In　this　study,　the　multiple-spring　(MS)　model　with　the　curve-approximated　hysteresis　rule　is　proposed　for　the　nonlinear　seismic　response　simulation　of　bidirectionally　loaded　hollow　square-section　steel　columns　such　as　cantilever　type　steel　piers.　To　represent　the　nonlinear　hysteresis　behavior　of　the　column,　an　effective　and　simple　optimization　procedure　is　introduced　to　identify　the　free　parameters　of　the　model.　A　parameter　determination　approach　for　approximate　modeling　in　preliminary　design　calculations　is　also　introduced.　The　results　of　quasi-static　and　pseudodynamic　tests　using　bidirectional　loading　are　compared　with　the　simulation　results　to　verify　the　accuracy　of　the　proposed　model.　The　proposed　method　is　shown　to　be　advantageous　in　achieving　accurate　simulation　of　the　seismic　response　of　a　bridge　model　involving　bidirectionally　loaded　steel　columns,　especially　the　hysteretic　force-displacement　relationship　and　time　history　of　the　dynamic　response.　©　2017　American　Society　of　Civil　Engineers.