SEISMIC VULNERABILITY OF REINFORCED CONCRETE BRIDGES IN PAKISTAN

Different researchers have performed seismic hazard assessment studies for Pakistan using faults sources which differ from Building Code of Pakistan (BCP 2007) with diverse standard deviations. The results of seismic hazard studies indicate that BCP requires gross revision considering micro and macro level investigations. The recent earthquakes in Pakistan also damaged bridge structures and some studies have been conducted by different researchers to investigate capacity of existing bridges. The most of bridge stock in Pakistan has been designed assuming seismic loads as 2%, 4% and 6% of dead loads following West Pakistan Code of Practice for Highway Bridges. The capacity of eight selected real bridges, two from each seismic zone 2A, 2B, 3 & 4 is checked against BCP demands. Static and dynamic analyses were performed and the piers were checked for elastic limits. It is established that piers are on lower side in capacity and the bridges in zone 2A are generally less vulnerable. Whereas the bridges in zone 2B, 3 and 4 are vulnerable from medium to very high level. Hence, an in-depth analytical vulnerability study of bridge stock particularly in high-risk zone needs to be conducted on priority and appropriate seismic retrofitting schemes need to be proposed.

Synthesis of Recent Paleoseismic Research on Quaternary Faulting in the Eastern Tennessee Seismic Zone, Eastern North America: Implications for Seismic Hazard and Intraplate Seismicity

ABSTRACT Causes of intraplate seismicity remain a great unsolved problem, in contrast with plate-boundary seismicity. Modern seismicity records frequent seismic activity in plate-boundary seismic zones, but in fault zones where seismic activity is not frequent, plate boundary or intraplate, resolution of prehistoric earthquake activity is critical for estimating earthquake recurrence interval and maximum expected magnitude. Thus, documenting prehistoric earthquakes is crucial for assessing earthquake hazard posed to infrastructure, including nuclear reactors and large dams. The ∼400 km long eastern Tennessee seismic zone (ETSZ), United States, is the third most active seismic zone east of the Rocky Mountains in North America, although the largest recorded ETSZ earthquake is only Mw 4.8. Ironically, it is the least studied major eastern U.S. seismic zone. Recent ETSZ field surveys revealed an 80 km long, 060°-trending corridor containing northeast-striking Quaternary thrust, strike slip, and normal faults with displacements ≥1 m. It partially overlaps a parallel trend of seismicity that extends 30 km farther southwest, suggesting this active faulting zone may extend ∼110 km within part of the ETSZ. Near Dandridge, Tennessee, a thrust fault in French Broad River alluvium records two earthquakes in the last 40,000 yr. About 50 km southwest near Alcoa, Tennessee, a thrust fault cuts Little River alluvium and records two earthquakes between 15,000 and 10,000 yr ago. About 30 km farther southwest at Vonore, Tennessee, a thrust fault displaces bedrock ≥2 m over colluvium, and alluvium is normal faulted >2 m. This corridor, just west of the Blue Ridge escarpment, overlies a steep gradient in midcrustal S-wave velocities, consistent with a basement fault at hypocentral depths. The corridor faults may be connected to a basement fault or localized coseismic faults above a blind basement fault. Our current data suggest at least two Mw≥6.5 surface rupturing events in the last 40,000 yr.

Dynamic Analysis on RCC and Composite Structure for Uniform and Optimized Section

This study examines the composite structure that is increasing commonly in developing countries. For medium-rise to high-rise building construction, RCC structures is no longer economical due to heavy dead weight, limited span, low natural frequency and hazardous formwork. The majority of commercial buildings are designed and constructed with reinforced concrete, which largely depends on the existence of the constituent materials as well as the quality of the necessary construction skills, and including the usefulness of design standards. Conventional RCC structure is not preferred nowadays for high rise structure. However, composite construction, is a recent development in the construction industry. Concrete-steel composite structures are now very popular due to some outstanding advantages over conventional concrete and steel structures. In the present work, RCC and steel-concrete composite structure are being considered for a Dynamic analysis of a G+25-storey commercial building of uniform and optimized section, located at in seismic zone IV. Response Spectrum analysis method is used to analyze RCC and composite structure, CSI ETABS v19 software is used and various results are compared such as time period, maximum storey displacement, maximum storey stiffness. Maximum storey shear and maximum stoey overturning moment. Keywords: RCC Structure, Composite Structure, Uniform Section, Optimized Section, Shear Connector, Time Period, Storey Displacement, Storey Shear, Storey Stiffness, Response Spectrum method, ETABS

A Literature Review on Seismic Response of Floating Column Building

Floating column building is a new fascination for engineers. As floating column buildings provides more space and good aesthetics to the building. But have high structural challenges, when a floating column is provided in a multi-story building in a high seismic zone. This paper reviews several studies conducted on the floating column building and its behavior under seismic loads. This paper studies that floating column building are vulnerable to the high seismic zones. The risk of damage also depends on the shape and size of the buildings.The ductile detailing of the joints is the promising solution for immediate failure of such buildings. Keywords: Floating Column, Response spectrum analysis. Vulnerable, damage, multi-story

Criteria of Using Optimum Size Approach for Reduction of Axial Forces in Column in Multi Storied Building under Seismic Zone III

In India, every industry has its own importance to make the country shift towards its future goal. The construction industry plays a very significant role with the introduction of high-rise structures that has been increasing regularly. Beside this, the structure should be strong enough that each element should be economic and strong. The criteria of using optimum size approach for reduction of axial forces in column in multi storied building under seismic zone is a new idea. It reduces the size of beams and columns at the different levels of the building. On other hand, the structural weight should be minimized when the self-weight of the same will be reduced and proved to be an economic structure. In this project a G+13 Storey structure is analyzed using six different cases named as AFR Case A to AFR Case F assumed to be situated in seismic Zone III. The plinth area is in use as 625 m2 and all the cases have compared with each parameter. The project concluded that efficient Case is AFR Case C on comparing 6 maximum axial force reduction cases that ultimately reduce the overall cost of the project. Keywords: Axial forces, Columns, Strength, Durability, Software Models, High-Rise Structures

FARMERS’ PERCEPTIONS OF CLIMATE CHANGE, ITS ASSOCIATED RISKS AND ADAPTATION METHODS: A CASE STUDY OF GHAZIABAD, UTTAR PRADESH, INDIA

This study makes an attempt to explore farmers’ perception of climate change, awareness of adaptation and techniques adopted by them. Study area is Ghaziabad, Uttar Pradesh because this district is located in seismic zone IV and due to this, district is exposed to natural and man-made calamities such as, floods, drought, wind storms. Non-parametric test named Mann-Kendall has been employed to observe monthly trend in the climatic variables. Minimum temperature and maximum temperature showed an upward trend in most of the months; however, rainfall shows an insignificant downward trend in most of the months. The primary survey results indicate that farmers are observing increase in temperature, erratic rainfall and other changes in climate but they are not aware of “climate change” per se. Most farmers believe that “Ancestral Spirits” are the main cause of the variations taking place in climate. The farmers are aware of the climate shocks and climate variability. Although farmers haven’t taken any concrete steps to combat the perceived climate changes, they are changing their farming practises.

Present-day stress field pattern in the Vrancea seismic zone (Romania) deduced from earthquake focal mechanism inversion

Vrancea seismogenic zone in the South-Eastern Carpathians is characterized by localized intermediate-depth seismicity. Due to its complex geodynamics and large strain release, Vrancea represents a key element in the Carpatho-Pannonian system. Data from a recently compiled catalogue of fault plane solutions (REFMC) are inverted to evaluate stress regime in Vrancea on depth. A single predominant downdip extensive regime is obtained in all considered clusters, including the crustal layers located above the Vrancea slab. The prevalent stress regime confirms previous investigations and requires some mantle-crust coupling. The S3 principal stress is close to vertical, while S1 and S2 are horizontal, oriented perpendicularly and respectively tangentially to the Carpathians Arc bend. This configuration is present at any depth level. According to seismicity patterns, there are two main active segments in the Vrancea intermediate-depth domain, at 55 – 105 km and 105 – 180 km, both able to generate major events. The configuration of the tectonic stresses as resulted from inversion is similar in both segments. Also, high fault instability (I > 0.95) is characterizing the segments. The only notable difference is given by the friction and stress ratio parameters which drop down in the bottom segment from μ = 0.95 to μ = 0.55 and from R = 0.51 to R = 0.29. This variation is attributed to possible weakening processes activated below 100 km depth and can explain the intensification of seismicity production as earthquake rate and average energy release in the lower segment versus the upper segment.

Evaluating landslide response in a seismic and rainfall regime: a case study from the SE Carpathians, Romania

There have been many studies exploring rainfall-induced slope failures in earthquake-affected terrain. However, studies evaluating the potential effects of both landslide-triggering factors – rainfall and earthquakes – have been infrequent despite rising global landslide mortality risk. The SE Carpathians, which have been subjected to many large historical earthquakes and changing climate thus resulting in frequent landslides, comprise one such region that has been little explored in this context. Therefore, a massive (∼9.1 Mm2) landslide, situated along the river Bâsca Rozilei, in the Vrancea seismic zone, SE Carpathians, is chosen as a case study area to achieve the aforesaid objective (evaluating the effects of both rainfall and earthquakes on landslides) using slope stability evaluation and runout simulation. The present state of the slope reveals a factor of safety in a range of 1.17–1.32 with a static condition displacement of 0.4–4 m that reaches up to 8–60 m under dynamic (earthquake) conditions. The groundwater (GW) effect further decreases the factor of safety and increases the displacement. Ground motion amplification enhances the possibility of slope surface deformation and displacements. The debris flow prediction, implying the excessive rainfall effect, reveals a flow having a 9.0–26.0 m height and 2.1–3.0 m s−1 velocity along the river channel. The predicted extent of potential debris flow is found to follow the trails possibly created by previous debris flow and/or slide events.