Wall Joints Research Articles

Numerical and experimental investigation on angle multiple slit bolted connections for precast wall panels

Flat Multiple Slit Devices (MSDs) have been introduced in steel constructions located in earthquake-prone areas as compact hysteretic dampers connected to braces, and were further proposed to be employed also in other structural typologies, including aligned precast concrete walls. Nevertheless, similar angle connections needed for horizontal joints of orthogonal walls are not tackled in literature. The shape of MSDs, obtained by selective weakening by removing part of the steel area of flat plates, may allow to attain a highly ductile and stable dissipative behaviour, given local plate buckling is avoided, protecting the bolted joints through capacity design. Laser cutting as an alternative to mechanical milling introduces the possibility to easily optimise the shape of the slits in order to attain better performance under laterally imposed cyclic load. This paper analyses the application of right-angle-bent MSDs for the horizontal connection between orthogonal precast walls typical of panel structures with rigid diaphragms. In particular, bolted angle plates with hourglass-shaped multiple slits obtained after laser cutting are investigated numerically via non-linear finite shell elements and experimentally with original cyclic tests. The effect of the aspect ratio of the plate and of the restraint condition, possibly affecting the performance under imposed shear deformation due to the presence of the bent corner, is investigated by parametric analysis. Finally, general design rules and recommendations are presented.

Study on the sealing performance of 105MPa conical core BOP in the fully sealed state

Achieving full sealing is a technical challenge in the simulation, manufacturing, and experimentation of annular anti-spray seals. Based on Yeoh rubber constitutive model and large deformation theory, the finite element simulation model of 105 MPa annular blowout prev conical core seal was established, the stress distribution and contact pressure law of the core under different working pressures and full sealing conditions were analyzed, the full sealing state simulation of 105 MPa annular blowout prev core was realized, and the sealing performance of the core was evaluated. The results show that the conical core can meet the sealing requirements at 105 MPa. The high stress of the conical rubber core of 323 MPa appears at the joint of the inner wall of the rubber core and the back of the support bar and the joint of the upper and lower convex of the support bar. The high stress of 892 MPa appeared in the neck and back of the upper plate and the rear area of the lower plate. When the piston operating pressure is constant, with the increase of the working pressure, the overall stress of the rubber core increases, which is easy to cause the fatigue failure of the rubber core.

Experimental study on seismic behavior of a novel RC slab- SC wall joint based on UHPC and rebar – steel plate lap splices

Steel plate concrete shear walls (SC walls) have been widely used in practical projects because of great mechanical properties. For the application in nuclear power plant containment, the joint of specially shaped reinforced concrete slab and SC walls is difficult to design and construct. By using ultra-high performance concrete (UHPC), a new type of joint with the non-contact lapping method is proposed in this paper, which has advantages of simple construction, superior performance, suitable cost, and wide application range. Five RC-UHPC slab-shear wall joints were designed and tested under reciprocating load to study the effects of structures of lapping steel plate, shear-resisting methods, and interfacial reinforcing methods on the mechanical properties of the joints. The test results showed that the joints adopting the new structures were damaged for the flexural failure of the concrete area, with no damage to the joint zone, while the other specimens failed in the shear failure of the joint zone. It can be demonstrated that the ribs formed by bars and studs on the lapping steel plates are effective measures for non-contact force transferring, and interfacial reinforcing bars can improve the strength of the interface between concrete and UHPC. The force transferring efficiency of the new joints was close to or more than 90%, which indicates that the proposed joint structures can effectively realize the non-contact lapping force transferring. The design formulas and suggestions are proposed based on the analysis of the mechanism of new structures.

Sonic P-wave attenuation based on fluid pressure differential between joint and matrix

When P-wave compresses in-situ rocks saturated with fluid, there is a fluid pressure differential between compliant joints and stiff matrix. The pressure differential automatically drives a mesoscale squirt between joint wall and matrix interior. This mechanism is likely to dominate sonic P-wave attenuation in the field. A new model of P-wave attenuation based on the mesoscale squirt is established, in which the first porosity is represented by matrix pores while the second porosity is represented by joint. Sonic log of a sandstone reservoir in Saudi Arabia is used to illustrate the model. Both estimated phase velocity and measured quality factor of sonic P-wave are accurately simulated. The results show that for the sandstone reservoir, the relative second porosity is 5%, inter-joint distance is 0.1 m, squirt permeability at very low frequencies is about half of Darcy permeability of the matrix, and joint gap is 800 μm (quadruple grain diameter of 200 μm). Surprisingly, the model of joint-matrix squirt is also capable of reproducing seismic P-wave attenuation measured in the shallow crust of southern California. Therefore, mesoscale squirt across the joint wall is probably the underlying mechanism of attenuation for sonic and seismic P-waves shallower than 10 km.

Seismic behavior of lightweight steel frame with thin-walled steel skeleton-lightweight concrete wall

In this study, an innovative prefabricated lightweight steel frame with thin-walled steel skeleton-lightweight concrete composite wall structure (LSF-TSLC) is proposed. The proposed LSF-TSLC has the lightweight steel frame (LSF) as the vertical load-bearing system, whereas the thin-walled steel skeleton-lightweight concrete composite wall (TSLC) acts as the main component for horizontal earthquake resistance. A full-scale LSF specimen and three full-scale LSF-TSLC specimens were prepared considering the variables of wall installation method (embedded, external) and thin-walled steel skeleton distribution (frame type, truss type). The corresponding seismic behavior was experimentally investigated by evaluating the hysteretic characteristics, failure mode, ultimate bearing capacity, deformation performance, stiffness degradation, energy dissipation, and strain characteristics. The results showed that the plastic hinges appeared at the beam ends and column bases of LSF. Due to the shear failure, the embedded and external TSLC exhibited grid cracks and diagonal cracks, respectively. The LSF and TSLC had a good coordinating deformation capacity, while the LSF-TSLC structure had two seismic fortification lines. Compared with LSF, the ultimate bearing capacity and stiffness of LSF-TSLC were increased by 2.1 times and 5.1 times, respectively. The deformation capacity and energy dissipation of LSF-TSLC were significantly improved compared to LSF. The self-tapping nail joint of the embedded wall and the high-strength bolt joint of the external wall had reliable connectivity performance. The numerical simulation of LSF were conducted to verify the plastic analysis model for LSF. And the ultimate bearing capacity calculation method for the LSF-TSLC structure was proposed based on the Strut-and-Tie model.

Vertical diaphragms for moment connection of thin-walled CFT column to steel beam

A vertical diaphragm scheme is proposed to connect the concrete-filled thin-walled steel tube (thin-walled CFT) column and steel beam, as an alternative to horizontal diaphragm connections: dual vertical diaphragms are installed inside the steel tube, considering poor out-of-plane resistance of the thin tube wall. For verification of the moment connection, two experimental programs were carried out. In the first experiment, an ultimate tension test was conducted for flange-to-column connections, to identify the fundamental behavior of the proposed connection (i.e., strength, failure mode, and out-of-plane deformation). The design parameters, such as the thickness, number, and continuity of the vertical diaphragms, were considered. All the test specimens exceeded the design strengths based on a yield line model (i.e., the tensile capacity-to-demand ratios ranged Tu/TYL = 1.11–1.31), without early fracture of welded joints. In particular, at the design strengths, the tube out-of-plane deformations were more limited with the heavier diaphragms. In the second experiment, beam-to-column connections using prototype I-section steel were tested under cyclic flexure, to verify the joint flexural strength and rigidity as well as the seismic performance. The beam-to-column connections failed by the beam flexural mechanism, whereas damage was marginal at the joint wall (i.e., the flexural capacity-to-demand ratios ranged Mu/Mj = 0.87–1.09). Overall, the dual diaphragms were effective in achieving rigid (full-strength) connections with satisfactory plastic rotation of the beam. On the basis of the test results, design considerations were recommended for the vertical diaphragm connections.

Investigation of Welding Heat Input Influences on the Characteristics of Welded Joint of Storage Tank Wall Using Multiple Passes

Investigation of Welding Heat Input Influences on the Characteristics of Welded Joint of Storage Tank Wall Using Multiple Passes

Hybrid machine learning models to predict the shear strength of discontinuities with different joint wall compressive strength

ABSTRACT The shear strength of discontinuities with different joint wall compressive strength (DDJCS) is an important mechanical property. In this paper, the prediction of shear strength of DDJCS is performed using a hybrid machine learning model of artificial neural network (ANN) model with particle swarm optimisation (PSO). To develop the proposed model, a total of 168 cases are collected. Two classical models are introduced, and four performance indexes (i.e. coefficient of determination R2, mean absolute error MAE, root mean square error RMSE, and variance account for VAF) are utilised to evaluate the comprehensive predictive performances of these models. Finally, a graphical user interface (GUI) for predicting the shear strength of DDJCS is developed. The comparison results demonstrate that compared to the remaining models, this hybrid model has a better predictive performance and generalisation capability, with R2, RMSE, VAF, and MAE values of 0.999, 0.02, 99.9%, and 0.01, respectively. GUI signifies that this novel model provides an intuitive, efficient, and visual production experience for researchers. These findings can provide valuable insights for developing accurate predictive models.

Paragoniastreavariabilis Kishi, Nomura & Fukami, sp. nov. (Cnidaria, Anthozoa, Scleractinia), a new coral species previously considered as a variant of Paragoniastreadeformis, from Japan and northern Taiwan.

A new zooxanthellate scleractinian coral, Paragoniastreavariabilis Kishi, Nomura & Fukami, sp. nov. (Scleractinia, Merulinidae), is described from non-coral reef regions of Japan and northern Taiwan. This new species was previously recognized as a morphological variant of Paragoniastreadeformis (Veron, 1990) and can be morphologically distinguished from that species by lacking groove-and-tube structures on corallite wall joints, and by having larger calices, numerous septa, and up to three corallites in one valley. The new species also formed an independent clade from its congeners, P.australensis (Milne Edwards & Haime, 1857), P.deformis and P.russelli (Wells, 1954), in the molecular phylogeny based on the mitochondrial intergenic region and nuclear ribosomal internal transcribed spacers.

Performance Analysis of Shear Wall Joint Connection in Highrise Building Using Finite Element

Multi-story buildings have a risk of structural failure, especially at joint connections, including raft elements and shear walls, due to the interaction behavior of the shear joints. The problem raised in this research is how to analyze the performance of raft foundation shear wall structural connections in high-rise buildings. The researchers started by simulating the initial model using the element method to find out the detailed capabilities of the raft foundation and shear walls and obtain values that could measure the capabilities of the substructure used. The results of this research explain the results of the evaluation of connection performance, namely, the pile raft phase with fc' 35 MPa and the shear wall phase with fc' 50 MPa. From the analysis in this research, visualization from the ABAQUS program of the force conditions acting on the connection structure was obtained, namely compression damage of 0.0021 at an ultimate compressive stress of 43 MPa and 0.0006 at an ultimate compressive stress of 57.97 MPa. We also perform analytical calculations to determine the tensile and compressive strain values. In the future, it is hoped that it will be possible to make part of the reference the use of connections with similar models and sizes at project work stages with the same characteristics as a contribution to developing building structural safety requirements.

Rate-dependent shear behaviors of rock discontinuities with different joint wall strengths

Rate-dependent shear behaviors of rock discontinuities with different joint wall strengths

Experimental study on direct shear resistance of horizontal grouted joints in PC shear walls under compression and in-plane bending moment

The upper and lower panels of the prefabricated concrete shear wall are usually connected via horizontal grouted joints to maintain structural integrity. The horizontal grouted joints are typically under compression and in-plane bending moment. In the current design practice, it is generally considered that the direct shear resistance of the horizontal grouted joint is identical to that of the new-old concrete joint, and not affected by the bending moment if no bending failure occurs. In fact, as far as the authors know, both considerations lack experimental evidences. In this study, eight horizontal joint specimens were tested, including four grouted joints and four new-old concrete joints, to investigate their direct shear performances under constant compression and different in-plane eccentricities. Test results indicated that the ultimate direct shear resistance of the grouted joints was averagely 15.9 % lower than that of the new-old concrete joints. For the joints under small eccentricities associated with full shear plane in compression, the ultimate direct shear resistances remained unchanged compared to the cases under no eccentricity. However, for the grouted joints under large eccentricities associated with partial shear plane in tension, the ultimate direct shear resistances reduced up to 27.8 % compared to the grouted joint under no eccentricity. In addition, the shear transfer mechanism was investigated with the aid of the extended shear-friction model. Finally, recommendations were proposed for direct shear design of the horizontal grouted joints.

Experimental study on bond-slip behavior of vertical connecting rebar in the horizontal joints of double- superimposed shear wall

The horizontal joint of double-superimposed shear wall is the important part affecting the seismic performance of the wall. The horizontal joint mainly relies on the synergistic action between the vertical connecting rebar and the cast-in-place concrete to transfer the horizontal and vertical loadings and coordinate the deformation. Therefore, it is necessary to study the bond-slip behavior between the vertical connecting rebar and the cast-in-place concrete. In this paper, the effects of the cast-in-place layer thickness, the concrete strength, the anchorage length, and the diameter of rebar on the interface bond properties of vertical connecting rebar were analyzed through pullout tests. Based on the experimental results, the calculation formulas for bond strength and peak slip were proposed. According to the distribution of bond stress along the anchorage length, the bond-slip constitutive model optimized by the bond position function was established to describe the bond-slip behavior between the vertical connecting rebar and the cast-in-place concrete.

Experimental and theoretical study on seismic behavior of a new UHPFRC sandwich wall and wall-wall joint

A new type of precast ultra-high performance concrete (UHPFRC) sandwich wall is proposed in this study. The proposed UHPFRC sandwich wall is composed of the UHPFRC layers, extruded polystyrene foam (XPS) board layer, and short UHPFRC columns connecting the UHPFRC layers. Compared with the traditional reinforced concrete wall, the UHPFRC sandwich wall possesses lower self-weight, less reinforcement, and higher strength. In addition, two types of wall-wall vertical joint connection methods, flexible cable connection and embedded steel plate welding connection, are proposed. The pseudo-static tests on five UHPFRC sandwich wall specimens were conducted to study the effects of UHPFRC layer thickness, reinforcement ratio, and width of edge solid area on the seismic behavior of the wall. Then, the seismic performance of different connection methods was studied by pseudo-static tests on two T-shaped UHPFRC sandwich wall-wall joint specimens. Test results demonstrate that the unreinforced UHPFRC sandwich wall, with 20–30 mm UHPFRC thickness and 150 mm edge solid area, showed excellent cracking resistance and seismic behavior. The cracking loads are more than 50% of the peak loads, and the bottom shear capacity to self-weight ratios are generally more than 35. The seismic behavior of the wall-wall joints connected by the flexible cable and embedded steel plate welding are both reliable. Finally, formulas for cracking and peak load of the UHPFRC sandwich wall are proposed and the fiber model is developed for analysis of the wall-wall joint, which is verified by the test results to be accurate and reasonable.

Behavior and design of steel beam to multi-celled corrugated-plate CFST wall joints

In recent years, there has been a notable increase in the utilization of multi-celled corrugated-plate CFST (MC-CFST) walls. In this paper, a connection joint between a steel beam and an MC-CFST wall was proposed. The joint consisted of MC-CFST walls, end columns, horizontal diaphragms, vertical plates, and steel beams, with each steel component being interconnected through welding. To investigate its mechanical properties, a refined finite element model was developed, and the accuracy of the modeling method was validated through existing test results. The stiffness and moment capacity of the joints were analyzed, focusing on the effects of various factors, including the insertion depth of the horizontal diaphragm, beam-to-column linear stiffness ratio, width-to-thickness ratio of the end column plate, diameter of the horizontal diaphragm opening, axial compression ratio, and concrete and steel strengths. Based on numerical and theoretical analyses, a calculation method for determining the moment capacity of the joint and establishing the lower limit value for the steel tube thickness of the end columns was proposed by using the yield line analysis. The predicted value of the moment capacity of the joint was found to deviate from the finite element result by no more than 10%, suggesting that the formula exhibited excellent accuracy and applicability. The minimum steel tube thickness of the end columns was determined by considering the yield of the beam flange section. The design method presented in this paper has the potential to offer a valuable reference for practical designs of the proposed connection joint.

Experimental investigation on shear strength deterioration at the interface between different rock types under cyclic loading

The shear strength deterioration of bedding planes between different rock types induced by cyclic loading is vital to reasonably evaluate the stability of soft and hard interbedded bedding rock slopes under earthquake; however, rare work has been devoted to this subject due to lack of attention. In this study, experimental investigations on shear strength weakening of discontinuities with different joint wall material (DDJM) under cyclic loading were conducted by taking the interface between siltstone and mudstone in the Shaba slope of Yunnan Province, China as research objects. A total of 99 pairs of similar material samples of DDJM (81 pairs) and discontinuities with identical joint wall material (DIJM) (18 pairs) were fabricated by inserting plates, engraved with typical surface morphology obtained by performing three-dimensional laser scanning on natural DDJMs sampled from field, into mold boxes. Cyclic shear tests were conducted on these samples to study their shear strength changes with the cyclic number considering the effects of normal stress, joint surface morphology, shear displacement amplitude and shear rate. The results indicate that the shear stress vs. shear displacement curves under each shear cycle and the peak shear strength vs. cyclic number curves of the studied DDJMs are between those of DIJMs with siltstone and mudstone, while closer to those of DIJMs with mudstone. The peak shear strengths of DDJMs exhibit an initial rapid decline followed by a gradual decrease with the cyclic number and the decrease rate varies from 6% to 55.9% for samples with varied surface morphology under different testing conditions. The normal stress, joint surface morphology, shear displacement amplitude and shear rate collectively influence the shear strength deterioration of DDJM under cyclic shear loading, with the degree of influence being greater for larger normal stress, rougher surface morphology, larger shear displacement amplitude and faster shear rate.

Effect of Interlayer Composition on the Properties of Laser-Directed-Energy-Deposition-Based Additively Manufactured Copper-Stainless Steel Wall Structures

Laser-directed energy deposition (LDED) is one of the advanced techniques used for the sustainable manufacturing of engineering components with minimal material wastage and higher performance. This paper reports an investigation on LDED-based additive manufacturing of compositionally graded Copper (Cu)-stainless steel (SS) wall structures for improved performance of tooling components. Three different approaches, such as Cu-SS direct joint, 20% graded Cu-SS, and 50% graded Cu-SS, are used to build the wall structures. Optical microscopy of LDED-built graded samples reveals defect-free deposition of Cu-SS direct joint and 50% graded Cu-SS wall structures at identified process parameters, whereas the 20%-graded wall yields micro-cracks in the lower Cu region. The elemental distribution shows gradual traditions in the weight percentages of Cu and Fe along the built wall. Furthermore, the ultimate tensile strengths of the direct Cu-SS joint wall structure and the 50%-graded Cu-SS wall structure are higher than the strength of LDED-deposited Cu, while the 20%-graded Cu-SS wall structure has lower ultimate tensile strength than the strength of LDED-deposited Cu. Lower ultimate strength and failure in the lower-Cu zone of 20% graded Cu-SS wall structure can be attributed to the presence of micro-cracks in the Cu20SS80 zone of 20%-graded Cu-SS wall structures. The study establishes LDED as a technique for building multi-material components promoting sustainability in terms of manufacturing and component performance.

Bipolar Head Perforation With Rhabdomyosarcoma of the Thigh: A Case Report With Literature Review.

High complication rates during the perioperative management of sarcomas around the pelvis have been reported; however, few include the detailed clinical course or complications in the late postoperative period. Radiotherapy is a multidisciplinary strategy for treating sarcomas. However, irradiated bone and soft tissues show a permanent loss of repair and immunocompetence. We present a case of pleomorphic rhabdomyosarcoma of the thigh that resulted in acetabular collapse induced by radiation and intestinal perforation during long-term follow-up. Additionally, we discuss the risk factors for late complications and pelvic reconstruction methods. A 75-year-old man presented with a 1-month history of a recurring fever. Ten years prior, he was diagnosed with pleomorphic rhabdomyosarcoma of the right thigh and underwent a wide resection and bipolar hip arthroplasty, followed by chemotherapy and radiotherapy. Radiographs showed central dislocation of the bipolar head. Computed tomography revealed free air in the hip joint and thickening of the colon wall. Colonoscopy revealed displacement of the bipolar head into the colon wall. Colon resection and hip disarticulation were performed, as the bipolar head was contaminated with intestinal contents. Currently, he is able to walk stably with a walker, and there is no evidence of recurrence or metastasis of the tumor. Irradiation of the periacetabular bone may induce resorptive destruction, resulting in future structural failure. Hardware should not be used for periacetabular bone reconstruction; the risk of pelvic organ damage should be considered when the acetabular collapse becomes deteriorated. Therefore, other reliable and permanent reconstruction options are required.

Evaluating Structural Performance of U-shaped Precast Concrete Modular Joints

We conducted a joint tensile test and a wall cyclic loading test to assess the structural performance of the U-shaped precast concrete (PC) modular joint. The rebar experienced fracture at the edge of the L-shaped steel during the joint tensile test. The calculated average ratio of the maximum load to the nominal strength, based on the strength of the rebar, was 1.07. The result of the wall cyclic loading test showed that the PW-1R specimen, featuring a single row of PC joints, exhibited ratios of the maximum moment to a nominal bending moment of 1.19 and 1.00 in the positive (+) and negative (-) directions, respectively. Meanwhile, the ratios of the maximum moment to the nominal bending moment for the PW-2R specimen with two rows of PC joints were 1.20 and 1.06 in the positive (+) and negative (-) directions, respectively. The adequate edge distance for the joint hardware must be ensured to increase the strength of the PC joint wall.

Comparative numerical study to simulate masonry with bed joint reinforced repointing

Bed joint reinforced repointing is a retrofitting technique for unreinforced masonry structures that is commonly applied in the Netherlands to repair settlement-induced damage. Using this technique, the bed joints of masonry walls are reinforced with steel rebars that are embedded in a high strength repair mortar. Due to the increase of induced seismic events in the northern part of the Netherlands, an experimental study was carried out at Delft University of Technology to investigate the performance of this retrofitting technique for combined settlement and seismic loading. This paper aims to simulate the experimental results, with a focus on the comparison of different finite element modelling approaches for studying both un-strengthened and strengthened full-scale tested walls. To that end, three different models are investigated – comprising both macro (continuum) and simplified and detailed micro (brick-to-brick) modelling approaches. The bricks and mortar joints are modelled as one homogenous continuum in the macro model, whereas in the two brick-to-brick models these structural components are modelled separately, with the detailed model including interface elements to simulate the brick–mortar bonds. Nonlinear pushover analyses are subsequently carried out using all three modelling approaches, for both monotonic and cyclic loading cases. Based on these analyses, the detailed brick-to-brick model was found unsuitable to simulate the strengthened wall because cracks in the model mainly occur in the form of opening of the brick–mortar bond interfaces, while smeared cracking in the plane stress elements of the mortar joints is very limited. Similarly, the continuum damage model was found to be inaccurate when pre-existing damage in the experiment needed to be taken into account. The continuum damage model also showed lower axial stresses in the rebars, compared with the simplified brick-to-brick model, as the former does not allow for the direct assignment of material properties for the high strength repair mortar in the strengthened joints.