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. 8ent B,,v: CENTURYWESTENGINEERING; 5032310964; Aug-16-99 8:05PM; Page 1/2 ~ V /~ (o/ 1 ~, `. CENTURY V1f EST ~ BNGINP~RING GORl'ORA j ~ L~ A D I N G 7 H R O U O N E F f E C T 1 V E SO L U T 1 O tJ S • ~A~ MEMORANUVM D~: August 16, 1999 . # of P~ges: 1 c~nox~ ~ ~"~ ~ ' pr~M~ wN~ fol~ow: N Tp: I,eonard Lodder, . . ~ ~1T~UC~~ COBt1C ~Cj11~CG4 , Fax #F: (503) 581-385 ~, " ~rom: ~ , - . T~t~n Teri~l./ Project #: 4UyUSUt~1tl4-~vv~- $~~~; Courthouse ~quare - Topping Slab Performance Ccmr+x~~ts: Leonard, You ~awe requested that we forecast the per~'oimance of the various topping alab designs for the .' transit mal! area. We anticipate t~he fallowin8: ~ The original 3" cancrete t,oPpinB slab was designed to ~'ansfer load tn th~ st~ucturai PT slab wilh virtually no movement in the waterproofing membrane system. It was later ~learned that the . membrane systesn may prov;de up bo 1/8" vf inevemmt under tire loading. This a~o`'emct-t wauld ha`r~ ccack,cd thc lighdy reinforced conerete. The craclcing cauld be betwcea ont to faur feet aPart, depan~ing on joint spaein$ and 1,os~ct is~~enaity. These cra.cks would move under continual traffte ,-. loade, and evenhc a lly b e g~ n 9Pallin$ at the edges. Aft~' 1-3 year~-, we estimate that the spalling wauld beoame uasightly and daagcroue to foot traffia The extensive cracking cAUld lead to , damageofthewa~rproofingmennbrane.Tbisslabw~ldnadrepairarpartialreplaceme,~tt within S yea~s af setv~ce. The ori~inal purposc of thc toppin$ siab ie tn protec~ the waterpmofing -. m~brane a~d absorb the extensive wear from continual bua t~ic. . Sincx Arbucl~lo eostic feels that the wateipr+oofing system cennat be changed, the design team hae ~ ~roposed two re-desig~n aptions: _ 1) incrcase the slab t6iickness and reinfoncing. ~ 2) Insta!! an interlocking Paver eyat~m_ . Option #1) The re-dssignCd slab will have addition reiaforcing and jointing - this will help . minim;~e cracking in the concxete. Minor cracking will still occur in this slab. The rein€orcing in the slab wiil pxovide more cantinuity and load distribution. Cracking that ocau~ is likely near . 825 NE Muhnomah, Suiie 425 Porttand. OR97232 ' ,~;~ `: '~;" - 1041Tapu~c.~nmo Phone: (503) 231-1i078 Fax: (503) 231-6482 ", ,, a~u-~R . ~ ~.:. . , .