What Is Empirical Design of Masonry
The empirical design of masonry is a method of proportioning and sizing unreinforced masonry elements based on historical performance.
It is commonly used for loadbearing structures with small wind loads and low seismic risk, exterior curtain walls, and interior partitions.
The design is governed by prescriptive criteria such as wall height to thickness ratios, shear wall length and spacing, and minimum wall thickness.
It is allowed for masonry structures assigned to Seismic Design Category A, B, or C and can be used for buildings up to 35 feet in height.
Additional measures, such as cross walls, pilasters, buttresses, and structural frame members, provide lateral support to the walls.
The design also specifies the requirements for metal wall ties, joint reinforcement, and load transfer when wall thickness is decreased.
Did You Know?
1. The use of empirical design in masonry refers to a calculation method based on observations and practical experience rather than theoretical analysis.
2. The concept of empirical design in masonry originated in ancient times, where builders relied on a trial and error approach to determine the most effective methods for constructing durable structures.
3. Empirical design of masonry takes into account various factors such as the type of mortar, the size and weight of the masonry units, and the intended loads the structure will bear.
4. One of the earliest examples of empirical design in masonry can be found in the Great Wall of China. The construction of the wall involved numerous experiments with different types of mortar, resulting in a structurally sound and long-lasting final design.
5. Empirical design in masonry continues to evolve with modern technology. Today, engineers combine traditional empirical design principles with advanced computer simulations to optimize masonry structures for strength, durability, and aesthetics.
Introduction To Empirical Design Of Masonry
Empirical design of masonry is a well-established procedure for proportioning and sizing unreinforced masonry elements based on historical performance. It relies on the principles of observed behavior and uses these experiences to inform design decisions. This approach has been found to be particularly suitable for:
- Loadbearing structures with small wind loads and low seismic risk
- Exterior curtain walls
- Interior partitions
Unlike analytical design methods that use complex mathematical models, empirical design focuses on prescriptive criteria that govern the vertical and lateral load resistance of masonry structures. These criteria include parameters such as:
- Wall height to thickness ratios
- Shear wall length and spacing
- Minimum wall thickness
- Maximum building height
By adhering to these criteria, designers ensure that the masonry elements have the necessary strength to safely withstand the loads imposed on them.
It is important to note that empirical design of masonry is not a one-size-fits-all approach. The specific design parameters and criteria may vary depending on the governing building codes and regulations in different regions. In the United States, for example, empirical design in masonry is based on the provisions outlined in Section 2109 of the International Building Code (IBC), which provides guidelines for the safe construction and design of masonry structures.
- Empirical design of masonry is a well-established procedure for proportioning and sizing unreinforced masonry elements based on historical performance.
- It is suitable for loadbearing structures with small wind loads and low seismic risk, exterior curtain walls, and interior partitions.
- Empirical design focuses on prescriptive criteria that govern the vertical and lateral load resistance of masonry structures.
- Criteria include wall height to thickness ratios, shear wall length and spacing, minimum wall thickness, and maximum building height.
- The specific design parameters and criteria may vary depending on building codes and regulations.
- In the United States, empirical design in masonry is based on Section 2109 of the International Building Code (IBC).
Application Of Empirical Design In Various Structures
The principles of empirical design are applicable to a wide range of structures, including loadbearing buildings with low to moderate seismic risk. Masonry structures assigned to Seismic Design Category (SDC) A, B, or C can be designed using empirical methods. The height limitations for buildings relying on empirically designed masonry walls for lateral load resistance are typically up to 35 feet.
Empirical design is commonly employed in the construction of exterior curtain walls, which serve as the non-structural envelope of a building. These walls are designed to withstand the imposed wind loads and protect the interior from environmental elements. Furthermore, interior partitions, which separate different functional spaces within a building, can also be designed using empirical methods.
The flexibility and versatility of empirical design make it a popular choice for architects and engineers. Its application spans across various construction projects, including residential, commercial, and institutional buildings.
- Empirical design principles are applicable to a wide range of structures.
- Masonry structures assigned to Seismic Design Category (SDC) A, B, or C can use empirical methods.
- *Height limitations for buildings relying on empirically designed masonry walls for lateral load resistance are up to 35 feet.
- Empirical design is commonly used in the construction of exterior curtain walls.
- Interior partitions within buildings can also be designed using empirical methods.
“The principles of empirical design offer flexibility and versatility, making it a popular choice for architects and engineers.”
Prescriptive Criteria For Vertical And Lateral Load Resistance
The design of masonry elements using empirical methods relies on a set of prescriptive criteria that govern their vertical and lateral load resistance. These criteria ensure that the masonry walls have the necessary structural integrity to resist the imposed loads and maintain the safety of the structure.
For vertical load resistance, the minimum thickness of empirically designed bearing walls for one-story buildings is 6 inches. For buildings that are more than one story in height, the minimum thickness increases to 8 inches. This requirement ensures that the walls have the necessary strength and stability to support the vertical load from the superstructure.
Lateral load resistance is achieved by providing adequate support to the masonry walls. This support can be provided horizontally by cross walls, pilasters, buttresses, and structural frame members. Alternatively, vertical support can be achieved through the use of floor diaphragms, roof diaphragms, and structural frame members. These elements contribute to the overall stability of the structure and help resist the lateral forces imposed by wind or seismic events.
Code Provisions For Empirical Design In Masonry
The empirical design of masonry is governed by specific code provisions to ensure adherence to safety standards. In the United States, these provisions are outlined in Section 2109 of the International Building Code (IBC). The IBC provides guidelines for the design, construction, and inspection of building structures, including masonry.
The code allows for the use of empirical design in masonry structures assigned to Seismic Design Category (SDC) A, B, or C. These categories represent varying degrees of seismic risk. By following the code provisions, designers can ensure that the masonry structures have the necessary strength and stability to withstand seismic events within these categories.
Adherence to building codes and regulations is essential to ensure the safety of structures and mitigate potential risks. Therefore, designers and engineers must stay updated with the latest code provisions and incorporate them into their empirical design processes.
Design Considerations For Empirically Designed Masonry Walls
When designing masonry walls using empirical methods, several important considerations ensure structural integrity and performance. These considerations include bonding of different masonry units and the spacing and use of wall ties.
In solid masonry construction, a certain percentage of each face’s wall surface must consist of headers that extend at least 3 inches into the backing. Additionally, there are specifications for the maximum distance between full-length headers, which should not exceed 24 inches horizontally or vertically. These requirements ensure proper load transfer and enhance the overall strength of the wall.
For hollow unit walls, stretcher courses must be bonded at vertical intervals not exceeding 34 inches by lapping at least 3 inches over the unit below. This bonding arrangement helps maintain the structural integrity of the wall and prevents potential vertical separation between courses.
To further enhance the strength and stability of masonry walls, metal wall ties can be used to bond wythes. The placement and spacing of these ties are crucial. Each 4.5 square feet of wall surface should have at least one tie, with spacing not exceeding 24 inches vertically and 36 inches horizontally. Additional bonding ties are needed at all openings, spaced a maximum of 3 feet apart around the perimeter and located within 12 inches of the opening.
In some cases, adjustable ties may be used, and their spacing should correspond to one tie for each 1.77 square feet of wall area. The maximum horizontal and vertical spacing for adjustable ties is 16 inches.
When considering the thickness of masonry walls, it is important to ensure load transfer. When the thickness of a wall decreases, at least one course of solid masonry or special units must be placed under the thinner section to ensure load transfer to the thicker section below. This strategy prevents potential weaknesses and maintains the overall structural integrity of the wall.
In conclusion, empirical design of masonry is a proven approach for proportioning and sizing unreinforced masonry elements based on historical performance. It finds application in various structures, including loadbearing buildings with low seismic risk, exterior curtain walls, and interior partitions. By adhering to prescriptive criteria and code provisions, designers ensure that masonry structures have the necessary strength and stability to withstand vertical and lateral loads. Through careful consideration of design details, such as bonding and spacing of masonry units and wall ties, the structural integrity and performance of empirically designed masonry walls can be effectively achieved.
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Frequently Asked Questions
What does masonry mean in design?
In design, masonry refers to the use of brick, stone, or concrete blocks as a decorative element. These materials are used to create visually appealing patterns, textures, and shapes in buildings and structures. Masonry design can bring a sense of solidity, durability, and natural beauty to architectural projects. The versatility of masonry allows for the creation of various patterns and designs, adding depth and character to a design. Whether used as a feature wall, a decorative facade, or a structural element, masonry design adds a timeless and elegant touch to architectural compositions.
What is the basic concept of masonry?
Masonry is the ancient art of constructing structures using stones or bricks. It involves arranging individual blocks or materials, such as concrete, hollow blocks, or even laterite, in horizontal courses and bonding them together with mortar. The concept of masonry lies in the meticulous placement of these materials to create a durable and visually appealing wall that can withstand the test of time. With a rich history dating back centuries, masonry remains a fundamental technique for building long-lasting structures.
What is the design code for masonry?
The design code for masonry is governed by the TMS 402. This code provides guidelines for the design and construction of masonry structures, ensuring their safety and reliability. It outlines the necessary requirements and considerations to be taken into account during the design process, incorporating updates from new referenced standards such as ASCE/SEI 7-22 and various ASTM Standards. In conjunction with TMS 402, the TMS 602 specification sets forth the minimum construction requirements for masonry in structures, further complementing the code to ensure the proper implementation and execution of masonry projects. These codes and specifications work together to establish industry standards and foster consistent and effective practices in masonry design and construction.
What are the main principles and considerations involved in the empirical design of masonry structures?
The main principles involved in the empirical design of masonry structures include ensuring the overall stability, load-bearing capacity, durability, and safety of the structure. These principles are achieved through careful consideration of several factors, such as the material properties of the masonry units (bricks or concrete blocks), mortar properties, wall geometry, and design loads. The design should also take into account regional or local building codes and regulations to meet the acceptable standards for masonry structures.
Considerations involved in empirical design of masonry structures include accounting for the behavior of masonry under different loading conditions, such as compression, bending, and shear. Additionally, considerations like the arrangement of reinforcement elements (if any), proper bond between units and mortar, and the avoidance of potential failure modes such as sliding, cracking, or excessive deflection should also be addressed. Overall, the empirical design of masonry structures involves a holistic approach that considers the interaction between different components and takes into account the intended function and service life of the structure.
