurements. The setup for each of these measurements is also simulated in Geant4 using experience gained after working with the real setup.