Proceedings of CIBv 2023

This paper presents a comprehensive analysis of the current state of research on the frost resistance of recycled aggregate concrete at home and abroad and finds that micro-cracks in recycled aggregates and the fragile interfacial transition zone of concrete have a significant impact on the frost resistance of recycled aggregate concrete. As the replacement rate of recycled coarse aggregate rises, recycled aggregate concrete becomes less resistant to frost. It is consequently advised that the replacement rate of recycled coarse aggregate not surpass 50%. At this rate, the frost resistance of recycled aggregate concrete is most similar to that of regular concrete. In addition, the addition of silica fume, ferronickel slag, glazed hollow bead, polypropylene fibres and air-entraining water-reducing agents can effectively improve the frost resistance of recycled aggregate concrete. In the future, more systematic and in-depth research on the freeze-thaw damage mechanism of recycled aggregate concrete is needed, and a more complete theoretical model should be established.

In this paper, the research status of shape-stabilized phase change particles at home and abroad was extensively investigated, and the composite phase change materials of decanoic acid and myristic acid were prepared by heating and fusion of decanoic acid and myristic acid, and the optimum mass ratio of decanoic acid and myristic acid was measured as 6:4 through the step-cooling curve and the DSC curve test, and the phase change temperature of decanoic acid-myristic acid composite phase change materials was 26 ℃ and the enthalpy of the phase change was 131.82 J/g. The adsorption performance and durability of shape-stabilized phase change particles were tested through vacuum adsorption and encapsulation. The phase change enthalpy was 131.82 J/g. The phase change particles were prepared by vacuum adsorption and encapsulation, and the adsorption performance and durability of the phase change particles were tested to find out the key problems affecting the performance, analyze the causes of the problems, and explore the solution paths to the causes, to reduce the energy consumption of heating and air conditioning during the operation phase of buildings, a new type of shaped phase change material that can buffer indoor temperature changes is prepared and its related parameters are measured to promote its application.

This study aims to determine the effect of wastes on the mechanical and durability characteristics of road concrete. Steel slag was used as replacement of aggregates in different percentages. Silica fume was used as replacement of 10% of cement. The mechanical characteristics such as: flexural strength, split tensile strength and compressive strength were experimental determined and analyzed. The behavior to frost-thaw cycles of road concrete with wastes was also analyzed. The mechanical strengths presented high values in comparison with that of the control mix (without wastes) for reduced percentages of aggregate replacement. The behavior to frost-thaw cycles was better in the case of road concrete with waste in comparison with the control mix.

In the article are presented the experimental and numerical researches on concrete blocks realized of green lightweight concrete. For preparing the hollow blocks the light weight concrete with wastes type chopped plastic bottles (PET), sawdust and fly ash was used. Experimental study on physical-mechanical and deformation characteristics of green lightweight concrete were done. The hollow blocks were tested in compression. Failure of blocks was ductile for both types of concrete, the blocks of lightweight concrete with saw dust presented a major degradation. The numerical analyses performed with ATENA software indicated a similar type of failure as that from the tests that indicates a good correlation of results.

The study of slender structures in mechanical or civil/industrial constructions represents a continuous challenge from the view point of the risk factors identifying and offering sustainable solutions and methods to extend their life span. One of the most common and dangerous sources for the lifetime limitation of this type of structure is the buckling. The use of numerical algorithms in the applications for analyzing the structures, algorithms based on the finite element method, is a frequent solution in approaching the problem. Today, there are various software applications that have as their starting point the classic approach to the problem according to the Strength of Materials. The purpose of this article is to compare the classical approach with the output of running the working environments/platforms to establish the obtained solution convergence, highlighting the dispersion degree as well. The analyzed subject is the double joint section. Regardless the used software, the high degree of complexity of the problem requires a two steps algorithm: a buckling analysis in the linear domain followed by a nonlinear analysis. In addition, compared to other similar approached of the phenomenon, the use of the finite element with full options regarding the structure discretization (meshing) will be considered.

Structural and material optimization remains crucial in today’s constructive design and machine building area. The importance of this topic relies on its applications for testing the behavior of different materials under the action of various loading and the evaluation of the computation error. When choosing the materials for a specific application, an important criterion is the global structure stiffness, which must be precisely determined. This paper presents a case study of a statically indeterminate, circular plane structure used in specific engineering devices. This structure’s particular construction requires determining a dimensional parameter from the viewpoint of optimal rigidity (structure stiffness) to ensure minimal device size. A dual approach, the traditional calculus versus the Finite Element Method simulation, is used to solve the problem. The results of the two finite element software (Axis and SolidWorks) used in this study are also compared. Correlating the structural stiffness to the material properties is the best approach to the optimal design solution.

In response to issues such as dispersed damage and difficult repair of assembled RC beam-column joints after earthquakes, this paper proposes an assembled (Reinforced Concrete) RC beam-column replaceable friction energy-consuming steel joint. The steel joint consists of a friction energy dissipation system and a U-shaped shear-resistant steel plate system. Numerical simulations using ABAQUS software were conducted on one cast-in-place joint and six steel joints under low-cycle reciprocating loading. The simulation results comparing the cast-in-place joint with the steel joints show that the steel joints have comparable initial stiffness and ultimate bearing capacity, but stronger energy dissipation capacity. After seismic action, the main structure remains in an elastic working state, achieving toughness and seismic resistance of the structure. The simulation analysis of the effect of the design bearing capacity coefficient μ on the functional recoverability and concentrated energy dissipation performance of the structure shows that energy dissipation is mainly concentrated in the steel joints. With the increase of the bearing capacity coefficient, the total energy dissipated in the steel joints initially increases and then decreases, but the proportion of energy consumption of steel joints will continue to decrease. Under the premise of meeting the demand of bearing capacity, selecting a reasonable bearing capacity coefficient can make the energy consumption of the steel joints reach over 95%, thereby achieving the purpose of centralized energy dissipation of the structure and rapid recovery of the functional use after earthquakes.

The mechanical properties of beam-to-column joints of steel frames are an important factor in determining whether steel frames can perform normally under seismic action, but the current research mainly focuses on the mechanical properties of semi-rigid connection such as cruciform or end-plate types, and the research on the performance and seismic performance of semi-rigid connection in steel frames is not sufficient. In view of this, finite element simulations of single-storey single-span experimental steel frames are carried out using finite element analysis software ABAQUS and verified by tests, and multi-parameter analysis is carried out on the width-to-thickness ratio of the column and the height-to-width ratio of the panel zones, to obtain the effects of different parameters on the mechanical properties of the steel frames with semi-rigid connection, and to provide support for the promotion of the use of semi-rigid connection in steel frame design. The research results indicated that: the initial stiffness, yield load and ultimate load of the steel frame increase with the increase of column width-to-thickness ratio; the structural load and initial stiffness increase with the increase of the height of the beam web, and the stress concentration phenomenon at the connection and beam flanges can be improved by reducing the height of the beam web, but the change of the aspect ratio of the panel zones has a small effect on the structural ductility.

The deterioration of reinforced concrete (RC) structures is the main issue throughout the globe. The researchers are persistently dedicated to resolving the issue of deterioration in RC structures. In the last few decades, fiber-reinforced polymer (FRP) has been continuously used to retrofit deteriorated structural members. The various advantages of FRP composites such as high-strength-to-low-weight, ease of use and transport, etc. increase the use of FRP composites in the retrofitting industry. The FRP-to-concrete bond strength is one of the main contributing parameters that decide the efficacy of the FRP composite with the concrete surface. Various analytical models are available to predict the FRP-to-concrete bond strength, but there is no analytical model that can estimate the FRP-to-concrete bond strength under moisture conditions. This study aims to evaluate the FRP-to-concrete bond strength under moisture conditions with an artificial neural network and analyse the durability of FRP composite under moisture conditions. The considered dependent parameters that affect the bond strength under moisture conditions were the width of the concrete block, bonded length of FRP composite, thickness of FRP composite, width of FRP composite, exposure type, temperature, relative humidity, duration, elastic modulus of FRP composite and compressive strength of concrete. The developed machine-learning model was accurate, fast, reliable, easy to use, and economical to predict the FRP-to-concrete bond strength under moisture conditions.

This paper studies the effect of window height to aspect ratios on the flame spread of high-rise buildings, and provides reference for the engineering and fire protection design of high-rise buildings. PyroSim is used to establish high-rise building models under six different window aspect ratios, and the temperature distribution isotherms of the model under different window aspect ratios are analyzed. The flame fusion height of longitudinal continuous four windows is increased by 0.3–0.7 m at 540 ℃ compared with that of three windows.It is concluded that the flame spread of the exterior walls of high-rise buildings is affected by the window aspect ratio and the number of Windows. The smaller the window aspect ratio is, the higher the flame fusion height is. Therefore, under the premise of meeting the building design specifications, the flame fusion height can be reduced by controlling the window aspect ratio in high-rise buildings, thus reducing the fire risk and gaining time for rescue.

This paper takes the continuous small radius curve tunnel around Wanghua Street Station of Shenyang Metro Line 4 as the background, aiming to explore the impact of different line types on surface settlement. By establishing three different shield construction finite element models of straight line, small radius curve and continuous small radius curve, the comparison and analysis of shield tunneling processes of various line types are carried out, and the basic rules of surface settlement caused by continuous small radius shield construction are summarized. The correctness of the conclusion is verified by using empirical formulas. The results show that the surface settlement caused by continuous small radius shield construction conforms to the Gaussian distribution law, and the maximum value of surface settlement is located at the starting end of shield tunneling, and the amplitude and range of soil disturbance caused also continue to increase. Under the same conditions, the surface settlement caused by continuous small radius shield construction increases by about 16.4% and 33.3% respectively compared with small radius shield construction and straight section shield construction.

This paper studies the bearing capacity and seismic performance of a new type of assembled joint with tenon. The finite element model of hollow sandwich concrete-filled steel tubular column-steel beam assembled joint system is established by ABAQUS software, and its mechanical mechanism is analyzed. The static performance and hysteretic performance of bolted and tenon assembled joint system with different ring plate width, embedded depth, axial compression ratio and concrete strength are compared. Through the comprehensive comparative analysis of the stress nephogram, hysteretic behavior and skeleton curve of the members, the results show that the assembled joint system of hollow sandwich concrete filled steel tubular column and steel beam has reliable bearing capacity and good energy dissipation performance. The assembled joints based on tenons form fully assembled non-permanent beam-column joints, which makes the space layout more flexible and solves the problem of limited middle height in temporary buildings.

In this paper, the fire resistance limit state of a new bolted prefabricated beam-to-beam joint exposed to fire, and the influencing factors of its fire resistance limit were studied. Based on the ABAQUS finite element software, a numerical simulation of bolted prefabricated beam-beam joints under temperature load and static load is carried out, and the mid-span deflection curve is drawn according to the fire exposure time for different components. The mid-span deflection of the bolted prefabricated beam-beam joints gradually increases with the increase of fire exposure time, and breaks away from the linear growth when approaching the fire resistance limit. With the increase of fire exposure time, the growth rate of the mid-span deflection of the components is constantly increasing, and the growth rate of the mid-span deflection of specimens with different fire resistance is also different, the greater the load ratio of the components, the shorter their fire resistance limit; the higher the concrete strength grade, the thicker the concrete protective layer, and the longer the fire resistance limit. The size of the bolt pretightening force and the bolt strength grade have no effect on the fire resistance rating in the present model design.

In GB50010-2010 ‘Code for design of concrete structures’, there is no clear stipulation on how to distinguish the spiral stirrup column from short column or medium-long column, which causes confusion to designers in practical engineering design. In order to quantitatively analyze the limit slenderness ratio of spiral stirrup axial compression short column and medium-long column, this paper establishes and verifies the finite element model of spiral stirrup axial compression column based on ABAQUS software. Based on the data obtained by finite element method, the load-displacement curve and ultimate bearing capacity of the component are analyzed, and the judgment method of the limit slenderness ratio of short column and medium-long column is given. Based on this judgment method, the finite element analysis of spiral stirrup axial compression column with different parameters is carried out. The results show that the limit slenderness ratio of the spiral stirrup axial compression short column and the middle and long column is 4.9 to 7.3, which is mainly related to the concrete strength and pitch of the component, and is negatively correlated with the two. The influence of concrete strength on the limit value is affected by the pitch. As the pitch increases, the influence of concrete strength on the limit value gradually decreases. On the basis of calculation and analysis, the proposed formula for calculating the boundary slenderness ratio of short columns and medium-long columns under axial compression of spiral stirrups is proposed.

Heinrich’s law identifies people as the primary cause of accidents. Human factors must be controlled in safety management to prevent production accidents. Therefore, to ensure the safe construction of the top die system, and improve the productivity of the top die system. Based on the theory of human factor engineering, this paper will conduct safety evaluation on the construction of top die system, deeply study the application of human factor engineering in the construction safety evaluation of top die system, and improve the safety management system of top die system construction. A neural network algorithm based on BP is used to test the scientific validity of the model. As a result of learning and training the sample data collected from the actual engineering project, the output value and predicted value of the final BP neural network algorithm are compared in order to determine the model’s scientific validity and effectiveness.

This paper aims to establish a stress-strain curve model for high-strength spiral hoop-restrained concrete that can be applied to different cross-sectional forms and different constraint conditions. Based on mathematical statistics methods, collect and process the axial compression test data of high-strength spiral reinforced concrete columns with 5 types of hoop reinforcement constraint forms under 2 cross-sectional forms from existing literature are processed. The material parameters of the collected test specimens are concrete strength of 35.2–83.07 MPa, hoop yield strength of 450–1318 MPa, volumetric reinforcement ratio of 0.48%–4.43%, and longitudinal reinforcement ratio of 0.45%–1.79%. Subsequently, regression analysis is conducted on the five characteristic parameters of the stress-strain curve to establish a model for the stress-strain curve of high-strength spiral confined concrete. Comparing the curve model in this paper with the experimentally measured stress-strain curves of the test components, it is concluded that the curve model in this paper has the ability to predict the behavior of high-strength spiral reinforced concrete circular and rectangular components under different constraint conditions. The results show that the proposed formulas for calculating the stress of hoop reinforcement, peak compressive stress, peak compressive strain, and ultimate compressive strain under peak compressive stress are more accurate. The established model of stress-strain curve for high-strength spiral hoop-reinforced confined concrete has a wide range of applicability, accurately predicts the behavior of structural tests, and is convenient for finite element analysis and engineering calculations.

In this paper, based on the computational fluid dynamics method, the k-ε turbulence model is used to establish a steady state model to investigate the leakage law of the pipeline with a single leakage point. Starting from the three basic information of leakage port shape, leakage port area, and pipeline pressure, when the variables are changed, we investigate the change of the pressure flow field inside the leakage port and the influence on the leakage volumetric flow rate of the pipeline. Numerical simulation results show that: The shape of the leakage port, the internal pressure of the pipe, and the area of the leakage port all have influence on the pressure flow field inside the leakage port; the leakage coefficient is directly proportional to the area of the leakage port, which in turn introduces the leakage influence coefficient, and accurately optimizes the discharge formula to obtain the leakage loss formula of the pipeline under different leakage port shapes.

Nowadays, with the continuous development of industrialization, liquid-filled pipeline is the most representative pipeline transportation system. The damage forms of pipes with cracks will affect the mechanical properties of reinforced concrete pipes to varying degrees and make their properties decline. We investigated the undamaged, damaged and liquid-filled reinforced concrete pipelines, and analyzed the propagation mechanism of piezoelectric sensing signals in reinforced concrete pipelines. When the ultrasonic guided wave touches the damaged position, part of the ultrasonic guided wave will reflect, while the other part of the guided wave will continue to propagate through the damaged position, which is the reflection and transmission phenomenon of the ultrasonic guided wave. The damage assessment of pipeline structure can be realized by using the reflection and transmission phenomenon of ultrasonic guided wave. The signals of undamaged hollow pipe and undamaged liquid-filled pipe were compared and compared undamaged signal and damaged signal in liquid filled pipeline. Based on pulse-echo method, the influence of damage on signal propagation in liquid-filled pipeline is obtained.

Numerical simulation research on pipelines subjected to explosion impact basically turns to ALE. Yet it suffers from unclear interfaces between flowing materials and fails to value the impact of soil compression state and pipe-soil sliding on pipeline stress. To streamline calculation and better demonstrate the damage process of soil under explosion load, this study applies SPH-FEM coupling to study the dynamic response of buried pipelines under explosion load, and compares results of this study with experimental results of Ambrosini et al., and good consistency was observed. This study dissects the dynamic response of the buried X65 pipeline under explosion load, considers the influence of different diameter-thickness ratios of the pipeline and the distance from the explosion, and compares the simulation results in virtue of numerical analysis. SPH-FEM coupling intuitively simulates the entire development process of explosion craters under the action of explosion load, and handles the SPH boundary problem well, found study outcomes. As the diameter-thickness ratio of the pipeline decreases and the explosion distance increases, the deformation and maximum equivalent strain of the pipeline gradually decreases, and the impact of the explosion distance is much greater than the diameter-thickness ratio. This study offers reference for upgrading the protection design of steel pipes.

In order to investigate the lateral impact resistance of GFRP concrete-encased steel members, a total of 26 members were established using ABAQUS. On the basis of correct models, the failure mode has been identified, and the parameters have been analyzed. The results indicate that the failure mode of the members is flexural failure under lateral impact. The increase of the impact energy and impulse caused further failure of the members. Conversely, the impact resistance of the members was improved with the increase of the concrete strength, yield strength of the steel, thickness of the GFRP tube, cross-section diameter, and steel ratio. It is recommended that the yield strength of the steel not be more than 390 MPa, while the optimum thickness of the GFRP tube is 6 mm.

The torsional response of single-story symmetric frame structure subjected to seismic wave passage excitation is studied by analytical method. The dynamic equilibrium equation is established for the single-story frame structure subjected to wave passage excitation. The analytical solutions of translational and angular displacements of the roof centroid, torque and column shear forces of the structure with wave passage excitation are derived. Four sets of column shear forces of two single-story frame structures with two wave passage excitations are calculated and compared with the corresponding results of the uniform excitation. The calculating results show that the column shear forces in the exciting direction with wave passage excitation are related to the distance between the column and the roof centroid in the propagation direction. Compared with uniform excitation, the peak shear forces of columns near the centroid reduce respectively by 79.5%, 81.5%, 23.6% and 31.2%, while the peak shear forces of columns away from the centroid increase respectively by 17.2%, 73.1%, 83.6% and 5.6% with wave passage excitation. The peak shear forces of the distal columns in the direction of wave passage propagation are bigger than those of the proximal columns (facing the wave input). The peak shear forces of the distal columns are 22.9%, 4.4%, 50.8% and 11.3% higher than those of the proximal columns respectively.

When a fire occurs in a Twin-tower high-rise building linked with connective structures, it will spread laterally through the connective structures, causing greater damage. In this paper, PyroSim is used to simulate the whole process of the “8·27” fire in Dalian Kaixuan International Building. The results show that within 50s, the compartment fire overflow occurs, the flame spreads upward at a speed of 0.79 m/s, and spreads to the top of the tower at 86 s. It spreads horizontally at a speed of 0.54 m/s, and 126 s spreads to another tower; The local maximum temperature of the outer surface of the tower fire area is 1200 °C. The maximum temperature of the outer surface of the corridor is 1143.13 °C. The concentration of CO in all rooms of the corridor in the burned area exceeded the critical concentration leading to death. When the flame passes through the corridor to another tower, the maximum temperature is 524.40 °C lower than before.

In order to determine the connection scheme of the high-level connection of a connected twin-tower structure, four models of different connection forms are established. Model I is rigidly connected to both ends of the tower. Model II is hinged with tower A and rigidly connected with tower B. Model III is slidingly connected with tower A and rigidly connected with tower B. Model IV is hinged with both ends of the tower. The elastic dynamic time-history analysis of structures of four different connection modes under earthquake action is carried out in ABAQUS. The results show that the connection mode of rigid connection at both ends under earthquake can not only reduce the structural displacement, but also realize the stiffness coordination between towers, and has the smallest the Inter-story Drift Ratio and vertex displacement, and the maximum displacement of key beam-column joints is small, and the damage of each connection mode is similar. Therefore, for the connected twin-tower structure, the rigid connection at both ends of the high-position connection is more favorable to the overall structure.

In order to investigate the impact of different types of grain storage silos on grain dust explosions during transportation and storage. FLACS software was utilized to construct building models of flat and cylindrical grain silos. The study systematically compared the flame propagation range, maximum explosion overpressure, and temperature variations of different silo types by altering the dust concentration, ignition position, and silo shape. The simulation results indicate that dust concentration, ignition position, and silo shape all influence the explosion process. Flame release in flat grain silos occurs horizontally, whereas in cylindrical grain silos, it occurs from the top. Within the mass concentration range of 200–700 g/m3, an increase in dust concentration leads to higher maximum explosion overpressure and elevated temperatures at observation points. As the ignition source moves closer to the center of the dust cloud, the flame shape becomes more ellipsoidal, leading to higher maximum explosion overpressure and a shorter time to reach it.

To reduce the harm caused by smoke spread in the event of a fire, this article proposes a vertical air curtain. The platform floor of an island style subway station is taken as research background, the impact of four types of air curtains on fire smoke control was investigated using FDS numerical simulation software, including upper air supply (US), downside air supply (DS), upper air supply and downside air exhaust (USDE), and downside air supply and upper air exhaust (DSUE), by analyzing the changes in visibility, CO concentration, and the temperature of smoke. The results show that the smoke control effect of the US air curtain and USDE air curtain are poor, because they cannot prevent the spread of smoke; The DS air curtain and the DSUE air curtain can effectively block the spread of smoke, among which the DSUE air curtain has the best smoke blocking effect. Within 360 s, it can ensure that the visibility at the height of the human eye in the protected area of the air curtain is maintained at 30 m, the CO concentration does not increase, and the maximum smoke temperature is 21 ℃. It proves that using the DSUE air curtain can ensure a safe evacuation time of more than 6 min for personnel, providing convenient conditions for personnel evacuation.

The uniform design experiment method was adopted to develop a grouting test plan. By conducting a simulated sleeve valve pipe grouting experiment, the impact of grouting pressure and water-cement ratio on the spreading of grout in sand layers can be analyzed: Under the pressure of grouting, the dominant position of the splitting effect combined with the permeation effect is filling the grout-receiving soil layer in multiple forms and coexisting with the permeation flow portion, which is well bonded to the grout-receiving soil layer. The nonlinear relationship between the diffusion radius of the slurry, grouting pressure, and water-cement ratio during the grouting process is obtained by employing regression analysis for test data design.

Hoisting engineering is an important part of building construction, and its safety problems can’t be ignored. To effectively assess and reduce the safety risk of hoisting operations in construction engineering, this paper introduces the T-S model based on the traditional accident tree model and combines it with the Bayesian network to establish a kind of safety evaluation model for the project of hoisting operation in construction engineering, and utilizes the model to evaluate the safety risk of the actual hoisting case. The results show that the model can quantitatively calculate the risk probability of the primary risk factors in the hoisting project. It can not only calculate the probability of the final event in a forward reasoning way to determine the critical control order of each risk factor but also carry out reverse reasoning to investigate the causes of safety accidents in the hoisting project. The safety evaluation model is close to the actual construction, which can provide theoretical support for the exemplary safety management of construction hoisting projects.

In this paper, a new type of prefabricated beam-column joint is proposed, which uses high-strength bolts and embedded steel plates to connect the prefabricated beam-column. The finite element software ABAQUS is used to establish the frame structure model of the new prefabricated beam-column joint, and then two natural ground motion records and one artificial ground motion record are selected to carry out the time history analysis under the action of rare earthquakes. The cast-in-place frame structure model with the same size and loading mode is established for comparative analysis. The core components of the new prefabricated beam-column joints have not yielded to damage under three ground motion records. The damage is mainly concentrated in the beam ends, which meets the design principle of ‘strong joints and weak components’. The inter-story shear force, vertex acceleration, and inter-story displacement angle of the prefabricated structure under the action of different ground motion records are slightly lower than those of the cast-in-place structure. The results show that the new prefabricated beam-column joints have good seismic performance, which meets the requirements of seismic code, and its overall seismic performance is slightly better than that of the cast-in-place structure.

According to the previous research on the simulation of corrugated plate explosion-proof wall, the corner cone explosion-proof wall is proposed by changing the structure of the explosion-proof wall. ANSYS/LS-DYNA finite element software was used to simulate and analyze the new explosion-proof wall with a cone height of 15, 22.5, 30, 37.5, 45 cm and a bottom edge of 30 cm under the same blasting height and proportional blasting distance. The feasibility of the model is verified by comparing the empirical formula, and then the overpressure peak of each test point is analyzed. Firstly, it is concluded that the triangular cone explosion-proof wall has a stronger weakening effect on the shock wave than the straight wall, and the cone heights of 15 cm and 30 cm are the most obvious. Secondly, the triangular cone wall will change the shape of the shock wave after passing through the explosion-proof wall to a certain extent. Finally, the peak value of superimposed overpressure at 1–1.5 times the height of the wall behind the triangular cone wall will be greater than that of the ordinary straight wall.

To investigate the influence of partial reinforcement failure in FRP-confined rebar splicing joints on the seismic performance of precast portal frames, based on the experimental results of anchorage performance and splicing performance of the joints, this paper established a macroscopic analysis model of precast concrete portal frames considering partial longitudinal reinforcement failure in the joints using OpenSees finite element analysis software. By combining fiber section modeling technique and strain penetration effect simulation technique, under low-cycle reversed loading condition, the influence of different positions and numbers of failed splicing rebars on the overall seismic performance of portal frames was analyzed. The results show that when the joints have defects, the area of the envelope curve of the structural hysteresis loop will significantly decrease, and it will increase with the increase of the number of failed rebars; the joint defects will slightly reduce the initial stiffness of the overall frame structure, but have a greater impact on the stiffness degradation in the middle and late stages of loading; compared with the defect-free precast frames, the cumulative energy dissipation capacity of the precast frames with edge-failed rebar connections is decreased by 6.40%–24.45%, and their ductility coefficient is decreased by 16.49%–24.45%, while the cumulative energy dissipation capacity of the precast frames with middle-failed rebar connections decreased by 5.26%–11.60%, and their ductility coefficient decreased by 14.11%–20.36%. In summary, for the precast frame structures with defective joints, their hysteresis performance, stiffness degradation, cumulative energy dissipation, ductility coefficient and other evaluation indicators are lower than those of the defect-free precast frames, and the position and number of failed longitudinal rebars in the joints have an impact on the overall seismic performance of the structure.

A new type of prefabricated beam-column connection T-joint is proposed, which connects prefabricated beams and columns through components such as high-strength bolts and embedded steel plates. The deformation and mechanical properties of this new fabricated T-joint under explosion load were studied, and its reliability was analyzed. The finite element analysis software LS-DYNA was used to establish respectively the finite element models of cast-in-place and prefabricated T-joint under the same conditions of the same size and loading mode. The failure characteristics, stress and displacement analysis of T-joints with two different construction techniques under blast load are compared and analyzed. The results show that compared with the cast-in-place joint, the local damage caused by the explosion shock wave to the new prefabricated T-joint is more serious, but there is no large area of concrete collapse. In addition, under the two different construction technologies, the change rules of the steel bar stress and the joint displacement of the T-joint are basically the same. Therefore, it can be concluded that the new prefabricated structure has good explosion resistance.

In the field of urban underground engineering, the identification of damage and the safety assessment of nearby existing tunnel structures due to vibrations from Metro Shield Construction are of paramount importance. With the continuous expansion of urban subway systems, the vibrations generated by shield excavation can have varying degrees of impact on existing underground structures, posing threats to their safety. To address this concern, researchers have conducted in-depth studies and proposed an advanced method based on wavelet packet analysis and neural networks. This method involves monitoring vibration response signals from multiple measurement points, extracting feature vectors, and utilizing a genetic algorithm for neural network training, successfully achieving damage identification. Additionally, the application of Dempster-Shafer evidence theory is anticipated to play a crucial role in dealing with uncertainties. This research provides essential technical support for ensuring the safety of urban underground transportation and infrastructure, contributing to a better understanding and assessment of the potential risks associated with vibrations caused by Metro Shield Construction.

In this paper, a set of new orthogonal-installed double steel corrugated plate wall structure is designed based on the stress characteristics of steel corrugated plate and stiffened steel plate. The finite element software ABAQUS was used for numerical simulation to study the effects of 30°, 45° and 90° on the hysteretic performance. The results show that the initial lateral stiffness of the specimens is higher than that of the other two groups when the bending Angle is 30°. When the bending Angle is 45°, the resistance of the specimen to out-of-plane buckling is strong, and its energy dissipation capacity is higher than that of the other two groups. When the bending Angle is 90°, the specimen can still be carried with a symmetrical and complete “X”-shaped tension band after yielding. After the specimen reaches the peak load, the load value drops slowly, which is conducive to the stability of the bearing capacity of the specimen in the later period.

Tripod pile foundations are an alternative foundation for offshore wind turbines. Three-dimensional finite element limit analyses are carried out to determine the bearing capacities of tripod pile foundations in non-homogeneous clay under combined vertical (V), horizontal (H) and bending moment (M) load. The undrained shear strength of the clay is considered to increase linearly with depth. Three-dimensional failure envelopes in V-H-M loading space are established through a simplified loading strategy considering the reality of the loading condition. The obtained results are finally presented in terms of normalized and dimensionless capacity factors. Moreover, the effects of length-to-diameter ratios (L/D), spacing-to-diameter ratios (s/D) for the tripod piles, and the gradient of undrained strength in terms of soil depth (k) on failure envelopes are further discussed. Several failure mechanisms are identified to be associated with different load combinations.

Urban infrastructure is the guarantee for cities to maintain normal socio-economic activities. Resilience assessment of infrastructure helps to ensure the safe operation of infrastructure. In view of the actual needs and important problems of urban safety at this stage, this study starts from the concept of resilience development and urban safety resilience, analyzes the characterization of safety resilience, and proposes a characterization model of urban infrastructure safety resilience. Based on the three basic elements of risk source, disaster bearing body and disaster reduction body, the framework of urban infrastructure safety resilience is constructed. This study analyzes and summarizes the main influencing parameters of the functional changes of infrastructure in each stage of resistance, adaptation and recovery, and establishes the indicator system of urban infrastructure safety resilience evaluation, which provides a reference for the evaluation of urban infrastructure safety resilience and urban safety improvement countermeasures.

This study presents a practical application in which the different samples made by ecological concrete are analyzed at mechanical characteristics tests of compression loads, bending loads and splitting loads for different samples made by eco-friendly concrete. In the concrete recipe for the experiment was used fly ash as cement replaced and it mixed different sort of recycled concrete aggregates (RCA) waste crushing and sorted they as replacement of sand and natural aggregate. The mechanical characteristics such as: compressive strength, tensile strength by bending and split tensile strength of concrete whit fly ash and RCA waste have been determined. The mechanical characteristics of concrete samples were influenced by the dosage and the mixture of RCA waste. Failure in compression loads, bending loads and splitting loads of concrete samples was gradual and ductile.

The practice of reusing ceramic waste is an environmental, economic and technical advantage. Brick and masonry waste contributes to the production of sustainable materials whose physical and mechanical performance can be improved. According to recent studies on plastering mortars with ceramic waste, by replacing up to 25% sand with brick waste, respectively 15% brick powder waste with cement, does not negatively influence the mechanical strengths. The present research work proposes to investigate by non-invasive SEM-EDX and NMR methods, plaster mortars with 35% ceramic waste for partial replacement of aggregates, respectively mortars with 30% ceramic waste partially replacing cement. The aim of these investigations is to examine the topographic surface, the elemental composition of the samples as well as the characteristics of pores and connections within the structure of the ceramic waste mortar samples. The results obtained identify an increase in the structural performance of the recipe with 35% brick waste, as well as relative pore water content. These investigations provide us with a com-prehensive view of the characteristics of mortars with technical performance within the limits of the standards in force and whose aim is to reduce CO2 emissions and the consumption of resources as much as possible and to obtain a sustainable material.