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Home My WebLink AboutBridge Abutment Assessment for BLD2008-00318 - BLD Engineering / Geo-tech Reports - 3/20/2008 Envirotech Engineering March 20, 2008 74 NE Hurd Road, Doug Neyhart Belfair, WA 98528 2297 Tahuya River Road Tahuya,Washington Reference: Bridge Abutment Assessment for property located at 2297 Tahuya River Road in Tahuya,Washington Dear Mr.Neyhart, Envirotech Engineering (Envirotech) completed a site visit on March 14, 2008, followed by this structural assessment of two existing reinforced concrete bridge abutments located at 2297 Tahuya River Road in Tahuya, Washington. The abutments will hold a prefabricated bridge with an approximate span of 82 feet. The bridge will have a dead load of about 46,000 pounds. The accompanying abutment details depict construction information for this project. The owner provided all construction information for the existing abutments. Envirotech verified abutment dimensions and assessed soil conditions during the site visit. The structural analysis provided herein is based on owner provided information and the aforementioned field verification by Envirotech. This assessment is structural,and does not assess hydraulics or river dynamics. Earth Pressures Back ill material:compacted SP, SW, SP-SM,or SW-SM Assume Active earth pressures. H= 10 ft height of wall y„,= 140 psf soil unit weight yW=62.4 psf water unit weight �=32' angle of internal friction c= 100 psf cohesion S=2/3�=21.3° angle of wall pressures K.= 1 -sin+=0.31 at-rest earth pressure coefficient Kh=3/4Ko=0.23 earthquake earth pressure coefficient Resultant Pressures R,= 1/2y ubWKo=224 psf Lateral earth pressure from soil P,= 1/2y if=3120 psf Lateral earth pressure from water R,=3/8yw,,,ll2Kh=599 psf Lateral earth pressure from earthquakes R,r=gHK,,=307 psf Lateral earth pressure from surcharges R=R,+Rq,+R,+R,r=4251 psf @ 3.83ft from the base of the wall RH=R cos S=3960 psf Resultant horizontal earth pressure Rv=R sin S= 1546 psf Resultant vertical earth pressure Rv,=69 psf vertical component of resultant active earth pressure used to counteract sliding RH,= 176 psf horizontal component of resultant active earth pressure used to counteract sliding OFFICE: 360-275-9374 CELL: 360-689-6045 FAX: 360-275-4789 EMAIL: envirotech@geotechnicalinfo.com Vertical Loads Bridge dead weight=46,0001b; 23,000 lb per abutment Snow Load=25 psf; 12,300 lb per abutment Live Load=45,000 lb per abutment Sliding and Overturning EWi=6410 lb sum of vertical weights on retaining wall T,Wixi=26686 ft-lb sum of vertical moments on retaining wall Rs,=(y_Wi+Rv+Rv,+Rv+W)tan 8+CB=5967 Resistance against sliding RH=3960 Sliding forces Rs,/RH>FS 1.51 > 1.5 o.k.against sliding Y—Wixi+Rvxv+Rv,xv, =32606 Resistance against overturning Rhys= 15167 Overturning forces (EWixi+Rvxv+Rvixvi)/(Rhys-RH,yxl)>FS 2.1 > 1.5 o.k.against overturning Wall Analysis f =3500 psi concrete compressive strength M„=wW16=21256 lb-ft Ultimate moment fy=60 ksi yield stress of rebar X=0.Id=0.825 in w= 1.4*R=5952 psf force of earth A,=M„/�fy(d-X)=0.404 si Steel area t= 16 in wall thickness at base k=fyA, 0.85f =8.14 si Concrete area H= 10 ft Ma=Aefy(d-X)=283 k-ft Nominal moment d=8.25 in critical depth �K=21.3 k-ft Design moment A,2=A,(M„W=0.404 si New Steel Area Use A.=0.404 si Flexural Steel: #4 bars @ 5.8 in.O.C. required Used Two#4 bars @ 6.0 in.O.C. o.k. A.=0.0018bt=0.3456 si Temperature Steel:#4 bars @ 6.82 in.O.C. Used Two#4 bars @ 6.0 in. O.C. o.k. Wall Foundation h=24 in footing thickness Mu=[q„(B-t)2]/8=75572 in-lb B=84 in footing width AB=M11/�fy(d-%)=0.0751 si d= 19.88 in effective footing depth k=fyA, 0.85f�= 1.515 si P„= 1.4D+1.7L+soil= 10546 lb/in factored loads X=Aa/2b=0.0631 in q„=P„/B= 126 psi load per unit length A.=M,f+fy(d-X)=0.0678 si v„=(q/d)[(B-t)/2)-d] =89.23 psi shear stress A.(min)=0.0018bh=0.5184 si 2of3 v,=2(f J = 100 psi concrete shear strength V.<0.85v, depth o.k. use A.=0.5184 si No of#6 bars per foot=1.17(Flexural);#6 bar spacing=10.23 in Used#6 mbar at 6"spacing o.k. AS =0.001813h=3.63 si spacing too close A.(min)=0.0018 si Spacing(max)= 5h or 18 in= 18 in Temperature Steel:#6 bars @ 18 in.O.C. Used#6 mbar at 6"spacing o.k. Bearing Capacity/Settlement Qall=(cNc+(gamma)DNq+0.5(gamma)Bng)/F.S. allowable bearing capacity =(100psf(35.5)+ 120pcf(Oft)(23.2)+0.5(120pcf)(7)(22.0))/3=4263 psf q„= 1465 psf Qall> q, Bearing Capacity o.k. These types of soils settle immediately upon loading,with virtually no consolidation or secondary settlements. Total settlement is estimated to be less than 1.0 inch,with a differential settlement of less than 0.5 inch.This is based on foundations constructed per the retaining wall design detail. Settlement o.k. Envirotech is pleased to submit this engineering analysis. If you have any questions or need additional information,please contact Michael Staten at 360-275-9374. Best Regards, Envirotech Engineering "LYDE 1 WAS �9T rO� 43045 �is rr�� ss��►NAL�N�1 EXPIRES JAN 10,2009 Michael Staten Project Manager 3 of 3 82FTt :. '• rrl • ;0 12' 7FT BRIDGE ABUTMENT (TYP) PROJECT/ LOCATION RETAINING WALL DESIGN ti CLy1) PLAN VIEW �y S' DOUG NEYHART WAS 2297'Y> TAHUYA TAHUYA, WASHI ROAD WASHINGTON CONTRACTOR- OUG NEYHART 2297 TAHUYA RIVER ROAD r U TAHUYA, WASHINGTON 045 DRAWN BY DATE MCS 03/20/08 ENGINEERt REVISIONS, �cS' cjSTV,R CJ DESIGNED BY, DATE, ENVIROTECH ENGINEERING SCRiPTM T DATE AL Michael Staten, P.E. 03/20/08 74 NE HURD ROAD SHEET BELFAIR, WASHINGTON 9B328 1 PHONEi (360) 275-9374 EXPIRES p 1 FAX, (360) 275-4789 SHEET 1 OF 2 16 IN (2) 12'xl2'xi6' BLOCKS. ONE ON EACH END OF ABUTMENT FOR LATERAL SUPPORT OF BRIDGE. NOTESi STRUCTURALLY TIED TO WALL WITH STEEL REINFORCEMENT 1, RETAINING WALLS CALCULATED USING ACTIVE EARTH PRESSURES. 2. RETAINING WALLS ARE LIMITED TO 10 FEET. 3. SLOPING EARTH RETENTION (BACKFILL) IS NOT PERMITTED. 4. FOOTING SUBGRADES ARE DENSE UNDISTURBED SOIL. 5• ALL CONCRETE IS 7-SACK, 6. REINFORCEMENT STEEL YIELD STRENGTH IS 60 ksl. ! 7. CONCRETE COVER FOR STEEL MUST BE A MINIMUM OF 1.5 M4 REINFORCEMENT STEEL COMPACTED GRAVEL, INCHES FOR WALLS, AND 3 INCHES FOR FOOTINGS, HORIZONTAL 2 6 IN O.C. E " SAND, SAND WITH SILT 8. BRACES AND TIE-DOWNS, IF USED, SHOULD HAVE A (TYP) a :OR GRAVEL WITH SILT.•' CORROSIVE RESISTENT COATING. BACKFILL 9.BACKFILL SHOULD BE COMPACTED TO A MEDIUM RELATIVE DENSITY (80%-85%), M4 REINFORCEMENT STEEL 10. ALL WORK IS EXPECTED TO BE IN ACCORDANCE WITH VERTICAL 2 6 IN D.C. • c PROPRIATE IBC, STATE AND LOCAL CODES. (TYP) It. ALTHOUGH NOT REQUIRED, 4' WEEP HOLES AT 4 FEET D.C, ARE SUGGESTED. CONCRETE RETAINING WALL AND FOOTING, 3500 psi 10.0 FT t 3 FT MIN • i 24I1 N 3/4' REINFORCEMENT STEEL 28 IN (VERTICAL) Q 6 IN D.C. 3/4' REINFORCEMENT STEEL PROJECT/ LOCATION (TEMPERATURE) 2 6' QC, CLY ) RETAINING WALL DESIGN (2) 30' STEEL REINFORCED CONCRETE 4,y �s+ PILES BENEATH FOOTING. STRUCTURALY Qlj,- DOUG NEYHART 7 FT TIED T❑ FOOTING �� .,�I�C�� TAHUYA, WASHINGT2297 TAHUYA ON ROAD IO F'C ABVIMBNP WAU-DBfAII, CONTRACTOR, ZlI@UG NEYHART NC?'P0SCALE .d 2297 TAHUYA RIVER ROAD �l J TAHUYA, WASHINGTON �� 43G45 DRAWN BYt DATEi s��GjS Mcs 03/20/08 ENGINEER, REVISIONS, DESIGNED BY, DATE, ENVIROTECH ENGINEERING SCRmno+ r TE `SIGNAL Michael Staten, P.E. 03/20/08 74 NE HURD ROAD SHEET BELFAIR, WASHINGTON 98528 PHONE- (360}-275-9374r XplRFS�& �Q, 1�* FAXi (360) 275-4789 ` i—r1 SHEET 2 OF 2