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DIVISION 3 CONCRETE SECTION 03310 CAST IN PLACE CONCRETE PART 1 GENERAL 101 WORK INCLUDED The Contractor shall furnish all labor tools and equipment for the construction of plain and reinforced concrete as shown on the Contract Drawings and herein specified 102 RELATED WORK A Section 03210 Reinforcing Steel B Section 03250 Concrete Accessories 103 QUALITY STANDARDS A American Society for Testing Materials ASTM ASTM C33Concrete Aggregates ASTM C150 Portland Cement ASTM C309 Liquid Membrane Forming Compounds for Curing Concrete AN SIASTM D994 Preformed Expansion Joint Fillers ASTM D1751 Preformed NonExtruding and Resilient Expansion Joint Fillers ASTM D3575 Test Methods for Flexible Cellular Materials made from Olefin Polymers ASTM C94 Ready Mixed Concrete ASTM C260 Airentraining Admixtures for Concrete ASTM C494 Chemical Admixtures for Concrete ASTM C618 Fly Ash in Portland Cement Concrete ASTM C979 Pigments for Colored Concrete HH OPOSQEJ HeP NE b O39 B American Concrete Institute ACI ACI 211 Standard Practice for Selecting Proportions for Concrete ACI 212 Guide for Use of Concrete Admixtures ACI 221 Guide for Use of Normal Weight Aggregates ACI 301 Structural Concrete for Buildings ACI 304 Guide for Measuring Mixing Transporting and Placing Concrete ACI 305 Hot Weather Concreting ACI 306 Cold Weather Concreting ACI 308 Standard Practice for Curing Concrete ACI 309 Standard Practice for Consolidating Concrete ACI 318 Building Code Requirements for Reinforced Concrete ACI 503 Use of Epoxy Compounds 12 ACI 504 Guide to Joint Sealants WSQEJ HeP NE o b O39 104 SUBMITTALS Submit product data for Admixtures Evaporative Retardant Films Curing Compounds Form Release Agents Ready Mixed Concrete Mix Designs Form Ties Bonding Agents Grouts Coatings 0208 Section 03310 Page 1 PART 2 MATERIALS AND EQUIPMENT 201 0208 MIX DESIGN Compressive Strength at 28 days psi CEMENT Cement shall be Portland cement in accordance with ASTM C150 and Type AGGREGATE A Fine aggregate shall consist of hard strong durable particles to the provisions of the Standard Specifications for Concrete Aggregates ASTM Designation C33 B Coarse aggregate shall conform to the provisions of Standard Specifications for Concrete Aggregates ASTM Designation C33 WATER A Water shall be clean and free from injurious amounts of oils acids alkalis salts organic materials or other substances that may be deleterious to concrete or steel Mixing water for prestressed concrete or for concrete which will contain aluminum embedments including that portion of the mixing water contributed in the form of free moisture on the aggregates shall not contain deleterious amounts of chloride ion B Unless otherwise permitted or specified the concrete shall be proportioned and produced to have a slump of four 4 inches or less if consolidation is by vibration The slump shall be determined by the quotTest for Slump of Portland Cementquot ASTM C143 ADMIXTU39RES Admixtures to be used in concrete shall be subject to prior acceptance by the Engineer The admixture shall maintain the same composition and performance throughout the work as the product used in the concrete proportions established in accordance with AC1 211 Admixtures containing chloride ions shall not be used in prestressed concrete or concrete containing aluminum embedments A Air Entrainment An air entraining agent shall be used in all concrete The agent used shall conform to ASTM Designation C260 The amount of air entraining agent used in each concrete mix shall be such as will effect the entrainment of the percentage of air shown in the following tabulation in the concrete as discharged from the mixer Water Reducing SetControlling Admixture Section 03310 Page 2 0208 The Contractor shall use a waterreducing set controlling concrete A waterreducing admixture shall be used in all concrete and shall conform to ASTM Designation C494 specifically Types A B C D and E C Finely Divided Mineral Admixtures Mineral admixtures shall be limited to fly ash conforming to ASTM specification C618 BAT CHTNG Measuring and batching of materials shall be done at a batching plant A Portland Cement Either sacked or bulk cement may be used No fraction of a sack of cement shall be used in a batch of concrete unless the cement is weighed Bulk cement shall be weighed on scales separate and distinct from the aggregate hopper or hoppers Batching shall be such that the accuracy of batching shall be plus or minus one percent i1 of the required weight B Water Unless water is to be weighed the watermeasuring equipment shall include an auxiliary tank from which the measuring tank shall be filled In lieu of the volume method the contractor will be permitted to use a water metering device C Aggregates Aggregates shall be handled from stockpiles or other sources to the batching plant in such a manner as to secure a uniform grading of the material Aggregates that have become segregated or mixed with earth or foreign material shall not be used Batching shall be so conducted as to result in the weights of material required for each type aggregate within a tolerance of two percent 2 Free water contents of the coarse and fine aggregates shall be continuously tested and concrete mixture adjusted for moisture conditions of the aggregate in order to meet the designated watercement ratio MleNG A Concrete may be mixed in a centralmix plant or in truck mixers Mixing time shall be measured from the time water is added to the mix or cement contacts the aggregate All concrete shall be homogeneous and thoroughly mixed and there shall be no lumps or evidence of undispersed cement Mixers and agitators which have an accumulation of hard concrete or mortar shall not be used Readymixed concrete shall be mixed and delivered in accordance with ASTM C94 B The temperature of mixed concrete immediately before placing shall not be less than i degrees Fahrenheit nor more than i degrees F Aggregates and water shall be heated or cooled as necessary to produce concrete within these temperature limits Neither aggregates nor mixing water shall be heated to exceed 150 degrees Fahrenheit C When mixed in a centralmixing plant the mixing time shall not be less than 50 seconds nor more than 90 minutes The time elapsing from the time water is added to the mix or the cement comes in contact with aggregate until the concrete is deposited in place at the site of the work shall not exceed 45 minutes when the concrete is hauled in nonagitating trucks nor more than 90 minutes when hauled in truck mixers or truck agitators D The batch shall be so charged into the drum that a portion of the mixing water shall enter in advance of the cement and aggregates The flow of water shall be uniform and all water shall be in the drum by the end of the first quarter 14 of the specified mixing time Section 03310 Page 3 0208 Cement shall be charged into the mixer by means that will not result in loss of cement due to the effect of wind or in accumulation of cement on surfaces of hoppers or in other conditions which reduce or vary the required quantity of cement in the concrete mixture TRANSPORTTNG MIXED CONCRETE Mixed concrete or truck mixers Transporting of mixed concrete shall conform to AC1 305R Truck agitators shall be loaded not to exceed the manufacturer39s guaranteed capacity They shall maintain the mixed concrete in a thoroughly mixed and uniform mass during hau ing No additional mixing water shall be incorporated into the concrete during hauling or after arrival at the delivery point unless ordered by the Engineer If additional water is to be incorporated into the concrete the drum shall be revolved not less than 30 revolutions at mixing speed after the water is added and before discharge is commenced The contractor shall furnish a water measuring device in good working condition mounted on each transit mix truck for measuring the water added to the mix on the site by the Engineer Each load of ready mixed concrete delivered at the job site except loads to be used for pavement shall be accompanied by the ticket showing volume of concrete the weight of cement in pounds percent of free water in course and dry aggregate and the total weight of all ingredients in pounds The ticket shall also show the time of day at which the materials were batched and the reading of the revolution counter at the time the truck mixer is charged The ticket shall contain the information in such a manner that the water to cement ratio can be readily calculated at the project site Each load of ready mixed concrete used for paving shall be accompanied by a ticket which shall be delivered to the Engineer stamped with the date and time when the truck mixer is charged CONCRETE MIX REQUIREMENTS A Structural concrete compressive strength requirements consist of a minimum strength which must be obtained before various loads or stresses are applied to the concrete and for concrete designated by strength a minimum strength at the age of 28 days Unless otherwise shown on the Drawings the concrete 28day compressive strength shall be a minimum of 4000 psi The mix shall be designed for strengths at least 15 percent in excess of this minimum The net water cement ratio of the concrete shall not exceed 7 by weight A minimum of six and a half 65 sacks of cement per cubic yard of concrete shall be utilized Maximum aggregate size shall be threequarter 34 Sampling and curing shall be in accordance with ASTM C172 and ASTM C31 testing shall be in accordance with ASTM C39 Slump shall be between four and six inches 46 when placed For small pours of 15 yards or less compression tests shall be made for each truck load For large volume continuous pours compression tests shall be made for every 20 yards of the pour approximately every other truck load A minimum of compression test cylinders shall be made by a representative of the approved testing laboratory performing the testing with the Contractor bearing the costs of all testing services Field slump watercement ratio air entrainment and unit weight tests shall also be performed by the representative of the approved testing laboratory for every truck load of concrete to be placed on the project The Contractor shall bear the costs for this service also GROUT OR DRY PACK Section 03310 Page 4 Mortar shall be composed of Portland Cement sand and water proportioned and mixed as specified in this section Mortar shall be furnished and placed in recesses and holes on surfaces under structural members and at other locations specified in these specifications the special provisions or shown on the plans The proportion of cement to sand measured by volume shall be one to two 1 2 unless otherwise specified The maximum size of sand shall not be larger than one half 12 the size of the recess hole or space where the mortar is to be placed The mortar shall contain only enough water to permit placing and packing Concrete areas to be in contact with the mortar shall be cleaned of all loose or foreign material that would in any way prevent bond between the mortar and the concrete surfaces and shall be kept thoroughly moistened with water for a period of not less than 24 hours immediately prior to placing mortar The mortar shall completely fill and shall be tightly packed into recesses and holes on surfaces under structural members and at other location specified After placing all surfaces of mortar shall be cured by the water method as provided in Part 3 304 quotCuring and Protection for a period of not less than three 3 days Keyways spaces between structural members holes spaces under structural members and other locations where mortar could escape shall be mortartight before placing mortar No load shall be allowed on mortar that has been in place less than 72 hours unless otherwise permitted by the Engineer All improperly cured or otherwise defective mortar shall be removed and replaced by the contractor at his expense 211 CONCRETE CURING COMPOUNDS Curing compounds shall be approved for potable water applications and shall meet or exceed California standards for volatile organic compounds VOC s Acceptable product is Cure and Seal 12 E Emulsion Acrylic Sealer as manufactured by Symons or approved equal 212 FORM RELEASE Form releases shall be approved for potable water applications and shall meet or exceed California standards for volatile organic compounds VOC s Acceptable product is Thrift Kote E concentrate as manufactured by Sym ons or approved equal PART 3 EXECUTION 301 FORMS A 0208 The concrete forms shall be constructed to the lines and dimensions as shown on the detailed drawings and shall be of acceptable material and adequately braced and tied to support all of the loads and pressures of the wet concrete without distortion or leaks and which will produce a smooth even surface Section 03310 Page 5 302 0208 The form facing material shall produce a smooth hard uniform texture on the concrete It may be plywood tempered concrete formgrade hardboard metal plastic paper or other approved material capable of producing the desired finish The arrangement of the facing material shall be orderly and symmetrical with the number of seams kept to the practical minimum It shall be supported by studs or other backing capable of preventing excessive de ection Material with raised grain torn surfaces worn edges patches dents or other defects which will impair the texture of the concrete surface shall not be used Tie holes and defects shall be patched All fins shall be completely removed A water tight form tie with a one inch 1 breakback cone waterstop with integral neoprene seal shall be used on all walls or slabs that form a water holding space Ties in these walls or slabs shall remain permanently in the concrete Drawings showing the general design and dimensions for forms for structures need not be submitted to the Engineer for acceptance unless the Engineer so requests such submittal Design and construction shall be in accordance with quotRecommended Practice for Concrete Formwork AC1 347 and quotFormworkquot AC1 301 Chapter 4 Before concrete is placed the surface of the forms shall be coated with commercial form release that will effectively prevent sticking of the concrete to the forms will not stain the concrete and is acceptable for potable water structures All bond breaking materials or processes shall be used only after acceptance by the Engineer Care shall be taken in applying form release to avoid contact with reinforcement steel Embedded material which becomes coated with form release shall be thoroughly cleaned or replaced at the expense of the contractor Supporting forms and shores shall not be removed from beams floors and walls until these structural units are strong enough to support their own weight and any approved superimposed load which at no time shall exceed the design live load When the forms are stripped there shall be no excessive de ection or distortion and no evidence of damage to the concrete due either to removal of support or the stripping operation Removal time of forms shall be determined by the Engineer PLACEMENT A Prior to pouring the concrete the Contractor shall remove all shavings pieces of wood or other debris and shall thoroughly wet the areas in which concrete is to be poured Placement shall conform to AC1 301 Chapter 8 Placing AC1 306 quotRecommended Practice for Cold Weather Concreting and AC1 305 quotRecommended Practice for Hot Weather Concreting No concrete shall be placed until all formwork reinforcement installation of parts to be embedded bracing of forms and preparation of surfaces involved in the placing have been approved by the Engineer No concrete shall be placed in water except with the written permission of the Engineer the method of depositing the concrete shall be subject to his approval All surfaces of forms and embedded materials that have become encrusted with dried mortar or grout from concrete previously placed shall be cleaned of all such mortar or grout before the surrounding or adjacent concrete is placed Immediately before placing concrete all surfaces upon or against which the concrete is to be placed shall be free from standing water mud debris or loose materials The surfaces of absorptive materials against or upon which concrete is to be placed shall be moistened thoroughly so that moisture will not be drawn from the freshly placed concrete The concrete shall be placed by equipment which will prevent segregation or loss of ingredients The stream of concrete shall not be allowed to separate by permitting it to fall freely over rods spacers or other embedded materials Section 03310 Page 6 0208 C All concrete shall be consolidated by vibration spading rodding or forking so that the concrete is thoroughly worked around the reinforcement around embedded items and into corners of forms eliminating all air or stone pockets which may cause honeycombing pitting or planes of weakness Internal vibrators of the largest and the most powerful size that can be properly used in the work shall be utilized They shall be used by competent operators Use of vibrators to transport concrete within the forms shall not be allowed Vibrators shall be inserted and withdrawn at points approximately 18 inches apart At each intersection the duration shall be sufficient to consolidate the concrete but not sufficient to cause segregation generally from five 5 to 15 seconds A spare vibrator shall be kept on the jobsite during all concrete placing operations Where the concrete is to have an ascast finish a full surface of mortar shall be brought against the form by the vibration process supplemented if necessary by spading to work the coarse aggregate back from the formed D All concrete placed in walls exceeding feet in height shall be spouted so that the maximum free fall shall be 7 feet E Concrete shall be placed in continuous layers of approximately 12 inches and the total elapsed time between placing of successive layers shall not exceed 30 minutes F All wood blocking spreaders and screens shall be removed as the concrete is poured and before the concrete sets CONSTRUCTION JOINT S The location of all construction joints will be subject to the acceptance of the Engineer The surface of all construction joints shall be thoroughly cleaned and all latence and standing water removed Clean aggregate shall be exposed by abrasive blast cleaning Wire brushing and air water jets may be used while concrete is fresh provided results are equal to abrasive blast cleaning Construction joints shall be keyed at right angle to the direction of shear Except where otherwise shown on the plans keyways shall be at least one and one half inch 112quot in depth over at least 25 percent of the area of the section CURING AND PROTECTION A General 1 Beginning immediately after placement concrete shall be protected from premature drying excessively hot or cold temperatures and mechanical injury and shall be maintained with minimal moisture loss at a relatively constant temperature for the period necessary for hydration of the cement and hardening of the concrete The materials and methods of curing shall be subject to acceptance by the Engineer 2 For concrete surfaces not in contact with forms one of the following procedures shall be applied immediately after completion of placement and finishing a Ponding or continuous sprinkling b Application of absorptive mats or fabric kept continuously wet 0 Application of sand kept continuously wet 1 Continuous application of steam not exceeding 1500 F or mist spray e Application of waterproof sheet materials conforming to quot Specifications for Waterproof Sheet Materials for Curing Concrete ASTM C171 Section 03310 Page 7 0208 f Application of other moisture retaining covering as accepted g Application of a curing compound conforming to quot Specifications for Liquid Membrane Forming Compounds for Curing Concrete ASTM C309 and approved for potable water applications The compound shall be applied in accordance with the 39 of the f 39 quot after any water sheen which may develop after finishing has disappeared from the concrete surface It shall not be used on any surface against which additional concrete or other material is to be bonded unless it is proven that the curing compound will not prevent bond or unless positive measures are taken to remove it completely from areas to receive bonded applications 3 Moisture loss from surfaces placed against wooden forms or metal forms exposed to heating by the sun shall be minimized by keeping the forms wet until they can be safely removed After form removal the concrete shall be cured until the end of the curing time by one of the previously described curing methods Curing shall be continued for at least seven 7 days in the case of all concrete except highearly strength concrete for which the period shall be at least three 3 days Alternatively if tests are made of cylinders kept adjacent to the structure and cured by the same methods moisture retention measures ma be terminated when the average compressive strength has reached 70 of the specified concrete strength Cold Weather When the mean daily outdoor temperature is less than 7 F the temperature of the concrete shall be maintain between 50 and 70 F for the required curing period When necessary arrangements for heating covering insulating or housing the concrete work shall be made in advance of placement and shall be adequate to maintain the required temperature without injury due to concentration of heat Combustion heaters shall not be used during the first 24 hours unless precautions are taken to prevent exposure of the concrete to exhaust gases which contain carbon dioxide Hot Weather When necessary provision for windbreaks shading fog spraying sprinkling ponding or wet covering with a light colored material shall be made in advance of placement and such protective measures shall be taken as quickly as concrete hardening and finishing operations will allow Rate of Temperature Change Changes in temperature of the air immediately adjacent to the concrete during and immediately following the curing period shall be kept as uniform as possible and shall not exceed 5 F in any one 1 hour or 50 F in any 24 hour period Protection From Mechanical Injury During the curing period the concrete shall be protected from damaging mechanical disturbances such as load stresses heavy shock and excessive vibration All finished concrete surfaces shall be protected from damage by construction equipment materials or methods by application of curing procedures and by rain or running water Self supporting structures shall not be loaded in such a way as to over stress the concrete Section 03310 Page 8 Additional Structural Design Notes CVEN 48304434 University of Colorado Boulder Spring Semester 2008 Moments in Walls Rectangular Tanks If the wall has an aspect ratio not exceeding 41 between supports including interior walls baf es and weirs use the twoway moment tables in PCAR pages 217 thru 222 If the aspect ratio is outside of the range of these tables analyze the wall as a vertical cantilever beam designing a 1 wide strip is the common practice This will yield a moment for the vertical strip designated as Mx in the PCAR tables For the horizontal moments the tables for an aspect ratio of 41 could be used which would conservatively result in higher moments My than the wall actually would experience Circular Tanks Moments are considered on vertical strips only The PCAC table on page A2 should be used to determine the moments Moments in Slabs For the rectangular tank the slab will span in the short direction as a continuous beam over several supports The formula Mu wuLzS can be used for the short span direction where L is the length of the short span This is only slightly conservative compared to more rigorous calculations for the maximum moment in continuous beams The short span rebar should be located at the top and bottom of the slab taking the concrete cover into consideration The long span rebar should be located inside of the short span rebar as illustrated below For the long span rebar it is conservative to use the same reinforcing as the short span The maximum moments in the long span direction will generally be less than 75 of the maximum moments in the short span direction depending on the aspect ratio and the assumed boundary conditions short span long span rebar The slab beneath the circular tank will be a slabon grade only Any considerations for slabongrade in the soils report should be adhered to If there are no recommendations in the soils report use the minimum thickness ofthe slab speci ed in ACT 350 H3 It is recommended that two layers of reinforcing be used for a minimum thickness of 6 Generally radial and circular reinforcing patterns are detailed for the slab of a circular tank These details will take into consideration the minimum reinforcing and maximum rebar spacing for the slab Ring Stress Tensile Cracks PCA Circular Concrete Tanks 4 eql This should be included in the ring stress hoop stress calculations in circular concrete tank analysis it is designed to limit the tensile cracking in the concrete C 00003 don t confuse this with Sc 0003 Ag gross area of concrete l ht gtlt wall thickness inz AS TOTAL area of steel in the 1 high section inz f c39 concrete compression strength psi EC 57000JE psi ES 29000000 psi n EsEC T unfactored hoop tensile force in 1 high strip of wall lb fCESAST si c AgnAs p fc lt 0lfc39 must be satis ed If the above requirement is not met increase AIg by increasing the wall thickness Flexural Cracks PCA Rectangular Concrete Tanks page 18 PCA Circular Concrete Tanks 6 eq3 This provision should be included in all exure section calculations it limits the concrete exural cracking M unfactored moment lbin AS area of tension steel for the exural section exure steel only not total steel inz p steel ratio Agbwd nEsEc k1l2pnpn2 pn jlild3 d distance from the extreme concrete surface in compression to the center of the exural steel in M fs PSI J dC distance between extreme concrete surface in tension and center of the exural steel this is NOT the same as clear concrete cover in bW width of section being analyzed usually taken as 12 A 2dcbw inz fdA s c 1000 z E 95 must be satis ed Pressure Relief Valves Pressure relief valves should be speci ed for all tanks These allow groundwater to enter the tank under conditions of low water inside the tank This relieves pressure on the bottom of the slab and reduces or eliminates otation of the tank It is recommended that the number of pressure relief valves specified be twice as many as the minimum number 39 39 J The 39 J 39 quot J 39 quot should be responsible for the design ofthe pressure relief valves There are many references available on the intemet listed below are three Clow PRV http wwwclowvalve comproductsindeXphp id24ampshowoverview I 1 httpwww engl39 39 p I 39vcai prlltml Anderson Greenwood PRV httpwwwandersongreenwoodcom Gravel Below Slabs It is common to designate gravel below the tanks It is suggested that a minimum of 6 of 3 gravel be placed before pouring all slabs and footings In addition 24 of gravel should be placed at locations of pressure relief valves 1 Pressure Relief Valve slab 34 gravel soil 24 24 Waterstops Waterstops are needed for all concrete construction joints The design of the waterstop consists of selecting the particular brand and model from a manufacturer and including it in the detail drawings and speci cation sheet Below are a few websites advertising waterstop products This is not a complete listing httpwwwadekacom httpwwwjpspecialtiescomhomehtml httpesvc000298bne102userverwebcomDocumentsTrelleborgWaterStopspdf httpwwwgamcoformcompvcwaterstoprcbhtml httpwwwwhitecapdirectcomproducts483GS701 httpwwwspeconceptscomcatalogWaterStopshtml httpwwwwrmeadowscomwrm000l6htm PVC Waterstop typ Circular Tank Design Considerations Ring Tension rebar tension capacity ring stress concrete tensile cracks minimum horizontal reinforcing for walls minimum reinforcing for temperature and shrinkage maximum rebar spacing Ring Compression concrete compression capacity minimum wall thickness Vertical Strip of Wall exure capacity of reinforced concrete section exural crack limit for concrete minimum vertical reinforcing for walls minimum reinforcing for exure sections minimum reinforcing for temperature and shrinkage maximum reinforcing for exure section shear capacity of concrete minimum wall thickness maximum rebar spacing Footing Design Flexure capacity of reinforced concrete section exural crack limit for concrete minimum reinforcing for exure sections minimum reinforcing for temperature and shrinkage maximum reinforcing for exure section shear capacity of concrete maximum rebar spacing SlabonGrade minimum slab thickness minimum steel for slabs maximum rebar spacing An alternative is to use the Army TM 580912 Concrete Floor Slabs on Grade Subjected to Heavy Loads available on the class website 39 TankDesignF 391 quot Vertical Strip of Wall exure capacity of reinforced concrete section exural crack limit for concrete minimum vertical reinforcing for walls minimum reinforcing for exure sections minimum reinforcing for temperature and shrinkage maximum reinforcing for exure section shear capacity of concrete minimum wall thickness maximum rebar spacing Horizontal Strip of Wall exure capacity of reinforced concrete section exural crack limit for concrete minimum horizontal reinforcing for walls minimum reinforcing for exure sections minimum reinforcing for temperature and shrinkage maximum reinforcing for exure section shear capacity of concrete minimum wall thickness maximum rebar spacing Footing Design Flexure capacity of reinforced concrete section exural crack limit for concrete minimum reinforcing for exure sections minimum reinforcing for temperature and shrinkage maximum reinforcing for exure section shear capacity of concrete maximum rebar spacing Slab Design exure capacity of reinforced concrete section exural crack limit for concrete minimum reinforcing for exure sections minimum reinforcing for temperature and shrinkage maximum reinforcing for exure section shear capacity of concrete minimum slab thickness maximum rebar spacing A Few Notes on the Design of Reinforced Concrete Tanks CVEN 48304434 University of Colorado Boulder Spring Semester 2008 Prepared by Ben Blackard Load Cases For Exterior Wall external earth pressure only ACI 3504R04 section 411 internal uid pressure only For Interior Wall Fluid pressure on one side of wall only Tank Flotation 125gtltUplift S Dead Load AC1 3504R04 section 312 Load FactorsCombinations 14D F AC1 35006 section 92 D dead load F uid load Flexural Analysis 085 f c 8c 0003 31quot NA d 0 As L i AS fy 85 Z fyEs assumed stress assumed strain bW distribution distribution compression tension 3 Bl c bw 085 fc39 AS fy A f gt c 2 s y Bl bw 085 f nominal moment capacity Mn As fy d 7 multiply Mn by a safety factor 1 09 design moment capacity IJMn 09 AS fy d AC1 35006 section 10273 085 if f 4000 psi f 105 if 4000 si f 8000 si 51 20000 p c p 065 if 8000 psi f B1 065 4000 psi 8000 psi Balanced Section 085 re sc 0003 d NA 0 As L 3 AS fy 85 fyEs assumed stress strain bw distribution distribution f E similar triangles from the strain distribution 00 gt c c 7 c 0003 4 ES equilibrium compression tension 3 Bl c bw 085 T Asvb 39fy 0003 d 3 Bl fbw 085 fc Ab fy 0003 iy ES j A sb f 0003 fy Shear The shear strength provided by concrete is Vc ZJf c39bwd as per ACI 35006 section 11311 Walls slabs and footings should be designed so that the concrete is capable of resisting the ultimate shear load at the same section that the ultimate moment is calculated Vu S 0VC where 1 075 Minimum and l12 imnm P 39 L for exure members in general ACI 35006 section 1051 3 f39 LdegAs and anwflgAs fy fy walls have an additional criteria to meet ACI 35006 section 1432 0003gtltAg S AS Ag gross area of the section Also see ACI 35006 section 71221 for minimum steel requirements for shrinkage and temperature There does not appear to be a maximum steel limit in ACI 35006 as there is in ACI 318 However it may be good to include it in the design ACI 31889 section 1033 A 075A 075 0003 085 51 bw d f 00019125 51 bw d f smax sb f f 0003 EL fy 0003 EL fy s s Slab Design One criteria for the design of the slab is that it must be able to resist the moment supplied by the cantilever walls This may or may not govern the design of the slab but it needs to be checked amp 05gtltMu The slab is designed as a large mat foundation for the tank walls and uid The bearing pressure on the soil is approximated as a constant pressure obtained from the total load unfactored diVided by the total area This bearing pressure must be less than the soil bearing capacity uid uid T T T T T T T soil bearing pressure total unfactored load total area Two loading scenarios are considered The rst involves soil which is not saturated so there is no water pressure uplift In this case the soil supports the uid walls and slab However for the design of the exural steel the weight of the uid and slab are resisted by equal soil pressures leaving only the weight of the walls E short span a uid uid T T T T T T T weight of uid total area T T T T T T T weight of slab total area T T T T T T T weight of walls total area Design for slab exure short span T T T T T T T weight of walls factored total area The second load scenario to consider is that of an empty tank with the groundwater table at it s highest elevation The loads for exural design of the slab are the weight of the slab and walls factored pushing down and the water pressure factored pushing up groundwater 09 X weight of walls slab total area i l l l l l l T T T T T T T 14 X density of water The larger of the two load scenarios governs the design of the slab A 1 wide strip of slab is considered as a continuous beam for the exural steel design Shear The shear in a slab or wall should be resisted by the concrete only AC1 35006 section 11311 gives the shear strength of a concrete section as V 2J3de Single or double shear conditions should be considered as seen below single shear critical lt section lt TTT V double shear critical section gt lt lt TTT TTT The critical sections to be checked for shear are at the face of the wall as per AC1 35006 section 1552 The design strength is then an ch where 1 075 as per ACI 35006 section 9323 Note that the loads causing the shear need to be factored Thickened Slabs If the ultimate shear in the critical section is greater than the capacity there are two options The simplest solution is to thicken the slab which is often done if the capacity is inadequate by only a small amount Another option is to thicken the slab at the location of the wall It is common practice to design the length of the thickened slab in the manner shown below The critical sections remain at the face of the wall The reinforcing for the slab extends through the thickened portion as illustrated below Additional rebar will be needed at the bottom of the thickened slab The rebar in the bottom of the thickened slab is mainly needed for the minimum reinforcing requirement in ACT 35006 section 71221 temperature and shrinkage steel this is due to the larger gross area of concrete Flotation AC1 3504R04 section 312 requires the weight of the empty tank exceed the uplift from the highest groundwater level with a factor of safety of 125 Dead Load Uplift 125 S No load factors for the dead load or the water pressure are used in this calculation I A Few Provisions to be 39 not an exhaustive list minimum steel for exure section ACI 35006 section 1051 minimum vertical steel in walls ACI 35006 section 1432 minimum horizontal steel in walls ACI 35006 section 71221 maximum spacing for vertical steel in walls ACI 35006 section 1435 maximum spacing for horizontal steel in walls ACI 35006 section 1435 walls more than 10 thick must have two layers ofrebar ACI 35006 section 1434 minimum wall thickness ACI 35006 section 146 additional bars around wall openings ACI 35006 section 1437 nominal shear strength ACI 35006 section 11311 slab thickness ACI 35006 section H3 concrete cover for slabs ACI 35006 section H44 and section 771 minimum steel for shrinkage and temperature ACI 35006 section 71221 strength reduction factors ACI 35006 section 93 tensile hoop stress in rebar for round tanks f5 S 20000 psi for normal environmental exposures 7 ACI 35006 section 9262 fS S 17000 psi for severe environmental exposures 7 ACI 35006 section 9263 concrete cover ACI 35006 section 771 reinforcing details ACI 35006 chapter 12 waterstops waterstops must be incorporated into construction joints ACI 3504R04 section 54 and ACI 35006 section 482 there is product information available on the intemet search for waterstop Area of Reinforcing Bar As inz 2 0049 3 011 4 020 5 031 6 044 7 060 8 079 9 100 10 127