HORROCKS. Engineering Review of Proposed Cast-in-Place. Reinforced Arch Culvert Specification. For. Rinker Material Concrete Pipe Division

Transcription

1 JO7 For Engineering Review of Proposed Cast-in-Place SPECS Item #6 December 12, 2018 Handout Date: December11, 201$ Prepared By: PLK Reviewed By: DAA HORROCKS PROJECT NO Phase 27 Rinker Material Concrete Pipe Division Reinforced Arch Culvert Specification M Exp.12/31,iS k AMES g Reviewe - E N (3 1 N E E R S N. Green Valley Parkway, Suite 160 Henderson, Nevada DANA A. CIVIL! RUCTURAL HORROCKS

2 Page 1 of 10 TABLE OF CONTENTS SECTION 1- INTRODUCTION 2 SECTION 2- CRITICAL AASHTO LRFD BRIDGE DESIGN SPECIFICATION SECTIONS 3 SECTION 3- CONSISTENCY BETWEEN CAST-IN-PLACE REINFORCED CONCRETE ARCH CULVERTS & PRECAST 6 REINFORCED CONCRETE BOX CULVERTS SECTION 4- CONSISTENCY WITH SIMILAR STANDARD SPECIFICATIONS S SECTION 5- CONSTRUCTION 10

3 November 27, 201$ Page 2 of 10 SECTION 1- INTRODUCTION This report presents the results of an engineering review of the proposed Cast-in-Place Reinforced Concrete Arch Culvert Specification (Arch Specification). This specification is proposed to be included in the Uniform Standard Specifications for Public Works Construction Off-Site Improvements, Clark County Area, Nevada (Standard Specifications.) The purpose of the review was to evaluate the specifications for the following areas: Does the proposed Arch Specification include all critical AASHTO LRFD design, construction, and load rating requirements? Are the basic design and construction requirements in the Arch Specification consistent with the proposed Pre Cast-Reinforced Concrete Box Culvert Specification frcb Specification)? Identify any unique requirements related to the design and construction of the Arch Culvert and verify they are included in the Arch Specification. Consistency with related standard specifications including NDOT standards.

4 0.125DE) Buried when Page 3 of 10 SECTION 2 CRITICAL AASHTO LRFD BRIDGE DESIGN SPECIFICATION SECTIONS After thorough review of both the AASHTO Design Specification and the Arch Specification it is our opinion that the Arch Specification is too general and should include the following sections and information concerning those sections. Section Limit States and (Section 1.3.4) Redundancy: the redundancy factor should eqlial 1.05 for Earth Loads per C and Section Load Factors (LF) and Load Combinations: LF used should be those in Table &2. DL= max 1.25 mm 0.9 EL(V) = max 1.3 mm 0.9 EL(H) = max 1.35 mm LL= 1.75 Section Unit Weights using 0.5(ELH) Section Unit Weight of Soil = 120 pcf unless otherwise noted in special provisions, geotechnical report or on project plans Section Multiple Lane Presence equal to 1.2 for single lane Sections and 3- Design shall be based on live loads of a minimum HL-93 design truck loading and the design tandem consisting of a pair of 25.0-kip axles space 4 apart. Section Distribution of Wheel Load through Earth Fills with a Live Load Distribution Factor (LLDF) equal to Section Design Loads for Decks, Deck Systems, and the Top Slabs of Box Culverts Section Dynamic Load Allowance IM = 33(1.0 - Section Static Pressure Structures > 0% DE = Minimum Depth of Cover Check load case with culvert filled with water H1 = 62.4 pcf Section Earth Pressure: Compaction Section At-Rest Lateral Earth Pressure Coefficient, ko The Maximum Lateral Earth Pressure shall be 60 psi as a minimum and increased as required by the geotechnical report. The Minimum Lateral Earth Pressure shall be 30 psf (Section ) Section Live Load Surcharge Section Equivalent Strip Widths for Box Culverts: this section applies per Section

5 Normal 2(2.3125) Page 4 of 10 Section Weight and Lightweight Concrete: Compressive Strength- Due to high sulfate attack in the valley we recommend the following requirements for all concrete The minimum compressive strength f c = 4500 psi Cement shall be Type V Section Reinforcing Steel Section Minimum Reinforcing shall be the lesser of the following Mr> 1.33Mu or Mcr Where y = 1.6 and y 0.67 Section Control of Cracking by Distribution of Reinforcement Use Exposure Factor Class 2 Ye = 0.75 We recommend requiring 2 mats of reinforcing steel. One layer of reinforcing in the center will not meet AASHTO crack control criteria. Past experience shows these structures are subject to cracking so it is our recommendation that the actual thickness should be used in the equations and no exclusion applied. Therefore, reinforcing must be placed at the edge of the tension face. Since the tension face moves from the corners to inside the center, rebar needs to be placed on both faces. See sample calculation below: Assume an 8 slab thickness and #5 bars Equation ( ) 3s = (h-dr) For 1 mat of reinforcing in the center of the slab: 13s = 1 + 4/0.7(8-4) = 2.43 For 2 mats of reinforcing and 2 of cover: 13s = /0.7( ) 1.58 Therefore: Equation ( ) s < 700 -y -2d gives us f3, (f35) For 1 mat S< 700(.75)/2.43(.6)(60)- 2(4) -2.0 (negative value) For 2 mats $ < 700f.75)/1.58(.6)(60) = Where: s = ratio of flexural strain at the extreme tension face to the strain at the centroid of the reinforcement layer nearest the tension face Ye = exposure factor = 1.00 for Class 1 exposure condition 0.75 for Class 2 exposure condition d, = thickness of concrete cover measured from extreme tension fiber to center of the flexural reinforcement located closest thereto (in.) fss = calculated tensile stress in nonprestressed reinforcement at the service limit state not to exceed 0.60 fy, (ksi) h = overall thickness or depth of the component (in.)

6 Page 5 of 10 Section Standard Hooks Section Minimum Spacing of Reinforcing Bars- Cast-in-Place Concrete Section Shrinkage and Temperature Reinforcing: Shrinkage and Temperature Reinforcing is to be placed near the surface of the outside face of the culvert For components 6.0 in. or less in thickness the minimum steel specified may be placed in a single layer. Section Development and Splices of Reinforcement Section a- Lap Splices in Tension Class B Splices are required Section Design for Shear in Slabs of Boxes Section Distribution Reinforcement Section 12- Buried Structures and Tunnel Liners Section Envelope Backfill Soils Section Limit States and Resistance Factors Service Limit State Buried structures shall be investigated at Service Load Combination I, as specified in Table for crack width in reinforced concrete structures. Section Strength Limit State Concrete Buried structures shall be investigated for construction loads and at Strength Load Combinations I and II, as specified in Table for o Flexure o Shear o Thrust o Radial tension Section Load Modifiers and Load Factors Table Resistance Factors for Buried Structures Resistance factors for Cast In Place Concrete use Flexure = 0.90 and Shear 0.85 Section Reinforced Concrete Cast-in-Place and Precast Box Culverts and Reinforced Cast-in-Place Arches Section Loads and Live Load Distribution Section Modification of Earth Loads for Soil Structure Interaction -Embankment and Trench Conditions With the Soil Interaction Factor Fe = f H/Bc); Fe max = 1.15 Section Distribution of Concentrated Loads to Bottom Slab of Box Culvert Section Minimum Reinforcement- Cast-in-Place Structures

7 cover shown on the plans is 10 feet or greater, design the structure for the cover shown on the plans plus an deal of cost to the precast RCB design. This would make the design requirements equal for both products. The 0 cover controlled by the height of cover shown on the plans and specified herein. If the cover shown on the plans is additional 5 feet of cover. Where a design height is specified on the plans, design the structure for the for RCBs drives up the cost with the addition of distribution reinforcement. Under Description- General Section paragraph E the following should be added Under Testing and Inspection the following should be added to be comparable to the RCB Spec for and performed by the Contractor a minimum of 30 days after final backfill has been placed and prior width shall require an evaluation by a Nevada licensed professional engineer. The Contractor s engineer allowed to be used there should be a specification written for it similar to NDOT Standard Specification Section 660. After the Arch has been poured and backfilled to subgrade level, internal quality inspection shall be paid Culvert and the Box Culvert could be allowed to be designed for the actual cover to 10 of cover, In our opinion the full range of live and dead loads for 0 to 10 feet of cover The specifications for both types of structures, the Arch height specified. Indicate the design cover and loading in the working drawing submittal. less than 10 feet, design the structure for the full range of live and dead loads for 0 to 10 feet of cover. If the Loading should be comparable to the Pre-Cast Reinforced Concrete Box Culvert (RCB Spec). We recommend this wording be added to the Description-General Section of the Arch Spec Design and construct a CIP Arch Culvert per the current AASHTO LRFD Bridge Design Specifications as & PRECAST REINFORCED CONCRETE BOX CULVERTS SECTION 3 CONSISTENCY BETWEEN CASTIN-PLACE REINFORCED CONCRETE ARCH CULVERTS requirement to design for 0 of fill is not practical, nor recommended, in the case of the Arch Culvert and adds a great Page 6 of 10 Include on the working drawings the contract number, the jobsite name of the structure as shown on the plans, bridge number (if applicable), material designations, and bill of materials. Culvert. Cracks in Arch Culverts (both longitudinal and circumferential) that are equal to or exceed -.10 inch in All inspection and testing results shall be submitted and approved by the Contracting Agency before Under Material We found a few other items that in our opinion need to be addressed in the Arch Spec. final payment. shall provide a recommendation regarding removal or repair in accordance with AASHTO and shall be visual physical measurement or other devices, including but not limited to calibrated television or video to final acceptance by the Contracting Agency. The line shall be cleaned and inspected for cracks using subject to the approval by the Contracting Agency. cameras, subject to approval by the Engineer. the table lists Structural Plate Pipe and Arch Culverts Section 606. This Or as an alternative to the requirement If the cover shown on the plans is less than 10 feet, design the structure for the section is actually titled Structural Plate Pipe and Pipe Arch Culverts and is not relevant to a CIP Arch General; There is no current specification for Pneumatically Placed Concrete Mortar (shotcrete). If shotcrete is

8 Arch Cci Ivert Specification Review Page 7 of 10 Under Reinforcement Paragraph 1 we recommend using the current AASHTO LRFD Bridge Design Specifications for development and lap length requirements. * Section 502 Paragraph H. Culverts; should include Arch Culverts which now only refers to box culverts in the subsequent paragraphs.

9 NDOT STRUCTURES MANUAL: Page 8 of 10 SECTION 4- CONSISTENCY WITH SIMILAR STANDARD SPECIFICATIONS In Section Concrete Arch Culverts it states: 2. The arch must be doubly reinforced meeting AASHTO LRFD requirements for minimum reinforcing and service limit state (crack control) criteria. 3. The arch must be poured in-place using Class A (AA) modified or Class D (DA) modified concrete. shotcrete construction is not permitted. Based on this information, our sample crack control calculations, and the historically poor performance of shotcrete arch culverts in the areas of cracking and spalling, we recommend that the Arch Spec require 2 mats of reinforcing steel and that shotcrete not be permitted for this type of construction. The Structures Manual also requires and we would recommend adding to the Arch Spec.: Design verification using the CANDE or SAP200 computer program is necessary. Provide design verification for a potential future condition that would require excavation of backfill material along one edge of the arch. The arch culvert must be constructed with a concrete invert. The saddle area of multiple-cell arch structures must be constructed with a waterproofing system and a suitable drainage system to control ponding and saturation of backfill soils. Provide weepholes in exterior walls at 50 ft. minimum spacing. All drains and weepholes shall be a minimum 3 in. diameter. A technical representative of the arch culvert supplier shall be on-site and shall supply the necessary technical assistance during the initial completion of major work activities including, but not limited to the placement of reinforcing, forming, concrete placement, form removal, waterproofing and backfilling. Upon completion of the culvert, provide certification from the Engineer of record that the arch was constructed with materials and procedures consistent with what was used for the arch design. Only rigid formwork and falsework conforming to Section 502 shall be used. We would recommend if the structure is federally funded or under a major roadway, and the culvert s overall span from out to out is > 20 (single or multi-barrel out to out dimension), that it be load rated per Chapter 28 Nevada Bridge Inspection Program with the following criteria: ERL (Estimated Remaining Life) = 75 years Section 28.3 Load Rating analyzed by CANDE or SAP200 or approved software with manual calculations and spreadsheets for the rating as required. The designer shall calculate the Inventory and Operating Ratings during the design phase of a project. Load rating shall be based on the Load Factor Rating Method. All bridges shall be load rated for HS-20 loading.

10 Page 9 of 10 NDOT STANDARD SPECIFICATIONS: ,21 In the Arch Spec. Section Arch Section Backfill, paragraph B, for control of long term creep deflections, we would recommend changing the paragraph to read: Arch culvert backfill may take place when the concrete or shotcrete has reached an age of 10 days mm, and when the concrete or shotcrete has reached the required 28 day compressive strength.

11 Page 10 of 10 SECTION 5- CONSTRUCTION It is our recommendation that the AASHTQ LRFD Construction Specifications latest edition be referenced and in particular the following: Section $ Concrete Structures Box Culverts Section 9 Reinforcing Steel If Pneumatically Applied Mortar (shotcrete) is allowed, Section 24 should be included as well as the following submittals Documentation of Nozzlemen s Qualifications o Use workers, including foremen, nozzlemen, and delivery equipment operators, experienced to perform the work. Shotcrete nozzlemen shall have experience on at least 3 projects in the past 3 years similar Proposed method of placement, controlling and maintaining alignment and thickness and reinforcement placement. It would be worth repeating Section Earth, as this has historically been a problem with using shotcrete. When pneumatically placed mortar is to be used against earth, the area will be accurately graded to the elevation specified in the contract documents and shall be thoroughly compacted, with sufficient moisture to provide a firm foundation and to prevent absorption of water from the mortar, but shall not contain free surface water. We would recommend adding that the compaction and water content be verified by a geotechnical engineer prior to placing the mortar. We recommend the following be added to the Arch Section Backfill; Take care in backfilling arches. Cover arches in layers conforming to the shape of the arch and tamp thoroughly. Backfill shall be placed in lifts no greater than 6 f due to how critical the compaction is to the soil interaction design of the Arch Culvert) We would recommend adding to Section Concrete/Shotcrete Placement paragraph I the following Preconstruction Testing: After taking the cores, break the test panel and allow the Engineer to carefully examine the interior portions. Ensure that they are substantially free of hollow areas and sand pockets, and ensure that the mortar is well bonded to the reinforcement. Have each crew proposed to perform this work fabricate a satisfactory panel before allowing that crew to apply mortar to the structure.