Full-scale Load Tests Research Articles

Performance Analysis of Full Assembly Glass Fiber-Reinforced Polymer Composite Cross-Arm in Transmission Tower.

The usage of glass fiber reinforced polymer (GFRP) composite cross-arms in transmission towers is relatively new compared to wood timber cross-arms. In this case, many research works conducted experiments on composite cross-arms, either in coupon or full-scale size. However, none performed finite element (FE) analyses on full-scale composite cross-arms under actual working load and broken wire conditions. Thus, this work evaluates the performance of glass fiber reinforced polymer (GFRP) composite cross-arm tubes in 275 kV transmission towers using FE analysis. In this study, the performance analysis was run mimicking actual normal and broken wire conditions with five and three times more than working loads (WL). The full-scale assembly load test experiment outcomes were used to validate the FE analysis. Furthermore, the mechanical properties values of the GFRP composite were incorporated in simulation analysis based on the previous experimental work on coupons samples of GFRP tubes. Additionally, parametric studies were performed to determine the ultimate applied load and factor of safety for both normal and broken wire loading conditions. This research discovered that the GFRP composite cross-arm could withstand the applied load of five times and three times working load (WL) for normal and broken wire conditions, respectively. In addition, the factor of safety of tubes was 1.08 and 1.1 for normal and broken wire conditions, respectively, which can be considered safe to use. Hence, the composite cross-arms can sustain load two times more than the design requirement, which is two times the working load for normal conditions. In future studies, it is recommended to analyze the fatigue properties of the composite due to wind loading, which may induce failure in long-term service.

Development of low-strength stabilization method for fouled ballasted tracks

In ballasted tracks on railways, fine fraction content (hereinafter referred to as “Fc”) mixed in ballast increases due to repeated train loads or track repair work using ballast tampers. When the Fc increases and becomes “fouled ballast”, settlement of ballasted track tends to increase even after track repair, which results in a rise in maintenance frequency. In such cases, ballast replacement is the standard measure applied to reduce frequency of maintenance. However, ballast replacement is costly, and railway operators therefore need countermeasures to prevent large settlement which are both low cost and quick enough to implement during periods of track work carried out at night. This study describes the development of a new repair method which reduces sleeper settlement by mixing super-quick hardening cement and polymeric stabilizer (hereinafter referred to as “stabilizing materials”) with fouled ballast. This method uses a ballast tamper and weakly stabilizes fouled ballast to allow tamping even after stabilization, hereinafter referred to as the “low-strength stabilization method”. This study investigates the relationship between sleeper settlement and amount of stabilizing materials needed for this low-strength stabilization method, and examines the settlement reduction mechanism through cyclic loading triaxial compression tests. Confirmation of settlement reduction was conducted through full-scale cyclic loading tests.

Vertical Fiberglass Micropiles as Soil-Reinforcing Elements.

This article is dedicated to developing a ground improvement technique using vertically oriented reinforcement elements prefabricated utilizing fiberglass pultruded pipe and helical shape wideners at the bottom toe. Structures of the prefabricated helical micropiles varied by the length and cross-section area introduced into the soil massive as reinforcing bearing elements. The effect of the reinforcements geometry variation was investigated through a reinforcement factor (µ), based on which a calculation method for measuring settlement of reinforced soil has been previously developed Full-scale field plate load tests were performed before and after reinforcing the soil to investigate the changes in the soil stiffness after the reinforcement process. Comparative analysis between the reinforced and reference soft sandy soil indicates an average increase in the deformation properties of the fiber reinforced soils by 8%, 30%, 63% at the applied pressures of 100, 300, and 550 kPa, respectively. The influence of the fiber reinforced polymers (FRP) geometrical properties on the final composite settlement was determined. A comparative analysis of the calculated and the actual plate load tests results reveals that the previously proposed settlement calculation method is adequate for further development.

Cyclic response of moment-resisting glulam hybrid joints with bolts and side steel plates

To improve the cyclic properties of moment-resisting bolted glulam joints, H-shaped steel flange plates with openings and side steel plates with reduced section are applied and connected with glulam members by self-tapping screws. Full-scale cyclic loading tests were conducted on the glulam hybrid joints and the experimental results indicated that with the contribution of supplemental steel components, significant improvement was achieved in the moment resisting capacity, elastic stiffness, and energy dissipation. The moment capacity and elastic stiffness of bolted glulam joints are increased by up to 91% and 67%, respectively. Furthermore, a three dimensional numerical model was established and validated by comparison with experimental results. Comprehensive numerical analysis was conducted on the cyclic response of bolted glulam joints with brittle failure modes, and it was indicated that with the application of supplemental steel components, high ductility behavior was observed from the hybrid joints with the constraint on wood splitting and crack opening. The moment capacity and elastic stiffness can be enhanced by up to 152% and 156%, respectively. The accumulated energy dissipation is up to 15.4 times that of bolted glulam joint, which demonstrates the application potential of the glulam hybrid joints.

Novel Method for an Optimised Calculation of the Cross-Sectional Distribution of Live Loads on Girder Bridge Decks

One of the main goals in the design of girder bridge deck systems is to determine the cross-sectional distribution of live loads across the different girders that make up the cross-section of the deck. Structural grillage models and current bridge design standards based on a Load Distribution Factor (LDF) provide oversized designs, as demonstrated in this paper. This research introduces a novel method that allows the cross-sectional distribution of live loads on girder bridge decks to be calculated by applying a matrix formulation that reduces the structural problem to 2 degrees of freedom for each girder: the deflection and the rotation of the deck-slab at the centre of the girder’s span. Subsequently, a parametric study is presented that analyses the structural response of 64 girder bridge decks to a total of 384 load states. In addition, the authors compare the outputs of the novel method with those obtained using traditional grillage calculation methods. Finally, the method is experimentally validated on two levels: a) a laboratory test that analyses the structural response of a small-scale girder bridge deck to the application of different load states; b) a real full-scale girder bridge load test that analyses the structural response of the bridge over the Barbate River during its static load test. Based on this analysis, the maximum divergence of the proposed method obtained from the experimental structural response is less than 10%. The use of the proposed novel analysis method undoubtedly provides significant savings in material resources and computing time, while contributing to minimizing overall costs. Doi: 10.28991/CEJ-2022-08-03-01 Full Text: PDF

Integrative structural design of a timber-fibre hybrid building system fabricated through coreless filament winding: Maison Fibre

Coreless filament winding is a robotic fabrication technique in which conventional filament winding is modified to reduce the core material to its minimum. This method was showcased and developed through a series of pavilions demonstrating its potential to create lightweight structures. The latest project, Maison Fibre, goes one step further and adapts the fabrication into a hybrid structure combining fibre-polymer composites (FPC) with laminated veneer lumber (LVL) to allow for walkability. The result is the first multi-storey building system fabricated with this novel technique. During the integrative design process of the slab system, the optimum fibre layup was negotiated between the timber support span, load induction, boundary conditions, and material amount required. A total of four iterations of the hybrid component were load tested and compared with the maximum enveloped forces resulting from the global structural simulation. The full-scale load tests were used to calibrate the refined structural simulation of the slab components. The experimental process allowed for material reduction and validated the structural system's capability to withstand the design forces. In addition, the fibre layup was tailored and load adapted for the non-tested wall and slab components of the installation using the test results and achieving further material optimization. This publication describes the integrative design process of the hybrid slab system from initial concepts to the iterative optimization of the structural system, demonstrating its potential for future applications.

Practical model updating of the Ting Kau Bridge through the MCMC-based Bayesian algorithm utilizing measured modal parameters

Bayesian model updating framework provides a reliable method for building high-fidelity finite element models (FEMs). To realize the efficient model updating of large-scale civil engineering structures, a practical Bayesian inference framework based on software interaction is proposed. The newly developed framework was applied to update the FEM of a long-span cable-stayed bridge, Ting Kau Bridge in Hong Kong, utilizing measured modal parameters from the literature. The model updating results are found to be highly sensitive to the selection of model classes. Furthermore, the area of the main girder of the bridge deck is a key parameter influencing the lower modes of the cable-stayed bridge. A full-scale vehicular load test is conducted on the Ting Kau Bridge to obtain the displacement influence line through the data recorded by GPS sensors on the bridge. The set of measured influence lines is employed to verify the accuracy of the updated FEM. The results demonstrate that the characteristics of the FEM updated using the proposed Bayesian model updating framework based on measured dynamic properties are consistent with the structural characteristics of the bridge. The proposed framework can facilitate the structural health monitoring of large-scale civil engineering structures.

Steel-concrete composite beam-column connections utilizing prefabricated permanent steel form

To facilitate fast-built and economical constructions, a unique composite moment frame system with prefabricated permanent steel form is presented. A conventional steel wide flange beam is used at the mid-span of horizontal member which has typically small design forces. The so-called composite mechanism between the concrete and steel is utilized selectively on the beam-column connection regions of the moment frame structure, which requires higher strength and ductility demands compared to those in the mid-span. For this purpose, the permanent steel plate forms are prefabricated to the beam-column connection regions before composite with cast-in-place concrete. Since the steel beam is first connected to the steel columns, no additional false work requires during constructions, and high seismic performances can be secured at the beam-column joints, where the structural integrity should be firmly ensured. In this study, full-scale cyclic loading tests were carried out considering the various details at the connection regions as the key experimental variables to evaluate the seismic performances of the proposed composite system. Test results showed that the proposed method fully satisfies the required performances to be accepted as the composite special moment frame specified in the current design code.

In situ flexural failure of unbonded fibre reinforced shotcrete linings in response to point loading

In shotcrete lining design there are a number of analysis methods available to estimate the ultimate point load resistance. However, little experimental evidence is available to confirm the validity of these estimates. To address this deficit, a series of full-scale load tests were undertaken on macro-synthetic fibre reinforced shotcrete (MSFRS) linings constructed in an underground coal mine in Queensland, and steel fibre reinforced shotcrete (SFRS) linings constructed as part of a tunnel project under construction in Sydney, Australia. Areas of lining were tested to destruction to identify the point load resistance. All the tests reported in this paper involved predominantly flexural failure of the shotcrete lining.The tests comprised regions of ∼70–100 mm thick FRS lining with bolts placed orthogonally at ∼1000–2500 mm centres. Load was applied using an inflatable lifting bag with a load capacity of about 500kN and maximum displacement capacity of 150 mm. Although the FRS used in the trials displayed post-crack strain-softening behaviour in accompanying ASTM C1550 tests, all the in situ tests resulted in strain-hardening behaviour with no evidence of a dip in load resistance upon cracking of the concrete matrix. The peak load resistance was many times greater than the load resistance measured at first crack, which was confirmed with numerical and analytical modelling. Substantial post-peak ductility was noted in all the tests.

Development and Validation of a Modified Equivalent Strut Model of Lightweight Masonry Block Infill Walls for Quasi-static In-plane Cyclic Analysis

ABSTRACT Lightweight masonry blocks (LMBs) are more environmentally favorable than solid clay bricks, and have gradually become the main material for the infill walls of modern buildings. It is of great importance for proposing a suitable hysterical model of LMBs infill walls to accurately predict the seismic responses of modern buildings. However, cyclic loading tests of LMB infill walls demonstrate that the existing formulas of equivalent strut models significantly overestimate the stiffness and underestimate the peak strength. To this end, the force-displacement curves of 24 cyclic loading tests of LMB infill walls sourced from existing literature are statistically analyzed. The modification coefficients of stiffness and peak strength are put forward, and other parameter values such as yield strength coefficient, unloading stiffness coefficient and pinching effect coefficient are also recommended. Then a full-scale cyclic loading test of an LMB infill wall is designed and conducted to verify the accuracy of the modified model. In addition, the applicability of the modified model is also verified by two infill wall tests from existing literature. The results indicate the modified model can accurately simulate the global hysteretic response of LMB infill walls, and the simulation accuracy of the peak strength is increased to more than 90%. This model provides a useful tool for the accurate evaluation of the seismic performance of modern buildings infilled with LMBs.

Experimental study of the load-deformation behaviour of the precast post-tensioned continuous girder for straddle monorail: Full-scale load test under service and ultimate loading conditions

This study presented the results of an experimental program conducted on a newly proposed Full-scale Precast Post-tensioned Continuous (FPPC) girder for straddle monorail. The investigated FPPC girder represents the actual size, design and construction details for a newly designed monorail transit system (Yellow Line and Pink Line Monorail) in Bangkok, Thailand. The salient features of the newly proposed girder system include lightweight, low-cost, easy and fast construction. The newly proposed FPPC girder is mainly comprised of three reinforced concrete (RC) hollow haunched girders, four piers or supports, two pier segments, four wet joints, and four bearings at each support. The FPPC girder was constructed at the casting yard of Sino-Thai Engineering and Construction Public Company Limited (STECON), Thailand. The FPPC girder was tested under different loading conditions (such as service and ultimate loading conditions). Both service and ultimate loads were applied as two-point loadings. Service load in a monotonic manner was applied on the right exterior span (two-point), middle span (two-point), and on the left exterior span and middle span (four-point). Meanwhile, the ultimate load in a monotonic manner was applied only on the left exterior and middle span as a four-point loading scheme. The test results indicate that the behaviour of the FPPC girder under service load conditions is elastic. Further, cracking of the concrete was not observed at any location. The observed maximum deflections under service load conditions were less than the permissible limits at all locations. Further, the maximum ultimate load-carrying capacity was observed to be much greater than the design load under ultimate loading conditions. This is an indication that the design details and construction procedure of FPPC girder are appropriate and further that this system could be used effectively to construct straddle monorail transit systems. Finite element analysis of FPPC monorail bridge girder was also performed by using a computer program ATENA which is a computational tool for nonlinear engineering analysis of bridges and culverts. The finite element analysis results indicate that the computer program ATENA is well capable to predict the ultimate load carrying capacity, displacement and cracking patterns of FPPC girder.

A Parametric Numerical Study for Diagnosing the Failure of Large Diameter Bored Piles Using Supervised Machine Learning Approach

The full-scale static pile loading test is without question the most reliable methodology for estimating the ultimate capacity of large diameter bored piles (LDBP). However, in most cases, the obtained load-settlement curves from LDBP loading tests tend to increase without reaching the failure point or an asymptote. Loading an LDBP until reaching apparent failure is seldom practical because of the significant amount of settlement usually required for the full shaft and base mobilizations. With that in mind, the supervised learning algorithm requires a huge labeled data set to train the machine properly, which makes it ideal for sensitivity analysis, forecasting, and predictions, among other unsupervised algorithms. However, providing such a huge dataset of LDBP loaded to failure tests might be very complicated. In this paper, a novel practice has been proposed to establish a labeled dataset needed to train supervised machine learning algorithms on accurately predicting the ultimate capacity of an LDBP. A comprehensive numerical parametric study was carried out to investigate the effect of both pile geometrical and soil geotechnical parameters on both the ultimate capacity and settlement of an LDBP. This study was based on field measurements of loaded to failure LDBP tests. Results of the 29 applied models were compared with the calibrated model results, and the variation in LDBP behavior due to change in any of the hyperparameters was discussed. Accordingly, three primary characteristics were identified to diagnose the failure of LDBPs. Those characteristics were utilized to establish a decision tree of a supervised machine learning algorithm that can be used to predict the ultimate capacity of an LDBP.

Inclined composite guardrails/safety barriers – Numerical and experimental evaluation of their transverse stiffnesses and compliance with standards

Three-point flexure and axial torsion tests were undertaken to establish the longitudinal elastic flexural and in-plane shear moduli of pultruded GFRP tubes. They were used to define one-dimensional two-node beam elements for modelling single- and two-bay inclined guardrails with inclinations up to 60°. Subsequently, three-dimensional FE models were developed to analyse more accurately single- and two-bay 30° inclined guardrails. The results from these analyses were compared with those of full-scale load tests on 30° inclined guardrails subjected to transverse normal preload, usability, and ultimate loads applied to the handrails. It is shown that the analysis results based one-dimensional elements significantly underestimate the mean handrail deflections and over-estimate the guardrails’ transverse stiffness. By contrast, using three-dimensional elements in the FE models give more accurate predictions, with mean handrail deflections 9% and 14–16% lower than single- and two-bay test values respectively. The corresponding percentages for mean transverse stiffnesses are 10% and 12.5 – 14.3% higher respectively. It was also observed that the responses of the guardrails were linear, the residual deflections on unloading were less than permitted for the preload, usability and ultimate loads. Furthermore, neither the single- nor the two-bay 30° inclined guardrails sustained any damage.

Installation of Bored Piles with a Protective Silicate Shell of a New Design in Saline Silty-Clayey Soils

Designing advanced methods of corrosion protection and increasing the bearing capacity of pile foundations on saline clayey soils is a priority geotechnical task in Kazakhstan. The formation of a suffusion-resistant waterproof shell was achieved by silicatization of a borehole before concreting, by the installation of a mold into the borehole and the impregnation of a sodium silicate solution into the space between the mold and the soil under pressure. After coagulation of the silicate solution, the mold was removed and the formed shell was filled with corrosion-resistant concrete. Full-scale static pile load tests were conducted in the construction site “Retaining wall on Mount Koktobe” in Almaty. The bearing capacity of the piles with the protective silicate shell exceeded the bearing capacity of an ordinary pile by 2.5 times on average without wetting the site, and 3.2 times after prolonged wetting. The numerical model had a close relationship with the average experimental curve obtained when conducting six static pile load tests with the protective shell. A large economic effect of the developed piling technology with a protective shell was achieved, with a significant reduction in the cost of piling, equal to 27.85%.

Strength and Plastic Rotation Capacity of I-Shaped Beams with Grid-Purlin System Subjected to Cyclic Loading

This paper introduces a grid-purlin system, which was composed of secondary rectangular-hollow-section grids welded onto the top flange of I-shaped beams of moment frames. The welded grid-purlin itself may play a role of a lateral bracing member for the welded beam. However, the ultimate strength, plastic rotation capacity, or other structural characteristics of this grid-purlin system remain poorly understood. This paper presents two full-scale cyclic loading tests on specimens with I-shaped beams 700 mm deep, 240 mm wide, and 13 m long. The diagonal length of grids in the square grid-purlin of the specimen was 1.3 m on-center, and two different depths of the sections were selected for the purlin sections. Both specimens successfully achieved fully plastic moments at a plastic rotation exceeding 0.04 rad. This shows that the grid-purlin system provides reliable lateral bracing. Continuum finite-element (CFE) analysis was performed to simulate the hysteretic experimental response of the grid-purlin system. This CFE model was used to examine the plastic rotation capacity for a variety of combinations of I-shaped beams and grid-purlins.

Tapered reduced deep beam connection for long span steel moment frames

Beam to column connection ductility and beam flexural stiffness are crucial parameters for seismic performance and drift control in moment-resisting frames. However, an increase in beam span and depth to obtain column-free flexible internal space affects these parameters negatively. In this paper, a new long-span deep beam-column connection detail is proposed with improved stiffness and adequate ductility for moment frames in low-to-moderate seismic zones. As panel zones can undergo plastic deformation beyond the joint rotation demand in low-to-moderate seismic zones, the beam flange and panel zone in the proposed connection are proportioned such that a stable yielding occurs in the panel zone and two plastic zones on the beam segment away from the beam-column interface. The beam flanges at the beam-column interface are thickened, widened, and tapered to control beam plastic hinge locations and mitigate distress resulting from significant panel zone plastic deformation. The performance of the proposed connection was evaluated through a full-scale cyclic load test and parametric finite element analysis on a beam-column connection with a 1200 mm deep beam. The test and finite element results showed the formation of plastic hinges at the anticipated locations. Furthermore, the connection exhibited stable hysteresis beyond the minimum rotation limits specified for intermediate moment frames (American code) and ductility class medium (Eurocode). Moreover, the connection effectively allowed balancing between beam and panel zone yielding while hindering beam flange distress associated with significant panel zone plastic deformation. Furthermore, a comparison between the proposed and welded unreinforced flange-welded web connection demonstrated improved ductility, stiffness, moment capacity, and energy dissipation capacity. Additionally, equations were proposed to quantify the improvements, and balance beam and panel zone energy dissipation.

Laterally loaded single piles – construction of the P–Y reaction curves from the DPT test in sandy soils

ABSTRACT The Dynamic Penetration Test (DPT) is one of the simplest and least expensive in-situ tests, used in geotechnical projects. However, in the literature, there is no available practical method for constructing the P–Y curves based on the DPT test (P is the soil-pile reaction and Y is the pile deflection). This paper is aimed at suggesting a new practical method of constructing the P–Y curves on the basis on the DPT data in sandy soils. This method was derived from the interpretation of five full-scale lateral loading tests on fully instrumented piles in sandy soils. Simple analytical formulation of the P–Y curves parameters, as well as design practical charts were proposed as function of the number of blows Nd of the DPT test. The results predicted by the proposed DPT based P–Y curve agreed relatively well with measured results within the margin of small to medium deflection.

Synergistic shear behaviour of cold-formed steel shear walls and reinforced edge struts

A composite structural system in which concrete-filled steel-tubular struts are bolted to a cold-formed steel (CFS) shear wall (C-CFS shear wall system) was proposed to improve the shear performance and stability of conventional CFS shear walls. Full-scale cyclic loading tests were performed to investigate the shear behaviour of the C-CFS shear wall. Furthermore, the synergistic mechanism of the interior shear wall and reinforced edge struts was explored, and a simplified method for calculating the shear capacity of the C-CFS shear wall was proposed. The results show that during the tests, the reinforced edge struts ensured the sufficient deformation of the screw connections in the interior CFS shear wall and maintained the postloading shear capacity of the composite system. Compared with a conventional CFS shear wall with the same dimensions, the shear capacity and elastic stiffness of the C-CFS shear wall were enhanced by approximately 60% and 100%, respectively; moreover, the C-CFS shear wall exhibited a better energy dissipation capacity and ductility after reaching its shear capacity, and the ductility factor of the C-CFS shear wall reached 4.7. The reinforced edge struts interacted with the interior shear wall, and the ratios of the shear forces in the former and the latter to the total structural shear forces stabilized at 20–30% and 70–80%, respectively, forming a reliable lateral resistant system. The shear capacities of the C-CFS shear walls were accurately predicted by the proposed simplified method, and the relative errors between the calculated results and the test results were within 5%.

STATIC PILE LOAD TESTS: CONTRIBUTION OF THE MEASUREMENT OF STRAINS BY OPTICAL FIBER

The use of optical fiber for measuring strain and or temperature is increasing in civil engineering. Optical fiber is known to be relatively cheap, compared to the more traditional sensors commonly used, and can, depending on the chosen technology, give a complete distribution along the instrumented element, which can be very interesting in case of an element with variable dimensions along the length of said element. Therefore, for static pile loading tests, the use of optical fiber should present many advantages, compared to more conventional methods of strain measurements. The aim of this paper is to shed new light on the advantages and disadvantages of using optical fiber for the measurement of deformations along a foundation element. After a review of the state of the art of the most commonly used methods, the contribution of the optical fiber for the instrumentation of the foundation elements is evaluated, by comparing the results obtained by the use of the fiber with those obtained with more traditional methods, in some examples of full-scale load tests. Finally, some recommendations are given to maximize the awareness of the potential use of optical fiber in foundation monitoring.

Resistance Factors at Serviceability Limit State Using the Texas Cone Penetrometer as the Predictive Model

This study presents the development and calibration of resistance factors for the serviceability limit state (SLS) condition (φSLS) used in the load and resistance factor design (LRFD) of deep foundations. The performance function was established based on load corresponding to tolerable displacement (Qδtol) and design load (Qd). A dataset of published full-scale load tests including projects from Texas, Missouri, Arkansas, Louisiana, and New Mexico was compiled and consisted of 60 load test cases comprising 33 driven piles and 27 drilled shafts. Resistance factors for SLS conditions were calibrated for tolerable displacements using both the Monte Carlo simulation (MCS) and the First Order Second Moment (FOSM) approaches. From the calibration study, resistance factors at SLS conditions were obtained ranging from 0.33 to 0.62 using FOSM method and 0.37 to 0.67 using the MCS for driven piles. In the case of drilled shafts, SLS resistance factors ranged from 0.37 to 0.77 following the FOSM method and 0.41 to 0.86 based on MCS.