Added: Jaron Reber - Date: 29.10.2021 23:35 - Views: 26449 - Clicks: 4681
This chapter explores Longbridge mill speed dating possibility of deing and constructing a super-long-span bridge with new materials in The proposed bridge de has a total span of m with two m end spans and a central span of m. The height of the two pylons is m, and the deck width is 40 m. The features of this structure include the combination of a suspension bridge and cable-stayed bridge, application of carbon fibre materials, extension of deck width and pretension techniques.
Linear static Longbridge mill speed dating, dynamic analysis and theoretical analysis are conducted under different loading cases. In linear Longbridge mill speed dating analysis, the stresses under critical load combinations are smaller than the ultimate strength of the materials. However, the maximum deflection under the dead and wind load combination exceeds the specified serviceability limit. The feasibility of deing a super-long-span bridge with new materials in is studied. Longer bridge spans have the benefits of increased horizontal clearances and reduced risk of ship collisions with piers [ 1 ].
The length of very long span suspension and cable-stayed bridges are often limited by the weight of the cables. As spans increase, the cables experience high stresses due to their own self-weight, and the overall structure becomes less stiff as the stiffening contribution of the deck becomes negligible [ 1 ]. Therefore, strong but light-weight materials must be used in the de of super-long-span bridges.
There are many new high-strength materials with low density like carbon fibre with epoxy, graphene oxide and alumina-polymer composites. Some materials have much better mechanical performances than steel or concrete but are only used in some high-tech industries such as aerospace, wind energy and automotive industries due to their high price.
Bythe new materials are likely to be used extensively in construction due to the reduced cost in the development process of new materials [ 2 ]. This paper presents and analyses a super-long-span bridge de which has a total span of m with 40 m width deck and two m-high pylons.
The bridge de is based on the Golden Gate Bridge and a finite element model is created in Strand7 [ 3 ] which is a modification to the Golden Gate Bridge model developed by [ 4 ]. The central span of the bridge is m, which is three times the span of the Golden Gate Bridge of m, while the length of the two end spans is the same at m.
studies have been conducted on super-long cable-stayed bridges using carbon fibre reinforced polymer [ 5 ] and on long-span suspension bridges using fibre-reinforced polymer [ 6 ]. Special techniques are adopted in this de where the bridge combines the advantages of a suspension bridge and a cable-stayed bridge to minimise the deflection of the superstructure and the pylons. The material of the catenary cables and stay cables are changed to a lightweight fibre carbon composite [ 7 ] with high stiffness and high strength, and standard carbon fibre is used in the superstructure and the vertical hangers.
Finally, the stayed-cables of the bridge are pre-strained in this de. Carbon nanofibres have cylindrical shapes with graphene layers constructed in the morphology of cones or plates or sheets, with an average diameter of 50— nm and an average length of 50— um, exceptional thermal and mechanical properties as high as elastic modulus of GPa, tensile strength of 8. These extraordinary properties of advanced hybrid composites have enabled the de engineers to use them in the renewal of civil infrastructure ranging from the strengthening of reinforced concrete, steel and iron, and for replacement of bridge decks in rehabilitation seismic repair, strengthen or retrofitting to the construction of new ultra super-long bridge and building structures with less cost.
Inhigh strength polymeric material roof structure with the shape of an umbrella was manufactured via hand lay-up fabrication process and transported from the UK to be erected at the international airport of Dubai. In s, it was replaced by advanced composites that were made with sophisticated glass fibre-reinforced plastics. Such advanced polymer composites with nanofillers e. These ACS components are cheaper with durability, light weight, low cost, speed of construction, ease of transportation, and they show superior mechanical properties e. Therefore, such advanced carbon fibre-reinforced polymer CFRP composite materials are promising candidates in the future for the construction of ultra-super-long bridges.
It is feasible to develop over 10, span stable super-long bridges using new concepts. A new concept of engineering that is used for nanoscale modelling of super-long bridges can be described in following sections. Finite element models were created in Strand7 [ 3 ], and the show that a maximum deflection of 8. Furthermore, a The de Longbridge mill speed dating this long-span bridge is based on the Golden Gate Bridge, therefore structural member types are essentially similar to the Golden Gate Bridge, which consists of a bridge deck with a supporting trusses and beams system, two pylons, catenary cables, vertical hangers and stayed cables and eight lanes of Longbridge mill speed dating traffic.
The de of the central span between the two pylons is based on a typical suspension bridge, while the two edge spans are similar to a cable-stayed bridge. The superstructure spanning between the two pylons is hung by vertical suspenders at m intervals, which is the same Longbridge mill speed dating a typical suspension bridge. These vertical hangers carrying the lo on the deck are supported by the catenary cables suspended between the two pylons. Additionally, the stay cables at the two edge spans connecting the top of the pylons and the ends of the bridge are anchored by the abutment anchors at each end of the bridge.
The cables directly running from the tower to the deck form a fan-like pattern on a series of parallel lines. The properties of the materials used in the bridge model are listed in Table 1 [ 789 ]. The material selection is further discussed for each structural member.
The superstructure of the bridge consists of four major components: the bridge deck, permanent formwork, the cross girder and the deck truss system. The 0. Figure 1 shows the details of the arrangement of the structural members in the superstructure without the bridge deck.
As shown in Figure 1the truss system resisting tensile or compressive force is attached to the cross girders running across the driving direction of the bridge. The concrete bridge deck sits on top of the truss system and Longbridge mill speed dating girders, and the live load and vertical wind load are directly applied on the top of the bridge deck.
Furthermore, the rectangular hollow section cross bracings distribute the lo on the deck onto the cross girders, and they also perform as the tensile reinforcement for the bridge deck above. Details of the bridge superstructure. The de uses three types of cables: catenary cables, vertical hangers and stayed cables. In the central suspended deck, cables suspended via pylons hold up the road deck, and the weight and the vertical lo are transferred by the cables to the towers, which in turn transfer to the pylons and the anchorages at the end of the bridge.
Since all of the cables are in tension, a lightweight carbon fibre or carbon fibre composite should be used in the cables based on material properties in Table 1. Firstly, the catenary cables with a diameter of 2. Carbon fibre composite i. The shape of the catenary cables is determined by selecting an appropriate interpolated shape between the catenary shape and the parabolic shape.
The detailed explanation of this process is introduced in Section 3. The catenary cables are formed by connecting the coordinates that mimicked the shape of the cable, so the cables are segmented instead of smooth. Secondly, there are pairs of vertical hangers at m intervals at the central span. The diameter of the vertical hangers is 0. Standard carbon fibre is used in vertical hangers due to the relatively low tensile stress. Two pylons are also built up at positions which are m from each end of the bridge.
The total height of a pylon is m. The superstructure is connected to the pylons at m from the foundations of the pylons. The lo on the catenary cables and the stayed cables are transferred to the pylons as a compressive force; therefore, Grade steel is used as the material of the pylons [ 10 ]. The sizes and materials of the structural elements of the long-span bridge are shown in Table 2. The vertical lo acting on the bridge mainly consist of the self-weight of the structural members, the live load due to traffic and the vertical wind load.
The vertical lo applied to the bridge deck are firstly carried by the reinforced concrete deck through bending, where the Longbridge mill speed dating is directly supported every 5 m by the cross girders I beams with web stiffeners. The web stiffeners act to increase the shear capacity of the deep I beams and decrease the chance of shear buckling in the web. Then the cross girders transfer lo from the bridge deck to the truss system below the deck through bending.
In the Strand7 model, the truss members are modelled as rectangular hollow sections to simplify the de. The members of the truss system can only carry axial force, so the top chords are in compression, and the Longbridge mill speed dating chords are in tension. The lo on the truss system are spread along the main longitudinal truss members, and further transferred to the vertical hangers which are hanging off the corresponding superstructure every 15 m.
These cables carry the lo from the bridge deck up to the catenary cables and the stayed cables through pure tension. On the Golden Gate Bridge, each catenary cable is made up of 27, galvanised steel cables which are grouped into 61 cable groups, which are then bunched together to form the 0. For the super-long-span de, the larger diameter of catenary cables and stayed cables requires more galvanised steel cables to group larger cables. These stayed cables are also anchored at the abutments to keep them in tension and to pass the tensile load into the Longbridge mill speed dating through the abutments.
The pylons supporting the catenary cables, the stayed cables and the bridge deck are loaded in compression Figure 2. Only wind load is considered as the lateral load acting on the bridge. Because this bridge is very long, the frequency of earthquakes is not consistent with the resonant frequency of the bridge.
Therefore, the action of the earthquake load is not ificant in this de.
For simplicity, it is assumed that the transverse wind load only acts on the superstructure and the pylons. Therefore, the primary system used to resist transverse wind lo consists of the superstructure at the central span which is mainly restrained by the two pylons, the vertical Longbridge mill speed dating which are further suspended from the catenary cables and two pylons resisting the wind transverse wind load. Dead load G s for the self-weight of the entire structure, which is calculated by multiplying member dimensions with the corresponding density.
Dead load is Longbridge mill speed dating calculated by multiplying the density by the gravitational acceleration. According to AS However, for simplicity, the live load is considered as a pressure acting on the bridge deck in the Strand7 model. The most severe load specified in AS It is recommended that the Load Influence solver in Strand7 can be used to determine the critical point for the live load and the sensitivity of structure members. Wind load is the dominant impact on super-long bridges.
The site wind speed is calculated as:. Then the wind load applied on each structure member can be calculated for each structural member. For simplicity, the transverse wind load is assumed to only act on the superstructure and the pylons. By applying fundamental principles in engineering de, analytical calculations were carried out to determine the optimum cable shape for the suspension bridge and to predict and verify the maximum stresses in the catenary cables and the natural frequency of the structure.
The shape of a flexible cable under self-weight is a catenary [ 13 ]. The equation for a catenary is:. Alternatively, when the cables are under heavy load i. However, in this de of a super-long-span suspension bridge, neither the self-weight of cables nor the applied uniformly distributed load from the deck can be ignored.
Therefore, the resulting shape of the catenary cable is between Longbridge mill speed dating shape of a parabola and a catenary [ 14 ]. To determine the optimum cable shape that in minimum deflection for the suspension bridge, an interpolation factor, K, is introduced to determine the final cable shape:.
Note that the cable shape will be a catenary when K is 1 or a parabola when K is 0. When only considering dead lo, the normalised maximum deflections of the middle span are plotted against different K values as shown in Figure 3. It is observed that for different K values, the maximum deflections for each case are different, and it reaches a minimum when K is about 0. It is also important to note that when the applied load has changed, the optimum K value will change as well. By considering different loading cases while maintaining relatively low deflections, a K value of 0.
Normalised maximum deflection under self-weight vs.Longbridge mill speed dating
email: [email protected] - phone:(893) 768-7204 x 6693
The Feasibility of Constructing Super-Long-Span Bridges with New Materials in