Journal of Rehabilitation in Civil Engineering
Volume:10 Issue: 4, Autumn 2022

Accidents from heights are rampant and are rising day by day, with a higher number of injuries and deaths recorded in the construction industry. Some of the impacts of these incidents are the characteristic nature of the construction sector; unfailing deadlines to be met, environmental conditions during construction, natural and man-made disasters, lack of skilled manpower, undue gain over the provision of the best materials for construction. This paper gives an account of investigations of 100 scaffolding structures erected on-site in South East of Japan in terms of conformity with safety guidelines specified by the Japan International Centre for Occupation safety and health (JICOSH). Different kinds of hazards associated with falls from heights as well as the possible collapse of scaffolding due to human error/negligence and structural problem were also collated randomly from different construction and rehabilitation sites and are presented. Qualitative appraisal of conditions of some scaffolding components such as bracing, guardrails, platforms, struts and dresses, etc., which are categorized into standardized and non-standardized operations were done. According to the investigation, the most significant factor influencing the scaffold accident is structural safety, particularly the improper use of clamps and connectors which are critical elements on site. It is indispensable that trained personnel are hired to carryout scaffolding operation for effective safety.

Recent studies showed that the inelastic seismic response of irregular structures can significantly differ from regular structures. Irregular distribution of mass in elevation is regarded as a structural irregularity by which the modes with high energy levels are excited and occasionally prevents the structure from developing nonlinear deformations and causes some unpredictable damages in structural elements. In this study, seismic reliability and risk assessment of a non-code-conforming concrete building reinforced by plain bars is investigated with consideration of the vertical mass irregularity effect. The framework of this study is based on the determination of fragility via incremental dynamic analysis (IDA). The analyses are carried out on a reference 3-story multi-bay 3D structure modeled in Opensees software. Seismic risk assessment for the complete collapse limit state is evaluated by integrating the site hazard and the structural fragility curves. Also, a relatively simple and efficient nonlinear model based on the experimental behavior of substructures reinforced by plain bars is used to simulate pre- and post-elastic behavior buildings. The results indicated that the effects of vertical mass irregularity of the building have almost significant effects on the represented building's fragility curve parameters and seismic reliability of the represented buildings. Probabilities of occurrence for the irregular bottom and median story are about 1.51 and 1.6 times of the building with regular mass distribution.

The application of concrete paving block of nickel slag waste (NSW) to develop low-cost construction materials attracts researchers worldwide owing to the high pessimistic environmental impact of the nickel ore processing industry. It has mild and hard properties which are suitable for the fabrication of paving blocks. This study presents optimization NSW mixed with stone ash for the practical manufacture of concrete paving blocks (CPB). It was prepared in a small aggregate by using disk mill process, then printed by using a mold size of 1200 cm3 with each variation of the composition. Based on these results, we discover the different compressive strength (CS) from CPB which is compared with the Indonesian standard (SNI). Sample D has excellently fabricated with a composition ratio of 1:1:1:1. It is evident from the results of testing CS and water absorption (WA) with a value of 385.00 Kg/cm2 and 4.58%, respectively; both values indicate an appropriate product for the city roads. Meanwhile, sample A represents a standard method that is usually applicable for the sidewalk, and samples B and C also have high durability representing the usage for parking areas.

Brick infill walls are one of the most common types of nonstructural elements used for exterior enclosures as well as interior partitions in steel frame buildings. The recent earthquakes have shown that damage to masonry infill walls may cause danger for human lives and dramatically affects economic losses. The damage estimation of masonry infill walls and the effects within the corresponding consequences of the performance-based earthquake engineering need fragility functions. The procedure implemented in this study is based on incremental dynamic analyses of two models, i.e. with and without brick infill walls. The primary objective is to develop fragility curves that permit the estimation of damage in masonry infill walls. Comparative analyses were conducted among the models considering four damage levels. The increase in the height has reduced the probability of damage to infill walls, so there was slight damage in drifts less than 3%. Therefore, with increases in stiffness, the probability of damages to the infill walls will increase. The fragility curves obtained by HAZUS show that there is a negligible variation in the infill walls seismic fragility estimated by the number of bays.

A host of great historical earthquakes from the Himalayas and Northeast India reportedly triggered liquefaction with the surface manifestation of sand boil, ground subsidence and lateral spreading in West Bengal and its capital city Kolkata located in the alluvium-rich Ganga-Brahmaputra river system, thus presenting a strong case towards systematic liquefaction potential analysis for this terrain using multivariate techniques based on a large Geophysical and Geotechnical data base. An integrated computational protocol has provided site classification of the terrain following standard nomenclature and its characterization in terms of absolute and generic spectral site amplification through equivalent linear/ non-linear geotechnical response spectral modelling as an intermediate step towards Liquefaction Potential and Risk assessment of the region. The large Geotechnical database is used for estimating Cyclic Stress Ratio (CSR) and Cyclic Resistance Ratio (CRR), which further delivered Factor of Safety (FOS), Liquefaction Potential Index (LPI), Probability of Liquefaction (PL), and Liquefaction Risk Index (IR) in the State and its capital Kolkata. The State including Kolkata have been classified into ‘Severe’, ‘High’, ‘Moderate’ and ‘Non-liquefiable’ zones based on LPI distribution while the liquefaction risk map classified the terrain into ‘Low (IR ≤20)’, ‘High (20<IR≤30)’ and ‘Extreme (IR>30)’ Risk Zones. An intensely liquefiable stratum with FOS<1 is identified in the 5-15m depth region consisting of coarse-grained variants of sand, silty-sand and clayey-silty sand with an approximately 0.5-12.7m deep groundwater condition. An understanding of the liquefaction potential and its associated risk will act as catalyst in reducing structural vulnerability of the terrain by improving sediment strength.

Considering the dependency of control algorithms to the structural dynamic properties that are affected by soil structure interactions (SSI), the investigation of SSI effect on different control methods has gained great importance. Backstepping design as a recursive lyapanov-based method is one of the powerful active control approaches. However, the effect of soil structure interaction on it has not yet been investigated. This paper studies the performance of backstepping design on mitigating the seismic response of a building structure subjected to base excitations, considering the SSI effect. For this purpose, the SSI model equations were entered in the control algorithm and various shear wave velocities were considered to demonstrate the performance of backstepping control design on soft and stiff soil. According to the numerical results, for structures rested on stiff soil, the variations in the responses of controlled structure caused by SSI is negligible. However, in the case of soft soil, SSI effects cause noticeable changes in dynamic responses of controlled structure that cannot be ignored.

Many structures exhibit non-orthogonal systems irregularity based on architectural design, which is a type of torsional irregularity. This paper evaluates the inelastic response of multi-story steel moment resisting frames with this type of irregularity. A parametric study is carried out on six building models exhibiting coupled behavior in lateral and torsional response with various degrees of torsional irregularity. Current code regularity limits for structures appear to be based on engineering judgment rather than on quantitative analyses, which indicates that these limits need to be investigated for different structural systems with different types of irregularities. Another goal of this paper is the evaluation and comparison of the response modification factor values of steel moment resisting frames with non-parallel systems irregularity derived by pushover analysis, as well as nonlinear time history analysis. A new torsional irregularity coefficient is proposed based on the response spectrum analysis results. It is shown that it is essential to undertake nonlinear dynamic analysis to design some structures with high irregularity in plan and to capture nonlinear mechanisms due to non-parallel systems irregularity.

Wind-induced loads are largely dependent upon the exterior shape of buildings, and one highly effective procedure to mitigate them is to apply aerodynamic shape modifications in the aerodynamic optimization procedure (AOP). This study presents the framework of an AOP for shape modifications of the trilateral cross-section tall buildings. The AOP is comprised of a combination of multi-objective optimization algorithm named non-dominated sorting genetic algorithm II (NSGA-II), artificial neural networks, and computational fluid dynamics. The building shape is designed based on the geometric description of its vertical and horizontal profile using seven geometric parameters (design variables) to apply different types and sizes of modifications. In addition, the mean moment coefficients in drag and lift directions are considered as the objective functions. The proposed procedure investigates the effect of the three types of modifications including varying cross-section sizes along the height, twisting, and curved-side on the reduction of objective functions. Finally, a set of optimal building shapes is presented as the Pareto front solutions, which enables the designers to select the optimal shape of the building with additional considerations. The results indicate the high capability of the proposed framework to make appropriate use of various aerodynamic modifications in order to upgrade the aerodynamic performance of the trilateral cross-section tall buildings.

Resilient modulus (Mr) of subgrade soils is considered as one of the most important factors for designing flexible pavements using empirical methods as well as mechanistic-empirical methods. The resilient modulus is commonly measured by a dynamic triaxial loading test, which is complex and expensive. In this research, back-propagation artificial neural network method has been employed to model the resilient modulus of clayey subgrade soils based on the results of the cone penetration test. The prediction of the resilient modulus of clayey subgrade soil can be possible through the developed neural network based on the parameters of the cone tip resistance (qc), sleeve friction (fs), moisture content (w), and dry density (γd). The results of the present study show that the coefficients of determination (R2) for training and testing sets are 0.9837 and 0.9757, respectively. According to the sensitivity analysis results, the moisture content is the least important parameter to predict the resilient modulus of clayey subgrade soils, while the importance of other parameters is almost the same. In this study, the effect of different parameters on the resilient modulus of clayey subgrade soil was evaluated using parametric analysis and it was found that with increasing the cone tip resistance (qc), the sleeve friction (fs) and the dry density (γd) and also with decreasing the moisture content (w) of soils, the resilient modulus of clayey subgrade soils increases.