浅论土建结构工程的安全性与耐久性

土建结构工程的施工过程不是单纯重复过程,它有极强的个性和变化,每一项土建项目都有着自身的特点。文章结合实践经验和土建结构工程的特点,探讨提高土建结构工程安全性与耐久性的有效策略。

Predictive maintenance and its applications in civil engineering structures:A review

Structural health monitoring and performance prediction are crucial for smart disaster mitigation and intelligent management of structures throughout their lifespan.Recent advancements in predictive maintenance strategies within the industrial manufacturing industry have inspired similar innovations in civil engineering,aiming to improve structural performance evaluation,damage diagnosis,and capacity prediction.This review delves into the framework of predictive maintenance and examines various existing solutions,focusing on critical areas such as data acquisition,condition monitoring,damage prognosis,and maintenance planning.Results from real-world applications of predictive maintenance in civil engineering,covering high-rise structures,deep foundation pits,and other infrastructure,are presented.The challenges of implementing predictive maintenance in civil engineering structures under current technology,such as model interpretability of data-driven methods and standards for predictive maintenance,are explored.Future research prospects within this area are also discussed.

Effects of RE on the Microstructure of Mg-8Zn-4Al Magnesium Alloys

The effects of RE on the microstrcture of as-cast Mg-8Zn-4Al magnesium alloys were investigated. The results show that the solidification range of Mg-8Zn-4Al-xRE alloys increases with RE additions. A binary eutectic reaction can arise and produce a new phase （Mg：Al：Zn：RE） and the temperature of phase transformation point of the new phase is 412.85 C. In Mg-8Zn-4Al-1.5RE alloy, a small amount of Mg：Al：Zn：RE phase and ε phases are found besides a（Mg）,φand r phases. Also microstructures of Mg-8Zn-4Al alloys can be refined by addition of 1.5% RE obviously.

A Real-Time System for Monitoring Distant Dynamic Displacement of Structures

Based on digital image processing technique, a real-time system is developed to monitor and detect the dynamic displacement of engineering structures. By processing pictures with a self-programmed software, the real-time coordinate of an object in a certain coordinate system can be obtained, and further dynamic displacement data and curve of the object can also be achieved. That is, automatic gathering and real-time processing of data can be carried out by this system simultaneously. For this system, first, an untouched monitoring technique is adopted, which can monitor or detect objects several to hundreds of meters apart; second, it has flexible installation condition and good monitoring precision of sub-millimeter degree; third, it is fit for dynamic, quasi-dynamic and static monitoring of large engineering structures. Through several tests and applications in large bridges, good reliability and dominance of the system is proved.

Characteristics of discontinuities in Heifangtai landslide area in Gansu,China

Loesses are widely distributed all over the world,especially in China.Meanwhile,long-term agricultural irrigation and extreme climate changes have led to frequent geological disasters in the Heifangtai area of Lanzhou,Gansu,China.Of these,landslides are one of the most frequent types of disasters that are harmful to humans and the environment.A landslide is closely related to the lithology,structure,and groundwater of the site and consists of a combination of structure units divided by discontinuities,such as faults,joints,and fi ssures.Therefore,geological surveys,engineering drilling,and trenching are typically used to identify the stratum lithology,structure,and groundwater in order to visually display underground information within a limited depth range.However,these methods have disadvantages.In particular,geological surveys can only describe geological phenomena on the surface,while the cost of drilling and trenching may be high,along with the ineffi ciency of exploration.In this research,the integrated geophysical exploration method was used to analyze the hidden joints,cracks,and other discontinuities and geophysical features of the discontinuities.The results were verified by trench exploration,and large amounts of underground information were obtained,especially the spread and distribution of discontinuities in landslide areas.Such information can be effectively used for carrying out and providing meaningful experiences and lessons in future comprehensive geophysical processing and interpretations related to the prediction and evaluation of landslides.

Engineering properties and microstructure of expansive soil treated with nanographite powder

To reduce geological disasters caused by expansive soil,it is crucial to use a new type of modified material to rapidly improve soil strength instead of traditional soil improvement materials such as lime and cement.Nanographite powder(NGP)has excellent properties,such as high adsorption,conductivity,and lubrication,since it has the characteristics of small size,large specific surface area,and high surface energy.However,previous studies on the improvement of expansive soil with NGP are not processed enough.To study the improvement effect of NGP on expansive soil,non-load swelling ratio tests,consolidation tests,unconfined compressive strength tests,mercury injection tests,and micro-CT tests on expansive soil mixed with different NGP contents were performed.The results show that the non-load swelling ratio,mechanical properties,and porosity of expansive soil show some increasement after adding NGP.The strength of expansive soil reaches the maximum when the NGP content is 1.450%.The cumulative mercury volume and compressive strain of expansive soil reach the maximum with the 2.0%NGP content.Finally,the modification mechanism of swelling,compressibility,microstructure,and compressive strength of expansive soil by NGP is revealed.

Dynamic limit equilibrium analysis of sliding block for rock slope based on nonlinear FEM

Traditional rigid body limit equilibrium method （RBLEM） was adopted for the stability evaluation and analysis of rock slope under earthquake scenario. It is not able to provide the real stress distribution of the structure, while the strength reduction method relies on the arbitrary decision on the failure criteria. The dynamic limit equilibrium solution was proposed for the stability analysis of sliding block based on 3-D multi-grid method, by incorporating implicit stepping integration FEM. There are two independent meshes created in the analysis： One original 3-D FEM mesh is for the simulation of target structure and provides the stress time-history, while the other surface grid is for the simulation of sliding surface and could be selected and designed freely. As long as the stress time-history of the geotechnical structure under earthquake scenario is obtained based on 3-D nonlinear dynamic FEM analysis, the time-history of the force on sliding surface could be derived by projecting the stress time-history from 3-D FEM mesh to surface grid. After that, the safety factor time-history of the sliding block will be determined through applying limit equilibrium method. With those information in place, the structure＇s aseismatic stability ean be further studied. The above theory and method were also applied to the aseismatic stability analysis of Dagangshan arch dam＇s right bank high slope and compared with the the result generated by Quasi-static method. The comparative analysis reveals that the method not only raises the FEM＇s capability in accurate simulation of complicated geologic structure, but also increases the flexibility and comprehensiveness of limit equilibrium method. This method is reliable and recommended for further application in other real geotechnical engineering.

Research and development of seismic base isolation technique for civil engineering structures

Base isolation is one of the most promising alternatives among the structure control methods. In recent decades, base isolation has been seriously considered for civil structures, such as buildings and bridges, subjected to ground motion. The research achievements and development of seismic base isolation technique for civil structures in Huazhong University of Science and Technology (HUST) are introduced. The achievements include project applications, experimental research results and theoretical innovation.

Behaviors of Bellows-Like Origami Patterned Tubes with Trapezoidal Patterns

In this paper, we show one of the possibility utilizing typical origami structures for civil engineering fields such as the bridge bearing support. We numerically investigate axial spring constants and buckling behaviors of bellows-like origami tube structures. The bellows-like origami tube structures, which can be folded because of elastic deformations, work as a kind of spring. If the initial heights of the bellows-like origami tubes are less than 90% of the height of the prismatic tubes without bellows-like folded lines, the spring constants of the bellows-like tubes are very low compared with those of the prismatic tubes. The buckling loads and patterns of the bellows-like tubes vary depending on the initial heights of the tubes.

Geotechnical and Structural Benefits of Utilizing Reinforced Soil in Earth Dams

Approximately, 75% of constructed dams in the world are earth dams. The use of an earth dam is restricted by its geometrical area, weir restriction, and the availability of sufficient amount of earth material. These restrictions can be alleviated by the use of reinforced soil. In this research study the use of geotextile to stabilize and increase the shear strength of clay soils has been investigated. The results show an increase of about 25% in shear strength and cause an enhancement of stability in sandy soil in earth dams.

Sustainability Issues Related to the Engineering Geology of Long Linear Developments

The development of long linear structures such as roads, rail roads, tunnels, canals and pipelines often has unique engineering geology challenges. These include geological modeling, the identification of material strength and support factors, stability and risk issues, material excavation characteristics and the proposal of techniques for overcoming geotechnical problems, which are normally assessed as part of the conventional engineering geological investigation. An additional factor that is becoming increasingly important but is seldom included in investigations is the sustainability of the geotechnical inputs, in contrast to the sustainability of the project which is generally included. Sustainability issues revolve around the non-renewable nature of most construction resources and there is no doubt that the injudicious use of these construction materials and construction water is not sustainable in the long term: it is thus essential that the engineering geo-logical investigation should take cognizance of such issues and be adapted to provide the design engineer with the information that will maximize the sustainability options. This will also require a closer on-going relation-ship between the engineering geologist and the design engineer. This paper highlights significant sustainability issues (note that these differ from conventional environmental issues) and suggests some mitigating solutions. The sustainability issues discussed include primarily material and water usage, with some reference to energy conservation (mostly through alternative material usage and processing techniques and transportation).

Comparative Analysis of Seismic Response Characteristics of Pile-Soil-Stnicture Interaction System

The study on the earthquake-resistant performance of a pile-soil-structure interaction system is a relatively complicated and primarily important issue in civil engineering practice. In this paper, a computational model and computation procedures for pile-supported structures, which can duly consider the pile-soil interaction effect, arc established by the finite clement method. Numerical implementation is made in the time domain. A simplified approximation for the seismic response analysis of pile-soil-structure systems is briefly presented. Then a comparative study is performed for an engineering example with numerical results computed respectively by the finite clement method and the simplified method. Through comparative analysis, it is shown that the results obtained by the simplified method well agree with those achieved by the finite element method. The numerical results and findings will offer instructive guidelines for earthquake-resistant analysis and design of pile-supported structures.

Melody- Usul - Poetic Prosodic Meter Relations in Ottoman-Turkish Music

Language, literature, customs and traditions, music and art are cultural items that were transmitted from generation to generation throughout history. In this context, literature is an important source of music culture that takes inspiration from the customs and traditions of a society. Prosodic meter is echoed in form, usul and general structure in works composed from the divan literature and almost lives in the work. In the same way, when examples of folk literature composed by composers and performed by poets and a^lks are examined, it is observed that there are parallels between literary features and form, structure and rhythmic features. The aim of this paper is to reveal the integral link between Melody-Usul and Meter in Ottoman Turkish Music

Variation law of microscopic pore of loess-like soil after several freeze-thaw cycles in seasonal frozen soil region

In seasonal frozen soil region,the engineering geological properties of loess-like soil will be deteriorated after freeze-thaw cycles.Through the freeze-thaw cycle experiment of remolded loess-like soil,under different freezing temperatures,the authors carried out freeze-thaw cycle tests for 3 times and 20 times,respectively.With mercury intrusion porosimetry and granulometric analysis,from the micro-structure,the authors studied the law that freeze-thaw cycle times and frozen temperature effect on the variation of microscopic pore of loesslike soil.This result can provide theoretical basis for comprehensive treatment of problems in the construction of the project in seasonal frozen loess-like soil region.

Comparative Analysis of High-Rise Reinforced Concrete Structures According to International Seismic Design Codes

The field of earthquake engineering and seismology is of great importance to structural engineers around the world. The location, size and consequences of an earthquake are variable depending on several conditions. Surface conditions, boundary/fault type, distance from the boundary and hypocenter are all elements that dictate the outcome of a seismic event. The paper presents a comparison of seismic provisions of two seismic design codes--EC8 （Eurocode 8） and IBC （International Building Code） 2006, to a high-rise reinforced concrete building. The building is irregular and composes of 20 floors. The equivalent lateral force analysis was performed using the well-known structure program--ETABS （Extended 3D Analysis of Building Systems）. Based on the analysis results （inter-storey index, global damage index, storey displacement, inter-storey drift ratio and base shear）, EC8 was found to be conservative when compared with IBC 2006. The conclusion is that for the design and analysis of high-rise reinforced concrete buildings with certain irregularity, EC8 provisions were considered to be conservative.

Analysis of Soil arching effect for Blind sheet-pile wharf based on ABAQUS

Combined with practical engineering, based on the introduction of soil arching theory, we explore the impact of barrier piles in blind sheet-pile bank connecting structure. Besides, we build a plane strain model by ABAQUS sot＇cware to study the impact of cross section type, the pile spacing and soil properties on soil arching effect. We find that cross section type of the pile has a certain influence on soil stress distribution in front of the barrier piles by comparing circular cross section and rectangular cross section. We also find that clear distance between the barrier piles and cohesive force of the soil have a great influence on that impact. We can increase clear distance between the barrier piles appropriately to improve the efficiency of construction and reduce the proiect cost.

Application Example of Reinforced Concrete Frame Structure Waste Dam in the Proiect of Valley Sanitary Landfill

waste dam is one of the most important infrastructures in the project of valley sanitary landfill. On one hand, it forms the landfill capacity required. On the other hand, it improves the slope stability of waste body. Consequently, I think it is very significant to maintain the stability of waste dana for the whole sanitary landfill. Combining with a project example, aiming at the special geological conditions, we have made three plans of waste dam structure, calculation and analysis comparison respectively. Reinforced concrete frame waste dam is highlighted in the project for its advantages, smoothly solving the three problems in the engineering.

Definition of the general initial water penetration fracture criterion for concrete and its engineering application

A general initial water penetration(seepage) fracture criterion for concrete is proposed to predict whether or not harmful water penetration(hydraulic fracturing),other than microcracking,will occur in concrete structures in a severe high water pressure environment.The final regression,of the different macroscopic failure types in concrete to microscopic ModeⅠ c racking,allows the use of only one universal criterion to indicate the damage.Thus,a general initial water penetration fracture criterion is approximately defined as a strain magnitude of 1000×10-6,based on the concept of tensile strain derived from experimental results in the relevant literature.Then,the locations of harmful water penetration fracture(hydraulic fracture) in the high arch dam mass of the Jinping first class hydropower project are analyzed using the nonlinear finite element method(FEM) according to the proposed criterion.The proposed criterion also holds promise for other concrete structures in high water pressure environments.

Recent researches on disaster prevention and mitigation in civil engineering

Disaster prevention and mitigation for civil engineering structures is an important research field. It involves disaster field forming mechanism, disaster dynamic responses and collapse analysis, disaster prevention and mitigation strategies, and so on. The recent researches and applications on disaster prevention and mitigation in civil engineering are commented, especially for the new researches published in Science China.