Asian journal of civil engineering
Volume:16 Issue: 6, Dec 2015

The aim of the present contribution is quantify the effect of material deterioration on the seismic collapse capacity of single-degree-of-freedom systems vulnerable to the destabilizing effect of gravity loads (P-delta effect). The outcomes are presented in terms of collapse capacity spectra, where for characteristic structural parameters median and dispersion of record-dependent collapse capacities is plotted against the initial structural period. The ultimate goal of this study is to isolate sets of material deterioration parameters, which do not affect substantially the collapse capacity of P-delta sensitive structures. These threshold values depend primarily on the post-yield stiffness ratio, the assigned hysteretic law, and the initial structural period.

This paper reports on optimal design of reinforced concrete cantilever retaining walls of a given height under static and earthquake loading conditions utilizing Colliding Bodies Optimization (CBO) and Democratic Particle Swarm Optimization (DPSO). The design is based on ACI 318-05. Two theories known as Coulomb and Rankine have been applied for estimating earth pressures under static loading condition and Mononobe-Okabe method have been applied for estimating earth pressures under dynamic loading condition. The objective function is the cost of materials used in retaining walls. This function is minimized subjected to the considered constraints. A numerical example is optimized to illustrate the performance of the CBO and DPSO algorithms compared with Particle Swarm Optimization (PSO) and Improved Harmony Search (HIS) algorithms.

Due to its convenience, speed, and quality of implementation, overusing of self consolidating concrete necessitates adopting new methods to optimize its designs. This study focuses on effective parameters in determining the decision variables related to the objective function of optimization concrete and introduces a set of optimization techniques; finally, based on the simplex method, the study presents the highly optimized mixing amounts of each self-consolidating concrete component such as cement, water, coarse and fine aggregates, superplasticizer, and powder, according to the strength standards. The results demonstrate that the optimization method selection depends on the objective function, decision variables, and constraints and has a significant impact on the calculation of concrete mix design. Besides, the component''s value parameter poses a large influence on the compressive strength of concrete.

Today for seismic behavior of structures, types of nonlinear static and dynamic analyzes are rapidly expanding. In this study, the nonlinear static method is used to evaluate the performance based on cold formed steel frames. Since these structures are typically performed with low levels, the first mode of vibration is dominate and evaluation of these structures with nonlinear static method, moreover reducing the analysis time, analytical results are obtained almost exact. In this research, after modeling 38 frames of cold formed steel with four different types of sheathing: OSB (Oriented strand board), DFP (Douglas fir plywood), CSP (Canadian softwood plywood) and GWB (Gypsum wall board) and considering different thickness of sheathings, target displacement and lateral drift ratio are calculates for different performance assessments. The results of the study in all the specimens indicates that the linear behavior of the structure is responsive to seismic design and performance point is elastic in the structural behavior.

This paper presents the main results of a numerical investigation on the three-dimensional (3-D) strain analysis of flexible pavement structures using a coupled Finite Element-Mapped Infinite Element (FE-MIE) model. The validation and numerical performance of this model are assessed by confronting critical pavement responses with Burmister’s solution and FEM simulation results for multi-layered elastic structures. The coupled model is then efficiently utilised to perform 3-D simulations of a typical flexible pavement structure in order to investigate the impact of two tire configurations (conventional dual and new generation wide-base tires) on critical pavement response parameters. The numerical results obtained show the effectiveness and the accuracy of the coupled FE-MIE model. In addition, the simulation results indicate that, compared with conventional dual tire assembly, single wide base tire caused slightly greater fatigue asphalt cracking and subgrade rutting potentials and can thus be utilised in view of its potential to provide numerous mechanical, economic and environmental benefits.

It is of substantial importance to minimize the roof displacement between two adjacent tall buildings under severe earthquakes. To eliminate the pounding effects, critical accelerations can be used to control of the structures. One of the methods to decrease the roof displacement is using active control systems. In this paper, a steel building strengthened by a belt truss system is considered. Two different constraint conditions are used, and critical accelerations which maximize the roof displacement of the structure are obtained for each. These critical accelerations are computed by solving an inverse dynamic problem, using nonlinear programming technique, based on the available information from the recorded ground motion obtained from the site of the structure or at region with similar properties to the site of building. Finally, different number of actuators are attached to the roof and other stories of the building. It shows that the active control system can reduce the roof displacement when the building subjects to the critical excitations effectively. In addition, it can be found that these critical excitations can be used to retrofit or construct the buildings which is equipped by active control system.

The construction industry is one of the largest consumers of freshwater. Ordinary mortar mix requires clean freshwater، a resource which is expected to vastly deplete as a result of global water scarcity. Therefore، the need for an abundant alternative source is necessary – seawater. With this method، not only the environmental issues are addressed، but also the economical aspect of construction projects. Utilization of readily available materials without the need of production or treatment، such as the seawater، would greatly contribute into preventing freshwater scarcity around the world. But the high chloride content of seawater may accelerate corrosion in reinforced concrete structures. Adding reactive inorganic materials like fly ash improves the resistance against chloride penetration. However، the influence of various fly ash replacement ratios on reinforced mortar mixed with seawater needs further studies to determine applicability in the construction industry. This study reports the results of using seawater as mixing and curing water and different fly ash replacement ratios on the properties of reinforced mortars. The compressive strength، corrosion potential، corrosion current density and chloride content were the key means of measurement in determining the effects of seawater. Mortar specimens with 0%، 10%، 20%، 30%، 40%، and 50% fly ash replacement ratios and ordinary Portland cement mixed and cured with seawater and freshwater were prepared. Cylindrical specimens were prepared for compressive strength while rectangular prism specimens of size 4 cm x 4 cm x 16 cm were used for corrosion monitoring. Ten millimeter in diameter round steel bars were suspended in the specimens with constant cover of 5 mm in order to accelerate the corrosion process. In addition، the 20% fly ash replacement specimens were also cured in seawater using full immersion or wet burlaps. Results show that using seawater as mixing water can produce comparable compressive strength as freshwater especially when cured for longer periods. A fly ash replacement ratio of 20%-30% can result to favorable strength values. In terms of corrosion، seawater mixed specimens did not yield a higher corrosion rate so long as it is cured with freshwater at longer curing period. In terms of curing processes، the use of wet burlaps can help achieve high compressive strength، low corrosion potential and low corrosion rate as it resulted to the lowest chloride content among the seawater mixed specimens.

In this study, the utilization of bottom ash as an aggregate in the production of lightweight building blocks was investigated. Pumice aggregate which was used in lightweight control mixture replaced by the bottom ash aggregate and on the other hand, cement replaced by high volume fly ash. Physical and mechanical properties of mixtures were determined after different curing regimes (standard water, in air, in oven, steam and autoclave curing) and in addition, water resistance of the mixtures was also determined. After that, microstructure of the specimens was investigated by using the scanning electron microscopy. Then, the thermal conductivity of the mixtures containing pumice and bottom ash was compared. Finally, in order to produce construction elements, prototypes of lightweight building blocks were manufactured. After these very procedures, it concludes that bottom ash is a good alternative for pumice aggregate in producing lightweight building blocks.

The paper presents a numerical study of wind pressure on the low-rise hip-roof building by varying the roof pitch using computational fluid dynamics (CFD). A Texas Tech. University building models with hip roof, reduced at a geometric scale of 1:50 were numerically simulated for the present study. Various hip-roof building models of different roof pitches as usually used in different parts of the world, such as, 15°, 20°, 30° and 40° were selected with different wind angle attack i.e. 0°, 45° and 90°. The numerically computed wind pressure coefficients on the roof of the hip-roof buildings were compared with the wind-tunnel results. Two RANS (Reynolds Averaged Navier-Stokes) turbulence models such as the Standard 𝑘−𝜀 (SKE) and the Renormalization group 𝑘−𝜀 (RNG-KE) were adopted in this study keeping in mind the computational resources available.Result shows that roof pitch does affect the magnitude of wind pressures coefficients but the pattern almost remains same. The model with roof pitch 30° amongst the various models was found to have maximum wind pressure. It was also found that the results obtained using the CFD turbulence models and the wind-tunnel data are in good agreement with in certain limit.

In geological point of view, part of Bangladesh, i.e. Sylhet is situated in high seismic zone. But still there is a lack of information on earthquake vulnerability assessment in a particular type of infrastructure like roads, bridges, water supply system etc. In this research work the probable damage scenario on road network has been carried out based on RADIUS and liquefaction method. 25.14km major roads of this city has been considered for vulnerability assessment where the major roads will experience different MMI intensity in case of recurrence of the Srimangal earthquake (M=7.6). According to RADIUS method 19.29% of total 25.14 km road will be damaged. A liquefaction map has been used to understand the relative potential damage of the roads as RADIUS method cannot identify the damage locations. This study will help to understand the actual earthquake damage scenario on the road network of Sylhet city and a possible improvement on earthquake management strategy for the above discussed road network can be considered by the respective authority.

The concept of reducing the damaging effects on structure during earthquake by introducing some type of support that isolates structure from the shaking ground is a well-known method, named as base isolation technique. The isolation system reduces the effects of an earthquake by essentially isolating the superstructure and its contents from potentially damaging ground motion. In case of base isolated system the behavior of system mainly depends on type of base isolators and their contact with the superstructure and substructure. In the present work, the contact analysis have been performed which is highly nonlinear and required significant computational efforts following the points on one surface relative to lines or areas of another surface. The dynamic time history analysis has been performed on single storey masonry building, which is modeled and analyzed using ANSYS.

Within minutes of shaking, the earthquake reveals the vulnerabilities of building structures, households, populace, and of a country. It acknowledges the influence of prevailing culture and way of life, on the capacity of the commonality to be preparedness for seismic hazard. Identifying buildings, whether having vulnerability or not is of critical importance both for reliable loss estimation as a result of an expected earthquake and setting priority criteria for strengthening of those buildings in order to save life and property. Few selected building stocks of Bhubaneswar Municipality (ward-7, ward-8, and ward-40) of Odisha State in India, were considered for damage evaluation corresponding to different construction typologies and soil characteristics. The RVS scores were correlated with damage potential. A total 2624 number of buildings were assessed during walk down survey. It was estimated that, a detail analysis needs to be performed on 890 buildings for calibrating RVS score but special attention should be given to 283 number of buildings with RVS score less than 0.7 as these buildings have the high probability of heavy damage.