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TEST RESULTS TV.ST DATA Complete t e s t data are presented i n Appendices B and C. Only the p r i n - c i p a l data are summarized i n the t e x t of t h i s paper. L i s t s of tables and figures precede the Appendices, the major categories of information pre- sented being: 1. Details of slab construction 2. Properties of reinforcement 3. Program of loading 4. Loading system hydraulic pressure 5. Ram ca l i b r a t i o n 6. Measured ram loads 7. Measured deflections 8. Measured strains 9. Slab properties at f a i l u r e areas BEHAVIOR Added dead plus one l i v e load was applied t o permit observation of service load behavior. Response to overload was then observed, and the ultimate strength of the loaded portion of the structure was deter- mined. F i n a l l y , a f t e r i n i t i a l f a i l u r e , loads were reapplied to evalu- ate load carrying capacity. Test I . The four panels i n Test I responded i n an essentially e l a s t i c manner under the applied load u n t i l ultimate strength was reached when Colvimn C4 punched through. Load-deflection relationships, as shown i n Fig. 28, did not deviate s i g n i f i c a n t l y from a stra i g h t l i n e . Some re- sidual deflection remained each time a f t e r the loads were removed. How- ever, residual deflections became smaller with each load cycle. 1- 21
Measured deflections at selected locations under 3k6 psf applied load (added dead plus 1.0 l i v e load) are shown i n Fig. 29. I t can be seen th a t deflections at the centers of the loaded panels were not the same. Maximum panel deflection was 0.3^ i n . at the center of Panel 3,4-B,C, over twice the 0.15 i n . deflection of Panel 4,5-C,D. Panels 4,5-B,C and 3,4-C,D each deflected about 0.25 i n . Relative magnitude of these panel deflections remained the same u n t i l the end of the t e s t . Deflec- t i o n s outside the loaded area were neglible. Load-strain relationships measured f o r the reinforcement were i n f l u - enced by cracking of the concrete. Gages located i n areas where cracks were present p r i o r to the t e s t showed a s t r a i g h t - l i n e relationship between load and s t r a i n . At gage locations where cracks formed during the t e s t , strains increased sharply with load when the concrete cracked. Strains measured i n the concrete and reinforcement were small under added dead plus one l i v e load. Changes i n reinforcement s t r a i n due t o applied load did not exceed 0.0003 at any location. Gage No. 63 mea- sured the highest steel s t r a i n under t h i s load, O.OOO29O tension. This gage was located on the positive moment stee l at midspan of the column s t r i p between Panels 3,l4-C,D and 4,5-C,D as shown i n Fig. 2k. Gage 60, si m i l a r l y located i n the positive moment region of the column s t r i p between Panels 3,l4-B,C and 3,lt-C,D showed a s t r a i n of O.OOO26O tension. Strains i n the reinforcement at the middle of Panel 3,4-C,D were about one-fourth the values recorded by Gages 60 and 63. A maximum concrete s t r a i n of 0.0004 compression at added dead plus one l i v e load was measured f o r Gage 5 on the bottom of the slab adjacent to Column Ck. The ultimate strength was reached abruptly by punching shear at Column Ck under an applied load of 895 psf. This load i n t e n s i t y i s equal t o added dead plus about 2.8 l i v e loads. Fig. 30 shows the pattern of de- f l e c t i o n s at an applied load of 8^3 psf, the load stage j u s t before punching occurred. Deflections given i n Fig. 31 are those j u s t a f t e r 1-22
punching occurred and d i f f e r s i g n i f i c a n t l y ; the four-panel area was "dished" with maximum deflections at Column Cl*-. I n the v i c i n i t y of Column Cl*-, f l e x u r a l cracks on the bottom of the slab formed a f t e r punching. These cracks are v i s i b l e i n the composite photograph i n Fig. 32. A f t e r f a i l u r e , t h i s region was subjected t o positive moments with the bottom of the slab i n tension. Positive moment reinforcement i n the slab was not continuous across the column l i n e s . Thus, no reinforcement was located i n the bottom tension zone of the slab, and moment resistance was nearly zero. Loading was continued a f t e r the i n i t i a l shear f a i l v i r e . Load carrying capacity of the structure became less as deflections increased. Load- deflection curves shown i n Fig. 28 I l l u s t r a t e t h i s behavior. The t e s t was terminated when the load necessary t o increase deflections was re- duced t o hjk psf. Spalling of concrete i n compression on the south face of Colimin Bl*- was observed j u s t before the t e s t was stopped. Spalling occurred i n the column concrete a t the bottom face of the roof slab. On the mezzanine side of Column B U, combined torsion-flexure cracking was v i s i b l e on the v e r t i c a l face of the slab where the'depth decreased from 2h to 8 i n . This cracking i s shown i n Fig. 33. During the t e s t , both before and a f t e r shear f a i l u r e at Column Ch, negative moment cracks were observed on top of the slab outside the t e s t area. These cracks circijmscrlbed the four panels and were located about 10 f t beyond the loaded area. The cracks were i n the v i c i n i t y where negative reinforcement over the colimn l i n e s was cut o f f . An outline of cracking on the top surface of the slab I s shown i n Fig. 3I*. Crack widths were not measured but were on the order of one-eight I n . wide j u s t a f t e r punching occurred. A f t e r the t e s t was complete and a l l load was removed, the cracks closed somewhat, though not more than about one- ha l f the maximum width observed during the t e s t s . 1- 23
