Life cycle analysis for design and construction of new structures

Life cycle costing analysis for design and construction of new infrastructure.

Life cycle analysis for design and construction of new structures

BCRC can assist owners as well as designers and contractors identify the most economical design option considering whole life cost analyses. From a structural design point of view, the major costs pertain to the initial costs related to design and construction and the future costs are mainly related to maintenance and repair of the structures over its service life. Energy and operating costs such as heating, and cooling could be significant components in the overall life cycle cost for a structure, but they generally do not depend on the structural design parameters concerning strength, reliability and serviceability.

Hence in a structural design development based on whole life cycle cost analysis, the primary objective would be to achieve an optimum balance between the initial costs of structural design and construction and the future/recurrent costs of repair and maintenance with respect to the various design parameters. The extent and timing of these future costs are dependent on the service life of the structure which, in turn, depends on the exposure environment and the level of structural performance expected to be maintained. Hence this design approach involves an integration of service life and the ensuing durability considerations into the structural design process.

We were recently involved in the design of a major coastal defence marine facility in WA, where we helped the design team identify the most economical design option for the main wharf using life cycle cost analyses (LCCA) between the compliant conventional construction materials and methods, and an alternative innovative solution. This LCCA comprised an economic assessment of the divergent elements of the two competing design options, considering selected costs of ownership over the economic life of each divergent alternative. Thus, the life-cycle cost would be the total discounted dollar cost of owning, maintaining, and disposing of the divergent structural elements over a period of 100 years. Hence, the LCCA focussed mainly on the following costs which the owner would incur on the divergent elements of the structure during its lifetime, to keep the structure operational.

  • cost of construction
  • structural inspection and maintenance costs
  • structural rehabilitation and protection costs

Life cycle analysis for design and construction of new structures

In addition to the construction and maintenance costs, the analysis could also incorporate the long-term environmental, socioeconomic and sustainability impacts of the two options to select the most economical and durable option.

BCRC’s approach to whole life cycle costing analysis usually comprises the following activities:

  • Review proposed systems to support 100-year design life of the structure – for compliant design as well as the proposed alternative design options.
  • Provide feedback to design team on possible improvements in alternative design.
  • Review and compile inputs into labour and material rates provided by the Client and other suppliers, sub-contractors.
  • Develop durability and maintenance strategies to ensure both options would result in a 100-year low maintenance structure, based on the specified minimum performance requirements.
  • Evaluate the level of effort required for the inspection, maintenance and rehabilitation of the structure over the design life.
  • Populate the life cycle cost report with key assumptions in maintenance intervals and performance of materials/ systems, over the life of the structure.
  • Develop the LCC model and analyse the life cycle costs of both options.
  • Provide a report outlining the effectiveness of the proposed alternative system, highlighting advantages in maintenance, and compare the lifecycle costs of the options.

Based on the study, the alternative option was observed to be the most economical not only in terms of the cost of construction but also the life cycle cost of maintenance and repairs. The Client used this report in their tender submission in support of their proposed steel module alternative.

Life cycle costing analysis for optimising structural repairs.

All structures deteriorate with age and, sometimes, prematurely due to aggressive exposure conditions that were not addressed in design and construction. Sooner or later, this results in damage to the structure and, hence, in a reduced service life. When a structure reaches such a level of deterioration that an intervention and repair decision must be made, it is necessary to first understand the cause of deterioration by carrying out a condition assessment of the structure and then analyse and select the most appropriate repair method, keeping the desired service life and the whole life cycle cost of the repair in mind.

BCRC can assist clients, repair engineers and repair contractors with their decision making based on economical as well as technical aspects. Based on our wide experience with all types of structures in various exposure conditions, we are able to identify the root cause of deterioration and the best technical solutions that could be applied for remediation. Thereafter, a comparison of different adequate and durable repair methods is done by means of life-cycle costs. To ensure that the existing budgetary resources are best used to preserve the optimal structural condition, the costs and future effects of repair methods are taken into account. Repair strategies are examined for their economical relevance, and this permits a comparison of different repair strategies, thereby optimizing the available financial resources.

Calculations or estimations of costs can be carried out in different ways by considering various types of costs. Lifecycle costs may be used as a valuable tool for the assessment of the cost effectiveness of various technical solutions for condition assessment, maintenance and repair strategies during operation of the structure.

As a basis for the life cycle costs of a concrete structure up to the end of desired service life, the net present value formula is used. Initial repair costs are generated from repair design, planning, surveying, through to implementation and final inspection. Follow-up costs refer to costs for future inspections, maintenance and rehabilitation. The functional unit of the life cycle costs is $ per m2 of repaired concrete surface. From the LCC analysis, it often turns out that repair methods with low initial costs at the end of the theoretical service life turn out to have higher life cycle costs.

In addition to the construction and maintenance costs, the analysis could also incorporate the long-term environmental, socioeconomic and sustainability impacts of the two options to select the most economical and durable option.

BCRC’s approach to whole life cycle costing analysis usually comprises the following activities:

  • Review available repair systems to support the desired service life of the structure.
  • Provide feedback to repair team on possible improvements in alternative design.
  • Review and compile inputs into labour and repair material rates provided by the Client and other suppliers, sub-contractors.
  • Develop durability and maintenance strategies to ensure the selected repair options would result in the desired service life with the expected level of maintenance and performance.
  • Evaluate the level of effort required for the future inspection, maintenance and rehabilitation of the structure over the design life.
  • Populate the life cycle cost report with key assumptions in maintenance intervals and performance of repair materials/ systems, over the life of the structure.
  • Develop the LCC model and analyse the life cycle costs of repair options.
  • Provide a report outlining the effectiveness of the proposed repair system, highlighting advantages in maintenance, and compare the lifecycle costs of the available options.