Excessive Deflection Research Articles

The failure of partition walls resulted from excessive deflection of the prestressed ribbed floor slab

The failure of partition walls resulted from excessive deflection of the prestressed ribbed floor slab

Comprehensive durability assessment of in-service concrete bridges based on combination weighting and extenics cloud model

In recent years, with the continuous development of urban transportation, the durability of concrete bridge structures has become increasingly prominent. Many in-service concrete bridges exhibit issues such as cracks, excessive deflection, and a significant reduction in load-bearing capacity during their service life. To meet the requirements of sustainable development, it is urgent to assess the durability of bridges accurately. Therefore, this paper establishes a scientific and reliable evaluation index system for the durability of in-service concrete bridges. Based on a review of the literature and relevant standards and specifications, this paper establishes an evaluation index system for the durability of in-service concrete bridges and calculates the weights using a combination weighting method. The durability of the bridges is assessed using the extension cloud model theory, and MATLAB is utilized for efficient and accurate computation and analysis, ultimately determining the durability grades of the bridges. The method was applied to the durability assessment of five in-service concrete bridges, and the results were in high agreement with the measured data, proving its effectiveness and accuracy. The research results provide a scientific basis for the management and maintenance of concrete bridges, which can help extend their service life. Future studies will expand the sample to cover more bridge types to comprehensively assess and enhance the durability of bridges.

Investigation of essential parameters for the design of offshore wind turbine based on structural reliability

The probabilistic-based design method is gradually gaining attention in the wind industry because it provides more accurate modeling of uncertainty variables than that of traditional methods. Unfortunately, the numerous uncertainty variables involved in structural design are major obstacles to the successful application of this method. Therefore, this study presents a sensitivity analysis (SA) of a benchmark monopile offshore wind turbine (OWT) to screen the top-ranking variables from the viewpoint of reliability. Primarily, a comprehensive reliability SA framework of OWT is proposed, in which a novel measurement of soil uncertainties is conducted using quantitative analysis from the perspective of soil structure interaction (SSI). Subsequently, a reliability SA is conducted to explore the crucial variables influencing the structural safety from the uncertain clusters. The results indicate that Young's modulus, structural geometry, and SSI have significant effects on the structural reliability of excessive vibration failure. The hydrodynamic and aerodynamic load variables exhibit the most prominent influence on excessive deflection failure. Additionally, the SSI uncertainties exhibit a non-negligible effect in affecting the structural reliability, i.e., the lateral bending stiffness shows more sensitivity to the normal operation cases, whereas the impact of joint stiffness is more remarkable in parked scenarios.

Методы прогнозирования долгосрочного поведения преднапряженных железобетонных мостов

Purpose: to analyze the causes of long-term deformations of prestressed concrete bridge spans and the problems associated with their prediction. To provide a brief overview of existing methods for predicting the long-term behavior of prestressed concrete bridges. The relevance of the problem is due to the need to ensure the reliability and durability of these structures, which are widely used in modern bridge construction. The objective of this paper is to identify factors that influence the development of long-term deformations and to develop approaches for their accurate prediction. Methods: the study examines the long-term deformations of prestressed concrete bridge spans and the problems associated with their prediction using existing bridge structures as examples. Existing methods for predicting long-term deformations in prestressed concrete are evaluated. In particular, the effects of high-strength reinforcement relaxation and the effects of concrete creep and shrinkage are analyzed. Results: accurate prediction of long-term deformations is a complex task that requires consideration of many factors, such as prestress losses, environmental conditions, material properties, and structural characteristics of bridges. The methods discussed in this paper, including the multiplier method and the approximate time interval method, demonstrate their effectiveness in evaluating long-term deformations. However, further research is needed to improve the prediction methods and increase the efficiency of prestressed concrete bridge design. Practical significance: provides design engineers with specific methods and approaches for evaluating the long-term behavior of prestressed concrete bridges. Application of these methods can reduce the risk of excessive deformations and deflections, ultimately ensuring the safety and reliability of bridge structures.

Stress and deformation response of pipe jacking in upper-soft and lower-hard strata: A case study in Changsha

Constructing underground structures using the pipe jacking technique presents challenges in upper-soft and lower-hard strata. The complicated strata conditions make pipes prone to deflection, leading to problems such as cracking, pipe joints failure and water leakage. To determine the stress and jacking force characteristics of pipe jacking during the entire construction period in upper-soft and lower-hard strata, this paper presents a case study of pipe jacking passing through upper-soft and lower-hard strata in Changsha, China. Pipes stresses at two wings, and the top crest in the longitudinal directions for six different pipe sections were monitored. Then, a jacking force model is proposed to describe the additional thrust after deflection in upper-soft and lower-hard strata. The results show that the jacking force induced by upper-soft and lower-hard strata exhibits a tortuous increase and causes pipe deflection. The stress and deflection patterns in different monitoring pipes are consistent. The maximum pipe stresses during the jacking were 9.26 MPa in the longitudinal direction and 394 % increasing after deflection. Axial stress in test pipes exhibit nonlinearly transfer, with the distribution of friction resistance forms a“W”shape between pipes. An excessive alignment deflection would generate incremental jacking force, which strengthens with larger deflection. By regarding the composite formation area as a fully contact model with the surrounding rock, and uniform formation as a contact with the bottom of the surrounding rock, and the formulas were corrected for deeply buried pipe under uniform formation. Combining the calculation results and field data, the predict model is validated. The calculation method that can effectively predict the jacking force after pipe alignment deflection in upper-soft and lower-hard strata. The results of this study can provide beneficial guidance for the design and construction of pipe jacking.

Construction control of rigid frame-continuous girder bridge based on grey theory

To address the issue of excessive mid-span deflection in rigid frame-continuous girder bridges during the later stages of normal use and to provide a basis for setting the pre-camber of this bridge type. This study focused on a specific rigid frame-continuous girder bridge. Based on the outcomes of finite element analysis, a GM(1,1) model developed using grey theory was utilized to forecast the vertical deflection of the primary girder in the construction phase of a rigid frame-continuous girder bridge, resulting in notable outcomes. The results suggest that the GM(1,1) model grounded in grey theory offers precise estimations of the vertical deflection of the primary girder during the prestressing tendon tensioning stage, displaying a minimal deviation of merely 1.73 mm compared to actual measurements. Consequently, applying the GM(1,1) model based on grey theory for projecting the vertical deflection of the primary girder in the construction process of rigid frame-continuous girder bridges can advance the accuracy of construction management. Through comparative analysis of measured values estimated values and theoretical values at the construction site, it is evident that the predictive model effectively controls the displacement, thus serving as a reference for construction control in similar projects.

Concealed Beam in Reinforced Concrete Structures: A Performance-Based Analysis

The use of hidden beams in reinforced concrete construction is seen as an effective method of reducing excessive deflection in large spans. However, despite its presumed advantages and growing usage, no mention of it in standard civil engineering literature, codes and standards. In this paper, performance-based analysis is carried out on three different cases of slab arrangement involving hidden beams using SAP2000. The process is performed under dead and live load combination and based on the design guidelines in BS8110. The result of the performance-based analysis shows a 4%, 2% and 11% decrease in deflection, stress distribution and area of bending steel reinforcement required for the case with hidden beam in comparison with the case without the hidden beam. This indicates that the presence of a hidden beam in a slab is significant. Thus, it is recommended for reducing excessive deflection in large spans, hidden beams can be introduced.

Experimental and numerical investigation on deck system of a 102 m simply supported prestressed UHPC box-girder highway bridge

To address two main challenges (excessive mid-span deflections and numerous cracks in the main girder) in long-span prestressed concrete (PC) box-girder bridges, this paper proposes a long-span simply-supported UHPC box-girder bridge. In comparison to conventional PC box-girder bridges with three-dimensional prestress, the proposed UHPC box-girder consists only one-dimensional (longitudinal) prestress, and the thickness of the bottom/top plate and web of the UHPC box-girder are relatively thin and are strengthened with dense diaphragms and stiffening ribs. The 4th Beijiang River Bridge adopts this type of bridge with a span of 102 m, which is the longest span simply supported prestressed UHPC box-girder highway bridge in the world. Considering the fact that the thickness of the top plate of the UHPC box-girder is relatively thin (only 20 cm) and the transverse prestress is removed from the top plate, thus, under the direct action of wheel loads, the risk of bridge deck cracking may correspondingly increase. To investigate the mechanical behavior of the deck system of UHPC box-girder bridges, a 1:2 scaled experimental specimen associated with the field bridge is tested. The mechanical behavior of the new deck system is investigated and discussed. It is found that because the support strength of the stiffening rib is significantly weaker than that of the web, the UHPC deck slab should still be regarded as a two-way slab rather than a one-way slab in the elastic stage. In addition, although the test load location is unfavorable to the UHPC deck slab and the first crack appears on the UHPC deck slab, this deck system finally suffers from bending failure of the transverse rib. Furthermore, finite element analysis is carried out to study the mechanical behavior of this new deck system. Parametric analysis considers some factors including the reinforcement ratio in the transverse rib, the height of the transverse rib, and the space between transverse ribs. The results provide a good reference for design and optimization in the new deck system of UHPC box-girder bridges.

GFRP COMPOSITES: A MATERIAL TO STRENGTHEN REINFORCED CONCRETE BEAMS WITH WEB OPENINGS FOR SHEAR

Buildings that require mechanical and electrical services must have utility pipes and ducts. The services include air conditioning, power supply, telephone lines, network cables, sewerage lines, water supply and etc. A reinforced concrete (RC) deep beam with web openings experiences excessive cracking and deflection, as well as a decrease in beam stiffness. Enlargement of these openings near supports would reduce beams’ capacity for shear. Hence, analysis and design of such beams require careful consideration, particularly with regard to their performance. In addition, design compliance to relevant codes and standards, and selection of suitable material properties and construction techniques are needed. When such an enlargement is unavoidable, strengthening of beam for shear and flexure is necessary. In this study, the use of GFRP (Glass-Fiber Reinforced Polymer) composites for strengthening of RC beams with openings is experimentally investigated. As compared to the control beam, test results showed that using GFRP was found to be effective in increasing the shear strength of beams with openings by 40% to 60%. Test results of beams with web openings exhibited higher shear strength than the predicted values whereas for strengthened beams with GFRP, code predictions are found conservative.

Incremental analysis of load handling device deflection considering lubrication degradation for predictive maintenance

In the Industry 4.0 era, unmanned automated factories heavily rely on load handling devices (LHDs), which are indispensable but susceptible to failures. Deflection is a crucial health indicator, with excessive deflection causing issues such as tilting and reduced positioning accuracy. This underscores the necessity for reliable deflection prediction methods in LHDs, a currently under-researched area, essential for informing predictive maintenance strategies. This study introduces an incremental analysis method that addresses the impact of internal cumulative wear and lubrication degradation on deflection increase. It involves iteratively updating a multiparametric model to represent the cumulative wear process and utilizes an empirical model based on the Stribeck curve to describe lubrication degradation. To enhance accuracy, particle filtering (PF) is employed to revise friction coefficients derived from the empirical model. Experimental data from an LHD operating in a load-carrying mission validates the accurate and robust nature of this method, particularly when compared with non-friction coefficient revising counterparts. As a typical application case study for preventive maintenance, this method is utilized to simulate various scenarios of lubrication replenishment and quantify the effect of timing on LHD lifespan enhancement through lubricant replenishment. The results facilitate the optimization of maintenance schedules and offer a new approach for updating lubrication-related parameters in digital twin models of equipment-level products, in line with preventative maintenance strategies.

Time-dependant effects on curved precast segmentally constructed balanced cantilever bridges

Excessive long-term deflections and diagonal cracking in the webs are two commonly reported issues in segmentally constructed balanced cantilever bridges. The design of superstructure in such bridges is rather complicated due to the staged construction, secondary restraint forces, and time-dependent effects such as shrinkage, creep, and steel relaxation. The influence of these factors significantly increases by the curvature of the bridge on plan, to the point where it can result in the failure of the bridge if special considerations are not made. In this study, stepwise numerical analyses of a curved pre-cast construction of a balanced cantilever bridge with time-dependent material properties are carried out. The results show the effects of time-dependent losses, especially creep, on deflections during cantilevering and in long-term. It is shown that the curvature of the bridge due to long-term effects can increase the transverse moments in segments that adversely affect the principal tensile stresses, which can lead to diagonal cracking in the web of the segments.

Identification and dynamic monitoring of electrospinning jet assisted by coaxial laser.

The accurate and rapid detection and recognition of jet features are key to dynamic monitoring and online control of the electrospinning process. In this study, a real-time recognition system based on OpenCV was introduced into a coaxial laser-assisted electrospinning system to solve the difficulties of accurate jet recognition and to promote an image processing algorithm response. The jet images with laser assistance were more clearly visible than those without laser assistance, and a significant contrast in grayscale levels existed in the jet image to help distinguish jet features. Subsequently, separate algorithms were designed for the jet visible length calculation, and the recognized visible length of the jet and algorithm running speed were compared. The average visible length of the jet with laser assistance was 11.49mm, which increased by 1.59mm compared to that without laser assistance. In addition, the running time of the algorithm with laser assistance was 24.89ms, reduced by 14.84ms compared to that without laser assistance, indicating the effectiveness of laser assistance to promote the accuracy and running speed of the jet image recognition process. Additionally, real-time detection of the jet angles was achieved to identify instances of excessive deflection during the electrospinning process. Overall, this study has significant potential to promote the dynamic monitoring of an electrospinning jet.

A laboratory investigation and numerical modeling on fiber reinforced lime and alkaline binder stabilized pavement subgrade soil

The differential settlement and excessive deflection in expansive subgrade soils lead to low volumetric stability upon moisture imbalance and cause severe damage to highway and airport field pavement surfaces. The present paper attempts to strengthen the stability behavior of expansive subgrade soil using an envirosafe alkaline binder (AB) with polypropylene fiber (PLF). AB was produced by combining dry aluminosilicate precursors (steel slag [SS] and sugarcane bagasse ash [SBA]) with a liquid activator (mixture of sodium hydroxide [NaOH] and sodium silicate [Na2SiO3]) in 0.4 water to binder (w/b) ratio. California bearing ratio (CBR) based resilient modulus, shear strength ratio (Sr), and consolidation tests were conducted as performance indicators of expansive subgrade soil reinforced with discrete PLF (0–0.5%) in 6% lime and 6% alkaline binder. The study also proposes the optimal sugarcane bagasse ash-steel slag-PLF dosage in the AB-stabilized subgrade layer. Moreover, mineralogical and morphological studies using powder X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) were also carried out to understand the crystalline compounds and micro surface texture of the soil-fiber mixture. It was revealed that AB-fiber-soil exhibits higher interfacial frictional bonding and interlocking density than lime-fiber-soil. Also, 2D finite element analyses were carried out to compare the behavior of subgrade under the influence of vehicular load on the surface. PLF-AB soil mixture shows 72% lower vertical deformation than unstabilized expansive soil. Based on the findings of this study, recommendations for the practical application of stabilizing expansive subgrade soils were proposed.

On the response of jointed rigid pipes under abrupt ground subsidence: A closed-form analytical solution

The structural safety of jointed rigid pipes can be jeopardized under abrupt ground settlements. Most previous studies have investigated the response and safety of jointed rigid pipes under abrupt ground subsidence using numerical and experimental methods at two specific positions, i.e., the shear band caused by the ground movements crosses the pipe at a joint and at the midspan of a pipe segment. In this work, a closed-form analytical solution for the deformation and mechanical response of jointed rigid pipes under abrupt ground subsidence with various crossing positions is presented. The pipe bending moment and the joint shear force are calculated, which match quite well with the results of finite element analysis. Then the maximum allowable settlements are examined, and the corresponding failure modes are identified. It shows that with the increase of burial depth and soil density, the main failure mode gradually changes from the excessive joint deflection to the barrel bending and bell cracking, and the maximum allowable subsidence distance decreases remarkably. The worst crossing position is at nearly 7/10 of the pipe length. The results offer new insights into the failure mechanism of jointed rigid pipe, and provide a basis for the protection of rigid pipes under abrupt ground subsidence.

Behavior of textile‐reinforced concrete columns

AbstractThis work aims to investigate the behavior of textile‐reinforced concrete (TRC) members subject to compressive loads. An experimental program including concentric compression tests on I‐section columns with different lengths and simply‐supported ends was carried out. From compression tests, load versus lateral deflection curves obtained experimentally are reported along with maximum loads and apparent imperfections determined using the Southwell technique. Failure modes were characterized by excessive lateral deflections for longer columns, whereas concrete crushing failure due to combined bending and axial load occurred for shorter columns. Surrounding concrete was effective in restraining the textile reinforcement against buckling, allowing it to sustain the compressive loads. A single degree‐of‐freedom model accounting for normal‐moment‐curvature relation and tension stiffening behavior is validated against experiments and used to carry out a parametric study. Results show that the nonsway moment magnification method recommended by the ACI Code 440.11‐22 can be applied to TRC columns, although leading to overestimated second‐order effects.

Longitudinal supports shape influence on deflection and stresses in solar receiver tubes

Longitudinal supports have a key role in solar central receivers, preventing tubes from excessive deflection. In this work, its influence on tube deflection and thermo-mechanical stresses has been studied. In exiting literature, the longitudinal supports are not modelled when the behaviour of solar receiver tubes is studied. In this research, they have been considered developing numerical models using a finite element analysis software. To carry out the analysis, a new geometry of the metal sheet attached to the receiver tubes has been proposed. With this new shape, different cases have been studied, varying the separation between supports and their size to study its impact on stress and deflection in the tubes. Results have shown that extremely rigid supports may induce additional stress in the receiver tube. With the geometry considered in this research, supports do not cause additional mechanical stress in tubes. Small supports are preferred to bigger ones due to the stresses arisen in the own support.

Revitalizing an Existing Reinforced Concrete Bridge: Deficiencies, Repair Techniques and the Role of FRPs

Italy, known for its large historical and cultural building heritage, boasts a vast network of reinforced concrete (RC) bridges that plays a crucial role in connecting various regions. However, over the time and due to the exposure to harsh environmental conditions, these bridges have exhibited structural deficiencies, including deterioration, cracking, and loss of load- carrying capacity. In a deeper scale, corrosion of the steel-reinforcement due to chloride ingress and carbonation are both evident. The latter leads to the deterioration of the concrete, the loss of the bond between steel-reinforcement and concrete, and the reduction of the structural integrity. Furthermore, bridges may experience excessive deflection, which compromise their serviceability performance. To address these drawbacks, a range of repair techniques have been employed. These include, among the others, conventional methods such as crack sealing, surface patching, and cathodic protection to mitigate corrosion.On the other side, advanced materials like fiber-reinforced polymer (FRP) have been relatively recent favored. It consists of high-strength fibers embedded in a polymer matrix (generally epoxy-based), which have gained prominence as a viable solution for the structural rehabilitation of RC-bridges. In fact, FRP offers several advantages including a high strength-to-weight ratio, corrosion resistance, and excellent durability. FRP-composites can be used for strengthening and retrofitting bridge components, such as beams, columns, slabs, and shear walls, to enhance their load-carrying capacity and structural performance. Various FRP- based rehabilitation techniques are commonly employed in Italy, including externally bonded FRP sheets/strips, near-surface mounted FRP rods, and FRP wraps for the confinement of concrete columns. The techniques involve the application of FRP materials to the external or internal surfaces of deteriorated elements, effectively enhancing their strength and/or stiffness.The present paper aims to report a success case-study concerning the external strengthening of a RC-bridge carried out using FRP-materials in the perspective of demonstrating the validity of the FRP-application for bridge strengthening and maintenance based on a proper design and time-dependent visual observations.

Residual bearing capacity of concrete-filled double-skin steel tube K-joints after lateral impact

With the application of jacket offshore wind turbines (OWT), the jackets are exposed to the risk of ship collision. However, concrete-filled double-skin steel tube K-joints (CFDST-K joints) in the jacket can still operate normally after slight impacts. To study the residual axial properties of the joints, eight CFDST-K joints and one hollow K-joint were tested by a long column testing machine, focusing on the failure mode, residual bearing capacity, displacement, and ductility after impact. Results indicated that the typical failure mode of the joints was characterized by overall bending resulting from excessive midspan deflection. The residual properties were negatively correlated with the initial damage. Specifically, the stiffness degradation was worsened as the impact energy and axial compression ratio increased, causing an evident decrease in residual bearing capacity and ductility. Moreover, increasing the outer tube thickness improved the bearing capacity by enhancing the confinement effect of the steel tube on the concrete. Furthermore, the hollow ratio exerted a great effect on ductility. A calculation method for the original loading capacity of CFDST-K joints was also proposed, and the damage index was introduced to assess the damage degree. The results verified that the joints still possessed excellent bearing capacity after impact.

Application and Experimental Validation of Seven-Degree-of-Freedom Beam Element for Girder Bridges during Deck Construction

During bridge deck construction, the deck finishing machine and the fresh concrete often produce large vertical loads and torsional moments acting on the bridge girder system. In some cases, these loads can cause excessive vertical deflection and transverse rotation in the bridge girders, leading to many maintenance and safety problems, such as changes in deck thickness and local and global instabilities during construction. To minimize the potential problems caused by deck construction, the AASHOTO LRFD Bridge Design Specification requires consideration of these torsional moments during the design procedure, and a detailed three-dimensional finite element analysis may be conducted. However, for bridge girders with open-section thin-walled sections, only the solid or shell element can be used to recognize the warping of the girder since the torsional warping effect is not included in the classical beam element. In this research, a warping degree of freedom was added to a beam element, and a three-dimensional beam element with seven degrees of freedom (7-DOF) at each node was derived as an alternative method for analyzing girder bridges during deck construction. A computer program based on the 7-DOF beam element was also developed in MATLAB. To assess the 7-DOF beam element, one bridge was selected to measure the transverse rotation, vertical deflection, and stress of the exterior girder and the first interior girder during deck construction. Also, three full-scale numerical models using solid elements, classical three-dimensional beam elements, and 7-DOF beam elements were created based on the geometries and loads of the experimental bridge. A comparative study was conducted by comparing the results from the numerical models and experimental monitoring data to evaluate the 7-DOF beam element. The results showed that the 7-DOF beam element had excellent behavior in analyzing the girder bridges under construction load, especially in the torsional analysis of bridge girders. Also, unlike the solid element model, which also provided reasonable results, the 7-DOF beam element model can compute the internal forces of the cross-sections along the bridge, which allows the 7-DOF beam element to be an alternative approach for design and research requiring less modeling effort and computational complexity.

A possible underground roadway for transportation facilities in Kathmandu Valley: A racking deformation of underground rectangular structures

AbstractThe increasing number of private cars, public transportation vehicles, and pedestrians, as well as the absence of adequate space for these ground amenities, are one of the primary causes of traffic congestion and accidents in the Kathmandu Valley. Investigations have indicated that the Kathmandu Valley has the greatest traffic accidents despite the heavy presence of the government and its agencies there. Most teens and young adults suffer injuries while using motor vehicles. The study's primary objective is to foresee and prevent such complications by planning for sufficient subsurface infrastructure (a cut‐and‐cover rectangular tunnel) for the Kathmandu Valley's transportation network. The overlying pressure, lateral earth pressure, live load, uplift pressure, and live surcharge are some of the forces acting on the tunnel, creating unique stress and moment zones. The tunnel meets the following geometric requirements: (a) Each of the tunnel's two cells has a clear span of 10 m and a clear height of 5.5 m. The side walls, inner walls, top slab, and bottom slab are all 700 mm thick. Soil has built up to a height of 4 m over the tunnel's roof. The analytical method is used in the tunnel segment's analysis. Furthermore, the designed tunnel has been evaluated for stability, considering the deflection and shear resistance. The analysis indicates that the tunnel meets the stability requirements. This implies that the structure is capable of withstanding the applied forces without excessive deflection. Non‐linear dynamic time history analyses of the El Centro earthquake and the Gorkha earthquake were computed. From the El Centro earthquake, the maximum displacement was 23.63 mm at 10.59 s, and from the Gorkha earthquake, the maximum displacement was 16 mm at 0.19 s for the modeled structures.