T-junctions are present in a wide range of industry and facilitate the mixing of fluids that are often at different temperatures. Temperature fluctuations introduced during the mixing process can result in thermal fatigue and consequently structural failure in the pipework. Predicting the magnitudes and locations of the stresses allows one to prevent and/or mitigate potential issues. A number of studies have investigated the fluid dynamics of T-junctions but very few have researched the impacts of the resulting flow field on the enveloping pipe materials especially where temperature fluctuations are significant. The present study employs steady-state one-way fluid-structure interaction analysis to determine the stress response of the pipework in a thermal-mixing T-junction situation. Firstly, the numerical flow field is simulated using CFD and validated against experimental data. Then, the effects of the fluid force fields on the pipe walls are modelled using structural analysis to predict the resulting stresses.