Experimental Validation of a Structural Glass Window Design for In-plane Seismic Strengthening

Abstract

Gas extractions are responsible for mostly all induced earthquakes in the Groningen area and this leads to damage of houses and buildings and issues regarding safety. Current strengthening measurements are mostly very visible. However, this can change by using the window frame as part of the structure, particularly interesting for Dutch houses characterized by large window openings. In this thesis, the focus is on the validation of the numerical model based on experimental testing. From this, the main research question was formulated as “How can the structural window frame be modelled to agree with the experimental results, in order to assess the seismic performance for unreinforced masonry structures?”. The structural window frame is made of a timber frame, an adhesive and a double-glazing unit. The timber frame is made of hardwood on the outside and plywood on the inside. The potential of the structural window frame is researched into several numerical, experimental and design studies using DIANA 10.4. It is concluded that a specific non-linear elastic interface model for the adhesive is the best suitable model. This numerical model is used as a loading protocol for the experiments. The structural window frames have been built and tested at the TU Delft. The experimental results showed that the structural window frame behaves plastically. Concluding, the glass panels and the hardwood are not damaged however, the plywood is pinched due to the glass panel. The numerical model is adjusted to include the pinching behaviour of the inner bar to suit the experiments. The next step is the masonry model. The masonry model including the structural window frame showed an increase of 15% for the in-plane shear force capacity and a decrease of 23% for the crack width for a displacement of 4 mm, compared to the unstrengthened masonry wall. The pushover calculation showed that both the unstrengthened and strengthened masonry wall can withstand the seismic loads in Appingedam. According to assumptions, the structural window frame results in an increase of the shear force capacity of 47% for larger displacements. The ductility of the structure can be increased by increasing the effective mass to 15000 kg. However, the calculation is only valid for the assumed values, these results should not be taken too strictly. The design of the window frame can be improved by using: a stiffer timber frame, a thinner adhesive and a more sustainable design. Using a frame that is twice as stiff and strong has resulted in: similar initial behaviour, higher maximum shear force and later stabilisation of the in-plane shear force. Using a thinner adhesive than 5 mm does not result in more beneficial results. Furthermore, making only screwed connections and maintaining the structural window frame frequently could increase the lifespan of the structural window frame. The structural window frame has potential however, more numerical and experimental research should be done.