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The reinforcing members are often added on an existing structure to improve stiffness of the structure up to required level. In general, the design targets for the reinforcing members need to be allocated for their designs. However, since the members are additively designed, it is difficult to predict behavior of the reinforcing members and their influence on the existing structure. Therefore, allocating the design targets is challenging task, and the targets based on engineering experience and intuition can lead to the repetitive design cycles. This paper proposes a method for determining target stiffness of a reinforcing member which makes an existing structure achieve the required performances. To utilize individual models of an existing structure and the reinforcing members in a design, the system of equations of the assembled structure is decomposed by using a substructuring technique. Additional boundary conditions are imposed on the interfaces between the structure and members to ensure consistency between models, and the target stiffness of the member is defined by using the boundary conditions. The optimal target stiffness and design of the members are determined through the use of a multidisciplinary design optimization technique, analytical target cascading. This method is applied to a simple portal frame and a body-in-white with reinforcing member of a vehicle manufactured by Hyundai Motor Company. By using the optimal target stiffness, reinforcing member of any shape can be designed independently and at little cost, without access of the existing structure model.

Formula Society Automotive Engineer (FSAE) is an engineering competition for university students conducted by SAE International Organization that challenges students to build a mini-formula-style prototype car. Some factors affecting the vehicle performance are mass and torsional stiffness of the chassis. This study aims to optimize the existing competed vehicle chassis using a combination methods in Computer Aided Engineering (CAE): parametric and structural methods, which varies the dimensions, support bracing direction, and number of support bracing of frame structures. The design criteria were required to meet the competition regulations, a safety factor of more than 1.5, and a torsional stiffness to roll rate ratio of more than 6, with a specific torsional stiffness target of 48.82 – 60.08 Nm/deg/kg. In the optimization process, 30 chassis variations were tested. The S24 variation showed a significant increase in torsional stiffness and specific torsional stiffness. The S19 variation showed the most significant effect on the safety factor. At the end, the S12 chassis was selected as the lightest mass (31.125 Kg), with torsional stiffness 1,614.59 Nm/degree, specific torsional stiffness of 51.87 Nm/deg/Kg, safety factor of 1.54, and torsional stiffness to roll rate ratio of 6.31.

The energy beam section in the eccentrically braced steel frame is separated from the frame beam and configured as an independent energy-dissipating connector. This design not only concentrates the inelastic deformation within the energy beam section but also enables the replacement of damaged components after an earthquake . To investigate the dynamic performance of buckling-restrained brace(BRB) eccentrically braced steel frame with replaceable links, this paper analyzes 10 finite element models with different parameters. The effects of cross-sectional dimensions, energy-dissipating link length, stiffener spacing, and the number of floors on the acceleration response coefficient, displacement response, and base shear of the frame under dynamic loading are examined. The results indicate that the longer the replaceable link, the greater the inter-floor displacement and top-column acceleration response. A large height-to-thickness ratio and smaller stiffener spacing can effectively improve the seismic performance of the structure. When the length of the replaceable links is 1.11~1.34 times Mp/Vp, and the stiffener spacing is 0.53~0.73 times the web height, the plastic deformation of the energy beam section is sufficient, and the overall stress distribution in the steel frame and bracing system achieves the expected performance.

To ensure structural safety of the stator foundation after constructing a dismantling channel for tile removal in an underground pumped-storage powerhouse, this study investigates the stress mechanisms under extreme operating conditions. Based on finite element theory, a refined solid model is established, incorporating the wind cover, machine pier, embedded foundation plates, and connecting components, while accounting for the synergistic working mechanism between steel and concrete. The structural responses under normal operation, accidental fault-synchronizing conditions, and the most unfavorable debonding scenario are analyzed in detail. The results indicate that during normal operation, the structure remains in the elastic stage. Under fault-synchronizing conditions, although local tensile stresses near the channel exceed the tensile strength of concrete, their impact is confined to a limited area, decaying to safe levels within 0.6 m. After implementing steel plate support reinforcement measures, the structural stiffness is effectively restored. Even under the extreme assumption of complete separation between steel and concrete, the reinforcement measures still provide sufficient safety margins. This study validates the feasibility of a design approach with no top connection but with reinforcement, providing theoretical guidance and engineering references for the localized opening-reinforcement design of similar power plant structures.

This study examines the dynamic interaction problem within \"hoisting vessel-reinforcement\" systems used in vertical shafts of coal mines and ore mines with rail conductors, which operate for extended periods under challenging mining and geological conditions. Such systems typically lack roller dampers to reduce dynamic loads on the conductors. In these setups, even slight misalignments in the conductors lead to high dynamic interaction levels between the vessel and conductors, resulting in dynamic stresses within the frames of vessels or conductors, and in bracing structures that may greatly exceed fatigue crack accumulation levels in the metal of the vessel or reinforcement. This situation necessitates the development of new methods and structural solutions for reinforcement elements to secure conductors to braces and to install bracing in shaft reinforcement. The article proposes a mathematical model of the dynamics of the \"vessel-reinforcement\" system, which accounts for new types of brace-end embedding in shaft reinforcement with the ability to actively respond to dynamic load levels on the conductors. This approach aims to mitigate extreme load conditions by controlled adjustment of the system’s amplitude-frequency characteristics.

Constructing seismic seismic-resistant structures is essential to be carried out in earthquake-hazard areas. A concentrically Braced Frame System (CBF) is an earthquake-resistant structure that relies on its brace to withstand seismic loading. Seismic loading is a series of loading histories composed of high (HA) and low-amplitude (LA) loading. When this loading hits the CBF system, it will perform various values of displacement. So far, many studies have been conducted to reveal seismic performance in CBF. However, studies on CBF’s response due to the variable displacement amplitude as the representation of the earthquake is still limited. This present study observed the seismic performance, i.e., strength, stiffness, and dissipated energy, of the CBF’s brace due to the variable amplitude loading. Variable amplitude loading is the loading history composed of high and low displacement amplitude levels. The brace was made of a single steel angle, L 40.40.4, and loaded with three different variable amplitude loading. Observing the dissipated energy as the main seismic performance of CBF discloses that the specimen which is loaded by the smaller number of cycles in a block amplitude reached the highest cumulative dissipated energy in the same applied displacement. This tendency is supposed to be presented since the specimen under a smaller number of loading repetitions in a block, leads to experiencing a small effect of fatigue and increases the strength in each cycle. Confirming the failure mode disclosed that all braces presented flexural and torsional buckling.

Reinforced concrete (RC) structure design codes stipulate various design limits to prevent the brittle failure of members, as well as ensure serviceability. In the structural design of RC walls, the maximum shear strength is limited to prevent sudden shear failure due to concrete crushing before the yielding of shear reinforcement due to over-reinforcement. Despite the increase in wall shear strength provided by a compression strut, the maximum shear strength limit for walls in the ACI 318-19 Code is the same as the maximum torsional strength. Consequently, the shear strength of large-sized walls with high-strength concrete is limited to an excessively low level. The ACI 318-19, Eurocode 2, CSA-19, and JSCE-17 standards provide similar equations for estimating wall strength, but their maximum shear strength limits for walls are all different. In this study, experimental tests were conducted on nine RC wall specimens to evaluate the maximum shear strength. The main variables of the specimens were shear reinforcement ratio, compressive strength of concrete, and failure mode. The experimental results showed that the maximum load was reached after yielding of shear reinforcement, even when the shear reinforcement ratio was 1.5 times higher than the maximum shear reinforcement ratio specified in the ACI 318-19 code. In addition, the measured shear crack width of all specimens at the service load level was less than 0.42 mm (0.017 in.). The shear strength limits for walls in the current codes were compared using 109 experimental results failing in shear before flexural yielding or shear friction failure, assembled from the literature. The comparison indicated that the ACI 318-19 Code limit underestimates the maximum shear strength of walls, and it particularly underestimates the maximum shear strength of walls with high-strength concrete or barbell-shaped cross sections. Additionally, this study proposes an equation for estimating the maximum shear strength limit of walls based on the truss model. The proposed equation predicted the maximum shear strength of RC walls with reasonable accuracy. Keywords: maximum shear strength limit; over-reinforcement; reinforced concrete (RC) walls; shear failure.

In this study, the optimal seismic design of traditional and buckling-restrained braces (BRBs) 3D-reinforced concrete (R/C) buildings is compared. The optimal buildings are obtained through the non-dominated sorting genetic algorithm (NSGA-II) multi-objective technique. Unlike most of this type of studies, the complete design of the 3D frames will be obtained considering the slabs, beams, columns, and braces as variables of the algorithm that are used to calculate dead and seismic loads. For this aim, two objective functions are established: (1) the first objective function is the cost of the structural building that includes materials and construction; (2) the second is the ratio between the maximum inter-story drift and the allowable drift, which is the most common structural performance parameter used by the earthquake building codes. For the purpose of this study, several R/C buildings are designed in accordance with the Mexico City Building Code (MCBC) using NSGA-II. The results demonstrate that as the height of the R/C buildings tend to increase, the frames with BRBs are more economical having similar level of structural performance in comparison with traditional moment resisting R/C framed buildings. In addition, the application of the evolutionary technique based on genetic algorithms for structural design improves considerably the structural performance and is able to reduce the total structural cost of the buildings.

Nonlinear pushover analysis involves an extremely iterative process necessary for satisfying the design requirements of performance-based codes. This analysis also demands significant computational resources and advanced scientific efforts. In this study, we introduce a computer-based method for 2D-braced steel buildings that incorporates pushover analysis, optimization techniques, and optimality criteria methods to automatically design the pushover drift performance. An ant colony metaheuristic optimization algorithm is employed to achieve optimal performance-based designs for columns, chevron braces, and beams in steel moment frames. The initial phase includes implementing optimization codes in MATLAB and OpenSees for conducting the nonlinear static analysis of the 2D-braced steel frames. Several optimal configurations are produced for each brace and frame by addressing the nonlinear optimization problem. In the second step, a nonlinear pushover analysis is conducted in accordance with the provisions of the FEMA 356 code. This analysis takes into account constraints on relative displacement and plastic hinge rotation to ensure that the structure achieves the specified performance levels. Finally, the third step involves selecting the optimal design for each frame and subsequently plotting the pushover, drift and convergence curves for each frame and performance levels. This selection process ultimately aims to satisfy the criteria of performance-based design, including life safety, collapse prevention, and immediate occupancy, while minimizing the total weight for three 2D steel chevron frames: a 5-story, a 9-story, and a 13-story configuration.

Self-centering earthquake-resistant structures have received increased attention due to their ability to reduce post-earthquake residual deformations and, thus, repair time and cost. This stimulated the development of recentering shape memory alloy (SMA) dampers that use superelastic nitinol wires to dissipate energy and self-center the structure. However, there are still a few case studies applications on full-scale RC buildings in the literature. Moreover, general guidelines or even simplified approaches for the practical design of SMA damped braces are still lacking. This paper focuses on evaluating the effect of using self-centering shape memory alloy dampers for buckling-restrained braces applied for the seismic retrofit of a complex RC building structure. A design method originally proposed for elastoplastic dampers was implemented to size the SMA dampers to be placed on selected spans and stories of a building. The effectiveness of the design procedure was demonstrated by nonlinear time-history analyses under different sets of earthquake strong ground motions. The analysis results show that the recentering shape memory alloy bracing system is effective in limiting the maximum transient inter-story drifts and reducing the residual inter-story drifts after strong seismic events, due to its excellent recentering behavior together with its not negligible energy dissipation capacity.