Construction and Installation Technology for Steel Tubular Trusses

The construction and installation of steel tubular trusses involve a meticulous,multi-stage process to ensure structural integrity,safety,and precision.The primary methodology can be broken down into the following key phases:

1.Preparation and Pre-Installation Works

This initial phase is critical for a successful installation.It begins with a thorough survey of the foundation and support structures,such as columns or walls,to verify their alignment,elevation,and anchor bolt positions.All measurements must conform precisely to the design drawings.Concurrently,the fabricated truss segments are delivered to the site and meticulously inspected for quality,dimensions,welding quality,and the integrity of protective coatings.The components are then strategically staged near the installation area for easy access.Comprehensive safety planning,including risk assessments and method statements,is established before any lifting operations commence.

2.Truss Assembly(if applicable)

For large-span trusses that are transported in segments,on-ground assembly is often necessary.The segments are laid out on pre-prepared level platforms or temporary supports.They are aligned and clamped according to the engineering drawings.The final site welding of these segments is performed by certified welders using qualified procedures to ensure the connections are as strong as the original factory welds.Non-Destructive Testing(NDT),such as ultrasonic or magnetic particle testing,is typically conducted on these critical site welds to verify their quality before lifting.

3.Hoisting and Lifting

The hoisting plan is tailored to the truss's size,weight,geometry,and site conditions.For smaller trusses,a single crane lift using a spreader beam to distribute forces and prevent bending is standard practice.For larger,more complex trusses,a dual-crane(or multi-crane)lift is employed,requiring impeccable synchronization between crane operators to maintain stability and control.Specialized lifting lugs or slings are attached at designated node points to avoid inducing undesirable stresses in the members.The entire lift is conducted slowly and deliberately under the supervision of a dedicated lift director.

4.Placement and Temporary Support

As the truss is lifted into its final position,it is carefully guided over the support structures.It is then slowly lowered onto temporary props or shoring towers if required.These temporary supports are crucial for stabilizing the truss until it is fully connected to all permanent supports and until the entire structural system is completed(e.g.,by connecting purlins and bracing).The truss is aligned both laterally and longitudinally,and its elevation is checked and adjusted to meet the specified tolerances.

5.Fixing and Connection

Once accurately positioned,the truss is permanently connected to its supports.This typically involves securing the base of the truss to bearing plates or directly to columns using high-strength bolts.The bolting process follows a strict procedure:first,pins are inserted to align the members,then temporary bolts are placed,and finally,they are replaced and tightened to the specified pre-tension in a defined sequence.For some designs,welded connections to embedded plates may be used.The connection method strictly adheres to the structural design specifications.

6.System Completion and Stability

A single truss is inherently unstable in the lateral direction.Therefore,immediately after the first truss is erected,it must be temporarily guyed for stability.Subsequent trusses are installed at designated bays.As soon as two or more trusses are in place,the connecting elements—such as purlins,edge beams,and most importantly,longitudinal bracing systems—are installed.This connecting work proceeds simultaneously with the truss erection to form a stable and rigid structural frame that can resist lateral loads like wind and crane forces.

7.Inspection and Handover

After the entire truss system is installed and fully connected,a final comprehensive inspection is conducted.This includes verifying the alignment and elevation of all trusses,checking that all bolts are properly torqued,and inspecting welds if applicable.Any damage to the protective coatings incurred during installation is touched up.As-built drawings are prepared,and the structure is formally handed over for the next phase of construction,which is typically the installation of the roofing and cladding systems.

Primary Installation Methods:

The two dominant installation strategies are the Separate Installation Method,where each truss is erected individually and stabilized with temporary works before connecting them,and the Integrated Bundle Installation Method,where multiple trusses are pre-assembled on the ground with their purlins and bracing into a stable bay section,which is then lifted into place as a single,large module,significantly reducing work-at-height and accelerating the project schedule.The choice depends on crane capacity,site space,and project requirements.