• Earthquakes and Structures
• /
• v.9 no.4
• /
• pp.911-936
• /
• 2015

This work evaluates the performance of a number of seismic assessment procedures when applied to a case study reinforced concrete (RC) wall building. The performance of each procedure is evaluated through its ability to accurately predict deformation demands, specifically, roof displacement, inter-storey drift ratio and wall curvatures are considered as the key engineering demand parameters. The different procedures include Direct Displacement-Based Assessment, nonlinear static analysis and nonlinear dynamic analysis. For the latter two approaches both lumped and distributed plasticity modelling are examined. To thoroughly test the different approaches the case study building is considered in different configurations to include the effects of unequal length walls and plan asymmetry. Recommendations are made as to which methods are suited to different scenarios, in particular focusing on the balance that needs to be made between accurate prediction of engineering demand parameters and the time and expertise required to undertake the different procedures. All methods are shown to have certain merits, but at the same time a number of the procedures are shown to have areas requiring further development. This work also highlights a number of key aspects related to the seismic response of RC wall buildings that may significantly impact the results of an assessment. These include the influence of higher-mode effects and variations in spectral shape with ductility demands.

• Structural Engineering and Mechanics
• /
• v.73 no.6
• /
• pp.699-714
• /
• 2020

Force based design (FBD) approach is prevalent in most of the national seismic design codes world over. Direct displacement based design (DDBD) and energy based design (EBD) approaches are relatively new methods of seismic design which claims to be more rational and predictive than the FBD. These three design approaches are conceptually distinct and imparts different strength, stiffness and ductility property to structural members for same plan configuration. In present study behavioural assessment of frame of six storey RC building designed using FBD, DDBD and EBD approaches has been performed. Lateral storey forces distribution, reinforcement design and results of nonlinear performance using static and dynamic methods have been compared. For the three approaches, considerable difference in lateral storey forces distribution and reinforcement design has been observed. Nonlinear pushover analysis and time history analysis results show that in FBD frame plastic deformation is concentrated in the lower storey, in EBD frame large plastic deformation is concentrated in the middle storeys though the inelastic hinges are well distributed over the height and, in DDBD frame plastic deformation is approximately uniform over the height. Overall the six storey frame designed using DDBD approach seems to be more rational than the other two methods.

• Computers and Concrete
• /
• v.21 no.4
• /
• pp.355-365
• /
• 2018

Five previously-tested reinforced concrete frames were modelled using a nonlinear finite element analysis procedure to demonstrate the accurate response simulations for seismically-deficient frames through pushover analyses. The load capacities, story drifts, and failure modes were simulated. This procedure accounts for the effects of shear failures and the shear-axial force interaction, and thus is suitable for modeling seismically-deficient frames. It is demonstrated that a comprehensive analysis method with a capability of simulating material constitutive response and significant second-order mechanisms is essential in achieving a satisfactory response simulation. It is further shown that such analysis methods are invaluable in determining the expected seismic response, safety, and failure mode of the frame structures for a performance-based seismic evaluation. In addition, a new computer program was developed to aid researchers and engineers in the direct displacement-based seismic design process by assessing whether a frame structure meets the code-based performance requirements by analyzing the analysis results. As such, the proposed procedure facilitates the performance-based design of new buildings as well as the numerical assessment and retrofit design of existing buildings. A sample frame analysis was presented to demonstrate the application and verification of the approach.

• Earthquakes and Structures
• /
• v.9 no.5
• /
• pp.1045-1067
• /
• 2015

A performance-based design (PBD) procedure, initially proposed for the seismic design of buildings, is tailored herein to the structural configurations commonly adopted in bridges. It aims at the efficient design of bridges for multiple performance levels (PLs), achieving control over a broad range of design parameters (i.e., strains, deformations, ductility factors) most of which are directly estimated at the design stage using advanced analysis tools (a special type of inelastic dynamic analysis). To evaluate the efficiency of the proposed design methodology, it is applied to an actual bridge that was previously designed using a different PBD method, namely displacement-based design accounting for higher mode effects, thus enabling comparison of the alternative PBD approaches. Assessment of the proposed method using nonlinear dynamic analysis for a set of spectrum-compatible motions, indicate that it results in satisfactory performance of the bridge. Comparison with the displacement-based method reveals significant cost reduction, albeit at the expense of increased computational effort.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2006.04a
• /
• pp.151-158
• /
• 2006

Structural health monitoring is concerned with the safety and serviceability of the users of structures, especially for the case of building structures and infrastructures. When considering the safety of a structure, the maximum stress in a member due to live load, earthquake, wind, or other unexpected loadings must be checked not to exceed the stress specified in a code. It will not fail at yield, excessively large displacements will deteriorate the serviceability of a structure. To guarantee the safety and serviceability of structures, the maximum displacement in a structures must be monitored because actual displacement is a direct assessment index on its stiffness. However, no practical method has been reported to monitor the displacement, especially for the case of displacement of high-rise buildings because of not to easy accessive. In this paper, it is studied displacement measuring method of high-rise buildings using LiDAR The method is evaluated by analyzing accuracy of measured displacements for existing building.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
• /
• 2006.04a
• /
• pp.223-228
• /
• 2006

Monitoring structures is important to maintain the safety and serviceability of the structures. The maximum displacement in the structure should be precisely and frequently monitored because it is a direct assessment index indicating its stiffness. However, no practical method has been developed to monitor such displacement precisely, particularly for high-rise buildings and long span bridges because they cannot be easily accessible. To overcome such difficult accessibility, we propose to use a LIDAR system that remotely samples the surface of an object using laser pulses and generates the coordinates of numerous points on the surface. By analyzing the LIDAR points sampled from the surfaces of a deformed structure, we can precisely determine the displacement of the structure. In this study, we thus develop a novel method based the LIDAR system and perform an indoor experiment to prove its performance. This experimental results strongly supports that the displacement measurement using the LIDAR system are enough accurate to be used for structural analyses.

• Structural Engineering and Mechanics
• /
• v.83 no.2
• /
• pp.229-244
• /
• 2022

This paper investigates the seismic performance of buildings designed using DDBD (Direct Displacement based Design) and FBD (Force based Design) approaches from the probabilistic viewpoint. It aims to estimate the collapse capacity of structures and assess the adequacy of seismic design codes. In this regard, (i) IDA (Incremental Dynamic Analysis) curves, (ii) interstory drift demand distribution curves, (iii) fragility curves, and (iv) the methodology provided by FEMA P-695 are applied to examine two groups of RC moment resistant frame buildings: 8-story structures with different plans, to study the effect of different span arrangements; and 3-, 7- and 12-story structures with a fixed plan, to study the dynamic behavior of the buildings. Structural modeling is performed in OpenSees software and validated using the results of an experimental model. It is concluded that increasing the building height would not significantly affect the response estimation of IDA and fragility curves of DDBD-designed structures, while the change in span arrangements is effective in estimating responses. In the investigation of the code adequacy, unlike the FBD approach, the DDBD can satisfy the performance criteria presented in FEMA P-695 and hence provide excellent performance.

• Journal of the Korean Society for Railway
• /
• v.5 no.3
• /
• pp.148-157
• /
• 2002

A health monitoring system becomes a useful tool to obtain information on long term behavior of the important railway structures such as very long span and special type bridges. The health monitoring system not only gives the direct measurement data of the railway bridges but also provides the basic data on the maintenance of the structures. Therefore, periodic calibrations of the health monitoring system will be a necessary step toward precise and accurate assessment of the railway bridges. In this study, the calibration and gauge factor readjustment process made for the health monitoring system installed in the railroad bridges is reviewed and some findings are explained in detail: specifically, the calibrators made for this purpose are illustrated and the regression processes of the calibration on long-term displacement using water level sensor, longitudinal displacement using LVDT sensor, instantaneous displacement using LVDT sensors and accelerometer are described in full length. Based on the regression results, it was found that the gauge factors need to be readjusted according to the regression equation but, since the deviation or shift is not serious so far, long-term observation on each sensor is also recommended. Future work will be concentrated on the long-term analysis of each sensor and on the database creation so that the assessment of the structures is possible.

• Journal of the Korean Geosynthetics Society
• /
• v.23 no.1
• /
• pp.27-37
• /
• 2024

In this study, direct algorithm-based back analysis was utilized to perform back analysis on two actual earth retaining wall fields, which was then compared with genetic algorithm-based method to evaluate the suitability of the back analysis. Additionally, in order to propose effective utilization methods of the program, the measurement data, as the input for the back analysis, was varied for each excavation step, and the applicability of the back analysis results(displacement, axial force) was examined. The research findings indicate that both direct algorithm and genetic algorithm show high applicability; however, the optimization for this program is better predicted by the direct algorithm. Moreover, in order to effectively use the back analysis program employing the direct algorithm, it was evaluated that relatively accurate prediction of the earth retaining wall behavior could be achieved by inputting measurement data from the 7th excavation step for fields with final excavation steps ranging from 8 to 11.

• International Journal of High-Rise Buildings
• /
• v.9 no.2
• /
• pp.175-185
• /
• 2020

Currently, few studies have been conducted to comprehend the seismic reliability of post-tensioned (PT) CLT shear wall structures, due to the complexity of this kind of structural system as well as due to lack of a reliable structural model. In this paper, a set of 4-, 8-, 12-, and 16-storey benchmark PT CLT shear wall structures (PT-CLTstrs) were designed using the direct displacement-based design method, and their calibrated structural models were developed. The seismic reliability of each PT-CLTstr was assessed based on the fragility analysis and based on the response surface method (RSM), respectively. The fragility-based reliability index and the RSM-based reliability index were then compared, for each PT-CLTstr and for each seismic hazard level. Results show that the RSM-based reliabilities are slightly less than the fragility-based reliabilities. Overall, both the RSM and the fragility-based reliability method can be used as efficient approaches for assessing the seismic reliabilities of the PT-CLTstrs. For these studied mid- and high-rise benchmark PT-CLTstrs, following their fragility-based reliabilities, the 8-storey PT-CLTstr is subjected to the least seismic vulnerability; while, following their RSM-based reliabilities, the 4-storey PT-CLTstr is subjected to the least seismic vulnerability