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This article deals with the proper numerical simulation of the response presented by an instrumented damaged-retrofitted building using a low computational cost linear-elastic model, using effective stiffness for its reinforced concrete structural members. The purpose is to identify the most appropriate criteria and considerations and to validate them against the actual behavior of the building registered during real earthquakes. Relevant structural aspects like concrete elastic modulus and soil–structure interaction effects are determined experimentally. Special attention is paid to select appropriate techniques to model the complex geometry of the North-South facades wall elements and their related coupling beams. Finally, time-history analyses of 20 March 2012 earthquake (service conditions demand) and 19 September 2017 earthquake (design conditions demand) are performed, both considering and ignoring the soil–structure interaction effects. Results point out that commonly adopted simplifications in numerical models of buildings must be correctly implemented to satisfactorily simulate their earthquake response.

The 19 September 2017 Puebla–Morelos earthquake provides a unique opportunity to (a) study the effectiveness of seismic rehabilitation methods implemented in Mexico City after 1985 and (b) collect large amounts of data on current building rehabilitation practices. This article presents and discusses seismic rehabilitation efforts conducted on concrete buildings after the 1985 and 2017 earthquakes. Building damage and vulnerabilities, code provisions for rehabilitation, and common repair and retrofit techniques used in these two periods of time are summarized. The performance of four buildings rehabilitated after 1985 is examined based on results from field investigations conducted after the 2017 event. These rehabilitations were effective in improving the performance of these buildings according to observed damages and estimated shaking intensities. To allow a more systematic assessment of seismic rehabilitations in future earthquakes, an inventory of rehabilitated buildings in Mexico City is currently under development. Preliminary data obtained from this inventory effort are presented and discussed.

On September 7, 2017, at 23:49 h (local time), a Mw8.2 intermediate-depth normal-fault earthquake occurred in the Gulf of Tehuantepec, 133 km away from Pijijiapan, Chiapas, and about 700 km away from Mexico City. This event caused 95 fatalities and severe damage to different types of structures located close to the epicenter. The main objective of this work is to present observed damages caused in the state of Oaxaca by this earthquake, which were mainly concentrated in self-built houses and historical and ancient buildings. The locations visited by the reconnaissance team of the Institute of Engineering from UNAM in Oaxaca included Salina Cruz, Tehuantepec, Ixtaltepec, Juchitan, Huatulco and La Ventosa.

Partially grouted reinforced masonry (PG-RM) shear walls have been widely used as structural elements in low- and medium-rise earthquake-resistant buildings. Nonetheless, assessing its shear strength represents a complex task mainly because the partial grouting provides a non-constant cross section, which results in heterogeneous stress–strain patterns. Consequently, refined modeling techniques are needed to reproduce local failure mechanisms taking place in these walls, which significantly influence the global response. In response to this issue, a detailed micro-modeling approach based on the finite element method was proposed in previous studies by the authors. Although the numerical strategy provided accurate results, further validation is required. Therefore, in this study, the experimental results of seven PG-RM shear walls of multi-perforated clay bricks with bed-joint reinforcement are employed as validation cases. These seven walls presented variations in five design parameters. The validated numerical model was then employed to perform a parametric study to assess the influence of the wall aspect ratio, axial pre-compression stress, and horizontal reinforcement ratio on the in-plane lateral behavior of PG-RM shear walls. The obtained results show that the three studied design parameters modified the crack patterns of the walls. Besides, increasing the axial pre-compression stress or reducing the aspect ratio resulted in higher walls’ shear strength. Additionally, decreasing the horizontal reinforcement ratio or increasing the aspect ratio generated a higher story-drift ratio at maximum lateral force. Finally, it was corroborated that the positive effect of the axial pre-compression stress on the walls’ shear strength decreases inversely proportional to the aspect ratio.

First published by the International Association for Bridge and Structural Engineering (IABSE), Zurich, Switzerland, www.iabse.org; in Structural Engineering International 2017, Vol.27, issue 3, pg. 422-428. A description of the deformations and damage that occurred in a segmental tunnel lining as a consequence of an unplanned surface load is presented, as well as the numerical analyses performed for its safety assessment. The tunnel in study is located in soft soil conditions and presents a low overburden. Few months after tunnel drilling, a new bridge was constructed at surface level, placing an access embankment over the tunnel path. Monitoring points were installed along the affected section which recorded the deformation of the tunnel caused by the embankment weight. More worryingly, despite no additional loads were introduced, the deformation of the lining continued increasing significantly along the next months, indicating the existence of soil consolidation phenomena. As a consequence, structural cracks emerged along the affected section. Non-linear finite element models that realistically simulate the behaviour of the non-linear segment joints and the concrete cracking were used to characterize the actual response and strength of the lining. The results showed that most significant damages should occur at the non-visible extrados side, and characterized how they evolve along the soil consolidation process. Finally, the adopted tunnel strengthening procedure is described.

Openings can have a significant effect on the seismic response of partially grouted reinforced masonry (PG-RM) walls. Despite this, very few investigations have been carried out to study their influence. Accordingly, this paper presents the results of an experimental and numerical research project aimed at increasing the knowledge of the shear response of PG-RM walls with openings. The experimental program includes test results of three full-scale walls (one solid wall and two perforated walls with a central window) tested under cyclic lateral loading up to failure. In addition, a complete characterization of the constituent materials and their interfaces is reported, with an emphasis on the experimental data needed for implementing advanced numerical models. The results obtained are used to validate a numerical model based on the detailed micro-modelling approach. Once validated, the models are used to conduct a sensitivity analysis that considers opening size variation and the horizontal reinforcement ratio at piers. The results show that a rise in the pier horizontal reinforcement ratio leads to an increase in shear strength and displacement ductility of the entire wall, while an increase in the pier aspect ratio decreases the shear strength and increases the displacement ductility in the entire wall. Keywords: Reinforced masonry, Detailed micro-modelling, Shear strength, Partially grouted, Perforated wall

In recent earthquakes in Chile (e.g., Maule’s 2010 earthquake), buildings built with bed-joint partially grouted reinforced masonry (BJ-PG-RM) shear walls made of multi-perforated clay bricks (MPCB) have not collapsed, although significant damages have been reported. Additionally, experimental data on the influence of the different design parameters that control its seismic behavior is scarce, and the available expressions for estimating their lateral resistance are inaccurate. To address these issues, nine full-scale BJ-PG-RM walls made of MPCB were tested under axial pre-compression and cyclic lateral loads. The study addressed the influence of the aspect (height-to-length) ratio, axial pre-compression, mortar compressive strength, mortar joints’ thickness, bricks’ height, and horizontal and vertical reinforcement ratio. The results were analyzed in terms of hysteretic response, damage evolution, seismic performance parameters (shear strength, equivalent viscous damping ratio, ductility, and lateral stiffness degradation). All designed walls failed in a diagonal tension failure mode. Besides, all studied variables influenced the stresses and crack patterns. Also, the shear strength increases when: (i) lower aspect ratio or joint thickness are used; and (ii) higher axial load ratio, horizontal reinforcement ratio, vertical reinforcement ratio, or mortar compressive strength are used. Moreover, when damage progresses, the lateral secant stiffness decays faster as a result of: (i) larger joint thickness or vertical reinforcement ratio; (ii) lower mortar compressive strength. Most walls exhibited an equivalent viscous damping ratio between 5% and 10% for an intermediate state of damage. However, the evaluated design parameters did not considerably affect the development of the viscous damping ratio as a function of the drift ratio. The displacement ductility of the walls ranged from 1.5 to 2.5, where the height of bricks and the vertical reinforcement ratio had positive effects, and the joint thickness, the mortar compressive strength, and the horizontal reinforcement ratio a negative effect. The lateral resistance of tested walls was also estimated with six expressions, but none of them provided accurate results.

The 1985 Mexico City earthquake resulted in extensive damage and collapse of concrete construction. In the months and years following this earthquake, there was an unparalleled effort to repair and retrofit concrete buildings. On September 19, 2017, a new strong earthquake struck Mexico City. This event represented the first severe test for concrete buildings retrofitted after 1985, providing an unprecedented opportunity to study the actual performance of the retrofitting techniques applied in these buildings. This paper presents results of a field investigation and damage assessment of three retrofitted concrete buildings after the 2017 earthquake. The structures studied suffered different levels of damage during the 1985 earthquake, and they were subsequently repaired and retrofitted using a variety of techniques (e.g., jacketing of columns and beams, addition of steel bracing, RC infill walls). Except for the excessive tilting of one of the structures, the buildings presented minor damage after the 2017 event. The shaking intensities of 2017 can be considered similar to those of 1985 in the period range of interest for these buildings, while the structures presented in general better performance thanks to an increase of their capacity and/or a decrease of the seismic demands.

Although multiple experimental investigations have been performed to characterize the structural behavior of partially grouted reinforced masonry (PG-RM) shear walls, still many knowledge gaps exist due to the complexity of their mechanical behavior. Furthermore, the fact that PG-RM is a composite material has limited the progress of the numerical modeling of these elements. In order to contribute to the knowledge of the in-plane response of PG-RM walls, this paper presents a detailed micro-modeling approach to simulate the behavior of these walls under in-plane lateral loads. Numerical results are validated by comparison with experimental results of PG-RM walls with bed-joint reinforcement. Special attention is given to the numerical implementation and solution strategy of the models due to the difficulties of solving the strong nonlinearities involved in the walls’ response. The obtained results allow us to conclude that the proposed approach is suitable for simulating the lateral response of PG-RM shear walls, including crack patterns observed during experimental tests. In addition, the performed parametric study shows that selecting adequate numerical parameters is vital to avoid misleading results.

Aiming towards a better understanding of the structural response presented by multi-perforated clay brick masonry, this paper presents the results of an experimental program focused on characterizing the behavior of its constituent materials and interfaces, and on providing numerical strategies to appropriately reproduce that behavior. Different displacement controlled test set-ups were carried out in the laboratory for this purpose, giving special attention to characterizing the shear response at horizontal unit-mortar interface in order to point out the influence that mortar spikes penetrating into the perforated bricks cavities can exert. According to its detailed consideration of materials and interfaces, the detailed micro-modeling numerical approach was selected for this study. The numerical strategies proposed have led to a satisfactory reproduction of the shear triplet tests and diagonal compression tests that were performed, showing that the complex structural response of multi-perforated clay brick masonry can be appropriately reproduced from experimental evidence.

During the last years the use of segmental linings in tunnels bored with tunnel boring machines (TBMs) have increased considerably. Despite this, uncertainties remain on the structural behavior of segmental tunnel linings. To overcome them, a new methodology for an in situ real scale test on this kind of tunnels was developed and applied on an experimental section placed at the new Line 9 (L9) of the metro of Barcelona. The main particularity of this test falls on its performance in the definitive placement of the rings and, therefore, in the real work conditions of the tunnel. The main advantage to previous real scale test experiences was the consideration of the real ground–structure interaction. The experimental section was composed by 15 rings built using steel fibers as a unique reinforcement. Significant loads were applied to the tunnel crown (max 3000 kN) by means of three hydraulic flat jacks embedded at the extrados of the loaded ring. A complete set of internal and external instrumentation was placed on the experimental section to obtain the necessary measurements to characterize the lining behavior. Such measurements were intensively treated and its main results are presented and analyzed in detail in this paper. This in situ test provides significant evidences of the structural response of SFRC segmental tunnel linings in hard ground conditions.

This study analyzes the structural response of a group of masonry buildings subjected to real ground movements experienced during the construction of the L9 Metro tunnel in Barcelona, bored by a earth pressure balance machine (EPB) tunnel boring machine (TBM). The studied one-story small dwellings represent a common building typology frequently used in those days in Barcelona's outskirts (more than 1000 were erected). Real settlement profiles are compared with the ones provided by empirical methods, which estimate the shape and the area of the trough according to the ground properties and the volume loss. The first aim of the study is to evaluate the effectiveness of two techniques used to predict damages in buildings resulting from tunneling subsidence: 1) the equivalent beam and its subsequent refinements, and 2) the use of a non-linear finite element (FE) macro-model. The real structural damage presented in the buildings is compared with the predictions given by these two methods. Main model parameters have been determined by means of characterization experiments developed on the site and in the laboratory, thus giving a much higher significance to the analysis. The obtained predictions present a high correspondence with the actual damage registered, particularly in crack patterns and widths.

The particular configuration of segmental tunnel linings produces that its structural response in front of usual design loads could present a significant three dimensionality due to the structural interaction between adjacent rings (coupling effects). The present paper studies the phenomena associated to coupling effects, determines the main involved parameters and analyzes their influence on a real lining structural response by means of a 3D numerical model. The comparison with the usual plane models currently employed in linings designs provide significant conclusions about the coupling effects implications and the conditions in which become more relevant.

The numerical simulation of the in situ test described in the part 1 of the paper is performed by means of two different approaches: a 2D plane stress model and a 3D shell elements model. A consistent modeling of the tunnel behavior is achieved through the proper simulation of the main phenomena involved on the structural response of the lining: (1) the steel fiber reinforced concrete (SFRC) post-cracking behavior, (2) the detailed behavior of the joints between segments and (3) the ground–structure interaction. The origin and the effects of all these phenomena and the modeling techniques employed to simulate them are carefully described and discussed. Finally, the results obtained are compared with the experimental evidences, showing the excellent accuracy achieved in terms of displacements, joints closures and crack patterns.

This paper presents results of an ongoing study on the seismic performance of a retrofitted concrete building located in the soft soil area of Mexico City. The original structure consisted of reinforced concrete frames in two directions. The building was repaired and retrofitted after having been damaged during a moderate earthquake in 1979. The retrofit strategy consisted mainly of installing external steel braces in one direction of the building, and reinforced concrete infill walls in the other direction. The retrofitted structure showed minor damage after the 1985 and 2017 earthquakes. The goal of this investigation is to assess the structural response of the building and the effectiveness of the retrofit strategy by combining post-earthquake damage inspections, analytical modeling and ambient vibration testing. This paper focuses on the development and calibration of a three-dimensional analytical model of the building, and on the analysis of the vibration properties of the retrofitted structure. The analytical model has been calibrated using data from ambient vibration tests conducted after the 2017 event. The study of the vibration properties of the building has shown the strong influence of soil-structure interaction in the response of this building.

The longitudinal forces introduced by tunnel boring machines (TBMs) to the segmental tunnel linings influence their structural response. The analyses of the linings construction process and the ground-structure interaction mechanisms have shown the influence of the lining creep on the progressive loss of the initial longitudinal force. An analytical formulation to predict the remaining compression of the linings as a function of time is proposed, supported by means of a complete numerical model, which considers the effect of creep during the sequential construction process. An experimental program to determine the creep of plastic packers was developed, revealing its significant influence on the global lining creep factor and the evolution of the remaining compressive stresses.

Segmental tunnel linings present a significant 3D response when they are subjected to localized loads or to other scenarios that produce different deformations of adjacent rings. The present paper analyzes the interaction mechanisms mobilized in such conditions, determining the most influence parameters and their repercussion on the structural response of the lining. A complete set of numerical analyses is carried out on a complex 3D numerical model that accurately reproduces a real tunnel section on multiple scenarios. Numerical results show the structural benefits of the lining three-dimensional response when subjected to localized loads, allowing the determination of the influence presented by the main involved parameters. The surrounding ground stiffness determines the interaction degree achievable between adjacent rings, whilst lining longitudinal compression determines the maximum load for which a complete interaction is produced.