Practice Periodical on Structural Design and Construction

Fiber-reinforced polymer (FRP) composites are widely used in concrete technology due to their high mechanical and durability properties. FRP has become a mainstream material not only to strengthen damaged elements but also to sustain more service loads and solve long-term ever-growing issues of new infrastructures. Therefore, this review aims to establish a database of research works that focus on the assessment of flexural, shear, and torsional strengthening of reinforced concrete (RC) beams using various types and application methods of FRP composites. The efficiencies of these strengthening techniques were compared in terms of structural behaviors of RC beams, types of FRPs, wrapping configurations, etc. This state-of-the-art review reveals that FRP composites can be used successfully to recover the strength of damaged beams or to improve the structural behaviors of new elements. Furthermore, a statistical analysis was conducted to determine the increment factors for various parameters affecting the structural behaviors of RC beams. It was found that FRP composites were more beneficial for torsional strengthening compared to flexural and shear retrofitting in terms of load capacity and ductility. In addition, the change of FRP layers was more significant than varying FRP wrapping methods, sizes, and types. Finally, based on the compiled database and statistical data, the article proposes some methods for using FRP composites to strengthen RC beams under various load conditions.

The spurt in terrorist activities worldwide has drawn the attention of engineers and researchers to the vulnerability of building structures to blast loads. Response of masonry-infilled reinforced concrete (RC) frames subjected to blast loads is a widely researched area that still poses considerable complexity and challenges. Most of the works are based on finite element (FE) methodology to simulate the blast-induced behavior of the masonry-infilled RC structures considering the material constitutive and interaction aspects. Many literature studies have focused on FE codes for numerical modeling of masonry-infilled RC frames and interpretation of their response to various blast load scenarios (far-field, near, and contact blasts). The review presented herein addresses the aspects to include: Estimation of the blast load parameters, including the code provision and its simulation in the analysis module; updated knowledge on geometric and material modeling; effect of strain rate on constitutive parameters while modeling the materials; macro, micro, and simplified micro approaches to model masonry infill walls and their response under blast loading; modeling of interaction between RC frame and masonry infills and the performance of the integral and nonintegral system under blast loading. It is envisaged that such studies, in turn, would facilitate evolving the rational design methodologies for the blast-resistant design of framed structures. At the end of this paper, some parametric studies of field interest that are carried out in the literature are reported to understand the behavior of masonry-infilled RC frames against blast loads and derived some valuable conclusions. The review presented in this study provides a thematic analysis of the available literature aimed to assist the analyst in selecting a suitable tool for investigating masonry-infilled RC frames exposed to blast loads.

Structural evaluations are important for monitoring performance and behavior changes that occur due to environmental or other loading conditions. As a renowned experimental mechanics technique, digital image correlation (DIC) has become a widely accepted tool for obtaining not only qualitative, but quantitative structural engineering measurements. In this review, the principles of DIC for displacement field measurements are presented through structural evaluation illustrations. Several developing studies of the method in combination with other techniques for novel assessment approaches are also discussed. The method has grown immensely from conception, and its significance for paving the way to infrastructure resiliency framework is further highlighted. Ongoing DIC measurement challenges can also be reviewed in addition to leading initiatives for addressing future needs in evaluating the structural infrastructure. Overall, this review promotes the flexibility of DIC for implementation as a fully deployable structural evaluation method with great sustainable implications.

Construction is one of the most hazardous industries with high fatal and nonfatal accidents rates. However, many accidents could be prevented by improving workers’ safety performance. Numerous factors impact their performance, such as safety culture and attitude, distraction, and personal characteristics. Among these factors, age has been widely cited in past research, but there is no unanimity among researchers regarding its impact on workers’ safety performance. Both positive and negative impacts of age on safety performance have been reported in studies, along with several researchers who found no significant difference in safety performance among workers of different ages. To demystify the impact of age on construction workers’ safety performance, this research hypothesizes that the relationship between age and safety performance is mediated by other factors such as experience and fatigue. A survey was conducted among 135 randomly selected participants from 38 construction sites in Iran. The survey consisted of three sections, namely demographic information, subjective fatigue assessment, and safety performance measurement. Statistical analysis revealed that the relationship between age and safety performance is mediated by experience and fatigue, explaining the disparity among past research findings. The findings of this study highlight that age does not have a direct impact, but an indirect impact mediated by multiple factors, on workers’ safety performance. Future research must consider mediating factors when studying the role of age in workers’ safety performance. The results suggest that researchers and practitioners should focus on other factors such as fatigue and safety training, which employers can positively influence.

Researchers and industrialist interest in fiber reinforced polymer (FRP) to be used as an alternative material to steel rebars in reinforced concrete structures (RC) steadily increases. That is due to its advantages over steel rebars. Some of these advantages are corrosion resistance, nonconductivity, high tensile strength, and low weight ratio. Several studies have been introduced to study the effect of using FRP rebars instead of steel rebars on the durability problem of reinforced concrete structures under different circumstances, such as bridge decks and roadbeds which may contain a massive amount of steel reinforcement. The reinforced concrete (RC) structure constituted by FRP rebars, called FRP-RC, possess less ductile behavior compared with the conventional reinforced concrete. One of the advantages of the ductility structural system is the ability to redistribute moments over critical sections, which allows more flexibility in structural design. To improve the ductility of FRP-RC, it is proposed to add a certain amount of steel rebars in FRP-RC, so the ductility of steel rebars can reduce the brittleness of FRP, called hybrid section. Eleven 3D models were carried out based on finite element software (ANSYS). Two different types of longitudinal rebars were used (FRP and steel) to reinforce the positive and the negative moments. The validation of numerical results was confirmed by experimental results, then the parametric studies were conducted to study and evaluate the effects of hybrid sections on the redistribution percentage ($\beta \%$) of continuous RC beam. The results of these models showed that a preferable redistribution percentage could be obtained through an appropriate percentage of steel reinforcement ratio to the FRP reinforcement ratio of hybrid sections.

An investigation of the dynamic behavior of a footbridge located at Jordan University of Science and Technology, Irbid, Jordan, is presented in this paper. The work includes the evaluation of vibrations serviceability and comfort criteria of the footbridge structure for which several pedestrians felt a level of discomfort when passing through. The authors conducted an experimental investigation in which they investigated various dynamic excitations (walking, jogging, and running with varying numbers of pedestrians). Nine different dynamic excitations were applied to the structure with one, two, five, eight, and nine pedestrians. It is recognized that the pedestrians exert both vertical and lateral dynamic forces on the footbridge structure; the maximum vertical and lateral accelerations as a result of various pedestrian excitations are compared to extensively used international vibration serviceability codes/guidelines. These guidelines are HIVOSS, British Standards 5400, Sétra, Ontario Highway Bridge Design Code, ISO-1992, Hong Kong Structures Design Manual for Highways and Railways, and Japanese Footbridge Design Code. Concerning vertical accelerations, for everyday walking, the structure is found acceptable for most of the codes and almost all dynamic excitations used in the study, whether there is only a single pedestrian or a group of pedestrians walking on the footbridge. There are a few dynamic excitations where the vertical accelerations exceed the comfort limits specified in the codes. Still, those are extreme excitations that would not occur during the daily use of the footbridge. Maximum accelerations (i.e., vertical and lateral) exceed the limiting criteria for the majority of relatively older codes, but for relatively recent standards (HIVOSS and Sétra), excitations are found to be acceptable with medium or minimum comfort classes. However, some dynamic excitations (running and synchronous walking excitations) are deemed unacceptable, although these are considered extreme excitations that would not occur during everyday footbridge use. The old or early used codes in the design of lightweight footbridges are concerned to study the serviceability of bridges under human-induced vibration and are used until nowadays, and the new codes are concerned to study the comfort criteria of bridges under human-induced vibration.

The basis for the design of any concrete structural element is the concrete building code. Since the requirements for different used codes are dissimilar, a detailed comparative analysis needs to be conducted to compare multiple structural design aspects of various codes used worldwide and find out if there is any significant differences in the design procedures. The main objective of this study is to compare 4 building codes: ACI Standard: Building Code Requirements for Structural Concrete; the European Standard: Eurocode 2: Design of concrete structures—Part 1-1: General Rules and Rules for Buildings; the Indian Standard: Plain and Reinforced Concrete—Code of Practice; and the Canadian Standard: CSA A23.3-19 Design of Concrete Structures to draw conclusions on the differences in the design requirements for general characteristics, flexure, and provisions for nonslender columns. The same column cross section was used to calculate axial capacities based on all four codes and the results were presented in a comparative table. All the codes have some differences in the provisions compared. In general, regarding column axial capacities, it was seen that estimates provided by the Indian code were more conservative compared to the remaining three codes.

Base isolation of structures with a friction pendulum system (FPS) has been a topic of great interest for research in the past. The efficiency of the FPS system in isolating a structure depends upon a number of crucial parameters, of which the coefficient of friction plays the most important role. Herein, two methods are presented for determining the optimum value of the dynamic coefficient of friction (${\mu }_{\mathrm{Fast}}$), which provides the maximum possible reduction of significant engineering demand parameters (EDP) simultaneously. The optimum value of ${\mu }_{\mathrm{Fast}}$ and the percentage of reduction of EDPs are obtained with respect to the safety gap. The procedures for determining the optimum value of ${\mu }_{\mathrm{Fast}}$ are illustrated with an example of a 10-story building frame base isolated with FPS under both far-field and near-field earthquakes. The results of the study show that the reduction in the number of plastic hinges formed was highly sensitive to the variation of the coefficient of friction: reductions in other EDPs showed mild to moderate sensitivity.

This paper discusses the novel multimaterial arbitrary-Lagrange-Euler (MM-ALE) based approach for modeling shear-thickening fluid (STF)–treated fabric under ballistic impact. The friction-based model of fabric implements the effect of interyarn friction on the ballistic performance of the neat and STF-treated fabric. Furthermore, this paper presents the limitations of friction-based modeling of STF-treated fabric under a wide range of projectile velocities. Such a limitation is the exact prediction of interyarn coefficients of friction for STF-treated fabric for the complex phenomenon of ballistic impact. The results obtained from the friction-based model for the ranges of interyarn coefficients and fabric sett showed that there is an enhancement in the ballistic performance due to an increase in the coefficient of friction up to a critical value of friction coefficients. It was observed that beyond the critical level, there was no improvement in the ballistic performance of the fabric. However, there was a decrease in the ballistic performance beyond the critical friction level. Moreover, the numerical model of neat fabric using friction-based models as validated and implemented in the development of MM-ALE-based modeling of STF-treated fabric. The novel MM-ALE-based modeling approach will enrich the understanding of the STF mechanism under ballistic impact for STF-treated fabric systems. The limitations of friction-based models shall be handled using the MM-ALE based technique.

Abstract

Reliability theory considers the effect of uncertainty in the modeling and design of structures. Uncertainty in variables such as the material properties, geometric dimensions, and external loads during the analysis of steel moment-resisting frames can have significant effects on structural safety. This study evaluated the safety probability of two two-dimentional steel moment-resisting frames and examined the effect of uncertainly on each design parameter on the maximum frame drift using sensitivity analysis. It also evaluated the robustness index of energy dissipated in the stories of the frames. The uncertainties were modeled with normal probabilistic distribution of random variables. The Monte Carlo simulation method and the maximum story drift constraint were used to calculate the probability of safety and define the limit state function, respectively. Nonlinear time-history analysis was performed on the frames under seven ground motion records having an exceedance probability of 10% in 50 years. The modified Ibarra-Krawinkler behavioral model has been used to define the potential plastic hinges of the frame. The results indicated that the values of the probability of safety may be appropriate for evaluation of the 3-story frame, but be undesirable for a design based on reliability assessment. Sensitivity analysis showed that the steel modulus of elasticity and yield stress values having the greatest effects, whereas the web thickness of the sections and gravity loads applied to the stories had the least effects on the maximum drift of the structure. Using the probability of safety and robustness index, this study has produced useful information for the seismic rehabilitation of structures relating to design variable uncertainty on the hysteresis response for steel moment-resisting frames.

Abstract

The application of appropriate safety coefficients for parameters with uncertainty and the modeling of these uncertainties have been extensively studied in recent years. Because there are uncertainties in the design parameters of existing structures, it is better to examine the effect of these uncertainties on the response of the structure. There is a special gap in rehabilitation studies that can be used to evaluate the existing structures. Therefore, a practical approach is required to evaluate the structures undergoing structural rehabilitation to investigate the effect of uncertainties in the design parameters on the hysteresis response of steel moment-resisting frames. In this regard, it is also better to evaluate the probability of safety and the robustness of the hysteresis response of steel moment-resisting frames. Also, the sensitivity of the desired output value to the parameters with uncertainty using nonlinear time-history analysis for this type of structures was one of the items preferred by the authors to be estimated.

Water storage tanks are essential structures in water distribution supply systems. During an earthquake, the damages incurred to water tanks may lead to disastrous loss of life and property. This is due to the low ductility, redundancy, and low energy dissipation characteristics of these structures in comparison to conventional building structures. In this study, the analytical effectiveness of pall friction dampers is investigated to enhance the seismic resistance capacity of existing and newly constructed elevated water tanks. This study evaluates the performance of three water tanks based on their capacities, namely small ($90{\mathrm{m}}^3$), medium ($600{\mathrm{m}}^3$), and large ($\mathrm{1,700}{\mathrm{m}}^3$). The selected elevated reinforced concrete (RC) water tank models are examined for staging heights equal to 16, 20, and 24 m. The main objective of the study is to develop a finite element model of elevated water tanks installed with pall friction dampers considering container weight and water mass using finite element software. Nonlinear time-history analyses of elevated water tanks subjected to an array of different ground motion records are performed. The study evaluates the optimal slip load of the friction dampers required to obtain optimal seismic responses of elevated water tanks. The results exhibit the efficiency of pall friction dampers in mitigating the structural responses of elevated water tanks exposed to seismic loads. The study ultimately concludes that the effectiveness of the pall friction damper is independent of tank capacities, and the efficiency of the damper reduces as the staging height increases.

The use of prestressed precast concrete pile (PPCP) has been increasing because of the advantages provided including accelerating and facilitating the construction operation at a site and increasing the durability of foundation systems. For various reasons including the shipping and transportation limitations and variable soil conditions, casting PPCPs with shorter lengths and splicing them at the site to achieve the required length becomes unavoidable or advantageous. As such, various techniques have been implemented to splice PPCPs at the site in preplanned and unforeseen situations. However, the current systems have shortfalls limiting their applications. These shortcomings are vulnerability to corrosion, inability to develop the required strength capacities in unforeseen situations, and on occasion requiring time-consuming and costly procedures. This study introduces a new method for splicing PPCPs to overcome the limitations that exist in current pile splices. As such, a near-surface-mounted fiber-reinforced polymer (NSM FRP) pile-splice system is introduced as an alternative to current splice systems. The effectiveness and feasibility of the suggested splice system are investigated according to national building code requirements and state standard design specifications. Accordingly, to demonstrate the capability to develop the required capacity in tension, compression, and flexure, as well as constructability, a splice system was designed in this study for an 457-mm (18-in.)-square PPCP. The results indicate the effectiveness of the proposed splice in satisfying the requirements set by both design references. Furthermore, details developed for the splice system have demonstrated their constructability. The NSM FRP splice offers an economical, labor-friendly method of splicing, and provides an advantageous option especially for unforeseen situations where other techniques are either impractical or fail to develop the required capacity. It is expected that the results of this study will pave the way for the implementation of this system in future construction.

This study aimed to evaluate the long-term sulfate resistance of green concrete with blended cement at different waste glass powder contents. The used cement was blended with 10%, 20%, 40%, and 60% of waste glass powder. To benchmark performance, the X-ray diffraction (XRD) test was used to estimate the pozzolanic effect of glass powder, which exhibits a calcium hydroxide decrease. The concrete natural aggregates were replaced by 50%, and 100% with glass at 60% glass powder replacement. There was a direct relation between the concrete diffusion coefficient and the waste glass powder in blended cement. Results of compressive strength loss show a high sulfate resistance with waste glass powder content increasing in cement. Concrete with 50% glass aggregates produced a comparable enhancement in sulfate resistance to that produced with natural aggregates.

The efficacy of magnetorheological (MR) dampers installed in a benchmark tall building under across-wind loads is investigated. The combined system is expressed as state-space variables, and the building response was obtained numerically. A comparison of semiactive control algorithms applied to the MR dampers installed in the benchmark building is studied. Initially, dampers are installed on every story of the building; later, the locations and numbers of dampers are optimized. This optimization of dampers is carried out along with a parametric study by varying the maximum command voltage for each control algorithm. It is observed that the MR dampers are quite effective at reducing all the performance criteria of the benchmark building. An optimization study of dampers had given an appropriate location of the dampers and reduced the number of dampers. The parametric study of maximum command voltage indicated that, in general, the larger the maximum command voltage, the better the performance of the MR damper.

This paper explains the use of practical methods and records of input motion in the investigation of vibration effects on structural subsystems (such as floors) and components. Six example cases are presented in which the analysis of vibration resulted in appropriate intervention methods for controlling vibration and abating its damaging effects. Each case demanded a different level of serviceability, for which remedial measures had to be implemented to meet the particular serviceability demand. Cases 1 and 2 each concerned vibrations induced in a floor system as a result of occupants’ exercise activities. Suggested solutions included doing nothing, implementing simple alterations and control of the activities, or relocating the exercise area. Case 3 involved vibrations in balconies in a church assembly area. The suggested solution in this case involved design of a dynamic absorber with an optimum installation location to alleviate the vibration effect. Case 4 dealt with the vibration of a floor system caused by operating commercial washing machines. The suggested solution included the installation of vibration isolators and absorbers and/or implementing structural retrofit to increase floor stiffness. Case 5, vibration in a hospital surgery room, and Case 6, vibration in a portable classroom, involved detailed data gathering and identification of the sources of vibration. The suggested solutions included controlling the source of vibration (in Case 5) and simple alterations of the floor of the portable classroom to change the mass and the frequency of vibration (in Case 6). The paper also summarizes (1) sources of vibrations that may affect structures, a brief overview of the damaging effects of each vibration type, and methods to mitigate these effects; and (2) general information on the frequency contents of vibrations from human activities and the threshold levels for structures of different construction types and usage, including those supporting sensitive equipment.

Since the enactment of the first New York City (NYC) facade inspection ordinance in 1980, eight five-year complete cycles have been registered. The paper is a commentary on the 40-year years’ evolution of the practice of facade inspection and repair as influenced by technical developments, changes in legislation and building owners’ attitudes. The large number of number of buildings (by now 16,000) and the number of cycles made NYC the principal terrain where methods of inspection and repair techniques were tested. The interpretation of the law was refined by rules issued in response to recurring failures. In 1980, there were few professionals knowledgeable of the causes of facade distress and effective repair methods. Gradually, the various types of facade distress found explanations and adequate repair solutions were developed; a professional specialty dedicated to facade conditions has reached maturity. The author supports the arguments with various descriptive statistics of inspection ratings, violations, applications to repair, all corelated with the NYC typologies. A quantitative proof of success could not be deduced from an analysis of inspection ratings of four successive cycles, as the rating definitions have evolved over the last 20 years. A reduction in number of decaying facades is noticeable, but accidents have continued to occur. The public awareness and concerns about the risks posed by facades has increased and as expectations remain high, the scope of the Facade Inspection and Safety Program (FISP) has evolved from minimizing the number of accidents to a timely protection from hazards.

Corrugated web plate girders (CWPGs) have grown in popularity in Canada in recent years because of their economic efficiency. Although research on the flexural performance of such members has increased in recent years, there are still additional advancements that can be made in their design, particularly in the calculation of lateral torsional buckling resistance. However, no research has been presented in Canada on this subject, and very minimal research has been published on CWPGs with sinusoidal corrugated webs. The purpose of this study was to examine the lateral torsional buckling strength of CWPGs with sinusoidal corrugated web profiles through experimental analysis of CWPGs that are currently being used in Canada. Nine simply supported specimens were loaded and failed in lateral torsional buckling (LTB). The nine specimens were chosen according to size in order to observe variations in LTB strength based on web thickness, web depth, and variations in identical beams. All beams tested recorded strengths far greater than conventional design strength, confirming the conservative nature of the current design procedure. As web thickness increased, a trend of ultimate capacity increasing was observed. The depth of the webs had no significant effect on LTB strength apart from what was gained by increasing the depth of the flanges. Based on the results, an equivalent web thickness equation is proposed for the purpose of calculating a more precise LTB resistance. A numerical analysis was run on a wide range of beam sizes and compared with the physical testing results. It was determined that the proposed equation effectively captured the physical testing results among more than just the tested beams. However, future work should further examine the reliability of the proposed equation by testing more specimens and/or using the finite-element method.

In all concrete infrastructure, there will be cracks that can lead to loss of structural strength and durability and create visual impact. While concrete repair entails material and labor costs, it is interesting that no quantitative information is available on the impact that cracks may have on costs and project performance. This research aims to better understand the quantitative impact of concrete cracking in building projects analyzing Chilean construction projects. With this aim, this research worked with residential building projects: (1) ten in the construction stage where the presence of cracks was measured directly, obtaining their form, repair method, and cost, and (2) seven in the stage of operation (aftersales) to evaluate the long-term impact of cracking. Finally, a survey involving 44 construction professionals of different projects and areas was carried out. Results showed that due to the lack of information, the global impact of cracking is obscured for reasons that include companies having the perception that cracks do not significantly affect project costs. Because of this, most companies do not have specific information about this issue and how it decreases project productivity, resulting in estimated annual losses of USD 3.48 million in Chile alone.

The construction sector is one of the most relevant to the world economy. Within it, the most used material is concrete given its excellent construction characteristics. However, this material suffers from different issues that can severely affect its performance and thus a construction project’s productivity. Of these issues, cracking is one of the most common and significant. It can affect the three most important aspects of construction: cost, deadline, and quality. Although its importance is recognized within the construction industry, to this day no clear vision exists as to the specific impact that cracking can have on a project. Consequently, this study aimed to determine that impact on mining, electrical, and civil infrastructure construction projects through a statistical analysis of 13 completed projects that suffered cracking. To obtain this information, companies involved in the construction of those projects in Chile were contacted. Additionally, this statistical analysis was complemented by a survey targeting professionals in the field who have dealt with cracking situations, with the objective of comparing the statistical results with the personal/professional survey responses. Analysis of project records indicated that concrete cracks represented a low percentage of total construction cost. This correlated with the surveyed professionals’ perceptions; however, the lack of proper recordkeeping by construction companies creates annual losses of several million in rehabilitation work, besides possibly hiding the real impact of cracking, creating an iceberg effect.

Long-span suspension bridges are flexible structures that are easily vibrated by external load changes. Their vibration characteristics are related directly to the safety of the structure. Although the free vibration characteristics of the structure can be calculated accurately by numerical simulation with mature commercial software, the practical and straightforward approximate formula still is of considerable value. The existing theoretical results of the vertical symmetrical frequency calculations are excessively complex and thus cannot be applied. Herein, a simpler formula, obtained via a reasonable mathematical derivation, is proposed. This formula can directly reveal the mechanism of vertical vibration in suspension bridges.