抱歉，技术问题没有情怀可谈：地震波选择的若干技术吐槽
(Note: The article is lengthy. If interested, it is recommended to save or read it carefully.)
超限设计的痛点：地震波选择
每栋塔楼的超限设计均需进行小震弹性时程分析与大震弹塑性时程分析。其中最棘手的环节莫过于地震波的选择——同事们常为此耗费大量精力，最终选出的波形往往只能勉强达标。
今年5月，AutoWave横空出世，显著缓解了这一难题（详见 《AutoWave自动选波及人工波生成工具操作演示》 和 《自动选波程序AutoWave更新日志》）。该工具已在公司内部全面应用，最新版本解决了诸多历史遗留问题。然而，波形选择仍存在大量值得探讨的槽点。以下为个人浅见，欢迎质疑与补充。
1. 选波真的”靠谱”吗？
“靠谱”本义指值得信赖，而本文的”谱”特指规范反应谱。根据规范要求，地震波需满足：
- 反应谱匹配：波形转换后的反应谱在结构主周期点的幅值偏差需控制在±20%以内；
- 基底剪力约束：
- 单条波的基底剪力需达到CQC（规范谱法）结果的65%~135%；
- 多条波平均值需达80%~120%；
- 同时满足持时与时间间隔要求。
![某150m框架核心筒结构，AutoWave选波结果示例]
现实困境
- 长周期结构的挑战：深圳超限高层普遍高度超百米，周期>2.5s，处于反应谱下降段，长周期波稀缺；
- 缩放陷阱：通过缩放系数可强制匹配关键周期点，但实际计算结果未必合理；
- 基底剪力矛盾：波形吻合但剪力不符的情况频发，尤其含裙房/地下室时（详见第4节）。
规范溯源
《高层建筑混凝土结构技术规程》（JGJ3-2010）【4.3.4】
弹性时程分析适用于：
- 高度>100m或质量/刚度不规则结构；
- 甲类建筑及复杂结构；
- 不满足竖向规则性条款的结构。
条文释义
弹性时程旨在补充验证构件内力与配筋调整——若时程结果大于CQC，需放大对应构件内力。
悖论：若仅以CQC为标准筛选地震波，是否违背了时程分析的补充意义？为何不直接采用统一放大系数？
2. 选波：求大还是求小？
规范允许在合理范围内选择波形幅值，引发争议：
- 保守派：主张选择大振幅波形以确保安全；
- 实用派：认为剪重比调整系数已足够，无需叠加时程放大系数。
个人立场：地震随机性无法预测，按规范要求选择即合规。若随机选到大振幅波，应按规则放大CQC结果。
3. 弹性与弹塑性结果的”大小之争”
专家审查会常提及大震弹塑性基底剪力应为小震CQC的3~5倍，但近年关注渐少。
核心矛盾：
- 弹性分析结果通常大于弹塑性，但刚度退化可能导致周期延长、激励增强；
- 结果高度依赖所选地震波。
Graham H. Powell警示
“非线性分析的目标不是精确模拟，而是为设计决策提供依据。模型无需完美，但需足够准确。”
4. 裙房/地下室：选波时该不该”带”？
含裙房/地下室的结构面临两难：
- 问题根源：现有软件无法合理处理裙房/地下室对基底剪力的影响；
- 解决方案：
- 建议排除地下室；
- 若含大面积裙房，仅纳入2跨裙房参与选波（全裙房会导致上部塔楼剪力过度放大）。
5. 多塔结构：单塔选波还是区域仿真？
规范基于单塔模型制定，多塔选波存在矛盾：
- 各塔周期/质量不同，需独立选波；
- 大底盘/裙房使多塔选波难以实现。
折中策略：
- 按单塔分别选波，独立输出时程结果；
- 若塔楼参数高度相似，可共享地震波。
6. 时程分析的深层价值待挖掘
当前应用局限：
- 弹性分析：仅关注放大系数；
- 弹塑性分析：聚焦基底剪力倍数与损伤模式。
未来方向：
- 深度挖掘时程数据，探索其在性能化设计中的潜力；
- 建立更合理的地震波筛选标准，提升弹塑性分析说服力。
本文观点纯属个人见解，不代表任何机构立场。欢迎交流探讨。
Apologies, Technical Issues Leave No Room for Sentimentality: A Rant on Seismic Wave Selection
(Note: The article is lengthy. If interested, it is recommended to save or read it carefully.)
Challenges in Exceedance Design: Seismic Wave Selection
Every tower’s exceedance design requires elastic time-history analysis for minor earthquakes and elasto-plastic time-history analysis for major earthquakes. The most challenging step? Seismic wave selection — colleagues often spend significant effort on this, yet the selected waveforms barely meet standards.
In May, AutoWave emerged, significantly alleviating this pain point (see AutoWave Wave Selection & Artificial Wave Generation Demo and AutoWave Update Log). This tool is now widely adopted internally, with its latest version resolving many historical issues. However, numerous technical gripes remain. Below are my personal reflections — open to critique and supplementation.
1. Does Wave Selection Rely on the “Spectrum”?
“Reliable” (literally “rely on spectrum”) here refers to compliance with design response spectra. According to codes:
- Spectrum Matching: The waveform’s converted response spectrum must align with the structural period at critical points, with amplitude deviations ≤±20%.
- Base Shear Constraints:
- Single-wave base shear: 65–135% of CQC (Code Spectrum Method) results.
- Multi-wave average: 80–120% of CQC.
- Duration and time intervals must also comply.
![Example of AutoWave wave selection for a 150m frame-core structure]
Practical Challenges
- Long-Period Structures: In Shenzhen, super high-rises (>100m) often have periods >2.5s, lying in the spectrum’s descending segment — long-period waves are scarce.
- Scaling Traps: Scaling factors may force matching at critical periods, but calculated results may still be unreasonable.
- Base Shear Mismatches: Spectrally matched waveforms often fail to meet shear requirements, especially with podiums/substructures (see Section 4).
Code Origins
Technical Code for Concrete Structures of Tall Buildings (JGJ3-2010) [4.3.4]
Elastic time-history analysis applies to:
- Structures >100m or with irregular mass/stiffness.
- Class-A buildings and complex structures.
- Vertically irregular structures.
Clause Interpretation
The goal is supplemental verification of member forces and reinforcement adjustments — if time-history results exceed CQC, local member forces must be amplified.
Paradox: If wave selection relies on CQC compliance, does this undermine the purpose of time-history analysis? Why not apply a unified amplification factor directly?
2. Wave Amplitude: Bigger or Smaller?
Codes allow flexibility in selecting wave amplitudes, sparking debate:
- Conservatives: Advocate larger amplitudes for safety.
- Pragmatists: Argue story-shear adjustment factors suffice — no need to叠加 time-history amplification.
My Stance: Earthquakes are random; code-compliant selection is sufficient. If a large-amplitude wave is randomly chosen, amplify CQC results as required.
3. Elastic vs. Elasto-Plastic Results: Which is Larger?
Experts often cite a 3–5x ratio between major earthquake base shear (elasto-plastic) and minor earthquake CQC results. However, this is fading from scrutiny.
Core Contradictions:
- Elastic results typically exceed elasto-plastic ones, but stiffness degradation may lengthen periods and amplify excitation.
- Outcomes heavily depend on selected waves.
Graham H. Powell’s Warning
“Nonlinear analysis aims not for precise simulation but for design-informing insights. Models need not be perfect, but sufficiently accurate.”
4. Podium/Substructure: To Include or Not?
Structures with podiums/substructures face dilemmas:
- Root Problem: Current software inadequately handles podium/substructure impacts on base shear.
- Solutions:
- Recommend excluding substructures.
- For large podiums, include only 2 spans (full podiums inflate upper tower shear forces).
5. Multi-Tower Structures: Single-Tower Selection or Regional Simulation?
Codes assume single-tower models, creating conflicts for clusters:
- Independent towers require unique wave selections due to differing periods/masses.
- Large podiums/podium-linked towers complicate multi-tower wave selection.
Pragmatic Approach:
- Select waves per tower, output time-history results separately.
- For identical towers, share seismic waves.
6. Unlocking the True Value of Time-History Analysis
Current Limitations:
- Elastic Analysis: Focuses on amplification factors.
- Elasto-Plastic Analysis: Prioritizes base shear ratios and damage patterns.
Future Directions:
- Deepen time-history data utilization for performance-based design.
- Establish rational wave-selection criteria to enhance elasto-plastic analysis credibility.
The views above are personal and do not represent any institutional positions. Feedback and discussions are welcome.