Damascus University Journal of Earthquake and Disaster Research
A specialised scientific journal published by the University of Damascus dedicated to the dissemination of research and studies in the fields of seismology, geology and earthquake engineering. The journal aims to advance scientific knowledge in these fields and supports research that improves the understanding and analysis of seismic phenomena and their effects. It also seeks to provide practical solutions to improve the earthquake resistance of structures. The journal adheres to rigorous academic standards of peer review and welcomes submissions from researchers in related disciplines. ISSN:3081-085X
Analytical Prediction of Damping Coefficient-Vibration Amplitude Relationship Changes of Reinforced Concrete Bridge Piers
The dynamic parameters like damping ratio and natural frequency are crucial, to explain the dynamic behavior of structures and predict their responses to various vibration motions. The analytical approach is thought to have inherent flaws, since the dynamic properties of structures are typically predicted analytically and do not take into account changes in amplitude vibration. Although the majority of earlier experimental investigations sought how variations in vibration amplitude affect dynamic properties, analytical discussion of these changes has not been done yet. This analytical and numerical study was conducted to better understand the effect of excitation changes on damping ratio in dynamic analysis of reinforced concrete bridge piers using Abaqus 6.14 program. In order to do this, analytical prediction of the relationship between the damping ratio changes versus vibration amplitude changes were investigated. Then, modal analysis and dynamic analysis on tested bridge pier specimens were carried out considering the damping ratio changes. To find that, the analytical responses, after defining the damping changes function in the analytical model, were closer to the experimental responses than those with constant damping coefficient by comparing the acceleration responses of the pier model.
Copyright (c) 2024 Damascus University Journal of Earthquake and Disaster Research
Shear capacity of composite beams using numerous bolted shear connectors under static loads
The structural system, which consists of composite slabs and steel beams, is considered an ideal structural architectural solution. It provides flexibility in the spans and reduces the dimensions of the structural elements. The shear connector is the most important part of composite beams. Moreover, the shear studs welded with the upper flange of the steel section are the most common. Several studies have focused on replacing these studs with a more efficient and effective type. Among them, a new technology called UPC has been introduced in Spain. This technology creates a complete shear connection, by forming small crown-shaped pieces into the steel sheeting, as an alternative to the usual embossing system in composite slabs. This paper tests the shear capacity of a new shear connector similar to the UPC technique to use in composite beams. The new shear connector is four steel angles fixed by bolts and looks like a crown. The push test was modeled with the new crown connector by Abaqus software. The failure modes were studied. The relationship between the force and slip was drawn for different concrete grades. The analytical model has been verified by comparing it with the results of previous studies conducted on different shear connectors. This paper introduces the idea of creating shear connectivity by using semi crown-shaped that could replace the old technology using welded studs. As result, the crown shear connector, which was made up of four bolted metal angles, provided a high shear capacity and could be used in place of welded studs. Furthermore, the crown shear connector demonstrated ductility when C58 concrete was used.
Copyright (c) 2025 Damascus University Journal of Earthquake and Disaster Research
The Influence of structural irregularities on response of the RC buildings subjected to mining tremors and earthquakes
The seismic design of structures seems to be a completely recognized subject. There are requirements and guidelines that must be looked at by planners in seismic zones. The problems occur while irregular structures are concerned especially while structures are subjected to dynamic earthquake-like excitements. An example of such vibrations is mining tremors. In Poland, the problem of seismic behavior of irregular buildings subjected to mining-induced seismicity is still an unsolved problem. In this paper numerical studies are carried out for five-storey building models with six various types of irregulars in plan. In this article, the response of the studied models was compared by linear dynamic analysis (Response Spectrum). The difference between the response of the structure to earthquakes and mining tremors is presented. Lately, several numerical simulations have been done to research the building behavior under mining tremors and earthquake shaking. There is still a necessity to research and compare the results of numerical analyses prepared for the same subject and the same soil cases. The aim of this paper is to present the differences between mining tremors and earthquakes.
Optimized Design Ratio of Frame Part Participation in Walled-Framed System of R\C Building
Buildings that are designed with seismic resistant dual shear walled – framed systems are required to fulfil the 25% minimum design lateral force resistance ratio for the frame part alone (without the contribution of the shear walls). This condition raises the question that what is the resulting ratio for the design lateral resistance of the frame part in dual system if an artificial intelligence algorithm was used in the designing process. For this purpose, a dual shear walled- framed system of three spans and five stories is analytically verified to have the nearest possible results to an experimental test by Devi, G. N. (2013). Then an optimum design for the same system is performed. A heuristic algorithm with two phase design variables is used in the optimized design. These variables are prepared at first to be suitably few for the search algorithm to be cost effective in the manner of time needed to have results. This is called phase-1 optimization. Then the number of variables is expanded to cover all the design aspects in the model in phase-2 while using the results of phase-1 as initial values of phase-2. The cost-based optimum design’s objective function takes into consideration the cost of building materials used (concrete and steel) and the cost of square meter of the formwork used to shape members during curing process. The cost of any section is estimated for unit length of member, then the total cost of the whole system is calculated by summing up the cost of all members. In this research an FEM nonlinear program used for analysis (Abaqus) and Python package for machine learning and optimization is used in the optimization process. The frame part participation ratio resulted, though exclusive to the system considered in this research, it ignites the curiosity to investigate several dual system configurations of R\C buildings that could be considered in future works.
Study the Behavior of Ground-Supported Cylindrical Tanks Considering the Soil Structure Interaction Using Finite Element Method FEM
The ground-supported Cylindrical Steel tanks are widely used in industrial and service domains to store various types of liquid. As a result of neglecting the interaction between the fluid and tank from one side and the interaction between the tanks and soil beneath them from the other side, it will likely be exposed to huge damages during and post-earthquakes. In this paper, the fluid-tank system considering Soil Structure interaction (SSI) has been studied. The 3D model has forming for the soil, tank and fluid in the finite element program (ABAQUS) to examine the two types of tanks. Two types of soil (hard-Conglomerate & silty gravel) and the frequency content of several earthquake records have been investigated. The results have apprenticed that the shear force of the water tank in the silty gravel soil is increasing by about 60% in the hard soil and may decrease by about 10% -20%. These ratios vary depending on the Frequency content of the seismic record and the role of properties of silty gravel soil in the amplification of the forces and displacement. The increase in wall displacement may arrive at 3 times in silty gravel soil in comparison to hard one. Also, the increase in displacement is accompanied by an increase in the stresses in the tank elements. In addition, the liquid wave height (sloshing) increases by a higher ratio in the case of silty gravel soil than in hard one. The results emphasize the necessity of considering the type of foundation soil for underground reservoirs and the seismic characteristics of the applied recordings. Additionally, it highlights the importance of improving the soil layers on which the foundations of the reservoirs are established, particularly for silty gravel soils.
Studying the Effect of Torsional Irregularity on Seismic Response Modification Factor in RC Dual System
In this research, the effect of torsion due to the irregularity of the reinforced concrete dual system on seismic response factors and building behavior was investigated. As the demands of modern architecture increase, the effects of twisting are amplified, altering the actual earthquake response of a structure. A fifteen-storey 3D building has been modeled using Incremental Dynamic Analysis )IDA (under 20 seismic records that are selected to match the seismological specifications of Syria country. Eleven different scales were used for each seismic record, and a force-displacement curve was derived to determine the necessary parameters and calculate the seismic response modification factor. These values were then compared with the values of the Syrian and American codes, and differences in decreases by 35% were observed relating to the eccentricity ratio 42%. These differences vary according to the eccentricity ratio and torsional effects in these systems. Therefore, it is recommended to use a dimensionless factor that considers the effect of the torsion ratio on the response modification factor instead of using a fixed value for the R factor as stated in the codes.
Free Vibration of Numerical and experimental study-Supported Cylindrical Steel Tanks
The recent seismic events in Syria highlight the necessity of studying and evaluating the seismic response of structures to save lives. Liquid storage tanks have a major role, and their operational integrity must be maintained following seismic events. Therefore, it is essential to evaluate the performance and study the seismic behavior for its. In this research, the dynamic characteristics, natural frequencies, and model shapes of ground tanks near Damascus were studied using an experimental method. The ambient noise measurement-Nakamura 1989- is executed in the case of an empty tank. The obtained results were compared with the results of the 3D numerical model of the finite element method (FEM) for the study tank using ABAQUS software. In addition, two tanks in the filling case with two different slenderness ratios (T1=0.36, T2=0.82) have been studied to clear the effect of the slender ratio. The natural frequency of the convective and impulsive components has been found analytically based on the Eurocode and numerically using the finite element method. The Couple Acoustic Structure (CAS) method has been used to model the fluid-tank interaction. The results of the paper have shown the possibility of using the ambient noise measurement to estimate the response of ground tanks, as the convergence rate with the finite element method arrived at 83% in the case of empty tanks. Also, the CAS method can be used to find the natural frequency of convective and impulsive components. The convergence rate with the Eurocode arrives at 97% 98% for the convective frequency of the (T1) and (T2), respectively, and convergence of 95% and 88% for the impulsive frequency of (T1) and (T2), respectively. Finally, the importance of research can be summarized in contributing to avoiding the occurrence of the resonance condition by adapting the engineering design for the liquid tank system
Study the seismic response of Reinforced Concrete Buildings Retrofitted with a Precast Concrete Frame Reinforced with a Steel Plate
Most of the buildings that have been built prior to the adoption of the Syrian Arab Code in 1995 and its Annex (2) in 2005 are structurally inadequate to withstand seismic loads. Many of these buildings are still in use with varying levels of seismic deficiencies. This research highlights the importance of improving the seismic performance of frame buildings by using one of the retrofit methods to increase efficiency by increasing the resistance of existing buildings by using precast concrete frames reinforced with steel plate. The research investigates the seismic behavior of a 10-story mid-rise frame building using ABAQUS software. Firstly, the behavior of the precast concrete frame PBSPC, armed with inverted V-shaped, reinforced with steel plates, was obtained by creating an analytical model using the finite element software ABAQUS. A load protocol (displacement control) was applied. The efficiency of the retrofit was evaluated by applying several earthquakes to the building frame and comparing the seismic response by comparing the period, accelerations, floor displacements, and base shear forces before and after the retrofit. The results between the model and the laboratory experiment showed similar hysteresis loops. The results also indicated that the external retrofit mechanism using a precast concrete frame is highly efficient in improving the seismic behavior of the building in all placements. It was observed that the best results were obtained with the pyramidal method compared to other methods, where the lateral displacement at the top of the frame decreased by 58.8%, the acceleration at the top of the frame increased by 8.03%, and the base shear forces increased by 194.25%, while the period decreased by 67.91%. Regarding max story drifts, the pyramidal method provided the highest values of relative differences across all stories, ranging between 65.69% on the fifth story and 83.11% on the fourth story.
Seismic Performance Assessment of Alqutiefeh Hospital Using Incremental Dynamic Analysis
The study of assessing the safety of health facilities is essential, especially in the case of exposure to disasters such as earthquakes. It is necessary to en sure the safety and operability of hospitals after earthquakes. Fragility curves help in assessing the expected seismic performance of the building and evaluating losses, which helps specialists develop emergency plans later. In this research, the seismic performance of Al-Qatifah National Hospital, which was designed seismically according to the Syrian Building Code, was evaluated by conducting an incremental dynamic analysis for developing the fragility curves for the structural elements, then evaluating the building's performance on the intensity corresponding to the design earthquake to verify reaching the immediate occupancy level, and on the intensity corresponding to the maximum considered earthquake to verify reaching the life safety level. the results show by the that although the studied building meets the general requirements for the acceptable drift ratios, some structural elements (such as shear-controlled walls, columns and beams forming the facade frame) did not achieve the required performance level. The results also showed that the incremental dynamic analysis provides a better view of the expected seismic performance of structural elements than other analysis methods.
The use of Remote Sensing applications for determining the vegetation decline resulting from the urban sprawl and reducing its environmental impacts in Daraya District in the Damascus Countryside
The integration of remote sensing technologies with geographic information systems results in advanced research tools and purpose maps that help in studying, evaluating and monitoring changes in natural resources. The analysis and evaluation of the data and information from these maps helps to better understand the current state of urban expansion in these areas, and thus suggest more realistic scenarios for planning these areas in an urban manner that is safer and more sustainable. The scientific importance of this research lies in determining the percentage of vegetation cover decline in the Daraya area in the Damascus countryside, by taking advantage of this technical integration in drawing urban sprawl maps for the studied area, and thus showing the extent of the spread of this sprawl based on both the natural change index of vegetation cover and the natural change index of urban growth. The current results show the expansion of the urban area compared to the decline in the area of agricultural land in the studied area, and the impact of this expansion on the increase of disasters and hazards that threaten the safety of the environment and food security in the Daraya region and its surrounding areas.
Using Numerical Modeling To Structural Safety Assessment
Explosions lead to large losses of life and property, and the study of this type of load has received a great attention from researchers in conjunction with the increase of terrorist attacks around the world, as it is known the explosions in Syria led to cracking and partial or complete collapse of important residential and vital buildings. In conjunction with preparing for the reconstruction phase, and studying the possibility of rehabilitating damaged facilities, it was necessary to search for advanced calculation methods for assessing the damage, and choosing effective strengthening methods that achieve efficiency and moderation in the consumption of materials and energy sources. Furthermore, achieving the principle of sustainability in preserving vital systems, and ensuring being continually as active and productive sources over time. The research presents an analytical study that aims to structural safety assessment, and study the possibility of rehabilitating a real building that has been subjected to a terrorist attack using a bomb car. The numerical model of the building was created and the explosion simulated using the ABAQUS program, and designing the engineering elements required according to the damage index values. The numerical modeling results gave a great convergence in terms of the values of deformations. The remaining resistance values in the damaged structural elements with the experimental measurements of the structural elements after the explosion has a relative differences not exceeding 5%. The design of the required strengthening and connection elements according to the damage index values has led to raising the efficiency of the damaged building. Achieving the principle of sustainability by reducing the use of materials and waste-producing activities, and reducing energy consumption which is harmful to the environment.
Studying the Effect of Nonlinear Modeling Methods of Shear Wall on the Behavior of Dual System under Lateral Loads
Dual systems are crucial for resisting seismic loads, and their optimal design relies on the interaction between frames and walls. This paper studies the RC dual system using the advanced finite element program ABAQUS and the finite element program for structural analysis and design ETABS. Three models were used: the detailed model according to ABAQUS, based on the CDP (Concrete Damage Plasticity), and two models in the ETABS program, the fiber hinge model and the multi-layered shell element model. A five-story 2D building with dual systems was modeled and analyzed, with frames contributing 29% of the total shear force. The models were analyzed under lateral loads using nonlinear static analysis, and a capacity curve was drawn to compare plastic hinge locations and stresses values. The response modification factor for the optimal model was calculated and compared with code values. The results showed that the multi-layer shell element model effectively represents the nonlinear behavior of shear walls and dual systems, but it also has a brevity and cost-effectiveness, especially for 3D buildings.
Using buckling restrained braces to improve the dynamic behavior of
The use of buckling restrained braces (BRBs) has significantly enhanced the seismic efficiency of steel frames, a recent and significant technique in the construction Industry. The study emphasizes the widespread adoption of buckling restrained braces and their role in resisting lateral stresses by examining their abilities to modify the seismic response of steel frames. The dynamic behavior of these braces is analyzed by the study using (Abaqus 19 software). The study examined the dynamic behavior of a multi - story steel frame with eccentric buckling restrained braces (BRBFES) under earthquake motions. Parameters like BRB location and frame height were adjusted to improve dynamic behavior. The response was evaluated by comparing acceleration, story drifts, base shear forces and dissipated energy. The outcomes demonstrated the efficiency of buckling restrained braces in medium - height steel frames, where the dissipated energy was raised and the acceleration, the story “drifts, and base shear forces were reduced.
Analytical study of a cast-in-place joint of a precast prestressed concrete frame under cyclic load
The researchers focused mainly on the types of connections in precast frame structures and the seismic behaviour of the different types of those connections. There are two types of connections in moment-resisting precast frames the first type is equivalent monolithic systems, which composed of precast concrete columns and beams connected by cast-in-place connections, the second type is jointed systems in which the connections are weaker than the adjacent concrete elements. The research presents an analytical study of the behaviour of one type of equivalent monolithic system consisting of a cast-in-place middle joint of a prestressed precast concrete frame under cyclic loading by using ABAQUS.19. The cast-in-place joint is provided with U-shaped steel reinforcing bars that overlap the pre-anchored cables and longitudinal reinforcement in the beam to ensure continuous transfer of loads. To improve the behaviour of the cast-in-place joint, several parameters were changed (the compressive strength of the cast-in-place concrete, the diameter of the U-shaped reinforcing bars and the dimensions of the shear key) The most important conclusions reached in this research are that by increasing the compressive Strength of cast-in-place concrete in the joint area, the joint strength increased and the plastic dissipated energy increased. As the diameter of the U-shaped reinforcing bars increased, the strength of the joint increased and the plastic dissipated energy in the joint decreased. The strength of the joint also increased, and the plastic dissipated energy increased as the dimensions of the shear key increased.
Studying the seismic response of reinforced concrete buildings using a hybrid isolation system
Seismic isolation systems are used to reduce floor accelerations and displacements in addition to the base shear forces compared to the building without isolation. Tradi tional rubber isolation systems are usually used, which have proven effective in raising the seismic efficiency of buildings. However, in special cases of buildings such as tall buildings and lightweight buildings, this isolation is considered It is not effective, so it was necessary to search for a hybrid isolation system that is effective in reducing the floor accelerations and displacements and the base shear forces of tall buildings. The research aims to study the effect of using hybrid systems consisting of cross linear bearings and rubber bearings in improving the seismic behavior of tall buildings under the influence of several earthquakes, using the ABAQUS program, by changing several parameters (change of building height, friction coefficient within the cross linear bearing, damping energy of rubber isolators accompaniment).The response to the isolated structure was evaluated by comparing the role, accelerations, floor displacements, and base shear forces with the structure without isolation.The results showed the effectiveness of the hybrid isolation system in reducing floor accelerations and displacements and reducing the base shear force in tall buildings, and that the change of the friction coefficient of the cross linear bearing had no effect on the response of the structure, increasing the capacity of the rubber bearing did not signifcantly affect the values of accelerations and drift ratio, on the contrary, it led to an increase in the amount of energy dissipated.
Seismic isolation systems are used to reduce floor accelerations and displacements in addition to the base shear forces compared to the building without isolation. Tradi tional rubber isolation systems are usually used, which have proven effective in raising the seismic efficiency of buildings. However, in special cases of buildings such as tall buildings and lightweight buildings, this isolation is considered It is not effective, so it was necessary to search for a hybrid isolation system that is effective in reducing the floor accelerations and displacements and the base shear forces of tall buildings. The research aims to study the effect of using hybrid systems consisting of cross linear bearings and rubber bearings in improving the seismic behavior of tall buildings under the influence of several earthquakes, using the ABAQUS program, by changing several parameters (change of building height, friction coefficient within the cross linear bearing, damping energy of rubber isolators accompaniment).The response to the isolated structure was evaluated by comparing the role, accelerations, floor displacements, and base shear forces with the structure without isolation.The results showed the effectiveness of the hybrid isolation system in reducing floor accelerations and displacements and reducing the base shear force in tall buildings, and that the change of the friction coefficient of the cross linear bearing had no effect on the response of the structure, increasing the capacity of the rubber bearing did not signifcantly affect the values of accelerations and drift ratio, on the contrary, it led to an increase in the amount of energy dissipated
Participation Ratio of Frames in Design Base Shear of Dual Shear Wall-Frames Systems According to Optimal Design of the Seismic Resistant R\C Buildings
Dual shear walls-frames system is considered one of the most efficient sytems to resist earthquake in high-rise buildings. Design codes dictates that a minimum of 25% of design base shear forces should be resisted by frames part only without giving a specific ratio. In this research an optimization algorithm that applies cost as an objective function, has been used to optimally design the structure of high rise buildings. That is to reach the minimum cost required with all design constraints fulfilled. After that the participation ratio of the frame part can be calculated. For this purpose an algorithm named after Nelder-Mead that applies simplex method was used in conjunction with Abaqus software to search for the least cost design. Abaqus’s models were analyzed during optimization process for hundred of times through time-history nonlinear dynamic analysis under base excitation that applies design earthquake acceleration records. The parametric model built on Abaqus was interconnected with the algorithm to be analyzed several hundred of times reaching the optimum design of this model. After processing three models in the same manner, one with central core and excitation about the weak direction of the model. And two with full symmetry about x and y axis. The results concluded that there is no specific ratio or range that result in cost effective dual system. But rather the participation ratio might change significantly with a minimum replacement of the shear walls in plan.
Studying the Seismic Behavior of Short Columns in Existing RCBuilding Considering the Effect of Different Types of Soils
Short columns in reinforced concrete structures are subjected to large shear forces and often show weak performance under the influence of earthquake loads due to their non-ductile response. When designing buildings we must concentrate on the elasticity of soil rather than concentrating on the idea that these buildings are fixed to the ground because elasticity of soil is of a very fundamental importance on the dynamic properties of the building and its response. The current research deals with the study of the dynamic behavior of short columns in an existing residential building located in Tartous city by comparing them with columns of greater height in the same building under the influence of seismic loads using ETABS-2016 software. The effect of soil-structure interaction was taken into consideration in representing the soil by using a set of elastic springs by selecting three types of soil with different properties. A comparison of the seismic response of the short columns was made by comparing the lateral displacements, lateral drift ratios and shear forces when the base is fixed and when applying the soil-structure interaction. The results showed an increase in the lateral displacements, drift ratios and shear forces in short columns and columns of greater height after the soil effect is taken into account so that the values of displacements and drifts in short columns were smaller than in columns of greater height but the values of shear forces in short columns were greater than in columns of greater height.
Comparison of Adaptive and non-AdaptiveNonlinear Static Analysis Methods for Estimating Seismic Demand
In this paper, we review several pushover analysis methods to illustrate the enhancements and refinements of the pushover analysis. In addition, how researcher could develop the procedures to overcome the disadvantages of the traditional pushover procedure. The traditional lateral analysis method has been developed to consider the contribution of higher modes as well as the change in the dynamic properties of structures after entering the nonlinearity and formation the hinges. We will study two structures of steel and others of reinforced concrete via the conventional method using first mode, modal pushover analysis (MPA), multi-mode adaptive displacement-based pushover (MADP), consecutive modal pushover (CMP) and non-adaptive displacement-based pushover (NADP) and then compare the results with nonlinear response history analysis to determine which of these methods is the most accurate. The result of the study shows that the MADP method gives the best estimate of the story drift than the rest of the methods compared to the nonlinear dynamic analysis, because it considers the higher modes effect and dynamic characteristics change of the model after entering the nonlinearity.
Assessment of non-Adaptive Pushover Analysis Methods forEstimation Seismic Demand for High Frame Structures
The nonlinear static pushover analysis is one of the methods used to study structures exposed to the influence of seismic ground motions. Extensive research has been conducted over time to improve the results of this method on high structures. In this article, some of non-adaptive pushover analysis methods were reviewed, and then applied to two reinforced concrete frame structures of two different heights ,20 and 25 floors,and compared the seismic response (story drift) with the nonlinear time history analysis method, which is considered the most accurate method for estimating the seismic response . The study showed that using the NADP method is the best among non adaptive pushover analysis methods for high structures , in which the effect of the high modes is clear .The study also showed that all non adaptive pushover analysis methods overestimated the seismic response in the lower floors while underestimatied it in the upper floors.Therefor , it is necessary to search for more accurate nonlinear static pushover analysis methods so that their results close to the accurate dynamic method for high concrete structures.
Rehabilitation RC Structure Using Eccentric Metallic Bracing and parametric study to Shear Link Thickness
Many existing buildings designed before the seismic code need effective bracing system to improves performance, the eccentric bracing can improve the resistance and ductility, and improve energy dissipation , compensate the lack of stiffness that may occur when deformation increases, beside many of important Advantages such as light weight, ease of installation and maintenance after exposure to strong shocks, and can contribute in torsion reduce in many irregular horizontally school buildings. The capacity curves of the studied building was found by applying pushover to it before and after bracing by using different thicknesses of the shear link, and determining the performance point and performance level. Proposed system increased stiffness, the maximum deformation, and the energy dissipation due to its high efficiency, which reduced the demand and the level of damage and improved the performance in the studied direction. It was performed by using a shear link of 5 cm thickness, as it increased to become an immediate occupancy level, while it remained at the level of life safety by using the two thicknesses 4 and 7.5 cm which are less than and more than 5 cm, thus achieving the best performance of the braced construction.
Improvement the Response for Tall R.C Building Under Lateral Loads by Using the Damped Outrigger Systems
The use of high-rise buildings has seen significant growth in recent years, however, the realization of such buildings faces many challenges in study and design due to the crucial role that lateral loads, whether wind loads or seismic loads, given that the outrigger system is one of the best ways to improve the response of tall buildings in resisting lateral loads. This research depends on that to examine the process of integrating viscous fluid dampers with the outrigger system to add complementary damping to the structure, which improves the accuracy of the dynamic response by providing a higher level of damping to the structure while also improving performance, in which two models were examined For high-rise reinforced concrete buildings consisting of 36 and 48 floors that were studied using the ETABS 19 program and the ASCE 7-05 code for both the static and dynamic states during modeling under the influence of seismic loads. The equivalent lateral forces (ELF) method was applied to the static state, and the response spectrum analysis method was applied to the dynamic state to account for the impact of time history records. the study focused on the performance of the structural outrigger systems during seismic lateral loads, where the linear analysis of the two studied buildings 36 and 48 floors was studied for the following cases: (building without outriggers and dampers, building with outriggers - building with outriggers and linked with fluid viscous dampers in their locations), the analysis includes lateral displacement, story drifts, shear forces, frequencies, and periods. The study results showed that the addition of outrigger systems to the structure significantly improved the lateral stiffness, which in turn improved the structure's response to resisting effective lateral loads. They also showed that the addition of fluid viscous dampers to the outrigger system can perform better than an outrigger without dampers. As a result, the damped outrigger system offers a practical and cost-efficient method of enhancing the structure's ability to withstand lateral loads.
Soil-Structure Interaction Effect on Seismic Response Modification Coefficient of Dual System Using Substructure Approach
Soil mainly affects the dynamic response of structures. Soil-Structure interaction (SSI) is effectively important in case of shear walls according to many international codes. This research aims to study the effect of (SSI) on the dynamic response of dual systems resting on raft foundations using the numerical software engineering program SAP2000. The research methodology relies on studying linear dynamic behavior for models using parameters (number of stories, earthquake frequency, soil type) and using substructure approach in modelling soil to see it’s impact on the overall response and design forces of these systems. Then perform pushover analysis to see the effects of parameters on the response modification coefficient (R). The study showed an increase in the natural period, lateral deflection, internal bending moment in columns of the structure, and a reduction in base shear value compared to the fixed base. The (R) value is different according to the number of stories and type of soil. It is not constant as is mentioned in the Syrian Arab code and ASCE. It increases by 20% in the case of four stories and sand soil compared to codes. The (SSI) increases designing requirements (elements section and analysis time) so it’s a higher cost.