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What is Vibroflotation Ground Improvement Method?

Vibroflotation is a technique developed in Germany in the 1930s for in situ densification of thick layers of loose granular soil deposits. Vibroflotation was first used in the United States about 10 years later. The process involves the use of a vibroflot (called the vibrating unit).

The device is about 2 m in length. This vibrating unit has an eccentric weight inside it and can develop a centrifugal force.

The weight enables the unit to vibrate horizontally. Openings at the bottom and top of the unit are for water jets. The vibrating unit is attached to a follow-up pipe. The figure below shows the vibroflotation equipment necessary for compaction in the field.

The entire compaction process can be divided into four steps:

Step 1. The jet at the bottom of the vibroflot is turned on, and the vibroflot is lowered into the ground.
Step 2. The water jet creates a quick condition in the soil, which allows the vibrating unit to sink.
Step 3. Granular material is poured into the top of the hole. The water from the lower jet is transferred to the jet at the top of the vibrating unit. This water carries the granular material down the hole.
Step 4. The vibrating unit is gradually raised in about 0.3 m lifts and is held vibrating for about 30 seconds at a time. This process compacts the soil to the desired unit weight.

Design Of Concrete Plate Elements From Finite Element Analysis Spreadsheet

A concrete slab is a common structural element of modern buildings. Horizontal slabs of steel reinforced concrete, typically between 10 and 50 centimetres thick, are most often used to construct floors and ceilings, while thinner slabs are also used for exterior paving.

In many domestic and industrial buildings a thick concrete slab, supported on foundations or directly on the subsoil, is used to construct the ground floor of a building. In high rise buildings and skyscrapers, thinner, pre-cast concrete slabs are slung between the steel frames to form the floors and ceilings on each level.

Calculation Reference
Reinforced Concrete Design

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Design of WT Braces Spreadsheet

In most commercial buildings, floor and roof diaphragms are used to distribute loads in the horizontal plane of the structure to the lateral load resisting system.

Due to the open nature of most industrial structures, diaphragms are not present, and horizontal bracing is often used to distribute the loads in the horizontal plane. Horizontal bracing is also used in heavily-loaded commercial structures, where a diaphragm is not present, or where the strength or stiffness of the diaphragm is not adequate.

When horizontal bracing is used, the beams at that elevation become members in a horizontal truss system, carrying axial loads in addition to the normal bending and shear gravity loads. Careful attention should be paid to the beam end connections within the truss system because the axial loads transferring through the connections can be large.

Selection of Structural Shapes: The most common shapes used for horizontal bracing are single angles and WT shapes.

Single angles are the most economical shape for resisting small and medium loads, because WT shapes must be split from W shapes and straightened by the fabricator. WT shapes can be used to resist larger loads and where long spans are required.

Calculation Reference
Design of Commercial Buildings

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Shear Lug Design Verification Spreadsheet

Design of shear lugs for column base plates. The design is based on the procedure presented in AISC Steel Design Guide 1, Base Plate and Anchor Rod Design, 2nd Edition and AISC Steel Design Guide 7, Industrial Buildings, Roofs to Anchor Rods, 2nd Edition.

Calculation Reference
Building Code Requirements for Structural Concrete, ACI 318-08, (ACI 318)

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Shackle Calculations and Lookup Tables Spreadsheet

Calculation Reference
Pad Eye

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SemiCircular Tension Fitting Calculation Spreadsheet

Purpose of calculation: Calculate stress in a ‘semi circular’ tension fitting (or bath tub fitting).
Calculation Reference: UK railway industry method (the British Rail “Brown Book” method).
Calculation Validation: Independent verification is required.

Calculation Reference
Peterson’s Stress Concentration

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Design For Roof Purlins Spreadsheet

This spreadsheet is to be used to check the adequacy of roof purlins for a specified combination of loads. The designis based on the maximum yeild strength (Mn = FySx) as stated in the AISC Manual 13th Ed. This spread sheet can only be used for load combinations with two variables. In most cases the worst case scenario is 0.6DL+W, so this should be adequate. Only the values in the highlighted cells need to be changed.

Calculation Reference
Roof Design

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