ECHOLLOWSLAB - Precast Concrete Hollowcore Slab Design

This part of user manual describes how to use ECHOLLOWCORE for the design of Precast Concrete Hollow Core Slab. ECPlus applications are designed as wizard type which is a step by step guided input procedure. If you are new to ECPlus applications, click here for a general guidance.

Prerequisites: The user is expected to have a basic understanding of precast and prestressed concrete design.
The minimum input data required to use this application is as follows:

• ❶ Hollow Core Slab Geometry
• ❶ Concrete Grade
• ❷ Prestressing Details
• ❸ Loading Details

Following sections are presented with various input pages of ECHOLLOWSLAB application with descriptions:

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Design Options

This page allows to select the design standard and unit.

Design Standard

Select the National Standard for the design.
Available Standards: ☉British, ☉European and ☉American.

British and American Standards are not available in current version.

Unit

It displays the active unit. The unit   Change   button is displayed when ☉American Standard is selected.

British and European Standards can not be selected when Imperial unit is active.

Change

Click this button to open the unit change pop-up dialog.

☐  Reset all Input Data
This option will reset the input data for the new unit. This option is recommended if the job is new and no input data has been entered yet.

☐  Convert Dimensions and Properties
This option allows to convert all the previously entered input data except Load data to the new unit.

☐  Convert Loads
This option allows to convert previously entered load data to the new unit.

Note: Both Convert Dimensions and Properties and Convert Loads options can be used simultaneously to convert all the previously entered input values to the new unit.

Incorrect option leads to out of range errors and should be manually corrected.

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Geometry

This page allows the input of geometry details of hollowcore slab.

Effective Span - L_e

Enter the effective span of the hollow core slab (It is not the clear span).
↔ Range: 500 to 10000 mm

Bearing Width - L_b

Enter the bearing width of the support.
↔ Range: 50 to 5000 mm

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Slab Details

This page allows the input of cross sectional details of hollow core slab.

Bottom Width of Slab - b

Enter the bottom width of the slab.
↔ Range: 190 to 5000 mm

Width of Top Flange - b_tf

Enter the width of the top flange.
↔ Range: 180 to 5000 mm

Slab Depth - h

Enter the overall depth (thickness) of the slab.
↔ Range: 50 to 1000 mm

Top Flange Thickness - h_tf

Enter the top flange thickness of the slab.
↔ Range: 15 to 500 mm
Bottom Flange Thickness is required if section properties are to be calculated by program. It is available in Section Properties page for the 'Program' option.

Inner / End Rib Width - b_wi / b_we

Enter the inner / end rib width (between the hollow cores) of the slab.
↔ Range: 15 to 500 mm

Number of Cores

Enter the number of (hollow) cores.
↔ Range: 2 to 15
The diameter / size of the core is auto calculated by program based on the dimensions entered above.

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Section Properties

This page allows the selection of the options if the section properties are calcualted or entered by the user and the input of geometric properties of hollow core slab.

Select the section properties option.
☉Program, and ☉User Defined.

Area - A_c (For User Defined Option only)

Enter the net concrete area of the hollow core slab cross section.
↔ Range: 10,000 to 2,000,000 mm²

Height of neutral axis from bottom - h_NA (For User Defined Option only)

Enter the height of the neutral axis from bottom of the slab.
↔ Range: 10 to 1000 mm

First Moment of Area - S_c (For User Defined Option only)

Enter the first moment of area for the area above the neutral axis.
↔ Range: 1,000,000 to 100,000,000 mm³

Moment of Inertia - I_c (For User Defined Option only)

Enter the moment of inertia about the neutral axis.
↔ Range: 10,000,000 to 100,000,000,000 mm⁴

Bottom Flange Thickness - h_bf (For Program Option only)

Enter the bottom flange thickness of the slab. This is to calculate the geometrical properties of the section for 'Program' option.
↔ Range: 15 to 500 mm

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Strand Details

This page allows the input of strand details.

Nominal Diameter - dia

Select the nominal diameter of the strand from the drop down. This nominal diameter drop down values will vary based on Strand Type in Prestressing Details popup.

Number of Strands - No

Enter the number of strands.
↔ Range: 1 to 20

Max Nos at Web - MNo

Enter the max number of strands placed in a web. (See the picture for example)
↔ Range: 1 to 20

Cover to Center of Strand - c_s

Enter the cover to the CG of all strands from bottom.
↔ Range: 10 to 200 mm

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Loads and Factors

This page allows the input of the loads and factors.

Loads

Live Load - F_live

Enter the live load acting over the hollowcore slab.
↔ Range: 0 to 300 kN/m²

Partitions - F_part

Enter the load due to partition walls acting over the holloecore slab.
↔ Range: 0 to 300 kN/m²

Finishes - F_fin

Enter the loads due to floor finishes.
↔ Range: 0 to 300 kN/m²

Load Factors

Partial Factor for Permanent Loads - γ_G

Enter the partial load factor for permanent loads.
↔ Range: 0.1 to 20

Partial Factor for Variable Loads - γ_Q

Enter the partial laod factor for variable loads.
↔ Range: 0.1 to 20

Quasi-Permanent Variable Load Factor - Ψ

Enter the quasi - permanent variable load factor.
↔ Range: 0 to 10

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Design Setting

Setting for various Design Data such as Concrete, Prestressing Details, Tendon Details, Deflection Limits and Relative Humidity are presented in this section. This setting pop-up can be accessed by clicking the bottom panel below the left navigation.

National Annex

Select the National Annex after selecting the European Standard in Design Option.

Nation

Select the National Annex option for the relevant factors to be considered in the design.

Reinforced Concrete Properties (BS EN 1992-1-1)

Enter the reinforcement concrete properties on selection of European Standard from Design Option.

Density of Concrete - γ_conc

Enter the dry density of the concrete.
↔ Range: 10 to 40 kN/m³

Compressive Cylinder Strength - f_ck

Enter the characteristic compressive cylinder strength of the concrete.
↔ Range: 10 to 150 N/mm²

Maximum Aggregate Size - h_agg

Enter the maximum size of aggregate.
↔ Range: 5 to 60

Aggregate Type - Type
Choose the type of aggregate from the drop down.
▽ Basalt: Select this option to choose Basalt as type of aggregate.
▽ Limestone: Select this option to choose Limestone as type of aggregate.
▽ Quartzite: Select this option to choose Quartzite as type of aggregate.
▽ Sandstone: Select this option to choose Sandstone as type of aggregate.

Cement Strength Class - Class
Select the class of cement strength.
▽ N: Select this option to choose N as cement strength class.
▽ R: Select this option to choose R as cement strength class.
▽ S: Select this option to choose S as cement strength class.

Tendon Details

Enter the tendon details such as its type, class and bond condition.

Strand Type

Select the type (grade) of the tendon (Strand or Wire)
▽ British, European and American
Select the grade from the respective standard from the dropdown list.

Strand Class

Select the strand class
▽ 1, 2 and 3 Select the class from the list.

Bond Condition

Select the Bond Condition
▽ Good, Fair/Poor Select the bond condition of the strand with concrete.

Modulus of Elasticity E_p

Select the modulus of elasticity of the prestressing strand.
↔ Range: 100 to 300 kN/mm²

Characteristic Strain at Maximum Load ε_uk

Select the characteristic strain at maximum load. (Enter zero for default value)
↔ Range: 0 to 0.05
This value is defined in certain National Annexes. If the national annex defines this value, the user input is ignored.

Tendon Release

Enter the details such as tendon release, installation and loading time.

Release Type - R

Select the type of tendon release.
▽ Gradual: Select this option to use gradual tendon release.
▽ Sudden: Select this option to use sudden tendon release.

Installation Time - Inst.

Select the time for slab installation.
▽ 15 days: Select this option to use 15 days as tendon installation time.
▽ 1 month: Select this option to use 1 month as tendon installation time.
▽ 2 months: Select this option to use 2 months as tendon installation time.
▽ 3 months: Select this option to use 3 months as tendon installation time.
▽ 6 months: Select this option to use 6 months as tendon installation time.
▽ 1 year: Select this option to use 1 year as tendon installation time.
▽ 3 years: Select this option to use 3 years as tendon installation time.

Loading Time - Loading

Select the time for loading (into service time).
▽ 2 months: Select this option to use 2 months as loading time.
▽ 3 months: Select this option to use 3 months as loading time.
▽ 6 months: Select this option to use 6 months as loading time.
▽ 1 year: Select this option to use 1 year as loading time.
▽ 3 years: Select this option to use 3 years as loading time.
▽ 10 years: Select this option to use 10 years as loading time.
▽ Infinity: Select this option to use infinity loading time.

Tendon Release - t₀

Enter the tendon release time in hours.
↔ Range: 5 to 1000 hours

Deflection Limits

This popup allows to enter the deflection limits for Initial camber, deflection after installation and Long term deflection.

Initial Camber at Time of Storing

Select / Enter the initial camber ratio (Span/camber) at the time of storing.
↔ Range: 5 to 2500

Deflection after Installation

Select / Enter the limit of deflection ratio (Span/deflection) after installation.
↔ Range: 5 to 2500

Long Term Deflection

Select / Enter the long term deflection ratio (Span/deflection) due to quasi permanent loads.
↔ Range: 5 to 2500

Relative Humidity

This popup allows to enter the relative humidity details.

Perimeter in Contact with Atmosphere

Select the face(s) that is(are) in contact with the atmosphere from the drop down.
▽ Bottom Face Only: Select this option if bottom face alone is in contact with the atmosphere.
▽ Top and Bottom Face: Select this option if both top and bottom faces are in contact with the atmosphere.

Relative Humidity at Release - R_Hr

Enter the relative humidity at realese.
↔ Range: 10 to 100 %

Ambient Relative Humidity - R_Ha

Enter the ambient relative humidity.
↔ Range: 10 to 100 %

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Error Handling

Errors and Warnings are generated to prevent any inadvertent error and ensure data integrity in the input. This section describes how to handle the errors and warnings. These errors are displayed at the bottom of the input page when the data in one or more input fields invalidate each other. Calculation can not be run if there is any error in the input data. While the calculation can proceed with warnings, the user must take a note of it and make necessary correction.