STRUCTURAL ENGINEERING FOR SUSTAINABLE BUILDINGS by ukx10137

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									                    STRUCTURAL ENGINEERING FOR SUSTAINABLE BUILDINGS

                                                            K K CHOY
                                                          REUBEN CHU
                                                             M F HUI
                                             The Hong Kong Institution of Engineers
                                  9/F Island Beverley, No 1 Great George Street, Causeway Bay,
                                                        Hong Kong China

                            Tel: +852 2895 4446 Fax: +852 2577 7791 Email: hkie-sec@hkie.org.hk

     The global environment has been seriously affected by the growth of population and the continuous development of
     urban areas. As building professionals, we bear important responsibilities for the sustainability of building developments
     such that the problem of pollution may be reduced in the course of construction as well as in the operation stage of the
     buildings. This paper attempts to illustrate how structural engineering can contribute in the planning, design, demolition,
     construction and operation stage for sustainable buildings.

     Keyword: Sustainability, green buildings, holistic life cycle, pre-design stage, green features, recycled materials, waste
     management, operation stage.

                                                                     method have a major bearing on the buildability,
1.   Introduction                                                    resources consumption and maintenance requirements,
The continuous growth of population in Hong Kong has                 which structural engineers should carefully consider
caused high demand for new building developments                     from sustainability point of view.
which in turn lead to the consumption of a significant
                                                                     3.   Pre-Design Stage
amount of energy and resources, and the production of
considerable amount of waste, and thus would seriously               Before the design of a building development project is
affect the environment.                                              commenced, it is necessary to coordinate among
This paper attempts to present a brief introduction of the           building professionals for the consideration of various
sustainable strategies, design and practices adopted in a            aspects regarding the environmental performance of the
variety of building projects in Hong Kong. It provides               project from demolition, construction to actual
an account of the effort that the construction industry              operation. Based on the environmental potentials of the
has offered in the direction of sustainable development.             development and the limitations of the project site, the
It will also illustrate the contributions that structural            project team should formulate the sustainable policies
engineering can be offered in the planning, design,                  and the major direction of the development scheme,
demolition, construction, and operation stage of the                 aiming at low pollution and low energy consumption.
buildings for achieving sustainability.                                   During this stage, the structural engineer may
                                                                     contribute in deciding suitable sustainable elements to
2.   Structural Engineer’s Role in Building                          be used in the building development such as targeting
     Developments                                                    the achievement of a particular grading of
Structural engineers bear significant responsibilities for           environmental assessment; the use of environmental and
the achievement of sustainability in building                        recycled construction materials; specifying the use of
developments, which include adopting a holistic life                 timber from sustainable forest; adoption of stringent and
cycle approach from planning, design, demolition,                    economical design standards; conducting relevant
construction and operation of the buildings. Any                     laboratory tests including microclimate studies and
decision made during a particular stage of a building                wind tunnel tests to enhance the understanding of the
project may have crucial implications on the remaining               effects of the development on the surrounding
stages. The choice of materials, design and construction             environment and optimizing the building orientation;


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providing more natural lighting and better ventilation       years, the Department has issued a series of new
for energy conservation; and introducing more green          standards including the Code of Practice for
features for the development.                                Foundations, Code of Practice on Wind Effects, Code
                                                             of Practice for Structural Use of Concrete, Code of
4.   Design Stage                                            Practice for Structural Use of Steel and Code of Practice
In the design stage, the strategies developed for the        for Precast Concrete Construction.          Apart from
adoption of suitable structural supporting system,           providing more comprehensive and updated guidelines
building materials and design standards would affect the     on design requirements, these codes of practice also
environmental performance of the building. It is also        allow the use of performance based design concept and
essential to consider the construction details as well as    the optimization of use of materials.
the operational and maintenance needs of the finished
                                                             4.3. Incorporation of Green Features and
building at the design stage. For instance, the structural
                                                                  Facilities in the Design
support system chosen should have considered
buildability to facilitate the adoption of sustainable       Green features and facilities such as energy efficient air
construction methods, and access and facilities for          handling unit, solar panels, natural ventilation and
maintenance should be provided for at this stage to          lighting, waste sorting and recycling system, green roof
enable efficient maintenance as well as establishing a       and green walls may be adopted in a building
balance between the capital and long-term maintenance        development.       The engineer should consider to
costs.                                                       incorporate them as far as possible in the design, based
                                                             on the site-specific requirements and limitations.
4.1. Engineering Studies for Sustainable                          The Hong Kong Government has been promoting
     Building Design and Construction                        green buildings for many years.          The Buildings
It is always encouraged to conduct relevant engineering      Department together with the Lands Department and the
studies to assist the overall design of the building         Planning Department have issued two Joint Practice
development for achieving better environmental               Notes in 2001 and 2002, providing incentives in the
performance during construction and after completion         form of exemptions from the gross floor area and/or site
of the project. These studies may include microclimate       coverage calculations for eleven types of green features
studies for the nearby region, wind tunnel tests for         in new buildings. These features include balconies,
assessment of wind effect on the building and                wider common corridors and lift lobbies, communal sky
environment. Other engineering studies such as use of        gardens, communal podium gardens, acoustic fins,
recycled aggregates for structural concrete, and fire        sunshades and reflectors, wind catchers and funnels,
engineering tests on structural elements are also            non-structural prefabricated external walls, utility
beneficial in terms of economical and environmental          platforms, mail delivery rooms, and noise barriers. For
design.                                                      the benefits of the development as well as the
                                                             environment, the engineer should incorporate as many
4.2. Adoption of Updated Design Standards                    as possible of these green features to their building
                                                             projects.
While the authority should take the lead to review and
update existing design standards and building                4.4. Choices of Structural System
regulations     towards      sustainability,    building
professionals should always be alert of the availability     Tall buildings generally entails a high ratio of height to
of new and innovative materials and the use of               building width, thus the efficiency of a building
performance based design standards. In this respect, the     structure may be significantly affected by the structural
Buildings Department of the Hong Kong Special                system chosen. For the selection of structural form, a
Administrative Region Government has carried out a           comparison can generally be made for various systems,
major review on a number of practice notes and codes         such as tube-in-tube, perimeter frame with central core
of practice incorporating the latest technological           wall, and outriggers. Consideration should be given for
findings, good practices and local experience. In recent     both the structural performance at the ultimate limit
                                                             state and the serviceability limit state. Moreover,
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factors such as method of construction, buildability,        5.   Construction Stage
cost, layout, flexibility and useful floor areas should      The choice of construction method, the handling of
also be taken into account to ensure efficient design.       construction waste and the effectiveness of construction
     Optimisation of a structural system can                 management have significant implication on the
significantly improve its efficiency, thus resulting in      environment. During construction stage, it is always
saving in materials and associated cost, and increase in     focused on the control of noise, air and water in view of
usable floor area.         Conventionally, optimisation      the statutory requirements on the environmental
involves engineering judgement and reiteration to            legislation. However, sustainable construction methods,
obtain the most optimum and efficient design.                proper handling of construction and demolition wastes,
     There are computer softwares available in the           and effective construction management can contribute
industry, which can take into account the efficiency of      to a large extent in the environmental performance of a
material use, cost, layout, usable floor areas and method    project.
of construction, and provide the engineer with an
optimum and efficient design for the project. A number       5.1. Effective Construction Management
of skyscrapers in Hong Kong have adopted such
computer programmes to optimize the structures of the        It is essential to ensure effective management during the
buildings and in certain cases, a saving of up to 15% in     construction stage. Each step of the construction
construction materials has been achieved comparing           process as agreed by the engineer should be properly
with the original design.                                    followed. It is always recommended that the contractor
                                                             should make detailed records and carry out accurate
4.5. Use of Materials                                        assessment of each construction process, including
                                                             consumptions in electricity, water, fuel, paper and
Reinforced concrete is the most common type of               timber, and the amount of waste produced. These data
construction material used in Hong Kong for structural       would enable further strengthening of the control and
elements. There are choices of different types of            management of construction cost and energy
reinforced concrete that may be adopted to enhance its       conservation.
strength and quality. For example, high strength                   Some sustainability conscious contractors in Hong
concrete may reduce the amount of material use and           Kong have good experience in managing the
minimize the size of structural elements; self               construction site and making valuable achievement in
compacting concrete can ensure quality and durability        minimizing the disturbance to the environment.
of the concrete for locations where there is difficulty in
compaction; the use of pulverized fuel ash as a partial      5.2. Construction Waste Management
replacement for ordinary Portland cement can be
beneficial technically and environmentally.                  It is of major concern in Hong Kong that a great portion
     On the other hand, where possible, environmentally      (about 40%) of the total solid waste disposed of in
friendly, reusable and recycled materials should be          landfills is generated from the construction industry.
chosen. There are a number of green construction             The problem is aggravated by the impending crisis of
materials that have been commonly used in Hong Kong.         the remaining short life of only a few years for landfill
These include reusable safety fences that can be easily      sites and the limited number of reclamation sites
installed and reused many times. Recyclable system           available.       Measures should be taken by the
formwork was also adopted in lieu of the traditional         construction industry to arrest this acute problem by
timber formwork for many projects. These have                way of reducing the amount of waste generated,
reduced the amount of timber used on site and provided       increasing the overall recovery rate and reducing
high quality finishes. Road paving made from trash and       disposal in landfills.
paint of low volatility are also available. In addition, a         For site formation works, the engineer should adopt
number of tailor-made facilities can be used for the         the balanced cut and fill principle where possible.
collection and recycling of wastewater on site.                    A Waste Management Plan prepared at the
                                                             beginning of the construction works, is a useful tool to
                                                             ensure that adequate measures are taken during the
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construction stage to reduce waste materials. Many                Regarding environmental precautions, and debris
civil engineering projects in Hong Kong have adopted          and waste handling in demolition of buildings, the Code
the Waste Management Plan Scheme and the objective            of Practice for Demolition of Buildings issued by the
of reducing waste can be achieved.                            Buildings Department has provided detailed guidelines.
     A measure to discourage the production of
excessive waste from construction sites has been              6.   Operation Stage
implemented since January 2006.            This is the        Comparatively, the operation stage of a building is
Construction Waste Disposal Charging Scheme, in               much longer than its other stages of planning, design
which disposal of construction waste to landfills is          and construction. Therefore, systematic and proper
subject to a charge of HK$125 per tonne, whereas,             building management and maintenance are particularly
illegal dumping is subject to a maximum penalty of            important. The engineer should incorporate his concept
HK$500,000 and 6 months imprisonment. Therefore,              of sustainability during the planning, design and
effective waste sorting and treatment not only allow          construction regarding the buildings inherent quality,
reusing and recycling, but also reduce disposal charges.      durability and maintainability, into the operation stage
                                                              by providing a concise manual for the maintenance and
5.3. Precast Concrete Construction
                                                              repair of building facilities to the users including the
Precast concrete construction is considered as a green        management team and the occupants.
construction method. Its benefits to the environment
include the reduction in noise and air pollution, efficient   7.   Conclusion
use of materials and faster construction cycle.               With increasing awareness in sustainability, it is positive
Therefore, precast concrete construction has been             to note that the construction industry and the Hong Kong
widely adopted in many public housing projects and            Government are making contributions to sustainable
private developments.                                         building developments. However, we consider that it is
     Since 2002, the Hong Kong Government provides            still only a small step in the direction of a sustainable city.
incentives in the form of gross floor area exemption for            As structural engineers, we should be aware that we
non-structural prefabricated external walls. As a result,     have an important role to play in the whole life cycle of a
more and more private developments have adopted this          building. We need to offer our best effort for the
construction method. In addition to using precast             achievement of sustainable building developments. It is
concrete facades, these developments also introduce           important for us to continue our mission with an open
other prefabricated units such as precast stairs, semi-       mind and instill a sense of responsibility for the protection
precast slabs and precast structural columns and beams        of the environment, into all the stakeholders as well as the
in the buildings although these do not attract any gross      younger generation such that a proactive attitude will be
floor area exemption.                                         taken in achieving sustainability in the long run.

5.4. Demolition
In Hong Kong, it is very common that staged                   References
demolition is carried out in a systematic manner. This        1.   Joint Practice Note No. 1 issued by the Buildings
enables efficient sorting and recycling of demolition              Department, Lands Department, and Planning
waste. In general, non-structural elements including               Department of the Hong Kong SAR Government
window frames, pipes, metal elements and timber such          2.   Joint Practice Note No. 2 issued by the Buildings
as doors and wooden floorboards are removed in                     Department, Lands Department, and Planning
                                                                   Department of the Hong Kong SAR Government
sequence, then followed by structural elements. Sorting,
                                                              3.   Code of Practice on Wind Effects in Hong Kong
selection and screening of materials are usually done at
                                                                   2004, published by the Buildings Department of the
source for easy recycling or reuse of materials.                   Hong Kong SAR Government
     In the adoption of demolition method, more               4.   Code of Practice for Structural Use of Concrete
environmental friendly tools should be used, such as               2004, published by the Buildings Department of the
hydraulic crasher, wire saw.                                       Hong Kong SAR Government
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5.   Code of Practice for Demolition of Buildings,
     published by the Buildings Department of the Hong
     Kong SAR Government
6.   Code of Practice for Foundations, published by the
     Buildings Department of the Hong Kong SAR
     Government
7.   Code of Practice for Precast Concrete Construction,
     published by the Buildings Department of the Hong
     Kong SAR Government
8.   Code of Practice for the Structural Use of Steel
     2005, published by the Buildings Department of the
     Hong Kong SAR Government



Presenters’ background




Ir CHOY Kin Kuen
Vice President, The Hong Kong                              Ir Prof CHU Pui Kwan
Institution of Engineers                                   Reuben
Vice Chairman, Professional Green Building Council         Vice President, The Hong Kong
                                                           Institution of Engineers
                                                           Managing Director, Meinhardt (C&S) Ltd and
                                                           Meinhardt Infrastructure and Environment Ltd

Ir CHOY Kin Kuen was graduated in 1975 at the Hong
Kong Polytechnic with an Associateship in Structural       Ir Prof Reuben CHU is the Managing Director of
Engineering.                                               Meinhardt (C&S) Ltd and Meinhardt Infrastructure and
    Ir CHOY is a Chartered Civil and Structural            Environment Ltd consisting of over 300 staff covering
Engineer, a Fellow of the Institution of Structural        civil, structural, geotechnical, infrastructural and
Engineers and the Hong Kong Institution of Engineers,      environmental engineering. He has over 30 years
and a Class 1 Registered Structural Engineer of the        experience in consulting engineering and has delivered
People’s Republic of China. He is a Council Member         services to Private Sectors, Government Departments,
of the Institution of Structural Engineers, United         MTRC, KCRC and London Underground in Hong
Kingdom. He also serves the Hong Kong Institution of       Kong, Macau, Mainland, and the UK. His involvement
Engineers as a Vice President and the Hong Kong            in major projects including projects of Hong Kong
Professional Green Building Council as a Vice              International Airport, Hong Kong Disneyland, MTRC
Chairman and the Chairman of the Board of Education        Airport Rail Link, MTRC Shenzhen Metro, KCRC
and Research.                                              Kowloon Southern Link, KCRC East Rail Extension,
    Presently, Ir CHOY is an Assistant Director of the     Eastern Harbour Crossing, Tate’s Cairn Tunnel and
Buildings Department responsible for all structural        London Underground Jubilee Line Extension etc. He
engineering and related matters. He has been appointed     was also a part-time Lecturer in Civil Engineering with
as an Adjunct Professor of the University of Hong          Hong Kong Baptist University and The Polytechnic
Kong and the Hong Kong Polytechnic University since        University of Hong Kong.
2004.                                                           Ir Prof CHU is also the Vice President of Hong
                                                           Kong Institution of Engineers, Past Chairman of the
                                                           Professional Green Building Council and Past
                                                           Chairman of the Hong Kong Association of Consulting
                                                           Engineers.
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