Shear Resistance Capacity Research Articles

Seismic Behavior of Reinforced Concrete Columns with Light Transverse Reinforcement under Different Lateral Loading Directions

Considerable progress has been made on the strength and ductility research of reinforced concrete (RC) columns over the last two decades. However, the seismic performance of RC columns under lateral loading in different directions remains limited. This paper presents an experimental and numerical investigation carried out on RC columns with light transverse reinforcement with an emphasis on how varying the directions of seismic loading influences the seismic failure mechanisms of the columns. Seven half-scale RC columns were tested with the columns subjected to axial load and cyclic forces under reversed double-curvature bending. The parameters varied in the test program included the axial load ratio and loading directions. The overall performance of each specimen is examined in terms of cracking patterns, hysteretic response, initial stiffness, shear strength, drift ratio at axial failure, and energy dissipation capacity. A three-dimensional (3-D) finite element (FE) model is developed to supplement the experimental results. The direction of seismic loads is found to have a significant effect on the drift capacities and failure modes of both rectangular and square columns. The extent of change in the shear resistance capacity resulting from the different angles of seismic load could be predicted. A simple upper limit for shear strength contributed by concrete is proposed.

Mechanics Characteristics of Expressway Tunnel Through Fault Fracture Zone at the Entrance

Guandoushan tunnel in the Yibin - Luzhou expressway passes through fault fracture zone at the entrance. Structure internal force are complex during or after the construction. It challenges the safety during construction and operation. Plane finite element model was used to calculate internal force of primary support in the cases of different buried depths and three dimensional finite element model was applied to calculate stress distribution of primary support and secondary lining of the tunnel through fault fracture zone. The results indicate: with the increasing of buried depth, the loads acting on the structure will increase. It leads to uneven stress distribution in longitudinal direction, especially in the border of fault zone. It is suggested to increase the longitudinal reinforcement to improve overall longitudinal shearing resistance capacity and set deformation joint in the intersection to strengthen the longitudinal deformation ability of structure.

Design Concept for Local Damage of Concrete Plates Subjected to High Velocity Impact

Local damage of concrete structures, i.e. spalling, scabbing and perforation, would occur when concrete structures are impacted by high velocity projectiles. To propose protective design of concrete structures against high velocity impact, failure mechanism of local damage of concrete plates should be investigated. The authors have studied on failure mechanism of the local damage through impact tests and numerical analyses. This study presents a design concept for the local damage of a concrete plate subjected to high velocity impact. In the design procedure, occurrence of scabbing is judged based on comparison between maximum impact load and scabbing resistant capacity of the concrete plate. Impact load history and penetration depth are calculated using the modified theoretical model, and scabbing resistant capacity is estimated by applying a modified formula for punching shear resistant capacity.

A Study on Gel Fracturing Fluid for Coalbed Methane at Low Temperatures

Active water and plant gum fracturing fluids are widely used for coalbed methane in China, however, the limitations of poor rheological property, high content of water insoluble substances, and high residual content need to be resolved. Considering the low temperature (20–40°C) and low permeability of the coalbed methane reservoir, gel fracturing fluid, which can solve the problems above, was studied in this article. The gel fracturing fluid is composed of nonionic polyacrylamide, cross-linker (ZrOCl2), pH modifier, gel breaker containing (NH4)2S2O8, and activator. The optimized formula and performance evaluation of gel fracturing fluid were also investigated. The experimental results show that this gel fracturing fluid has the advantages of easy preparation, low cost, strong shearing resistance capacity, low filtration coefficient, rapid break, lack of residual after gel breaking, and ease of flow back. The performance of the gel fracturing fluid is superior to that of active water and vegetable gum, and it is very suitable for use as a fracturing treatment in coalbed methane at low temperatures.

The Shear Resistant Effect of RC Beam Strengthened with SWR External Prestressing under Cracking Width of the Original Beam

Through the experiment of the four RC beams strengthened with SWR externally prestressing, the shear resistant effect of Strengthened beams under cracking width of the original beams is studied in the paper. The ultimate load was confirmed by the test of the basic beam. First the presplitting load were respectively 50%, 60%, 70%, 80% of the ultimate load of basic beam, and seconly cracks were repaired with JN-L low viscosity pouring sealant, lastly experiment beams were strengthened by shear reinforcement of the external prestressing with steel wire rope. Loading method is the single point loading, and the shear span ratio is 2.0. The results show that: the cracking width of original beam has certain effect in shear resistant capacity. When the cracking width was less than 0.2 mm, the effect of injecting glue was not ideal and the shear resistant capacity is lower. When the crack width was bigger, the effect of injecting glue was more ideal, so the effect of reinforcement was better. When the cracking width was greater than 0.28 mm, the ultimate load was no longer improved. The smaller inclined cracking width in strengthening is, the worse repairing effect and the bigger strain value of stirrup is. Each strengthened beams’ wire rope strain increment was nearly close before cracking. As the decrease of original beams crack width, crack repair effect was weak, and the external strain increment of wire rope becomes bigger under the same load. The trend was very clear after the stirrup yielding.

Stress Analysis of Metro Shield Tunnel Segment — Based on 3D Discontinuous Contact Computational Model

Based on the 1# shield tunnel of SU ZHOU rail transit, a 3D discontinuous contact computational model of shield tunnel segment and bending bolts is built. This paper study about the stress and the deformation of shield tunnel segment with actual loads ,and the influences on shield tunnel segment by properly install the bolts. Result shows that timely apply pre-stress on the bolts could effectively decrease the deformations on segment joint by the shear resistance capacity of the bolts. The maximum deformation reduces from 3.580mm to 0.302mm. And there appear an open-angle which turn to outside or inside on segment joint. The maximum spacing of the open-angle is 0.66mm, and the maximum angle is 0.108 degree. In most position about shield tunnel segment, installed bolts reduced the axial forces and increased or reduced the bending moments.

Experimental Study and Finite Element Analysis of the Seismic Behaviors for Steel Fiber Reinforced High-Strength Concrete Frame Exterior Joints

Based on the experimental results of three steel fiber reinforced high-strength concrete frame exterior joint under the low cycle loading, the numerical simulation by nonlinear finite element method was adopted to analyze their behaviors and to explore the influence of axial compressive ratio on seismic capacity of the joint. The results indicate that the increase of the axial compressive ratio enhances the restriction role to the joint core area concrete, slows down the degeneration degree of shearing-resistance capacity and stiffness, enhances the shearing-resistance capacity of the core area, the joint ductility and the energy dissipation capacity. The finite element analysis coincides well with the experimental results. In finite element analysis, steel fiber was equated with micro-reinforcement, and then put evenly into the concrete unit. Compared with the test results, the method of taking the steel fiber and concrete as a holistic model was thus validated.

Nonlinear Seismic Behaviors of Girder Bridge with Single-Column Pier

Based on the shortcomings of the continuous girder bridge with single column pier, two-span T-shape rigid-frame bridges with single integral pier and two separated piers are put forward in this paper. Using time-history analysis and considering the material nonlinearity of reinforced concrete of the pier, the nonlinear seismic responses of the three bridge structures subjected to horizontal seismic wave are analyzed. The results show that, compared with continuous girder bridge, the shear forces of the two types of T-shape rigid-frame bridge are bigger, the moments of the T-shape rigid-frame bridges is smaller, and rotation angle of plastic hinge of T-shape rigid-frame bridge is much smaller. The energy dissipation and the anti-seismic capacities of T-shape rigid-frame bridges are better than continuous girder bridge under the condition that the shear resistance capacity of pier is secure.

Punching shear reinforcing using studs with steel plates in reinforced concrete flat plates

Flat plate structures of reinforced concrete buildings have many advantages. However, a drawback of flat structures is that they are vulnerable to punching shear failure at the column–slab connections. This study proposes a new novel technique to improve the punching shear resistance capacity in new flat plate structures using the studs with perforated steel plate reinforcement at column–slab connections. Tests were carried out on specimens of ¾ scale, which were designed to fail as a result of punching shear. The specimen variables were as follows: the first case used a stud rail and a base specimen; the second case used four stud specimens with perforated steel plates with different lengths; and the third case used a perforated steel plate with the same length as the stud with the steel plate. From the test results, the following conclusions were drawn: (a) the ultimate strengths of specimens have been designed to resist punching shear based on ACI 421 and Eurocode 2-04, and shear reinforcement for slabs has been compared with the results from the structural experiments; (b) the studs contributed substantially to the increase of ultimate strength; (c) the studs with steel plates contributed to the increase of the ultimate strength. The ratio of ductility in the specimen was larger than that of the total increase in strength.

A methodology for improving shear performance of marine grade sandwich composites: Sandwich composite panel with shear key

Researchers have developed several measures to improve shear resistance capacity of sandwich structures composed of thin composite face sheets of Eglass/epoxy and low density PVC foam core, but these methodologies are either costly or result in damage to the sandwich composites before being placed for production. A novel, innovative cost-effective methodology of introducing fiberglass shear keys attached to face skins to improve the stiffness and strength of the sandwich composite panel is being proposed in this manuscript. Manufacturing of the sandwich composite panels along with experimental and numerical investigations have been performed in this manuscript to demonstrate the potential of the proposed simple methodology which can be utilized for shear-sensitive design and analysis of sandwich composite structures and/or components. A parametric study has also been carried out to determine the effect of change in shape, size, spacing and material of the shear keys on the sandwich composite panel global response.

Exploration of numerical simulation on paleo-tectonic stress field

This paper analyzed the numerical simulation method of Paleo-tectonic stress field from three aspects: tectonic simulation target, establishment of the tectonic model, and tectonic modeling. Taking Chengzhuang coal mine of Jin city in Shanxi Province as an example, based on field investigations on macro and micro tectonic features, we established plane-stress model and 3d geological model at first, and selected mechanical parameters of rock mass, boundary condition and failure criterion of rock, then, determined the magnitude of palaeo-tectonic stress and the loading sequence of stress by using of large scale numerical simulation software ANSYS and FLAC. The simulation results show that two stages of large tectonic movement should have taken place at Chengzhuang coal mine in history, that is it is in east-west direction at first, and then turned to south- north direction; and the magnitudes and directions of tectonic stress are 60Mpa, east- west direction, and then 110 Mpa, south north direction respectively. This tectonic action could meet most shear joints on the earth and in the 3# coal rock taken place simultaneity. The region with a weak resistance capacity to deformation is easily destroyed in uniform stress field, because the shearing resistance capacity of rock mass namely internal friction angle was different. This analysis has an important significance to risk zoning and gas outburst regional predicting in coal mine.

Lateral force-displacement ductility relationship of non-ductile squat RC columns rehabilitated using FRP confinement

Post-earthquake reconnaissance and experimental research indicate that squat reinforced concrete (RC) columns in existing buildings or bridge piers are vulnerable to non-ductile shear failure. Recently, several experimental studies were conducted to investigate upgrading the shear resistance capacity of such columns in order to modify their failure mode to ductile one. Among these upgrading methods is the use of fibre-reinforced polymer (FRP) jackets. One of the preferred analytical tools to simulate the response of frame structures to earthquake loading is the lumped plasticity macromodels due to their computational efficiency and reasonable accuracy. In these models, the columns' nonlinear response is lumped at its ends. The most important input data for such type of models is the element's lateral force-displacement backbone curve. The objective of this study is to verify an analytical method to predict the lateral force-displacement ductility relationship of axially and laterally loaded rectangular RC squat columns retrofitted with FRP composites. The predicted relationship showed good accuracy when compared with tests available in the literature.

Behavior of beams with dowel action

The phenomenon of dowel action as a shear transfer mechanism across cracks has long been recognized as an important component of the overall shear resistance capacity of reinforced concrete beams. In this paper, a simple analytical model for the dowel action of reinforcing bars crossing cracks is developed for analysis of reinforced concrete beams. This model is incorporated into a computer program that uses the displacement method and the initial stiffness procedure. The nonlinear behaviors of several reinforced concrete beams tested by others are analyzed. The beams are analyzed first with the dowel action neglected and then with the dowel action considered. It is found that in certain cases, the dowel action can have significant effects on the shear strength of reinforced concrete beams and that the theoretical results of the proposed model generally agree better with the experimental values when the dowel action is accounted for.

Research on Shear Resistant Capacity and Reliability of Multi-Ribbed Composite Wall in High-Rise Building

As a new structural system, MRSS (multi-ribbed slab structure) has some applications in multistory building. But theoretical investigation and application study on multi-ribbed composite wall in high-rise building should be developed with various factors composing shear resistant capacity of wall under complicated loads. By means of model test and numerical simulation with FEM (finite element method), shear resistant expression of slab in tall building is set up and reliability index of a representative wall under small earthquake is figured out. Sensitivity of each factor affecting shear strength is evaluated. These works disclose the wall’s load bearing mechanism and make the structure application more feasible and assure the new system safety in practice.

Shear strengthening of beam-column joints

Shear failure of beam-column joints is identified as the principal cause of collapse of many moment-resisting frame buildings during recent earthquakes. Effective and economical rehabilitation techniques for the upgrade of the joint shear-resistance capacity in existing structures are needed. The objective of this research is to develop effective selective rehabilitation schemes for reinforced concrete beam-column joints using advanced composite materials. Several reinforced concrete beam-column joints were constructed. The joints were designed to simulate nonductile detailing characteristics of pre-seismic code construction. The control specimens showed joint shear failure when subjected to cyclic loading at the beam tip. Different fibre-wrap rehabilitation schemes were applied to the joint panel with the objective of upgrading the shear strength of the joint. The tested rehabilitation techniques were successful in improving the shear resistance of the joint and in eliminating or delaying the shear mode of failure.