In the industrial construction industry, steel structures are considered the "skeleton" that supports the entire project. The solidity, safety and longevity of a project depend directly on the quality of each steel component. Therefore, the application of technical standards is not only a legal regulation but also the highest commitment to quality and safety. In Vietnam, the National Standards System (TCVN) plays the role of a fundamental technical framework, mandatory for all construction projects, ensuring consistency and safety.
For project owners and engineers, understanding these standards is a “vital” factor to control quality and evaluate the contractor’s capacity. A reputable steel structure manufacturer must demonstrate its ability to strictly and comprehensively comply with the TCVN system throughout the entire product life cycle. This article will provide an analytical perspective, systematizing the core TCVNs related to the process from design, material selection, processing, welding, surface protection to erection and acceptance of steel structures.
TCVN 5575:2012 (and update 2024)
TCVN 5575, with the latest version TCNV 5575:2012 and the updated version TCVN 5575:2024, is considered the core standard in the field of steel structure design for civil and industrial works. This standard does not apply to special works such as traffic or irrigation. The content of TCVN 5575 sets out the basic principles and requirements, shaping the entire production and assembly process later.
Core design principles
The most basic and important principle that TCVN 5575 provides is the method of calculating structures according to limit states, which means that the structure is designed so as not to exceed the states that can cause it to lose its normal working capacity. There are two main groups of limit states:
- Bearing capacity limit state (First limit state): These are safety-related conditions of the structure, where failure or collapse is likely. Situations include strength failure, global or local instability, brittle failure or yielding of the material.
- Use Limit State (Second Limit State): These are conditions that affect the normal exploitation and operation of the construction, such as the structure having too much deflection or deformation, causing excessive vibration or damage to architectural components and equipment.
To ensure safety, the standard requires that reliability factors must be used in calculations, including load factors (according to TCVN 2737), material factors and working condition factors. The determination of internal forces must be calculated with the most unfavorable load combination that can occur.
Requirements for bonding materials
TCVN 5575:2012 does not exist independently but forms a closely linked network with a series of different standards on materials and testing methods, requiring manufacturers to have a strong enough quality management system for synchronous control.
- Steel material: Steel grades and applicable standards must be clearly stated on the design drawings. The standards also encourage the priority use of steel produced in Vietnam.
- Welding materials: Welding rods and welding wires must comply with standards such as TCVN 3223:2000 and TCVN 3909:2000, ensuring compatibility with base materials and creating welds with required mechanical properties.
- Bolts: Bolts used in steel structures must comply with TCVN 1916:1995, with a minimum strength level of 4.6.
The reference to these details shows the systematic and complex nature of compliance. A professional manufacturer not only applies TCVN 5575 but also has to manage and control the input quality of a series of materials according to the relevant standards.
Processing, Installation and Acceptance Process according to TCVN 170:2007 (and TCVN 13194)
If TCVN 5575 is the guideline for design, then the TCXD 170:2007 standard set (now replaced and updated by parts of TCVN 170:2022 and TCVN 13194) is the standard for the process of "realizing" drawings, from the factory to the construction site.
Factory processing
The quality of the components is determined from the very first steps at the factory.
- Prepare materials: 100% of steel plates and profiles must be inspected, straightened, cleaned of rust, grease and impurities before being processed. Classification, labeling and marking with different color paint for each steel grade is mandatory to avoid confusion.
- Cut and shape: The cutting lines must ensure dimensional and geometric accuracy within the tolerances allowed in the design.
- Structural assembly: The cut parts are then assembled into complete components. This process requires high precision to ensure that the joints and connections are tight when assembled at the construction site.
Erection at site
- Foundation Check: Before erection, the position and elevation of the anchor bolts buried in the concrete foundation must be checked and accepted. Errors in this step will affect the entire steel frame later.
- Assembly sequence: Erection usually starts from the locked compartment (compartment with full bracing system), then develops to the remaining compartments. This ensures the stability of the structural system throughout the construction process.
- Tighten bolts: This is a very important step. The standard requires that 100% of structural bolts be tightened to the design torque. Torque checks must be performed with a calibrated torque wrench and marked upon completion.
Project acceptance
Acceptance is a continuous process, not only taking place when the project is completed. It includes acceptance of input materials, acceptance of processing stages at the factory, and acceptance of assembly at the construction site.
A complete set of acceptance documents as prescribed must include:
- Design drawings and completion drawings (recording actual deviations from design).
- Quality certificates of input materials (steel, bolts, welding rods).
- Certificate of practice of welder, high strength bolt assembler.
- Minutes of inspection and acceptance of weld quality (ultrasonic, magnetic…).
- Minutes of acceptance of protective paint layer.
- Detailed construction log.
Providing a complete and transparent set of documents is not only a legal requirement but also a demonstration of the contractor's professionalism and reputation.
Welding and Surface Protection Technical Standards
Welding and painting are two auxiliary stages but directly affect the integrity and longevity of steel structures.
Welding techniques
Standards such as TCVN 1691:1975 prescribe the basic shapes and dimensions of manual arc welds, while TCVN 9391:2012 deals with welded wire mesh. The general requirements are that the weld must have even penetration, be free from defects such as cracks, porosity, sagging and must be carried out by a suitably qualified welder. The quality of the weld is checked by non-destructive methods (NDT) such as visual inspection (VT), ultrasonic (UT), magnetic powder (MT) or penetrant (PT).
Corrosion protection (Paint)
Steel structures operating in the tropical climate of Vietnam are very susceptible to corrosion. Therefore, protective painting is extremely important. TCVN 8790:2011 and TCVN 12705 standards are the core regulations for this work.
- Paint system: A standard paint system includes the following layers: primer (enhanced adhesion and rust resistance), layer intermediate paint (increase thickness, create barrier layer) and layer coating (weatherproof, UV resistant and aesthetic color).
- Construction process: Steel surfaces must be cleaned to standard levels (e.g., shot blasting, sand blasting) before painting. The application of paint coats must comply with the dry film thickness (DFT) and drying time between coats as specified by the paint manufacturer.
- Acceptance: The finished paint layer is checked for appearance, color, adhesion and most importantly, the dry film thickness must meet design requirements.
