In the recent years, the displacement-based seismic design (DBD) method of structures has been recognized as the alternative design method to the conventional force-based seismic design (FBD) method. The problems inherited in the FBD method are mostly overcome by the DBD method as it better correlates the structural damage with displacement-based quantities. In this study, the seismic response of multi-span bridges with varying number of spans and unequal pier heights was evaluated using the DBD method and compared with the conventional FBD method. Two approaches were employed in the DBD method, such as the traditional direct displacement-based seismic design (DDBD) approach and the proposed approach in this study entitled as alternative-to-direct displacement-based seismic design (ADBD). For seismic evaluation of the bridge structures with the FBD method, acceleration response spectra as suggested in the Bangladesh National Building Code were used; while in the DBD method, displacement response spectra for different damping ratios were developed keeping consistency with the above-mentioned design acceleration spectra. Five bridge models were used in the analysis to compare the seismic response in both the longitudinal and transverse directions taking into account the number of spans and height irregularity in the bridge models. Numerical analysis showed very obvious results that the base shear calculated by both approaches of the DBD method is found to be smaller than the FBD method indicating that an economic member section be attained for meeting the same design objective. More specifically, the ADBD approach provides the design professionals a more conservative design approach in compared with the DDBD approach keeping an economic design approach comparing with the FBD method.

近年来，结构的基于位移的抗震设计（DBD）方法已被认为是常规基于力的抗震设计（FBD）方法的替代设计方法。FBD方法中继承的问题大部分可以通过DBD方法克服，因为它可以更好地将结构损伤与基于位移的量相关联。在这项研究中，使用DBD方法评估了不同跨度和不等墩高的跨度桥梁的地震响应，并将其与常规FBD方法进行了比较。DBD方法中使用了两种方法，例如传统的基于直接位移的地震设计（DDBD）方法和本研究中提议的名为基于直接位移的替代地震设计（ADBD）的方法。用FBD方法对桥梁结构进行抗震评估时，使用了孟加拉国国家建筑规范中建议的加速度响应谱。而在DBD方法中，开发了不同阻尼比的位移响应谱，并与上述设计加速度谱保持一致。考虑到桥梁模型的跨度和高度不规则性，在分析中使用了五个桥梁模型来比较纵向和横向的地震响应。数值分析显示了非常明显的结果，发现通过DBD方法的两种方法计算的基础剪力都小于FBD方法，这表明达到了满足相同设计目标的经济构件截面。进一步来说，