Overall buckling analysis of frames- Approximate methods

method of overall buckling load are included because it indicates an upper bound for the critical gravity load and it allows an assessment of the relative vulnerability of the building to transverse buckling or torsional buckling and for structures which an approximate p-delta analysis to amplification factor for the displacements and moments.

Shear mode

this mode is when double bending of the columns and girders buckling occurs in resistant frames as a result of story sway.

shear buckling

Flexural mode

in this mode, the entire structure buckles as a flexural cantilever by axial deformations of the columns. the greater the slenderness of structure it becomes more vulnerable  to instability in the flexural mode as opposed to the shear mode.

flexural buckling in structure

Combined shear and flexural modes

this is a contribution of shear and flexural modes, in this case of the buckling of a vertical cantilever with a gravity load as its top, below solution exists

1/Pcr = 1/Pf + 1/Ps

Pcr, Pf and Ps = critical loads for the combined, flexural and shear modes of buckling respectively.

flexural-shear buckling in structure

Common types of roof truss - wood or steel truss

what we call a truss is a structural composed of slender members joined at there end points making a frame sort a thing, in construction industry its widely used either with wood struts, metal bars, angles or channels. these thing are joined with bolts, nail, or welding depending on the material used.

Truss used to support roof depends on the span, slop, and the roof materials. below are the common types used:

1. scissors
2. Howe
3. Pratt
4. Fan
5. Fink
6. Cambered fink
7. warren
8. Sawtooth
9. Bowstring
10. Three-Hinged arch

1. Scissors

2. Howe

3. Pratt

4. Fan

5. Fink

6. Cambered fink

7. warren

warren truss used in bridges

8. Sawtooth

sawtooth is very famous used in factory roofs

9. Bowstring

bowstring roof

10. Three-Hinged arch

below is a list of truss used in construction industry depending on design and use.

steps on How to do New floor screeding

for a new cement/sand floor screeding, its better for the floor if the mix ratio can be 1:4, 1 part cement to 4 parts sand.  if you are not planing to put over load goods or things there is no need for reinforcement, the thickness of the screeding slab can be 50mm or 2 inch thick.

Step 1; do floor blending with a good earth compactor.

Step 2; Using a tube level, bench mark every 2m or 6 feets so that the whole floor is even

Step 3; if your not using a pipe, use the mixed cement and make a trench with a ruler section

 now that there are two side with same height as the above pic, and center is with no cement mix.

Step 4; pour the cement mortar and spread it and using a trowel you can fine smooth it.

Source; www.yd-mv.com

How to do toilet floor

Top of the slab
 Courtesy of YD Works

Toilet to be constructed on top of a slab with dimension 4 feet x 5 feet, so for this job, there is a 4inch dia UPVC Pipe drilled in to the slab, make sure you have the correct gap between the wall the pipe.

Bench marked for floor screeding
Courtesy of YD Works

Point "A" is the floor drain after drilling hole of 2inch with a pipe fitted, than find the top level of drain and find the top level of "B", make sure the levels differs by 12mm, so that it creates a slop. "C" is where WC is to be fitted.

Floor screeding completed
courtesy of YD Works

ones the floor screeding is completed, now that there is a slop of 12mm from one end to the drain, now that its ready for tiles work

floor tiles completed

Wall Tiles completed

after the tiles is completed, fill the gaps with white water resisting cement. after all the caps been filled, fit the WC on top of the pipe and secure the WC with sealant.

Monster Foundation

The 800-meter (1,827 feet) Burj Dubai will need the mother of all foundations to support a super-structure that is expected to weigh 500,000 tons. The tower will rest on a 3.7m-thick triangular frame foundation supported by 192 rounded steel piles or support cylinders measuring 1.5m in diameter and extending 50m (164 ft.) below the ground.

Soil Compaction for better construction project

What is soil Compaction?
Soil compaction is when soil particles are pressed together making the air voids minimum as possible.

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reasons why we need to compact soil ;

• Increases load-bearing capacity
• Prevents soil settlement and frost damage
• Provides stability
• Reduces water seepage, swelling and contraction
• Reduces settling of soil

Machines used for compaction;

• Smooth wheel Rollers
• Sheepsfoot Rollers
• Rubber- tiered Rollers
• Vibratory Rollers
• Stumpers
• Walk-Behind Roller

Smooth wheel Rollers
Smooth wheel Rollers suitable for proof rolling sub grades and for finishing.














Sheepsfoot Rollers
This roller is most effective to compact Clayey soils.














Smooth wheel Rollers
This type have the most advantage because it can compact both soil and clayey soils

How many days is it for curing?

The recommended minimum curing time is 28 days, but most contractors typically wait only 7 to 14 days just to save time and money, but depending on the size of the concrete its very important to cure for 28days cos it will gain full or almost full strength.

pouring water (curing) of concrete after it been poured

What is the name given for the procedure of pouring water on concrete?
its called curing, a processed where concrete is left moist due to the exothermic reaction that takes place which may give cracks on the concrete.

Why Cure?
The major objective of concrete curing applications is to prevent the rapid loss of water from the concrete. As concrete loses water due to evaporation from the top surface, differential drying shrinkage can occur. This is a major contributor to shrinkage cracking. The application of curing methods reduces the loss of water from the surface of the concrete. It also permits more complete hydration of cement in the concrete itself. Minimizing evaporation also helps control the temperature of the concrete during its early-age stage.

Curing operations should begin after the water sheen disappears from the surface, and after any texturing operations have been completed. In the case of a curing compound, the membrane formed by the compound should not be disturbed after it is placed.

Rapid Drying Conditions
In rapid drying conditions, a light water fog may be necessary to maintain moist surface conditions prior to the application of curing methods. Light water fogging can be accomplished during a short period of time when the concrete surface begins to dry but before the curing operations can begin, such as prior to texturing operations have been completed.

Use of Ambient Weather Condition Information
Ambient weather conditions, such as wind speed, relative humidity, and air temperature can interact with the temperature of the concrete to cause excessive water evaporation from the concrete surface. Since different curing methods provide different levels of protection, knowing the amount of protection required is important in determining the method to use. In order to know the required level of protection, the ambient conditions and concrete temperature must be known. A portable weather station that records the ambient conditions and automatically predicts evaporative water from the concrete surface can be an invaluable tool for controlling water loss from the concrete surface. Such a tool can also warn in advance when conditions approach predefined limits of evaporation.
Curing Methods
Various concrete curing methods are available, and each provides different levels of protection. A single coat of liquid curing compound generally provides the least protection, but additional coats can improve its performance. Polyethylene sheets, cotton mats and wet burlap provide additional protection.

Liquid Curing Compound

White-pigmented, liquid membrane curing compound is used most often due to its low cost and ease of application. It does not require great amounts of labor, nor does it expensive, bulky material, such as cotton mats. It's disadvantages are that it provides the least amount of protection, and the membrane can be ruptured inadvertently.

The liquid curing compound should be white, to avoid excess heat absorption from the sun (Figure 4.1). Also, the white color enables construction workers to check more easily for coverage uniformity and gaps in the coverage. The liquid compound must be constantly agitated during application to ensure that the mixture is applied correctly. The curing compound spraying operation should be shielded from the wind throughout the process.

The compound must cover all exposed surfaces, including the sides of the pavement slab. The compound should not, however, be applied into any joints in the pavement. For ultra-thin whitetopping, curing compound should be applied at twice the normal application rate, due to its extra sensitivity to drying shrinkage.

Figure 4.1 - White-Pigmented, Liquid Membrane Curing Compound.

Plastic or Waterproof Paper

Plastic, or polyethylene, sheeting provides good protection to the concrete from water evaporation from the surface (Figure 4.2). It requires more labor than liquid curing compound, yet it is not as bulky as cotton mats or burlap. Waterproof paper may also be used in the same manner described here for plastic sheeting, but is not as common.

The plastic sheeting must not have any rips or tears through which water can escape. The sheets should overlap to provide full coverage for the concrete surface. Just as with curing compound, the sheeting should cover all exposed concrete surfaces, including the edges of the pavement slab. Active methods must be used to hold the sheeting in place. Do not assume that they will remain in place of their own accord.

Figure 4.2 - Polyethylene Sheeting Used as a Curing Method.

Cotton Mats or Burlap

Cotton mats represent a great increase in evaporation protection, both by providing additional moisture if needed, and by protecting the concrete from ambient conditions such as low humidity, high wind speeds, and high temperatures. Cotton mats and wet burlap must be kept continually moist. When the mats get dry they can become more harmful than without them due to "wicking" action which draws moisture from the concrete into the mat.

Importance of a geologist in construction project

An engineering Geologist is an individual who applies geologic data, principles, and interpretation so that geologic factors affecting planning, designing, construction and maintenance of civil engineering works and properly recognized and utilized.

They also advise on procedures required for such developments and the suitability of appropriate construction materials. Majority of subsurface exploration for civil engineering project is performed by engineering geologist.

In a construction project an engineering geologist needs are a lot, and plays a very major role in a project, they can predict or forecast of future events and conditions that my develop, they can recommend ways to handling and treating various earth material and process, even provide criteria for excavation and also they can do inspection during construction to confirm conditions of geological environment patterns.

Typical Work Activities Typical activities cover three key areas:

Office-based activities, including:

• consulting geological maps and aerial photographs to advise on site selection;
• undertaking desk studies and assessing sources of site information prior to field investigations;
• assisting with the design of built structures, using specialised computer software or calculations;
• assessing findings for construction engineers;
• collating data and producing reports;
• undertaking additional project management duties;
• overseeing the progress of specific contracts.

Site-based activities, including:

• planning detailed field investigations by drilling and analysing samples of deposits/bedrock;
• supervising site/ground investigations;
• maintaining technical control of a site;
• making visits to new project sites.

Liaising with staff and clients, including:

• advising on and testing a range of construction materials, for example sand, gravel, bricks and clay;
• making recommendations on the proposed use of a site;
• advising on problems such as subsidence;
• providing information and advice to clients as required;
• ensuring that a site investigation progresses to budget;
• managing staff, including other engineering geologists, geotechnical engineers, consultants and contractors;
• attending professional conferences and representing the company or organisation at other events.

When building a tunnel, Prior to tunnel inspections, a general site reconnaissance should be performed by a geologist to observe the existing ground surface

conditions and geology in the vicinity of the tunnel portals and ventilation building located on the side of the tunnels. The purpose of the site reconnaissance is to evaluate the existing surface conditions in an attempt to identify possible causes of the groundwater infiltration experienced within the tunnel structures.

Reference:

- Geotechnical and foundation Engineering Design and Construction, Robert W.Day, New York.

- Journal of Geotechnical and Geoenvironment Engineering, November 2006. volume 132, number 11, American society of civil engineers.

- http://www.prospects.ac.uk/cms/ ShowPage/Home_page/Explore_ types_of_jobs /Types_of_Job/p!eipaL?state=showocc&pageno=1&idno=111
- OCCUPATIONAL PROFILE, Engineering geologist
- 57th ANNUAL HIGHWAY GEOLOGY SYMPOSIUM HOSTED BY :The Colorado Geological Survey, The Colorado Department of Transportation.