Earthquake Forces Research Articles

Effect of base slab mass and number of rubber layers on base isolation system performance in enhancing building dynamic response

Purpose Traditional designs might not withstand earthquake forces adequately, potentially leading to structural damage. This paper aims to examine the impact of varying the base slab mass and the number of rubber layers in isolators on the performance of isolation systems to improve the seismic performance of buildings. Design/methodology/approach The isolated structure is modeled as a two-degree of freedom system, and its corresponding equation of motion is established. Displacement expressions for the base slab and roof are derived using the mode superposition method. Findings A base isolation system improves the buildings’ behavior, particularly when higher rubber layer numbers and a heavier base slab are assumed. At an excitation frequency of 8 rad/s, an increase in the rubber layer numbers from 9 to 11 led to a 30% reduction in relative displacement. At an excitation frequency of 6 rad/s, a 40% reduction in relative displacement was observed passing from a base slab mass (mb) of 7.5 tons with damping ratios of 12% and 10% in the first and second modes to a mass (mb) of 30 tons with lower damping ratios of 9.5% and 4.2%. Originality/value The high damping ratio in the isolation mode significantly increases the damping ratio of the fixed-base building. However, higher damping ratios in the first and second modes do not necessarily lead to better seismic performance. Besides, an increase in the base slab mass and the number of rubber layers enhances the dynamic response of the isolated structure by shifting its fundamental frequency away from the excitation frequency.

Analysis of the Structural Performance of the State Treasury Services Office Building Against the Latest Earthquake Regulations SNI 1726 - 2019

This research aims to analyze the structural performance of the Tanjung Balai State Treasury Services Office Building (KPPN) against the latest earthquake provisions in SNI 1726-2019. This analysis is important to ensure that existing building structures meet the latest regulations and are able to withstand anticipated earthquake loads. The research methodology includes collecting building technical data, structural modeling using SAP2000. Building technical data includes information regarding dimensions, materials and main structural elements. Structural modeling is carried out to create a digital representation of the building. The results of the structural analysis program show that the natural period value according to both regulations and modeling is 0.196769 seconds. The basic earthquake force obtained from SNI 1726-2019 is 51,314 kN for the However, the base reaction is considered safe in both regulations because of the static earthquake force, namely 38,962 kN for SNI 1726-2019 and 31.17 kN for SNI 1726-2012. Then the story drift in the X direction of SNI 1726-2019 is 0.114 mm, in the Y direction 0.437 mm with a clearance deviation of 80 mm. And SNI 1726-2012 X direction 0.096 mm, Y direction 0.3 mm with a clearance deviation of 80 mm. According to the ATC-40 analysis which was analyzed using SAP2000 software, the building performance that occurs on soft soil (SE) has a drift value of 0.015 which is included in the Damage Control phase. From the results of this analysis, it can be concluded that the Tanjung Balai State Treasury Services Office Building (KPPN) meets the security criteria in accordance with SNI 1726-2019. These findings are expected to provide valuable recommendations for building owners to ensure the safety and suitability of existing building structures against earthquake risks in Indonesia.

Insights from large‐scale shake table testing: Key criticisms and potential solutions

AbstractThis article presents the authors' experience with large‐scale shaking table tests conducted in Japan using the E‐Defense shaking table. The discussion focuses on four criticisms often addressed regarding the utilities of large‐scale shaking table tests. Potential solutions to mitigate such criticisms are discussed based on shaking table tests conducted for a pair of three‐story wooden houses. The first criticism is that the test specimen anchored rigidly to a rigid shaking table is not a reproduction of actual structures supported by soils and foundations. A model ground was developed in a large sandbox, which occupied about 85% of the total specimen weight, supported the house, and the entire soil‐structure system was shaken. Considerable sliding occurred, having lessened the earthquake forces exerted and resultant damage to the superstructure. The second criticism is that a single specimen test, regardless of its size, cannot provide sufficient information for generalizing the behavior and performance. Empirical equations between the maximum story drift and the change in the natural frequency were developed from a series of shaking table tests. Using such empirical equations might promote quick damage assessment of individual houses when suffering from actual earthquakes. The third criticism is the importance of public appeal and eventual support from the general public to secure the budget to operate large‐scale testing facilities. The example test featured two nearly identical specimens placed on the table with different support conditions. The apparent difference in response revealed the effect of support conditions on seismic performance. The fourth criticism is the importance of increasing the number of experimental projects to balance the operation budget. Most of the preparation in the example test was accomplished in an open yard adjacent to the shaking table, and the test specimens were quickly assembled on the table using indoor cranes. The table occupation was four out of 35 weeks of the entire test duration.

Seismic Design of Underground Structures’ Vulnerability – Review.

This article examines the vulnerability of underground structures to seismic activity, with a particular focus on design and mitigation strategies. Underground buildings are essential to the development of modern infrastructure and must include tunnels, subway stations, and storage facilities. Because of its deep location, seismic design and earthquake performance are both more challenging. In this study of seismic susceptibility, topics such as ground motion characterization, soil-structure interaction, structural reaction, and failure mechanisms specific to underground structures are discussed. According to the paper, their susceptibility can be affected by geotechnical conditions, the kind of structures they have, and the construction methods that are used. The seismic stability design and analysis process involves measuring the dynamic response of subsurface structures to seismic loads. The goal is to keep earthquake and seismic forces from toppling structures in any way that is possible. Advanced analytical and numerical approaches are used in seismic stability design. Some examples of these methods are finite element analysis (FEA), discrete element modeling (DEM), and the boundary element method (BEM). In addition to that, it investigates contemporary methodologies for assessing seismic vulnerability as well as international design standards. In addition, seismic retrofitting and design advances for underground structures are analyzed and discussed in this paper. This document compiles and evaluates previous research to gain an understanding of the seismic susceptibility of subsurface structures and to promote more seismic engineering research on this extremely important topic.

Seismic isolation strategy via controlled soft first story with innovative multi-stage yielding damper: Experimental and numerical insights

While the presence of a soft story within a building is typically discouraged in structural engineering due to potential vulnerabilities, this research proposes a strategy that incorporates seismic isolation concepts by integrating a soft first story within the structural framework. This approach challenges traditional reluctance by demonstrating the potential benefits of such a configuration. The primary objectives are twofold: firstly, to diminish seismic responses and enhance structural resilience when subjected to earthquake forces, and secondly, to reduce construction costs as compared to conventional passive control methods. The seismic responses assessed and compared in this study encompass story displacements, story drifts, floor accelerations and base shear of the structure. Furthermore, an investigation is conducted into a replaceable or repairable shear fuse that serves as a controller in the Controlled Soft First Story (CSFS) strategy, namely, an innovative Multi-stage Steel Yielding Damper (MSYD). Notably, the numerical analysis of the introduced damper has been carried out, followed by rigorous validation testing under experimental conditions. This study elucidates the implementation of this strategy within the structural framework. The overarching principle behind employing the CSFS results in outcomes akin to those achieved with base isolation techniques. However, it distinguishes itself by significantly mitigating the construction costs around 70% associated with this system when juxtaposed with traditional base isolation systems.

Improvement of seismic performance of concrete structures using magnetized concrete: an empirical study

High-Performance Concrete (HPC) offers better workability, compressive strength, and durability compared to ordinary concrete. One type of high-strength concrete is magnetic concrete. The primary objective of this empirical research is to investigate the potential of magnetized concrete in enhancing the seismic properties of concrete structures, in this technology, the physical structure of water is altered by inducing a magnetic field. The research employs empirical methods, including experimental testing and analysis, to assess the seismic performance of magnetized concrete compared to traditional concrete. As a result, the number of molecules in a molecular cluster decrease from 13 to 5 or 6, and the surface tension of the water is reduced. Using this water in concrete preparation increases the workability of the concrete mix and reduces the required water. Additionally, by facilitating cement hydration, it increases the compressive strength and durability of the concrete. This increased compressive strength enhances the stability and resistance of the structure against earthquake forces. Moreover, maintaining the compressive strength of the concrete while using magnetic water can reduce cement consumption. This reduction in cement consumption can lower the weight of the structure, which is very effective in reducing earthquake forces in tall buildings.

Comparative Seismic Analysis of Regular and Irregular Multistorey Structures with and without Bracings and Shear wall

Abstract Seismic effect is one of the main factors which has to be considered during the design of structure. Earthquake is one of the supreme hazards for living and assets on earth. It is a natural phenomenon, occurring with uncertainties as a result of sudden release of energy within earth crust in the form of seismic waves. As the earthquake forces affects the stability of the building and about 60% of region in our country is under the influence of seismic forces, the buildings are provided with alternatives to withstand the horizontal forces and to increase the strength, stability and stiffness. Present paper investigates the performance of different structures provided with seismic resisting components. In this paper Shear walls and bracings are incorporated to make the structure moment resisting frame. A comparative seismic analysis of high-rise structures with and without shear walls and bracings is included in this discussion which is done using ETABS 2019 software by Response Spectrum Analysis. The parameters considered for analysis are natural frequency, natural time period, base shear, story stiffness, story displacement and story drift. in constructing both.

Seismic Analysis of Irregular Multistorey Building

Abstract: The seismic analysis of buildings is crucial for ensuring structural safety and resilience against earthquake forces. Irregularities in building configurations pose unique challenges, influencing the distribution of seismic forces throughout the structure. This study focuses on the seismic analysis of a G+12 building characterized by irregularities in plan and elevation using STAAD.Pro software. Here we have taken four models consisting of bare bay frame , bay frame with shear wall on one corner, , bay frame with shear wall on two opposite corners, , bay frame with shear wall on all corners for the further analysis. This research contributes to enhancing understanding and design practices for irregular high-rise buildings, emphasizing the importance of advanced analytical tools in seismic engineering. From this analysis we can conclude that within all four models ,building having shear wall on all four sides shows minimal deflection attributed to its maximum stiffness characteristics, hence considered most stable

Steel truss reinforced concrete composite walls: Numerical investigation and design consideration

Conventional design practices for reinforced concrete (RC) structural walls in the lower stories of super high-rise buildings involve employing large thickness and dense reinforcement to ensure satisfactory seismic performance. This is necessary to withstand the considerable gravity and seismic forces caused by the superstructure. However, this approach brings a design challenge in engineering practice because excessively thick RC walls not only occupy useable space but also magnify earthquake forces due to the increased self-weight. For this reason, steel truss RC (STRC) composite walls have been developed to address the above-mentioned shortcomings of conventional designs. This paper elucidates the working mechanism of STRC walls under cyclic loading, indicating that these two diagonal embedded steel elements mainly exhibit truss behavior. The working mechanism is further verified through computational models developed in OpenSees with high accuracy and efficiency. Moreover, the design provisions in the current specification are evaluated in terms of the flexural strength and shear strength of STRC walls. Results show that the flexural strength of the design equations for STRC walls in the current specification is underestimated because the contribution of steel trusses is not considered. The findings of this study offer valuable insights into the engineering application of STRC walls.

Influence of Repeated Earthquake events on Structural Response of Multi‐storeyed RC buildings

Over the past decade, reinforced concrete (RC) multi-storeyed buildings have become more prevalent in urban environments. In addition, it has been well established in literature, that collapse of several RC buildings and resulting causalities, thereof are mainly attributed to the repeated nature of occurrence of earthquakes, more often leading to collapse. However, most existing design codes consider only a scenario earthquake characterized by the response spectrum specified by local codes of practice. This consideration do not address the repetitive nature of earthquakes, leading to inadequate estimation of design earthquake force. Hence, the present investigation focusses on proposing a probabilistic model to logically address the number of earthquake sequences to be considered at a chosen location. In addition, to ascertain attainment of collapse state of code designed 3D RC buildings, under a pattern of earthquake sequences (with simultaneous bi-directional ground motion data), a simple and computationally less intensive NLTHA (Nonlinear Time History Analysis) approach has been considered. Moreover, this approach captures the effect of sequential earthquakes and provides a quick rational decision on the structural behaviour, necessary for further analysis. Hence, eliminating the need to resort always for complex IDA (Incremental Dynamic Analysis) approaches to illustrate the structural behaviour. Moreover, the structural behaviour of RC buildings are represented in terms of base shear experienced and their corresponding response parameters (Horizontal displacement, Inter-story drift ratio (IDR), etc.,). The outcome of the results clearly contemplates the accumulation of damages in terms of response parameters, emphasizing the need for consideration of repeated earthquake sequences in seismic analysis.

Analysis of Diaphragm Force on Reinforced Concrete Building Structures with Horizontal Irregularities of Diaphragm Discontinuity

The diaphragm plays a crucial role in distributing seismic forces within buildings during earthquakes, affecting both regular and irregular structures differently. This study investigates the seismic behavior of diaphragms in various building geometries resembling the letters I, T, L, and O, focusing on their influence on structural performance and reinforcement requirements. Using analytical methods, diaphragm seismic forces, slab shear stresses, and internal forces were calculated for a sample of buildings with different geometrical irregularities. The study reveals significant differences in diaphragm earthquake forces between regular and irregular buildings, with irregular geometries exhibiting distinct patterns of shear stress distribution. Particularly, the building with an L-shaped plan and concentrated stress points showed the highest maximum shear stresses in both orthogonal directions. Analysis of internal forces—axial, shear, and moment—highlighted varying reinforcement needs among the studied buildings. While axial and shear forces necessitated minimal additional reinforcement across all structures, moment forces indicated substantial reinforcement requirements, particularly in the L-shaped building. These findings underscore the importance of tailored diaphragm design strategies for buildings with irregular geometries to mitigate potential structural vulnerabilities during seismic events. The study contributes insights into optimizing diaphragm design practices and emphasizes the need for further research in this critical area of structural engineering.

Analysis of Non-Linear Static Procedure Based on Fema 356 to Evaluate Structural Performance in the Alton Apartment Building

Alton Apartment is a high-rise residential building. The city of Semarang, within a radius of 500 km, has a fault range with a strength of up to 8.3 magnitude. The purpose of this study is to calculate the performance level of the structure, find out the nonlinear static procedure conditions and whether the analysis results can be used, calculate the value of ductility R, check the boundaries between levels, check the influence of P-delta, adjust horizontal irregularities, and check the vertical irregularity conditions. This study uses the FEMA 356 method. New regulations are used in the analysis, such as peak acceleration maps and response spectra from PuSGeN in 2021, deaggregation maps of Indonesian earthquake hazards for planning and evaluation of earthquake-resistant infrastructure from the Director General of Cipta Karya in 2022, and earthquake resilience planning procedures for building and non-building structures from SNI 1726-2019. The result of the structure performance of the drift value is below 1% for the life safety (LS) performance level on the 250-year earthquake map, and the result of the drift value is below 2% for the collapse prevention (CP) performance level on the 100-year earthquake map. The results of the FEMA 356 condition one analysis show that the strength ratio (μstrength) value of less than μmax has been met for 250-year and 1000-year earthquake maps with a review of the x and y directions of the earthquake. The value of the R ductility in 250-year and 1000-year earthquakes is above seven according to the earthquake force holding system of special reinforced concrete sliding walls.

A Comparison Analysis of Buildings as per Norwegian and Ethiopia ES-EN1998-1 Seismic Code

An earthquake is one of the most significant and shocking natural disasters ever documented anywhere on the planet. Throughout history, it has claimed millions of lives and wreaked devastation on infrastructure. Because earthquake forces are spontaneous and unpredictable, engineering methods must be honed to investigate buildings under the impact of these forces. The dynamic and static computations of four RC multistory structure prototypes with various elevations in a high seismic zone are compared in this paper. The project under review is modeled as a 3, 6, 12, and 18-story establishment, and it is analyzed employing ETABS vs. 2019. The Equivalent Lateral Force (ELF) Procedure is used for static experimentation, while the Response Spectrum (RS) Procedure is employed for dynamic investigation. Both calculations are performed as per the EUROCODE 8-2004 recommendation. The ELF seismic load practice utilized was for the country of Norway, which has similar parameters to the ES-EN 8-15 seismic regulation Type I target RS, with ag/g = 0.1, spectrum type = I, soil factor S = 1.3 ground type, spectrum period (Tb, Tc, and Td) 0.1 s, 0.25 s, and 1.5 s. For the RS investigation, the parameters employed are as per ESEN-2015, ag/g = 0.1, and the spectrum type = I and ground type = B parameters were involved in the same manner for the RS analysis. The soil factor was set to 1.35; the spectrum period was set to (Tb, Tc, and Td) 0.05 s, 0.25 s, and 1.2 s. The behavior factor = 3.8, the lower bound factor = 0.2, and the damping ratio = 0.05. The results are then compared by employing different components such as displacement, story drift, story stiffness, base story shear, and story moment. Ultimately, a comparison of static and dynamic investigations has been carried out. Compared to the RS approach, the ELF technique produces more additional displacement, total drift, and base shear. As per the findings of this paper, for high-rise and tall buildings, dynamic analysis such as RS should be used rather than static analysis (ELF).

Adaptive Real Time Efficient Control Algorithm for Buildings Under Wind and Earthquake Forces

The study aims to tackle two key issues: the dependency of optimal controllers on available training data and their limited capability in managing multi-component structural responses. Real Time Fuzzy Logic Efficient Control system (RTFLEC) was developed to address these challenges. This system integrates a fuzzy logic inference system with a multi-verse optimization algorithm and utilizes real time training for real-time optimal controller derivation. It incorporates decentralized systems and optimal controller memory concepts and employs a magnetorheological damper (MR) for adjustable vibration control. Two case studies were conducted to evaluate the RTFLEC system's effectiveness. The first study focused on a three-story shear building under seismic loads, while the second analyzed a 76-story building facing multi-directional wind loads. The results showed that RTFLEC system reduced structural drifts by 28.33% and 51.5% during near-field and far-field earthquakes, respectively. It also decreased structural acceleration by 27.66% and 53% during near-field and far-field earthquakes, respectively. For wind-induced structures, it reduced story displacement by 37.5%, 14.5%, and 12% against across-wind, along-wind, and rotational forces, respectively. RTFLEC system demonstrated robust performance against uncertainties in external excitations, providing exceptional structural responses. Its key advantage lies in real-time adaptability, requiring minimal training data and computational processing. These findings highlight its significant potential in enhancing the performance of adaptive vibration control systems under unpredictable real-world loads.

Evaluation of Lateral Load Resisting Systems in High-Rise Buildings

The rapid urbanization and the scarcity of residential space in metropolitan areas necessitate the construction of tall structures to meet the growing accommodation demands. This research paper focuses mainly on the structural act of high-rise structures under lateral loads, especially earthquake forces. Three lateral load resisting systems, namely outrigger system, shear wall at core and shear wall at corner are compared and analysed. The study reviews relevant literature, discussing parameters affecting the fundamental time period of structural models and the effectiveness of distributed belt wall systems. The research methodology involves the analysis of a 40-storey regular office building using three different lateral load resisting systems. The results obtained through response spectrum analysis, shows that the outrigger system exhibits efficient structural capability in tall buildings. The maximum lateral displacement is significantly reduced in the outrigger system compared to core shear-wall and corner-shear wall. The study concludes that enhancing lateral load resistance and providing a transition path to perimeter columns subjected to lateral load, as seen in the outrigger-system, proves effective in mitigating the impact of earthquake loads on high-rise buildings.

Design and Nonlinear Dynamic Response of a Steel Stack

AbstractIndustrial stacks are built in order to reduce atmospheric pollution and release gases to the higher level of the atmosphere. Since they are high and slender structures, they are significantly affected by lateral forces, in particular, induced by winds and earthquakes. This paper aims to summarize the design principles for steel stacks given in the international standards, codes and specifications considering the evaluation of the results from the investigation on nonlinear dynamic response of a typical steel stack subjected to the earthquake. For this purpose, a typical self-supporting steel stack has been designed and its performance under earthquake and wind forces has been investigated in terms of the applied design principles, such as the displacement limit and the potential plastic deformations. The study is accomplished by using finite element models employing nonlinear time history and pushover analyses. The numerical results are presented particularly by considering the design principles used for the model. The results show that wind loads considered are more pronounced in the design of industrial steel stacks than earthquake especially in terms of limiting top displacement. The flue openings which reduce strength and lateral stiffness of the stack web is significantly effective in the lateral behavior of the stack. Moreover, the principles considered are found applicable for the design of such steel stacks. Based on the results from nonlinear time history analyses, no yielding and plastic deformation are detected along the stack.

A Review on Seismic Performance of Asymmetric Buildings with Shear Walls

There is an increasing trend in the construction field to build structures that are asymmetric both horizontally and vertically due to the need for unique aesthetic appearance. Also, the increase in population forces people to build structures in densely populated cities leading to scarcity of land for construction. Many other circumstances pave the way for structures to be irregular in nature. These structures have to be made seismically resistant in order to avoid loss of life and property. Shear walls are one among the solutions to conditions that don't satisfy seismic resistance. They have high stiffness which counteracts the lateral loads of the building due to earthquake forces. This study aims at providing insight to major findings about the behavior of asymmetric structures with different locations of shear walls in terms of seismic response parameters.

An analytical solution to account for the earthquake body force for twin circular tunnels in elastic media using complex variable approach

An analytical solution to account for the earthquake body force for twin circular tunnels in elastic media using complex variable approach

Shape Optimisation of Grooves in Grooved Gusset Plate Damper used in X-Braced Frame

The X-braced frame represents a specialized variation of concentric-braced frames. It can be used as a resistance towards the lateral load acting on the structural system. X-braced frames generally exhibit lower flexibility when compared to eccentrically braced and moment frames, which is often perceived as a drawback of this structural system. To address this limitation, energy dissipation devices can be integrated into the system with X-bracings to absorb the plastic action and safeguard other structural elements, such as columns, beams and connections from earthquake forces. Specifically, X-concentrically braced frames are tailored through variations in groove shapes. Furthermore, the investigation determines the dampers' load-bearing and energy dissipation capacities. The assessment commences with cyclic load testing conducted using the ANSYS software. The grooves present in GGPD help dissipate seismic energy. The energy dissipation and load-bearing capacity of the X-concentrically braced frame equipped with a grooved gusset plate damper were compared based on different groove shapes. The different shapes used for the analysis were L shape, oval, rectangular and stadium shape. It was observed that oval-shaped grooves have more energy dissipation capacity among four groove shapes, with an increase of 10.74%.

Influence of Concrete Compressive Strength on L-Shaped Shear Wall Performance in Buildings within High-Seismicity Zones

Reinforced concrete mid-rise structures are supported by shear walls to withstand lateral forces resulting from earthquakes. In this context, the presence of openings in these walls is essential both functionally and aesthetically. This study employed L-shaped shear walls with varying vertical opening ratios, ranging from 15% to 50%, and compressive strengths ranging from 20MPa to 40MPa in a ten-story building. The study results demonstrate the significant role played by openings and the compressive strength of concrete in reinforced concrete walls to ensure buildings withstand earthquake forces. In this regard, we have developed reference models that adhere to seismic design principles and utilize optimized dimensions for openings based on the compressive strength of the concrete.