Showing papers on "Earthquake resistant structures published in 2015"

Application of shape memory alloy bars in self-centring precast segmental columns as seismic resistance

Abstract: The objective of this study is to investigate analytically the performance of self-centring precast segmental bridge columns with shape memory alloy (SMA) starter bars under nonlinear static and lateral seismic loading. For this purpose, a 3D finite element model for hybrid post-tensioned bridge column has been developed. The precast post-tensioned segmental bridge columns possessing a central tendon and adequate transverse confinement provided by the steel tube jacketing as self-centring bridge columns have an undesirable high lateral seismic demand due to their low energy dissipation. In order to eliminate this deficiency while keeping the residual displacement small, SMA starter bars are applied in this system. The effect of post-tensioning (PT) forces of the central strands and SMA bar size are investigated. The results indicate that in high seismicity zones, bridge columns with SMA bars at a higher level of PT forces have a superior performance against earthquake loading.

Optimal seismic design of reinforced concrete structures under time-history earthquake loads using an intelligent hybrid algorithm

Abstract: A reliable seismic-resistant design of structures is achieved in accordance with the seismic design codes by designing structures under seven or more pairs of earthquake records. Based on the recommendations of seismic design codes, the average time-history responses (ATHR) of structure is required. This paper focuses on the optimal seismic design of reinforced concrete (RC) structures against ten earthquake records using a hybrid of particle swarm optimization algorithm and an intelligent regression model (IRM). In order to reduce the computational time of optimization procedure due to the computational efforts of time-history analyses, IRM is proposed to accurately predict ATHR of structures. The proposed IRM consists of the combination of the subtractive algorithm (SA), K-means clustering approach and wavelet weighted least squares support vector machine (WWLS-SVM). To predict ATHR of structures, first, the input-output samples of structures are classified by SA and K-means clustering approach. Then, WWLS-SVM is trained with few samples and high accuracy for each cluster. 9- and 18-storey RC frames are designed optimally to illustrate the effectiveness and practicality of the proposed IRM. The numerical results demonstrate the efficiency and computational advantages of IRM for optimal design of structures subjected to time-history earthquake loads.

Lateral Loading Behaviors of Lightweight Wood-Frame Shear Walls with Ply-Bamboo Sheathing Panels

Abstract: This paper presents lateral-loading test results of lightweight wood-frame shear walls with ply-bamboo sheathing panels. Twenty shear walls of five different types of sizes, nailing, and lo...

Experimental Study on Beam-to-Column Connections of Steel Frame Structures with Steel Slit Dampers

Abstract: After the Northridge and Kobe earthquakes important experimental programs on beam-to-column connections were developed because of brittle fractures at welded beam-to-column connections. A number of studies are being carried out on a variety of materials and systems that dissipate the seismic loading effects in order to improve the seismic performance of steel frames. In the research reported in this paper, a slit steel damper system was developed to prevent the damage formation of standard columns and beams by dissipating lateral loads at the beam-to-column connections of steel frames. Therefore, the columns and beams of steel frames will not be damaged after a heavy earthquake, and the structures might be put into the service again simply by replacing the dampers at the connection sites. The seismic performance of the studied connection was verified through cyclic tests of two full-scale steel frames that had slit dampers and of one specimen that had a conventional extended end-plate connection. ...

Active control of highway bridges subject to a variety of earthquake loads

Abstract: In this paper, a wavelet-filtered genetic-neuro-fuzzy (WGNF) control system design framework for response control of a highway bridge under various earthquake loads is discussed. The WGNF controller is developed by combining fuzzy logic, discrete wavelet transform, genetic algorithms, and neural networks for use as a control algorithm. To evaluate the performance of the WGNF algorithm, it is tested on a highway bridge equipped with hydraulic actuators. It controls the actuators installed on the abutments of the highway bridge structure. Various earthquakes used as input signals include an artificial earthquake, the El-Centro, Kobe, North Palm Springs, Turkey Bolu, Chi-Chi, and Northridge earthquakes. It is proved that the WGNF control system is effective in mitigating the vibration of the highway bridge under a variety of seismic excitation.

Performance of posttensioned seismic retrofit of two stone masonry buildings during the Canterbury earthquakes

Abstract: Seismic retrofitting of unreinforced masonry buildings using posttensioning has been the topic of many recent experimental research projects. However, the performance of such retrofit designs in actual design-level earthquakes has previously been poorly documented. In 1984, two stone masonry buildings within The Arts Centre of Christchurch received posttensioned seismic retrofits, which were subsequently subjected to design level seismic loads during the 2010/2011 Canterbury earthquake sequence. These 26-year-old retrofits were part of a global scheme to strengthen and secure the historic building complex and were subject to considerable budgetary constraints. Given the limited resources available at the time of construction and the current degraded state of the steel posttension tendons, the posttensioned retrofits performed well in preventing major damage to the overall structure of the two buildings in the Canterbury earthquakes. When compared to other similar unretrofitted structures within Th...

Seismic Performance Evaluation and Retrofit of Fixed Jacket Offshore Platform Structures

Abstract: In this study the seismic performances of the fixed-base jacket structures with various bracing configurations were evaluated by nonlinear static and dynamic methods, and the effects of various retrofit schemes were compared. It was observed that the conventional retrofit methods of increasing member size were somewhat effective in increasing the strength of fixed steel jacket platform structures but were not so effective in increasing ductility. However, the ductility of the structures retrofitted with buckling-restrained braces turned out to be increased significantly. In the structures with conventional bracing, plastic hinges or buckling generally occurred at the upper half of the jacket structures. On the contrary, they were more uniformly distributed along the structure height in the structure retrofitted using buckling restrained braces. The capacity curves obtained from incremental dynamic analysis generally corresponded well with those obtained from nonlinear static analysis using a later...

Observations on the Van Earthquake and Structural Failures

Abstract: Turkey is located in one of the most seismically active regions in the world. In the 1999 Marmara earthquake in Turkey, more than 20,000 people died. On October 23, 2011, an earthquake with a magnitude of 7.2 on the Richter scale struck the Van and Ercis cities, causing more than 600 casualties. The epicenter was located in Zone 1 in the earthquake zones map of Turkey. In this paper, the results of a field reconnaissance survey of the affected earthquake area were reported and common structural failures in reinforced concrete (RC) structures were summarized. The observed failure modes included weak column–strong beam formations, hinging in the columns, column–beam joint failures, lap splice inadequacies, poor concrete quality, insufficient transverse reinforcement, buckling of longitudinal column reinforcement, pancake type of collapse mechanism, soft- and weak-story failures, and short column formations. The buildings in Van and Ercis have also several undesired architectural features, such as th...

Seismic Loads: Guide to the Seismic Load Provisions of ASCE 7 - 10

Abstract: \bFinley A. Charney, Ph.D., P.E., F.ASCE, F.SEI, is a professor of structural engineering at Virginia Tech and is president of Advanced Structural Concepts, Inc., both located in Blacksburg, Virginia.

Implementation of the damage index approach for the rapid evaluation of earthquake resistant buildings

Abstract: This paper presents a promising approach to modeling the building resistance in the seismic rehabilitation process. The damage index model (DIM) can be interactively utilized into the Geographical Information Systems (GIS) in order to compute parameters and to analyze data for a quality management purpose. It can perform an easy accessibility of the data to evaluate buildings for earthquake mitigation and preparedness. This research article intended to introduce a software program by using an integration system to design and to dissect the data for evaluating a building resistance against earthquakes. This paper promises a new integrated system for rapid evaluation of buildings, further a city planning by combination of GIS, civil engineering and industrial engineering upon the Federal Emergency Management Agency (FEMA) accompanied by seismic data, structure, parcel, material type, foundation, ceiling, wall, floor, the interior and the exterior. This software has been programmed based on the Damage Index (DI) algorithm that was developed by Pirasteh et al. (Int J Geoinformatics 5(4): 34–41, 2009). Later, based on the proposed algorithm or model the essential parameters have been adopted in Matrix laboratory (MATLAB) environment to yield a new software program for the meliorating earthquake mitigation and preparedness processes. This software program can identify vulnerability of the buildings ranking from 1 to 100. In addition, this paper recommends establishing a scientific procedure in determining the vulnerability of the buildings for earthquake preparedness within a GIS environment. However, this software program can amend in detecting weak structures for rehabilitation.

Earthquake Hazards and Risk Mitigation in Pakistan

Abstract: Earthquakes proved to be the most devastating natural disaster with a high mortality rate and wide spread destruction. Earthquake induced ground shaking plays a key role in excessive ground deformation and infrastructure damage, and in triggering secondary hazards such as landslides, flooding, tsunamis, fire and liquefaction. The intensity and duration of an earthquake induced ground shaking depends on magnitude, depth of hypocenter, medium traversed by seismic waves; and physical and geotechnical characteristics of the site. Tools of GIS and remote sensing are frequently and effectively used for earthquake hazard, vulnerability and risk assessment and assist in developing risk reduction strategies. Pakistan is located in one of the most earthquake prone region with many devastating earthquakes in the past and active tectonic shows that there might be more earthquakes in future. Hence it is crucial to perform earthquake hazard assessment across the country and subsequently develop and implement strategies for earthquake risk mitigation. Subsequent to facing extensive devastation by the 2005 Kashmir earthquake, the government has realized the importance of earthquake management and hence encouraged the scientific research aiming for earthquake hazard assessment and strategies for risk reduction. Moreover, organizations have been established mainly dedicated for natural disaster management. However, the magnitude of prevailing earthquake induced risk needs detailed earthquake hazard assessment, design earthquake resistant structures; implement the seismic building codes and public awareness to adopt for earthquake risk reduction.

The Effect of Vertical Shear-Link in Improving the Seismic Performance of Structures with Eccentrically Bracing Systems

Abstract: Passive control methods can be utilized to build earthquake resistant structures, and also to strengthen the vulnerable ones. In this paper, we studied the effect of this system in increasing the ductility and energy dissipation and also modeled the behavior of this type of eccentric bracing, and compared the hysteresis diagram of the modeled samples with the laboratory samples. We studied several samples of frames with vertical shear-links in order to assess the behavior of this type of eccentric bracing. Each of these samples was modeled in finite element software ANSYS 9.0, and was analyzed under the static cyclic loading. It was found that vertical shear-links have a more stable hysteresis loops. Another analysis showed that using honeycomb beams as the horizontal beam along with steel reinforcement has no negative effect on the hysteresis behavior of the sample. Keywords—Vertical shear-link, passive control, cyclic analysis, energy dissipation, honeycomb beam.

High-Performance Composite-Reinforced Earthquake Resistant Buildings with Self-Aligning Capabilities

Abstract: This paper describes the experimental procedures and presents preliminary results of the international project entitled “High- Performance Composite-Reinforced Earthquake Resistant Buildings with Self-Aligning Capabilities”. The goal of the project was to increase our understanding of the seismic performance of woodlaminated frames with locally reinforced members. Two sets of experiments were performed. First, a full-scale one-story frame with relatively rigid connections was tested on a shaking table, Kasal et al. (J Perform Constr Fac, 2013). To achieve a stiff connection, hardwood blocks and self-tapping screws 120–250 mm long were used to facilitate the connection between beams and columns. Next, a scaled three-story frame was tested. Highly stressed regions of beams and columns of the second frame were reinforced with glass fiber (GF) sheets to mitigate potential brittle failure in anticipated weak zones. Frictional connections between beams and columns permitted a control of the magnitude of dissipated energy in the system. The connections were expected to behave stiffly under small excitations, dissipate energy through friction during moderate seismic excitation, and degrade at higher seismic loads. While the friction can be relatively well predicted, the degradation of the connection cannot, due to the uncertainty in properties of wood.

Bidirectional-Ductile End Diaphragms for Seismic Performance and Substructure Protection

Abstract: This project proposes a bi-directional ductile end diaphragm concept to implement ductile end diaphragms in straight or skew bridge superstructures. The proposed concept relies on easily replaceable hysteretic energy dissipating devices (structural fuses) arrayed such as to provide ductile response to horizontal bidirectional earthquake excitations. Buckling Restrained Braces (BRBs) are explored here as a possible solution to serve as the ductile diaphragm’s seismic fuses. In Stage 1 of this research project, bi-directional ductile end diaphragm systems were designed for benchmark skew- and nonskew bridges and analyzed using nonlinear time history analysis to examine their seismic performance. Variations in skew, fundamental period of vibration, and earthquake excitation characteristics were also considered. In Stage 2 of this research project, quasi-static experiments were conducted to subject BRBs to a regime of relative end-displacements representative of the results predicted from the Stage1’s parametric analytical studies. Detailed analyses of cumulative inelastic deformations and low-cycle fatigue life of all BRBs using data from the experiments were performed. A recommended design procedure is presented for the EDSs in both non-skew and skew bridges was developed based on the parametric analyses and experimental results.

Seismic Fragility of Weir Structures due to Sliding Effect

Abstract: The failure of hydraulic systems as flood defence structures can cause extensive catastrophic damage in upstream and downstream areas during an earthquake. Consequently, dams or weir structures as hydraulic systems must remain functional and operational during and after an earthquake. In recent years, in order to mitigate the risk or secure the safety of the hydraulic systems, the Probabilistic Seismic Risk Assessment (PSRA) has been issued as a key area of research. The primary objective of this paper was to evaluate the seismic fragility of weir structures by incorporating a nonlinear Finite Element (FE) model for the contact interfaces among weir-mass concrete-soil foundation in the weir structure. Gangjeong-Goryeon weir, located in Daegu Metropolitan City in the southeastern part of Korea was selected in this study. The seismic fragility of the weir structure corresponding to the sliding Limit State 13 mm (LS I) and 153 mm (LS II) was determined from multiple nonlinear time-history analyses based on Monte-Carol simulation accounting for the uncertainties such as material nonlinearity and ground motions with respect to near field faults and far field faults. The results showed that the sliding failure of the weir structure corresponding to LS I started from 0.1 g, but the weir system under LS II had no failure up to 0.4g. Besides, in the case of LS I and LS II, the weir subjected to both near field faults and far field faults was more fragile than that subjected to far field faults.

Vulnerability Assessment of Reinforced Concrete Building Subjected to Seismic Loads Using Pushover Analysis

Abstract: Building s should be designed to withstand an earthquake based on earthquake planning standard. However, the references used in the regulation could not show building performance to the actual earthquake directly. Therefore, it required an assessment of the existing buildings, in order to evaluate their vulnerability (structural performance level). This study discussed the vulnerability assessment of reinforced concrete buildings from the analysis of the relationship between base shear and displacement , and any failure that occurred. The first step of the evaluation was analyze d the seismic loads with Static Nonlinear (Pushover) Analysis using SAP2000 software. The pushover analysis results showed the level of damage to assess the building damage s . This research was based on SNI 03-1726-2002, Federal Emergency Management Agency (FEMA) 273/356, FEMA 440, and the Applied Technology Council (ATC)-40 . Displacement values obtained from Pushover Analysis compared with the field studies. From the pushover analysis, the results obtained the capacity curve showing the relationships between the base shear s and the displacements , reviewed at each elastic conditions, ultimate, plastic and collapse . The numerical results turned out to be closed to the performance level of the structure in the field. Thus the analysis can be used as a reference on an assessment level of performance and behavior of the existing structure as well as the vulnerability of the structure. Normal 0 false false false IN X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;}

Comparative study of Seismic Performance of multistoried R.C.C buildings with Flat slab & Grid slab

Abstract: The objective of this study is to assess the comparative seismic performance of flat slab buildings vis-a-vis grid slab buildings. Dynamic analysis of three different high rise buildings having 12, 15 & 18 stories is performed using response spectrum method for all four seismic zones of India, as categorized by the Indian code for earthquake resistant structures. The assessment of the seismic response is based on the maximum inter-story drift, roof displacement, Time period and the base shear. E-TAB v9.7.3 software is used for the analysis. It is observed that the seismic performance of grid slab buildings was better as compared to that of flat slab buildings.

Comparative Structure Behavior System of Fixed Base and Base Isolation as Earthquake Result in Irregular Building Configuration

Abstract: Indonesia is prone to earthquakes because the region is traversed by some of the world's most active seismic lines as the Mediterranean and the Circum-Pacific earthquake belt. Thus has happened thousands of times smaller to large earthquakes that occurred both documented and undocumented. Such conditions should be designed buildings in Indonesia earthquake resistant. One of the basic principles for the design of earthquake resistant buildings is regularity. But in reality is not inevitable either irregular building with functional and subjective reasons. While in designing earthquake-resistant building structures to make the building into a relatively flexible is relatively new compared to the fixed base system structure that is by using base isolation. If the base isolation mounted on irregular building configuration, positive or negative whatever effect on behavior than building structures using fixed base system? In this study uses quantitative methods to study the type of simulation experiments. Architecture and structures datas used as a model hospital in STAADPRO software then analyzed the numerical results with existing theories. The research results: • The use of base isolation reduce the base shear force than the fixed base system. • The use of base isolation minimize the drift between floor levels than the fixed base system. • The use of base isolation building eccentricity relative increase it than the fixed base system. Keywords: earthquake, irregular, fixed base, base isolation url: http://jurnalppkm.unsiq.ac.id/index.php/ppkm/article/view/73

A Promising Approach in the World: Tensile Structures Roofing

Abstract: Civil engineering roof systems for outdoor environments find use in bazaars, car park areas, outdoor sport facilities and places built to protect people or their goods from environmental effects such as sun and heavy rain. Therefore, such roofing systems have great amount of application and each country spends huge volumes of materials to build these roof systems to improve life quality of people in cities. Thus, it is evident that further research on these civil engineering structures has the potential to decrease the cost of these roof systems and build more efficient ones. Generally these roof systems are manufactured employing structural steel material. As is well known, steel has promising mechanical properties such as high strength and high stiffness which can be exploited in structures that expected to receive very high magnitude of loadings, such as earthquake resistant buildings. However, there also exist some disadvantages of completely using steel in these roof systems. For instance, due to unit weight of material the roofs manufactured using steel are very heavy. So, construction process requires significant labour and time. Also steel construction is an expensive process considering measure of covered area for outdoor roof systems. Moreover, these kinds of roofs manufactured using completely steel are not flexible in use, that is to say, when it is unnecessary for some period of time it is not possible to remove the roof covering and re-cover it when it is necessary again. This paper investigates a novel concept in the world called as “tensile structures” used to cover wide outdoor areas. This concept actually combines civil engineering designs and some architectural aspects. Instead of using materials with high stiffness, tensile structures adapt membrane materials to cover wide areas. Cable elements accompany those membranes to transmit the internal forces and stresses to structural columns or ground. Although membrane materials have lower strengths compared to steel, these structures offer flexibility in use, light coverings, lower costs and faster construction time. Since these structures are built utilizing membrane materials and cables which support tension forces only, conventional stress office methods are not capable of handling their analyses and designs. Consequently, specific computational methods must be used to perform such designs. In this paper special commercial software is used to investigate behaviour of tensile structures. Three different configurations are employed to cover a wide area. Structural analysis procedures of those configurations are undertaken and stress distributions in membranes are investigated. Discussions pertaining to motivation behind these structures, load carrying capabilities and working principles are provided. Outcomes of this study illustrate that these tensile structures have the potential to replace some applications of steel roofs to lead lighter, flexible, low cost and more aesthetic structures for outdoor environments.

Seismic behavior analysis of multi-story reinforced concrete buildings having torsional irregularity

Abstract: Earthquakes are one of the most important and hazardous natural disasters in the world and in our country. They also have lots of characteristics from the point of effects caused by them. For this reason it requires special engineering approach to analyze those effects and to design earthquake resistant structures. Almost all of the life losses caused by the earthquakes are related with improperly designed buildings safety of which are not ensured against severe earthquakes. Structural damages and collapses cause very important economical losses. So, understanding of the characteristics of an earthquake and correct determination of the behavior of buildings under earthquake excitation turn out to be the most important requirement to build earthquake resistant buildings. When we take into consideration the destructive effects of severe earthquakes that happened especially in recent years (Kocaeli 1999, Duzce 1999) one can easily see the importance of knowing the behavior of buildings under earthquake loads. In this study torsional effects that occur during earthquake excitations are analyzed in multi-story reinforced concrete buildings. In that manner the behavior of reinforced concrete structures under earthquake loads are examined and by the way the behaviors of structures having torsional irregularities are enlightened and clarified. Moreover the effects of rigidity, ultimate capacity and ductility on the behavior of structures under ground motion are summarized. Torsional irregularity is a key irregularity in determination of the method to be used in earthquake analysis. Definition of the torsional irregularity of a multi-story reinforced concrete building is explained in accordance with Turkish Earthquake Code and the related principles of computations that have to be followed according to the code are given. Multi-story reinforced concrete buildings are classified according to their plan geometry and the effects of plan geometry on the torsional irregularity are explained. While in certain structures torsional irregularity may happen in very high levels in some structures it may happen so small that can be safely omitted. For that reason buildings forming torsional irregularity are classified and their characteristics and torsional irregularity parameters are given. Shear walls without causing any torsional irregularity on buildings having different plan geometries are shown.