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High-performance concrete (HPC) shows obvious autogenous shrinkage in the early stage. In actual engineering, the interior of HPC undergoes a variable temperature evolution, and the impact of variable temperature conditions on the autogenous shrinkage of HPC is unclear. This paper examines the impact of different curing temperatures on the material properties of HPC, as well as the evolution of HPC autogenous shrinkage. Three measured temperature histories and four constant temperatures were used as curing conditions. Additionally, an HPC autogenous shrinkage prediction model was established considering the impact of curing temperature. The test results indicate that the compressive strength and elastic modulus of HPC increase with increasing curing temperature. Furthermore, there is a significant increase in the autogenous shrinkage rate of HPC as the curing temperature increases. Existing maturity methods overestimate the impact of temperature on the autogenous shrinkage process of HPC. The proposed autogenous shrinkage prediction model enhances the accuracy in predicting the autogenous shrinkage of HPC under constant and variable curing temperature conditions. • The autogenous shrinkage of high-performance concrete (HPC) was studied under variable curing temperatures. • The compressive strength and elastic modulus of HPC both increased with higher curing temperatures. • The autogenous shrinkage of HPC increased as the curing temperature increases. • An autogenous shrinkage of HPC prediction model considering the influence of temperature was established. [ABSTRACT FROM AUTHOR]

· A special prestress distribution function with geometry parameters is created for initial geometry-force interactive design. · A novel interactive design method for geometric design, prestress design and shape optimization is presented. · Feasible prestress distribution can be directly obtained by the prestress distribution function without algebraic operation. · Design and optimization of geometric shape using prestress distribution function do not depend on specific load conditions. · The geometric shape optimized by particle swarm optimization can significantly improve the structural performance. Cable dome is a typical flexible structural system. Its initial geometry determines the prestress distribution and affects the structural performance. Using geometric parameters to establish the mechanical equation of initial state can effectively realize the geometric-force interactive design and optimization of cable dome structure. Consequently, a standardized equation is established in this paper to uniformly express the geometric-force relationship, utilizing a feasible prestress distribution function expressed by geometric parameters. Subsequently, an interactive design method for initial geometry and prestress is presented. The proposed method is theoretically expounded in terms of geometric design, prestress design and shape optimization. Two typical cable dome cases, Geiger and Levy, are successfully applied to accomplish the geometric-force design and optimization of the initial state. The results show that the efficient design of initial state can be completed by establishing the interaction between geometry and force without repeated algebraic calculation. The optimized initial geometry can significantly improve the Structural stiffness. [ABSTRACT FROM AUTHOR]

Cable–truss structure is a typical form of cable–strut tensile structures, which consists of upper cable system, lower cable system and several vertical struts. As with the general cable–strut tensile structure, only when the reasonable geometric shape matches the feasible prestress distribution can the cable–truss structure obtain structural stiffness and bear the external load. Once the geometric shape is unreasonable, the cable–truss structure is just a mechanism without bearing capacity and cannot be stiffened by introducing prestress. Consequently, a reasonable geometry is the premise for cable–truss structure to become an effective load-bearing system. In this paper, an equivalent equilibrium force model, called EEFM, is proposed according to the geometric-mechanical characteristics of cable–truss structures. A cable–truss structure in this model is split into upper and lower cable systems with equivalent nodal forces. The geometric rationality can be easily evaluated from the equivalent nodal force relationship. According to the geometric topology and equilibrium equation of two cable systems, the self–stress mode of the structure with reasonable geometry can be directly obtained. For structures with unreasonable geometry, the node coordinates of one cable system are corrected based on the other cable system. Several cases are presented to verify the accuracy and validity of the proposed method. This method can be used for shape design, geometric correction and force finding, and has greater advantages for cable–truss structures with asymmetric or complex space configuration. • An equivalent equilibrium force model is proposed for determining feasible geometry and prestress of cable–truss structures. • The proposed method integrates force finding and geometry design into a solution framework without iterative calculation. • Several cases written in the Python language are presented to verify the accuracy and validity of the proposed method. • This method can accurately identify and correct the unreasonable node coordinates in the cable–truss structure. • The feasible prestress of the cable–truss structure with reasonable geometry can be obtained directly by projection geometry. [ABSTRACT FROM AUTHOR]

Air-supported membrane structures are widely used in stadiums, malls, and museums. The stiffness and shape of such structures are dependent on the pressure difference between the indoor and outdoor environments. As the leakage of indoor air may lead to the collapse of the structure, it is necessary to study the deflation deformation process, including the properties that can cause air-supported membrane structures to collapse. In this study, a rectangular air-supported membrane structure is fabricated using a PVC-coated polyester fabric membrane with dimensions of 38 m × 20 m × 7 m, and a leakage experiment is performed. The relationship between the initial leakage area and the pressure difference is obtained, and a new algorithm to determine the equivalent initial leakage rate is proposed. A collapse test is then conducted, with results illustrating that there are two distinct phases of collapse. There is a quick drop in the pressure difference in the first phase, whereas the pressure difference declines rather slowly in the second phase. Computational formulae for collapse and escape times are established, and finally, a quasi-equilibrium status-based algorithm to determine the collapse time of air-supported structures is proposed. Using the new algorithm, several main parameters that influence the collapse of air-supported structures are studied, including the cables, initial pressure, and leakage area. Results show that the initial pressure has a minimal effect on the collapse of structures, while excessive cables accelerate the process of collapse. • Theoretical formula between equivalent initial leakage area was presented. • Considering the visibility of safety gate, a new method for calculating escape time was proposed. • A quasi-equilibrium status-based deflect analysis method was proposed. • Collapse of air-supported structures with different parameters were researched. [ABSTRACT FROM AUTHOR]

• A modified force density method utilizing the concept of relation matrix was proposed in this paper. The modified method realized the establishment of a clear correspondence between members and nodes of cable net structures. • The modified force density method was used in the single-layer spoke cable net structures, and the effect of pretension on form-finding was analyzed. • The surface equation of circular single-layer crossed cable net structure without inner ring was derived. Combined with the modified force density method, the form-finding process of this type of structure is achieved. Form-finding is crucial for the design of typical cable net structures. Based on the original basic force density method, a modified force density method utilizing the concept of relation matrix is proposed in this paper. The modified method realizes the establishment of a clear correspondence between members and nodes of cable net structures. On the basis of the relation matrix, the find function is introduced, and the calculation formula of the modified branch-node matrix is derived. Meanwhile, the corresponding analysis steps and calculation process are given. The modified method is verified by the analysis of representative structural forms. The results show that for the saddle-shaped orthogonal cable net structure, the outcomes obtained from the modified force density method highly agree with the theoretical values, providing preliminary verification of the method's effectiveness. For single-layer spoke cable net structures, the relative error between the results calculated by the modified force density method and the numerical solution is approximately 5 %. The results of both methods are relatively consistent, and the relative error varies in relation to the ratio of inner ring cable force density to radial cable force density. For circular single-layer crossed cable net structure without inner ring, the results of the modified force density method are very close to the numerical solution. The maximum relative error between the two is 6.95 %, and the accuracy is higher than that of the nonlinear finite element method. The outcome of this research demonstrates the accuracy of the modified force density method and its effective application in the form-finding of actual cable net structures. [ABSTRACT FROM AUTHOR]

Abstract Investigating the mechanical properties of Galfan-coated steel cables at elevated temperatures is important for the fire-resistant design and fire-simulation analysis of pre-stressed structures. Unlike conventional structural types, Galfan-coated steel cables comprise several steel wires encircling a core wire in different layers. The overall mechanical property of a Galfan-coated steel cable is attributed to the individual properties and collaborative mechanism of Galfan-coated steel wires. The mechanical properties of a Galfan-coated steel cable at elevated temperatures are substantially different from those of conventional structural steel or the single steel wire. In this study, 42 Galfan-coated steel cables with 19, 37, and 61 wires were tested under steady state tension at ambient and elevated temperatures ranging from 100 to 600 °C. The test results show that the cables exhibit typical non-linear characteristics with a lower proportional limit and no clear yield plateau. The reduction factors in the mechanical properties of Galfan-coated steel cables at elevated temperatures are obtained and compared with values predicted in Eurocode 2 part 1–2 and ACI 216, and other studies. Equations for nominal yield strength, elastic modulus, ultimate strength, and ultimate strain for Galfan-coated steel cables at elevated temperatures are proposed in this study. Furthermore, a modified two-stage Ramberg-Osgood model for Galfan-coated steel cables at ambient and elevated temperatures is proposed. Highlights • Forty-twoGalfan-coated steel cables tested at ambient and elevated temperatures • Forty-two Galfan-coated steel cables tested at ambient and elevated temperatures • Cables exhibit typical non-linear characteristics with a lower proportional limit • Equations for predicting mechanical properties considering elevated temperature • Modified two-stage Ramberg–Osgood model for stress–strain relationship prediction [ABSTRACT FROM AUTHOR]

Highlights • Internal forced convection heat transfer coefficient was gained from in situ tests. • Air pipe cooling technique was proved effective by cooling tests on massive walls. • Accuracy of FE analysis with the proposed formula was verified by the cooling tests. Abstract Air pipe cooling is an emerging technique in dealing with the hydration heat and thermal induced cracking of massive concrete structures. In order to investigate the influence of air pipe cooling on temperature distribution in large-dimension concrete walls, in situ experiments of heat transfer coefficient for internal forced convection were conducted on one experimental wall of 3.6 m × 3.6 m × 0.8 m in dimension with properly embedded corrugated pipes. The relationship between average inlet air velocity and average heat transfer coefficient for internal forced convection was then obtained and fitted to a proposed formula. In addition, air cooling experiments were performed on another three experimental walls to monitor the temperature variations of internal concrete. Meanwhile, finite element (FE) thermal analysis with the proposed formula was carried out and compared with the results of air cooling experiments to verify the accuracy of the proposed FE method. As the comparison results show, the calculated temperature curves are in good agreement with the tested data, with an average deviation of 0.07 °C, 0.13 °C and 0.19 °C under average inlet velocity u ¯ in of 3.78 m/s, 8.12 m/s and 11.64 m/s, respectively. It indicates that the FE analysis with the proposed heat transfer coefficient formula for internal forced convection is effective in estimating concrete temperature variations, providing a reliable fundamental approach for further thermo-mechanical coupling analysis and ventilation design in practical engineering projects. [ABSTRACT FROM AUTHOR]

• Carrying out the fire temperature field analysis of air-supported membrane structure considering thermal–fluid–solid coupling and dynamic boundary conditions. • Modifying the traditional fixed boundary analysis method, and comparing different fire temperature field analysis methods. • Regressing and fitting the parameters of fire temperature fields model of air-supported membrane structure. • Carrying out the high-temperature mechanical properties test of the membrane material and analyzing the fire temperature field of structures considering the time-varying membrane material properties. The study analyzed and compared the effects of thermal–fluid–solid coupling dynamic boundary conditions and traditional fixed-boundary conditions on the distribution of the temperature field under fires. The feasibility of simulating the temperature field distribution was confirmed by using thermal–fluid–solid coupling dynamic boundary conditions. Then, the traditional temperature field analysis methods were corrected by including a flow-based heat exchange coefficient, and the feasibility of this approach was also confirmed. The fire temperature field in a rectangular air-supported membrane structure was analyzed through parameterization. The fire temperature field model of the air-supported membrane structure was established using temperature field data fitting. Furthermore, the study explored the high-temperature material properties of P-type membranes and analyzed and compared the temperature field of the air-supported membrane structure with time-varying mechanical properties of the membrane material to that without time-varying properties. [ABSTRACT FROM AUTHOR]

• The mechanical properties of 24 M-C cables were tested with 6 kinds of diameters. • M-C cable exhibit typical nonlinear characteristic as the increasing of stretching. • An improved constitutive model predicts well mechanical properties of M-C cable. • FE models simulate well stress-strain behaviours of cables with varying diameters. • Friction has slight influence on the longitudinal mechanical properties of cable. This study investigated the mechanical properties of zinc-5% aluminum-mixed mischmetal alloy-coated steel strand cables (M-C cables) with diameters ranging from 12 mm to 22 mm. A total of 24 tensile tests were conducted to obtain the nominal yield strength, ultimate strength, elastic modulus, fracture strain, and stress-strain curves for M-C cables with varying diameters. The stress-strain curves of the test specimens were fitted using the modified Ramberg and Osgood models to obtain stress-strain models for M-C cables with different diameters. Based on the actual boundary of the cable used in engineering practice, a new finite element model was established with ABAQUS finite element analysis software. Based on the finite element model, the development of the stress in each layer of steel wire, change in the contact pressures between the wires, and the friction energy dissipation between the wires were analyzed with continuous elongation of the cable. [ABSTRACT FROM AUTHOR]

Air-supported membrane structures are being widely used for coal-sheds or the enclosed buildings of stockyards. With the emergence of new functional requirements for buildings, the demand for an increase in both the span and size of air-supported membrane structures has been rapidly increasing in China. Till now, the largest span and length of structures in China have reached 200 m and 1300 m respectively. For air-supported membrane structures, the load-bearing capacity comes from the difference in air pressure between the interior and exterior, which causes the structure to be sensitive to wind and snow loads. This paper studies the wind-induced response of a constructed air-supported membrane structure for a coal-shed cover building with a span of 115 m and width of 317 m, which is located in the southeast coastal city of Yueqing in Zhejiang Province. It is well known that the typhoon-induced response is closely related to the safety and stability of the structure. To ensure the safety of the structure, a newly improved Structure Health Monitoring System (SHMS) has been implemented on a membrane building which is one of the largest scale field monitoring projects anywhere in the world, from where the wind-induced response data was obtained for this paper. Based on the measured wind speeds, the wind pressure distribution coefficient of the membrane surface is derived by numerical simulation with Fluent software. Meanwhile, the displacement response is also calculated by ANSYS APDL. Detailed simulation results and field measurement data are compared for the displacement response caused by Typhoon "Chan-Thu". It is shown that the former is larger than the latter with the treatment of equivalent wind load. However, the extreme value of the displacement response of the structure with consideration of fluctuating wind load is relatively much more consistent with the measured value. In conclusion, the wind-induced displacement response calculated by the equivalent static wind load method controlled by the principle of maximum displacement equivalence is suitable for engineering applications and wind resistance design, which will result in a slightly higher displacement response evaluation than the real cases. • Newly developed membrane structure health monitoring system first application for coal-shed building covered by large-span air-supported membrane structure. • Based on the data monitored by the health monitoring system, the wind induced response of a real project with span of 115 m and length of 317 was tested, and the response includes acceleration, displacement, surface wind pressure. • The Typhoon "In-Fa" induced wind displacement response comparison between the simulation result and in-site measured data was carried in detail. [ABSTRACT FROM AUTHOR]

In recent years, air-supported membrane structures have been widely used in China's environmental protection of closed coal yards and in sports stadiums. There have been breakthroughs year by year in the numbers constructed, unit area, and span. At present, the largest span of an air-supported membrane structure coal shed has reached 198 m. As the span increases, the force-bearing performance of the structure is more closely related to its shape. In this paper, based on a 225m × 198m × 66m(Length × width × height) long-span air-supported membrane structure test model, the form-finding and state-finding analysis of the air-supported membrane structure with longitudinal and transverse cable nets were carried out, and the results were compared with the forming test results. The results show that the prestressed state of the structure obtained by the state-finding analysis is closer to the test results. However, there is a specific difference with the target height. At the same time, the form-finding analysis can accurately find the target height, but the structure's cable force and section shape are quite different from the test results. • The shape of the membrane surface and the force characteristics of the cable net was measured through the experiment. • Two numerical analysis methods are used to obtain the force characteristics of the air-supported membrane structure. • The advantages and disadvantages of the two methods are obtained by comparing the experimental and simulation results. • The problems that should be paid attention to in the design of large-span air-supported membrane structures are put forward. [ABSTRACT FROM AUTHOR]

• Mechanical property parameters of ETFE membrane at different temperatures are given. • The thermal expansion coefficient of the ETFE membrane is given. • The thermal deformation model is given. • The thermal deformation mechanism is proposed. This study focused on the mechanical properties of the ethylene tetrafluoroethylene (ETFE) membrane at temperatures between −20 and 140 °C, the thermal expansion performance from the ambient temperature of 25 °C to 140 °C, and the thermal deformation performance from the ambient temperature of 25 °C to 80 °C. According to the experimental study, the mechanical properties, the glass transition temperature, the coefficient of thermal expansion (CTE), and the thermal deformation strain model of ETFE at different temperatures were obtained. Finally, the thermal deformation mechanism is proposed, namely that the thermal deformation strain is equal to the thermal expansion strain and elastoplastic strain produced by the change of the strain–stress relationship. [ABSTRACT FROM AUTHOR]