Tough times brings tighter designs

5 tips to optimize the engineering on your development for a tougher economic marketplace.

Todays landscape for the commercial and development sector has changed significantly since the onset of the GFC. The increased pressure on funding availability, combined with conservative valuations and high pre-sales and pre-commitment lease requirements have made it difficult to get projects out of the ground. Smarter and more innovative engineering is becoming critical to keeping construction costs down and can be the difference between a project moving, or staying dormant.
But what is there that a structural and/or civil engineer should really consider and challenge to make a design smarter, and reduce the cost of construction?

1. Get it out of the ground.

Getting out of the ground is often the most expensive part of the structure and also poses the highest risk to the contractor particularly where there are deep basements excavations in the CBD area. the key is to assess the geotechnical conditions carefully and come up with the most cost and time effective solution that also minimises risk. A retention system that can be installed up front and quickly is the best solution. If the site dimensions are suitable, cross-lot strutting of the excavation may be considered to eliminate the use of anchors, thus eliminating the need for a longer and more variable approval processes, time delays and costs in excavation particularly where anchors may need to be long due to deep layers of silt or marine clays You need your team to carefully assess the need for how deep basement structures should be, minimizing structural depths of slabs and eliminating deep transfers caused by changes to column positions in the basement or at ground level. This, if done correctly will reduce the excavation depth which in turn will reduce time in the ground, minimize excavation volumes, reduce the length of retention and anchors required and decrease risk overall. If a water table is present, reducing the excavation depth significantly reduces costs associated with dewatering and makes the structure water-tight.

2. Understand the foundations for your project well

Investing money upfront into a detailed geotechnical investigation will potentially save you significant dollars both in the retention and also the foundations. It is important to investigate several options when assessing the most suitable foundation system for a project. High-level pads and strip foundations are the best solutions where high-level rock is found. Post-tensioned raft foundations offer a cost effective alternative to piled foundations in weaker material and will save significant time on the construction program.

3. invest time in planning to minimise transfers in your vertical structure

It is important to invest time during the planning and DA phase of the project to ensure that columns, core and shear walls are located in a way that maximises the functionality and floor area of the development, but also minimises the need for transfers. Transfers are not only expensive, but they take time to install and pour, and also break the rhythm of the project cycle on site. On high-rise and slender projects avoid transferring shear walls, their effectiveness and efficiency can be significantly impacted.

4. Carefully consider the systems and materials you select

You must also carefully consider the materials and systems adopted in the building in conjunction with the site location, site logistics and constraints. In Australia each region and city has different factors that influence how a structure can be built cost effectively. Trades that are readily available in one city will be scarce in another and may attract a premium. Your engineers and designers need to be aware of the local market and take this into consideration.

Prefabrication and minimization of labour on site may also provide cost and time efficient. Explore the use of precast and alternative systems and materials. Keep formwork simple; where possible adopt flat plate slabs or simple banded slabs in commercial projects. Look to maximize the column grid to get the most efficiency out the horizontal slabs. Fewer columns and vertical elements will result in fewer foundations and increase cycle time.

5. Consider Wind Studies on buildings over 20 stories.

Investing in a wind study for projects exceeding twenty levels may also have a significant impact on the cost of facades and the vertical structure. A wind study will take into account the building and its surrounding environment when impacted by high winds of varying types. In the process, a scale model of the project and its surrounds are created, tested and monitored in a wind tunnel. The results are more in-line with the site conditions and may be significantly lower than standard code requirements allowing you to adjust the engineering designs based on statistical evidence.