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Recently, The University has purchase the North Kowloon Magistracy building located at No, 292 Tai Po Road in Sham Shui Po. They wish to demolish the two-storey temporary building located at south side of the site and build a new three-storey teaching facilities center at the north side. Thus, I would like to write the proposal to University.
The proposal is divided into two parts:
Section 1 -Temporary Building Removal
This section contains the consideration on demolition of temporary building. How can reduce the disturbance to public and how can be more safely and health during demolition.
Section 2 - Construction of New Building
Site condition of new building:
Foundation Design Consideration:
The Type of foundation to be used:
The site condition is important to the foundation design. According to Practice Notes for Registered Contractors, PNRC46 (2006) that Site investigation should be carried out to obtain adequate geotechnical and other relevant data for design and construction of building works such as foundation. The geotechnical investigation report should be carried out by registered special contractor (ground investigation field category) in order to know the performances of the types and bearing capacity of the soil which is important information to design the foundation.
Referring to geotechnical investigation report shown that the loose and soft sand was on the surface and Grade III type rock bed was on at 2.5m in the depth from ground level. Water table was 3m
Water Table/ Groundwater
In any situation, it would be better that the foundation is distant from the water table or ground water in order to avoid the ground water attacking the foundation which may make the reinforcement being rust or reducing the bearing capacity of soil nearby the foundation.
Referring to the site investigation repots, the water table is 3m in depth from the ground level. Thus, using the shallow foundation can be avoid the water table to attack the foundation
Design of the Building
The design of floor layout, external wall design, location of loading (heavy loading such as plant room) will affect the design of building directly.
The cost would be saved if using right type and size of foundation. Using deep foundation would be more expensive than shallow foundation generally if the site condition can support to use shallow foundation. Structural Engineering should be appointed to design the right foundation for avoiding overdesign on foundation.
Impact to adjacent building
Construction of difference foundations would make difference impacts to adjacent building. As
The Type of foundation to be used:
Referring to geotechnical investigation report shown that the loose and soft sand was on the surface and Grade III type rock bed was on at 2.5m in the depth from ground level. Water table was 2.8m
Due to the level of water table was at 2.8m from ground level, using the shallow foundation is the good choice in this case which can avoid the water table to attack the foundation.
According to Geoguide 3 - Guide to Rock and Soil Description and the Code of Practice of foundations 2004 Table 2.1, the Grade III type rock can allow high bearing pressure (5,000kpa) .Many difference type of foundation cab be used in this good nature ground condition. In view of economical, using pad foundation is more cost efficient and feasible in this case.
Pad foundation is
Why use Pad foundation?
The advantages of using pad foundation:
The new teaching facilities center would be designed as environmental building so as to promote the important of environment to public.
External Wall Enclosure
The Curtain wall with double glazing would be the external wall design. The nature light can be irradiated into the internal
Steel Roof Decking
two-way steel-deck composite floor system.
Referring to the Revitalising Historic Buildings Through Partnership Scheme that there is no Old and Valuable Tree (OVT) at the site in the OVT Register maintained by Leisure and Cultural Services Department . However, there are two mature trees located along the vehicular access to the south-east car park.
Accorinding to the Code of Practice of foundation said that dry soil where the highest anticipated groundwater level is at a depth of not less than 1 m or the width of the foundation, whichever is the greater, below the base of the foundation;
Temporary Structure Removal
The Temporary Building was located at the south side of the site which was two-storey (8.7m(L) x 20m (W) x 6m(H) ). Adjacent to the temporary building is a church and school located at the south side of temporary building, the car park is at the east side, the North Kowloon Magistracy is at the north side.
The temporary building was made by reinforcement concrete and the structure is simple beam- column system. The structural engineer has checked that the structure condition of temporary building is safety which means that the framings, slabs or walls would not be premature collapse. No hazardous material was found in this building such as asbestos containing material.
The Surveyor had check that one of underground gas pipe was found. All of the flushing water, potable water, and electric, data and telephone line were gotten from the North Kowloon Magistracy directly. One sewer manhole and one storm water manhole were collecting all waste water drained off from the temporary building. One fire hose reel was found at each floor but no sprinkles were found. The building was using window type air-conditioning.
Prior of demolition work, the hoarding, the covered walkway & catch platform must be provided for protecting some of the objects and debris pitched out from the construction site to public area. The hoarding design should be complied with the Code of Practice for demolition work 2004, P13 (hoarding and covered walkway). In this case, the hoarding is adequate complied with statutory requirement. The hoarding would be erected at least 3m from the temporary building.
The temporary electric, water, lighting should be set up for demolition work.
Some utilities were supplying to the temporary building which gotten from public directly; relevant departments should be noticed before terminating or rerouting such as gas pipe, manhole & FS service. Authorized Person should double checks and ensures all of the utilities were After termination or rerouting for avoiding the incident occurred during construction.
During demolition work is carrying out, the large of dust would be resulted, thus, spraying water is needed to minimize the dust pollution during demolition work caused;
The temporary supporting is needed to avoid the structure collapsed during demolition work.
Full time safety supervisor should be employed during whole demolition work;
The sufficient waste area should be provided for within the site boundary the debris within the site boundary which would not interrupt the site operation.
The saw-cut method to demolish the temporary RC building would be used. The RC structure should be divided into numbers of piece (approx. 3m x 3m for easy transportation) from top to down by saw-cut machine (see figure 01) and the piece of RC structure should be stabilized by mobile crane during saw cutting. According to the Code of Practice for demolition work 2004, P63, the Sequence of demolition, the sequence of demolition should be slab, secondary beam, then, main beam from top to down and from inward to outward.
Setting out line should be marked on the RC surface to indicate the cutting line for avoiding the cutting machine crashed to temporary supports.
Use coring machine to make the holes on the RC for fixing omega bolts;
Installs the omega bolt and connects to mobile crane by wire;
Follow the sequence of demolition to saw-cut the concrete according to the cutting line and stabilized by mobile crane;
Lift away and land the piece of concrete;
Repeat 3 to 5 until completion of demolition work.
F:\Cityu\Construction Management\Construction and Enviromental Technology\Assignment 1 - City Campus Expansion\Diamond wall saw,hydraulic concrete wall cutting machine and hydraulic concrete saw.jpg
Advantages of using this demolition method:
Less dangerous than manual, long distance control
The debris is easy to clean & cart away from site quickly.