Beam design:
The design selected for the beam element encompasses the use of precast prestressed concrete. Two symmetrical beams supporting a cast in-situ slab was used so as to provide longitudinal torsional restraint. All in-situ concrete and formwork shall be carried out in accordance to SANS 10100 specifications as described by the calculations attached herein.
Precast design was selected since the beam can be produced under factory conditions and not necessarily cast on-site. Quality can be controlled and costs reduced since there is no need for complex scaffolding, and hence erection time and labour is lowered.
Construction method: Pre-tensioning
The wires are tensioned prior to concreting by means of jacking systems fitted to the beam mould. The concrete is then poured. When hardened, the prestressed beam is removed from the mould. It tends to bend upwards due to prestressing, but deflects to an approximately horizontal position when loaded. The contractor shall satisfy that during casting of concrete, the beds do not deform and contribute to loss of prestress. Only stressing steel that is clean and rust free will be accepted for tendon purposes. If deemed necessary by the engineer, all wires and strands must be treated with an approved anticorrosive before assembly.
Design specifications:
• Two 1200 x 400mm beams supporting a composite insitu slab.
• Beam concrete properties of 50 MPa characteristic strength with an elastic modulus of 35GPa. Unit weight of 24kN/m3 is used. A minimum cover of 30mm must be provided to all reinforcing.
• Class 1 beam, i.e. no tensioned induced throughout the beam in transfer and service conditions. Permissible stresses in accordance to design code specifications. The compressive strengths obtained according to the grade of concrete used is 20MPa in transfer and 16.5 MPa in service conditions.
• Analysis of loading conditions yields a permanent action of 20.55 kN/m and variable actions of 5kN/m2. Serviceability limit state is used to check bending in the beam while ultimate limit state is used for shear.
• The magnel diagram (see calcualtions) was plotted inorder to obtain the feasible region in determining the prestress force at a particular eccentricity. To increase accuracy, the diagram encompasses the service, transfer and construction conditions. A maximum eccentricity of 375mm at midspan with a prestress force of 3705kN was obtained. 18mm diameter 19 wire strands tensioned to 75% of the characteristic strength (370kN), while taking into account elastic losses of 5%, produced a requirement of 15 strands to carry the specified loading conditions.
The cables are supported by four steel towers, one at each corner of the grid.
A schematic of the SHPB facility used in the present work is presented in Figure 2.1. The Split Hopkinson Pressure Bar consists of an incident bar, transmission bar and a projectile termed as the striker bar all made of maraging steel which holds a nominal yield strength of 2500
Elastic strain region at small and big end of connecting rod is shown in figure no. 10. The maximum and minimum equivalent strain values are 0.00033975 and 2.1407e-10 respectively. Due to applied pressure there will be change in original dimensions of the connecting rod and hence strain developed can be
3.13 Static-load rating: The utmost load which will be applied to a stationary screw and nut assembly while not damaging it.
The architecture and engineering firm hired with the task of designing and constructing the tower, SOM, assigned Bruce Graham and Fazlur Khan to the project. They implemented a bundled tube design that was the first of its kind on such a large project that paved the way for the design and construction of future skyscrapers. This design allowed for 4.5 million square feet of office space, more customization of the floor layouts, up to 3 foot of sway within the building, and the stiffness needed to stay standing at the height in which it was built. The tubular design also allowed Sears to save about $10,000,000 on steel alone compared to previously used steel frame designs. Additionally, SOM managed to save 95% of the time usually spent welding by using prefabricated parts referred to as Christmas trees. This not only majorly sped up the process, but allowed Sear to save on labor costs. In addition to 3 trussed layers in the building, there were trusses and spandrel beams designed into every floor to help the load distribute more evenly.
In the past two decades, light gauge (cold-formed) steel has rapidly become a frequently-specified construction material for commercial, institutional, and industrial projects - including the recent trend toward using steel as the main load bearing system. Despite the myths that still surround the use of light gauge steel framing, it has come to the forefront as the best and most feasible alternative building material for residential construction.
Figs 21-22 in Case 3 and 25-26 in Case 4 show the normal bending behavior for the box girder under 100% of the total applied load. The load-displacement graphs in both cases clearly indicate the elastic behavior of the bridge, because the girder was able to carry all of the applied load with no failure, Fig 23 and 27. Since the truck loads in Case 4 are acting on one side of the bridge only, the stress concentration is high at that part as observed in Fig 25-26. The bending displacement in Case 3 is 0.024 inches, which is less than that in Case 4 (0.026 inches) because the bridge in Case 3 under the dead load only as mentioned
The first is for control of buckling in the main girders during construction. The wet concrete imposes significant bending of the bare steel girders and the compression flange needs to be restrained against buckling. The second function is that bracing can be used to distribute the vertical bending effects between the main girders, and to ensure that lateral effects such as wind loading and collision loading are shared between all the girders. The third function is dimensional control, as a result of unequal loading, the horizontal distance between the flanges of adjacent girders will vary if not constrained. Bracing was placed at every transverse stiffener location for both girder sizes. 4 x 4 x ½ inch angles were used for bracing elements (Figure
Many existing bridges structure has been designed without seismic provisions are vulnerable which has demonstrated by recent earthquake. The consequent of the extensive damage to bridge structure include potential loss of life and property, and interruption of transportation system that can contribute to major economic and impact to the society. Concern about the vulnerability of bridges being damage, there are significant need to perform adequate seismic retrofit technique prior to future seismic event. Furthermore, for ensuring the existing bridge meet current safety seismic design requirement consist of detailing schemes that can offer flexural ductility, high-energy dissipation and preventing shear failure. Thus, this paper only focuses on retrofitting of bridge column/pier. Therefore, it is very important to identify potential deficiencies and examine the strategies for retrofit these bridge pier in the rehabilitation of existing bridge pier, which can upgrade the performance and extension of its service life. Common deficiencies for reinforced concrete column and piers as shown in Figure 1.
Mechanical Engineering 130.2 (2008): 6 - 7. Academic Search Complete. Web. The Web. The Web.
Because the cable stayed design allowed for support towers on the land rather than in the water, this avoided potential collisions from large ships with the support piers. The bridge deck itself was constructed in 10metre concrete segments, with the first three segments initially supported by the scaffolding (as seen in Fig 4.2.2). During construction, each segment cast of the land size was also paired with an equal segment over the water to ensure they were all adequately balanced. This segments would individually weigh around 460 tonnes. Upon the completion of the tower, the first stay cables were installed and attached to the allocated slots within the tower.
Bhatt, P. P. (n.d). Prestressed concrete design to Eurocodes / Prabhakara Bhatt. London; New York: Spon Press, 2011.
However, there are some disadvantages in the processes. First, it is very consume time in the pre contract process due to the strategy is sequential and construction cannot be started before the completion of design. Also, the contractor is not appointed in the design stage, so the contractor and supply chain are no input into the design or planning of the project. Mo...
Chua, Ian Y. H. Civil and Structural Engineering Resource Web. 29 Jan. 2000. 2 Mar.