Quantification of Different Sources of Over-Strength in Seismic Design of a Reinforced Concrete Tall Building

An over-strength factor in seismic design plays an important role in computing actual forces in a structural member designed to remain elastic. However, sources contributing to this over-strength have not yet been systematically quantified for tall buildings. This paper aims to investigate the contribution from different sources of the over-strength factor in a reinforced concrete (RC) tall building. The contribution of slab-column gravity load framing to the lateral load capacity of the building is also investigated. A 39-story RC tall building subjected to earthquake ground motions in Bangkok was first designed according to the current building codes. Then, pushover analysis was conducted to compute the capacity curves of the building with three different specified strengths: design strength (with f factor), nominal strength (without f factor), and actual strength (with material over-strength). It was found that slab-column framing action contributes about 60% of the total lateral load capacity of the building.  The building has an overall lateral over-strength factor of 3.36 to 3.71. The over-strength factor arising from the design is 2.12 to 2.42 in which the contributions from strength reduction factor, material over-strength, and other sources involving the design requirements are about 1.10, 1.17, and 1.77, respectively. The over-strength factor arising from the redundancy due to the redistribution of internal forces is about 1.55 and the contribution from the steel strain hardening to the over-strength factor is relatively small

An Investigation on the Adaptive Modal Combination Procedure for Seismic Evaluation of Buildings Considered Soil Structure Interaction

Nonlinear response history analysis (NL-RHA) is a powerful tool for seismic analysis of structures. The seismic performance of structures can be estimated accurately due to a set of ground motions. However, NL-RHA is an onerous task to estimate seismic demands due to its complexity for practical design applications. Therefore, nonlinear static procedures (NSPs), which are rooted in structural dynamic theory, are developed as an alternative to rigorous NL-RHA. NSPs are now widely used in engineering practice to evaluate seismic responses of structure in the inelastic range. The main objective of this study is to assess the bias and accuracy of the adaptive modal combination (AMC) procedure, which is modified from the modal pushover analysis (MPA) procedure, for seismic evaluation of buildings.   Three-, 9-, 18-storey buildings were analyzed due to two sets of strong ground motions having 2% and 10% probability of being exceeded in 50 years. The influence of soil-structure interaction in the analysis was also considered by using Beam-on-Nonlinear-Winkler-Foundation modeling. The assessment is based on comparing seismic displacement demands such as target roof displacements, peak floor displacements and inter-storey drifts. The AMC estimates are compared to results from nonlinear response history analysis (NL-RHA) and results from AMC procedure considered only first mode (AMC- 1st mode). The obtained results show that the AMC procedure provides reasonably accurate results in estimating seismic demands of studied buildings

Evaluation of Seismic Shear Demands of RC Core Walls in Thailand Determined by RSA Procedure

ASCE 7 allows structural engineers to use Response Spectrum Analysis (RSA) procedure to compute the seismic design forces of the structures. However, seismic shear demands of reinforced concrete (RC) walls determined by RSA have been found to be inadequate by many researchers. This paper aims to investigate the seismic shear demands of RC core walls from low-rise to high-rise buildings. RC split core walls in five buildings varying from 5 to 25 stories subjected to earthquake ground motions in Bangkok and Chiang Mai of Thailand were first designed by RSA procedure in ASCE 7-10. Then nonlinear response history analysis (NLRHA) was conducted to compute more accurate seismic demands of the structures. The results demonstrated that shear demands of core walls from NLRHA were significantly larger than those from RSA procedure. The shear amplifications of core walls in cantilever-wall direction were larger than those in coupled-wall direction. The two building locations having different spectrum shapes led to different shear amplifications. Hence, an empirical formula cannot be applied to every location. In Bangkok, it is found that Rejec et al. (2012)’s equation could well estimate shear forces in cantilever direction of core walls but it significantly overestimated shear forces in coupled direction of core walls. In Chiang Mai, Luu et al. (2014)’s equation provided good estimation of shear forces in both directions of core walls. Beside these two equations, the shear magnification factor equation in EC8 is found acceptable to be adopted to multiply with shear force from RSA procedure before using it as design shear force of RC core wall in both Bangkok and Chiang Mai.ASCE 7 allows structural engineers to use Response Spectrum Analysis (RSA) procedure to compute the seismic design forces of the structures. However, seismic shear demands of reinforced concrete (RC) walls determined by RSA have been found to be inadequate by many researchers. This paper aims to investigate the seismic shear demands of RC core walls from low-rise to high-rise buildings. RC split core walls in five buildings varying from 5 to 25 stories subjected to earthquake ground motions in Bangkok and Chiang Mai of Thailand were first designed by RSA procedure in ASCE 7-10. Then nonlinear response history analysis (NLRHA) was conducted to compute more accurate seismic demands of the structures. The results demonstrated that shear demands of core walls from NLRHA were significantly larger than those from RSA procedure. The shear amplifications of core walls in cantilever-wall direction were larger than those in coupled-wall direction. The two building locations having different spectrum shapes led to different shear amplifications. Hence, an empirical formula cannot be applied to every location. In Bangkok, it is found that Rejec et al. (2012)’s equation could well estimate shear forces in cantilever direction of core walls but it significantly overestimated shear forces in coupled direction of core walls. In Chiang Mai, Luu et al. (2014)’s equation provided good estimation of shear forces in both directions of core walls. Beside these two equations, the shear magnification factor equation in EC8 is found acceptable to be adopted to multiply with shear force from RSA procedure before using it as design shear force of RC core wall in both Bangkok and Chiang Mai

การพัฒนาหลักสูตรฝึกอบรมสำหรับบุคลากรวัยทำงาน รองรับการจัดการความเสี่ยงและภัยพิบัติ: The Development of Training Program for Working Adults on Risk and Disaster Management

This research aims to study the knowledge, skills and attributes related to riskand disaster management which are necessary for working adults and develop a riskand disaster management training program. This research deploys a qualitative methodusing in-depth interview. The sampling are executives from six medium and largeenterprises who have more than five years’ working experience and are responsible forrisk management in the organization. The result shows that risk management, businesscontinuity, and laws for risk and disaster management are knowledge required forworking adults. The essential skills for working adults in risk and disaster managementare communication skills, analytical skills and systematic thinking skills. The requiredattributes for risk and disaster management are enthusiastic, visionary and deliberateness.The knowledge, skills and attributes are used to develop risk and disaster managementtraining program for working adults. It will be used as a guideline for education institutionto promote working adult education in the area of risk and disaster management

Application of Conditional Mean Spectrum in Nonlinear Response History Analysis of Tall Buildings on Soft Soil

The uniform hazard spectrum (UHS) and conditional mean spectrum (CMS) are commonly used as target spectra in selecting and scaling of records to be used in nonlinear response history analysis (NLRHA). When using CMS with tall buildings, CMS ground motions conditioned at multiple natural periods of the buildings should be considered. The application of CMS ground motions in NLRHA to estimate seismic demands for design of tall buildings located on soft-soil layers in Bangkok is investigated in this study. The seismic demands computed using multiple sets of CMS ground motions are compared with those computed using a single set of UHS spectral matching ground motions. Four existing tall buildings subjected to earthquake excitations in Bangkok were considered. The NLRHA was conducted using multiple sets of CMS ground motions, where periods of interest  were considered at the periods closest to the periods of the first-three translational modes of the building in the direction of excitation. It was found that CMS ground motions conditioned at the higher-mode periods result in larger force demands than CMS ground motions conditioned at the fundamental period for some locations along the height of the building. The envelope of demands obtained by using multiple sets of CMS ground motions conditioned at different periods should be used in design but requires significant computational effort. Using UHS spectral matching ground motions can provide results close to such an envelope and reduce the computational effort significantly

Seismic Shear Forces in Shear Walls of a Medium-Rise Building Designed by Response Spectrum Analysis

According to ASCE7-05, response spectrum analysis (RSA) procedure can be used to determine the seismic demands of the structures for the seismic design of any type of structures. However, this design procedure has been found to be inappropriate for medium-rise and high-rise buildings. This paper is aimed at verifying the RSA procedure prescribed in the current Thai seismic design code which is based on ASCE7-05 and proposing appropriate modification to the design shear force from RSA procedure. A 16-story medium-rise reinforced-concrete core-wall case-study building was first designed based on RSA procedure and then the non-linear response history analysis (NLRHA) was performed to determine the more accurate seismic demands of the structure. The results show that seismic shear demand of the shear wall from non-linear analysis is about 2 times the shear capacity of the wall designed by RSA procedure. This could lead to shear failure in the shear walls designed by RSA procedure. To avoid shear failure in the shear wall elements, the shear demands in the wall elements designed by RSA procedure needs to be amplified by a factor of 2, which is equivalent to reducing the response modification factor R = 5.5 in ASCE7-05 to R = 2.75 (for shear force in the shear wall only)

The Acceptance of Using Information Technology for Disaster Risk Management: A Systematic Review

The numbers of natural disaster events are continuously affecting human and the world economics. For coping with disaster, several sectors try to develop the frameworks, systems, technologies and so on. However, there are little researches focusing on the usage behavior of Information Technology (IT) for disaster risk management (DRM). Therefore, this study investigates the affecting factors on the intention to use IT for mitigating disaster’s impacts. This study conducted a systematic review with the academic researches during 2011-2018. Two important factors from the Technology Acceptance Model (TAM) and others are used in describing individual behavior. In order to investigate the potential factors, the technology platforms are divided into nine types. According to the findings, computer software such as GIS applications are frequently used for simulation and spatial data analysis. Social media is preferred among the first choices during disaster events in order to communicate about situations and damages. Finally, we found five major potential factors which are Perceived Usefulness (PU), Perceived Ease of Use (PEOU), information accessibility, social influence, and disaster knowledge. Among them, the most essential one of using IT for disaster management is PU, while PEOU and information accessibility are more important in the web platforms

Statistics of Single-Degree-of-Freedom Estimate of Displacement for Pushover Analysis of Buildings

Investigated is the basic premise that the roof displacement of a multistory building can be determined from the deformation of a single-degree-of-freedom (SDF) system. The responses of both systems are determined rigorously by nonlinear response history analysis, without introducing any of the approximations underlying the simplified methods for estimating the deformation of a SDF system (see, e.g., FEMA-273 or ATC-40 guidelines). The statistics of the SDF system estimate of roof displacement are presented for a variety of generic frames and six SAC buildings subjected to ground motion ensembles. Data obtained for generic frames indicate that the first ‘‘mode’’ SDF system overestimates the median roof displacement for systems subjected to large ductility demand µ, but underestimates for small µ. The bias and dispersion tend to increase for longer period system for every value of µ. Similar data for SAC buildings demonstrate that the bias and dispersion on the SDF estimate of roof displacement increases when P-delta effects (due to gravity loads) are included. The modal pushover analysis procedure has the advantage of reducing the dispersion in the roof displacement and the underestimation of the median roof displacement for elastic or nearly elastic cases at the expense of increasing slightly the overestimate of roof displacement of buildings responding far into the inelastic range