2016 Specification Updates Overview BrDR... · 2016-08-30 · 2016 Specification Updates Overview...

AASHTOWare BrDR 6.8

Feature Tutorial 2016 Specification Updates Overview

2016 Specification Updates Overview

Last Modified: 8/9/2016 1

Topics Covered:

Wind load changes

Different Service III live load factor for PS beams depending on the loss method used

New LRFD article to compute Concrete density modification factor and its implementation in other articles

Initial allowable compressive stress in PS revised to 0.65f'ci

Bolt edge distance changes

This session covers changes to BrDR 6.8 in accordance with the AASHTO 2016 specification updates.

Specification changes are voted on by AASHTO members at the annual SCOBS meeting held each summer.

Approved changes are then incorporated into the next publication of the specification.

For 2016, AASHTO has published the 2016 Interim of 7th Edition of the LRFD Specifications. These Specification

editions are set as the system default specifications in BrDR 6.8.



The following table summarizes the changes that were approved in the summer of 2015 and incorporated into BrDR

6.8.

Agenda

Item

Article Number Summary of Change

2 Various articles Wind load changes

4 3.4.1 Different Service III LL load factor for PS beams depending on the loss

method used

5 5.4.2.6 Item #5: Modify for lambda

5.4.2.8 Item #6: New LRFD article to compute Concrete density modification

factor (lambda)

5.5.4.2.1 Item #7: Revise shear and torsion resistance factor for lightweight

concrete

5.8.2 Item #8: Modify for lambda

5.8.2.5 Item #10: Modify for lambda


5.8.3.4.3 Item #12: Modify for lambda

5.9.4.1.2 Item #15: Modify allowable initial tension in PS for lambda

5.9.4.2.2 Item #16: Modify allowable final tension in PS for lambda

5.11.2.1.1 Item #20: Modify rebar development length for lambda

5.11.2.1.2 Item #21: Modify rebar development length for lambda

5.11.2.4.1 Item # 22: Modify rebar development length for lambda

5.13.3.6.3 Item #30: Modify for lambda


7 5.9.4.1.1 Item #1: Initial allowable compressive stress in PS revised to 0.65f'ci

15 6.13.2.6.6 Bolt edge distance changes



Agenda 2: Wind load changes

In 7th Edition 2016 Interim, “Gust speed” wind load basis has been introduced. In BrDR 6.8, Wind Load Basis -

Gust speed is selected as default whenever a new bridge is created.

Major difference between Gust speed and Fastest-mile speed is that Gust speed is defined based on limit states

where as Fastest-mile speed has a single common value.

Open bridge BID 23 “LRFD Substructure Example 4” in the sample database.

Select and open the Environmental Conditions window.



“Fastest-mile speed” is selected in this window as this bridge was created in previous version. Now select the “Gust

speed” button.

Strength III gust wind speed in the Environmental Conditions window is considered using the value entered in the

system defaults.



Now open the Superstructure Environmental Loads window in the pier alternative.



While opening the window, loads are computed. Click OK on the computation dialog and the loads are displayed.



These computed loads can be overridden by selecting the “Override” button, check “Use override values” and click

“Override” button to enter the values. In the Override Values window, values are based on the limit state selected in

the Limit State drop-down box.



Now click on WS-Over tab. The computed loads are diplayed.



In this tab, computed values can also be overridden by selecting the “Override” button, check “Use override values”

and click “Override” button to enter the values.



Now click on WL tab. The computed loads are diplayed. These computed loads can be overridden by selecting the

“Override” button, check “Use override values” and click “Override” button to enter the values. In the Override

Values window, values are based on the limit state selected in the Limit State drop-down box.



Now select and open the Substructure Loads window in the pier alternative.



In the WS-Sub tab, the computed loads are dispalyed.



In the WS-Sub tab, computed values can be overridden by selecting the “Override” button, check “Use override

values” and click “Override” button to enter the values. Override values are entered based on the limit state.



Wind Gust loads can also be set in the General Preferences.



Now go to the superstructure definition and open the Load Case Description window.

In this window, add a Wind Load load case as shown below.



Open the Superstructure Loads window



In the Superstructure Loads window, go to the Wind tab. In this tab, select Load Case Name as Wind from the drop-

down box. Select Wind Load Basis as “Fastest-mile speed” and enter wind load as 115 psf as shown below.

Now run design review on “G1” using the “HL-93 Design Review” template. After analysis is complete, go to view

specification check and open Article “4.6.2.7.1 I-Sections”. Only single value of wind load and moment due to

wind load are computed.



Now go back to the Superstructure Loads window’s Wind tab. Change the Wind Load Basis selection to “Gust

speed” and enter wind loads as shown below.

Now re-run the design review on “G1” using the “HL-93 Design Review” template. After analysis is complete, go

to view specification check and open Article “4.6.2.7.1 I-Sections”. Now wind loads and moments due to wind

loads are computed based on the limit states as shown below.



Wind Load factors are revised in 2016 Interim and has been set to 1.0.



Agenda 4: Different Service III live load factor for PS beams depending on the loss method

used

In 2016 Interim live load factor for Service III in PS beams is dependent on the loss method selected for the analysis

of the beam.

New Live Load factors for 2016 Interim for LRFD and LRFR analyses are as shown in the following screen shots.



To verify the application of the new live load factor for Service III for PS, open bridge BID 10 “Example 7” in the

sample database.

Select and open the AASHTO Losses, select AASHTO Refined loss method and check Include elastic gains.



Now perform LRFR analysis on G1 using the “LRFR Design Load Rating” template. After the analysis is

completed, open Article 6A.4.2.1 Design Load Rating Service III Tensile Stress at 60 ft location.

In this article we can see Live Load factor of 1.0 is used.



Now go back to the AASHTO Losses, select AASHTO Approximate loss method and re-run the LRFR analysis on

G1 using the “LRFR Design Load Rating” template.

After the analysis is completed, open Article 6A.4.2.1 Design Load Rating Service III Tensile Stress at 60 ft

location. In this article we can see Live Load factor of 0.8 is used.



Agenda 5: Concrete density modification factor for light weight concrete

Item #6: New LRFD Article 5.4.2.8 to compute lambda

New article to compute Concrete density modification factor (λ) - Article 5.4.2.8 is introduced in 7th Edition 2016

Interim. Concrete density modification factor (λ) is considered as 1.0 for normal weight concrete and is computed

based on Equation 5.4.2.8-1 or 5.4.2.8.-2 for light weight concrete as shown in below flow chart.

Concrete Density Modification Factor

Article 5.4.2.8

NormalweightConcrete?

Yes

No

No

= User Inputctf Yes 0.1

'

*7.4

f

f

C

ct

0.1

0.15.775.0 cw

(5.4.2.8-1)

(5.4.2.8-2)



In Equation 5.4.2.8-1, fct is the splitting tensile strength and the value is entered in the Bridge Materials - Concrete

window. The input box is disabled if normal weight concrete is selected and is enabled when light weight concrete is

selected. If the splitting tensile strength value is empty, the Concrete density modification factor (λ) is computed

using Equation 5.4.2.8-2 where wc is the unit weight of concrete.



Item #5: Implementation of Concrete density modification factor (λ) in Article 5.4.2.6

Concrete density modification factor (λ) computed in Article 5.4.2.8 is applied while calculating modulus of rupture

in Article 5.4.2.6. Revised flow chart for Article 5.4.2.6 is shown below.

Modulus of RuptureArticle 5.4.2.6

F c >15.0 ksi

NormalweightConcrete?

Sand-LightweihtConcrete?

All-LightweightConcrete?

Issue warning that article only applies to concrete strengths up to 15 ksi

When used in Articles 5.7.3.4 and 5.7.3.6.2

When used in article 5.7.3.3.2

When used in Article 5.8.3.4.3

Yes

Yes

yes

Yes

No

No

No

cff r '24.0

cff r '20.0

cff r '20.0

cff r '17.0

cff r '24.0

'24.0 cr ff

2016 Interim Change

2016 Interim Change



Item #8: Implementation of Concrete density modification factor (λ) in Equation 5.8.2.1-4

Concrete density modification factor (λ) computed in Article 5.4.2.8 is applied while calculating torsional cracking

resistance (Tcr) in Equation 5.8.2.1-4. Revised Equation 5.8.2.1-4 is shown below.

2

0.125 10.125

cp pc

cr c

c c

A fT f

p f

2

0.125 10.125

cp pc

cr c

c c

A fT f

p f (5.8.2.1-4)

Item #10: Implementation of Concrete density modification factor (λ) in Equation 5.8.2.5-1

Concrete density modification factor (λ) computed in Article 5.4.2.8 is applied while calculating area of transverse

reinforcement (Av) within distance of the given reinforcement spacing(s) in Equation 5.8.2.5-1. Revised Equation

5.8.2.5-1is shown below.

0.0316v

v c

y

sbA f

f

0.0316 v

v c

y

sbA f

f (5.8.2.5-1)


Concrete density modification factor (λ) computed in Article 5.4.2.8 is applied while calculating nominal shear

resistance provided by tensile stresses in concrete (Vc) in Equation 5.8.3.3-3 and while calculating shear resistance

provided by the shear reinforcement (Vs) in Equation 5.8.3.3-5. Revised equations are shown below.

0.0316c v vc = f V b d

0.0316 c v vc

= f V b d (5.8.3.3-3)

sin 0.095s v y c v vV A f f b d

sin 0.095 s v y c v vV A f f b d (5.8.3.3-5)



Item #12: Implementation of Concrete density modification factor (λ) in Article 5.8.3.4.3

Concrete density modification factor (λ) computed in Article 5.4.2.8 is applied while calculating Vci in Equation

5.8.3.4.3-1 and Vcw in Equation 5.8.3.4.3-3. Revised equations are shown below.

Vci = nominal shear resistance provided by concrete when inclined cracking results from combined shear and

moment.

max

0.02 0.06 i cre

ci c v v d c v v

V MV f b d V f b d

M

max

0.02 0.06 i cre

ci c v v d c v v

V MV f b d V f b d

M (5.8.3.4.3-1)

Vcw = nominal shear resistance provided by concrete when inclined cracking results from excessive principal

tension in the web.

0.06 0.30cw c pc v v pb d VV f f

0.06 0.30 cw c pc v v pb d VV f f (5.8.3.4.3-3)


Concrete density modification factor (λ) computed in article 5.4.2.8 is used for computing stress limits in Article

5.9.4.1.2. Revised equations are shown in below table.

Bridge Type Location Stress Limit

Other Than

Segmentally

Constructed Bridges

In precompressed tensile zone without bonded

reinforcement

In areas other than the precompressed tensile zone

and without bonded reinforcement

In areas with bonded reinforcement (reinforcing bars

or prestressing steel) sufficient to resist the tensile

force in the concrete computed assuming an

uncracked section, where reinforcement is

proportioned using a stress of 0.5 fy, not to exceed 30

ksi.

For handling stresses in prestressed piles

N/A

0.0948f ci ≤ 0.2 (ksi)

0.0948 λ f ci ≤ 0.2 (ksi)

0.24f ci (ksi)

0.24 λ f ci (ksi)

0.158√ f ci (ksi)

0.158 λ √f ci (ksi)




Concrete density modification factor (λ) computed in Article 5.4.2.8 is applied while calculating stress limits in

Article 5.9.4.2.2. Revised equations are shown in below table.

Bridge Type Location Stress Limit

Other Than Segmentally

Constructed Bridges

These limits may be used

for normal weight

concrete with specified

compressive strengths up

to 15.0 ksi.

Tension in the Precompressed Tensile Zone, Assuming

Uncracked Sections

For components with bonded prestressing

tendons or reinforcement that are subjected to

not worse than moderate corrosion conditions

For components with bonded prestressing

tendons or reinforcement that are subjected to

severe corrosive conditions

For components with unbonded prestressing

tendons

0.19√ f c ≤ 0.6 (ksi)

0.19 λ √ f c ≤ 0.6 (ksi)

0.0948√ f c ≤ 0.3 (ksi)

0.0948 λ √ f c ≤ 0.3 (ksi)

No tension


Concrete density modification factor (λ) computed in Article 5.4.2.8 is applied while calculating tension

development length of the reinforcement bar. Revised equations is shown below.

d db rl cf lw rc erλ λ λ λ λ

rl cf rc er

d db λ

λ λ λ λ

(5.11.2.1.1-1)

in which:

2.4y

db b

c

fd

f

(5.11.2.1.1-2)




As Concrete density modification factor (λ) computed in Article 5.4.2.8 is applied while calculating tension

development length of the reinforcement bar, the light weight concrete modification factor 1.3 is deleted.

Concrete depth below bar > 12"

Yes

Lightweight concrete

Yes

No

Evaluate Art. 5.11.2.1.2


No

Start


Go To Page 4

Bundled Bar? Yes

No

Use db = equivalent diameter =2 Bar bundle db = 2*sqrt(2*Ab/PI)3 Bar bundle db = 2*sqrt(3*Ab/PI)4 Bar bundle db = 2*sqrt(4*Ab/PI)

3.1rl

f c > 10.0 ksi

Yes

No 0.1rl

3.1lw

0.1lw

Epoxy Coated? Yes Bar cover < 3db

Yes

NoBar clear spacing & side cover values available

Yes

Bar clr. spacing < 6db Yes

No

No

No

Bar clr. spacing < 0 Yes

Issue ErrorNo

0.1cf 5.1cf

2.1cf

2.1cf

2.1cf

5.1cf

7.1x cfrl 7.1x cfrl Yes

Modification Factors which Increase d

Article 5.11.2.1.2

2016 Interim Change




Concrete density modification factor (λ) computed in Article 5.4.2.8 is implemented while calculating basic

development length of hook bar. Revised equations is shown below.

38.0

60.0

ybhb

c

fd

f

38.0

60.0

yb

hb

c

fd

f

(5.11.2.4.1-1)


Concrete density modification factor (λ) computed in Article 5.4.2.8 is applied while calculating nominal shear

resistance in Article 5.13.3.6.3. Revised equations is shown below.

0.1260.063 0.126n c o v c o v

c

V + f b d f b d

0.1260.063 0.126n c o v c o v

c

V + f b d f b d

(5.13.3.6.3-1)

0.192n c s c o v

V V + V f b d

0.192n c s c o v

V V + V f b d

0.192n c s c o v

V V + V f b d (5.13.3.6.3-2)

0.0632c c o v

V = f b d

0.0632c c o v

V = f b d (5.13.3.6.3-3)




Concrete density modification factor (λ) computed in Article 5.4.2.8 is implemented for slabs of box culverts with 2

ft or more fill while calculating shear strength Vc. Revised equations is shown below.

0.0676 4.6 s u e

c c e

e u

A V dV = f + bd

bd M

0.0676 4.6 s u e

c c e

e u

A V dV = f + bd

bd M

0.0676 4.6 s u ec c e

e u

A V dV = f + bd

bd M

(5.14.5.3-1)

but

Vc <= 0.126√f c bde

Vc <=0.126 λ√f c bde



Item #7: Revise shear and torsion resistance factor for low density concrete

Shear and torsion resistance factor for low density concrete has been changed from 0.8 to 0.9 in 7th Edition 2016

Interim.



Agenda 7: Item #1 - Initial allowable compressive stress in PS revised

The Initial compressive stress limit for pretensioned and post-tensioned concrete members shall be considered

0.65 f ci (ksi) in 2016 Interim. We can observe the application of this change in bridge BID 10 “Example 7” in the

sample database.



Agenda 15: Item #1 - Bolt edge distance changes

Table 6.13.2.6.6-1 to compute bolt edge distance has been revised in 2016 Interim as follows.

Table 6.13.2.6.6-1—Minimum Edge Distances

Bolt Diameter, d

in.

Sheared

Edges

in.

Rolled Edges

of Plates or Shapes, or Gas Cut

Edges

Minimum Edge Distance

in.

5/8 1-1/8 7/8

3/4 1-1/4 1

7/8 1-1/2 1-1/8

1 1-3/4 1-1/4

1-1/8 2 1-1/2

1-1/4 2-1/4 1-5/8

1-3/8

Over 1-1/4

2-3/8

1-3/4

1-1/4 d



To verify the application of the new “Bolt edge distance” open bridge BID 29 “Splice Example” in the sample

database.



Analyze spice location using the “HL-93 Design Review” template which has 7th Edition 2016 Interim specification

selected as default for LRFD design review.



After analysis is complete, select and open Article 6.13.2.6 Spacing of Bolts.



Now go to the Member Alternative window and override the LRFD specification with LRFD 7th Edition. Re-run the

design review on the splice location.

After analysis is complete, select and open Article 6.13.2.6 Spacing of Bolts.

2016 Specification Updates Overview BrDR... · 2016-08-30 · 2016 Specification Updates Overview...

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