Problem 3 The plan and elevation of an earth retaining structure used for support excavation is shown in Figs. 2 and 3 respectively. The retaining structure is made of wood planks supported in the horizontal direction on vertical steel piles (HP sections). The HP piles shape of an H and are typically used for piles. The section properties of these sections (A, I, S, etc...) are given in Part 1 of the AISC steel manual. The spacing of the supporting HP piles is 20ft. The height of the piles is 15 from top of the pile to top of the footing. The height of the water table from the top of the footing is 9 ft as shown in the elevation in Fig. 3. The pile beight and soil properties and the earth pressure distribution behind the retaining structure are shown in Fig. 3. Figs. 4 shows the equations for earth pressure. q is a live load surcharge that accounts for traffic on top of the embankment; q is typically assumed to be 250 psf (per AASHTO). Use Fy-50 ksi Required 1. Determine the maximum horizontal force at the bottom of a typical interior HP pile due to lateral earth pressures and the live load on top of the embankment. 2. Determine the maximum moment at the bottom of a typical interior HP pile due to lateral earth pressures and the live load on top of the embankment. 3. If the maximum stress due to bending at the bottom of a typical interior HP pile cannot exceed 0.66Fy, what should be the minimum required section modulus Sx of
Problem 3 The plan and elevation of an earth retaining structure used for support excavation is shown in Figs. 2 and 3 respectively. The retaining structure is made of wood planks supported in the horizontal direction on vertical steel piles (HP sections). The HP piles shape of an H and are typically used for piles. The section properties of these sections (A, I, S, etc...) are given in Part 1 of the AISC steel manual. The spacing of the supporting HP piles is 20ft. The height of the piles is 15 from top of the pile to top of the footing. The height of the water table from the top of the footing is 9 ft as shown in the elevation in Fig. 3. The pile beight and soil properties and the earth pressure distribution behind the retaining structure are shown in Fig. 3. Figs. 4 shows the equations for earth pressure. q is a live load surcharge that accounts for traffic on top of the embankment; q is typically assumed to be 250 psf (per AASHTO). Use Fy-50 ksi Required 1. Determine the maximum horizontal force at the bottom of a typical interior HP pile due to lateral earth pressures and the live load on top of the embankment. 2. Determine the maximum moment at the bottom of a typical interior HP pile due to lateral earth pressures and the live load on top of the embankment. 3. If the maximum stress due to bending at the bottom of a typical interior HP pile cannot exceed 0.66Fy, what should be the minimum required section modulus Sx of
Chapter2: Loads On Structures
Section: Chapter Questions
Problem 1P
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Transcribed Image Text:Problem 3
The plan and elevation of an earth retaining structure used for support excavation is shown in
Figs. 2 and 3 respectively. The retaining structure is made of wood planks supported in the
horizontal direction on vertical steel piles (HP sections). The HP piles shape of an H and are
typically used for piles. The section properties of these sections (A, L, S, etc...) are given
Part 1 of the AISC steel manual. The spacing of the supporting HP piles is 20ft. The height of
the piles is 15 from top of the pile to top of footing. The height of the water table from
the top of the footing is 9 ft as shown in the elevation in Fig. 3. The pile height and soil
properties and the
he earth pressure distribution behind the retaining structure are shown in Fig.
3. Figs. 4 shows the equations for earth pressure. q is a live load surcharge that accounts for
traffic on top of the embankment; q is typically assumed to be 250 psf (per AASHTO). Use
Fy-50 ksi
Required
1. Determine the maximum horizontal force at the bottom of a typical interior HP pile
due to lateral earth pressures and the live load on top of the embankment.
2. Determine the maximum moment at the bottom of a typical interior HP pile due to
lateral earth pressures and the live load on top of the embankment.
3.
If the maximum stress due to bending at the bottom of a typical interior HP pile
cannot exceed 0.66Fy, what should be the minimum required section modulus Sx of
the HP pile? What is the lightest HP pile that can be used?
4.
If the maximum stress due to shear at the bottom of a typical interior HP pile cannot
exceed 0.
0.3Fy, what should be the minimum required web area (dx tw) of the HP pile?
5. What will be the factored LRFD horizontal force and bending moment? (use the
values obtained from parts 1 and 2 and use load factor of 1.6 for earth pressure
and 1.75 for live load).
6. If the section used was HP16x162, what would the deflection at top of pile?
20¹
20'
20
M
Cologne
typical HP
interior pile
K₂ YH,
Y = 120 pcf (16/ft³)
Ka 0.32
Compressed
CHASE
Fig 3-3D View
Y=120 pef
Kanu 32
JED
Yat 140 pat
Ka=0.32
% = 140 pcf ? Saturated soil
f}
Ka 0,32
Fig 2-PLAN
14
Yw H₂
Ka Oki Xu) H₂
k₂q
20¹
Fig 4-Lateral earth pressure forces, live load surcharge forces.
wood plank
Б. КҮНН
F3 azka (Yst-w) H₂ L
F4 = = X H² L
Fs = K₂q (H₂ + H₂) L
IT
H₂
th₂
F₁ is located at y = H₂ + H₁/3
From battom
To is located at y = HE
Fs is located at yo= H₂/₂
Fa is located at y = H₂/3
Fs is located at y = (H₁+ H₂)/2
Att +
1₂
Jul₂ kq
K₂ (X-X) H₂
Fig 5- Equations for lateral earth pressure forces and live load surcharge forces
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