Ebook: Advances in Frontier Research on Engineering Structures

The 2023, 7th International Conference on Civil Architecture and Structural Engineering (ICCASE 2023) was successfully held in Guangzhou, China from 14 to 16 April 2023 as a virtual event. This Seminar was the seventh in a series of topical meetings. ICCASE 2023 was attended by about 250 participants from different countries.

For this seventh meeting we chose Guangzhou as our conference venue and met with old and new friends. The location of the conference may have changed, but what remained unchanged is the aim of these meetings, which is to discuss recent advances and new perspectives in civil architecture and structural engineering in a pleasant and friendly atmosphere. At this meeting, we had a comprehensive overview of this fascinating field, and of future scenarios, thanks to the participation of leaders of some important projects.

The Conference presented an outstanding program of papers covering the most recent advances in civil architecture and structural engineering, including high-rise buildings and large-span structures, monitoring and control of structures, tunnels and underground structures, calculation principles of seismic design of structures, seismic isolation technology of structures, etc. The papers in this proceedings, published by IOS Press, represent a collection of the invited talks.

The conference program consisted of fifteen keynote speeches presented in plenary sessions, including many speeches on hot topics, highlighting the most recent advances in related fields, and various oral and poster presentations. The program included speeches by Professor Xiangsheng Chen (Shenzhen University; Chinese Academy of Engineering; Russian Academy of Engineering). The professor is a famous expert in the field of tunnel and underground construction, urban rail transit engineering, special geotechnical construction, and well construction. Over the past 40 years he has completed more than 60 research projects supported by the National Natural Science Foundation of China (NSFC) and the National Programs for Science and Technology Development. He has published nine monographs, five of which were authored by him, and delivered over 100 papers at home and abroad.

We would like to thank the participants, especially those who contributed speeches, posters and manuscripts, for making ICCASE 2023 such an exciting and memorable conference. We thank the Academic Committee for their advice and suggestions and the Organizing Committee for their tireless and expert efforts in the organization of ICCASE 2023. Finally, we extend our gratitude to all our colleagues whose friendly and efficient service contributed much to the success of the conference.

The Committee of ICCASE 2023

This paper aims to introduce structural health monitoring techniques. The health monitoring of the bridge structure is mainly divided into three stages. The data collected by the sensor can be extracted and its characteristics can be evaluated. For the detection of bridge structures, scholars at home and abroad have conducted a lot of research on data collection and sensor arrangement. In the health monitoring of bridge structures, the most critical link is to use sensors for data collection. This article focuses on two types of sensors, EME and FBG, which are used to measure strain and temperature, respectively. With the development of science and technology, more and more precision measurement techniques have been proposed. GNSS and Novelty detection are the main representatives of bridge safety monitoring.

The neural network based on the deep learning theory has a profound theoretical basis and broad application prospects in the field of bridge structure damage identification. The comparison and analysis are made from three aspects of input vector, finite element model and neural network, which provides reference for further research on neural network in bridge structure damage identification. Through analysis, it is found that the ability of neural network to extract relevant information can be effectively improved by selecting the finite element model or the original data obtained in the actual situation as far as possible for the input vector. When the stress of bridge structure is simple, neural network with shallow layers and simple network structure can be selected. When the stress of bridge structure is complex, the neural network model with strong complexity should be selected first.

Based on the study of geotechnical dynamics characteristics, this paper analyzes its influence on tunnel engineering design. Tunnel engineering is an important part of underground engineering construction, and the characteristics of geotechnical dynamics are important factors affecting the design of tunnel engineering. It is found that the geotechnical dynamics characteristics have obvious influence on tunnel engineering design, including influence on tunnel technology selection, influence on tunnel construction safety, influence on tunnel design specifications, etc. Therefore, the study of geotechnical dynamic characteristics not only provides important technical support for the design of tunnel engineering, but also has important significance for the safety and stability of tunnel engineering. The research of this paper provides important theoretical guidance for tunnel engineering design and helps to improve the level of tunnel engineering design.In summary, the construction design of a tunnel project requires not only specialised technical the construction progress and the quality of the work, but also Large equipment and tools are also required to work together with the construction personnel to complete the construction of the tunnels. Before construction, specialised units are required to carry out specialised geological forecasts and The construction of the tunnels will require specialised geological forecasting and advanced exploration work to inform the construction requirements. Timely feedback on the construction situation to geological survey and design and construction units, especially in the case of rock mechanics in tunnels. The need for experts in the field of mechanics to carry out multifaceted investigations, only through the rational use of Only by making reasonable use of the rock mechanics in the tunnel can the tunnel be designed in a reasonable way and the use of the tunnel in the Only by making reasonable use of the rock structure of the tunnel can the design of the tunnel be rationalised and the frequency of accidents be reduced.

Bridges are subject to large-amplitude vibrations, known as wind-induced vibrations, which can cause various problems in high winds. Flutter is the most serious vibration caused by self-excited force. In addition, long-span suspension bridges are flexible frames that are prone to large deformations. Many researchers have shown that flutter instability is affected by non-linear characteristics. In this paper, the equivalent linearisation method (ELM) is used to solve the flutter state of the nonlinear flutter system of a long-span suspension bridge with cubic torsional stiffness. By solving the equivalent linearisation equations, the wind speed of the critical flutter vibration was obtained, and the supercritical Hopf bifurcation and limit cycle oscillations (LCOs) were analysed.

Under the condition of super-shallow coverage and small spacing, the tunnel construction is easy to cause large structural deformation. The mechanical properties and supporting effect of tunnel with small spacing are summarized. Finite element software is used to simulate the effect on construction of tunnel group by changing the distance. The results show that with the increase of the distance, the settlement value of the middle tunnel has a smaller and smaller distribution law, when the distance exceeds 3 m, the maximum main stress reduction changes less as the distance increases further, and the research results can provide a reference for the design and construction of similar tunnel group.

In order to solve the problems of the shortage of waste slag resources, the difficulty of Engineering abandoned earthwork and the outward transportation of bored pile mud, and realize the resource utilization of Engineering abandoned earthwork and mud, five processes are used for field comparative tests, and the research on the replacement of traditional waste slag as subgrade filler by cushion cap excavation earthwork and bored pile mud solidified material is carried out. The results show that inorganic materials with a mix ratio of 3% cement + 1% mineral powder + 5% lime are selected as the main curing materials. Under the condition that the amount of solidified material remains unchanged, the water stability of solidified backfill subgrade is better than that of the one-time lime mixing method by using the secondary lime mixing and the sludge soil site solidification construction technology without strong mixing head. The application of this technology can effectively solve the problem of shortage of slag supply, reduce environmental pollution and save construction costs on the premise of ensuring the use function of the road.

In this paper, a simple supported to continuous small box beam skew bridge is taken as an example to conduct static load tests. Firstly, a finite element model of the bridge is established by using Midas Civil to obtain the theoretical bending moment of the precast beam. Then, the measurement point arrangement and loading program of the precast beam are designed. Finally, the load is applied to the precast beam in multiple stages, and displacement and strain data are measured. Through the analysis of displacement and strain, the research results show that the precast beam is in an elastic working state, the strain conforms to the assumption of a flat section, and the bearing capacity and stiffness meet the use requirements.

The high embankment is divided into two types of zones according to the settlement amount, the pavement settlement affected zone which mainly controls the embankment settlement and the non-pavement settlement affected zone which mainly controls the slope stability. Based on the functions and bearing capacity of the two types of zones, according to the characteristics analysis of the packing gradation and compaction curve, the relationship between the compaction degree and the elastic modulus and CBR, the classification method of the filling, the pre-zoning method of the excavation area and the filling selection method are proposed; taking the high fill embankment of granite residual soil as an example, this paper also analyzes the zoning filling methods of high fill embankment from excavation zoning, filling selection, zoning paving and filling to intelligent compaction control, which provides a new idea for controlling the construction quality of high embankment; Finally, by using finite element software to compare and analyze the non soil rock mixed filling scheme, the bottom cushion soil rock mixed filling scheme and the partition filling scheme, it is concluded that the partition scheme can achieve the effect of land saving by steepening the slope with its high stability coefficient advantage over other filling schemes.

The tunneling machine for the Hanjiang to Weihe River Water Diversion Project is expected to encounter complex and unpredictable geological conditions, which could result in accidents such as large deformations of soft rock and segment failure. To address this, a refined numerical simulation model using FLAC3D was utilized to study the coupling mechanism of shield-support-surrounding rock under loess geological conditions. Results show that the overall rock deformation is significant, but due to the support effect of the face, displacement at the cutter head is minimal. Deformation of the surrounding rock increases gradually from the back of the face to the pipe segment. Stress redistribution occurs within a certain range of the gap reserved at the shield, with the maximum principal stress in the secondary stress located near the tail of the shield. A typical cave section of Bailu Tableland exhibits a layered stress distribution phenomenon, with stress release from the cave wall to the outer rock mass. This includes zones of concentration, transition zones, and non-interference zones. In the excavation direction of the tunnel, the maximum principal stress is relatively high at the junction of the shield tail and the segment structure, as well as at the entrance of the tunnel.

This study aimed to investigate the effect of external water pressure on the construction of shields in complex loess geological conditions. The Hanjiang to Weihe River Water Diversion Project water conveyance tunnel was used as an engineering case, and a seepage-mechanics coupling model was developed using Phase2 finite difference software. The model was based on the geological parameters of typical tunnel sections in Bailu Tableland. The results of the calculations indicate that the external water pressure outside the lining is distributed unevenly, with high pressure on the lower side of the tunnel, low pressure on the upper side, and equal pressure on the left and right sides. The maximum external water pressure of the lining increases significantly with the rise of the underground water level. Although the maximum principal stress of the segment structure decreases as the underground water level increases, the difference between the maximum and minimum values is only 1.015 times. The maximum deformation and the maximum principal stress of the surrounding rock increase with the distance between the underground water level and the caving roof but are not sensitive to changes in the groundwater level. As the surrounding rock in the collapsible loess stratum lacks self-stability, its overall displacement remains high even after lining is applied. Therefore, appropriate measures need to be taken during construction to prevent potential environmental and hydrogeological issues.

In order to explore the surrounding rock disturbance in the shallow buried double-sided biased small clear distance tunneling process, relying on a national highway project, the finite element Midas Gts Nx was used to conduct numerical simulation analysis of the tunnel construction process, in order to analyse the law of surrounding rock stress and strain in the shallow buried double-sided biased small clear distance tunneling process. The results show that the subsidence shape of surface slope develops from “V” shape to “W” shape, and the vertical horizontal displacement shape of septal rock changes from “V” shape to “W” shape. The surrounding rock produced a certain amount of uplift halfway up the mountain. When the rear tunnel is driven, the centre of gravity of the septum rocks migrates towards the rear tunnel side, which reduces the stress of the surrounding rock at the front tunnel and is conducive to the stability of the front tunnel structure. The stress increase of the middle barrier rock at the arch foot is obvious and it has the characteristic of through-through. The stress of the structure at the tunnel wall foot should be monitored emphatically during construction. When the rear tunnel is driven, the plastic zone of surrounding rock appears on the diagonal of the septum rock, and the safety factor of surrounding rock is increased and the speed is reduced. Numerical simulation can provide theoretical guidance for field monitoring and measurement.

Based on the parameter changes of strong collapsible loess in Xi’an before and after humidification, a finite element model of pile group was established, and the pile group effect and negative skin friction characteristics of pile foundation after loess collapse caused by the rise of groundwater table were analyzed. The results show that the effect of pile diameter change on negative skin friction is not obvious, and with the increase of pile diameter, negative skin friction has a weak tendency to decrease. The pile group effection has a significant weakening effect on the negative skin friction, and the pile group effect weakens as the pile spacing increases, and when the pile spacing exceeds six times the pile diameter, this effect is minimal. When the pile spacing is six times the diameter, the total negative skin friction of the edge pile in the group pile is very close to that of the single pile. The axial force have a strong correlation with the friction resistance of the pile side, from the top of the pile downward, the friction resistance changes from negative to positive at the neutral point, while the axial force of the pile body has a vertex at the neutral point. In addition, due to the weight of the cushion cap, not only the neutral surface depth ratio is reduced, but also the axial force of the pile group increases.

When the tunnel and underground engineering construction encounters water-rich soft and broken surrounding rock, it is very easy to occur serious disasters such as mud inrush, water inrush and collapse, threatening the safety of engineering construction. Taking the water-rich ultracataclasite stratum exposed by the 4th construction branch of Xianglushan Tunnel in the Central Yunnan Water Diversion Project as an example, this stratum has strong compactness, weak permeability, softening in water and other unfavorable geological characteristics. During the excavation process, several major mud and water inrush geological disasters have occurred. In this paper, the basic physical and mechanical properties of water-rich ultracataclasite rock are tested based on field engineering examples, and the grouting diffusion law under this stratum condition is studied based on PFC^2D numerical calculation software. The research results show that according to the basic physical and mechanical parameters such as density, water content, permeability coefficient, particle size distribution, specific gravity, porosity, cohesion and internal friction angle obtained from the laboratory test of ultracataclasite rock, the analysis shows that the shear strength of the water-rich ultracataclasite stratum is low, further leading to mud outburst and collapse disasters. Under the comprehensive consideration of the number of split grout veins, the distribution of diffusion range and the risk of damage to the existing support, the optimal grouting pressure is determined.

In this paper, taking a typical roadway in broken and soft rock strata in No. 10 Mine of Pingdingshan coal field as an example, the deformation and failure mechanism of rock mass was deeply analyzed based on field testing. Then the technology of high-strength prestressed bolt-grouting support, such as the new combined high-strength grouting bolt, high-strength hollow grouting anchor cable, were developed. Based on this, a repair support scheme using the new technology was designed for on-site roadway, and was successfully implemented in the field. The monitoring results after the repair of field roadway show that the maximum of roadway surface convergence deformation is 56 mm. The maximum force of the grouting bolt is 122 kN, the grouting anchor cable is 256 kN. The new technology can fill the cracks of rock mass and the borehole interstice at the free part by using grouting materials. It can effectively enhance the self-bearing performance of soft broken rock mass on the premise of ensuring the diffusion of prestressed active supporting effect in rock mass, and then suppress the deformation and failure of roadway. The research works can provide references for the stable control and support design for roadways in soft and broken rock strata.

In order to explore the influence of different ratios of compressive stress to roof and floor on the long-term performance of the bridge, this paper takes a long-span PC continuous rigid-frame bridge in Xiangxi Autonomous Prefecture as the research object, establishes the whole bridge model by Midas/Civil, and analyzes the changes of long-term stress and deflection of the main beam with different ratios of compressive stress to roof and floor by changing the longitudinal prestressed steel tendons. The results show that the greater the ratio of compressive stress between top and bottom plates, the better the long-term mechanical properties of the bridge.

This paper investigates the deformation characteristics and control methods of support structures during deep foundation pit excavation, using the foundation pit at the Diejiao Station of Foshan Metro Line 3 as a case study. A 3D nonlinear finite element software is employed for excavation simulation, adopting coupled pore fluid diffusion and stress analysis. The numerical model is verified by comparing the field monitoring data with the finite element results. The study systematically analyzes the influence of reinforcement position, reinforcement parameters, and reinforcement depth on the maximum lateral displacement of the diaphragm wall of the foundation pit. The research results reveal that reinforcing the soil on both sides of the diaphragm wall can effectively reduce the lateral deformation of the foundation pit. Furthermore, the study shows that external reinforcement of the diaphragm wall can reduce the maximum lateral displacement of the wall to a certain extent, but the reinforcement effect is limited. The reinforcement effect of the inner side of the diaphragm wall improves with the increase of the excavation depth. Properly increasing the Young’s modulus of the reinforcement can reduce the adverse effect of excavation on the foundation pit. Finally, the optimal depth of reinforcement is found to be the excavation depth of the foundation pit of 28.2 m. The research results can provide a reference for the foundation pit reinforcement scheme in watery sandy soil areas.

A grouting material composed of water glass and phosphoric acid was proposed aimed to the formation reinforcement problem during shield chamber opening. Then the gelation time of the material and the interfacial shear strength between the solidified grouting material and metal was analyzed. Finally the grouting material was applied in practical engineering. The test results show that when the pH value of phosphoric acid is constant, the gelation time of the mixture of phosphoric acid and water glass gradually decreases as the Baume degree of water glass increases. When the Baume degree of water glass is the same, as the pH value of phosphoric acid decreases, the gelation time of the mixture of phosphoric acid and water glass gradually increases. As the Baume degree of water glass increases, the interfacial shear strength between the solidified grouting material and metal gradually increases. Under the same concentration of water glass, the lower the pH value of phosphoric acid, the smaller interfacial shear strength between the solidified grouting material and metal.

The project of Emergency Treatment Complex Building in Shanghai Tenth People’s Hospital is presented in this paper to illustrate the behaviors of the two-floor top-down excavation and its complicated surroundings in Shanghai soft clay. In order to restrict excavation deformations and expand construction site, the two layers of permanent floor slabs were adopted as horizontal supporting systems and the B0 slab was meanwhile exploited as working place and traffic passageway. Before construction, numerical simulations were conducted to predict the responses of the pile walls and the structure slabs. Based on the calculation results and monitoring data, it can be concluded that buildings without piles have significant impacts on the wall deflections while those with piles hardly influence the ground movements during excavation. Furthermore, the magnitude of displacements is related to the length of side and the construction loads around excavation. Buildings subside larger as their distances to excavation get closer. Settlements of buildings without piles are much more remarkable than those with piles.

This paper presents a study on the reliability analysis and online measuring of sensors in Structural Health Monitoring (SHM) systems. As sensors are critical components in SHM, their reliability and accuracy are vital for the precise and effective operation of the monitoring system. By utilizing a strain testing platform and online measurement methods, this study analyzes the reliability and effectiveness of in-service sensors by comparing measurements on similar positions and applies the indoor experiment to an actual bridge structure. The results demonstrate that the proposed method can achieve precise reliability analysis and online measuring, ensuring the effectiveness and smooth operation of the SHM system and further enhancing the fundamental safety level of bridges while providing convenience to bridge management.

As opposed to traditional symmetrical two-way pylons, the sail-shaped pylon presents an arched shape on the longitudinal bridge, and the flow field generated around it presents more obvious three-dimensional spatial effects when air flows. Therefore, the static and dynamic characteristics of sail-shaped pylons under the action of wind load are also different from those of conventional pylons. In order to study the wind resistance performance of the sail-shaped pylon in free-standing stage, taking the sail-shaped bare pylon of a certain cable-stayed bridge as the engineering background, an aeroelastic model satisfying the first 2 order frequency similarity ratio was designed by using the method of metal core beam plus wooden outer moldel. On this basis, the responses of vortex vibration and galloping in uniform flow field and turbulent flow field, as well as buffeting response in turbulent flow field were obtained by wind tunnel test of aeroelastic model, and the wind resistance performance of sail-shaped pylon of cable-stayed bridge was studied. The results show that when the wind direction is 0°, Vortex-induced vibration(VIV) may occur at the wind speed of 25.3 m/s ∼ 30.67 m/s, and the unilateral amplitude of VIV at the top of the tower is 79.5 mm. The wind tunnel tests of turbulence aeroelastic model show that, under the action of the design reference wind speed under construction condition, when the wind direction Angle is 80°, the root mean square of buffeting displacement in the transverse direction of the top of the pylon is the largest, which is 13 mm; when the wind direction Angle is 90°, the root mean square of buffeting displacement in the transverse direction is the largest, which is 14 mm, which does not affect the construction safety of the pylon.

Circular underground continuous walls are widely used in deep and large excavation projects. The tensile stability is the main reason for the loss of strength and failure of continuous underground walls. A three-dimensional numerical analysis is conducted on the stability of a continuous wall bottom tube supporting a circular base hole using the strength attenuation method. Firstly, based on the foundation pit anchored by the Wuhan Yanglao Bridge as the engineering background, a finite element symmetrical axis was formed, which was created on the basis of the software PLAXIS. By reducing the shear force of the soil at the bottom of the hole, the shape of the sliding surface and the safety factor of the foundation were discussed, and stability failed. Then use FLAC 3D software to create a three-dimensional digital model. The following conclusion is drawn by changing the inner diameter of the foundation pit, the depth, thickness, and stiffness buried in the continuous underground wall. The thickness and stiffness of the lining, as well as the internal friction angle and soil adhesion. The tensile durability of circular continuous wall base holes is affected by the omnidirectional impact—safety factor obtained by the element method. The symmetry limit of the axis is higher than the safety factor given by two-dimensional plane analysis. As the inner diameter of the hole increases and the embedding depth, pad stiffness, internal friction, and adhesive force increase. Low sensitivity to changes in lining thickness and wall thickness. When using the strength attenuation method for finite element analysis Axisymmetric continuous wall base hole, circular guide, loss stability mainly due to the infiltration of plastic area, and soil at the bottom of the turn hole. The displacement of various feature points can serve as auxiliary guidelines.

In order to make the bridge finite element model more accurately and effectively reflect the state of the real bridge, this paper uses the dynamic response of the on-site structural vibration frequency and static load and strain, and proposes a method of combining static and dynamic forces to construct the objective function for optimal analysis. The finite element model of the approach structure of the Yihe Super Bridge has been corrected. By using the “ANOVA” method to find out the significant parameters, and then according to the actual situation of the project, the elastic modulus of concrete, the thickness of the bridge deck pavement, the concrete bulk density and the moment of inertia of the beam section are selected as the parameters to be corrected for the structure.