Prediction of Nonlinear Cyclic Behaviors of Shear Wall Composed of Acacia mangium Framing and Fiber Cement Board Sheathing ()
1. Introduction
From recent damage due to earthquakes in various places in Indonesia, it appears that residential houses made of concrete and/or masonry was insufficient and collapsed in severe earthquakes. More than fifteen years ago in Kobe, Japan, there was also a severe earthquake and devastating damage was observed on many timber houses. Since then, not only the Japanese government but also universities, institutes and commercial companies have been paying effort to make timber residential houses stiffer, stronger and tougher. Following this good previous example, an attempt was initiated in Indonesia to make residential houses more capable of surviving severe earthquakes in the future.
This paper aimed for establishing reliable shear walls by using Akasia wood frame, sheathed with Fiber Cement Board (FCB), which is similar to those being used for earthquake-resisting house in Indonesia.
In order to understand the mechanism of earthquake resisting performance of shear wall, we need to investigate non-linear behaviors of shear walls. For this end, the new theoretical equations derived, which can not only solve arbitrary nail pattern shear wall but also nonlinear behavior after yielding for obtaining skeleton curve. In addition to this, the Normalized Cyclic Loop (NCL) models for predicting hysteresis loops were used. And by combining these two theoretical approaches, intended to predict whole non-linear cyclic behaviors of shear walls, which were composed of Akasia wood frame and nail on FCB sheathing.
2. Material and Methods
2.1. Framing Materials
The Indonesian Akasia wood (Acacia mangium) of 40 × 80 × 3000 mm solid timber was used for all of framing member material shown in Figure 1, whose mechanical and physical properties are shown in Table 1.
The Spruce glulam beam of 120 × 120 mm cross-section was used for loading girder.
Figure 1. Akasia wood used as shear wall frames member.
Table 1. Akasia’s wood mechanical and physical of material property.
2.2. Sheathing Materials
The Sheathing material is Fiber Cement Board (FCB), in which Silica (35% by weight), calcium (35% by weight), pulp and wooden fiber (15% by weight) and others (15% by weight) produced by the Japanese commercial company with size of 1800 × 900 × 12 mm shown in Figure 2. The material properties of FCB are given in Table 2.
2.3. Fasteners
Two kinds of nails were used and their specification is shown in Table 3.
The N100 nails, which were used for fastener connection between frame member and the N75 used as fastener of FCB that were attached to the frame member shown in Figure 3.
2.4. Shear Wall Specimen
Two types of specimen were prepared as shown in Figures 4 and 5. Test specimens named, as SWC is conventional type shear wall, which has been used in Indonesia currently; while test specimen named as SWB is an alternative shear wall type, which was proposed in previous study [1]. Nailing pitch in both type of shear walls were 150 mm.
2.5. Testing Methods of Single Shear between Sheathing and Frame Member
The single shear test between Akasia wood and FCB sheathing material was carried out, to obtain non-linear load slip curve, which dominates non-linear behavior of shear wall. Akasia specimen size; 40 × 80 × 150 mm, 12 mm thick of FCB and fastened by N75 nail, shown in Figures 6 and 7. Test speed was 1 mm per minute on Universal Testing Machine (UTM).
2.6. Cyclic Testing Methods
Figure 8 shows testing set-up and location of measuring devices. Loading protocol used in this study was tentatively determined in accordance with usual shear wall testing method in Laboratory of Structural Function, Kyoto University. Therefore, only one cyclic loading in each target deformation angle loop were used, as shown in below.