Papers by Keyword: Seismic Evaluation

Abstract: The recent discovery of the Central Davao Fault System leads to assessing the buildings' seismic performance close to the area. DOST-PAGASA released the Earthquake Atlas, "Metro Davao Earthquake Model," that shows research data and valuable information that would be used in designing new structures and seismic evaluation. Using this Earthquake Atlas, a Four Storey Professional School Building in the University of Mindanao was assessed using ASCE/SEI 41. Structural Engineers and Practitioners widely use the code for Seismic Evaluation of Existing Buildings. As-built plans were acquired first for data collection and structural modelling, analyze using SAP 2000 software and perform a seismic evaluation using the results of the analysis in accordance with ASCE 41 standard; and for the output, provide an evaluation report of the structure’s performance. Using first (ATC 40), second (FEMA 356), and next-generation (FEMA 440 and ASCE 41-13) seismic design principles, the structure was evaluated according to the selection of performance objectives and seismic level. Linear and Nonlinear analyses were employed. Pushover curve was drawn from SAP 2000 for two actions of plastic hinge behavior, deformation-controlled and force-controlled actions. The target performance objective of the structure in this study is Life Safety Level at 10 % probability of exceedance in 50 years with 5% damped based on ASCE 41-13 standard. The assessment results show that the structure did not meet the criteria for life safety level requirements in ASCE/SEI 41 for columns, particularly on the first and last floor level for linear analysis procedure. A few numbers of beams also did not meet the standards, specifically on the roof beam level. The displaced ductility ratio was found to be 3.47 (moderately ductility demand). In nonlinear analysis, the structure also failed to meet the base shear requirements for both deformation and forced controlled actions in Pushover analysis. Performance base shear Vp of 3.233 exceeded the acceptable limit of less than 1.0. The first modal period 1.976 seconds was also notably higher than the building period of 0.647 seconds which indicates structure's low stiffness. These findings were evidence that the structure should undergo retrofitting procedures to meet seismic performance objectives and strengthen the structure's resilience to earthquake damages.

Abstract: In recent years, Italian technical-scientific community has increased its interest on the evaluation of the seismic response of existing structures. Among this wide range of structures, reinforced concrete bridges stand out for their strategic relevance and technical complexity. Most of these structures were built between 60ies and 70ies, according to design procedures which ignored nowadays knowledge in seismic engineering. Thus, the necessity to evaluate the real strength capacity of these structures with modern analysis techniques has become essential, leading to the determination of their safety level in case of an earthquake. In particular, for the assessment of several bridges of a motorway network, a multi-modal pushover analysis approach has been considered. This analysis technique allows considering the nonlinear behaviour and the complex dynamic response of such structures without exceeding in high computational costs. Some basic rules were defined (constitutive laws of materials, finite element type, plastic hinge models, etc.) for the modelling of bridges, in order to guarantee homogeneous comparable results among different structures of a network. At the end, some of the results are compared to see the variation of the verification level with respect to both the number of modes considered and the analysis’s accuracy in terms of number of loading steps.

Abstract: The objective of this paper is to research seismic performance of the weak-axis column-tree connections. For this purpose, two specimens CTY600 and CTY900 were fabricated and tested in this experiment. From the test results, the CTY specimen successfully achieved a 5% rad story drift ratio without brittle fracture and the total plastic rotation reached over 0.04rad.

Abstract: This study focuses on one of the historic structures located in Shanghai. In order to meet modern occupants’ needs, safety inspection, seismic evaluation and strengthening design for the historic building are carried out. This building, completed in 1930s, was designed without considering the effect of possible earthquakes which cannot meet the current seismic criteria. An analytical investigation of the retrofitted structure is performed. Safety and seismic behavior are analyzed. According to the evaluation, structural performance was better understood which led to the more efficiently use of retrofit methods.

Abstract: Based on the current seismic codes, the elastic capacity calculation under frequent earthquake and ductile details of seismic design should be used for both seismic design of new buildings and seismic evaluation of existing buildings to satisfy the seismic fortification criterion, namely/no damage under frequent earthquake, repairable under moderate earthquake, and no collapse under severe earthquake0. For the evaluation, rebuilding and extending of existing structures which dissatisfy the ductile details of current seismic codes, the elastic capacity calculation under frequent earthquake is obviously not enough. In this paper, the advanced performance-based seismic theory is introduced while story drift ratio and deformation of component are used as performance targets to solve the problems of seismic evaluation and strengthening for existing reinforced concrete structures.

Abstract: All types of school buildings were seriously damaged in Taiwans 921 Chi-Chi earthquake. Seismic evaluation and retrofit of these numerous vulnerable school buildings has become an important issue to be resolved. The National Center for Research on Earthquake Engineering (NCREE), Taiwan assisted the Ministry of Education on the arrangement of programs to accelerate retrofit and rebuilding works of elementary school, junior high school, senior high school and vocational school buildings, as part of the project called, Economic Recovery Act. Based on the database for seismic assessments and retrofits of school buildings, this study recommends a seismic upgrading procedure of near-fault school buildings. The proposed procedure can control effectively the seismic upgrading progress of near-fault school buildings. It also provides suggestions on the seismic retrofitting and reconstruction plans of near-fault school buildings to reduce damages and losses in a possible seismic event.

Abstract: This paper experimentally presents the effects of different bolted connection types on the seismic performance of column-tree steel moment connections used in moment resisting frames. Two full scale test specimens were fabricated and tested: one specimen with slip critical bolted beam splices and the other one with bearing type bolted beam splices. The bearing type splice specimen was expected an improved deformation capacity by means of bolt slippage. The experimental results showed that the slip critical splice specimen successfully developed ductile behavior without brittle fracture until 5% story drift ratio, however for the bearing type splice specimen, the beam bottom flange fractured at 4.0% story drift ratio due to stress concentration around the weld access hole area. However the energy dissipation capacity of the bearing type splice specimen was better than that of the slip critical splice specimen until 4.0% story drift ratio.

Abstract: The old prefabricated reinforced concrete buildings have been designed with old standards that are lower than the present design code provisions. These buildings are likely to be vulnerable to severe damage or total collapse under strong seismic excitations. Hence, it is necessary to evaluate these buildings seismic performance and to retrofit them using appropriate methods. Buckling-restrained brace (BRB) is a kind of prospective energy dissipation component. As a brace, it is also a lateral force resistant member. Based on the characteristics of prefabricated frame and BRB, the time history analysis of a prefabricated frame strengthening by BRB is carried out by using software ANSYS to input the seismic wave. Then, the seismic behavior of this kind of frame is studied. It is observed that the seismic response of the retrofitted structures reduces significantly in comparison with the corresponding original structure without any retrofit measures.

Abstract: Strengthening the brick walls with reinforced concrete splint is a conventional and effective method of strengthening masonry structures. To the method, the text process and analysis of 6 brick walls strengthened with reinforced concrete splint and the existing calculation analysis method about bearing capacity are introduced in this paper. Through the series of low-cycle repeated load experiments, we study the different performance between unreinforced brick wall and brick wall strengthened with reinforced concrete splint. Based on the analysis, we find the seismic capacity of the brick wall strengthened with reinforced concrete splint such as the bearing capacity and ductility is enhanced clearly. Meanwhile, the calculation parameter in technical specification for seismic strengthening of buildings has good accordance with the experiment results.

Abstract: "six two building" in ocean university of china has been used over 90 years, which can not meet the requirements for earthquake resistance protection. In order to ensure its safe use, at the same time keeping the original building style, this paper proposes the seismic appraisal method after field detection, structure calculation and appraisal regulation check. Then this paper presents corresponding strengthening suggestion. It can be used for reference in other similar old building.