MODULE 3: SPECIALIZATIONS IN CIVIL ENGINEERING
3.1 STRUCTURAL ENGINEERING
What is Structural Engineering?
Structural engineering is the science and art of planning, designing, and constructing safe and economical structures that will
serve their intended purposes. Structural analysis is an integral part of any structural engineering project, its function being the
prediction of the performance of the proposed structure.
Focuses on the framework of structures, and on designing those structures to withstand the stresses and pressures of their
environment and remain safe, stable, and secure throughout their use. In other words, structural engineers make sure that
buildings don’t fall down and bridges don’t collapse.
How to become a Structural Engineer?
One may become a structural engineer if they are recognized by one of the following:
1. Association of Structural Engineers of the Philippines (ASEP)
2. Philippine Institute of Civil Engineers (PICE)
3. Commission on Higher Education (CHED) Recognized University (Graduate School – Masters)
What do Structural Engineers do?
Structural engineers “design roof framing (beams, rafters, joists, trusses), floor framing (floor decks, joists, beams, trusses,
girders), arches, columns, braces, frames, foundations, and walls,” according to the National Council of Structural Engineers
Association.
In bridges, they design the deck, or riding surface, girders or stringers, and piers. The materials they use include steel, concrete,
wood, masonry, and aluminum. Engineers design the structure to resist forces from gravity, earthquakes, high winds, water,
soil, collisions, and blast explosions.
Structural Engineering Basics
This guide will provide you with the MUST-KNOW information with regards to Structural Engineering if you have time or money
invested in a building or structure.
Loads. Structures are designed to resist loads. These loads are forces applied to the structure that are either vertical or horizontal
and ultimately cause stresses on the load-bearing elements. Vertical loads can include the weight of the structural materials and
finishes, the weight of furniture, the weight of people, and the weight of snow or rain. Horizontal loads can include pressure on a
building due to wind, the weight of soil pushing against a wall, and seismic loads from earthquakes.
Building Materials. Structures can be built out of many different types of building materials. The most common types of materials
are wood, reinforced concrete, steel, and masonry. Each of these materials has different properties, characteristics, and costs
associated with them that make some more suitable than others, depending on the type of structure, look of the structure, and
budget.
Here is a breakdown of each of these common building materials:
★ Wood - is a readily available and economically feasible natural resource that is lightweight and easy to use for
construction. It also provides good insulation from the cold, which makes it an excellent building material for homes and
residential buildings. There are many different species of wood used in construction that have varying strengths and
properties that make some more suitable than others, depending on the application. Wood is very flammable, which
requires additional costs for a fire rating if required by code. It is a great construction material to use when the loads on
the structure are not too large and the span between load-bearing walls and beams is not too long.
★ Reinforced Concrete - is a composite material made up of steel reinforcing and concrete. Concrete is very strong when
placed in compression; however, it’s brittle and weak when placed in tension. Steel reinforcing, or rebar, is used to resist
tension loads in a concrete element. Combined with steel rebar, reinforced concrete is stronger and more suitable for a
wide range of structures, such as tall multi-story buildings, bridges, roads, tunnels, and so many other applications.
Reinforced concrete can be cast in place directly at a job site, or it can be cast in a controlled environment prior to
installation. Building with concrete is fairly labor-intensive as it requires formwork to be installed and rebar to be in place
prior to pouring or installing the concrete. Overall, reinforced concrete is a very desirable building material as it has
excellent fire resistance ratings, durability, and strength.
★ Steel - is one of the strongest building materials available, with excellent strength capacity in both tension and
compression. It has a high strength-to-weight ratio, which makes it ideal for the structural framework of tall buildings and
large industrial facilities. Structural steel is available in standard shapes such as angles, I-shaped beams, and C-
channels. These shapes can be welded together or connected using high-strength bolts to build structures capable of
resisting large forces and deformations. Steel is a relatively expensive building material, but it is quick to install and can
support large loads without taking up much space, which is desirable for owners and architects as they often want to
maximize the space in a building.
★ Masonry - Construction uses individual units to build structural elements, along with mortar to bind the units together.
The most common material used in the design of masonry structures is concrete block with vertical steel reinforcing if
necessary. Because masonry is strong at resisting compression stresses, it is ideal for it to be used in the construction
of load-bearing walls where the load is applied vertically to the masonry units. Similar to reinforced concrete, steel
reinforcing is used in concrete block walls to resist tension loads or bending in the wall if lateral loads are applied. Grout
can be installed in the hollow cores of concrete block structures to increase their strength and to hold the reinforcing in
place to make the materials act compositely. Other masonry materials include brick, stone, and glass blocks. Masonry
is highly durable and easy to construct; however, its properties and strength limit how it is used as a building material.
Stress. Structural engineers design structures based on the stresses imposed on the load-bearing elements that make up the
structure. The amount of stress depends on the magnitude of the load and the geometry of these elements. Each type of material
has different stress limits. A very large load on an element does not necessarily mean that the stress on that element will be large
as well. Stress is defined as a load over an area; therefore, a load spread over a smaller area will have a higher stress than a
load spread over a larger area. The types of stresses depend on the direction of the load being applied to the structural element.
The stresses structural engineers design for include the following:
- Bending
- Compression
- Tension
- Torsion
- Shear
- Bearing
Beams, Joist and Trusses. These are the horizontal members that resist vertical loads on a floor or roof structure. Beams,
joists, and trusses transfer load to the vertical members of the structure. Joists are often smaller and lighter than beams. Joists
transfer load to larger beams that take load to vertical columns. Usually, the deeper the beam, joist, or truss, the longer it can
span without deflecting too much or becoming overstressed. Trusses are an economical option for long spans and are built up of
multiple horizontal, vertical, and diagonal elements that are placed in either compression or tension. Trusses are often used in
the construction of roofs in homes and in bridges.
Columns. These are the vertical, often slender, members that resist axial loads from a floor or roof structure. A beam transfers
its load into columns, which take the load down to the foundation. Columns are most often loaded in compression; unless there
is uplift on a structure, they are loaded in tension.
Load Bearing Walls. This is a wall in a structure that transfers vertical load from a floor or roof structure down to the foundation
or structure below.
Lateral Load Resisting System. This is what stabilizes a building and provides bracing in order to prevent the structure from
collapsing under an earthquake or wind loading. These could be in the form of steel bracing, solid walls, stair or elevator shafts,
rigid connections, and floor or roof structures.
Connections. This is a critical part of any structure where load is transferred from one structural element to another. It could be
between two structural elements with the same material or two different materials. Examples of connections include bolts and
welds for steel, nails and screws for wood, and anchors and studs for concrete and masonry.
Foundations. The loads that a structure is designed to resist need to be transferred to the ground below the earth's surface.
Foundations are the element of the structure that transfers the building loads to the soil below, either near the earth's surface or
deep into the ground. Footings are an example of a shallow foundation and are the foundation of choice for lightly loaded
structures such as a house. Piles are examples of deep foundations and are often the foundation of choice for heavily loaded
structures, such as high-rise buildings.
Building Codes. Building codes are rules and requirements that must be followed when designing a structure. They will tell you
the loads the building should be designed to resist based on occupancy and geographical location. The codes are based on
testing and experience and are ultimately there to protect the public and ensure a building is safe for people to occupy.
Structural Drawings. Structural drawings are the blueprints that contractors use to build a structure. These drawings have
information as to what materials are used and how they come together to form the structure. Structural drawings often include
plans, details, sections, and general notes or specifications.
Load Transfer and Load Path. Structural engineers need to make sure they design a load path that can safely transfer the load
from its point of application through the structure all the way to the foundation, where the structure meets the earth’s surface. An
example of a load path when designing a house could be that if snow is applied to a roof, the load will enter the roof joists or
trusses and be transferred to beams, which will transfer loads to vertical columns or walls that will bear on a foundation that takes
the load into the ground below. Another example would be a gymnast on a balancing beam. The weight of the gymnast gets
transferred into the balancing beam, then into the supports on each end, and down into the floor structure. The closer the gymnast
is to a support, the higher the load the support will attract.
Factor of Safety. These are used in the design of structures to account for uncertainty in the load, strength and quality of
material, and workmanship.
Phases of Structural Engineering Projects
1. Planning Phase. This usually involves the establishment of the functional requirements of the proposed structure, the
general layout and dimensions of the structure, consideration of the possible types of structures that may be feasible,
and the types of materials to be used. This phase may also involve consideration of nonstructural factors, such as
aesthetics, the environmental impact of the structure, and so on.
2. Preliminary Structural Design. The sizes of various members of the structural system selected in the planning phase
are estimated based on approximate analysis, past experience, and code requirements. The member sizes thus
selected are used in the next phase to estimate the weight of the structure.
3. Estimation of Loads. It involves the determination of all the loads that can be expected to act on the structure.
4. Structural Analysis. The values of the loads are used to carry out analysis of the structure in order to determine the
stresses or stress resultants in the members and the deflections at various points of the structure.
5. Safety and Serviceability Checks. The results of the analysis are used to determine whether or not the structure
satisfies the safety and serviceability requirements of the design codes. If these requirements are satisfied, then the
design drawings and the construction specifications are prepared, and the construction phase begins.
6. Revised Structural Design. If the code requirements are not satisfied, then the member sizes are revised, and phases
3 through 5 are repeated until all the safety and serviceability requirements are satisfied.
References
Noah Moscovitch, M. E.-M. (2019). STRUCTURAL ENGINEERING BASICS. From https://structuralengineeringbasics.com/wp-
content/uploads/2019/05/Ultimate-Guide-to-Structural-Engineering-Basics-2.pdf
Structural Engineering. (2020, October 20). From https://www.youtube.com/@bebangmapagmahal6658
Structural Engineering. (2020, October 13). From https://www.youtube.com/@gerrythelion136
