As the civil engineering industry undergoes a significant transformation, intelligent technologies have introduced novel technical means and tools for the innovation and advancement of structural health Monitoring （SHM） in civil engineering, thereby broadening the research scope in various aspects of SHM systems. This paper systematically sorts out and comprehensively reviews the current status of research on intelligent technologies applied in the field of SHM, covering areas such as computer vision, machine Learning, intelligent robots, and drones. Based on the review of existing research results, this paper looks forward to the development trends and prospects of intelligent technologies in the field of SHM, and deeply explores the innovations and challenges brought about by the integration of SHM and intelligent disciplines.

This paper presents main aspects of the structural design of Sichuan University Multi-Discipline Cross-Integration Platform and Art Education Center,including foundation,basement,structural arrangement,seismic fortification measures,structural analysis results and performance-based seismic design.The building characterizes complex shape,connected structure,large span and long cantilever.Critical issues of the structural design and methodology are presented with abovementioned characters. Analysis method and conclusions may be useful to similar projects.

With the continuous refinement of metallurgical technology in recent years, more and more high-strength structural steel has been emerging, its excellent physical and mechanical properties make it quickly applied to related projects. Similar to plain steel, the problem of fire resistance of high-strength steel structure is still very prominent. In the past ten years, the research on the fire resistance of high-strength steel has also started, and this paper makes a systematic investigation and summary on the high-strength steel fire-fighting high temperature and post-fire mechanics performance, high-strength steel components and node fire resistance, and high-strength steel structure fire resistance, and finally discusses and looks forward to the problem of under-research. At present, the research on the fire resistance performance of high-strength steel structure is still in the preliminary stage, and studies have shown that the high-temperature mechanics and fire resistance of high-strength steel have different degrees of deviation from the existing domestic and foreign relevant codes, and cannot be directly used.

Scientific and reasonable structural seismic damage assessment is of great significance for improving urban seismic resilience and smart operation and maintenance. Aiming at the actual needs and important problems in the construction of resilient cities at the present stage, and catering the latest paradigm of structural seismic damage assessment oriented to “global, dynamic and real-time”, allocating digital-based multi-model feature fusion and physical-based multi-level numerical simulations as two basic elements and relying on new techniques of deep learning, digital twin and knowledge fusion, a theoretical framework for near-real-time seismic damage assessment of structures based on digital-physical model hybrid interactive feedback is established. The main research content and key scientific issues in the framework are elaborated. The proposed theoretical framework is expected to improve the real-time and intelligence of structural seismic damage assessment, and help promote the construction of resilient cities and the smart operation and maintenance of urban systems.

Nondestructive testing technology of timber structure plays an important role in the preventive protection of ancient wood buildings and the intelligent operation and maintenance of modern timber structures. This paper classifies ten testing methods according to their basic principles, and introduces their application scope, research status and existing problems, including visual testing, stress wave, drilling resistance, and cutting-edge exploratory methods such as computer vision, piezoelectric sensing, Electromagnetic wave. Finally, the development trends of wood structure nondestructive testing are discussed.

Li Zijian Art Museum is a mega-steel-structure with mega-frames and braces.A ring atelier is supported by 17 main trusses suspended by 3 mega-columns.The main trusses are connected as a whole by an inside ring truss and an outside ring truss.The largest span along the ring atelier is 44.6 meters.Based on the performance-based design method,the performance objectives and design specifications of key components are proposed.Performances of the structure are verified under different levels,including elastic analysis under frequent earthquake,unyielding verification and elastic analyses under medium earthquake and elasto-plastic analysis under rare earthquake.The results show that a few plastic hinges formed in some braces and the first layer of the mega-columns.Good seismic behavior performed and seismic indices of key components can satisfy the predefined performance requirements.

Deterioration of steel infrastructure due to service loads and environmental agents has been one of the major concerns in civil engineering community. Recently, iron based shape memory alloy （Fe-SMA） materials have been considered as an anlternative in retrofitting of aging steel structurs. Based on the shape memory effect, they can be conveniently used to apply prestress in comparison with traditional prstress techniques. This paper presents a state-of-art on fatigue strengthening of steel structures by using Fe-SMA materials, including the recovery stress of Fe-SMA materials, fatigue strengthening based on Fe-SMA materials, and effects of environmental temperatures and fatigue loading on the strengthening systems. The Fe-SMA retrofitting system is also compared with that by NiTinol-FRP hybrid materials.

Combined with engineering examples, in the case of a single-storey garage and a two-storey garage respectively, the foundation form of raft and column pier and anti-uplift pile （reduced settlement pile） is adopted, and the number of anti-uplift piles is calculated according to the anti-floating requirements; under-column compensation piles, four piles under the column are used in this project to balance the settlement in two directions; the method of inverted beam and girder floor is used to verify the high water level anti-floating requirements of the foundation; the composite foundation method is used to verify that the water level is below the foundation; strive to achieve reasonable calculations for both anti-floating and compressive working conditions. This method is a relatively simplified algorithm, but it relies on the refinement of parameters such as soil coefficient of subgrade reaction, pile stiffness coefficient, and cap effect coefficient.

Combined with the actual project,use SAP2000 finite element software to establish a 5×5 span underground garage structure model without beams, comprehensively consider factors such as the thickness of the soil, the type of construction vehicles and the parallel situation,and determine the unfavorable layout of construction vehicles according to the principle of influence lines,and obtain construction vehicles,etc. The effect of uniformly distributed load is compared with the commonly used construction load of 5 kN/m² in the design.The results show that the equivalent uniform load of construction vehicles is mostly greater than 5 kN/m²,and the equivalent uniform load value of construction vehicles decreases with the increase of the cover soil thickness,and increases with the increase of the vehicle load.Comprehensively considering the equivalent uniformly distributed loads of the four construction vehicles,the recommended values for the equivalent uniformly distributed loads of the construction vehicles are put forward, and the results can be used as reference for engineering design.

With development of the construction industry,construction of large span steel structures in our country started extensively in our country.On the one hand,this promotes improvement of large span steel structural design,on the other hand, it also highlights some common design problems in the steel structures.This paper discusses basic steps for large span steel structural design and research.This study also discusses the design process of elastoplastic analysis in structural design and effect of structural form on ultimate bearing capacity,and summarizes frequently asked questions in the structural detail design about the selection of bearing types and the influence of the joint detail on mechanical properties of the structure.Finally,this paper presents design considerations and improvement measures to these common problems.

Offshore wind turbines bear more complex environmental loads than onshore wind turbines. It is essential for the design and safety operation of offshore wind turbines to reasonably assessment environmental loads. The method of wind and wave load calculation in offshore wind turbine specifications are roughly same, but there are differences in the selection of calculation parameters, which may make the calculation results of wind and wave load different. It is necessary to carry out comparative analysis on the calculation methods of wind and wave load in wind turbine specifications to explore the influence of different methods on the calculation of wind and wave load. This paper selects the latest specifications, including CCS specification, DNV GL specification and IEC specification to compare the differences of wind load and wave load calculation. Combined with typical examples, the comparative analysis is carried out. The results show that the maximum wind load of CCS and IEC is larger than that of DNV GL, and the consideration of wind turbulence is more conservative. For rough components, the peak wave load of DNV GL specification is about 4 %~14 % larger than that of CCS. According to the above analysis results, some suggestions are put forward for the selection of wind and wave load calculation methods and parameter selection of offshore wind turbines, which can be used for reference in the design of offshore wind turbines.

In civil engineering, steel or concrete beams need to be reinforced to increase its load-bearing capacity and service life due to damage, aging and bearing capacity degradation under service conditions. At present, the application of Fe-based shape memory alloys （Fe-SMA） to reinforce the structure has been proved to be an efficient and reliable method. This article reviews the shape memory properties, activation recovery properties and basic mechanical properties of Fe-SMA. And the principle of thermal excitation for structural reinforcement using Fe-SMA is described. On this basis, the connection methods between Fe-SMA members and the reinforced structure are reviewed from the aspects of reinforcing steel beams and concrete beams, and the existing research and applications are classified, analyzed and summarized according to the needs and purposes of reinforcement. Finally, in view of the shortcomings of the current research and application, this paper puts forward the perspectives that need to be researched, in order to promote the reasonable application of Fe-SMA in the field of civil engineering.

The code for Seismic Design of Buildings （GB 50011—2010, 2016 edition） and the Technical Specification for Concrete Structures of Tall Buildings （JGJ 3—2010） both have provisions for performance-based seismic design, albeit with slight differences. Engineers, in their execution, may inevitably encounter confusion due to these variations. This paper analyzes the provisions of both codes regarding seismic performance design, and explains the meanings of seismic performance objectives and seismic performance levels from the perspective of load-displacement curves. It also compares the design parameters of the two codes. By listing 29 engineering cases adopting performance-based design methods, this study analyzed the basis for determining displacement indicators. Based on the analyses of these two aspects, the differences in the specifications regarding performance-based design are summarized, and design recommendations are provided.

The paper takes the tied arch bridge of steel tube truss arch rib as the research object. The combined stiffness of the arch rib is calculated by the combined column. Considering the triangular truss as the assembly in the rib surface,after the layout optimization, the corresponding combined effect coefficient is obtained, and the critical axis force of in-plane stability is determined by the interaction between arches and beams. For out-of-plane stability, the critical axis force is determined by the k-type truss as the longitudinal joint system.For the four-tube combination of the single arch rib arrangement, considering the non-directional load effect of the suspender tensile force offset,this arrangement provides the arch with the uprighting force to enhance the stability.Through an example,the practicality of the method described in this paper is demonstrated by the whole process of checking the stability of the concrete-filled steel tubular truss tied arch bridge with a main span of 120 m.

On Dec.22,2021, an earthquake with magnitude of 4.2 occurred in Changzhou, Jiangsu Province, which is sensible in Shanghai. The field-structure seismological array,which is recently established at different campuses of Tongji University, got the efficient acceleration signal of this earthquake. The peak ground and building acceleration of five stations are in the range of 1-5 cm/s² and 1-6 cm/s² respectively. By comparative analysis of the field and building signal in time and frequency domain, the peak ground acceleration, response spectrum of ground signal along with the dynamic characteristic of the building signal were studied. The influence of the earthquake on Shanghai is relative sensible to low buildings of short natural period. Rapid intensity assessment by field and structure signal is discussed and the intensity of different campus is 1 to 3.

With the development of longer blade and higher tower,vibration problems of large-scale wind turbines operating continuously in harsh environment have become increasingly prominent, which brings great risks to the sustainable development of wind power industry.Under operation in generating electricity, the vibration of wind turbine has obvious aerodynamic damping and periodic components due to the spinning of the wheel.It thus becomes important to accurately obtain the dynamic characteristics of wind turbine under operation. In addition, due to the sources of uncertainty such as measurement errors, modeling errors, and data length,the precision of identified modal parameters results is also a key issue for the evaluation of safety performance.In this paper,operational modal analysis and uncertainty quantification is conducted using stochastic state-space model and maximum likelihood estimation considering harmonic components in measured vibrational data. The Expectation-Maximization （EM） algorithm for calculating the maximum likelihood and the Cramér-Rao Bound （CRB） bound for uncertainty quantification of modal parameters are adopted. With a large-scale wind turbine in service as a case study,the differences of modal parameters in different tower directions and the variations of modal parameters and their uncertainties of the wind turbine under different working conditions are analyzed and compared.

Taken a super high-rise frame-core wall structure as an example,comprehensive optimization of the original structural design calculation parameters,structural loads,walls,columns,beams,plates,roof steel structure brackets and raft foundation was conducted,where the structural stiffness,weight and cost were set as control objectives,while meeting the structural specifications and transfinite review requirements.Comparison of the stiffness,seismic performance and cost between the original design and the optimized one was conductedby PKPM software.The results show that all the indicators meet the specification requirements,and benefits such as reduced structural weight,reduced earthquake action, more reasonable stiffness distribution,increased ductility and structural safety,increased indoor space,shortened construction period and reduced construction cost of 22 million 946 thousand and 800 yuan profit.

In order to study the performance of complex joints of an transfinite steel structure building under rare earthquake, the finite element software ABAQUS was used to simulate the stress and destruction effect under ultimate load of key joints of transfer truss. The results show that： the Mises stress in other areas of the joint is significantly lower than the yield strength of the material, except that the local contact angle of each component reaches the yield strength and enters into plasticity. The whole joint basically keeps elastic state without obvious plastic development, which meets the performance target under rare earthquake. When the ultimate destruction occurs, the component area is destroyed prior to the node area, and the design of each joint meets the requirements of safety reserve. It can be seen that in the joint design of this project, the joint diaphragm and stiffening steel frame are taken as the main load transfer components, and the equivalent area principle is adopted to ensure that the bearing capacity of the joint is greater than the sum of the bearing capacity of each member entering the joint, and the structural design requirements of strong joint and weak member are ensured.

At present, there are various types of external thermal insulation composite systems （ETICS）used in China and the corresponding anti-peeling design method needs to be improved. Further studies are also needed on the insufficient interlayer bonding strength and the detailing defects, deterioration mechanism, identification and evaluation of falling-off of ETICS. Focusing on the complexity of pealing mechanism and difficulties on evaluating deterioration and identifying falling-off risk, this research summarized the main detailing systems, anti-peeling design method and defect types. The deterioration mechanism was discussed. The research status of falling-off risk identification and repairing method of ETICS was also analyzed.

The response displacement method is widely used for seismic design and analysis of underground structures,however,it has several shortages and limitations as a simplified method.Based on the basic principles of the response displacement method,a novel calculation method,named response shear stress method,is proposed with the soil-structure model in this paper.Both the soil-structure interaction and the shear stress distribution of soil layers can be easily and accurately incorporated into the proposed method.Because the uniform shearing interaction between the soil and structures is the principal reaction under seismic loadings,the seismic action can be assumed as the shearing force of soil layers,and then imposed on the soil-structure model.The seismic responses of the structure are finally obtained by the quasi-static method.The dynamic time-history analysis method is taken as the benchmark model to calibrate the proposed method.The optimum dimension of the soil-structure model used in the presented method is determined by comparison with the benchmark model.Furthermore,the validation of the proposed method is verified and approved to be applied for different geological conditions and structural section configurations.Results show that,the proposed response shear stress method could achieve consistent results with the benchmark model when the boundary dimension is over five times the structural diameter or height.Compared to the response displacement method,the response shear stress method could be widely applied in seismic analysis with different ground conditions and structure types.In addition,the design process of the proposed method is simpler and convenient,which provides a novel method for seismic design and analysis of underground structures.

In order to rationally design simply supported precast channel steel concrete composite beam for urban viaduct, structural design factors such as mid-span cross-beam layout, cross-section layout （number of main beams）, beam height, and bridge deck width were selected, and various parameters were set. The calculation and analysis of the determined composite girder bridge deck and steel girder slabs have resulted in the following conclusions： ① Under the premise of meeting the structural stress requirements, the installation of the mid-span beams will slightly increase the cost and affect the construction speed and landscape performance. Only the end beams can be installed; ② Generally, the arrangement of large openings and fewer beams is more cost-effective than the arrangement of small openings and multiple beams; ③ The economic beam height of the 30 m span composite beam is 1.6~1.8 m, the 35 m span economic beam height is 1.8~2.2 m, and the 40m span economic beam height is 2.0~2.4 m。

The self-drilling hollow grouting anchor is a new anchor incorporating functions of drilling, grouting and anchoring. Engineering issues such as collapse, shrinkage and unsaturated grout in soft and fractured rock can be solved effectively by application of such anchor in the underground anti-floating design. The paper carries out practical comparisons between the self-drilling hollow grouting anchor and fully grouted anchor in the fracture zone and non-fracture zone respectively for anti-floating applications. In the fracture zone, the two anchors are comprehensively analysed regarding anti-floating capacity, deformation characteristics, grouting pressure and grout amount. The test results show that the maximum pullout force of the self-drilling hollow grouting anchors is 400 kN, much larger than that of fully grouted anchors with a range of 310 kN-328 kN; the maximum deformation is 3.6 mm and residual deformation is 2.5 mm, much less than 7.6 mm and 5.7 mm of fully grouted anchors. The grouting pressure of hollow anchor and fully grouted anchor are 1.3 MPa and 1.0 MPa respectively, while the grout amount of the former is 20% higher than that of the latter. Therefore the anchorage behavior, grouting effects and durability of self-drilling hollow grouting anchor are evidently superior to those of fully grouted anchor. In addition, the self-drilling hollow grouting anchor becomes tensile prestress-typed after applying prestress.

To study the influence of stiffness ratio on the performance of buckling-restrained brace-concrete frame structural systems and its likely reasonable value range, three concrete frames with different initial storey drifts are designed and analyzed respectively. By means of dynamic time history analysis of frequent earthquakes and rare earthquakes, the influences of different stiffness ratios on seismic performance of the frame structure, such as the inter-storey drift angle, inter-storey shear force, hysteretic energy dissipation ratio of bracing, plastic damage distribution, etc. Based on the analysis results, the likely suitable stiffness ratios are proposed for structures with different initial drift angles.

The base isolated structure of a multi-tower building with unified base-floor is analyzed and designed by YJK. The analysis results show that the base isolated structure can significantly reduce the earthquake action of the upper structure. With bearings and dampers reasonably used in the design, the torsion caused by the irregular structure plane can be reduced. Base isolation of multi-tower building is very suitable for use in high intensity areas. The main structure of the project has been basically completed. This paper can be used as a reference for the design of similar projects.

For 15 MW high-power wind turbine, a composite wind power tower structure with double-layer steel shell filled with concrete is proposed. In order to clarify the rationality of the wind power tower design, the mechanical properties of the composite tower and the steel tower are compared through solid-shell finite element analysis and theoretical calculation. The results show that compared with the large-diameter steel tower, the composite tower designed according to the equivalent bending capacity of cross-section can reduce the outer diameter of the tower by about 15%, and the maximum steel tower wall thickness by about 50%. The composite tower provides lateral restraint for the steel tower wall and avoids local buckling of the steel tower, which increases the compressive capacity of the composite tower section by about 30%-45%. The composite tower improves the section bending modulus and reduces the maximum live load bending stress of the steel tower wall by about 13%, which is conducive to reducing the wind load fatigue effect. The combination of double-layer steel shell and concrete can improve the mechanical performance of wind power tower, reduce the difficulty of processing and hoisting, and save the amount of steel. This paper can be used as a reference for the design of high-power wind power towers.

Deterioration of steel infrastructure due to service loads and environmental agents has been one of major concerns in civil engineering community. Carbon fiber-reinforced polymer （CFRP） materials have high strength-to-weight ratio, good resistance to fatigue and corrosion, and ease of installation. They are showing great promise in rehabilitation and strengthening of aging steel structures. In external bonding systems, the interfacial performance between CFRP and steel plays an important role to ensure the retrofitting efficiency. This paper presents a state-of-art on the CFRP-steel bond behavior when subjected to fatigue loading. Experimental scenarios, failure modes, bond strength, load-displacement curves, and bond-slip relationships from literature review are summarized and compared.

Based on the Shanghai Urban Renewal Regulations and the Medium and Long-term Development Plan of Shanghai Engineering Construction Standards （2021—2025）, this paper introduces system engineering methodology for multi-dimensional analysis through research on the current situation and development trend of relevant standards systems and special technologies at home and abroad, composes and summarizes the visionary objectives, scope boundaries and guiding principles for the preparation of the table of technical standards for the renovation of existing buildings. The draft of Shanghai Existing Building Renovation Technical Standard System Table was developed, and the suggestions for the improvement of Shanghai existing building renovation standard system by 2025 were proposed.

Recent years, modular steel construction has become a new type of prefabricated building system which is increasingly promoted by the state with its advantages including high efficiency and environmental protection in construction. Scholars at home and abroad have done numurous research on the mechanical property of modular steel construction. This paper systematically summarizes the application and research of modular steel construction in recent years from the aspects of inter-module connection, lateral force resisting system of the module, mechanical property of the group column, overall structure analysis, etc. The further research direction and development trend in this field are given combined with the existing relevant regulations and standards of modular steel construction, which will provide useful references for engineering practice and scientific research.

Aspect ratio for tower transfinite structure can lead to insufficient capacity to resist capsizing and stiffness to resist lateral force, lack of tensile strength for wall limb.One can solve the problems by changing the structural plane arrangement,connecting the bottom of adjacent low and high towers to form an L-shaped combined tower at the bottom of the tower,and the equivalent resistance to the capsizing lever at the bottom of the structure can be increased.According to a number of plane and vertical irregular situations induced by the combined towers,corresponding seismic performance objectives are set up.Stress analysis on the floor weak parts and parts with contracted facade under frequent earthquakes was conducted. Stress analysis on the floor under medium earthquake static elasto-plastic pushover analysis and dynamic elasto-plastic time history analysis of the tower under rare earthquake were also conducted to study the nonlinear properties of the structure.The deformation mode,plasticity development and damage of the members as well as the elasto-plastic behaviors of the whole structure were investigated.According to the calculation results and the elasto-plastic behaviors of the structure, seismic performance of the structure was evaluated and instructions for the follow-up structural design were given.

The deviated pre-tensioned girder with discounted reinforcement avoids the shortcomings of post-tensioned prestressed concrete girder in tunnel construction technology and durability, and improves the mechanical adaptability of prestressed concrete structure, so it has a broad application prospect in bridge engineering. In practical engineering, the concept of load transverse distribution coefficient is often used to simplify the spatial multi-beam system into single beam system for analysis and calculation. However, with the increase of span, bridge width and the adjustment of beam spacing, this simplified calculation method will have a significant impact on the spatial stress state of the actual structure. Therefore, this article established the three-dimensional finite element model of I-beam, this paper studies force behavior of I-beam, through comparing all kinds of load transverse distribution coefficient calculation method and the error of the actual space force, put forward the reasonable and applicable method by studying the transverse beam spacing on force of main girder space, put forward reasonable design reference.

At present, there are few experimental studies on the shear behavior of H-beam recycled aggregate concrete slab composite beams. The shear performance of five full-scale specimens of H-beam recycled aggregate concrete slab composite beams is tested. The size of each specimen is the same. The clear span is 3 000 mm, the model of H-shaped steel is HN200×200×6×6, the width of recycled aggregate concrete slab is 300 mm and the thickness is 100 mm. H-shaped steel and recycled aggregate concrete slab are connected by studs. The replacement rate of recycled coarse aggregate （RCA） is 0%, 50% and 100% respectively, and the design strength grade of concrete is C30 and C60 respectively. The shear performance of the specimens with different design parameters are compared and discussed, and the influence of design parameters on the shear performance of the specimens is analyzed. The results show that the structure of the composite beam with stud connection is reliable, and the H-shaped steel and recycled aggregate concrete slab have good joint performance. The shear performance and failure mode of composite beams with different replacement ratio of RCA are similar. The stiffness, shear capacity and deformability of specimens with high strength are improved.

The stability of concrete structure is not considered as vital as that of steel structure. This paper compares the provisions on overall stability of structure and members’ stability in concrete design codes of China, Europe, USA and New Zealand, some relevant design suggestions are given by combining examples and formula deduction. For the overall stability, the rigid-gravity ratio value is affected by the resultant position of lateral forces, the magnitude and position of building gravity. The overall stability of different buildings should not be simply judged by the stiffness-weight ratio. For the stability of members, several common but easily ignored problems are analyzed： second-order effect should be considered for columns supporting bridges and cross-story columns; by reference foreign codes, the height-width ratio and lateral unbraced length of beam should be controlled for long-span and long cantilever beams; loads should be applied correctly when solving the effective length of columns by buckling analysis. The stability of shear walls is strictly restricted in China. In this paper, the critical height of outer wall in staircase and L-shaped shear wall limited by stability is given by comparing the equivalent load of stability of wall limbs with the limit load of axial load ratio.

The project in the case is China's first monolithic precast concrete frame-corewall structure. The project is an AAA prefabricated building and a three-star green building. Through a pre-planning of prefabricated structural system selection and prefabricated scheme, combined with design, production,transportation and hoisting conditions, the structural design and splitting of prefabricated enclosure walls, fabricated floors,prefabricated core tubes and prefabricated concrete columns are planned.The logic of each planning is elaborated and the application of precast corewall technology is explored to provide a reference for the planning,structural design and splitting of similar prefabricated office buildings.It lays a foundation for the successful construction and standardized design of such projects,and promotes the development of concrete assembly technologies in the industrialization of new buildings in China.

The slotting treatment after bellows are blocked in the prestressed construction process of long-span bridges will greatly weaken the bridge panel section and affect the bearing capacity and service performance of the structure. This paper studies the reinforcement treatment of large span bridge after the bellow is clogged, and puts forward the reinforcement scheme of adding prestressed tendons on the top surface of the original bridge panel and replacing the cushion layer on the original roof with new reinforced concrete composite layer. With this reinforcement method, the calculation results show that the total thickness of the bridge deck and the load on the bridge deck do not increase. In addition, the re-stretched original prestressed tendons and supplementary prestressed tendons together ensure the crack resistance of the structure. The thickness of the structural layer of the bridge deck increases, which ensures and improves the load-bearing capacity of the structure. It can provide reference for the reinforcement treatment of the same type of engineering.

The research is carried out on the ultra-deep pit of Qingxiushan Station with excavation depth of 58.7 m, taking the construction of rail transit pit in semi-diagenetic strata area of Nanning as the background. Through theoretical analysis, field monitoring data and numerical simulation, the influencing factors of deformation and mechanical characteristics are systematically analyzed. The formation mechanism and main influencing factors of double-peak or even multi-peak deformation mode of ultra-deep foundation pit retaining structure in semi-diagenetic strata are revealed. The calculation method of lateral pressure of semi-diagenetic strata is proposed. Reasonable earth pressure calculation methods and structural calculation models for ultra-deep foundation pits are given, of which the practicability is verified.

In order to explore the influencing factors of the seismic response of the interaction system of soil-complex structure, a case study of a typical complex structure was conducted. A 3D finite element model of the interaction system was established by the finite element code ABAQUS. The equivalent linearization method was used to consider the nonlinearity of the soil. The Port Island wave of the Kobe earthquake in 1995 is selected, and the inverted wave was used as input motion of the interaction system. On this basis, the seismic response analysis of the interaction system was carried out. The effects of soil-structure contact surface simulation, vertical seismic wave action, and soil-structure flexibility ratio on the seismic response of the complex structure were discussed. The results show that the soil-complex structure adopts the contact surface simulation method, which reduces the axial force, shear force and bending moment of the central column, while the axial force, shear force and bending moment of the side wall have increased. Considering the vertical ground motion, the internal force of the central column and side wall has increased, and the axial force of the central column has increased by about 20%. In this paper, when the soil-structure flexibility ratio is less than 12, the interaction effect of soil-complex structure is obvious.

In recent years, with the development of building industrialization, precast concrete shear wall has been widely used. To reduce the wet operation in the construction process and ensure the connection joint quality of precast concrete shear walls, a new bolted connection method for the precast concrete shear wall is proposed. In the core area of the shear wall, edge component, the design of the bolt number is based on the principle of equal strength replacement, the tensile strength of the bolt is much higher than the original steel bars. Then, according to the current national concrete design code, the bearing capacity of the bolt connected shear wall is calculated and compared with the finite element simulation results. It shows that The calculated value of normal section bearing capacity is consistent with the finite element simulation results; Through the calculation of shear capacity, it is concluded that the shear failure occurs in the wall with a low shear span ratio, which is compared with the damage cloud chart of concrete. The calculation of the shear capacity of the horizontal joint shows that the bolt connection has a great safety reserve in the horizontal direction, and there is no horizontal slip in the loading process.

After earthquakes, it is found that the coupling beams and the bottom corners of traditional shear wall structures easily suffer damage which is very difficult to be repaired, thus causing economic lost. To solve this problem, a type of shear wall structure with viscoelastic dampers as replaceable coupling beams was investigated. A case study of a 10-story coupled shear wall was carried out. Finite element software OpenSees was utilized to build a traditional structure and a structure with replaceable beams, and conduct elastoplastic time history analysis of both structures under four-level seismic fortifications. Then the seismic performance indexes such as inter-story drift ratio, story shear force, plastic damage of the coupling beams and the bottom corners of shear walls were compared and analyzed. The results show that compared with the traditional shear wall structures, the seismic performance of shear wall structures with viscoelastic dampers as replaceable coupling beams is improved because of smaller seismic response and less damage to the main structure．

To study the influence of stud height and stud spacing on the shear behavior of short headed studs in ultra-high performance concrete （UHPC） composite deck, the connection project of Xihong Bridge was taken as the engineering background and push-out test and FEM parametric analysis were conducted. The push-out test revealed that the failure mode of short stud in UHPC was shear failure at the root of stud, and there was only partial crush in UHPC. The push-out test also found that there was a significant difference between the tensile and bending stress ratios of the upper and lower rows of studs along the load direction. According to the FEM analysis, shear rigidity tends to increase with the decrease of stud height when the stud height of 13 mm diameter stud ranges from 15 mm to 50 mm. When stud height decreases, stud will be pulled out and the crush area of UHPC will become larger. However, stud height has little impact on shear capacity of short headed stud. On the other side, stud spacing does not have significant influence on shear performance of short studs when changing in the range from 150 mm to 300 mm.

In this study, actual engineering cases serve as the background for analyzing the influence of viscous damper parameters on the additional damping ratio under different seismic intensities. The calculation differences of the additional damping ratio between the normative method and the energy ratio method are also examined. Taking into account factors such as damping coefficient, damping index and seismic intensity, parametric analysis is carried out using Etabs software. It was found that the relationship between the damping coefficient and damping index and the additional damping ratio under earthquakes of different intensities is parabolic, where it initially increases and then decreases. There exists an optimal solution, and as earthquake intensity increases, the optimal solution parameters become larger. When the damping coefficient or index is small, the damping ratio is maximum under frequent earthquakes. When moderate, it is maximum under design basis earthquakes,and when large is maximum under rare earthquakes. The normative method yields larger results than the energy ratio method when the floor is low, torsional effects are small, or seismic intensity is low, with the relationship between the two varying accordingly.