Carrier aggregation (CA) has been proposed to aggregate two or more component carriers (CCs) to support a much wider transmission bandwidth for LTE-Advanced systems. With carrier aggregation, it is possible to schedule a user equipment (UE) on multiple component carriers simultaneously. In this paper, we evaluate the performance of uplink CA in LTE-Advanced systems with different CC allocation schemes. We first present the radio resource management (RRM) framework of multi-component carrier LTE-Advanced systems, with special attention on CC selection, adaptive transmission bandwidth, and uplink power control. Simulation results show that with CA and advanced CC selection algorithm, the cell edge user throughput of LTE-Advanced UEs maintains the same as Rel'8 UEs, but substantial performance gains can be achieved in terms of average and cell center user throughput, especially in low load traffic conditions.