《水工混凝土结构设计规范》(NB/T 11011—2022)是水电工程钢筋混凝土结构设计的主要依据。然而该标准中有关设计基准期与分项系数等条文在应用中仍存在一些疑难点或不易明确的问题,易造成工程应用偏差。结合笔者团队多年大中型水电站水工结构设计经验,对标准中设计基准期、使用年限、目标可靠指标、可变作用取值、分项系数设置、地震组合等方面的问题进行了分析探讨,发现水电行业的结构目标可靠指标β_t相比国内其他行业处于较低水平,相关规范关于统计类可变作用设计基准期的规定缺失,目前的持久状况分项系数取值不能保证水工混凝土结构安全度总是高于房建工程;基于此,提出了提高目标可靠指标、 增加楼面及平台活荷载设计基准期 100 a规定等相应建议措施,以期为工程设计应用及标准修编提供参考。

[Objective] The Code for Design of Hydraulic Concrete Structures (NB/T 11011—2022) is the main reference for the design of reinforced concrete structures in hydropower projects. However, certain provisions in the standard, such as those concerning the design reference period and partial factors, remain difficult to apply or insufficiently clear, which may cause deviations in engineering practice. [Method] Drawing on many years of design experience with hydraulic structures of large and medium-sized hydropower stations, we analyze and discuss the issues related to the design reference period, service life, target reliability index, variable action values, partial factor setting, and seismic combinations. We also conduct cross-industry comparisons with building construction, highway, railway, and port codes, parameter back-analysis, and engineering practice verification. [Result] The structural target reliability index β_t in the hydropower sector was set at a relatively low level compared with that of other domestic industries, and that the statistical data on which it was based were outdated, making it difficult to reflect the current reliability level of hydraulic structures. Moreover, relevant provisions on the design reference period of statistical variable actions were missing, while the prescribed live load values for main and auxiliary powerhouse buildings and platforms of hydropower stations were found to match more appropriately with large and medium-sized plants designed for a 100-year reference period. Although the categories of partial factors differ from those in other sectors, the variability of the basic variables and their interactions that these factors account for is essentially consistent, and inclusions and overlaps exist in their conceptual definitions. The current values of partial factors for persistent design situations cannot always ensure that the safety level of hydraulic concrete structures is higher than that of building structures. In addition, treating seismic action solely as an accidental effect is inappropriate, as it ignores the fact that small- and medium-scale earthquakes are now statistically analyzable, which may lead to insufficient reliability in seismic combination limit states. [Conclusions] In response to these problems, we suggest that 1) future revisions of the standard improve the setting of the target reliability index β, differentiate the values of β according to the design reference period, and strengthen reliability research as well as statistical studies for different structure types such as dams, tunnels, powerhouses, and frame structures, so as to gradually achieve differentiated β settings across structure types; 2) specify a single design reference period for hydraulic concrete structures, with 100 years set as the benchmark in line with the service requirements of most major structures and a corresponding β value to match current engineering practice; 3) limit the design reference period, remove the specification of controllable variable actions, and adjust partial factor values to improve the safety level for persistent design situations. Finally, the paper outlines the equivalence relationship between partial factors in hydropower projects and those in other industries. The conclusions are intended to serve as a reference for engineering design practice and for future code revisions.