The Structural Engineer's Corner

Eng. Onorio Francesco Salvatore

Sizes of reinforcing bars – Nominal size vs. Maximum size

Written By: Lexatus - Oct• 13•14

Reinforcing bars

When designing and detailing the reinforcement in a concrete structure, the dimensions referred to for bars and wires are based on “nominal sizes“.

The word nominal size is used in place of diameter, referring in this way to diameter of a circle with an area equal to the effective cross-sectional area of bar or wire.

For example, for a 16 bar, because of surface deformations, there are no cross dimensions measuring 16 mm. Usually, the deformed bar can be contained in a circumscribing circle 10% (with peak values of 13 or 14%) larger than the nominal size of bar.

Preferred sizes of high yield reinforcing bars are 8, 10, 12, 16, 20, 25, 32 and 40 mm. Additional sizes, not preferred, are 6 and 50. The reason for these last to being not preferred regards the availability of the material by fabricators.

The following list below provides a comparison between the nominal size and the maximum size (in red are shown the non-preferred sizes): (more…)

How to model the piping loads on the transverse beam of pipe racks

Written By: Lexatus - Sep• 28•14

Pipe rack 6 - Onorio Francesco Salvatore

As seen in previous posts, a pipe rack is composed by transverse beam required to support the longitudinal piping. The piping arrangement can be very different from one project to another and specific Engineering judgment is required. The main problem discussed in this post is how to model the loads applied to the transverse beam.

Let’s discuss some different cases that a Structural Engineer could need to deal with:

Case 1: rack full of same size pipes equally spaced;

Case 2: rack full of different size pipes;

Case 3: rack full of small pipes except one or two large pipes;

Case 4: rack almost empty, very few pipes.

As appear obvious, a standard approach is not feasible for all the four cases listed above. Let’s see then how to manage these loading conditions. (more…)

Structural design of steel pipe racks

Written By: Lexatus - Sep• 28•14

Pipe rack - Onorio Francesco Salvatore

Pipe racks are structures used in the petrochemical, chemical and power plants industries. They are meant to support pipes, power cables and instrument cable trays. Sometimes, pipe racks support mechanical equipment, vessels and valve access platforms. Basically, they are a connection between equipment and storage or utility areas.

The main structural components of the pipe rack superstructure are:

transverse beams (supports for piping, etc.);


longitudinal struts;

vertical bracing.

When designing pipe racks, the Structural Engineer shall (more…)

Dead loads according to the Process Industry Practices (PIP)

Written By: Lexatus - Sep• 28•14

Dead loads - Onorio Francesco Salvatore

In this post we are going to discuss about the loads defined in the Process Industry Practices (PIP). The PIP is a self-funded consortium of process industry companies that publishes common industry practices for projects and maintenance work. PIP develops “Practices” that are a compilation of Engineering standards from different Engineering disciplines.

According to PIP, but the definition is common in every standard, dead loads are the actual weight of materials forming the building, structure, foundation and all permanently attached appurtenances.

Fixed process equipment machinery, piping, valves, electrical cable tray, including their contents, are considered as dead loads.

In PIP STC01015 – Structural Design Criteria, PIP adopts a specific nomenclature for the various types of loads: Ds, Df, De, Do and Dt.

They are defined as: (more…)

Exposure conditions for concrete according to British Standard 8110

Written By: Lexatus - Sep• 17•14

Exposure conditions

Similarly to other international standards, the British Standard 8110-1 defines different exposure conditions based on the design environment.

The environment can be:

– Mild;
– Moderate;
– Severe;
– Very severe;
– Most severe;
– Abrasive.


The mild environment is defined as:
Concrete surfaces protected against weather or aggressive conditions

The moderate environment is defined as: (more…)

[DOWNLOAD] Excel spreadsheet for evaluation of crack width according to Eurocode 2

Written By: Lexatus - Nov• 23•13

Crack width 6 - Onorio

Another addition for the Downloads section. In this post we’ll discuss about an Excel spreadsheet for the evaluation of the crack width in concrete structures.

The inputs required are:

Characteristic compressive cylinder strength fck 30 N/mm²
Characteristic tensile strength of reinforcement fyk 500 N/mm²
Base b 300 mm
Height h 500 mm
QP moment M 100.0 kNm
Age at cracking 14 days
Cement type N [-]
Creep factor j 2.0 [-]
Area of tension steel As 600 mm²
Area of compression steel As2 314 mm²
Bar diameter Øeq 12 mm
Maxmum tension bar spacing S 200 mm
Short term or Long term? Long [-]
Cover to As c 25 mm
Depth for tension bars d 469 mm
Depth for compression bars d2 31 mm

The first output is related to the evaluation of the cracking moment. The software checks firstly if the section is cracked: (more…)

[DOWNLOAD] Annual Probability of Exceedance for structures in New Zealand according to AS-NZS 1170

Written By: Lexatus - Nov• 17•13

Return Period 4 - Onorio

In this post an Excel spreadsheet based on the AS/NZS 1170 is available. Scope of the tool is to define the Annual Probability of Exceedance, P (and, hence, Average Recurrence Level, R), for Ultimate State Limit and Serviceability Limit States. The values are referred to New Zealand, as per Section 3, Table 3.3.

The Annual Probability of Exceedance is the probability that a given event over a given duration will be exceeded in any one year; it is the inverse of the Return Period, also know as Recurrence Interval.

The Return Period/Recurrence Interval is (more…)

[DOWNLOAD] Torsional section properties for concrete sections according to ACI 314

Written By: Lexatus - Nov• 16•13

Torsional properties 7 - Onorio

In this post, an Excel spreadsheet for the evaluation of the torsional section properties of concrete sections according to the ACI 318 is available. The sections are:

– rectangular near the edge;

– rectangular in interior position;

– L-shaped;

– inverted tee.

The design for torsion as per ACI 318 is based on a thin-walled tube, space truss analogy. A beam subjected to torsion is idealized as a thin-walled tube with the core concrete cross section in a solid beam neglected as shown below: (more…)

[DOWNLOAD] Moment of Inertia of the cracked section transformed to concrete for T-sections according to ACI 314

Written By: Lexatus - Nov• 16•13

Cracked section 14 - Onorio

Following the Excel spreadsheet for the rectangular section, in the following you can download the spreadsheet for the evaluation of the Moment of Inertia of the cracked section transformed to concrete, Icr, for T-sections. The reference is the ACI 314R-11 “Guide to Simplified Design for Reinforced Concrete Buildings“.

Basically, starting from the gross section: (more…)

[DOWNLOAD] Moment of Inertia of the cracked section transformed to concrete for rectangular sections according to ACI 314

Written By: Lexatus - Nov• 16•13

Cracked section 7 - Onorio

New addition for the Download section: the following Excel spread sheet calculates the Moment of Inertia of the cracked section transformed to concrete, Icr, for rectangular sections. The reference is the ACI 314R-11Guide to Simplified Design for Reinforced Concrete Buildings“.

Basically, starting from the gross section: (more…)