Eleven 6 × 12-in grout cylinders were made during the fabrication of the reinforced masonry walls, and cured under similar conditions as the walls. The compressive strengths ranged from 1857 psi to 2900 psi and averaged 2290 psi when tested at ages from 8 to 47 days. Individual test results are tabulated in table 3.3. It was observed that in general the strengths increased with an increase in age of the grout cylinder. The cylinders tested at the least age, 8 days, gave the lowest compressive strength. Since the test results indicated that the majority of the cylinders, a total of 8, had compressive strengths within 300 psi of the average value, the average value of compressive strength can be assumed to be a representative value for all the grout cylinders.

It has been observed [6] that because of the water absorption by the masonry units, grout within the walls achieves a significantly higher strength than the same grout when cured as cylinders. It may therefore be assumed that the grout within the walls had a compressive strength higher than the 2290 psi cylinder strength.

3.1.4. Steel Reinforcement

Vertical and horizontal steel in the reinforced wall panels consisted of ASTM A615 [7] No. 5 deformed bars with a minimum specified yield strength of 60,000 psi.

3.2. Construction of Specimens

3.2.1. General

The wall panels and prisms were built and cured in the laboratory at approximately 73 °F and 50 percent relative humidity. Wall panels were cor structed in pairs between wooden guides to assure proper alignment and plumbness. Joint thickness was controlled at in by horizontal lines at 16-in intervals which correspond to the height of two blocks and two joints. This method led to oversized joints in four unreinforced panels, where block which were undersized in height were used.

3.2.2. 6-in Reinforced Walls

Wall panels were constructed in three nominal sizes: 4 X 10-ft, 4 × 16-ft and 4 × 20-ft. Walls were built of the 6 × 8 × 16-in concrete block which were laid in running bond.

A wall cross section is shown in figure 3.2(a). Faceshell bedding was used for the horizontal and verti the cal mortar joints, and mortar was also placed on cross webs around the cores which were to be grouted. The mortar joint thickness was in. One No. 5 bar was grouted into each of the two outside cores of the wall as shown in figure 3.2(a). Vertical bars in the 16- and the 20-ft walls were spliced near

height over a length of 30 bar diameters (19 in). izontal reinforcement consisting of one No. 5 ormed bar was installed in each bond beam as wn in figure 3.2(b). These bars were grouted into 8 × 16-in lintel block laid horizontally. The 10-ft ls had bond beams at the top and bottom course, ereas the 16- and 20-ft walls had an additional ad beam at midheight. The actual cross-sectional ensions of the walls were 47 in by 5 in; actual el heights were 9 ft 3 in, 15 ft 11 in, and 19 3 in. Present design practice [2] specifies an area of el not less than 0.0013 times the cross-sectional a of the wall in one direction and not less than 007 in the other direction. The area of vertical el used in the reinforced walls of this investigawas equal to 0.0023 times the cross-sectional a. The area of principal reinforcement was, theree, about twice the minimum area required. The ea of horizontal reinforcement varied from 0.0007 hes the cross-sectional area for the 20-ft walls to 001 times the cross-sectional area for the 10-ft lls.

The reinforced walls were constructed in the folving manner: The first course of each wall conted of three whole lintel units (see fig. 3.1) which -re laid on a full mortar bed on a plastic sheet aced on the laboratory floor. These units formed a

horizontal trough into which the horizontal reinforcement could be grouted. A strip of painted 2.5 lb/yd2 diamond-mesh metal lath was placed over the top of these lintel units in the middle 32-in of the wall to contain the grout. Wall construction was then continued to the bottom of the next bond beam course.

After completion of every three courses of block, mortar protrusions were removed from the two end cores by a 2-ft long stick, to keep these cores clean for grouting. Clean-out holes were provided at each end of the bond beam. Sand was placed at the bottom of the vertical cores to be grouted to facilitate removal of the mortar droppings. Before grouting, the end cores and the bond beam were inspected and cleaned by compressed air.

Horizontal and vertical reinforcement bars were then placed and tied together, to prevent dislocation of the bars during grouting. Prior to grouting, the clean-out holes were covered by boards.

Walls were at least 16 hours old before grouting. In the first few walls, grout was consolidated by rodding. Subsequently, a vibrator was used to insure filling of voids. particularly in the bond beams. Grout was poured to within one inch from the top of the lift and reconsolidated after 30 minutes to remove air voids caused by water absorption by the masonry units. The grout in the first lift was permitted to set overnight before construction of the second half of the wall was started. The second half of the 16-ft walls contained two bond beams which had only two lintel blocks. At the outer end of these beams regular half-block were used. Openings were cut into these half-block to accommodate the horizontal bar and to provide cleanout holes at mid height. In the 20-ft walls all bond beams were built of three whole lintel block. The upper bond beam of the 10-ft walls also consisted of three whole lintel units. The 10-ft walls were constructed in one lift. Two lifts were used in the 16- and 20-ft walls.

3.2.3. 8-in Unreinforced Walls

Wall panels, as in the case of the reinforced walls, were constructed in nominal sizes of 4 × 10 ft, 4× 16 ft and 4 × 20 ft, built in running bond with 8 × 8 × 16in masonry units. Face shell bedding was used for the horizontal and vertical joints and additional mortar was placed on the cross webs at the two wall ends. Mortar-joint thickness was in. Actual crosssectional dimensions of the walls were 47 in X 7 in. Actual wall heights were 9 ft 3 in, 15 ft 11 in and 19 ft 3 in.

404-485 O-70-2

FIGURE 3.3. 20-ft high 8-in unreinforced wall panel. The first course was constructed from three whole masonry units. Each alternate course contained two half-block at the wall ends. Kerf block were used as half-block, and corner block were used where whole units were required at the wall ends (refer to fig. 3.1). A typical 20-ft high wall panel is shown in figure 3.3.

3.2.4. Prism Specimens

Prism specimens were built in stacked bond (one) block wide) using the 8 × 8 × 16-in block and the 6× 8 16-in block. Mortar was applied in face shell bedding as in the walls with -in thick mortar joints. Three-block high as well as two-block high specimens were constructed.

Prisms were built at random during construction of the walls, using the same mortar batches, and

FIGURE 4.1. Loading system and frame.

cured under the same conditions as the walls. Before testing, prisms were capped with high-strength plaster.

4. Test Procedure and Instrumentation

Wall panels were tested in a steel frame with an adjustable top cross-beam that could be raised of lowered to accommodate the various wall heights Eight 30-ton capacity hydraulic rams were attached to the cross-beam. Figure 4.1 shows the loading system and the frame with a 20-ft wall in place.

Figure 4.2 shows a diagram of the test setup. At the base a 1-in thick steel plate was cemented to the laboratory floor by high-strength plaster. The wall panel was set on top of this plate on another bed f high-strength plaster. When the wall was set, care was taken to assure wall plumbness and alignment Another 1-in thick steel plate was cemented to the top of the wall, to prevent wall failure by stress con centration. A 4 4-in diameter steel half-round was set on this steel plate with the flat side toward the wall The load was applied to the curved top of this steel half-round through a 4-in thick steel plate which

FIGURE 4.2. Test setup.

ansmitted the load from the eight symmetricallycated hydraulic rams. The loading head is shown figure 4.3. The test setup described above was signed to prevent rotation at the base of the wall, hile permitting free rotation at the top. Sidesway of e top of the wall was minimized by tying the loadg frame to the laboratory wall at a height of 23 ft bove the floor level. Great care was taken to posion the wall and the steel half-round precisely in der to apply the load at the desired eccentricity. Wall instrumentation is also illustrated schematially in figure 4.2. Aluminum tubes of 2-in diameter ere attached to the sides of the walls. At the upper nd these tubes had a pinned connection to the wall nd at the lower end they were attached to a guide hich kept the tubes in line with the centerline of e wall but permitted them to slide downwards as e wall contracted under the load. For the first four 5-ft reinforced wall specimens, aluminum tubing of in diameter was used. It was observed, however, at this tubing tended to deflect slightly, and 2-in ameter tubes were used in subsequent tests.

All instruments for the measurement of deflecons were attached to these aluminum tubes. orizontal deflections and wall shortenings were measured by linear variable differential transformers VDT's), capable of reading 0.0001 in. Instrument eadings were electronically scanned at every 20 kip crement of vertical load and recorded in digital orm. These data were manually key punched onto ards and automatically reduced, analyzed and

FIGURE 4.3. Loading head.

plotted by computer. Computer output consisted of tabulated test results and plotted load-deflection

curves.

Instruments were installed to measure wall shortening and horizontal deflections at 4-height, midheight and -height of the wall. The instruments were installed symmetrically at both wall ends.

One 10-ft unreinforced wall was also instrumented over a 24-in gage length on each wall face to determine the modulus of elasticity of the masonry.

Tests were carried out in duplicate for the same wall height and eccentricity. The first of the two walls tested was not instrumented and only failure load was recorded. The second specimen was instrumented, but the instrumentation was removed at about of the failure load of the first specimen. Deflection readings at wall failure are therefore not available. This procedure was adopted to protect the instrumentation from damage by explosive wall failures.

The walls were moved from the fabrication area to the test frame by a fork lift truck. Before moving, the walls were carefully braced to prevent damage to the specimen. A wall being moved by the fork lift truck is shown in figure 4.4.