Tweet Share Share Share Share Share

September 30, 2018
The Shanghai Tower is the tallest building in China and second tallest in the world. In order to achieve its height, the geometry of the tower had to be optimized to resist lateral loads.

The cross sectional geometry is a spiral equilateral triangle with each floor rotated slightly from below, creating a 120 degree angle between the topmost floor and the lowest level.

The spiral geometry actually increases lateral resistance by 24%, as opposed to tapered box geometry. This saved $58 million in materials and construction procedures. There are over 7000 different geometries and 20000 dual-skinned curtain wall panels that make up the structural geometry.

Due to its complexity, it is quite difficult to utilize AutoCAD and other traditional 2D modeling methods to present and to analyze the spiral geometry. However, with Autodesk Revit Structure, the design team can design the geometry in 3D. Structural engineers can use this BIM model to analyze how the wind and seismic loads affect the spiral geometry. They were able to optimize both building materials and the structural framing system, by producing and choosing from more than 20 options of structural geometries.

Eventually, the design team chose the structural spiral geometry frame with super columns, outrigger trusses, and an inner concrete core due to its combined strong lateral resistance.

Revit and Naviswork were used for BIM clash detection. During the design of the tower’s basement, the team found seven design clashes using those BIM software. During construction, there were no more clashes and they focused their BIM efforts in combining Revit models and fabrication models in Navisworks for coordination.
Source: http://du.gensler.com/

Read more »
Tweet Share Share Share Share Share

September 30, 2018
Introduction

Water  jet  cutting  can  reduce  the  costs  and  speed  up  the  processes  by  eliminating  or reducing expensive secondary machining process. Since no heat is applied on the materials, cut edges are cleanwith minimal burr. Problems such as cracked edge defects, crystallization, hardening, reduced weldability and machinability are reduced in this process.

Water jet technology uses the principle of pressurizing water to extremely high pressures, and allowing the water to escape through a very small opening called “orifice” or “jewel”. Water jetcutting uses the beam of water exiting the orifice to cut soft materials. This method is not suitable for cutting hard materials. The inlet water is typically pressurized between 1300 – 4000 bars. Thishigh pressure is forced through a tiny hole in the je el, hich is typically 0.18 to 0.4 mm in diameter. Picture of water jet chinning process.


Applications

Water jet cutting is mostly used to cut lower strength materials such as wood, plastics and aluminum. When abrasives are added, (abrasive water jet cutting) stronger materials such as steel and toolsteel.

Advantages of Water Jet Cutting

•   There is no heat generated in water jet cutting; which is especially useful for cutting    tool steel and other metals where excessive heat may change the properties of the material.
•   Unlike machining or grinding, water jet cutting does not produce any dust or particles that are harmful if inhaled.
•   Other advantages are similar to abrasive water jet cutting

Disadvantages of water jet cutting

•   One of the main disadvantages of water jet cutting is that a limited number of materials can be cut economically.
•   Thick parts cannot be cut by this process economically and accurate ly
•   Taper is also a problem with water jet cutting in very thick materials. Taper is when the jet exits the part at different angle than it enters the part, and cause dimensional inaccuracy.




Read more »
Tweet Share Share Share Share Share

September 30, 2018
Many successful people get promoted into management and quickly find the pressure to be higher than anything they felt in the past. As an individual contributor, it is much easier to control the outcomes of your work. It may not seem like that at times, but you have a lot more control than when you are a manager of people. I am not referring to people that receive a management title and have nobody to manage. A real manager has the authority and responsibility to manage: financial performance (includes holding others accountable), people activities (hire, keep and grow people), and positioning/strategizing the firm or department in a way that provides a competitive advantage in the marketplace.
One key issue a manager faces is that there are always detractors within the larger organization and the smaller team. These people may have been detractors all along, felt they should have gotten your position, or do not know you well enough to realize you are qualified for your position. In his book, “Managing Right for the First Time,” David C. Baker recommends that managers not overreact and to approach detractors as follows:
1.       It is natural to have detractors, and you just need to be aware of who they are and acknowledge they are there.
2.       It is important that a new manager avoid actions that give their detractors power.
3.       One should not try to bully or overstep a detractor by using the power of one’s new position.
4.       When dealing with issues, it is important to treat everyone with equal fairness and respect and focus on “right action.”
The key in any management position is to be a leader that staff wants to follow. This does not mean being weak or attempting to be everyone’s friend. Instead, Baker identifies the following characteristics as key to being someone people want to follow.
●        Approachability – Do you actively listen first before reacting?
●        Articulateness – When you communicate, do you do it directly enough so that people truly understand what you are thinking and feeling?
●        Authenticity – Are your actions and behaviors consistent with the how you really feel inside?
●        Honesty – Do you say what you mean and deliver difficult feedback effectively?
●        Consistency – How much consistency is there between vision communicated and reality? Do you do what you say or change when it suits you?
●        Competence – Are you competent enough to understand the issues and evaluate what is being said?
●        Confidence – Do you have the balance between being able to inspire others to follow you but not so much confidence that you fail to recognize you are heading down the wrong path?
●        Curiosity – Are you always observing and inquiring to test original beliefs against new information and showing a willingness to refine strategies and action plan accordingly?
●        Decisiveness – Are you willing to make choices that may not be popular?
●        Discipline – Do you get things done, do what you say, plan, and execute?
●        Fairness – Can people trust you will look out for others’ best interests when the others are not in the room?
●        Hopefulness – Most people would choose not to walk down the path to hell! Can you lead the way down a difficult path with a positive and winning attitude?
If you are entering management for the first time or experiencing less-than-optimal cooperation from your team, challenge yourself with the above questions and consider reading “Managing Right for the First Time,” by David C. Baker.
Missing any of the above characteristics can hinder your effectiveness. It takes a strong manager to keep all of them in perspective. It is natural to violate them when detractors enter the picture or when encountering challenges in a role.




Read more »
Tweet Share Share Share Share Share

September 30, 2018
The primitive man had to use his muscle power to carry out different works in his attempt of obtaining the necessities of life. The demand for more power and the scarcity of man power and the ready availability of natural resources like wind, water, etc., might have formed the reason why the ancient man turned his attention to the utilization of these resources as sources of power; thus originated the early prime movers namely wind mill and water wheel.

Principle of wind mill:
Wind flow is created as an effect of solar heat. Winds are caused due to the absorption of solar energy on the earth surface and the rotation of earth about its own axis and around the sun.because of this, alternate heating and cooling occurs and difference in pressure is obtained and the air movement is caused.

The flowing wind which has kinetic energy is used to rotate the wind turbine which is also known as wind mill. Although wind mills have been used for more than a dozen centuries for pumping water and grinding grains, interest in large scale power generation had developed over the past 50 years.

The earth’s atmosphere is thus a marvelous solar driven heat engine. It is estimated that roughly 10 million MW of energy is continuously available in the earth’s winds.

Types of winds mills
Wind mills are classified as

●      Horizontal axis type and
●      Vertical axis type,  Depending on their axis of rotation.


Horizontal axis wind mills are further classified as single-bladed, double-bladed and multi-bladed types.

Horizontal axis wind mill with double blade rotor:
In the horizontal axis single blade type, the blade is of propeller type with counter weight arrangement. The double blade type gives a better performance than the single blade type.

In the double-blade type, the blade has thick cross section of an aerofoil. At the tip of the blade, the velocity is about six times the wind velocity. The blade is set at right angles to the direction of the wind. Ideally the blades should be twisted, but because of construction difficulties this is not always achieved.
The blade rotor drives a generator through a gear box. It is mounted on a bed plate attached on the top of the tower.
Blade material: the blades are made from aluminum or sheet metal. Not a single large wind turbine – generator with metal blades has operated for longer than one year without a blade failure. The suitable material required is a major problem in developing wind mills of higher power generation capacity.
With rotor, the tower is also subjected to the wind loads which may cause serious damage. Hence the structure of the tower should be so designed to withstand the wind load.
The best sites for the wind energy are found off-shore and sea coast. The second best sites are in mountains. The lowest level of wind energy is found in plains, where values are generally three or four times lower than that at the coast.
Multiblade rotor:
It is shown in image below. Rotors with more than two blades will produce high power.
Sail type blades:
It is of recent origin. The blade surface is made from cloth, nylon or plastic arranged as sail wings. There is also variation in the number of sails used.
The horizontal axis types generally have better performance than vertical types. They are mainly used for power generation and pumping water. The biggest wind mill erected for power generation is of 2500kW capacity in U.S.A.
Advantages of Wind Power Generation:
1.    The wind energy is a renewable source of energy. It is free and inexhaustible.
2.    The power requirements for irrigation, lighting and small industrial units can be fulfilled with the use of wind energy. Power generation on large scale using wind energy is not yet so successful, but the small wind mills will play a vital role in the present condition of power shortage.
3.    It does not need transportation.
4.    Like all forms of solar energy, wind power systems are non-polluting.


Disadvantages of Wind Power Generation:
1.    Wind velocity is fluctuating which makes the complications in designing a wind power plant.
2.    Some form of storage of wind energy is essential to maintain a constant supply of power.
3.    The wind is a very hazardous, treacherous and unpredictable source of energy. Blowing in strong gusts from varying directions causing hurricanes, the wind may smash the whole plant within no time. To avoid this, special and costly designs and controls are always required.
4.    It is considered suitable and economical to generate power on a small scale of order of 2 MW.
5.    Power production cost with the present technology available may not compete with the conventional power generating systems. This is because, 1000s of units are required to provide the power output of one fossil-fueled plant.
6.    Wind energy systems are noisy in operation. A large unit can be heard many kilometers away.





Read more »
Subscribe to: Comments (Atom)
Powered by Blogger.