The Effect of Suffusion Phenomenon in the Increasing of Land Subsidence Rate

Land subsidence is defined as gradually ground surface settlement in an aquifer due to the compaction of unconsolidated sedimentary deposits. Since in an aquifer, deposits consist of cohesive or non-cohesive alluvial soil layers. The consolidation theory cannot be explained as the only reason for land subsidence. According to the susceptibility of alluvial soils to suffusion, internal erosion is also considerable to enhance the rate of the local settlement. Suffusion is explained as a process of soil particle movement in the soil body due to the effect of seepage flow on it. The subsidence rate in southwest and south of Tehran in Iran is very considerable whereby some structures have suffered significant damages due to this phenomenon. In this research, the contribution of suffusion and land subsidence was investigated in damaged building located at Ghale Morghi Street in southwest of Tehran, as a case history. Because of the incapability of available methods, in this article, a probability pattern is also proposed using statistical analysis for determination the likelihood of internal instability in alluvial soils in regard to soil cohesiveness

A Plastic Design Method for RC Moment Frame Buildings against Progressive Collapse

<p class="MsoNormal" style="margin-bottom:0in;margin-bottom:.0001pt;text-align: justify;direction:ltr;unicode-bidi:embed"><span style="font-size:12.0pt; line-height:115%;font-family:&quot;Times New Roman&quot;,&quot;serif&quot;;mso-ascii-theme-font: major-bidi;mso-hansi-theme-font:major-bidi;mso-bidi-theme-font:major-bidi">In this study, progressive collapse potential of generic 3-, 8- and 12-storey RC moment frame buildings designed based on IBC-2006 code was investigated by performing non-linear static and dynamic analyses. It was observed that the model structures had high potential for progressive collapse when the second floor column was suddenly removed. Then, the size of beams required to satisfy the failure criteria for progressive collapse was obtained by using the virtual work method; i.e., <span style="font-size:12.0pt;line-height:115%; font-family:&quot;Times New Roman&quot;,&quot;serif&quot;;mso-ascii-theme-font:major-bidi; mso-fareast-font-family:&quot;Times New Roman&quot;;mso-hansi-theme-font:major-bidi; mso-bidi-theme-font:major-bidi;mso-bidi-language:AR-SA">using the equilibrium of the external work done by gravity load due to loss of a column and the internal work done by plastic rotation of beams. According to the nonlinear dynamic analysis results, the model structures designed only for normal load turned out to have strong potential for progressive collapse whereas the structures designed by plastic design concept for progressive collapse satisfied the failure criterion recommended by the GSA code.&nbsp;</p

Yüksek mukavemetli beton (HSC) ve köpük beton için izin verilen katkıların in vitro değerlendirilmesi

Malzeme bilimindeki önemli ilerlemeler sayesinde araştırmacılar, yüksek mukavemetli beton (HSC) ve köpük beton gibi yeni beton teknolojilerinin uygulanmasına orantılı olarak farklı beton tipleri üretip geliştirmeyi başardılar. Bu yazıda köpük beton ve uygulamaları üzerine deneysel çalışmaların sonuçları sunulmaktadır. Ayrıca çimento içeriği, su / çimento oranı ve katkı maddeleri gibi çeşitli parametrelerin etkisi karışım tasarımında incelenmiştir. HSC'de beton kurucu maddeler arasındaki etkileşim, betonun mekanik özelliklerinde ve basınç dayanımında önemli rol oynamaktadır. Bu nedenle, bu faktörlerin uygun bir şekilde anlaşılması, istenen davranış ve dayanıklılığı olan bir betonun yapılması için uygun tür ve miktarda malzemeyi seçmemize yardımcı olur. Çalışmada kullanılan yöntemler ve teorik prosedürler ACI kodlarına dayanmaktadır. Bu çalışma, HSC'nin mukavemetine Micro Silica ve plastikleştiricilerin kullanmasının etkisini araştırmayı amaçlamaktadır. Elde edilen sonuçlara göre, beton karışımı tasarımı için kullanılan optimum oran ve bu malzemelerin beton mülkiyet üzerindeki olumlu etkileri doğrulanmıştır

Using Fragility Curves for the Evaluation of Seismic Improvement of Steel Moment Frames

There are numerous methods for buildings’ seismic improvement, one of which is to increase    the lateral force demand. To do so, adding different types of frames or a shear wall in structures is quite common as a new structural element. The present study selects three steel moment frame structures with four, seven, and twelve stories, all of which have similar floor plans and are designed based on the old seismic design code (UBC 1997 code), which is vulnerable in accordance with FEMA 356 code. For seismic improvement Concentrically Braced Frame (CBF), Buckling Restrained Brace (BRB), and shear wall have been used. The seismic performance level of the primary structure and improved structures were compared by means of seismic fragility curve. Earthquake intensity index is “PGA”. Finally, by selecting an appropriate damage index, fragility curves of the original structure as well as the improved structures were presented and compared with a normal log distribution, the results of which was analyzed.Bu çağlarda binalarin titreşimle iyi Olması için çoklu yollar var. Bu yollardan biri binani yan sertlikinin çok olmasıdır buna göre perde yada canlandırıcı yeni yapi elemanlari çok yaygındır. Bu çalişmada uç yapida dört,yedi,ve oniki. Katlarda çelik moment cevcevleri kalaninlmiştir ki her üç plani ortak zemindedir eski versiyonu bina titreşimi güçlendirilmiş  duzenleme (UBC 1997code) tasarlanmıştır ki FEMA 356 düzenlemesine göre binalar çok savunmasız dir ve seçilmişdir binanin titreşim gelişmesine göre CFB ve BRB ve perde bulabilmiştir sismik bina performans düzeyini ve geliştirilmiş  binalari eğer ile kirilgan olduğunu binalar karşılaşırmış. PGA deprem şiddet indeksi seçilmiştir ve sonunda sismik kırılma ayarlari uygun yaralanma şiddeti şeçilerek asil bina ve geliştirilmiş bina karşılaştırilmiş ve sonuçları araştırılmışti

Comparing Hysteretic Energy and inter-story drift in steel frames with V-shaped brace under near and far fault earthquakes

Different researches have shown that during destructive earthquakes, most structures enter non-reactionary range. Hysteretic Energy, which is wasted after the yield within its hysteresis rings, is very influential on generating structural damage of the system, being the most important component in the equation of the energy, inflicted on the structures. Therefore, controlling this amount of energy leads to controlling the structure behavior. The amount of Hysteretic Energy in a structure could be an index of its damage level or its malleability. The current paper carries out a nonlinear dynamic analysis on steel buildings with a V-shaped (Chevron) brace, hence surveying Hysteretic Energy distribution as well as maximum inter-story drift in the stories of these buildings, under the influence of equalized near and far fault records. Results show that the inter-story drift need for equalized near fault records is more than the far fault ones. Also the results show Hysteretic Energy caused by near fault records that are more than the far fault ones. What is more, as the building height rises, the share of building’s higher stories from the Hysteretic Energy increases. Keywords: Inelastic dynamic behavior, Energy concepts, Hysteretic Energy, Equalized near and far records, Nonlinear dynamic analysi

SEISMIC FRAGILITY ANALYSIS OF IMPROVED RC FRAMES USING DIFFERENT TYPES OF BRACING

Application of bracings to increase the lateral stiffness of building structures is a technique of seismic improvement that engineers frequently have recourse to. Accordingly, investigating the role of bracings in concrete structures along with the development of seismic fragility curves are of overriding concern to civil engineers. In this research, an ordinary RC building, designed according to the 1st edition of Iranian seismic code, was selected for examination. According to FEMA 356 code, this building is considered to be vulnerable. To improve the seismic performance of this building, 3 different types of bracings, which are Concentrically Braced Frames, Eccentrically Braced Frames and Buckling Restrained Frames were employed, and each bracing element was distributed in 3 different locations in the building. The researchers developed fragility curves and utilized 30 earthquake records on the Peak Ground Acceleration seismic intensity scale to carry out a time history analysis. Tow damage scale, including Inter-Story Drifts and Plastic Axial Deformation were also used. The numerical results obtained from this investigation confirm that Plastic Axial Deformation is more reliable than conventional approaches in developing fragility curves for retrofitted frames. In lieu of what is proposed, the researchers selected the suitable damage scale and developed and compared log-normal distribution of fragility curves first for the original and then for the retrofitted building

AN EVALUATION OF MULTI-HAZARD RISK SUBJECTED TO BLAST AND EARTHQUAKE LOADS IN RC MOMENT FRAME WITH SHEAR WALL

Over the recent decades, many public buildings located in a region of highseismic hazard have been subjected to simultaneous effect of abnormal loads against which they were not specifically designed. Hence, it is necessary to investigate the critical events occurring on the structure during its lifetime in order to investigate the structure’s performance based on a multi-hazard approach. The current study proposes a probabilistic framework for multihazard risk associated with collapse limit state of RC moment frame with shear wall structure, which is subjected to blast threats in the presence of seismic risk. The annual risk of structural collapse is calculated taking into account both the collapse caused by an earthquake event and the blast-induced progressive collapse. The blast fragility is calculated using a simulation procedure of Monte Carlo for generating blast scenarios. As a case study, the blast and seismic fragilities of a generic eight-story RC moment frame with shear wall building located in high seismic zone and subjected to the effect of blast load are calculated and implemented in the framework of a multi-hazard risk. The findings of the current research show a considerable risk; finally, the importance of taking the blast measure into account when designing strategic structures in areas of high seismic risk is highlighted