i can`t sleep uwaa.......

aku sekpat tido lah...haiyah....tok mesti kesan daripada minum white coffee before nangga opening ceremony of the olympic rah athens...started from 1.30 to 5.10am..yang megiknya aku dapat tahan..sampe lah kinek tok..nang hebat lah aku haha...tok dah angol palak aku. kaktok mok tdo lah walaupun sekejap, tapi mun ekot sejarah lampau..mun dah malam sik tido..kakya pagi bok tdo..ada sampe tengahari hehe..marathon tido lah katakan..best juak lah opening ceremony ya..lamak nunggu bah..4 taun ahaks...masa rah sydney ya sik sempat nangga..apa masa ya gago belaja pre-science..kakya masa ya aku di kuantan..ney da masa mok nangga olimpik ya, lain lah journey to the east ada la ku nangga..nasib dorm mate ada mbak tv rah ikip ya keh keh keh. sekurangnya ada juak hiburan di kala aku homesick hahaa...

anyway secara keseluruhan opening ceremony ya menarik, menakjubkan dan melelahkan aku nantik kontijen malaysia melimpas..bayangkan..ada 202 kontijen seluruh alam...opss...seantero dunia lah..sampe ada negara nok pelik- sik penah dengar nama keh keh keh..adalah dalam berbelas negara yang belum pernah aku dengar sebelum tok- jahil na aku eh ..sik tauk ..mok orang lain sejahil aku nak?? semakin banyak negara baru di dunia tok bah..negara apa yang cgek ya cdak paling simple..bendera kaler ijo jak..mesti kitakorang sik cayak..tapi nang benar..pelik tapi benar hahaha...

actually aku dah type awal tek..kakya pande ilang inda..ney ndak frust..sampe hal sampah ada dicerita tek keh keh keh..tadik mah..around 6.30am tek..tengah online tok suddenly dengar bunyi lori trienekens..sahla lori sampah datang..cdak salu bertandang ke sitok awal pagi haha..maka mun sidak datang secara transmisi automatiknya bau / aroma terapi yang enak sebagai sarapan pagi menyelubungi kawasan bukit pending perdana tok ( kah kah kah...sejak bila aku diam area pending perdana?? hu hu hu ) ...kakya terfikir la aku sekpat cium bau ya walaupun sekejap..sedangkan cdak nok kerja angkut sampah ya dah lali..hmm..dah keja cdak nak? rezeki halal bah..bukan cdak merompak sampe ditembak polis kedak rah kl ari marek ya..haaa padan muka ko nok merompak kenak tembak...hahaha...rasakann...huwa huwa huwaaaa.

..owh ya..back to the topic..aku sebenar- benarnya kagum ngan stadium athens ya..very magnificent...nya mpun bumbung stadium..ada arches ...wah..memang hebat sapa yang design ya..mampukah aku mendesignkan structure sehebat itu in future??? hehe...itulah cabaran buat diriku....haha..so aku surf rah icivilengineer.com and i got this..mun rajin bacalah...for engine students..memang menarik...

Olympic Marvel Is A Tribute To Engineering Ingenuity

When the world watches the opening of the Athens Olympics this month, it will behold an engineering marvel. The Athens Olympic Stadium has a suspended arched roof construction, designed by the world-renowned Spanish architect, Santiago Calatrava. The roof is easily the most visually striking part of the total refurbishment of the original stadium.

This “jewel in the crown”, as the stadium’s roof has come to be known, is sure to be the trademark of the 2004 Olympic Games. Its two giant arches have a total span of 1,000 feet and soar to a maximum height of 262 feet.

Athen's Oaka Olympic Stadium is being refurbished with two double bowstring tied arches

Each arch supports the cables that hold the polycarbonate roof panels, which weigh a total of 17,000 tons and cover an area of 107,500 square feet, covering the 75,000 spectators and athletes alike. Ninety-five percent of the stadium’s seating will be covered, as compared to thirty-five percent in the original stadium.

The graceful sweeping roof structure is constructed of metal and glass with a special coating designed to reflect 60% of the sun - a feature very important during the Greek summer. Its unique architectural and structural design makes it a particularly unique project, because the existing stadium was refurbished while the roof and arches were being constructed and erected.

The graceful sweeping roof structure is constructed of metal and glass with a special coating designed to reflect 60% of the sun - a feature very important during the Greek summer. Its unique architectural and structural design makes it a particularly unique project, because the existing stadium was refurbished while the roof and arches were being constructed and erected.
The roof structure - the design of which is a double bowstring tied arch - was assembled close to the sides of the stadium. Arches and roof were constructed separately in two halves, positioned 230 feet from either side of the stadium. They were built remotely so as not to interfere with the underlying stadium.
This remote construction, however, gave rise to an important question, namely; how to move and position the two roof halves, each weighing 8,500 tons.

Double acting pull cylinders are attached to shoes in a sliding and guiding system pulling the arched roof assembly step by step into the final position.

The arched roof is built on two shoes supported by four Teflon sliding pads.
The original plan was to move each roof assembly by pulling it ste-by-step using long strands, chucks and short-stroke hydraulic jacks. This technique meant the structure’s shoes had to slike over thin stainless steel plates welded onto special rails resting on huge concrete beams.

However, computer simulations highlighted potential problems using strands to pull the roof into position. It was calculated that, because of significant elastic energy stored by the strands, the difference between the static and dynamic frictions of Teflon and stainless steel could create a stick-slip issue related to the relatively high acceleration and stops during each step of the pulling process. This was unacceptable to the designers, who sought another solution.

Enerpac, Integrated Solutions Specialist, was consulted because of their expertise in major construction and civil engineering projects. Enerpac is currently involved in a number of world-first engineering projects, including the 1,200 foot high Millau Viaduct in France, the highest bridge in the world.
For the Athens Stadium, Enerpac proposed long stroke-pulling cylinders powered by PLC-controlled hydraulic pumps. Used for the step-by-step pulling process, these would have very little impact on the existing design.
Four pulling cylinders were proposed for each shoe of the pulling assembly. Because each arch had two shoes and each shoe had four sliding pads, this meant a total of eight hydraulic cylinders were necessary to move and position each half of the roof.

A two-stage PLC-controlled pump was specified to power each group of four cylinders. This arrangement offered full control of speed, acceleration and deceleration during hydraulic movement. The PLC control was also necessary to ensure digital monitoring of the pump parameters. This integrated hydraulic system was designed to provide smooth movement and positioning of the arch.During the roof positioning, which took place in May and June, the PLC-controlled pumps were located on the sides of each arch and carried with them during the pulling process. Each pump supplied all four cylinders with the same hydraulic pressure and the same pulling force while the stroke synchronization is assured by the shoe structural strength. Both pumps were connected with a 1,300-foot cable and synchronized by the PLC-unit to control the start and stop of the hydraulic movement of the 8,500-ton roof half.

Very smooth starts and stops (while maintaining an acceptable speed) were facilitated by using a microprocessor-controlled variable-frequency AC motor drive. This unit controlled the electric motor speed, thus controlling the pumps’ oil flow and therefore the retracting speed of the pulling cylinders.
The PLC-controlled unit was used to vary motor speed (rpm) linearly, within the operator’s defined time intervals, from a minimum to a maximum and vice versa. In this way, a very low operational speed was achieved once the arch movement was started. The speed was kept low for a period in order to stabilize the system.

In the next step, the pumps’ oil flow was increased linearly (acceleration ramp) to ensure a constant and carefully controlled acceleration up to the pulling speed as defined by the roof design team.The pulling process continued with the cylinder stroke at a constant speed. Once the cylinder mounted micro switch detected the end of the plunger stroke, the hydraulic system automatically decreased linearly (deceleration ramp). This reduced cylinder retraction speed to a minimum then stopped the pulling process altogether.

The process started again after reloading (extending) all cylinders at high speed.

The Athens Olympic Stadium project shows how integration of hydraulics and electronics into one system for controlled hydraulic movement can solve important problems where conventional and traditional methods fail. With the use of PLC-controlled systems, hydraulic movements become very simple. reliable and safe. Every step in the process can be monitored at any time. Advantages of an integrated solution include:

• Use of double-acting, long stroke pulling cylinders considerably increases system rigidity, compared with using strands. This reduces the amount of elastic energy stored during the start of structure movements. Furthermore, double-acting cylinders, with their powered extending and retracting, improve the control of heavy load in case of unexpected external forces (wind, inertia due to sudden stops, etc).

• PLC-controlled integrated hydraulic solutions make synchronization of movement and speed control simple and accurate, reducing the risk of additional stress in the structure.

• Pulling instead of pushing makes the movement more stable, cancels the risk of buckling and contains the cylinder size.

• Two stage pumps with a high oil flow consistently reduce the cylinder reload time.

gtg now la..dah kol 7 lebih tok hehe..tapi mata lom ngantok gik..pandeylah aku mok mendodoikan diriku hehe..adios amigos...

p/s jerebu makin terok laa...walaupun sejuk di awal pagi tok, burung berkicauan dengan gumbiranya..hari ini pasti akan panas lagi....huhhh....heheh