Seismic Resistance Design and Setup Strategies for Reinforced Concrete Frame Structures

Core Seismic Characteristics of RC Frame Structures

Different from shear wall and tube structures, RC frame structures rely entirely on beams and columns to resist lateral seismic loads. The primary seismic weaknesses include excessive lateral displacement under seismic excitation, brittle shear failure of columns and beam-column joints, and progressive collapse risks caused by unbalanced force distribution. Unlike masonry structures with poor ductility or steel structures with flexible deformation, RC frames have moderate ductility, which allows targeted seismic optimization through structural detailing optimization and auxiliary seismic devices.

The fundamental design principle for RC frame seismic resistance is thestrong column-weak beam mechanism, which prioritizes beam plastic hinge failure over column failure. This controlled failure mode ensures the structure dissipates seismic energy through beam deformation while maintaining overall vertical bearing capacity, effectively preventing sudden structural collapse during earthquakes.

1. Conventional Seismic Setup: Standard Structural Optimization Design

For RC frame buildings in low-to-medium seismic intensity zones (6 to 7-degree fortification) and ordinary civil buildings, conventional seismic design is the most cost-effective solution, focusing on structural system optimization and construction detailing reinforcement.

First, optimize the structural layout to ensure planar and vertical regularity. Irregular torsion, sudden stiffness changes, and vertical discontinuities will amplify seismic responses. Designers should arrange columns and beams evenly, avoid large openings and asymmetric layouts, and maintain consistent vertical stiffness of the frame. Limiting structural height and aspect ratio is also critical; a reasonable aspect ratio effectively reduces structural overturning risks under earthquakes.

Second, strictly implement the strong column-weak beam, strong shear-weak flexure, and strong joint-weak member design criteria. Improve the flexural capacity ratio of columns to beams to ensure plastic hinges form on beams rather than columns. Enhance shear reinforcement for beams and columns to prevent brittle shear failure before flexural yielding. Beam-column joints, as key force-concentrated parts, need dense stirrup reinforcement to improve core-area confinement and avoid joint cracking and damage.

In addition, standardized construction details are essential. Continuous floor slabs act as rigid diaphragms to transfer seismic loads evenly to each frame. Reasonable stirrup spacing, longitudinal reinforcement anchorage length, and concrete strength grade directly determine the ductility and seismic toughness of RC frames. This conventional scheme is suitable for most ordinary residential and office buildings with low maintenance costs and stable performance.

2. Energy Dissipation Seismic Setup: Damping Reinforcement Scheme

For mid-rise RC frame buildings in high seismic intensity zones (8 to 9-degree fortification) and important public buildings such as schools and hospitals, simple conventional design cannot meet high-level seismic safety requirements. Adding energy dissipation devices is the preferred optimized solution for RC frame structures.

Buckling Restrained Braces (BRB) are the most widely used energy dissipation components for RC frames. Different from ordinary steel braces that easily buckle under compression, BRBs maintain stable tensile and compressive bearing capacity and fully dissipate seismic energy through plastic deformation under earthquakes. Installed between frame columns and beams, BRBs significantly improve structural lateral stiffness, control inter-story drift, and reduce seismic load transmission to the main frame. This protects the original RC beams and columns from damage and greatly improves structural post-earthquake recoverability.

Viscous fluid dampers are another ideal choice for RC frame seismic reinforcement. As velocity-dependent energy dissipation devices, they consume seismic energy through fluid viscous resistance, effectively suppressing structural vibration and reducing floor acceleration and inter-story displacement. Viscous dampers feature small structural damage, no residual deformation after earthquakes, and are suitable for frame structures requiring high comfort and post-earthquake normal use.

The core advantage of energy dissipation seismic setup is that it transfers seismic energy consumption from the main RC structure to additional damping devices. The main frame remains elastic during moderate and small earthquakes and suffers minimal damage during strong earthquakes, realizing the performance-based seismic design goal of "no damage in minor earthquakes, repairable in moderate earthquakes, and no collapse in major earthquakes".

3. Base Isolation Seismic Setup: High-Level Seismic Protection Scheme

Base isolation technology is applicable to low and mid-rise RC frame public buildings with high seismic fortification requirements. Unlike energy dissipation structures that reduce seismic response through energy consumption, base isolation structures extend the structural natural vibration period through isolation bearings, avoiding resonance with ground seismic waves and isolating most seismic energy from the superstructure.

The common isolation system for RC frames adopts Lead Rubber Bearings (LRB) or High-Damping Rubber Bearings (HDRB) arranged at the foundation top. The isolation layer effectively cuts off seismic force transmission, keeping the superstructure RC frame in a nearly rigid state with extremely small deformation and almost no structural damage after earthquakes.

It is important to note that base isolation has strict applicability limits. It is not suitable for high-rise RC frames and structures with large height-width ratios, as excessive overturning moment may cause bearing tension and failure. For regular low-rise RC frame buildings, base isolation is the most reliable seismic scheme, especially suitable for key buildings that need normal operation after earthquakes.

4. Scheme Selection Guidelines for RC Frame Seismic Design

Reasonable selection of seismic schemes based on building conditions is the key to balancing safety and economy. For ordinary low-rise RC frame residences in 6–7 degree seismic zones, optimize conventional structural detailing and adopt standard strong column-weak beam design to meet specification requirements. For mid-rise frames in high-intensity zones and important public buildings, prefer energy dissipation schemes with BRBs or viscous dampers to improve seismic performance economically.

For key public buildings requiring post-earthquake emergency use, base isolation systems are prioritized to achieve ultra-high seismic protection. Irregular RC frame structures with torsional effects and uneven stiffness should adopt energy dissipation devices for targeted stiffness adjustment and vibration control to eliminate seismic weak parts.