The Importance of Application of EN ISO 3834 and EN 1090 in Production of Steel Structures

. Fractures of welded structures in operational conditions most often occur in the welded joint or its immediate vicinity. Due to this, special attention is paid to ensuring the quality of the welded joint. The application of the EN ISO 3834 and EN 1090 standards in the manufacture of steel structures aims to ensure the highest possible quality of welded joints, and thus the quality of the structures as a whole. Weld quality is achieved by welding, whereas weld quality control provides a check of product reliability. Increasing requirements in terms of reliability, better use of materials, lower weight and cost of constructions, but also high use of load-bearing structural elements, and thus welded joints, leave less room for errors in welded joints, which is why constant control and monitoring of documented procedures is required.


Introduction
Some authors emphasize the importance of applying standards in the process of welding and manufacturing of steel structures, which implies constant quality control.EN ISO 3834 is suitable when proving the suitability of the manufacturer to produce welded structures, meeting the specified quality requirements, which are contained in the specifications, product standards, and regulations.
Pereira et al. [1] provides guidelines for the implementation of the welding quality management system in metal structure, and presents numerous valid standards, both for the welder and the welding coordinator, as well as for the process and product.The author also provides an overview of the applicable normative branches and how to get the CE mark for product.
Stenberg T et al. [2] gave a comprehensive overview of control and quality assurance of welded structure welds which hold the main prevention of failure due to fatigue loads.They described the shortcomings and limitations of quality control systems, international welding quality standards and guidelines used in today's welding production.The collected information can be used to determine the level of weld quality in relation to fatigue strength, but also to improve process control.
Toivanen et al. [3] have examined the production and conformity of welded products and the importance of the cooperation of different functions for the quality of welding.They come to the conclusion that coordinating welding operations would benefit production quality and profitability.
Komljen P K [4] shows the method of inspection and the procedure of professional supervision over the construction of steel structures in accordance with the standards EN 1090-1, EN 1090-2 and EN 3834.The complexity of professional supervision stems from the requirements of the project documentation.Supervision must be based on an overall understanding of the behavior of the steel structure, knowledge of the state regulatory framework in the field of construction, and knowledge of the requirements for construction performance according to EN 1090-2.In their work, Bajramovic E et al. [5] emphasize that the assessment of the integrity of structures depends largely on a comprehensive analysis of the welded joint as the most critical point of welded steel structures and the importance of quality control during welding.They show the analysis of the process of crack formation and crack propagation in welded joint.
The aim of this paper is to point out the importance of the implementation of EN ISO 3834 and EN 1090, which significantly reduces the possibility of nonconformities, both during the production of steel structures, and in case of failure of the structure during use.

Implementation
Steel assemblies are crucial for safety and must ensure that the end result, which is steel structure, is safe and reliable.Therefore, welded connections in such assemblies and structures must comply with strict quality requirements (EN ISO 3834) and standards for conformity assessment (EN 1090-1) and manufacturing (EN 1090-2) of steel structures.
The quality of the weld is achieved by welding, whereas the reliability of the structures is checked with the quality of the weld.In addition to quality requirements, welding also has a significant impact on costs, so, it is crucial that welding be carried out as quickly as possible while keeping all quality standards.

Standard EN ISO 3834
Welding requires constant control and monitoring of documented procedures.Based on that, the EN ISO 3834 series of welding standards was prepared.The series of standards consists of five parts, which are shown in Table 1.
Table 1.Series of welding standards EN ISO 3834 [6] Therefore, EN ISO 3834 defines comprehensive requirements for the quality of fusion welding of metal materials, both in production and in the field.The following sections of the welding standard EN ISO 3834 apply depending on the level of execution: Level exexution [7] The EN ISO 3834 standard is an international standard that refers to quality systems for welding.It defines quality requirements and provides a framework for the development of a quality system for welding in the production of products or services.It is used in different industries and sectors.It applies to all stages of production, including design, production, assembly and service.It applies to all types of welding, including welding, soldering, joining and other techniques of joining metal materials.
The aim of this standard is to help organizations to improve their welding processes and to increase their reliability and compliance with international standards.The field of application of this standard is, among other things, the following: • It provides precise criteria for the quality of welding in production and on the construction site.
• In structures where a weld failure could lead to a complete failure of the product with successive financial consequences and a significant risk to human health.
Aspects to consider when applying the standard include the following: • The product standards to be implemented and any additional requirements

Standard EN 1090
EN 1090-1 is a harmonized standard that defines requirements for compliance of performance characteristics for steel and aluminum structures.Given that this is a harmonized standard, the CE mark is mandatory for the production and sale of structure components or assemblies as a whole.Series of standards EN 1090 consists of five parts, which are shown in Table 3.
Table 3. Series of standards EN 1090 [7] In accordance with EN 1090-1, CE Marking is a self-declaration, therefore it needs to be signed by a representative who accepts responsibility for the information stated in declaration.There are additional third-party requirements that must be met in order for you to get CE Mark, that is certification of Factory Production Control [8].3rd step: Choose the Production Category (PC1 or PC2) 4th step: Using the results of steps 1, 2 and 3 and the matrix (Table 5) to determine the execution class

Conclusion
The aim of applying the ISO EN 3834 and EN 1090 standards is primarily to ensure quality, but also to remove technical obstacles and thus ensure the smooth flow and free trade of all building structures within the European Union.It is necessary to establish a high-quality and correct procedure for the implementation of standards whose main purpose is to prevent incorrect manufacturing and installation that would cause technical, financial or other consequences.
Furthermore, the growing demands of customers in terms of safety and economy leave less room for non-conformities in production, which is why constant control and follow-up with documented procedures is required.Thorough monitoring of production parameters is key to achieving product quality requirements and optimizing the production process.By monitoring and maintaining quality documentation and records, it is possible to trace back the causes that caused product non-conformity.The results of measurement and control are crucial in the analysis of the causes of non-conformity and their elimination.
Constant control and monitoring of documented procedures are achieved through the implementation of the EN ISO 3834 and EN 1090.Implementation of the above standards has a very significant role in the production of steel welded structures from multiple aspects.
Ultimately, all companies that want to place their steel construction products on the single market of the European Union must have a certified Factory Production Control system that will enable them to issue a Declaration of conformity and CE mark.