The Structural Engineer's Corner

Eng. Onorio Francesco Salvatore

Hydrodynamic effects during earthquakes on dams and retaining walls: von Karman’s theory

Written By: Lexatus - Oct• 27•13

Von Karman for dams 2 - Onorio

In a previous post we went through the Westergaard’s theory for the analysis of gravity dams under seismic actions (“Hydrodynamic effects during earthquakes on dams and retaining wall: Westergaard’s theory“). In this post we’ll see the von Karman’s theory of the same subject.

Following the discussions on Westergaard’s theory, there were some proposals by different Authors on the same subject. Experts like von Karman, Bauman, Rowe, Pearce, Brahtz and Heilbron, Bakhmeteff, etc. agreed on the Westergaard’s solution. (more…)

Hydrodynamic effects during earthquakes on dams and retaining walls: Westergaard’s theory

Written By: Lexatus - Oct• 27•13

Westergaard for dams 14 - Onorio

During an earthquake, there are dynamic effects on dams and retaining walls that can be highly variable. They can go from no damages at all up to massive destruction.

One of the first studies on the evaluation of the hydrodynamic actions on a massive gravity dam during horizontal solicitations was given by H. M. Westergaard with his “Water pressures on dams during earthquakes“, Transactions of American Society of Civil Engineering, November 1993.

Westergaard studied a dam with vertical surface under horizontal seismic accelerations (normal to the surface), with sinusoidal law. The assumptions were: (more…)

Design for durability, part II – surface of members in interior environments

Written By: Lexatus - Oct• 19•13

Interior Concrete - Onorio

Following the previous post on durability (“Design for durability, part I – surface of members in contact with the ground“), in the following there are the requirements for surface of members in interior environments. (more…)

Design for durability, part I – surface of members in contact with the ground

Written By: Lexatus - Oct• 19•13

Concrete durability - Onorio

Similarly to European Codes, the Australian Standards specify the durability requirements according to the exposure classifications. In the following, the requirements for the surface of members in contact with the ground.

  • Members protected by a damp-proof membrane;
    • Exposure classification = A1;
    • Minimum concrete strength, f’c = 20 MPa;
    • Minimum initial curing = continuously for at least 3 days;
    • Minimum average compressive strength at the time of stripping of forms or removal from moulds = 15 MPa;
    • Required cover where standard formwork and compaction are used = 20 mm.
  • Residential footings in non-aggressive soils; (more…)

Acid-soluble chloride, sulfate, shrinkage strain and other characteristic attributes for Normal-class concrete

Written By: Lexatus - Oct• 19•13

Concrete cylinder - Onorio

In a previous post we have seen as the concrete in Australia is divided in Normal-class and Special-class. For the first one, the following are characteristic attributes:

  • Mass per unit volume in the range of 2100 kg/m³ to 2800 kg/m³;
  • Acid-soluble chloride shall not exceed:
    • 0.8 kg/m³ for exposure classifications A1 and A2;
    • the lesser of 0.8 kg/m³ or the customer’s specified limits for exposure classifications other than A1 and A2.
  • Acid-soluble sulfate shall not exceed 50 g/kg of cement;
  • Shrinkage strain (more…)

Strength grade of concrete in Australia

Written By: Lexatus - Oct• 19•13

Concrete strength - Onorio

The standard strength grade is basically the compressive strength capacity of the concrete. The standard grades in Australia, as per AS 1379 and AS 3600, are the following: (more…)

Class of concrete in Australia according to AS 3600 and AS 1379

Written By: Lexatus - Oct• 19•13

Concrete - Australia - Onorio

In Australia, two different types of concrete are specified and are:

– Normal-class;

– Special-class.

The Normal-class should have some attributes as defined in the AS 1379 and specified through some basic parameters. The parameters are:

– standard strength grade;

– slump at the point of acceptance;

– maximum nominal size of aggregate;

– method of placement;

– (if required) project assessment;

– (if required) level of air entrainment up to a maximum of 5%.

Concrete other than Normal-class shall be specified as (more…)

Strength of soils at Serviceability and Ultimate Limit States

Written By: Lexatus - Oct• 13•13

Soils type - ONORIO

In a previous post we discussed about the relations to use in order to evaluate the embedment depth of the utility services poles direct-planted. To whom could have missed it, the post is the following:

Embedment depth for utility services poles according to Australian Standard 4676

The relation discussed requires values for the foundation soil. The following can be used as a reference (more…)

Embedment depth for utility services poles according to Australian Standard 4676

Written By: Lexatus - Oct• 13•13

Embedment depth AS 4676 - ONORIO

When dealing with methods for proportioning footings and poles, an useful reference is the Australian Standard 4676, titled “Structural design requirements for utility services poles”.

For direct-planted poles, hence not on square pads, the Engineer can make some reasonable assumptions on the location of the centre of rotation of the footing and the vertical distribution of bearing stress in the foundation material.

In order to define the embedment depth ‘D’, the following assumptions are considered: (more…)

Coefficient of exposure for wind action – Difference between ISO 4354 and AS/NZS 1170.2

Written By: Lexatus - Oct• 01•13

Australia

The Australian Standards adopt in many parts recognized International Standards. For what regards the Wind Action the reference is the ISO 4354 “Wind action on structures”.

One of the differences between the AS/NZS 1170.2 and the ISO 4354 is the exposure factor Cexp. The Australian Standard decided to not adopt that factor because it has to be considered as dependent on wind direction and cannot be expressed as a single factor in a directional standard. Another difference regards how to apply the factors: (more…)