Highlighting Differences between Force-Based and Displacement-Based Design Solutions for Reinforced Concrete Frame Structures

Abstract

Over the past two decades, the earthquake engineering community has become increasingly aware of fundamental shortcomings in the current code force-based design methods. In light of this, a large number of displacement-based seismic design (DBD) methods have been proposed, and the most developed of these is currently the Direct DBD method. In order to illustrate how significantly design solutions obtained by Direct DBD can differ from those obtained using current code methods, design strengths obtained by the Eurocode 8 equivalent lateral force (ELF) method and the Direct DBD method are compared for over 1000 regular case study reinforced concrete ( RC) frame buildings. The research examines buildings from 1 to 12 storeys in height, investigating the impact of structural proportions, material properties, design drift limits, gravity loads and design intensity on the seismic design strengths required. The findings illustrate that the design strengths required by the Eurocode 8 ELF method can be significantly smaller but can also be significantly greater than the Direct DBD solution. The conceptual reasons for the observed differences are discussed. Furthermore, the research uses the results of the large number of Direct DBD solutions to identify means of simplifying the Direct DBD procedure for regular RC frames so that it can be applied with similar ease to the current code ELF approach.