Deep Xcav Waler Beams Theory Man
WALE BEAM THEORY MANUAL DeepXcav software program (Version 2011) (ParatiePlus within Italy)
Version 1.0 Issued: 1-Nov-2010 Deep Excavation LLC www.deepexcavation.com
TABLE OF CONTENTS A. INTRODUCTION B. DESIGN OF THE BRACING Walings C. MODELING WALE BEAMS WITH DEEPXCAV 1. Program presentation - Inserting a waler 2. Load cases 3. Vertical spacing options 4. Results D. REFERENCES
A. Introduction This document describes how DeepXcav can analyze wale beams. Wale beams are structural elements that are used to brace the walls horizontally and mainly transfer the loads exerted on the walls more or less uniformly to the bracing (tiebacks, struts, etc). The following sections include brief theoretical descriptions of typical wale beams as well as user instructions. Within the software, wale beams can be added on any support graphically. The walers do not contribute in the support stiffness within the non linear analysis but are treated solely as structural elements.
B. DESIGN OF THE BRACING Walings Whereas retaining walls span vertically, walings are needed to transfer loads from the sheeting to the struts, which provide the bracing, or to the anchors, which retain the sheeting. The do not need to be continuous as, for example, in hammer head struts used against diaphragm wall panels where separate waling reinforcement may be included within the panel reinforcement of the wall. Alternatively, with anchored diaphragm walls it is common to incorporate waling rebar steel to the full panel width without external walings. Where secant pile walls are used in cofferdams, and where every pile or alternate piles are anchored, walings may not be necessary. Common waling arrangements are shown in Figure B1. Where steel walings are subjected to heavy loads it may be convenient to use steel beams in pairs in order to provide adequate width on which to seat the bracing struts. It is often convenient to weld end plates to each length of waling to connect them together. It is vital that where rakers or sloping struts are used the tendency for the waling to turn on its support must be resisted. Figures B.2 and B.3 show a typical detail. Where anchors are used with walings, the spacing between steel beams must be sufficient to accommodate the inclined tendon between them, or the pair of beams must be inclined, with an adequate gap. If steel sheet piling is used it is usual to make the walings continuous over two supports. Unless the piling can be driven to good tolerances in the vertical and horizontal alignment it is prudent to allow walings to cantilever mid-way between struts without connecting one to the other. Where tolerances are likely to be well maintained, it is advantageous to connect the ends of walings behind the incoming strut (Figure B.4). Where walings are continuous over two spans and joined behind struts the design moment is WL/10, but where they cantilever to half span the design moment becomes WL/8. When steel sheet piles are braced by steel walings any irregular alignment of steel piles is rectified by steel packers or hardwood wedges. Where the alignment is particularly poor, concrete infilling can be used between the waling and the sheeters. If diagonal struts transfer longitudinal thrust into the walling, the waling must be designed to take both this thrust and bending stresses due to the span between the struts. It may be necessary to weld steel angles to the back of the walings, prior to erection in order that horizontal acting shear keys can be formed by concreting the leg of the angle in to the pan of the sheet pile. This will be required if the available length of waling is short and therefore the frictional resistance between waling and sheet pile is insufficient to transfer the thrust (Figure B.5). Alternatively steel shear plates occupying the whole pile pan can be welded to the waling and the face of the sheet pile. Where heavily loaded struts or highly loaded anchors bear on steel walings it will be necessary to use web stiffeners to avoid web buckling on the waling. A typical detail is shown in Figure B.6. DeepXcav does not handle the stiffener design.
Figure B.1. Typical waling details, steelwork and reinforced concrete. (Adapted from Deep Excavations Manual, 2nd Edition)
Figure B.2. Typical steelwork detail at junction of rakers and waling with bracing to prevent rotation of waling.
Figure B.3. Typical connection detail to avoid rotation of waling at junction with strut.
Many times, reinforced concrete diaphragm walls use internal walings within the reinforcement cages, such cages must be reinforced for shear where the anchor or strut bears on the waling but must avoid impeding the passage of tremie tubes through the waling beam reinforcement. Figure B.7 shows typical arrangements of both steel and reinforced concrete waling. Walings used with inclined anchors may themselves be inclined, with the anchor plate bearing directly on the face of the waling. Gusset plates welded to each pile face incline the waling. Alternatively, the waling may bear directly on to the sheeting with the bearing plate inclined. Figure B.8 illustrates the arrangements.
Figure B.4. Sheet piled cofferdam construction: Shear keys at rear of waling transfer thrust from diagonal strut into short waling length and through sheeters into soil a rear of piles
Figure B.5. Typical detail of web stiffener in waling to avoid web buckling.
Figure B.6. Waling systems used with diaphragm walls. 11
Figure B.7. Wailing details with inclined anchors, shown with typical Berlin wall.
C. MODELING WALE BEAMS WITH DEEPXCAV 1. Program presentation – Inserting a Wale Beam As presented in the previous chapter, walings are needed to transfer loads from the walls to the struts, which provide the bracing, or to the anchors, which retain the sheeting. The walings can be either steel or concrete beams, which are placed at the intersection point of the wall and the support. The following Figures show a waling beam placed on a wall supported with a tie-back (C.1 , C.2), a strut (C.3 , C.4), a raker (C.5 , C.6) and a spring (C.7 , C.8), as well as two walls connected with a strut (C.9), as presented in the program.
Figure C.1. A steel section (HE-Type) waler used with a tie-back.
Figure C.2. A concrete section waler used with a tie-back.
Figure C.3. A steel section (HE-Type – 2 Beams) waler used with a strut (on one wall).
Figure C.4. A concrete section waler used with a strut (on one wall). .
Figure C.5. A steel section (HE-Type – 2 Beams) waler used with a raker.
Figure C.6. A concrete section waler used with a raker.
Figure C.7. A steel section (UPN-Type – 2 Beams) waler used with a spring.
Figure C.8. A concrete section waler used with a spring.
Figure C.9. A steel section (HE-Type) waler used on the left side and a concrete section waler used at the right side of the strut that connects two walls. In order to insert a new waling, the user has first to go to “Loads/supports” tab and then to choose the “Wales” button (Figure C.10a). Next, the user has to select the support at which he wants to add the waling (Figure C.10b). This will cause the Wale Beam window to open (Figure C.11). Then, by clicking the “Edit” button of this form, the “Wale Sections” window is opened (Figure C.12), where the user can choose the section that he wants to use for the waler. This can be either a concrete section with user specified characteristics, or a steel beam section, chosen from a wide list of choices.
Figure C.10b. Wale beam button on “Loads/Supports” tab.
Figure C.10b. Choice of Support.
Figure C.11. Wale Beam window. (Click on edit to modify the wale section)
Figure C.12. Wale Sections window. In case of tiebacks or spring supports, the user may decide to use multiple steel beams with the same wale section, or rotate the wale beams (Figure C.13). In these two cases, the wale section may use the angle of the spring or the tieback supports, or another custom value entered by the user. (Figure C.14). With other support types or when a single beam is used as a waler, the waler cannot be inclined. As Figure C.12 shows, many different wale sections can be added. These wale sections can later be used on any other wale beam and in any other design section.
Figure C.13. Choices for multiple beams and rotation angle (for steel walers).
Figure C.14. Three steel section (HE-Type) walers used with a tie-back (Autorotation option 20
C. MODELING WALE BEAMS WITH DEEPXCAV C2. Load cases As shown in Figure C.11, the user can choose the waler’s load model. He can choose between point loads and uniform loads. • Point loads The user can define the waler’s loading by selecting one loading option from the following (Fig. C15 – C.17):
Figure C.15. Point Load Types 0 and 1
Figure C.16. Point Load Types 2 and 3
Figure C.17. Point Load Types 4 and 5 • Uniform loads The user can define the waler’s loading by selecting one loading option from the following (Fig. C18 – C.22):
Figure C.18. Uniform Load Types 0 and 1
Figure C.19. Uniform Load Types 2 and 3
Figure C.20. Uniform Load Types 4 and 5
Figure C.21. Uniform Load Types 6 and 7
Figure C.22. Uniform Load Type 8 In addition, the user can define the value of the axial force. The program provides the following options: • Zero Axial Force: The axial force receives a value equal to zero. • Percentage of support reaction: The axial force receives as value equal to a user defined percentage of the support reaction. • User defined value: The axial force receives a specific value, defined by the user. All these are shown in Figure C.11.
C. MODELING WALE BEAMS WITH DEEPXCAV 3. Vertical spacing options The vertical spacing is the distance between the vertical support points that connect the wale beam with the wall. The program provides the following options for modeling the vertical spacing: • Use support spacing: This means that as vertical spacing will be used the horizontal spacing as entered in the supports form (spacing between the tiebacks, struts, etc). • Use wall spacing: As vertical spacing will be used the distance between the wall parts. • User defined value: The user defines a specific value for the vertical spacing. All these are shown in (Figure C.23) below.
Figure C.23. Choosing Vertical spacing.
C. MODELING WALE BEAMS WITH DeepXcav 4. Results The program calculates the maximum value of the moment for the span and the supports in both directions, the maximum value of the shear and the stress. Also, it calculates the force and the moment capacity of the wales in both directions, as well as the factor of safety (FS). The user has to press the calculation button at the down right side of the main screen to calculate either the specific or all the design sections (Figure C.24), and has to double click on the waler in order to see the results for the Wale Beams. The results are presented not only for the current stage (Figures C.25 and C.26) but also for all stages in form of a table (Figure C.27).
Figure C.24. Calculation Buttons.
Figure C.25. Loads applied on the walers. Fxx = F cos(β-α)* Fyy = F sin(β-α)* Mxx = General equation(Fxx , LHorizontal) Mxx = General equation(Fyy , LVertical) 26
Mxx,Dead = (Wl2/8) cos(β-α) FS** Myy,Dead = (Wl2/8) sin(β-α) FS** * F includes all factors for each design approach ** FS is a multiplying factor for dead loads
Figure C.26. Results for current stage (Steel section waler)
Figure C.27. Results for current stage (Concrete section waler)
Figure C.28. Results for all construction stages (Steel section waler)
D. REFERENCES 1. Puller M., “Deep Excavations: A practical manual”, WILEY, 2003. 2. NAVFAC, “Foundations and earth structures”, Design Manual 7.02, 1996.