Bolted Steel Plates Research Articles

Investigating corrosion-induced deterioration in bolted steel plate joints using guided wave ultrasonic inspection

AbstractBolted steel plate joints encounter challenges posed by joint corrosion, which impact the quality of interfacial contact among the bolted components. Unfortunately, no correlation between corrosion-induced joint damage and preload, nor an existing numerical model capable of capturing such effects, has been identified. This study aims to utilize guided wave ultrasonic investigation to examine the deterioration of interfacial contact caused by corrosion in bolted joints. Additionally, a contact modification-based numerical approach is presented to capture the effects of changing interfacial stress during joint corrosion. Guided wave mode selection was conducted with some preliminary experiments supplemented with the theory of wave mode dispersion, hence leading to the selection of S0 and A0 mode existing at 300 kHz. The joint was then corroded in a controlled manner using an electrochemical process while simultaneous ultrasonic measurements were taken. The experimental observations highlighted the progressive dispersion in the transmitted A0 mode across the bolted joint, potentially due to changing interfacial stress boundaries between the plates. A damage parameter, termed the dispersion index, was developed based on the energy ratio of different signal sections. A linear change in the dispersion index was observed with the increase in corrosion-induced mass loss. The insight was further established through a numerical investigation by studying the effect of changing bolt preload and the corresponding interfacial stress distribution. The findings revealed that monitoring the changes in the stress distribution at the bolted interface can provide insight into interfacial corrosion. Eventually, destructive tension test results confirmed the effect of joint corrosion on the load-bearing capacity of the joint. The change in failure mode of the pristine and corroded specimen is observed. The reported approach establishes the potential of ultrasonic inspection to investigate the interfacial health of a bolted joint in corroding conditions.

Bond Shear Tests to Evaluate Different CFRP Shear Strengthening Strategies for I-Shaped Concrete Cross-Sections.

I-shaped concrete girders are widely used in precast bridge and roof construction, making them a common structural component in existing infrastructure. Despite well-established strengthening techniques using various innovative materials, such as externally bonded carbon fibre reinforced polymer (CFRP) reinforcement, the shear strengthening of an I-shaped concrete girder is not straightforward. Several research studies have shown that externally bonded CFRP reinforcement might exhibit early debonding at the concave corners of the I-shape, resulting in a marginal increase in shear capacity. This research study aims to assess the performance of two different CFRP shear strengthening strategies for I-shaped concrete cross-sections. In the first strategy, CFRP was bonded along the I-shape of the cross-section with the provision of additional anchorage. In the second strategy, the I-shape was transformed into a rectangular shape by using in-fill blocks over which the CFRP was bonded in a U-configuration. In addition to the strengthening strategies, the investigated parameters included two different materials for the in-fill blocks (conventional and aerated concrete) and two different anchoring schemes (bolted steel plate anchor and CFRP spike anchor). To avoid testing on large-scale girders, a new test methodology has been implemented on concrete I-sections. The test results demonstrate the feasibility of comparing different shear strengthening configurations dedicated to I-sections. Among other findings, the results showed that the local transformation of the I-shape to an equivalent rectangular shape could be a viable solution, resulting in shear strength enhancement of 12% to 53% without and with the anchorages, respectively.

Failure analysis of bolted steel plate connections with three-dimensional flexibilities

Steel plates are widely used in construction to connect different structural elements using welding or bolts. The fracture in these plates may lead to catastrophic consequences such as structural collapse. The paper investigates steel plates' deformation capacity and fracture behavior in bolted connections in three-dimensional (3D) flexibility. The peridynamic method is utilized to model the excessive deformation and fracture of steel plates in bolted connections when they are influenced by shear, moment, and torsion. The mesh-free nature of peridynamics enables modeling the extreme deformation and fracture in ductile materials such as steel. We validate the 3D peridynamic model by comparing its fracture and deformation results with experimental measurements and observations in several loading and boundary conditions. The paper highlights the following novelties: (1) a new and highly efficient 3D peridynamic model is proposed to model fractures in steel plates when exposed to combined actions of shear, moment, and torsion simultaneously; (2) the proposed 3D peridynamic model overcomes the difficulties faced by the mesh-based methods in modeling excessive deformation in ductile materials such as steel; (3) the study also reveals a shift in the fracture behavior of steel plates from ductile to brittle when exposed to high values of moment and torsion. This shift in fracture behavior has not been thoroughly addressed, impacting the integrity of steel structures and the warning stage for yielding. Overall, utilizing the 3D peridynamic model as a modeling and simulation tool can help engineers and researchers examine the behavior of steel plates under various loading conditions, thus allowing for optimization of the design of steel plates used widely in steel construction.

EXPERIMENTAL STUDY ON THE STRUCTURAL BEHAVIOUR OF RECYCLED PLASTIC ONE STORY HOUSES

Recycling plastic materials may constitute a relief measure to the global plastic problem. Several companies are now producing recycled plastic for use as construction material in single-story houses. One commercially available layout involves assembling Recycled Plastic Lumber units in a running bond pattern, forming panels confined by horizontal and vertical tie elements joined through bolted steel plate connections. As production of houses is industrialized, the architectural layouts are standardized according to specific distribution and dimensions. This paper presents the findings of an experimental program aimed to characterize the seismic behavior and properties of a one-story house model. To facilitate practical application, the model is referred here as Architectural Standard Model (ASM). The objectives of the test campaign were to investigate the structural behavior of the constituting members and assemblies, and the response of structural walls to cyclic static lateral loads. Three natural scale wall specimens were tested in-plane and two out of plane. Results of natural scale cyclic loading tests demonstrated that structural system of the ASM can perform acceptably safely under high seismic loads if it is adequately fixed to the foundation. The results showed that out of plane loading was the critical pattern and behaved like a unidirectional plate that transmitted load to the columns. In plane observed behavior exhibited predominating rocking component, which suggests considering an evaluation of the system's response using dynamic methods.

Behavior of FRP-Retrofitted Wall-like RC Columns after Preloading to Simulate In-Service Conditions

In the Middle East, wall-like reinforced concrete (RC) columns are a common choice in multistory buildings. Sometimes, these columns need axial retrofitting for increased load capacity. In practice, unstrengthened columns bear their load, and if retrofitting is necessary, the load is released before the upgrade—unlike in past research studies that overlooked this real-world scenario. This study aimed to investigate the response of preloaded wall-like RC columns after being retrofitted using different configurations. In the experimental campaign, two half-scale columns were cast and axially loaded to 80% of their capacity, and the load was then totally released. After that, these specimens were strengthened with two different schemes, and hence, they were concentrically loaded until failure. In both schemes, the section shape was not modified. The first scheme comprised wrapping carbon FRP (fiber-reinforced polymer) sheets together with near-surface mounted (NSM) steel rebars. However, the second technique was composed of wrapping glass FRP (GFRP) sheets together with NSM steel rebars and bolted steel plates. The second scheme was found to be superior to the first one due to the extra confinement provided by the bolted steel plates. This scheme improved the peak load, stiffness, and dissipated energy by 115%, 75%, and 524%, respectively. Other than the testing campaign, nonlinear numerical modeling was undertaken to examine the behavior of tested specimens. The models were utilized to conduct a parametric study, exploring the influence of the percentage of preloading and the amount of load release on the response of columns strengthened with the second scheme.

Design approach and its optimization for bolted steel plate strengthened RC beams considering the effect of connection bolt slip

The use of bolted steel plates (BSP) has been found to be an effective method for increasing the flexural capacity of reinforced concrete (RC) beams. However, slip in bolt connections is an inevitable occurrence that affects the mechanical behavior of the BSP beam. While prior studies have thoroughly examined the effects of bolt connection slip on the flexural capacity of BSP beams, assuming unlimited slip, experimental results revealed that bolt connection failure takes place when slip surpasses a specific threshold. The current design methodology does not accommodate this finding. To address this issue, a simplified design method for practical applications is proposed. Comprehensive parameter studies were conducted on the enhanced moment capacity ratio and maximum bolt slip, involving a total of 13,824 and 276,480 calculations, respectively. It is found that several parameters (e.g., the aspect ratio of RC beam, the tensile longitudinal reinforcement ratio, the height of steel plate) affect the two above-mentioned indexes. Equations were then developed to determine the enhanced moment capacity ratio and maximum slip. It is noteworthy that the recommended effective yield slip (0.55 mm) is obtained based on adhesive anchor, which should be checked when other types of anchors would be used. Relying on these equations, an optimized design approach for BSP beams is introduced that avoids complex iterative processes. The effectiveness of the optimized design methodology is substantiated through a practical example.

Experimental study on CFRP-strengthened bolted splicing modular steel plate shear wall

The seismic performance of the steel plate shear wall (SPSW) structure will be weakened by the modular splicing of the infill steel plates. To address this, carbon fiber reinforced plastic (CFRP) was used to strengthen its splicing joints. First, the specimens of CFRP-strengthened bolted joints with different CFRP laying methods were tested in uniaxial tensile control, and the corresponding design method was proposed. Next, this method was introduced into the vertical splicing joints of modular SPSWs. Three 1/3-scale SPSW specimens, with and without CFRP-strengthened modular SPSW and complete SPSW, were tested under quasi-static cyclic loading. The failure modes and hysteresis performance of the three structures were compared, and the effects of using CFRP-strengthened splicing joints on various properties of the SPSW structure were investigated. The force mechanism of the CFRP-strengthened bolted splicing modular SPSW structure was further investigated by finite element (FE) analysis. The results indicated that the CFRP strengthening vertical splicing joints can effectively reduce the stress concentration around the hole walls of the infill steel plate, improve the performance loss of wall plates due to modular segmentation, and reduce slippage of splicing joints and out-of-plane deformation amplitude of wall plate. The CFRP-strengthened vertically bolted modular SPSWs increased the stiffness and load capacity of the structure, with yield bearing capacity and stiffness increased by 11.40% and 19.57% compared with those of the vertically bolted modular SPSW, respectively.

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.

Shear strengthening design of pre-cracked reinforced concrete beams using bonded and bolted steel plates

ABSTRACT A design guideline for shear strengthening of pre-cracked reinforced concrete (RC) beams using steel plates has been presented in this research by modifying the available shear capacity formulas. An experimental investigation was also carried out in order to validate the proposed guideline. Total five RC beams were fabricated, among which four beams were pre-cracked in shear by applying preloads. Two of the cracked beams were then strengthened with adhesive bonded steel plates while the rest two were strengthened with bolted steel plates. Variation was made in plate depth and bolt layers. The shear performance of the strengthened beams was evaluated by testing the beams to their ultimate capacity. Experimental results indicated that the shear capacity, ductility and stiffness of the pre-cracked beams increased significantly after strengthening with continuous steel plates. The shear capacity varied from 131% to 201% for strengthened beams compared to the control beam. Deeper plates offered better shear performance than the shallower plates. Modification of the existing formulas by introducing preload factors for estimating the shear capacity of the strengthened beams showed a good agreement with the experimental shear capacity.

Numerical investigation on seismic resilient steel beam-to-column connections with replaceable buckling-restrained fuses

The detailed finite element model (FEM) of a new replaceable fuse steel beam-to-column joint proposed previously, where bolted steel plates located between the beam and C-shaped shear tab flanges in the beam splicing region behave as structural fuses to dissipate energy with their buckling controlled by the surrounding flanges, was developed in this paper and subjected to cyclic loading at the beam end. The simulated results matched the test results well in terms of the hysteresis curves (and the corresponding backbone curves) and failure modes. Based on the validated FEM, subsequent parametric studies were carried out to investigate the influences of the fuse plate type and slenderness ratio, and the slip coefficient between the steel plates, on seismic performance of this joint. The parametric analysis indicated that, the joint could accommodate an ultimate story drift angle of 6% without damaging the beam or shear tab flanges by using flat-type (FP) fuse plates, which are recommended over slotted-type (SP) and double-slotted-type (DSP) fuse plates, as the latter both types developed earlier buckling than the former FP-type. Eccentric-type (EP) fuse plates are also suggested, with which the joint equipped sustained an ultimate story drift angle of at least 8%. In addition, the slenderness ratio of FP-type fuse plates is recommended to be controlled within 44 since the fuse plates with higher slenderness ratios introduced damage through buckling to the shear tab flanges at an earlier stage, while the slip coefficient presented no significant impact on the joint seismic performance.

Experimental investigation on earthquake-resilient steel beam-to-column joints with replaceable buckling-restrained fuses

A new seismic resilient steel beam-to-column joint using replaceable buckling-restrained plates for energy dissipation was proposed in this paper. Such a joint consists of a column tree and an interior beam segment connected on site through bolted steel plates located inside beam flanges. The steel plates are considered as structural fuses to attract inelastic damage and dissipate energy. Their potential buckling is restrained by intentionally designed C-shaped shear tabs, which are also used to connect the beam webs to transfer the beam shear. Thus, both stable strength and superior energy dissipation capacity can be guaranteed. Six cyclic tests were conducted to study the seismic behavior and post-earthquake repair performance. The results evidenced that this joint was able to develop a normalized cumulative plastic rotation of 550 to 1100 until failure. Fuse plates could be quickly replaced after testing and the repaired joint developed nearly identical seismic performance as the original one. The proposed new joint provides an alternative solution, which is both economical and effective, for seismic resilient steel structures.

Seismic retrofitting of RC joints using steel cage and haunch with bolted steel plate

Two novel combination retrofitting systems for RC joint have been proposed and investigated experimentally in this research. The beams and columns were strengthened by bolted steel plates, and the joint panel zones were strengthened by the steel cages or steel haunches. Based on cyclic loading tests, the seismic behaviours of retrofitted RC joints were studied compared with a non-retrofitting counterpart, in terms of failure mode, strength, ductility, stiffness degradation, hysteretic curve and energy dissipation. For the retrofitted joint with steel cage, the ultimate load capacity, initial stiffness and ductility factor were increased by a maximum proportion of 94%, 75% and 28 %, respectively. For the retrofitted joint with steel haunch, the ultimate load capacity and initial stiffness were significantly increased by 134 % and 239 %, while the ductility factor was decreased by 23 %. The shear deformation of core area, curvature of beam and strain of steel element are also evaluated. The proposed rehabilitations seismically upgrade the joint panel zone together with the adjacent members and thus enhance the joint performance comprehensively. The combination retrofitting of bolted steel plate and steel cage provided superior ductility and energy dissipation, while the combination of bolted steel plate and steel haunch caused the undesirable shear failure due to the shorter deformable length and insufficient shear strengthening of the beams. The efficiency and feasibility of the proposed combination retrofitting systems were validated and the recommendations for improvement are provided.

Advances in Shear Strengthening of Concrete Bridge Girders

Bridge design values for axle load and truck volume have increased since the 1960s, following the introduction of modern vehicle configurations, such as those of permit, special hauling, and emergency vehicles. Many highway bridges in the U.S. are estimated to be structurally inadequate, especially with respect to the shear capacity of the superstructure to carry these loads, and there have been numerous efforts to consider strengthening options for such older shear-deficient bridges. Techniques for enhancing the shear capacity of concrete bridge girders range from traditional approaches using steel and concrete (e.g., bolted steel plates) to newer approaches that utilize novel concepts and advanced materials, such as fiber-reinforced polymer (FRP) composites and shape-memory alloys. This paper reviews these shear strengthening techniques from a practical application standpoint, particularly with respect to their structural efficiency and constructability. The conceptual basis of each technique is described along with a summary of the advantages and shortcomings of each technique, followed by an overview of some representative field implementations and relevant design guidelines, if available. Finally, the concept of developing an assessment rubric is introduced to aid in identifying a potential shear-strengthening scheme for a particular project.

Bolt preload monitoring based on percussion sound signal and convolutional neural network (CNN)

ABSTRACT The general approach to percussion-based monitoring of bolt preload is to train a classifier model to map the preloads and acoustic characteristics of percussion signals. However, the traditional percussion-based approach can only classify the preloads of bolts into certain ranges, and cannot accurately predict the exact bolt preload. This paper proposes an approach to estimate bolt preload using a convolutional neural network (CNN). The frequency contents of the percussion signals are analysed with the Fast Fourier Transform (FFT), and the magnitudes of signals in different frequencies ranges are reconstructed into a matrix, which can be treated as an image. Each image is labelled with the corresponding bolt preload. Then the labelled images are used to train the CNN model, and the trained model is used to detect the actual preload of a selected bolt. The proposed model was experimentally verified using a bolted steel plate. The results show that the proposed model can accurately predict the preload values outside the range of training samples with an accuracy over 95%. Meanwhile, compared with the predicted effect of the traditional regression models, the predicted validity of the proposed model is further verified.

One-sided shear retrofit of reinforced concrete beams in existing high-rise buildings

This paper presents the evaluation of one-sided shear retrofit schemes for reinforced concrete (RC) coupling beams in existing buildings. Three full-scale beam Specimens CB1, CB2 and CB3 are planned for cyclic tests. Specimen CB1 represents a RC coupling beam in existing 24-story RC buildings, completed in Taiwan, 2017. Specimens CB2 and CB3 are retrofitted by added stirrups in the increased beam cross section and a bolted a steel plate from only one side of the RC beam, respectively. Test results showed that the shear strengths of the two retrofitted specimens exceeded the force of the RC coupling beam expected at the maximum considered earthquake (MCE) level. Specimen CB1 exhibited flexural-shear failure during the cycle of 5% drift. Specimens CB2 and CB3 exhibited shear failure during the cycle of 4% drift, and then concrete crushing associated with longitudinal bar buckling in the plastic hinge region. The peak shear forces of the added stirrups in Specimen CB2 and of the added steel plate in Specimen CB3 were 34 and 22% of the total shear forces, respectively, at large drifts. The added stirrups in the increased beam cross section provided larger shear force than the bolted steel plate. Both schemes were used to retrofit RC beams in the existing high-rise buildings in New Taipei City.

Experiment and numerical study of a new bolted steel plate horizontal joints for precast concrete shear wall structures

In a non-emulative precast shear wall structures, joints are the key to influence the overall mechanical performance under seismic actions. While wet joints are widely used in the precast reinforced concrete shear wall structure, they present problems such as collision of steel bars, inconsistency of the post-casting area and importantly, they cannot achieve the best potential of precast concrete structures. Hence, this paper proposes a new dry joint, which is a bolted C-shaped steel plate for the horizontal joint of precast shear walls. Four identical sub-assembly precast shear wall panels bolted with four distinct configurations of steel plates (plain, X-stiffeners, horizontal slots and vertical slots) were tested under reversed cyclic loading. It was discovered that the bolted steel plate with horizontal slots could improve the ductility and energy dissipation of the joint. Numerical models were calibrated by benchmarking with the experimental results. Through a systematic parametric study on the number and spacing of slots, thickness of steel plates and number of bolts, the results indicated that the number of bolts is the critical parameter that will affect initial stiffness, peak strength capacity and ductility of the proposed joint.

Service and Ultimate Behavior of Adjustable Bolted Steel Plate Connections

AbstractThis paper experimentally and numerically investigates the service and ultimate behavior of adjustable bolted steel plate connections—slip-critical, splice plate connections that can join w...

YARI-RİJİT BAĞLI PREFABRİK ENDÜSTRİYEL BİNALARIN DEPREM PERFORMANSININ DEĞERLENDİRİLMESİ

In this study, the performances of 120 precast factory buildings consisting of five different types in an industrial area in Istanbul, Turkey are examined before and after the applications of retrofit methods through nonlinear time history analyses. The factory buildings were constructed and became operational before the 1999 Kocaeli earthquake. Following the earthquake, they were operationally safe, however, after the evaluation according to the 1998 Turkish Earthquake Code (TEC), most of the connections were found to be inadequate. The buildings were retrofitted by using bolted steel plates in the connection regions and diagonal steel braces in 2005. A detailed finite element model of the connection was developed before and after the retrofit methods and the behavior of the region was implemented in the three-dimensional models of the structures. The buildings were analyzed according to the Turkish Earthquake Code 2007. The number of damaged beams by the TEC-2007 was higher than the rate of damaged beams per the FEMA-356. In three-dimensional performance analysis of buildings, the importance of examination of connection regions and implementing the results to the full building model were emphasized. The performance of the building were increased by reducing the distance between the plane frames in the longitudinal direction and the beam length in the transverse direction.

Effective length and area of bolted steel plates attached externally to strengthen reinforced concrete beams

In this research an investigation has been done on eight reinforced concrete beams. Each beam was strengthened by bolted steel plates attached to their bottom side, of which length and thickness ratio varied, except one beam which has been tested without steel plate as controlling test. Two limits have been introduced upon the maximum plate area used and its minimum length. The first limit is to insure a ductile tension failure, and the latter is to prevent loss of interaction between the two components. Bolts with head were used to provide suitable connection through the specimens of concrete beams and the steel plates through predrilled holes in the steel plates. All beams have similar dimensions and tested simply supported over an effective length of 1600 mm and loaded with central load. Test results show that the plated beam gain an increase in strength over that of unplated beam of about 145%. Also, beams with relatively thin plates, the plate length has little effect upon the ultimate strength, however, for beams with thicker plates the results show a decrease in strength of about 16%.

Flexural behavior of precast UHPC beam with prestressed bolted hybrid joint

Ultra-high performance concrete (UHPC) is suitable for precast and assembled bridges due to its unique characteristics. Therefore, an efficient, safe, and durable joint connection that fits between the precast UHPC beam segments is of crucial importance. In existing conventional prestressed joints, a potential safety hazard exists because steel strands corrode under long-term detrimental environmental conditions. To address this issue, a prestressed bolted hybrid joint was proposed in this study. Eight precast UHPC beams with different types of joints were constructed. Experimental tests were conducted to examine the flexural behavior and load-bearing mechanism of the prestressed bolted hybrid joint, prestressed joint, and bolted joint. The flexural capacity, characteristic loading values, deformation characteristics, and the failure modes of the three types of joints were investigated and the influences of the bolts and epoxy resin adhesive on the flexural capacity of the joints were also discussed. The test results showed that the failure of the hybrid joint was characterized by the local crushing of the UHPC at the top compression zone together with shearing off of some of the bolts. The flexural capacity of the hybrid joint was significantly improved and was 46.8–60.3% higher than that of the conventional prestressed joint. The overall flexural capacity of the hybrid joint can be divided into two parts, the contributions of the prestressed UHPC joint and bolted connection. The epoxy resin adhesive had little effect on the slip resistance of the bolted joint; however, its bonding effect increased the cracking moment and flexural capacity of the joint by 16.5–29% and 11.5–21.8%, respectively. Besides, due to the strengthening effect of the bolted steel plates and the prestressing, the overall stiffness of the UHPC beam with the hybrid joint was significantly higher than that of the prestressed joint and the bolted joint after joint opening. Based on the test results, a computational method was proposed for calculating the slip moment, joint-opening moment, and ultimate flexural capacity of the prestressed bolted hybrid joint and the prestressed joint, and the feasibility of the hybrid joint was verified.