Core Considerations for the Design and Construction of Circular Tube Truss Systems As a core form of long-span spatial structures, Round Tube Truss circular tube truss systems require a balanced approach to structural safety, functional requirements, and engineering feasibility during design and construction. Key considerations are outlined below, divided into two main phases: the design phase and the construction phase. I. Design Phase: Core Principles – "Safety, Adaptability, Economy"
Design serves as the foundation of a circular tube truss system. Backdrop Truss for Photo Booths It must comprehensively integrate multiple factors such as loads, materials, joints, and spatial form to avoid potential safety hazards or functional failures caused by design oversights. 1. Load Calculation and Structural Force Analysis (Top Priority)
Loads are the fundamental basis for structural design. They must fully cover "permanent loads + variable loads + accidental loads" to prevent omissions or calculation errors:
Permanent loads: Include the self-weight of the truss (weight of circular steel tubes and joints), roof finishes (e.g., waterproofing and thermal insulation layers), Background Truss for Stage Design and the weight of suspended ceilings and equipment (e.g., lamps and air ducts). These loads must be accurately calculated based on the specifications of circular tubes (diameter and wall thickness) and steel density. Variable loads:
Roof live loads (e.g., weight of maintenance personnel), Adjustable Background Truss typically valued at 0.5–1.0 kN/m² (specific values must comply with local codes). Wind loads: Calculated based on the basic wind pressure of the building’s location, truss height, and shape coefficient. For long-span structures, wind vibration coefficients must be considered to avoid resonance.
Accidental loads:
Seismic loads: In seismic fortification zones, Round Tube Truss System horizontal and vertical seismic actions must be calculated based on the seismic intensity level. Circular tube trusses are flexible structures, so the seismic performance of joints requires focused verification. Temperature loads: Long-span structures expand and contract due to diurnal or seasonal temperature differences. Expansion joints or sliding joints should be installed to prevent member cracking caused by temperature stress.
2. Material Selection: Matching Force Requirements and Environment
The core materials of circular tube trusses are steel tubes and joint connectors. Selection must balance strength, corrosion resistance, round tube truss structure and economy:
Steel tube material:
Low-carbon steel such as Q235B (for ordinary loads) or Q345B (for long-span, heavy-load scenarios) is preferred due to its stable welding and mechanical properties.
In coastal or high-corrosion environments, galvanized steel tubes or stainless steel tubes (e.g., 304 stainless steel) should be used to prevent steel corrosion and extend the structure’s service life.
Steel tube specifications:
Diameter (commonly Φ50–Φ300 mm) and wall thickness (commonly 3–12 mm) are selected based on the force borne by members. round tube truss frame This avoids "over-engineering" (increasing costs) or "under-engineering" (insufficient load-bearing capacity).
Uniformity of steel tube specifications within the same truss should be ensured to reduce processing complexity.
Joint materials:
Joints are critical for force transmission in trusses.
Steel plates (e.g., thick Q345B steel plates) cut into gusset plates.
Finished cast steel joints (suitable for complex joints).
The material strength round tube truss design of joints must not be lower than that of steel tubes to prevent joint failure prior to member failure.
3. Joint Design: Ensuring "Reliable Force Transmission and Rational Structure"
Joints are the weak links of circular tube trusses. Design must address "steel tube connection" and "effective force transmission". Common joint types include welded joints (most widely used) and bolted joints (for detachable scenarios):
Welded joints:
The weld quality between steel tubes and gusset plates must be guaranteed. Weld height and length should be determined by force calculations (typically, weld height is no less than 0.8 times the steel tube wall thickness).
When connecting circular tubes to gusset plates, "grooves" must be made at the ends of the tubes to ensure full weld penetration and avoid "cold welding" (which causes weld cracking under load).
Direct contact between steel tubes at joints should be avoided; a 5–10 mm gap should be reserved to facilitate welding operations.
Bolted joints:
Suitable for temporary structures (e.g., stage frames, temporary exhibition booths). High-strength bolts (e.g., Grade 8.8 or 10.9 friction-type high-strength bolts) should be used. The number and diameter of bolts are calculated based on shear and tensile load-bearing capacity.
Bolt holes on gusset plates must be precisely positioned to ensure tight between steel tubes and gusset plates, preventing additional bending moments on bolts.
Joint structural details:
Stress concentration at joints should be avoided. For example, the ends of steel tubes should be "rounded," and the edges of gusset plates should be chamfered.
When multiple steel tubes meet at a single joint, their angles should be rationally arranged to ensure force from each tube is directly transmitted to the gusset plate without generating additional forces.
4. Spatial Form and Span Adaptability
The form of a circular tube truss must be designed in conjunction with building functions (e.g., roof slope, clear height) and structural force characteristics:
Span control:
The economic span of ordinary Q235B steel tube trusses is 15–30 m, while Q345B steel tube trusses can reach 30–60 m.
For spans exceeding 60 m, a "truss + bracing" composite form (e.g., column bracing, roof bracing) or larger-specification steel tubes should be adopted to prevent excessive truss deflection (codes require the maximum deflection of trusses to not exceed 1/250 of the span).
Roof slope:
The slope should be designed based on drainage requirements (typically no less than 3%) to avoid water accumulation on the roof (which increases load).
Slope design must be coordinated with the angle of truss members to ensure rational force distribution in the bottom chord (in tension) and top chord (in compression), and prevent "compression member instability" (the slenderness ratio of compression members should generally not exceed 200).
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