Thermal Stress Analysis of Continuous Rigid Frame Bridges Using Finite Element Methods

Introduction

Continuous rigid frame bridges play a vital role in modern transportation networks, especially in long-span highway infrastructure. However, these structures are highly sensitive to environmental temperature variations, which can generate thermal stresses capable of reducing structural durability and service life. Recent civil engineering research has focused on understanding how temperature gradients influence stress distribution within prestressed concrete box girder bridges. This article presents a clear and accessible summary of a finite element–based ACEE study that evaluates thermal stress behavior at both global and structural detail levels. For more peer-reviewed civil and environmental engineering research, visit https://www.civilenvironjournal.com/index.php/acee/home.

Why Thermal Stress Is Critical in Bridge Design

Concrete box girder bridges are continuously exposed to:

• Solar radiation
• Daily and seasonal temperature fluctuations
• Differences between internal and external temperatures

Because concrete has relatively low thermal conductivity and tensile strength, uneven temperature distribution can create internal stresses that lead to cracking and long-term deterioration.

Common consequences of unaccounted thermal stress

• Surface and internal cracking
• Reduced load-bearing capacity
• Accelerated material degradation
• Increased maintenance requirements

Study Methodology and Numerical Modeling

The ACEE study investigated a prestressed concrete continuous rigid frame bridge using advanced finite element analysis (FEA) techniques.

Key methodological features

• Whole-bridge thermal stress analysis using beam elements
• Detailed zero-block modeling with refined solid elements
• Temperature gradients defined according to Chinese bridge design specifications
• Evaluation of multiple improved temperature gradient scenarios

A detailed analysis can be found in our main journal article, where the modeling approach and simulation assumptions are explained in depth.

Major Findings of the ACEE Study

Global Bridge Temperature Effects

• Temperature rise produced compressive stress in upper sections and tensile stress in lower sections
• Temperature drop reversed this stress pattern
• Thermal stress magnitude showed a linear relationship with temperature gradient amplitude

Zero Block Stress Characteristics

• Maximum thermal stress occurred near the surface of the box girder roof
• Stress values decreased rapidly with increasing depth
• Transverse thermal stress was higher between diaphragm plates due to redundant structural constraints

Impact of Temperature Gradient Improvemen

Reducing the temperature gradient significantly lowered thermal stress levels:

• Central zero-block stress decreased by approximately 60%
• End zero-block stress decreased by around 75%
• Stress reduction was most pronounced within the top 20 cm of the roof slab

These results demonstrate that temperature gradient control is an effective strategy for improving bridge durability.

Engineering Safety and Infrastructure Standards

From an infrastructure safety perspective, organizations such as the American Society of Civil Engineers (ASCE) emphasize the importance of accounting for thermal loads in long-span bridge design to minimize cracking and improve service performance. Similarly, the Federal Highway Administration (FHWA) highlights temperature effects as a key factor in structural evaluation and lifecycle management of highway bridges.

Readers interested in related civil and environmental engineering studies can naturally explore additional categories and articles at https://www.civilenvironjournal.com/index.php/acee/about-acee.

Access to the Original Research

The complete ACEE research article, including finite element models, stress distribution figures, and detailed conclusions, is available at:
👉 Read the full study at https://doi.org/10.29328/journal.acee.1001002

Conclusion

This ACEE study confirms that thermal stress is a dominant factor influencing the structural behavior of continuous rigid frame bridges. Finite element simulations reveal that thermal stresses are primarily concentrated near surface regions and can be substantially reduced by improving temperature gradient conditions. These findings provide valuable guidance for bridge designers and engineers seeking to enhance structural safety, durability, and long-term performance.

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