Building construction methods and materials

Details Building construction methods and materials Building construction methods and materials

1993-10-29

1995-09-05

Taylor, Dennis L.

Hydraulic and earth engineering

Earth treatment or control

Shoring, bracing, or cave-in prevention

405274, 405281, F02D 502

Patent

active

054473934

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

This invention relates to improvements in building and civil engineering construction methods and materials particularly related to sheetpiling for ground support and site drainage.


BACKGROUND ART

Sheetpiling has been used in the construction industry for over 200 years (for example) to support excavations, create cut-offs and stabilize ground slopes. The sheetpiling can be used as either a free-standing structure or used in conjunction with tie-backs, props or ground anchors. The earth pressure and groundwater forces on the sheetpiles are dispersed along and across the sheetpiles making flexural strength of the sheetpile the main factor in design of the sheetpile.
Conventional sheetpiling consists of hot rolled steel sections (+5 mm thick) manufactured to `unit` profiles which are linked through interlocking joints to create composite structures. Since 1933, a variety of light sheetpiles have been developed using thin (t=<5 mm), steel plate cold formed or rolled into lighter versions of conventional sheetpile profiles. Some use has also been made of pleated or corrugated profiles as light sheetpiles.
Sheetpiling can be divided into two types representing to create a U or Z profile in a narrow (ws<600 mm) sheetpile that are linked with interlocking joints to form a repetitive and/or deeper section profile; and trapezoidal profiles that repeat across a wider sheet (w=400 to 800 mm), where (t) is the thickness of the material and (w) is the effective width of the sheetpile). lateral stability, joint design, driving capacity, manufacture and construction aspects. The types of sheetpile can be categorized by section profile parameters (d, f, i, w, n and t) and overall sheet parameters (Ws, N) as defined further below.
Conventional sheetpiles are usually made up in a single `U` or `Z` profile linked through the joint between sheetpiles to form a symmetrical section profile. The eccentric loads created during driving and loading of these unsymmetrical sheetpile units can be accommodated by the heavier construction of conventional (t>5 mm) sheetpiles. However, light (t=<5 mm) sheetpiles have to be formed to a symmetrical section profile to avoid eccentric loads during driving and loading of the sheetpiling. Thus the full profile has to be formed within each sheetpile, including the jointing system. On light sheetpiles (t=<5 mm), the lateral load distribution across the sheetpile has been a factor in limiting the sizing, and effective width of the profile. These two requirements have been key factors in restricting the sizing section profiles of light sheetpiles.
The structural form of the section profile adopted for sheetpiling can be related to a flange width (f) to section depth (d) by the (f/d) ratio and the web inclination (i). These parameters fit within specific ranges which determine the structural performance of the sheetpiling. Conventional sheetpiles have adopted a limited range of flange widths (f) which results in a progressive decrease in the f/d ratio as the section depth (d) increases, viz:


______________________________________ DEPTH (f) RATIO (mm) (d) ______________________________________ <120 1.6 < f/d < 4.0 120 < d < 250 0.8 < f/d < 2.4 250 < d < 450 0.5 < f/d < 1.5 450 < d no examples ______________________________________
Light (t=<5 mm) sheetpiles have adopted a wide range of (f/d) ratios (0.3<f/d<3.5) due to the shallow (d<100 mm), profiles used in this type of sheetpile. The web inclination (i) verses (f/d) ratio reflects the limits existing on the (f/d) ratio and section depth (d).
Lateral stiffness and strength of the sheetpile control the sheetpile's effective width (ws) and thickness (t). A survey of typical sheetpiling systems indicates that conventional sheetpiles lie within sheetpile width to thickness (ws/t) ratios of 20 to 140. The (ws/t) ratio for light (t=<5 mm) sheetpiles ranges from 40 to 190. Structural Codes impose upper limits of 60 to 100 on (ws/t) ratios, although (ws/

REFERENCES:
patent: 1085493 (1914-01-01), Schiffler
patent: 1951152 (1934-03-01), Janssen
patent: 3822557 (1974-07-01), Frederick
patent: 4419030 (1983-12-01), Butkenper

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