Bridge Seismic Analysis Seismic Field_Bridge Category_Knowledge Structure Type_Bridge Design Code_AASHTO
Field_Bridge Category_Knowledge Category_How-to Structure Type_Bridge Design Code_Eurocode Design Code_CSA Design Code_AASHTO
Pushover is a nonlinear static procedure that incrementally applies lateral loads to a bridge model, typically until a target displacement is reached or the structure reaches global instability. The analysis is instrumental in identifying inelastic behavior, hinge formation, redistribution of internal forces, and the progression of failure mechanisms.
3 Comments Click here to read/write comments
Eurocode Bridge Tips & Tutorials MOTIVE Tool Field_Bridge Category_Knowledge Category_Industry Structure Type_Bridge Design Code_Eurocode Design Code_AASHTO Design Code_ACI
🕖 Surviving in times of change
I felt one thing while working as a structural engineer who designs concrete bridges(RC/PSC) according to various countries' design standards: A profound understanding of ACI318(AASHTO) and EN2 is essential to successfully working on bridge projects. Most countries' standards are developed based on those standards. (Of course, it is my personal opinion.) Personally, I believe that my design career was successful because I recognized these facts.
Reviewing the ACI318 and EN once is not enough because design standards change over time. Revision is an indispensable process, and I expect two things before the new edition is released.
First, to be precise, the existing vague parts; the other is simplifying the calculating equations to apply the practical design process. Fundamentally, those are relevant problems. Complexity usually brings unclear parts.
Unfortunately, the newly updated 2G:Eurocode 2 did not meet these expectations. Standards are more convoluted than before, and this has indeed led to an increase in unclear areas.
Now, the moment has come to prepare for the future.
⚙️ Introduction to Our New Tool
Now, let's talk about tools.
The primary function of this tool is to easily output stress-strain curve graphs, which are strength characteristics of concrete, and graphs of time-dependent characteristics such as creep and drying shrinkage.
Notably, by providing the existing EN1992-1-1 and the new 2G:EN1992-1-1 together, the user can compare those results and experience the calculating processes. I believe it would be a handy tool to validate that new standards align with user understanding before implementing them in practice.
❓How to use it?
🔢 Input values
1. Select Graph
- Concrete Properties (Stress-strain diagrams)
- Time-Dependent Behavior
2. Select Standard Code
- 2G:EN 1992-1-1
- EN 1992-1-1
3. Put values
4. Click the calculation button
📈 Review a result
1. Select Graph type
- A. Concrete Properties
- Non-linear
- Parabola rectangle
- Bi-linear (Not include 2G:EN 1992-1-1)
- B. Time-Dependent Behavior
- Creep coefficient
- Shrinkage strain
- Elastic modulus
- Mean compressive strength
- Mean tensile strength
2. View a result as a table
3. Check additional information
4. Graph tool (save, zoom in and out, move, restore)
😜 Conclusion
The 2nd Generation Eurocode is continually being released and is targeted to start use in 2028. In line with this, MIDAS provides tools to compare the modifications between the 1st and 2nd generations. This work will only be possible with the support of ongoing research and constant user interest. We ask for your interest and anticipation for the upcoming tools.
Are you curious about this tool?
Click the link below to access MIDAS Tools for free.
0 Comments Click here to read/write comments
5 Comments Click here to read/write comments
1 Comment Click here to read/write comments
MIDAS CIVIL Tips & Tutorials Temperature Gradient Thermodynamics Self-Equilibrating Field_Bridge Category_How-to Category_Industry Structure Type_Bridge Design Code_Eurocode Design Code_BS Design Code_AASHTO
1. Why do bridge engineers consider Non-linear Temperature Gradients?
Temperature loads threaten bridge safety, especially for long-span bridges. If the bridge is located with a big temperature difference, A structural engineer analyzes and designs a bridge based on the beam theory. The temperature gradient should be considered with the beam theory. The beam theory assumes the beam deforms primarily in one direction, the material behaves linearly elastic, and the beam has a uniform cross-section. It means even if the beam cross-section gets a different thermal expansion depending on the depth, the cross-section does not change, and it is also possible to substitute thermal stress as a self-equilibrating stress in restraint conditions.
0 Comments Click here to read/write comments
Bridge Insight Grillage Models Curved Bridges Field_Bridge Category_Knowledge Structure Type_Bridge Design Code_AASHTO
A. Introduction
Designing a curved bridge was a challenge for me in every aspect. The tendon profile in MIDAS Civil, which we covered before, it’s a very well-known issue,
11 Comments Click here to read/write comments
Bridge Insight AASHTO LRFD AASHTO Standards AASHTO Classification Field_Bridge Category_Knowledge Structure Type_Bridge Design Code_AASHTO
1. Why do we need design codes?
Numerous impressive structures were created before the formulation of standardized design codes, but challenges existed. The shift to modern design codes introduced a systematic and scientific approach to bridge engineering, enhancing safety, consistency, and reliability in design and construction. Design codes also play an important role in protecting bridge engineers by providing a framework for legal compliance, standardization, risk mitigation, and professional accountability.
4 Comments Click here to read/write comments
Bridge Insight Temperature Gradient Non-Linear Elements Field_Bridge Category_Knowledge Structure Type_Bridge Design Code_Eurocode Design Code_BS Design Code_AASHTO
📢 To check the entire series, click here
- Non-linear Temperature Gradient Part 1. AASHTO LRFD
- Non-linear Temperature Gradient Part 2. BS Code & Eurocode
- Non-linear Temperature Gradient Part 3. Effects on Beams
- Non-linear Temperature Gradient Part 4. Effects on Bridges
4. Nonlinear Temperature Effects on PSC Box Section
The above example is difficult to consider in terms of practical use. Therefore, to make a calculation that can be applied to an arbitrary cross-section, we will go over one-by-one through the formulas and calculations that are needed.
(1) Section Information
The example cross-section is a PSC box shape as shown below, and the input of the cross-section is in the form of consecutive coordinates. When using the calculation program, the input should be in a general coordinate system, but for the convenience of the calculation in the example, the following coordinate system is used where the upper right corner is the origin (0,0) and the lower left direction is positive.
Figure 1. Example of a PSC box cross-section
(2) Section Property
Sectional properties are calculated using Green's theorem from the input coordinate data. The required section properties for the calculation are the area, second moment of area, and distance from the section's top edge to its centroid.
Figure 2. Cross-Sectional Properties
(3) Differential Temperature Load
AASHTO LRFD Heating case - Zone 3 is considered.
Figure 3. Differential Temperature load
(4) Section Coordinates and Temperature Gradient Load
To ensure the accuracy of the calculation, the change point of the temperature gradient load must be included. Therefore, the change point of the temperature gradient load was added to the cross-sectional coordinates, and the temperature gradient load was applied to each node.
Figure 4. Temperature gradient load at Each node
(5) Restraint force
The restraint force can be calculated using the equation derived in section 3, but since the temperature and width vary linearly on the z-axis and y-axis, respectively, we can write linear equations in terms of z for temperature (t) and y for width (b) and substitute them into the equation. Therefore, the equation can be expressed as follows:
Figure 5. Equation of a straight line based on changes in width and temperature
Figure 6. The formula for calculating restraint force
Now, if we apply the formula for calculating restraint force that has been determined to each straight line and calculate it, we can obtain the following restraint force.
Figure 7. Restraint force
(6) Residual Stress
Using the calculated acceleration and temperature gradient load, the residual stress at each node is determined as follows.
Figure 8. The equation for Residual Stress
Figure 9. Residual Stress
(7) Calculation and Verification
This is an Excel spreadsheet designed using VBA based on the formulas introduced above. It allows users to input the loads examined in Part 1/Part 2, calculates the residual stress accordingly, and generates a graph.
Figure 10. Sample Calculation
Now, let's verify the created spreadsheet. First, we will use the same cross-section as in the example, and the loads are defined as follows, and the results are shown in the spreadsheet accordingly.
Figure 11. Calculation example for verification 1
Figure 12. Calculation example for verification 2
Figure 13. Calculation example for verification 3
The verification was performed using MIDAS CIVIL. The four simple spans with the same cross-section are created as shown in below the example and analysis is performed by applying the loads according to each design standard.
Figure 14. MIDAS CIVIL model for verification
The results are as follows.
Figure 15. Top Stress - MIDAS CIVIL
Figure 16. Bottom Stress - MIDAS CIVIL
As expected, the results show a 99% match with the values obtained from the spreadsheet.
Figure 17. Values obtained from the spreadsheet
(8) Conclusion
We have examined the effect of temperature gradient loads on beams according to each design standard. Hopefully, this has provided a basic understanding of temperature gradient loads.
We can take this one step further by using these results to calculate axial strain and bending moment, which can then be converted into equivalent linear temperature loads. By doing so, we can predict the impact of temperature gradient loads in indeterminate structures.
In design, temperature loads are often included in most load combinations, and if the design is done within the range that does not allow tensile stress, the impact of temperature loads can be significant and cannot be ignored. I hope that the following article will be helpful in design.
#Temperature Gradient #Non-linear Temperature #Temperature Gradient #Temperature difference # Design Calculation #BS EN # AASHTO LRFD #BS 5400 #NCHRP #DMRB #CS 454
GOODNO, Barry J.; GERE, James M. Mechanics of materials. Cengage learning, 2020.HAMBLY, Edmund C. Bridge deck behaviour. CRC Press, 1991.
Would you like to use the Excel Spreadsheet in the content?
Submit the form below right away, and receive the file for calculating temperature gradient loads.
(Note! This spreadsheet requires access to the MIDAS CIVIL API for utilization.
If you have any inquiries regarding the CIVIL API, please feel free to leave a comment.)
3 Comments Click here to read/write comments
Eurocode Bridge Insight Temperature Gradient BS Code AASHTO Classification Field_Bridge Category_Knowledge Structure Type_Bridge Design Code_Eurocode Design Code_BS Design Code_AASHTO
📢 To check the entire series, click here
- Non-linear Temperature Gradient Part 1. AASHTO LRFD
- Non-linear Temperature Gradient Part 2. BS Code & Eurocode
- Non-linear Temperature Gradient Part 3. Effects on Beams
- Non-linear Temperature Gradient Part 4. Effects on Bridges
Nonlinear Temperature Effects on Beams
(1) Basic Concept
Through Part 1 & 2, we looked at how the temperature gradient load of a bridge is calculated based on the design criteria. Now, let's examine how the calculated load affects the bridge deck.
7 Comments Click here to read/write comments
Bridge Insight AASHTO LRFD Temperature Gradient Field_Bridge Category_Knowledge Structure Type_Bridge Design Code_AASHTO
📢 To check the entire series, click here
- Non-linear Temperature Gradient Part 1. AASHTO LRFD
- Non-linear Temperature Gradient Part 2. BS Code & Eurocode
- Non-linear Temperature Gradient Part 3. Effects on Beams
- Non-linear Temperature Gradient Part 4. Effects on Bridges
Temperature gradient load is one of the loads that is generally used in the design of the superstructure of a bridge. For designing a bridge superstructure, you will likely need to consider the effects of temperature gradient load.
Many structural analysis programs, including MIDAS Civil, allow for the input of temperature gradient loads and can relatively accurately calculate their effects. However, as one becomes more familiar with using structural analysis programs, it is easy to overlook the impact of these loads on the structure and why certain results are obtained.
AASHTO LRFD (American Association of State Highway and Transportation Officials Load and Resistance Factor Design) and BS EN (British Standards European Norms) are two major design standards used for bridge design. Let's take a closer look at how temperature gradient loads are calculated in these design standards.
1. AASHTO LRFD - Bridge Design Specifications (2020)
(1) Temperature Gradient
AASHTO LRFD's temperature gradient load is described in section 3.12.3 "Temperature Gradient," and it has remained unchanged from the 1998 2nd edition to the most recent 2020 9th edition. The same calculation method has been used consistently in all editions, without any significant changes.
AASHTO LRFD - Temperature Gradient
The temperature gradient load in AASHTO LRFD is relatively simple in its calculation method, making it easy to apply and consider for the design.
Now let's take a brief look at how AASHTO LRFD calculates its temperature gradient load.
According to the commentary of AASHTO LRFD, the loads applied to concrete bridges are based on NCHRP Report 276.
NCHRP report 276 - Figure A-3 Positive vertical temperature gradient within superstructure concrete
NCHRP report 276 - Figure A-5 Negative vertical temperature gradient within superstructure concrete
Loads are classified according to pavement conditions. Plain/Unpaved, 2 in. Blacktop, or 4 in. Blacktop.
In the case of positive loads, the current AASHTO LRFD load size and load distribution are similar, but for negative loads, there is a significant difference.
The changes in these differences can be seen in "Design of segmental bridges for thermal gradient, KW Shushkewich, PCI journal, 1998". The figure below compares the temperature gradient load for each standard in the case of a plain concrete surface with a height of 8ft, Zone 3.
- AASHTO Segemtnal Guide Specification (AASHTO 89)
- AASHTO LRFD Bridge Design Specifications (AASHTO 94)
- AASHTO proposed segmental Guide Specifications (AASHTO 98)
Design of segmental bridge for thermal gradient - fig 2. Comparison of thermal gradients
As seen in the figure, AASHTO 89 directly cites NCHRP Report 276.
AASHTO 94 has since changed to a form that is similar to the current one, but for Negative values, it still uses -0.5 times the value for Positive values.
AASHTO 98 is currently the most similar to the current form, using Negative values as -0.3 times Positive values. According to this article, the results have been validated for the AASHTO 98 standards.
For steel bridges, the pattern of the Australian bridge specifications was used, and AS 5100.2 states that the temperature after passing through the slab is applied directly to the entire steel girder. AASHTO LRFD also uses the same concept.
AS 5100.2 Figure 18.3 Design effective vertical temperature gradients
(2) Calculation of Temperature Gradient - AASHTO LRFD
The Excel Spreadsheet is created for calculating AASHTO LRFD temperature gradient loads as follows.
Calculation Example - AASHTO LRFD
Would you like to use the mentioned Excel Spreadsheet in the content?
Submit the form below right away, and receive the file
for calculating AASHTO LRFD temperature gradient loads.
(Note! This spreadsheet requires access to the MIDAS CIVIL API for utilization.
If you have any inquiries regarding the CIVIL API, please feel free to leave a comment.)
4 Comments Click here to read/write comments
MIDAS CIVIL Bridge Design Civil Engineering Field_Bridge Category_Knowledge Structure Type_Bridge Design Code_AASHTO
This part checks the stability of the abutment with a spread footing. The stability review will follow the "AASHTO LRFD section 11 - Abutments, Piers and Walls". The Service Limit State and Strength Limit State will be reviewed following details below.
24 Comments Click here to read/write comments
4 Comments Click here to read/write comments
Structural Design Post-tensioned Slab Prestressing Steel Loading Conditions Member Forces Post-Tensioning Structure Type_Building Field_Bridge Category_Knowledge Category_How-to Structure Type_Bridge Design Code_AASHTO
Post-Tension Slab Analysis & Design
18 Comments Click here to read/write comments
7 Comments Click here to read/write comments
Bridge Analysis MIDAS CIVIL Eigenvalue Analysis Dynamic Analysis Seismic Analysis Blast Analysis Impact Analysis Field_Bridge Category_Knowledge Structure Type_Bridge Design Code_Eurocode Design Code_AASHTO
Interpretation of Dynamic Eigenvalue Analysis in Bridges
15 Comments Click here to read/write comments
MIDAS CIVIL Bridge Design Bridge Insight Moving Load Optimization Traffic Loads Traffic Lane Moving Load Case Field_Bridge Category_Knowledge Category_How-to Structure Type_Bridge Design Code_Eurocode Design Code_BS Design Code_AASHTO
Please fill out the Download Section (Click here) below the Comment Section to download the Model Files!
5 Comments Click here to read/write comments
MIDAS CIVIL Bridge Design Prestressed Concrete Bridge Insight Structural Design Bridge Construction Prestressed Concrete Bridges Elongation of Tendons Elongation Tolerance Postensioned Concrete Structural Assesment Elongation of Cables Estimated Elongation Field_Bridge Category_Knowledge Structure Type_Bridge Design Code_AASHTO Design Code_ACI
Elongations of Prestressing Steels
When we build prestressed concrete structural members, which is a frequently used material for bridges worldwide, the benefit in material savings and reduction of dimensions is guaranteed only when it is built correctly. Structures behave the way they are built, and not the way they are designed, so it is imperative that the designer and reviewer engineers provide the necessary information so that the construction process is oriented towards a structure that meets all safety requirements.
Figure.1 Bridge span and length
In this article, we present, in a concise way, the reasons why the elongations of prestressing steels in bridges should be controlled, and in the end, we provide a comparison of a real case in contrast to what is obtained from numerical modeling. Also, you can download a spreadsheet template (Click here) for the manual calculations of the friction loss and elongations that you can use to compare with the reliable results of midas Civil.
6 Comments Click here to read/write comments
MIDAS CIVIL Bridge Insight AASHTO LRFD Bridge Span Field_Bridge Category_Knowledge Structure Type_Bridge Design Code_AASHTO
🗂️ Download Now
Please fill out the Download Section (Click here) below the Comment Section to download the Complete Guide to Composite Sections
8 Comments Click here to read/write comments
MIDAS CIVIL Project Tutorial Live Load Limit State Design Composite Section Field_Bridge Category_Knowledge Category_How-to Structure Type_Bridge Design Code_AASHTO
Bridge Rating in Midas
Table of Contents
2 Comments Click here to read/write comments
Bridge Insight Strut-and-Tie Model STM Nodal Zone Extended Nodal Zone Subdivision Nodal Zone Truss Model Truss Analogy 45-Degree Truss Model Variable Angle Truss Components of Strut-and-Tie Model Struts Tension Ties Field_Bridge Category_Knowledge Structure Type_Bridge Design Code_Eurocode Design Code_AASHTO Design Code_ACI
Please fill out the Download Section (Click here) below the Comment Section to download the 3D Strut-and-Tie Model for 4 Piles Cap Calculator
Strut-and-Tie Model
Contents
68 Comments Click here to read/write comments