SPAN STRUCTURE GROUP MEMBERS M. DANIAL MAULA ABU BAKAR - 2012617322 AHMAD FAIZ BIN ABD KARIM - 2012850668 WAN NOOR AZEAN BT WAN MAHMUD - 2012601764 NURUL FARHANA BT NORROL AKHLA - 2012469216
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.
MATERIAL Steel 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 isthe dynamic effect of wind, which causes an undesirable flutteringof 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 stabilityare the following:Additional permanent loadsupported on, or suspended from,the roof, sufficient to neutralize the effectsof asymmetrical variable actions or upliftFigure 14 a)This arrangement has the drawback that iteliminates the lightweight nature of thestructure, adding significant cost to theentire structure.(ii) Rigid members acting as beams, wherepermanent load may not be adequate tocounteract uplift forces completely,but where there is sufficient flexuralrigidity to deal with the net uplift forces,whilst availing of cables to help resist effectsof gravity loading (Figure 14b).
CASE STUDY SINGLE-CURVATURE STRUCTURE• The Akashi-Kaikyo Bridge alsoknown as the Pearl Bridge, has thelongest central span of anysuspension bridge in the world, at1,991 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.
• The steel cables have300,000 kilometres(190,000 mi) of wire: eachcable is 112 centimetres(44 in) in diameter andcontains 36,830 strands ofwire. Strands of wire Bridge girders•The Akashi-Kaikyo bridgehas a total of 1,737illumination lights: 1,084for the main cables, 116 forthe main towers, 405 for thegirders and 132 for theanchorages. Illumination lights
DOUBLE-CABLE STRUCTUREBridge 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 m Height of Bridge Above Water: 33 m Main Span: 225 m End Span: 107.5 m Other Span: 40 m Speed limit: 80 km/h Maximum Gradient: 3.0%