Search Results (7)

The seismic assessment of existing strategic and highly occupied reinforced concrete buildings, such as schools located in moderate-to-high seismic regions, is a critical task, especially because they have been constructed in periods lacking performance-based seismic design requirements. Following a review of possible local and global structural strengthening strategies, this study presents the seismic evaluation and retrofit design of an existing reinforced concrete school building designed before the introduction of modern seismic codes. The assessment is supported by an in situ investigation campaign including destructive and non-destructive materials testing, geotechnical investigations, and a detailed survey of the original construction details. A three-dimensional numerical model, calibrated on the in situ survey and material test results, enables the evaluation of the building’s seismic performance in both the pre- and post-intervention configurations. The model also supports the optimization of retrofit costs: a constraint of relevance because the intervention was funded through a dedicated public budget allocated by the national authority and subject to public validation. This represents a procurement framework that explicitly links the achievable retrofit performance level to a fixed cost ceiling, unlike standard practice in most seismic-prone countries. A global strengthening strategy was implemented including new reinforced concrete shear walls structurally connected to the foundations of the existing walls, whose capacity was enhanced through the installation of micropiles. Fiber-reinforced polymer (FRP) wrapping was applied to improve both flexural and shear beam capacity, while steel jacketing was adopted for some vertical elements. The combined interventions significantly improved the seismic performance of the building, ensuring a safer and more reliable response under future seismic events, respecting the initial publicly available budget. Full article

To address the issue of structural tilting caused by uneven foundation settlement in soft soil areas, this study combined a specific engineering case to conduct numerical simulations of the rectification process for an inclined reinforced concrete building using ABAQUS finite element software. Micropile-raft combined jacking technology was employed, applying staged jacking forces (2400 kN for Axis A, 2200 kN for Axis B, and 1700 kN for Axis C) with precise control through 20 incremental steps. The results demonstrate that this technology effectively halted structural tilting, reducing the maximum inclination rate from 0.51% to 0.05%, significantly below the standard limit. Post-rectification, the peak structural stress decreased by 42%, and displacements were markedly reduced. However, the jacking process led to a notable increase in the column axial forces and directional changes in beam bending moments, reflecting the dynamic redistribution of internal forces. The study confirms that micropile-raft combined jacking technology offers both controllability and safety, while optimized counterforce pile layouts enhance the long-term stability of the rectification system. Based on stress and displacement cloud analysis, a monitoring scheme is proposed, forming an integrated “rectification-monitoring-reinforcement” solution, which provides a technical framework for building rectification in soft soil regions. Full article

In this contribution, the classical Cauchy first-gradient elastic theory is used to solve the equilibrium problem of a bidimensional (2D) reinforced elastic structure under small displacements and strains. Such a 2D first-gradient continuum is embedded with a reinforcement, which is modeled as a zero-thickness interface endowed with the elastic properties of an extensional Euler–Bernoulli 1D beam. Modeling the reinforcement as an interface eliminates the need for a full geometric representation of the reinforcing bar with finite thickness in the 2D model, and the associated mesh discretization for numerical analysis. Thus, the effects of the 1D beam-like reinforcements are described through proper and generalized boundary conditions prescribed to contiguous continuum regions, deduced from a standard variational approach. The novelty of this work lies in the formulation of an interface model coupling 1D and 2D continua, based on weak formulation and variational derivation, capable of accurately capturing stress distributions without requiring full geometric resolution of the reinforcement. The proposed framework is therefore illustrated by computing, with finite element simulations, the response of the reinforced structural element under uniform bending. Numerical results reveal the presence of jumps for some stress components in the vicinity of the reinforcement tips and demonstrate convergence under mesh refinement. Although the reinforcement beams possess only axial stiffness, they significantly influence the equilibrium configuration by causing a redistribution of stress and enhancing stress transfer throughout the structure. These findings offer a new perspective on the effective modeling of fiber-reinforced structures, which are of significant interest in engineering applications such as micropiles in foundations, fiber-reinforced concrete, and advanced composite materials. In these systems, stress localization and stability play a critical role. Full article

Unstable sandy soils pose significant challenges for buried pipelines due to soil–infrastructure interaction, leading to settlement that increases the risk of displacement and stress-induced fractures. In earthquake-prone regions, seismic-induced ground deformation further threatens underground infrastructure. Fiber-reinforced polymer (FRP) composites have emerged as a sustainable alternative to conventional piling materials, addressing durability issues in deep foundations. This paper introduces novel explicit models for predicting the maximum settlement of oil pipelines supported by concrete or polymer micropiles under seismic loading. Using genetic programming (GP), this study develops closed-form expressions based on simplified input parameters—micropile dimensions, pile spacing, soil properties, and peak ground acceleration—improving the models’ practicality for engineering applications. The models were evaluated using a dataset of 610 data points and demonstrated good accuracy across different conditions, achieving coefficients of determination (R²) as high as 0.92, among good values for other evaluation metrics. These findings contribute to a robust, practical tool for mitigating seismic risks in pipeline design, highlighting the potential of FRP micropiles for enhancing infrastructure resilience under challenging geotechnical scenarios. Full article

In this paper, joint precast piles with a cross-section of 400 × 400 mm and a pin-joined connection were considered, and their interaction with the soil of Western Kazakhstan has been analyzed. The following methods were used: assessment of the bearing capacity using the static compression load test (SCLT by ASTM) method, interpretation of the field test data, and the dynamic loading test (DLT) method for driving precast concrete joint piles, including Pile Driving Analyzer (PDA by ASTM) and Control and Provisioning of Wireless Access Points (CAPWAP) methods. According to the results, the composite piles tested by the PDA (by ASTM) method differ by 15 percent compared to the static load method, while the difference between the dynamic DLT (by ASTM) method and the static load (by ASTM) method was only 7 percent. So, according to the results, the alternative dynamic method DLT (by ASTM) is very effective and more accurate compared to other existing methods. Full article

Building foundations are usually retrofitted with directly connected micropiles; however, at the present time, there are different approaches for predicting shear capacity in the micropile–foundation connection. At first, the concrete shear strength was considered. Nowadays, in the EU countries, it is prescribed to use the shear strength of the interface between successive concrete casts at different times. This implies a reduction of the connection capacity by half, and these values are not in consonance with the lab results. This work analyses the economic impact of the previous considerations on retrofit projects with micropiles. To this aim, firstly, seven different formulations were applied to 29 building projects, and the results were compared. Secondly, a Monte Carlo sensitivity analysis was performed using bond stress distribution data obtained from lab tests. Thus, numerical results acquired by comparing European and American regulations show an average difference in cost of around 40%, which may reach up to 50%. Moreover, the Monte Carlo simulation confirms that the connection strength may become a limitation in retrofit projects, also indicating that the application of European codes usually leads to the most expensive designs. Finally, the results show that it is not worth improving the connection to exceed a bond stress of 0.60 MPa, since no relevant savings are produced by achieving higher values. Full article

Chemical injection of expansive polyurethane resin in the ground is a well-known technology that is also used for underpinning shallow foundations. It is noteworthy that it has been recently used with success on buildings of great historic value that are part of the country’s architectural heritage. This article describes the work undertaken on a historic building located in the city of Cuenca (Spain), for improving ground condition through injecting below foundation, in order to stop the differential settlements detected in the structure. This technology has proven to be, at least, as effective as the more conventional methods used in the past as supporting the foundation by concrete shafts or micropiles. Full article