A Comprehensive Analysis of Standard TCVN 5574:2018

Part 1: Overview and Fundamental Principles of TCVN 5574:2018

1.1. Introduction, Validity Status, and Historical Context

National Standard TCVN 5574:2018, “Design of Concrete and Reinforced Concrete Structures,” is the core technical document, serving as a foundation in Vietnam’s construction standards system. This standard specifies the requirements and fundamental principles for the analysis, calculation, and detailing of structures using concrete and reinforced concrete (RC) materials in civil and industrial projects.

Validity Status and Latest Version

TCVN 5574:2018, issued by decision on December 10, 2018, is the latest version and is currently in “Active” status. This standard completely supersedes its predecessor, TCVN 5574:2012. Therefore, all design consulting activities for new construction projects must mandatorily apply the provisions of the 2018 version. Continuing to use TCVN 5574:2012 in new design documentation is no longer compliant with current regulations and must be updated to ensure legal and technical validity.

Historical Context and Reference Basis

The development history of RC structure design standards in Vietnam reflects a continuous process of absorbing and updating advanced technical knowledge. This process can be summarized in key stages:

• TCVN 5574:1991: The initial version, laying the groundwork for design practice in Vietnam.
• TCXDVN 356:2005: A significant update compiled by the Institute for Building Science and Technology (IBST), later converted to TCVN 5574:2012.
• TCVN 5574:2012: Based on the Russian Federation’s SNiP 2.03.01-84*, continuing the established technical tradition.
• TCVN 5574:2018: The current version, developed based on direct reference to the Russian Federation’s SP 63.13330.2012 and its 2016 amendments.

The close relationship with the Russian standards system is not just a simple reference but an inheritance of a technical legacy. The Russian standard SP 63.13330.2012 is itself a modernized version of previous SNiP standards, which has also harmonized some content with European standards (Eurocode). This process creates a logical link: as the Russian standards system is updated to more closely align with international practices, Vietnam’s standards system, through reference, is also driven in a corresponding modernization process. This implies that Vietnamese engineers experienced with older versions will find familiarity in the design philosophy, but must also grasp the changes influenced by the indirectly integrated European standards.

1.2. Scope of Application and Limitations

Clearly defining the scope and limitations of TCVN 5574:2018 is the first and most crucial step to ensure the standard is used for its intended purpose.

Applicable Structures:

This standard specifies design requirements for concrete and reinforced concrete structures in buildings and construction projects with various functions. Specifically, the standard applies to structures made from the following types of concrete:

• Heavyweight concrete.
• Fine-grained concrete.
• Lightweight concrete.
• Autoclaved aerated concrete.
• Self-stressing concrete.

Operating Conditions:

The standard applies to structures operating in non-aggressive environmental conditions and subject to systematic temperatures ranging from -70°C to +50°C.

Important Exclusions:

TCVN 5574:2018 does not specify design requirements for certain special structures and materials, including:

• Steel-concrete composite structures.
• Fiber-reinforced concrete structures.
• Special structures such as hydraulic works, bridges, road pavements, and airport runways.
• Special types of concrete such as: concrete with an average bulk density less than 500 kg/m³ and greater than 2500 kg/m³, polymer concrete, concrete based on lime, slag, or gypsum binders, concrete with special or organic aggregates, and no-fines concrete.

For structures outside this scope, the design must comply with other relevant specialized standards.

1.3. Key Updates Compared to TCVN 5574:2012

TCVN 5574:2018 introduces many landmark changes and additions compared to the 2012 version, not only updating calculation formulas but also changing the design philosophy and methodology.

Fundamental Change: From Stress Model to Deformation Model

This is the most fundamental and important change. TCVN 5574:2018 recommends prioritizing the use of the section calculation method based on the nonlinear deformation model, adopting the plane sections remain plane hypothesis.8 This method allows for a more accurate description of the actual stress-strain state of the section under external forces, and is particularly effective for members with complex cross-sectional shapes or those subjected to biaxial bending. It replaces the ultimate strength method in the old standard, which was based on simplified (rectangular) stress blocks and was somewhat more limited.

Updated Stress-Strain Relationships for Materials

To support the deformation model, the standard has added new stress-strain (σ – ε) diagrams for both concrete and reinforcement, a topic the old standard did not cover in detail. These diagrams are the basis for more accurately determining the strength and deformation capacity of members.

Improvements in Punching Shear Calculation

One of the new points with great practical significance is the improvement in the punching shear calculation method for flat elements like slabs and footings. TCVN 5574:2018 has rectified a significant shortcoming of the 2012 version by accounting for the effect of bending moments acting simultaneously with the concentrated force. This helps make the safety check for column-flat slab connections or eccentrically loaded spread footings more accurate and more consistent with the actual working behavior of the structure.

Enhanced Requirements for Structural Modeling

TCVN 5574:2018 is the first version to systematically address the concepts of structural calculation models.2 The standard requires engineers to thoroughly consider factors affecting the building’s behavior when developing the analysis model, such as:

• Elastic or inelastic behavior of materials.
• The actual stiffness of connections and the release of restraints.
• The necessity of using multiple calculation models for different load cases.
• Soil-structure interaction models.
• Global stability of the structure.

This addition is a significant effort to “catch up” with modern design practice, which relies heavily on structural analysis software. Previously, engineers often tended to just build the geometry, define materials and loads, and treat the software as a “black box” to get force results. The new requirements in the standard compel engineers to have a deeper understanding of the physical nature of the structure, thereby using software tools more effectively and accurately. The release of ETABS v23, which directly supports this standard, is also a natural consequence of this modernization process.

Adjustment of Concrete Cover

The regulations for the minimum thickness of concrete cover in TCVN 5574:2018 have been increased compared to the 2012 version (an increase of 5 mm to 10 mm in many cases). The purpose of this adjustment is to enhance the protection of the reinforcement, better ensuring requirements for:

• Composite action between steel and concrete.
• Anchorage and splicing of reinforcement.
• Protection of reinforcement from environmental impacts (corrosion resistance).
• Fire resistance of the structure.

Update on Deflection Limits

An important change related to cited standards is the regulation on allowable deflection limits. Previously, this content was mentioned in Annex M of TCVN 5574:2018. However, all regulations on deflection limits for all types of structures (reinforced concrete, steel, etc.) are now uniformly specified in Annex G of TCVN 2737:2023 – Loads and Actions.16 This is a critical update that design engineers must be aware of.

Table 1: Summary of Key Changes from TCVN 5574:2012 to TCVN 5574:2018

Item	Provision in TCVN 5574:2012	Provision in TCVN 5574:2018	Implication for Design
Basis of Section Calculation	Primarily based on the ultimate strength method with a rectangular stress block.	Prioritizes the nonlinear deformation model, based on the actual stress-strain diagrams of materials.	Allows for more accurate calculations, especially for complex sections and combined force cases.
Punching Shear Calculation	Only considers the effect of concentrated force.	Considers the simultaneous effect of concentrated force and bending moment.	Safer and more realistic design for flat elements like flat slabs and eccentrically loaded footings.
Structural Modeling	Hardly mentions concepts of calculation models.	Provides clear requirements for considering elastic/inelastic models, connection stiffness, and soil-structure interaction.	Requires engineers to have a deeper understanding of structural behavior, avoiding the use of software as a “black box”.
Concrete Cover	Lower minimum thickness.	Increased minimum thickness in many cases (up 5-10 mm).	Improves durability and fire resistance of the structure, but may slightly increase member dimensions.
Deflection Limits	Specified in Annex M.	Superseded. Deflection limits are moved to Annex G of TCVN 2737:2023.	Engineers must reference TCVN 2737:2023 to check deformation conditions.

Part 2: Comparative Analysis with International Design Standards

To position TCVN 5574:2018 in the global technical landscape, a comparison with the world’s leading design standards, such as ACI 318 (USA) and Eurocode 2 (EN 1992-1-1) (Europe), is essential. This analysis not only highlights similarities and differences but also provides deep insights into the safety levels and economic efficiency of the Vietnamese standard.

2.1. Comparison of Design Philosophies and Safety Factors

Fundamentally, all three standards systems are based on a common philosophy of ensuring the structure does not reach a “limit state” (either strength or serviceability) during its service life.

• TCVN 5574:2018 and Eurocode 2: Both use the Limit State Design (LSD) method. This method uses partial safety factors for loads (load factors) and for materials (material reliability factors).
• ACI 318: Uses the Load and Resistance Factor Design (LRFD) method. In essence, LRFD is very similar to Limit State Design. It also multiplies loads by factors greater than 1 and multiplies the member’s resistance by strength reduction factors (Φ) less than 1.

Although the general philosophy is similar, the specific values of the safety factors differ, leading to different overall safety levels for each member type and loading condition.

Table 2: Comparison of Design Philosophies and Basic Safety Factors

Factor	TCVN 5574:2018	ACI 318-19	Eurocode 2 (EN 1992-1-1)
Method	Limit State Design	Load and Resistance Factor Design (LRFD)	Limit State Design
Load Factor (Dead Load)	1.1 – 1.3 (typically 1.2)	1.2	1.35
Load Factor (Live Load)	1.2 – 1.4 (typically 1.3)	1.6	1.5
Material Safety Factor	Working condition factors (γb) and material reliability factors (embedded in design strengths Rb, Rs).	Strength reduction factors (Φ) vary by member type (e.g., Φ=0.9 for flexure, Φ=0.75 for shear, Φ=0.65 for spiral columns).	Partial safety factors for materials (γc=1.5 for concrete, γs=1.15 for steel).

2.2. In-depth Comparison of Flexural and Shear Design (Beams)

The differences in calculation formulas and assumptions lead to significantly different design results, especially in the load-bearing capacity of beams.

Flexural Design:

A quantitative comparative study showed that, for the same beam section (250×400 mm) and the same amount of reinforcement, the ultimate moment capacity (Mu) calculated according to TCVN 5574:2018 is 160 kNm, while according to ACI 318-19 it is 165 kNm. This difference is not large (less than 5%), but it shows that TCVN 5574:2018 is slightly more conservative in flexural design compared to the American standard.

Shear Design:

In contrast to flexure, the difference in shear calculation is very large and alarming. The same study indicated that, for the same member and stirrups, the ultimate shear capacity (Vu) calculated by TCVN 5574:2018 is up to 214 kN, while by ACI 318-19 it is only 168 kN. This means the shear capacity calculated by the Vietnamese standard is up to 27% higher than by the American standard.

This large discrepancy is not a minor detail but a fundamental difference in calculation models and safety assumptions. Shear failure is a brittle failure, occurring suddenly and without warning, making it much more dangerous than ductile flexural failure. International standards are typically very cautious in their shear provisions. The fact that TCVN 5574:2018 allows for a significantly higher shear capacity may stem from different formulas for calculating the concrete’s contribution (Vc) and/or the stirrups’ contribution (Vs). This implies that a design considered ‘just barely’ safe for shear under TCVN 5574:2018 might not meet the stricter safety requirements of ACI 318. This is a potential risk that engineers must be particularly aware of, especially when working on international projects or referencing technical documents based on American standards.

2.3. In-depth Comparison of Members Subject to Combined Axial and Bending Loads and Special Structural Regions (Columns, Corbels)

For more complex members, such as columns under combined axial load and biaxial bending, or for special structural regions (Discontinuity regions or D-regions), the methodological differences become even more pronounced.

A comparative analysis of corbel design between TCVN 5574:2018 and the Strut-and-Tie Model (STM) from ACI 318-14 showed very different results.

• TCVN 5574:2018’s method: Approaches it traditionally, calculating the corbel’s flexural capacity and shear capacity separately.
• ACI 318’s Strut-and-Tie Model: Views the corbel as a virtual truss, where compressive forces are transferred through concrete struts and tensile forces are resisted by steel ties. This model more closely reflects the actual flow of stresses in regions with abrupt changes in geometry or loading.

The comparison results showed that, to resist the same load, the design using the ACI Strut-and-Tie model required significantly less reinforcement: 27.9% less main tension rebar and 50.4% less shear stirrup rebar. In total, the ACI method saved about 13.1% of the total steel mass compared to the TCVN method. This suggests that for complex structural regions, the calculation methods in TCVN 5574:2018 may be quite conservative and not economically optimized.

2.4. Differences in Material Properties (Modulus of Elasticity)

One of the most fundamental and far-reaching differences lies in determining the material’s deformation characteristics, specifically the modulus of elasticity of concrete (Ec). A detailed study has shown that the Ec value specified in TCVN 5574:2018 (and the Russian standard SP 63) is significantly higher than in most other international standards.

For example: For B35 grade concrete, the Ec value according to TCVN 5574:2018 is 34.5 GPa. This value is about 8% higher than Eurocode 2 (32.0 GPa) and up to 38% higher than ACI 318 (25.0 GPa).

The reason for this difference lies in the definition method: TCVN 5574:2018 defines Ec as the initial tangent modulus, which is the slope of the stress-strain curve at the origin. In contrast, American and European standards define Ec as the secant modulus, which is the slope of the line connecting the origin to a specific stress point (e.g., 40% of the compressive strength), which more accurately reflects the concrete’s stiffness under normal service load levels.

This seemingly small difference in one material parameter causes a “ripple effect,” impacting the entire structural analysis and design process:

• Member Stiffness (EI): Because Ec is higher, the flexural stiffness of members calculated according to TCVN will be greater.
• Internal Force Distribution: In statically indeterminate systems (like multi-story building frames), members with greater stiffness will “attract” more internal forces (moments, shears). Using a higher Ec value can lead to a distribution of internal forces in the calculation model that differs from the actual distribution.
• Deformation (Deflection) Calculation: The deflection of a member is inversely proportional to its stiffness EI. Therefore, a higher Ec value will lead to an “optimistically” lower calculated deflection. This can mask potential serviceability limit state issues, leading to structures that may deflect excessively in reality even if calculations show they meet requirements.
• Stability (Slenderness) Calculation: The critical buckling load of a column (Ncr) is proportional to the stiffness EI. A higher Ec evaluation will lead to a larger Ncr, which can slightly reduce the calculated impact of slenderness effects (P-Delta effects) in slender columns.
• Dynamic Analysis: The natural period of vibration of a structure depends on its mass and stiffness. Higher stiffness leads to a shorter period of vibration, which directly affects the determination of seismic loads acting on the structure.

In summary, engineers need to be clearly aware that using the Ec value from TCVN 5574:2018 may lead to deformation and stability calculations that are more optimistic than reality.

Part 3: Practical Application Guide and Calculation Examples

Mastering the standard’s theoretical regulations must go hand-in-hand with the ability to apply them to practical design problems. This part provides a general workflow and detailed calculation examples for basic structural members.

3.1. Overall Design Process

A typical design process according to TCVN 5574:2018 includes the following sequential steps:

1. Determine Input Parameters:
   • Loads and Actions: Determine all types of loads acting on the structure (dead loads, live loads, wind loads, etc.) according to the provisions of TCVN 2737.
   • Material Properties: Select the concrete strength grade (e.g., B20, B25) and reinforcement group (e.g., CB300-V, CB400-V), and from there, determine the design strengths (Rb, Rbt, Rs, Rsc).
   • Preliminary Sizing: Based on architectural requirements and experience, perform preliminary sizing of member cross-sections for beams, columns, and slabs.
2. Select Method and Build Calculation Model:
   • Build the structural model in analysis software (e.g., ETABS, SAP2000).
   • Apply the modeling principles mentioned in the standard (connection stiffness, soil-structure interaction, etc.).
3. Structural Analysis:
   • Run the model analysis to determine internal forces (moments, shears, axial forces) and deformations (displacements, deflections) in the members under the various design load combinations.
4. Member Design and Verification:
   • Check Ultimate Limit State (for strength): Based on the calculated internal forces, proceed to calculate the required reinforcement area for each member to ensure its load-bearing capacity.
   • Check Serviceability Limit State (for usability): Check conditions for deformation (deflection) and crack formation to ensure the structure functions normally during its service life.
5. Final Detailing:
   • Arrange reinforcement details according to the standard’s detailing requirements (cover thickness, rebar spacing, anchorage, splices).
   • Present the results on the design drawings.

3.2. Design and Detailing of Reinforced Concrete Slabs

Slabs are one of the most common structural elements. TCVN 5574:2018 provides detailed provisions to ensure their effective and safe performance.

Reinforcement Ratio:

• Minimum (μmin): Section 10.3.1.1 specifies that the minimum reinforcement ratio in all cases shall not be less than 0.1% of the concrete cross-sectional area.
• Maximum (μmax): Calculated according to the formula in section 8.1.2.2.3 to ensure the member does not suffer a brittle failure due to over-reinforcement.
• Reasonable: Practical experience shows that a reasonable reinforcement ratio in slabs typically ranges from 0.3% to 0.9%.

Reinforcement Spacing:

• Maximum (Smax): To control crack width and ensure uniform stress distribution, section 10.3.3.3 specifies the maximum spacing between bars: Smax ≤ 200mm if the slab thickness hs ≤ 150mm; and Smax ≤ min{1.5hs; 400mm} if hs > 150 mm.
• Minimum (Smin): Must be large enough to ensure constructability (concreting and compaction). Section 10.3.2 specifies the minimum clear spacing between bars shall not be less than the largest bar diameter and not less than 25 mm (for the top layer) or 30 mm (for the bottom layer).

Rules for Curtailing Reinforcement:

• The general principle is to cut off reinforcement at locations where the moment diagram allows, to optimize material use.
• Common concepts for curtailing support reinforcement (e.g., cutting at 1/4 or 1/3 of the span) are for reference only and depend heavily on the support conditions, the ratio of dead to live loads, and the span differences between adjacent slabs.

Arrangement of Additional Reinforcement: Additional reinforcement must be placed at locations of stress concentration, such as around openings or under walls built directly on the slab.

3.3. Detailed Calculation Example: Column Subject to Biaxial Bending with Compression

This section illustrates the reinforcement calculation process for a column under biaxial bending with compression according to TCVN 5574:2018, based on a typical calculation example.

Input Parameters:

• Column section: Cx*Cy = 250 * 300 mm.
• Column height: L = 3300 mm.
• Materials: B20 Concrete (Rb = 11.5 MPa), CII Steel (Rs = 280 MPa).
• Concrete cover: a = 40 mm.
• Design internal forces at the critical section: N = 91.94 kN; Mx = 24.25 kNm; My = 1.63 kNm.
• Reinforcement ratio limits: μmin = 1%, μmax = 3%.

Calculation Steps:

1. Determine Initial and Accidental Eccentricities:
   • Initial eccentricity: e1x = Mx/N = 264 mm; e1y = My/N = 18 mm.
   • Accidental eccentricity is calculated and taken as 10 mm for both directions.
   • Initial design eccentricity: e0x = max(264, 10) = 264 mm; e0y = max(18, 10) = 18 mm.
2. Check Slenderness Effects (Buckling):
   • Effective length: L0 = 0.7*L = 2310 mm (assuming pinned ends).
   • Slenderness: λx = L0 / (0.288*Cx) ≈ 32.08; λy = L0 / (0.288 *Cy) ≈ 26.74.
   • Since λmax = 32.08 is greater than the limit, slenderness effects must be considered.
3. Calculate Slenderness Coefficient (η):
   • The η coefficient is calculated based on the ratio of the axial force N to the critical buckling load Ncr.
   • Result: ηx ≈ 1.013; ηy ≈ 1.019.
4. Determine Design Moments Including Slenderness Effects:
   • M1x = ηx * Mx = 1.013 * 24.25 ≈ 24.57 kNm.
   • M1y = ηy * My = 1.019 * 1.63 ≈ 1.66 kNm.
5. Calculate Required Reinforcement Area:
   • Convert the biaxial bending problem to an equivalent uniaxial bending problem. Equivalent moment M ≈ 25.84 kNm.
   • Determine the compression zone height x ≈ 26.6 mm.
   • Since the eccentricity is large (e0/h0 > 0.3), apply the calculation formula for large eccentricity cases.
   • Required reinforcement area: Ast ≈ 817 mm².
6. Check and Arrange Reinforcement:
   • Actual reinforcement ratio: μ = Ast / (Cx * Cy) ≈ 1.3%.
   • Check condition: 1% = μmin < 1.3% < μmax = 3%. Satisfied.
   • Selected arrangement: 4 ∅18 bars (Provided Ast = 1018 mm² > 817 mm²).

3.4. Calculation of Deformation (Deflection) and Cracks

Checking the Serviceability Limit State (SLS) is an indispensable part of design, especially for flexural members like beams and slabs.

• Calculation Principles: Deformation calculations are performed using standard loads (unfactored loads).
• Long-Term Effects: To get accurate results, it is necessary to consider the long-term behavior of RC structures, which includes two main factors: creep and shrinkage of concrete.
  • Creep: Accounted for through the creep coefficient φb,cr (denoted as CR in some documents), found in Table 11 of TCVN 5574:2018, which depends on the concrete strength grade and the relative humidity of the environment.
  • Shrinkage: Accounted for through the relative shrinkage strain ϵb,sh (denoted as SH).
• Application in Software: Specialized analysis software like SAFE allows users to input creep and shrinkage coefficients to perform cracked analysis and calculate long-term deflections accurately.
• Important Note: As mentioned, the allowable deflection limits for members must be taken from TCVN 2737:2023; they are no longer in TCVN 5574:2018.

Part 4: Calculation Tools and Workflow Integration

The development of software technology has profoundly changed the workflow of structural engineers. The effective selection and use of calculation tools are key factors in ensuring design quality and optimizing productivity.

4.1. Analysis of the Software Ecosystem

The Revolutionary Change with ETABS v23

ETABS software by CSI is a high-rise building analysis and design tool widely used in Vietnam. However, its support for TCVN 5574:2018 has undergone a significant development process.

• Before v23: Older versions of ETABS did not directly support TCVN 5574. Engineers often faced many difficulties, forced to use indirect methods such as converting material properties to a supported standard (e.g., ACI 318 or Eurocode 2) to calculate reinforcement.25 This method was not only time-consuming but also prone to errors due to the philosophical differences between standards.
• From v23 onwards: ETABS has officially integrated TCVN 5574:2018 directly into the Concrete Frame Design module. This is a revolutionary step, allowing engineers to perform the entire process from modeling, analysis, to design and verification of the structure completely within a single, seamless, and accurate software environment. Engineers can define materials, load combinations, and run member checks directly according to the clauses of the Vietnamese standard.

Other Software and Supplementary Tools

Besides comprehensive analysis software, an ecosystem of specialized tools and spreadsheets also plays an important role.

• SAFE: Still the leading tool for the detailed design of slab and foundation elements, with particular strengths in analyzing and calculating long-term, cracked-section deflections.
• Specialized Vietnamese Software: Local software companies have developed many useful tools to automate calculations according to TCVN. For example: KetcauSoft’s tools like RCC (column design), RCBc (beam design), or RC Pro by KetcauPro. This software often has a user-friendly interface and exports detailed calculation reports, suitable for checking and documentation.
• Excel Spreadsheets and Web Applications: These are flexible and very commonly used tools. Many engineers and firms have developed their own Excel spreadsheets to solve specific problems like biaxial column design or slab design. Recently, web-based applications like those from Cemcons even allow for the batch design of beams and columns by directly importing force files from ETABS, significantly speeding up the detailed design process.

The development of software tools has reshaped the engineer’s workflow through various stages. Initially, it was a manual phase or one using temporary workarounds. This was followed by a phase where an ecosystem of supplementary tools formed, automating tasks but leaving the process fragmented. We are now in a phase of comprehensive integration, where major software directly incorporates the standard, making the workflow seamless. The role of supplementary tools has also changed, from “replacement tools” to “enhancement tools” for specialized tasks like batch processing or detailed report generation.

Table 5: Software Support Matrix for TCVN 5574:2018

Software	Level of Support	Key Features	Strengths	Limitations/Notes
ETABS < v23	Indirect	Structural analysis.	Powerful internal force analysis.	Must convert materials for design, potential for errors, inefficient.
ETABS v23+	Direct, Comprehensive	Analysis and design of RC frames.	Fully integrates TCVN 5574:2018, seamless workflow, high accuracy.	The design module may not cover all special member types.
SAFE	Indirect	Analysis and design of slabs, foundations.	Excellent analysis of cracking and long-term deflection.	Reinforcement design still needs conversion or re-checking with other tools.
KetcauSoft (RCC, RCBc)	Direct, Specialized	Detailed design of columns, beams.	User-friendly interface, exports detailed reports, strictly follows TCVN.	Only solves individual members, needs internal forces from other software.
Cemcons Tools (Web App)	Direct, Automated	Batch design of beams, columns.	Handles large data, imports forces directly from Etabs, increases productivity.	Dependent on internet connection, may not be as flexible as spreadsheets.
Excel Spreadsheets	Customizable	Solves specific problems.	Maximum flexibility, user has full control over algorithms.	Prone to errors if not carefully verified, difficult to manage versions.

4.2. Optimized Workflow

Based on the current tool ecosystem, an effective and optimized workflow for structural design engineers in Vietnam can be proposed as follows:

1. Global Analysis (ETABS v23+): Use ETABS to build the 3D model, assign loads, perform structural analysis, and run the Preliminary Design module to get the required reinforcement area for the main frame members.
2. Detailed Slab and Foundation Design (SAFE): Export the model from ETABS to SAFE to design the slab and foundation systems in detail. Pay special attention to checking long-term deflection and punching shear.
3. Verification and Refinement (Specialized Tools/Spreadsheets): Export internal forces from ETABS to specialized tools (KetcauSoft, Cemcons) or verified Excel spreadsheets to:
   • Re-check the design results from ETABS.
   • Design complex or special members not fully supported by ETABS.
   • Automate reinforcement arrangement and quantity take-offs.
4. Prepare Calculation Report: Use the results from the specialized tools and spreadsheets to create detailed, transparent reports for design review and record-keeping.

4.3. Recommendations for Design Engineers

When applying the standard in a software environment, engineers need to note several important points to ensure the accuracy of the results:

• Understand the Software’s Assumptions: Always check the Design Preferences and parameters in the software to ensure they are consistent with the clauses of TCVN 5574:2018.
• Do Not Skip Manual Checks: For critical or complex members, re-checking with manual calculations or spreadsheets is essential to validate the software’s results.
• Interpret Results Intelligently: The output from the software is an “output,” not “the truth.” Engineers must use their professional knowledge and experience to assess the reasonableness of the internal forces, deformations, and reinforcement areas proposed by the software.

Part 5: Conclusion and Expert Recommendations

5.1. Summary of Key Points

TCVN 5574:2018 marks a significant step forward in modernizing Vietnam’s design standards system for concrete and reinforced concrete structures. It not only updates calculation methods but also shifts the design mindset, moving towards convergence with international standards and becoming more aligned with modern, software-based design practices.

The core points to be summarized include:

• Modernization: The transition to the nonlinear deformation model, the updated punching shear calculation that includes moments, and the introduction of clear requirements for structural modeling have significantly enhanced the standard’s accuracy and scientific basis.
• Differences from International Standards: Despite many improvements, TCVN 5574:2018 still has significant differences compared to leading standards like ACI 318 and Eurocode 2. These differences are particularly pronounced in two areas:
  • Shear Capacity: Calculations according to TCVN result in a design that is significantly less conservative (less safe) than ACI.
  • Modulus of Elasticity of Concrete (E_c): The higher E_c value in TCVN can lead to an underestimation of deformation and an overestimation of structural stiffness.
• Technology Integration: The direct integration of TCVN 5574:2018 into leading structural analysis software like ETABS has created a revolution in the workflow, helping to increase productivity and reduce errors.

5.2. Recommendations for Engineering Practice

Based on this in-depth analysis, the following recommendations are made for the structural engineering community in Vietnam to enhance the quality and safety of designed structures:

Maintain a Systems-Thinking Approach and Stay Updated: It must be remembered that TCVN 5574:2018 does not exist in isolation. It is part of a tightly interconnected system of standards and regulations. Engineers must always stay updated and synchronously apply related standards such as TCVN 2737 (Loads and Actions), TCVN 9386 (Design of structures for earthquake resistance), and national technical regulations like QCVN 06:2022/BXD (Fire safety of buildings and constructions), as they may modify or supplement the design requirements specified in TCVN 5574:2018. are made for the engineering community.

Exercise Special Caution with Shear Design: As the calculated shear capacity under TCVN 5574:2018 is significantly higher than international practice, engineers should adopt a cautious approach. For members with high shear forces and high importance (e.g., transfer beams, corbels, slab-column connections), consider applying an additional safety factor or performing a cross-check against another standard (like Eurocode 2) to get a multi-dimensional safety assessment.

Carefully Check Deflection and Long-Term Deformation: Because the high E_c value in TCVN can lead to optimistic deflection calculations, engineers must pay special attention to checking deformation conditions under the serviceability limit state. An analysis that considers the long-term effects of creep, shrinkage, and crack formation is mandatory, especially for deformation-sensitive structures like long-span slabs, cantilever beams, or structures supporting partitions prone to cracking.

Maximize the Use of Integrated Workflows: It is strongly recommended to use the latest software versions (like ETABS v23 and later) to leverage the benefits of direct standard integration. This not only minimizes errors from manual conversions but also frees up time for engineers to focus on more critical aspects, such as conceptualizing the structure and verifying the model’s reasonableness. Concurrently, seamlessly combine these with supplementary tools to accelerate detailed checks and complete design documentation.