Currently, I am working on the site supervision for a construction of 20 stories building in a country in SE asia. Last week I did several researches on the technical papers relavant to the building collapse that might occur during the construction to be one of my top priorities in preventing the unsafe work processes and procedures in my site.
I found one of the paper that describes the building collapse during construction. The collapse is due to the soil and foundation unstability problem that was induced by the transported soil from the excavation work.
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Showing posts with label building. Show all posts
Showing posts with label building. Show all posts
Wednesday, October 20, 2010
Friday, October 15, 2010
WTC Collapse : New Scrutiny After Crucial Explosive Dust Samples Found
Evidence indicating that the collapse of the World Trade Center was a controlled demolition has been propelled back under the national spotlight following the University of Copenhagen’s announcement that dust obtained from the rubble of the twin towers contains evidence of highly explosive material.The Earthquake-Proof Building That Is Built to Collapse
The Brilliant Idea: A replaceable, building-wide system to help hospitals, apartment buildings and office towers survive severe seismic shaking.
Innovators: Gregory Deierlein, Stanford University; Jerome F. Hajjar, Northeastern University
"Elastic high-strength steel cables run down the center of the system’s frame. The cables control the rocking of the building and, when the earthquake is over, pull it back into proper alignment."
"A steel frame situated around a building’s core or along exterior walls offers structural support. The frame’s columns, however, are free to rock up and down within steel shoes secured at the base."
Innovators: Gregory Deierlein, Stanford University; Jerome F. Hajjar, Northeastern University
"Elastic high-strength steel cables run down the center of the system’s frame. The cables control the rocking of the building and, when the earthquake is over, pull it back into proper alignment."
"A steel frame situated around a building’s core or along exterior walls offers structural support. The frame’s columns, however, are free to rock up and down within steel shoes secured at the base."
Tuesday, October 12, 2010
What is Underwater Antiwash Concrete?
PDF version here
Although underwater concreting has been in use for a long time, development of the technique has mainly proceeded in the areas of concrete placing method and improvements to the construction machinery. The prepacked concrete method, tremie method, concrete pump method, and others are now the representative underwater concreting methods. With all these concreting methods, the essential aim of technological development has been to improve how the concrete is placed and to minimize contact between the water and mortar so as to prevent the concrete from segregating under water.
Although underwater concreting has been in use for a long time, development of the technique has mainly proceeded in the areas of concrete placing method and improvements to the construction machinery. The prepacked concrete method, tremie method, concrete pump method, and others are now the representative underwater concreting methods. With all these concreting methods, the essential aim of technological development has been to improve how the concrete is placed and to minimize contact between the water and mortar so as to prevent the concrete from segregating under water.
On the other hand, antiwashout underwater concrete is quite different in concept from the methods mentioned above; the developmenta1aim in this case was improved performance of the fresh concrete. That is, the viscosity of the concrete was increased and its resistance to segregation under the washing action of water was enhanced by mixing an antiwashout admixture with the concrete. The effect of this is not only to greatly improve the reliability of Concrete placed underwater, but it also has remarkable effects on environmental preservation in the construction area. In addition, the earlier tremie and concrete pump placing methods can be adopted for construction.
The specific advantages of antiwashout underwater concrete include the following:
- Compared with ordinary concrete, antiwashout underwater concrete is highly resistant to the washing action of water, and rarely separates even when dropped under water
- Its yield value is small and viscosity high, so the concrete components never segregate and it displays high fluidity.
- As a result of the high fluidity, filling property and self-leveling ability are improved.
- Almost no bleeding occurs.
These qualities are taken full advantage of in work which would be difficult to handle using conventional underwater concrete. This includes work where high reliability is required, work in flowing water, work where water turbidity is restricted due to environmental considerations, and work where construction stretches over a considerable area and good flatness is necessary. On the other hand, however, handling is more difficult than with ordinary concrete, and in order to produce concrete of the required quality and a structure of the required performance, careful consideration of mix proportion, mixing, transport, and placing, etc. is necessary when antiwashout underwater concrete is used.
In particular, when producing the underwater antiwash concrete it is necessary to mix it for longer than ordinary concrete in a mixer large enough to uniformly disperse the antiwashout admixture. Also, when using concrete pumps for placement, it is necessary to design a pumping plan with care as regards pumping equipment, pumping distance, etc., because the pumping resistance is increased by the higher viscosity.
Monday, October 11, 2010
The Era of Flexible Concrete?
PDF version here
Looks like the brittle concrete has been tamed at last!
A team of researchers at the University of Michigan has developed a concrete material that bends like rubber, cracks very little, heals itself with no manual intervention, and is almost as good as new concrete upon recovery, with its stiffness and strength intact.
The research team led by Professor Victor C. Li more here , Professor of Civil and Environmental Engineering
at the University of Michigan, has achieved this by designing the new material with tiny crack widths. This ensures that any damage caused due to overloading and subsequent tensile strain manifests itself as small cracks that are autogenously healed.
Here’s how the self-healing mechanism works. The extra dry cement that is exposed on the surface of the crack reacts with water and carbon dioxide to form calcium carbonate, a strong and resilient compound that brings back the material to its original state. But this works only if the crack width is tiny, a factor that is taken care of by the nature of the material itself. The new material is an improvement over the bendable engineering cement composite (ECC) that Li and his team have been developing for the past decade and a half. The research team discovered that the brittleness of concrete could be altered by limiting the crack width to 150 microns, preferably 50 microns to enable full healing. The average crack width in the ECC was found to be 60 microns, half the width of human hair.
While traditional concrete is brittle and rigid, prone to failure and breakage under strain, the flexible ECC is held together with reinforcing fibers. So while traditional concrete fractures under a tensile strain of 0.1%, experiments revealed that the ECC is able to withstand a tensile strain of up to 5%. That makes it an astounding 500 times more durable than concrete.
The flexible ECC has several obvious advantages over traditional concrete as a construction material.
However, the one crucial factor that could put a wrench in the works is that the self-healing process is almost entirely dependent on the availability of water. Under laboratory conditions, ECC was found to require about one to five cycles of wetting and drying in order to self-heal. Extrapolating this finding to large structures such as bridges, it can be concluded that the ability for the material to self-heal is likely to be seasonal in nature. This leads one to question whether the new material would be suitable for commercial use in dry arid lands, and under all climatic conditions. And, would the alternate freeze-thaw cycles during our cold winters, complicated by use of de-icing salts, affect ECC’s material properties? These are some of the questions that should be addressed.
All said and done, should ECC prove to be a success in terms of industrial and commercial use, we are likely to see safer, smarter and more durable structures being erected.
Looks like the brittle concrete has been tamed at last!
A team of researchers at the University of Michigan has developed a concrete material that bends like rubber, cracks very little, heals itself with no manual intervention, and is almost as good as new concrete upon recovery, with its stiffness and strength intact.
The research team led by Professor Victor C. Li more here , Professor of Civil and Environmental Engineering
at the University of Michigan, has achieved this by designing the new material with tiny crack widths. This ensures that any damage caused due to overloading and subsequent tensile strain manifests itself as small cracks that are autogenously healed.
Here’s how the self-healing mechanism works. The extra dry cement that is exposed on the surface of the crack reacts with water and carbon dioxide to form calcium carbonate, a strong and resilient compound that brings back the material to its original state. But this works only if the crack width is tiny, a factor that is taken care of by the nature of the material itself. The new material is an improvement over the bendable engineering cement composite (ECC) that Li and his team have been developing for the past decade and a half. The research team discovered that the brittleness of concrete could be altered by limiting the crack width to 150 microns, preferably 50 microns to enable full healing. The average crack width in the ECC was found to be 60 microns, half the width of human hair.
While traditional concrete is brittle and rigid, prone to failure and breakage under strain, the flexible ECC is held together with reinforcing fibers. So while traditional concrete fractures under a tensile strain of 0.1%, experiments revealed that the ECC is able to withstand a tensile strain of up to 5%. That makes it an astounding 500 times more durable than concrete.
The flexible ECC has several obvious advantages over traditional concrete as a construction material.
Stronger Structures
Presently, concrete structures are reinforced with steel reinforcement (aka “rebar”) to minimize concrete cracking, as well as provide tensile strength for bending moments for structural beams and columns. While ECC cannot replace rebar for structural tensile strength, it can reduce the need for rebar to limit concrete cracking. In addition, ECC has the added benefit of self-healing these cracks, thereby reducing the risk of water and de-icing salts penetrating into the structure, causing corrosion of reinforcement steel that might be present.
Presently, concrete structures are reinforced with steel reinforcement (aka “rebar”) to minimize concrete cracking, as well as provide tensile strength for bending moments for structural beams and columns. While ECC cannot replace rebar for structural tensile strength, it can reduce the need for rebar to limit concrete cracking. In addition, ECC has the added benefit of self-healing these cracks, thereby reducing the risk of water and de-icing salts penetrating into the structure, causing corrosion of reinforcement steel that might be present.
Decreased Costs
While ECC is three times as expensive as traditional concrete, these costs are outweighed in the long run since the structure would not require extensive repair and maintenance. Li claims that ECC could help do away with repair and rebuilding processes for about an additional five to ten years. It could also eliminate the need to monitor seismic stresses on structures.
While ECC is three times as expensive as traditional concrete, these costs are outweighed in the long run since the structure would not require extensive repair and maintenance. Li claims that ECC could help do away with repair and rebuilding processes for about an additional five to ten years. It could also eliminate the need to monitor seismic stresses on structures.
Reduced Environmental Impacts
Use of the ECC is also expected to reduce the energy and carbon footprints of infrastructure, thereby reducing the detrimental effects of construction on the natural environment.
Use of the ECC is also expected to reduce the energy and carbon footprints of infrastructure, thereby reducing the detrimental effects of construction on the natural environment.
Quieter Structures
In 2006, a bridge over Interstate 94 in Michigan was built with a similar self-healing concrete, which was reinforced with toothed metal slats that allowed concrete to expand and contract without bending. However, this structure turned out to be a noisy affair as vehicles rattled over the metal slats. In contrast, ECC is a silent material.
The research certainly bodes well for the construction industry. In addition to the obvious applications in buildings and infrastructure, self-healing concrete could also very well be the solution to potholes and cracks on roads and bridges, and leaky walls. Flexible ECC is also being considered for use in irrigation channels in Montana.In 2006, a bridge over Interstate 94 in Michigan was built with a similar self-healing concrete, which was reinforced with toothed metal slats that allowed concrete to expand and contract without bending. However, this structure turned out to be a noisy affair as vehicles rattled over the metal slats. In contrast, ECC is a silent material.
However, the one crucial factor that could put a wrench in the works is that the self-healing process is almost entirely dependent on the availability of water. Under laboratory conditions, ECC was found to require about one to five cycles of wetting and drying in order to self-heal. Extrapolating this finding to large structures such as bridges, it can be concluded that the ability for the material to self-heal is likely to be seasonal in nature. This leads one to question whether the new material would be suitable for commercial use in dry arid lands, and under all climatic conditions. And, would the alternate freeze-thaw cycles during our cold winters, complicated by use of de-icing salts, affect ECC’s material properties? These are some of the questions that should be addressed.
All said and done, should ECC prove to be a success in terms of industrial and commercial use, we are likely to see safer, smarter and more durable structures being erected.
Sunday, October 10, 2010
Friday, October 1, 2010
Reinforced concrete Design philosophy and concepts
Reinforced concrete Design philosophy and concepts
The design of a structure may be regarded as the process of selecting proper materials and proportioned elements of the structure, according to the art, engineering science and technology. In order to fulfill its purpose, the structure must meet its conditions of safety, serviceability, economy and functionality.
| Serviceability: No excessive deflection, no excessive deformation and no cracking or vibrations No excessive reinforcement. Must be able to perform the function, it is built for. |
Strength design method
It is based on the ultimate strength of the structural members assuming a failure condition, whether due to the crushing of concrete or due to the yield of reinforced steel bars. Although there is additional strength in the bar after yielding (due to Strain Hardening), this additional strength in the bar is not considered in the analysis or design of the reinforced concrete members. In the strength design method, actual loads or working loads are multiplied by load factor to obtain the ultimate design loads. The load factor represents a high percentage of factor for safety required in the design. The ACI code emphasizes this method of design.
Working stress design
This design concept is based on elastic theory, assuming a straight line stress distribution along the depth of the concrete. The actual loads or working loads acting on the structure are estimated and members are proportioned on the basis of certain allowable stresses in concrete and steel. The allowable stresses are fractions of the crushing strength of concrete (fc') and the yield strength (fy). Because of the differences in realism and reliability over the past several decades, the strength design method has displaced the older stress design method.
Limit state design
It is a further step in the strength design method. It indicates the state of the member in which it ceases to meet the service requirements, such as, loosing its ability to withstand external loads or local damage. According to limit state design, reinforced concrete members have to be analyzed with regard to three limit states:
- Load carrying capacity (involves safety, stability and durability)
- Deformation (deflection, vibrations, and impact)
- The formation of cracks
The aim of this analysis is to ensure that no limiting sate will appear in the structural member during its service life.
what is Reinforced Concrete ?
Concrete is a stone like substance obtained by permitting a carefully proportioned mixture of cement, sand and gravel or other aggregate and water to harden in forms of the shape and of dimensions of the desired structure.
Reinforced cement concrete:
Since concrete is a brittle material and is strong in compression. It is weak in tension, so steel is used inside concrete for strengthening and reinforcing the tensile strength of concrete. The steel must have appropriate deformations to provide strong bonds and interlocking of both materials. When completely surrounded by the hardened concrete mass it forms an integral part of the two materials, known as "Reinforced Concrete".
Advantages and disadvantages of reinforced concrete
Reinforced Concrete is a structural material, is widely used in many types of structures. It is competitive with steel if economically designed and executed.
Advantages of reinforced concrete
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Disadvantages of reinforced concrete
- It needs mixing, casting and curing, all of which affect the final strength of concrete.
- The cost of the forms used to cast concrete is relatively high.
- It has low compressive strength as compared to steel (the ratio is about 1:10 depending on material) which leads to large sections in columns/beams of multistory buildings Cracks develop in concrete due to shrinkage and the application of live loads
How to install Solar Panel? : a step by step installation
This general information guide to solar panel installation will address the following topics:
* Solar Panel Purchases
* Solar Panel Installation Tips
* Solar Panels and Power Meters
Where can I purchase solar panels?
You can purchase solar panels from a variety of solar panel producers, including Sunwize, Evergreen, and Mitsubishii Electric. Prices change constantly, but a good solar panel report comparing cost/kilowatt is available here.
You can also buy solar panels securely online, from a wide variety of retailers.
Solar Panel Installation Tips
Solar Panels are typically installed on rooftops, building tops, or stand-alone facilities. It is vital to install your solar panel so that it gets the most direct sun exposure - you want to make sure your solar panel is maximally effective year round. To do this, there are several web-based solar resources to help you properly set up and install your solar panels by tracking the position of the sun in the sky over the course of the year.
Position your solar panel in direct sunlight
Solar Panels perform at optimum capacity when placed in direct sunlight. Try to position your photovoltaic array directly under the noontime sun for maximum efficiency from your photovoltaic unit.
Notice obstructions to sunlight
Remove all items unnessary items or trim branches that may be blocking sunlight to your solar unit. Trace the path of the sun in the sky to determine if an object is casting a shadow over your solar photovoltaic panels. If this is the case, then the operating efficiency of your unit will undoubtedly suffer.
Mounting your Solar Panel
Solar Panel Mounts are used to install photovoltaic solar panels. Solar panel mounts come in three main varieties: pole mounts, roof-ground mounts, and flush mounts. Using these mounts, you can install your solar panel onto an RV, on top of or against the side of a pole, on your roof, or even install them as a free-standing unit. You can learn more about installing solar panels using mounts in our mounts section.
Water pumping with solar panels
A good way to put solar panels to use is to install a solar-powered water pump for your well. Although windmills have traditionally been used to power such systems, a solar-powered system works just as well, and is equally friendly to the environment.
Your Well Pump
It is important to choose a quality well pump for use with your solar powered well pump system, one that makes the best use of your power and doesn't require an inefficient, wasteful transformer. Your well drilling provider is likely to offer you the industry standard well pump, a 220 volt alternating current model. The problem with such a high-voltage pump system is that the required transformer is extremely wasteful and can be a huge strain on your inverter during startup. This can cause the power to home to dip, and the lights to dim, which can cause a full-out inverter failure unless you have a top-quality inverter. Avoid such a high voltage system if you can, and instead, opt for a 120 volt AC model, which is much more efficient and does not put nearly as much of a burden on your inverter.
The Solar Panel
Your solar panel does not have to have a very high wattage rating in order to run your solar pump, just check with your well-drilling company to determine what wattage rating you need from your solar panel. An important consideration when setting up an outdoor solar panel system for your well pump is to ensure that you purchase a mounting rack that offers plenty of clearance between the ground and your solar panel and keep in it an open area away from trees. You don't want any large pets, floodwater, or falling branches to damage your system.
Solar Panels and Power Meters
As you purchase more and more solar panels for your home, your reliance on the city's power grid will progressively decline until your power meter doesn't turn at all. As you continue to buy solar panels, you wonder, what happens beyond that point? What happens on the days when my home produces more energy from solar panels that it needs?
Also, we reccomend using a true sine wave inverter with your solar powered pump system. True Sine wave inverters tend to work better when motors are involved (such as those found in a water pump).
If you are interested in reaping benefits from your solar panel investment, read on to discover how you can turn your power meter backwards for profit.
The design concept of the world tallest building
"Structural Design of the World’s Tallest Building:
The Burj Dubai Tower"
By:
William F. Baker, SOM Partner in Charge of Structural and Civil Engineering , Chicago, IL
D. Stanton Korista, SOM Director of Structural Engineering, Chicago, IL
Lawrence C. Novak, SOM Associate Partner,
Chicago, IL
The Burj Dubai Tower, when completed, will be the world’s tallest structure. The superstructure is currently under construction and as of the start of 2007 has reached near 100 stories. The final height of the building is a “well-guarded secret.” The height of the multi-use skyscraper will “comfortably” exceed the current record holder of 509 meter (1,671 ft) tall Taipei 101. The 280,000 m2 reinforced concrete multi-use Tower is utilized for Retail, a Giorgio Armani Hotel, Residential, and Office. The goal of the Burj Dubai Tower is not simply to be the world’s highest building; it’s to embody the world’s highest aspirations.
Designers purposely shaped the structural concrete Burj Dubai—“Y” shape in plan—to reduce the wind forces on the tower, as well as to keep the structure simple and foster constructability. The structural system can be described a “buttressed” core. Each wing, with its own high performance concrete core and perimeter columns, buttresses the others via a six-sided central core, or hexagonal hub. The result is a tower that is extremely stiff torsionally. SOM applied a rigorous geometry to the tower that aligned all the common central core and column elements to form a building.
Each tier of the building steps back in a spiral stepping pattern up the building. The setbacks are organized with the Tower’s grid, such that the building stepping is accomplished by aligning columns above with walls below to provide a smooth load path. This allows the construction to proceed without the normal delays associated with column transfers.
The setbacks are organized such that the Tower’s width to change at each setback. The advantage of the stepping and shaping is to “confuse the wind.” The wind vortexes never get organized because at each new tier the wind encounters a different building shape.
The 280,000 m2 (3,000,000 ft2) Tower and 185,000 m2 (2,000,000 ft2) Podium structures are currently under construction and the project is scheduled for topping out in 2008.
The Burj Dubai Tower"
By:
William F. Baker, SOM Partner in Charge of Structural and Civil Engineering , Chicago, IL
D. Stanton Korista, SOM Director of Structural Engineering, Chicago, IL
Lawrence C. Novak, SOM Associate Partner,
Chicago, IL
The Burj Dubai Tower, when completed, will be the world’s tallest structure. The superstructure is currently under construction and as of the start of 2007 has reached near 100 stories. The final height of the building is a “well-guarded secret.” The height of the multi-use skyscraper will “comfortably” exceed the current record holder of 509 meter (1,671 ft) tall Taipei 101. The 280,000 m2 reinforced concrete multi-use Tower is utilized for Retail, a Giorgio Armani Hotel, Residential, and Office. The goal of the Burj Dubai Tower is not simply to be the world’s highest building; it’s to embody the world’s highest aspirations.
Designers purposely shaped the structural concrete Burj Dubai—“Y” shape in plan—to reduce the wind forces on the tower, as well as to keep the structure simple and foster constructability. The structural system can be described a “buttressed” core. Each wing, with its own high performance concrete core and perimeter columns, buttresses the others via a six-sided central core, or hexagonal hub. The result is a tower that is extremely stiff torsionally. SOM applied a rigorous geometry to the tower that aligned all the common central core and column elements to form a building.
Each tier of the building steps back in a spiral stepping pattern up the building. The setbacks are organized with the Tower’s grid, such that the building stepping is accomplished by aligning columns above with walls below to provide a smooth load path. This allows the construction to proceed without the normal delays associated with column transfers.
The setbacks are organized such that the Tower’s width to change at each setback. The advantage of the stepping and shaping is to “confuse the wind.” The wind vortexes never get organized because at each new tier the wind encounters a different building shape.
The 280,000 m2 (3,000,000 ft2) Tower and 185,000 m2 (2,000,000 ft2) Podium structures are currently under construction and the project is scheduled for topping out in 2008.
What is Burj Khalifa (formerly Burj Dubai)?
General Information
Burj Khalifa (formerly Burj Dubai)
Dubai, United Arab EmiratesBurj Khalifa, formerly Burj Dubai, at the center of a large-scale development, is the tallest building in the world. The design combines cultural influences with cutting-edge technology to achieve a high-performance building. Its massing is manipulated in the vertical dimension to minimize the impact of wind on the tower's movement.
Site Area: 104,210 m2
Project Area: 454,249 m2
Building Height: 828 m
2010 • Chicago Athenaeum • International Architecture Award
2010 • Cityscape Awards for Real Estate in the Middle East and North Africa • Best Mixed Use Built Development
2010 • CTBUH • Best Tall Building Middle East & Asia
2010 • LEAF Awards • Best Structural Design of the Year: Shortlisted
2010 • Structural Engineers Association of Illinois • Excellence in Structural Engineering: Most Innovative Structure
2010 • World Architecture Festival • Award: Shortlisted
2010 • World Architecture Festival • Award: Shortlisted / Structural System
see more about the design concept of the building
Project Facts
Completion Year: 2010Site Area: 104,210 m2
Project Area: 454,249 m2
Building Height: 828 m
Project Awards
2010 • Arab Investment Summit • Arab Achievement Award 2010: Best Architecture Project2010 • Chicago Athenaeum • International Architecture Award
2010 • Cityscape Awards for Real Estate in the Middle East and North Africa • Best Mixed Use Built Development
2010 • CTBUH • Best Tall Building Middle East & Asia
2010 • LEAF Awards • Best Structural Design of the Year: Shortlisted
2010 • Structural Engineers Association of Illinois • Excellence in Structural Engineering: Most Innovative Structure
2010 • World Architecture Festival • Award: Shortlisted
2010 • World Architecture Festival • Award: Shortlisted / Structural System
see more about the design concept of the building
Conference 2010-on Engineering Design Technology
The Engineering Design Technology eConference is a national one-day learning event bringing together professionals to facilitate software implementation, product selection, technology training, and business strategy as it relates to emerging technology.
Register today for this groundbreaking online conference—it’s FREE! Learn and discuss the latest innovations and applications in engineering design technology!
Produced By: CE News, Structural Engineering & Design
When: Coming Soon
Cost: Free!
Five Reasons you must attend The Engineering Design Technology eConference:
1. Earn up to 2 FREE Professional Development Hours
2. Attend up to 3 live webcasts throughout the eConference.
3. Visit virtual booths and pick up product information, and white papers and have a live Q&A with booth representatives.
4. Find, and network with, your peers using the chat feature.
5. All from the convenience of your office or home computer - no travel or expenses necessary!
Fore more info go for "technology" website
1. Earn up to 2 FREE Professional Development Hours
2. Attend up to 3 live webcasts throughout the eConference.
3. Visit virtual booths and pick up product information, and white papers and have a live Q&A with booth representatives.
4. Find, and network with, your peers using the chat feature.
5. All from the convenience of your office or home computer - no travel or expenses necessary!
Fore more info go for "technology" website
How Sika success in Industrial Building
How Sika success in Industrial Building
Introduction to Industrial Construction
Industrial buildings consist of many different structures with their own specific function and specification. This in return will demand different requirements and of course specific system for each of the structures.
Warehouse for example, is exposed to heavy traffic such as forklift and this will demand a high abrasion resistance floor. While food and beverage production area may need a hygienic and easy-to-clean floor system.
Sika with its knowledge and experience is in best possible position to provide a total project based solution to its customers.
Below its some examples of Sika’s products involvement in industrial building projects.
1. Concrete works
Base on concrete requirements (workability, strength) a wide range of admixture (mainly Sikament and Sika Viscocrete range) is available for producing high quality and durable concrete. Use of silicafume based material, Sikacrete PP1 is also common to reduce concrete permeability, increase strength and resistance to aggressive environment (chlorides, sulfates). Following good concrete practice and use of reliable formwork release agent (Separol) and curing compound (Antisol) shall give the best possible concrete work quality.
2. Industrial Floor
Floor of a factory & warehouse has a key factor in ensuring the convenience of the production process. Bad condition floor will cause the disruption in productivity rate and furthermore, in some cases this will adversely affect the quality of goods produced.
Heavy traffic floor such as in warehouse or parking lot will require a high abrasion and mechanical resistance floor and this is best achieved by using Sikafloor Chapdur, non-metallic floor hardener, finished by power-float. For high abrasion requirement, Sikafloor 2 Syntop, dry shake floor hardener is a reliable solution. Pharmaceutical and food production area demand a seamless, easy-to-clean flooring system and sometimes require certain degree of chemical resistance.
Epoxy resin based flooring system has been used widely for this purpose where the type and thickness of epoxy layer are very dependant on the mechanical/chemical exposure and also the design life of the floor.
Sikafloor 2530-W New, coloured, 2-part epoxy dispersion, has been widely used in numerous projects in Vietnam. This epoxy coating produces a smooth, tough finish appearance and very suitable for use in food industry and light industry factory. If anti-skid appearance is required like in wet area such as kitchen, toilet and liquid contaminated floor then Sikafloor 7530 or Sikafloor 261 textured / screed system can be applied.
Besides these two products, Sika also provides various others flooring systems for other flooring requirements such as anti-static, high chemical and mechanical resistance floor.
3. Machine and Column Base Plate Grouting
To reach maximum effective bearing area, column base plate shall be grouted using non-shrink flowable grout such as SikaGrout 214-11. For heavy machine base plate, usually it is required to use high vibration resistant and high ultimate strength grout, Sikadur 42 MP, a 3-component castable epoxy grout, is suitable for this purpose.
How to repair the cracked concrete structures yourself
Crack injection repair to concrete structures
Scope of work:
Injection of dead cracks with low viscosity 2 components epoxy resin in order to repair the concrete structures.
Injection of dead cracks with low viscosity 2 components epoxy resin in order to repair the concrete structures.
PREPARATION FOR INJECTION WORK
- 14mm holes must be drilled along the crack path between 200 – 300 mm centres. The holes must be deep enough to receive the ‘metal pipe sleeves’ (approx. 20mm)
- Insert Sika ‘metal pipe sleeves’ into all the holes and epoxy into position using Sikadur 731
- Clean the concrete surface adjacent to the crack with a wire brush or sandpaper.
- Wipe down the concrete with a clean rag to remove any dust and loosely adhering particles.
- The cleaned surface is then sealed using Sikadur 731 applied by a spatula or trowel.
CRACK INJECTION
- Following the curing of the Sikadur 731 (minimum of 12 hours at 30oC) the epoxy injection can commence.
- Starting from one side or the lowest point of the crack a Sika ‘nipple’ is screwed into the first pipe sleeve and Sikadur 752 injected into the crack until the epoxy is seen to ooze from the adjacent pipe sleeve, this pipe sleeve is then sealed with a nipple, continue to inject the current port until refusal (epoxy resin can not be injected more) and then start the injection of the adjacent port and so on. This procedure is continued in the sequence indicated until all have been completed.
- Beginning at the first nipple filled, the nipple is removed and checked for incomplete filling. If any of the pipe sleeves are found to be incompletely filled, the injection of Sikadur 752 must recommence from the previous pipe sleeve to the one found incomplete until full and the nipple replaced. This checking process is continued (without interruption) along the crack until all have been checked.
- After a curing time of 12 hours the sleeve and nipples are trimmed off with an angle grinder or other suitable equipment.
How to do yourself for home energy saving using solar panels
How to make solar panels for home energy
Plenty of people have been looking into installing solar panels in an effort to combat rising energy costs. When most of these people see the prices of the professionally installed panels they realize it may not be a luxury they can afford. There is an easier, more cost efficient way to harness power from the sun and that is to learn how to make solar panels for your self.
Any motivated do-it-yourselfer can learn how to make solar panels for their home, workshop or business. When compared to the cost of purchasing and installing a pre-made solar energy system, learning how to make solar panels for your energy needs and the materials you need to execute the project are far less. By learning how to make solar panels for yourself, you have greater control over the size and design of your system as well.
Once you have a quality manual and you have learned how to make solar panels, the supplies are fairly simple to find. Most can be found at your local hardware store like, plywood, sheets of glass, and a roll of copper wire. It is also easy to locate inexpensive solar or photovoltaic cells to use in your project. Many are available over the Internet or you may have a retailer available locally. One you’ve learned how to make solar panels and you have your supplies, it usually takes about a day to assemble a 100-watt panel. This is the perfect amount of electricity to operate small appliances or a small workshop.
The most important step is finding a quality manual with detailed instructions for learning how to make solar panels. In many cases you get what you pay for, so don’t be afraid to spend a few extra dollars on a well-reviewed instruction manual. Overall, the cost of the making your own panels is so low, the price of the how to guide is minimal-you will still be paying way less learning how to make solar panels on your own than purchasing a professionally installed system.
With a little bit effort, you can be on your way to learning how to make solar panels to meet your energy needs. Then sit back and bask in the pride the next time the power goes out on your block. Your lights will still be on because you learned how to make solar panels and your energy supply is still in your battery bank.
Thursday, September 30, 2010
what are B and D regions?
B-Regions are parts of a structure in which Bernoulli's hypothesis of straight-line strain profiles applies. D-Regions, on the other hand, are parts of a structure with a complex variation in strain. D-Regions include portions near abrupt changes in geometry (geometrical discontinuities) or concentrated forces (statical discontinuities). Based on St. Venant's principle, the extent of a D-Region spans about one section depth of the region on either side of the discontinuity. 
Figure 1 and Figure 2 show examples of the division between B-Regions and D-Regions in building and bridge structures, respectively. In the figures, the unshaded area with a notation B indicates B-Region, and the shaded area with a notation D is used to indicate D-Region. The notations h1, h2, h3, ... are used to denote the depth of structural members. The notations b1 and b2 denote the flange width of structural members.
Figure 1 Example of D-Regions in a Common Building Structure
(Click here to view a larger image)
(Click here to view a larger image)
Figure 2 Example of D-Regions in a Common Bridge Structure
(Click here to view a larger image)
(Click here to view a larger image)
Most design practices for B-Regions are based on a model for behavior. As examples, design for flexure is based on conventional beam theory while the design for shear is based on the well-known parallel chord truss analogy. By contrast, the most familiar types of D-Regions, such as deep beams, corbels, beam-column joints, and pile caps, are currently still designed by empirical approaches or by using common detailing practices. For most other types of D-Regions, code provisions provide little guidance to designers. The Strut-and-Tie Method (STM) is emerging as a code-worthy methodology for the design of all types of D-Regions in structural concrete.
It is worth noting that although the STM is equally applicable to both B- and D-Region problems, it is not practical to apply the method to B-Region problems. The conventional beam theory for flexure and parallel chord truss analogy for shear are recommended for those designs.
Best Introduction to Earthquake Engineering Available!
This is the book for everyone who is not familiar with Earthquake and would like to explore more what is Earthquake. You can also read some information in my blog first and then probably read more in the book on Fundamentals of Earthquake Engineering
.
Book is designed for a graduate level course that introduces a "source to society" model for earthquake engineering that wonderfully captures the importance of interaction between the structural engineers (whom the book is primarily written for) and geologists, seismologists, geotechnical engineers, and public policy planners. The majority of the technical content focuses on the "source to structure" path of demand imposed by seismic events coupled with structural evaluation of the supply of buildings. This is a perfect introductory book to the topic, which covers selection of records for use in seismic analysis better than other books of its type. The book stops where the seismic codes start, so the text will not be outdated by future changes to codes. The author has put great effort into compiling a thorough list of top quality sources at the end of each of the four chapters (two focusing on demand and two on supply) that will be useful to the student desiring to delve deeper into various topics covered. Included with the text are access to powerpoint slides for all 4 chapters and 2 appendices, solutions to the example problems given throughout the chapters, and source data from several events discussed in the text.
You might would like to read more on Product Description and its back cover.Fundamentals of Earthquake Engineering combines aspects of engineering seismology, structural and geotechnical earthquake engineering to assemble the vital components required for a deep understanding of response of structures to earthquake ground motion, from the seismic source to the evaluation of actions and deformation required for design.
The nature of earthquake risk assessment is inherently multi-disciplinary. Whereas Fundamentals of Earthquake Engineering addresses only structural safety assessment and design, the problem is cast in its appropriate context by relating structural damage states to societal consequences and expectations, through the fundamental response quantities of stiffness, strength and ductility. The book is designed to support graduate teaching and learning, introduce practicing structural and geotechnical engineers to earthquake analysis and design problems, as well as being a reference book for further studies.
Fundamentals of Earthquake Engineering includes material on the nature of earthquake sources and mechanisms, various methods for the characterization of earthquake input motion, damage observed in reconnaissance missions, modeling of structures for the purposes of response simulation, definition of performance limit states, structural and architectural systems for optimal seismic response, and action and deformation quantities suitable for design. The accompanying website at www.wiley.com/go/elnashai contains a comprehensive set of slides illustrating the chapters and appendices, as well as a set of problems with solutions and worked-through examples. The book, slides and problem set constitute a tried and tested system for a single-semester graduate course. The approach taken avoids tying the book to a specific regional seismic design code of practice and ensures its global appeal to graduate students and practicing engineers.
From the Back Cover
Fundamentals of Earthquake Engineering combines aspects of engineering seismology, structural and geotechnical earthquake engineering to assemble the vital components required for a deep understanding of response of structures to earthquake ground motion, from the seismic source to the evaluation of actions and deformation required for design.
The nature of earthquake risk assessment is inherently multi-disciplinary. Whereas Fundamentals of Earthquake Engineering addresses only structural safety assessment and design, the problem is cast in its appropriate context by relating structural damage states to societal consequences and expectations, through the fundamental response quantities of stiffness, strength and ductility. The book is designed to support graduate teaching and learning, introduce practicing structural and geotechnical engineers to earthquake analysis and design problems, as well as being a reference book for further studies.
Fundamentals of Earthquake Engineering includes material on the nature of earthquake sources and mechanisms, various methods for the characterization of earthquake input motion, damage observed in reconnaissance missions, modeling of structures for the purposes of response simulation, definition of performance limit states, structural and architectural systems for optimal seismic response, and action and deformation quantities suitable for design. The accompanying website at www.wiley.com/go/elnashai contains a comprehensive set of slides illustrating the chapters and appendices, as well as a set of problems with solutions and worked-through examples. The book, slides and problem set constitute a tried and tested system for a single-semester graduate course. The approach taken avoids tying the book to a specific regional seismic design code of practice and ensures its global appeal to graduate students and practicing engineers.
.Book is designed for a graduate level course that introduces a "source to society" model for earthquake engineering that wonderfully captures the importance of interaction between the structural engineers (whom the book is primarily written for) and geologists, seismologists, geotechnical engineers, and public policy planners. The majority of the technical content focuses on the "source to structure" path of demand imposed by seismic events coupled with structural evaluation of the supply of buildings. This is a perfect introductory book to the topic, which covers selection of records for use in seismic analysis better than other books of its type. The book stops where the seismic codes start, so the text will not be outdated by future changes to codes. The author has put great effort into compiling a thorough list of top quality sources at the end of each of the four chapters (two focusing on demand and two on supply) that will be useful to the student desiring to delve deeper into various topics covered. Included with the text are access to powerpoint slides for all 4 chapters and 2 appendices, solutions to the example problems given throughout the chapters, and source data from several events discussed in the text.
You might would like to read more on Product Description and its back cover.Fundamentals of Earthquake Engineering combines aspects of engineering seismology, structural and geotechnical earthquake engineering to assemble the vital components required for a deep understanding of response of structures to earthquake ground motion, from the seismic source to the evaluation of actions and deformation required for design.
The nature of earthquake risk assessment is inherently multi-disciplinary. Whereas Fundamentals of Earthquake Engineering addresses only structural safety assessment and design, the problem is cast in its appropriate context by relating structural damage states to societal consequences and expectations, through the fundamental response quantities of stiffness, strength and ductility. The book is designed to support graduate teaching and learning, introduce practicing structural and geotechnical engineers to earthquake analysis and design problems, as well as being a reference book for further studies.
Fundamentals of Earthquake Engineering includes material on the nature of earthquake sources and mechanisms, various methods for the characterization of earthquake input motion, damage observed in reconnaissance missions, modeling of structures for the purposes of response simulation, definition of performance limit states, structural and architectural systems for optimal seismic response, and action and deformation quantities suitable for design. The accompanying website at www.wiley.com/go/elnashai contains a comprehensive set of slides illustrating the chapters and appendices, as well as a set of problems with solutions and worked-through examples. The book, slides and problem set constitute a tried and tested system for a single-semester graduate course. The approach taken avoids tying the book to a specific regional seismic design code of practice and ensures its global appeal to graduate students and practicing engineers.
From the Back Cover
Fundamentals of Earthquake Engineering combines aspects of engineering seismology, structural and geotechnical earthquake engineering to assemble the vital components required for a deep understanding of response of structures to earthquake ground motion, from the seismic source to the evaluation of actions and deformation required for design.
The nature of earthquake risk assessment is inherently multi-disciplinary. Whereas Fundamentals of Earthquake Engineering addresses only structural safety assessment and design, the problem is cast in its appropriate context by relating structural damage states to societal consequences and expectations, through the fundamental response quantities of stiffness, strength and ductility. The book is designed to support graduate teaching and learning, introduce practicing structural and geotechnical engineers to earthquake analysis and design problems, as well as being a reference book for further studies.
Fundamentals of Earthquake Engineering includes material on the nature of earthquake sources and mechanisms, various methods for the characterization of earthquake input motion, damage observed in reconnaissance missions, modeling of structures for the purposes of response simulation, definition of performance limit states, structural and architectural systems for optimal seismic response, and action and deformation quantities suitable for design. The accompanying website at www.wiley.com/go/elnashai contains a comprehensive set of slides illustrating the chapters and appendices, as well as a set of problems with solutions and worked-through examples. The book, slides and problem set constitute a tried and tested system for a single-semester graduate course. The approach taken avoids tying the book to a specific regional seismic design code of practice and ensures its global appeal to graduate students and practicing engineers.
Composite Construction
COMPOSITE CONSTRUCTION
In composite construction, steel beams and a concrete slab are connected so that they act together to resist the load on the beam. The slab, in effect, serves as a cover plate. As a result, a lighter steel section may be used.
Construction In Buildings
There are two basic methods of composite construction.
Method 1. The steel beam is entirely encased in the concrete. Composite action in this case depends on the steel-concrete bond alone. Because the beam is completely braced laterally, the allowable stress in the flanges is 0.66F y , where F y is the yield strength, ksi (MPa), of the steel. Assuming the steel to carry the full dead load and the composite section to carry the live load, the maximum unit stress, ksi (MPa), in the steel is
F s = ( M D / S S ) + ( M L / S t r ) ? 0.66F y
where M D = dead-load moment, in-kip (kN-mm)
M L = live-load moment, in-kip (kN-mm)
S s = section modulus of steel beam, in 3 (mm 3 )
S t r = section modulus of transformed composite section, in 3 (mm 3 )
An alternative, shortcut method is permitted by the AISC specification. It assumes that the steel beam carries both live and dead loads and compensates for this by permitting
a higher stress in the steel:
f s = M D + M L / S s ? 0.76 F y
Method 2. The steel beam is connected to the concrete slab by shear connectors. Design is based on ultimate load and is independent of the use of temporary shores to support the steel until the concrete hardens. The maximum stress in the bottom flange is
F s = M D + M L / S t r £ 0.66 F y
To obtain the transformed composite section, treat the concrete above the neutral axis as an equivalent steel area by dividing the concrete area by n, the ratio of modulus of elasticity of steel to that of the concrete. In determination of the transformed section, only a portion of the concrete slab over the beam may be considered effective in resisting compressive flexural stresses (positive-moment regions). The width of slab on either side of the beam centerline that may be considered effective should not exceed any of the following:
1. One-eighth of the beam span between centers of sup- ports
2. Half the distance to the centerline of the adjacent beam
3. The distance from beam centerline to edge of slab
There are two basic methods of composite construction.
Method 1. The steel beam is entirely encased in the concrete. Composite action in this case depends on the steel-concrete bond alone. Because the beam is completely braced laterally, the allowable stress in the flanges is 0.66F y , where F y is the yield strength, ksi (MPa), of the steel. Assuming the steel to carry the full dead load and the composite section to carry the live load, the maximum unit stress, ksi (MPa), in the steel is
F s = ( M D / S S ) + ( M L / S t r ) ? 0.66F y
where M D = dead-load moment, in-kip (kN-mm)
M L = live-load moment, in-kip (kN-mm)
S s = section modulus of steel beam, in 3 (mm 3 )
S t r = section modulus of transformed composite section, in 3 (mm 3 )
An alternative, shortcut method is permitted by the AISC specification. It assumes that the steel beam carries both live and dead loads and compensates for this by permitting
a higher stress in the steel:
f s = M D + M L / S s ? 0.76 F y
Method 2. The steel beam is connected to the concrete slab by shear connectors. Design is based on ultimate load and is independent of the use of temporary shores to support the steel until the concrete hardens. The maximum stress in the bottom flange is
F s = M D + M L / S t r £ 0.66 F y
To obtain the transformed composite section, treat the concrete above the neutral axis as an equivalent steel area by dividing the concrete area by n, the ratio of modulus of elasticity of steel to that of the concrete. In determination of the transformed section, only a portion of the concrete slab over the beam may be considered effective in resisting compressive flexural stresses (positive-moment regions). The width of slab on either side of the beam centerline that may be considered effective should not exceed any of the following:
1. One-eighth of the beam span between centers of sup- ports
2. Half the distance to the centerline of the adjacent beam
3. The distance from beam centerline to edge of slab
PONDING CONSIDERATIONS IN BUILDINGS
PONDING CONSIDERATIONS IN BUILDINGS
Flat roofs on which water may accumulate may require analysis to ensure that they are stable under ponding conditions. A flat roof may be considered stable and an analysis does not need to be made if both of the following two equations are satisfied:
C p + 0.9 C s £ 0.25
I d ³ 25S 4 / 10 6
Where C p = 32 L s L 4 p / 10 7 I p
C s = 32 SL 4 s / 10 7 s
L p = length, ft (m), of primary member or girder
L s = length, ft (m), of secondary member or purlin
S = spacing, ft (m), of secondary members
I p = moment of inertia of primary member, in 4
(mm 4 )
I s = moment of inertia of secondary member, in 4
(mm 4 )
I d = moment of inertia of steel deck supported on secondary members, in 4 /ft (mm 4 /m)
For trusses and other open-web members, I s should be decreased 15 percent. The total bending stress due to dead loads, gravity live loads, and ponding should not exceed 0.80F y , where F y is the minimum specified yield stress for the steel.
C p + 0.9 C s £ 0.25
I d ³ 25S 4 / 10 6
Where C p = 32 L s L 4 p / 10 7 I p
C s = 32 SL 4 s / 10 7 s
L p = length, ft (m), of primary member or girder
L s = length, ft (m), of secondary member or purlin
S = spacing, ft (m), of secondary members
I p = moment of inertia of primary member, in 4
(mm 4 )
I s = moment of inertia of secondary member, in 4
(mm 4 )
I d = moment of inertia of steel deck supported on secondary members, in 4 /ft (mm 4 /m)
For trusses and other open-web members, I s should be decreased 15 percent. The total bending stress due to dead loads, gravity live loads, and ponding should not exceed 0.80F y , where F y is the minimum specified yield stress for the steel.
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