Current Issue : April-June Volume : 2023 Issue Number : 2 Articles : 5 Articles
In response to housing shortages in densely inhabited urban areas, there is a search for structural engineering solutions for serial and modular construction. Prefabricated concrete columns can make an important difference. Using industrial manufacturing processes, it is possible to produce highly loadable, durable and true-to-size columns that enable accelerated construction progress and dismantling or reuse of the components at the end of the structure’s economic life. However, there are challenges in designing the detachable connection between highly loaded columns due to an undesired reduction of the load-bearing capacity on the one hand and a high sensitivity to geometrical deviations on the other hand. To investigate the load-bearing and deformation behaviour of butt-jointed columns, large-scale component tests as well as three-dimensional numerical analyses using the finite element method were carried out. The analyses show that measures to increase the stiffness of the joint, such as thicker steel plates, lower mortar thickness, etc., lead to an increase of the ultimate load. It could also be demonstrated that butt-jointed columns are very sensitive to unevenness of the end faces. Finally, the investigations allow first conclusions on the design and detailing of detachable compression connections between prefabricated concrete columns....
A number of factors have combined to put excessive pressure on the finite available freshwater resources. These include increasing population, rapid urbanization, industrialization, changed land pattern usage and land cover, change in the overall ecological system, and increased temperature and unscientific compromises in the extraction of water are at alarming threshold putting pressure on the finite available freshwater resources. As a result, many countries have been stressed or are at the verge of being stressed. The problem is worsened day by day by prolonged drought, unchecked discharge of untreated or partially treated wastewater to the freshwater reservoirs and lack of proper water quality control measures and management. Many initiatives such as Zero Liquid Discharge of industrial wastewater into freshwater bodies such as reservoirs, lakes, and ponds, and the use of recycled wastewater for irrigation and domestic purposes have started to be embraced as measures to put a check on the fast depleting freshwater resources for sustainable socio-economic development. The construction industry is the second largest consumer of freshwater just after agriculture. Concreting alone consumes, annually, over one trillion m3 of freshwater globally while the concept of the use of wastewater and/or recycled water in the concrete-making processes is yet to be adopted. Hence, this paper presents a general review of the current state of knowledge and practice on concrete production and curing using recycled wastewater from industrial, commercial, and domestic activities. An extensive review of the existing literature revealed that recycled water is fit for concrete production and curing purposes. The observations made are based on the assessment of wastewater quality parameters and their impacts on some selected concrete properties such as initial setting time and compressive strength. Due to scanty research on the impacts of varying concentrations of different ingredients in any questionable water on selected properties of reinforced concrete and its durability, thus, further research is recommended....
Increasing construction and demolition (C&D) waste generation has faced serious challenges in the metropolitan areas of Iran. Theobjective of this research is to present a system dynamics model for C&D waste management of Tehran. In particular, variables such as energy consumption and carbon dioxide (CO2) emissions for the city of Tehran to the horizon of 2041 are studied and predicted. Increasing the rate of construction of housing and urban infrastructure will increase C&D waste and, on the other hand, increase the demand for raw materials, which is contrary to the principles of sustainable development. The increase in quarries exploitation and the increase in C&D waste generation can reduce the buildable area of the city. The impacts of such factors are in a cyclic and systemic approach that either reinforces a destructive factor or balances the existing solution. In general, the assessment of the implementation or nonimplementation of C&D waste recycling in each city requires a system insight that examines the aspects of the subject with a systemic perspective over time. To this end, the system dynamic approach, along with the environmental and economic approach of the life cycle, can clarify the hidden dimensions of the problem. One of the important limitations of the research is the large number of variables in the model and finding reliable historical information for these variables....
The gravity-retaining wall is a common retaining structure in geotechnical engineering. The inertial load acting on the retaining wall itself (the horizontal seismic action) under earthquake conditions is one of the major loadings to be elaborately considered for the design of gravity-retaining walls.Thehorizontal seismic action of the retaining walls under seismic loading is dominated by the combination of the mass distribution of the wall body and the acceleration distribution along wall height. The mass distribution can be calculated by the wall geometry and density of the wall body. By contrast, due to the whipping effect, horizontal seismic acceleration along wall height often shows obvious amplification in relation to ground acceleration. Such a distribution of acceleration amplification is of great importance to comprehend the safe design of retaining walls. Nonvertical retaining walls, such as inclined and reclined retaining walls, are often used in practical engineering, and their dynamic responses under seismic actions will be different from those of vertical walls. This paper focused on the examination of the influence of the wall-back inclination angle of retaining walls on the dynamic acceleration distribution along wall height due to seismic actions. Dynamic responses of vertical, inclined, and reclined gravity retaining walls under various earthquake loads were tested on a shaking table system. Seismic acceleration time-history curves were recorded under different seismic waves and intensities. The influence of the wall-back inclination angle of retaining walls on the seismic effect was thus analyzed. The tested results showed that the wall-back inclination angle of retaining walls has a significant influence on the seismic dynamic response. The amplification coefficients of peak acceleration of the gravity retaining wall follow the order of the reclined type > the vertical type > the inclined type. Based on the experimental results, the amplification coefficient of peak acceleration was statistically analyzed under the commonly used risk level in engineering seismic design. A formula for the calculation of the horizontal earthquake action distribution coefficient along wall height was proposed involving the effect of the wall-back inclination angle, which might improve the existing calculation method of retaining wall design. The results of this work would guide the earthquake resistance dynamic design of retaining walls....
Cemented paste backfill (CPB) plays an increasingly important role in the mining industry due to its operational and environmental benefits. CPB is placed in the mined-out stope to form a self-supporting structure. The strength and stability of the CPB is of great concern in its engineering applications. Indeed, CPB must remain stable during the extraction of adjacent stopes to ensure the safety of the mine operations. Although significant research has been conducted on the shear properties of CPB, there are limited studies on its post-failure behavior, in particular the yield characteristics of CPB. This paper presents the finding on the post-peak and yield property of CPB. The study is conducted on three cemented contents and six stress intervals based on the mining practice and field study. The results show that CPB exhibits dilative behavior under strain softening and contractive property under strain hardening conditions. Our study demonstrates that pure frictional resistance could exceed the cohesion strength at high stress levels....
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