Beam Frame Research Articles

Response modification factor of high strength steel frame with D-eccentric brace using improved pushover analysis method

The high-strength steel frame with D-eccentric brace presents a novel structural system that demonstrates exceptional plastic deformation capabilities when exposed to high levels of earthquake hazards. This system employs ordinary steel links with a yield strength below 345 MPa, while the frame beam and column utilize high-strength steel (yield strength above 460 MPa, such as Q460 or Q690 steel) to reduce cross-sectional dimensions while ensuring elasticity of non-energy consuming components. The resulting structure exhibits outstanding ductility and energy-dissipating capacity. The response modification factor (R), a crucial parameter in performance-based seismic design, plays a significant role in achieving appropriate and cost-effective seismic designs. Unfortunately, the 2016 edition of China's code for Seismic Design of Buildings (GB50011-2010) did not consider the concept of R and instead employed a constant value for all structural systems, which is unreasonable. Therefore, a comprehensive investigation of the R value for the high-strength steel frame with D-eccentric brace is imperative to enhance structural performance design, provide guidance for future designs, and promote the widespread implementation of this structure in seismic regions, where it exhibits superior seismic performance. This study utilizes the performance-based seismic design approach to design structures with varying numbers of stories (4, 8, and 12), link lengths (900, 1000, and 1100 mm), and different steel strengths (Q460 and Q690). An improved pushover analysis method is employed to calculate the R values for each prototype, considering the number of structural stories (N) and the link length (e). The derived values of each performance coefficient serve as valuable references for future performance designs of novel structural systems.

Collapse Resistance of Reinforced Concrete Frame Beams under Sustained Loads

Collapse Resistance of Reinforced Concrete Frame Beams under Sustained Loads

THE MULTI-STOREY BUILDINNGS STEEL FRAMES VITALITY IN THE FIRE INCREASING

In the article multi-story buildings steel frames in the fire before and after the first destruction is investigated, the frames vitality in the fire is investigated. It is emphasized on the relevance of the research during the war of the russian federation against Ukraine. An overview of previous domestic and foreign scientists’ studies, devoted to the multi-story buildings steel frames vitality, in particular in a fire. The frame model for research was selected and simplifications was required in the study for the clarity of comparisons in research. There were compared different mechanisms of multi -story buildings steel frames collapse in a fire. It is proved that with the first destruction in the steel frame beam the vitality loss time will be longer than with the column first destruction. Various measures vitality increasing frames are considered and investigated. Outrigger systems were investigated as a measure vitality increasing, and their impact on the forces distribution in the frame during heating of frame elements under the action of temperature loads from a fire. The dependence of various measures vitality increasing of multi-story buildings steel frames in the fire from the frame geometric sizes is established. It is established that the load -bearing capacity factor at the fire beginning in the most loaded column should be smaller than the most loaded beams. It is proved that the difference between the initial load-bearing capacity factor in the beam and column that necessary to increase the vitality loss time, is different for different ratios of beam span to the column height. It is revealed that the frame elements cross-sections shape affects its vitality in the fire. The importance of the limited plate deformations development in the frame elements cross-sections is emphasized. Recommendations for civil engineers to enhance the of multi-story buildings steel frames vitality in a fire are formed.

Experimental and numerical investigations on interaction between reinforced‐concrete grid frame and ceramsite foam concrete infill

AbstractExperimental and numerical studies were conducted to investigate interaction between reinforced‐concrete grid frame (CGF) and ceramsite foam concrete (CFC) infill. In the experiments, compressive tests were performed on the CGF and RC grid frame filled with the CFC which forms a composite wall, namely CGFW. To investigate the mechanical properties of the CGFW and the interactions between the CGF and CFC infill, the failure modes, integral stiffness, local strains, and load distribution coefficients of the composite wall were analyzed. The experimental results indicated that the CFC infill could uniformly transmit loads and significantly improve the bearing capacity and vertical stiffness of the CGFW while reducing the ductility of the composite wall. The load distribution coefficients of the CFC infill were stable at 0.51 ± 0.06 before peak load and damage evolutions in concrete columns were effectively alleviated due to obvious interactions between the CGF and CFC infill. To evaluate the interaction mechanisms of the two, numerical analysis was carried out by changing the sizes of central grid, opening rates, and reinforcement ratios of the composite walls. The finite element model with plastic damage constitutive of concrete was calibrated by comparing the experimental results. The numerical results indicated that the interaction between the CGF and CFC infill was insensitive to changes in grid sizes, and the interaction between the two was significantly different with the same reinforcement method of frame beams and columns. In addition, the CFC infill played an important role in the stability of CGF as the opening rate significantly affected the mechanical properties of the CGFW, and a stable path of load transfer was the key factor to ensure the interaction between the CGF and CFC infill.

Seismic performance of eccentrically braced precast reinforced concrete columns-steel beams frame with replaceable shear links based on plastic design

To promote the seismic performance of reinforced concrete column-steel beam (RCS) frame, eccentric braces were creatively introduced into it. An improved plastic design method considering the differences in the combination of concrete and steel was proposed for the structure. The plastic design method not only adopts the energy-balance criterion considering the pinch effect of the concrete column and the influence of damping to accurately determine the base shear force but also considers the reasonable value of the story shear distributions along the height and the shear-sharing ratio between MRF and EBF substructures in detail. By considering cases with different heights, this paper verifies the effectiveness of the proposed method with a refined finite element model based on Sap2000. Meanwhile, a case based on the elastic design method was also presented for comparison. To prove its practicability in real engineering, the results of extensive nonlinear static and dynamic analyses of the 6-story and 9-story frames were conducted in terms of base shear, yield mechanisms, link plastic rotations, and inter-story drifts. The results show that the elastoplastic base shear and yield mechanisms predicted by the plastic design method have an acceptable agreement with the numerical simulation results under nonlinear analysis conditions. In addition, average inter-story drifts obtained by the nonlinear time history analysis met the calculation expectation, and the distribution coefficient adopted in this paper has good applicability to the eccentrically braced RCS frames, demonstrating that the structural elastoplastic response could be controlled by the proposed design procedure.

Three-Dimensional Stability of Unsaturated Soil Slopes Reinforced by Frame Beam Anchor Plates

The frame beam anchor plate (FBAP) is a new supporting structure to reinforce backfill. The current studies of slope stability concentrate on homogeneous isotropic dry or saturated slopes according to two-dimensional assumptions. In engineering practice, however, the soils are heterogeneous and anisotropic and exhibit evident unsaturated characteristics, and the failure surface shows obvious three-dimensional (3D) characteristics universally. A new method for evaluating the 3D stability of unsaturated soil slopes reinforced with FBAPs is established in this paper. The upper-bound analytical solution of slope safety factor (Fs) is derived based on the energy balance equation incorporated with the 3D spiral failure mechanism and the gravity increase method (GIM). Comparisons verified the effectiveness of the methodology and the optimization program. The influence of unsaturated characteristics, support structure design parameters, and seismic force on the 3D slope stability is evaluated through parameter analysis. The results show that the shear strength prediction model is crucial in slope stability assessments. The stability of slopes can be significantly improved by about 29%–52% by using FBAPs. Seismic action has a significant negative impact on the slope stability. When kh increases from 0 to 0.3, Fs generally decreases by about 40%–55%.

Seismic behaviour of a novel demountable joint connecting FTCES columns and RC beams

Fiber-reinforced polymer (FRP) tube-concrete-encased steel (FTCES) column shows excellent strength, stiffness and ductility owing to composite action. However, its practical application is very limited because there is a lack of knowledge on the behaviour of the entire structural system, which includes the beam-column joint. Indeed, the design of the connection between FTCES columns and beams is the most challenging task, which governs the reliability and safety of the entire structural system. To fill up the research gap, a novel demountable beam-column joint was proposed to connect the FTCES columns and reinforced concrete (RC) frame beams using high-strength bolts. The joint consisted of two cover plates, two steel ring plates, two connecting beams (with end plates) and a hollow steel tube infilled with core concrete. A total of four specimens were designed to study the seismic behaviour of the proposed joint, considering the effect of the steel tube / plate (ring plate and flange of connecting beams) thickness and the axial load ratio. Test results showed that the proposed demountable joint could provide an effective and simple connection with favourable seismic performance. Besides, with thinner steel tube and steel plate, specimen failed due to steel fracture in the joint region and few minor cracks were observed on the RC beams. Under this circumstance, the material strength of RC beams was not fully utilized, leading to smaller peak load. For specimens with thicker steel tube and steel plate, the failure was due to serious concrete crushing on the RC beams and excellent seismic performance was achieved. Lastly, an analytical model was proposed to estimate the peak load of the joint and by comparison, it is concluded that the proposed model could give a very accurate prediction.

Seismic performance and shear capacity of modular steel structures infilled with cold-formed steel walls using a novel connection system

A reusable connection system between a cold-formed steel wall (CFSW) and modular steel frame was developed to provide effective seismic resistance while ensuring repairability. Three steel frame specimens were cyclically loaded along the lateral direction to study the influence of the CFSW infill and its connection to the frame on seismic performance, thereby exploring the feasibility of the proposed connection configuration. The results indicated that modular steel structures infilled with cold-formed steel walls (MSS-CFSWs) using the proposed connection exhibited the “strong frame, strong connection, and weak infilled wall” failure mode. The use of a CFSW resulted in increments of 149.8%–307.5% and 53.4%–80.2% in the initial lateral stiffness and shear capacity, respectively. Connecting the CFSW to both the frame beams and columns resulted in superior mechanical performance and energy dissipation capacity. No separation between the CFSW and frame was observed, proving that the proposed connection configuration is safe and reliable. Furthermore, the connector plates and angles in the connection exhibited no evident deformation or damage, allowing the replacement of damaged CFSW components and the reuse of frames. The shear capacity of the MSS-CFSW was calculated by considering plastic hinge formation at the beam end as the critical state and using a modified global analysis method to determine the shear capacity of the CFSW. The resulting equation was verified using the test data and was found to be safely conservative. The results of this study can therefore serve as a reference for the design of MSS-CFSWs.

Higher-order modeling of a thin-walled beam with a welded multicell cross-section and its application to welding line optimization

Thin-walled multicell structures observed in vehicle frames are partially welded to lower the welding process cost while maintaining their overall structural stiffness comparable to those of fully-welded multicell structures. A fast and reliable beam-based model for analyzing such structures is required in the concept stage of the design process. In this investigation, an analysis method for a thin-walled beam of a multi-cell cross-section partially welded along its axial direction is newly established using a higher-order beam theory (HoBT). Our approach uses the Lagrange multipliers to impose the partial welding condition along the common edges of multiple thin-walled closed sections using the three-dimensional field derived from a higher-order beam theory. The developed method in this study can be an accurate and effective alternative without full finite element analysis employing shell and solid elements. To find the optimal welding locations, we introduced binary design variables parameterized through their corresponding welding constraints to identify the status of welding or non-welding along a candidate welding line. A genetic algorithm is adopted to solve optimization problems. After establishing the analysis method and optimization technique, their validity was checked using double-cell and triple-cell sectioned beams and beam frame structures, including a bus structure. The stiffnesses of the structures with optimized partial welding lines (20%) drop less than 6% from those of fully welded counterparts.

A textile architecture-based discrete modeling approach to simulating fabric draping processes

Fabric draping, which is referred to as the process of forming of textile reinforcements over a 3D mold, is a critical stage in composites manufacturing since it determines the fiber orientation that affects subsequent infusion and curing processes and the resulting structural performance. The goal of this study is to predict the fabric deformation during the draping process and develop in-depth understanding of fabric deformation through an architecture-based discrete Finite Element Analysis (FEA). A new, efficient discrete fabric modeling approach is proposed by representing textile architecture using virtual fiber tows modeled as Timoshenko beams and connected by the springs and dashpots at the intersections of the interlaced tows. Both picture frame and cantilever beam bending tests were carried out to characterize input model parameters. The predictive capability of the proposed modeling approach is demonstrated by predicting the deformation and shear angles of a fabric subject to hemisphere draping. Key deformation modes, including bending and shearing, are successfully captured using the proposed model. The development of the virtual fiber tow model provides an efficient method to illustrate individual tow deformation during draping while achieving computational efficiency in large-scale fabric draping simulations. Discrete fabric architecture and the inter-tow interactions are considered in the proposed model, promoting a deep understanding of fiber tow deformation modes and their contribution to the overall fabric deformation responses.

Numerical analysis on seismic behavior of the assembled modular steel plate shear wall with inclined slots

This paper proposes a novel multi-grids steel plate shear wall with inclined slots (called MSPSW). This MSPSW composed of the steel plates with inclined slots, precast concrete panels, the transverse and longitudinal (T&L) connecting stiffeners, and external frame components. Smaller single plates can be used in the design and installation process since the space size of individual frames inside the frame is reduced as a result of the T&L connecting stiffeners. The direction of inclined slots in the adjacent grids is opposite, which makes the lateral resistance and stiffness close to symmetry. Numerical analysis is conducted to evaluate the seismic behavior. With the correct finite element model, finite element analysis is performed on the key parameters of MSPSW, such as the cross-sectional dimension of T&L connecting stiffeners, the thickness of steel plate, the width of inclined slots and the width of plate slot strips. The Mises distribution and development regular pattern of MSPSW are also explored. The FE numerical analysis discovered that the MSPSW increased the bearing capacity and energy consumption capacity of the members due to the installation of T&L connecting stiffeners. Additionally, the thickness required for concrete panels is lowered when the components are subjected to cyclical loads. Finally, the internal force development curves in frame beams and columns are extracted, it can be found that the internal forces become smaller, which weakens the demand of frame members. The theoretical calculation formulas of the maximum internal forces of frame beams and columns are provided.

Deep learning enables MV-based real-time image guided radiation therapy for prostate cancer patients

Objective. Using MV images for real-time image guided radiation therapy (IGRT) is ideal as it does not require additional imaging equipment, adds no additional imaging dose and provides motion data in the treatment beam frame of reference. However, accurate tracking using MV images is challenging due to low contrast and modulated fields. Here, a novel real-time marker tracking system based on a convolutional neural network (CNN) classifier was developed and evaluated on retrospectively acquired patient data for MV-based IGRT for prostate cancer patients. Approach. MV images, acquired from 29 volumetric modulated arc therapy (VMAT) prostate cancer patients treated in a multi-institutional clinical trial, were used to train and evaluate a CNN-based marker tracking system. The CNN was trained using labelled MV images from 9 prostate cancer patients (35 fractions) with implanted markers. CNN performance was evaluated on an independent cohort of unseen MV images from 20 patients (78 fractions), using a Precision–Recall curve (PRC), area under the PRC plot (AUC) and sensitivity and specificity. The accuracy of the tracking system was evaluated on the same unseen dataset and quantified by calculating mean absolute (±1 SD) and [1st, 99th] percentiles of the geometric tracking error in treatment beam co-ordinates using manual identification as the ground truth. Main results. The CNN had an AUC of 0.99, sensitivity of 98.31% and specificity of 99.87%. The mean absolute geometric tracking error was 0.30 ± 0.27 and 0.35 ± 0.31 mm in the lateral and superior–inferior directions of the MV images, respectively. The [1st, 99th] percentiles of the error were [−1.03, 0.90] and [−1.12, 1.12] mm in the lateral and SI directions, respectively. Significance. The high classification performance on unseen MV images demonstrates the CNN can successfully identify implanted prostate markers. Furthermore, the sub-millimetre accuracy and precision of the marker tracking system demonstrates potential for adaptation to real-time applications.

Force-Displacement Hysteresis Model of Exterior PCRB Joints under Low Cyclic Loading.

The seismic behaviors of exterior polyvinyl chloride-carbon-fiber-reinforced polymer (PVC-CFRP) confined concrete (PCCC) column-ring-beam joints (hereafter referred to as exterior PCRB joints) under low cyclic loading were investigated. A total of 11 specimens were tested to analyze the effects of the structural parameters (i.e., the reinforcement ratio of the ring beam, the CFRP-strip spacing, the ring-beam width, the reinforcement ratio of the frame beam, and the axial compression ratio) on the failure modes and hysteretic behavior. Three different failure modes, including the failure of the frame beam, the failure of the junction between the frame beam and the ring beam, and the shear failure of the ring-beam joint, were observed. The experimental results showed that the pinching effects of the hysteresis curves decreased and that the slope of the descending stage of the skeleton curves gradually decreased with the enhancement of the reinforcement ratio of the ring beam, axial compression ratio, and ring-beam width. The effects of the CFRP-strip spacing and the reinforcement ratio of the frame beam on the hysteresis loops and skeleton curves were marginal, while the reinforcement ratio of the frame beam exerted significant effects on the failure modes. Therefore, a model for predicting the skeleton curves of exterior PCRB joints and hysteresis rules was proposed, based on the softening constitutive relation of the concrete and a regression analysis of the test data. Ultimately, a load-displacement hysteresis model of the exterior PCRB joints was established and validated by the test data, with good agreement.

Shear-resistant capacity and design of orthogonal double-corrugated-plate shear walls

The orthogonal double corrugated plate shear wall (ODCPSW) is composed of the wall element and the vertical edge members. The wall element consists of two identical corrugated plates installed in an orthogonal pattern, and high-strength bolts are adopted to directly connect them at the corrugation valley regions. The vertical edge members may be installed in two sides of the ODCPSW by employing single steel plates. Since the strong axis of one corrugated plate coincides with the weak axis of the other corrugated plate, the flexural rigidity of each corrugated plate in its weak axis can be improved significantly, thus enhancing its shear resistance. An ODCPSW is connected with frame beams by T-shaped fishplates, leading to characteristic of a flexible layout, standardized design and production, and assembly construction. This paper studies the shear-resistant capacity of the ODCPSW theoretically and numerically to obtain its strength design method. First, the orthogonal double corrugated plates are transformed into orthogonal plates, and accordingly the rigidity constants, including flexural rigidity constants (Dx=Dy) and torsional rigidity constants (H), are defined and introduced as basic feature in investigating its behaviors. Then, the formula for predicting the shear elastic buckling load of ODCPSW is obtained by fitting its elastic buckling coefficient form the elastic buckling analysis results of a large number of examples. Then the normalized height-to-thickness ratio, as a key design parameter, is established from the shear elastic buckling load. Finally, the shear-resistant capacity of the ODCPSWs is investigated by using numerical examples. The shear-resistant capacity of the ODCPSW may be considered to be equal to the superposition of that of the ODCPSW with two vertical sides simply supported and that of the moment-resistant frame formed by two edge members.

The deterioration state and degradation mechanism of historical timber structures from the Yunnan Military Academy

ABSTRACT Wood structural timbers at three locations (eave, beam frame, and column) were exploited to elucidate the deterioration state and mechanism of historical timber structures from the Yunnan Military Academy (Kunming, Yunnan Province). The morphological structures, physical and mechanical characteristics, and chemical components were measured to illustrate the deterioration state and elucidate the degradation mechanism. The results demonstrated that the deterioration of structural timbers was closely dependent on their locations in the architecture. The outside eave was in the worst deterioration state, which was caused by natural factors (ultraviolet rays, rain, and fungi), resulting in severe distortion of wood structures and a significant reduction in basic density and compressive strength. Significant carbohydrate losses that occurred in the eave and beam frame were mainly contributed by the brown rot fungi, predominantly due to the frequently wet condition and humid environment. Moreover, column structures were mainly attacked by insects (weevils) due to their location near the ground, accordingly in an obvious decline in mechanical properties. Collectively, structural timbers exhibited different deterioration states contributed by the degradation mechanism, predominantly influenced by their locations in architecture.

Mechanical Behavior of Two-Side Bolted Steel Plate Shear Wall Considering Top-Seat Constraints with Frame Beams

A steel plate shear wall (SPSW) is a useful component for resisting lateral action. To improve the performance of frame columns, some studies focus on a two-side connected SPSW, in which the wall plate is not connected with the frame columns. However, few studies conducted on a two-side connected SPSW consider the effect of frame constraints or the connections between the infill plates and frame beams. In this study, by using finite element modeling (FEM), two unstiffened SPSW models with two-side fixed connections and six unstiffened SPSW models with two-side bolt connections were simulated. Their performance under the presence of out-of-plane frame beam flange constraints and different numbers of bolts between the infill plates and frame beams was analyzed. The mechanical performances such as hysteretic behaviors, the capacity of energy dissipation and the out-of-plane deformation of the members were investigated by applying monotonic and cyclic loading. The results revealed that non-negligible deformation would be generated at the lateral border of the bolt connections and that the out-of-plane deformation of the frame could be significantly affected by constraints. These findings can guide the engineering design of SPSWs in the future.

The influence of component defect states on bandgaps of 2D composite beam frame structures

This paper investigates the vibration bandgap properties of two-dimensional (2D) periodic composite beam frame structures with component defects. Combined with the topological characteristics of the structure, a generalized position coordinate system is proposed, and an assembly method of the stiffness matrix for the virtual full component model is presented. Then the spectral equations of motion of the whole 2D periodic composite beam frame structures and the ones with component defects are established. Compared with the frequency-domain solutions calculated using the finite element method, the accuracy and the feasibility of the spectral element method (SEM) solutions are verified. It can be shown that the SEM is suitable for analyzing the vibration bandgap properties, and the influence of different component defects and their combination on the bandgap characteristics of 2D periodic frame structures is studied. The results show that forbidden gap splitting will occur in the main bandgap of the structure, but the degree of influence varies. The results also show that the influence of component defects on unsymmetrical or irregular positions of the vibration bandgaps of periodic frame structures is greater than the one in symmetrical or regular positions.

Genetic algorithm model of PEC column-steel plate shear wall with flush end-plate joints based on component method

The partially encased concrete (PEC) column-steel beam frame steel plate shear wall (SPSW) structure of semi-rigid joint has good cooperative working performance and seismic performance. In this paper, based on the EC3 component model, considering the contribution of the new concrete components in the PEC column to the initial rotational stiffness of the joint domain, the component model of the flush end-plate PEC column joint was established. A 1/3-scale two-story single-span flush end-plate PEC column-steel beam frame SPSW structure was tested under quasi-static cyclic loading. The OpenSees model of this structure was established, which was validated by test results. Parametric analysis of the additional damping ratio for semi-rigid joints was conducted using OpenSees. The suggested value of additional damping ratios for semi-rigid joints was given. Finally, based on Matlab and OpenSees, the model was input in the form of tool command language (TCL), an optimal arrangement model of flush end-plate PEC column joints with the genetic algorithm (GA) as the main procedure was designed. The effects of different arrangement schemes of semi-rigid joints on the seismic response of PEC column-steel beam frame SPSW structures were analyzed. The results show that the seismic performance of the flush end-plate PEC column-steel beam frame SPSW structures is reliable. The results of the finite element (FE) are in good agreement with the test results, which indicates that the established OpenSees model is effective. The contribution of the new concrete components to the initial rotational stiffness of the middle joints, top and bottom joints is 45.02% and 49.68%, respectively. The optimal arrangement scheme of semi-rigid joints can be efficiently computed by the proposed GA model.

Intelligent Damage Assessment for Post-Earthquake Buildings Using Computer Vision and Augmented Reality

The most negative effects caused by earthquakes are the damage and collapse of buildings. Seismic building retrofitting and repair can effectively reduce the negative impact on post-earthquake buildings. The priority to repair the construction after being damaged by an earthquake is to perform an assessment of seismic buildings. The traditional damage assessment method is mainly based on visual inspection, which is highly subjective and has low efficiency. To improve the intelligence of damage assessments for post-earthquake buildings, this paper proposed an assessment method using CV (Computer Vision) and AR (Augmented Reality). Firstly, this paper proposed a fusion mechanism for the CV and AR of the assessment method. Secondly, the CNN (Convolutional Neural Network) algorithm and gray value theory are used to determine the damage information of post-earthquake buildings. Then, the damage assessment can be visually displayed according to the damage information. Finally, this paper used a damage assessment case of seismic-reinforced concrete frame beams to verify the feasibility and effectiveness of the proposed assessment method.

Research on the Application of Reinforced Concrete Building Structure Reinforcement Technology in Engineering

Old buildings because of long service life or natural damage, easy to appear durability, bearing capacity, stability decline, in order to ensure the safe use of building structure must take reinforcement measures. Increasing section method, carbon fiber cloth outsourcing, pasting steel plate method, planting reinforcement method and so on are commonly used reinforced concrete building structure reinforcement technology, but each technology is not the same application conditions and application effect. In this paper, the reinforcement and renovation project of a frame structure industrial plant in Tonglu, Zhejiang Province is taken as an example. Firstly, the basic ideas of reinforcement design and the basis of selection of reinforcement and renovation technology are outlined. Then, the application points of different reinforcement and renovation technologies are emphatically analyzed from four parts: basement frame column, first floor frame column, frame beam and sandwich structure. It provides some reference for the reinforcement and renovation of modern steel concrete building structure.