What is the Difference Between Jumpform and Slipform ...

Jumpform, also known as jump system formwork, and slipform are both techniques used in concrete construction. Most commonly, they are self-climbing forms utilized in the construction of tall buildings or large structures. These systems are particularly effective for constructing shafts and cores, as well as bridge pylons, silos, and chimneys. Both jumpform and slipform may be categorized as 'climb-form' systems.

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Similarities

Both jumpform and slipform allow for concrete to be poured into self-climbing molds until the desired height of the structure is achieved. Electric motors or hydraulic rams typically assist in the vertical climbing of these forms, minimizing the need for cranes. Both systems utilize work decks or platforms that ascend alongside the forms, facilitating easy concrete pouring and reinforcement at various levels. Notably, neither jumpform nor slipform requires support from other parts of the construction; they are both self-supporting, relying on the concrete cast below each vertical level or other built-in support mechanisms.

Despite their similarities, several key differences set them apart. Here are the main distinctions.

Jumpform Differences

Jumpform involves a sequential process of 'jumps,' with concrete poured at each level and allowed to set before proceeding to the next. This approach ensures a stable foundation for ascending. For instance, if the jumpform is designed for ten-foot sections, concrete will be poured and cured at the first ten-foot level before the form 'jumps' to the next level. This process continues until the structure reaches its final height, making jumpform ideal for applications where joints between levels will be concealed in the final structure.

There are several types of jumpform. The most common include:

• Traditional Jumpform – This type uses cranes to lift formwork to each level.

• Guided Jumpform – Similar to traditional jumpform, but the units remain anchored to the concrete structure as they are lifted by the crane, providing improved safety.

• Self-climbing Jumpform – This category does not require cranes, as it ascends using rails.

Slipform Differences

Slipform shares many characteristics with jumpform, but the key difference is that slipform utilizes a structure's core or shaft for support and rises gradually through one smooth, continuous pour. This process eliminates the need to wait for each layer to dry. Slipform is excellent for creating tapered structures with walls that may vary in thickness at different levels. Generally, this self-climbing formwork system is deemed more efficient than jumpform for very tall buildings, especially those above ten stories. Typically, slipform involves three platform stations; the lowest one is used for finishing the concrete, the middle station for pouring, and the topmost for storing project materials.

Slipform delivers a smooth and precise concrete finish without joints from jumping, making it ideal for structures that will not hide these joints, like chimneys and bridge pylons. However, slipform is often more expensive and requires workers to oversee concrete pouring for extended hours compared to jumpform.

In conclusion, both jumpform and slipform offer unique advantages, making them effective choices for building slender, tall concrete structures.

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In the domain of vertical formwork, people often visualize a wall or a column. However, for high-rises, one must construct one floor after another. The equipment used to build each floor must be physically moved to the next level, typically accomplished with a crane, representing substantial material to shift.

Hydraulic or self-climbing forms have emerged to address this challenge, as insufficient time exists for a tower crane to move all the forms for every project that advances formwork from one level to another without utilizing a tower crane. Here are seven facts about self-climbing systems you may find surprising.

They’re Fast, but Not in the Way You’re Thinking

You can certainly build a structure without a self-climbing system; people have been doing so for thousands of years, though it would take longer. Suppose there are 20 or more platforms to independently move, with each platform taking 20 to 30 minutes just to cycle the core formwork. If you have seven days for this task, that might be acceptable. But what if the schedule shrinks to four or even two days? This scenario drives the advancement of self-climbing systems.

By implementing a self-climbing system, what could be an entire day’s endeavor can be reduced to just a few hours with little to no crane interactions. This release allows the crane to work on other parts of the project.

According to PERI,

They’re Actually Fast, You Just Can’t Really Tell

Hydraulic-powered self-climbing systems can ascend approximately 8 inches per minute, which translates to traveling over 13 feet in a 20-minute timeframe.

Although a shorter pour may be quicker and taller pours might take longer, the ascent speed is calibrated to avoid shifts during climbing. Most of the time is consumed by removing bolts, preparing the system, and resetting, which should not be hurried. Contractors have termed the ascension a 'comfortable speed'; moving at a pace so gradual that one might barely notice it in progress.

These movements are known as 'jumps.' The transition from floor 2 to 3 constitutes one jump.

Investing in these machines can be pricey, and projects generally require them for a substantial duration or specific number of jumps to justify their rental costs. Besides high-rise buildings, this technology can be applied to bridge pylons for cable-stayed bridges or bridge piers and any project intended to be sufficiently tall or where crane access presents challenges.

According to PERI,

A 160 Ton Push-Up

Previously, we highlighted the speed of hydraulics, but here we focus on strength.

For instance, PERI's ACS-400 system is equipped with four hydraulic cylinders, each with a 40-ton capacity. All are moved collectively with the push of a single button. ACS stands for Automatic Climbing System, by the way.

Each hydraulic cylinder operates in sync, powered simultaneously by an intelligent pump. This ensures perfectly level climbing. Instead of executing 20 crane picks, these systems lift the entire core box as one unit. It’s essential to clarify what can be lifted—it's not just the formwork; it also includes tools, generators, hydraulic equipment, pumps, a working corridor, and stair tower access platforms. Some self-climbing frameworks even integrate concrete placing booms.

According to PERI,

They’re Self-Sufficient

Some systems require a 'starter wall,' the initial piece of concrete the system must attach to while others can create this starting point through installed integrated forming, enabling immediate climbing.

The process hinges upon the setup sequence ensuring accuracy from the ground level. After the first pour, when a crane assists in installing the system, the system can operate autonomously.

Information obtained from PERI suggests that installation can be achieved in roughly four days for a typical core, provided optimal crew size, crane availability, and site logistics align. This success hinges on the various connections, pre-assembly tasks, and engineering incorporated to expedite the installation time.

With a placing boom installed, contractors can initiate slab work and other columns. The quicker the core becomes self-sufficient and independent from the crane, the better. This timing enables all other aspects of a project to proceed. Typically, a self-climbing system can prepare for the next floor's core setup the day following form removal. For example, if you pour on level five today, forms can be struck the next morning, allowing the system to ascend to level six the subsequent day. The anchors are crafted to function with green concrete.

According to PERI,

They Can Be Manned By a Smaller Crew

In projects across the U.S., utilizing generally one tower crane is the norm. In contrast, projects in Europe often deploy multiple tower cranes per site, providing a different perspective on construction.

The cost of a tower crane, alongside operator fees, is significant. In scenarios where a traditional jumping system might necessitate eight workers for an entire day, a self-climbing system may only require three or four individuals for a few hours.

This consideration is crucial in areas with elevated labor costs. As per industry insights, this could explain the prevalence of self-climbing systems in these high-cost regions.

Furthermore, safety concerns arise since everything in the system is relocated together, promoting a safer working environment.

According to PERI,

Work with a Buffer

In many construction scenarios, slabs are poured first, then vertical walls are constructed, with wall forms ascending to the next slab level simultaneously. It's common for walls to be elevated ahead of the slabs by three or four stories. There’s no necessity to sequence this work; if the self-climbing system is ready to create the next level core, it can do so.

There are compelling reasons for adopting this high-rise construction style. Firstly, it mitigates operational risks; for instance, if issues arise with the core due to delayed rebar deliveries, the impact is reduced.

Secondly, such methods segment the tasks, enabling two distinct crews to work without hindering one another. When all personnel work on the same slab, tasks can become congested, potentially delaying the schedule. The self-climbing system creates a buffer, allowing crews to operate concurrently without conflicts. For illustration, while carpenters focus solely on the core, the slab operations can concentrate on their jobs, eliminating overlapping work.

The next time you gaze up at a high-rise, reflect on the contractor responsible for seamlessly orchestrating schedules, allowing subcontractors to work in harmony while managing the project's hydraulic robot that climbs the building it's constructing.

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