Research On Evaluation Method Of Hygrothermal Durability Of Lightweight Steel-framed Building Exterior Wall Assembly In Hot-humid Climate Regions

To achieve high-quality development and implement the concept of green development,the Chinese construction industry takes green construction,saving resources,reducing emission,protecting environment and improving the quality of building as the important ways.Although lightweight steel-framed(LSF)building can theoretically promote the realization of the goal of sustainable development and transformation in the construction industry,it is faced with durability issues such as moisture,mould growth and corrosion in the practice and promotion of hot-humid regions.Failure to achieve the expected building performance and design service life may result in a more serious waste of building resources.Nowadays,the importance of building durability and design service life has become a consensus in the research field,however,it is still not paid attention to in practice,and there is a lack of accurate and practical predictive evaluation methods.Therefore,after exploring the causes and mechanisms of the durability problems of LSF buildings,this research puts forward the concept of hygrothermal durability;and then through the establishment and verification of hygrothermal simulation models,the introduction of three key evaluation indicators including time of wetness(TOW),mould growth risk(RHTT)and predicted service life(Est.life)of lightweight steel for quantitative analysis of hygrothermal durability,as well as the analysis of related influencing factors and mechanisms of hygrothermal durability,and finally summarized and established a method for evaluating hygrothermal durability of LSF wall assemblies.First of all,in view of the durability problem caused by the insufficient hygrothermal performance of the exterior wall assembly of LSF buildings in hot-humid regions,through literature review and research on the application status of LSF building technology,the relationship of "material and construction-hygrothermal performance-durability" is demonstrated and helps to put forward the concept of "hygrothermal durability"(see Chapter 2).Secondly,to achieve quantitative evaluation and prediction of the hygrothermal durability of the LSF wall assembly,the research has conducted the measurement of the hygrothermal performance,the simulation and verification of the hygrothermal performance,and the evaluation of hygrothermal durability and the uncertainty and sensitivity analysis on the influencing factors of the LSF wall assemblies.These four stages laid the foundation for the establishment of a hygrothermal durability evaluation method.First,determine the typical exterior wall assemblies of LSF building based on literature review and research on the current practice(see Chapter 2),and then select four exterior wall assemblies as experimental specimens for 12 months of measurement.Through the experiment,the temperature and relative humidity parameters of different locations and interfaces in the LSF wall assemblies under different indoor and outdoor environmental conditions throughout the year were obtained and to summarize the hygrothermal performance characteristics of different LSF wall assemblies by comparison.(see Chapter 3);Second,use WUFI 2D software to establish the hygrothermal simulation models of the above four typical LSF wall assemblies,and then perform a comprehensive accuracy check on the model predictions with the measured data to verify the effectiveness of the simulation models(see Chapter 4);Third,study and introduce three indicators of TOW,RHTT and Est.life to quantitatively evaluate hygrothermal durability of LSF wall assembly(see Chapter 5);Fourth,to further ensure the robustness of the simulation and evaluation of hygrothermal durability,the study adopts the uncertainty and sensitivity analysis method.The material parameters,meteorological parameters,building environment,climate and indoor conditions that may appear in the process of LSF building design and practice are analyzed to clarify the possible impact of each element on the hygrothermal durability of LSF wall assemblies.The influence and its mechanism of action provide a more comprehensive reference and guidance for the evaluation and application of hygrothermal durability of LSF wall assembly in hot-humid regions(see Chapter 6).Finally,based on the above work,a hygrothermal durability evaluation method of LSF wall assembly is established,and then an effective hygrothermal durability optimization frame is proposed based on the evaluation method and related research results.Design principles of hygrothermal durability of LSF wall assemblies in hot-humid regions are summarized(see Chapter 7).The results of this research have significance in both research and practice: In the field of research,it provides references for research on the hygrothermal durability evaluation methods of LSF buildings or similar lightweight buildings in hot-humid climates and other climatic regions.In the practical field,it helps for improving the hygrothermal durability of LSF buildings in hot-humid regions and provides references and methods for the hygrothermal durability design of LSF wall assemblies and other envelope components to ensure LSF building become a truly effective and sustainable solution to promote the sustainable development and transformation of the building construction industry.