Steel Structure FAQs —
Technical Questions, Expert Answers
Twenty frequently asked questions covering spatial grid structures, pipe trusses, beam-string systems, prefabricated buildings, welding quality, cold-climate engineering, and overseas project delivery — answered by the engineers who design and fabricate them.
Answers From the Engineers Who Build the Steel
These are not generic marketing answers. Each response is written from the perspective of our engineering and production teams, based on the structures we have actually designed, fabricated, and erected over 25 years and 200,000+ tons of annual production. If your question is not listed here, send it to our engineers and we will respond within 24 hours.
Grid, Truss, and Composite Technologies
FAQ 01What is a spatial grid structure and when should I use one?
A spatial grid structure is a three-dimensional load-bearing system composed of steel members arranged in a repeating geometric pattern, typically forming a flat or curved roof. Unlike a conventional beam-and-column frame that transfers load in one direction, a grid distributes forces in multiple directions simultaneously, which drastically reduces the steel weight per square meter of coverage. You should use a spatial grid when you need a large column-free space such as a sports arena, exhibition hall, airport terminal, coal shed, or industrial warehouse with spans exceeding 30 meters. Grid structures also excel where the roof must support heavy suspended loads like HVAC units, lighting rigs, or material handling systems. Their inherent redundancy means that if one member fails, adjacent members redistribute the load, improving structural safety.
FAQ 02What is the difference between bolted sphere and welded sphere grid?
In a bolted sphere grid system, each node is a solid steel sphere drilled and tapped with threaded holes. Individual members (steel tubes with high-strength bolts welded to their ends) are bolted into the sphere on site. This allows rapid assembly, easy transport in compact containers, and the ability to replace individual members if damaged. The bolted system is ideal for projects with many repetitive node types and where site welding must be minimized. In a welded sphere grid, hollow steel spheres are factory-welded to the connecting tubes, forming a monolithic joint that must be welded on site. Welded spheres achieve higher stiffness and can handle heavier loads at each node, but they require certified site welders, welding inspection (UT/RT), and more complex logistics. We hold the Special-Class manufacturing qualification for bolted sphere grids, the highest grade issued in China.
FAQ 03What is a beam-string structure and what is the world record span?
A beam-string structure is a hybrid system that combines a rigid steel beam (or truss) with a tensioned cable or rod strung beneath it. The cable is prestressed so that it pulls downward on the beam's midspan, creating an upward reaction that counteracts gravity loads. This prestress significantly reduces the beam's bending moment and deflection, allowing far longer clear spans with less steel than a conventional truss of equivalent capacity. Beam-string structures are commonly used for coal storage sheds, sports halls, and exhibition centers where interior columns must be eliminated. Permanent Steel Structure designed and fabricated the world's longest-span prestressed beam-string coal shed at the Guodian Ningxia Fangjiazhuang Power Plant, achieving a clear span of 229 meters with no interior columns — a world record for this structural type.
FAQ 04How does a steel pipe truss compare to an H-beam truss?
A steel pipe truss uses circular hollow sections (CHS) as its chord and web members, while an H-beam truss uses wide-flange sections. Pipe trusses offer several advantages: the circular cross-section has equal strength in all directions, making it ideal for resisting wind and seismic loads from any angle; the smooth surface reduces wind drag and snow accumulation, which matters for large-roof canopies in harsh climates; and the closed section resists torsion better than an open H-section. However, pipe truss joints are more complex to fabricate because multiple tubes meet at different angles and require full-penetration groove welds with carefully profiled cut ends. H-beam trusses are simpler and cheaper to fabricate using gusset plates and bolted joints, but they are heavier per unit of load capacity and less aesthetically refined. We hold the Special-Class manufacturing qualification for pipe truss structures.
FAQ 05What are the advantages of prefabricated steel buildings over concrete?
Prefabricated steel buildings offer decisive advantages over reinforced concrete in industrial and commercial construction. Speed is the primary benefit: steel components are fabricated off-site in a controlled factory environment while foundations are being poured simultaneously, cutting total project time by 30 to 50 percent. Steel is 5 to 10 times lighter than an equivalent concrete structure, which reduces foundation costs and makes steel the only viable choice for long-span, column-free interiors. Steel is also fully recyclable, generating no demolition waste. Quality is more predictable in steel because fabrication is machine-controlled via our CAD-CAM system, whereas concrete quality depends on on-site mixing, curing temperature, and workmanship. Steel structures can be disassembled, relocated, and re-erected, giving them genuine lifecycle flexibility that concrete cannot match. The trade-off is that steel requires fireproofing and anti-corrosion treatment, which we provide as part of our fabrication package.
FAQ 06What is the PEC (prefabricated steel-concrete composite) system?
PEC stands for Partially Encased Concrete, a composite structural system where a steel section (typically an H-beam or cross-shaped column) is partially filled with concrete that is cast around the web and flanges. The concrete is confined by the steel, which prevents spalling and increases compressive capacity, while the steel provides tensile strength and ductility. The result is a column or beam that is stronger, stiffer, and more fire-resistant than a bare steel section of the same size, while being lighter and faster to erect than a fully reinforced concrete column. PEC is one of our nine core technology systems and is particularly suited for multi-story residential and commercial buildings where fire rating, seismic performance, and floor vibration control are critical. Our PEC fabrication capability includes specialized formwork, concrete placement, and curing procedures integrated into our production line.
FAQ 07What is ultra-light steel construction and how thin is the steel?
Ultra-light steel construction uses cold-formed steel sections with wall thicknesses as thin as 0.8 mm to 3.0 mm, formed by roll-forming galvanized steel sheet into C-sections, U-sections, and Z-sections. These sections are assembled into wall panels, floor cassettes, and roof trusses using self-drilling screws, creating a framed building system that weighs only 25 to 40 kg per square meter of floor area. Ultra-light steel is used for low-rise residential buildings (up to 3-4 stories), modular rooms, interior partitions, and roof systems where rapid assembly and low self-weight are priorities. The galvanized coating provides corrosion protection without additional treatment. Because the steel is so thin, connection design is critical: every screw placement, bridging strap, and shear panel must be engineered to prevent buckling. This is one of our nine core technology systems, approached with the same structural rigor we apply to heavy industrial structures.
FAQ 08What is a modular integrated building system?
A modular integrated building system is a construction method in which entire three-dimensional room modules (complete with walls, floors, ceilings, electrical, plumbing, and finishes) are fabricated in a factory, transported to site, and stacked or arranged into a complete building. Each module is a self-contained steel-framed box, typically 3 to 6 meters wide and 9 to 18 meters long, with all interior work completed under factory quality control. On site, modules are bolted together, interconnected for utilities, and sealed, reducing on-site construction time to weeks rather than months. Modular construction is ideal for hotels, dormitories, hospitals, schools, and military housing where repetitive room layouts allow factory production at scale. The steel frame of each module is engineered for both transport loads (lifting, road vibration) and in-service loads (occupancy, wind, seismic). We treat modular construction as one of our nine core technology systems.
FAQ 09How does BIPV (Building Integrated Photovoltaics) work with metal roofs?
BIPV integrates photovoltaic (solar) cells directly into the building envelope rather than mounting them on top of an existing roof. In our Metal Roof and BIPV system, solar cells are laminated into standing-seam metal roof panels or integrated into skylight glazing, so the roof itself generates electricity while performing its primary function of weatherproofing and insulation. This eliminates the need for a separate racking system, reduces structural load, and improves aesthetics. A standing-seam BIPV roof panel clips onto the purlins without penetrating the weatherproof membrane, maintaining roof integrity. The electricity generated can offset a significant portion of a building's operational energy, which is increasingly mandated by green building codes. We engineer the roof structure, electrical integration, and solar panel layout as a single coordinated package, not as separate subcontracts handed to different vendors.
FAQ 10What steel grades do you use and what is Q355B?
Q355B is a Chinese standard structural steel grade with a minimum yield strength of 355 MPa and a B-quality grade designation for ambient-temperature impact testing at 20 degrees Celsius. It is roughly equivalent to European S355JR or American ASTM A572 Grade 50. Q355B is the workhorse grade for most steel structure projects because it offers a good balance of strength, weldability, and cost. For higher-strength applications, we use Q390, Q420, or Q460. For low-temperature service (below -20 degrees Celsius), we specify Q355C, Q355D, or Q355E, which are tested for impact toughness at 0, -20, and -40 degrees Celsius respectively. For the Antarctic Ross Sea station, we used low-temperature steel with specialized welding procedures to prevent brittle fracture at extreme cold. We also fabricate to ASTM A36, A572, A992 (US) and EN 10025 S235, S275, S355 (European) when required, with full material test certificates traceable to heat numbers.
Capacity, Qualifications, and Quality Control
FAQ 11What is your manufacturing capacity (tons/year, workshop area)?
Our manufacturing base in Xuzhou, Jiangsu Province covers over 300 mu (approximately 200,000 square meters of land), of which 100,000 square meters are enclosed production workshops. Our annual fabrication capacity is 200,000 tons of steel structures, including spatial grid structures, pipe trusses, prefabricated buildings, steel bridges, and structural steel components. On the construction side, we erect over 3,000,000 square meters of steel structure buildings per year. This capacity is backed by our self-developed CAD-CAM intelligent production system, which feeds design data directly to CNC cutting, drilling, and welding equipment, ensuring batch-to-batch consistency across production runs. The workshops house heavy lifting equipment, automated welding stations, shot-blasting lines, and multi-layer painting booths, enabling us to process steel from raw plate to finished, coated, packaged component under one roof without outsourcing any fabrication step.
FAQ 12What qualifications and certifications does your company hold?
Permanent Steel Structure holds Six Special-Grade Licenses, the highest qualification portfolio in China's steel structure industry. These include: Class-A Steel Structure Design License (authorizing design of any span and complexity), Class-1 Steel Structure Manufacturing License (the highest manufacturing grade), Class-1 Steel Structure Specialized Contracting (authorizing erection of fabricated structures), Special-Class Manufacturing License for Bolted Sphere Grid Structures (held by only a handful of manufacturers in China), Special-Class Manufacturing License for Pipe Truss Structures (equally rare), and Class-1 General Contracting for Construction (the legal framework for turnkey delivery). We are a National High-Tech Enterprise and a National Specialized Little Giant enterprise. We have won the Luban Prize (China's highest construction quality award) and the Steel Structure Gold Award. We hold over 100 patents, employ over 50 R&D engineers, and in 2023 established a joint research center with Shanghai Jiao Tong University for intelligent construction of spatial steel structures.
FAQ 13Do you provide design services or only manufacturing?
We provide both. Permanent Steel Structure is a full-industry-chain manufacturer, not just a fabrication shop. Our Class-A Steel Structure Design License authorizes us to engineer structures of any span, height, and complexity classification. We employ over 50 R&D engineers, over 60 percent of whom hold senior professional titles. In 2023, we established the Research Center for Intelligent Construction of Spatial Steel Structures jointly with Shanghai Jiao Tong University, giving us access to advanced academic research for complex projects. We can take your architectural concept, loading requirements, or even a sketch and develop it into a fabrication-ready, code-compliant design. We design to Chinese (GB), European (Eurocode), and American (AISC) standards, and we can optimize your design for material efficiency, constructability, and long-term performance. For clients who already have approved drawings, we fabricate to those drawings while offering engineering review and value-engineering suggestions.
FAQ 14What is the typical lead time for a steel structure project?
Lead time depends on project complexity, steel tonnage, and our production schedule at the time of order. After shop drawings are approved, fabrication of a standard industrial warehouse (500 to 1,000 tons of steel) takes 30 to 45 days. Larger or more complex projects (2,000+ tons with custom trusses, curved members, or thick-plate welding) take 60 to 90 days. Design and drawing preparation typically takes 2 to 4 weeks before fabrication begins, depending on how many revision cycles are required. We provide engineering review within 24 hours of receiving your drawings or concept, followed by a preliminary quotation and production schedule. Our CAD-CAM production system allows us to sequence multiple projects through shared equipment efficiently, and our 200,000-ton annual capacity means we can accommodate rush orders that smaller factories cannot. For overseas projects, add 7 to 21 days for container shipping depending on destination port.
FAQ 15Can you handle projects in cold climates (below -30C)?
Yes. Our most demanding reference project is the Antarctic Ross Sea New Station, China's first new-era year-round Antarctic research station, where winter temperatures drop below -40 degrees Celsius and katabatic winds exceed 200 km/h. For this project, we selected low-temperature structural steel grades (Q355D or Q355E equivalent) tested for impact toughness at -20 and -40 degrees Celsius, and developed specialized welding procedures (WPS) with preheat and interpass temperature controls to prevent cold-cracking in the heat-affected zone. Every weld was inspected by ultrasonic testing (UT) and magnetic particle testing (MT) to ensure no defects that could initiate brittle fracture under extreme thermal cycling. We also applied cold-climate-grade anti-corrosion coatings rated for polar conditions. For projects in Scandinavia, Russia, Canada, or northern China, we apply the same protocols: low-temperature steel selection, qualified welding procedures, and cold-climate coating systems, all documented in the project's welding and quality plans.
FAQ 16What is the maximum span you can achieve?
Our maximum span depends on the structural system selected. For bolted sphere grid structures, we routinely design and fabricate roofs with clear spans of 60 to 120 meters for sports halls, exhibition centers, and industrial facilities. For prestressed beam-string structures, we achieved a world-record clear span of 229 meters at the Guodian Ningxia coal shed, the longest span of this structural type ever built. For pipe truss canopies and roofs, we regularly produce spans of 50 to 90 meters for airport terminals, railway stations, and stadium roofs. For steel bridges, we fabricate box-girder and truss bridges with main spans of 100+ meters. The governing factor is not fabrication capability but load: a longer span requires heavier members, larger foundations, and more sophisticated erection methods. Our design team will assess your span requirement, loading conditions, and site constraints to recommend the most efficient structural system.
FAQ 17How do you ensure welding quality?
Welding quality is controlled through a documented system covering three layers: procedure, qualification, and inspection. First, we develop Welding Procedure Specifications (WPS) for every joint type and steel grade, specifying preheat temperature, interpass temperature, electrode type, amperage, voltage, and travel speed. These WPS are qualified by Welding Procedure Qualification Records (WPQR) through mechanical testing of test welds. Second, our welders are certified to Chinese, European (EN ISO 9606), or American (AWS D1.1) standards, with certificates maintained in our personnel database. Third, every structural weld is inspected by non-destructive testing: ultrasonic testing (UT) for internal defects, magnetic particle testing (MT) for surface cracks, and radiographic testing (RT) for full-penetration butt welds in critical locations. We maintain one of our ten core manufacturing technologies as thick-plate narrow-gap welding, a specialized process for heavy structural connections. All inspection results are documented in reports delivered before shipment.
FAQ 18Do you provide installation services?
Yes. We hold a Class-1 Steel Structure Specialized Contracting license and a Class-1 General Contracting license, which legally authorize us to erect the structures we fabricate. Our annual construction capacity exceeds 3,000,000 square meters of steel structure buildings. Every specialized worker is certified, and we are fully equipped with cranes, welding machines, and lifting systems. We master four advanced construction methods: jacking (raising entire roof systems hydraulically with millimeter precision), lifting (hoisting pre-assembled truss segments with synchronized cable systems), sliding (pushing bridge and roof structures along temporary rails), and tensioning (applying prestress to cable-strut and beam-string structures). These methods are essential for complex spatial structures where crane access is impossible or where the space below must remain operational during construction. For overseas projects, we can send installation supervisors to guide your local erection crew, or provide a full erection team depending on project requirements.
FAQ 19What is your experience with overseas projects?
We have delivered steel structures to projects across more than 30 countries, including Antarctica, Southeast Asia, the Middle East, South America, Africa, and Europe. Notable overseas references include the Antarctic Ross Sea Station, the Qatar Doha International Airport, the Pakistan Tarbela and Karot Hydropower Stations, the Brazil Vitoria Jurong Shipyard, the Kazakhstan Aktogay Copper Concentrator, and the Angola Housing Project. We fabricate to AISC (US), BS (UK), EN (Europe), and GB (China) standards, and our welding procedures are prepared to European CE standards with WPS and WPQR documentation. We provide English engineering documentation including shop drawings, calculation reports, and technical specifications. Our export packaging includes anti-corrosion VCI packaging for long sea voyages, and our logistics team optimizes container loading to reduce freight cost per ton. We prepare customs documentation (Certificate of Origin, Form A, Form E) and can quote in FOB, CIF, or DDP terms.
FAQ 20How do I get a quote for my project?
Send us your project requirements via email at market@permanentsteelstructure.com or WhatsApp at +86 18621689980. The most useful input is a set of structural drawings or architectural drawings with loading requirements, but we can also work from a concept sketch, a span requirement, and a building function description. Within 24 hours, our engineering team will respond with a feasibility assessment and a preliminary quotation. Our quotations include a transparent cost breakdown showing steel material (by weight and grade), fabrication labor, surface treatment, packaging, and inland transport to the port of loading. We quote in FOB, CIF, or DDP terms as you prefer. For a more precise quotation, provide the steel tonnage, span, building dimensions, design code (GB, AISC, EN, or BS), surface treatment requirement, and destination port. The more detail you provide, the more accurate and faster the quotation will be.
Have a Question Not Listed Here?
Our engineers are available to answer any technical question about your steel structure project — from material selection and welding specifications to span optimization and overseas logistics. Send your question and we will respond within 24 hours.
Contact Our Engineers