Geotechnical Engineering Circular No. 9 Design, Analysis, and Testing of Laterally Loaded Deep Foundations that Support Transportation Facilities

Step a Determine nominal flexural resistance by plastic moment

Download 6.03 Mb.

View original pdf

Page	128/205
Date	29.05.2022
Size	6.03 Mb.
	#58903

1 ... 124 125 126 127 128 129 130 131 ... 205

hif18031
Soldier Rev B

Step b Determine nominal flexural resistance by local buckling
11.4.6 Combined Flexure and Axial Compression

Step a Determine nominal flexural resistance by plastic moment
The nominal flexural resistance can betaken as follows
𝑀𝑀
𝑚𝑚
= 𝑀𝑀
𝑝𝑝
= Equation 11-44) Where
𝑀𝑀
𝑚𝑚
= Nominal flexural resistance (kip-in).
𝑀𝑀
𝑝𝑝
= Plastic moment (kip-in).
𝑍𝑍
𝑦𝑦
= Plastic section modulus about weak axis (in.
𝐹𝐹
𝑦𝑦
= Yield strength of steel (ksi).
Step b Determine nominal flexural resistance by local buckling
Where local buckling will limit the nominal flexural resistance, the following checks apply. If
𝐷𝐷
𝑡𝑡 ≤ 0.31
𝐸𝐸
𝑠𝑠𝑡𝑡
𝐹𝐹
𝑦𝑦
𝑀𝑀
𝑚𝑚
= �
0.021 𝐸𝐸
𝑠𝑠𝑡𝑡
𝐷𝐷
𝑡𝑡
+ 𝐹𝐹
𝑦𝑦
� Equation 11-45) in which
𝑓𝑓
𝑐𝑐𝑐𝑐
=
0.33 Equation 11-46) Where
𝐷𝐷 = Outside diameter of pipe (in.
𝑡𝑡 = Pipe thickness ins Elastic modulus of steel (ksi).
𝐹𝐹𝑦𝑦 = Yield strength of steel (ksi).
𝑀𝑀𝑚𝑚 = Nominal flexural resistance (kip-in).
𝑆𝑆𝑦𝑦 = Elastic section modulus about weak axis (in.
𝑓𝑓
cr = Elastic local buckling stress (ksi).

169
11.4.6 Combined Flexure and Axial Compression
Combined axial and flexure checks are only applied to pile groups with vertical piles. At this time,
AASHTO (2014) does not have a recommendation to include battered piles. For combined flexure and compression of vertical piles, AASHTO (2014) requires the factored Structural Limit State to satisfy the following Limit State checks. If
𝑃𝑃
𝑢𝑢
𝑃𝑃
𝑐𝑐
< 0.2
𝑃𝑃
𝑢𝑢
2.0 𝑃𝑃
𝑐𝑐
+ �
𝑀𝑀
𝑢𝑢𝑥𝑥
𝑀𝑀
𝑐𝑐𝑥𝑥
+
𝑀𝑀
𝑢𝑢𝑦𝑦
𝑀𝑀
𝑐𝑐𝑦𝑦
� ≤ 1.0
(Equation 11-47)
𝑃𝑃
𝑢𝑢
𝑃𝑃
𝑐𝑐
+
8.0 9.0
�
𝑀𝑀
𝑢𝑢𝑥𝑥
𝑀𝑀
𝑐𝑐𝑥𝑥
+
𝑀𝑀
𝑢𝑢𝑦𝑦
𝑀𝑀
𝑐𝑐𝑦𝑦
� ≤ 1.0
(Equation 11-48)
Where:
𝑃𝑃
u
= Factored axial compressive load (kips).
𝑃𝑃
r
= Factored compressive resistance (kips).
M
u𝑥𝑥
= Factored moment about x-axis (kip-ft).
M
r
𝑥𝑥
= Factored flexural resistance about x-axis (kip-ft).
M
u
𝑦𝑦
= Factored moment about y-axis (kip-ft).
M
r
𝑦𝑦
= Factored flexural resistance about y-axis (kip-ft).

Download 6.03 Mb.

Share with your friends:

1 ... 124 125 126 127 128 129 130 131 ... 205