International Journal of Civil Engineering
Volume:17 Issue: 3, Mar 2019

This paper deals with the dynamic increase factor (DIF) to consider the dynamic effects in the nonlinear static analysis of RC frame buildings subjected to sudden loss of a first-storey column. The study applies nonlinear static and dynamic analyses and focuses on typical seismically designed reinforced concrete buildings. The analysis of these structures until failure requires considering both the geometric and material nonlinearities since the behaviour following sudden column loss is inelastic and possibly implicate catenary effects. Moreover, quantifying the robustness of this type of structure requires the implementation of detailed three-dimensional models. This paper investigates the effects of building properties including the number of storeys, the number of bays and the location of the removed column. The results show that the buildings designed for seismic loads reveal enough capacity to avoid the global collapse, both considering and neglecting the contribution of RC floor slab. The progressive collapse resistance is greater for the external column removal scenario than for the internal column removal scenario. Both the number of floors and the number of bays are not very sensitive parameters for the progressive collapse resistance. The nonlinear static approach leads to a conservative estimation of the collapse resistance when a DIF of 2 is used as the dynamic amplification factor. For the study cases, the response of the building subjected to column loss never involves the hardening phenomenon associated with the catenary action. In this situation, the DIF decreases monotonically with increasing vertical deflection. The lower bound value of DIF is very close to 1, which is the typical value of structures that fully develop their inelastic behaviour after column removal. The simulation results show that the floor slabs can greatly improve the progressive collapse resistance, but have a minor influence on the dynamic increase factor. Thus, the simplification of the problem into 3D bare frames can lead to an accurate estimation of DIF with less computationally intensive analyses.

Very little is known about the project risk factors that affect construction management (CM) firms, which often struggle due to a lack of effective risk management practices. This study investigates the risk factors critical to project execution in CM firms and ranks them using the analytic hierarchy process (AHP) and failure mode and effects analysis (FMEA) methods. Interviews with executives at the top 15 Korean CM firms are carried out to identify major risk factors in the CM sector, and a survey is used to develop priority ranking. We find that payment delays and project delays are the two most critical risk factors affecting CM firms because of (1) lack of communication between headquarters and field offices, (2) shift of responsibility from headquarters to a field office, (3) absence of regular monitoring of project progress, and (4) ex-post management practices. The findings presented in this study should assist CM firms in establishing more robust risk management practices, thereby improving firms’ profitability, project performance, and customer satisfaction.

Dams are extremely strategic structures that must be carefully designed for human and environmental safety. This paper aims to analyse the influence of probabilistic and deterministic seismic hazards, defined for the site, on the singular points of the Rules dam in southern Spain. A comparison with the data from a recent seismogenic zone (2015) has been made; the adopted criteria for the comparison have been carefully explained. Seismic input from the Safety Evaluation Earthquake has shown that maximum accelerations are three times higher than the Spanish code value. Consequently, the stress has exceeded the maximum allowed tension, creating a number of plastic hinges. To consider the fluid–structure–foundation interaction, 2D and 3D mathematical models have been developed via finite element and gravity methods. A good calibration between the observations and modelling output has been obtained.

A novel concrete masonry wall for enhancing seismic behavior is adopted and justified in this paper, namely, ungrouted posttensioned confined concrete masonry (PTCCM) wall with unbonded tendons. The wall is posttensioned as well as confined by the ring beam placed on the top and constructional columns placed at the both ends of the wall. To validate the effectiveness of this technique, 14 walls were tested under lateral cyclic loads. The main parameters studied in this research are prestressing level, opening and horizontal reinforced concrete strip as well as axial load. The damage pattern and failure mode, force deformation response, ultimate strength, ductility and damping coefficient of each wall were carefully studied as well as stiffness degradation. The effects of posttensioning, opening and horizontal reinforced concrete strip on the seismic behavior of the PTCCM walls were analyzed in detail. The test results indicate that the posttensioning is significantly effective in improving the cracking resistance and seismic behavior, slowing down the stiffness degradation, as well as enhancing the shear and energy dissipation capacity of the PTCCM walls. The confinement effect provided by the ring beam and constructional columns can effectively improve the seismic behavior of the concrete masonry walls. By utilizing unbonded posttensioning, the ungrouted PTCCM walls had little residual deformation after cyclic loading. It can also be concluded that horizontal reinforced concrete strip can increase the cracking resistance, ductility and energy dissipation capacity of the walls. Based on the test results, a simple analysis method for predicting the shear strength of the PTCCM walls is proposed.

High wind speeds produced by hurricanes or synoptic winds can cause considerable damage and the failure of structural and nonstructural elements. The use of glass façades in buildings has become very popular; in Mexico, a large number of buildings along the coast are designed with glass façades. Glass façades provide light, temperature control, and an esthetic view; however, this type of glass system is particularly vulnerable to high wind-induced pressures. A methodology to determine the fragility curves of glass façades under turbulent wind loading is proposed. This methodology could be used to select the appropriate glass thickness of a façade. The procedure employs an autoregressive and moving average model to simulate the wind field and Monte Carlo techniques to simulate the glass resistance of the windows. The methodology to construct the fragility curves is illustrated with a numerical example of a glass façade of a 96-m tall building. Three cases of glass resistance associated with coefficients of variation equal to 0, 10, and 20% were considered. The results of the numerical example show that the uncertainty in the glass resistance plays an important role in the development of the fragility curves of the glass façades for high mean wind speeds between 38 and 67 m/s at a height of 10 m.

11 integrated multi-cell concrete-filled steel tubular (CFST) stub columns were tested under concentric compression. The key factors of width-to-thickness ratio (D/t) of steel plates in column limb and prism compressive strength of concrete (fck) were considered and their influence on failure mode, bearing capacity, and ductility of the columns were investigated. The experimental results show that: (1) the constraint effect for concrete provided by the multi-cell steel tube cannot be overlooked; (2) the ductility decreases with the increasing ratio D/t of the connecting steel plates for the multi columns; and (3) the bearing capacity increases, while the ductility decreases, with the increasing fck. The finite element (FE) method was used to simulate the integrated multi-cell CFST stub columns and to verify the test results. A parametric analysis using the FE method was carried out to study the effects of the steel ratio α, steel yield strength fy, concrete strength fck, and D/t on the stiffness, bearing capacity, and ductility of the columns. Furthermore, the measured bearing capacity values were compared to those estimated by the Chinese, European, and American design codes. This study shows that the bearing capacity of integrated multi-cell CFST stub column can be reasonably predicted by the design method specified in GB 50936-2014 or EC4-2004 code.

Reinforced concrete (RC) column–beam joints are one of the most critical elements in RC structures which have a big impact on the seismic response of structures under different loads. To investigate the effect of beam and column dimensions on the seismic behavior of RC wide column–beam joints, 27 numerical models were created using nonlinear finite element method (FEM) software. Displacement-control condition was applied to the top surface of columns in all of the models and boundary conditions and material properties were considered the same as the experimental model. Three numerical models were verified by similar experimental study. The other models were changed in width and depth to find the effect of dimension changes on the displacement ductility and curvature ductility by evaluating force–displacement and moment–curvature diagrams. In general, it could be concluded that by increasing the ratio of beam width to beam height, displacement ductility of RC joint and curvature ductility of beam increase. Moreover, based on the FE analysis by increasing the ratio of column width to column height, displacement ductility increases, while curvature ductility decreases. Results also indicated that increasing the area of column section could lead to increase in displacement ductility and decrease in curvature ductility of RC wide column–beam joints. In addition, the influence of mesh size on the analytical outcome of FE analysis was also investigated. After evaluating the results, equations for estimating seismic parameters, displacement ductility and curvature ductility, in RC wide column–beam joints were suggested.

Industrialized building system (IBS) was presented to complete construction projects at the lowest cost and time. The connection of precast components in IBS structures plays a significant role to provide stability of buildings subjected to various loads. Hence, structural engineers have quite a lack knowledge on the proper connection and detailed joints of IBS structure, especially when subjected to dynamic/static loads such as earthquake, wind, vehicle, machinery and so forth. The loop connection considered as a conventional connection is the most interesting precast wall-to-wall connection in construction. However, this study presents a unique method for connecting two adjacent precast wall panels by using two steel U-shaped channels which are attached in the side of walls and tied together as male and female joints by using bolts and nuts make proper integrity of connection. A U-shaped rubber is implemented between the two channels in order to dissipate vibration effect in structure. The results of this study consist of the loading from the actuator, the displacement at the connection of the different LVDTs at different levels, and the crack pattern at the ultimate failure of the specimen. Upon collecting and analyzing the load test data from the data logger, the load versus displacement curves are plotted to study the actual behavior of the connection under axial, shear and flexural loads. Furthermore, the results of experimental tests showed that precast wall-to-wall equipped with U-shaped steel channel is capable of exceeding the capacity of precast walls subjected to lateral load, thereby improving its flexibility behavior in all directions. The average deformation of the proposed connection in all the LVDs was nearly 3 and 1.5 times greater than the loop connection. Additionally, the maximum average relative rotation deformation of the proposed connection in all LVDs is nearly 36% greater than the loop connection, which means that the U-shaped steel channel connection is more flexible.

Poor construction labour productivity is a major issue within the construction industry because it directly contributes to cost and schedule overrun. Although considerable research has been done on labour productivity factors, few studies have researched construction labour productivity in developing countries. Therefore, in consideration of improving productivity, a questionnaire survey was conducted with construction practitioners involved in the Nepalese construction industry to identify critical factors and to examine the underlying relationships among these factors using fuzzy analytical hierarchical process. The results show that the most critical factors for poor labour productivity are lack of monetary incentive, tools unavailability, insufficient periodic meetings, and unsafe working conditions. The top-ranked factors were compared to those obtained from other countries. The causal relationship diagram and system dynamic models were constructed to examine the inter-relationship between the perceived 30 factors and four criteria to identify the root cause of a decrease in productivity. The system dynamic models will help researchers determine the productivity growth rate in terms of cost and time, and policy makers to revise policies so that the decision maker can draw upon the policy process and its implications. The results not only coincide with the existing body of knowledge on the labour productivity improvement, but also contribute to the growing body of the construction labour productivity research by providing an evaluation method for multi-criteria decision making.

This study simulated the operation of discharge ducts in desalination plants to examine the effects exerted by the convergence and longitudinal slope of discharge channels on the spreading of horizontally flowing convergent and inclined rectangular surface jets over the bed of deep and stagnant ambient water. To this end, a 3.2 × 0.6 × 0.9 m3 flume was used, and rectangular channels with convergence angles of 12.5°, 25°, 45°, and 90° were designed. The used jet fluid was a salt water solution with a concentration of 45 g/L. The channels were activated to discharge jet fluid tangentially at a constant depth of 0.7 m into the ambient water surface. After the experiments, data analysis was carried out through image routing. Results indicated that flow distribution over the bed was circular and elliptical. The relationship between radial distance from the impingement point to the outer boundary of flow and time was determined to a power of 0.45 under discharge conditions without a longitudinal slope and to powers of 0.57 and 0.42 under discharge conditions characterized by an inclined slope. Finally, the spreading coefficients of the jets at average, major, and minor radial distances are 4, 2, and 4.5, respectively.