SABP Q 004 Hx Hor Vessels

Previous Issue: 31 August, 2002 Next Planned Update: 5 November 2012 Page 1 of 55 Primary contact: Abu-Adas, Hisham on phone 874-6908

Best Practice SABP-Q-004 6 November 2007 Heat Exchanger and Horizontal Vessel Foundation Design Guide Document Responsibility: Onshore Structures Standards Committee

Heat Exchanger and Horizontal Vessel Foundation Design Guide

Developed by: Hisham Abu-Adas Civil Engineering Unit/M&CED Consulting Services Department

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Document Responsibility: Onshore Structures Standards Committee SABP-Q-004 Issue Date: 6 November 2007 Heat Exchanger and Horizontal Next Update: 5 September 2012 Vessel Foundation Design Guide

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Heat Exchanger and Horizontal Vessel Foundation Design Guide

Table of Contents Page

1. INTRODUCTION .............................................................................................................. 3

1.1 PURPOSE ........................................................................................................ 3

1.2 SCOPE ............................................................................................................. 3

1.3 DISCLAIMER.................................................................................................... 3

1.4 CONFLICTS WITH MANDATORY STANDARDS ............................................ 3

2 REFERENCES ................................................................................................................. 4

2.1 SAUDI ARAMCO REFERENCES .................................................................... 4

2.2 INDUSTRY CODES AND STANDARDS.......................................................... 4

3 GENERAL......................................................................................................................... 5

4 DESIGN PROCEDURE .................................................................................................... 6

4.1 DESIGN CONSIDERATIONS........................................................................... 6

4.2 VERTICAL LOADS ........................................................................................... 6

4.3 HORIZONTAL LOADS ..................................................................................... 8

4.4 LOAD COMBINATIONS ................................................................................. 11

4.5 ANCHOR BOLTS ........................................................................................... 13

4.6 SLIDE PLATES............................................................................................... 14

4.7 PIER DESIGN................................................................................................. 15

4.8 COLUMN DESIGN ......................................................................................... 17

4.9 FOOTING DESIGN......................................................................................... 17

4.10 REINFORCED CONCRETE FOOTING DESIGN........................................... 22

APPENDIX: Tables, Figures, and Examples

TABLE 1 - THERMAL EXPANSION DATA.............................................................................. 28

TABLE 2 - BASIC DEVELOPMENT LENGTH OF STANDARD 90 HOOKS IN TENSION .... 30

FIGURE A - APPROXIMATE EXCHANGER WEIGHTS ......................................................... 31

FIGURE B - APPROXIMATE TUBE BUNDLE WEIGHTS....................................................... 32

FIGURE C - SOIL PRESSURE FOR BIAXIALLY LOADED FOOTINGS ................................ 33

EXAMPLE 1 - HEAT EXCHANGER FOUNDATION................................................................ 34

EXAMPLE 2 - HORIZONTAL VESSEL FOUNDATION........................................................... 53

Document Responsibility: Onshore Structures Standards Committee SABP-Q-004 Issue Date: 6 November 2007 Heat Exchanger and Horizontal Next Update: 5 November 2012 Vessel Foundation Design Guide

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1 Introduction

1.1 Purpose

This Practice establishes guidelines and recommended procedures for the analysis and design of heat exchanger and horizontal vessel foundations for use by Saudi Aramco engineers and engineers working on Saudi Aramco projects. It shall be used where applicable unless otherwise specified.

1.2 Scope

This design guide defines the minimum requirements for the analysis and design of heat exchanger and horizontal vessel foundations in process industry facilities at Saudi Aramco sites. In the ensuing sections, pertinent references are given, and design loadings and general design consideration are presented and discussed. This Practice addresses isolated foundations supported directly on soil. Pile supported footings are not included in this practice. Process Industry Practice PIP STE03360 Heat Exchanger and Horizontal Vessel Foundation Design Guide forms the basis for the development of this design guide.

1.3 Disclaimer

The material in this Best Practices document provides the most correct and accurate design guidelines available to Saudi Aramco which complies with international industry practices. This material is being provided for the general guidance and benefit of the Designer. Use of the Best Practices in designing projects for Saudi Aramco, however, does not relieve the Designer from his responsibility to verify the accuracy of any information presented or from his contractual liability to provide safe and sound designs that conform to Mandatory Saudi Aramco Engineering Requirements. Use of the information or material contained herein is no guarantee that the resulting product will satisfy the applicable requirements of any project. Saudi Aramco assumes no responsibility or liability whatsoever for any reliance on the information presented herein or for designs prepared by Designers in accordance with the Best Practices. Use of the Best Practices by Designers is intended solely for, and shall be strictly limited to, Saudi Aramco projects. Saudi Aramco is a registered trademark of the Saudi Arabian Oil Company. Copyright, Saudi Aramco, 2002.

1.4 Conflicts with Mandatory Standards

In the event of a conflict between this Best Practice and other Mandatory Saudi Aramco Engineering Requirement, the Mandatory Saudi Aramco Engineering Requirement shall govern.


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2 References

This Best Practice is based on the latest edition of the references below, unless otherwise noted. Short titles will be used herein when appropriate.

2.1 Saudi Aramco References

Saudi Aramco Engineering Standards (SAES)

SAES-A-112 Meteorological and Seismic Design Data SAES-A-113 Geotechnical Engineering Requirements SAES-A-114 Excavation and Backfill SAES-A-204 Preparation of Structural Calculations SAES-M-001 Structural Design Criteria for Non-Building

Structures SAES-Q-001 Criteria for Design and Construction of Concrete

Structures SAES-Q-005 Concrete Foundations

Saudi Aramco Best Practices

SABP-Q-001 Anchor Bolt Design and Installation SABP-Q-002 Spread Footings Design SABP-Q-006 Wind Loads on Pressure Vessels

2.2 Industry Codes and Standards

American Concrete Institute (ACI)

ACI 318-02 Building Code Requirements for Reinforced Concrete

American Society of Civil Engineers (ASCE)

ASCE 7-02 Minimum Design Loads for Buildings and Other Structures

Wind Load and Anchor Bolt Design for Buildings and Other Structures

Process Industry Practices (PIP)

PIP STE03360 Heat Exchanger and Horizontal Vessel Foundation Design Guide


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3 General

3.1 The design and specifications for construction of heat exchanger and horizontal vessel foundation shall be adequate for the structure intended use, in accordance with commonly accepted engineering practice, Saudi Aramco Engineering Standard SAES-Q-005 and this guideline.

3.2 A geotechnical investigation is required for all new structures and foundations as described in SAES-A-113. (Ref. SAES-Q-005, Para. 4.1.1)

3.3 The allowable soil bearing pressure shall be based on the results of the geotechnical investigation, and a consideration of permissible total and differential settlements. Soil pressures shall be calculated under the action of vertical and lateral loads using load combinations that result in the maximum soil pressures. The maximum soil pressure shall not exceed the applicable allowable value. (Ref. SAES-Q-005, Para. 4.1.2)

3.4 Foundations shall be founded on either undisturbed soil or compact fill and at least 600 mm below the existing or finished grade surface, unless a detailed soils investigation indicated otherwise. In the case of foundations supported on compacted fill, the geotechnical investigation and/or SAES-A-114 shall govern the type of fill material and degree of compaction required. (Ref. SAES-Q-005, Para. 4.1.3)

3.5 The minimum overturning stability ratio for service load combinations including wind loads shall be 1.5. (Ref. SAES-Q-005, para. 4.2.1)

3.6 The minimum factor of safety against sliding for service loads other than earthquake shall be 1.5. (Ref. SAES-Q-005, para. 4.2.6)

3.7 The minimum factor of safety against buoyancy shall be 1.2 using actual unfactored service loads. (Ref. SAES-Q-005, para. 4.2.7)

3.8 The design and construction of all concrete foundations shall comply with the requirements of SAES-Q-001, SAES-Q-005 and ACI-318. (Ref. SAES-Q-005, para. 4.3.1)

3.9 The design concrete compressive strength of concrete shall be 27.6 MPa (4000 psi) at 28 days. (Ref. SAES-Q-005, Para. 4.3.2.b)

3.10 Reinforcing steel bars shall be hot-rolled, high tensile 422 Mpa (60.0 ksi), deformed steel per ACI 318M. (Ref. SAES-Q-001, Para. 5.2)

3.11 The structural calculations shall be prepared in accordance with the requirements of SAES-A-204.


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4 Design Procedure

4.1 Design Considerations

4.1.1 Heat exchanger and horizontal vessel wind and seismic loads shall be in accordance with Saudi Aramco Engineering Standard SAES-A112.

4.1.2 Heat exchanger and horizontal vessel foundation design shall be based on final approved certified vendor drawing.

4.1.3 For general foundation requirements and guidelines, refer to Saudi Aramco Best Practice SABP-Q-002 Spread Footings Design.

4.1.4 The engineer shall verify anchor bolts design, type and size to ensure compliance with ACI 318-02 Code Appendix D, Saudi Aramco Standard Drawing AB-036322 and with the Vendor specific requirements.

4.2 Vertical Loads

4.2.1 Dead Loads

4.2.1.1 The following nominal loads shall be considered as dead loads when applying load factors used in strength design.

a. Structure dead load (Ds) Vessels foundation weight which is defined as combined weight of footing, pedestal dead load (Dp), and the overburden soil.

b. Erection dead load (Df) - Fabricated weight of the exchanger or vessel, generally taken from Vendor certified exchanger or vessel drawings.

c. Empty dead load (De) - Empty weight of the exchanger or vessel including all attachments, trays, internals, bundle, insulation, fireproofing, agitators, piping, ladders, platforms, etc. The eccentric load defined in paragraph 4.2.1.2 shall also be added to the empty dead load weight.

d. Operating dead load (Do) - Empty dead load of the exchanger or vessel plus the maximum weight of contents (including packing/catalyst) during normal operation. The eccentric load defined in paragraph 4.2.1.2 shall also be added to the operating dead load weight.

e. Test dead load (Dt) - (horizontal vessels only) Empty dead load of the vessel plus the weight of test medium contained in the system. The test medium should be as specified in the contract documents. Unless otherwise


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specified, a minimum specific gravity of 1.0 should be used for test medium. Cleaning load shall be used for test dead load if cleaning fluid is heavier than test medium. Whether test or cleaning will actually be done in the field shall be determined. It is generally desirable to design for test dead load because unforeseen circumstances may occur. Test load shall be taken from certified Vendor drawings. The eccentric load defined in paragraph 4.2.1.2 shall also be added to the test dead load weight.

4.2.1.2 Eccentric load - Unless more exact information about piping supported on the exchanger or horizontal vessel is available, the following guidelines shall be used:

a. A load of an additional 20% of the applicable weight (empty or operating) for exchangers with diameters less than 24 inches.

b. A load of an additional 10% of the applicable weight (empty or operating) for exchangers with diameters equal to or greater than 24 inches.

c. A load of an additional 10% of the applicable weight (empty, operating, or test) for horizontal vessels.

d. This additional load shall be applied at a perpendicular horizontal distance of D/2 plus 18 inches from the longitudinal centerline of the vessel, where D is the basic diameter (basic diameter = vessel I.D. + 2 times the wall thickness + 2 times the insulation thickness). This additional eccentric load (vertical load and moment caused by eccentricity) shall be distributed to each pedestal in proportion to the distribution of operating load to each pedestal. For stacked exchangers, the weight of only the largest exchanger shall be used to estimate the eccentric load.

Comment: These eccentric loads are only guidelines and shall be checked against actual conditions when they become available.

4.2.1.3 Load distribution (exchangers) - For most common shell and tube heat exchangers, vertical dead loads should normally be distributed with 60% to the channel end support and 40% to the shell end support. However, the actual exchanger shape and support configuration should be reviewed when


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determining weight distribution because in many cases load distribution may vary.

4.2.2 Live Loads (L)

4.2.2.1 Live loads should be calculated in accordance with SAES-M-001.

4.2.2.2 Load combinations that include live load in Table 5 and Table 6 of Section 4.4 do not normally control any portion of the foundation design.

4.3 Horizontal Loads

4.3.1 Wind Loading (W)

4.3.1.1 Wind loads shall be calculated in accordance with the requirements of SAES-A-112, SAES-M-001 Structural Design Criteria for Non-Building Structures, and Saudi Aramco Best Practice SABP-Q-006 Wind Loads on Pressure Vessels.

4.3.1.2 The engineer is responsible for determining wind loads used for foundation design. Wind loads from vendor or other engineering disciplines shall not be accepted without verification.

4.3.1.3 Partial wind load (Wp) shall be based on the requirements of ASCE 37-02, Section 6.2.1, for specified test or erection duration. The design wind speed shall be 75% of the actual wind speed.

4.3.1.4 Transverse Wind - The wind pressure on the projected area of the side of the vessel should be applied as a horizontal shear at the center of the exchanger or vessel. Including the wind loading on projections such as piping, manways, insulation, and platforms during the wind analysis is important. The saddle-to-pier connection should be considered fixed for transverse loads. The saddle design is a function of either the vessel supplier or the Designers Mechanical/Vessel Group.

4.3.1.5 Longitudinal Wind - The wind pressure on the end of the exchanger or vessel should be applied as a horizontal shear at the center of the exchanger or vessel. The flat surface wind pressure on the exposed area of both piers or both columns should also be included, applied as a horizontal shear at the


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centroid of the exposed area. The saddle-to-pier connection will be considered pinned for longitudinal loads unless more than one row of anchor bolts exists.

4.3.1.6 Shielding - No allowance shall be made for shielding from wind by nearby equipment or structures except under unusual conditions.

4.3.2 Earthquake Loads (E)

4.3.2.1 Seismic forces shall be calculated in accordance with SAES-A-112 and the requirements of SAES-M-001 Structural Design Criteria for Non-Building Structures.

4.3.2.2 Seismic loads calculated by the Vessel Vendor shall be independently verified as appropriate by the Engineer prior to performing foundation design to ensure compliance with the project specifications and the applicable Saudi Aramco Standards.

4.3.2.3 For low-friction slide plates ( 0.2), all the longitudinal earthquake loads shall be applied at the fixed pier. For higher friction slide plates ( > 0.2), 70% of the earthquake loads shall be applied at the fixed pier. Transverse and vertical earthquake loads shall be distributed in proportion to the vertical load applied to both piers. The piers are normally designed for the fixed end, and then the pier for the sliding end is made identical, to avoid potential errors in construction and to reduce engineering time. If this proves to be uneconomical, the sliding end should be designed for 30% of the longitudinal earthquake load if using low-friction slide plates, and for 50% of the longitudinal earthquake load if using higher friction slide plates.

4.3.2.4 For the load combinations in Section 4.4, the following designations are used:

EO = Earthquake load considering the unfactored operating dead load and the applicable portion of the unfactored structure dead load.

Ee = Earthquake load considering the unfactored empty dead load and the applicable portion of the unfactored structure dead load.


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4.3.3 Bundle Pull Load (Bp) - (Exchangers)

4.3.3.1 Foundations supporting heat exchangers subject to bundle pulling shall be designed for a horizontal load equal 1.0 times the weight of the removable tube bundle but not less than 2,000 lb (9.0 kN). If the total weight of the exchanger is less than 2,000 lb (9.0 kN), the bundle pull load is permitted to be taken as the total weight of the exchanger.

4.3.3.2 Bundle pull load shall be applied at the center of the bundle.

Comment: if it can be assured that the bundles will be removed strictly by the use of a bundle extractor attaching directly to the exchanger (such that the bundle pull force is not transferred to the structure or foundation), the structure or foundation need not be designed for the bundle pull force. Such assurance would typically require the addition of a sign posted on the exchanger to indicate bundle remover by an extractor only.

4.3.3.3 The portion of the bundle pull load at the sliding end support shall equal the friction force or half the total bundle load, whichever is less. The remainder of the bundle pull load shall be resisted at the anchor end support.

4.3.3.4 Consideration should be given to reducing the empty weight of the exchanger owing to the removal of the exchanger head (channel) to pull the bundle. The weight of the exchanger head (channel) typically is within the range of 8% to 15% of the empty weight of the exchanger.

4.3.4 Thermal Force

4.3.4.1 Calculate thermal growth using maximum design temperature. Thermal coefficients can be found in Table 1. Thermal force is defined as the force due to growth of the horizontal vessel or exchanger between supports.

4.3.4.2 The thermal force used for design should be the smaller value resulting from the following two calculations:

a. The force required to overcome static friction between the exchanger or vessel support and the slide plate:

Ff = (Po) (Eq. 1)


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where,

Ff = static friction force

= coefficient of friction, refer to the values given in Section 4.6, Slide Plates

Po = nominal operating compression dead load on slide plate

b. The force required to deflect the pier or column an amount equal to half of the thermal growth between exchanger or vessel saddles:

3H2I E 3 =T (Eq. 2)

where, T = force from thermal expansion required to deflect

pier or column

= total deflection between exchanger/vessel saddles = L

= thermal expansion coefficient in accordance with Table 1

L = length of exchanger/vessel between saddles

E = modulus of elasticity of concrete pier

I = pier moment of inertia

H = pier height

The thermal force should be applied at the top of the piers.

4.3.5 Load Distribution

The horizontal loads shall be divided equally between piers unless otherwise required by Section 4.3 of this Design Guide.

4.4 Load Combinations

4.4.1 Heat exchangers and horizontal vessel foundations shall be designed using load combinations in accordance with Tables 5 and 6 of Section 6.2.3 of SAES-M-001 (as listed in Tables 5 and 6 of this Design Guide).

4.4.2 Foundations for fin exchangers (double pipe exchangers) should not be designed to resist thermal or bundle pull forces.


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4.4.3 Piping thermal loads shall be included in combinations when deemed advisable and shall be considered as dead loads when applying load factors.

4.4.4 The loads used for footing design shall be service loads reactions obtained from certified vendor drawings. In computing footing soil pressure, the service load reactions are used. The weight of the footing and soil overburden shall be combined with the service loads. The effect of buoyancy shall be considered in footing design when applicable.

4.4.5 Service load combinations shall be used to check soil bearing pressures and foundation stability against overturning and sliding. In computing moments and shears for footing slab design, the service loads are factored. In designing the pedestal, load factors are applied to the service loads reactions and the pedestal is designed in accordance with Section 4.7.

Table 5 Allowable Stress Design (Service Loads)

Load Comb. #

Load Combination

Allowable Stress

Multiplier

Description

1 Ds + Do + (T or Ff)b 1.00 Operating Weight + Thermal Expansion or Friction Force

2 Ds + Do + L + (T or Ff)b 1.00 Operating Weight + Live Load + Thermal Expansion or Friction Force 3 Ds + Do + (W or 0.7 Eo) 1.00 Operating Weight + Wind or Earthquake

4 Ds + De + W 1.00 Empty Weight + Wind (Wind uplift case)

5a 0.9 (Ds + Do)+ 0.7 Eo 1.00 Operating Weight + Earthquake (Earthquake uplift case)

5b 0.9 (Ds + De)+ 0.7 Ee 1.00 Empty Weight + Earthquake (Earthquake uplift case)

6 Ds + Df + Wp 1.00 Erection Weight + Partial Wind (Wind uplift case)

7 Ds + Dt + Wp 1.20 Test Weight + Partial Wind (for Horiz. Vessels Only)

8 Ds + DeC + Bp 1.00 Empty + Bundle Pull (For Heat Exchangers Only)

Notes: a. Wind and earthquake forces shall be applied in the both transverse and longitudinal directions,

but need not be applied simultaneously. b. The design thermal force for horizontal vessels and heat exchangers shall be the lesser of T or Ff. c. Heat exchanger empty dead load will be reduced during bundle pull due to the removal of the

exchange head. d. Sustained thermal loads not relieved by sliding due to vessel or exchanger expansion should be

considered in operating load combinations with wind or earthquake.


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e. Thrust forces caused by thermal expansion of piping should be included in the calculations for operating load combinations, if deemed advisable. The pipe stress engineer should be consulted for any thermal loads that are to be considered.

Table 6 Loading Combinations and Load Factors - Strength Design

Load Comb. # Load Combination Description

1 1.4(Ds + Do) + 1.4 (T or Ff)b Operating Weight + Thermal Expansion or Friction Force

2 1.2(Ds + Do) + 1.6 L + 1.2 (T or Ff)b Operating Weight + Live Load + Thermal Expansion or Friction Force

3 1.2(Ds + Do) + (1.6 W or 1.0 Eo) Operating Weight + Wind or Earthquake

4 0.9(Ds + De) + 1.6 W Empty Weight + Wind (Wind uplift case)

5a 0.9(Ds + Do) + 1.0 Eo Operating Weight + Earthquake (Earthquake uplift case)

5b 0.9(Ds + De) + 1.0 Ee Empty Weight + Earthquake (Earthquake uplift case)

6 0.9(Ds + Df) + 1.6 Wp Erection Weight + Partial Wind (Wind uplift case)

7 1.4 (Ds + Dt) Test Weight (For Horizontal Vessels Only)

8 1.2 (Ds + Dt) + 1.6 Wp Test Weight + Partial Wind (For Horizontal Vessels Only)

9 1.2 (Ds + Dec) + 1.6 Bp Empty Weight + Bundle Pull (For Heat Exchangers Only)

10 0.9 (Ds + Dec) + 1.6 Bp Empty Weight + Bundle Pull (For Heat Exchangers Only)(Bundle pull uplift case)

Notes:

a. Wind and earthquake forces shall be applied in the both transverse and longitudinal directions, but need not be applied simultaneously.

b. The design thermal force for horizontal vessels and heat exchangers shall be the lesser of T or Ff. c. Heat exchanger empty dead load will be reduced during bundle pull due to the removal of the

exchange head. d. Sustained thermal loads not relieved by sliding due to vessel or exchanger expansion should be

considered in operating load combinations with wind or earthquake. e. Thrust forces caused by thermal expansion of piping should be included in the calculations for

operating load combinations, if deemed advisable. The pipe stress engineer should be consulted for any thermal loads that are to be considered.

4.5 Anchor Bolts

4.5.1 Anchor bolts shall conform to requirements of Para. 4.8 of SAES-Q-005 Concrete Foundations and SABP-Q-001.

4.5.2 Friction force at the bottom of the saddle shall be overcome before lateral load is assumed to produce shear in the anchor bolts.

4.5.3 For earthquake loads, horizontal shear forces shall be applied to the anchor bolts, assuming no friction resistance.


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4.5.4 Anchor bolts shall be designed based on final approved vendor certified drawings.

4.6 Slide Plates

4.6.1 A steel slide plate or low-friction slide plate assembly should typically be provided at the sliding end of every exchanger or vessel regardless of the flexibility inherent in the structural support. Small, lightly loaded exchangers or vessels may not require slide plates.

4.6.2 Low-friction manufactured slide plate assemblies should be used to reduce high-frictional resistance, especially for heavy exchangers or for exchangers with significant thermal growth.

4.6.2.1 For exchangers with bundle pull, steel slide plates instead of low-friction slide plate assemblies may be more cost efficient.

4.6.2.2 Typically, a low-friction slide plate assembly consists of multiple individual slide plate components spaced out along the length of the saddle. Each slide plate component consists of an upper element and a lower element, and the sliding surface is at the interface of the upper and lower elements. The elements should be fabricated with a carbon steel backer plate attached to the elements to facilitate welding of the upper elements to the saddles and the lower elements to the steel bearing plate.

4.6.3 Typical coefficients of friction are as follows. For low-friction slide plate assemblies, manufacturers literature should be consulted because coefficients of friction vary with slide plate material, temperature, and pressure.

a. No slide plate (steel support on concrete) 0.60 b. Steel slide plate 0.40 c. Low-friction slide plate assemblies 0.05 to 0.20

4.6.4 Suggested criteria for sizing low-friction slide plate elements are as follows. Manufacturers literature should be consulted for temperature restrictions, pressure limitations, and other requirements that may affect the size and types of materials used for the slide plate elements.

Element widths (where = total thermal growth between exchanger or vessel saddles):

a. Upper element = saddle width + 1-inch minimum to allow for down-hand welding on the element-to-saddle weld (larger upper element


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width may be required for exchangers or vessels with large values).

b. Lower element = upper element width - 2 () - 1 inch (minimum of 1 inch narrower than upper element)

Element lengths (use 18-inch maximum clear distance between lower elements):

a. Lower element = based on allowable contact pressure in accordance with the manufacturers literature and lower element width

b. Upper element = lower element length + 1 inch

Plates should be aligned with saddle stiffeners where practical.

A continuous steel bearing plate should be provided under the lower elements so that lower elements can be welded to the bearing plate. Minimum width of bearing plate should be 1 inch larger than the width of the lower elements. Minimum length of bearing plate should be 1 inch larger than the saddle length. Bearing stress on concrete should be checked in accordance with ACI 318.

4.6.5 Suggested criteria for sizing steel slide plates are as follows:

a. Minimum width = saddle width + 2 () + 1 inch b. Minimum length = saddle length + 1 inch

Bearing stress on concrete should be checked in accordance with ACI 318.

4.7 Pier Design

4.7.1 Pier dimensions should be sized on the basis of standard available forms for the project. When form information is not available, pier dimensions should be sized in 2-inch increments to allow use of standard manufactured forms. Minimum pier dimensions should equal the maximum of the saddle, bearing plate, or steel slide plate dimensions plus 4 inches and should be sized to provide adequate anchor bolt edge distance. Minimum pier width should be no less than 10 inches or 10% of the pier height.

4.7.2 Anchorage Considerations

It is normally desirable to make the pier high enough to contain the anchor bolts and to keep them out of the footing. Consideration must be given to anchor bolt development and foundation depth requirements.


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4.7.3 Reinforcement

4.7.3.1 Piers should normally be designed as tension-controlled members (cantilever beams) with two layers of reinforcement. If the pier is a compression-controlled member, the pier should be designed as a column. Size and reinforcement for each pier should normally be the same. Dowel splices are not required if the vertical pier reinforcing projection is less than the larger of 6 ft or the rebar size in feet above the top of footing. For example, #8 rebar can extend up to 8 ft above the mat without dowel splices. For cases that exceed this limit, dowels with minimum projections required for tension splices should be used in accordance with ACI 318.

4.7.3.2 The vertical reinforcement in the piers may need to be increased to account for shear friction. The following formula should be used to calculate the area of reinforcement required for shear friction, Avf:

Avf = [Vu/() Pupier]/fy (Eq. 3) Vu = strength design factored shear force at bottom of pier

= coefficient of friction, normally use 0.6. If it can be assured that the concrete at the construction joint at the interface between the pedestal and the mat will be intentionally roughened, then 1.0 may be used for .

= strength reduction factor = 0.75 Pupier = strength design factored axial force at bottom of pier

fy = yield strength of vertical reinforcement

4.7.3.3 Minimum reinforcement for piers is #5 at 12 inches on each face with #4 ties at 12 inches. A minimum of two #4 ties (or three ties if moderate or high seismic risk) should be placed within 6 inches of the top of concrete of each pier (not including grout) to protect anchor bolts. All ties should encircle the vertical reinforcement, unless special tie reinforcement for boundary elements is required.

4.7.3.4 For tension-controlled piers, as is normally the case, intermediate ties are not required.


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4.8 Column Design

4.8.1 Sizing

Columns (if needed) should be round, square, or rectangular depending on the job criteria or the construction contractors preference. Column dimensions should be sized on the basis of standard available forms for the project. If form information is not available, column dimensions should be sized in 2-inch increments to allow use of standard manufactured forms.

4.8.2 Reinforcement

Size and reinforcement for both columns should normally be the same. Dowels should be used to transfer the column loads to the footings. Minimum dowel projections should be as required for a tension splice (Class B) in accordance with ACI 318.

4.9 Footing Design

4.9.1 Sizing

a) Footings must be designed to safely resist the effects of the applied factored axial loads, shears and moments. Provisions of Chapter 15 of ACI Code apply primarily for design of footings supporting a single column (isolated footings).

b) The size of spread footings may be governed by stability requirements, sliding, soil bearing pressure, or settlement. Plan view footing dimensions should be in 2-inch increments. The footing thickness shall be 12 inches minimum and thickened in 2-inch increments. Size for both footings should normally be the same. For short exchangers or vessels, a combined footing may be used.

c) The footing thickness should be adequate for shear and embedment of pier or column reinforcement in accordance with ACI 318, Chapter 12 (see also attached Table 2).

4.9.2 Foundation Stability

a) All foundations subject to buoyant forces shall be designed to resist a uniformly distributed uplift equal to the full hydrostatic pressure. The minimum safety factor against floatation shall be 1.20, considering the highest anticipated water level (Ref. SAES-Q-005, Para. 4.2.7).


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b) The minimum safety factor against overturning for load combinations which include wind forces shall be 1.5; (Ref. SAES-Q-005, Para. 4.2.1). Overturning caused by earthquake shall be checked in accordance with SEI/ASCE 7, Chapter 9; (Ref. SAES-Q-005, Para. 4.2.2).

Compute the Stability Ratio (S.R.) using the following formula:

S.R. = MR/ MO.T or S.R. = L/2e

where

MR = Resisting Moment

M O.T. = Overturning Moment

L = dimension of footing in the direction of the overturning moment, ft.

e = eccentricity = overturning moment at the base of the footing divided by the total vertical load, ft.

Eccentricity e = MO.T./P 4.9.3 Foundation Sliding

The minimum safety factor against sliding for service loads other than earthquake shall be 1.5. The coefficient of friction used in computing the safety factor against sliding for cast-in-place foundations shall be 0.40, unless specified otherwise in a detailed soil investigation. Passive earth pressure from backfill shall not be considered in computing these safety factors (Ref. SAES-Q-005, Para. 4.2.6).

4.9.4 Soil Bearing Pressure

A common assumption in the design of soil bearing footings is that the footing behaves as a rigid unit. Hence, the soil pressure beneath a footing is assumed to vary linearly when the footing is subjected to axial load and moment. The ensuing rectangular footing formulas are based on the linear pressure assumption. We will consider the following conditions:

Case 1 - Resultant is within middle third of footing e L/6 The resultant R consists of the applied vertical load plus the weight of the footing.


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In this case, all of footing area in compression, and the direct soil pressure PT/A is larger than the bending pressure Mc/I = M/S.

When bending occurs about one axis only (Figure 1 Case 1), and the entire footing is subjected to compression pressure,

Qmax = PT/A + M/S = PT/BL (1 + 6e/L) Uniaxial Loading Eq. 4-1 Qmin = PT/A - M/S = PT/BL (1 - 6e/L) Uniaxial Loading Eq. 4-2

Eccentricity e = M/PT = (M + H x h) /PT Eq. 4-3

When bending occurs about both the x and y axis, and the entire footing is subjected to compression pressure (i.e., eccentricity of the footing ex and ey lie within their respective kern points),


Page 20 of 55

qmax = PT/A + My/Sx + Mx/Sy = PT/BL (1 + 6ex/L + 6ey/B) Biaxial Loading Eq. 4-4 qmin = PT/A - My/Sx - Mx/Sy = PT/BL (1 - 6ex/L - 6ey/B)

Biaxial Loading Eq. 4-5

ex = My/PT Eq. 4-6 ey = Mx/PT Eq. 4-7

where A = Area of footing = (L) (B)

L = Footing Length Dimension Parallel to X-Axis

B = Footing width dimension parallel to Y-axis

PT = Vertical design load including soil overburden, foundation weight, and buoyancy

Mx = Moment About X-Axis of Footing Plan

My = Moment About Y-Axis of Footing Plan

Sx = L (B2/6) Ix = L B3/12

Sy = B (L2/6) Iy = B L3/12

The values of ex and ey are obtained using equation 4-6 and 4-7 first about the x-axis and then about the y-axis

Case 2 - Resultant is outside middle third of footing e>L/6 The resultant R consists of the applied vertical load plus the weight of the footing and soil overburden.

When bending occurs about one axis only:

In this case, as the load acts outside the middle third, tensile stress results at the left side of the footing as shown in Figure 1- Case 2.

Figure 1 - Case 2 shows the distribution of soil pressure beneath the footing when the resultant is outside the middle third of the base. According to the laws of static, the total upward force must be equal to and collinear with R. These two conditions may be expressed by

R = (qmax B x) / 2 Eq. 4-8 and

x/3 = (L/2) - e2 x = 3 (L/2 e2) Eq. 4-9


Page 21 of 55

qmax = 2PT/3B (L/2 e2) Eq. 4-10 q = 0 at x = 3 (L/2 e2) Eq. 4-11

When bending occurs about both the x and y axis, and the values of ex and ey are obtained using equation 4-6 and 4-7 first about the x-axis and then about the y-axis. If the resulting point of application of eccentricity e falls outside of the kern of the section (as labeled in Figure 2), a special case exists and the points of zero pressure must be determined by trial. It should be noted that tension cannot exist between the soil and the footing.

For the spread footings that are subject to biaxial bending with the resultant lies outside or inside the kern, numerical solutions can be found in many soil mechanics textbooks. Commercial software is also available for this situation. Figure C is a design aid that is based on accurate numerical solutions and graphically provides the results.


Page 22 of 55

4.9.5 Settlement

Footings shall be designed so that under sustained loads (operating loads) the total settlement and the differential settlement between footings do not exceed the established limits. The maximum allowable amount of total settlement and differential settlement is typically set by the Project Structural Engineer based on the sensitivity of the equipment or structure being supported.

4.10 Reinforced Concrete Footing Design

4.10.1 General

a) Reinforced concrete footing design shall conform to the requirements of ACI 318. The strength method shall be used for all reinforced concrete footings design.

b) The footing thickness is generally controlled by shear or rigidity requirements. However, thickness may be controlled by flexural considerations where the thickness is increased to avoid tension top steel or to keep less than bal. In any case, the minimum thickness of a soil bearing footing shall be 12 inches.

4.10.2 Flexural Considerations

a) Footings shall be designed considering two-way action. The procedures outlined in ACI 318, Chapter 15 shall be followed for footing design.

b) The strength method outlined in ACI 318, Chapter 10 shall be used for all design.

c) Reinforced concrete design shall be in accordance with ACI 318 using factored loads. The critical section for moment shall be taken at the face of the pier. The moment shall be calculated for a 1 foot-wide strip as a simple cantilever from the edge of the pier. The resulting reinforcing steel shall be placed continuously across the entire footing in a grid pattern with the minimum bottom reinforcing being #5 bars at 12 inches on-center, each way.

d) The minimum amount of bottom steel (grade 60 ksi) shall not be less than the minimum shrinkage reinforcement:

As (min) = 0.0018 b h

where,

b = width of footing


Page 23 of 55

d = distance from top of footing to center of bottom bars

h = depth of footing

e) If a footing has uplift, there will be a moment at the heel that will cause tension in the top of footing. Provide top steel to account for the moment resulting from the footing weight and soil overburden weight. Development length of top steel shall be per Table 5. The bars may be hooked 90 downward to achieve the required development length if straight embedment is not adequate. If top reinforcing is required, minimum reinforcing shall be #4 at 12 inches on center, each way. For top reinforcement, concrete stress can be checked in accordance with the following procedure:

Top Reinforcement Check:

Except where seismic effects create tensile stresses, top reinforcement in the footing is not necessary if the factored tensile stress at the upper face of the footing does not exceed the flexural strength of structural plain concrete, as follows:

ft = 5(fc)1/2 (Eq. 7) where,

ft = flexural strength of structural plain concrete, psi

fc = compressive strength of concrete, psi

= strength reduction factor for structural plain concrete = 0.55 The effective thickness of the footing for tensile stress calculations should be 2 inches less than the actual thickness for footings cast against soil (ACI 318-02, Section R22.7.4). For footings cast against a seal slab, the actual thickness of the footing may be used for the effective thickness. If the factored tensile stress exceeds the flexural strength of structural plain concrete, top reinforcement should be used if an increase in the footing thickness is not feasible.

The following formulas are for calculating the required footing thicknesses with no top reinforcing steel:

For footings cast against soil:

treqd = teff + 2 inches (Eq. 8a)


Page 24 of 55

For footings cast against a seal slab:

treqd = teff (Eq. 8b)

With teff calculated as follows:

teff = (6Mu/ft)1/2 (Eq. 9)

where,

treqd = required footing thickness with no top reinforcing steel, inches

teff = effective footing thickness, inches Mu = strength design factored moment caused by the weight

of soil and concrete acting on a 1-inch strip in the footing at the face of the pier, inch-pounds per inch, using a load factor of 1.4

ft = flexural strength of structural plain concrete, psi (from Eq. 7)

If tensile stress in the upper face of the footing exceeds ACI plain concrete design requirements, top steel should be used if increasing the footing thickness is unfeasible. If top reinforcement is required, minimum reinforcement is #4 at 12 inches c/c.

4.10.3 Shear Considerations

Both wide-beam action and two-way action must be checked to determine the required footing depth. Beam action assumes that the footing acts as a wide beam with a critical section across its entire width. Two-way action for the footing checks "punching" shear strength. The critical section for punching shear is a perimeter bo around the supported member with the shear strength computed in accordance with ACI Code Sect. 11.12.2.1. Tributary areas and corresponding critical sections for wide-beam action and two-way action for an isolated footing are illustrated in Figure 3 below:


Page 25 of 55

Figure 3 Tributary Area for Wide-Beam and Two-Way Action Shear

(Adapted from Notes on ACI 318 - 02 by PCA)

Tributary Areas and Critical Sections for Shear

For footing design, the depth must be selected so that shear reinforcement is not required. The shear strength equations may be summarized as follows:


Page 26 of 55

Figure 4 Shear Strength of Concrete in Footings

Revision Summary 31 August, 2002 New Saudi Aramco Best Design Practice SABP-004. 6 November, 2007 Revision 1 to comply with ACI 318-02, ASCE 7-02 and revised SAES-M-001 & SAES-Q-005.


Page 27 of 55

APPENDIX:

Tables, Figures, and Examples


Page 28 of 55

Table 1 Thermal Expansion Data

Total linear expansion between 70F and indicated temperature (inches/100 ft)

Temp.

(F) Shell Material Temp.

(F) Carbon Steel

Carbon - Moly Low-Chrome

(through 3 Cr Mo)

5 Cr Mo through 9 Cr Mo

Austenitic Stainless

Steels 18 Cr 8 Ni

12 Cr 17 Cr 27 Cr

12 Cr 20 Ni

Monel 67 Ni 30 Cu

3-1/2 Nickel

Ni-Fe-Cr

70 100 125 150 175

0.00 0.23 0.42 0.61 0.80

0.00 0.22 0.40 0.58 0.76

0.00 0.34 0.62 0.90 1.18

0.00 0.20 0.36 0.53 0.69

0.00 0.32 0.58 0.84 1.10

0.00 0.28 0.52 0.75 0.99

0.00 0.23 0.42 0.61 0.81

0.00 0.28 0.52 0.76 0.99

70 100 125 150 175

200 225 250 275

0.99 1.21 1.40 1.61

0.94 1.13 1.33 1.52

1.46 1.75 2.03 2.32

0.86 1.03 1.21 1.38

1.37 1.64 1.91 2.18

1.22 1.46 1.71 1.96

1.01 1.21 1.42 1.63

1.23 1.49 1.76 2.03

200 225 250 275

300 325 350 375

1.82 2.04 2.26 2.48

1.71 1.90 2.10 2.30

2.61 2.90 3.20 3.50

1.56 1.74 1.93 2.11

2.45 2.72 2.99 3.26

2.21 2.44 2.68 2.91

1.84 2.05 2.26 2.47

2.30 2.59 2.88 3.18

300 325 350 375

400 425 450 475

2.70 2.93 3.16 3.39

2.50 2.72 2.93 3.14

3.80 4.10 4.41 4.71

2.30 2.50 2.69 2.89

3.53 3.80 4.07 4.34

3.25 3.52 3.79 4.06

2.69 2.91 3.13 3.35

3.48 3.76 4.04 4.31

400 425 450 475

500 525 550 575

3.62 3.86 4.11 4.35

3.35 3.58 3.80 4.02

5.01 5.31 5.62 5.93

3.08 3.28 3.49 3.69

4.61 4.88 5.15 5.42

4.33 4.61 4.90 5.18

3.58 3.81 4.04 4.27

4.59 4.87 5.16 5.44

500 525 550 575

600 625 650 675

4.60 4.86 5.11 5.37

4.24 4.47 4.69 4.92

6.24 6.55 6.87 7.18

3.90 4.10 4.31 4.52

5.69 5.96 6.23 6.50

5.46 5.75 6.05 6.34

4.50 4.74 4.98 5.22

5.72 6.01 6.30 6.58

600 625 650 675

700 725 750 775

5.63 5.90 6.16 6.43

5.14 5.38 5.62 5.86

7.50 7.82 8.15 8.47

4.73 4.94 5.16 5.38

6.77 7.04 7.31 7.58

6.64 6.94 7.25 7.55

5.46 5.70 5.94 6.18

6.88 7.17 7.47 7.76

700 725 750 775

800 825 850 875

6.70 6.97 7.25 7.53

6.10 6.34 6.59 6.83

8.80 9.13 9.46 9.79

5.60 5.82 6.05 6.27

7.85 8.15 8.45 8.75

7.85 8.16 8.48 8.80

6.43 6.68 6.93 7.18

8.06 8.35 8.66 8.95

800 825 850 875

900 925 950 975

7.81 8.08 8.35 8.62

7.07 7.31 7.56 7.81

10.12 10.46 10.80 11.14

6.49 6.71 6.94 7.17

9.05 9.35 9.65 9.95

9.12 9.44 9.77

10.09

7.43 7.68 7.93 8.17

9.26 9.56 9.87

10.18

900 925 950 975


Page 29 of 55

Table 1 (continued)

Total linear expansion between 70F and indicated temperature (inches/100 ft)

Temp.

(F) Shell Material Temp.

(F) Carbon Steel

Carbon - Moly Low-Chrome

(through 3 Cr Mo)

5 Cr Mo through 9 Cr Mo

Austenitic Stainless

Steels 18 Cr 8 Ni

12 Cr 17 Cr 27 Cr

12 Cr 20 Ni

Monel 67 Ni 30 Cu

3-1/2 Nickel

Ni-Fe-Cr

1000 1025 1050 1075

8.89 9.17 9.46 9.75

8.06 8.30 8.55 8.80

11.48 11.82 12.16 12.50

7.40 7.62 7.95 8.18

10.25 10.55 10.85 11.15

10.42 10.75 11.09 11.43

8.41 10.49 10.80 11.11 11.42

1000 1025 1050 1075

1100 1125 1150 1175

10.04 10.31 10.57 10.83

9.05 9.28 9.52 9.76

12.84 13.18 13.52 13.86

8.31 8.53 8.76 8.98

11.45 11.78 12.11 12.44

11.77 12.11 12.47 12.81

11.74 12.05 12.38 12.69

1100 1125 1150 1175

1200 1225 1250 1275

11.10 11.38 11.66 11.94

10.00 10.26 10.53 10.79

14.20 14.54 14.88 15.22

9.20 9.42 9.65 9.88

12.77 13.10 13.43 13.76

13.15 13.50 13.86 14.22

13.02 13.36 13.71 14.04

1200 1225 1250 1275

1300 1325 1350 1375

12.22 12.50 12.78 13.06

11.06 11.30 11.55 11.80

15.56 15.90 16.24 16.58

10.11 10.33 10.56 10.78

14.09 14.39 14.69 14.99

14.58 14.94 15.30 15.66

14.39 14.74 15.10 15.44

1300 1325 1350 1375

1400 1425 1450 1475 1500

13.34 12.05 16.92 17.30 17.69 18.08 18.47

11.01 15.29 16.02 15.80 16.16 16.53 16.88 17.25

1400 1425 1450 1475 1500


Page 30 of 55

TABLE 2 Basic Development Length lhb of Standard 90 Hooks in Tension

Ref. ACI Code 318-02 Sections 12.5.2 & 12.5.3 Ref. ACI Design Handbook Publ. SP-17(97) F'c = 4000 psi & Fy = 60,000 psi ldh = (0.02 fy / f'c ) db Development length ldh > 8 db > 6 in. alpha = 0.7 = 1.0 For normal weight concrete = 1.2 for Epoxy coated bars Tmin = ldh+ 3" cover + 1.5

Bar Size Bar Dia. lhb Alpha Beta *ldh 8 db B TMin (db) - in. in. in. in. in. in.

#4 0.500 9.5 0.7 1.2 8.0 6 8 12.5 #5 0.625 11.9 0.7 1.2 10.0 6 10 14.5 #6 0.750 14.2 0.7 1.2 11.9 6 12 16.4 #7 0.875 16.6 0.7 1.2 13.9 7 14 18.4 #8 1.000 19.0 0.7 1.2 16.0 8 16 20.5 #9 1.128 21.4 0.7 1.2 18.0 9 19 22.5 #10 1.270 24.1 0.7 1.2 20.2 10 21.5 24.7 #11 1.410 26.8 0.7 1.2 22.5 11 24 27.0

*ldh can be further reduced by the ratio alpha = As required / As provided

db T ldh B 4.5 on FOOTING ELEVATION


Page 31 of 55

Figure A Approximate Exchanger Weights

These curves give the approximate weight of standard heat exchangers, all in tons. The curves are for a 192-inch type ET exchanger with two passes in the tubes. The tubes are 3/4 inch on a 90 layout. The tube material is 14-gage steel. For the weights of heat exchangers with other tube lengths, multiply by the following factors:

Length in inches: 240 192 168 144 120 96 Heat exchanger factor: 1.10 1.00 0.95 0.90 0.85 0.80

20

App

roxi

mat

e W

eigh

t (to

ns)

Exchanger Diameter (inches)

15 48464442403836343230282624222018

Weight of water to fillshell and tubes

7

14

15

16

18

19

17

8

9

10

11

12

13

0

1

2

3

4

5

6

300

450 P

ound

Clas

s15

0


Page 32 of 55

Figure B Approximate Tube Bundle Weights

These curves give the approximate weight of standard tube bundles, all in tons. The tubes are inch, 14 gage, and 192 inches long. The tubes are two pass on a square pitch. The baffle spacing range from 8 inches on the 15-inch exchanger to 16 inches on the 48-inch exchanger. For the weight of bundle with other lengths, multiply by the following factors:

Length in inches: 240 192 168 144 120 Heat exchanger factor: 1.20 1.00 0.90 0.80 0.70

15

Exchanger Diameter (inches)

484644424038363430282624 32222018

15060

0 Pou

nd C

lass

10

9

8

7

6

5

4

3App

roxi

mat

e W

eigh

t (to

ns)

0

1

2


Page 33 of 55

Figure C Soil Pressure for Biaxially Loaded Footings

Location of SBmax

a

b

SBmax = K (P/ab)

Load P

e 2

e 1

K coefficient

Ratio e1/a

0.40

0.38

0.02

0.00

12 0 10 9 8 7 6 5 4 3 2 1 11

12 0 10 9 8 7 6 5 4 3 2 1 11

0.36

0.34

0.32

0.30

0.28

0.26

0.24

0.22

0.20

0.18

0.16

0.14

0.12

0.10

0.08

0.06

0.04

0.40

0.38

0.02

0.00

0.36

0.34

0.32

0.30

0.28

0.26

0.24

0.22

0.20

0.18

0.16

0.14

0.12

0.10

0.08

0.06

0.04e2/b = 0.40

0.375

0.350.325

0.30

e2/b = 0.0

0.275 0.25

0.225

0.05

0.100.15

0.20

0.175


Page 34 of 55

Example 1 Heat Exchanger Foundation

1ft -

4 in

c hes

1ft -

4 in

c hes

3 ft

-6 i n

ches

5 ft

-6 in

ches

11 ft -0 inches

8 ft -0 inches

1ft -4 inches

PIERSP

IER

(Fix

e d e

nd)

PIE

R

(Slid

ing

end )

Cc c Steel slide plate

3 ft -1 inchby 11 inchesby 3/8 inch

2 - 1 1/4 inch diameterASTM F1554, Grade 36anchor bolts per pierP = 4 inches (fixed end w/1 nut)P = 5 1/4 inches (sliding end w/2 nuts)

Dimensions typical both piers

PLAN

SECTION "A - A"

A A

# 4 ties @ 11 inches

5 - #8 each face

# 6 @ 10 incheseach way

Grade

6 ft

- 6 in

ches

1 ft

-6 in

ches

Top of grout elevation (fixed end)Top of steel slide plate (sliding end)

# 4 @ 10 incheseach way


Page 35 of 55

11ft -0 inches

23 ft -6 inches

8 ft

-0 in

ches

4 ft

-0 in

ches

Shellend

Channelend

42 inchesDiameter

Slide plate

5 ft

-6 in

ches

2 ft -9 inches

ELEVATION

(Example 1, continued)

DESIGN DATA

Exchanger Data: Empty weight = 32 kips each Operating weight = 44 kips each Bundle weight = 19 kips each Channel weight = 3.5 kips each Basic diameter = 42 inches,

or 3.5 ft Max. design temperature

= 550F Exchanger material: carbon steel Bolts: 2 - 1-1/4-inch diameter ASTM

F1554, Grade 36 (galvanized) per pier

Bolt spacing = 2 ft - 8 inch c/c Saddle: 3 ft - 0 inch by 9 inches Load distribution: 60% at channel end,

40% at shell end

Design Criteria: Concrete: f'c = 4,000 psi Reinforcing: fy = 60,000 psi Soil unit weight: = 100 pcf Allowable net soil bearing: SBnet = 5.5 ksf (at 4-ft depth) Wind load: SEI/ASCE 7-02 Earthquake load: SEI/ASCE 7-02

DETERMINE LOADS

Empty and Operating Loads Exchanger weight supplied by outside manufacturers does not include the weight of attached pipes and insulation. Increase exchanger weight by 10% of the larger exchanger to account for these attached items (refer to this Practice, Section 4.2, vertical loads, empty and operating dead loads).


Page 36 of 55

40% at

Shell/Fixed End 60% at

Channel/Sliding End Empty dead load (De) = 32 kips + (32 kips)(1.1) = 67.2 kips 26.9 kips 40.3 kips Operating dead load (Do) = 44 kips + (44 kips)(1.1) = 92.4 kips 37.0 kips 55.4 kips

Transverse Moment from Pipe Eccentricity Eccentricity = (basic diameter)/2 + (1.5 ft) = (3.5 ft)/2 + (1.5 ft) = 3.25 ft Empty MTe (channel end) = (32 kips)(0.1)(0.6 channel end)(3.25 ft) = 6.24 ft-k Empty MTe (shell end) = (32 kips)(0.1)(0.4 shell end)(3.25 ft) = 4.16 ft-k Operating MTo (channel end) = (44 kips)(0.1)(0.6 channel end)(3.25 ft) = 8.58 ft-k Operating MTo (shell end) = (44 kips)(0.1)(0.4 shell end)(3.25 ft) = 5.72 ft-k

Wind Loads Wind load calculations are beyond the scope of this Practice. Exchanger wind load is applied at the center of each exchanger. Transverse wind: Hw = 1.28 kips (per exchanger) Longitudinal wind: Hw = 0.25 kips (per exchanger) Transverse or longitudinal wind on each pier: Hw = 0.039 ksf

Earthquake Loads Earthquake load calculations are beyond the scope of this Practice. Exchanger earthquake loads are applied at the center of each exchanger. Note that the following are strength design loads:

Empty (Per Exchanger)

Operating (Per Exchanger)

Pier

Transverse 5.42 kips 7.45 kips 0.154 W Longitudinal 8.80 kips 12.10 kips 0.250 W

For calculations based on allowable stress design (service loads), the strength design loads shown in the preceding table should be converted to service loads by multiplying by 0.7, in accordance with Table 5.

Empty

(Per Exchanger) Operating

(Per Exchanger)

Pier Transverse 3.79 kips 5.22 kips 0.108 W

Longitudinal 6.16 kips 8.47 kips 0.175 W

Bundle Pull VBp = 1.0 (bundle weight) = 1.0 (19 k) = 19.0 kips The minimum is the lesser of 2 kips or exchanger weight (Section 4.3.3.1). Therefore, use the bundle weight.

Use VBp = 19.0 kips (applied at centerline of top exchanger.) Note that a reduction in the empty load of the exchanger owing to the removal of the exchanger head (channel) to pull the bundle is not included in this foundation calculation because the reduction in the empty load is not considered to have a significant effect on the design.

Thermal Force 1. Compute sliding force (assume that a steel slide plate is used):


Page 37 of 55

Coefficient of friction, = 0.40 (Ref. Section 4.6.3) Operating load, Ff = (Po) = (0.40)(55.4 kips at channel end) = 22.2 kips (Ref. Eq. 1)

2. Compute force required to deflect pier:

Assume pier is 42 inches long by 16 inches wide by 78 inches high. Moment of inertia, I = b(h)3 / 12 = (42 inches)(16 inches)3 / 12 = 14,336 inches4 Modulus of elasticity, (ACI 318-02, Section 8.5.1) E = 57,000 cf' = 57,000 psi 4,000 = 3,605 ksi Thermal expansion coefficient for carbon steel at 550F: = 0.0411 inch/ft (Ref. Table 1) Thermal growth between saddles, = ()(L) = (0.0411 inch/ft)(11 ft) = 0.452 inches T = 3 E I / 2 H3 = 3 (0.452 inch)(3,605 ksi)(14,336 inches4) / 2 (78 inches)3 = 73.8 kips

(Ref. Eq. 2) Because Ff < T and because a lower friction factor will not help the distribution of earthquake and bundle pull

loads, use steel slide plate.

DESIGN ELEMENTS

Size Steel Slide Plate Width = (saddle width) + 2() + 1 inch = (9 inches) + 2 (0.452 inches) + (1 inch)

= 10.90 inches, say 11 inches Length = (saddle length) + 1 inch = (36 inches) + (1 inch) = 3 ft - 1 inch Check bearing stress (operating and longitudinal earthquake): PEo = (12.10 kips)(2.75 ft + 8.25 ft) / (11 ft between piers)

= 12.1 kips (downward load caused by overturning)

Pu = 1.2 (Po) + 1.0 (PEo) = 1.2 (55.4 kips) + 1.0 (12.1 kips) = 78.6 kips (Table 6, Load Combination 3) Pn = 0.85 f'c A1 = (0.65)(0.85)(4 ksi)(11 inches)(37 inches) = 899 kips > Pu OK

(ACI 318-02, Section 10.17) Use a steel slide plate that is 3 ft - 1 inch by 11 inches by 3/8 inches.

Pier Size Pier length

(c/c bolts) + (2)(5-inch minimum anchor bolt edge distance) = (2 ft - 8 inches) + 2 (5 inches) = 3 ft - 6 inches controls

(steel slide plate length) + (4 inches) = (3 ft - 1 inch) + (4 inches) = 3 ft 5 inches

Pier width 10 inches 10% of pier height = (0.10)(78 inches) = 7.8 inches (based on assumed pier height) (2)(5-inch minimum anchor bolt edge distance) = 2 (5 inches) = 10 inches (steel slide plate width) + (4 inches) = (11 inches) + (4 inches) = 15 inches controls, but use 16 inches for forming in 2-inch increments


Page 38 of 55

Use a pier size of 1 ft - 4 inches by 3 ft - 6 inches.

Anchor Bolt Design Anchor bolt design is beyond the scope of this Practice. Refer to SABP-Q-001 for procedures.

Use two 1-1/4-inch diameter, ASTM F1554, Grade 36 anchor bolts per pier.

Pier Design At base of pier (assume footing to be 1.5 ft thick):

Pier height = 8.0 ft - 1.5 ft = 6.5 ft Pier weight = (0.15 kcf)(1.33 ft)(3.5 ft)(6.5 ft) = 4.54 kips

Use load combinations and strength design load factors from Table 6. Operating and longitudinal earthquake at fixed end:

Apply 70% of exchanger earthquake loads at fixed end (Ref. Paragraph 4.3.2.3,) Horizontal load at fixed end,

VuFX = 1.0 [(0.7)(12.10 kips)(2 exchangers) + (0.25)(4.54 kips)] = 16.94 kips + 1.14 kips = 18.08 kips (Table 6, Load Combination 3)

Shear and moment at bottom of pier,

VuFX = 16.94 kips + 1.14 kips = 18.08 kips MuFX = (16.94 kips)(6.5 ft) + (1.14 kips)(6.5 ft/2) = 113.8ft-k


Page 39 of 55

Empty and bundle pull at fixed end:

Bundle pull force, VuBp = 1.6(19.0 kips) = 30.4 kips (Table 6, Load Combination 9 or 10)

Vertical load at top of pier due to bundle pull on top exchanger, PuBp = (30.4 kips)(2.75 ft + 5.5 ft) / (11 ft between piers) = 22.8 kips

Net vertical load on sliding pier pushing top bundle in (use 0.9D for load factor, Table 6, Load Combination 10),

PuSL = (0.9)(40.3 kips) - (22.8 kips) = 13.5 kips

Horizontal load at sliding end, VuSL = (PuSL) = 0.40 (13.5 kips) = 5.40 kips < 1/2 bundle pull force (VuBp)

Horizontal load at fixed end,

VuFX = (VuBp) - (VuSL) = (30.4 kips) - (5.40 kips) = 25.0 kips

Shear and moment at bottom of pier, VuFX = 25.0 kips MuFX = (25.0 kips)(6.5 ft) = 162.5 ft-k

Operating and thermal at fixed end:

Thermal force, VuThermal = 1.4(22.2 kips) = 31.08 kips


VuFX = VuThermal = 31.08 kips

Shear and moment at bottom of pier, VuFX = 31.08 kips controls MuFX = (31.08 kips)(6.5ft) = 202.0 ft-k controls

Check diagonal tension shear:

d = (16-inch pier) (2-inch clear) (0.5-inch ties) (say 1.0-inch bar) / 2 = 13.0 inches

Vc = 2 cf' bw d (ACI 318-02, Eq. 11-3) = (0.75)(2) psi 4,000 (42 inches)(13.0 inches) / 1,000 = 51.8 kips > Vu = 31.08 kips OK

0.5 Vc = (0.5)(51.8 kips) = 25.9 kips < Vu = 31.08 kips

Minimum tie requirements from Section 4.7.3.3 of this Practice is #4 ties at 12-inch spacing; however, because Vu > 0.5 Vc, spacing requirement should be checked for #4 ties to meet minimum shear reinforcement requirements of ACI 318-02, Section 11.5.5:

Av = 0.75 cf' bw s / fy but not less than 50 bw s / fy

sreqd = Av fy / 0.75 cf' bw = (0.20 in2)(2)(60,000 psi) / (0.75) psi 4,000 (42 inches) = 12.0 inches but not more than Av fy / 50 bw = (0.20 in2)(2)(60,000 psi) / (50)(42 inches) = 11.4 inches controls

Use #4 ties at 11-inch spacing.

Design for moment: F = b d2 / 12,000 = (42 inches)(13.0 inches)2 / 12,000 = 0.592


Page 40 of 55

Ku = Mu / F = (202.0 ft-k) / (0.592) = 341.2 = 0.00674 As = b d = (0.00674)(42 inches)(13.0 inches) = 3.68 inches2

The following equation is provided for illustration only; it should not control unless f 'c > 4,440 psi,

As min = 3 c'f bw d / fy = 3 psi 4,000 (42 inches)(13.0 inches) / (60,000 psi) = 1.73 inches2 (ACI 318-02, Eq. 10-3)

As min = 200 bw d / fy = 200 (42 inches)(13.0 inches) / (60,000 psi) = 1.82 inches2 (ACI 318-02, Section 10.5.1)

Find total As requirement including shear friction, Avf at fixed end with LF = 1.4 for (Po + pier weight) at bottom of pier:

Avf = [Vu/() - Pupier] / fy = [(31.08 k)/(0.6)(0.75) - (1.4)(37.0 k + 4.54 k)] / 60 ksi = [69.07 - 58.16] / 60 = 0.18 inches2 (Ref. Eq. 3)

As (total on each face) = As (moment) + Avf/2 = 3.68 + 0.18/2 = 3.77 inches2 controls Use five #8 bars each face (As provided = 3.95 inches2).

Determine #8 splice length:

ld / db = )/(f' 40

))()()(( f 3

c

y

btr dKc + =

)5.2(psi 4,000 401.0)1.0)(1.0)(psi)(1.0)( 3(60,000 = 28.5

(ACI 318-02, Section 12.2.3) ld = (28.5) db = (28.5)(1.0 inch) = 28.5 inches Class B splice = 1.3 (ld) = 1.3 (28.5 inches) = 37.1 inches (ACI 318-02, Section 12.15.1)

Do not use a splice because the pier height is 6 ft - 6 inches < 8 ft -0 inch for #8 bar.

(Ref. Section 4.7.3.1)

Footing Size Determine minimum footing thickness to develop standard hook for #8 pier reinforcing:

ldh = (0.02fy / c'f )(db)(0.7)(Asrequired/Asprovided) (ACI 318-02, Section 12.5)

= [(0.02)(1.0)(1.0)(60,000 psi) / psi 4,000 ](1 inch)(0.7)(3.77 in2/3.95 in2) = 12.7 inches

Minimum thickness = (12.7 inches) + (2 layers)(0.75-inch rebar) + (3 inches clear) = 17.2 inches

Use 18-inch footing thickness.

SBallow = (5.5 ksf net) + (4.0 ft deep)(0.10 kcf soil) = 5.9 ksf gross Try an 8-ft by 5.5-ft footing, 1.5 ft thick.

Weights: Pier = (0.15 kcf)(3.50 ft)(1.33 ft)(8 ft - 1.5 ft) = 4.54 kips Footing = (0.15 kcf)(8 ft)(5.5 ft)(1.5 ft) = 9.90 kips Soil = (0.10 kcf) [(8 ft)(5.5 ft) - (3.50 ft)(1.33 ft)] (4 ft - 1.5 ft) = 9.84 kips Total = (4.54 k) + (9.90 k) + (9.84 k) = 24.28 kips

Soil-bearing and stability ratio checks: Use load combinations for allowable stress design (service loads) from Table 5

Check operating and thermal and eccentric (channel/sliding end):


Page 41 of 55

Thermal force at top of pier, VThermal = 22.2 kips

Maximum axial load at bottom of footing, Pmax = Ps + Po = (24.28 k) + (55.4 k) = 79.68 kips (Table 5, Load Combination 1)

Moments at bottom of footing, ML = (22.2 k)(8 ft) = 177.6 ft-kips MTo (from pipe eccentricity) = 8.58 ft-kips

Check soil bearing using maximum axial load,

e1 = ML / Pmax = (177.6 ft-k) / (79.68 k) = 2.23 ft e2 = MTo / Pmax = (8.58 ft-k) / (79.68 k) = 0.108 ft e1 / a = (2.23 ft) / (8 ft) = 0.279 e2 / b = (0.108 ft) / (5.5 ft) = 0.020 Read Figure C, this Practice: K = 3.20 SBmax = K (Pmax/ab) = (3.20)[(79.68 k)/(8 ft)(5.5 ft)] = 5.79 ksf < SBallow = 5.9 ksf OK

Check operating and longitudinal earthquake and eccentric (channel/sliding end):

Longitudinal operating earthquake load on exchangers,

0.7 VLEo = 8.47 kips applied at the center of each exchanger Vertical load at top of piers from longitudinal operating earthquake load on exchangers (owing to overturning moment),

0.7 PEo = (8.47 kips)(2.75 ft + 8.25 ft) / (11.0 ft) = 8.47 kips

Axial loads at bottom of footing, Pmax = Ps + Po + 0.7 PEo = (24.28 k) + (55.4 k) + (8.47 k) = 88.15 kips (Table 5, Load Combination 3) Pmin = 0.9 (Ps + Po) - 0.7 PEo = (0.9)(24.28 k + 55.4 k) - (8.47 k) = 63.24 kips (Table 5, Load Combination 5a)

Moments at bottom of footing, ML = (0.3 at sliding end)(8.47 k)(2 exchangers)(8.0 ft)

+ (0.175)(4.54 k pier wt)(6.5 ft/2 + 1.5 ft) = 44.43 ft-kips

MTo (from pipe eccentricity) = 8.58 ft-kips

Soil-bearing check using maximum axial load,

e1 = ML / Pmax = (44.43 ft-k) / (88.15 k) = 0.504 ft e2 = MTo / Pmax = (8.58 ft-k) / (88.15 k) = 0.097 ft e1 / a = (0.504 ft) / (8 ft) = 0.063 e2 / b = (0.097 ft) / (5.5 ft) = 0.018 Read Figure C, this Practice: K = 1.50 SBmax = K (Pmax/ab) = (1.50)[(88.15 k)/(8 ft)(5.5 ft)] = 3.00 ksf < SBallow = 5.9 ksf OK

Stability ratio check using minimum axial load, OTML (overturning moment) = [ML + (0.7PEo)(a/2)] = [(44.43 ft-k) + (8.47 k)(8 ft)/2]

= 78.31 ft-k RML (resisting moment)= 0.9(Ps + Po)(a/2) = (0.9)(24.28 k + 55.4 k)(8 ft)/2 = 286.8 ft-k

Stability ratio = RML / OTML = (286.8 ft-k) / (78.31 ft-k) = 3.66 > 1.0

Check operating and longitudinal earthquake and eccentric (shell/fixed end):

Longitudinal operating earthquake load on exchangers, 0.7 VLEo = 8.47 kips applied at the center of each exchanger


Page 42 of 55

Vertical load at top of piers from longitudinal operating earthquake load on exchangers (owing to overturning moment),

0.7 PEo = (8.47 kips)(2.75 ft + 8.25 ft) / (11.0 ft) = 8.47 kips

Axial loads at bottom of footing, Pmax = Ps + Po + 0.7 PEo = (24.28 k) + (37.0 k) + (8.47 k) = 69.75 kips (Table 5, Load Combination 3) Pmin = 0.9 (Ps + Po) - 0.7 PEo = (0.9)(24.28 k + 37.0 k) - (8.47 k) = 46.68 kips (Table 5, Load Combination 5a)

Moments at bottom of footing,

ML = (0.7 at fixed end)(8.47 k)(2 exchangers)(8.0 ft) + (0.175)(4.54 k pier wt)(6.5 ft/2 + 1.5 ft) = 98.64 ft-kips

MTo (from pipe eccentricity) = 5.72 ft-kips

Soil-bearing check using maximum axial load, e1 = ML / Pmax = (98.64 ft-k) / (69.75 k) = 1.41 ft e2 = MTo / Pmax = (5.72 ft-k) / (69.75 k) = 0.082 ft e1 / a = (1.41 ft) / (8 ft) = 0.176 e2 / b = (0.082 ft) / (5.5 ft) = 0.015 Read Figure C, this Practice: K = 2.15 SBmax = K (Pmax/ab) = (2.15)[(69.75 k)/(8 ft)(5.5 ft)] = 3.41 ksf < SBallow = 5.9 ksf OK

Stability ratio check using minimum axial load, OTML (overturning moment) = [ML + (0.7PEo)(a/2)] = [(98.64 ft-k) + (8.47 k)(8 ft)/2]

= 132.5 ft-k RML (resisting moment) = 0.9(Ps + Po)(a/2) = (0.9)(24.28 k + 37.0 k)(8 ft)/2

= 220.6 ft-k Stability ratio = RML / OTML = (220.6 ft-k) / (132.5 ft-k) = 1.66 > 1.0 OK

Check empty and longitudinal earthquake and eccentric (channel/sliding end) loads:

Longitudinal empty earthquake load on exchangers,

0.7 VLEe = 6.16 kips applied at the center of each exchanger

Vertical load at top of piers from longitudinal empty earthquake load on exchangers (owing to overturning moment),

0.7 PEe = (6.16 kips)(2.75 ft + 8.25 ft) / (11.0 ft) = 6.16 kips

Minimum axial load at bottom of footing, Pmin = 0.9 (Ps + Pe) - 0.7 PEe = (0.9)(24.28 k + 40.3 k) - (6.16 k) = 51.96 kips (Table 5, Load Combination 5b)

Longitudinal moment at bottom of footing, ML = (0.3 at sliding end)(6.16 k)(2 exchangers)(8.0 ft)


Stability ratio check using minimum axial load, OTML (overturning moment) = [ML + (0.7PEe)(a/2)] = [(33.34 ft-k) + (6.16 k)(8 ft)/2]

= 57.98 ft-k RML (resisting moment)= 0.9(Ps + Pe)(a/2) = (0.9)(24.28 k + 40.3 k)(8 ft)/2 = 232.5 ft-k


Check empty and longitudinal earthquake and eccentric (shell/fixed end):


Page 43 of 55

Longitudinal operating earthquake load on exchangers,

0.7 VLEe = 6.16 kips applied at the center of each exchanger

Vertical load at top of piers from longitudinal empty earthquake load on exchangers (owing to overturning moment),

0.7 PEe = (6.16 kips)(2.75 ft + 8.25 ft) / (11.0 ft) = 6.16 kips

Minimum axial load at bottom of footing, Pmin = 0.9 (Ps + Pe) - 0.7 PEe = (0.9)(24.28 k + 26.9 k) - (6.16 k) = 39.90 kips (Table 5, Load Combination 5b)

Longitudinal moment at bottom of footing, ML = (0.7 at fixed end)(6.16 k)(2 exchangers)(8.0 ft)


Stability ratio check using minimum axial load, OTML (overturning moment) = [ML + (0.7PEe)(a/2)] = [(72.77 ft-k) + (6.16 k)(8 ft)/2]

= 97.41 ft-k RML (resisting moment)= 0.9(Ps + Pe)(a/2) = (0.9)(24.28 k + 26.9 k)(8 ft)/2 = 184.2 ft-k


Check operating and transverse earthquake and eccentric (channel/sliding end):

Transverse operating earthquake load on exchangers, 0.7 VTEo = 5.22 kips applied at the center of each exchanger

Axial loads at bottom of footing,

Pmax = Ps + Po = (24.28 k) + (55.4 k) = 79.68 kips (Table 5, Load Combination 3) Pmin = 0.9 (Ps + Po) = (0.9)(24.28 k + 55.4 k) = 71.71 kips (Table 5, Load Combination 5a)

Transverse moment at bottom of footing, MT = (5.22 kips) [(2.75 ft + 8.0 ft) + (5.5 ft + 2.75 ft + 8.0 ft)] (0.6 channel end)

+ (0.108)(4.54 k pier wt)(6.5 ft/2 + 1.5 ft) + (8.58 ft-k pipe eccentricity) = 95.47 ft-kips


e = MT / Pmax = (95.47 ft-k) / (79.68 k) = 1.20 ft > b/6 = (5.5 ft)/6 = 0.92 SBmax = 2 Pmax / [3 a (b/2 - e)] = 2 (79.68 k) / [3 (8 ft) (5.5 ft /2 - 1.20 ft)]

= 4.28 ksf < SBallow = 5.9 ksf gross OK (Ref. Eq. 5)

Stability ratio check using minimum axial load, RMT = (Pmin) (b/2) = (71.71 kips)(5.5 ft / 2) = 197.2 ft-k Stability ratio = RMT / OTMT = 197.2 ft-k / 95.47 ft-k = 2.07 > 1.0 OK

Check operating and transverse earthquake and eccentric (shell/fixed end):

Transverse operating earthquake load on exchangers,

0.7 VTEo = 5.22 kips applied at the center of each exchanger

Axial loads at bottom of footing, Pmax = Ps + Po = (24.28 k) + (37.0 k) = 61.28 kips (Table 5, Load Combination 3)


Page 44 of 55

Pmin = 0.9 (Ps + Po) = (0.9)(24.28 k + 37.0 k) = 55.15 kips (Table 5, Load Combination 5a)

Transverse moment at bottom of footing, MT = (5.22 kips) [(2.75 ft + 8.0 ft) + (5.5 ft + 2.75 ft + 8.0 ft)] (0.4 shell end)



e = MT / Pmax = (64.43 ft-k) / (61.28 k) = 1.05 ft > b/6 = (5.5 ft)/6 = 0.92 SBmax = 2 Pmax / [3 a (b/2 - e)] = 2 (61.28 k) / [3 (8 ft) (5.5 ft /2 - 1.05 ft)]

= 3.00 ksf < SBallow = 5.9 ksf gross OK (Ref. Eq. 5) Stability ratio check using minimum axial load,

RMT = (Pmin) (b/2) = (55.15 kips)(5.5 ft / 2) = 151.7 ft-k Stability ratio = RMT / OTMT = 151.7 ft-k / 64.43 ft-k = 2.35 > 1.0 OK

Check empty and transverse earthquake and eccentric (channel/sliding end):

Transverse empty earthquake load on exchangers,

0.7 VTEe = 3.79 kips applied at the center of each exchanger

Minimum axial load at bottom of footing, Pmin = 0.9 (Ps + Pe) = (0.9)(24.28 k + 40.3 k) = 58.12 kips (Table 5, Load Combination 5b)

Transverse moment at bottom of footing, MT = (3.79 kips) [(2.75 ft + 8.0 ft) + (5.5 ft + 2.75 ft + 8.0 ft)] (0.6 channel end)


Stability ratio check using minimum axial load,


Check empty and transverse earthquake and eccentric (shell/fixed end):

Transverse empty earthquake load on exchangers,

0.7 VTEe = 3.79 kips applied at the center of each exchanger

Minimum axial load at bottom of footing, Pmin = 0.9 (Ps + Pe) = (0.9)(24.28 k + 26.9 k) = 46.06 kips (Table 5, Load Combination 5b)

Transverse moment at bottom of footing, MT = (3.79 kips) [(2.75 ft + 8.0 ft) + (5.5 ft + 2.75 ft + 8.0 ft)] (0.4 shell end)




Check empty and bundle pull and eccentric (channel/sliding end; pulling top bundle out):

Vertical load from bundle pull on top exchanger,

PBp = (19.0 kips)(2.75 ft + 5.5 ft) / (11 ft) = 14.25 kips

Vertical load on sliding end at top of pier,


Page 45 of 55

PSL = Pe + PBp = (40.3 kips) + (14.25 kips) = 54.55 kips

Horizontal load at sliding end, VSL = (PSL) = (0.4)(54.55 kips) = 21.82 kips Note that the horizontal load on the sliding end computed on the basis of friction is greater than half of the total bundle pull (19.0 kips). Therefore, because the two pedestals and footings are equal in size and thus even in stiffness, the actual horizontal load will be the same on both pedestals. VSL = VFX = 19.0 kips/2 piers = 9.5 kips

Maximum axial load at bottom of footing,

Pmax = Ps + PSL = (24.28 k) + (54.55 k) = 78.83 kips (Table 5, Load Combination 8)

Moments at bottom of footing, ML = (VSL)(8.0 ft) = (9.5 kips)(8.0 ft) = 76.0 ft-kips MTe (from pipe eccentricity) = 6.24 ft-kips


e1 = ML / Pmax = (76.0 ft-kips) / (78.83 kips) = 0.96 ft e2 = MTe / Pmax = (6.24 ft-kips) / (78.83 kips) = 0.08 ft e1 / a = (0.96 ft) / (8 ft) = 0.120 e2 / b = (0.08 ft) / (5.5 ft) = 0.015 Read Figure C, this Practice: K = 1.80 SBmax = K (Pmax/ab) = (1.80) [(78.83 k) / (8 ft)(5.5 ft)] = 3.23 ksf < SBallow = 5.9 ksf OK

Check empty and bundle pull and eccentric (shell/fixed end; pulling top bundle out):

Vertical load from bundle pull on top exchanger,

PBp = (19.0 kips)(2.75 ft + 5.5 ft) / (11 ft) = 14.25 kips

Vertical load on fixed end at top of pier, PFX = Pe - PBp = (26.9 kips) - (14.25 kips) = 12.65 kips


VFX = VSL = 19.0 kips/2 piers = 9.5 kips

Minimum axial load at bottom of footing, Pmin = Ps + PFX = (24.28 k) + (12.65 k) = 36.93 kips (Table 5, Load Combination 8)

Moments at bottom of footing, ML = (VFX)(8.0 ft) = (9.5 kips)(8.0 ft) = 76.0 ft-kips MTe (from pipe eccentricity) = 4.16 ft-kips


RML = Pmin (a/2) = (36.93 kips)(8.0 ft / 2) = 148 ft-k Stability ratio = RML / OTML = 148 ft-k / 76.0 ft-k = 1.94 > 1.5 OK

Use 8-ft by 5.5-ft by 1.50-ft footing.

Footing Design

Use load combinations and strength design load factors from Table 6. Operating and thermal and eccentric (channel/sliding end):

Load factors are from Table 6, Load Combination 1. Thermal force at top of pier,

VuThermal = 1.4 (VThermal) = 1.4 (22.2 k) = 31.08 kips


Page 46 of 55

Axial load at bottom of footing,

Pu = 1.4 (Ps + Po) = 1.4 (24.28 k + 55.4 k) = 111.6 kips

Moments at bottom of footing, MuL = (VuThermal)(8 ft) = (31.08 k)(8 ft) = 248.6 ft-kips MuTo (from pipe eccentricity) = 1.4 (MTo) = 12.01 ft-kips

Maximum factored soil bearing,

eu1 = MuL / Pu = (248.6 ft-k) / (111.6 k) = 2.23 ft > a/6 = (8 ft)/6 = 1.33 ft eu2 = MuTo / Pu = (12.01 ft-k) / (111.6 k) = 0.108 ft Because transverse eccentricity is very small, it can be ignored in calculations of factored soil bearing for design of footing reinforcing. SBumax = 2 (Pu) / (3b)(a/2 - eu1) = (2)(111.6 k) / (3)(5.5 ft)[(8 ft)/2 - (2.23 ft)] = 7.64 ksf

Calculate bearing length according to Equation 6, this Practice,

Bearing length (longitudinal direction) = 3 (a/2 - eu1) = 3 [(8 ft)/2 - (2.23 ft)] = 5.31 ft

Factored soil bearing at face of pier (for checking moment), SBuface of pier = (7.64 ksf)(5.31 ft - 3.33 ft) / (5.31 ft) = 2.85 ksf

Factored soil bearing at distance d from face of pier (for checking shear),

d = (18-inch footing) - (3 inch clear) - 1.5 (0.75-inch rebar) = 13.87 inch = 1.16 ft SBud from face of pier = (7.64 ksf)(5.31 ft - 3.33 ft + 1.16 ft) / (5.31 ft) = 4.52 ksf

2.85

ks f

4.52

ksf

7 .64

ks f

1.16 ft3.33 ft

8.00 ft5.31 ft

Operating and longitudinal earthquake and eccentric (shell/fixed end

SABP Q 004 Hx Hor Vessels

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