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Floor systems constructed from slabs and beams are critical structural elements of reinforced concrete (RC) frame structures, allowing them to resist progressive collapse. To elucidate the complex effects of the slab and its thickness on the progressive-collapse resistance of RC spatial frame structures, three 1/3-scale 2 × 2 span substructure specimens, including one three-dimensional (3D) skeletal frame substructure and two 3D frame–slab substructures with different slab thicknesses, were tested in a middle-column-removal scenario. The test results indicated that the frame–slab substructure exhibited two resisting progressive-collapse stages: a primary mechanism stage, with small deformations, and a secondary mechanism stage, with large deformations. The slab contributions were separated from the floor system and quantified by comparing the results for the skeletal frame substructure and frame–slab substructure. Although there were no in-plane confinements, the slab also significantly improved the resistance against progressive collapse, owing to the compressive and tensile membrane action in the primary and secondary mechanism stages, respectively. Increasing the slab thickness increased the compressive membrane action of the slab, which significantly enhanced the progressive-collapse resistance under small deformations. However, under large deformations, the beam and slab did not work synergistically, which limited the development of secondary mechanisms against progressive collapse.

We analyze the global and local uncertainties of ground motion-macroseismic intensity conversion equations and derive new probabilistic relationships between the macroseismic intensity and peak gro...

Nanoparticles based on biodegradable polymers are well-known as approved carrier systems for a diversity of drugs. Despite their advantages, such as the option of an active drug targeting or the physicochemical protection of instable payloads, the controlled drug release often underlies intra- and interindividual influences and is therefore difficult to predict. To circumvent this limitation, the release behavior can be optimized using light-responsive materials for the nanoparticle preparation. The resulting light-responsive nanoparticles are able to release the embedded drug after an external light-stimulus, thereby increasing efficacy and safety of the therapy. In the present study light-responsive self-immolative polymers were used for the nanoparticle manufacturing. Light-responsive polycarbonates (LrPC) as well as PEGylated LrPC (LrPC-PEG) were synthesized via ring-opening polymerization of trimethylene carbonate-based monomers and fully physico-chemically characterized. Light-responsive nano formulations were obtained by blending LrPC or (LrPC-PEG) with the FDA-approved polymer poly(DL-lactide-co-glycolide) (PLGA). The nanoparticles were loaded with the photosensitizer 5,10,15,20-tetrakis(m-hydroxyphenyl)chlorin (mTHPC). The light-induced nanoparticle degradation was analyzed as well as the drug release behavior with and without illumination. Furthermore, biological safety of the degradation products was investigated in an in vitro cell culture study.

Discovering renewable energy resources is receiving increased attention both in industrial and academic research. Vegetable oils are a promising route to renewable chemicals and polymers due to their ready availability, inherent biodegradability, and low toxicity. Also, bio-renewable fuels have been prepared from vegetable oils. Here, the soy oil monoglyceride has been obtained from the soybean oil by alcoholysis, and its structure was confirmed by the spectral analyses. To increase the yield of the monoglyceride formation and to prevent the ester interchange reversible reaction, we found that rapid cooling of the mixture with high-speed stirring allowed the best yield of soy oil monoglyceride. Then, three new polyester resins have been synthesized by the reaction of the monoglyceride with phthalic and/or maleic anhydrides with different ratios. The synthesized resins have been characterized by spectral analyses, and their morphological and physico-chemical properties such as acid value, iodine value, volatile matter content, and viscosity have been studied. The three polyester resins were soluble in common organic solvents. The effect of phthalic and maleic anhydrides ratio on the physical and chemical properties of the resin was also studied. The incorporation of maleic anhydride decreases the iodine value of the resins compared to phthalic anhydride-based resin.

In this work, poly(dimethylacrylamide)-b-poly(trimethylene carbonate) (PDMAAm-b-PTMC) block copolymers containing a pH-sensitive imine linkage were successfully synthesized by combination of ring-opening polymerization (ROP) and reversible addition–fragmentation chain transfer (RAFT) polymerization. A variety of vanillin terminated PTMC block copolymers were prepared by ROP of trimethylene carbonate (TMC) initiated by modified vanillin in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as an organo-catalyst. The analysis of the resultant homopolymers by 1H NMR spectroscopy, size exclusion chromatography (SEC) and ESI-ToF masspectrometry (ESI-ToF-MS) revealed the excellent control of molar masses (Mn up to 14 000 g mol−1), dispersities (ĐM < 1.15) and end groups. The PTMC homopolymer was subsequently end-capped with an amino functionalized RAFT-agent leading to a macroinitiator containing imine group. Using this macroinitiator, PDMAAm-b-PTMC block copolymers with various molar masses were successfully prepared. In aqueous solution at pH 7.4, micelles could be formed by self-assembly of the amphiphilic block copolymer using a dialysis method. The hydrodynamic diameter (Dh) of the micelles was 76.3 ± 2.4 nm with a polydispersity index (PDI) of 0.179 ± 0.002. Under weak acidic conditions (pH 6.0), the hydrophilic PDMAAm block could be cleaved from micelles by hydrolysis of the imine linkage, while PTMC nanoparticles formed in situ with an average size of 149.8 ± 4.5 nm (PDI = 0.287 ± 0.007). Based on our strategy, these pH-cleavable PTMC-based amphiphilic block copolymers will expand the range of biodegradable synthetic polymers available for potential biomedical applications, such as controlled drug and gene delivery.

In this work, a variety of hyperbranched polymers (HBPs), such as hyperbranched polycarbonates, polyesters, polyurethanes and polyacetals, was successfully synthesized from castor oil and soybean oil based monomers via a A2 + B3 polycondensation. First, B3 monomer triols (TriOL), trialdehydes (TriAD), and tricarboxylic acids (TriAC) were obtained by ozonolysis of castor oil and soybean oil with following reductive or oxidative treatment. Their structures were characterized by 1H NMR and ATR-FTIR spectroscopy as well as electrospray ionization-Time of Flight-mass spectrometry. These trifunctional B3 monomers were applied in the preparation of HBPs. The resulting HBPs had number averaged molar mass (Mn) up to 9400 g/mol and weight averaged molar mass (Mw) up to 40,000 g/mol. Through adjusting the initial molar ratio of A2 to B3 monomers, hydroxyl terminated (from TriOL monomers) or carboxylic acid (from TriAC monomers) terminated HBPs could be obtained. All the HBPs were characterized by 1H NMR, size exclusion chromatography, and DSC. These HBPs are potential candidates for the synthesis of cross-linked polymeric materials or in biomedical applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 2104–2114

A new eco-friendly strategy for the preparation of linear and hyperbranched polycarbonates was developed. Our work referred to a one-pot condensation polymerization of various alcohols (diols and triols) with equivalent amounts of eco-friendly dimethyl carbonate (DMC) at 120 °C, atmospheric pressure and in 1,4-dioxane solution using 4-dimethylaminopyridine (DMAP) or lithium acetylacetonate (LiAcac) as a catalyst. Polymer chains were built by pure transesterification of hydroxyl and methyl carbonate chain ends, and the single byproduct (methanol) was removed using a pressure-equalized addition funnel filled with 4 A molecular sieves as the crucial equipment in this work. Using this strategy, hyperbranched polycarbonates with high molar masses (Mn up to 10 000 g mol−1 and Mw up to 64 000 g mol−1) and high hydroxyl end group contents (up to 94%) were successfully prepared using dimethyl carbonate instead of toxic phosgene or phosgene-based monomers for the first time. In addition, linear aliphatic polycarbonates of various diols were also synthesized with Mn up to 16 000 g mol−1 and low molar mass distributions (ĐM < 1.70). Another eco-friendly aspect of this work was the use of equimolar amounts of DMC to avoid waste and the disposal of excess DMC; in a classic 2-step polycondensation for polycarbonate synthesis excess DMC is a prerequisite in order to obtain high molar masses.

Reinforced concrete (RC) coupled wall systems, compared with RC shear wall without opening, have more complex nonlinear behavior under the extreme earthquake loads due to the existence of coupling beams. The behavior characteristics induced by nonlinear shear deformation such as shear–flexure interaction, pinching effect, strength and stiffness deterioration are clearly observed in numerous cyclic tests of RC coupling beams and shear walls. To develop an analytical model capable of accurately and efficiently assessing the expected seismic performance of RC coupled wall systems, it is critical to define the appropriate key components models (i.e., nonlinear models of RC wall piers/shear walls and coupling beams). Classic fiber beam element based on the theory of Euler–Bernoulli beam is frequently adopted to simulate the nonlinear responses of slender RC wall piers and coupling beams in the literature because it is able to accurately model the response characters from interaction of axial–bending moment at the section level. However, classic fiber beam element cannot capture the nonlinear behaviors of non-slender structures mainly controlled by nonlinear shear deformation. To overcome this shortcoming, a modified force-based fiber element (MFBFE) including shear effect is introduced and used as the analysis element of non-slender RC coupling beams and shear walls. At the section level, a novel shear model for RC coupling beams and an existed shear model for RC shear walls are respectively added to this fiber element to simulate nonlinear responses of these two key components. The analytical model for RC coupled walls hence is formed through integrating the proposed models of these two key components. The validations with different experimental results of cyclic tests including key components and structural system reported in the literature using these proposed models are performed. Good agreements are achieved for all of these proposed models via comparisons between predicted results and experimental data.

Ultra-high-voltage (UHV) cup-type transmission towers supported with long-span transmission lines are unavoidably subjected to the coupling action between the towers and the transmission lines. Therefore, investigating how tower-line coupling affects UHV cup-type transmission towers is important. In this study, three shaking table array tests of an UHV cup-type transmission tower-line system were carried out to investigate the dynamic characteristics of the coupling action between the towers and transmission lines based on the following four comparative models: a single-tower model, a single-tower model with suspended lumped masses, a three-tower-two-line model, and a five-tower-four-line model. The test results demonstrated that the tower-line coupling interaction had a significant effect on the dynamic characteristics and seismic responses, as the suspended conductor line and the suspended lumped mass decreased the frequency of the transmission tower. Under longitudinal ground motion, the model with the suspended lumped mass had the lowest peak acceleration response and the largest peak displacement response. Under the same ground motion, the four models had similar peak strains in the longitudinal direction. Under transverse-the-line ground motion, the model with the suspended lumped mass had the lowest peak acceleration response and the smallest peak responses for displacement and strain in the transverse direction; therefore, this model is inappropriate for the simulation and seismic evaluation of transmission tower-line systems.

Aliphatic polycarbonates have attracted significant attention for biomedical application over the last few years due to their biodegradability, low toxicity and good biocompatibility. However, in most cases, the use of metal-based catalysts is required for the preparation of aliphatic polycarbonates by the polycondensation method, which is difficult to remove completely from the final polymer. For this reason, our work is focused on the synthesis of high-molecular-weight aliphatic polycarbonates using organo-catalysts via a two-step polycondensation of dimethyl carbonate and a linear alkane diol as monomers. A variety of organo-catalysts have been surveyed for the synthesis of aliphatic polycarbonates. The influence of thiourea with mono- or bi-electron acceptor groups as cocatalysts, which were found to activate the carbonyl groups of lactide and trimethylene carbonate in the ring opening polymerization successfully, was investigated in the polycondensation. In summary, high-molecular-weight aliphatic polycarbonates, such as poly(1,4-butylene carbonate) (PBC), poly(1,5-pentamethylene carbonate) (PPC) and poly(1,6-hexamethylene carbonate) (PHC), were successfully prepared with number averaged molar masses (Mn) up to 23 000 g mol−1, dispersities below 1.8 and high yield of >80% under relatively mild operating conditions (T < 130 °C) using 4-dimethylaminopyridine (DMAP) as the catalyst. At 170 °C the poly(1,4-butylene carbonate) with Mn of 52 000 g mol−1 was synthesized. Additionally, hydroxyl group terminated poly(1,4-butylene carbonate) with Mn up to 17 000 g mol−1 was obtained and characterized by 1H NMR spectroscopy and ESI-TOF-mass spectrometry. The ratio of end groups (–OH/–OC(O)O–CH3) could be adjusted by using different feed ratios or catalysts.

Masonry-infilled timber frames are widely used for residential houses in underdeveloped rural and mountainous areas in southwestern China. As suggested by the identified dynamic properties of three typical timber houses of this type, the structure can be taken as a dual system in which the masonry infills provide the most lateral resistance, while the timber frame withstands the vertical loads. The seismic damage to the houses, either of masonry or of masonry-infilled timber structures, in a small town near the epicenter of the 2013 M7.0 Lushan earthquake in southwestern China was inspected and compared, in order to show that the masonry-infilled timber houses exhibited much better seismic performance than the unreinforced masonry ones during the earthquake.

In the present work, a new and facile strategy for the synthesis of light-responsive polyurethanes (LrPUs) based on serinol with o-nitrobenzyl pendent groups is developed. Stable monodisperse nanoparticles from these LrPUs can be formulated reproducibly in a simple manner, which is shown by dynamic light scattering (DLS) measurements. Upon irradiation with UV light, both polymers and nanoparticles undergo rapid degradation, which is investigated by DLS, scanning electron microscopy, size exclusion chromatography, and UV-vis spectroscopy. The nanoparticles are also employed for the encapsulation of the model drug Nile Red, and by exposure to UV light, a burst release of the payload is detected via fluorescence spectroscopy. This strategy can be easily applied to the straightforward synthesis of various new serinol-based monomers with different stimuli-responsive properties and therefore expand the family of biodegradable polymers.