Info

l/240d

a Limit not intended to safeguard against ponding. Ponding should be checked by suitable calculations of deflection, including added deflections due to ponded water, and consideration of long-term effects of all sustained loads, camber, construction tolerances, and reliability of provisions for drainage.

Long-term deflection should be determined in accordance with Equation 7.74, but may be reduced by the amount of deflection calculated to occur before attachment of nonstructural elements. This amount should be determined on the basis of accepted engineering date relating to time deflection characteristics of members similar to those being considered. c Limit may be exceeded if adequate measures are taken to prevent to supported or attached elements. d Limit should be greater than the tolerance provided for nonstructural elements. Limit may be exceeded if camber is provided so that total deflection minus camber does not exceed limit.

requirements (see Table 7.8). Lateral deflections of columns may be a function of occupancy comfort under high wind or seismic drift criteria (e.g., H/200).

7.19 Drawings, Specifications, and Construction

Although this chapter has focused mainly on the structural mechanics of design, design procedures and formulas, and rules that apply to reinforced concrete construction, the importance of drawings and specifications as part of the end products for communicating the structural design must not be overlooked. Essential information that should be included in the drawings and specifications are: specified compressive strength of concrete at stated ages (e.g., 28 days) or stage of construction; specified strength or grade of reinforced (e.g., Grade 60); governing design codes (e.g., IBC, AASHTO); live load and other essential loads; size and location of structural elements and locations; development lengths, hook lengths, and their locations; type and location of mechanical and welded splices; provisions for the effects of temperature, creep, and shrinkage; and details of joints and bearings.

The quality of the final structure is highly dependent on material and construction quality measures that improve durability, construction formwork, quality procedures, and inspection of construction. Although many of these aspects may not fall under the direct purview of the structural designer, attention and knowledge are necessary to help ensure a successful execution of the structural design. Information and guidance on these topics can be found in the ACI Manual of Concrete Practice, which is a comprehensive five-volume compendium of current ACI standards and committee reports: (1) Materials and General Properties of Concrete, (2) Construction Practices and Inspection, Pavements, (3) Use of Concrete in Buildings — Design, Specifications, and Related Topics, (4) Bridges, Substructures, Sanitary, and Other Special Structures, Structural Properties, and (5) Masonry, Precast Concrete, Special Processes.

Notation a = depth of concrete stress block As = area of compression reinforcement Ab = area of an individual reinforcement Ac = area of core of spirally reinforced column measured to outside diameter of spiral Ac = area of critical section Acp = area enclosed by outside perimeter of concrete cross-section Ag = gross area of section Al = area of longitudinal reinforcement to resist torsion Ao = gross area enclosed by shear flow path Aoh = area enclosed by centerline of the outermost closed transverse torsional reinforcement As = area of tension reinforcement As,min = minimum area of tension reinforcement Ast = total area of longitudinal reinforcement At = area of one leg of a closed stirrup resisting torsion within a distance s Atr = total cross-sectional area of all transverse reinforcement that is within the spacing s and that crosses the potential place of splitting through the reinforcement being developed Av = area of shear reinforcement Av,min = minimum area of shear reinforcement b = width of compression face b1 = width of critical section in l1 direction b2 = width of critical section in l2 direction b0 = perimeter length of critical section bt = width of that part of the cross-section containing the closed stirrups resisting torsion bw = web width

C = cross-sectional constant to define torsional properties = (1 _ 0.63(x/y))/ (x3y/3) (total section is divided into separate rectangular parts, where x and y are the shorter and longer dimensions of each part, respectively). c = distance from centroid of critical section to itsperimeter(Section7.13.2.1) c = spacing or cover dimension c1 = dimension of column or capital support in l1 direction c2 = dimension of column or capital support l1 =

in l2 direction cc = clear cover from the nearest surface in tension to the surface of the flexural l2 =

reinforcement

Cc = resultant concrete compression force lc =

Cm = factor relating actual moment diagram ld =

to an equivalent uniform moment d = distance from extreme compression ldc =

fiber to centroid of tension reinforcement d' = distance from extreme compression fiber ldh =

to centroid of compression reinforcement db = nominal diameter of bar di = distance from extreme compression fiber l^ =

to centroid of reinforcement layer i Ec = modulus of elasticity of concrete =

Ecb = modulus of elasticity of beam concrete lw =

Ecs = modulus of elasticity of slab concrete M1 =

EI = flexural stiffness of column Es = modulus of elasticity of steel reinforcement M2 =

/c = specified compressive strength of concrete Fn = nominal structural strength

/ = modulus of rupture of concrete Ma =

/ = reinforcement stress

Fsi = resultant steel force at bar layer i Mc =

/ = specified yield stress of reinforcement Mcr =

fyl = specified yield strength of longitudinal Mm =

torsional reinforcement Mn =

/yt = specified yield strength of transverse reinforcement Mns =

fyv = specified yield strength of closed transverse torsional reinforcement h = overall thickness of column or wall M0 =

hc = diameter of concrete core measured Ms =

out-to-out of spiral h» = total height of wall Mu =

Ib = moment of inertia of gross section Munb =

of beam

Icr = moment of inertia of cracked section n =

transformed to concrete NC =

Ie = effective moment of inertia NT =

Is = moment of inertia of gross section of slab Nu =

Ise = moment of inertia of reinforcement about centroidal axis of cross-section Jc = equivalent polar moment of inertia of Pc =

critical section pcp =

k = effective length factor for columns Km = material constant ph =

Ktr = transverse reinforcement index

center-to-center span length in the direction moments are being determined center-to-center span length transverse to l1

center-to-center length of columns development length of reinforcement in tension development length of reinforcement in compression development length of standard hook in tension, measured from critical section to outside end of hook clear span length, measured from face-to-face of supports unsupported length of columns horizontal length of wall smaller factored end moment in a column, negative if bent in double curvature larger factored end moment in a column, negative if bent in double curvature maximum moment applied for deflection computation factored magnified moment in columns cracking moment modified moment nominal or theoretical moment strength factored end moment of column due to loads that do not cause appreciable side sway total factored static moment factored end moment of column due to loads that cause appreciable side-ways moment demand unbalanced moment at slab-column connections modular ratio = Es/Ec resultant compressive force of concrete resultant tensile force of reinforcement factored axial load occurring simultaneously with Vu or Tu, positive sign for compression critical load outside perimeter of concrete cross-section perimeter of centerline of outermost concrete cross-section nominal axial load strength of column

0 0

Post a comment