Journal of Civil Engineering Researchers

Crack analysis and modeling in concrete beams reinforced with FRP composite sheets

Amir Nazarinejad — 2023-05-07

In this article using the principles and relationships governing fracture mechanics and finite elements cracking in the first mode for reinforced concrete beams reinforced with FRP sheets are analyzed and modeled. In this method to simulate the crack in reinforced beams, the relations for determining the stress intensity coefficients with the presence of rebars and reinforcement sheets are developed. Here, it is assumed that a composite sheet is completely bound to the bottom surface of the beam under pure bending moment. In the proposed method beam components are divided into two categories, including components without cracks and components with cracks. In components without cracks, relations, equations, and the conventional stiffness matrix governing the beam are used, taking into account the changes in the moment of inertia caused by the presence of reinforcements and FRP sheets. In the finite component with a crack, the crack profile is simulated by creating a geometric defect in the beam section. So that the reduction in the hardness of the component with a crack is equivalent to the change in the dimensions of the discontinuity. Here, the changes in the hardness of the cracked component are calculated and presented as a function of the modified stress intensity coefficients. To ensure the correctness and accuracy of the presented method, all the analyzes are implemented in Abaqus software. The comparison of the obtained results shows that the presented method is a suitable method for the analysis of reinforced concrete structures resistant to cracking. So that it can be extended and developed for other models with proper accuracy.

Investigating the effect of using Multi-Level Yielding Pipe Damper dampers in steel structures under earthquake force in the horizontal direction

Lobat Hosseinzadeh — 2023-05-07

Multi-level Pipe Damper (MPD) recently proposed by the authors is a passive control device to reduce the seismic vibration. In this research, seismic response of steel structures equipped with MPD is studied. To evaluate the effects of the proposed damper, typical 8 story steel buildings are modeled and their seismic responses under three earthquake excitations are investigated using dynamic nonlinear time-history analyses by ETABS program. Results show the effectiveness of MPD to altering the seismic response of the structures. Moreover, using MPD decreases the structural and nonstructural damages noticeably by limiting the inter story drifts because of the secondary hardening branch of force-displacement respectively proving the effectiveness of the proposed damper as a retrofitting technique for structures at high seismic risk areas.

Investigating the implementation and performance of architecture in zero energy buildings in order to producing passive energy

ghasem azizi — 2023-05-07

Challenges in recent decades for humans and the rapidly changing planet. The increase in pollution and difficult access to energy despite the problems of war and political and economic disputes between countries and the rapid decrease in the amount of energy in the world, which with this growth rate, is a tangible danger for the whole world. It prompted scientists to look for new methods of energy production and consumption. In this article, we are looking for a topic of such projects, which are called zero energy buildings. As it is understood from the name of this project, the result of all energy consumption and production in these buildings must be zero or the energy production of the building should be more than its consumption, which is the concept of energy related to all the energy in the building such as thermal, electrical and ... which should be considered in the initial calculations and construction. For this purpose, this research, which is a descriptive analytical research, was conducted using library resources and electronic books and articles. We will review the execution and performance of architecture in zero energy building and concepts related to passive energy and building orientation for energy production, architectural components and materials of zero energy building, review the economic approach and leading challenges, construction and operation in connection with zero energy building. The results obtained from this research, zero energy buildings are faced with upcoming challenges such as technical knowledge, efficient and trained staff, and existing laws and regulations. Accordingly, the need to reduce energy consumption and optimize it is felt more and more. Zero energy buildings are the best solution to moderate energy consumption in housing. But reaching this goal has basic and fundamental needs that must be met.

Geometric optimization of stepped spillways using genetic algorithm

pouria niknafs — 2023-05-07

Recent advances in technology have created wide possibilities for building large dams, reservoirs and canals. These advances require the development of design and construction methods, especially for systems that can discharge sufficient flood. Shots and overflows are designed in such a way that no major damage is caused to the structure itself or to the surrounding environment to pass large flows through a hydraulic structure. During the flow of water over the spillway, it is necessary to consume some energy in order to prevent damage to the toe of the dam and its surroundings and finally to the dam itself. In this research, a method was presented to optimize the geometric parameters of the stepped overflow. For this purpose, using laboratory model data (275 tests in total). And the use of strong statistical software WEKA and MATLAB software obtained a formula to predict the amount of energy consumption. This formula was given to the genetic algorithm as an objective function. Entering the Yc/Hdam parameter, which includes both the flow rate and the total height of the dam, and the desired energy consumption value, this program is optimized by genetic algorithm and obtains the optimal number, length and width of steps. The results of this research show that: with the increase in flow rate, the amount of maximum energy consumption decreases, and with the increase of the head slope at a constant flow rate, the number of optimal steps for equal energy consumption increases.

Seismic Assessment of Combined Effects of Knee Bracing and Dog-bone Connections in Dual Moment Frame Systems for Tall Steel Structures

Ali Zahmatkesh — 2023-05-07

The growing population and urbanization have led to an increasing interest in constructing tall buildings, particularly in large cities. However, the frequent occurrence of earthquakes worldwide has necessitated the development of systems with high ductility and sufficient lateral stiffness. The special dual system of moment frame with bone connections and knee bracing systems are two examples of such systems. In this study, the seismic behavior of these two systems in combination with tall structures was investigated. Ten, thirteen, and sixteen-story frames with four different combinations of bone joints and knee bracing were analyzed using ETABS software. Linear and nonlinear static (pushover) analyses, as well as linear and nonlinear dynamic (time history) analyses, were conducted. Seismic parameters were then calculated for each case and compared. The results emphasized the importance of considering multiple factors and coefficients when evaluating the seismic performance of structures.

Case Study of Mechanically Stabilized Earth (MSE) Retaining Wall Failure in the State of Tennessee; Recommendations for Future Design and Constructions

Hossein Alimohammadi — 2023-05-07

This study presents an investigation into the failure of a Mechanically Stabilized Earth (MSE) retaining wall in Tennessee, USA. The wall was constructed to support an embankment development, but it failed catastrophically, causing damage to the road and posing a significant safety risk to the public. The investigation involved a comprehensive site visit, field data collection, laboratory testing, and numerical modeling. Our investigation revealed that the failure of the retaining wall was caused by inadequate construction practices. Specifically, the wall was not constructed in accordance with design specifications, and the backfill material used was not properly compacted. The construction issues resulted in the differential settlement of the wall, which ultimately caused it to fail. Based on our findings, we propose a set of recommendations for the design and construction of future retaining walls in similar geotechnical conditions. The recommendations include the proper selection and use of backfill material, proper compaction of backfill, and adherence to design specifications. The results of this study are expected to contribute to the development of improved design standards and construction practices for MSE retaining walls in Tennessee and other regions with similar geotechnical conditions.