Column Elements Research Articles

EXTENDED MONITORING AS SUPPORT IN NUMERICAL MODELLING OF COMPLEX HISTORICAL TIMBER STRUCTURE

To support the conservation efforts regarding a wooden church in Domachowo, extensive research and design work was required to strengthen its weakened structure. A variety of data and analyses are necessary to make an accurate assessment, including obtaining a computational model, monitoring the behavior of the structure and its response to external forces and also performing strength analyses and verifying them with measurement data. For accurate geometric evaluation, static and dynamic measurements were required. A mathematical model and a flowchart of the necessary tasks were developed, along with the selection and installation of measuring devices. For this particular structure, static measurements were made using an automatic total station and dynamic measurements using tilt sensors. The purpose of the analysis was to correlate the inertia measurements with the absolute tachymetric observations related to reference points fixed outside the object in order to accurately assess the behavior of the object. Another important issue was to model the column element under study in such a way that its horizontal displacements could be determined from the measured inclinations. The obtained results indicated the need to strengthen the joints of the two main parts of the structure in order to minimize the impact of dynamic weather conditions. The paper describes the measurement process, the method of calculating displacements and the correlation of both types of data. Selected results confirming the conclusions are also presented.

Probing 4 × 4 quark mixing matrix

Without adhering to any specific model, we have presented 4 [Formula: see text] 4 quark mixing matrix as an extension of the 3 [Formula: see text] 3 Particle Data Group (PDG) parametrization of the Cabibbo–Kobayashi–Maskawa (CKM) matrix Using unitarity constraints as well as the hierarchy among the elements of the 3 [Formula: see text] 3 CKM matrix, we have found the hierarchy among the fourth row and fourth column elements of the 4 [Formula: see text] 4 quark mixing matrix. Further, for the fourth generation case, we have explicitly found the nine independent rephasing invariant parameters [Formula: see text]. Also, using phenomenological estimates of the fourth row and fourth column elements, we have numerically evaluated these nine parameters.

Frictional Axial Resistance of Clamped Split Pocket Mechanism Steel Structural Joint: An Experimental Study

The Clamped Split Pocket Mechanism (CSPM) prefabricated joint system was developed for a single-story steel instant house, designed to be compact and rapidly constructed without modifying the end of the beam and column element member. The CSPM bolted joint system was proposed as an optimal solution for post-disaster housing, especially after earthquakes. Despite its potential, the frictional tensile resistance behavior of the CSPM bolted joint system has not been previously studied, necessitating experimental investigation. This study examined the frictional tensile resistance behavior of the CSPM joint system by monitoring the effective friction coefficient under axial tension force. The experiments considered both the strong and weak axes of the joint and utilized two configuration types of specimens (L and T) with varying bolt pretensions of 2.5, 5, 7.5, and 10 kN. Results indicated that the effective friction coefficient of the CSPM bolted joint system ranged from 0.19 to 0.26, correlated to bolt pretension. Increased bolt pretension resulted in larger surface deformation of the split pocket, triggering a not uniform frictional tensile resistance across the steel surfaces of the split pocket joint. From this study, the achieved effective friction coefficients could guide the design of minimum pretension forces for clamps in prefabricated steel instant houses. Doi: 10.28991/CEJ-2024-010-09-07 Full Text: PDF

Evaluasi Desain Struktur Gedung Pondok Pesantren At-Tibyan Deli Serdang

The structural design of this three-story Islamic boarding school building, the results obtained after analysis include; risk category II so that the earthquake priority factor is 1. The soil site class is soft soil. In the structural system, it is designed using a special moment resisting frame system (SRPMK). The seismic design category obtained is category D. Seismic inspection starting from checking irregularities, diaphragm design, checking the number of structural vibration variations, determining the fundamental period of the structure, seismic response coefficient values, seismic base shear, checking the deviation between floors is carried out based on SNI 1726-2019. for column elements, beams and also plates in existing conditions after analysis have met the requirements based on SNI 2847-2019. The conclusion in this final project research is based on the results of the analysis that the design of the Attybian Islamic boarding school building still meets the requirements based on SNI 1726-2019 concerning procedures for earthquake resistance planning for buildings and non-buildings and also for beam, column and plate elements have met the requirements based on SNI 2847-2019 concerning reinforced concrete structures. However, for the beam elements for the reinforcement requirements, it is still too wasteful so that in this analysis, the amount of reinforcement is reduced because in the planning principle it must be safe and economical.

Interactive buckling behaviour of Q420–Q960 steel welded thin-walled H-section long column

Considering the broad application prospect of high-strength steel (HSS) in engineering structure, and the limitations present in existing studies on interactive buckling of HSS welded thin-walled box-section long column, both test and finite element analysis were employed to investigate the interactive buckling behavior exhibited by 12 specimens fabricated from Q420–Q960 steels. The detailed analysis considered various aspects, including the failure mode, axial deformation, interaction of local and overall buckling deformation, and the ultimate bearing capacity. Observations revealed that the utilization rate of steel strength diminished with an escalation in both the plate width–thickness ratio and steel strength. An increase in the plate width–thickness ratio correlated with an earlier onset of local buckling, and the influence of steel strength was found to be negligible. More importantly, the limit of the plate width–thickness ratio for columns undergoing interactive buckling increased with a rise in column slenderness and decreased with an increase in steel strength. Taking into account the influence of column slenderness and steel strength, a novel calculation formula for determining the limit of the plate width–thickness ratio was derived. It is noteworthy that Eurocode 3 and JGJ/T 483–2020 were found too conservative for calculating the ultimate bearing capacity, while ANSI/AISC 360–22 was found suitable. Additionally, a calculation method for the ultimate bearing capacity of Q420–Q960 steel welded thin-walled H-section long column was proposed based on the direct strength method.

Plastic hinge length in reinforced HPFRCC beams and columns

The use of ductile concrete materials such as High Performance Fiber Reinforced Cementitious Composites (HPFRCCs) within plastic hinge regions of structural components has garnered research interest in order to improve the seismic resistance of reinforced concrete structures. While experimental and numerical results appear promising in reducing component damage and probability of system level collapse, accurate nonlinear analysis tools capable of capturing the influence of axial load well into a component’s inelastic regime is needed. In this study, a series of 180 high fidelity numerical simulations of HPFRCC beam–column elements are simulated and used to calibrate new plastic hinge length expressions for concentrated and distributed plasticity models for use in system level structural analysis. The numerical models cover a range of HPFRCC material properties, reinforcement ratios, shear span lengths, and axial load levels. The ability of the newly developed expressions to predict component inelastic rotations are subsequently compared to hinge length expressions in the literature and the inelastic rotations of 47 experimental components. The results of this study provide new insights into the effects of axial load on the plastic hinge behavior of HPFRCC components, significantly improves on the accuracy of past plastic hinge length expressions allowing for more accurate modeling of HPFRCC component responses and system level behavior.

Axial performance of concrete-filled GFRP tube columns jacketed by outer stainless steel tube and sandwiched concrete

The concrete-filled FRP tube (CFFT) column, a prevalent and crucial structural element in marine environments, requires reinforcement measures to enhance its operational performance. This paper introduces a novel strengthening technology involving sandwiched concrete and stainless steel tube jackets. By conducting axial compression tests on two CFFT columns and nine reinforced columns, the failure modes, load-axial deformation curves, and load-strain relationships were analysed in this study. Additionally, the influence of outer steel tube thickness (3.0 mm, 4.0 mm, 5.0 mm) and sandwiched concrete strength grades (C50, C60, C70) on the axial compressive performance of the reinforced columns was investigated. The findings indicated that the proposed reinforcement method effectively mitigated the brittle failure associated with the original CFFT column. The external stainless steel tube played a crucial role in restraining lateral deformation of the internal CFFT column, thereby enhancing the axial compressive bearing capacity. Through theoretical analysis on the components in reinforced columns, a calculation formula for the axial compressive capacity of the reinforced column was derived according to the unified theory and the double-shear unified strength theory.

Improved lumped parameter model for shear wall–frame structures with geometric and material nonlinearities

Lumped parameter macroscopic structural models, such as those consisting of springs and rigid sticks, are useful for parametric studies and probabilistic analyses of individual building structures as well as for regional-level assessments on building stock. The existing lumped parameter models (LPMs) for shear wall–frame dual systems exhibit some drawbacks. There is a discrepancy in their arrangement of springs. They are calibrated to match only two modal periods of the original multi-story or even high-rise building structure. The existing models also have limitations when confronted with the P-Δ effect. After a careful investigation, this paper developed new schemes of spring-stick assemblies that accurately reproduce the elastic stiffness matrix of a two-dimensional Euler–Bernoulli or Timoshenko beam–column element and cope with geometric and material nonlinearities. The developed assemblies, which are essentially lumped parameter substitutes for beam–column elements, can be used to build LPMs for moment frames and shear walls. For moment frames, the traditional fishbone model is converted into a LPM that not only reflects the beam-to-column stiffness ratio and strength ratio but also captures the P-Δ effect. Combining the LPM for shear wall with the lumped parameter fishbone model results in an improved LPM for wall–frame dual systems. Together with lumped floor masses, the improved LPM is able to accurately predict all the global vibration modes and nonlinear seismic responses of a dual system. The proposed LPM possesses distinct advantages when simplified macroscopic models are preferred for building structures.

Importance of building inspection on the seismic response of a severely damaged RC structure during the February 6, 2023 Kahramanmaraş earthquake sequence

Large magnitude February 6, 2023 earthquakes in Türkiye created a devastating effect on the building stock on a vast region. For earthquakes of this magnitude, severe damage and collapses are indispensable to the old building stock with deficiencies certified in previous earthquakes. But unexpectedly, the newly constructed buildings that were designed by recent version of Turkish Building Seismic Code (TBEC 2018) also experienced severe damage. After conducting site investigations on one of the recently constructed and severely damaged RC building, a detailed numerical study was performed to identify the reasons for the observed seismic damage. This study pinpoints the main cause of such damage due to lack of thorough building inspections during construction to ensure the implementation of the seismic reinforcement detailing specified in blueprints for providing required ductility, as revealed by field investigations. Additionally, it identifies potential issues stemming from a lack of full comprehension of the seismic design philosophy within the code. The existing design pushes the limits on the axial load level on slender column elements and fall short in capturing the soft story irregularity. Although there is a soft base story in the investigated building, using structural walls only in one direction with moderately confined boundary zones increased its vulnerability. This example shows that in Türkiye, where seismic activity is very high and quite lethal, seismic design codes should set stricter limits and measures, and building inspection system must be strictly enforced.

Evaluasi Keandalan Struktur Atas Gedung Kantor Bupati Ngada di Nagekeo

Evaluation of the reliability of the upper structure of the Ngada Regent's Office building in Mbay aims to determine the strength of the existing upper structure in accordance with SNI 1726: 2019 concerning Procedures for earthquake resistance planning for building and non-building structures, and SNI 2847: 2019 concerning Requirements for structural concrete for buildings and explanations. From the results of the analysis and evaluation of the cross-sectional strength of structural elements, it was found that there were 16 beams that were unsafe and needed to be strengthened, while the column and plate elements were quite strong and safe.

Economic Study of Strengthening of Existing RCC Building

Many structures fail or deteriorate before completion of its intended life span due to poor quality of material used, lack of mix design, poor workmanship, attacked by environmental agencies, etc. Sometimes due to slenderness of column or less reinforcement provided than actual requirements, less depth/thickness provided in flexural members, etc. feels excessive vibration during walking on floor ultimately develops cracks. Strength of such structural elements can be found by using non-destructive tests like Rebound hammer test, ultrasonic pulse velocity test, etc. If strength of existing structural elements is less than desired strength then structural consultant suggested strengthening of structural elements. There are various methods used in strengthening of existing structural elements like pressure grouting, fibre wrapping, chemical treatment, structural steel support, jacketing, etc. But these techniques are very costly and need precise quality control activity. In the present of investigation, strengthening of beam and column elements of a building by ferrocement techniques and steel jacketing were carried out and cost and cost comparison and strength results before and after strengthening are presented. It is observed that the strength og structural by ferrocement technique is cost effective than steel jacketing technique. And also has increase in the strength of RCC elements

A Fully Coupled Numerical Model for Unbonded Post-tensioned Timber Structures

The paper presents a fully Lagrangian mesh-free solver to simulate the dynamic behavior of post-tensioned timber structures. Weakly Compressible Smoothed Particle Hydrodynamics (SPH) is employed to model both the timber and the tendon. An efficient and simple coupling method between the timber and the tendon is proposed by considering the numerical stability. Besides, the same coupling algorithm is used to model the interaction between column and beam elements. Although the column is treated as rigid in the simulations, the coupling algorithm accounts for the initial compression of the column resulting from post-tensioning. For the verification of the code for solids and material nonlinearity of timber, benchmark problems available in the literature are used. Finally, the solver's capability is demonstrated through dynamic analysis of post-tensioned timber structures. The solutions obtained for all the cases are in good agreement with the experimental and theoretical data, which indicates the applicability and accuracy of the solver.

Lateral load response and collapse probability of reinforced concrete shear walls retrofitted for repairability

AbstractThis paper demonstrates the efficacy of a new reinforced concrete shear wall seismic retrofit method through a series of nonlinear static and incremental dynamic analyses. Unlike traditional retrofit methods, the method investigated aims to convert conventional walls into self‐centering walls whose behavior is governed by rocking and flexure. The retrofit involves creating a cold joint at the foundation–wall interface, cutting some reinforcing bars to allow rocking, adding external post‐tensioning to enable self‐centering, and externally confining wall toes to prevent concrete crushing. The retrofit was applied to two building archetypes, each with two different shear wall designs. The four walls were retrofitted by varying retrofit parameters (portion of the vertical reinforcement bars cut, and external post‐tensioning amount). Nonlinear static and nonlinear response history analyses were performed using experimentally validated, computationally efficient models that simulate walls with fiber‐based beam–column elements. Incremental dynamic analysis was used to create collapse fragility functions for pre‐ and post‐retrofit walls. The results show that the retrofit is effective when some vertical reinforcement bars are left uncut across the foundation–wall interface. The retrofit is more effective for walls with vertical reinforcement distributed across cross‐section as compared to walls with reinforcement concentrated near boundary elements and for walls with structurally efficient amounts of reinforcement as compared to walls with higher amounts of reinforcement. This is attributed to the larger amount of reinforcement bars cut in walls with concentrated reinforcement layouts or heavy reinforcement amounts, leading to a larger loss of strength, recovery of which requires larger amounts of post‐tensioning.

Seepage evolution characteristics and water inrush mechanism in collapse column under mining influence

To obtain the seepage evolution rule and water inrush mechanism of the collapse column, a multi-field coupled mechanical model for water inrush disasters caused by the collapse column is established in this paper, on the basis of the specific engineering conditions of the 1908 working face in the Qianjin coal mine. The mechanical model is composed of internal column elements within the collapse column and surrounding rock masses. The research focuses on the seepage evolution rule in the roof collapse column under different mining conditions and investigates the permeation instability mechanism of collapse column based on the transition of flow state. The research results indicate that the seepage pathway evolves continuously, ultimately forming a channel for water inrush, as the working face advances towards the collapse column. Besides, the water inflow increases rapidly when the working face advances 100 m, then gradually stabilizes, indicating that the seepage channel entry of the collapse column is in a stable stage. Meanwhile, mass loss in the collapse column gradually moves upward. the collapse column remains stable as a whole in the initial stage of water flow, with a small permeability, exhibiting linear flow. As time steps increases, particle loss in collapse column gradually extends to the upper part, forming a stable seepage channel. The flow velocity shows fluctuations with a slow declining trend over time.

New Multiaxial Concrete Column Element with Adaptive Calibrated Constitutive Models

New Multiaxial Concrete Column Element with Adaptive Calibrated Constitutive Models

Small Strain Shear Modulus of the Ljubljana Marsh Soil Measured with Resonant Column and Bender Elements under Isotropic and Anisotropic Stress Conditions

The increasing use of finite element analysis in modern infrastructure design emphasizes the importance of determining soil stiffness at small strains. This is usually represented by the normalized shear modulus degradation curve, which is crucial for accurate design. In the absence of specific measurements on the local soil, engineers often rely on empirical correlations and assume comparable behavior of soils with similar intrinsic properties. However, the application of this approach leads to uncertainties, especially for unique geological formations such as the soft cohesive soils of the Ljubljana Marsh. The main objective of this study was to determine the small strain shear modulus of Ljubljana Marsh soil with a plasticity index between 11 and 35%. Isotropic and anisotropic stress conditions were investigated as part of an extensive laboratory test program that included 45 bender element and 89 resonant column tests on 20 soil samples. By emphasizing the importance of measuring soil stiffness at small strains, this study not only provides reliable data for the development of the built environment in the Ljubljana Marsh and similar areas, but also underlines its necessity.

Global vibration control of offshore wind turbines with a flexible monopile foundation using a pendulum-tuned mass damper: Risk mitigation and performance incrementation

This study investigates an optimized design approach for a passive-adaptive pendulum-tuned mass damper (PTMD). The PTMD is used to mitigate structural vibrations in offshore wind turbines (OWTs) with flexible monopile foundations considering Pile-Soil Interaction (PSI). The model OWT is based on the 5-MW design proposed by the National Renewable Energy Laboratory (NREL). The PSI incorporates a pile that is modeled as beam–column elements supported by nonlinear springs and accounts for lateral loads (p-y curves) and axial loads (t-z and Q-z curves) at nodal points. Wind and wave spectra estimation, as well as hydrodynamic and aerodynamic load analysis, are performed using a bespoke MATLAB® program operated in conjunction with an ANSYS® 3-D finite element global model. The resultant peak response at the OWT hub was evaluated through power spectral density (PSD) analysis. Optimal design choices for PTMD parameters are obtained via parametric analysis, which assesses the dynamic response in the along and across directions at the hub and stress at the tower base. A systematic representation considers the uncertainties stemming from the geometric and mechanical properties of the tower, environmental loads, and rotating blade dynamics. To address these uncertainties, a Monte Carlo simulation is employed to assess the structural risk via the Performance-Based Wind Engineering (PBWE) framework. Consequently, the probabilistic evaluation of structural response, foundation stresses, and power production assists in the optimal design process of PTMDs that mitigate the global structural vibrations of OWTs.

Influence of Joint Strengthening on the Seismic Performance of Non-Engineered Buildings

Non-engineered buildings (NEBs) are prone to earthquake damage. One type of damage that often occurs in NEBs is the separation of beam and column elements owing to joint failures. Strengthening joints with steel plates is expected to improve the seismic performance of this type of building. Strengthening with steel plates is cheap and easy to apply, so it will be a preferable choice in preventing damage to the NEB due to earthquake loads. This study investigated the seismic performance of reinforced concrete frames, representing an NEB whose beam–column joints were strengthened with L-shaped steel plates. Two widths of L-shaped steel plates were proposed: 75 mm (NEB-075) and 100 mm (NEB-100). An NEB without strengthening (NEB-000) was used as a control. Both experimental and numerical investigations were performed to determine the seismic performance of NEBs. The results showed that damage to the NEB-000 and NEB-075 models occurred at the joints, but less damage was observed in NEB-075 than in NEB-000. Furthermore, damage in the NEB-100 model occurred at the column. The undamaged limit levels of the NEB-000, NEB-075, and NEB-100 models were 56.49, 81.54, and 82.46%, respectively. These results show that strengthening the NEB with steel plates effectively improves its seismic performance. According to an analysis of the performance of the tested models, the NEB-100 model exhibited the best seismic performance.

Performance study on cold-formed steel structural frame made with lipped channel column and beam elements subjected to lateral loading

Performance study on cold-formed steel structural frame made with lipped channel column and beam elements subjected to lateral loading

Parametric Study on Seismic Performance of Slender T-Shaped RC Walls Subjected to Biaxial Loading

To investigate the effects of parameters on the seismic performance of slender T-shaped RC walls subjected to a biaxial seismic action, a numerical model was established using a fiber-based cross-section and displacement-based beam–column element. The axial load ratio, shear span ratio, flange width to web height ratio, concrete strength grade, stirrup ratio, and longitudinal reinforcement ratio were selected for the parametric study, and the effects of these parameters on the performance degradation under biaxial loading were investigated. Furthermore, a sensitivity analysis of various parameters for the decrease was conducted. The results showed that the bearing and deformation capacities under biaxial loading were both decreased, and the total energy consumption was greater than that under uniaxial loading. The impacts of different parameters and loading paths on the decrease extent were significantly different, and the overall reduction was greater in the flange direction than in the web direction. Under the square loading path, the T-shaped wall had the greatest reduction in its seismic performance, followed by the eight-shaped and cruciform loading paths. The changes in the axial load ratio, shear span ratio, and concrete strength significantly affected the performance degradation under biaxial loading. Accordingly, it is recommended to reasonably consider the values of these three parameters in a multidimensional seismic design to maintain safety redundancy.