INTRODUCTION
Lintels pertain to a structure, just like a beam that is located above two columns in a horizontal perspective that support other structure like walls, and windows. It is a system that composed of three members, in which the two is held in an upright position, which is commonly known as the posts and the third member is laid horizontally across their top surfaces.
Lintels are usually seen on structures that have an opening, which will carry the load of the wall above it. Lintels are made not only to support the load above it but also to decorate a structure. That is why the study on lintels does not only include the structural design but also the aesthetic value. It gives an image illustration on how lintels will carry the weight above it. Almost all structure that has openings was developed from this system because this is considered as the simplest structure with an opening.
The main objective of this paper is to show or give a literature review about lintels. The objective is to look at the limits of knowledge and how this is handled and could be handled better. In particular, how the different way people know about the area affects the outcome in practice. The determination of the knowledge of the person in expertise will be in the form of an interview where key points or important questions must be answered to have a clear understanding on lintels. Moreover, some problems that are being faced by the three experts will be analyzed and how they handle these problems.
Expertise involves both having knowledge and experience. However the ability to use expertise depends on the circumstances of the situation. Both Technology and the Law have a clear knowledge base and methods of determining truth. However, in problem situations this truth, and method of determining it, is pressurised.
For this paper, the three persons that will guide us to their expertise in studying lintels and will give us the factual knowledge that will aid us in understanding fully the main topic of this paper will be the civil engineers, architects and interior designers. The three people were chosen because they are the one who have direct application or hands on. The factual knowledge will includes, what the three experts now about this area, problem characteristics that occur in the construction and design of lintels and lastly the analysis of the nature of the knowledge and the difference in thinking which will affect the outcome of the final structure (Sampaio).
REVIEW OF RELATED LITERATURE
The use of lintels has a long history; it started on the well-known ancient stone artwork, the Stonehenge. Stonehenge was believed to be constructed by the ancient people to have a system of time measure. As the sun shine in the place where the Stonehenge is built, it produces a shadow of the erected stone thus these shadows act like an hour hand. There are also other ancient forms of lintels around the world. There were many studies that have been conducted to determine the authenticity of the ancient lintels. According to the Fine Arts Department (FAD) director, Narai Banthom Silp (Vishnu-Reclining Lintel) at Bhanomrung Stone Shrine was accurate and real.
Post and lintel is a simple construction technique, also called “post and beam”, where a horizontal member (the lintel) is supported by two vertical posts at either end. This very simple form is commonly used to support windows and doors. The biggest disadvantage to this type of construction is the limited weight that can be held up, and the small distances required between the posts. Roman developments of the arch allowed for much larger structures to be constructed. A lintel or header is a horizontal beam used in the construction of buildings, and is a major architectural contribution of ancient Greece. It usually supports the masonry above a window or door opening.
The use of the lintel form (rather than as a construction technique) has been employed in the architecture of many cultures over time. In non-classical architecture a lintel was frequently used for purely ornamental purposes, having no structural function. For example, the architectural use of a lintel is purely ornamental in the case of Indian rock-cut architecture.
Prehistoric Buddhist temples in India were wooden structures with load-bearing lintels above openings. Subsequently excavated rock cave temples were preferred as more durable, allowing creative ornamental use of classical architectural elements; the carved stone lintels were not load-bearing. Highly skilled artisans were able to simulate the look of a wood, imitating the nuances of a wooden structure and the wood grain in excavating cave temples from monolithic rock. This use of the lintel form was purely decorative and not load-bearing.
Civil and Structural Engineers
What is a lintel in a civil or structural engineer? Are lintels constructions important?
A lintel which is commonly known to us as headers is one component of framing system. It is a framing system in such a way that it is surrounded by other structure like walls, and windows. It is like a beam that has a horizontal orientation and is being supported by two columns known to us as posts. Thus the main purpose why lintels are constructed is that they support other structures in a house or building. This is the main reason why it is important to have lintels in a given structure.
What are lintels made of and is there a classification of lintels?
In engineering aspect, lintels are classified based on the material used, and based on the purpose. There are lintels made of wood, stone, concrete and bricks. But because more and more buildings need more people to accommodate, tougher and more rigid materials are needed to meet the demands and the use of steel was introduced. Today, steel lintels are mostly used but not limited because concrete and bricks lintel are still incorporated to many engineering structures.
What are the characteristics of a stone lintel? And why will I choose stone lintels over the other kinds of lintels?
Stone lintels can be made from solid, like wood, or a system, like brick. However, the same rules apply for each condition. If solid, they should run the width of the opening, overlapping slightly at the edges. If a system, they should be broken at appropriate points along the opening. Stone lintels often give an excellent opportunity for ornamentation.
What are the characteristics of a wood lintel? Are wood lintels strong enough to withstand the pressure or load they support?
Wooden lintels are used because, from their unusual mechanical properties, woods do not break or there no fracture is generated unlike on stone lintels. Wooden lintels can be imagined with a wooden beam. They should have wide spanning board, or several attached side by side that together span the width of the window. Most wooden lintels are not visible on the naked eye because the structure of wooden construction is often entirely covered by the sheathing material.
What are the characteristics of a brick lintel? What are the differences between stone and brick lintel?
Brick lintels have to work as a system, collectively bearing the weight of the wall above them. They may be set out slightly from the wall, and they are usually collectively a single form, different from the system of the wall around them. Brick lintels can come in a number of forms, but soldier courses, stretcher arches and jack arches are the most used. A soldier course is a straight row or multiple rows of bricks turned on end and stacked next to each other (Brick Institute of America).
Being an engineer who has excellent knowledge on lintel construction, can you give me a concise and accurate discussion on the engineering concepts underlying lintel construction?
For this part, the engineering component of lintels will be analyzed. From the different fields of engineering, the civil engineering side will be the best choice because it deals with construction of structure. The main reason why we, the civil and structural engineers are one of the options from the three experts is because we are concerned on erecting lintels given many factor to consider like stress and forces.
From the civil engineering aspect, a more detailed study journey will be done by going to the strength of material which is a specialized subject in civil engineering. Strength of materials deals with relations between externally applied loads and their internal effects on bodies. Moreover, though the materials’ deformation is small, the bodies are not considered rigid. In mechanical design, the engineer must consider both dimensions and material properties to satisfy requirements of strength and rigidity. When loaded, a structure should neither break, nor deform excessively.
To construct a simple lintel, there are many forces to consider in such a way that it will erect safely and not reaching the material’s strength and rigidity. These forces are the tension, compression and shear stress. Tension force pertains to the force perpendicular to the surface that pulls or makes a material’s length longer whereas a push is a compressive force that tends to shorten a material. Shear force is the total resistance to sliding the portion to one side of the exploratory section past to other.
What are tension, compression and shear force? Do these concepts help in the design of lintel construction?
After analyzing the weight and properties of the material to be used in constructing a lintel, then it is time to incorporate the formulas for tension, compression and shear force. When a member or beam is put above a two columns to support another structure at the top of the beam or lintel, then this member is subjected to the three forces mentioned earlier. Because beams are deflected, the upper portion of the beam experience compressive force while the lower part is tension. The tensile and compressive strength of the member must be higher than the tension and compression force in order for the member not to break (Sampaio).
The principle behind tension and compression force applies also to shear force but differ on the application of the force. Imagine a beam being supported by two columns, the point of contact of the surface of the beam and one of the columns will tend to have a sliding or slicing force and this force is the shear. The shear strength of the materials must exceed the shearing stress in order to erect lintels safely.
The second step to design lintels is the study on beam deflections. Frequently, the design of lintels or beams is determined by its rigidity rather than by its strength. For example, in designing metalworking equipment for precision work such as lathes, milling machines, grinders or lintels, the deformation must be kept below the permissible tolerances of the work being constructed. One of the most important focuses of study on lintels is the beam deflection and this is done by formulating equations that will answer every questions. The formulation of equation involves the combination of the conditions of static equilibrium, and statistically indeterminate beams.
What are the new methods, materials used in today’s lintel construction?
Because most building or ant application of lintels are now more complicated and sophisticated, there is a need to have lintels that are lightweight, not visible and are more stable than wood and concrete. Today, we civil and structural engineers are incorporating steel lintels because this kind of material has the characteristics I mentioned a while a go.
Architecture
What is the difference between the role of an engineer and architect in designing lintel construction?
Another aspect or application of lintels is in the field of architecture. Structurally, lintels in terms of engineering and architecture are the same but differ in the purpose, the former aims to build a structure to support another structure while the latter intends to beatify the whole structure itself.
What are the main purposes or objectives of an architect in designing a lintel construction?
The use of lintels as a decorative application has been employed in many cultures through time. In a non-classical architecture, lintels are widely used as purely ornamental reason, meaning, the structure concept is not employed. A good example of this is the Indian rock-cut architecture. The said architecture structure used lintels for decoration purposes only.
The prehistoric period shows also some application of lintels for decorative reasons. Famous Buddhist temples were usually made of wooden lintels. But because these kinds of lintels are hard to decorate, excavated rock cave temples were favored. Toughness and the ease to decorate rock lintels were the reason why there was a shift of utilization of lintels from wood to rock.
The Greek architecture was one of the pioneers of lintels decoration. This was begun by the sculptor Scopas in the Temple of Athena at Tegea. All these buildings suggest that the 18th-century Enlightenment idea of Greek architecture as a system based solely on post-and-lintel construction, in which the columns carried the load, was erroneous.
The Maya civilization was one of the ancient civilizations in the world who had the first application of lintels for decorative function. They are known for its spectacular art and monumental architecture. Because of this, they are known to be specialized in this kind of work.The Mayan city of Yaxchilan specialized in the carving of ornamental stone lintels. At the archaeological site on the Usumacinta River, there are 58 lintels spanning the doorways of major structures. Among the finest Mayan carving to be excavated anywhere are three temple door lintels that feature narrative scenes of a queen celebrating her husband’s anointing by a god.
In the architecture aspect, the use of lintels as decoration portrays many message. That is why emperors and kings from different countries hire many artists just to design the structure of their palace which imply or show the power of the regime. People of privilege have always been the best clients of designers, artists, and artisans, and in their projects the best work of a given period is often represented. Today large corporations, governments, and universities play the role of patron in a less personal way.
How can an architect employ the concept of art in a lintel design?
The concept of art is employed in an architecture aspect. Some of the properties of art are the shape of the material used, the position, and color. Different shapes like circle, square or rectangle have unique meanings. Position also implies some message. A lintel that has an erect position implied power, masculinity and love while a lintel that has a horizontal position means peace and happiness, while every color implies many meaning depending on the culture where lintel will be constructed.
Interior Designer
What is the main difference between an architect and an interior designer in respect to lintel designing?
In this part of analysis, we consider an interior designer because they are the one who design almost every part of a house or building and it is very evident nowadays that lintel are almost present on the said structures. Although, the word architect and interior design are interchangeable, the main difference of these two professions is that, the former pertains to the aesthetic value of the structure using art and science while the latter focus on the art itself.
Interior designers focus on every part of a house or buildings including lintels to add beauty on the structures. The task of an interior designer includes, interior and exterior restoration, historic restoration and preservation, building envelope, building maintenance, facade inspection, landmark restoration and restoration assembly.
CIVIL ENGINEERS IN FOCUS
After discussing the three persons that have knowledge on lintels construction, the next part is to choose among these three persons and then have a deep analysis to have a factual knowledge, some characteristics problems and discussion of operation of knowledge.
Factual Knowledge
For this part of the paper, factual knowledge will be the center of attention but there are many topics that can be classified as factual knowledge if construction of tinsels is concerned. We will not anymore talk about the basic information or principle behind tinsel like the mentioned above but will focus on how structural engineers construct. The first step on constructing lintels is the main design of the construction (Sampaio).
The design must conform on all the basic requirements set by the engineer. Some of the requirements are, stress condition, material to be used as well its properties, good estimate of the load with at least 10% safety factor, time frame of construction and budget of the project or lintel construction.
The design is like a blue print copy where all the instruction and guidelines are written in order for the engineer to construct lintel in right path and right manner. A good design shows all the procedures as well possible problems with solutions.
The design must determine the stress and force requirements in order for the engineer to choose the right material that can withstand all possible loads. It is important to specify the safety factor of the load requirement so that to minimize the possibility of the constructed lintel to breakdown.
Time frame must also be included in the design and the engineer must conform on the specified dates of completion in order to have an efficient work. Last part of the design is the budgetary requirement. We all know that engineers must know how to allocate their resources so that it can minimize possible losses (Liston et al.).
Problems
A lintel is a structural member placed over an opening in a wall. In the case of a brick masonry wall, lintels may consist of reinforced brick masonry, brick masonry arches, and pre cast concrete or structural steel shapes. Regardless of the material chosen for the lintel, its prime function is to support the loads above the opening, and it must be designed properly.
To eliminate the possibility of structural cracks in the wall above these openings, the structural design of the lintels should not involve the use of “rule-of thumb” methods, or the arbitrary selection of structural sections without careful analysis of the loads to be carried and calculation of the stresses developed. Many of the cracks which appear over openings in masonry walls are due to excessive deflection of the lintels resulting from improper or inadequate design.
Though most civil and structural engineers use steel lintels nowadays to minimize the problem of formation of cracks, there are still anticipated hitch for this. The said problem is the deflection and rotation of the steel. Due to the load that is support, there are times that the material cannot overcome anymore these torsion and shear stresses. These stresses are evident when the material had bent of deflected.
There is another problem in constructing lentils, we know that the buildings in nowadays are becoming more complicated thus the construction will also follow to be more complicated. Different designs are now in demand but the implementation of these designs is the hard part of the construction. Newer designs are in demands but the materials to be used to execute the design are not yet available in the market (Leinonen et al.). Also, the scope of these designs is wide making it for the structural designer to have a successful design given their limited resources.
And the last known problem in construction of lintels in an engineering aspect is the number of accidents that is associated when constructing lintels. Construction has the highest rate of musculoskeletal disorders (MSDs). These are mostly back injuries from manual handling. There were 56,000 Work Related MSD cases in construction in 2004/5. Handling injuries (to employees in 2004/2005) accounted for 38% of over 3 day injuries and 15% of major injuries.
Operation
Because of the problems in terms of the cracks created from using brick lintels and concrete, structural engineers are now using steel that are more durable. Also, steels are easily modified in accordance to the design of the engineer. There are machine that can easily modify the size and shape of steel. But the utilization of steel needs many factors to consider in order for the structural design to be a successful one. Some of these factors are loading, type of lintel, structural design, material selection and maintenance, moisture control around the opening, provisions to avoid movement problems and installation of the lintel in the wall (American National Standards Institute).
The above figure show different types of steel lintels. The first type is loose angle lintels. These kinds of lintels are used in brick veneer and cavity wall constructions where the lintel is laid in the wall and spans the opening. This type of lintel has no lateral support. Another type of steel lintels is combination lintels.
As the name implies, combination lintels is composed of tow or more loose angle lintels. In solid masonry walls, single loose angle lintels are usually not capable of doing the job. Therefore, combination lintels are required. These combination lintels can take many forms, from a clustering of steel angles. And the last type of steel lintels is what they called shelves lintels. This type of steel lintels are used in panel walls systems, the exterior wythe of brickwork may be supported by shelf angles rigidly attached to the structural frame. These shelf angles, in some cases, also act as lintels over openings in the masonry (American Institute of Steel Construction).
Structural steel lintels must be properly designed for construction no matter what type to be used. First, structural requirements must be met. Second to consider is the serviceability requirements. Lastly of course, are the loads, stresses and deflections must be considered. Safety factors on all the calculation must be consider to increase the strength of steel lintels. The British and European Standards of Lintels have a chart where the engineer can choose the right properties of lintels to be used given the physical and mechanical requirements. The figure below shows the chart for standards duty loading.
Besides design, material specification is also indispensable. Proper selection and maintenance of it would contribute to the durability of the structural steel. In selecting steel for lintels, as a guide, the minimum should be in compliance with the British and European standards. Appendix A shows the minimum requirements for steel lintel construction.
In installing the steel lintels, conventional way of construction must be used. In doing so, walls must be built to the height of opening; lintel meanwhile must be built over the opening. Other than designing per se, structural design is also very important. In structural designing, computations are considered. Loads, stresses and serviceability are very important to regard as. This is to avoid cracking and failure of the design.
Good design also minimizes the possibility occurrence of accidents. Engineers nowadays are more focused in this issue because of the safety concern. Engineers are now using special methods like kerbs construction, building blocks and bagged aggregates to strengthen the framework. Regular inspection on the development and construction of the building helps also to minimize this problem.
CONCLUSION
The paper major objective was the analysis of lintel construction as well the significance of the key players who has a major role in the said area of study. And base from the discussion, the three people who has direct link in lintel construction were civil or structural engineers, architects and interior designer. These three different people were chosen by the author is because they are the one who study deeply lintel construction and applications and designs.
After obtaining factual knowledge from these three people, the civil and structural engineer’s knowledge was focused to give more a detail explanation on their factual knowledge. One of the main problems that engineers are now facing is the durability and serviceability of their current material like stone, brick, concrete and wood lintels because of these, they are now using steel lintels because on the advantage that the latter are more durable and serviceable over the formers.
Having understood and experienced most of the concepts, theories, events, flaws, system and methods of constructing lintels, the author would like to recommend a few things. Consider other materials that can overweight and has more advantage on using steel lintels. The said material must be cost effective, lightweight, and more stable and has higher mechanical strength.
For me, the most important to consider to have a successful lintel construction and with the introduction of technical and mechanical problems, proper design is the best solution for these kind of problems. Having a good design will overcome all the problems because part of the design is how to redirect these problems. Thus, the first thing to do is to design and plan the procedures, materials, and other pertinent data to help in obtaining a good design.
References
- AISC. 1980, Manual of Steel Construction. American Institute of Steel Construction, Inc., New York, New York, Eighth Edition.
- BIA. 1969, Building Code Requirements for Engineered Brick Masonry, Brick Institute of America, McLean,Virginia.
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- Liston, K., M. Fischer, and T. Winograd 2001, “Focused sharing of information for multi-disciplinary decision making by project teams”, International Journal ITcon, vol. 6, pp. 69-82.
- Sampaio, A., and A. Recuero. 2004, “A geometric modeling of box girder deck for integrated bridge design”, International Journal of Computer Applications in Technology, IJCAT, Special issue on Interoperability for SME- based environments, 20(1), pp. 54-61.
- Sampaio, A., P. Henriques, and P.S. Ferreira. 2004, “A virtual environment tool applied to visualize construction processes”, in Proc. TP.CG.04 – Theory and Practice of Computer Graphics 2004 Conference, Bournemouth (U.K.).
