3315 15TH ST 2016-01-01 MF Import

TABLE I1. Supporting str2ngth of concreto pipe' of constn�ction since the fond resulting from the same per linear foot of pipe in thousands of pounds(kips) fill on a negative projecting conduit is much less than �i� that on a projecting conduit. I'or a more complete Standard strength Exira strength (IISCUSSIOfI o[ the theory and londs on negative pro- ASTM concrete sewer plpe concreta�i�er pipe je�Ling CO[I(�UItS 5('C 1VCgnl{VC Projectinr� Cond¢iLs, �>y spec.no. C 14 sarety�acior= ts Safety facmr= 1.5 �f. G. Spnngler und �V. ,J. Schlick, �ngineering Report eedainq �o• bl, town �nginecring Esperiment Stution, Iowu d�ss o c e A o c e n State Colfege, 1953. racio 1.i i.s 1.9 a.o i.i i.s i.e 3.o Imperfect trench conduits 6 0.8 1.1 1.a 2.2 1.5 2.o z.s aA This i.s a term applied to n method of construction that a o.9 t.s i.5 z.e 1.5 2.0 2.s a.o �ecreases the backfill or embankment lond on the con- �" duit, thereby increusing the snfe height oP fill H thnt vt io 1.0 1.a i.e 2.e 1.5 2.0 2s a.o can be carricd by thc conduit. In this method of con- E� aV t2 1.1 1.s t.9 a.o 1.e 2.2 z.e a.s struction the bnckfill is thoroughly compacted around �d i5 1.2 t.� z.2 a.5 2.0 2.e as 5.5 and over the conduit, usually to a height equul to the ;;n 1s i.a z.o 2.5 a.o 2.4 3.3 a.z e.e outside dinmeter of the conduit plus 1 tt. A trench of �° 21 i.5 2.z z.s a.a 2.a a.a a.9 �.e width equal to the Ureadth of the conduit is dug down za 1.� z.a a.o a.s 2.� a.o s.i e.o to within I ft. of the top of the conduit and refilled n•ith loose uncompacted mnterial, after which the �s�p porting strenglhs shown in (able are for concrete pipe mee��g remainder of the fill is eom leted in a normal manner.* ASTM specifications 3�etlqe bearing test) an� inclutle satety antl P bcdding factors as in��aiza. E�perience in this type of cons6ruction by n number of state highway depnrtments indicates that it is both correct in principle nnd pr�ctical." Example: Use uf tables Assume a 15�in.�diameter concrete pipe is to be •Em6nnAment Conduit D-Londa Jor R/C Cula�ert Pipe.Avnilable laid in 8 3-ft.-wide t�enCh undEr 10 ft. of covB�. without chnrge ouly in 6he United Stutes nnd Cnnndn Erom thr. The backfill materiai has a unit weight of 120 Ib. Portland Cemr.nt Associntion. pef CubiC foot and CIa55 B b0dding is 5pedfied. ReinJorced Conerete Pipe CuA�erls-Cnleria Jor Slrudural De- To determine the backfill load W„ refer to nBn and (nstaltatfon, Bridge Divieion, O(fice of �ngincering, Table 8 on page 34. For H equal to 10 ft. and a 1�umnu ot Public Ronds. 3•ft.•wide trench, it is seen that W�is 2,2001b. per "R. Robinsnn Rowe, "Rigid Culverts Undcr High Over611s," linear foot From Table 11 on this page it is seen Pnper No. 823, Proceedir�ps oJ the A,nerican Society oJ Ciui! that a 15•in. nonreinforced concrete sewer pipe, Enginters� October 1055. s?andard 5trength (C14), with CIasS 6 bedding, Concrde Pipe 77ighway CulverL Surve�, Americ¢� Conerete , has a supporting strength of 2,200 Ib. per linear P'PQ�0cintion, t�62. foot,and thus wil�carry the expected load. Ta61e 12 gives supporting strengths for rein• i4 . forced concrete sewer pipe (C76), and it is seen o 0 0 that 15•in.-diameter Class II pipe with Class B o o "' � o o° bedding has a supporting strength of 2,400 Ib. i2 ° ° ^' perlinearfootand could be used if desired. ; It is obvious that all of the stronger pipe classifi• `� cations in the tables wo�ld also support the load io given in the exampie. � s H by extrapolation. IP more accuratc vnlues of the load Bc fuctor for various vnlucs of r,e are desired, they cnn be 6 computed (rom the equntion for load Inctor I.� given abov^. The safe lond thnt cnn be cnrricd by the con- 4 duit is determined by apptying the proper snfety factor (see page 30) to thc load-carrying cnpacity of the pipe conduit as detcrmined from the 3�edge bearing trst, z and multiplying the result by the load factor. (SanA on0 GraveU Negative projecting conduits o A nepalive projecting conduit is one tliat is instnlled in � z 3 a undisturbed naturnl soil in n nnrrow ditch extending vawes or Bd where tronch lood eQuals embankmem loaa upwanl some distnnce Crom the top of the conduit. Bc 'Chere is considernble advnntngc in the u=e of this typc Fig, 17. Transition•width ratio eurves. 36 " . _'. _.__. .�':'.,_..,�..:r.<.e..^� '