CABLE LONG SPAN

GROUP MEMBERSM. DANIAL MAULA ABU BAKAR - 2012617322AHMAD FAIZ BIN ABD KARIM - 2012850668WAN NOOR AZEAN BT WAN MAHMUD - 2012601764NURUL FARHANA BT NORROL AKHLA - 2012469216

STRUCTURE

CABLE SYSTEM MAJOR SYSTEM

Form active structure systems

Non rigid, flexible matter shaped in a certain way and secured by fixed ends, support itself & span space. The transmit loads only through simple normal stresses, either tension or through compression.

Two cables with different points of suspension tied together form a suspension system. A cable subject to external loads will deform in a way depending upon the magnitude and location of the external forces. The form acquired by the cable is called the FUNICULAR SHAPE of the cable.

Form Active Structure Systems redirect external forces by simple normal stresses : the arch by compression, the suspension cable by tension. The bearing mechanism of form active systems vests essentially on the material form.

The natural stress line of the form active tension system in the funicular tension line.

Any change of loading or support conditions changes the form of the funicular curve.

MATERIALSteel Cables : The high tensile strength of steel combined with

the efficiency of simple tension, makes a steel cable the ideal structural element to span large distances.

Nylon and plastics are suitable only

for temporary structures,

spanning small distances.

DYNAMIC EFFECTS OF WIND ON TYPICAL FLEXIBLE ROOF STRUCTURE :

A critical problem in the design of any cable roof structure is the dynamic effect of wind, which causes an undesirable fluttering of the roof.

PREVENTIVE MEASURES :There are only several fundamental ways to combat flutter.

• One is to simply increase the deal load on the roof.• Another is to provide anchoring guy cables at periodic points to tie the structure to the ground.

• To use some sort of crossed cable on double-cable system.

The principal methods of providing stability are the following:

Additional permanent load supported on, or suspended from,the roof, sufficient to neutralize the effects of asymmetrical variable actions or uplift Figure 14 a)

This arrangement has the drawback that it eliminates the lightweight nature of the structure, adding significant cost to the entire structure.

(ii) Rigid members acting as beams, where permanent load may not be adequate to counteract uplift forces completely,but where there is sufficient flexural rigidity to deal with the net uplift forces, whilst availing of cables to help resist effects of gravity loading (Figure 14b).

CASE STUDY

• The Akashi-Kaikyo Bridge also known as the Pearl Bridge, has the longest central span of any suspension bridge in the world, at 1,991 metres (6,532 ft).

• The bridge has three spans. The central span is 1,991 m (6,532 ft), and the two other sections are each 960 m (3,150 ft). The bridge is 3,911 m (12,831 ft) long overall.

SINGLE-CURVATURE STRUCTURE

• The steel cables have 300,000 kilometres (190,000 mi) of wire: each cable is 112 centimetres (44 in) in diameter and contains 36,830 strands of wire.

•The Akashi-Kaikyo bridge has a total of 1,737 illumination lights: 1,084 for the main cables, 116 for the main towers, 405 for the girders and 132 for the anchorages.

Strands of wire Bridge girders

Illumination lights

Bridge specificationsOverall Length:  13.5 km (8.4 mi)Length Over Water:  8.4 km (5.2 mi)Penang Island Viaduct & Approach:  1.5 km (0.93 mi)Prai Approach:  3.6 km (2.2 mi)

Height of Tower Above Water:  101.5 mHeight of Bridge Above Water:  33 mMain Span:  225 mEnd Span:  107.5 mOther Span:  40 mSpeed limit:  80 km/hMaximum Gradient:  3.0%

DOUBLE-CABLE STRUCTURE

CABLE STRUCTURE INFOMATION