Two-way Shear Research Articles

Effect of cyclic jacking on sand-pile interface shear behaviour

Pile jacking is a kind of competitive method for pile installation due to its less noise and vibration pollution. In this paper, the pile jacking process has been numerically simulated by considering the friction fatigue, and the characteristics of sand-pile interface shear paths at different depths were thoroughly investigated. It is found that during the cyclic jacking process, the interface shear path at a specified depth tends to transform from one-way shear to two-way shear, especially for the shallow to middle depth. But for the deep soil layer, one-way cyclic shear is still the dominated loading mode. Focusing the effects of different paths on the sand-pile interface shear behaviours, a series of cyclic interface shear tests have been conducted, in which two types of sands and four typical shear paths were adopted. It has been revealed that during continuous jacking process, the sample volume response changes significantly with different interface shear paths. The previous shear path also plays a key role in the cyclic degradation of interface strength with CNS (constant normal stiffness) condition. If the sample contraction is small during jacking process, the cyclic degradation of interface strength is obvious. But, when the sample contraction during jacking process is significant, the interface strength degradation is largely suppressed. This is mainly because the abundant broken fine particles along the pile shaft will fill into the voids and make the sand sample near the interface much denser. It is shown that the changes of pile-soil interface characteristics will affect the pile responses.

Design of lightweight concrete slabs under two-way shear without shear reinforcements: A comparative study and a new formula

Developing design models that are accurate compared to experimentally measured strength, yet physically sound, continues to be the ultimate research goal. For this purpose, the two-way shear design provisions of the American design codes have been updated. While that of the European design codes are being investigated. The two-way shear failure of slabs is a sudden one, which can be catastrophic. In addition, lightweight concrete (LWC) is gaining a lot of attention due to its economic advantage, however, very limited studies focus on investigating LWC slabs under two-way shear loading. The purpose of this study is to examine existing design codes and ongoing proposals for the case of LWC slabs under two-way shear. A comprehensive literature review of the available two-way shear testing for LWC slabs was conducted. An extensive database with a total of 129 tested LWC slabs was compiled. Selected design codes were used to calculate the two-way shear strength of the tested slabs. The Strength ratio (SR) was compared for selected codes, which is calculated as the ratio between the experimentally measured strength and that calculated using different design codes. In addition, the effect of various parameters on the SR was assessed. Concluding remarks were outlined and discussed. Moreover, a design formula for LWC slabs under two-way shear, which is physically sound and simple was developed and validated using experimental results. It was found to be more accurate, and more consistent compared to existing design codes with regard to experimentally measured strength. It is worth noting, that the investigated draft of the Eurocode is not final. However, these findings could help develop future design provisions for two-way shear of LWC slabs, which have to be physically sound, more consistent, and more accurate compared to existing one.

Study on shear behavior and capacity of biaxial ellipsoidal voided slabs

The numerous advantages of solid slabs, including adequate rigidity, appropriate fire resistance, and sound insulation, have further extended the system’s applications. The main disadvantage of this system is, however, its extreme weight, especially in long spans. Since concrete is not involved in bearing in the tensile zone, its removal can lower the weight without affecting the load bearing of the slab. In a number of systems, namedbiaxialvoided slabs, ellipsoidal or spherical sacrificial plastic balls are used to create voids within the concrete. As this system has just been introduced, considerable uncertainties have been raised about one-way and two-way shear behaviors of the system. Accordingly, four full-scale specimens were built in order to investigate these behaviors. Two one-way and two two-way full-scale shear specimens with dimensions of 3500 × 1200 × 200 mm and 2300 × 2300 × 200 mm (length × width × height) were constructed, respectively. These specimens were used to compare the shear capacity, cracking distribution, and deflection in solid andbiaxialvoided specimens. Also, the effect of vertical rods of steel cages on the shear behavior was investigated. The results show the steel cages clearly contributed to shear bearing; and although the shear capacity of voided specimens was less than solid ones, the failure mode of all specimens was shear. Finally, a new method was proposed to predict the ratio of shear capacity ofbiaxialvoided slabs to solid slabs. Hence, the proposed method can predict the ratio of biaxialvoided capacitytosolid slab capacity with an adequate precision.

Fiber Reinforced Polymer Laminates for Strengthening of RC Slabs against Punching Shear: A Review.

Reinforced concrete flat slabs or flat plates continue to be among the most popular floor systems due to speed of construction and inherent flexibility it offers in relation to locations of partitions. However, flat slab/plate floor systems that are deficient in two-way shear strength are susceptible to brittle failure at a slab–column junction that may propagate and lead to progressive collapse of a larger segment of the structural system. Deficiency in two-way shear strength may be due to design/construction errors, material under-strength, or overload. Fiber reinforced polymer (FRP) composite laminates in the form of sheets and/or strips are used in structurally deficient flat slab systems to enhance the two-way shear capacity, flexural strength, stiffness, and ductility. Glass FRP (GFRP) has been used successfully but carbon FRP (CFRP) sheets/strips/laminates are more commonly used as a practical alternative to other expensive and/or challenging methods such column enlargement. This article reviews the literature on the methodology and effectiveness of utilizing FRP sheets/strips and laminates at the column/slab intersection to enhance punching shear strength of flat slabs.

Two-way Shear Behavior Analysis of Transfer Slab-Column Connection with Reverse Drop Panel Through Nonlinear FE Analysis

최근 건축구조물에서 전이슬래브 시스템의 사용이 증가하고 있다. 하지만 과도한 전이슬래브의 두께로 인한 경제적, 시공적인 문제가 많이 발생하고 있다. 따라서, 본 연구에서는 피트층의 설비 공간을 활용하여 전이슬래브의 두께를 절감하기 위하여 역드랍 패널을 적용한 전이슬래브 시스템을 고려하였다. 역드랍 패널을 사용하여 전이슬래브의 2면 전단강도를 증진시킴으로써 전이슬래브의 두께를 줄이고자 하였다. 따라서, 역드랍 패널을 이용한 전이슬래브 시스템의 유효성을 검증하고 전단거동을 조사하기 위하여 다양한 설계변수에 대한 역드랍 패널을 적용한 전이슬래브-기둥 접합부의 전단거동을 기존연구에서 검증된 비선형 FEM 해석방법을 사용하여 분석하였다. 최종적으로 비선형 FEM 해석결과와 기존의 2면 전단강도 평가식으로 예측한 전단강도를 비교·분석하여 기존 평가식의 역드랍 패널을 적용한 전이슬래브-기둥 접합부의 2면 전단강도 평가에 대한 유효성을 검증하였다.

A comparative study of shear design methods for straight and skew concrete slabs

The shear behaviour of concrete members has been long investigated; however, there is still no consensus on a single design approach. Shear failures are generally brittle, hence highly undesired. Failure modes are traditionally classified into one-way and two-way (punching) shear. Nevertheless, in concrete slabs intermediate cases are observed when a concentrated load is located close to the supports. These cases are not considered in most codes of practice, despite some investigative efforts conducted in recent years. Furthermore, knowledge about the shear behaviour of skew slabs is still limited.This paper reviews the shear design provisions of main codes of practice, as well as relevant research on concrete slabs subjected to concentrated loads close to supports. Procedures for extending the code provisions to the design of skew slabs are proposed. These are illustrated and validated through the case studies of two skew railway decks, one simply-supported and the other continuous. Some scatter is found across different codes of practice, broadly reflecting their predominant parameters. The procedures are also compared to the limited experiments on skew slabs available in the literature. It is found that the predicted shear strengths are considerably smaller than the experimental values. Unexpectedly, the experiments highlighted a modest influence of the reinforcement grid orientation, which confirms that the mechanisms underlying shear design in slabs still need to be fully understood.

Scale-up of NiTiHf shape memory alloy tubes with high torque capability

High-torque, NiTiHf high-temperature shape memory alloy tubes were examined by means of constant-torque thermal cycling experiments. The alloy, with a Ni-rich composition of Ni50.3Ti29.7Hf20 (at%), was hot worked via extrusion from large ingots to produce final rods with an outer diameter of 25.4 mm. After aging at 550 °C for 3 h and air-cooling, the manufactured torque tubes were subjected to shear stresses from 0 to 500 MPa (torques of 0–1400 N m) and thermally cycled 20 times under stress, and twice after stress removal to evaluate the two-way shape memory effect. A transformation shear strain of 6% was obtained, and a maximum work output of 27.5 J cm−3. Two-way shear strains approached 3% strain without any extended training or cycling. The strain values obtained for the first time in this large-diameter, high-torque tube consistently matched smaller diameter tubes previously reported. This highlights the successful production and scale-up of both the material and the component level in torque tubes without degrading the actuation response, while providing much higher torque capability.

Efficient Two-Way Shear Grillage Model Solution for Bridge RC Four-Pile Caps under Wall Loading

Reinforced concrete four-pile caps under wall loading occur in heavily loaded foundations in bridge construction. The failure mode of shear across the full width of the cap may occur in these deep structural elements. A statically determinate two-way grillage model, comprising orthogonal deep beam grillage elements obeying a predetermined test observing deflection pattern and boundary conditions, is established to solve the structure’s shear capacity. The model gives more accurate and faster solutions than the traditional strut-and-tie method and commercial nonlinear numerical modeling. A key step to solving the model is a linear constitutive (load-deflection) relationship developed for the grillage elements. The grillage model is verified against laboratory experiments for nine pile caps at the University of Southampton (UoS) with the results of a numerical modeling parametric study. A Visual Basic Userform-based design software is developed, incorporating the model and enabling engineers to obtain the shear capacity, full-field reinforcement stress distribution, and cap deflections within seconds.

Experimental and analytical investigation of punching shear capacity of biaxial voided slabs

Biaxial voided slab is an emerging slab system which reduces its self-weight up to 50% in comparison with the conventional reinforced concrete solid slab. The reduction in the concrete volume does not affect its flexural capacity significantly, however, it reduces both one-way and two-way (punching) shear capacity about 40%. Therefore, an effective way of predicting the punching shear capacity is investigated as the presence of voids alters the critical failure section. The applicability of conventional methods for solid slabs in the design standards, such as ACI 318 (2014), EN 1992-1-1 (2004) and IS 456 (2000) to predict the punching shear capacity of the voided slab is examined. In addition, eight full-scale specimens were tested with the sphere and cuboid shape of voids. Finally, experimental results of present study and test data collected from literature (33 specimens) were compared with predictions by the relevant code provisions. The estimation of punching shear capacity of biaxial voided slab by existing provisions for solid slabs in standards does not lead to satisfactory results. Hence, the presence of voids is considered by modifying the critical section depending on the void location. Further, only the effective concrete area is considered to predict the punching shear capacity. After the modifications, the predictions by all three building standards lead to satisfactory results.

Experimental study of shear-key equipped pile to grout connection under cyclic loading

A technical solution for tidal turbine foundation in granite seabed consists of grouted steel piles. The piles would be subjected to cyclic loading due to the severe service conditions. The mechanical behaviour at the interface between the pile and the surrounding media is one of the key points that determine the bearing capacity of the foundation system. Experimental research work has been carried out in the laboratory to study the grouted pile-to-rock connection (GPRC) and focused more precisely on the pile to grout connection when the pile is equipped with shear-keys that enhance the interface capacity. Monotonic and cyclic shear tests were performed using a specific direct shear test device (BCR3D), allowing application of sample confining conditions close to the in-situ conditions, namely constant normal stiffness conditions. Cyclic tests - either under one way or two-way shear loading application - were performed on several samples, under both constant volume and various constant stiffness boundary conditions. This study has shown that the strength of the interface is highly dependent on the combination of mean load, cyclic amplitudes and number of cycles applied to the interface. Cyclic failure was observed with less than 30 cycles for two-way and one-way cyclic loading.

Numerical study for the effect of hairpin shaped shear reinforcement on one-way shear capacity of reinforced concrete beams

This study investigates the effectiveness of using Hairpin shaped stirrups to increase the shear capacity of beams and slabs. The hairpin system consists of inverted U-shape stirrups welded to flexural corner rebar. Previous research works proved the increase of the hairpin system in increasing the two-way shear capacity compared to conventional punching reinforcement. However, the system’s ability to increase the shear capacity of beams has not been explored. This paper presents the results of Finite Element simulation of two beams performed using ABAQUS Software; one beam is reinforced with conventional shear stirrups, and the other is reinforced with hairpin stirrups. The load capacity, deflection and damage pattern of the two beams were compared. Results showed that beams reinforced with hairpin stirrups have higher load capacity and ductility compared to beams with conventional stirrups. However, the reinforcement type had little effect on the shear damage pattern.

Two-way Shear Strength Evaluation of Transfer Slab-Column Connections Through Nonlinear FE Analysis

최근 국내에서는 고층 벽식 아파트 건설 시, 하부 주차공간과 공용공간 확보를 위하여 RC 전이슬래브 시스템을 사용하는 경우가 증가하고 있다. 하지만 두께가 얇은 RC 무량판 슬래브를 위해 개발된 설계방법 및 구조성능평가 방법을 두께가 매우 두꺼운 전이슬래브 구조설계에 그대로 사용하고 있다는 문제점이 있다. 따라서 합리적인 전이슬래브의 구조설계를 위해서는 RC 전이슬래브 시스템의 2면 전단거동 양상에 대한 명확한 분석이 필요하다. 이에 따라 본 연구에서는 전이슬래브의 두께, 콘크리트 강도, 전단경간비, 철근비 등 다양한 설계변수에 따라 비선형 FEM을 이용하여 전이슬래브의 2면 전단거동을 분석 하였다. 또한 비선형 FEM 해석결과와 기존의 2면 전단강도 평가식으로 예측한 전단강도를 비교분석하여 기존 평가식의 전 이슬래브 2면 전단강도 평가 유효성을 검토하였다.

STUDI PERENCANAAN STRUKTUR PONDASI TIANG PANCANG GEDUNG FAKULTAS SYARIAH IAIN PONOROGO

ABSTRACTThe foundation is a basic construction of a building that functions to carry away dead loads, live loads and angina loads and earthquake loads of a building to the soil layer which is at the bottom without causing excessive soil collapse. In this calculation I use the mayerhoff method and the calculation based on the results of the analysis of the carrying capacity of single and group foundations can be concluded that: 1. the results of loading analysis that occurred in the IAIN Ponorogo Sharia Faculty Building 379,198.5 kg. 2. the calculation of the sondir which is carried out by the hard soil depth reaches a depth of 5.8 meters. Calculation of pile foundation using a diameter of 40 cm with reinforced iron D16 iron spacing 125 with 5 reinforcement contents, and said SAFE. 3. The results of the shear force control calculation: a. Calculation of One-Way Shear Control = 1,085.34 tons> Nominal Shear Force = 348.05 tons said SAFE b. Calculation of Two-Way Shear Control = 1.272.45 tons> Nominal Shear Force = 877.91 tons said SAFE, 4. The pile foundation will experience cracking when there is a moment of 58,278,400 tons / m2 <150 tons / m2 maximum moment SAFE is permitted and said the decrease that will occur is 4,644 mm <360 mm, a decrease that is permitted and said SAFE. Keywords: pile foundation, meyerhoff method, fracture of pile foundation, reduction / pile foundation stability.

Constant-torque thermal cycling and two-way shape memory effect in Ni50.3Ti29.7Hf20 torque tubes

Ni-rich Ni50.3Ti29.7Hf20 (at%) high-temperature shape memory alloy tubes were thermomechanically cycled under constant torques. Four loading configurations were examined that consisted of a series of ascending stresses (low-to-high stress from 0 to 500 MPa outer fiber shear stress), a series of descending stresses (high-to-low stress from 500 to 0 MPa), and a series of thermal cycles at a constant stress of 500 MPa, all using an upper cycle temperature (UCT) of 300 °C. The last configuration consisted of another series of ascending stress levels using a lesser UCT of 250 °C. It was found that the descending series trial stabilized the material response in fewer cycles than the other loading paths. Similarly, cycling at a constant stress of 500 MPa for approximately 100 cycles reached near stabilization (<0.05% residual strain accumulation). Transformation shear strains were the highest and most stable when cycled from lower-to-higher stresses (ascending series), reaching 5.78% at 400 MPa. Cycling to lesser UCTs of 250 °C (versus 300 °C) resulted in the highest two-way shape memory effect (TWSME), measuring over 3.25%. This was attributed to the effect of retained martensite and any transformation dislocations that served to stabilize the TWSME at the lower UCT. Results of this study suggest that different training paths might be used, depending on actuator performance requirements, whether the principal need is to maximize transformation strain, maximize the two-way shear strain, or stabilize the response in fewer cycles.

Experimental Study on Flexural Behavior of Precast Concrete Shear Walls with Vertical Joint

Background: To study the flexural behaviors of the concrete shear walls with precast hollow slab, one cast in-situ reinforced concrete shear wall and two precast two-way hollow slab shear walls (PTHSWs) vertical joint were tested under low cyclic loading. Objective: The study showed that vertical joints of PTHSW are safe and reliable to ensure the effective connection between the assembly units. The ductility coefficient of shear wall is larger than 7, so this kind of shear wall has good ability of deformation especially under earthquake load. Results: The interface can effectively ensure the integral performance of PTHSWs and its effect on the flexural behaviors of PTHSWs could be ignored.

Transition from one-way to two-way shear in slabs under concentrated loads

The long-standing problem of shear in structural concrete elements is typically studied as one-way shear in beams, or as two-way shear in slab–column connections. The problem of one-way shear in slabs, as encountered by bridge engineers when considering the concentrated live loads on slab bridges, is not described by codes. This paper reviews the literature regarding one-way slabs and wide beams failing in shear. The mechanisms of shear transfer and the existing models and code methods for one-way and two-way shear are reviewed. Subsequently, the similarities, differences and the transition zone between one-way and two-way shear, and the models representing these failure modes, are studied. This overview of the literature highlights that knowledge of one-way shear is limited to the comparison with small, heavily reinforced slender beams and of two-way shear to the comparison with slab–column connections. The transition zone between these two failure modes, which often occurs in structural concrete elements used in practice, is typically not studied. Possible solutions for the transition zone between the two failure modes are listed.

Database of wide concrete members failing in shear

Shear in reinforced members has been a topic of study for many decades. Recently, the shear capacity of slabs subjected to concentrated loads – the case between one-way shear (also called beam shear) and two-way shear (or punching shear) – has been given more attention because this case is encountered in bridge engineering. This paper aims to give an overview of the existing code methods for shear and to bring together experiments from the literature on wide beams and slabs failing in shear. The database of collected experiments is then compared with the Eurocode provisions. A large scatter was found in the ratio of experimental to predicted values. This observation indicates that the experiments under consideration should be studied in subsets according to the failure mode and that better methods for determining the shear capacity of wide concrete members are necessary. The database also shows the need for experiments aimed at studying shear in one-way slabs and the effect of different parameters on the shear capacity.

Research on Shear Performance of Asphalt Mixture Based on RSCH

On the use of the Superpave Shear Test which was developed by Stratagem Highway Researching Plan in America (SHRP),this paper simulates the effect of two-way shear load in asphalt concrete (AC) overlay on the existing cement concrete pavement. According to the RSCH research on 7 kinds of asphalt mixtures,evaluating the shear performance of asphalt mixtures. The results showed that: 1. There was a significant correlation between the repeated shear times and shear strain using logarithmic curve; 2. void ratio had a greater influence on the shear performance of asphalt mixture.With greater void ratio, the shear strain is more sensitive to load. It takes more shear deformation to enter the stage on shear stability, and the stronger the ability to adapt for shear deformation; 3.with the same gradation and different asphalt variety, shear performance are different. When asphalt mixture is subjected the shear action, especially the instantaneous load, a high viscosity bitumen asphalt mixture can be given a large viscous resistance.

Research on Performance of Precast Two-Way Hollow Slab Shear Wall with Cast-&lt;i&gt;In Situ&lt;/i&gt; Boundary Elements

Low cyclic loading tests were carried out for one precast two-way hollow slab shear wall with cast-in-situ boundary elements and one RC shear wall. The seismic performance of precast two-way hollow slab shear wall was analyzed. The test results indicated that macroscopic vertical cracks appeared along precast slab vertical holes of precast two-way hollow slab shear wall. The failure characteristics of the precast two-way hollow slab shear wall were significantly different from that of the reinforced concrete shear wall. Shear failure could be avoided and seismic performance of the new type shear wall was good.

Comparative Study for Punching of FRP-Reinforced Concrete Slabs

The noncorrosive fiber-reinforced polymer (FRP) composite bars are an excellent alternative reinforcement. In this paper, a review of the available punching load equations of two-way FRP-reinforced slabs and shear strength equations of one-way FRP-reinforced slabs is provided. All the models were verified against results for test specimens from the literature. The equivalent steel ratio model of Theodorakopoulos and Swamy produced the best estimates for the punching load while the model of Deitz, Harik, and Gesund yielded the best predictions of shear capacity. One of the punching strength models was modified in the current research and it gave excellent results. Using this modified model, it is proved that the increase in the reinforcement ratio is accompanied by an increase in the punching strength.