Tutorial

Heat of Hydration Analysis by Construction Stages

Heat of hydration analysis by construction stages

CONTENTS
Overview

Structural data for analysis model / 4

Material and thermal properties / 6
Analysis modeling

Setting work environment / 7

Defining material properties / 8
Defining time dependent material properties / 9
Linking general and time dependent material properties / 10
Structural modeling / 11
Division of element / 115
Defining Structure Groups / 119
Assigning elements to Structure Groups / 20
Defining Boundary Groups / 22
Defining Load Group / 26
26

Entering heat of hydration analysis data

Heat of Hydration Analysis Control / 26
Entering ambient temperature / 27
Entering convection coefficient / 28
Defining constant temperature condition / 32
Defining heat source functions / 33
Defining construction stages / 35
Structural analysis

38

Analysis results

38

Checking change in temperatures / 39

Checking change in stresses / 41
Checking time history graphs / 43
Checking results in animation / 47

Heat of hydration analysis by construction stages

Overview
The rate and amount of heat generation are important in concrete structures having
considerable mass.

A rise in temperature accompanies thermal expansion, and non-

uniform cooling of mass concrete creates undesirable stresses.

Thermal cracking in a

concrete structure tends to be wide and propagates through the structure. This naturally
has adverse effects on strength, durability and permeability.
structures are cast in many stages with construction joints.

Moreover, mass concrete

Individually constructed

segments exhibit different heat source properties and time dependent properties. Therefore,
construction stages must be incorporated in a heat of hydration analysis model to truly reflect
a real construction process.
Stresses due to heat of hydration are classified as Internal Constraining Stress and
External Constraining Stress.

The Internal Constraining Stress results in from the

restraining effect of volumetric changes due to different temperature distributions within the
concrete structure.

For instance, at the initial state of hydration, temperature differences

between the surface and inner parts result in surface tension. Whereas at a latter stage,
contracting deformations in the inner parts are greater than those at the surface, thereby
resulting in tension stresses in the inner parts. The magnitude of the Internal Constraining
Stress is proportional to the temperature difference between the surface and inner parts.
External Constraining Stress is caused by restraining the volumetric change of fresh
concrete in contact with subsoil or the substrate of previously cast concrete. The change in
concrete heat results in the change of volume, and the restraining effect is dependent on the
contact area and stiffness of the external constraining objects.
Heat of hydration analysis can be accomplished through Heat Transfer Analysis and
Thermal Stress Analysis.

Heat Transfer Analysis entails the process of calculating the

change of nodal temperatures with time due to heat source, convection, conduction, etc.,
which take place in the process of generating heat of hydration of cement. Thermal stress
analysis provides stress calculations for mass concrete at each stage based on the change
of nodal temperature distribution with time resulting from the heat transfer analysis. The
stress calculations also account for time and temperature dependent material property
changes, time dependent shrinkage, time and stress dependent creep, etc.
This tutorial demonstrates the process of construction stage analysis and analyzes the
results for a foundation structure constructed in two stages or pours.

The tutorial also

outlines the procedure of generating a construction stage model for heat of hydration
analysis and reviewing the analysis results:

Heat of hydration analysis by construction stages

Enter general material properties

Modulus of elasticity, Specific heat, Coefficient of

heat conductivity

Enter time dependent material

properties

Consider Creep & Shrinkage and change in modulus

of elasticity

Create a structural model

Create elements, define boundary conditions & input

loads

Heat of Hydration Analysis

Control

Define integration factor & initial temperature.

Input whether to consider Creep & Shrinkage and the
calculation method.
Select whether to use Equivalent Age and to
consider the self weight load.

Ambient Temperature Functions

Convection Coefficient Functions
Element Convection Boundary

After entering ambient temperature and convection

coefficient functions, use them to define convection
boundary conditions

Prescribed Temperature

Assign constant temperature conditions to the parts,

which do not undergo any temperature changes with
time

Heat Source Functions

Assign Heat Source

Enter heat source functions and assign them to the

corresponding elements

Pipe Cooling

Enter relevant data if pipe cooling is used.

Construction Stage

Define elements, boundary conditions and load

conditions corresponding to each construction stage.
Set initial temperature of elements being activated.

Perform analysis

Perform heat transfer analysis and thermal stress

analysis

Check analysis results

Analyze temperature distribution and variation of

thermal stresses with time

* Pipe cooling is not included in this tutorial for clarity in demonstrating the interaction of the two concrete
parts while analyzing the results of heat of hydration analysis.

Heat of hydration analysis by construction stages

Structural data for analysis model

This example represents a simple foundation structure often encountered in practice.

It

consists of subsoil mass and two parts of mass concrete cast in two stages as shown in
Figure 1. The 2nd pour takes place after 170 hours of casting the 1st pour. Heat of hydration
analysis is performed for the period of 930 hours after casting the 2nd concrete mass.
If the subsoil mass, that is interfaced with the concrete, is modeled as soil springs to
represent the boundary condition, the transfer of the concrete heat cannot be properly
represented.

Therefore, we will create a model which includes the foundation having

properties of specific heat and thermal conductivity, to closely represent the true behavior as
shown in Figure 1.
Subsoil mass

: 24 x 19.2 x 3 m

Mat foundation (1st pour)

: 14.4 x 9.6 x 2.4 m (170 hours)

Mat foundation (2nd pour)

: 14.4 x 9.6 x 2.4 m (930 hours)

Cement type

: Low-heat of hydration cement

2nd pour concrete

1st pour concrete

2.4 m

Subsoil mass
2.4 m

3m

9.6 m

14.4 m

19.2 m

24 m

Figure 1 Heat of hydration model for construction stages

Heat of hydration analysis by construction stages

In this tutorial, due to symmetry of the structure, we will model and analyze only one quarter of
the entire structure as shown in Figure 2. The use of symmetry not only reduces the analysis
time, it also provides convenience in checking the internal temperature and stress distribution.

9@0.8=7.2

4@0.6=2.4
4@0.6=2.4
5@0.6=3
6@0.8=4.8

12@0.8=9.6

15@0.8=12

Figure 2 Heat of hydration model for construction stages (1/4 symmetry model)

Heat of hydration analysis by construction stages

Material and thermal properties

The material and thermal properties are summarized in Table 1 below.
Table 1. Material and thermal properties

Part
Lower foundation

Upper Foundation

Subsoil

0.25

0.25

0.2

Density (kgf/m )

2400

2400

1800

Rate of heat conduction (kcal/m hr )

2.3

2.3

1.7

12

12

12

12

12

20

20

20

19

270

270

Property
Specific heat (kcal/kg )
3

Convection

Surface exposed

coefficient

to atmosphere

(kcal/m hr)

Steel form

Ambient temperature ()
Casting temperature ()
2

91-day compressive strength (kgf/cm )

a=13.9

Compressive strength gain coefficients

b=0.86

a=13.9

b=0.86

91-day modulus of elasticity (kgf/cm )

2.7734105

2. 7734105

1.0104

Thermal expansion coefficient

1.010-5

1.010-5

1.010-5

Poissons ratio

0.18

0.18

0.2

320

320

Unit cement content (kg/m )

K=33.97

Heat source function coefficients

a=0.605

K=33.97

a=0.605

This example uses low heat of hydration cement. The maximum adiabatic temperature rise
(K) and reactive velocity coefficient (a) are based on experimental values pertaining to the unit
cement content.

Heat of hydration analysis by construction stages

Analysis modeling
Setting work environment
Open a new file (

New Project) and

File /

New Project

File /

Save (Heat of Hydration)

Save it as Heat of Hydration.mcb.

Select a unit system, which is often used for thermal property data, namely m and kgf, as
shown in Figure 3.
Tools / Unit System

Length>m ; Force> kgf

Figure 3 Assigning a unit system

Heat of hydration analysis by construction stages

Defining material properties

Define the properties of mat foundation and subsoil.

Model / Properties /

Material

General>Material Number > 1 ;

Name>(Mat Foundation) ; Type>Concrete

Concrete>Standard> ASTM(RC) ; DB>C4000

Thermal Coefficient>Celsius (on)
Thermal Transfer>Specific Heat>(0.25) ; Heat Conduction>(2.3)
General>Material Number>2

; Name>(Subsoil) ; Type>User Defined

Modulus of Elasticity>(1.0e+8) ; Poissons Ratio>(0.2)

Thermal Coefficient>(1.0e-5)

; Weight Density>(1800)

Thermal Transfer>Specific Heat>(0.2)

; Heat Conduction>(1.7)

Figure 4 Defining material properties

Heat of hydration analysis by construction stages

Defining time dependent material properties

Define time dependent material properties to account for creep, shrinkage and change of
modulus of elasticity.
Model / Properties /

Time Dependent Material (Creep/Shrinkage)

Name>(Creep/shrinkage) ;

Code> ACI

Compressive strength of concrete at the age of 28 days>(2700000)

Relative Humidity of ambient environment (40~99)>(70)
Volume-surface ratio>(0.12)
Age of concrete at the beginning of shrinkage>(3)
Init Curing Method>moist cure

Refer to Using
MIDAS/Civil > Model
> Properties > Time
Dependent Material
(Elasticity) in the
On-line Manual.

Material factored ultimate value

Type>ACI Code ; Slump>(0.12) ; Fine aggregate percentage>(40)
Air content>(4) ; Cement content>(320)
Model / Properties /
Time Dependent Material (Comp. Strength)
Name>(Elasticity)

Type>Code

; Code>ACI

Concrete Compressive Strength at 28 Days (f28)>(2700000)

Concrete Compressive Strength Factor (a, b)>(13.9, 0.86)

Figure 5 Defining time dependent material properties

Heat of hydration analysis by construction stages

Linking general and time dependent material properties

It is now necessary to link the previously defined general and time dependent material
properties as per Figure 6.

Model / Properties /

Time Dependent Material Link

Time Dependent Material Type>Creep/Shrinkage>Creep/Shrinkage

Time Dependent Material Type>Elasticity>Elasticity
Select Material for Assign>Materials>1: Mat Foundation
Operation>

Even if Effective Modulus

is used to consider Creep,
select the Creep / Shrinkage
functions and link them to
general materials to assign
elements for which the
creep is to be calculated.

Figure 6 Linking general and time dependent material properties

10

Heat of hydration analysis by construction stages

Structural modeling
First, generate a plate element representing the base of the subsoil mass by creating a node
at a lower corner and extending it to the remaining corner nodes. This plate element is then
extruded into a solid using Extrude Elements.

Point Grid (off) ;

Point Grid Snap (off) ;

Line Grid Snap (off)

Node Number (Toggle on)

Top View
Auto Fitting
Model>Nodes>

Create Nodes

Coordinates (0,0,0)
Model>Elements>

(12,0,0)

(12,9.6,0)

(0,9.6,0)

Create Elements

Elements Type>Plate
Type>Thick (on)
Material>1 : Mat Foundation
Nodal Connectivity>(1, 2, 3, 4) 

Figure 7 Creating a plate element representing the base of subsoil mass

11

Heat of hydration analysis by construction stages

Using Extrude Elements, create a solid element.

Iso View
Model>Elements>

Extrude Elements

Select All
Extrude Type>Planar Elem. Solid Elem.
Source>Remove (on)
Element Type>Solid ; Material>1: Mat Foundation
General Type>Translate ; Number of Times = 1
Translation>Equal Distance (on) ; dx,dy,dz>(0, 0, 7.8)

Figure 8 Creating a solid element

12

Heat of hydration analysis by construction stages

Division of element
Next we divide the element using Divide Elements. The size of mesh depends on the total
configuration.

We should also pay attention to the parts, where we anticipate significant

changes in stresses, for fine meshing. The subsoil part does not need fine meshing, and
yet it needs to be meshed such a way that no significant change in stresses takes place
within an element. For the sake of simplicity, we will divide the element uniformly as shown
in Figure 9.
Model / Elements /

Divide Elements

Select All
Divide Elements>Element Type>Solid

; Equal Distance

Number of Divisions x: (15)

y: (12)

z: (13)

Hidden (Toggle on)

Node Number (Toggle off)
Display>Node tab>Node (off)

Figure 9 Division of solid element

13

Heat of hydration analysis by construction stages

Now that we created a mesh consisting of brick elements using Extrude Elements and
Divide Elements, we will now delete unnecessary elements from the overall model.

Front View
Shrink
Model>Elements>

Delete Elements

Select Window ( in Figure 10)

Type>Selection

; with Free Nodes (on)

Front View

Figure 10 Deleting elements

14

Heat of hydration analysis by construction stages

Now change the view point to

Left View, and delete the elements which do not belong

to the model.

Left View
Model>Elements>

Delete Elements

Select Window ( in Figure 11)

Type>Selection

; with Free Nodes (on)

Iso View

Left View

Figure 11 Deleting additional elements

15

Heat of hydration analysis by construction stages

When we created the 3-D solid element using Extrude Elements, we assigned it as a
concrete material. We will now revise the material to that corresponding to the soil material.

Change
Element
Parameters can be
also used to change
the
properties
of
elements.

Tree Menu>Works tab

Front View
Select Window ( in Figure 12)

Properties>Material>2: Subsoil (Drag & Drop)

Drag & Drop

Figure 12 Assigning subsoil material properties

16

Heat of hydration analysis by construction stages

Defining Structure Groups

In order to perform construction stage analysis, we need to define the element and boundary
condition groups that activated or deactivated at each construction stage. These groups
are then used to define the construction stages.
C

First, we create Structure Groups.

Group>Structure Group >New (by right-click on Structure Group)

Define Structure Group>Name>Subsoil
Define Structure Group>Name>Mat Foundation (Lower part)
Define Structure Group>Name>Mat Foundation (Upper part)

Figure 13 Creating Structure Groups

17

Heat of hydration analysis by construction stages

Assigning elements to Structure Groups

We now assign relevant elements to the Structure Groups created and, thus, define the
Structure Groups. First, we group the elements pertaining to the subsoil into the Subsoil
Structure Group.

Tree Menu>Group tab

Select Window ( in Figure 14)
Structure Group>Subsoil (Drag & Drop)

Drag & Drop

Figure 14 Defining the Structure Group Subsoil

18

Heat of hydration analysis by construction stages

Assign Structure Groups for the Mat Foundation, 1st poured lower part and the 2nd poured
upper part.

Tree Menu>Group tab

Select Window ( in Figure 15)
Structure Group>Mat Foundation (Lower Part) (Drag & Drop)
Select Window ( in Figure 15)
Structure Group>Mat Foundation (Upper Part) (Drag & Drop)

Drag & Drop

Drag & Drop

Figure 15 Defining Structure Groups for Mat Foundation (Lower & Upper Parts)

19

Heat of hydration analysis by construction stages

Defining Boundary Groups

We now create boundary groups as Figure 16.

Group>Boundary Group >New

Define Boundary Group>Name>CS1

Boundary Surface
group represents the
construction
joint
surface between the
1st and 2nd pours.

Define Boundary Group>Name> CS1-Boundary Surface

Define Boundary Group>Name> CS2

Figure 16 Creating Boundary Groups

20

Heat of hydration analysis by construction stages

Next, we enter the Subsoil boundary conditions for each group.

We will create a multi-window showing

Front View (in Model View) and

Left View

(in Model View : 1) for the ease of modeling.

Window / New Window
Left View

Point Grid (off)

Hidden
;

Shrink

Point Grid Snap (off) ;

Line Grid Snap (off)

Model View
Window / Tile Horizontally
Zoom Fit (Model View & Model View : 1)
Model / Boundary / Supports
Select Window ( in Figure 17)
Select Window ( in Figure 17)
Boundary Group Name>CS1
Options>Add

Solid elements do not

retain rotational degrees
of freedom. Therefore, we
need to restrain only
translational DOFs.

Support Type>D-All (on)

Figure 17 Defining Subsoil boundaries

21

Heat of hydration analysis by construction stages

Since it is a 1/4 symmetrical model, we need to specify the symmetric boundary condition.
First, we will enter the symmetry condition pertaining to the 1st pour.

Model / Boundary / Supports

Select Window ( in Figure 18)
Boundary Group Name>CS1

Options>Add

Support Type>Dx (on)

Select Window ( in Figure 18)
Boundary Group Name> CS1

Options>Add

Support Type>Dy (on)

Front View
X axis
symmetric condition

Left View
Y axis
symmetric condition

Figure 18 Entering symmetric boundary conditions

22

Heat of hydration analysis by construction stages

We continue on to specify the symmetric condition for the 2nd pour.

Model / Boundary / Supports

Select Window ( in Figure 19)
Boundary Group Name>CS2

Options>Add

Support Type>Dx (on)

Select Window ( in Figure 19)
Boundary Group Name> CS2

Options>Add

Support Type>Dy (on)

Front View

X axis
symmetric condition

Left View

Y axis
symmetric condition

Figure 19 Entering symmetric boundary conditions

23

Heat of hydration analysis by construction stages

Defining Load Group

Define Load Groups and Load Cases to include static load in the construction stages of heat
of hydration analysis. Static load cases entered in heat of hydration analysis must be input
as Construction Stage Load Type.
Model View>

Maximize

Group>Boundary Group >New

Define Boundary Group>Name>Self
Load>Static Load Cases
Name>Self
Type>Construction Stage Load (CS)

Figure 20 Definition of Load Group & Load Case

24

Heat of hydration analysis by construction stages

Heat of hydration analysis can consider static load cases for construction stage analysis.
First, self weight is assigned.
Load>Self Weight
Load Case Name>Self
Load Group Name>Self
Z : (-1)

Figure 21 Inputting self weight

25

Heat of hydration analysis by construction stages

Inputting heat of hydration analysis data

For assigning the

conditions for analysis,
refer
to
Heat
of
Hydration Analysis in
Analysis
for
Civil
Structures
and
the
Online manual Using
MIDAS/Civil > Analysis >
Hydration Heat Analysis
Control.

Heat of Hydration Analysis Control

Now that the analysis model is completed, we will enter the required data noted below (time

integration factor, initial temperature & stress output location) for heat transfer analysis.
Analysis / Heat of Hydration Analysis Control
Final Stage>Last Stage
Integration Factor>(0.5)
Initial Temperature>(20)

The Initial Temperature

can be superseded by the
values entered in the
Compose
Construction
Stage for Hydration dialog
box.

Element Stress Evaluation>Gauss

Creep & Shrinkage (on) ;

Type>Creep & Shrinkage

Creep Calculation Method>General

Number of Iterations=5 ; Tolerance=0.001

Use Equivalent Age by Time & Temperature (on)

If creep is to be
considered by reducing
the modulus of elasticity
without using general
creep functions, select
Effective Modulus.

If a general creep
function is to be used,
define the function and
select General.

Figure 22 Data entry for Heat of Hydration Analysis Control

26

Heat of hydration analysis by construction stages

Inputting ambient temperature

Ambient temperature is now entered as a function of time. This example assumes a
constant temperature of 20.
Load / Heat of Hydration Analysis Data / Ambient Temperature Functions
Function Name>(Ambient Temperature)
Function Type>Constant
Constant>Temperature>(20)

Select User type and

enter the Time and
Temperature variations,
if they are not constant.

If ambient temperature
varies
at
different
locations due to exposure
to the atmosphere, being
partly immersed in water,
etc., a number of Ambient
Temperature
Functions
can be defined and
applied.

Figure 23 Entering ambient temperature function

27

Heat of hydration analysis by construction stages

Inputting convection coefficient

Next we enter the convection coefficient as a function applicable at the concrete surface.

User type can be

used if the heat
exchange condition
between the concrete
surface
and
the
atmosphere
varies
with time due to the
change in curing
conditions.

Load / Heat of Hydration Analysis Data / Convection Coefficient Functions

Function Name>(Convection Coeff)
Function Type>Constant
Constant>Convection Coefficient>(12) ;

Figure 24 Entering convection coefficient function

28

Heat of hydration analysis by construction stages

Boundary Surface
group represents the
construction
joint
surface between the
1st and 2nd pours.

We now assign the previously defined ambient temperature and convection coefficient function
to the concrete surface, which is exposed to the atmosphere.

Depending on the construction

stages, the surface exposed to the atmosphere changes as well.

Accordingly, we assign the

corresponding ambient temperature and convection boundary conditions to the previously

defined CS1, CS1-Boundary Surface and CS2. First, we assign the ambient temperature
and convection coefficient to the concrete surface exposed to the atmosphere at the time of
1st pour. Since the concrete surface between the 1st and 2nd pours will not be exposed to the
atmosphere at the time of the 2nd pour, it is defined as another group.
Window / New Window
Window / Tile Horizontally
Load / Heat of Hydration Analysis Data / Element Convection Boundary
Select Window ( in Figure 25)
Select Window ( in Figure 25)
Boundary Group Name>CS1
Option>Add/Replace
Convection Boundary>Convection Coefficient Function>Convection Coeff
Ambient Temperature Function>Ambient Temperature
Selection>By Selected Nodes

Front View

Left View

Figure 25 Defining convection boundary at the 1st pour stage

29

Heat of hydration analysis by construction stages

We now define the convection boundary condition at the surface joining the 1st and 2nd pours.
Load / Heat of Hydration Analysis Data / Element Convection Boundary
Select Window ( in Figure 26)
Boundary Group Name>CS1-Boundary Surface
Option>Add/Replace
Convection Boundary>Convection Coefficient Function>Convection Coeff
Ambient Temperature Function>Ambient Temperature
Selection>By Selected Nodes

Front View

Left View

Figure 26

Defining convection boundary condition at the boundary surface

30

Heat of hydration analysis by construction stages

We now move on to define the convection boundary surface of the 2nd pour.
Load / Heat of Hydration Analysis Data / Element Convection Boundary
Select Window ( in Figure 27)
Boundary Group Name>CS2
Option>Add/Replace
Convection Boundary>Convection Coefficient Function>Convection Coeff
Ambient Temperature Function>Ambient Temperature
Selection>By Selected Nodes
Select Window ( in Figure 27)

Front View

Left View

Figure 27

Defining the convection boundary condition at the 2nd pour stage

31

Heat of hydration analysis by construction stages

Defining constant temperature condition

We enter a constant temperature condition for those parts where temperature remains
unchanged.

Assign a constant temperature to those surfaces, which have not been

assigned the symmetric boundary condition or the convection boundary condition (for
example, boundary surface in contact with the soil).
Load / Heat of Hydration Analysis Data / Prescribed Temperature
Select Window ( in Figure 28)
Select Window ( in Figure 28)
Boundary Group Name>CS1
Option>Add
Temperature> Temperature (20)

Front View

Left View

Figure 28 Inputting a constant temperature condition

32

Heat of hydration analysis by construction stages

Defining heat source functions

Heat source functions define the state of emitting heat in the process of hydration, which are
dependent on the type of cement and unit cement content.

For commonly used concrete

mix design, maximum adiabatic temperature rise and reactive velocity coefficient are
automatically calculated based on experimental equations and entered if the cement type,
casting temperature and unit cement content are specified.
Load / Heat of Hydration Analysis Data / Heat Source Functions
Function Name>(Heat Source Function)
Function Type>Code

This example assumes

that low hydration heat
cement is used, and
experimental values of K
& a are considered.

Function>Maximize adiabatic temp. rise (K)>(33.97)

Reactive velocity coefficient (a)>(0.605) ;

Function>Maximize adiabatic temp. rise (K)

Reactive velocity coefficient (a)

Refer
to
Heat
of
Hydration Analysis in the
Analysis Manual.

If experimental value for

the maximum adiabatic
temperature
rise
for
concrete is available, the
User Function Type can
be used.
The User
Function Type can be
inputted either by Heat
Source or by Temperature
method.

Figure 29 Defining heat source function

33

Heat of hydration analysis by construction stages

Assign the defined heat source function to the concrete.

Load / Heat of Hydration Analysis Data / Assign Heat Source
Select Window ( in Figure 30)
Option>Add/Replace
Heat Source>Heat Source Function

Figure 30 Assigning heat source function

34

Heat of hydration analysis by construction stages

Defining construction stages

Using the previously defined Structure Groups, Boundary Groups and Load Group, we will
now specify times for heat of hydration analysis and initial temperature.

We will first define

the construction stage CS1 for the stage of 1st concrete pour.
Load / Heat of Hydration Analysis Data / Define Construction Stage for Hydration
Stage> Add> Name>(CS1)
Initial Temperature>(20)

Times inputted in
Step are accumulative,
not incremental.

Step>Time(hr)>(10 20 30 50 80 120 170)

Element>Group List>Subsoil ; Mat Foundation (Lower part)

Activation>
Boundary>Group List>CS1 ; CS1-Boundary Surface
Activation>

Load>Group List>Self
Activation>

Figure 31 Defining the stage for 1st concrete pour

35

Heat of hydration analysis by construction stages

We then define the construction stage CS2 for the 2nd concrete pour. The duration for the
heat of hydration analysis will be 930 hours after the 2nd pour.
Load / Heat of Hydration Analysis Data / Define Construction Stage for Hydration
Stage>

Define the initial

temperature for the
elements
that
are
activated
at
the
corresponding stage.

Name>(CS2)
Initial Temperature>(19)

Step>Time(hr)>(10 20 30 50 80 120 170 300 400 500 600 750 930)

Element>Group List>Mat Foundation (Upper part)
Activation>
Boundary>Group List> CS2
Activation>
Boundary>Group List > CS1-Boundary Surface
Deactivation>

Figure 32 Defining element and boundary groups for the 2nd pour stage

36

Heat of hydration analysis by construction stages

From the Model View, we can check if the Construction Stages are properly defined.

User can either

select a stage on the
Stage Toolbar or use
the keyboard arrows
to toggle between
different stages while
the
Toolbar
is
activated.

Stage>CS1
Display
Misc tab

Element Convection Boundary of Heat of Hydration (on) ;

Prescribed Temperature of Heat of Hydration (on)

Heat Source for Heat of Hydration (on)

Figure 33 Checking the defined construction stages on the Model View

(Stage for the 1st concrete pour)

37

Heat of hydration analysis by construction stages

Structural analysis
We have thus far completed a construction stage model for heat of hydration analysis. We
can begin the analysis.
Analysis /

Perform Analysis

Analysis results
In this example, the major cause for thermal stresses is due to the temperature differences
within the concrete mass resulting in internal constraints. Recapping the overview, Internal
Constraints are caused by unequal volume changes. Initially, cooling surface and warm inner
parts cause tension at the surface and compression at the inner parts.

At a later stage,

after the rise in temperature due to heat of hydration reaches the peak level, the cooling
(contracting) inner parts relative to the surface cause tension in the inner parts and
compression at the surface.

The magnitude of the stresses is proportional to the

temperature differences between the inner parts and surface. It is also anticipated that the
two concrete masses of two separate pours of different ages will exhibit different heat
transfer characteristics.
We will analyze the characteristics of thermal stresses in concrete by reviewing the results of
heat of hydration analysis reflecting construction stages by graphics, tables, graphs,
animations, etc.

38

Heat of hydration analysis by construction stages

Checking change in temperatures

We will check temperature distribution at each step of the construction stages based on the
heat of hydration analysis.

Figure 34 shows the maximum temperature distribution at the

stage of the 1st concrete pour.

Rotate Dynamic (adjust the model view point so that the boundary planes of
symmetry can be seen as shown in Figure 34. Ctrl+Mouse wheel can be also used)
Result / Heat of Hydration Analysis / Temperature
Stage Toolbar>CS1
Step>HY Step 6, 120 Hr
Type of Display>Contour (on)

; Legend (on)

Figure 34 Temperature distribution (1st pour stage)

39

Heat of hydration analysis by construction stages

Next, we will check the temperature distribution at the construction stage 2. The fact that
the analysis accounted for construction stages, we note in Figure 35 that heat source action
progresses in the lower part of the mat foundation, which was already cast.
Stage Toolbar>CS2
Result / Heat of Hydration Analysis / Temperature
Step>HY Step 4, 220 Hr
Type of Display>Contour (on)

; Legend (on)

Figure 35 Temperature distribution (2nd pour stage)

40

Heat of hydration analysis by construction stages

Checking change in stresses

We will check the stress distribution of the 1st concrete pour. Figure 36 depicts the stress
distribution at which the maximum tension stress occurs on the surface. We will change the
unit system to kgf & cm to check stresses.

Status Bar> kgf ;

cm

Stage Toolbar>CS1
Result / Heat of Hydration Analysis / Stress
Step>HY Step 6, 120 Hr
Stress Option>Global ;

Avg.Nodal

Components>Sig-XX
Type of Display>Contour (on)

; Legend (on)

Status Bar

Figure 36 Stress distribution (1st pour stage)

41

Heat of hydration analysis by construction stages

We will check the stress distribution at the 2nd pour stage.

As shown in Figure 37, the

boundary surface of the first pour shows tension stresses at the early stage of the 2nd pour.
The tension stresses at the boundary surface are caused by the increase in volume due to
increased temperature in the 2nd pour. This exerts tension on the previously cast concrete.

Stage Toolbar>CS2
Result / Heat of Hydration Analysis / Stress
Step>HY Step 4, 220 Hr
Stress Option>Global ;

Avg.Nodal

Components>Sig-XX
Type of Display>Contour (on)

; Legend (on)

Figure 37 Stress distribution (2nd pour stage)

42

Heat of hydration analysis by construction stages

Checking time history graphs

We will check the graphical results of heat of hydration analysis at various construction
stages for specific points.
stresses are anticipated.

Generally, a user checks the parts where maximum tension

In this example, we will select a few points simply based on

convenience to sufficiently demonstrate the trend of the analysis results as shown in Figure
38. We will first assign the nodes for generating results.
1st pour concrete: Interior (1476), Surface (1988)
2nd pour concrete: Interior (2308), Surface (2818)
Result / Heat of Hydration Analysis / Graph
>Node Define>Node (1476) ; Stress Components> Sig-XX
>Node Define>Node (1988) ; Stress Components> Sig-XX
>Node Define>Node (2308) ; Stress Components> Sig-XX
>Node Define>Node (2818) ; Stress Components> Sig- XX

2818

1988
2308

1476

Figure 38 Defining nodes for generating graphs

43

Heat of hydration analysis by construction stages

The time history graph for an interior point (node: 1476) during the 1st pour is shown below.
Result / Heat of Hydration Analysis / Graph
Defined Nodes>N1476-X(on)
Graph Type> Stress + Alw. Stress Graph (on)

; Temperature Graph (on)

Crack Ratio Graph (on) Normal (on)

X-Axis Type>Time

1st Pour

Figure 39 Time history graph of stresses at an interior point of the 1st pour

44

Heat of hydration analysis by construction stages

Next, we will review the results of time history of a point (node: 1988) on the construction
joint surface between the 1st and 2nd pours.

We will also note that the expansion of the 2nd

pour due to temperature rise exerts tension on the 1st pour.

Result / Heat of Hydration Analysis / Graph
Defined Nodes>N1988-X (on)
Graph Type>Stress + Alw. Stress Graph (on)
Temperature Graph (on)
X-Axis Type>Time

1st Pour

Figure 40 Time history graph of stresses at a surface point of the 1st pour

45

Heat of hydration analysis by construction stages

We will finally check the temperature time history of the interior and surface points during the
1st pour.
Result / Hear of Hydration Analysis / Graph
Defined Nodes>N1476-X(on)

; N1988-X(on)

Graph Type> Temperature Graph (on)

X-Axis Type>Time

Interior (1476)

1st Pour

Surface (1988)

Figure 41 Temperature history graphs of interior and surface points of the 1st pour

46

Heat of hydration analysis by construction stages

Checking results in animation

Finally, we will review the change in temperature (or stress) by construction stages by
animation.
Result / Heat of Hydration Analysis / Temperature
Type of Display>Contour (on)

; Legend (on) ;

Animation Details>Animate Contour (on)

Animate

; Repeat Full Cycle

Construction Stage Option>Stage Animation>From>CS1 ; To>CS2

Record

Close
In order to save the animation in a file, click the

Save button while the animation is in

progress, upon which it is saved as an .avi file.

Close

Save

Record

Figure 42 Checking change in temperature by animation

47