Truck platooning attracts considerable attention thanks to the promising fuel consumption benefits and business model. Nevertheless, concerns over the influence of long truck platoons on other traffic are raised by road operators. It is intriguing to understand under what conditions truck platooning will influence other traffic and what are the magnitudes of the influence. To this end, this paper reports a simulation study on examining the effects of truck platooning on freeway operations near an on-ramp. Systematic experiments were conducted with varying demand, market penetration rates (MPRs), intra-platooning gap, and platoon size. Moreover, three alternative strategies for truck platooning to accommodate merging traffic were tested: allowing courtesy lane change of trucks, active yielding, and keeping a larger intra-platoon gap than the acceptable gap for human drivers to change lane. Simulation results show that at high MPRs of truck platooning, the system mitigates congestion and increases throughput, at the expense of merging failures. The merge location distributions shift toward the end of the acceleration lane at congested flow and high MPRs. The effect on average merging speed is insignificant, but the merging speed in saturated traffic with truck platooning shows larger variability. At free flow and low MPRs, the influence is insignificant. Evaluation of the three alternatives concludes that the yielding strategy is most effective in resolving the merging problem with truck platooning. Courtesy lane change is not always possible because of the high speed difference between lanes and keeping a larger time gap suppresses the benefits in congestion mitigation and throughput increase.