In this project, the construction of the superstructure involves a single storey building which has dimensions of 30m by 45m and 18m height. The superstructure will be the main structure which will house the combined heat and power (CHP) energy generation facility. The requirement for the construction of such housing has to take care of the safety measures and the strength factors which are meant to enhance durability. The design and construction of the facility has to meet the crucial aspects of the use of the facility (British Cement Association., & European Concrete Building Project 2010). In addition, the heat factors have to be taken into consideration during the construction of the superstructure and cladding details. Due to the height of the superstructure, safety will be an important factor which needs to be considered during the construction process. In addition, the current construction procedures take much consideration for the durability issue. This means that the cladding details have to ensure that the structure is durable enough to meet the required specification and use of the structure. This means that the methods of construction have to make sure that the structure attains the design lifespan (El-Reedy & Keshavarz 2015). The superstructure will involve the construction of the skeletal frames which will ensure that the superstructure has the required stability. The design process will ensure that the materials adopted for the skeletal framework has the relevant materials which withstand the different forces and heat experienced during the use of the structure.
The cladding system will be key to ensure that the heat from the CHP facility in the internal section does not affect the external envelop. The framed skeleton will also be used to separate the internal and external envelope. This section will ensure that the internal environment conditions are well insulated using the cladding systems from the external conditions. The superstructure will have a height of 18m and the skeletal frame will be important in the loads transfer (Chudley 2011). This skeleton will ensure that the loads from the top such as wind, self and earthquake loads are well transfered for safety purposes (Foster, Harington and Greeno 2006). As noted earlier, this structure will be a single storey building and this means that the structure will have a reduced self weight. Proper mechanism will be applied to ensure that further reduction of the self weight is achieved (International Code Council 2017). The current construction methods have proper materials which can be used to achieve lighter weight and they will be highly implemented in this project. These materials are also tailored to enhance the cost effectiveness of the construction process. Therefore this is another factor which will be considered.
Construction Methods for Tunnel
On the materials section for the superstructure and cladding, they will be chosen such that they can withstand heat and stability factors. Some of the materials which will be utilized in the construction of these structural elements such as columns and tie beam include insitue and precast reinforced concrete (El-Reedy & Keshavarz 2015). The concrete structure will be able to enhance stability and durability of the superstructure and also take care of load transfer. High thermal mass for the structure will also be enhanced by the concrete structure elements (United States., & United States 2011). In the CHP design, the durability and heat transfer will be highly considered.
As part of the temporary works, the structure will utilize the shuttering, scaffolding and the on-site formwork for the construction of the concrete segments. The scaffolding elements will be used to ensure working at heights is safer through creation of the necessary platforms. Since the superstructure has a height of 18m, which is too high, the scaffolding will be an important temporary works on site (BS 5930 1999). Another key temporary works which can be employed on the site is the use of crane supports. This will be used to move the materials to the required heights to the construction area. Shuttering and formworks will be essential for the insitu casting of concrete. These services will ensure that the works are casted to the required forms. The formwork moulds will provide the different shapes of the construction elements such as the beams and columns and also required strength. These temporary works will only be availed on site when required (Grey & Reading Production Engineering Group 2012). The formworks may be from the available materials such as wood, steel, glass or fibre reinforced plastics. Concrete plants and earth-moving plants will also be required at certain times. During foundation works, the earthmovers will be utilized will during casting of concrete the concreting plants will be utilized.
During the construction of the FOG storage shaft, different methods can be adopted. The shaft will be required to meet special specification which will ensure that the FOG storage is stable and durable. Therefore the construction method used is usually important to achieve the construction specification (Chudley 2011). Concrete flat bottom and a spherical or cylindrical shape are some of the methods which are utilized in the construction of such structures. This section will analyze a proposed method to enhance the construction of the FOG shaft.
Construction of Superstructure for CHP Facility
The bottom up method is one of the key proposed methods to enhance the construction of the FOG shaft on this project. Additionally, the method is also known as the traditional construction method of the shaft. This is because the method has been utilized a lot due to its ease in the construction of the shaft. The method is simple and involves the construction of the shaft from the bottom section all the upwards and finished with the roof section. When this method is utilized, the base of the shaft is assembled first and its sections are well constructed. Through this method, steel reinforcements are erected first and then the formwork follows next (Grey & Reading Production Engineering Group 2012). After the formwork, the in-situ concrete is used and poured to form the sides of the shaft. This ensures that the shaft will have the required strength to enhance durability and use of the FOG shaft. Different sections will always be set up one after another until the required height is reached. This will ensure that the structure has the required timeline to attain the required strength since concrete gains strength with time (Moss et al, 2009). The roof section will lastly be made and the shaft will be completed. This is one of the easiest methods which are used in the construction of the FOG shaft.
One of the key temporary works which will be utilized in the construction of the shaft is the use of scaffolding. Since the shaft will be high enough, working at heights will require key platforms to enhance safety at those heights. The scaffolding mechanisms will ensure the safety when working at height is well achieved. In addition to the scaffolding, the lifting cranes will also be important to ensure that materials and those working at heights have their safety measures taken care of (Canadian Institute of Steel Construction 2016). The lifting careens will ensure that when materials are needed at high heights they are delivered. In addition, the formwork for the in-situ concrete will be a major temporary works. Since the concrete will have high flow, the requirement of the formworks will be important. They will be able to hold the concrete until the casted concrete cured and able to withstand on its own. Moreover, the formworks will also ensure that the concrete is able to attain the required strength. The formworks also help to form the shape of the shaft as it is designed. The formwork will be designed to suit the different sections of the design structure of the shaft. In addition, since the shaft may be high enough, support cranes is another major temporary work which may be important on this project. The contractor may acquire the tower cranes to ease the movement of the loads up when the construction of the shaft is too high (Illingworth 2009). In addition, trench support at foundation level can also be applied. This will ensure that the foundation does not fail. Timber trenching will be utilized in enhancing stability of the foundation trenching during the construction of the shaft. This will be an important temporary work at this stage on the foundation stage.
Temporary Works for Superstructure Construction
For the construction of the bridge and viaduct, different methods can be used to enhance their proper and safe construction taking into account the cost and safety measures. This section will analyze some of the key construction methods of these elements.
Precast span-by-span construction method – this methods will be utilized for both construction of the viaduct and the bridge. Since traffic distraction is involved in this project, this method will be able to provide short time distraction and speed of the construction of these elements. During the construction of the bridge, this method uses an erected truss which is under the bridge segments or an overhead erected gantry, which helps to guide the precast construction elements to their positions. In addition, this method consists of permanent tiers, which are used to hold the recast elements of the bridge. Installation of the stressing longitudinal PT tendons is also applied in this method, and they enhance in spanning of the segments on their own. In addition, this method has an advancing erection girder which leads into the place where the erection of the adjacent span is. The utilization of this method helps to save time and resources as well as the traffic distraction time during the construction period. More importantly, the significance of the benefits through this method is achieved with increase on the spanning distance.
Incremental launching method- another method which is proposed for the construction of the viaduct and bridge is the incremental launching method. Some of the key benefits achieved through the use of this method are savings on time, resources, space and ease on disruption of the traffic. This method is used in the construction of the continuous post tensioned span bridges and viaduct. Through this method, the different sections are cast continuously on a placed stationary formwork, which is usually behind the abutment and therefore pushing into a completed section through forward jacks (Chudley 2011). Through this method, the different sections are cast continuously and then stressed together. In addition, the superstructure of the bridge and viaduct is launched over the sliding bearings, which are placed on piers. This method also aims to keep the bending moments low. The moments are kept low during the construction process, where the nose launching is usually attached to the front of the bridge deck. Due to the minimal disturbances to the environment and the small assembly zone requirement, the method is more advantageous when used in the construction. Moreover, the method has high safety factors during the construction process since most of the works are done on the ground level. Another key advantage of the method is that there is usually an easy access to the restricted area and the area is limited. Lastly, when used, the method leads to high quality of finishes and performance.
Construction of FOG Storage Shaft
One of the key plants which will be used in the project is an excavator. This plant will be used will be used during the excavation process for the piers and viaduct section. The foundation for the bridge and viaduct section will require excavation will utilize this plant (Chudley & Greeno 2004). In addition, hauling trucks will also be needed to transport the cut away from the construction sites.
For the completion of this project, some important temporary works will be required. One of the key temporary works required in this project is the temporary mobile towers. These will be less than 10m. The towers will be able to cater for the segments which are out of balance during the erecting process of the precast elements of both bridge and viaduct. Moreover, temporary scaffolding which will provide the platform system for the precast system installation will be provided (Hughes & Ferrett 2005). The system will ensure that the monolithic connections are well done together with the piers and the correct quality is achieved. The temporary scaffolding structure will be mounted on the piers top positions. Additionally, another temporary works which will be provided will be temporary stabilizing systems which will be used for balancing the cantilever on the bearings (Illingworth 2009). Temporary towers will also be utilized for erecting the long cantilever structures at times when the piers are not able to resist huge unbalancing forces (In Ratay 2012). Another key temporary work will be clamping systems used for the closure of the middle stitch for two adjacent cantilevers.
The structure through this method is built within an excavated area and then backfilled to cover the area after the construction is completed. In the construction, this method is used for the shallow profiles and low level excavation from surfaces. Moreover, this method is highly economical, easy to use and acceptable for the tunnel construction (International Code Council 2017). Through this method, a trench is excavated and then roofed with proper ad strong overhead supports, which are strong enough to carry the tunnel load. Using this method, two methods are mostly common, which include the bottom-up and top-down methods. In the bottom-up, the trench is excavated using ground supports and the tunnel is constructed. Precast concrete, in situ concrete, precast arches may be utilized for tunnel construction (Warren 1996). Afterwards, the area is backfilled. On the other hand, through the to-down method, the sides of the tunnel are first done for the support walls and capping beams from the ground. Then shallow excavation is done to make the tunnel roof. Then the surface is later reinstated leaving only open areas for manholes inspection.
Temporary Works for FOG Storage Shaft Construction
This method is also known as pipe jacking and it is a tunneling method which is utilized for small diameters while installing underground pipelines. This method utilizes the tunnel boring machines as well as hydraulic jacks when tunneling. The hydraulic jacks help to push the designed pipes through the ground during the tunneling process and shielding behind the excavations. This method is able to provide flexible, structural, watertight fines of the pipe networks (Holmes 1995). Moreover, when using this method, thrust and reception pits are constructed mostly at the manhole sections. In addition, in order to ensure proper tunneling, the jacking forces are equally distributed on the pipes circumference. The equal distribution ensures the horizontal jacking is equally achieved.
Boring machine is applied during the tunneling process in this method. The machines help to achieve a circular cross sections excavation which passes through different soil and rock strata. The TBM machine in addition varies and therefore analysis of the soil and rock strata has to be done to determine which machine will be applied (Watts 2014). The major challenge of tunneling through this method is the expensive nature of assembling and transporting the TBM machine on site.
The appropriate runway clearance method is the lateral runway tunnel clearance method. This clearance method helps to provide enough space for the different elements on the tunnel to ensure that incidents and accidents do not happen. The major assumption for this clearance method will be made on the minimum edge of the runway tunnel structure. On the road sections, at least 3.0m will be allocated on the tunnel sections. For the tunnel clearance, the minimum clearance between the edge and the inner face will be estimated to be able to allow proper spacing for the pedestrians to pass (Chudley 2001 and Foster, Harington and Greeno 2006). In addition, the clearance method will ensure that proper lighting is achieved on the tunnel section. The lateral sections will assume proper lighting systems are in place with proper signages. The signages will be assumed to be at proper lateral distances from the tunnel runway to avoid distractions. This is meant to ensure that the obstruction by the signage does not happen within the tunnel runway section.
References
British Cement Association., & European Concrete Building Project, 2010, Improving concrete frame construction. Crowthorne, Berkshire: British Cement Association on behalf of the project partners.
BS 5930: 1999 Site Investigation BSI Elsevier
Canadian Institute of Steel Construction, 2016, Handbook of steel construction. Longman
Chudley, R & Greeno, R., 2004, “Building construction handbook”5th edition Butterworth
Chudley, R., 2011, “Building Construction Handbook” Longman
El-Reedy, M. A., & Keshavarz, A., 2015, Combined cooling, heating and power: Decision-making, design and optimization. College of Estate Management
Foster J. S., Harington, R., and Greeno R. 2006, Structure & Fabric parts 2 & 2 Mitchell building Series 7th ed. Routledge.
Grey, C., & Reading Production Engineering Group, 2012, In situ concrete frames. Reading: Reading Production Engineering Group.
Holmes, 1995, ‘introduction to civil Engineering’ 3rd Edition College of Estate Management
Hughes, P. & Ferrett, E., 2005, “Introduction to Health & Safety in Construction” 2nd Ed Elsevier
Illingworth, J. R., 2009, Temporary works: Their role in construction. London: Thomas Telford Ltd.
In Ratay, R. T. 2012, Temporary structures in construction. New York, N.Y: McGraw-Hill Education LLC.
International Code Council, 2017, 2018 International Fire Code. London: Construction Research Communications Ltd.
Moss, S. A., Building Research Establishment., & Construction Research Communications Ltd. 2009, Potential carbon emission savings from combined heat and power in buildings. London: Construction Research Communications Ltd.
United States., & United States, 2011, Thermal Energy Corporation Combined Heat and Power Project. Washington, D.C: United States. Dept. of Energy.
Warren, D., 1996, “Civil Engineering Construction Design and Management” MacMillan
Watts, A. 2014, Modern construction envelopes. London: Construction Research Communications Ltd.