Influence of non-structural infill wall elements on the seismic response and retrofit of steel structures

This paper provides a methodology to evaluate the influence of non-structural infill wall elements and quantify the interrelation between them and structural damage analytically observed under strong ground motions. For this reason, nonlinear dynamic analyses for a set of five steel frame structures were carried out taking into consideration all essential material characteristics as well as four different infill wall topologies.
Initially, a set of spectrum compatible artificial accelerograms were composed and nonlinear dynamic analyses have been carried out to evaluate the seismic response for each individual structure. In addition, several structural response characteristics, the overall structural damage index (OSDI) after Park/Ang (OSDIPA) and the maximum inter-story drift ratio (MISDR) have been selected to represent the structural response. The work focuses on DIPA in both its localized form as well as the global damage manifestation.
The steel frame models were designed in compliance with EC3 and EC8 Eurocode requirements for steel and antiseismic structures, respectively. During the nonlinear dynamic analyses carried out to evaluate the structure’s seismic response, utilizing the IDARC computer program, the OSDIPA response parameters were calculated as simple, yet effective and widely accepted ways to represent seismic damage.
This work focus upon quantifying the interdependency between topology of infill walls in a steel structure and its seismic response. As the numerical results have shown, infill walls proved to have a very positive contribution in the structure’s seismic response giving an average of 47% reduction of the maximum recorded OSDIPA as well as an 72 - 81% decrease of the mean OSDIPA values between bare frame structure and its infill wall reinforced counterparts. Similar results were observed on a localized basis when investigating the mode and structural damage accumulation on a level to level basis where reductions in the range of 68 - 82% of the mean values for the ground floor (Level 1) and almost eliminate the seismic damage that is observed on the bare frame’s Level 6.
Finally, a comparative study has been performed to quantify the influence of non-structural infill wall topology on the analytically observed seismic induced structural damage. In that effect the different damage distribution characteristics have been studied revealing the importance of non-structural elements in a buildings response under such conditions.