Application of Key Technologies in Green School Buildings: Taking Sino-German Future City Primary School as an Example

Green building is a manifestation of the response to the national“dual carbon”strategy.With the large-scale promotion of green buildings,the country has successively issued multiple evaluation standards for green buildings.Schools are places for preaching,teaching,and solving doubts,and the campus environment plays an important role in improving students’learning efficiency and promoting their physical and mental health.This article is based on the“Green Building Evaluation Standards”GB/T 50378-2019,analyzing and exploring the integration and application of key technologies in green schools,providing reference for green building designers.

Current situation and development of solar heating technology in China

It is introduced the current situation and development for solar heating technology including passive solar heating and solar heating combisystems in China in this paper. Combined with the engineering application projects, the author gave the technical and economic analysis of the passive solar and solar heating combisystems in China and summarized the developing obstacle and the spreading tactics for raising marketing of the solar heating in China.

New Approach and Alternate Criterion for Heat-transfer Analysis of Building Walls and Its Applications

Energy consumed by buildings accounts for approximately one-third of the total energy consumption of the society.Moreover,energy systems employed in buildings emit hazardous pollutants,such as,NOx,PM2.5 and CO2,into the environment.Consequently,increasing the energy efficiency of buildings constitutes an important problem concerning the field of building-energy and environment conservation.Thermal resistance and capacitance are two important thermophysical properties of building walls significantly impacting their heat-transfer performance.Traditional theories concerning these properties,however,face certain limitations:(1)the concept of thermal resistance is only valid for one-dimensional,steady heat conduction without existence of an internal heat source;(2)thermal resistance and capacitance are relevant,and can,therefore,not be used to analyze heat-transfer and storage performance,respectively,of building walls.Based on the entransy-dissipation-based impedance theory,a new approach towards realization of heat-transfer analysis and optimization has been proposed in this study.The weightiness of thermal resistance and capacitance with regard to heat-transfer performance has been described along with deduction of the corresponding substitutional relation via illustrative examples.The proposed approach has been demonstrated to effectively overcome aforementioned limitations of building energy conservation problems.

An adjusted energy-saving quantity calculation method for building energy-efficient retrofit

Aiming at a comprehensive assessment of energy-saving retrofitting effect on existing buildings,a calculation method is developed to adjust energy-saving quantity in standard condition for comparison under the same conditions. A mathematical model,method theory and calculation steps are given. Error analysis results show that this method can be applied accurately to practical engineering projects. In a case study of energy-saving quantity assessment before and after retrofitting on a certain hospital in Shanghai,with energy simulation software TRNSYS,detailed application of this method is introduced and analyzed. The method is applied to the case of energy-saving quantity assessment to a hospital in Shanghai before and after retrofitting with the energy simulation software TRNSYS.

Utilization of Basalt Saw Mud as a Spherical Porous Functional Aggregate for the Preparation of Ordinary Structure Concrete

To promote the production and application of artificial aggregates,save natural sand resources and protect the ecological environment,we evaluated the feasibility of using spherical porous functional aggregates(SPFAs) formed by basalt saw mud under autoclave curing in ordinary structural concrete.In our work,two types of prewetted functional aggregates were taken as replacements for natural aggregates with different volume substitution rates(0%,5%,10%,15%,20%,25%,and 30%) in the preparation of ordinary structural concrete with water-to-binder ratios(W/B) of 0.48 and 0.33.The effects of the functional aggregate properties and content,W/B,and curing age on the fluidity,density,mechanical properties and autogenous shrinkage of ordinary concrete were analyzed.The experimental results showed that the density of concrete declined at a rate of not more than 5%,and the 28 d compressive strength could reach 31.0-68.2 MPa.Low W/B,long curing age and high-quality functional aggregates were conducive to enhancing the mechanical properties of SPFAs concrete.Through the rolling effects,SPFAs can optimize the particle gradation of aggregate systems and improve the fluidity of concrete,and the water stored inside SPFAs provides an internal curing effect,which prolongs the cement hydration process and considerably reduces the autogenous shrinkage of concrete.SPFAs exhibits high strength and high density,as well as being more cost-effective and ecological,and is expected to be widely employed in ordinary structural concrete.

Clean-energy utilization technology in the transformation of existing urban residences in China

Clean-energy substitution technology for existing residential buildings in cities is an inevitable choice for sustainable development and low-carbon ecological city construction.In this paper,the current status of energy-saving renovation and renewable-energy applications for existing residential buildings in various cities in China was summarized by using statistical methods.The geographical distribution of clean-energy power generation in primary energy production in China was explored in depth.According to different climatic divisions for existing urban residences,clean-energy production and consumption were analyzed and predicted based on the STIRPAT model.The results show that the energy consumption of urban residential buildings in 2016 increased by 43.6%compared with 2009,and the percentage of clean energy also increased from 7.9%to 13.4%.Different climatic regions have different advantages regarding clean energy:nuclear power generation leads in the region that experiences hot summers and warm winters,whereas wind and solar power generation lead in the cold and severely cold regions.The present results provide basic data support for the planning and implementation of clean-energy upgrading and transformation systems in existing urban residences in China.

The Influence of Two Natural Reinforcement Fibers on the Hygrothermal Properties of Earthen Plasters in Mogao Grottoes of China

Murals in Mogao Grottoes consist of three parts:support layer,earthen plasters and paint layer.The earthen plasters play a key role in the preservation of murals.It is a mixture of Dengban soil,sand,and plant fiber.Two different natural fibers,hemp fiber and cotton fiber,were reinforced to earthen plasters in the same percentage to evaluate the influence on hygrothermal performance.The two types of earthen plasters were studied:one containing hemp fiber in the fine plaster(HFP)and the other containing cotton fiber in the fine plaster(CFP).Specific heat capacity,dry thermal conductivity,water vapor permeability,and sorption isotherms were investigated.The results showed that the difference between two natural fibers has much more impact on the hygric properties(water vapor permeability and sorption isotherms)of earthen plasters than on their thermal performance(specific heat capacity and dry thermal conductivity).The CFP with higher density has higher thermal conductivity than the HFP with lower density.But no significant differences of specific heat capacity were observed.Compared with HFP,CFP used in murals can reduce the rate of water transfer and prevent salt from transferring water to the mural surface.The overall findings highlight that all these features of CFP are beneficial to the long-term preservation of murals.The study of the earthen plasters in Mogao Grottoes is of general significance,and the measured properties can be used to obtain coupled heat and moisture analysis of the earthen plasters and to dissect the degradation mechanism of murals.

A Theory on Increasing the Heat Transfer Performance of Building Wall

The target of traditional thermal conductivity of wall research is the spatial distribution form.In these studies,the change of thermal conductivity with temperature is neglected.Meanwhile,case studies are always used.This method needs large computation and it is hard to obtain the optimal result.In order to overcome the problems,a new approach has been put forward in this paper.Different from the traditional approach,the new approach solves an inverse prob­lem under the concept of passive ideal energy-saving buildings to obtain the optimal distribution of heat ability with temperature on an external wall.The result for a typical summer day shows the heat ability distribution of a wall in summer is a staircase.It is similar to the heat pipe.It is also found that the optimal heat transfer property of the exter­nal wall is closer to the heat pipe when its heat capacity per square meter(ρc_(p)L)is of extreme value.This study can provide guidance to researchers in building materials.

Window Views of Wards in Foreign Hospitals

Through the collection and systematic analysis of documents related to window views of hospitals,it is found that natural window views had a significant impact on patients’health benefits.The research focused on three aspects:“shortening length of stay”,“pain reduction”and“improvement of recovery rate”,mainly covering three types of patients:“heart patients”,“postoperative patients”and“patients of rehabilitation centers”.Based on the above analysis,summary and sorting,new directions and perspectives of hospital environment design and research under the concept of comprehensive health of people’s physiological,psychological and social adaptation will be obtained to provide references for the research and practice of health architecture,rehabilitation architecture,biophile design and other fields.

Review on the recent progress of nearly zero energy building frontiers in China

Energy efficiency improvement in Chinese construction has progressed rapidly over the past two decades.Nearly zero energy buildings(NZEBs),as an integrated solution for energy-efficient construction,have gained significant attention during China's 13th Five-Year Plan period,with continuous maturation of the technical system.In this study,a research framework built upon the accomplishments of China's National Key Research and Development Program is developed,and an in-depth analysis of the most cutting-edge research is provided by thoroughly reviewing the work conducted earlier.Developing NZEB in China has been categorized into three stages based on the characteristics of technological development:(1)definition and standards,(2)demonstration and promotion,and(3)cross-domain integration.This study discerns four noteworthy development trends by examining comprehensive data spanning the last decade from 100 NZEB and zero energy building.Further,a comprehensive analysis of essential technology advancements in line with these identified trends is performed.The issues and challenges arising from the increased application of renewable energy in the context of China's carbon peak and carbon neutrality goals have also been discussed.Finally,based on this analysis,the challenges and corresponding suggestions for future research directions were proposed to help guide future studies exploring emerging trends in the NZEB field.

Lessons learned from the “5.12” Wenchuan Earthquake:evaluation of earthquake performance objectives and the importance of seismic conceptual design principles

Many different types of buildings were severely damaged or collapsed during the May 12, 2008 Great Wenchuan Earthquake. Based on survey data collected in regions that were subjected to moderate to severe earthquake intensities, a comparison between the observed building damage, and the three earthquake performance objectives and seismic conceptual design principles specified by the national ＂Code for Seismic Design of Buildings GB50011-2001,＂ was carried out. Actual damage and predicted damage for a given earthquake level for different types of structures is compared. Discussions on seismic conceptual design principles, with respect to multiple defense lines, strong column-weak beam, link beam of shear walls, ductility detailing of masonry structures, exits and staircases, and nonstructural elements, etc. are carried out. Suggestions for improving the seismic design of structures are also proposed. It is concluded that the seismic performance objectives for three earthquake levels, i.e., ＂no failure under minor earthquake level, ＂＂repairable damage under moderate earthquake level＂ and ＂no collapse under major earthquake level＂ can be achieved if seismic design principles are carried out by strictly following the code requirements and ensuring construction quality.

Modified precise time step integration method of structural dynamic analysis

The precise time step integration method proposed for linear time-invariant homogeneous dynamic systems can provide precise numerical results that approach an exact solution at the integration points. However, difficulty arises when the algorithm is used for non-homogeneous dynamic systems, due to the inverse matrix calculation and the simulation accuracy of the applied loading. By combining the Gaussian quadrature method and state space theory with the calculation technique of matrix exponential function in the precise time step integration method, a new modified precise time step integration method （e.g., an algorithm with an arbitrary order of accuracy） is proposed. In the new method, no inverse matrix calculation or simulation of the applied loading is needed, and the computing efficiency is improved. In particular, the proposed method is independent of the quality of the matrix H. If the matrix H is singular or nearly singular, the advantage of the method is remarkable. The numerical stability of the proposed algorithm is discussed and a numerical example is given to demonstrate the validity and efficiency of the algorithm.

Comparison of seismic actions and structural design requirements in Chinese Code GB 50011 and International Standard ISO 3010

This papcr presents a comparison between the Chinese Code GB50011-2001 and the International Standard ISO3010:2001(E),emphasizing the similarities and differences related to design requirements,seismic actions and analytical approaches.Similarities include:earthquake return period,conceptual design,site classification,structural strength and ductility requirements,deformation limits,response spectra,seismic analysis procedures,isolation and energy dissipation, and nonstructural elements.Differences exist in the following areas:seismic levels,earthquake loading,mode damping factors and structural control.

Practical elasto-plastic damage model for dynamic loading and nonlinear analysis of Koyna concrete dam

The elasto-plastic damage model for concrete under static loading,previously proposed,was extended to account for the concrete strain-rate through viscous regularization of the evolution of the damage variables.In order to describe the energy dissipation by the motion of the structure under dynamic loading,a damping model which only includes stiffness damp stress was proposed and incorporated into the proposed rate dependent model to consider the energy dissipation at the material scale.The proposed model was developed in ABAQUS via UMAT and was verified by the simulations of concrete specimens under both tension and compression uniaxial loading at different strain rates.The nonlinear analysis of Koyna concrete dam under earthquake motions indicates that adding stiffness damp into the constitutive model can significantly enhance the calculation efficiency of the dynamic implicit analysis for greatly improving the numerical stability of the model.Considering strain rate effect in the model can affect the displacement reflection of this structure for slightly enhancing the displacement of the top,and can improve the calculation efficiency for greatly reducing the cost time.

Electrical conductivity changes of bulk tin and Sn-3.0Ag-0.5Cu in bulk and in joints during isothermal aging

The changes of electrical conductivity （resistance） between Sn-3.0Ag-0.5Cu solder joints and printed circuit board （PCB） assembly during aging at 125℃ were investigated by the four-point probe technique. The microstructural characterizations of interfacial layers between the solder matrix and the substrate were examined by optical microscopy and scanning electronic microscopy. Different types of specimens were designed to consider several factors. The experimental results indicate that electrical conductivities （resistances） and residual shear strengths of the solder joint specimens significantly decrease after 1000 h during isothermal aging. Microcracks generate in the solder matrix at the first 250 h. Besides, the evolutions of microstructural characterizations at the interface and the matrix of solder joints were noted in this research.

Effects of Vibration Technology and Polyvinyl Acetate Emulsion on Microstructure and Properties of Expanded Polystyrene Lightweight Concrete

To prevent expanded polystyrene （EPS） beads from rising up to the surface in the molding process of EPS lightweight concrete, vibration with pressure was applied and the polyvinyl acetate （PVA） emulsion was adopted to improve its mechanical properties. The mechanical properties, thermal properties and durability of EPS lightweight concrete were tested. The microstruetures of EPS lightweight concrete were observed by scanning electron microscope （SEM）. Vibration with pressure reduces the number of small cracks. The 180 d compressive strength and flexural strength increase obviously as a large amount of PVA was added. The mixed amount of PVA has no obvious influence on the thermal performance when it is not more than 10% of the cement. Vibration with pressure and surface modification of EPS beads by PVA improve the combination of EPS beads with cement stone and the mechanical properties of EPS lightweight concrete.

Life Estimation of Reinforced Concrete Members after Fire

To solve the problem of life estimation of reinforced concrete （RC） members after fire, an analysis is made of the resistance of RC members after fire. On basis of the resistance, the life of RC members after fire is analyzed by using JC （Jukes and Cantor） method. Then the calculation models for the resistance and the life estimation of RC members after fire are put forward, and an example analysis proves their reliability and accuracy.

Experimental study on heat exchange of several types of exchangers

Aiming at the ground-coupled source heat pump that possesses the shortcomings of occupying larger land,this article studies the heat exchanged of heat exchanger in piling,and compares it with common heat exchangers buried directly. The result indicates that the heat exchanger makes the best use of structure of building,saves land,reduces the construction cost,and the heat exchanged is obviously more than exchangers buried directly. In winter condition,when W-shape pipe heat exchanger in pile foundation is 50 m deep and diameter is 800 mm,it transfers 1.2-1.3 times as large as the one of single U-shape buried directly at the flow rate of 0.6 m/s,whose borehole diameter is 300 mm. And in summer condition it does about 2.0-2.3 times as that of U-shape one.

On precise time integration method for non-classically damped MDOF systems

In the complex mode superposition method, the equations of motion for non-classically damped multiple-degree-of-freedom （MDOF） discrete systems can be transferred into a combination of some generalized SDOF complex oscillators. Based on the state space theory, a precise recurrence relationship for these complex oscillators is set up; then a delicate general solution of non-classically damped MDOF systems, completely in real value form, is presented in this paper. In the proposed method, no calculation of the matrix exponential function is needed and the algorithm is unconditionally stable. A numerical example is given to demonstrate the validity and efficiency of the proposed method.

Prevention and Control of Chlorella for C30 Concrete Surface with Coral Aggregate

C30 coral aggregate concrete with chlorella control effect was prepared by adding nano-TiO_(2) and hydrophobic material,and the effects of nano-TiO_(2) and hydrophobic material on the basic properties of C30 coral aggregate concrete and chlorella control effect under different experimental conditions were compared.The experimental results show that nano-TiO_(2) and hydrophobic materials have a certain degree of influence on the basic properties of concrete,but the influence is not significant.Under long-term immersion,nano-TiO_(2) and hydrophobic materials can inhibit the growth of Chlorella vulgaris.The maximum fluorescence value of concrete is decreased by 53.6% after adding TiO_(2),and the maximum fluorescence value of concrete is prolonged by 20%(1 day).The maximum fluorescence value of concrete is decreased by 67.7% after adding hydrophobic materials,and the maximum fluorescence value of concrete is also prolonged by 20%(1 day);Under the condition of simulated tidal water,the inhibition effect of Nano-TiO_(2) on the growth degree and growth rate of Chlorella vulgaris is weakened,at this time the maximum fluorescence value of concrete mixed with nano-TiO_(2) is decreased by 50.5%,and the maximum fluorescence value is only prolonged by 14.3%;while the inhibition of hydrophobic materials on the growth degree and growth rate of Chlorella vulgaris is enhanced significantly,and the maximum fluorescence value of concrete with hydrophobic materials is decreased by 80.3%;the maximum fluorescence time is prolonged by 114.3%.