Dynamic and Static Behaviors of Shear Wall with Openings Composed of LVL and Fiber Cement Board Sheathing ()
1. Introduction
In Indonesia, housing privation for low-income peoples increases year by year, so that house design by taking requirements of its withstand to the earthquake, healthy, simple and instantaneous in the construction process with a low cost of construction is required. For these ends, the authors have been carried out experimental and analyticcal researches on shear walls composed of LVL and fiber cement board (denotes as FCB hereafter) sheathing with no openings for applying them to structural components of low-cost earthquake-resisting houses. While in actual design situations, it is necessary to design various types of shear walls having windows or/and door-type openings. Therefore, in this study, we extended our focus on such shear walls having openings.
Studies on wooden house that was structurally designed by utilizing shear walls with and without openings made of wooden frame and various sheathing materials has been done in past by many researchers [1-8]. In this study, not only static properties but also basic dynamic properties such as natural frequency and damping coefficient are estimated for understanding the effect of openings on the fundamental mechanical properties of nailedon sheathed shear walls to be installed in wooden residential houses.
2. Experimental Study
To predict thetangible behavior of shear walls with openings made of LVL and FCB by applying rigorous theoretical design equations, some material testswere done.
2.1. Materials
2.1.1. Framing Materials
LVL made of falcataria and rubber wood (Paraserianthes falcataria and Hevea braziliensis) of 45 × 90 × 3000 mm was used for framing material as shown in Figure 1, whose mechanical and physical properties are shown in Table 1. The LVL beam of 45 × 90 mm cross-sections was attached on top of shear wall for loading girder.
2.1.2. Sheathing Materials [10]
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 a Japanese commercial company in a size of 1800 × 900 × 12 mm as shown in Figure 2. The material properties of FCB are given in Table 2.
2.1.3. Fasteners
The steel nails were used as fastener of all shear wall component connection and there were two kinds of nails
Table 1. Mechanical and physical property of LVL [9].
Figure 1. LVL wood used as shear wall frames member.
Figure 2. FCB used as frame specimen sheathed.
Table 2. Mechanical and physical property of FCB.
were used and their specification is shown in Table 3.
The N100 nails were use for fastening frame members and double heads nails that are equivalent to the normal N75-nail shown in Figure 3 were used as fastener for connecting FCB sheathing to the frame member due to convenience of dismantle of tested specimens.
2.2. Specimens
2.2.1. Single-Nail Shear Test between Sheathing and Frame Member
The single-nail shear test between LVL and FCB sheathing material was carried out, to obtain load-slip relationship, which dominates non-linear behavior of shear wall. The size of LVLwas 45 × 90 × 300 mmand 12 mm thick of FCB was connected byusing double heads N75 nails as shown in Figures 4. Test speed was 1 mm per minute on Universal Testing Machine (UTM).
2.2.2. Shear Wall Specimens
Three different types of shear wall specimens were prepared. These were composed of LVL of 45 × 90 cross section as framing members assembled with each other by N100 nails and FCB as sheathing members of 910 × 2730 mm size nailed on the framing members by double heads N70 nails. The nailing pitch in all types of shear walls was 150 mm. The shear wall specimens without openings were named as SWS (Figure 5).
Shear walls with window opening was named as SWWOS, where the size of openings was 910 × 878 mm (Figure 6). And shear wall with door-type opening was named as SWDOS; the size of openings was910 × 1777 mm (Figure 7).
All specimens composed of three sizes of panel, the individual panel-A, panel-B and panel-C has different nailing pattern as shown in Figure 8. Based on those three panels, the mechanical models were constituted for predicting static and dynamic performance of three different shear walls.
Figure 3. The steel nail used as fastener between sheathing and frame member.
Figure 4. Single-nail shear test specimen of LVL and FCB fastened by double heads N75 nails in parallel (left-hand side) and perpendicular to the grain (right-hand side) under test machine.
Figure 5. Wall type test specimen (SWS).
Figure 6. Window-typetest specimen (SWWOS).
Figure 7. Door-typetest specimen (SWDOS).
Figure 8. Nailing pattern in panel-A, panel-B and panel-C.
2.3. Testing Methods
Experimental studies in laboratory commenced with the test of connection between the LVL with FCB fastened by steel nails, then dynamic test was done by using a portable shake excitation machine (Figure 9) which can generate harmonic horizontal vibration. After dynamic tests, static push-pull cyclic loading tests were carried out on the same specimens.
2.3.1. Dynamic Test Method Using Portable Shake Excitation Machine
Dynamic test was done to obtain the values of natural frequency and dumping factors on each test specimen. The test were performed by fixing the specimen on a steel reaction portal frame apparatus by using 4 anchor bolts on sill members and hold-down connectors on both side-studs so that it was assumed that the specimens were fixed rigidly on the steel base. The vibration generator mounted on the top of the specimen, while the specimen is free to move in the direction of horizontal vibration.
Portable Shake Excitation Machine A portable shake excitation machine (DTH-500-30, Asahi-factory Corp.) shown in Figure 10 was used for measuring such dynamic properties of test specimens as the natural frequency and damping factor. Nominal excitation force of the machine was 490 N, nominal maximum acceleration without dead load was 7.3 m/s2 and the weight of movable part of the machine was 27 kg (machine) + 40 kg (additional weight) = 67 kg.
2.3.2. Static Push-Pull Cyclic Testing Methods
Figure 9, 11, 12 shows testing set-up and location of measuring devices. Loading protocol used in this study