Shear Force Transfer Research Articles

Investigation of the structural effect induced by stagger joints in segmental tunnel linings: Direct insight from mechanical behaviors of longitudinal and circumferential joints

It is generally accepted that cross joint tunnels have bigger deformation capability, while T joint tunnels have larger safety coefficients of bearing capacity, when it comes to difference in structural mechanics. The major cause of this different behaviour is the transfer loading mechanism through circumferential joints. However, there are few direct experimental investigations focusing on such transfer loading mechanism to the authors’ knowledge. In this work, systematic experiments are conducted to analyze the inter-ring transfer mechanism, which include a three-ring compression-bending test, a single-ring compression-bending test and a shear test on circumferential joints. Based on the outcome, the experimental results of the T joints configuration are discussed in terms of stresses and inter-ring shear forces. The results show that the inter-ring effect of the T joint segments is mainly due to the incompatibility of the deformation between rings as well as their capacity to transfer shear force. The loading level of the longitudinal force along the tunnel and the circumferential joint technology are the main factors influencing the transfer loading mechanism in such a staggered configuration. Moreover, the coefficient of moment adjustment, which is a vital parameter during the design of segmental tunnel linings, can be further defined and computerized. The investigation presents a deep insight into the effects of the segment layout and connection details along longitudinal and circumferential joints.

The theoretical principles of the critical shear crack theory for punching shear failures and derivation of consistent closed‐form design expressions

The mechanical model of the critical shear crack theory (CSCT) has been used in the past to investigate a number of shear‐related problems, such as punching of slab–column connections with and without transverse reinforcement. In this paper, a discussion on the differences and analogies between slender slabs and squat members (footings) without transverse reinforcement is presented on the basis of the CSCT. This discussion highlights how bending and shear deformations influence the opening of the critical shear crack and eventually its ability to transfer shear forces. On that basis, it is investigated and justified a power‐law expression to characterize the failure criterion of the CSCT. This criterion, in combination with a suitable load–deformation relationship, can be used to derive closed‐form expressions for punching shear design. The accuracy of these expressions is verified against databases of slender slabs (121 specimens) and footings (34 specimens) with consistent agreement.

Assessing the pry-out resistance of open rib shear connectors in cracked concrete – Engineering model with aggregate interlock

In steel and concrete composite structures, an efficient type of open rib shear connector, the so called composite dowel connector, can be used to transfer shear forces between the concrete slab and the steel section. In regions with negative bending moment, where concrete cracking occurs, the shear capacity of composite dowels with pry-out failure is significantly reduced. Concrete cracks appear as discrete discontinuities in the pry-out cone, which induce a pry-out cone detachment. In the cracks, the shear stress transfer is restricted to aggregate interlock. So far, the well-known design models do not account for concrete cracking. Therefore, they usually overestimate the composite dowels’ shear resistance in cracked concrete. To resolve that structural safety deficit, the present article proposes a mechanical model for the assessment of the pry-out resistance of composite dowels. The novel approach can be applied to cracked and uncracked concrete slabs and shows good agreement with experimental investigations. The model is validated by a test data base and afterwards converted to the design load level. In the future, the approach can be assigned to other types of shear connectors, for example to fasteners and headed studs in cracked concrete.

A piecewise linear transverse shear transfer model for bolted side-plated beams

The performance of bolted side-plated (BSP) beams is affected by the degree of transverse partial interaction, which is a result of the interfacial slip caused by transverse shear transfer between the bolted steel plates and the reinforced concrete beams. However, explicit formulae for the transverse shear transfer profile have yet to be derived. In this paper, a simplified piecewise linear shear transfer model was proposed based on force superposition principle and simplification of shear transfer profiles derived from a previous numerical study. The magnitude of shear transfer was determined by force equilibrium and displacement compatibility condition. A set of design formulae for BSP beams under several basic load cases was also derived. Then the model was verified by test results. A worked example was also provided to illustrate the application of the proposed design formulae. This paper sheds some light on the shear force transfer mechanism of anchor bolts in BSP beams, and offers a practical method to evaluate the influence of transverse partial interaction in strengthening design.

Experimental and analytical study on load paths of RC squat walls with openings

Two series of experimental tests on reinforced concrete (RC) squat walls with irregular openings were analysed. The experimental evidence indicated that flanges significantly affect the failure modes, initial stiffness, ultimate strength and deformation capacity. Given the complexity of the stress distribution in walls with irregular openings, strut-and-tie models are generally used in design and analysis to explicitly demonstrate the shear force transfer and load distribution paths. A comparison of experimental data with analytical results from the existing strut-and-tie model indicated that the latter may underestimate the ultimate strength by 51%. Although the strut-and-tie model is a lower-bound solution, the underestimation of 51% is still very large and may lead to unfavourable shear failure. An improved strut-and-tie model was thus developed, based on test observations. The improved strut-and-tie model can provide a more accurate prediction for the ultimate strength of walls with irregular openings. Based on the model, design recommendations and suggestions for reinforcement details in RC walls with irregular openings are also presented.

Numerical study of an innovative SMA based beam-column connection in reducing the seismic response of steel MRF structures

During recent years, Shape Memory Alloys (SMAs) have been e ectively used to control the seismic response of structural systems. Recovering the residual strains upon unloading (super-elasticity) or by heating (shape memory e ect) is the main characteristic of SMA materials. This paper explores the eciency of a proposed application of steel & SMA bolts in improving the seismic behavior of connections in steel Moment Resisting Frame (MRF) structures. A new semi-rigid, end-plate, beamcolumn connection is introduced, which is based on parallel application of steel and austenite-phase SMA bolts. A number of 3-D steel MRF structural models with di erent numbers of stories and mass eccentricities are considered. These structural models that are designed by employing the conventional rigid and the proposed semi-rigid connections are subjected to bi-directional earthquake records that have been scaled according to ASCE7-05 procedure. Extensive nonlinear dynamic time history analyses are conducted to evaluate the eciency of the steel & SMA based connections in enhancing the seismic performance of the structural models. The obtained results indicate that the proposed steel-SMA connection is highly promising and can eciently reduce the seismic response parameters of the structural systems. Steel bolts of the end-plate connections contribute both to shear force transfer (from beam to column) and dissipation of the input seismic energy through hysteresis behavior. On the other hand, parallel application of steel and SMA bolts in the connections reduces the story drifts as well as the induced forces in the structural elements while decreasing the permanent story displacements. The main goal obtained is to keep the beams away from the formation of plastic deformation. OpenSees platform is used for generating the structural models and performing the numerical analyses.

Experimental Study on the Seismic Behaviour of an Innovative Hybrid Concrete Connection Used as Thermal Break System

In Europe, the simultaneous introduction of new energy efficiency standards and majored seismic requirements has lead concrete constructors to find innovative solutions. In case of internal insulation, slab to wall connections have to be designed to maintain continuity of the insulation in structural connections while ensuring the transfer of shear forces from the slab to the wall. For this purpose, INGENOVA, a French civil engineering office, has developed a robust and ductile system, called SLABE®: stainless steel Z-shaped profiles are used as shear keys, creating an innovative hybrid concrete connection. An important research program has been carried out in order to characterize the SLABE® system behaviour under cyclic loads. Nearly true scale specimens including concrete slabs and walls have been tested in order to determine the stiffness and resistance under cyclic horizontal and vertical shear actions. Tests demonstrate a very stable behaviour of the system up to its theoretical yielding capacity and a large reserve of ductility due to the material of steel members. At last the effect of the SLABE on the overall seismic answer of buildings has been investigated numerically, in order to predict both the force redistribution between external and internal concrete walls, and the magnitude of horizontal forces transmitted by the shear link.

Timber Beam Bearing Reinforcement with GFRP Glued-In Plates: Strength and Hydrothermal Effects

AbstractThis paper presents a simplified method of analysis and design for the repair of deteriorated timber beam ends using glass fiber–reinforced product (GFRP) bonded rigid plates. It assesses the load-bearing capacity of the plate-timber connection and assumes two failure modes: shear stresses at the bonding interface and in the timber piece. An experimental method was developed to verify the theoretical model for bending moment and shear force transfer. Ten short span beam specimens of Pinus radiata D. Don were spliced with bonded-in plates in one end, and they were tested by bending with different anchorage lengths to establish a relationship with load-carrying capacity. Furthermore, the effect of temperature (−20 to 50°C) and moisture content (9–30%) changes were analyzed in two groups of six short beam specimens and in bonding shear test specimens using two different epoxy formulations. The theoretical model predicts conservative values of load-carrying capacity. Temperature and moisture changes c...

Surface waves affect frontogenesis

AbstractThis paper provides a detailed analysis of momentum, angular momentum, vorticity, and energy budgets of a submesoscale front undergoing frontogenesis driven by an upper‐ocean, submesoscale eddy field in a Large Eddy Simulation (LES). The LES solves the wave‐averaged, or Craik‐Leibovich, equations in order to account for the Stokes forces that result from interactions between nonbreaking surface waves and currents, and resolves both submesoscale eddies and boundary layer turbulence down to 4.9 m × 4.9 m × 1.25 m grid scales. It is found that submesoscale frontogenesis differs from traditional frontogenesis theory due to four effects: Stokes forces, momentum and kinetic energy transfer from submesoscale eddies to frontal secondary circulations, resolved turbulent stresses, and unbalanced torque. In the energy, momentum, angular momentum, and vorticity budgets for the frontal overturning circulation, the Stokes shear force is a leading‐order contributor, typically either the second or third largest source of frontal overturning. These effects violate hydrostatic and thermal wind balances during submesoscale frontogenesis. The effect of the Stokes shear force becomes stronger with increasing alignment of the front and Stokes shear and with a nondimensional scaling. The Stokes shear force and momentum transfer from submesoscale eddies significantly energize the frontal secondary circulation along with the buoyancy.

Performance of shear connectors at elevated temperatures - A review

Shear connectors are key components to ensure the efficient composite action and satisfactory transfer of shear forces at the steel'concrete interface in composite beams. Under hazardous circumstances, such as fire in a building, the performance of a composite beam significantly relies on the performance of shear connectors. Studies on the behavior of shear connectors subjected to elevated temperatures performed in the last decade are reviewed in this paper. The experimental testing of push-out specimens, the design approaches provided by researchers and different codes, the major failure modes, and the finite element modeling of shear connectors are highlighted. The critical research review showed that the strength of a shear connector decreases proportionally with the increase in temperature. Compared with the volume of work published on shear connectors at ambient temperatures, a few studies on the behavior of shear connectors under fire have been conducted. Several areas where additional research is needed are also identified in this paper.

Numerical Simulation on the Die Filling Process of the Thixo-Forging of Al-7 wt pct Si/Al-22 wt pct Si Bimetal Composite

A bimetal semi-solid fluid has more complicated flow behaviors than a normal semi-solid fluid during thixo-forging. In order to clarify the detailed properties of the bimetal thixo-forging, the effects of billet temperatures and frictions on flow behaviors of the Al-7 wt pct Si/Al-22 wt pct Si bimetal thixo-forging were investigated by commercial software DEFORM-3D. The simulation results show that shear force was unable to be transferred from the upper billet on the drop die side to the bottom billet on the counter die side efficiently in the initial stage of die filling. Only when the upper billet severely deformed, did the shear force deform the bottom billet. A stiffer upper billet can enhance the efficiency of shear force transfer. The processing temperature, the relative stiffness between the upper billet and bottom billet, and frictions between dies and billets, as well as friction between billets, were important factors to control the interface outline of the bimetal parts. The experimental results are consistent with the simulation results.

Espirito Santo: Design and Operational Expereince of the Use of Steel Risers on a Turret-Moored FPSO

Summary The floating production, storage, and offloading (FPSO) facility Espirito Santo, located offshore Brazil in the Parque das Conchas (BC-10) field, is the world's first turret-moored FPSO facility to use steel risers for fluid transfer. The FPSO facility is moored in a water depth of 1780 m, and the internal turret incorporates a total of 21 riser and umbilical slots. The steel risers, which are in a lazy-wave configuration, were pulled into the turret through inclined I-tubes. Clamps at the top of the I-tubes retain the risers, thus transferring axial loads from the risers to the turret. A clamp casting welded at the bottom of the I-tubes houses a stopper arrangement designed to transfer shear forces and moments from the risers to the turret. The FPSO facility began oil production in July 2009, and now has more than 5 years of operational experience. During this period, inspection of the riser system and the associated flex joint has confirmed the integrity of the design, giving further confidence in the use of steel risers in turret-moored systems. This paper summarizes the basis for selecting steel risers for the development, how the risers and umbilicals interface with the turret, and the impact of the riser choice on the turret design. The in-service inspection of the riser system is described, and the results are reported.

Connections in towers for wind converters, Part II: The friction connection behaviour

A novel friction connection consisting of a single lap joint with long open slotted holes is proposed for use in tubular towers for wind converters for in-situ connections. This is a competitive alternative to the common ring flange connection as it has been shown in the European Project “HISTWIN”. Two sets of experiments are analysed: the down-scaled tubular steel tower 4-point bending experiments using high-strength bolts M20 and a single lap joint using plate thickness 25mm and tension control bolts M30.The main motivation for this paper is a much higher bending resistance obtained in the 4-point bending experiments compared to predictions based on hand-calculation models.Results of experiments are used to validate finite element analysis (FEA). Explicit solver and the most realistic geometry of the bolts are the main characteristics of the FEA performed. Very good agreement between the experiments and FEA results is obtained, which provides credibility of the computational approach used to thoroughly examine experimental results. New evidences of the friction connection behaviour are provided: a short-term loss of preloading force due to external loading, transfer of shear force in the single lap joint and influence of the slotted hole on the joint resistance.Results obtained from hand-calculation models are used to predict the loss of preloading, the bending resistance of the connection and meridional stresses in the tower shell in the vicinity of the connection, which are compared to the experiments and the FEA. Recommendations related to use of the hand-calculation models in the design are provided.

Viscoelastic characterization of extraocular Z-myotomy.

Z-myotomy is an extraocular muscle (EOM) weakening procedure in which two incisions are made from longitudinally-separated, opposite EOM margins for treatment of strabismus. We examined the in vitro biomechanics of Z-myotomy using tensile loading. Fresh bovine rectus EOMs were reduced to 20 × 10 × 2-mm dimensions, and clamped in a microtensile load cell under physiological conditions. Extraocular muscles were elongated until failure following scissors incisions made from opposite sides, spaced 8 mm apart and each encompassing 0%, 40%, 50%, 60%, or 80% EOM width. Initial strain to 30% elongation was imposed at 100 mm/s, after which elongation was maintained for greater than 100 seconds during force recording at maintained deformation. Stress relaxation tests with nonincised specimens having widths ranging from 1 to 9 mm were conducted for viscoelastic characterization of corresponding equivalence to 20% to 80% Z-myotomy. Data were modeled using the Wiechert viscoelastic formulation. There was progressively reduced EOM failure force to an asymptotic minimum at 60% or greater Z-myotomy. Each Z-myotomy specimen could be matched for equivalent failure force to a non-Z-myotomy specimen with a different width. Both tensile and stress relaxation data could be modeled accurately using the Wiechert viscoelastic formulation. The parallel fiber structure results in low shear force transfer across EOM width, explaining the biomechanics of Z-myotomy. Z-myotomy progressively reduces force transmission to an asymptotic minimum for less than 60% surgical dose, with no further reduction for greater amounts of surgery. Equivalence to EOM specimens having regular cross-sections permits viscoelastic biomechanical characterization of Z-myotomy specimens with irregular cross-sections.

Cyclic loading tests for precast concrete cantilever walls with C-type connections

This study investigates the behavior of precast concrete cantilever wall systems with new vertical connections under cyclic loading. C-type steel connections for PC wall systems are proposed for the transfer of bending moments between walls in the vertical direction, whereas a shear key in the center of the wall is prepared to transfer shear forces by bearing pressure. The proposed connections are assembled easily because the directions of the slots are different at the edges of the walls. Structural performance characteristics such as the strength, ductility, and failure modes of test specimens were investigated. The longitudinal reinforcing steel bars, which are connected to the C-type connections, yielded first. Ultimate deformation was terminated owing to premature failure of the connections. The strength and deformation obtained from the cross-sectional analysis were generally similar to experimental data.

Experimental investigation on structural performance of mega column to spandrel beam connections used in high‐rise building

SUMMARYIn this paper, a new type of concrete mega column to steel spandrel beam connection was developed for the application to a high‐rise building under construction in Korea. To transfer shear force from the spandrel beams to columns, shear connectors were used, which are steel subassemblies composed of embed plates, connection plates, dowel bars and bearing plates. Experimental studies were performed using two test specimens with a 1/5 scale; in one test specimen, dowel bars welded on embed plates in a column were used, while in the other test specimen, both dowel bars and bearing plates were used. According to the test results, the design methods of the current design codes used in this study effectively addressed the failure mechanisms of the mega column‐spandrel beam connections, and the test specimens developed greater strengths than those evaluated by the current design codes. It was also found that the use of bearing plates at the connections significantly reduces the number of dowel bars used for shear transfer purposes. Copyright © 2013 John Wiley & Sons, Ltd.

Experimental Analysis of the Structural Behavior of Timber-Concrete Composite Slabs made of Beech-Laminated Veneer Lumber

AbstractComposite, timber-concrete slabs as structural floor systems for office and residential buildings, offer several technical advantages over traditional, exclusively timber floors. The connection between timber and concrete in current systems made of spruce relies on mechanical steel fasteners to transfer shear forces between the two materials. The mechanical properties of beech-laminated veneer lumber (LVL), which are higher and more reliable than spruce, allow the development of an innovative timber-concrete composite slab made of a thin beech-laminated veneer lumber plate and a concrete layer. The connection between the two materials is accomplished with notches in the timber plate instead of mechanical steel fasteners. The structural performance of this system was evaluated with a series of bending tests. The results demonstrated that this type of timber-concrete composite system was able to reach high load-carrying capacity and that the structural behavior and failure modes of the composite ele...

Fatigue of headed studs welded with improved ferrules under rotating shear force

This paper presents an evaluation of the fatigue strength of headed studs welded with improved ferrules under rotating shear force. In steel–concrete composite structures, shear connectors are essential components to transfer shear forces at the interface between steel and concrete. Particularly, headed studs in steel–concrete composite decks for highway bridges are subjected to rotating shear force when vehicle loads pass through the steel–concrete composite decks. The authors have developed welding ferrules for headed studs with higher fatigue duration than conventional headed studs. In this study, the rotating shear force was applied to the improved headed studs by using a specially developed testing machine in order to determine the fatigue strength in association with the concrete strength. The fatigue strength of the headed studs increased with the higher concrete strength and two failure modes were observed. Finally, the average S–N curves in correspondence with concrete strengths were determined for the improved headed studs.

How hydrological factors initiate instability in a model sandy slope

AbstractKnowledge of the mechanisms of rain‐induced shallow landslides can improve the prediction of their occurrence and mitigate subsequent sediment disasters. Here, we examine an artificial slope's subsurface hydrology and propose a new slope stability analysis that includes seepage force and the down‐slope transfer of excess shear forces. We measured pore water pressure and volumetric water content immediately prior to a shallow landslide on an artificial sandy slope of 32°: The direction of the subsurface flow shifted from downward to parallel to the slope in the deepest part of the landslide mass, and this shift coincided with the start of soil displacement. A slope stability analysis that was restricted to individual segments of the landslide mass could not explain the initiation of the landslide; however, inclusion of the transfer of excess shear forces from up‐slope to down‐slope segments improved drastically the predictability. The improved stability analysis revealed that an unstable zone expanded down‐slope with an increase in soil water content, showing that the down‐slope soil initially supported the unstable up‐slope soil; destabilization of this down‐slope soil was the eventual trigger of total slope collapse. Initially, the effect of apparent soil cohesion was the most important factor promoting slope stability, but seepage force became the most important factor promoting slope instability closer to the landslide occurrence. These findings indicate that seepage forces, controlled by changes in direction and magnitude of saturated and unsaturated subsurface flows, may be the main cause of shallow landslides in sandy slopes. Copyright © 2013 John Wiley & Sons, Ltd.

Investigation of shear transfer mechanisms in repaired damaged concrete columns strengthened with RC jackets

The study presents the results of an experimental program concerning the shear force transfer between reinforced concrete (RC) jackets and existing columns with damages. In order to investigate the effectiveness of the repair method applied and the contribution of each shear transfer mechanism of the interface. It includes 22 concrete columns (core) (of 24,37MPa concrete strength) with square section (150mm side, 500 mm height and scale 1:2). Ten columns had initial construction damages and twelve were subjected to initial axial load. Sixteen columns have full jacketing at all four faces with 80mm thickness (of 31,7MPa concrete strength) and contain longitudinal bars (of 500MPa nominal strength) and closed stirrups spaced at 25mm, 50mm or 100mm (of 220MPa nominal strength). Fourteen of them contain dowels at the interface between old and new concrete. All columns were subjected to repeated (pseudo-seismic) axial compression with increasing deformation cycles up to failure with or without jacketing. Two load patterns were selected to examine the difference of the behavior of columns. The effects of the initial damages, of the reinforcement of the interface (dowels) and of the confinement generated by the stirrups are investigated through axial- deformation (slip) diagrams and the energy absorbed diagrams. The results indicate that the initial damages affect the total behavior of the column and the capacity of the interface to shear mechanisms and to slip: a) the maximum bearing load of old column is decreased affecting at the same time the loading capacity of the jacketed element, b) suitable repair of initially damaged specimens increases the capacity of the jacketed column to transfer load through the interface.