LONDON SWAYING FOOTBRIDGE
A. In September 1996 a competition was organized by the Financial Times in association with the London Borough of Southwark to design a new footbridge across the Thames. The competition attracted over 200 entries and was won by a team comprising Amp (engineers), Foster and Partners (architects) and the sculptor Sir Anthony Caro.
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B. The bridge opened to the public on 10 June 2000. Up to 100,000 people crossed it that day with up to 2000 people on the bridge at any one time. At first, the bridge was still. Then it began to sway, just slightly. Then, almost from one moment to the next, when large groups of people were crossing, the wobble intensified. This movement became sufficiently large for people to stop walking to retain their balance and sometimes to hold onto the hand rails for support. It was decided immediately to limit the number of people on the bridge, but even so the deck movement was sufficient to be uncomfortable and to raise concern for public safety so that on 12 June the bridge was closed until the problem could be solved.
C. The embarrassed engineers found the videotape that day which showed the center span swaying about 3 inches side to side every second. The engineers first thought that winds might be exerting excessive force on the many large flags and banners bedecking the bridge for its gala premiere. What’s more, they also discovered that the pedestrians also played a key role. Human activities, such as walking, running, dumping, swaying, etc. could cause horizontal forces which in turn could cause excessive dynamic vibration in the lateral direction in the bridge. As the structure began moving, pedestrians adjusted their gait to the same lateral rhythm as the bridge. The adjusted footsteps magnified the motion – just like when four people all stand up in a small boat at the same time. As more pedestrians locked into the same rhythm, the increasing oscillations led to the dramatic swaying captured on film.
D. In order to design a method of reducing the movements, the force exerted by the pedestrians had to be quantified and related to the motion of the bridge. Although there are some descriptions of this phenomenon in existing literature, none of these actually quantifies the force. So there was no quantitative analytical way to design the bridge against this effect. An immediate research program was launched by the bridge’s engineering designers Ove Arup, supported by a number of universities and research organizations.
E. The tests at the University of Southampton involved a person walking on the spot’ on a small shake table. The tests at Imperial College involved persons walking along a specially built, 7.2m-long platform which could be driven laterally at different frequencies and amplitudes. Each type of test had its limitations. The Imperial College tests were only able to capture 7-8 footsteps, and the walking on the spot tests, although monitoring many footsteps, could not investigate normal forward walking. Neither test could investigate any influence of other people in a crowd on the behavior of the individual being tested.
F. The results of the laboratory tests provided information which enabled the initial design of a retro-fit to be progressed. However, the limitations of these tests was clear and it was felt that the only way to replicate properly the precise conditions of the Millennium Bridge was to carry out crowd tests on the bridge deck itself. These tests done by the Arup engineers could incorporate factors not possible in the laboratory tests. The first of these was carried out with 100 people in July 2000. The results of these tests were used to refine the load model for the pedestrians. A second series of crowd tests was carried out on the bridge in December 2000. The purpose of these tests was to further validate the design assumptions and to load test a prototype danger installation. The test was carried out with 275 people.
G. Unless the usage of the bridge was to be greatly restricted, only two generic options to improve its performance were considered feasible. The first was to increase the stiffness of the bridge to move all its lateral natural frequencies out of the range that could be excited by the lateral footfall forces, and the second was to increase the damping of the bridge to reduce the resonant response.
Questions 14 – 17
Choose FOUR letters, A – H. Write the correct letters in boxes 14 – 17 on your answer sheet.
Which FOUR of the following situation were witnessed on the opening ceremony of the bridge?
A The frequency of oscillation increased after some time.
- All the engineers went to see the ceremony that day.
- The design of the bridge astonished the people.
- Unexpected sideways movement of the bridge occurred.
- Pedestrians had difficulty in walking on the deck.
- The bridge fell down when people tried to retain their balance.
- Vibration could be detected on the deck by the pedestrians.
- It was raining when the ceremony began.
Questions 18 – 22
Complete the following summary of the passage, using NO MORE THAN THREE WORDS from the Reading Passage for each answer.
After the opening ceremony, the embarrassed engineers tried to find out the reason of the bridge’s wobbling. Judged from the videotape, they thought that 18……………………. and 19……………………. might create excessive force on the bridge. The distribution of 20……………………. resulted from human activities could cause 21……………………. throughout the structure. This swaying prompted people to start adjusting the way they walk, which in turn reinforced the
Questions 23 – 26
Complete the table below. Choose NO MORE THAN THREE WORDS from the passage for each answer.
Research programs launched by universities and organizations
|Test at 23…………………….||Limited ability to have 7-8 footsteps|
|Walking on the spot at Southampton||Not enough data on 24…………………….|
|Crowd test conducted by 25…………………….||Aim to verify 26…………………….|
A In 1877, Giovanni Schiaparelli, an Italian astronomer, made drawings and maps of the Martian surface that suggested strange features. The images from telescopes at this time were not as sharp as today’s. Schiaparelli said he could see a network of lines, or canali. In 1894, an American astronomer, Percival Lowell, made a series of observations of Mars from his own observations of Mars from his own observatory at Flagstaff, Arizona, USA. Lowell was convinced a great network of canals had been dug to irrigate crops for the Martian race! He suggested that each canal had fertile vegetation on either side, making them noticeable from Earth. Drawings and globes he made show a network of canals and oases all over the planet.
B The idea that there was intelligent life on Mars gained strength in the late 19th century. In 1898, H.G. Wells wrote a science fiction classic, The War of the Worlds about an invading force of Martians who try to conquer Earth. They use highly advanced technology (advanced for 1898) to crush human resistance in their path. In 1917, Edgar Rice Burroughs wrote the first in a series of 11 novels about Mars. Strange beings and rampaging Martian monsters gripped the public’s imagination. A radio broadcast by Orson Welles on Halloween night in 1938 of The War of the Worlds caused widespread panic across America. People ran into the streets in their pyjamas-millions believed the dramatic reports of a Martian invasion.
C Probes are very important to our understanding of other planets. Much of our recent knowledge comes from these robotic missions into space. The first images sent back from Mars came from Mariner 4 in July 1965. They showed a cratered and barren landscape, more like the surface of our moon than Earth. In 1969, Mariners 6 and 7 were launched and took 200 photographs of Mars’s southern hemisphere and pole on fly-by missions. But these showed little more information. In 1971, Mariner 9’s mission was to orbit the planet every 12 hours. In 1975, The USA sent two Viking probes to the planet, each with a lander and an orbiter. The landers had sampler arms to scoop up Maritian rocks and did experiments to try and find signs of life. Although no life was found, they sent back the first colour pictures of the planet’s surface and atmosphere from pivoting cameras.
D The ALH84001 meteorite was found in December 1984 in Antarctica, by members of the ANSMET project; The sample was ejected from Mars about 17 million years ago and spent 11,000 years in or on the Antarctic ice sheets. Composition analysis by NASA revealed a kind of magnetite that on Earth, isonly found in association with certain microorganisms. Some structures resembling the mineralized casts of terrestrial bacteria and their appendages (fibrils) or by-products (extracellular polymeric substances) occur in the rims of carbonate globules and preterrestrial aqueous alteration regions. The size and shape of the objects is consistent with Earthly fossilized nanobacteria, but the existence of nanobacteria itself is controversial.
E In 1965, the Mariner 4 probe discovered that Mars had no global magnetic field that would protect the planet from potentially life-threatening cosmic radiation and solar radiation; observations made in the late 1990s by the Mars Global Surveyor confirmed this discovery. Scientists speculate that the lack of magnetic shielding helped the solar wind blow away much of Mars’s atmosphere over the course of several billion years. After mapping cosmic radiation levels at various depths on Mars, researchers have concluded that any life within the first several meters of the planet’s surface would be killed by lethal doses of cosmic radiation. In 2007，it was calculated that DNA and RNA damage by cosmic radiation would limit life on Mars to depths greater than 7.5 metres below the planet’s surface. Therefore, the best potential locations for discovering life on Mars may be at subsurface environments that have not been studied yet. Disappearance ofthe magnetic field may played an significant role in the process of Martian climate change. According to the valuation of the scientists, the climate of Mars gradually transits from warm and wet to cold and dry after magnetic field vanished.
F No Mars probe since Viking has tested the Martian regolith specifically for metabolism which is the ultimate sign of current life. NASA’s recent missions have focused on another question: whether Mars held lakes or oceans of liquid water on its surface in the ancient past. Scientists have found hematite, a mineral that forms in the presence of water. Thus, the mission of the Mars Exploration Rovers of 2004 was not to look for present or past life, but for evidence of liquid water on the surface of Mars in the planet’s ancient past. Liquid water, necessary for Earth life and for metabolism as generally conducted by species on Earth, cannot exist on the surface of Mars under its present low atmospheric pressure and temperature, except at the lowest shaded elevations for short periods and liquid water does not appear at the surface itself. In March 2004, NASA announced that its rover Opportunity had discovered evidence that Mars was, in the ancient past, a wet planet. This had raised hopes that evidence of past life might be found on the planet today. ESA confirmed that the Mars Express orbiter had directly detected huge reserves of water ice at Mars’south pole in January 2004.
G Two metres below the surface of the Atacama Desert there is an ‘oasis’of microorganisms. Researchers from the Center of Astrobiology (Spain) and the Catholic University of the North in Chile have found it in hypersaline substrates thanks to SOLID, a detector for signs of life which could be used inenvironments similar to subsoil on Mars. “We have named it a ‘microbial oasis’because we found microorganisms developing in a habitat that was rich in rock salt and other highly hygroscopic compounds that absorb water”, explained Victor Parro, researcher from the Center of Astrobiology (INTACSIC, Spain) and coordinator of the study. “If there are similar microbes on Mars or remains in similar conditions to the ones we have found in Atacama, we could detect them with instruments like SOLID”Parro highlighted.
H Even more intriguing, however, is the alternative scenario by Spanish scientists: If those samples could be found to have organisms that use DNA, as Earthly life does, as their genetic code. It is extremely unlikely that such a highly specialised, complex molecule like DNA could have evolved separately on the two planets, indicating that there must be a common origin for Martian and Earthly life. Life based on DNA first appeared on Mars and then spread to Earth, where it then evolved into the myriad forms of plants and creatures that exist today. If this was found to be the case, we would have to face the logical conclusion: we are all Martian. If not, we would continue to search the life of signs.
The reading Passage has seven paragraphs A-H.
Which paragraph contains the following information?
Write the correct letter A-H, in boxes 27-32 on your answer sheet.
NB You may use any letter more than once.
27 Martian evidence on Earth
28 Mars and Earth may share the same life origin
29 certain agricultural construction was depicted specifically
30 the project which aims to identify life under similar condition of Mars
31 Mars had experienced terrifying climate transformation
32 Attempts in scientific investigation to find liquid water
Choose the correct letter, A,B,C or D.
Write your answers in boxes 33-36 on your answer sheet.
33 How did Percival Lowell describe Mars in this passage?
A Perfect observation location is in Arizona.
B Canals of Mars are broader than that of the earth.
C Dedicated water and agriculture trace is similar to the earth.
D Actively moving Martian lives are found by observation.
34 How did people change their point of view towards Mars from 19th century?
A They experienced Martian attack.
B They learned knowledge of mars through some literature works
C They learned new concept by listening famous radio program.
D They attended lectures given by famous writers.
35 In 1960s, which information is correct about Mars by a number of Probes sent to the space?
A It has a landscape full of rock and river
B It was not as vivid as the earth
C It contained the same substance as in the moon
D It had different images from the following probes
36 What is the implication of project proceeded by technology called SOLID in Atacama Desert?
A It could be employed to explore organisms under Martian condition.
B This technology could NOT be used to identify life on similar condition of Mars.
C Atacama Desert is the only place that has a suitable environment for organisms.
D Life had not yet been found yet in Atacama Desert.
Do the following statements agree with the information given in Reading Passage 1?
In boxes 37-40 on your answer sheet, write
TRUE if the sataement agrees with the information
FALSE if the statement contradicts the information
NOT GIVEN if there is no information on this
37 Technology of Martian creature was superior than what human had at that time in every field according to The War of the Worlds.
38 Proof sent by Viking probes has not been challenged yet.
39 Analysis on meteorite from Mars found a substance which is connected tosome germs.
40 According to Victor Parro, their project will be deployed on Mars after they identified DNA substance on earth.
14-17 A D E G
20 horizontal forces
21 (excessive dynamic) vibration
23 Imperial College
24 normal forward walking
25 Arup engineers
26 (the) design assumptions
37. NOT GIVEN
40. NOT GIVEN