Shear Strength Of Walls Research Articles

Low Cycle Test Research on Seismic Performance of Recycled Concrete Block Wall

The use of concrete aggregate from earthquake damaged building to make blocks which needed for post-disaster reconstruction has brought the social, environmental, economic and other benefits, at the same time respond to the basic state policy of low carbon energy saving. At home and abroad currently focused on the materials properties of recycled aggregate and recycled concrete block basic physical mechanics to study, but research for the material block wall structure performance is less, the research for the wall shear strength and anti-seismic performance of this kind of wall is of great significance. Based on the recycled concrete aggregate from Mianyang, Sichuan where is disaster area to make three hole hollow block wall (no reinforcement) to perform low cycle experiment, collecting four samples, and achieved anti-seismic indicators such as the hysteresis curves, skeleton curves of recycled concrete block wall, analyzes the influence of the axial pressure, the loading method on seismic performance of block wall.

Simulation of reinforced concrete short shear wall subjected to cyclic loading

This paper addresses the strength and deformation capacity of stiff squat shear wall subjected to monotonic and pseudo-static cyclic loading using experiments and analysis. Reinforced concrete squat shear walls offer great potential for lateral load resistance and the failure mode of these shear walls is brittle shear mode. Shear strength of these shear walls depend strongly on softening of concrete struts in principal compression direction due to principal tension in other direction. In this work simulation of the behavior of a squat shear wall is accurately predicted by finite element modeling by incorporating the appropriate softening model in the program. Modification of model of concrete in the softening part is suggested and reduction factor given by Vecchio et al. (1994) is used in the model. The accuracy of modeling is confirmed by comparing the simulated response with experimental one. The crack pattern generated from the 3D model is compared with that obtained from experiments. The load deflection for monotonic loads is also obtained using softened truss theory and compared with experimental one.

An Evaluation of Design Code Expressions for Estimating in-plane Shear Strength of partiallY Grouted Masonry Walls

This paper aims to evaluate the in-plane shear strength expressions of partially grouted masonry (PGM) walls in four international design codes, including masonry design codes of practice in the United States, New Zealand, Canada and Australia. Experimental results of 89 partially grouted masonry walls that displayed shear failure were collected from published research. The shear strengths of the walls in the database were calculated using the different code equations and compared with those from the experimental results. In addition, the parameters that influence the shear strength of the walls, including masonry tensile strength, level of axial compressive stress, wall aspect ratio, and the amount and spacing of vertical and horizontal reinforcement are studied. Both univariate and multivariate regression analysis have been employed to investigate the effect of each parameter on the accuracy of the code shear strength predictions. This study illustrates poor correlation between code predictions and test results, indicating that current codes are unable to predict the shear strength of PGM walls. In some cases the code shear strength predictions are three to four times the experimentally measured shear strength, indicating that modifications are needed as the current provisions are unconservative. An equation is therefore proposed which better estimates the strength of PGM walls.

壁許容耐力に基づく木質制振住宅の簡易設計法

In order to mitigate seismic damage of timber houses, application of passive control devises is demanded. The authors have developed high performance shear walls with various types of dampers, which are called “energy dissipation walls”. For the future, new design method has to be proposed to generalize passively controlled timber structures. In this paper, a method to evaluate allowable strength of shear wall is proposed. Advantage of passively controlled structure is to reduce maximum deformation, and energy dissipation walls are added to a structure so that maximum deformation angle of the structure subjected to level2 earthquake is less than target deformation. Accuracy of the method is demonstrated through a lot of non linear time history analyses.

Reinforcement contribution to the behavior of low-rise concrete walls

Based on steel strains recorded during shake table tests of six wall specimens, the effect and contribution of steel reinforcement to peak shear strength and displacement capacity of low-rise concrete walls is assessed and discussed. The experimental program included four variables such as wall geometry, concrete type, web steel ratio and type of web reinforcement. Wall response was assessed through effective steel strains in vertical reinforcement, efficiency factors of wall reinforcement, contribution of web horizontal reinforcement to wall shear strength, and the effect of type of web reinforcement to wall displacement.

The Study of Sand Hole Collapse Mechanism

When constructed the bored pile in sand layer, it is easily to appear the under-reaming and hole collapsed phenomenon. Then it will lead to the engineering disasters, such as hole collapsed, burying drilling and super party amount of concrete. Through the mechanics analysis of the fine sand in the hole process, we found that the mud turbulence will be broken in the drilling process which can cause the water in the hole to be turbulent fluctuation. The result of turbulent fluctuation is making the slurry wall inside and outside the test pressure difference exceeds the wall shear strength which results in the wall off block. At the end, the sand soil collapse dropping leads to the engineering disaster.

A statistical and experimental investigation into the accuracy of capacity reduction factor for cold-formed steel shear walls with steel sheathing

Buildings constructed of cold-formed steel members are increasingly used in many countries. In recent years, cold-formed steel shear walls with steel sheathing were introduced as lateral force resisting systems. Design provisions of these structures require that the shear strength of shear walls with a height to width aspect ratio (h/w) greater than 2:1 be reduced by the factor 2w/h for satisfying allowable story drift limit. In this research, the accuracy of the factor is investigated using the results of previous tests and the tests performed by the researcher. Results show that the reduction factor (2w/h) is conservative. Thus, a relation is proposed for the reduction factor.

A model for pushover analysis of confined masonry structures: implementation and validation

Confined masonry (CM) is a typical building technique in Latin American countries. This technique, due to its simplicity of construction and similarity with traditional practices of reinforced concrete building, presents a potential of use in European regions with moderate-to-high seismicity. However, most of the procedures for seismic design in codes for Latin America are force-based, which appears to be inadequate due to the high dissipative response observed for CM. This paper presents a simplified numerical-analytical approach to model CM structures using pushover analysis, aiming to apply performance-based design procedures. First, a data mining process is performed on a database of experimental results collected from lateral tests on CM walls to adjust prediction models for the wall shear strength and to determine the input relevance through a sensitivity analysis. Then, an analytical model of CM structures for pushover analysis is proposed with basis on a wide-column approach that employs an adaptive shear load-displacement constitutive relation. The proposed method is compared with a discrete element model that represents explicitly the confinements-masonry interaction, against the experimental results obtained in a quasi-static test of a full-scale tridimensional CM structure. The accuracy of the predictions from both methods is very satisfactory, allowing to capture the base shear-displacement envelope and also the damage patterns of the structure, thus, demonstrating the ability of the methods to be used in performance-based seismic assessment and design of CM buildings.

Cyclic Performance of Glued Laminated Guadua Bamboo-Sheathed Shear Walls

AbstractThis paper presents a study aimed to determine the cyclic performance of wood-frame shear walls sheathed with glued laminated Guadua bamboo (GLG) panels as a first step to evaluate their potential application. GLG-sheathed walls having 2:1 and 1:1 aspect ratios and three different sheathing nail spacing were tested under cyclic conditions. Parameters, such as peak shear strength, shear modulus, displacement ductility demand, and energy dissipation of the walls, were examined. Values for peak shear strength were then compared with those of walls sheathed with wood or wood-based panels. The wall aspect ratio was found to be a parameter with lesser impact than nail spacing. It was also found that the reduction in nail spacing increases to some extent the strength, stiffness, and energy dissipation, but lowers the ductility of the wall. The peak cyclic shear strength of shear walls sheathed with GLG panels was found to be within the shear strength reported for wood or wood-based panels and the tested ...

Autoclaved Fly Ash-Lime Brick Wall of the Proposed Shear Strength Formula

In this paper, the author by 12 slices fly ash brick masonry wall (solid brick and cork brick) slice, 2 slices of sintering ordinary brick masonry wall under cyclic horizontal and vertical loading experiment (including different normal stress, different mortar strength, and presence of post) is given, according to three of the most popular theory. The author suggest the autoclaved fly ash brick masonry proposed formula with Changsha university of science and technology, and Chongqing university the relative test data after that compared, autoclaved fly ash brick wall shear strength calculation formula is recommended. The method of the present paper may provide an important reference to engineering design as well as code revision.

A new proposal to reinforce planked timber shear walls

Timber is one of the most common materials used in traditional buildings worldwide. Our previous research has suggested that timber shear walls play an important role in resisting external loadings, such as earthquakes. Thus, improving the structural performance of in-filled shear walls can also improve that of the entire structure. In the traditional Taiwanese timber shear wall system, the embedment strength of beams and friction between wooden planks and beams significantly affect the strength of the shear wall. This article proposes a new method of reinforcing traditional timber shear walls in Taiwan by inserting teak and padauk strips into the grooves between wooden planks and beams to increase the embedment strength of beams and the friction between wooden planks and the hardwood strips. A total of 18 full-scale specimens were tested under reversed cyclic loading. The results revealed that the strength and energy dissipation capacities of a wooden shear wall can be significantly increased by inserting teak and padauk strips into the grooves between planks and beams. Furthermore, the simplified calculation method proposed in this study can be used to calculate the strength of both reinforced and unreinforced wooden shear walls with satisfactory agreement.

Retrofitting Effect of Unreinforced Masonry Walls Using FRPs

Unreinforced masonry buildings have significant portion of existing and historical buildings around the world. Recent earthquakes have shown the needs of seismic retrofitting for these types of buildings. There are many types of retrofitting materials for URM(unreinforced masonry buildings) such as shotcrete, ECC and FRPs. Many engineers use many types of fiber reinforced polymers because these types of material enhance the shear strength of wall without expansion of wall sectional area and additional weight of total structure. However, the complexity of mechanical behavior of masonry shear wall and the lack of experimental data of masonry wall which was retrofitted by FRPs may cause the problem that engineers hard to determine the retrofitting level. Determining and providing the information for retrofitting effect of FRPs for masonry shear wall, this paper investigate in-plane shear behavior of URM and retrofitted masonry shear walls using two types of different FRP materials. Specimens were designed to idealize the wall of low rise apartment which was built in 1970s Korea with no seismic reinforcements and have 1 aspect ratio. Retrofitting materials were carbon FRP and Hybrid sheet which have different elastic modulus and ultimate strain. Consequently, this study will evaluate the structural capacity of masonry shear wall and retrofitting effect of FRP sheet for in plane shear behavior comparing with evaluation method for reinforced concrete beam which was retrofitted by FRPs.

개구부를 갖는 철근콘크리트 전단벽의 전단강도 저감률

리모델링에는 여러 형태가 있을 수 있다. 그 중 건축주나 리모델링 수행자가 선호하는 방법이 두 개의 주거공간을 하나로 만들어 평면 확장을 목표로 하는 세대 병합형 리모델링이다. 그러나 이러한 방법을 현재 국내에서 리모델링 대상이 되고 있는 벽식 구조의 아파트에 적용할 경우 주요 횡력 저항 요소인 전단벽에 큰 손상을 가하게 될 수 있다. 그러나 아직 이러한 주요 구조 부재인 철근콘크리트 전단벽에 개구부가 발생할 경우의 명확한 손상 정도를 정의해주는 연구는 진행되고 있지 않은 실정이다. 현행 ACI 기준은 이러한 철근콘크리트 전단벽 내의 개구부에 대한 명확한 고려 방안을 제시하지 않고 있다. 반면 AIJ 기준은 철근콘크리트 전단벽 내부의 벽체에 대한 고려 방안으로 강도 저감률 γ를 제시하고 있다. 그러나 이 강도 저감률은 탄성 판 이론으로부터 제시된 것으로 철근콘크리트 부재에 있어서의 강도 저감률을 제대로 표현하지 못하고 있는 실정이다. 그러므로 이 연구에서는 AIJ에서 제시하고 있는 강도 저감률 γ에 대하여 현재까지 진행되었던 실험 결과에 대한 통계적 분석과 유한요소해석을 통한 변수 분석을 통해 개구부에 의한 강도 저감률에 대한 연구를 수행하였다. 통계적 분석 결과 현재 제시되어 있는 강도 저감률은 개구부의 벽체면적에 대한 비율만을 변수로 설정하여 그 저감률이 실험 결과보다 크게 나타나고 있었다. 또한 개구부의 형상비를 면적과 통합적으로 고려하며 철근비에 대한 고려를 하지 못하는 것으로 나타났다. 이에, 기존의 실험 결과와 이를 토대로한 유한요소해석을 통한 변수분석을 수행하여 새로운 강도 저감률을 제안하였다.

Weighted operation structures to program strengths of concrete-typed specimens using genetic algorithm

This study introduces weighted operation structures (WOS) to program engineering problems, in which each WOS adopts a fixed binary tree topology. The first WOS layer serves as the parameter input entrance. The target is produced at the eventual layer using both values and a mathematical formula. Each WOS element is operated by two front nodal inputs, an undetermined function, and two undetermined weights to produce one nodal output. This study proposes the novel concept of introducing weights into a WOS. Doing so provides two unique advantages: (1) achieving a balance between the influences of two front inputs and (2) incorporating weights throughout the generated formulas. Such a formula is composed of a certain quantity of optimized functions and weights. To determine function selections and proper weights, genetic algorithm is employed for optimization. Case studies herein focused on three kinds of concrete-typed specimen strengths: (1) concrete compressive strength, (2) deep beam shear strength, and (3) squat wall shear strength. Results showed that the proposed WOS can provide accurate results that nearly equal the results obtainable using the familiar neural network. The weighted formula, however, offers a distinct advantage in that it can be programmed for practical cases.

ANALYTICAL SIMULATION OF DISPLACEMENT RESPONSES FOR TWO-STORY WOOD FRAMES WITH OIL-DAMPERS SHEAR WALL AND DESIGN VALUE FOR WOOD SHEAR WALL WITH DAMPER

The main objective of this study is to analyze a two-story wood structure consisting of shear wall with oil-damper and structural plywood wall using time history response analysis. It is important to evaluate the nonlinearity of support members for connecting damper and structural frame in wood structure. To evaluate the characteristic of support members, shear load tests were conducted. The feature for time history analysis is a point taken after the model of series coupling of nonlinear spring and nonlinear dashpot. First, Shear wall with oil-damper was conducted and it was confirmed that numerical model corresponded to the test result. Then time history analysis was conducted and test result and numerical model agreed well. Finally, seismic design value “Equivalent evaluation of shear wall strength” used in evaluating shear wall with dampers for seismic retrofit in wood structure was also confirmed using Incremental Dynamic Analysis.

A STUDY ON THE CALCULATION METHOD FOR THE SHEAR STRENGTH OF SHEAR WALLS

The calculation method for the shear strength of shear walls was shown in [Design Guidelines for Earthquake Resistant Reinforced Concrete Buildings Based on Inelastic Displacement Concept] published by ARCHITECTURAL INSTITUTE OF JAPAN (following, called AIJ equation). The calculated results by AIJ equation correspond with experiment results. But, the assumption that all horizontal bars in shear walls yield when shear walls reach at shear strength does not correspond with real phenomena. So, the new calculation method was developed. In the proposed method, the shear strength was determined with concrete compressive strength or horizontal bars yield strength. The calculation results by the proposed method corresponded better with experiment results than AIJ equation.

Shear Strength of Lightly Reinforced Wall Piers and Spandrels

Between the 1950s and 1970s, a significant number of buildings were constructed using lightly reinforced perimeter walls with openings. Evaluation and rehabilitation of such buildings requires accurate assessment of the expected shear strength, stiffness, and ductility of the wall segments (wall piers and spandrels) that comprise the primary lateral load-resisting elements. Assessing wall shear strength is complicated by factors such as use of a single curtain of distributed reinforcement, lack of hooks, and use of weakened plane joints, which are all common in older construction. To address these issues, a database of existing test results was assembled and reviewed; and tests were conducted on lightly reinforced wall piers and spandrels to address significant gaps in the available test data. Observations indicate that the amount of boundary reinforcement provided, presence of axial load, and the location of a weakened plane joint on the wall are the most important factors in the assessment of nominal shear strength.

On mechanical behavior of traditional timber shear wall in Taiwan II: simplified calculation and experimental verification

In the previous report of this ongoing study, results of an extensive field survey were collated and a theoretical model was proposed to predict the mechanical behavior of timber shear walls of traditional design in Taiwan. The initial objective of the present report was to propose a simplified calculation method for estimating the initial stiffness and yield strength of traditional timber shear walls. Based on the results of the field survey, a total of 15 full-scale specimens were tested to verify the theoretical model and simplified calculation proposed previously. Good agreement was found from comparison of analytical and experimental results. The results of this study show that the friction behavior between board units and beams plays the major role in resisting the lateral force applied on the timber shear wall, followed by the resistance supplied by embedment. The resistance provided by bamboo nails is minor due to the small section. Another trend found was that for set dimensions of a timber shear wall, the board width can be increased to obtain higher stiffness and strength of the shear wall.

Tests and finite element models of wood light‐frame shear walls with openings

AbstractShear walls are the primary means by which low and medium rise wood light‐frame buildings resist effects of lateral loads caused by wind, seismic or other events. Traditionally, adequacy of shear walls has been a minor concern because wood light‐frame buildings tended to be small, their shapes were regular, the amount of external and interior walls available to resist lateral forces was considerable, and the number and extent of openings in walls was limited. In modern times however, changes in the range of wood‐based construction products used, changes in construction detailing, increased geometric irregularity of buildings, more open interiors, and more numerous and larger wall openings, has raised concerns about the lateral resistance of wood frame buildings. Shear walls and how they interact with the rest of the system needs to be properly understood. They should be analysed based on generalized engineering principles that are comprehensively validated.This paper addresses proper understanding of wood light‐frame shear walls and engineering models for their analysis. Focus of analysis is on detailed finite element models suitable for representing shear walls with openings. Predictive abilities of models are verified against results of specially designed laboratory tests on shear wall segments containing a window or door opening and different hold‐down construction detailing. There is no intent that finite element models need be adopted by structural designers. Rather, the purpose of such models is that once rigorously verified they provide a benchmark against which the acceptability of simpler ‘design level’ models can be rationally assessed.Very good agreement exists between finite element models presented here and test results for shear walls loaded to destruction, with correct prediction of failure mechanisms for different configurations. Both experiments and modelling clearly demonstrate that both stiffness and strength of shear walls reduces disproportionately in relation to the extent of openings in them. This suggests that neither simplistic conceptualization of how shear walls behave nor simple design practices will lead to solutions that are both economic and safe, across a broad range of situations. However, comparison of test results and model predictions with state‐of‐the‐art design code rules indicates that the code rules quite accurately predict actual strengths of the shear walls tested by the authors.Further work is required to elucidate fully reliable design practices for buildings containing wood light‐frame shear walls. Emphasis within this will need be on the question of how to apportion lateral loads between various shear walls within a complete building.

Analytical Model for Predicting Shear Strengthof Squat Walls

A softened strut-and-tie model for determining the shear strength of squat walls is proposed in this paper. The proposed model originates from the strut-and-tie concept and satisfies equilibrium, compatibility, and constitutive laws of cracked reinforced concrete. The shear capacities of 62 squat walls were calculated and compared with the available experimental results, and reasonable agreement was obtained. Based on the collected experimental data in this paper, the proposed physical model was used to study the effects of boundary elements, cyclic loading, and vertical loads on the wall shear strength. The softened strut-and-tie model can be further developed to improve the current shear wall design procedures by incorporating the actual shear resisting mechanisms in predicting shear strength of walls.