The temperature shrinkage effect is a very important factor causing the cracking of super-long frame structures. Current design codes and recommendations for reinforced concrete (RC) structures consider the influence of the construction process on the temperature shrinkage effect by adopting a uniform reduction coefficient and neglect the influence of the construction method. However, different construction processes can vary the temperature stress of the structure. In this paper, under cooling action, the temperature stress of a one-layer, super-long frame structure with different quantities and indwelling times of post-cast strips is calculated with a spatial nonlinear simulation analysis program by adopting the degenerated spatial solid virtual laminated element method. With this approach, the internal force state of each construction stage during the construction process is accounted for in a nonlinear mechanical model of the structure. The results show that the quantity and the indwelling time of post-cast strips can effectively vary the temperature stress of the structure. Meanwhile, the quantity of the post-cast strips can have a more obvious effect than the indwelling time. Therefore, the construction process is an important factor affecting the temperature shrinkage effect of the structures. The research results can provide a valid reference for the design and construction of super-long frame structures.

When compared with conventional replacement reinforcement methods, the method of replacement using a local reinforcement with an unsupported roof has the advantages of shortening the reinforcement cycle and reducing material loss, and many scholars have carried out useful explorations thereof. At present, the formula for the bearing capacity of reinforcement by replacing concrete in the Code does not consider the effect of stress hysteresis on the parts of the reinforcement; so when the initial stress level is greater than 0.4, the Code’s strength utilization coefficient of 0.8 for the new concrete in the replaced area is on the side of insecurity. In this study, we are trying to improve and supplement the formula in the Code through the following work. Firstly, 18 groups of shear wall models were constructed using a VFEAP finite element analysis program to analyze the bearing performances of the shear walls after the replacement. The results showed that the replacement concrete strength, the initial stress level and the size of the replaced area had a significant influence on the bearing capacity of the shear wall after the replacement. Secondly, utilizing the replacement concrete strength, the initial stress level and the size of the replacement area as key parameters, then introducing the strength improvement coefficient considering the constraints of the stirrups, the modified strength utilization coefficient of new concrete in the replaced area was formulated. Finally, based on the modified strength utilization coefficient, the replacement bearing capacity formulas for the one-batch, two-batch, and three-batch replacements were derived, and an N-batch replacement bearing capacity formula was regressed and fitted on the basis of these equations, which are less discrete and more secure than the Code’s formula.

The correlation analysis between current surface cracks of structures and external loads can provide important insights into determining the structural residual bearing capacity. The classical regression assessment method based on experimental data not only relies on costly structure experiments; it also lacks interpretability. Therefore, a novel load estimation method for RC beams, based on correlation analysis between detected crack images and strain contour plots calculated by FEM, is proposed. The distinct discrepancies between crack images and strain contour figures, coupled with the stochastic nature of actual crack distributions, pose considerable challenges for load estimation tasks. Therefore, a new correlation index model is initially introduced to quantify the correlation between the two types of images in the proposed method. Subsequently, a deep neural network (DNN) is trained as a FEM surrogate model to quickly predict the structural strain response by considering material uncertainties. Ultimately, the range of the optimal load level and its confidence interval are determined via statistical analysis of the load estimations under different random fields. The validation results of RC beams under four-point bending loads show that the proposed algorithm can quickly estimate load levels based on numerical simulation results, and the mean absolute percentage error (MAPE) for load estimation based solely on a single measured structural crack image is 20.68%.

The region of the RC slab–column connection is subject to complex forces and is susceptible to localized damage, leading to progressive collapse incidents, which has raised considerable concern among the engineering community. At present, the research on slab–column connections exhibits several shortcomings, including a limited number of specimens, incomplete consideration of various factors, and unclear boundaries in defining failure modes. A comprehensive consideration of the punch–span ratio (a/h₀) and longitudinal reinforcement eigenvalues (ρƒ_y/ƒ_c) is lacking, and the calculation formula for load bearing is not subdivided based on distinct failure modes. In this study, finite element software is utilized to construct 42 models of slab–column connections. The variables considered encompass three factors: the punch–span ratio, the longitudinal reinforcement ratio, and concrete strength. The examination and evaluation encompass the analysis of the load–displacement curve, reinforcement stress change curve, section crack distribution pattern, and stress contour map obtained through model loading. The primary parameters defining the boundaries of the three failure modes in the slab–column connection are the punch–span ratio and longitudinal reinforcement eigenvalues. Utilizing the punch–span ratio and longitudinal reinforcement eigenvalues as key parameters, a punching and flexural failure model for slab–column connections without abdominal bars is formulated. The calculation formula for bearing capacity, encompassing flexural, flexural and punching, and punching shear failure, is derived. A comparison between the revised formula and the standard formulas from major countries indicates that the revised formula is more comprehensive, providing a more accurate and secure prediction within the scope of this study.

In this paper, three-dimensional degenerated virtual laminated element nonlinear finite element method is utilized to simulate the whole process of vertical anti-continuous collapse of ten-storey RC frame structure with nine-palace lattice under the failure of the bottom corner columns. It can be found that the axial force redistribution of the same story column shows relationship with the load range and the distance from the failure column. Besides, the integral collapse resistance mechanism and the axial force of the vertical column of the failure column are different from that before failure.

Temperature stress analysis is of prime importance to ensure the adequate servicing of super-long frame structures during their service life. The existing design codes and recommendations for reinforced concrete (RC) structures provide methodologies for the reinforcement of design elements that neglect differences in the linear expansion coefficients of steel and concrete. In this paper, we present a numerical method based on a degenerated three-dimensional solid virtual laminated element for simulating and analyzing the temperature stress of a two-layer super-long frame reinforced concrete structure subjected to allover cooling action, whereby the difference in the linear expansion coefficients of steel and concrete are taken into consideration. The results show that the difference in the linear expansion coefficients of steel and concrete, with different constraints, affects the temperature stress experienced by each material in the structure, and this difference adversely affects attempts to avoid structure cracking.