1. Crack Width Calculation As Per Aci 318 14 Online
2. Crack Width Calculation As Per Aci 318 1400

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In ETABS, shell or area element has two types of stiffnesses i.e. inplane stiffness refers as f11, f22 and f12 and out-of-plane stiffness refers as m11, m22 and m12. Refer to the below Figure which shows the direction of local axes and their corresponding stiffnesses:

ACI 318 - 89, 99, Gergely-Lutz equation ACI requirements based on stress limits derived from the Gergely-Lutz equation: Code provisions for crack widths x)-x)/(d-(h 3 Adfz cs unitsmNzw 12 max 1011 Samirsinh P Parmar, Asst.Prof. DDU, Nadiad, Gujarat, India 15. ACI 318.2, rather than ACI 318.1? Answer: This is because it was initially planned that ACI 318-11 Chapter 22 on plain concrete would become a separate standard: ACI 318.1. The number was reserved for that purpose. It was later decided to place the contents of ACI 318-11 Chapter 22 in ACI 318-14 Chapter 14. 22 - ACI 318-14 Organization. Crack width calculation methods in large concrete structures” carried out by Reignard Tan. The seminar is to be hosted by NTNU and Multiconsult ASA in a joint collaboration. The main goal is to increase the understanding and knowledge of crack width calculations for relatively large concrete structures in the Serviceability Limit State.

For shear wall (both piers and spandrels), the flexural and axial behavior is modified by either f11 or f22 depending on the orientation of the local axis and the shear behavior is controlled by f12. In column and code terms f11 or f22 would correspond to modifications of EI or EA and f12 would correspond to modifications to GA_shear. The code recommendations in Section 10.10 of ACI 318 code are related to slenderness effects where flexural deformations govern so they have recommended modifying EI (corresponding to f11 or f22 for shear walls). There is no recommendation about reducing the GA_shear. You should, however, note that some of our users use modifiers for f12 also, where they expect deterioration of shear stiffness and want to be realistic in their modeling.

The above discussion applies assuming the local axes 1 and 2 of the shear wall area object are either vertical or horizontal. This is under user control. When drawing in ETABS the default is to have the 1 axis horizontal and the 2 axis vertical. This means that the flexural modifier for EI should be applied to f22 for wall piers and to f11 for spandrels. If you apply the modifier to both f11 and f22 it hardly affects the results.

For slabs where bending is always in the out-of-plane direction, modifiers m11, m22 and m12 are required to model cracking behavior.

Summary

Assuming beams and columns are modeled as frame then the stiffness modifier table is as follows:

ACI ETABS

Beams........................................0.35*Ig I22 = I33 = 0.35

Columns....................................0.70*Ig I22 = I33 = 0.70

Walls-Uncracked.................0.70*Ig modeled as shell – f11, f22 = 0.70

Walls-Cracked......................0.35*Ig similar to Walls-Uncracked (with modifiers of 0.35)

NOTE:

Walls are generally not designed for out-of-plane bending to avoid excessive longitudinal reinforcement. In this case, use a small modifier say 0.1 for m11, m22 and m12 so numerical instabilities could be avoided. However, use m11, m22, m12 = 0.70 (or 0.35) when considering the out-of-plane bending in wall.

Flat Plates & Flat Slabs....0.25*Ig modeled as membrane – f11, f22, f12 = 0.25 / modeled as shell – f11, f22, f12, m11, m22, m12 = 0.25 (for both cases fxx is not important if rigid diaphragm is assigned)

Eurocode 2 part 1-1: Design of concrete structures 7.3 Crack control

The crack width, w_k, may be calculated as follows:

wk = sr,max⋅(εsm - εcm)

(7.8)

where:

s_r,max

is the maximum crack spacing

ε_sm

is the mean strain in the reinforcement under the relevant combination of loads, including the effect of imposed deformations and taking into account the effects of tension stiffening

ε_cm

is the mean strain in the concrete between cracks.

(7.9)

where:

σ_s

is the stress in the tension reinforcement assuming a cracked section,
see application for a rectangular section or application for a T-section

E_s

is the design value of the modulus of elasticity of the reinforcing steel, see § 3.2.7 (4)

α_e

is the ratio E_s/E_cm

with

E_cm

the secant modulus of elasticity of concrete

f_ct,eff

is the mean value of the tensile strength of the concrete effective at the time when the cracks may first be expected to occur:
f_ct,eff = f_ctm or lower, (f_ctm(t)), if cracking is expected earlier than 28 days

ρ_p,eff

= (As + ξ1⋅A'p)/Ac,eff

(7.10)

with

A_s

the cross sectional area of reinforcement

A'_p

the area of pre or post-tensioned tendons within A_c,eff

A_c,eff

the effective area of concrete in tension surrounding the reinforcement or prestressing tendons of depth, h_c,ef, where h_c,ef is the lesser of 2,5(h - d), (h - x)/3 or h/2 (see Figure 7.1)

ξ₁

the adjusted ratio of bond strength taking into account the different diameters of prestressing and reinforcing steel:

ξ1 =

(7.5)

with

ξ

the ratio of bond strength of prestressing and reinforcing steel, according to Table 6.2

Φ_S

the largest bar diameter of the reinforcing steel

Φ_P

the diameter or equivalent diameter of prestressing steel:
Φ_p = 1,6⋅√A_P for bundles, where A_P is the area of a prestressing steel,
Φ_p = 1,75⋅Φ_wire for single 7 wire strands,
Φ_p = 1,20⋅Φ_wire for single 3 wire strands, where Φ_wire is the wire diameter.

k_t

is a factor dependent on the duration of the load:
k_t = 0,6 for short term loading,
k_t = 0,4 for long term loading.

• Where the bonded reinforcenlent is fixed at reasonably close centres within the tension zone (spacing ≤ 5(c + Φ/2), cf. Figure 7.2), the maximum crack spacing s_r,max may be calculated as follows:

sr,max = k3c + k1k2k4Φ / ρp,eff

(7.11)

where:

Φ

is the bar diameter. Where a mixture of bar diameters is used in a section, an equivalent diameter, Φ_eq, should be used.

c

is the cover to the longitudinal reinforcement

ρ_p,eff

see the difference of the mean strains above

k₁

is a coefficient which takes account of the bond properties of the bonded reinforcement:
k₁ = 0,8 for high bond bars,
k₁ = 1,6 for bars with an effectively plain surface (e.g. prestressing tendons).

Crack Width Calculation As Per Aci 318 14 Online

k₂

is a coefficient which takes account of the distribution of strain:
k₂ = 0,5 for bending,
k₂ = 1,0 for pure tension.
Intermediate values of k₂ should be used for cases of eccentric tension or for local areas:

k2 = (ε1 + ε2)/(2ε1)

(7.13)

where ε₁ is the greater and ε₂ is the lesser tensile strain at the boundaries of the section considered, assessed on the basis of a cracked section.

k₃

is a Nationally Determined Parameter, see § 7.3.4 (3)

k₄

is a Nationally Determined Parameter, see § 7.3.4 (3).

• Where the spacing of the bonded reinforcement exceeds 5(c + Φ/2) (cf. Figure 7.2), or where there is no bonded reinforcement within the tension zone, the maximum crack spacing s_r,max may be calculated as follows:

sr,max = 1,3(h - x)

(7.14)

where:

h

is the overall depth of the section (see Figure 7.1)

x

is the neutral axis depth of the section (see Figure 7.1).

This application calculates the crack width w_k from your inputs. Intermediate results will also be given.

Crack Width Calculation As Per Aci 318 1400

First, change the following option if necessary:

Output