Expansive soils are a worldwide challenge. Straight shaft drilled pier foundation and thernbelled drilled pier foundation are rational and reliable solutions to combat the problem ofrnexpansive soils. The belled drilled pier foundation is especially preferred when deep depthsrnof the swelling zone exist and large uplift forces have to be resisted. Various investigationsrnhave studied the behavior of straight shaft drilled pier foundations when they are employedrnin expansive soils, while very few investigations exist for belled drilled pier foundationsrnemployed in expansive soils. The only in-depth investigation concerned with the study ofrnthe behavior of belled piers in expansive soils is the elastic pier approach. Yet, this approachrnhas limitations and is majorly focused on straight shaft piers. Concerning the design ofrnbelled piers in expansive soils, the rigid pier design method is commonly used. However,rnthis method has limitations as well. To address the limitations of the elastic pier approachrnand the rigid pier design, a nite element based investigation of the behavior of belledrnpiers in expansive soils is conducted using the nite element software Abaqus. The niternelement model was validated using several mechanisms. The e ect of various parametersrna ecting belled pier behavior in expansive soils was investigated. A cost comparison amongrndi erent types of piers was conducted. Finally, trend lines that can serve as design chartsrnwere developed. The parametric investigations indicated that when designing belled piers inrnexpansive soils increasing the shaft diameter is preferred to increasing the length or the bellrnsize; the limiting diameter for belled piers is much higher than that for straight shaft piers;rnmost belled piers in expansive soils in Ethiopia do not need tensile reinforcement and thernapplied load needed to fully eliminate tensile stresses in belled piers is less than that neededrnin straight shaft piers. The cost comparison indicated that for smaller values of the swellingrnpressure and the depth of the swelling zone, straight shaft piers are more cost e ective; whilernfor medium to large values of the swelling pressure and the depth of the swelling zone, largernbell size belled piers are more cost e ective. The trend lines indicated that in Ethiopia belledrnpiers with the minimum possible values of the shaft diameter, base to shaft diameter ratiornand length can be used.