The paper presents results of experimental research involving assessment of the impact of temperature, fire exposure time, and the applied cooling method on the residual load-bearing capacity of high-strength construction steel bolts quenched and tempered (QT) in the production process, and their behavior under loading. The tests consisted in subjecting the bolts to simulated thermal impacts reflecting the environmental conditions of a real fire. During the experiment, a series of static tensile and shear tests were carried out on M20-8.8 construction bolts, exposed to selected fire temperatures for the periods of 30', 60', 120', and 240'. Moreover, the research took into account different cooling methods and analyzed their impact. After heating, the first batch of bolts was cooled in air. In the case of the second batch, the bolts were cooled down rapidly by immersion in water, thus simulating the effect of a firefighting operation. In each series 3 samples were tested in order to verify correctness and repeatability of the results. Residual values of the post-fire tensile and shear strengths as well as values of reduction coefficients of the residual post-fire load-bearing capacities were determined. In addition, the article discusses changes in the plasticity and behavior of bolts subjected to described environmental impacts and points out to the observed failure mechanisms. Attention was drawn to causes of the observed phenomena, arising from microstructural changes of the bolt material that occur in the process of heating and cooling, depending on the temperature reached during the simulated fire exposure.