Practice Periodical on Structural Design and Construction

For many decades, both the lateral-torsional and local buckling strengths of fiber-reinforced polymer (FRP) structural members have been studied extensively by numerous researchers and designers. Many complex prediction models and equations of the buckling strength have been proposed. Typically, most design communities prefer simpler design procedures and equations. Simplified, albeit approximate, buckling-strength equations of pultruded FRP structural beams have been proposed with acceptable accuracy. Herein, the proposed buckling-strength results were compared with those based on prestandard equations and available experimental data. The proposed simplified prestandard lateral-torsional buckling equation provided higher strength results than the experimental data based on the upper-bound experimental results by approximately 11%. Also, the proposed simplified lateral-torsional buckling-strength equation was reasonably acceptable for the design purpose (within 18% difference) compared to the predicted strength provided by the prestandard equations. For local buckling strength, the maximum percentage difference in local flange buckling strength was found to be less than 15%, whereas the proposed web local buckling-strength equations provided excellent agreement with the predicted strength (i.e., less than 5% difference for all cross sections). The proposed design equations are very useful in enabling improved design calculations of FRP structural members.

The British Standards Institution (BSI) permits core and nondestructive tests (NDTs), such as ultrasonic pulse velocity (UPV), rebound hammer, and pull-out tests, to estimate the in situ compressive strength of existing concrete structures. The ASTM test method, in addition, also permits the use of a penetration resistance test (e.g., Windsor probe). Sound engineering judgment and the appreciation of factors influencing each NDT and core test are required in developing the testing plan for estimating in situ compressive strength of concrete structures. There are precautions and practical considerations that must be recognized. The issues in using such tests for estimating in situ compressive strength would be discussed. The different approaches of the BSI codes to determine the in situ strength are illustrated with examples. Results obtained are compared to demonstrate the practical limitations of such approaches. Using any one of the NDTs or core tests yielded estimated in situ concrete compressive strengths that differed substantially.

The present study can be divided into five groups following its five goals. The first goal was to check the effect of compressive strength on the structural behavior of tapered and prismatic beams. The second goal was to study the effect of the tensile reinforcement ratio on the structural behavior of reactive powder concrete (RPC) tapered beams. The third goal was to study the influence of the tapering ratio on the structural behavior of RPC beams. The fourth goal was to study the influence of the shear reinforcement ratio. The last goal was to check the effect of the tapering direction on the structural behavior of RPC beams. Therefore, nine simply supported beams were tested under one-point loading action at their midspans. Seven of the beams were tapered [six of them were made with RPC, and one of them was constructed with a normal concrete (NC)]. The last two beams had rectangular prismatic shapes (one of them was RPC, and the second was NC). All beams had the same overall length of 2,000 mm, a clear span distance equal to 1,850 mm, and the same width of 200 mm. The test results show that the tapered beam made with RPC had a superior ultimate load compared with the NC tapered beam and that the ultimate load increased when the tapering ratio increased. The ultimate load of the tapered beam was also found to be increased when the longitudinal and shear reinforcement ratio increased. In addition, the ultimate load of the tapered beam was greater than that of the prismatic beam.

American, European, and Australian construction markets are facing a shortage in quality and quantity of skilled craft workers. There are initial indications that the shortages are already having a significant impact on project performance in the industrial construction sector. With construction craft workers becoming a critical commodity whose supply can impact a project performance, an accurate metric is needed to estimate the supply. Unfortunately, labor supply metrics based on publicly available data are rate and often inaccurate. This paper’s contribution to the overall body of knowledge is to create and apply a new multi-indicator metric, using a public dataset, to measure national and regional craft worker availability in the construction industry. The metric can be applied for any country using the country’s respective public datasets. The metric is demonstrated using data from the United States. Of the many available indicators for identifying the shortage, the authors of this paper focused on three: employment growth, wage growth, and unemployment. The multi-indicator metric’s ranking scale is applied using the US Bureau of Labor Statistics’ Current Population Survey (CPS) dataset. The findings show that craft worker availability at the national level is different than the craft worker availability at the regional level for different occupations. The most affected occupation among the observed data was “pipelayers, plumbers, pipefitters, and steamfitters,” which is related to industrial projects, and the most affected regions were the West and South regions of the United States.

This paper studies the behavior of concentrically braced frames (CBFs) and eccentrically braced frames (EBFs) under a progressive collapse scenario, by using the alternate load path method, recommended in progressive collapse guidelines. The model structure is a 10-story steel moment frame with five bays in each direction. The present study has investigated the CBF with two types of failure scenarios, each of which examines the effects of reducing the brace’s sections, and the EBF, including three types of failure scenarios, each of which investigates the effects of link beam length on structural capacity. Failure scenarios include the sudden removal of a column with one or more adjacent braces on the ground floor, which, for simplicity, is examined in a two-dimensional form in a perimeter bay of the building. The ability of the structure to absorb and withstand extra load after the sudden removal of the members in each of the states is examined, and their capacity and ductility are compared. According to the results, both EBF and CBF systems can withstand the progressive collapse. Moreover, in the CBF system, while the cross sections of braces decrease, the ductility of the CBF structure increases.

This study was conducted to investigate the horizontal thrust of vertically curved reinforced concrete (VCRC) beams. The middle portion of beam is curved like an arch; such beams are said to be vertically curved beams. In this investigation, 15 VCRC beams were cast, of which, 8 beams had a constant rise of 200 mm and varying chord length of curved portion from 490 mm to 1832 mm, and the remaining 7 beams had a constant rise of 300 mm and varying chord length of curved portion from 690 mm to 1844 mm. The vertically curved portions of VCRC beams are in a parabolic shape. Tie bars were used to arrest longitudinal (horizontal) displacement while testing the VCRC beams. VCRC beams were subjected to a gradually increased central concentrated load until collapse occurred. The behavior of the beams was intensely observed from the beginning until collapse occurred. The first crack load, ultimate loads, deflection, and horizontal displacement have been recorded. The force in the tie bars was calculated based on the measured horizontal displacement. The total force in the tie bars is the available horizontal thrust at each end of a VCRC beam. Theoretical horizontal thrust of VCRC beams is calculated based on the force method. These theoretical thrust values and experimental results have been compared. The average value of the ratio of theoretical horizontal thrust to experimental horizontal thrust is found to be very satisfactory.

Vulnerability assessment of structures in an earthquake is one of the most important topics in structural engineering. HAZUS instruction is the code widely used for assessment of structures for satisfied damage based on the interstory drift. In a structure, there are several parameters, such as forces and responses in elements, which cause damage to the structure simultaneity, and therefore, the use of only one parameter, such as interstory drift, could be unrealistic. In this paper, reinforced concrete (RC) beam–column joints are studied, with the aim of determining the maximum shear capacity of RC joints as a key parameter in the damage of RC structures. For this purpose, two strong approaches, including group method of data handling (GMDH) and adaptive neuro-fuzzy inference system (ANFIS), were used. The selected models were created based on a large experimental database. The results indicated that the considered methods are capable of determining the shear capacity of RC joints with high accuracy.

The depth-to-span ratio is not only an important part of steel-concrete composite rigid-frame bridges (CRFBs) but is also one of the important parameters in designing CRFBs, determining the appearance of the bridge, volume of work for the whole bridge, arrangement of the prestressed reinforcements, clearance of the bridge, mechanical performance, and so on. However, there is little research about the effects of depth-to-span ratio with the steel section length on the structural mechanical behavior. This study examined the influence of depth-to-span ratio on the structural behavior of a rigid-frame bridge (e.g., bending moment and stress) and conducted the optimization of the depth-to-span ratio using the bending strain energy as the objective function. Taking a CRFB with a span combination of (84 + 200 + 84 m) as an example, the structural optimization yielded an optimal center-span depth-to-span ratio of 1:32 and support depth-to-span ratio of 1:16, which had the least bending strain energy and acceptable magnitudes of bending moment, bending stress, and structural deformation. The sensitivity study via parametric analysis indicated that the depth-to-span ratio had a significant influence on the mechanical responses of the CRFB, including the bending moment and bending stress at the critical locations. The outcome of this study provides guidance for the structural design of CRFBs regarding the steel section length.

Continuous reinforced concrete rigid-frame bridges in China have undergone rapid development in recent decades. Great progress has been made in the design and construction of these types of bridges. Therefore, it is useful to summarize some experiences from these recent developments in bridge design and construction. For this purpose, 349 continuous reinforced concrete rigid-frame bridges built in China during the period from 1988 to 2016 were evaluated. Because of the different design loads, certain design parameters of highway bridges and railway bridges were analyzed, including the span-to-height ratio between girder height and span length, the slab thickness, and the concrete strength. The results provide some guidance for the design and research of continuous rigid-frame bridges.

Postinstalled anchors are frequently installed with unpredictable abandoned drilled holes (ADHs) at the job site. While ADHs may have a reducing impact on the original ultimate tensile strength (N_u) of the anchor per the design code, this effect was not adequately investigated. In this study, 60 wedge anchors in three diameters (d) and two (deep and shallow) effective embedment depths (h_ef) per d were tested in tension in five repeats. Half of the tests (30) served as the reference scenario for the other half (30) that included one ADH drilled at 2×d offset from the anchor. The ADH scenario resulted in (4.5–21%) reduction in N_u, regardless of the failure modes, and the percent reductions decreased as d and/or h_ef increased. Based on the results, an area method was proposed to predict the reduced N_u in the ADH scenario. This method can be used to predict reduced N_u when ADH conditions occur in the field and calculate the increased d and/or h_ef to minimize the reducing effect if the application allows.