Guidelines For Earthquake Resistant Building Construction: Low-Strength Masonry
Introduction
Earthquakes pose significant threats to human life and infrastructure, especially in regions with high seismic activity. The development of earthquake resistant buildings has become a crucial endeavor to mitigate these risks. In 1993, under the National Building Code Development Project (NEP/88/054/21.03), several documents were prepared to enhance seismic-resistant constructions. One such document, “Guidelines for Earthquake Resistant Building Construction: Low Strength Masonry (LSM),” has been particularly influential. Originally prepared in 1993, this document was revised by the DUDBC in July 2014 to provide updated and comprehensive guidelines for the earthquake resistance of low-strength masonry construction. This article delves into the importance of these guidelines, their content, and their implementation, highlighting how they contribute to the seismic safety of low-strength masonry buildings.
The Need for Earthquake Resistant Building Guidelines
Earthquakes can cause catastrophic damage to buildings, leading to loss of life and significant economic losses. Traditional construction methods, especially those involving low-strength masonry (LSM), are particularly vulnerable to seismic forces. LSM buildings, commonly found in many regions, are often constructed using stones or semi-burnt bricks set in mud mortar, which lacks the integrity and strength needed to withstand seismic events. The Guidelines for Earthquake Resistant Building Construction: Low Strength Masonry (LSM) were developed to address these vulnerabilities and enhance the seismic safety of such buildings.
Key Features of Earthquake Resistant Building Guidelines
The guidelines aim to improve the seismic performance of LSM buildings through several key features and practices:
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Symmetrical Configuration: Symmetrical buildings tend to perform better during earthquakes as they distribute seismic forces more evenly. The guidelines recommend avoiding asymmetrical shapes and overhanging parts that can create torsion during shaking.
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Improved Integrity: Enhancing the integrity between building components is crucial. This includes ensuring that walls, floors, and roofs are well-connected to resist separation during seismic events.
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Reduced Mass: Reducing the mass of the building can minimize the forces generated during an earthquake. The guidelines suggest using lightweight materials where possible to achieve this.
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Confinement of Masonry: Confined masonry, where walls are confined by reinforced concrete elements, can significantly improve the seismic resistance of LSM buildings. This technique helps to prevent the out-of-plane failure of walls.
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Regular Wall Placement: Walls should be uniformly distributed to balance lateral forces. Doors and windows should not be too close to the building corners or concentrated in one area, as this can weaken the structural integrity.
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Foundation Considerations: The guidelines emphasize the importance of proper foundation design. Buildings should not be constructed on soft, saturated, or liquefiable soils. If unavoidable, soil improvement and deep foundation systems should be considered.
Implementation of the Guidelines
The implementation of these guidelines is intended to be carried out by the owner/builder, with some assistance from technicians. The guidelines are designed to be practical and accessible, allowing for their application in various construction contexts. They can also serve as a basic reference for architectural design and construction detailing of LSM buildings. By following these guidelines, builders can significantly enhance the seismic safety of LSM buildings, reducing the risk of collapse and loss of life during earthquakes.
Case Studies and Real-World Applications
Several case studies have demonstrated the effectiveness of these guidelines in enhancing the seismic safety of LSM buildings. For instance, in regions with high seismic activity, buildings that have incorporated these guidelines have shown better performance during earthquakes. These case studies highlight the importance of adhering to the guidelines to achieve meaningful improvements in seismic safety.
Conclusion
The development and implementation of earthquake resistant building guidelines, such as those for low-strength masonry construction, are essential for enhancing seismic safety. By incorporating key features like symmetrical configuration, improved integrity, reduced mass, and confined masonry, these guidelines provide practical and effective solutions for improving the seismic performance of LSM buildings. Their application can significantly reduce the risk of collapse and loss of life during earthquakes, making them a vital resource for builders and technicians in seismic-prone regions.
For more detailed information on earthquake resistant building guidelines and practices, you can refer to the following resources: