Identificación de unidades procesadas y estudiadas:

Ten RC wall specimens with a boundary column on only one side were prepared to investigate the differences in deformation capacity. Figure 1 shows the cross sections of the specimens used in this research. Each specimen is named as follows:

1. Perpendicular end wall: The first letter of the speci- men’s name—“P” or “N”—means with or without a perpen- dicular wall, respectively. For example, Specimen PM5 in Fig. 1(g) has a perpendicular end wall 130 mm (5.1 in.) long and 60 mm (2.4 in.) thick. All the perpendicular end walls have single-layer reinforcement (D4 at 80 mm [3.15 in.], where D4 is a deformed bar with a nominal diameter of 4 mm [0.16 in.]) and do not have confinement.

2. The ratio of wall panel length to wall thickness (lwp/t):

The second letter of the specimen’s name—“S,” “M,” or “L”—expresses that the lwp/t ratio is 6, 12, or 18, respec-

tively, where the wall panel length lwp is defined, excluding

the column. For example, the ratio of Specimen PM5 in Fig. 1(g) is 1200/100 = 12.

3. The ratio of neutral axis depth to wall thickness (c/t): The vertical arrows in Fig. 1 indicate the location of the

Susumu Takahashi is a PhD Student of architectural engineering at Nagoya Institute of Technology, Nagoya, Japan.

Kazuya Yoshida is a Master’s Student of architectural engineering at Nagoya Insti- tute of Technology.

ACI member Toshikatsu Ichinose is a Professor of architectural engineering at Nagoya Institute of Technology.

ACI member Yasushi Sanada is an Associate Professor of architecture and civil engi- neering at Toyohashi University of Technology, Toyohashi, Japan.

Kenki Matsumoto is a Master’s Student of architectural engineering at Nagoya Insti- tute of Technology.

ACI member Hiroshi Fukuyama is a Chief Research Engineer at the Building Research Institute, Tsukuba, Japan.

Haruhiko Suwada is a Research Engineer at the Building Research Institute.

neutral axis, whose computation method will be shown in a later section of the paper. The number of the specimen’s name expresses the approximate ratio of c/t. For example, the ratio of Specimen PM5 in Fig. 1(g) is 493/100 = 4.9. Although the sections of Specimens NM5 and NM4 are identical, as shown in Fig. 1(a), the locations of the neutral axis are different because of the difference of axial forces, as shown in a later section.

4. With or without crosstie in boundary element: Figure 2 shows the detail of the boundary elements of the specimens, except Specimens NM5, NM4, and NM2′. The horizontal bars have a 135-degree hook, as shown in Fig. 2(a). The cap bars have a 90-degree hook at both ends, as shown in Fig. 2(b), and the cap bars’ vertical spacing is 35 mm (1.4 in.), as shown in Fig. 2(c). The crossties have 90- and 135-degree hooks, as shown in Fig. 2(b), and are staggered with a spacing of 70 mm (2.8 in.), as shown in Fig. 2(c). The crossties in Specimens NM5 and NM4 are located at a spacing of 35 mm (1.4 in.), as shown in Fig. 3(a).

Specimen NM2′ does not have crossties, as shown in Fig. 3(b).

The detailing of the wall reinforcement for Specimen NM3 is shown in Fig. 4. The spacings of the horizontal and vertical bars are 35 and 100 mm (1.4 and 4.0 in.), respectively. The reinforcement details of the wall panels of the other speci- mens are the same as those in Fig. 4. Because the wall thick- ness of each specimen is different, the lateral and vertical wall reinforcement ratios vary from 0.54% to 0.84% and from 0.19% to 0.30%, respectively. The lengths of boundary elements (220 mm [8.7 in.] in Fig. 2(a)) are longer than half the length of the neutral axis in most specimens, as specified by the seismic requirements of ACI 318-08.1 _{In the vertical}

direction, crossties are provided from the bottom to one-third of the clear height h, as shown in Fig. 4. This value of h/3 is much shorter than the requirement of ACI 318-08.1 _The

spacing of the crossties (70 mm [2.8 in.] in most specimens) does not satisfy the requirements of ACI 318-081 _{either. The}

cross-sectional areas of the crossties vary from 15 to 31% of ACI 318-08.1

The clear heights of Specimens NM4 and NM5 are 1000 mm (3.3 ft), whereas those of the other specimens are 1200 mm (4.0 ft), as shown in Fig. 4. Eight No. 3 (D10) longitudinal bars are provided in the boundary element of all specimens (Fig. 2(a)). Twelve No. 5 (D16) longitudinal bars are provided in the boundary column, except that of Specimen NL2, where eight No. 4 (D13) bars are provided (Fig. 1(e)) so the longitudinal reinforcement ratio (2.5%) is similar to that of the other specimens.

All specimens are designed to fail in flexure; the shear- to-flexural-capacity ratios vary from 1.2 to 2.3, where the flexural and shear capacities are calculated based on the Architectural Institute of Japan (AIJ) standards13 _and

ACI 318-08,1 _{respectively. The material properties of the}

steel bars are indicated in Table 1, where fy is the yield

strength, fu is the tensile strength, and Es is the elastic

modulus. The material properties of concrete are indicated

Fig. 1—Specimen sections. (Note: Dimensions in mm; 1 mm = 0.039 in.; No. 4 is D13; No. 5 is D16.)

in Table 2, where fc′ is the compressive strength, Ec is the

elastic modulus, and fr is the modulus of rupture.

Test setup

Figure 5 shows the test setup. Lateral force was applied by a hydraulic jack to a stiff loading steel beam fastened to the specimen. All specimens had stiff RC stubs at both the top and bottom for fixing with the loading frame. No axial force was applied for Specimen NM4. For the other specimens, two vertical hydraulic jacks were force-controlled so the moment around the center of the boundary column is zero, as shown in Fig. 5. The amount of the axial force was approximately 20% of the axial capacity of the boundary column (fc′Ag),

where Ag is the gross cross-sectional area of the column.

The applied axial load was approximately 240 kN (54 kips) for Specimen NL2, 400 kN (90 kips) for NM5, and 540 kN (121 kips) for the other specimens. Horizontal load was applied 2425 mm (8.0 ft) above the bottom of the wall panel for NM5 and NM4 (Fig. 5). The height of the horizontal load was 2525 mm (8.3 ft) for the other specimens. The shear- span ratio of NL2 is 2525/2000 = 1.26, which is the smallest. The shear span ratio of NS3 is 2525/1020 = 2.48, which is the largest.

OBSERVED DAMAGE