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Ye J.,Y and V Engineering | Fu G.,Wayne State University | Fu G.,Illinois Institute of Technology | Fu G.,Tongji University | Poudel U.P.,Structural Engineer
Journal of Engineering Mechanics | Year: 2011

This paper proposes a close-range digital photogrammetric system based on edge detection for structural deformation measurement. Different from traditional photogrammetric applications using discrete points, continuous edges in digital images are used here as the controlling feature in this new system. This makes it possible to acquire spatially intensive information. The system uses several digital images of the structure, taken from a number of different stations before and after the deformation is induced. Then, an image-matching algorithm based on the coplanarity condition developed here is applied to establish spatial relationships of the interested edges, identified by using a new high-precision method. These relationships are subsequently employed to acquire full-field deformation measurement of the structure. A series of experiments was conducted in the laboratory to investigate the capability of the new photogrammetric system. Results show that the system is highly accurate and suitable for structural deformation measurement. It offers noncontact, full-field, and spatially intensive measurement, in contrast with conventional contact and point-measurement. © 2011 American Society of Civil Engineers.

Gross C.,Structural Engineer | Walker P.,University of Bath
Construction and Building Materials | Year: 2014

Hemp-lime is a natural, sustainable low carbon insulating material. It is formed from three main constituents: hemp shiv; lime based binder; and, water. Its use within the construction industry is a relatively recent development. In the UK hemp-lime is most widely used for solid wall insulation in conjunction with structural timber studwork, either cast in situ or more recently innovative prefabricated panels. Current design practice assumes that the hemp-lime does not contribute towards the structural capacity of the wall. Previous work by the authors has confirmed that hemp-lime significantly benefits vertical load bearing capacity of the timber studs. This paper presents research that has been undertaken to establish the enhancement hemp-lime provides to the in-plane racking strength of timber studwork framing. Laboratory testing was undertaken on a series of timber studwork frames both with and without hemp-lime. It was found that the hemp-lime significantly increases both the racking strength and stiffness. © 2014 Elsevier Inc. All rights reserved.

Morbiato T.,Structural Engineer | Vitaliani R.,University of Padua | Saetta A.,IUAV University of Venice
Computers and Structures | Year: 2011

The pedestrian-structure interaction is considered by developing a non-linear double pendulum model, representing the lateral walking of the pedestrian and the horizontal vibration mode of the structure. To understand the synchronization phenomenon, the two oscillators were considered in their phase spaces, and a ring-dynamics approach was applied. As synchronization occurs, pedestrian motion becomes in phase quadrature with a quarter-of-period in advance of the bridge motion: this ensures stability of walking conditions on a moving deck, but causes random cancellation of forces typical of an incoherent crowd. Correspondingly, the lateral force transmitted to the structure increases its value, approaching resonance conditions. © 2011 Elsevier Ltd. All rights reserved.

Paultre P.,Université de Sherbrooke | Eid R.,Sami Shamoon College of Engineering | Langlois Y.,Structural Engineer | Lvesque Y.,Group SM International
Journal of Structural Engineering | Year: 2010

This paper presents tests that were performed on square large-scale steel-fiber-reinforced high-strength concrete (HSC) columns under concentric compression loading. The experimental program was mainly designed to examine the effect of the volumetric steel-fiber ratio on the behavior of reinforced HSC large-scale elements subjected to axial compression loading. The test program was also designed to examine the combined confinement effect of steel fibers and transverse steel reinforcement. Thus, the test variables studied herein are the steel-fiber volumetric ratio and the volumetric ratio, yield strength, and spacing of the transverse steel ties. The results show that adding discrete fibers to HSC mixtures in reinforced concrete columns not only prevents the premature spalling of the concrete cover but also increases the strength and ductility of the axially loaded reinforced member. This behavior was predicted by the proposed fiber-reinforced concrete stress-strain model, which takes into account most of the parameters that influence confinement effectiveness: the concrete strength; the spacing, yield strength, volumetric ratio, and configuration of the transverse reinforcement; the distribution of the longitudinal reinforcement; and the diameter, length, shape, volumetric ratio, and frictional bond strength of the fibers. Predictions were found to be in good agreement with experimental results. © 2010 ASCE.

El Howary H.A.,Structural Engineer | Mehanny S.S.F.,Cairo University
Earthquake Engineering and Structural Dynamics | Year: 2011

A multi-level seismic vulnerability assessment of reinforced concrete moment frame buildings located in moderate seismic zones (0.25g) is performed on a set of ductile versions of low- to mid-rise two-dimensional moment frames. The study is illustrated through application to comparative trial designs of two (4- and 8-story) buildings adopting both space- and perimeter-framed approaches. All frames are dimensioned as per the emerging version of the seismic design code in Egypt. These new seismic provisions are in line with current European norms for seismic design of buildings. Code-compliant designs (CCD), as well as a proposed modified code design relaxing design drift demands for the investigated buildings, are examined to test their effectiveness and reliability. Applying nonlinear inelastic incremental dynamic analyses, fragility curves (FC) for the frames are developed corresponding to various code-specified performance levels. Code preset lower and upper bounds on design acceleration and drift, respectively, are also addressed along with their implications, if imposed, on the frames seismic performance and vulnerability. Annual spectral acceleration hazard curves for the case study frames are also generated. Estimates for mean annual frequency (MAF) of exceeding various performance levels are then computed through an integration process of the data resulting from the FC with the site hazard curves. The study demonstrates that the proposed design procedure relaxing design drift demands delivers more economic building designs relative to CCDs, yet without risking the global safety of the structure. The relaxed design technique suggested herein, even though scoring higher, as expected by intuition, MAF of exceeding various code-limiting performance levels expressed in terms of interstory drift ratios, still guarantees a reasonably acceptable actual margin against violating code limits for such levels. © 2010 John Wiley & Sons, Ltd.

Papastergiou D.,Structural Engineer | Lebet J.-P.,Ecole Polytechnique Federale de Lausanne
Journal of Constructional Steel Research | Year: 2014

This paper deals with the design method and the experimental verification of a new type of steel-concrete composite beam under static and fatigue loading. The connection is an alternative solution for steel-concrete composite bridges suitable for prefabrication and fast erection, while guaranteeing durability. The composite action of the beam is established through an innovative shear connection by adhesion, interlocking and friction. The resistance of the connection to longitudinal shear is based on the development of shear stresses in the confined interfaces that form the connection. The interfaces include a steel-cement grout interface and a rough concrete-cement grout interface. Confinement is provided by the reinforced concrete slab that encloses the connection. A composite beam was designed according to the design method for such type of composite beams in order to resist cyclic loading and to guarantee in the sequence its bearing capacity at ultimate limit state. The beam was initially subjected to cyclic loading and did not present signs of important damage after five million cycles. The damage on such type of connections is expressed by the development of a small residual slip in the interface which with the appropriate design stabilizes with the number of cycles. Finally the composite beam was statically loaded up to failure. The results show the capability of such a composite beam to develop its plastic moment at ultimate limit state. © 2013 Elsevier Ltd.

Bazargani P.,Structural Engineer | Adebar P.,University of British Columbia
Journal of Structural Engineering (United States) | Year: 2015

Shear strains may have negligible influence on maximum displacements at the top of slender shear walls, but may significantly increase interstory drift ratios at lower levels where gravity-load columns are often less flexible. A nonlinear finite-element (FE) model calibrated with experimental results confirmed that large shear strains occur in flexural tension regions of concrete walls due to vertical tension strains in the presence of diagonal cracks and in the absence of demand on the horizontal shear reinforcement. A fan of diagonal cracks will form at the base of flexurally hinging walls independent of the shear stress level. A parametric study confirmed that a principal strain angle of 75° can be used to estimate shear strains from vertical tension strains. Thus interstory drift ratios due to shear strains can be estimated from the easily calculated flexural demands. A simple and safe estimate of interstory drift ratio due to shear strains is 60% of the global drift ratio. Interstory drift ratios from shear strains up to 0.8% have been measured in slender wall tests. © 2015 American Society of Civil Engineers.

Mehanny S.S.F.,Cairo University | El Howary H.A.,Structural Engineer
Engineering Structures | Year: 2010

Building code restrictive seismic design provisions and building systems type and configuration have remarkable implications on seismic performance of reinforced concrete moment framed structures. Seismic assessment of ductile versions of low- to mid-rise moment frames located in moderate seismic zones is carried out through comparative trial designs of two (4- and 8-story) buildings adopting both space and perimeter framed approaches. Code-compliant designs, as well as a proposed modified code design relaxing design drift demands for the investigated buildings, are examined to test their effectiveness and reliability. Fragility curves for the frames are generated corresponding to various code-specified performance levels. Code preset lower or upper bounds on either design acceleration or drift, respectively, that would control the final design are also addressed along with their implications, if imposed, on the frames' seismic performance. The trial design study demonstrates that built-in static overstrength is generally larger for space frames than for perimeter frames, whereas the force reduction attributable to inelastic dynamic response differs from one frame type to the other for various investigated heights and for different target performance levels. Nonetheless, all trial designs are shown to meet the minimum performance implied by building code provisions but with varying margins. However, the study suggests that more consistent reliability for designed structures can be achieved by disaggregating the force reduction factor into its static and dynamic parts and that code default values of this factor for some building types would be better reduced for a more reliable performance. © 2010 Elsevier Ltd.

Smyl D.,North Carolina State University | Ghasemzadeh F.,Structural Engineer | Pour-Ghaz M.,North Carolina State University
Construction and Building Materials | Year: 2016

The deterioration rate of concrete structures is directly influenced by the rate of moisture ingress. Modeling moisture ingress in concrete is therefore essential for quantitative estimation of the service life of concrete structures. While models for saturated moisture transport are commonly used, concrete, during its service life, is rarely saturated and some degree of damage is often present. In this work, we investigate whether classical isothermal unsaturated moisture transport can be used to simulate moisture ingress in damaged mortar and concrete and we compare the results of numerical simulations with experimental measurements of water sorption. The effect of hysteresis of moisture retention is also considered in the numerical simulations. The results indicate that the unsaturated moisture transport models well simulate early stages of moisture ingress at all damage levels, where capillary suction is the prominent mechanism. At later stages of moisture transport, where air diffusion and dissolution have a more significant contribution, simulations that consider moisture hysteresis compare most favorably with experimental results. © 2016 Elsevier Ltd

Carpenter J.,Structural Engineer | Zhou J.,Southern Illinois University at Edwardsville
ICSDEC 2012: Developing the Frontier of Sustainable Design, Engineering, and Construction - Proceedings of the 2012 International Conference on Sustainable Design and Construction | Year: 2013

Forty percent of the global energy consumption is related directly to commercial and residential buildings. Homeowners of energy inefficient housing have an opportunity to reduce energy consumption and to assist in mitigating climate change. This paper reports a study on retrofitting flat roofs of energy inefficient housing in St. Louis, MO. A life cycle analysis was conducted on a 120-year-old house to evaluate two design options: a green roof vs. a white roof (solar reflective paint). Both options were studied at a 10-year-of-roof- maintenance cycle. The study found that the green roof would require more retrofit embodied energy than that of the white roof because the green roof requires soil transportation, soil pan fabrication, roof joist retrofit kit, and the ceiling replacement, while the white roof requires only the manufactured paint. However, the green roof would still outperform the white roof over a 10-year period on total energy consumption. Furthermore, both options would provide energy savings over the no-retrofit option. © 2013 American Society of Civil Engineers.

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