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HomeMy WebLinkAbout; Carlsbad Blvd Las Encinas Creek & Bridge; Carlsbad Blvd Las Encinas Creek & Bridge; 2005-08-31structural Assessment Report For Carlsbad Boulevard Over Las Encinas Creek Bridge No. 57C-0214 City of Carlsbad August 31, 2005 BEYOND ENGINEERING TABLE OF CONTENTS Location 1 Background Information 2 History: 2 Stmcture Description: 3 Current Condition of Structure: 3 Concrete Railing - West Side 3 Concrete Railing - East Side 4 Deck Surface 4 Girders 6 Cost Estimates 10 Bridge Constmction Costs 10 Life Cycle Costs 11 Summary / Recommendations 12 Appendix A - Vicinity Map Appendix B - Capacity Calculations & 1928 As-Built Details Appendix C - Additional Photographs LOCATION The bridge is located in the City of Carlsbad within San Diego County, Califomia. It crosses Las Encinas Creek carrying southbound traffic along Carlsbad Boulevard approximately 0.6 miles south of Palomar Airport Road, and approximately 1 mile north of Poinsettia Lane (see Figure 1 below). Pacific Ocean MapQuestcom, Inc, ©iO05 N)^VTESJ Figure 1: Location Map Background Information History: Based on our extensive research of Caltrans' records which included As-Builts and Bridge Maintenance Books and Reports, we were able to determine the following: The original stmcture was built in 1913, widened in 1924, and widened again in 1928. No plans are available for the original stmcture or the 1924 widening. The plans for the 1928 widening were prepared by the State Division of Highways and are entitled "Widening of Bridge Across Las Encinas Creek". The "Details" sheet clearly shows a widening on both sides of the stmcture. Three "T"-Beam girders were added on the west side and placed parallel to the roadway centerline, while five "T"-Beam girders were added on the east side. Four of the five girders were placed parallel to the roadway centerline, and the fifth one which is closest to the existing stmcture at the time, was placed perpendicular to the abutments, and therefore parallel to the original (1913 and 1924) girders. Originally, this stmcture carried two direcfions of highway traffic. In 1951, the State constmcted a box culvert upstream of the bridge to carry the northbound traffic thereby splitting the highway at that location by approximately 200 feet horizontally, and some 10 feet +/- vertically. (See Figure 1 and aerial photo). Once Interstate 5 was completed, highway traffic was diverted, and this stmcture began receiving local and beach traffic which is sfill the case today. In 1967, the bridge was relinquished by the State to the City of Carlsbad. Our review of the available records and reports which dated back to 1937 clearly indicates that this bridge has had quite a history of reinforcement corrosion, concrete cracking and spalling. The concrete girders and deck soffit have been repaired numerous times over the years in an attempt to stop the invasive nature of corrosion. All repairs were done with gunite, except that in 1964 both rails were completely replaced after 36 years of service. Structure Description: The stmcture consists of 12 cast-in-place reinforced concrete T-beam girders simply supported by reinforced concrete closed end cantilever abutments on spread footings. The stmcture is approximately 24' long and 68' wide. The deck surface currently carries two lanes of traffic with shoulders. The Bridge Railing consists of the old concrete baluster type. Current Condition of Structure: Concrete Railing - West Side Being closest to the ocean side, this railing showed the most deterioration due to exposure to corrosive environment. The south end post shows heavy discoloration (mst stains) of the concrete. A portion of the top rail appears to have been repaired some time ago. One of the vertical members has a large chunk of concrete that has broken off, exposing the corroded reinforcement. It appears that several areas have been patched in the past in an attempt to stop the propagation of corrosion, and make the stmctural members whole again. There is approximately a 2-foot long piece of concrete on the outside face that appears imminent for failure (Figure 5). This could become a major liability to the City as such an incident could cause serious injuries to any person walking below the stmcture. (See photos below and additional photos at the end of this report). Figure 4 Figure 5 Concrete Railing - East Side Although several cracks, longitudinal, vertical, and horizontal, are visible in the concrete railing and posts, there is no discoloration of the concrete. Ice plants are begiiming to intmde and cover the base of the barrier on the south side. For the most part, it appears that the east railing has not had any major repairs done to it. Figure 6 Figure 7 Deck Surface The deck surface is overlaid with approximately 5" of Asphalt Concrete to match the approach roadway. Therefore it was not possible to inspect the concrete deck surface within the traveled lanes. We did see some transverse cracks in the AC surfacing near the Abutment areas. We did notice at first glance a small transverse and longitudinal crack in the concrete deck on the east side. As we got closer and tried to clear up the debris, the concrete was clearly deteriorated, and we uncovered a large crack that needs to be investigated further, and potentially repaired. There is a 6"± AC dike on the west side approximately 12'± from the barrier and 5'-6"± from the shoulder line. The 12 foot area is completely covered with dirt. The AC overlay on the bridge was terminated approximately 10'± from the barrier on the east side, and 13'± from the left shoulder line. It appears that there was some re-aligimient of the traffic some time ago by shifting the lanes to the west side of the bridge, and abandoning the eastem portion of the bridge deck. Figure 8 Figure 9 Girders Girders are identified in numerical order from west to east for clarity. Girder # 1 ~ there is a large 5-foot long section, 6.5' from the south abutment face, where the concrete has spalled off. The void is approximately 12 inches deep, completely exposing the bottom layer of girder reinforcement, and partially exposing the upper layer from the east side. There is clear evidence that an attempt has been made previously to repair this girder with gunite coating. Corrosion is quite extensive and has caused a loss of cross sectional area in the reinforcing bars. A shear stirmp tie has broken off and therefore has been rendered ineffective. See photos below. Figure 11 Girder #2- the bottom cover of this girder is almost completely gone, exposing the reinforcement 7.5' from the south abutment face all the way to the north abutment. The cover concrete on the west face is barely attached to the girder; spalling of that piece appears to be imminent. Girder # 3 Girder # 4 transition to the original stmcture, and past repair is evident. The bottom of the girder is much wider here because it has been designed as a seat to carry the older stmcture when it was widened in 1928. The concrete cover on the west face of the girder has spalled off from 13' of the south abutment face to the north abutment face exposing the corrosion inhibited bottom longitudinal reinforcement as well as the transverse shear stirmps. Figure 13 two girders of uneven depth appear to be side-by-side at this location. The west face cover of the deeper girder is spalled off in several locations exposing the severely corroded reinforcing bars. There is an intermediate diaphragm between girders 4 and 7 indicating that this section is most likely the older bridge stmcture. Everything shows signs of past repair work with gunite, even the underside of the bridge deck. Figure 14 Figure 15 Girder # 5 ~ there is a very large crack on the west face of the girder. This is most likely the gunited cover from the previous repair work that is ready to fall off Figure 16 Girder #6- the concrete cover has spalled off near the north abutment face. Again, the reinforcing steel is so badly corroded that it disintegrated to the touch. Reinforcing bars are exposed on the north face of the intermediate diaphragm between girders 6 and 7. Figure 18 Girder # 7 ~ longitudinal reinforcing bars are greatly exposed near the south abutment face. One of the bars is completely broken off and exhibits a major reduction in cross-sectional area. Figure 19 Girder # 8 ~ a 6' long crack approximately V-i' wide or more can be seen along the west face of the girder. This piece of concrete can fall off at any fime. Although the east face is in much better condition, there are some small %" cracks that are beginning to form. Figure 20 Girders # 9 thm # 12 ~ these girders are in generally good condition. Figure 21 Cost Estimates Bridge Construction Costs Cost esfimates were prepared using the Caltrans 2005 Comparative Bridge Costs using square foot factors which is typical at this stage of the project. We also increased the cost to try and account for stage constmction and the removal of the exisfing bridge. If re- alignment of the roadway is substantial enough to allow traffic to continue using the existing stmcture while the new one is being built, then the stage constmction factor would not apply, thereby reducing the overall bridge cost. Because corrosion was so advanced, we did not consider that repairing the stmcture would be a viable altemative, considering the benefits of a new stmcture compared to continuously having to repair the existing one. In addition, the life expectancy of a new stmcture properly designed, should be in the order of 75 years or more. 10 Although the existing bridge is only 24' ± long, we have increased the total length to 65' to account for a minimum clearance of 14' under the bridge with 1.5:1 end slopes in front of the new open end abutments. The 14' clearance is provided to allow for dredging equipment if necessary in the future. If that clearance is not required, the bridge length can be reduced accordingly. With respect to the bridge width, we have assumed two l2'-0" lanes, two 8'-0" shoulders, 6'-0" sidewalk and barrier on the west side, and a r-5" Type 732 concrete barrier on the east side. The tabulated costs below do not include any of the following items: Approach roadway costs and associated items of work Special architectural renderings Right-of-Way costs, if apphcable Engineering costs for design Constmction management and constmction inspection costs Environmental documentation costs Environmental mitigation costs, if applicable City's administrative costs All costs shown in this report reflect the present value for the year 2005. To determine future value constmction costs, one must include anticipated future inflation and market conditions. Table 1. Bridge Construction Costs for Different Alternatives Alternative Superstructure Type Approximate Bridge Length Bridge Width Approximate Construction Cost 1 CIP/PS Slab 65' 47'-5" $900,000 2 RC Box 65' 47'-5" $800,000 3 PC/PS I 65' 47'-5" $930,000 Life Cycle Costs Life cycle costs consider the total cost of a proposed project over the life of the project. Typically, these costs include constmction, maintenance, rehabilitation, and repair. A 11 qualitative evaluation of the maintenance, rehabilitation, and repair of the existing and replacement altematives for the Carlsbad Boulevard Bridge over Las Encinas Creek is summarized in the following table: Table 2. Maintenance, Rehabilitation, and Repair Costs Items of Work Existing Structure Replacement Stmcture Inspection Due to the severity of the corrosion, inspection should be done at shorter intervals than the usual 2-year cycle. Every 2 years. Rehabilitation The existing concrete baluster type of railing is considered to be substandard in accordance with Federal guidelines, and therefore will need to be replaced or retrofitted at some point in time. The new barriers used for the replacement stmcture meet today's guidelines and are not anticipated to require replacement during their lifetime. Repair The existing stmcture is so severely corroded that the cost of repairing it would be very close to replacing it, if done properly. As indicated in this report, however, we do not believe that this can be done effectively. Repairs will most likely be on-going with shoring that would become permanent. No repair is anticipated with the new stmcture with a proper design and constmction. Summary / Recommendations For any repair to be effective, all corroded areas have to be fully exposed, and sandblasted clean. New bars would then be spliced to the existing ones as necessary and gunited appropriately. Based on our field investigation, it is very clear that corrosion has spread over 70% or more of this bridge, and any attempt to repair properly will require substantial effort, and most likely will not be cost effective. Given the fact that this has been an on-going problem since 1938^ and maybe even earlier, we are convinced that every attempt over the past years to stop corrosion has been unsuccessful. This is evident by the extent of the corrosion propagation and the severe loss of cross sectional area in some of the exposed reinforcing. Once corrosion of the reinforcement starts, it is 12 extremely difficult to stop. It is our opinion that corrosion has progressed over the years, and continues to progress today at an accelerated and alarming rate. Therefore, based on our field investigations, our review of all the available records, and our capacity calculations, it is our opinion that this bridge is a prime candidate for replacement, and the City should begin the HBRR process as soon as possible by requesting a "Field Review" with the District Local Assistance Engineer; and a Stmctures Representative. Although it is very difficult to predict the remaining life of this stmcture, the City should give serious consideration to shoring it in order to avoid a potential catastrophic failure and collapse, and also posting signs to keep beach goers at least 10' away from the westem edge of the bridge to avoid injuries caused by falling chunks of concrete. At a minimum, we recommend the following: 1. Posting the bridge for a reduced speed limit. 2. Posting the bridge for a reduced weight limit. 3. Continued inspection on a 6 months minimum interval to monitor the continuous propagation of corrosion and any additional loss of concrete sections and steel cross-sectional areas. Ultimately, we recommend replacing the stmcture and re-aligning Carlsbad Boulevard to the east at the same time. This will allow the City to reclaim beach area and provide additional parking, which in tum, will potentially facilitate the issuance of a Coastal Commission Pennit for the Project. 13 Appendix A VICINITY MAP Appendix B CAPACITY CALCULATIONS C/^EF.K T^RlhaE SUBJECT — — JOB NO, DESIGNED BY NOLTE CHECKED BY (G3 fia'is) hi PLF L0/lCpr0hli4flL '^ECTIVU A CO 4 SECT/OA' A-A p L(,ff.) = (a,30.i) + 1^" = 7^^' G,lE- /FIR FA/r^/A/j^s CREEK ^^ih&B SU BJ ECT JOB NO, DESIGNED BY DATE CHECKED BY NOLJE E::>ERh Lonhs> Eecl. - Tillth ^ ^ RC ^ Giunift ^ ^.^0 ^ 8A. X OJ^K^cF IJ^\ L'fl^ 0.1^ 4 /A 0 .K ^,so\ d^p = 0. ^ K/ff 1 o 3 0. L 3>HI Un)'^ Eu&^ - u&e. .z / 6 limp3cf pE?c'fo^. L 3 tF) AJP/Y} PLRTE 2' fa.Lii in ^'--r J. p 'iLi-I 7F' 9.9.. l<f^fl /A7,Q tur.fAJfl^ SUBJECT JOB NO, DESIGNED BY DATE CHECKED BY NOITE ^eaLc'l'iha fill Lailom Im/eh^ cy^f uLsb.,. Jut lo ih^t /7 V - rA" = 3.0^ in. Z) - - 3^0f. . 0. 0O/9Z 0.2/3 /_ _|_ ^^ 0,929 ij'l'^ ; 3,0^ in} + /(^^^^) = 4,^9 inl- /' J = IC.I^ p - ^.^9 _ 0.002^^ / pn 0, 0¥/3 i iU25.XC / SUBJECT JOB NO, DESIGNED BY DATE CHECKED BY /O / Lf < 99. CK-fi jfivenAly ffsh^ USE Jf = /8,009 psi] Pf.e ^2. J OE)eh.aTin a • // U&l J a^\dW p^i- \ M.^iniman ci, f • J , fs / i Hsnvsi (Tn^) . /8y^OJii.^TiT ^ 9.^9 ^ /^9T K'Ff if^ (i2pr) 9C, . " '7 ^ 22IA K-Fl. Ihs/s-n'/o^^ f^^linq yfjclo^. = /59A-8Lj ^ Oo 919. < (.0 7 J 8^.d^2H'is) Opt'ialina n // - 191. y - A/J - A iJors /» CRLcuLETfOMZ FE^ EPPRO X.)MF)TB , ffAlb ARE &BSBh O// TFB I^JS PE CTVR's. Job C-,BMFAIT- OF lOSS //V STEei cFOSS- SBdTic?AJFL RREP . li , 77/£ 6>RHE!EE LpFh/AJC-, WR& RS,S.UH£b 79 BE BVEA/IF t/srR)BV7Eb OVER TFxEE E/lFbEF.^ i~ P^RY BB /^PF& PRVAJWh/tEb DVBE FHt £/.rBFjOfl (?iiFhER. S. COEEV&iO^f HE3, ijUHlQ/TEh TEE MRTOR/EY VFT>-I)& ^TR UCEi^F E , TO SOcp/ RH E>^7EAJT TEPIE IF HRY A/OE EE POSSIBLE TV EFOPERLY RBPRIH IF. 4, IT is, ovE oriAfioA} TURF inh ^TFVCTIJPS sEou/h BE PEPLECBh m S.O0P} fl^ POSS>I.B>LB. , •• • pdusf'haf /ess fEon'A¥o' hours'armors ff?p'7 fhree /Tours- Carhs no^ '' '-^ 'be 'pot/h:dur^fi/.af^ beens/ruck. AUcancns^/'^ ra//ino ane^pos/s '/a he C^oss £oshcns/c n/nff socAs of cemeni per Ci/.yd.af concrete. - . Allof/ierosncrafe /fo 6e C/asa'A"^s/^csacks ofceTrenfperca-yc/.of 'c6r>cr^/<s- Alt exposed ec^s ^ 6e c/jomfsfreef ona/^ch.SJ'cep^na/Eng^ ond posfs wh!c/7 ore fo be c/x3/r)/er-ed €3ne~^uar/sr ifTc/j- fhrh'ons ofexi'sf'ripsA'i/cA/re //^o/ Pn/er-fSgr-e iv/^ n^i^ ^/vor/c be removed. - All sur/oces of'a&concre/e /<s 6e roa^henedand kepf ePofn^ iv-PtenrJoined. hy new cqncrei^e. ' •. • ri^'fifhrcfrrg s/s^/ !^ bs 's<^i/om deEbrmed hors • AU dimensioris hs^eelgiytsn /a i. ofhor- Alt skel h bs embedded so os io provide r>olless ihon Avo irKhes Coyerin^ of cxiricreie- idhere ,bar^ are Spliced, /opshof/ be noi Jess ihon forty d/omefers. . Ifaf/er ^f/rj^sare eifcoyahd )/» /bund Uiat piles are noi rvqOired, quanHHes in Ihrns_ l&Z of Special Provisions mil be reduced- E^pfe io be reoessed^dhd/oco/ed OS shotvn- QTATE OF CALIFORNIA •DCPARTMm(fPlj6U(:i ' iyy/SJONOF'HlGmAYS - • HV/OCN/NQ OF BRIDGE. ACROSS- :-LAS £mNA5\CRtCi< SAN DIEGO CbuNfy DETAILS ScalGS <3s\shot^n Appendix C ADDITIONAL PHOTOGRAPHS Close Up of East Side of Deck-Looking North Crack in AC 2-North Abutment Crack in AC 3 North Abutment Crack in AC North Abutment Crack in AC-South Abutment Crack in AC North Abutment East Railing 3 East Railing 2 Girder IB Girder IC Girder 2B Girder 3A Girder 4C Girder 7C Girder 7A Girder 7D Girder 7E Looking North Overall West 2 NE Abutment Corner Overall West View of Bride Approach Looking North View of East Railing View of East Side of deck Looking South View of West Sidewalk Looking North I Close-up of North Abutment Corner West Face of North Abutment West Railing 1 West Railing 2 West Railing 3 West Railing 4 West Railing 5 West Railing 6 West Railing 7 West Railing 8 West Railing 9 West Railing 10 West Railing 11