Base Shear Research Articles

Action of liquid tune mass dampers and base isolation in high rise buildings

In areas where earthquakes are common, high-rise structure seismic resistance is a major concern. The purpose of this research is to determine whether base isolation and liquid tuned mass dampers (LTMDs) can improve tall building seismic performance. A symmetrical G+8 story RCC structure in Zone V with medium grade soil is analyzed using ETABS software, Response Spectrum Analysis, and Equivalent Static Analysis to see how the structure behaves under different load combinations. For various structural configure rations, including basic models, models with water tanks, and models with base isolation, key factors such joint displacement, storey drift, base shear, and time period are evaluated. The results show that as compared to baseline models, models with damping and isolation systems exhibit much lower joint displacements, base shear forces, and story drift. In particular, base isolation models perform better in terms of reducing structural deformations and resisting lateral forces. Furthermore, shorter time periods and higher frequencies are routinely observed in base isolated models, suggesting enhanced dynamic response and energy dissipation capabilities. The paper also covers the flexibility and benefits of using LTMDs and base isolation to reduce seismic threats. Buildings can be successfully separated from ground motion by base isolation systems, and dynamic response can be countered by LTMDs using regulated liquid sloshing. The attraction of LTMDs in improving overall stability is increased by their adaptability in minimizing torsional and lateral vibrations. The study concludes by emphasizing how crucial it is to use cutting-edge structural retrofitting methods, including base isolation and LTMDs, to improve the seismic resistance of high-rise structures. In earthquake-prone areas, engineers and legislators may proactively protect tall buildings and guarantee a safer, more robust built environment by incorporating these technologies into construction standards and design procedures.

Nonlinear dynamic study on existing masonry-infilled concrete frames retrofitted with timber panels

This study investigates the dynamic performance of a timber-based seismic retrofit for existing reinforced concrete (RC) buildings, named RC-TP. The core of the proposed retrofit intervention is the replacement of the existing masonry infills with structural timber panels that are connected to the concrete elements using metal dowel-type fasteners and a timber subframe. The unreinforced frames were designed according to codes in force in the 60 s and 70 s, considering exclusively gravity loads to simulate a condition common to a large part of the built heritage across Europe. The seismic performance of single-storey single-bay frames before and after the application of the RC-TP retrofit was assessed via nonlinear simulations, for which the incremental dynamic analysis method was adopted. The results of the extensive dynamic study show the effectiveness of the RC-TP retrofit in increasing the seismic acceleration resisted by the frames and their base shear capacity and in promoting a more ductile failure mechanism. Some general considerations helpful in guiding the implementation of the retrofit system were also drawn.

Comparison of a 10-Story Tunnel Formwork Structure with Different Soil Classes According to the 2018 Earthquake Regulations

In this study, elastic design spectra were defined and compared for a 10-story tunnel formwork structure based on different soil types according to the new earthquake regulations implemented in March 2018. The tunnel formwork project used in the comparison was obtained from a static project author in Istanbul Esenyurt. Earthquake data affecting the design were selected for soil classes ZA, ZB, ZC, ZD, and ZE using coordinates 41.0114327 latitude and 28.676468 longitude from AFAD. Earthquake loads were applied in both X and Y directions to the building under consideration. The maximum relative floor displacements, overturning moments, and base shear forces in the structure were obtained using earthquake data for the ZC soil class.

Steel Structures in Context of Safety, Resilience & Sustainable Construction: Minimizing Environmental Impacts

The study analyzes a G+4 residential building subjected to seismic loads, comparing vertical base shears, material strengths, and foundation design requirements. The results reveal that RCC structures generate significantly higher vertical base shears due to their heavier loads, necessitating larger foundation areas, especially at critical points, and leading to increased construction costs. In contrast, Steel structures, with lower base shears, require smaller foundation areas, reducing both material use and environmental impact. The findings emphasize that Steel structures offer superior seismic performance, cost efficiency, and sustainability by minimizing foundation requirements and associated environmental burdens. This research highlights the importance of material choice in achieving resilient and sustainable construction, particularly in seismic zones, where Steel structures provide a more efficient and environmentally friendly solution compared to RCC structures.

An improved Chinese load code method for the evaluation of wind‐induced base shear force on base‐isolated buildings

AbstractThe isolator units in a seismically isolated structure shall have a surplus yield strength under wind loads. The isolation interface must have enough strength to state at an elastic stage under wind loads. This necessitates an accurate evaluation of wind‐induced base shear force. Initially, to calculate the equivalent static wind load (ESWL) and the base shear force of a base‐isolated building, the validity of the inertial wind load (IWL) method and Chinese load code (CLC) method, the simplification based on the IWL method, are examined via comparison with response‐history analysis results. Comparative analysis reveals that the IWL method was more accurate in evaluating the ESWL and the base shear force of base‐isolated building, while the CLC method underestimated them due to the following reasons: inaccurate fundamental modal shape, a reduced peak factor, the omission of the ESWL contribution from the isolation interface, and flawed assumptions of uniform mass distribution. Subsequently, an improved CLC method that combined the exponential modal shape and first modal generalized mass modification coefficient is proposed and verified by a case study. Compared with the CLC method, the fluctuating base shear force calculated by the improved CLC method increased by 10% in the case study. Finally, the effect of non‐uniformly distributed mass is further considered in the proposed method by devising a mass conversion coefficient, and the case study has also validated this method. Without considering the effect of the non‐uniform mass, the fluctuating base shear force will be underestimated by 7.8% in the case study.

Seismic Performance of Reinforced Concrete Frames on Sloped Ground Using Non-Linear Static Pushover Analysis

Nepal, renowned for its majestic Himalayan Ranges, is also highly vulnerable to seismic activity. Buildings on hill slopes often endure more significant damage during earthquakes than those on flat terrain. Traditional seismic analyses of buildings typically employ linear-static and dynamic methods, which might not fully represent the building's behavior under actual seismic conditions. This research addresses this gap by assessing the seismic performance of buildings on hill slopes using non-linear static analysis techniques. Specifically, the study evaluates the seismic response of 5-story buildings with stepback and stepback-setback configurations on slopes of 15°, 30°, and 45°. This evaluation is conducted through non-linear static analysis, also known as Pushover Analysis, using ETABSv20 software. Key performance metrics analyzed include the building's period, topstorey displacement, and base shear. The findings reveal that buildings with stepbacksetback configurations demonstrate superior seismic performance on the sloping ground compared to those with stepback configurations. This study underscores the importance of employing non-linear analysis methods to better understand and improve seismic resilience in hilly terrains.

A case study comparing seismic retrofitting techniques for a historically significant masonry building’s minaret

Historical masonry structures are extremely susceptible to earthquakes due to their characteristic features. Seismic performance and corresponding damage patterns vary between these buildings. Even though the main structure was undamaged, many minarets suffered damage or collapsed due to the transmission of large forces from the main mass to the minaret and the abrupt changes in cross-section due to the geometry of the minaret. This study uses an ancient masonry mosque as a case study, whose minaret and main building are constructed as a single structure. The mosque’s minaret under seismic excitation is the focus of this study. The adopted model is called Alaeddin Bey Mosque in Muş, Türkiye. The seismic performance assessment of the minaret, considering various retrofitting options, is mainly based on four critical parameters: base shear, acceleration, displacement, and maximum tensile forces in all three dimensions. The analyzed retrofitting methods include base isolation located in the basement of the mosque, viscous dampers placed only in the upper part of the minaret, Carbon Fiber-Reinforced Polymer fabric fitted to only the minaret, and steel plates applied to only the minaret. Representative structural models of the mosque have been modelled with SAP2000 software. The main novelty of this study is the use of viscous dampers in the minaret. It is the first time a design methodology has been introduced for viscous damper applications in minarets. This methodology aims to prevent local damage to the minaret due to the forces generated by the dampers, while also considering the constraints of limited internal space within the minaret. The finding of this study shows that viscous damper application yields significantly better results compared to the application of Carbon Fiber-Reinforced Polymer fabric and steel plates. However, although base isolation reduces the tensile stress values throughout the entire mosque to levels well below the material’s strength, viscous damper application in the minaret significantly reduces tensile stresses only in the minaret. As a result, viscous dampers are recommended for damage reduction in the minaret only. Otherwise, base isolation should be considered for reducing stress values throughout the entire mosque including the minaret. This study contributes towards the development of new seismic retrofitting methods for historic masonry buildings ‘minaret.

Unsymmetricity effects on seismic performance of multi-story buildings

The unsymmetrical configurations in buildings lead to non-uniform distributions in their strength, mass, and stiffness, and they are consequently prone to damage during seismic hazards. In this study, the seismic performance of multi-story buildings with 5, 8, 10, and 12 stories of square, ‘L’, ‘T’, and ‘U’-shaped buildings have been investigated. The research deals with the variation of the natural time periods and how it affects the seismic performance of unsymmetrical multi-story buildings. The coupled and uncoupled equations of motion, based on the symmetricity of the buildings about both axes, were solved to obtain natural time periods that influence the spectral acceleration of the ground accelerations. Six important ground accelerations were considered. Nonlinear static analysis, such as pushover analysis, was also carried out on all the buildings. Comparisons were made on the seismic behavior of both the symmetrical and unsymmetrical structures. The results revealed that the spectral acceleration influences dynamic responses, such as base shear, base moment, base torsion, roof displacement, roof rotation, and story drifts of the buildings. Moreover, it was found that even though the ‘L’-shaped buildings are unsymmetrical about both axes, they are less vulnerable than the ‘T’ and ‘U’-shaped buildings, which are unsymmetrical about one axis.

Assessment of structural performance, materials efficiency, and environmental impact of multi-story hybrid timber structures in high seismic zone

Advancements in wooden manufacture and the inherent sustainable merits of timber have stimulated studies on high-rise wooden structures and their structural performances. Considering the height restrictions of timber structures in Taiwan, two types of hybrid structure systems, reinforced concrete (RC) structure mixed with timber components, were proposed as substitution solutions to explore their feasibility and environmental impact in high seismic zones. A fifteen-story RC structure was adopted as the benchmark building, and building weight, material substitution efficiency, and embodied carbon were thus compared with the proposed hybrid timber structures after determining wind and seismic impacts. The results showed that structure system Type 1, which replaced original RC slabs and RC walls with timber, weighs only 61.3 % of the RC structure, reducing seismic forces by 38.7 % and base shear by 30.6 %, while inter-story drift ratio was smaller than that of RC structure; meanwhile, Type 2, which maintained the original RC service core and replaced timber structure for rest of the area, was only 44.5 % of the structural weight of RC structure, with a reduction of 36.4 % in seismic forces and 21.1 % in base shear. Furthermore, Type 1 featured reduced embodied carbon of 34.8 % and 35.4 % respectively using imported and domestically produced timber, while Type 2 features reductions of 47.4 % and 49.3 % respectively. The study indicated that the RC-timber hybrid structure system not only has significant structural performance in the face of the challenges of high seismic zones but also offers new solutions in terms of environmental sustainability.

Seismic assessment of cylindrical storage tanks to records with different frequency contents considering fluid–structure–soil/foundation interaction

This study aims to primarily assess the dynamic behavior of ground-supported cylindrical tanks to real near-fault earthquake records with different frequency contents including soil-structure interaction effects. A cylindrical tank’s fluid-tank-soil interaction is modeled using a three-degree-of-freedom lumped mass model for the fluid. A mass-spring-dashpot model with frequency independence is used to model the soil/foundation system. Broad, medium, and slender tank models are developed considering and ignoring the soil flexibility effect. An algorithm based on discrete-time state-space approaches is developed for performing numerical simulations of the modeled tanks excited by the low-, medium-, and high-frequency contents. The obtained results for the modeled tanks in terms of base shear, overturning moment, and connective and impulsive mass displacements incorporating the influence of supporting soils as well as the frequency contents of excitation records are evaluated and compared with the corresponding results for modeled tanks with a fixed base. In addition, the liquid sloshing height for all aspect ratios is also evaluated and compared. The study’s findings clearly indicate that records with low-frequency contents require significantly more seismically demanding than other records for the considered soil types. Remarkably, soil-tank interaction under earthquake motions substantially amplifies the induced response.

Advanced seismic resilient performance of steel MRF equipped with viscoelastic friction dampers

This paper demonstrates the enhanced resilience performance of steel structures with viscoelastic friction dampers (VEFDs) based on numerical simulations of building responses. Velocity-dependent dampers, which are widely used to increase seismic resilience, may increase the axial force of the column under strong earthquake conditions because the generated force depends on the interstory velocity. This often leads to plastic hinges being placed on the columns of the structure, which can lead to structural collapse via weak-layer failure. In addition, while viscoelastic dampers are effective in reducing story drift, peak acceleration, and peak velocity, the proposed hybrid VEFD offers the additional benefit of reducing base shear via the friction damper. Simulation results for 10- and 20-story buildings with the novel VEFDs show that the proposed dampers can control drift and plastic deformation in structural members. Nonlinear dynamic analysis of 20 far-fault seismic ground motion records conducted using OpenSees also reveals lower peak absolute floor acceleration and velocity. Overall, the results suggest that the proposed VEFD has excellent potential for use in the performance-based seismic design of structures because it can reduce both structural and nonstructural damage. The results verify the damper's effectiveness in controlling story drift without a significant increase in the base shear. Collapse probability assessment also demonstrates the collapse resistance of moment-resisting frames when used in conjunction with VEFDs.

Modeling the response of a shallow foundation using advanced soil constitutive models

Shallow foundations are a common type of foundation used for many significant structures. These foundations can be subjected to vertical loads, moments, and base shear, which induce stresses and strains in the supporting soil. Consequently, understanding soil behaviour is crucial in geotechnical engineering. This paper presents a numerical analysis of a shallow foundation using various soil behaviour laws, utilizing finite element methods implemented in Plaxis software. The primary objective of this study is to conduct numerical modeling of a foundation under a centered load. Specifically, it aims to compare the results obtained using different constitutive models, including the Mohr-Coulomb (MC) model, the Soft Soil model, and the modified Cam-Clay model. By employing these models, we aim to evaluate their effectiveness in predicting soil response under load and to identify the most accurate model for specific soil conditions. The comparative analysis provides insights into the advantages and limitations of each model, highlighting the importance of selecting appropriate soil behaviour laws for accurate geotechnical design. Furthermore, this study underscores the significance of advanced numerical tools in enhancing our understanding of soil-structure interaction and improving the reliability of foundation design. The findings contribute to the broader field of geotechnical engineering by offering guidance on the selection of constitutive models for various soil types and loading conditions, ultimately aiding in the design of safer and more efficient shallow foundations. This research also emphasizes the role of precise modeling in predicting settlement and bearing capacity, which are critical factors in the performance and longevity of shallow foundations. Overall, this study aims to improve foundation design practices significantly.

Evaluasi Desain Struktur Gedung Pondok Pesantren At-Tibyan Deli Serdang

The structural design of this three-story Islamic boarding school building, the results obtained after analysis include; risk category II so that the earthquake priority factor is 1. The soil site class is soft soil. In the structural system, it is designed using a special moment resisting frame system (SRPMK). The seismic design category obtained is category D. Seismic inspection starting from checking irregularities, diaphragm design, checking the number of structural vibration variations, determining the fundamental period of the structure, seismic response coefficient values, seismic base shear, checking the deviation between floors is carried out based on SNI 1726-2019. for column elements, beams and also plates in existing conditions after analysis have met the requirements based on SNI 2847-2019. The conclusion in this final project research is based on the results of the analysis that the design of the Attybian Islamic boarding school building still meets the requirements based on SNI 1726-2019 concerning procedures for earthquake resistance planning for buildings and non-buildings and also for beam, column and plate elements have met the requirements based on SNI 2847-2019 concerning reinforced concrete structures. However, for the beam elements for the reinforcement requirements, it is still too wasteful so that in this analysis, the amount of reinforcement is reduced because in the planning principle it must be safe and economical.

Numerical investigations of seismic-resilient techniques for legged fluid storage tanks utilising magnetorheological dampers

Different energy-dissipating devices have been proposed in the literature to attenuate the destructive effects of base excitations over fluid storage tanks. These structures have numerous applications in strategic industries and their failure can result in environmental hazards and huge economic losses. Proposed techniques in the literature for seismic energy dissipation of fluid-contained tanks are mostly centred on passive and active control mechanisms. Semi-active control devices using materials with adjustable properties offer advantages of both active and passive systems while removing their drawbacks. In this paper, the performance of a Magnetorheological (MR) damper on the seismic response reduction of fluid storage tanks through the application of three different control strategies including H2/LQG, PID, FOPID, and two passive techniques, i.e. Passive On, and Passive Off has been investigated. Parameters of the semi-active controllers are optimally designed for each aspect ratio and the applied ground motion using the Hunger Game Search (HGS) technique and finally, the semi-active Clipping algorithm commands the voltage to the damper. The fluid-tank-MR damper system has been examined under three Far-Fault and three Near-Fault ground motions. Numerical simulations have demonstrated that depending on the aspect ratio, applied ground motion, and the control strategy, the MR damper can mitigate the peak relative displacements and absolute accelerations of the two major modes of the system, i.e the rigid and impulsive modes, up to 72% and 67%, respectively. This proves the efficacy of these dampers in reducing the maximum base shear and overturning moment, hence mitigating the damage risks in these structures.

Clutching inertial system for base-isolated liquid storage tanks: Seismic performance and optimal parameters

Liquid storage tanks (LSTs) are susceptible to significant damage during earthquake events, necessitating their continued functionality and additional protection through isolation techniques. The sloshing response and overall base shear of LSTs are critical factors, particularly in base isolated (BI) tanks. This study aims to enhance the seismic resilience of LSTs by leveraging a newly developed advanced inerter-based vibration control methodology for structures. This innovative approach integrates a supplemental clutching inertial system (CIS) with a laminated rubber isolator (LRB). Utilizing an equivalent linearization technique, the study evaluates the equivalent damping and inertance constants to account for the nonlinear behavior of the CIS. These equivalent parameters are then used to assess the stationary peak response of the isolated tank structure, which encompasses sloshing and bearing displacements, forces within the CIS and the isolator, and the total base shear. Further, the analysis employs the stationary power spectral density function (PSDF) model of earthquake excitation by Kanai-Tajimi and the performance of the inerter-based hybrid control strategy is examined by varying system parameters, such as isolation period, isolation damping, CIS inertance mass ratio, and the tank's aspect ratio (i.e., broad or slender). An optimal inertance of the CIS is identified, leading to the least overall base shear for both isolated tank configurations. The impact of these parameters inertance mass ratio of the CIS is also investigated. Subsequently, the isolated tanks are exposed to eleven near-fault (NF) and far-field (FF) real-time earthquake excitations. The study evaluates the CIS's performance as an auxiliary system during these seismic events and contrasts the outcomes with the seismic response under stochastic excitations. The results highlight the effectiveness of the advanced inerter-based hybrid control strategy in reducing the seismic response of isolated tank configurations.

Development of Fragility Curves and Assessment of Mass Irregular Structures with Fixed Base and Base Isolated Under Multiple Earthquakes

ABSTRACT Structures are usually built to withstand the mainshock, aftershocks offer extra difficulties. Aftershocks frequently occur following an earthquake result in multiple earthquakes, therefore they are not isolated events. Due to damage advancement, and stiffness and strength deterioration, a damaged structure might collapse under a multiple earthquakes. Based to a probabilistic perspective, the current study investigates the effect of multiple earthquakes on the likelihood of buildings to collapse. This study’s primary objective is to determine how multiple earthquakes affect fixed- and base-isolated structures. In this context, recorded 14 single and 7 multiple earthquakes with various properties were used to examine and assess three-dimensional reinforced concreteframes with four-storey, having fixed base and isolated base. Dynamic analysis, of the three-dimensional structures are carried out in SAP2000. Fragility curves for fixed base and base isolated structures were produced using the incremental dynamic analysis approach. To find the effect of mass irregularity due to single and multiple earthquakes, mass irregularity is placed at every floor level in each structure. The results are compared in terms of floor displacements, floor accelerations, storey drift, base shear, residual displacement, and probability of collapse for fixed base and base isolated structures. The findings highlight the importance of analyzing the structures subjected to multiple earthquakes. The probability of collapse is reduced for mass irregular structures with base isolation in comparison with fixed base structures, when subjected to multiple earthquakes. The designer’s should select base isolation over the fixed base system when the building’s location may suffer multiple earthquakes more frequently.

Seismic Performance Assessment of Steel Buildings Equipped with a New Semi-active Displacement-Dependent Viscous Damper

This paper investigates numerically the seismic behavior of multi-degree-of-freedom (MDOF) systems with novel 2–4 direction and displacement-dependent (2–4DDD) and 2–4 Displacement-Velocity- (2–4DVD) Semi-Active (SA) controls. This study builds upon the novel SA 2–4DDD control system, in which the damper forces are controlled by inter-story drifts. For the first time, this paper investigates numerically the behavior of an MDOF system with 2–4DDD controls. A 3-story steel frame is modeled in OpenSees and then subjected to real earthquake records. The frame is modeled considering three control systems: (i) conventional passive nonlinear viscous dampers (NVDs), (ii) SA 2–4DDD dampers, and (iii) a new 2–4DVD SA damper. Parametric studies are conducted to determine the optimal parameters of 2–4DVD control in the designed frames. New design methodologies for MDOF systems with 2–4DVD and 2–4DDD controls are also proposed. The results are discussed in terms of inter-story drift, base shear force, acceleration, dissipated energy and required damper force. Results from Nonlinear Time History Analyses show that, compared to a frame with traditional NVDs, the inter-story drifts and base shear of the frame with 2–4DVD control are up to 72% and 32% lower, respectively. 2–4DVD control also reduces damping forces and acceleration by up to 60% and 87%, respectively, compared to 2–4DDD control. It is also shown that the 2–4DDD control was not stable in high-frequency earthquake records. Conversely, the new 2–4DVD control leads to smoother damping force changes between quadrants for the case study investigated in this paper. This study contributes toward the development of new seismic retrofitting dampers for nonlinear MDOF systems.

Effect of Flexible Tank Wall on Seismic Response of Horizontal Storage Tank

Horizontal storage tanks are integral to the petrochemical industry but pose significant risks during earthquakes, potentially causing severe secondary disasters. Current seismic designs predominantly assume rigid tank walls, which can lead to an underestimation of seismic responses. This study introduces a novel analysis method for assessing the dynamic response of flexible-walled horizontal storage tanks. By separating the liquid velocity potential into convective and impulsive components and integrating these with beam vibration theory, we developed a simplified mechanical model. A parameter analysis and dynamic response research were conducted using numerical methods. Results indicate that flexible tank walls amplify seismic responses, including liquid dynamic pressure peaks, base shear, and overturning bending moments, compared to rigid walls. Additionally, the impact of flexible walls is more pronounced in tanks with larger radii, aspect ratios, diameter–thickness ratios, and H/R ratios. These findings highlight the necessity for revised seismic design approaches that consider wall flexibility to enhance the safety and resilience of horizontal storage tanks.

Seismic Behaviour of Steel Building with And Without Bracing System by Performance Point

Steel structures have been playing an important role in the construction industry in recent years. It is necessary to create a model that performs well under seismic loading. Seismic performance of multi-storey steel framed buildings is designed as per the provisions of the Indian Code (IS 800 -2007). The ductility of the structure can be increased by adding steel support to the structure. There are different types of support for retrofitting. X-brace, diagonal brace, V-shaped brace, inverted V-shaped brace etc. There are many ways to prepare steel supports such as: The frame of the building is designed with or without different types of connections such as diagonal, X-brace, V-brace and inverted V-brace, which will be considered in this study. The performance of each frame was examined by nonlinear static analysis (pushover analysis) using the ETABS-2021 software package. The comparison of braced and unbraced frames was based on the examination of base shear forces, hinge consequences and lateral displacements of different frames. Compare the response curves and performance points of different frames with and without support systems to know the relationship between the various frames involved.

The Influence of Variations in Shape and Placement Sliding Walls on The Behavior of Multi-Story Building Structures to Withstand Earthquake Loads (Case Study: Building Pasar Raya Inpres Block)

System the structure of Building a Pasar Raya Inpres Padang Block IV, namely system double that uses wall shift as retainer lateral load and SRPMK as retainer style gravity, but cold sliding on the building the only there is on the 1st floor only if wall shifts No continuously until building roof floor so can influence behavior structure building the like mark style shift basis, displacement, deviation between the floor and p-delta influence. The study this aims to compare mark style shift basis, displacement, and deviation between which floor and p-delta later will compared against 4 variation models shape and placement wall shift. The method used that is method comparative with analysis uses response spectrum using ETABS software. Results of the study show model 2 structure has a mark base shear namely 3658,658 kN. Model 2 has a mark displacement the smallest in the x direction is 3,766 mm and Model 4 has a mark displacement the smallest in the y direction is 2,347 mm. Model 2 has a mark deviation atar floor smallest namely 8,019 mm for the X direction and 4,015 for the Y direction. All models are confirmed safe at the moment checking the P-Delta effect, with model 2 having the mark lowest for the X direction and Y direction.