Tilt-Up Safety — Inherent When Planned
By Jim Baty, Tilt-Up Concrete Association
There is a buzz in the construction industry that is growing at an annual rate of 14-18 percent per year. Growing perilously close to a billion square feet of enclosed building area per year, the Tilt-Up industry offers a great deal of excitement to all that are realizing the tremendous benefits to construction and project cost-efficiency as well as design and construction creativity and flexibility. With a rapid expansion continuing across the globe, the need to provide quality assurance to the expertise that is responsible for the construction method is of primary importance. Fortunately, six years ago, the Tilt-Up Concrete Association (TCA) and the American Concrete Institute (ACI) instituted a Tilt-Up Certification program that fills this need. Qualifying industry professionals as a Certified Tilt-Up Technician through examination of their knowledge has led the industry to develop an incredible 1079 certified personnel. By providing verified work experience of not less than five years, 205 of these have been upgraded to the status of Certified Tilt-Up Supervisor. This past World of Concrete, held in January, a record 155 contractors sat for the examination—many of whom are certain to go on to the Certified Supervisor status.
Hidden within this significant growth throughout the industry, are the necessary changes and improvement to continue evaluating the knowledge and understanding of the workers building these projects on a daily basis. Much information has been updated and many areas strengthened in the exam to continue qualifying those that are the best in the industry.
TILT-UP SAFETY
One of the most significant advantages of Tilt-Up construction is its inherent safety qualities. Face it, the high-strength, reinforced concrete wall panels are constructed entirely in a horizontal position on the ground and then lifted only once to a vertical position and set into place with a continuous operation. Ground crew personnel are limited during this phase of the process and once in place, the panels are secured for life safety until they are fully integrated into the building structure. This area of knowledge for the Certification process has seen the greatest increase from the original exam to the new 2007 edition.
What constitutes the areas of safety that need to be considered for a Tilt- Up project?
Let’s start with the steps taken before panels are ready to be lifted. One of the key elements of a successful Tilt-Up project is the planning that must take place. Safety begins in this phase along with the quest for efficiency. During planning, the selection of an erection subcontractor and perhaps crew experienced in handling Tilt-Up panels must occur. This experience is vital to knowing the orchestrated movements that will occur as panels as heavy as 250,000 pounds or more are lifted and moved into position. Tilt-Up contractors will affirm that if you plan, you plan to succeed; if you don’t plan, you are in essence planning to fail.
The day of erection is a highly-anticipated event. There are many decisions to be made and items to check before that day arrives. The site inspection is key to the progress of the plan. Underground and overhead hazards such as wires, rough terrain and soft or eroded subgrades must be identified. The path of the crane is imperative to this search to make sure the operator and crew are fully aware of the surrounding conditions they must maneuver around.
The crane is ultimately the work- horse for this stage of the process and it must be thoroughly inspected and verified to be in good working condition prior to the erection day. This means confirming the condition of cables, tracks and tires, engine operation and hydraulics. The operator must verify that his/her equipment is checked and prepared to proceed. The contractor must also verify that the crane is the proper size to do the work at the given conditions. Although a crane has the capacity to ultimately lift the panel, can it make the lift at the angle and distance that must be maintained for the specific site? A rule of thumb typically used is that the crane capacity is two to three times the weight of the heaviest panel to allow for variation in boom angle and distance.
Connecting the crane to the panels is a series of cables, bars and pulleys varying in design based on the company who owns the equipment or has produced the design. All lifting inserts (embedded connections in the panels) must be checked for proper alignment and be able to cleanly attach with the lifting clutches to the rigging. The cables must be inspected for any damage or excessive wearing. Subsequently, the lifting beam that gathers the loads from the multiple attachment points to the panel and concentrates those loads to the single crane cable must be checked for fatigue and proper connection.
A final check of the site prior to erection day should be made and re- checked the morning of erection to make sure the site is clean of debris and free of standing water. This will ensure that the paths taken during the maneuvering of the panel will not cause the crew to stumble and fall into an unsafe position as well as making sure that excessive force is not needed to pull the panel from its resting position.
Lift day — we’ve now arrived at the moment of truth — the day all have been waiting for. Tilt-Up projects have been known to back-up traffic on busy streets as multi-story panels are lifted from horizontal to a vertical position and buildings suddenly appear in the span of one afternoon. Now that panels are reaching nearly 100 feet in the air, the drama of lift day is only heightened.
Before any equipment is started or any preparations are made, lift day must start with a safety meeting. It is imperative that each crew member understand his/her responsibility for the day. Everyone involved must know that only one person is to communicate with the crane operator (panel foreman) and that individual must be confident that the signals to be used are easily understood by the operator. Crew size is also important—maintaining a minimum crew size (i.e. a crane operator, rigger foreman, two journeyman riggers and welders only as required) will reduce the chance that a person is out of position when panels begin to move. It is also highly-recommended that the safety meeting involves individual safety cards/checklists that can be signed by the crew member and entered into the job record.
During the safety meeting, crew members must understand that no one is to ever be positioned under a panel. No one is to be on the blind side (side not visible by the crane operator) of the panel while it is moving and no one is to be between the crane and the panel or between the panel and an adjacent panel either on the ground or in the air. Crew members must remain alert at all times and looking out for each member of the team. Finally, no one should be in the vicinity of the lift without the proper protective clothing (e.g. gloves, hardhats, steel-toed shoes, etc.).
Further, the crane operator must be present at the safety meeting. As stated before, he/she must understand the signals that will be given only by the rigging foreman. The crane operator must also understand the sequence, the path of travel (if necessary) and the weights of each panel.
When the lifting begins, the rigging foreman must start by looking up. Hundreds of thousands of pounds in tension is applied by the crane through this rigging to the panel. If cables are twisted or out of position, the entire system may fail due to the stress. Since the erection crew has been identified, all other personnel around the site must stay clear of the operation. The crane operator’s responsibilities are to maintain complete control of the crane. This includes fully-extended outriggers and proper cribbing. Charts available to the operator will show the capacity reductions for any condition less than full extension of the outriggers or unstable outrigger positions. The crew will be connecting rigging to each panel according to the established sequence. Prior to tensioning the system, the clutches must be checked for clean operation and the rigging itself must be inspected for proper alignment per the design provided.
The operation is simple but stressful. The crane applies a load. If the panels do not release under that load, the crew will be required to apply ground force to the panel by way of pry bars or wedges. These must be placed in-line with the lifting inserts where the additional reinforcement exists to handle that stress. Once the panel has separated from the slab, there will be movement in a designed direction. The path of travel, whether the crane is to move or not, must remain clean and clear of obstacles—especially crew members. As the panel is set into position, there will be necessary crew responsibilities to verify alignment and setting position on the temporary shim stacks that will support the panel. Braces that were connected to the panel before the lift began will be extended to the proper angle location on the slab or to the exterior and secured. At no point in this process is any equipment to be put in service that shows signs of damage such as bent braces or excessive wear on bolts. Now that the panels are in place and secured by braces, the final safety measures are taken. Although very rare in the Tilt-Up industry, the few safety issues that do happen occur when panels are moving or when they are assumed to be “properly braced” or connected. The panel bracing is designed to hold the panels in a vertical position for the normal design wind speeds for the local climate. Although bracing designs can be attained to secure the panels in more damaging winds, this brings excessive cost and risk to the project when life safety would not be of concern. TCA will continue examining the performance of bracing and the elements of safety that are attributed to this system and others in future articles.
