How To Plan A Slip Construction Build
What are the top concerns a project manager needs to be cognizant of in planning for any size slip construction build?
A. Let’s start out with an extremely generalized definition of "slip construction."
This type of construction involves the continuous pouring of concrete into a moving form—the key word being "continuous." Ideally the pour should be non-stop until complete in order to maintain and achieve optimum continuity. With vertical slip construction, the cured concrete exits the bottom of the upward (usually hydraulically jacked) moving or "slipping" form while fresh concrete is placed in a controlled, consistent manner to the top of the form. Steel rebar is placed in a specific manner as well to aid in structural integrity.
Ultimately, the resultant structure is one entity without seams and joints that are normal with sectional construction.
In the industries that we serve, we typically use the slip-form construction method to develop any or all of the following: receiving buildings, storage silos, mill towers, pelleting annexes, load-out towers, and warehouses, etc. It is possible for other types of constructed buildings to cohabitate with the completed slip-form structure, such as brick, block, tilt-up concrete, metal, or other construction means dependent upon client preference. These usually entail smaller, lower-elevation outposts, such as offices, liquid tank farms, truck wash areas, and employee facilities.
Thorough planning prior to any slip is key to ensure project success. There are many components that play critical roles leading up to the execution of the event. In general, we can classify these into four main categories—materials, equipment, personnel, pre-slip meeting/communication, as follows:
The supply of materials that are needed on-site prior to slip construction is paramount. As previously mentioned, "continuous" is the theme. Any material deficiencies incurred after slip commencement can potentially result in unwanted costs.
Mix design of concrete alone is a long process. Design strength requirements, aggregate specifications, availability, and weather all play a part in mix development and supply. Other materials that may be considered "off-the-shelf" commodities, in addition to custom fabrications, will have availability challenges that need to be proactively procured. These can include: rebar, fabricated framed openings, embeds, beams, finishing sand/cement, water supply, etc. Project managers will need to work very closely with engineering, suppliers, purchasing, field supervisors, and sub-contractors to guarantee that all materials are accounted for long before the slip begins.
You can have all the material you need on-site tenfold but, without applicable equipment, all of your procurment work is for naught. Equipment supply and availability is a very sensitive process. Slip location in relationship to equipment accessibility may be a challenge. Today’s "instant gratification" society may lead one to believe that any equipment can be obtained 24/7. If that’s what you believe, slip construciton will never be one of your crowning acheivements as a project manager.
However, as the project manager, equipment accountability is your burden. Crane rental—including backup crane and fuel—is the heart of the project. Site lighting (remember that "continuous" means the slip continues throughout the night!), generators, pumps, welding equipment, down to what might be thought of as small items such as hammers, shovels, and crowbars will surely enhance production.
Usually a week prior to the start of the slip, all involved groups are requested to send a representative to attend a "pre-slip meeting." This meeting is championed by the project manager and/or senior-level management of WL Port-Land Systems Inc. This typically takes place on-site which is convenient for all to attend. The purpose of the meeting is to discuss and explain expectations during the slip.
Agenda topics include safety, start time and duration, manpower, emergency considerations, communications, electrical supply, permitting, pumps, cranes, lighting, rebar, concrete (including quantity and supply frequency, quality, truck routing, backup, clean out, and ticketing), concrete testing, and anticipated weather. We encourage open conversation during the meeting to ensure that all areas are addressed.
Slip construction involves many external resources that require management. The "weakest link" cliche applies here. If there is one person who falls short in their efforts, a trickle-down effect is inevitable.
The matrix of responsibility is complex. The first consideration is always safety. Our safety director is on-site performing pre-slip orientation to all involved as well as safety scrutinization throughout the entire phase policing OSHA compliance. The concrete supplier has people behind the scenes working around the clock batching and delivering product. Slip construction crews have a workforce that involves many people with specific responsibilities varying from concrete buggy/shovel, vibrator, rebar, welders, hydraulic jack, finishers, ground-deck personnel, carpenters, and superintendants. The construction crew can work together as a finely choreographed unit with the right direction. Independant concrete testing services are appropriate. They, too, have non-stop, on-site duties. Lastly, as the design builder, we also staff a quality control group that monitors all facets of slip. The project manager is the liaison among all the players. If there is a void, it is our duty to address and rectify it.
Lastly, upon completion of the meeting, and once all contact information is confirmed, an organization chart is developed encompassing all pertinent information. This organization chart is the cover of the slip drawing design package that is distributed throughout. A set is also laminated and placed on the slip deck for accessibility. Published material includes contact numbers for local fire/police/ambulance/utilities and all members of the project who have a supervisory or management role. Everyone is required to be available at anytime, or have a contingency plan in place.
As with any project, you get what you put into it. A slip-form project is a unique process that presents many challenges. With pre-planning done correctly, a successful slip is inevitable and truly rewarding.
Answered by WL Port-Land Systems Inc.