DEGAS: An innovative earthquake‐proof AAC wall system
Authors: Canbay Erdem , Binici Baris , Demirel Ismail Ozan , Aldemir Alper , Uzgan Uğur , Eryurtlu Zafer , Bulbul Koray 
Published: September 2018

Background

The in‐plane response of infill walls independent of the material used has been investigated thoroughly in the literature and the common observation on the response was the formation of both compression struts and tension struts. These struts in the diagonals of the infill walls are the main reason for the cracking and crushing of the infill wall material. Researchers have proposed some techniques that enhance the performance of infill walls. Most of the proposed methods include a special device or connection detailing to isolate the infill wall from the RC frame even during excessive lateral displacement demands.

Aim

The objectives of the current study are: to devise and test a seismic isolation system for AAC infill walls that is capable of eliminating the damage due to in‐plane demands while being stable under out‐of‐plane demands. The outcomes of this study are believed to provide a sound alternative for constructing earthquake safe AAC infill walls.

Materials & Methods

In this study, a new method is devised to protect and enhance the performance of AAC infill walls, i.e. DEGAS. The DEGAS system is thought to increase both the ductility of the AAC infill walls in in‐plane demands and to stabilize the AAC infill wall during out‐of‐plane demands. To this end, an experimental program was formed to investigate the IP and OOP interaction for AAC infill walls with the application of the DEGAS system. In the scope of this study, three different tests were conducted to simulate i‐ IP only, ii‐ OOP only and IP + OOP cases. Two‐way cyclic displacement excursions were applied to the test specimens to mimic the in‐plane demands. Furthermore, uniform pressure was applied to simulate the OOP related demands. The OOP demands are considered by applying OOP pressure.

Results

Some crushing was observed during the testing of the Specimen S1. However, no visible cracks were detected in the AAC infill wall. This observation could be attributed to the application of DEGAS system along with the presence of the gap between the AAC infill wall and the RC frame. The maximum out‐of‐plane load of the Specimen S2 was determined to be about 20 kN. No sudden collapse‐type failure was observed in this test. This showed the importance of the application of the DEAGS system. Because, the out‐of‐plane failure of the AAC infill walls are generally total or partial sudden collapse of the wall. The Specimen S3 had a drift capacity of 2.5%. At this drift limit, the capacity reduction was determined to be only 8%. In addition, no sudden out‐of‐plane collapse of the infill wall was observed during the testing of Specimen S3.

Discussions & Conclusions

In this study, three half‐scaled tests were conducted on AAC infilled frames with the DEGAS system. The DEGAS system was shown to increase the stability of the AAC infill walls as none of the specimens was observed to fail by total or partial collapse of the AAC infill wall. In addition, the cracking of the AAC infill walls were also limited at drift ratios of about 2%, which is the drift limit for TEC 2007. This proved that the AAC infill with the DEGAS system would not show premature cracking at lower demands. The only observed damage was the disintegration along the interface of the AAC infill wall after 1.5% drift ratio.