Delle Chiaie Larocca Engineering s - LUSAS · Software Description Viale Donato Bramante n. 41 - 05100 - Terni - Tel 0744 390250 - [email protected]

Software Description

Viale Donato Bramante n. 41 - 05100 - Terni - Tel 0744 390250 www.lusas.it - [email protected]

2

GENERAL DESCRIPTION

Ponti EC4 is a standalone software program carrying out comprehensive calculations for multiple

sections on steel-concrete composite bridge decks according to the procedures proposed by the

Eurocodes. EN1994 on composite sections makes reference to many other parts of the Eurocode

suite, making design calculations time-consuming and error-prone without use of Ponti EC4.

Ponti EC4 software, developed in Visual Basic dot Net language and fully integrated in Windows,

provides ULS, SLS and Fatigue Limit State assessments for many composite sections at the same

time.

Input of geometric data is managed in "segments", several sections with the same basic data can be

assigned to the same segment, a tree structure of segments and sections offers an easy access to

data.

Material properties are defined in a window dialog with libraries and wizards, that guide the user in

the choose of main data.

Forces and moments are organized in construction stages, and are input in a spreadsheet style, an

input interface via Excel is also available. For each design combination 4 sets of forces and

moments should be input, in which respectively are minimized and maximized the bending and

shear effects.

Primary effects of shrinkage and thermal variation are automatically calculated by the software.

The results of processing data of Ponti EC4 are directly available in dialog windows, and a MS

Word report is produced including all input and output data in tabular and graphic format, as well as

code of practice references.

3

MATERIALS

The form "Materials" is for the input of all the mechanical parameters of concrete slab, of steel

beams, of reinforcing bars and of shear connectors.

The input data is organized in the following areas:

- Concrete slab

- Environment

- Concrete Age

- Modular ratios

- Impressed strain in the slab

- Steel

- Shear connection

- Fatigue: damage equivalent factors

4

User is supported with dialog windows including code of practice reference in the choose of many

input data.

Window dialog for the calculation of equivalent damage factor 3, v,3

The impressed shrinkage deformation and the creep coefficients for the calculation of long-term

concrete properties are calculated automatically. The primary (isostatic) effects of shrinkage and of

thermal variation are calculated by the software.

5

GEOMETRY

The form "Geometry" is dedicated to the input of all geometric data related to a specific beam

segment; also it allows to introduce some mechanical parameters or the safety coefficients whose

value could change from segment to segment.

The input data is organized in the following areas:

Segment name (and sections)

Structural steel

Slab concrete

Reinforcing bars of slab

Vertical stiffeners

Longitudinal stiffeners

Fatigue

Shear Connection

The input of geometric data is managed in "segments", each of which can contain any number of

sections, sharing all geometric data; it can also be possible to manage segments with variable height

(steel sections characterized by different heights).

The sections are organized in a tree structure for a better access to data.

6

It is also available a table in the menu "Utilities> Table X-beff slab" for the calculation of the

effective width of the slab to be inserted in the text box "bcls" of the area "Slab Concrete”, (each

sections of composite beam can have different effective width).

The data relative to the fatigue verification of details are introduced in a specific window that is

possible to open clicking on the button “Detail categories data”.

7

FORCES AND MOMENTS

Forces and moments can be introduced directly in input tables, or importing all values from a Excel

model file, copy/paste from spreadsheet is also available.

Each design combination requires the input of 4 sets of forces and moments, in which respectively

are minimized and maximized the bending and shearing effects.

Forces and moments are organized in construction phases too.

Forces and moments required, for each section, are:

N Normal action in N

V Vertical shear in N

M Bending moment in vertical plane in N*m

T Torsional moment in N*m

The design envelopes considered are:

ULS Fundamental Fundamental combination of ultimate limit state. EN 1990 6.4.3.2 (3)

SLS Characteristic Characteristic combination of service limit state. EN 1990 6.5.3 (2a)

SLS Frequent Frequent combination of service limit state. EN 1990 6.5.3 (2b)

FLS Fatigue limit state combination. EN 1992-1-1 6.8.3

The maximized/minimized forces and moments in design envelopes are:

M max Bending moment max

M min Bending moment min

V max Shear max

V min Shear min

8

The phases considered are:

Phase 1 Self weight

Phase 2a Permanent loadings

Phase 2b Shrinkage

Phase 2c Impressed deformations and/or stresses

Phase 3a Thermal variation

Phase 3b Traffic

The forces and moments has to be input already multiplied by safety coefficients () and

coefficients of combination ().

In the following picture a scheme of the organization of input of forces and moments is reported.

9

RESULTS

The results of Ponti EC4 are directly available in the dialog window “Results” made by a fixed

upper part and by a second multi-page part. At the top part, on the left the user can select the section

and the design combination, and on the right forces and moments in the various phases, primary

effects of shrinkage and of thermal variation and additional moments determined by the variation of

position of neutral axis are displayed. In the bottom multi-page part it is possible to choose the

group of results to be analyzed, organized as in the following list.

- Plastic verification

- Stresses

- Shear

- Geometrical properties

- Diagrams Mpl-N

- Connectors. ULS, SLS

- SLS Web Breathing

- FATIGUE 1

- FATIGUE 2

10

Following checks are performed:

Calculation of geometrical properties of sections and of coefficients of shrinkage and creep

(EN 1992-1-1, Appendix B)

Classification of sections (EN 1993-1-1,Tab. 5.2)

Plastic bending check of sections in class 1 and 2 (EN 1993-1-1, 6.2.5)

Stress check of sections in class 3, and of sections in class 4 with effective geometric

properties (EN 1993-1-5, par. 4)

Plastic shear and Shear buckling check (EN 1993-1-5, par. 5)

Interaction bending-shear (EN 1993-1-5, par. 7)

Calculation and graphic representation of domains of interactions M-N, both considering

and ignoring the web contribution.

Elastic calculations for stresses check at SLS (EN 1994-2, 7.2.2 (5) and EN1993-2, 7.3)

Web-breathing check at SLS (EN1993-2, 7.4)

Fatigue check of steel components details and of reinforcing bars of slab.

Cracking check of the slab (EN 1994-2, 7.4.2)

ULS, SLS and Fatigue limit state check of connectors (EN 1994-2, 6.6 and 6.8)

All results are available in detail on screen in the dialog window "results".

At any time the user can go back to the input windows (Geometry, Materials, Forces and moments)

and change any data, then results are updated opening again the window "Results".

It is also possible to analyze all the results in synthetic way in the dialog window "Summary

Results" and set up an automatic report, in the window "Report".

11

PLASTIC VERIFICATION

In the page “Plastic verification” of window “Results” is reported the classification of the section

according to EN 1994-2, 5.5.1.

The classification is made at the end of phase 3 in function of forces and moments Ned and Med

total; if you tick the option “Consider the top flange always in class 1” top flange will be assumed

in class 1, independently from its thickness and its stressing state.

The classification of section is made in phase 1 too: in this case, without slab, the top flange is

classified regularly in function of its stressing state and its thickness; The option “Consider the top

flange always in class 1” is ignored.

For the sections in class 1 and 2, a green writing indicate that plastic verification is applicable,

whereas for sections in class 3 and 4 a red writing indicate that plastic verification is not possible. In

both cases it is reported in tabular form:

- plastic normal action Npl,Rd

- plastic moment Mpl,Rd, calculated without normal force

- plastic moment Mpl,Rd, calculated with normal force NEd

The calculation of resistant values is executed according to EN 1994-2, 6.2.1.2, then the coefficients

used to the verification at normal force, simple bending moment and combined compressive and

bending action (NM interaction) are reported.

On the same page is also reported a graphic representation of the section, the position of the neutral

axis and the plastic and elastic stress diagrams.

12

STRESSES

In the page “Stresses” of window “Results” are reported the elastic stresses in 9 characteristic

fibres, numbered from 0 to 8.

For each constructive phase, referring to geometric properties of the examined phase, the

calculation is reported according to the followings:

- Concrete NOT CRACKED (N.C.)

- Concrete CRACKED (C.)

At the end of phase 2 and 3 stresses are reported in all fibers, in both hypotheses with

CRACKED/UNCRACKED concrete and the correct solution is chosen according to the stress

values of the concrete.

Coefficient of utilization eta1 is given in correspondence to ULS design combinations. Equivalent

Von Mises stresses and the corresponding coefficient of utilization c.u. are calculated for

characteristic and frequent SLS combinations,. The check of the limit state of stresses is executed

according to EN 1994-2, 7.2.2 (5), which refers to EN 1993-2, 7.3.

For the combination of fatigue SL are reported the stresses as for the limit state of stresses, and in

addition are reported the variations of normal and tangential stress at the end of phase 3. The control

of concrete state is made each time separately for the two combinations analyzed; for example for

the combination of max moment it is:

Not cyclic Loads (M max) + Cyclic Loads (M max) => (M max), (M max) (1)

Not cyclic Loads (M max) + Cyclic Loads (M min) => (M min), (M min) (2)

= (M max) - (M min), = (M max) - (M min)

Class 4 sections

The normal stresses in the sections in class 4 are calculated using the method of the effective

section, defined according to EN 1994-2, 6.2.1.5 (1), which refers to EN 1993-1-5, 4.3, 4.4, 4.5 (and

Annex A.1, A.2).

13

The approach based on the reduction of transversal section is divided into the following steps:

a) Determination of the distribution of normal stresses on the gross section

b) Reduction of flanges in class 4

c) Calculation of the distribution of normal stresses on effective section

d) From this distribution, determination of the section with reduced web

e) Determination of normal stresses on the effective section calculated at the step d)

f) Comparison between distribution of stresses at the step c) and those at the step e): if these are

very different (it is defined an limit of error and a max number of iterations in “Utilities>Options”)

steps d) and e) are repeated.

The calculation of the section with reduced web (step d) is executed according to the following

scheme:

The normal stresses are calculated on the effective section on the basis of effective properties

determined in this way.

14

SHEAR

It is calculated the plastic shear, the resistance to Shear Buckling (eventual) and the shear-bending

moment interaction.

- Plastic shear Vpl,Rd

The calculation is executed according to EN 1993-1-1, 6.2.6.

- Resistance Shear Buckling Vb,Rd

At first, the necessity to verify or not verify the shear buckling according to EN 1993-1-5, 5.1 is

considered. A red message indicates if the section has to be verified to shear buckling too.

The shear buckling check is executed according to EN 1993-1-5, 5.2 e 5.4.

- Shear check

If check to shear buckling is necessary:

),min( ,, RdplRdb

Ed

VV

V 1.0

If check to shear buckling is not necessary:

Rdpl

Ed

V

V

,

1.0

- Bending moment-Shear Interaction

The interaction between bending moment and shear is checked according to EN 1993-1-5, 7.1.

15

GEOMETRIC PROPERTIES

The geometric properties are organized in two pages of the dialogue window “Results”; in the first

page “Geometric properties 1” the following groups of data are included:

- Local buckling of web panels

The reduced dimensions are determined to consider the local buckling of web subpanels according

to EN 1993-1-5, 4.4.

- Compressed part, without ribs

In tabular form are reported the areas of compressed web parts.

- Compressed part, without ribs, depurated for local buckling

16

In tabular form are reported the areas of compressed web parts, reduced to consider the local

buckling of web subpanels.

- Global behaviour with longitudinal stiffeners

In tabular form are reported the critical stresses calculated at the stiffeners and then extrapolated to

the compressed edge, according to the plate (p) and column (c) behaviour.

- Coefficients of reduction for global buckling

The coefficients of global reduction are reported according to plate and column behaviour.

In the second page “Geometric properties 2” the following groups of data are included:

- Compressed part, depurated for global and local buckling

The final coefficient of reduction c which considers the interaction between plate and column

behaviour is reported, then Ac,eff.

- Global reduction to apply to the section

The quantities of area to subtract from whole sections are reported.

- Geometric gross/effective properties

In tabular form are reported all geometric gross or effective properties used in the calculation.

17

DIAGRAMS Mpl-N

The software calculates the diagrams of interaction Moment-Axial Force action according to the

following assumptions:

- The tensile concrete is ignored

- The Areas of reinforcing bars are schematized as rectangles of equivalent thickness, that

As = slab base x equivalent thickness

Two calculations are executed: complete section and section without web. In the graphic

representation is drawn the domain MRd-N and the point of current Moment-Axial Force

MEd/NEd.

18

CONNECTORS ULS, SLS

The resistance of connectors is calculated according to EN 1994-2, 6.6.3.1 in which two different

mechanisms of failure are supposed: shear of connector and crushing of concrete (elastic

verification).

If there is a yielded zone in the span it is not correct to calculate the connectors with the elastic

theory, so plastic calculation of connectors is executed in this yielded zone.

SLS WEB BREATHING

The verification is executed according to EN 1994-2, 7.2.3, which refers to EN 1993-2, 7.4.

19

FATIGUE 1, FATIGUE 2

In these two pages the fatigue verifications are executed. In the page FATIGUE 1 the fatigue checks

of connectors and of reinforcing bars are displayed in two different output areas.

In the page FATIGUE 2 the fatigue verifications relative to steel beam details are displayed.

20

SUMMARY OF RESULTS AND GRAPHS

In the dialog window “Summary of results” there is a summary of all coefficients of utilization

calculated in the performed checks. The coefficients are organized in a grid with section checked

and design combination (in rows) and with type of check (in columns).

It is possible to copy and to paste the contents of tables from Word or Excel, simply by clicking on

them with the right mouse button, after the selection of the whole table or only of a part of it.

Through “Graphs” menu, available in “Utilities”, it is possible to graph the main coefficients of

utilization versus the abscissa of sections.

These graphs are particularly useful in the check of many sections along a beam: of course it is

important to insert carefully the X abscissa of each section in the “Segment name” of window

“Geometry”.

21

REPORT

In this dialog window it is possible to produce, in Word format, a selective report of the checks and

of the calculations performed.

As many files will be created as the sections for which at least an output option have been ticked.

Each report can be easily supplied with an index directly in Word, in fact all titles of paragraphs of

report are formatted with styles properly organized.

Example of table created in the report: pre-classification of elements of steel section:

Pre-Classification of elements of section

Classification Flanges Classification web

c/t

M+

classe

M-

classe

c/t alfa Psi (*) class

M+ 224.5 1.005 -0.611 1

Top 19.8 1 1 M- 224.5 0 -0.08 1

Bottom 18.167 4 1

N- 224.5 1 1 1

Epsabf = 1 Epsatf = 1 Epsaw = 1 (*) calculated in Phase 3

22

CRACKING

In this dialog window the results of cracking checks are reported.

The check of the required minimum reinforcement area is executed according to EN 1994-2 7.4.2.

Where:

z0 = distance between the uncracked slab concrete centroid and the neutral axis of the uncracked

cross-section (Phase 3, n0 short-term loading)

23

The control of cracking under indirect loadings is performed as shown in the following flow-chart:

The control of cracking under direct loadings is performed as shown in the following flow-chart: