The paper focuses on different approaches to the safety assessment of concrete structures designed using nonlinear analysis. The method based on the concept of partial factors recommended by Eurocodes, and methods proposed by M. Holicky, and by the author of this paper are presented, discussed and illustrated on a numerical example. Global safety analysis by M. Holicky needs estimation of the resistance coefficient of variation from the mean and characteristic values of resistance, and requires two separate nonlinear analyses. The reliability index value and the sensitivity factor for resistance should be also identified. In the method proposed in this paper, the resistance coefficient of variation necessary to calculate the characteristic value of resistance may be adopted from test results and the resultant partial factor for materials properties, and may be calculated according to Eurocodes. Thus, only one nonlinear analysis from mean values of reinforcing steel and concrete is required.

Technologia przepuszczalnych reaktywnych barier (PRB) należy do metod remediacji wód gruntowych. W technologii tej zanieczyszczenia usuwane są bezpośrednio w warstwie wodonośnej poprzez przepływ skażonego strumienia wód gruntowych przez wypełnioną odpowiednim materiałem (aktywnym) barierę aktywną. W artykule przedstawiono problemy związane z tworzeniem się osadów w żelazie metalicznym stosowanymjako material aktywny technologii PRB. Osady te mogą zmniejszać aktywność materiału i jego zdolność filtracyjną. Tworzeniu się osadów mogą towarzyszyć zmiany pH, potencjału redox oraz stężenia tlenu. Zmiany te były obserwowane w badaniach laboratoryjnych przedstawionych w artykule. Ponadto w artykule przedstawiono i udowodniono następującą zasadę: aby zwiększyć skuteczność działania typu Funnel-and-Gate technologii PRB przez zwiększenie szerokości strefy oczyszczania, stosunek współczynnika filtracji materiału aktywnego do współczynnika filtracji warstwy wodonośnej (k,,,/k,ą) powinien przyjąć wartość 6. Ze względu na tworzenie się osadów w żelazie metalicznym, które mogą zmniejszyć jego zdolność filtracyjną, założono jednak, iż stosunek ten powinien wynosić I O. Wartość ta daje pewność, że zmniejszenie się wartości współczynnika filtracji materiału aktywnego na skutek tworzenia się osadów, nie wpłynie w znaczący sposób na szerokość strefy oczyszczania. Przedstawione rozwiązanie może zapewnić skuteczne i długotrwale oczyszczanie wód gruntowych w typie Funnel-and-Gate technologii PRB.

The objective of the article involves presenting innovative approach to the assessment of structural reliability analysis. The primary research method was the First Order Reliability Method (FORM). The Hasofer–Lind reliability index in conjunction with transformation method in the FORM was adopted as the reliability measure. The implicit limit state functions were used in the analysis. The formulation of the random variables functions were created in the Matlab software by means of neural networks (NNs). The reliability analysis was conducted in Comrel module of Strurel computing environment. In the proposed approach, Hybrid FORM method (HF) used the concept in which NNs replaced the polynomial limit state functions obtained from FEM (Finite Elements Method) for chosen limit parameters of structure work. The module Comrel referenced Matlab files containing limit state functions. In the reliability analysis of structure, uncertain and uncorrelated parameters, such us base wind speed, characteristic snow load, elasticity modulus for steel and yield point steel are represented by random variables. The criterion of structural failure was expressed by four limit state functions – two related to the ultimate limit state and two related to the serviceability limit state. Using module Comrel values of the reliability index with the FORM method were determined. Additionally, the sensitivity of the reliability index to random variables and graph of partial safety factors were described. Replacing the FEM program by NNs significantly reduces the time needed to solve the task. Moreover, it enables the parallel formulation of many limit functions without extending the computation time.

Prestressed anchor cables are active reinforcement to improve slope stability. However, the anchoring is not a permanent guarantee of stability, and the slope retains a potential risk of instability. From the perspective of the internal force of anchor cables, a new early warning method for the safety of the slope is provided, and a slope analysis model is established. With the increase in the strength reduction factor, the internal force increment curves of anchor cables under different prestresses are obtained. The point corresponding to strength reduction factors λ1 and λ2 represents a warning point. Key conclusions are drawn as follows: (1) The internal force of an anchor cable can be used to judge the stability of the slope strengthened by a prestressed anchor cable. (2) A warning index based on the internal force increment ratio of anchor cables is established. (3) The internal force increment ratio of anchor cables eliminates the influence of the initial prestress and is convenient for engineering applications.

The optimization process of design parameters for composite lining of heavy haul railway tunnel is a key problem to be solved in tunnel engineering design. In order to put forward a better design scheme of composite lining for heavy haul railway tunnel, combined with field measurement and numerical simulation, the optimal working condition design is carried out by changing the thickness of shotcrete layer, the type of grid steel frame and the thickness of secondary lining. The influence of the above design parameters on the stress state of the composite lining is analyzed to obtain the optimal design parameters. Finally, the safety performance of the optimized lining is evaluated by the ultimate bearing capacity curve of the secondary lining section. The research shows that: 1) The optimal design parameters of the composite lining of the tunnel are the thickness of the shotcrete layer of 25 cm, the type of the grid steel frame of H180, the thickness of the secondary lining arch waist and the side wall of 40 cm and 35 cm respectively; 2) Different from the single-track heavy haul railway tunnel, the displacement value of the vault settlement of the double-track heavy haul railway tunnel is significantly greater than that of the inner convergence. Increasing the thickness of the shotcrete layer and changing the type of the grid steel frame have better effects on reducing the vault settlement, and have little effect on the inner convergence.