THE CORRECT WAY TO TIE DOWN A SEA CONTAINER IN CYCLONIC AREAS
In simple terms, sea containers are steel shipping containers used as storage while shipping goods. For the most part, when you think of shipping containers, you usually picture large colourful containers atop massive cargo ships carrying various goods of different types across the ocean. Containerisation has reshaped the transportation industry for the better and made a true revolution in freight transportation, changing international trade in many ways.
Apart from the shipping industry, many other industrial and commercial sectors also use sea containers, as they are versatile products. Many also use sea containers as their home or for on-land storage space near properties.
For example- construction sites invariably require storage sheds to stock expensive building materials. Used shipping containers are apt for this purpose. Unlike traditional sheds, you can install and immediately use the sea containers.
Image: Shipping containers being used for office space
Because they are made from high-grade steel, shipping containers are also extremely strong and difficult to break into. Also, since they are air, water, and windproof, the valuables inside stay safe from moisture and weather extremes. The same goes for the manufacturing industries. Businesses require plenty of raw materials for manufacturing processes. Hence, to store everything securely, many industries have turned towards using shipping containers as a secure and cost-effective means of storage.
Container storage is handy for storing off season-merchandise or large bulky items that need racks, such as tires. Not only that, but sea containers can also be used to build site shelters at construction or mining sites. Lack of space at homes for work-related privacy has similarly resulted in using intermodal shipping containers as alternative workplaces.
Sea Containers and Wind Speed
Due to the sheer enormity of said boxes, a shipping container at a given weight will need to be secured with tie-downs to its carrier or ground placement once the associated wind speed threshold has been met.
Given below are calculations for individual requirements based on container size and weight.
Typical weight ranges (in kilograms) for empty ISO Shipping Containers made of steel vs. Resistance to overturning due to wind load in kilometres per hour (kph)
|10 meter Standard||1,056 – 1,360 kgs|
|20 meter Standard||2,177 – 2,358 kgs|
|40 meter Standard||3,628 – 3,900 kgs|
|40-meter High Cube||3,991 – 4,354 kgs|
|45-meter High Cube||4,399 – 4,762 kgs|
|Wind Speed (km/h)||209 kph||225 kph||241 kph|
Example: A 12-meter standard container will need to have tie-downs applied should the wind load exceed 225 kilometres per hour.
Having said that, before a container even begins its travels, it must meet International Organization for Standardization (ISO) standards. The public and private sector organisations use the ISO Standard to ensure the quality, safety, and efficiency of products, services and systems. ISO standards for shipping containers substantiate that containers can weather transport by ocean or rail without failure. The stresses of these journeys are extensive; containers can be loaded to hold 25,0000 kg and stacked nine loaded shipping containers high.
A series of ISO-specified tests on the container’s walls, frame, and corner castings confirm that a shipping container is safe for use by manufacturers. This testing provides reliable measures of container strength that can apprise regulatory decisions.
Consider the rigidity test. The manufacturer secures the sea container’s bottom corner castings and then applies 150 kN, or 15,300 kg, of force to its top edge. To get a sense on a smaller scale, imagine pushing the upper edge of a cardboard box glued to a tabletop. The measure of how much force can be applied to the top edge before the container begins to collapse or warp can be interpreted into an equivalent wind load. According to the rigidity test standards, a shipping container can withstand wind speeds of 290 km/h without wavering.
Tropical Cyclones in Australia
Speaking about sea containers and wind speed, we need to take into consideration Australia’s cyclonic elements. Cyclones in the Australian region are predominantly non-frontal, low-pressure systems that develop within an environment of warm sea surface temperatures and little vertical wind shear aloft in either the Southern Indian Ocean or the South Pacific Ocean.
Within the Southern Hemisphere, there are officially three areas where tropical cyclones develop regularly. These areas are the South-West Indian Ocean between Africa and 90°E, the Australian region between 90°E and 160°E, and the South Pacific basin between 160°E and 120°W.
Each tropical cyclone year within the Australian basin usually starts from the beginning of July and runs throughout the year, encompassing the tropical cyclone season that runs from the beginning of November and lasts until the end of April. Within this region, a tropical disturbance is classified as a tropical cyclone when it has 10-minute sustained wind speeds of more than 65 km/h. On the other hand, a severe tropical cyclone is classified when the maximum 10-minute sustained wind speeds are greater than 120 km/h.
Given below is the Australian Tropical Cyclone Intensity Scale-
|Five||>107 knots>198 km/h||>151 knots>280 km/h|
|Four||86–107 knots158–198 km/h||122–151 knots226–280 km/h|
|Three||64–85 knots118–157 km/h||90–121 knots167–225 km/h|
|Two||48–63 knots89–117 km/h||68–89 knots126–166 km/h|
|One||34–47 knots63–88 km/h||49–67 knots91–125 km/h|
As you can see, there is a chance of containers being damaged when category four or five cyclones hit. Hurricanes especially have the potential for 240+ km/h winds, and they can even reach much higher speeds in certain pockets depending on how big the storm is. This lends the question, can shipping containers withstand cyclones on their own?
The answer, unfortunately, is not cut and dry and requires a bit further explanation. A lot of the strength and integrity lies in how you can modify the container anchor it to the ground. The three main areas to focus on while securing sea containers during the hurricane season are foundations, protection of any windows with shutters, and speaking to an engineer about wind loads. However, from a core perspective, a shipping container can be an excellent way to protect your belongings through a hurricane if installed and secured correctly.
Securing Sea Containers during Cyclones
The placement of shipping containers after their delivery and staging on-site is a critical task. Once placed the first time, containers usually cannot be hastily relocated.
When considering wind speeds again, the overturning moment from the long side of a 12-meter shipping container can be as much as 100,000 meters -kilograms. This is resisted by the weight of the container contents and tie-down straps/anchors. Empty containers are at the highest risk of overturning and being displaced during cyclones. They can even possibly harm people, destroy properties, or destroy work in progress. However, if they are secured to the ground in such a way that prevents them from breaking loose, a container will withstand the sudden pressure changes of a cyclone.
To secure sea containers, always place container clusters close together. Have them be shielded as much as possible by buildings or vegetation. If the sea containers are placed in an open space, one of the best ways to anchor sea containers is to use concrete tie-down blocks.
How to Use Concrete Tie Down Blocks for Sea Containers
Typically, an empty 6-meter shipping container weighs between 1,800-2,200 kg, and an empty 12-meter shipping container weighs around 3,800 to 4,200 kg, depending on its type. For example, high cube containers can be a lot heavier.
No matter how heavy they are, category four and five cyclones can move them like toys and even turn them upside down. Furthermore, a flood can also make it float like a piece of cork and will take it as far as it can. To keep the containers secured, you should attach them to concrete tie-down blocks designed and engineered for holding them in all conditions.
(Image: a sea container of a Dome Shelter held down by concrete tie-down blocks. Image by Dallcon)
Concrete tie-down blocks can hold down containers against cyclones. The colossal density of concrete blocks grounds the containers and does not let them be heaved about by strong winds or harsh weather elements during tropical cyclones.
Heavily reinforced Concrete Tie Down Blocks are available in a wide range of sizes for all applications. They are ideal for the tie-down of containers, buildings, and general cargo. Most concrete blocks are also engineer-approved and have swift lifters/fork pockets cast-in for ease of placement. Generally, concrete tie-down blocks are placed on either side of the containers and secured in place with heavy-duty rope or metal chains.
Concrete tie-down blocks offer a great solution as they are designed and engineered to the required container specifications to keep everything safe and secure regardless of the weather conditions. Furthermore, not only are the blocks adaptable, but they are also versatile products used to secure any object that could be stolen or blown away. These tie-down blocks are also easily placed with swift lifters or fork pockets. What’s more, concrete tie-down blocks are great alternative solutions to secure assets onto the ground without penetrating the earth with an anchoring system. Using concrete tie-down blocks is also a quick, cheap, and easy way to secure your container.
(Image: concrete tie-down blocks used to secure the containers, placed on either side and secured with heavy-duty chains. Image by Dallcon)
As each site and container is specific to engineering requirements, the number of cyclone blocks needed to withstand the uplift force is determined by the site engineer.
DALLCON designs durable cyclonic tie-down concrete blocks specified to withstand the dangerous uplift of high wind speeds. These blocks are part of a comprehensive range of precast solutions we provide to the Australian civil and mining sectors.
Our cyclone concrete tie-down blocks are particularly well-suited for the Australian climate, withstanding harsh weather and cyclonic conditions. This makes them ideal for use in a wide variety of projects, both large and small. Contact us to let us help choose the best product for your project.