To make the buildings “earthquake safe”, the key ingredients are lateral stiffness and strength. There are simplified procedure in evaluating the two which requires calculation of reduction coefficient and analytical and experimental investigations.
Retrofitting is technical interceding in structural system of a building that improve the resistance to earthquake by enhancing the strength, adaptability and earthquake loads. The strength of the building is generated from the structural dimensions, materials, shape, and number of structural elements.
The resiliency of the building is generated from good detailing, materials used, degree of seismic resistant, and other considerable factors. Earthquake load is generated from the site seismicity, mass of the structures, important of buildings, and degree of seismic resistant. Due to the variety of structural condition of building, it is hard to develop typical rules for retrofitting. Every building has different approaches depending on the structural deficiencies.
Clearly, this evaluation can only be certified by highly expert structural engineers who have long-term experience when it comes to soft story retrofit.
Ordinance 183893 requires the retrofit of pre-1978 wood-frame soft-story buildings and non-ductile concrete buildings. The goal of the said mandatory retrofit programs, is to reduce these structural deficiencies and improve the performance of these buildings during earthquakes. Without proper strengthening, these vulnerable buildings may be subjected to structural failure during or after an earthquake.
The following are the catagories in retrofitting process:
1. Assessment and Analysis
In decision-making measures, vulnerability assessment plays an important role. The purpose of carrying this out is to analyze an existing building to determine the level of risk associated with loss of serviceability and grave damage or collapse. With the risk quantified, wise decisions can be made as to whether the buildings should be retrofitted or replaced.
2. Design of Retrofitting Techniques
The retrofitting approach adopted should consider the degree of seismic resistance required for the buildings. The buildings must be designed to provide enough strength and ductility when subjected to earthquake forces. It should also be noted that the buildings must be designed for a certain acceptable damage level. For school buildings, the buildings must not have structural damage due to earthquake.
The chosen approach is simple and economical to apply. In designing the retrofitting approach, the techniques should be compatible to the skill of the workers.
3. Construction and Implementation
The construction of the buildings should consider duration of construction. The process must be supervised intensively to ensure the quality of works.
Improve the flexural capacity, by casting a new chord member integral with the slab after removing the edge of diaphragm slab and reducing the flexural stress by providing additional vertical-resisting elements.
To do so, a team of highly experienced engineers that specialized in retrofit build and design can provide the most optimized and cost-efficient retrofit solutions. It is always best to get the services of engineering and construction team that provides smart solutions and efficient design and construction techniques. In this way, the beginning to the accomplishment of the projects is fully supported.