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Between t e s t s , equipment was stored i n a t r a i l e r adjacent t o the t e s t structure. Office space and telephone were also provided i n the t r a i l e r . I n preparing f o r the tests as much work as possible was done i n the l a - boratory before a r r i v i n g at the t e s t s i t e . Dummy s t r a i n gages were made i n the laboratory, gag@ leeid wires were cut t o length and tagged, ajid instruments were calibrated. Data forms were made and conduct of each t e s t was planned. I n addition, a l l equipment was designed and ordered, and a l l necessary supplies were l i s t e d and ordered. A l l of t h i s was done t o minimize the time required a t the t e s t s i t e i n preparation f o r each t e s t . Some common items were l e f t t o be purchased l o c a l l y during t e s t preparation. However, delays resulted when l i g h t s , extension cords, e l e c t r i c a l tape, etc. were not on hand at the t e s t s i t e . Often, several hours were needed t o locate a supplier and obtain the quantity and type of a r t i c l e s required. LOADING SYSTEM Closely spaced concentrated loads were applied t o the waffle slab t o approximate a uniform load. At each load point a 30-ton capacity hy- draulic ram was used to push down on the slab. Reaction from the ram was transferred t o the foundation slab through a 0 .6 -in. prestressing strand coupled t o a rock anchor set i n the foundation slab of the t e s t building. A detailed sketch of the loading system i s shown i n Fig. 1. Holes were d r i l l e d both through the roof slab and in t o the foundation at each load point. A 1-in. diameter, l+-ft long rock anchor with heavy r o l l e d threads was inserted i n the foundation holes. The base of the rock anchor f i t i n t o a s p l i t wedge as shown i n Fig. 2. As the rock anchor was screwed down through the wedge, the wedge expanded and locked against the foundation concrete. From private correspond- ence, i t was learned that i n s t a l l a t i o n s of anchor bo l t s were more re- l i a b l e when grout was used t o supplement mechanical anchorage of the 2-1+
s p l i t wedge. After the wedge was expanded, the space around the b o l t was f i l l e d w ith grout. A commercial product, Por-Rok, made f o r s e t t i n g anchor bo l t s was used t o grout the anchors i n place. Holes with a minimum of 1 i n . were core d r i l l e d through the roof concrete, using diamond b i t s to give a smooth hole and t o prevent s p a l l i n g of the concrete as tlie b i t penetrated the slab. Penumatic rock d r i l l s with r o t a t i n g b i t s were used t o d r i l l holes i n the foundation. The b i t s were standard moil points. These holes were d r i l l e d to a depth of 2k i n . leaving a nominal k in. of concrete between the bottom of the hole and the bottom surface of the foundation slab. The diameter of holes i n the foundation slab was maintained between I.5625 and 1.6875 i n . Practice i n s t a l l a t i o n s showed that t h i s tolerance i n hole dieuneter was necessary to permit proper locking of the s p l i t wedge on the rock anchor. The top of the roof slab was cleared of debris by the demolition con-- t r a c t o r . Remnants of the waterproofing membrane were removed by a concrete surface grinder manufactured by G. H. Tennant Company. This type of grinder i s shown i n Fig. 3. Grinding i s done by a set of blades i n a v e r t i c a l position t h a t rotate about a horizontal shaft. Steel load d i s t r i b u t i o n plates 1.25 i n . t h i c k were used at each load point. V/here load was applied near the middle of a pan l o c a t i o n , 12 X 12-in. plates were used. For load points near r i b s , 8 x 8 -in. load d i s t r i b u t i o n plates were used. Each plate was set i n plaster ajid leveled with a mason's l e v e l . As indicated i n Fig. 1, a strand g r i p , a center-hole hydraulic ram, and a second strand grip were located immediately above the plate. The 0 .6 -in. prestressing strand passed through the ram, the grips, and the roof slab t o the rock ajichor i n the foimdation slab. A section of standard rectangular s t r u c t u r a l s t e e l tubing, 0.5 x U x 8 i n . and seven inches long, was used t o couple the strand t o the rock anchor. The strand and rock anchor passed through holes i n the top and bottom of -Ì 2-5
the tube. Two nuts were threaded over the rock anchor, and a strand gr i p held the strand w i t h i n t h i s t r a n s i t i o n device. As the ram ex- tended and reacted against the upper strand g r i p , the strand and rock anchor passed the load i n t o the foundation. Photographs of the assem- bly above and below the roof are shown i n Fig. k and 5- Wedges were omitted from the strand g r i p between the ram and the slab during application of cycles of low load. During the t e s t t o f a i l u r e , the wedges were inserted so that when ram stroke was e^diausted and hydraulic pressure was released, the lower gr i p would gr i p the strand and maintain load. The upper g r i p was then pushed down t o recover ram stroke. Thus, by continuing t o reset the top strand g r i p , the system coiild accommodate a t o t a l d e flection of several f e e t . The loading system was designed f o r a capacity of 45 kips per load point. Nominal t e n s i l e strength of the 0 . 6 -in. diameter strand was kips. The rock anchor had a 1-in. diameter and was made of higjh strength steel. Cores taken from the foundation slab indicated an average concrete strength of about 5300 p s i . Before the tests were started, a t y p i c a l load u n i t was assembled and proof-tested t o 50 kips. The hydraulic rams were center-hole type with a nominal capacity of 30 tons. Maximum stroke of the rams was 6 i n . Nominal e f f e c t i v e area of the rams was 9.28 in? A t o t a l of 212 rams were manufactured es- p e c i a l l y f o r use on these t e s t s . Before and a f t e r the t e s t s , the rams were calibrated i n the laboratory. During c a l i b r a t i o n the rams reacted against a set of c o i l springs as shown i n Fig. 6. Under hydraulic press\ire, the rams extended deform- ing the springs a t a rate of about 0.5 i n . f o r each 10 kips of load. I n t h i s manner, f r i c t i o n e f f e c t s developed by a moving ram piston were determined. 2-6
