•Behavior of a full-scale masonry building strengthened with CRM on one-side.•Quasi-static cyclic loading test.•The CRM coating modified the stiffness, strength and the failure mode.•The CRM coating ...can effectively improve the ductility of the structure.•Evaluation of the equivalent hysteretic damping coefficient.
The results of an experimental study on a full-scale, two-storey rubble stone masonry building, strengthened with a Composite Reinforced Mortar (CRM) system applied on the external face of the walls, are herein presented. The CRM system consisted of a mortar coating reinforced with Glass Fiber Reinforced Polymer (GFRP) mesh and injected steel transverse connectors, which connect the separated wythes of the masonry. The aim of the research is to investigate the effectiveness of this strengthening technique. The study concerns two cyclic experimental tests: the first was carried out on the unreinforced masonry building up to a damage level not far from the ultimate limit state. Then, the building was repaired, strengthened with the proposed technique, and tested again. The second test was carried out up to a near-collapse condition. This allowed to evaluate the effectiveness in terms of seismic performances provided by the reinforcement.
The cyclic horizontal load, with increasing amplitude, was applied to each of the two longitudinal walls of the building by means of servo-controlled hydraulic jacks pinned to a vertical steel beam. This beam allowed the distribution of the total lateral force between the first floor and roof level, in the fundamental mode shape. The experiments proved the effectiveness of the proposed strengthening method: with respect to the unreinforced masonry building, the resistance increased by 2.4 times, the displacement capacity by 4 times and the total dissipated energy by about 7.2 times. These benefits were due to the GFRP mesh reinforced coating’s capability to prevent the formation of isolated thick cracks, instead promoting a wider dispersion of many closely spaced thin cracks. Moreover, the importance of transverse connectors in preventing the separation of the masonry leaves in the strengthened walls was also clearly observed.
Cutouts are usually used in orthotropic steel decks (OSDs) of bridges and subject to complex stresses under loads. This research performed experimental and theoretical investigations to evaluate the ...effect of a thin UHPC layer on the fatigue performance of upper cutouts in OSDs. A full-scale specimen was fabricated and tested under static and fatigue loads before and after the specimen was strengthened with the UHPC layer. The results show that a fatigue crack initiated from the weld toe at the upper cutout after 1.15 million cycles of fatigue load with a load range of 216 kN. The use of the UHPC layer generated a steel-UHPC composite specimen subject to an extra fatigue loading for 2 million cycles with the same load range. The propagation length of the fatigue crack was only 1.2 mm, and the propagation rate was reduced from 0.61 × 10−4 mm/cycle to 0.0095 × 10−4 mm/cycle, with a reduction of 98.4%. The peak stress at the crack tip decreased from 139.0 MPa to 51.6 MPa, by 62.9%. A series of finite element analyses was performed to evaluate the fatigue damage. It was found that the use of the UHPC layer significantly reduced fatigue damage in the fatigue-prone detail around the upper cutouts and extended the fatigue life accordingly.
•The mechanism of fatigue-prone detail near the upper cutouts in OSDs was explored.•Experimental tests were conducted for a full-scale OSD specimen prior to and after strengthening.•The UHPC-based strengthening technique was effective for crack inhibition around upper cutouts.
•Conducted eccentric compression tests on 18 CFSST-CFRP long column.•Investigated eccentrically loaded behavior and resistance of CFSST-CFRP column.•Evaluated effects of slenderness ratios and load ...eccentricity ratio.•Analyzed load bearing capacity and load-transferring mechanism.•Performed parametric studies on column bearing capacity.•Developed design equations to predict ultimate eccentric load capacity.
This study investigated behavior of concrete filled square steel tubular (CFSST) columns encased with I-shaped CFPR under eccentric compression. Full-scale eccentric compression tests were conducted on eighteen column specimens consisting of square steel tube, concrete, and an I-shaped CFRP profile. The test program considered effects of load eccentricity ratio and column slenderness ratio. The eccentrically loaded column behavior was investigated with respect to the mid-height deflection, load, and failure modes. The development and distribution of longitudinal strain and neural axis for the column were also studied. Finite element models were developed and validated against tested results to further analyze the load-transferring mechanism of the composite column and perform detailed parametric studies. The results indicated that the CFSST column encased with I-shaped CFRP behaved in a ductile manner with the improved capacity and increased stability. Finally, design equations were developed using tested and simulated data to estimate ultimate bearing capacity of the CFSST column encased with I-shaped CFRP when subjected to eccentric compression. The predicted column capacities using the design equations matched well with the tested and simulated capacities.
The objective of this study is to investigate the structural behaviors of a modular thin-walled steel trestle bridge structure that is used to convey bulk cargo and found widespread use in coal and ...electric power industries. This modular thin-walled steel trestle utilizes corrugated sheets as both structural and enclosure component along with top and bottom stringer components and adopts a modular construction. As a new structural format, its behavior has not been well understood and no related literature was available. This study provides a first full-scale experimental investigation on this thin-walled trestle and establishes a detailed computational model with a focus on the modeling assumption of the modular connection. The experimental test showed the ultimate loading capacity of the trestle under vertical loading and revealed that the failure was initiated by the buckling of the top stringers near the middle span, which shed light on the understanding of behavior of the whole structure for design and analysis. The detailed computational model was validated with the experimental test and parametric studies were carried out to investigate the influence of several selected structural components, such as the corrugated sheet, the top stringer, and the bottom stringer, on the behavior of the proposed trestle. Ultimately, the results indicate how these components may be optimized.
•Experimentally investigated the structural behaviors of a thin-walled steel trestle bridge.•Investigate the influence of several selected structural components via parametric analysis.•Propose a detailed computational model validated by the experimental test.•Studied the load capacity of the trestle under vertical loading.•Revealed the loading and failure mechanism of the thin-walled trestle steel bridge under vertical loading.
Prefabricated cement concrete pavement (PCCP) is utilized more frequently in airport projects. Load transfer efficiency (LTE) is an essential mechanical index of PCCP. This study proposes a novel ...PCCP surrounded by tongue and groove joints. It uses both physical and numerical modeling to perform the investigation, and the mechanical responses and the LTE of the novel PCCP are presented in the experiments. The experimental results showed that the presence of tenon and mortise causes a difference in the stresses of two longitudinal and two transverse joints. Subsequently, a finite element model is developed to simulate the PCCP with and without transverse tongue and groove joint. In addition, the influence of different slab thicknesses, joint rigidity, and base elastic modulus on LTE is also discussed. The findings demonstrated that the transverse joints change the pavement slab's stress state. The LTE of the slab without a transverse joint is slightly larger than that with a transverse joint, while the maximum horizontal tensile stress of the slab without a transverse joint is 395% higher than that with a transverse joint on average. It is also observed that increasing the joint rigidity improves the LTE, whereas increasing the slab thickness decreases the LTE, and increasing the base modulus has no discernible effect on the LTE. Comparing the experimental and numerical results reveals a good agreement.
The paper presents an experimental and Finite Element (FE) numerical analysis of the behavior of unprotected log-haus timber walls in fire conditions under in-plane compressive loads. The aim is to ...assess their overall structural performance and to provide possible design suggestions. In doing so, the main results derived from a full-scale experimental test of a log-haus specimen subjected to the standard fire curve and loaded in-plane in compression are first described. FE numerical simulations are then carried out, to further assess the test results and to perform - based on the rather close correlation between test and FE results - a parametric study on the examined structural system. The effects of several influencing parameters are then investigated, including the presence of an initial geometrical out-of-plane global curvature, the possible exposure to fire of orthogonal logs and carpentry joints acting as lateral outriggers for the main log-haus wall, and the compressive loading ratio acting in combination with the fire loading. The most significant effects of such influencing parameters are highlighted in terms of overall buckling resistance and failure mechanisms for the examined walls in fire conditions, providing evidence for the reduction of their actual load carrying capacity. In conclusion, aiming to derive useful design suggestions, a possible extension to log-haus systems of the “Reduced Cross-Section Method” (RCSM) currently in use for the verification of fire exposed timber members is proposed.
•The fire behavior of unprotected log-haus timber walls under in-plane compressive loads is investigated.•A full-scale experimental test is presented for a log-haus wall, giving evidence of the observed fire performance.•Finite-Element numerical models are developed, to further explore the experimental findings and perform sensitivity studies.•The effect of some key input aspects on the overall buckling performance of log-haus systems is investigated.•Simplified formulations for log-haus systems in fire conditions are preliminary assessed.
This paper investigates the nonlinear behavior of wall-beam-strut joints with mechanical couplers, which are proposed for prefabricated underground constructions, under monotonic and cyclic loading ...conditions using full-scale experimental tests and three-dimensional finite element modelings. The nonlinear behavior of the joint is discussed in terms of the load–displacement curves, concrete cracking distributions, and strains in the reinforcements obtained from both the experimental tests and the numerical modeling. The comparison indicates that the trends of both load–displacement curves are similar, although the cracking, yield and ultimate loads of the joints determined by the numerical modeling are 2.5% lower, 2.6% higher and 3.8% higher, respectively, than those determined by the experimental tests. The numerical simulation can capture the concrete cracking process in the joint in the early loading stage but cannot accurately model the crack distribution in later stages. Moreover, the reinforcement strains and the skeleton curve from the numerical modeling show the same tendency as those from the experimental test, but it is difficult to compare their exact values, especially after yielding. The differences are believed due to the fact that the numerical modeling idealizes the materials and fails to model the slippage between the reinforcements and concrete after the concrete cracking. On the basis of the experimental and numerical investigations, it is concluded that the proposed wall-beam-strut joint has not only an ultimate bearing capacity that is at least 3 times higher than the design load but also a good ductility. Therefore, the design of the wall-beam-strut joint satisfies the requirements for the prefabricated underground construction.
In achieving medium-to-long span slab, steel-concrete composite beams may offer an alternative over pre-stressed beams for the so-called disadvantages of the latter; for example the heavy weight of ...pre-stressed beams makes their handling expansive. However, the use of composite beams by concrete builders is still limited due to the lack of specific tools and skills for on-site erections and the need for a supplementary fire protection. This article presents an innovative steel-concrete moment resisting portal frame that overcomes these difficulties. It is composed of composite tubular columns, and a composite beam made of a U-shape steel profile used as permanent formwork to encase a concrete beam. The steel-concrete duality of the proposed beam allows an erection on site without any weld or bolt by a wise positioning of the construction joints. As only steel elements have to be handled on site, there is no need of heavy cranes. This system has been used to build a research center near Rennes, in France. As it is not covered in present norms, an experimental validation was required. In this paper, a series of full-scale experimental tests that have been performed in order to assess the global and the local behaviour of the frame and its connections are presented. A series of asymmetrical push-out tests were carried out in order to determine the ductility and resistance of shear connectors; one 4-point bending test was made to investigate the resistance under sagging bending moment; and, two tests of the beam-to-column joint were performed in order to validate a strut and tie design model of the joint. Finite element simulations have also been made in order to acquire more information for the development of the analytical models.
The recent development of high-speed trains over the last decade led to a growing interest in their aerodynamics. A train at full operational speed generates a strong induced airflow that may damage ...infrastructures near the trackside and endanger people near the rails. Nowadays the tests required for the train homologation are based on full scale measurements of the airspeed taken in specified positions close to the railway line. An important part of the work was initially dedicated to the data analysis of an extensive experimental campaign performed on the Italian high-speed line, in order to obtain reliable results to be used for comparison with CFD results. These ones have been performed on the full-scale train geometry using an URANS approach with a wall treatment based on wall functions, checking mesh and turbulence models dependencies. The full-scale simulations highlighted the great complexity of the problem being the comparison with the experimental measurements performed close to the shear layer of the train boundary layer. Encouraging results are obtained from the numerical analysis on the full-scale train geometry indicating the ability of the URANS coupled with the SST turbulence model in the prediction of both the train induced flow and the turbulent structures around it.
•Flow statistics strongly influenced by crosswind.•CFD provide good estimation of the 3D flow around a full scale high speed train in operational conditions.•k-omega SST turbulence model showed a strong stability and versatility in reproducing high turbulence flow.
•Manufacturing of full-scale large-size FREIs with polyester fibre and soft rubber compound.•Full-scale testing of two FREI large-size prototypes in unbounded configuration under static and dynamic ...loading.•Initial type tests as per standard provisions for conventional laminated rubber bearings EN15129.•Stable hysteretic behaviour up to 100% shear strain with damping ratio up to 20% of critical.•Satisfactory performance via numerical analysis of a case-study frame building isolated at the base with FREIs in comparison to laminated rubber bearings.
Fiber reinforced elastomeric isolators (FREIs) have shown to be a promising option as an alternative to classical steel reinforced elastomeric isolators (SREIs). Previous investigations were limited to scaled-geometries without any attempt to test such devices under code-compliant protocols as per international standards. In the present study the authors investigated two circular full-scale (diameter 620 mm) FREIs manufactured with a non-standard process adopting a soft rubber compound and polyester fibers. Experimental tests were performed in unbounded configuration through the large anti-seismic device test facility at the EUROLAB of the University of Messina, Italy. A significant number of protocols were imposed to the prototypes in order to demonstrate the effect of different loading conditions, i.e., strain level, frequency of the excitation, axial load and repeated loading. The tests confirmed the significant dependency of mechanical behavior on axial load which tends to increase damping (i.e., higher friction mechanisms) while reducing stiffness (i.e., lower stability limits). Due to internal slippage at the fiber-rubber layers interface, damping capacity of FREIs achieved 20% of critical, i.e., significantly higher than that commonly achieved in SREIs with the same rubber compound. Even if adequate capacity was reached in compression, the run-in effect would limit the axial stiffness of FREIs. A significant roll-over phenomenon was detected under lateral loading up to a maximum shear strain of 100% without damage and permanent deformation after unloading. A numerical study finally demonstrated the effectiveness of FREIs when compared to SREIs in a base isolation system designed for a 3-storey reinforced concrete frame located in a high seismicity region in Italy. Lower axial stiffness of FREIs did not affect the seismic performance of the building due to limited rocking motion component and beneficial higher damping mechanism. This paper provides a significant contribution to the standardization of FREIs to be adopted in base isolation of conventional buildings.
PDF
