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Codes
ACI 318-14
Mild Reinforcement
The development length of mild reinforcement is calculated individually for each bar and line wire following section Section 25.4 of ACI 318-14. The development length is calculated at from the end of each reinforcement entity object using the end point’s calculated spacing and cover. When The development length is also calculated individually for each wire in a WWR sheet and not computed once for the entire sheet.
When computing the spacing for the given entityobject, only similar reinforcement types are considered. For example, when computing the development length for a piece of rebar, the spacing calculation only considers the nearest piece of rebar rebar and will ignore nearby strand and mesh.
Straight Ends
Straight end tension The development length of straight ends in tension is computed per ACI 318-14 section Section 25.4.2. Per this provision, the base length can be computed using either equation Equation 25.4.2.2 or equation Equation 25.4.2.3. Eriksson Beam uses checks both above equations and uses the minimum development length of the two computed values. For equation Equation 25.4.2.3 to be accurate the user must should input a value for Ktr Ktr as leaving this term equal to the default value of zero can be overly conservative. The confinement term, KtrKtr, can be difficult for the program to compute as transverse reinforcement more or may not be presentis typically difficult to detect programmatically without considerable additional input from the user. When using section Section 25.4.2.2, a conservative assumption is made by ignoring the following condition: “Clear spacing of bars or wires being developed or lap spliced not less than dbdb, clear cover at least dbdb, and stirrups or ties throughout ℓd not less than the Code minimum.”
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The development length of standard hooks in tension is computed per ACI 318-14 section Section 25.4.3. The confining reinforcement modification factor, 𝜓r𝜓r, is assumed to be equal to 1.0. This is a conservative assumption and can be made per section Section 25.4.3.22 . The cover modification factor, 𝜓c𝜓c, can be reduced from 1 to 0.7 if the following is true: “For No. 11 bar and smaller hooks with side cover (normal to plane of hook) ≥ 2-1/2 in. and for 90-degree hook with cover on bar extension beyond hook ≥ 2 in.” When interpreting the clause above, Eriksson Beam assumes that the hook direction is vertical, so when checking the side cover (normal to plane of hook) it checks in the left and right directions. It also uses the bars start and end position is equal to the cover on the bar extension beyond the book. For example, an Inverted T with hooked ends starting 2 inches into the member will use 2 inches as the start cover.
Headed Bars
Development The development length of headed bars in tension is computed per ACI 318-14 25.4.4. The conditions below , from section Section 25.4.4.1 are checked, and if any are not satisfied the tension development length is computed as if it had straight-ends. The These conditions below are not all the conditions listed in section Section 25.4.4.1, just all the that Eriksson Beam is able to check with the current input.
Bar yield strength shall not exceed 60 ksi.
Bar size shall not exceed #11.
Concrete shall be normal weight.
Clear cover for bar shall be at least two times the bar diameter.
Clear spacing between bars shall be at least four times the bar diameter.
Mechanically AnchoredAnchored
The development length of mechanically anchored bars in tension and compression is assumed to be 0.
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Development length of wires in tension is computed using ACI 318-14 25.4.6 for deformed wires and 25.4.7 for plain wires. When computing development length, the first cross wire location is conservatively assumed to be located at the cross wire spacing into the line wire. This is a conservative assumption but is the maximum distance it can be from the end of the line wire for the distance equal to the cross wire spacing the be satisfied.
Compression Development Length
Development length of both bars and line wires in compression is computed using ACI 318-14 section Section 25.4.9 and assumes the confining reinforcement modification factor is 1.0.
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Strand development length is computed using ACI 318-14 section Section 25.4.8. The development length is a function of the effective stress in the strand after losses and the stress in the strand at ultimate. The effective stress after losses is computed at the center mid-point of the strand (typically the midspan of the concrete member) and uses the corresponding prestress losses at the same location. The stress at ultimate is assumed to be equal to the ultimate stress in the strand which is a conservative assumption that minorly increases may increase the development length slightly. Debonded Debonding the strand should double doubles the development length per ACI 318-14 section Section 25.4.8.1b which Eriksson Beam handles by using the debonded strand development length multiplier.
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The area of reinforcement at a given location is reduced in areas where the reinforcement is not fully developed. For mild reinforcement, the percent developed at a given location is equal to that locations distance from the end of the bar divided by the given bar’s development length. The development length above depends on whether the bar is in tension or compression. For strand, the effective area calculation of the strand depends on what you are using strand forthe analysis type. For a stress analysis, percent developed is computed the same way as mild reinforcement but using the transfer length in place of the development length. For an ultimate computationsanalysis, the development behaves bilinearly and can be seen in ACI 318-14 figure development length is calculated based on a bilinear development model that is shown in Figure R25.4.8.3.