{"id":9455,"date":"2026-08-14T10:51:38","date_gmt":"2026-08-14T03:51:38","guid":{"rendered":"https:\/\/giaanh.vn\/?post_type=kien-thuc&p=9455"},"modified":"2026-10-15T09:25:22","modified_gmt":"2026-10-15T02:25:22","slug":"reducing-truck-body-structural-weight-every-kilogram-saved-is-one-more-kilogram-of-payload","status":"publish","type":"kien-thuc","link":"https:\/\/giaanh.vn\/en\/knowledge\/truck-body-structural-weight-reduction-from-mass-reduction-to-load-bearing-design\/","title":{"rendered":"Truck body structural weight reduction: From mass reduction to load-bearing design"},"content":{"rendered":"

A truck body that uses more steel, thicker plates and a heavier structure does not necessarily have greater load-carrying capacity. For specialized transport vehicles, the heavier the structure, the less mass remains available for payload.<\/p>\n

Using high-strength steel can make it possible to reduce thickness at suitable locations while still meeting strength requirements. However, reducing thickness affects more than load-carrying strength. The structure must also control deflection, local stability, weld fatigue and actual fabrication capability.<\/p>\n

Structural weight reduction should therefore be treated as a combined material and structural design problem rather than simply replacing thicker steel with thinner steel.<\/p>\n

This knowledge series provides principles and evaluation methods for identifying where weight can be reduced, selecting high-strength steel, controlling the relevant technical limits and demonstrating that the structure remains suitable after the design is changed.<\/p>\n

1. How tare weight affects payload capacity<\/span><\/h2>\n

Tare weight is the mass of the vehicle and truck body structure itself, excluding the transported load.<\/p>\n

Based on the permissible gross vehicle weight, the basic relationship is:<\/p>\n

Payload = Permissible gross vehicle weight – Tare weight<\/strong><\/p>\n

If tare weight is reduced by 1 kg while the permissible gross vehicle weight remains unchanged, the vehicle may gain 1 kg of payload capacity within the overall weight limit.<\/p>\n

However, the actual benefit also depends on the type of cargo, body volume and axle load limits.<\/p>\n

1.1. Three benefits of reducing tare weight<\/span><\/h3>\n\n\n\n\n\n\n\n
Benefit<\/th>\nValue to the operator<\/th>\nBasis for evaluation<\/th>\n<\/tr>\n<\/thead>\n
Increased payload capacity<\/td>\nMore cargo mass may be transported per trip<\/td>\nWeight reduction, number of trips and transport value<\/td>\n<\/tr>\n
Reduced vehicle mass carried during operation<\/td>\nMay contribute to lower fuel consumption<\/td>\nOperating conditions, loaded and unloaded travel distance<\/td>\n<\/tr>\n
Support for axle load control<\/td>\nMay reduce the risk of exceeding axle load limits<\/td>\nWeight distribution and actual load on each axle<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

For vehicles that frequently carry heavy loads and operate close to the permitted weight limit, additional payload capacity can provide significant value.<\/p>\n

For example, the weight saved on a truck body can be considered together with the number of trips per year and the remaining operating life to evaluate the economic benefit.<\/p>\n

However, reducing tare weight does not always mean that more cargo can actually be carried.<\/p>\n

If a vehicle carries low-density cargo and reaches its volume limit before reaching the weight limit, reducing tare weight may not increase the amount of cargo carried per trip.<\/p>\n

Similarly, reducing total vehicle mass without considering load distribution across the axles may still not resolve axle load requirements.<\/p>\n

1.2. Actual tare weight needs to be established before evaluating a solution<\/span><\/h3>\n

A vehicle that has had its body replaced, repaired or reinforced several times may have a different tare weight from its original configuration.<\/p>\n

Before evaluating weight reduction potential, the vehicle documentation therefore needs to be compared with the actual condition.<\/p>\n

In particular, it is not enough to identify only the total tare weight. It is also necessary to understand how that mass is distributed across the individual components.<\/p>\n\n\n\n\n\n\n\n\n\n
Component<\/th>\nInformation to record<\/th>\n<\/tr>\n<\/thead>\n
Body floor and dump body floor<\/td>\nMass, thickness and material group<\/td>\n<\/tr>\n
Lower side wall<\/td>\nMass, thickness and cargo-contact conditions<\/td>\n<\/tr>\n
Upper side wall<\/td>\nMass, thickness and load requirements<\/td>\n<\/tr>\n
Longitudinal and transverse beams<\/td>\nMass, cross-sectional geometry and material group<\/td>\n<\/tr>\n
Frame and supports<\/td>\nMass, cross-sectional geometry and loading conditions<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

When individual components cannot be weighed separately, their mass can be calculated from drawings, actual dimensions and thicknesses.<\/p>\n

However, two types of data need to be distinguished:<\/p>\n

WEIGHED:<\/strong> Mass determined by actual weighing.<\/p>\n

CALCULATED:<\/strong> Mass determined from dimensions, geometry and material density.<\/p>\n

Calculated results may not fully include welds, bolts, paint or auxiliary components.<\/p>\n

When comparing the structure before and after a design change, the same method of determining mass and the same component scope should therefore be used.<\/p>\n

The starting point for structural weight reduction is to establish the actual mass first, then identify where thickness reduction or structural changes may be possible.<\/p>\n

This topic is covered in detail in Part 1: Reducing tare weight and increasing payload capacity<\/strong><\/a><\/span>.<\/p>\n

2. Why can high-strength steel help reduce thickness?<\/span><\/h2>\n

When designing a load-bearing structure, thickness is not the only factor that determines how the material performs.<\/p>\n

One important property is yield strength, which indicates the stress level at which permanent deformation begins.<\/p>\n

High-strength steel has a higher yield strength and can therefore meet strength requirements at certain locations using a smaller cross-section.<\/p>\n

However, three mechanical properties need to be distinguished when selecting the appropriate material.<\/p>\n\n\n\n\n\n\n\n
Property<\/th>\nTechnical meaning<\/th>\nRole in material selection<\/th>\n<\/tr>\n<\/thead>\n
Yield strength<\/td>\nStress level at which permanent deformation begins<\/td>\nImportant basis for structural strength calculations<\/td>\n<\/tr>\n
Tensile strength<\/td>\nMaximum tensile stress reached during a tensile test<\/td>\nUsed to evaluate the tensile characteristics of the material<\/td>\n<\/tr>\n
Elongation<\/td>\nAmount of deformation before fracture under the specified test conditions<\/td>\nUsed to assess deformation capability and fabrication limits<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

2.1. Higher yield strength increases stress-carrying capability<\/span><\/h3>\n

When thickness is reduced, the load-bearing cross-section of the steel plate changes.<\/p>\n

If the load and remaining geometry stay unchanged, stress in the plate may increase.<\/p>\n

Using steel with a higher yield strength can help maintain the required stress-carrying capability without permanent deformation occurring.<\/p>\n

This provides the material basis for many structural weight reduction solutions.<\/p>\n

However, a higher yield strength does not automatically make the structure stiffer or reduce deflection.<\/p>\n

Resistance to deformation also depends on geometry, thickness, span between supports and structural arrangement.<\/p>\n

2.2. Higher-strength grades may reduce formability<\/span><\/h3>\n

When selecting high-strength steel, elongation and bending radius need to be considered in addition to yield strength.<\/p>\n

For the perform\u00ae grades referenced in thyssenkrupp technical documentation, elongation generally decreases as the yield strength grade increases.<\/p>\n\n\n\n\n\n\n\n\n
Yield strength grade<\/th>\nDeclared elongation<\/th>\n<\/tr>\n<\/thead>\n
300-355 MPa<\/td>\n19-25%<\/td>\n<\/tr>\n
460-500 MPa<\/td>\n12-17%<\/td>\n<\/tr>\n
650-700 MPa<\/td>\n10-12%<\/td>\n<\/tr>\n
1,100 MPa<\/td>\n8%<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

These values are compiled from perform\u00ae product documentation. The ranges may include different test conditions and different bases for determining elongation. They should not be used directly for comparison or acceptance inspection unless the test basis has been aligned.<\/p>\n

This shows that the steel grade with the highest yield strength is not necessarily the most appropriate choice.<\/p>\n

If the design requires deep-formed sections, formed ribs or tight-radius bends, material formability may become the limiting factor.<\/p>\n

2.3. Steel selection needs to match the fabrication method<\/span><\/h3>\n

Two standard groups are used in this knowledge system:<\/p>\n\n\n\n\n\n\n
Standard<\/th>\nMaterial scope<\/th>\nFabrication considerations<\/th>\n<\/tr>\n<\/thead>\n
EN 10025-6<\/td>\nHigh-strength quenched and tempered steel<\/td>\nStructures need to consider the characteristics of quenched and tempered plate, particularly during cutting and welding<\/td>\n<\/tr>\n
EN 10149-2<\/td>\nHigh-strength hot-rolled steel for cold forming<\/td>\nComponents requiring bending and formed sections<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Structural requirements and the fabrication method should be defined first, followed by selection of the yield strength grade and specific steel grade.<\/p>\n

A steel grade that meets the load requirement but cannot be formed into the required section is still not an appropriate solution.<\/p>\n

This topic is covered in detail in Part 2: Principles of reducing structural thickness with high-strength steel<\/strong><\/a><\/span>.<\/p>\n

3. Three common technical limits when reducing thickness<\/span><\/h2>\n

High-strength steel can help meet strength requirements, but it does not address every change in structural performance caused by thickness reduction.<\/p>\n

Three issues need to be controlled: deflection, local stability and weld fatigue<\/strong>.<\/p>\n\n\n\n\n\n\n\n
Technical issue<\/th>\nWhy it needs to be considered<\/th>\nPossible sign on the vehicle<\/th>\n<\/tr>\n<\/thead>\n
Deflection<\/td>\nReduced thickness and geometric stiffness<\/td>\nFloor visibly deflects under full load<\/td>\n<\/tr>\n
Local stability<\/td>\nThin plate may become unstable under compressive stress<\/td>\nSide wall or plate develops a wavy appearance<\/td>\n<\/tr>\n
Weld fatigue<\/td>\nRepeated loading and stress concentration at welded details<\/td>\nCracks appear and grow at the weld toe<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

3.1. Deflection increases as thickness decreases<\/span><\/h3>\n

A steel plate may still meet the strength requirement while deflecting more than the design allows.<\/p>\n

Two conditions need to be distinguished:<\/p>\n

Elastic deflection:<\/strong> The structure deforms under load and returns to its original shape after unloading.<\/p>\n

Permanent deformation:<\/strong> The structure does not return to its original shape after unloading.<\/p>\n

Inspection should therefore be performed both under load and after the cargo has been unloaded.<\/p>\n

If measurement is carried out only while the vehicle is fully loaded, it may be difficult to determine whether the observed deformation is still within the elastic range.<\/p>\n

3.2. Local stability depends strongly on geometry<\/span><\/h3>\n

A thin plate under compression may buckle before the material reaches its yield strength.<\/p>\n

A common sign is a wavy surface, particularly in compressed regions between stiffeners.<\/p>\n

Local buckling needs to be distinguished from impact denting.<\/p>\n

Buckling is generally related to the stress state and plate geometry, while impact dents usually appear at locations directly struck by objects or cargo.<\/p>\n

These two mechanisms require different evaluation and corrective approaches.<\/p>\n

3.3. Weld fatigue is associated with repeated loading<\/span><\/h3>\n

Vehicle structures are regularly subjected to dynamic loading during operation.<\/p>\n

Locations such as weld toes, the ends of intermittent welds or stiffener-to-plate connections can develop stress concentrations.<\/p>\n

Under repeated loading, fatigue cracks may initiate and propagate.<\/p>\n

In particular, when thickness reduction changes structural stiffness and natural frequency, the vibration response may also change.<\/p>\n

If the natural frequency moves closer to the excitation range encountered during operation, vibration levels may increase and affect fatigue life.<\/p>\n

Structural weight reduction therefore needs to be considered together with weld design and dynamic loading conditions.<\/p>\n

Methods for identifying these conditions and taking measurements directly on the vehicle are covered in Part 3: Three technical limits when reducing thickness: Deflection, local buckling and fatigue<\/strong><\/a><\/span>.<\/p>\n

4. How does a 20% thickness reduction affect the structure?<\/span><\/h2>\n

A simple calculation illustrates why it is not sufficient to increase the steel grade and then reduce thickness.<\/p>\n

Consider a flat plate bending between two stiffeners. Assume that load, span and the other calculation conditions remain unchanged, then reduce the thickness by 20%.<\/p>\n

The new thickness is 80% of the original thickness.<\/p>\n\n\n\n\n\n\n\n
Parameter<\/th>\nRelationship with thickness in the model<\/th>\nResult after reducing thickness by 20%<\/th>\n<\/tr>\n<\/thead>\n
Bending stress<\/td>\nInversely proportional to thickness squared<\/td>\nIncreases by approximately 1.56 times<\/td>\n<\/tr>\n
Deflection<\/td>\nInversely proportional to thickness cubed<\/td>\nIncreases by approximately 1.95 times<\/td>\n<\/tr>\n
Critical buckling stress<\/td>\nProportional to thickness squared<\/td>\nReduced to approximately 0.64 times<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Calculation basis: a flat plate bending model in which load, span and corresponding geometrical and support conditions remain unchanged. These are mechanical relationships for the stated assumptions, not ratios that apply to every truck body structure.<\/p>\n

The table shows that the three effects change at different rates.<\/p>\n

First, stress increases by approximately 56%. Steel with a higher yield strength may be considered to meet the strength requirement.<\/p>\n

Second, deflection nearly doubles. Increasing yield strength does not directly increase the elastic stiffness of the steel plate when the geometry remains unchanged.<\/p>\n

Third, resistance to buckling decreases significantly. The plate may lose stability before the full stress capacity of the material is utilized.<\/p>\n

Thickness reduction therefore needs to be accompanied by structural recalculation.<\/p>\n

Higher yield strength expands the range of possible cross-sections. Structural geometry largely determines the ability to control deflection and stability.<\/p>\n

5. Structural compensation options when reducing thickness<\/span><\/h2>\n

Once the governing technical limit has been identified, the design team can consider changes to geometry or material.<\/p>\n\n\n\n\n\n\n\n\n
Option<\/th>\nMain effect<\/th>\nPoints to evaluate<\/th>\n<\/tr>\n<\/thead>\n
Change the cross-sectional geometry<\/td>\nCan improve resistance to deflection and stability while reducing the need for separate stiffeners<\/td>\nFormability, actual geometry and dynamic loading<\/td>\n<\/tr>\n
Add stiffeners<\/td>\nReduces the free span of the plate and can improve deflection and local stability<\/td>\nAdded mass and number of welds<\/td>\n<\/tr>\n
Increase thickness again<\/td>\nImproves stiffness and resistance to instability<\/td>\nReduces the weight-saving benefit<\/td>\n<\/tr>\n
Use a higher-yield-strength steel grade<\/td>\nIncreases the stress-carrying capability before permanent deformation occurs<\/td>\nDoes not automatically resolve deflection, buckling or fatigue<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

5.1. Changing the cross-sectional geometry<\/span><\/h3>\n

Instead of using a flat plate with multiple welded stiffeners, a U-shaped section or another suitable formed geometry can be considered to increase geometric stiffness.<\/p>\n

This approach can improve resistance to deflection without necessarily increasing the number of welds.<\/p>\n

Reducing welds in dynamically loaded regions may also reduce some stress concentration locations.<\/p>\n

However, any improvement in fatigue performance still needs to be evaluated according to the structural detail and actual loading conditions.<\/p>\n

5.2. Adding stiffeners<\/span><\/h3>\n

Stiffeners reduce the unsupported span of a plate and can therefore improve deflection and buckling resistance.<\/p>\n

The trade-off is additional mass and more welded locations.<\/p>\n

If stiffeners are positioned in dynamically loaded areas, weld design needs to be evaluated carefully to avoid unfavorable stress concentrations.<\/p>\n

5.3. Increasing thickness or changing the steel grade<\/span><\/h3>\n

Increasing thickness can improve plate performance but reduces the tare-weight benefit.<\/p>\n

Changing to a higher-strength steel grade can support the strength requirement, but it does not directly resolve all geometry-related limitations.<\/p>\n

The appropriate solution therefore needs to be selected according to the governing technical issue, not only according to the desired weight reduction.<\/p>\n

6. Bendability determines which sections can be fabricated<\/span><\/h2>\n

Changing the cross-sectional geometry is an important option in structural weight reduction. However, its feasibility also depends on the bending radius that the material and fabrication equipment can achieve.<\/p>\n

As the yield strength grade increases, bending-radius requirements may change significantly.<\/p>\n

6.1. Test bending radii for high-strength steel<\/span><\/h3>\n

Transverse 180\u00b0 bend-test data according to ISO 7438 in perform\u00ae product documentation shows differences between steel grades.<\/p>\n\n\n\n\n\n\n\n\n\n\n
Yield strength grade<\/th>\nBend radius under the declared test conditions<\/th>\n<\/tr>\n<\/thead>\n
300-315 MPa<\/td>\n0 times thickness<\/td>\n<\/tr>\n
340-420 MPa<\/td>\n0.5 times thickness<\/td>\n<\/tr>\n
460-500 MPa<\/td>\n1.0 times thickness<\/td>\n<\/tr>\n
550-600 MPa<\/td>\n1.5 times thickness<\/td>\n<\/tr>\n
650-700 MPa<\/td>\n2.0 times thickness<\/td>\n<\/tr>\n
900-960 MPa<\/td>\n8.0 times thickness<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

These values are bend-test results under the conditions stated in the manufacturer’s documentation. They should not be used directly as recommended fabrication radii for every processing condition.<\/p>\n

The table shows that increasing the steel grade may also introduce greater formability limitations.<\/p>\n

A steel grade with high yield strength but requiring a large bending radius may not be suitable for a design with deep ribs or narrow sections.<\/p>\n

6.2. Distinguishing bend-test results from fabrication recommendations<\/span><\/h3>\n

When material is introduced into the workshop, the correct fabrication guidance for the specific steel grade needs to be used.<\/p>\n

For example, the source documentation provides the following recommendations:<\/p>\n\n\n\n\n\n\n\n\n\n
Material<\/th>\nRecommended fabrication bending radius<\/th>\n<\/tr>\n<\/thead>\n
perform\u00ae 700, thickness \u2264 8 mm<\/td>\n1.2 times thickness<\/td>\n<\/tr>\n
perform\u00ae 700, thickness > 8 mm<\/td>\n1.6 times thickness<\/td>\n<\/tr>\n
XAR\u00ae 400<\/td>\n2.5-3.0 times thickness<\/td>\n<\/tr>\n
XAR\u00ae 450<\/td>\n4.0-4.5 times thickness<\/td>\n<\/tr>\n
XAR\u00ae 500<\/td>\n5.0-6.0 times thickness<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

These values are manufacturer fabrication recommendations under the corresponding conditions. The XAR\u00ae values are stated for bending perpendicular to the rolling direction. When bending parallel to the rolling direction, the source documentation requires the bending radius to be increased by approximately one plate thickness.<\/p>\n

The two tables serve different purposes.<\/p>\n

The first table presents bend-test results under specified test methods and conditions. The second provides guidance for actual fabrication.<\/p>\n

The values from these two tables should therefore not be compared directly unless compatibility has been established for test conditions, bending direction, thickness and steel grade.<\/p>\n

Another point to note is that for the perform\u00ae 650 and 700 grades referenced in the documentation, when thickness exceeds 8 mm, the minimum yield strength is reduced by 20 MPa, to 630 MPa and 680 MPa respectively.<\/p>\n

Structural calculations need to use the guaranteed level applicable to the actual thickness range.<\/p>\n

7. Zoning high-strength steel and wear-resistant steel on truck bodies<\/span><\/h2>\n

A specialized truck body may be exposed to two different groups of demands:<\/p>\n