Typical Frame Structure Research Articles

Automated architectural spatial composition via multi-agent deep reinforcement learning for building renovation

This paper focuses on utilizing deep reinforcement learning technology to explore how to achieve automated architectural space composition under established built environment conditions to address the extensive demands of old building renovation. A reinforcement learning platform has been develop0065d, centered around the multi-agent deep deterministic policy gradient (MADDPG) algorithm. The paper leverages functional blocks as agents within Grasshopper to simulate existing architectural structures and their interactions, establishing a task-based reward system to guide the design process. Furthermore, data exchange between algorithmic and modeling software is facilitated through UDP communication. Training results using typical frame structure spaces indicate a significant increase in cumulative rewards around the 650,000th training step, effectively achieving the given design tasks. The paper demonstrates the potential of automated architectural space composition methods, based on deep reinforcement learning, to enhance design efficiency, optimize spatial arrangements, and promote human-machine collaborative design in building renovations.

Comparative analysis of track damping effect of structure jointly constructed by subway tunnels and high-rise buildings

The joint construction of subways and other public buildings is a relatively newer type of construction. There is little research experience in the vibration characteristics and track damping design for this type of structure. In this study, a field test was adopted to conduct site measurement analysis on the vibration response of the joint construction project consisting of a subway tunnel and a building with typical frame structures. Numerical simulation methods were also adopted to, respectively, assume the use of ordinary tracks and steel-spring floating slab tracks for the subway for the situation where the Cologne-egg high-elastic fasteners were used on the track for damping purposes. Comparisons were performed to analyze the difference in the system vibration response between three different types of track. The results showed that the high-elastic fastener track and floating slab track both have a certain degree of damping effect compared with an ordinary track. Specifically speaking, the former has a damping advantage for frequency bands below 20 Hz, while the latter has the advantage for frequency bands above 20 Hz under the impact of the structural vibration characteristics for this joint construction. For this jointly construction structure, affected by the natural vibration characteristics of the structure, the natural frequency of the floating slab track is within 4 ∼ 10 Hz, and the similar vibration reduction effect can be achieved. This indicates that the structural vibration characteristic of the jointly constructed structure is an important factor determining the appropriate natural frequency of the floating slab track.

Prior knowledge‐infused neural network for efficient performance assessment of structures through few‐shot incremental learning

AbstractStructural seismic safety assessment is a critical task in maintaining the resilience of existing civil and infrastructures. This task commonly requires accurate predictions of structural responses under stochastic intensive ground accelerations via time‐costly numerical simulations. While numerous studies have attempted to use machine learning (ML) techniques as surrogate models to alleviate this computing burden, a large number of numerical simulations are still required for training ML models. Therefore, this study proposes a prior knowledge‐infused neural network (PKNN) for achieving efficient structural seismic response predictions and seismic safety assessment at a low computation cost. In this approach, first, the prior knowledge inherently within a theoretical dynamic model of a structure is infused into a neural network. Then, by utilizing the few‐shot incremental learning technique, this network would be further fine‐tuned by only a few numerical simulations. The resulting PKNN would be able to accurately predict the seismic response of a structure and facilitate seismic safety assessment. In this study, the PKNN's accuracy and computational efficiency are validated on a typical frame structure. The results revealed that the proposed PKNN could be used for accurately predicting the structural seismic responses and assessing the structural safety under a low computational cost.

Investigation of Effect of Wind-Induced Vibration on Typical Frame Structures on the Open Decks of Large Cruise Ships Based on the Subdomain Method

Due to the tall and large superstructures of cruise ships, the wind-induced vibration of frame structure on open decks cannot be neglected. This study investigated the wind-induced vibration of a typical frame structure on a cruise ship by using wind tunnel tests and numerical simulations. Wind tunnel tests were conducted to explore the simulation methods of the fluid–structure interaction (FSI). CFD simulations were performed to obtain the wind field data of the entire ship, which was utilized as an input for the open deck through the subdomain method. Subsequently, wind-induced vibration simulations of the guide rail frame structure on the open deck was carried out under various wind conditions. The results revealed that employing the turbulence model SST k-ω had a good agreement with the experimental data. The entire ship’s CFD results have a significant impact on the subdomain’s wind-induced vibration results. The vibration frequency of the guide rail frame structure was mainly concentrated between 0.8–10.1 Hz. The most unfavorable conditions appear at the wind attack angles of 0° and 120°. This study can provide some instructive insights for the prediction of wind-induced vibration and control of typical structures on the open decks of large cruise ships.

Dynamic Analysis of Bottom Subsidence of Benthic Lander

The geomorphology of the deep-sea environment is complex, including seamounts based on hard rocks and seabeds based on rare soft sediments. Therefore, the frame of the benthic lander needs to be shock and subsidence resistant. In this paper, the static model of the benthic landers is established to analyze their force and deformation under different loads, and the dynamic model of the benthic landers is established to derive the motion equation of their landing on the sediment. Some typical frame structure of benthic landers is analyzed with the ANSYS Workbench static analysis module and Explicit Dynamics module. The sea trial data of the benthic lander prototype were analyzed to provide reference for the design and application of the lander’s framework. The research done in this paper provides the basis for the impact resistance design and bottom speed design of the benthic lander and proposes a simulation analysis method for the calculation of the bottom subsidence of the benthic lander.

Residual Axial Behavior of Restrained Reinforced Concrete Columns Damaged by a Standard Fire

A simplified procedure to predict the residual axial capacity and stiffness of both rectangular and circular reinforced concrete (RC) columns after exposure to a standard fire provides the means to replace the current descriptive methods. The availability of such a procedure during the design phase provides engineers with the flexibility to come up with better designs that ensure safety. In this paper, finite difference heat transfer and sectional analysis models are combined to determine the axial behavior of RC columns with various end-restraint conditions at different standard fire durations. The influence of cooling phase on temperature distribution and residual mechanical properties is considered in the analysis. The ability of the model to predict the axial behavior of the damaged columns is validated in view of related experimental studies and shown to be in very good agreement. A parametric study is then conducted to assess the axial performance of fire-damaged RC columns. A procedure is proposed to determine the residual strength and stiffness of fire-damaged RC columns in typical frame structures.

Optimization of an RC frame structure based on a plastic analysis and direct search of a section database

For the optimum design of RC frame structures, a simplified but effective discrete optimization algorithm is introduced in this paper. To determine the member force to be based on the design procedure, a plastic analysis considering the sequential development of plastic hinges in beams and columns up to the point of collapse is conducted, with the subsequent optimum design then devised via a direct search method. The construction of a database for predetermined discrete RC sections and interconnections of all design variables in an RC section with a single design variable associated with the section identification number makes it possible to adopt the direct search method instead of a sophisticated mathematical approach that includes many complicated descriptive functions pertaining to RC beams and columns. The use of the plastic analysis also reduces the maximum member force through moment redistribution, and the direct search method makes it possible to find a true optimum section regardless of the assumed initial section. The efficiency and applicability of the introduced algorithm are verified through correlation studies for typical frame structures. In particular, given that all design criteria in design codes and practical limitations required when undertaking the actual design are already considered while determining RC sections in the section database, the obtained results can be directly applied to the creation of designs. In advance, the use of the obtained optimum design results as initial sections in the preliminary design stage will greatly reduce the number of design steps for the determination of RC sections.

JUSTIFICATION OF FILLERS USING IN THE BEARING STRUCTURES COMPONENTS OF FREIGHT CARS

To reduce the load on the freight cars frames under operational conditions, it has been suggested that to use fillers in their components. Fillers using is advisable in the most loaded elements of the bearing structure, namely, the spine beam. Therefore, a necessary condition for filler using in the spine beam is the creation of its closed structure. The dynamic load of railcars was carried out, taking into account the proposed provisions. Calculations have shown with filler using, the maximum accelerations acting on the bearing structures of wagons are 4% lower than those accelerations obtained for bearing structures without fillers. The results of determining the main strength indicators of bearing structures of freight cars are presented, taking into account the fillers using in their components. It has been established that the strength of the frames of the considered types of wagons under the main operating conditions is ensured. At the same time, the maximum equivalent stresses in the bearing structures of wagons are 4-9% lower than those in typical frame structures. The conducted research will contribute to the creation of innovative structures of rolling stock and reduce the cost of its maintenance work in operation.

Thickness-based subdomian hybrid cellular automata algorithm for lightweight design of BIW under side collision

Body-in-white (BIW) is a typical frame structure formed by a great many thin-walled structures, and the optimal design of its lightweight and crashworthiness is a typical nonlinear dynamic response optimization problem with multiple design variables. Here, we propose a thickness-based subdomain hybrid cellular automata (T-SHCA) algorithm to solve the lightweight design of BIW under side collision, in which there are two loops: one is the outer loop to conduct crash finite element analysis, calculate output responses, and update internal energy density (IED) and target mass; the other is the inner loop to adjust cell thicknesses according to IEDs of current cell and its neighboring cells to make the actual mass of current cells converge to target mass. The concept of "subdomain cellular automata (SCA)" model was introduced, so that the T-SHCA can solve nonlinear dynamic response optimization in discrete and separated design spaces. The step IED target update rule and the cell thickness update rule based on a PID control strategy were implemented in the inner loop to improve the global optimal solution search capability and the robustness of the proposed algorithm, respectively. The thicknesses optimization of a BIW was carried out by the proposed method and a parallel efficient global optimization algorithm to verify its convergence and efficiency. The results show that the T-SHCA algorithm can be implemented to effectively solve nonlinear dynamic response structural optimization problem with many thickness variables in discrete and separated design spaces.

Structural model updating based on metamodel using modal frequencies

Modal frequencies are often used in structural model updating based on the finite element model, and metamodel technique is often applied to the corresponding optimization process. In this work, the Kriging model is used as the metamodel. Firstly, the influence of different correlation functions of Kriging model is inspected, and then the approximate capability of Kriging model is investigated via inspecting the approximate accuracy of nonlinear functions. Secondly, a model updating procedure is proposed based on the Kriging model, and the samples for constructing Kriging model are generated via the method of Optimal Latin Hypercube. Finally, a typical frame structure is taken as a case study and demonstrates the feasibility and efficiency of the proposed approach. The results show the Kriging model can match the target functions very well, and the finite element model can achieve accurate frequencies and can reliably predict the frequencies after model updating.

Fast Accurate Beam and Channel Tracking for Two-Dimensional Phased Antenna Arrays

The sparsity and the severe attenuation of millimeter-wave (mmWave) channel imply that highly directional communication is needed. The narrow beam produced by large array requires accurate alignment, which is difficult to achieve when serving fast-moving users. In this paper, we focus on accurate two-dimensional (2D) beam and channel tracking problem aiming at minimizing exploration overhead and tracking error. Using a typical frame structure with periodic exploration and communication, a proven minimum overhead of exploration is provided first. Then tracking algorithms are designed for three types of channels with different dynamic properties. It is proved that the algorithms for quasi-static channels and channels in Dynamic Case I are optimal in approaching the minimum Cramer-Rao lower bound (CRLB). The computational complexity of our algorithms is analyzed showing their efficiency, and simulation results verify their advantages in both tracking error and tracking speed.

Application of the internal substructure method for seismic wave input in structural dynamic analysis considering SSI effect

A new internal substructure method for seismic wave input in soil-structure systems was proposed very recently. This method simplifies the calculation of equivalent input seismic loads, and avoids the participation of artificial boundaries in the process of seismic wave input. In this study, we introduce the application of the internal substructure method in the structural seismic analysis considering soil-structure interaction (SSI). A typical frame structure is taken as the example, and the effect of SSI on the structural dynamic response is studied.

Evaluating the ductility characteristics of self-centering buckling-restrained shape memory alloy braces

Recently, self-centering earthquake resistant systems have attracted attention because of their promising potential in controlling the residual drifts and reducing repair costs after earthquake events. Considerable portion of self-centering research is based on using short-segment superelastic shape memory alloy (SMA) braces as strengthening technique because of the lower modulus of elasticity of SMA in comparison with that of steel. The goal of this study is to investigate the ductility characteristics of these newly proposed short-segment SMA braces to evaluate their safety levels against fracture failures under earthquake loading. This goal has been achieved by selecting an appropriate seismic performance criterion for steel frames equipped with SMA braces, defining the level of strain capacity of SMA and calculating the strain demands in the SMA braces by conducting a series of pushover and earthquake time history analyzes on typical frame structure. The results obtained in this study indicated the inability of short-segment SMA designs to provide adequate ductility to the lateral resistant systems. An alternative approach is introduced by using hybrid steel-SMA braces that are capable of controlling the residual drifts and providing the structure with adequate lateral stiffness.

Drift-sensitive non-structural damage to masonry-infilled reinforced concrete frames designed to Eurocode 8

Post-earthquake surveys indicate that losses come from non-structural damage more than from structural damage. Current performance-based design would prevent excessive non-structural damage as well, but the effectiveness of relevant code provisions has not been assessed in depth. This study investigates the drift-sensitive non-structural damage to reinforced concrete frame buildings complying with the European seismic code. Damage to non-structural unreinforced masonry infill walls in contact with the frame is quantified in terms of numerical fragility curves with the same quantities considered in the design: the peak ground acceleration measures the seismic intensity; the peak value of the interstorey drift ratio is the damage index. The methodology for the fragility computation is described in detail. Peculiar is the use of probabilistic parameters of the drift capacity coupled to the fuzziness in the damage state. The drift demand is estimated by member-by-member modelling of typical frame structures and non-linear time–history analyses under spectrum-compatible artificial accelerograms. The kind of the infills and their modelling, the number of storeys, the ground type, and the ductility class are covered. Modelling the infills results to be essential. Any code-compliant verification is on the safe side, but the margin appears to be inconsistent among the frames under consideration. Furthermore, there is one case where occupancy appears to be not ensured despite the code verification is satisfied. The effect of the number of storeys may be misrepresented. The ductility class may be unimportant, however the damage seems to be correlated with the likely strength.

Probabilistic Evaluation of Effects of Column Moment Magnification Factor on Seismic Performance of Reinforced Concrete Frames

Enhancing column flexural capacity is the key measure in seismic capacity design to achieve strong column-weak beam failure mode and determinate the probabilistic relation between column moment magnification factor (CMMF). In the paper the effects of column moment magnification factor on seismic performance of reinforced concrete (RC) frames are evaluated to limit the occurrence probability of column-hinging failure modes within an acceptable tolerance. Monte Carlo simulation methodology is used to calculate the probability of drift demand exceeding drift capacity of two typical frame structures with consideration of major uncertainties. And fragility curves are constructed to obtain the relationship between CMMF and probability of structural damages and assess the seismic vulnerability of RC frame structures. Results show that the seismic performance of RC frame structures can be significantly enhanced by improving CMMF. The CMMF is required to be equal to or greater than 2.0 to achieve acceptable probability of exceedance of column-hinging failure mode.

Topology optimization of frame structures with flexible joints

A method for structural topology optimization of frame structures with flexible joints is presented. A typical frame structure is a set of beams and joints assembled to carry an applied load. The problem considered in this paper is to find the stiffest frame for a given mass. By introducing design variables for beams and joints, a mass distribution for optimal structural stiffness can be found. Each beam can have several design variables connected to its cross section. One of these is an area-type design variable which is used to represent the global size of the beam. The other design variables are of length ratio type, controlling the cross section of the beam. Joints are flexible elements connecting the beams in the structure. Each joint has stiffness properties and a mass. A framework for modelling these stiffnesses is presented and design variables for joints are introduced. We prove a theorem which can be interpreted as the fact that the removal of structural elements, e.g. joints or beams, can be modelled by a small strictly positive material amount assigned to the element. This is needed for the computations of sensitivities used in the applied gradient based iterative method. Both two and three dimensional problems, as well as multiple load cases and multiple mass constraints, are treated.

Modal analysis of damaged structures by the modified finite element method

The classical 3D beam element has been modified and developed as a new finite element for vibration analysis of frame structures with flexible connections and cracked members. The mass and stiffness matrices of the modified elements are established basing on a new form of shape functions, which are obtained in investigating a beam with flexible supports and crack modeled through equivalent springs. These shape functions remain the cubic polynomial form and contain flexible connection (or crack) parameters. They do not change standard procedure of the finite element method (FEM). Therefore, the presented method is easy for engineers in application and allows to analyze Eigen-parameters of structures as functions of the connection (or crack) parameters. The proposed approach has been applied to calculate natural frequencies and mode shape of typical frame structures in presented examples.

１次元４次モーメント近似による構造物の信頼性解析

This paper proposes a method to evaluate the reliability of structures by using moments up to the fourth-order, which are the minimum number of terms reflecting the shape of probability distributions. The one-dimensional cumulative distribution function (c.d.f.) is asymptotically expanded into Edgeworth's series expressed in terms of moments up to the fourth-order. The expanded c.d.f. gives a negative value at the tail of the distribution for some cases of the combination of skewness and kurtosis. Modification is made in the approximation formula to remedy this draw-back, thus making it possible to evaluate any general non-Gaussian c.d.f.The proposed method is applied to the reliability analysis of typical frame structures where the random variables follow non-Gaussian probability distributions. It is shown that the proposed method is very effective for evaluating quantitatively the effects of probability distributions on the resulting structural reliability or failure probability.