1,720,963 research outputs found
Use of Structural Steel Frames for Structural Restoration of URM Historical Buildings in Seismic Areas
No full textHistoric buildings and monuments are an important part of our cultural heritage that must be protected and their sustainability ensured, especially when earthquakes occur. In this paper, a technique that uses structural steel frames is proposed as one way of strengthening unreinforced masonry (URM) in historical buildings. The idea underpinning this technique is to reduce the earthquake displacement demand on non-ductile URM walls by attaching steel frames to the building floors from inside. These frames run parallel to the structural system of the building and are fixed at their base to the existing foundation of the building. Furthermore, they are constructed rapidly, do not occupy architectural space, save the building's historic fabric, and can be easily replaced after an earthquake if some minor damage ensues. The proposed technique was applied to a five-story historical masonry building in Istanbul. The results of seismic performance analysis indicate that even though the building has plan irregularities, the proposed steel frames are able to effectively enhance the building's seismic performance by reducing inter-story drifts and increasing lateral stiffness and strength
SEISMIC PROTECTION OF EXISTING RC BUILDINGS USING FUSE ELEMENTS
No full textThis paper presents a new concept on collapse prevention of existing RC buildings during a seismic event. The idea is to install steel panels in specified locations in the structure to reduce inter-story drifts. The panels are expected to work as a fuse in an electric circuit when a major earthquake occurs; the panels will attract the seismic forces and they may totally damaged but they will prevent severe damage in the main structural system. The proposed panels are light-weight, easy to handle, and can be constructed very quickly. Moreover, they are cheap and do not need formwork or skilled workers. To test the concept, a half-scale, single-story 3D reinforced concrete frame specimen was constructed at the shake-table laboratories of the Kandilli Observatory and Earthquake Research Institute of Bogazici University, and subjected to recorded real earthquake base accelerations. The amplitudes of base accelerations were increased until a moderate damage level is reached. Then, the damaged RC frames was retrofitted by means of steel panels and tested under the same earthquake. The seismic performance of the specimen before and after the retrofit was evaluated using FEMA356 standards, and the results were compared in terms of stiffness, strength, and deformability. The results have confirmed effectiveness of the proposed retrofit scheme
Low-Rise 3D Panel Structures for Hot Regions: Design Guidelines and Case Studies
No full textMore than 40 years ago, lightweight composite panels fabricated from polystyrene, steel, and shotcrete concrete were used to construct nonload-bearing walls such as partition walls and fa double dagger ade cladding. Recently, many private companies all over the world have started manufacturing these panels commercially to be used as load-bearing walls or floor slabs in the construction of low-rise structures up to three stories high by proposing a new building system called a 3D panel building system. The light weight of these panels, along with the fact that they are easy to handle, enhance the speed of construction, offer good heat insulation properties, and they cost less by avoiding the need for either formwork or skilled workers, make it an acceptable construction practice. Tests reported in the literature indicate that the degree of heat insulation of a 3D panel wall significantly exceeds that of partitions or curtain walls obtained with the traditional systems. This produces energy savings equal to 40% with both heating and cooling, making these panels suitable for construction in hot regions and especially in rural areas. In the literature, there are several reports of experimental works conducted by the author and by many researchers worldwide in an effort to determine the mechanical properties of the panels and to investigate the efficiency of its building system in terms of resistance to gravity and seismic loads. However, there is not enough information on their design rules. In this paper, some design guidelines are proposed. The guidelines rely on experimental findings and on reinforced concrete (RC) design building codes such as ACI-318 [Building Code Requirements for Reinforced Concrete (ACI 318-95), American Concrete Institute] and UBC. Two design case studies in Turkey using the proposed guidelines are presented. The first case is the design of a small 3D panel house and the second case is the design of a 3D panel factory. The proposed design rules are conservative and follow the rules specified for designing reinforced concrete structures with some modifications
Cyclic lateral load behavior of CFS walls sheathed with different materials
No full textIn recent years, cold formed steel (CFS) buildings have been recognized as viable alternatives to reinforced concrete buildings especially in seismic areas. This is because they are lightweight, fast to construct, recyclable, dimensionally stable, and do not need formworks. Under vertical loading the design principles of these buildings are well established and codified, however, under lateral loadings such as earthquake loads efficient design is needed. In this paper the effects of sheathing material type on the cyclic lateral load behavior of CFS walls were investigated. Ten full scale CFS wall specimens sheathed with four different material types were tested under lateral cyclic loads. The sheathing types are Trapezoidal steel sheet, steel sheet, reinforced cement board, and thin ribbed steel sheet shotcreted with cement mortar. The effect of wall foundation connection details on the lateral load response of the walls were also investigated. Test results indicate that the lateral load carrying capacities of the walls increased by about 3 times when sheathed with the proposed materials. Furthermore specimens sheathed with steel sheets have almost the same lateral load carrying capacities of specimens sheathed with Trapezoidal steel sheets. However the hysteresis damping is higher in the steel sheet sheathed specimens. That means corrugating the steel sheets as Trapezoidal will not increase the strength and damping characteristics of the walls. Walls sheathed with 12 mm thick reinforced cement boards show 1.5 times higher lateral load carrying capacity than all the tested specimens. Depending on the material sheathing type and the sheathing thickness the specimens fail due to local failure in the edge studs, or screw tears out or buckling of the steel sheet. Lastly CFS wall lateral permanent deformations can be reduced by improving the wall-foundation connection details. (c) 2015 Elsevier Ltd. All rights reserved
Seismic Collapse Prevention of Non-Structural Infill Masonry Using eq-top: an Easy Earthquake Fibre Retrofitting System
No full textSpecially manufactured technical textile and polyurethane glue, called eq-top system is proposed to save life and prevent collapse of non-structural masonry, e.g. in filled walls during a seismic event with a minimum cost. The idea is to attach glass fiber textile on the brittle brick partition walls in the buildings and connect them with the peripheral structural frames. During an earthquake it is expected that the system will hold the non-structural elements in place and prevent their out of plan failures; also it will improve their in-plane stiffness making them working as structural infill walls. The proposed technical textile is light-weight, easy to handle, fast in application, and cheap compared to the well-known FRP and CRP. To test the eq-top system, shake table on full scale brick wall specimens was conducted at Bogazi double dagger i University in Turkey. The strengthened specimen and the non-strengthened specimens were fixed on the same shake table for a direct comparison and the amplitudes of base accelerations were increased until severe damage is reached in the non-strengthened and/or strengthened specimen. The seismic performance of the 2 x 2 specimens (two without and two with strengthening) was compared in terms of stiffness, strength, deformability and ductility. All thought that the specimens were excited under their resonance frequencies, no damage at all occurred in the strengthened specimen and total collapse happened already in the non-strengthened panel under low amplitudes. The results have confirmed effectiveness of the proposed retrofit scheme
Bina kaplama sistemlerinin sismik performansı: Deneysel çalışma
No full textCladding accounts for up to 25% of the cost of a building, has a major impact on its integrity, service life and preserves its appearance. In this paper the dynamic behavior of cladding systems of two projects in practice was investigated. The first project is the Great mosque project in Algeria and the second project is a high rise building in Almaty- Kazakhstan. In the first project stone cladding system was used and in the second project glass aluminum panel cladding system was used. Shake table tests were performed to verify the adequacy of the cladding system connection details. Test results shows that the designed façade detailing was appropriate and permit free movement of the curtain wall from the building structure without getting failures. The paper presents test specimens details, test results and the recommendation that the architect or the design engineer should take into consideration in designing cladding system connection details.Modern binalar genellikle doğal taş veya cam alüminyum panellerin kaplama sistemlerine sahiptirler. Kaplama, bir binanın maliyetinin% 25'ini oluşturur, bütünlüğü ve hizmet ömrü üzerinde büyük bir etkiye sahiptir ve görünümünü korur. Bu makalede, iki büyük uygulama projenin kaplama sistemlerinin dinamik davranışı araştırılmıştır. İlk proje Cezayir'deki Ulu cami projesidir ve ikinci proje Almatı-Kazakistan'da bir kule projesidir. İlk projede taş kaplama sistemi, ikinci projede cam alüminyum panel kaplama sistemi kullanılmıştır. Bu çalışmada kaplama sistemi bağlantı detaylarının yeterliliğini doğrulamak için sarsma tablası testleri yapılmıştır. Test sonuçları, tasarlanan cephe detaylandırmasının uygun olduğunu göstermektedir ve kaplama duvarı hasar görmeden bina yapısından serbestçe hareket eder. Bu makalede test örnekleri detayları, test sonuçları ve mimar veya tasarım mühendisinin kaplama sistemi bağlantı detaylarının tasarımında dikkate alması gereken tavsiyeler sunulmaktadır
Kütle sönümleyici çelik çatı sistemli betonarme bir binanın deprem davranışı
No full textIn this paper Tuned-Steel Roof system is proposed to reduce the earthquake effects on existing RC buildings. The idea is to replace the conventional wooden truss roof system by a steel roof system which will be connected to the RC building with low lateral stiffness steel bars. The steel roof can be tuned to have the same natural frequency of the building. All the construction works are applied from outside of the building and do not affect the building function, that there is no need to evacuate the building. Time history analysis on a RC building finite element model was performed to investigate the effectiveness of proposed technique. Analysis results shows that the building with tuned roof get a reduction of top displacement , top acceleration , and base shear by about 20 to 50 percent compared with the building without tuned roof. The reduction is affected by earthquake characteristics and roof mass.Kütle Sönümleyici Sistemleri (TMD), demiryolu trenleri gibi rüzgar ve trafikten kaynaklanan titreşimin azaltılması için yaygın olarak kullanılmaktadır. Bu makalede, mevcut betonarme binalar üzerindeki deprem etkilerini azaltmak için TMD Çelik Çatı sistemi önerilmektedir. Bu öneride, geleneksel ahşap kafes çatı sisteminin yerini, düşük yanal sertlik çelik çubuklarla betonarme binaya bağlanacak bir çelik çatı sistemi ile değiştirmektir. Çelik çatı, binanın aynı doğal frekansına sahip olacak şekilde ayarlanabilir. Tüm inşaat işleri binanın dışından uygulanır ve bina işlevini etkilemez, binanın boşaltılmasına gerek yoktur. Önerilen tekniğin etkinliğini araştırmak için betonarme yapı sonlu elemanlar modelinde zaman tanım analizi yapılmıştır. Analiz sonuçları, önerilen çatı sistemine sahip binanın, geleneksel çatılı binaya kıyasla yer değiştirme, ivme ve taban kesme kuvvetini yaklaşık yüzde 20 ila 50 oranında azalma elde ettiğini göstermektedir. Azalmanın değeri deprem karakteristiklerinden ve çatı-bina kütle oranından etkilenir. Analiz sonuçları önerilen tekniğin etkinliğini gösterir
Load carrying capacity enhancement of cold formed steel walls using shotcreted steel sheets
No full textRecently worldwide cold formed steel buildings are recognized as viable alternatives to reinforced concrete buildings especially in seismic areas. This is because they are lightweight (easy to handle), fast constructed, energy efficient (green houses), economical, dimensionally stable and they do not need skilled worker. Under vertical loading the design principles of these buildings are well established and codified, however, under lateral loadings such as wind and earthquake loads efficiently design is needed. In this paper a new sheathing technique uses shotcreted ribbed steel sheets is proposed to improve the stability and increase the lateral load carrying capacities of the CFS walls in order to withstand earthquake and wind loads safely. The idea is to sheath the outer side of CFS structure external walls with thin ribbed steel sheets, then shotcreted the sheets with cement or gypsum mortars. To test the concept full size wall specimens were prepared in the laboratory and tested under monotonic vertical and lateral loads. Some of the specimens were sheathed with the traditional fiber cement boards or gypsum boards with mat reinforcement, while the others were sheathed with the proposed technique. Test results indicates that the lateral load carrying capacities of the walls sheathed with the proposed technique increases by about two times compared with the walls sheathed with traditional boards. And under ultimate loads they fail in local failure modes rather than overall buckling failure modes which commonly occur in the walls sheathed with traditional boards. (C) 2012 Elsevier Ltd. All rights reserved
Comparison of neural networks and neuro-fuzzy computing techniques for prediction of peak breach outflow
No full textAccurate prediction of peak outflows from breached embankment dams is a key parameter in dam risk assessment. In this study, efficient models were developed to predict peak breach outflows utilizing artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS). Historical data from 93 embankment dam failures were used to train and evaluate the applicability of these models. Two scenarios were applied with each model by either considering the whole data set without classification or classifying the set into small dams (48 dams) and large dams (45 dams). In this way, nine models were developed and their results were compared to each other and to the results of the best available regression equations and recent gene expression programming. Among the different models, the ANFIS model of the first scenario exhibited better performance based on its higher efficiency (E = 0.98), higher coefficient of determination (R-2 = 0.98) and lower mean absolute error (MAE = 840.9). Moreover, models based on classified data enhanced the prediction of peak outflows particularly for small dams. Finally, this study indicated the potential of the developed ANFIS and ANN models to be used as predictive tools of peak outflow rates of embankment dams
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