Wall Deflection Research Articles

Experimental and numerical study on the deflection of multi-storey light-frame timber shear walls

This study aims at investigating the deflection behavior of multi-storey shear walls, including the effect of the diaphragm out of plane stiffness. Two-storey half-scale light-frame shear walls were investigated experimentally and numerically. Each level was loaded separately in order to isolate the effect of load transfer and deformation from one level on the other. The study shows that the deflection estimated based on the cumulative effect assumption was reasonably close to that observed in the experimental study, when no consideration for the floor diaphragm’s out of plane stiffness was included. It was observed that the majority of the cumulative effect stems from the rigid body rotation due to deformation in the hold-down devices. Results from a numerical model showed that the assumption of cumulative effects due to rigid body rotation is valid for stacked shear walls when consideration for the floor diaphragm’s out-of-plane stiffness is not included. The design expression showed a slight tendency to over-estimate the deflection especially at higher storey levels. The results of investigating the effect of the diaphragm’s out of plane stiffness showed that a significant reduction in the shear wall deflection. Diaphragm supported on multiple wall panels was found to further reduce the deflection of the shearwalls.

Soil movement mechanism associated with arching effect in a multi-strutted excavation in soft clay

Arching effect behind the wall in a multi-strutted excavation is a soil stress transfer process related to differences in stiffness between the well-braced soil and the underlying soil. This effect has been demonstrated by studies on soil stress transfer and lateral wall pressure in the literature. However, the soil movement mechanism associated with the arching effect is still unknown. In this study, a multi-strutted excavation in soft clay in Ningbo was closely monitored to determine the contours of the total soil movement and engineering shear strain, and these data were then used to produce a detailed interpretation of soil arching development and its influence on soil movement. It is found that plastic flow occurs behind the wall as soil arching develops to the ground surface, resulting in a large soil movement zone and a dramatic increase in ground surface settlement. The soil in the shear zone is also disturbed and verified by cone penetration tests. In addition, this study proposes that the ratio between soil volume loss due to ground surface settlement and soil volume gain due to wall deflection can be used to characterize soil arching development and its influence on soil movement. This study improves the understanding of the soil movement mechanism behind walls in multi-strutted excavations in soft clay, which is very important for protecting adjacent structures and facilities.

Numerical assessment of lateral deflection equation of single-storey light-frame wood shear walls

Based on the decomposition of the deflection into bending, panel shear, nail slip, and base rotation terms, the nonlinear four-term equation specified by the Canadian wood design code provides an estimate of the total lateral deflection of light-frame wood shear walls. This paper reports the creation of a numerical procedure for separating the responses for each term using a detailed nonlinear finite element modeling (FEM) that simulates individual components of shear walls. Since sheathing panel stiffness is not considered in computations of the bending term, the study reveals that bending deformation results calculated using the equation are more conservative than the FEM results. The nail slip term does not reflect the real nail base connection properties. A new equilibrium equation for determining the lateral deflection due to base rotation is presented. The equation is generally conservative because of the omission of some practical considerations.

Design and Application of a Digital System for Information Management and Synchronous Analysis in a Foundation Pit Group

When several adjacent foundation pits are excavated simultaneously and alternately, the foundation pit group has the interactions which will aggravate the excavation-induced adverse impact on surrounding environment. However, due to the massive construction information and monitoring data during excavation, the effect of interactions on performance of the foundation pits is hardly examined. In this study, a digital system is developed to manage the construction information and monitoring data of the foundation pit group. On the one hand, a visualization management system based on Autodesk Revit is developed to record information such as geometry information, excavation stages, and instrument layout. The complex construction information can be inquired dynamically. On the other hand, a dynamic and synchronous analysis system is developed based on SQL Server external database, Visio, and Excel software. The SQL Server software is capable to facilitate data classification and standardization management. The excavation process and monitoring data are fused through the secondary development of Visio and Excel software to help visualize, respectively. The developed system is applied to the foundation pit group of Shanghai World Expo Project. The lateral deflection of diaphragm walls is investigated and the rebound phenomenon of diaphragm wall is interpreted. It confirms that the developed system can improve the information management so that the deformation behavior of the foundation pit group can be analyzed efficiently.

Experimental investigation and optimization of wall deflection and material removal rate in milling thin-wall parts

The selection of optimal process parameters is essential while machining thin-wall parts since it influences the quality of the product and affects productivity. Dimensional accuracy affects the product quality, whereas the material removal rate alters the process productivity. Therefore, the study investigated the effect of tool diameter, feed per tooth, axial and radial depth of cut on wall deflection, and material removal rate. The selected process parameters were found to significantly influence the in-process deflection and thickness deviation due to the generation of unfavorable cutting forces. Further, an increase in the material removal rate resulted in chatter, thus adversely affecting the surface quality during the final stages of machining. Considering the conflicting nature of the two performance measures, Non-dominated Sorting Genetic Algorithm-II was adopted to solve the multi-objective optimization problem. The developed model could predict the optimal combination of process variables needed to lower the in-process wall deflection and maintain a superior surface finish while maintaining a steady material removal rate.

Allowable wall deflection of braced excavation adjacent to pile-supported buildings

To protect adjacent buildings is a major concern for the construction of excavation in urban areas. In practice, the impacts on neighboring pile-supported buildings are normally minimized by limiting the deflection of earth retaining wall. Existing deflection criteria, however, are often empirical. In this work, we employ an analytical model to relate the wall deflection of braced excavation to the response of adjacent pile-supported buildings and thus forming a theoretical tool for determining the allowable deformation of excavation support structures based on the tolerance of buildings to distortion. The model combines closed-form excavation-induced free-field soil movements with elastic continuum solution that explicitly accounts for the interactions between raft, piles, and soils. Following validation against field model test and finite element simulation, the model is utilized to reveal the correspondence between the angular distortion of pile-supported buildings and the maximum retaining wall deflection under different combinations of excavation geometry, soil properties, and parameters of pile foundation potentially encountered in practice. A dimensionless factor composed of these influencing variables is proposed, and its correlation with the ratio of the building angular distortion over the maximum retaining wall deflection provides a rational way to determine the serviceability limit states of braced excavation.

Parametric Sensitivity Study of Deep Excavation in Singapore Old Alluvium Formation

Deep excavation supported by vertical retaining walls together with strutting system is commonly used in Singapore for the construction of underground infrastructure. In this paper, a series of numerical scenarios simulated by PLAXIS software are carried out to study the influence of different design parameters such as pre‐auger loosening effect, the embedded depth of retaining wall into the stiff soil layer, and the elastic modulus of the ground improvement layer on excavation design especially on strut force, retaining wall deflection, and bending moment. The results show that there is high risk if only a single set of parameters are used as input to predict the performance of the retaining system. Sensitivity analysis shall be carried out to evaluate the effects of these parameter variations within a reasonable range on strut force, retaining wall deflection, and bending moment.

Deformation mechanism in wax supported milling of thin-walled structures based on milling forces stability

At mesoscale, dynamic alternating milling forces and relative stiffness of thin wall are the main factors affecting the deformation of thin-walled structures. To improve the machining accuracy and effectively control the thin wall deformation, this paper investigates the control strategies of dynamic milling forces and deformation mechanism in milling of different thin-walled structures. The instantaneous deformation of thin wall in high temperature casting wax supported milling is analyzed. A deformation control method of thin wall based on the dynamic stability of micro milling forces is proposed in high-speed milling process. Three representative milling experiments on microchannel cold plate with cantilevered boundary, single impeller blade with mixed boundaries, and cantilevered structure shaped like variable curvature wavy line are presented. The milling deformation mechanisms of these three thin-walled structures with different target thickness are further investigated in free milling and casting wax supported milling. Compared with free milling, the milling forces and thickness dimension of thin wall machined under different control strategies are analyzed. By monitoring the milling forces in milling of different micro-walled structures, the small difference and fluctuation of milling forces at different positions, together with the reduced thickness errors verify the effectiveness of the control strategies, using high temperature precision casting wax as auxiliary support in reducing the thin wall deflection. Additionally, the optimal milling control strategy of thin wall is determined.

Observed Performance of a Deep Excavation in the Historical Center of Rome

The C Line of the Rome underground underpasses the historical city center, facing significant problems for the presence of archaeological artefacts and the necessity to prevent damage to the historical and monumental heritage. This paper describes the field performance of a 30-m-deep excavation that has been constructed at a short distance from the Aurelian Walls at Porta Asinaria (third century). An extensive instrumentation program was conducted during construction, as well as field observations including deflection of the diaphragm walls, ground movements, pore water pressures, settlements, and rotation of the Aurelian Walls. Observed ground settlements and diaphragm wall displacements were smaller than those monitored in other case histories worldwide, inducing no damage to the Aurelian Walls. The lessons learned from this case study showed that a stiff retaining system and a strict control of the construction sequence were the key to minimize the effects of a deep excavation with millennia of history at risk.

Cross-Section Deformation and Bending Moment of a Steel Square Tubular Section.

When bending thin-walled profiles, significant distortion of the cross-section occurs, which has a significant impact on the course of the bending moment characteristics and on the value of allowable bending curvatures. This paper presents the results of experimental and numerical modeling of the box profile bending process, which was carried out in order to determine the dependence of the cross-sectional shape and bending moment of bending curvature. Extensive numerical calculations were used to model the process of shaping a square pipe from a circular tube and to model the bending process, especially when taking into account the effects of such a deformation path. The pure bending moment characteristics and the deformation of the cross-section were performed for a 25 × 25 × 2 mm square tube made of S235JR structural steel. The innovative approach for determining the parameters of cold bending square tubes pertained to considering the stress state in the preserved material in individual areas of their cross-section. The results of numerical modeling—after considering the history of deformation (i.e., the process of forming a square pipe from a pipe with a circular cross-section)—gave a satisfactory agreement with the results of experimental tests, both in terms of the degree of pipe wall deflection and the characteristics of the bending moment.

Full-scale fire test on a high-rise RC wall

This paper describes a full-scale test carried out on a high-rise reinforced concrete wall subjected to fire loading conditions in the special Vulcain furnace (very large and modular gas furnace) at CSTB, France. The test sample was designed to represent a slender wall with a very large height/thickness ratio. The experimental results showed a large deflection of the high wall in fire conditions (almost equal to the wall height/24) even for a fire exposure time of 90 min. Such a deflection was significantly higher than the maximum value recommended by design codes (about the wall height/30 for 120 min of fire exposure). Furthermore, other test results (full-field displacements in the 3 directions, residual deformed shape after the heating and cooling phases) may also provide additional useful experimental data for validating available or future models (which are usually based on some specific assumptions). In addition, the measurements of thermal-induced deformed shape of the wall are compared to those predicted by an analytical solution derived from a simplified one-dimensional (1D) beam model, as well as to those obtained from non-linear finite-element simulations (with 2D plate elements), in order to assess the practical applicability of these simulations. These comparisons show a reasonably good agreement between the experimental results and the predictions of these models, thereby providing a first validation of the latter.

The experimental investigation of the failure of load-bearing masonry walls supported by a deflecting structure

The paper presents selected results of tests of full-scale masonry walls linearly supported on a deflecting beam. The walls with thin bed joints and unfilled head joints were 4.55 m long and 2.45 m high, and were made of group 1 calcium silicate masonry units. The tests included walls with and without openings. The tests were carried out in a specially designated and constructed test stand, which allowed simultaneous vertical load on the upper edge of the wall and vertical deflection of the beam supporting this wall. During the test, measurements of mutual displacements of six points on the wall surface were carried out. On both faces of masonry specimens, the changes of the length of the measuring bases connecting these six points were recorded. Walls without openings were detached from the central part of the supporting beam at a deflection not exceeding 2 mm. Walls with one door opening also cracked at an early stage of tests. In this case, a detachment from the supporting beam and cracking at the ends of the lintel occurred because of the rotation of the pillars connected by the lintel above the opening. In walls with two door openings, first cracks were formed at the ends of lintels due to the rotation of pillars with a small deflection of the supporting beam, less than 3 mm. Whereas, in walls with door and window openings, first cracks occurred under the window and at the end of the lintel in the outer pillar of the wall.

Numerical investigation of flow structures resulting from the interaction between an oblique detonation wave and an upper expansion corner

Abstract

Effect of Wall Deformation on Dewatering-Induced Ground Surface Settlement

In practice, dewatering for pressure relief is commonly undertaken during ongoing excavation to secure bottom stability against basal upheaval. Simultaneously, through unloading, wall deflection is obviously observed. Noticing that both cause soil deformations, this research is to study the effect of wall deformation on dewatering-induced settlement. A coupled numerical analysis of finite-difference software is employed to model Shanghai soft soils under multi-aquifer-aquitard systems (MAASs) by analyzing the results in association with an empirical approach. Consequently, through gradual force reduction, shear strength at soil-wall interface is significantly diminished. As wall deformation increases instantaneously upon lower loading, wall surface becomes deformedly bending; this condition causes the challenge to workability of shear strength. Moreover, wall deformation caused by unloading affects dewatering-induced settlement substantially. Under smaller loading, large wall deflection is observed; soil plane of failure caused by both sliding and compression occurs along slip curve, with weaker shear-strength soils at rD = 0.4 and stronger shear-strength soils between rD = 0.4 and rD = 0.65, where rD is the distance from the wall that is normalized by the depth measured from ground surface. During dewatering, stronger soils tend to drag weaker soils upward to reduce large differential settlements caused by additional compression. Consequently, settlement becomes larger at rD = 0.4 and smaller at rD = 0.65. Remarkably, at rD > 2.3, both settlement curves that result from numerical analysis and empirical method show overlapping; this indicates that the unloading effect on dewatering-induced settlement at rD > 2.3 is insignificant. Furthermore, as wall reaches maximum allowable wall deflection by 67% applied force, additional compression caused by dewatering after loading remains smaller than that under 70% applied force, contributing to smaller dewatering-induced settlement.

Deflection of cross-laminated timber shear walls for platform-type construction

Cross-laminated timber (CLT) is becoming popular in the North American construction market as a feasible option for mid- to high-rise timber buildings. CLT shear walls are effective in resisting lateral forces resulting from wind and seismic loads and design standards allow to estimate their capacity. These standards however do no not include provisions to estimate the deflection of CLT shear walls. In this paper, formulas are proposed to estimate the in-plane deflection for single and coupled walls in platform-type buildings under lateral loading based on the assumed kinematic behaviour (rocking or combined rocking and sliding). It is postulated that the perpendicular walls and the floors above the shear walls also influence the in-plane deflection. Therefore, in addition to the CLT panel (bending and shear) and the connection contributions (sliding and rocking), also the contributions of perpendicular walls and floors above are accounted for. A parameter study evaluates the influence of connection, including those to perpendicular wall and walls above on the total deflection of single and coupled CLT shear walls. The proposed equations to estimate the deflection of CLT shear walls under lateral loads are compared against full-scale tests and the good agreement suggest that the formulae can be applied in the design of CLT platform-type buildings.

Injection printing: additive molding via shell material extrusion and filling

Material extrusion is a popular process for both prototyping and digital manufacturing, yet it is lacking in terms of part strength, feature resolution, and production rate relative to alternative processes. Injection printing addresses these issues by combining material extrusion of the outer surfaces of the part at fine resolution with injection molding of larger interior cavities at high flow rates. Injection printing thus aims to utilize the full melting capacity of material extrusion printers to mitigate the curse of dimensionality that plagues additive manufacturing. Simple governing models for flow in the formed cavities as well as the stress and deflection of the shell walls are presented. To validate the performance of injection printing relative to material extrusion, impact specimens and tensile bars were printed of acrylonitrile butadiene styrene (ABS). The tensile and impact results of the samples were compared, and image analysis was performed on the post-test samples. It was found that injection printing increased print speeds by an average factor of 3.2 relative to conventional material extrusion using the same linear print velocities. With respect to properties, the stiffness, strength, and strain to failure of injection printed tensile bars (in-plane) were respectively increased by 21 %, 47 %, and 35 % compared to material extrusion. Properties of impact specimen and vertically printed tensile bars also showed promising gains albeit with constraints related to the printer’s melting capacity. Even still, injection printing is shown as a broadly applicable and readily accessible process for increasing part strength and production rate while enabling improved feature resolution without greatly extended print times.

Data-Driven Field Observational Method of a Contiguous Bored Pile Wall System Affected by Accidental Groundwater Drawdown

This paper presents the use of a 700 mm-diameter contiguous bored pile (CBP) wall for a main basement deep excavation project with cut-and-cover tunnel. Due to the presence of cement grout columns between piles behind the CBP wall, the main basement was considered to be ‘impermeable’. However, site observations have shown that installation of ground anchors have unintentionally punctured the water tightness of the wall, creating leakages through the CBP wall and the possibility of localized groundwater lowering, as evidenced by the relatively large settlements. In the absence of cement grout columns at the cut-and-cover tunnel section, immediate groundwater drawdown was observed with the excavation rate. Settlement induced by the excavation and groundwater drawdown only slowed down upon the casting of skinwall to prevent groundwater from flowing through the wall. The accidental groundwater leakage led to small wall deflection. The ratio of maximum settlement to maximum deflection is atypical to those reported in the literature. The analysis also revealed that corner effect is significant with smaller settlement registered at the corners of the wall.

Study on Non-Engineered Building Vulnerability with Red Brick Masonry Wall through Finite Element Analysis

In this study comparing two types of simple house forms that were built without using count analysis. The building uses beams and columns that are usually used in a simple house in Indonesia. The modeled building consists of a square cross section and L cross section, also the modeled wall consists of a full wall, a wall with door openings, walls with door and window openings. Modeling using STERA 3D software to model non-engineered building comprise beams and columns and STERA FEM software for modeling walls. Modeling was carried out to analyze building shear stiffness, earthquake acceleration, and wall deflection when receiving loads. The loading in this study uses dead loads and earthquake loads using the time history method. The results of the modeling are the largest shear stiffness of a simple house building with a square cross-section of 35 kN/cm. The maximum land acceleration resulting is 8.72 m/s2. The largest wall deflection occurs at a load of 20 kN with a deflection value of 58.83 mm on the wall with door and window openings. The high deflection value is caused by the influence of the width openings on the wall and the load go down to the wall.

Behavior of cantilever secant pile wall supporting excavation in sandy soil considering pile-pile interaction

This study presents the results of a numerical investigation performed to investigate the behavior of a cantilever secant pile wall (CSPW) used to support excavation in sandy soil. These types of excavations have the potential to cause severe ground movement and possible damage to the adjacent structures. A major concern in supporting excavation is to predict and control ground movement associated with excavation particularly in cohesionless soils, as it could trigger global instability and catastrophic failure. The magnitude and distribution of lateral earth pressure and ground movement depend mainly on soil properties, excavation depth, excavation plan geometry, the stiffness of the supporting wall, and the contact between the secant piles themselves. Three-dimensional finite element model has been developed in this study to capture the excavation and wall geometry. A parametric study has been performed using a wide range of sand density, excavation depth, wall flexural stiffness, and bonding between piles within the wall. The results allowed for the development of an approach to predict both the wall deflection for the case of fully and partially bonded piles. This will help engineers to predict ground movement and select an appropriate supporting system that can maintain the stability of the adjacent structures.

Cantilevered RC Wall Subjected to Combined Static and Impact Actions

A displacement-based (DB) model is introduced in this article alongside its detailed derivations to predict the flexural response behaviour of a cantilevered reinforced concrete (RC) wall that is subjected to combined actions of boulder impact and sustained load (e.g. debris flow). In order to validate the model, a large-scale experiment was carried out by striking a 1.5 m tall, 3 m long and 0.23 m thick reinforced concrete wall using of two impactors weighing 280 kg and 435 kg to simulate different boulder impact intensities. A sustained load of 36 kN was applied to the wall using two prestressed custom-fabricated spring assemblies. Wall deflection and reinforcement tensile strain values measured from the experimental tests are shown to be within about 10–20% of predictions calculated from the proposed DB model. Errors of the predictions are consistently conservative across all the considered impact scenarios. These experimental findings are original given that no impact tests of the scale presented in this paper, which incorporate the effects of co-existing sustained lateral forces (e.g. debris flow), can be found in the literature. The proposed DB model was found to accurately predict both the deflection of the wall as well as the amount of tensile strain experienced by the reinforcement at the base of the wall. This paper concludes with a step-by-step design procedure that utilises the proposed DB model for designing RC rockfall barriers, which will be useful for practitioners aiming for a more optimised barrier design.