Concrete Footings Research Articles

Variant Concept of Elevation of a Steel Grid Tower

The article presents the stages of analysis of an existing steel structure of a 35m-high lattice tower, located in a woodland. The assessment of the condition of the tower’s structural elements and connections was made in the aspect of plans for its elevation, in order to install an observation camera warning against fire hazard. The tower up to 30 m was made of five segments with a square section, with decreasing width from 4.86 m to 2.05 m. The last segment, 5m high, was made as a cuboid. Truss walls and horizontal truss membranes were used. Technical platforms were installed inside the shaft. Rolled sections of St3S steel with a yield point fd = 215 MPa were used as structural elements. The tower was erected on concrete spot footing. Static and strength analyses of the existing structure were carried out, taking into account the actual condition of materials and connections in the aspect of the planned modernization. The influence of wind gusts and the load from ice were taken into account. The user planned to install an observation camera on an additional mast with a height of 12 m. Initially, the concept of an additional construction made of Ø60.3 × 4 mm steel pipe set in a steel sleeve fastened to the bridge plates was adopted. The support tube was stabilized with four steel stay rope with diameter of 5 mm, fixed to the corners of the platform at 35m. As a result of the conducted calculations, it was justified that the adopted concept is inappropriate due to the fact that the limit values of horizontal displacement of the end of the mast, also unacceptable due to excessive vibrations of the image from the observation camera, would have been exceeded. Therefore, another concept was developed, in which a 12 m mast would be made with an aluminium lattice construction. In the horizontal section, the mast would have the shape of an equilateral triangle with a side length of 450 mm (420 mm in the axes). The mast branches would be made of RO35x2 round tubes, and the gratings would be made of rectangular, full profiles with a 20 x 10 mm cross section. The mast would consist of three latticed segments with a length of 4.0 m. The stays would be made of Ø5 mm steel ropes. Mast with sliding support would be stabilized with lashings, mounted on three levels. In order to obtain a proper tilting of the lashings in relation to the vertical axis of the mast, it is planned to use additional horizontal expansion elements made of square profiles RK80x5, located at the level of the highest platform. As a result of the calculations carried out, it was shown that a construction designed as presented would meet the conditions of limit states defined in the current standards of fire safety. The work was summarized by providing user guidelines for ensuring the durability of the modernized structure in the anticipated period of usage.

Seismic Resistance and Displacement Mechanism of the Concrete Footing

A realistic seismic simulation of the concrete footing has been made by using finite element method (FEM) software called ABAQUS. The effect of concrete footing embedment in soil on concrete footing‐soil foundation interaction has numerically been simulated for considering displacement, stress, strain, and seismic acceleration load response at the base of a concrete footing. The results showed that the height of embedded concrete footing in soil foundation controls (i) mechanism and magnitude of lateral, vertical, and differential displacements of the concrete footing, (ii) strain energy, the acceleration load response, and stress paths, and (iii) concrete footing‐soil foundation interaction. Compared with various theoretical and experimental results reported in the literature, the present study provides realistic seismic behavior of concrete footing‐soil foundation interaction.

The Effect of Concrete Footing Shape in Differential Settlement: A Seismic Design

This paper presents the numerical results of concrete footing‐soil foundation seismic interaction mechanism. The concrete footing has been made with two different shapes, but with the equal volume of concrete material. The concrete footing‐soil foundation has been analyzed using nonlinear finite elements, with the fixed‐base state. The simulated near‐fault ground motions have been applied to the concrete footing‐soil foundation. The problem has been formulated based on the settlement controlled analysis. The local geotechnical conditions of all configurations have been analyzed. The numerical analysis results indicate that the shape of a concrete footing alters seismic response, revises inertial interaction, enhances damping ratio, improves load carry capacity, modifies cyclic differential settlement, revises failure patterns, minimizes nonlinear deformation, and changes cyclic strain energy dissipation. The novelty of this research work is the strain energy has more been dissipated with artistic concrete footing design.

Design of Tall Cable-Supported Windbreak Panels

The design and construction of tall and slender steel structures is always challenging. This paper discusses several design aspects (structural information, analysis methods, applied loads, cost optimisation) and a case study regarding the design and construction of 10-m-tall windbreak panels for a Greek electricity producer. The purpose of the panels is to reduce wind turbulence and improve the performance of the electricity producer’s air-cooled condenser. In this case, the main wind load acts in the longitudinal direction, with friction inducing only a small amount of wind load in the transverse direction. The steel columns are constructed from 10-m-tall hot-rolled IPE 270 (S235) cross-sections, and are supported by cables in the longitudinal direction and bracing systems in the transverse direction. Concrete anchorages and concrete footings are used for the cables and steel columns, respectively. System optimisation is investigated in terms of the steel weight, cable length, and overall cost, and practical issues are explained regarding technical decisions. Furthermore, the construction details, construction methods, and cost estimation are discussed.

Punching shear behavior of reinforced concrete footings with a varying amount of shear reinforcement

The existing punching shear design provisions according to current codes have either a semi‐empirical (e.g., Eurocode 2) or a more physical (e.g., Model Code 2010) background. Although the design procedures are very similar, the predicted punching shear capacities may differ significantly, depending on the background of the design provisions and the considered influences. Recent test series on reinforced concrete footings without shear reinforcement and with high amounts of shear reinforcement are available and can be used for the evaluation and improvement of the current provisions. Nevertheless, the evaluation of the code equations for the design of the shear reinforcement (failure inside the shear‐reinforced zone) is still not possible since systematic test series on footings with a varying amount of shear reinforcement have not yet been conducted. To investigate the punching shear behavior of reinforced concrete footings with low and medium amounts of shear reinforcement, three systematic test series (11 specimens) with stirrups as shear reinforcement were conducted. In the tests, the amount of shear reinforcement was varied by changing the stirrup diameter only. Further investigated influences were the shear span‐depth ratio and the effective depth. In this paper, the results of the test series are discussed and compared to the predictions according to Eurocode 2, Model Code 2010, and the draft of the second generation of Eurocode 2.

Theoretical and Experimental Analysis of the Cracking Moment in Reinforced Concrete Footing Supported in Granular Soil"

Objective: To analyze flexural behavior of insulated footings supported on granular material and subject to low loads. Methods/Analysis: Experimental program included tests on 30 square reinforced concrete footings, 450 mm in length and reinforced with 6.3 mm bars. Experimental results were compared with theoretical results, according to the ACI 318- 14 Code. Findings: Results showed an average relationship between moment of experimental and theoretical cracking, in a range from 1.03 to 1.55. It was discovered that the value of rupture modulus recommended by the code was conservative. Application: It is required to continue with a more detailed study to establish influence of steel amount on the magnitude of the cracking moment of isolated footings. Keywords: Cracking Moment, Flexural Tensile Strength, Modulus of Rupture, Spread Footing

A hysteretic model for the rotational response of embedded column base connections

Embedded Column Base (ECB) connections are commonly used in mid- and high-rise steel moment frames, to connect the steel column to the concrete footing. Although recent research has shown these connections to be highly ductile, they are typically designed to be stronger than the adjoining column, resulting in significant cost. To enable assessment of strong-column-weak-base systems that leverage the inherent ductility of these connections, an approach is presented to simulate their hysteretic and dissipative response. The proposed approach simulates ECB connections as an arrangement of two springs in parallel, to reflect moment contributions due to horizontal and vertical bearing stresses. This is informed by recent work that provides physical insight into the internal force transfer within these connections. The springs’ response is defined by the pinched Ibarra-Medina Krawinkler (IMK) hysteretic model, which is able to capture both in-cycle and cyclic degradation in strength and stiffness. The model is shown to reproduce the response of ECB connections with reasonable accuracy. Guidelines to calibrate model parameters are presented; these include physics-based estimation of selected parameters such as strength and stiffness, accompanied by empirical calibration of ancillary parameters associated with cyclic deterioration. Limitations are discussed.

Laboratory and numerical investigation of machine foundations reinforced with geogrids and geocells

The manuscript describes the results of large scale field tests and numerical studies conducted on geosynthetics reinforced soil beds supporting model machine foundation. A series of vertical mode block resonance tests are conducted over a rigid concrete footing resting on different reinforced soil conditions. The tests are performed in a test pit of size 2 m × 2 m × 0.5 m using a concrete footing of size 0.6 m × 0.6 m × 0.5 m. Four different conditions, namely, unreinforced, single layer geogrid reinforced, two layer geogrid reinforced and geocell reinforced conditions were considered. The tests are performed under six different dynamic force levels using a Lazen type mechanical oscillator. In total, 38 number of field tests are conducted. The dynamic response is studied in terms of reduction in resonant amplitude, peak particle velocity (PPV) and improvement in dynamic properties of the soil. Experimental results revealed that the displacement amplitude of vibration significantly reduced in the presence of geosynthetics. The maximum reduction is observed in the presence of geocell reinforcement as compared to the other conditions. In the presence of geocell reinforcement, resonant amplitude is decreased by 61% and the natural frequency of the soil system is increased by 1.38 times as compared to the unreinforced condition. In addition, the geocell reinforcement found to reduce the PPV by 48% at a distance of 0.5 m from the footing face. The elastic uniform compression of the foundation bed is improved by 91% in the presence of geocell reinforcement. Further, the experimental results are validated with the numerical studies conducted by using finite difference package FLAC3D. The encouraging agreement in the dynamic behavior of reinforced soil is observed between the numerical and experimental studies. The numerical results revealed that the lateral spreading of vibrations is significantly controlled in the presence of geocell reinforcement.

Metaheuristic Optimization of Reinforced Concrete Footings

The primary goal of an engineer is to find the best possible economical design and this goal can be achieved by considering multiple trials. A methodology with fast computing ability must be proposed for the optimum design. Optimum design of Reinforced Concrete (RC) structural members is the one of the complex engineering problems since two different materials which have extremely different prices and behaviors in tension are involved. Structural state limits are considered in the optimum design and differently from the superstructure members, RC footings contain geotechnical limit states. This study proposes a metaheuristic based methodology for the cost optimization of RC footings by employing several classical and newly developed algorithms which are powerful to deal with non-linear optimization problems. The methodology covers the optimization of dimensions of the footing, the orientation of the supported columns and applicable reinforcement design. The employed relatively new metaheuristic algorithms are Harmony Search (HS), Teaching-Learning Based Optimization algorithm (TLBO) and Flower Pollination Algorithm (FPA) are competitive for the optimum design of RC footings.

Punching shear resistance of reinforced concrete footings: evaluation of design codes

Abstract Punching is a possible failure mode for slender footings and it may lead a structure to ruin through progressive collapse. Although footing present different geometric characteristics, their punching shear design is based on the empirical methods used for flat slabs. This paper uses experimental results from 216 tests to evaluate the performance of design code recommendations presented by ACI 318 (2014), ABNT NBR 6118 (2014) and Eurocode 2 (2010) to estimate the punching shear resistance of reinforced concrete footings. Great dispersion between theoretical and experimental results was observed, being evident that the test system affects the punching shear capacity of footings. The more complex method proposed by Eurocode 2 resulted in a better correlation with experimental results.

Vibration of the steel frame of the primary sand classifier

Article deals with the presentation of measurement that have been carried out on the steel frame of the primary sand classifier. The aim of the investigation was to identify the sources of the abnormal vibration of the frame. The vibration significantly reduces the effective performance of the classifier. The frame anchorage has been stripped out from concrete footing by these vibrations. The measurement of dynamic properties of the frame were performed. The displacements of the particular trusses have been experimentally investigated by accelerometers. The tensile test were performed in the places of expected maximum amplitude of the vibration. Based on the experiment results and new design calculation of the steel frame (truss construction), the new construction design was developed and improved by frame reinforcing. The new designed construction was investigated by vibration measurements again. The acceleration and total amplitude of particular trusses were recorded. The steel construction of the supporting frame has frequencies in range from 13.07 to 13.10 Hz. The significant enhancement of the noise and vibration of the main bearing have been observed during the classifier operation. The system of precautions was proposed to improve operation of the classifier and after realization the classifier run with no limitation.

Staging Creolization: Women's Theater and Performance from the French Caribbean by Emily Sahakian

Reviewed by: Staging Creolization: Women's Theater and Performance from the French Caribbean by Emily Sahakian Jodie Barker Sahakian, Emily. Staging Creolization: Women's Theater and Performance from the French Caribbean. University of Virginia Press, 2017. Pp [i]-xiii; 274. ISBN 978-0-8139-4007-6. $75.00 (cloth). ISBN 978-0-8139-4008-3. $35.00 (paper). ISBN 978-0-8139-4009-0. $75.00 (eBook). Motion, contradiction, ambiguity, tension…these concepts comprise the multi-faceted lens through which Emily Sahakian's Staging Creolization investigates women's theatre and performance from the French Caribbean, as its subtitle suggests. The work's five chapters study seven theatrical texts from the [End Page 182] pens of Ina Césaire, Maryse Condé, Gerty Dambury, and Simone Schwarz-Bart, yet its most valuable contribution to the genre lies in its documentation and analysis of the theatrical works' original productions in the Caribbean or in France, as well as their U.S. premieres, notably at Ubu Repertory Theater in New York City. Sahakian's unique perspective as both a community-based theatre artist and a scholar on theatre and French and Francophone literature privileges the interaction between text and performance. This dynamic becomes the microscope under which she employs close readings, analyses, and evaluations of the texts, their gestures, staging choices and dramatizations, and even interviews and analysis of data on audience reception. All of these elements lead her to the book's primary premise that staging creolization "is akin to theatrical syncretism, which, according to Christopher Balme, "utilizes the performance forms of both European and indigenous cultures in a creative recombination of their respective elements, without slavish adherence to one tradition or the other" (4-5). The performances are crucial because, as Sahakian postulates, they act as "a space of creativity and transformation" that "embody, carry forth, and materialize the process of creolization" (5). Chapters one through three, which the author considers "the first half" of her book, analyzes the plays according to the themes of "Unsettling the Gendered Stereotypes of Plantation Culture," "Remixing Unity and Difference," and "Syncretizing Performance and Moral Codes." The second half of the work focuses on the performances at Ubu Repertory Theater through the lenses of diaspora performances, and recasting the Francophone Caribbean couple. In a vein similar to the French Caribbean women playwrights whom she designates as "bricoleurs who work […] from cultural, historical, and epistemological fragments" (14), Sahakian builds a text based on multiplicities that dissects and questions performance practices of the Caribbean that ultimately, according to the author, "carry out cultural reinvention" (15). Theorizing both the concept and practice of creolization as a process of uncertainty, tension and constant becomings certainly challenges the conventional tenets of Créolité. The term, Créolité, is known for its inward-looking, homemaking gesture via an unconditional acceptance of Creoleness as outlined in the canonical work "In Praise of Creoleness" where Bernabé, Chamoiseau and Confiant describe it as "the cement of our culture…[which] ought to rule the foundations of our Caribbeanness" (Bernabé et al. 1990; 891). Some of Staging Creolization's most animated moments break up the historical cement upon which Creoleness has been rooted over the last three decades and takes its canon to task not only for its failure to incorporate women's voices in its theory, but especially for its characterization of Créolité as fixed and stable. Instead of relying upon the traditional Caribbean theoretical canon, Sahakian assembles diverse literary and performance theorists that include Christopher Balme, Stéphanie Bérard, Édouard Glissant, Christiane Makward, Judith Miller and Joseph Roach as part of the theoretical foundation of Staging Creolization. It is surprising that neither Henri [End Page 183] Bergson nor Gilles Deleuze are cited considering the text's insistence on multiplicity and active and dynamic "becomings" that are inherent in the staging of creolization itself. Yet even in spite of this, the theoretical assemblage of Sahakian's book is fascinating and strong. It is thrilling to read a work that transparently engages with the more thorny issues of its genre. Staging Creolization does this throughout its study and ultimately calls its own name into question, further destabilizing any last concrete footing to which text and...

Evaluation of the seismic retrofitting of an unreinforced masonry building using numerical modeling and ambient vibration measurements

Ambient vibration measurements and 3-D nonlinear time-history numerical modeling are used to assess the retrofitting measures conducted in a 6-story unreinforced masonry building (URM) built in the end of the 19th century in Switzerland. Retrofitting measures were taken in order to improve the soundproofing and possibly the seismic performance of the building. Reinforced concrete (RC) footings were added under the walls and horizontal steel beams were added to link the walls together with a RC slab at each floor, though the wooden beams were left in place. Several ambient vibration recordings were performed before, during and after the retrofitting work in order to monitor the evolution of the dynamic behavior of the structure. Moreover, numerical models representing the state of the building before and after the retrofit work have been developed to perform nonlinear dynamic analyses using various ground motion records. The change in the modal vibration frequencies, mode shapes, and failure mechanism are presented and discussed in further details. According to ambient vibration measurements, the performed retrofitting resulted in an increase of about 25% of the fundamental frequency. From the results of both the numerical modeling and the ambient vibration measurements, it is confirmed that the in-plane behavior of the slabs evolved from non-rigid floors with in-plane deformation to rigid floors with diaphragm effects. The ambient vibration measurements show that the new stiff slabs could lead to torsion behavior in the building as the result of the diaphragm effect and to higher seismic demand. However, the numerical models show that the displacement capacity of the building increases as a result of those new stiff slabs. Consequently, higher deformation capacity, indicated by the inter-story drift values, on average, are observed for all the damage grades in the post-retrofit state of the building. Finally, the overall seismic safety was only slightly improved.

Experimental study of the punching behavior of GFRP reinforced lightweight concrete footing

This paper presents the results of an experimental study of structural lightweight concrete with glass fiber reinforcement (GFRP) bar for prefabricated single footing. In this study, seven full scale concrete single footings specimens, which were reinforced by GFRP bar located on a bed of soil, were tested. One of the specimens was made of normal weight concrete and the others were made of structural lightweight concrete. Four of the lightweight footing specimens contained polymer fibers. Also, two of the lightweight footing specimens contained shear reinforcement. Results indicated that the maximum GFRP strain on normal weight and lightweight concrete footing with polypropylene fibers are about 55 and 23% of the ultimate strain, respectively. Furthermore, adding polypropylene fiber and shear reinforcement enhanced the structural behavior of footings and limited the extent width of cracks which was wider in lightweight footings than that of normal weight concrete.

Punching Behaviour of Reinforced Concrete Footings at Testing and According to Eurocode 2 and fib Model Code 2010

Punching shear resistance of column footings and foundation slabs varies significantly in different standards. The reason for this is because standards define differently the position of the critical perimeter in which the punching shear resistance should be determined, and quantify the influences of the main parameters like effective depth, shear slenderness, compressive strength of concrete, longitudinal reinforcement ratio and tension yield stress of reinforcement in different ways. In order to quantify the level of safety in Eurocode 2 and in fib MC 2010, their design results are compared with the test results of the series of footings tested in completely realistic boundary conditions in terms of the subgrade soil. Besides the performed tests results, the analysis of the other investigations of the footing punching rested on the real soil is also included. Thus was obtained the answer to the question how individual characteristics of the footings and of the soil affect the punching bearing resistance and how accurately Eurocode 2 and fib MC 2010 predict the bearing capacity of the tested column footings. At the end, based on the test results and on the tests of others, and on and performed numerical analyses, a possible modification of Eurocode 2 in the field of reinforced concrete footing was proposed.

A comparative study for design of boundary combined footings of trapezoidal and rectangular forms using new models

This paper shows a comparative study for design of reinforced concrete boundary combined footings of trapezoidal and rectangular forms supporting two columns and each column transmits an axial load and a moment around of the axis X (transverse axis of the footing) and other moment around of the axis Y (longitudinal axis of the footing) to foundation to obtain the most economical combined footing. The real soil pressure acting on the contact surface of the footings is assumed as a linear variation. Methodology used to obtain the dimensions of the footings for the two models consider that the axis X of the footing is located in the same position of the resultant, i.e., the dimensions is obtained from the position of the resultant. The main part of this research is to present the differences between the two models. Results show that the trapezoidal combined footing is more economical compared to the rectangular combined footing. Therefore, the new model for the design of trapezoidal combined footings should be used, and complies with real conditions.

Punching Strength of Reinforced Concrete Footings with New Punching Shear Reinforcement Elements

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Experimental investigation of bond and tube thickness effect on the flexural behavior of concrete-filled FPR tube under lateral cyclic loading

The effect of bond and tube thickness on the flexural behavior of concrete-filled fiber reinforced polymer tube (CFFT) are investigated experimentally in this research. Two different kinds of tubes were used in this research, pultruded tubes and filament winding tubes. Two full scale CFFT column specimens are tested under lateral cyclic load only to study the effect of bond between the concrete core and the tube internal surface under lateral cyclic load only. One of them was prepared with sand-coating on the internal surface of the tube and the other specimen was kept without sand-coating. The CFFT columns were embedded 500mm into a rigid square reinforced concrete footing with 1200mm side dimension and 800mm depth. The two specimens are pultruded FRP tubes having the same mechanical properties and 305mm exterior diameter. Another two full-scale CFFT columns were reinforced with steel reinforcement and were fabricated with tube thicknesses of 4mm and 8mm. These two column were tested to study the tube thickness effect. The columns were embedded 400mm into rigid reinforced concrete footings, which were anchored to the laboratory floor. The columns were loaded under a constant axial load and lateral cyclic load. These two columns are filament winding FRP tubes were manufactured in the Composite Material Reinforcement Laboratory of the Sherbrooke University with the same interior diameter 324mm and with two different thicknesses 4mm and 8mm. The results indicate a significant improvement in the full composite action of CFFT in terms of flexural capacity and stiffness due to the sand-coating. The increasing of the tube thickness delays the yielding of steel and increases the ultimate flexural capacity of the CFFT.

Punching-shear behaviors of RC-column footings with various reinforcement and strengthening details

In this study, various reinforcement and strengthening details for the improvement of the punching-shear behavior of concrete footings were developed. Eight test specimens of reinforced-concrete (RC) footings were constructed and tested to investigate the punching-shear behavior of the concrete footings with the developed details. The test parameters include the additional placement of a longitudinal reinforcement around the column-footing connections, the inclination of the shear reinforcement, an additional cast of high-strength concrete, and an additional concrete cast with amorphous metallic fibers (AMFs). The test specimens were supported on a bed of steel car springs that simulate the elastic behavior of soil. The test results show that the punching strength was significantly enhanced by the additional placement of the longitudinal reinforcement around the column-footing connections and by the addition of the retrofit materials (high-strength concrete and AMF-reinforced concrete). Contrarily, the shear reinforcement that was placed around the connections did not significantly affect the punching-shear strength of the footings. The test results were also compared with strength predictions for which the current design codes and the existing theoretical models were used.

Wood frame house construction project in Mexico

DOI: 10.7764/RDLC.16.2.307 Building wood frame houses is viewed as an excellent alternative to meet the growing demand for housing in Mexico. The aim was to design a pinewood house construction project, based on the stud structural system, to show how to proceed when building a particular housing model. The methodology is based on RCDF-2004, NTCRCDF-2004, ONNCCE S.C. Mexican standards and construction manuals. The blueprints, area and volume were derived using the AutoCAD 2010 program. Pinewood at MC≤18%, preserved with CCA (chromated copper arsenate) salts and graded with the Class A industrial rule was considered. Studs were placed every 24 and plywood boards were used as bracing. As a result, a one-story dwelling with a gable roof and 74 m 2 of living space was designed; the construction sequence, from the foundation (slab, chain and concrete footings) to the application of finishes and coverings (mortar and asphalt shingles), was performed. It is concluded that it is possible to properly design a wood frame house by following the recommendations and technical specifications in regulations, standards and manuals, thereby making it a practical alternative in housing construction.