Building Seismic Design Code (GB50011-2001)
Introduction
Seismic design is integral to the design of buildings and other structures in seismically active areas. Seismic design focuses on protection of the structure and its occupants during earthquakes, and includes both the design of the structure itself, and the means by which it is to be constructed and maintained.
GB50011-2001, Building Seismic Design Code, is the current national building code used in China with special emphasis on structure safety during an earthquake. This code is based on the latest achievements in seismic design and construction techniques, and is intended to help architects, engineers and designers to effectively design new buildings and retrofit existing ones to withstand seismic activities.
Seismic performance principles
The primary principle of seismic performance is that a structure must be capable of resisting a particular level of earthquake motion, generally defined as the peak ground acceleration (PGA) or the peak ground velocity (PGV) prior to significant damage or collapse of the structure. To determine the applicable design levels of earthquakes, the Building Seismic Design Code looks at the potential for seismic activity in the vicinity of the building, as determined by available seismic zone maps.
The Building Seismic Design Code also provides criteria for evaluating a structure’s seismic performance in the event of an earthquake. These criteria focus on evaluating both how well the structural elements., such as beams, columns, walls, and foundations, are designed to withstand seismic forces, and how well the building’s structure as a whole is designed to achieve an acceptable level of earthquake performance.
Seismic design objectives
The main objectives of seismic design are to reduce the physical damage a building will sustain during an earthquake, minimize the loss of human life, and reduce the amount of economic loss due to damage or disruption of service.
The Building Seismic Design Code makes use of several different types of design objective. These design objectives are intended to help designers choose the most appropriate design characteristics for a particular structure, and ensure that the structure is adequately designed and constructed to meet the seismic performance goals.
The first objective is Appropriate Level of Performance (ALOP). This objective is used to determine the allowable level of physical damage that a structure can sustain in the event of an earthquake, and includes both acceptable levels of damage and loss of life. The ALOP is calibrated to both the potential intensity of the ground motion in the specific area, and the type of structure that is being designed.
The second objective is Performance-Based Design (PBD). This objective is used to determine the design characteristics that are necessary to achieve a particular level of seismic performance without consideration for the potential intensity of the ground motion. This allows for customization of design characteristics for a structure in different areas.
The third objective is Seismic Damage Avoidance (SDA). This objective is used to provide additional design measures that may be necessary to achieve acceptable levels of seismic performance and reduce the risk of damage beyond the level allowed by the ALOP.
Impact on the design process
The Building Seismic Design Code has a significant impact on the design process for buildings in seismic activity prone areas. The code requires that all structures, new and existing, adhere to certain design and construction requirements in order to achieve an acceptable level of resilience and performance during an earthquake.
Designs must take into account the different types of ground motions that can be expected in the specific area, the potential for ground displacement, and the soil and foundation conditions in the area. Attention is also paid to the design of nonstructural elements, such as doors, windows and walls, which could be affected by the seismic activity.
Conclusion
GB50011-2001, Building Seismic Design Code, is the mandated building code in China with special emphasis on structure safety during an earthquake. The code sets forth specific design criteria and objectives to ensure that buildings are adequately designed and built to withstand anticipated earthquake activity. The code has a significant impact on design processes, and requires that all new and existing buildings adhere to certain safety standards.
