Full-scale Specimens Research Articles

Behavior of T-shaped sandwich composite walls with truss connectors under eccentric compression

Sandwich composite walls are composed of two external steel faceplates and concrete infill and have been increasingly applied in infrastructure to resist either gravity or lateral loads. They combine the advantages of both steel and concrete and offer excellent structural behavior. In this paper, the performance of a new type of T-shaped sandwich composite walls with truss connectors was studied. Three full-scaled specimens with T-section were tested under eccentric compression. The failure mode was identified as the sectional strength failure. Load versus axial and out-of-plane displacement responses, buckling stress, axial stiffness, ductility, and strength utilization were discussed. Based on CECS 159, the interaction model between the compression and bending moment was proposed to estimate the sectional strength of sandwich composite walls under eccentric compression. The comparison between the test data and the proposed curve shows that the proposed method offers reasonable and conservative predictions on the strength of sandwich composite walls.

Cycle performance tests and numerical modeling of infilled CFS shear walls

The infilled CFS shear walls with FGD gypsum were developed in the paper. For lightweight design, the FGD gypsum was mixed with glazed hollow beads and air-entraining agents. Five full-scale specimens were investigated under cyclic horizontal loads. The configuration of the specimens varied in compressive strength of infilled gypsum and sheathing types. The shear performance of the walls can be improved obviously due to the participation of infilled material. The failure modes are characterized by the loss of stressed skin provided by sheathings together with compressive failure of infilled gypsum. Besides, a series of tests concerning fastener responses and material characteristics of gypsum was conducted. Furthermore, the numerical models based on OpenSEES were proposed. After calibration of parameters, a combination of beam elements with pinned joints, zero-Length elements with Pinching-4 material and equivalent truss elements with Concrete-01 material was employed to describe the nonlinear behaviour of the infilled walls. The comparison between tests and simulations was then carried out. The results of numerical models have an agreement on test results. The developed numerical model can be used for predicting cycle performance of the infilled CFS walls and related analysis of structural systems in further studies.

Experimental investigation of self-centering steel reinforced concrete coupled wall panels with replaceable energy dissipaters

Resilience of structures is already the new issue and challenge in the field of earthquake engineering. In order to enhance the restorability of concrete wall panels and further use them in steel moment frames, a novel self-centering steel reinforced concrete coupled wall panels with replaceable energy dissipaters is presented in this paper. For this purpose, subassembly tests of the coupled walls with frame beams as boundary were carried out. Four full-scale specimens were tested under cyclic lateral loads. The initial prestress of post-tensioned (PT) steel bars and configuration of energy dissipaters were varied to investigate their impacts on lateral responses of the walls. The failure process, load-displacement relation, energy absorption capacity, residual deformation and force of PT steel bars were also investigated. Test results show that the three-stage nonlinear response is characterized by the sequential failure process of wall rocking, yielding of energy dissipater and yielding of PT steel bars. The initial prestress of PT steel bars greatly affects the initial stiffness, rocking load and residual deformation of the walls. Failure of the walls is mainly concentrated on the energy dissipaters. With the increase of energy dissipaters in quantitative terms or in type terms, the capacity of energy absorption is accordingly improved, but self-centering capacity is accordingly weakened.

Long-term behavior of continuous composite slabs made with 100% fine and coarse recycled aggregate

A composite slab is an efficient modern structural member. Recycled fine and coarse aggregates are alternative green materials for the depleting natural sand and natural gravels in the composite slabs. In recent years, the nonuniform shrinkage occurring in single-side-exposed concrete has been discovered to significantly affect the long-term behaviors of composite slabs, which have been included in newly published codes. Applying recycled aggregate concrete (RAC) would further increase the effect of nonuniform shrinkage on the long-term behaviors of composite slabs. However, most studies, with RAC or not, have only focused on simply- supported composite slabs. For continuous composite slabs (CCSs), in addition to increasing deflections, a nonuniform shrinkage would induce a larger negative bending moment, which would further increase the crack width at the interior support region. Hitherto, no experiment has been conducted regarding the time-dependent crack width of CCSs and CCSs with RAC. Therefore, the aim of this study is to investigate the effects of nonuniform shrinkage and RAC on the deflections, strains, and cracks of CCSs. Hence, a 500-d experiment was conducted on three full-scale specimens. Finally, a finite element (FE) model was established and benchmarked against the test results of this study and those reported in the literature. The results indicated that (1) nonuniform shrinkage significantly increased the crack width at the negative bending moment region; (2) the use of RAC resulted in a more significant effect of the nonuniform, e.g. mid-span deflections, soffit strains, and crack widths increased by 40%, 64%, and 38%, respectively; and (3) the FE model can predict the long-term behaviors of CCSs well.

Seismic performance of squat thin reinforced concrete walls for low-rise constructions

Thin reinforced concrete (RC) walls with single layer reinforcement have been used for houses and buildings in several Latin American countries. Although some design codes include recommendations for squat thin walls in low-rise constructions, its seismic performance has not been validated adequately in past earthquakes. This article presents the results of an experimental campaign of nine full-scale specimens conducted to characterize the influence of the steel type, the reinforcement ratio, and the wall thickness on the seismic behavior of squat thin RC walls with single layer reinforcement. Both welded wire and deformed bars were used as web reinforcement. Experimental results are used to develop nonlinear models to assess the seismic behavior of a prototype two-story house with welded wire reinforcement and deformed bars by means of incremental dynamic analyses. The experimental results show that the type of steel has the largest influence on wall seismic performance. The numerical results suggest that RC walls with single layer reinforcement are suitable for housing applications up to two stories in high seismicity regions, particularly walls detailed with deformed bars.

Experimental Seismic Performance of Partly-Sliding Partition Walls

ABSTRACT Plasterboard partition walls typically used in commercial buildings are especially sensitive to earthquakes, with the onset of cosmetic damage initiating at small values of interstorey drift. The most common partition wall systems are constructed of gypsum board attached to either steel or timber framing which is fixed directly to the floor system at the top and bottom interfaces. This study investigates the seismic performance of a novel partly-sliding steel-framed partition system examined in the past and used by industry, with minor modifications incorporated within the partition detailing. This novel system involves removing top track anchors within the proximity of wall intersections, thus allowing the tracks to ‘bow’ out at these locations. In this study three full-scale specimens were subjected to quasi-static cyclic testing; two identical plane specimens and the third including a doorway. The specimens were built in a y-shape and angled at 30° to the direction of applied loading, which allowed bi-direction behaviour to be examined. The specimens included an acoustic/fire sealant. The progression of damage in a partition can be categorized by three sequential damage states associated with distinct levels of repair: superficial damage requiring cosmetic repair (damage state 1 (DS1)), damage requiring local repairs or replacement of only portions of the partition assembly (damage state 2 (DS2)), and severe damage requiring complete removal and replacement of the wall (damage state 3 (DS3)). Damage was first observed as cracking of the wallboard at the wall ends, at external junctions, and propagating from the corners of the door opening. The onset of DS1 and DS2 occurred simultaneously at a median in-plane drift of 0.29%. DS3 was not observable until the linings had been removed at the end of the tests. In addition to providing drift capacities, the force-displacement behaviour is also reported, the dissipated energy was computed, and the parameters of the Wayne–Stewart hysteretic model were fitted to the results. The specimen with the door opening behaved significantly different to the plane specimens: damage to the doorway specimen began as cracking of the wallboard propagating from the corners of the doorway following which the L- and Y-shaped junctions behaved independently, whereas damage to the plane specimens began as cracking of the wallboard at the top of the L-junction and wall system deformed as a single unit. The results suggest that bi-directional behaviour is important even if its impact cannot be directly quantified by this experiment. Damage to sealant implies that the bond between plasterboard and sealant is important for its seismic performance, and careful quality control is advised, as defects in the bond may significantly impact its ability to withstand seismic movement.

Behavior of Hollow Core Slabs Reinforced with GFRP Prestressing Bars

An experimental program was designed to study the behavior of full-scale hollow core slabs prestressed with Glass Fiber-Reinforced Polymer (GFRP) bars in the concrete laboratory at the college of engineering, Mataria, Helwan University, Cairo, Egypt. The hollow core slabs were load-tested under uniformly distributed load. The GFRP bars were manufactured from locally available materials with a 10 mm nominal diameter. To improve the bond properties between the bars and concrete, GFRP threads were axially wrapped around the bars manually. The mechanical properties of the bars were investigated in the laboratory. The bars average ultimate tensile strength (fu) and elastic modulus (E) were 1000 MPa and 46 GPa, respectively. Four full-scale concrete hollow core slab specimens with characteristic strength of 80 MPa were constructed and solely reinforced with a single prestressed GFRP bar. Each slab specimen represented one complete vent with a width of 140 mm, 150 mm thickness and 4000 mm total length. These specimens were simply supported during the experiments where the GFRP bar was placed at the centerline of the vent near the soffit. The Bars were prestressed to different stress levels, namely (10, 20, 30 and 40%) of their ultimate tensile strength (fu). All slab specimens were load-tested under uniformly distributed load. The deflection, strain and crack pattern were investigated during load-testing. From the obtained results, it was observed that the optimum prestressing level was 20% of the ultimate tensile strength of the bar for both the moment carrying capacity and the deformation.

Seismic behaviour of Taiwanese timber complex brackets subjected to out-of-plane loading

The Taiwanese Dieh-Dou-type complex brackets used in traditional timber buildings are commonly believed to sustain both in-plane and out-of-plane loadings of the main frame during seismic events. From past statistical investigation, single-tier, double-tier and triple-tier asymmetric bracket designs were chosen as test subjects. A series of quasi-static cyclic tests was applied to full-scale specimens to evaluate their seismic behaviour when subjected to out-of-plane loading. The test specimens generally exhibited significantly higher resistance when all horizontal members sustained compression. The Gong members functioned like braces and subsequently led to enhanced resistance. However, when the global structure was subjected to tension, the joints of Gong, purlin support and purlin members were more likely to be pulled out. The counter-resistance force observed from the tension side resembled that of rigid-body rotation. The triple-tier specimen sustained more serious damage than the other two types, where the middle Dou member was more prone to split due to stress concentration. The proposed bi-linear semi-rigid spring models were in good agreement with the test results, so the general assumptions made were valid.

Increasing fatigue life of gte compressor disks made of titanium alloys by discs treatment in fluidized abrasive layer

Purpose. Increasing fatigue life of GTE compressor disks made of titanium alloys by discs treatment in the fluidized abrasive bed.Investigation methods and equipment. The investigations were carried out using LPC stage I discs of ВТ3-1 alloy and HPC stages IV and V discs made of ВТ-9 titanium alloy of Д-36 aircraft engine.In the process of discs manufacture the following manufacturing methods were used: ultrasonic hardening and treatment in the fluidized abrasive bed.The ultrasonic hardening was carried out using Motor Sich serial installation and the fluidized abrasive bed treatment – using the АПС-600А installation.The discs were tested before and after the treatment on a special electrohydraulic test bench with a multi-axis loading system using a fixture reproducing radial and circumferential stresses at the base of an inter-slot projection.The testing was carried out at specimens temperature of 390 °С and 430 °С.For measuring the length of cracks and the time of their occurrence in the slots, the discs were inspected by ЛЮМ-1-ОВ method ant using the МПБ-2 microscope and КМ-8 cathetometer.Obtained results. It has been established that for LPC stage I discs made of ВТ3-1 alloy the increased fillet radius combined with subsequent treatment in the fluidized abrasive bed increases fatigue life of the discs by 6 times before crack occurrence, and increases durability of the disc with a crack by 5.5 times.Durability of a disc is within 41 % to 77.8 % of their total fatigue life .Treatment of the compressor dics made of ВТ-9 titanium alloy in the fluidized abrasive bed creates residual compression strain up to 300 MPa in the surface layer.Testing of the LPC stage 1 discs showed that frequency and shape of the discs effect both fatigue life prior to a crack occurrence and durability prior to discs destruction within the entire investigated loading frequency range of 0.01 Hz to 1.0 Hz.Testing of HPC stages IV and V discs of ВТ-9 titanium alloy showed that temperature variation within 390 °С to 430 °С did not contribute significantly to the fatigue life change. Introduction of endurance into the loading cycle has a considerable effect on the low-endurance fatigue of the compressor discs.Increase of the soak time up to 60 seconds under the same loading conditions decreased fatigue life of the full-scale specimens by 10 times.Scientific novelty. It was demonstrated that treatment of the compressor disks made of titanium alloys in the fluidized abrasive bed increases their cyclic life by 5 to 6 times in comparison with their treatment in accordance with serial technology.Practical effect. A process sheet was proposed and the modes of compressor discs treatment in the fluidized abrasive layer were developed that provide increase of the fatigue life by 5 to 6 times as compared with a serial technology.

Обґрунтування впливу робочих органів зернозбиральних комбайнів на пошкодження і якість насіння

Goal. To justify the possibility of improving seed quality due to the reduction of damage at all stages of the process of collecting, processing, preparation, and planting; to develop the equipment for implementing these processes in production. Methods. Theoretical studies and calculations were performed using mathematical modeling of the technical means and technological processes. They used basic laws of mechanics and modern methods of computer calculations. Experimental studies were carried out in laboratory and manufacturing conditions using full-scale specimens and equipment according to the developed and standard methods. Results. They studied the strength and destruction, that is, macro-trauma of grains, depending on the mechanical influence, strain and stress. The influence of external means was studied on the occurrence and the distribution of deformations and cracks, as well as how many of them at a certain load reaches the critical length. The origin and direction of cracks and their number in most cases depended on the direction of the action of external forces and internal biological characteristics of corn. The strength of the grain, in addition to cracks, also has a significant impact of micro-trauma of the embryo, endosperm and seed and flower shells. As independent parameters, which optimize the energy acceleration of the grain to minimize deformations and micro-trauma of seeds, they took angular and linear acceleration of deformation of the volume of the grain and angular acceleration at the point of impact of the grain with the spherical surface of the working body. Theoretical calculations were made, and the influence of drum and rotary threshing devices was substantiated on deformation and damage to the seed. Conclusions. Calculation and graphic dependencies confirm the conclusion of experimental-manufacture research: macro- and especially micro-trauma of seeds of winter wheat and rye at harvesting with rotary threshing apparatus is much less than at use of drum one, which significantly influences the quality of seed.

Flexural buckling of cold-drawn oxygen-free copper tubular columns with circular hollow sections under axial compression

Abstract Oxygen-free copper (OFC) has been increasingly used in engineering applications due to many advantageous properties. In order to investigate the flexural buckling behaviour of OFC tubular columns under axial compression, seven full-scale specimens were tested. The buckling failure modes of the specimens were analyzed, and the flexural buckling strengths were obtained. Subsequently, two finite element models were developed and verified against the test data. A parametric study was performed as well. The results showed that the OFC columns with small slenderness failed by elastic-plastic buckling, while those with high slenderness failed by elastic buckling. Eqs. (9) and (11), which are based on the Perry formula, suitably described the buckling curves of the OFC tubular columns. The value of α in Eq. (9) was 0.293; and the values of α1, α2, and α3 in Eq. (11) were 1.647, 1.041, and 0.175, respectively.

Studies on Axial Tensile Loading Capacity of CHS T-joints Reinforced with External Stiffening Rings

To analyze the effects of stiffening external rings on the brace axial tension capacity of circular hollow section T-joints (CHS-T), loading experiments and finite element model analysis were utilized. Three groups of full-scale specimens (reinforced and unreinforced T-joints) of different brace-to-chord diameter ratios were tested under tension to validate the strengthening effect (Three unreinforced specimens were previously tested and the other three reinforced samples were newly completed). The experimental equipment and parameters are described in detail. Load–ovalization and load–displacement curves in addition to the failure modes were analyzed. It is concluded that the ultimate strength and initial stiffness are significantly enhanced for the reinforced CHS joints compared to the unreinforced specimens. SHELL181 elements were utilized in the finite element analysis to accurately simulate the loading capacity with and without external stiffening rings of the joints, within 10% error.

Experimental evaluation of the seismic performance of retrofitted masonry walls

Unreinforced masonry (URM) buildings are known as seismically vulnerable systems and require retrofitting. In this study, the in-plane seismic behavior of URM walls with and without an opening before and after retrofitting using different developed methods was investigated. Retrofitting methods involving a combination of metal laths, steel plates, connecting steel plates (CSPs) and polymer coating material were considered. Twelve masonry walls, including three non-retrofitted (as reference specimens) and nine retrofitted walls, were tested by subjecting the specimens to cyclic loads. The experimental study was carried out on full-scale specimens, which were tested simultaneously under the conditions of gravity and in-plane cyclic loads. The performance evaluation of each specimen was performed in terms of the lateral strength and deformation, hysteretic response, and energy dissipation. The double side retrofitting/upgrading approach substantially enhanced the lateral strength, displacement, and energy dissipation capacity of the test specimens. Furthermore, it was found that the specimens involving the combination of the polymer coating with the steel plates and CSPs could be an alternative method in terms of high energy dissipation capacity owing to the ultimate strength and displacement enhancement.

Flexural performances of pre-stressed concrete piles reinforced with hybrid BFRP and steel bars

In this study, pre-stressed concrete (PC) piles were reinforced with high-strength basalt fibre-reinforced polymer (BFRP) bars and steel bars to improve their flexural strengths and behaviours. Full-scale specimens with total lengths of 12000 mm and diameters of 600 mm were constructed and implemented with bending tests. Efforts were made to evaluate effects of non-prestressed reinforcement type and longitudinal reinforcement ratio on flexural performances of specimens. Meanwhile, J-factors were calculated to quantify deformability of all specimens. It’s experimentally demonstrated that PC piles reinforced with BFRP bars exhibit much higher flexural capacity than those with steel bars. Moreover, cross sections of all specimens basically conformed to the assumption of plane section. Failures of PC piles reinforced with BFRP bars were attributed to gradual concrete crushing, while those with steel bars were speculated to result from excessive crack width. A simplified method for predicting flexural capacities of PC piles reinforced with BFRP bars was proposed. The predicted flexural capacities using the proposed method were in good agreement with the experimental results. Results of this study were expected to provide theoretical basis for broadened engineering applications of PC piles reinforced with hybrid BFRP bars and steel bars in marine structures.

Postearthquake fire performance of cavity-insulated CFS shear walls with gypsum and calcium-silicate sheathing

Abstract This paper presented a detailed postearthquake fire investigation of cavity-insulated cold-formed steel (CFS) shear walls lined with face-layer gypsum (GP) boards and base-layer calcium-silicate (CS) boards on both sides. Four identical full-scale specimens with 3.0 m lengths and 3.0 m widths were constructed. The first specimens were subjected to ISO834 fire without earthquake damage. The other three specimens were first tested under cyclic loading to different drift ratios, and then the fire experiments were conducted. Three types of failure modes of CFS frame are identified and the corresponding generation mechanism is discussed. The relationship between the drift ratio and fire resistance time (FRT) is presented for the shear walls with the load ratio of 0.27. Meanwhile, by substituting GP board with CS board as the base-layer sheathing, the FRT was extended from 48 min to 66 min, and the shear strength and initial stiffness were increased by 21.5% and 39%, respectively; moreover, the postearthquake FRT was extended from only 8 min to 40 min when the drift ratio reached 3.5%. The degradation mechanism of postearthquake FRT is also discussed. In addition, it is found that the fire experiments of the same CFS walls can have good repeatability, especially regarding the FRT, failure mode and time-temperature curves. Finally, for the fire design practice, the overlapped board joints on the same side of double-layer sheathing should be avoided to the greatest extent and the CFS walls with GP and CS board sheathing on either side are recommended in mid-rise CFS buildings.

Friction Characteristics of Post‐Tensioned Tendons of Full‐Scale Structures Based on Site Tests

In the design of prestressing concrete structures, the friction characteristics between strands and channels have an important influence on the distribution of prestressing force, which can be considered comprehensively by curvature and swing friction coefficients. However, the proposed friction coefficient varies widely and may lead to an inaccurate prestress estimation. In this study, four full‐scale field specimens were established to measure the friction loss of prestressing tendons with electromagnetic sensors and anchor cable dynamometers to evaluate the friction coefficient. The least square method and Bayesian quantile regression method were adopted to calculate the friction coefficient, and the results were compared with that in the specifications. Field test results showed that Bayesian quantile regression method was more effective and significant in the estimation of the friction coefficient.

Shear behavior and shear capacity prediction of precast concrete-encased steel beams

A novel precast concrete-encased steel composite beam, which can be abbreviated as PCES beam, is introduced in this paper. In order to investigate the shear behavior of this PCES beam, a test of eight full-scale PCES beam specimens was carried out, in which the specimens were subjected to positive bending moment or negative bending moment, respectively. The factors which affected the shear behavior, such as the shear span-to-depth aspect ratio and the existence of concrete flange, were taken into account. During the test, the load-deflection curves of the test specimens were recorded, while the crack propagation patterns together with the failure patterns were observed as well. From the test results, it could be concluded that the tested PCES beams could all exhibit ductile shear behavior, and the innovative shear connectors between the precast concrete and cast-in-place concrete, namely the precast concrete transverse diaphragms, were verified to be effective. Then, based on the shear deformation compatibility, a theoretical model for predicting the shear capacity of the proposed PCES beams was put forward and verified to be valid with the good agreement of the shear capacities calculated using the proposed method and those from the experiments. Finally, in order to facilitate the preliminary design in practical applications, a simplified calculation method for predicting the shear capacity of the proposed PCES beams was also put forward and validated using available test results.

Seismic performance evaluation of reinforced concrete beam-column joints of existing buildings

Common computer programs generally model beam-column joint (BCJ) as a finite point without physical property that will neither yield nor fail. However, this assumption is not appropriate for modelling existing buildings without seismic provisions where the shear capacities of BCJs were uncertain. This paper presented the finite element analysis and cyclic load test results of four full-scale edge column BCJ specimens with and without column and BCJ shear link detailing according to seismic provisions. The aim was to compare the numerical analysis and experimental results to establish a reduction factor between BCJ with and without seismic detailing provisions and to verify the accuracy of numerical analysis results. With the proposed reduction factor, non-seismic provisioned BCJ that will fail under seismic actions can be determined from general computer analysis programs and correspondingly strengthened if necessary to ensure that yielding occurs in structural members connected to the joint instead of brittle joint shear failure. Furthermore, splitting crack along the lower column axis was observed in all non-seismic provisioned specimens due to eccentricity between the upper and lower column load centre and inadequate link confinement in the lower column.

Implementation of real-time hybrid shake table testing using the UCSD large high-performance outdoor shake table

Large shake tables can provide extended capabilities to conduct large- and full-scale tests examining the seismic behaviour of structural systems that cannot be readily obtained from reduced scale or quasi-static testing conditions. Assessing the behaviour of large or complex structural systems introduces challenges such as high cost of full-scale specimens or capacity limitations of currently available shake tables. Some of these limitations may be overcome by employing the real-time hybrid shake table test method that requires only key subassemblies to be evaluated experimentally on the shake table while the remainder of the structure is modelled numerically. As a demonstration of the applicability of this testing method using a large shake table, a series of hybrid shake table tests were conducted on the University of California, UC San Diego large high-performance outdoor shake table (LHPOST) with capabilities to test full scale structural models. A physical specimen was coupled with a numerical model using hybrid simulation techniques and shown to reproduce reliable results with adequate mitigation of experimental errors.

Implementation of real-time hybrid shake table testing using the UCSD large high-performance outdoor shake table

Large shake tables can provide extended capabilities to conduct large- and full-scale tests examining the seismic behaviour of structural systems that cannot be readily obtained from reduced scale or quasi-static testing conditions. Assessing the behaviour of large or complex structural systems introduces challenges such as high cost of full-scale specimens or capacity limitations of currently available shake tables. Some of these limitations may be overcome by employing the real-time hybrid shake table test method that requires only key subassemblies to be evaluated experimentally on the shake table while the remainder of the structure is modelled numerically. As a demonstration of the applicability of this testing method using a large shake table, a series of hybrid shake table tests were conducted on the University of California, UC San Diego large high-performance outdoor shake table (LHPOST) with capabilities to test full scale structural models. A physical specimen was coupled with a numerical model using hybrid simulation techniques and shown to reproduce reliable results with adequate mitigation of experimental errors.