What do Structural Engineers do? Do Structural Engineers report to a city? What is the cost of hiring Structural Engineers? A lot has been asked about Structural Engineers and this article takes a close look at the roles, pay, and cost of hiring a Structural Engineer. To begin with, let’s take a close look at who is a Structural Engineer.
Who are Structural Engineers?
Structural Engineers are mostly concerned with the stability of a structure. The Architects design the structures while considering the aesthetics and unique aspects of the design. Structural Engineers, on the other hand, receive the Architectural blueprints from the Architects and Draughtsman/women and analyze, design, plan, and research the structural components and structural systems to ensure the stability of the structure and safe use.
This will in most cases include calculating the bearing capacity of the soil and designing the structural components of the structure to safely transmit the dead and live loads of the structure to the bearing soil. They then come up with the correct concrete mix ratios, correct reinforcement bars diameters, correct bar bending schedules, correct spacing of the reinforcement bars, correct concrete covers, and so on and so forth to ensure the structure remains standing irrespective of even wind loads which are also considered in the design.
Yes. A Structural Engineer can come up with an Architectural drawing and still manage to design and produce the Structural drawings, especially on smaller projects. This is because they are trained in Building Technology and Drawing as a unit too. The Builders, who are Diploma holders, are also considered “Jack of All Trades”. This is because they cover Soil Mechanics, Building Technology and Drawing, Survey, Measurements and Costing, Structural Mechanics, Mathematics, and Construction Management as units in their course of study.
As JOAT, they can also be Structural and Architectural Drafters and at the same time junior Quantity Surveyors. However, while they can produce the aforementioned blueprints and bills of quantities, they must submit them to registered Structural Engineers, Architects, and Quantity surveyors. This is so they can be approved and stamped before they are approved by the relevant local authorities and bodies.
What are the roles of Structural Engineers?
Structural Engineers are concerned with the stability of the structures designed by the Architects. They analyze the Architectural drawings, design the structural stability of the structure, and then produce the structural drawings. As a Structural Engineer, your work is to ensure buildings and other structures don’t deflect, rotate, vibrate excessively or collapse throughout their use.
Structural Engineers design:
1. The reinforced concrete design
The Structural Engineer uses the Code of Practice CP 114 (1948) to design the reinforced concrete in buildings. The method of design used should accord with the laws of mechanics and the general principles relating to the design of reinforced concrete. There are two methods of concrete design used; the Elastic Method and the Load Factor Method.
In the structural concrete design, the structural engineers consider the following aspects:
- Calculation of the resistance of structural members to shear and compression.
- Calculation of maximum bending moments.
- Permissible loads and stresses in members.
- Stiffness of members.
- Reinforced concrete wall designs.
- Fire resistance design of reinforced concrete.
- Chemical resistance of reinforced concrete.
- Distribution of loads on stairs and stair design.
2. The Structural steel design
When designing the steel framework, the structural engineer considers the following:
- The materials such as the structural steel, electrodes, and other materials and the standard dimensions.
- The dead loads, imposed loads, dynamic loads, and temperature range.
- Design and details of construction of steel framework.
- Resistance to horizontal forces.
- Foundations, the minimum thickness of metal, and stresses due to wind forces.
- Combined stresses, deflection of beams, the overhang of walls, sectional areas, and separators and diaphragms.
- Design of members subject to bending. This involves analyzing the bending stresses (beams other than plate girders), bending stresses (plate girders), bending stresses (cased beams), bearing stress, and shear stress. The effective span of beams, maximum slenderness ratio of compression flanges, the effective length of compression flanges for beams and girders, beams with solid webs including plate girders, web stiffness, and filler joists.
Other considerations in steel design
3. The timber design
Structural Engineers also design timber to ensure the safety and comfort use of the structure.
The following drawings consist of the structural engineer’s blueprints:
Roof trusses structural drawings
Structural Engineers begin structural analysis from the roof structure going down to the beams, the slabs, the columns, all the way to the bases. On the roof design, they consider the different types of roof trusses based on the span and size of the structure, the dead loads, live loads, and wind loads. The roof structural drawings are an important part of a construction project because a poor design will lead to structural failure irrespective of how aesthetically appealing the building is. This is why the Architects have to involve the Structural Engineers in their designs.
This drawing includes the roof trusses, braced frames in steel design, purlins, connections, lug angles, steel castings, side, and end sheeting rails, etc.
Structural beams drawings
They analyze the total loads acting on the structures such as dead loads (weights of the beams), live loads (weights of the users), and wind loads. While doing the analysis, they consider bending moments, and shear failure, among other failures, and provide a factor of safety in their designs.
Structural columns drawings
Columns are an integral part of any structure including bridges, buildings, skyscrapers, etc. This is because columns receive the dead, live, and wind loads from the roofs, slabs, and beams, and transfer this total weight to the soil through the bases. The Structural Engineers take their time to analyze these loads and come up with the structural column drawings.
Structural bases drawings
The base design involves calculations that consider failures such as shear, compression, and punching at the base. The drawings normally indicate the required bar diameters of the top and bottom reinforcement members, with designed spacing, bending, cover, and concrete mix ratio.
Retaining walls drawings
Design consideration involves ensuring safety on different types of failures such as bearing on the ground, rotation at the heel, sliding at the base, and lateral thrust, among others. The drawing consists of the reinforcement bars approved diameters and spacing.
Structural slabs drawings
Slabs are designed as either one-way or two-way types. The slab structural drawing includes reinforcement bars diameters of the bottom, top, cantilever, and peripheral tie members. It also includes the correct minimum spacing, the thickness of the slab, and the concrete mix ratio.
What’s the Cost and Pay of the Structural Engineers?
Hiring a Structural Engineer can vary depending on the size of the project. This can cost between $100 to $200 per hour. The drawing plan’s cost also varies on the magnitude and complexity of the structure, type of the building, cost of living, structural issues in your region, and building regulations fees. The average cost of a structural drawing can range from $200 to $20,000 and even beyond this.
The role of Structural Engineers in any project is an essential component to ensure the stability of the structure. Although hiring a structural engineer will cost you more than going with an Architect alone, it is worth it since, without the structural stability of any project, the project will incur hefty losses in terms of massive regular repairs, demolition, or collapse of the structures.